1. © 2008 BC Decker Inc ACS Surgery: Principles and Practice
1 BASIC SURGICAL AND PERIOPERATIVE CONSIDERATIONS 3 PERIOPERATIVE CONSIDERATIONS FOR
ANESTHESIA — 1
3 PERIOPERATIVE CONSIDERATIONS
FOR ANESTHESIA
Steven B. Backman, MDCM, PhD, FRCPC, Richard M. Bondy, MDCM, Alain Deschamps, MD, PhD,
Anne Moore, MD, and Thomas Schricker, MD, PhD
Advancements in modern surgical care are complemented by associated with general or regional anesthesia (see below)
alterations in anesthetic management to provide maximum should be discussed in an informative and reassuring manner;
patient benefit. During the last two decades, anesthesia prac- a well-conducted preoperative anesthesia interview plays an
tice has changed enormously—with the proliferation of airway important role in alleviating anxiety.
devices; the routine employment of patient-controlled anal- The medications the patient is taking can have a substantial
gesia; the wider popularity of regional anesthesia, including impact on anesthetic management. Generally, patients should
thoracic epidural anesthesia and peripheral nerve blocks; the continue to take their regular medication up to the time
development of computer-controlled devices for infusing of the operation. It is especially important not to abruptly
short-acting drugs; the discovery and use of quickly reversible discontinue medications that may result in withdrawal or
inhalational drugs, opiates, and muscle relaxants; the avail- rebound phenomena (e.g., beta blockers, alpha antagonists,
ability of online monitoring of central nervous system (CNS) barbiturates, and opioids). With some medications (e.g., oral
function; and the increased application of transesophageal hypoglycemics, insulin, and corticosteroids), perioperative
echocardiography, to name but a few examples. Our aim dosage adjustments may be necessary [see 8:10 Endocrine
in this chapter is to offer surgeons a current perspective on Problems]. Angiotensin-converting enzyme inhibitors have
perioperative considerations for anesthesia to facilitate dia- been associated with intraoperative hypotension and may
logue between the surgeon and the anesthesiologist and be withheld at the discretion of the anesthesiologist.3 Drugs
thereby ensure optimum care for our patients. The primary that should be discontinued preoperatively include mono-
focus is on the adult patient: the special issues concerning amine oxidase inhibitors (MAOIs) and oral anticoagulants
pediatric anesthesia are beyond the scope of our review. In [see Table 1].
Many surgical patients are taking antiplatelet drugs.
addition, the ensuing discussion is necessarily selective; more
Careful consideration should be given to the withdrawal of
comprehensive discussions may be found elsewhere.1,2
these agents in the perioperative period [see Table 1] because
of the possibility that discontinuance may lead to an acute
Perioperative Patient Management coronary syndrome. Patients with recently placed coronary
artery drug-eluting stents (< 1 year) may be at particular risk,
Preoperative medical evaluation is an essential component
so elective surgery should be postponed.4 If surgery is neces-
of preoperative assessment for anesthesia. Of particular
sary, and patients are deemed to be at increased risk for
importance to the anesthesiologist is any history of personal
medication-related bleeding during surgery, the longer-acting
or family problems with anesthesia. Information should be
agents (e.g., aspirin, clopidogrel, and ticlopidine) can be
sought concerning difficulty with airway management or
replaced with nonsteroidal antiinflammatory drugs (NSAIDs)
intubation, drug allergy, delayed awakening, significant post-
that have shorter half-lives. Typically, these shorter-acting
operative nausea and vomiting (PONV), unexpected hospital
drugs are given for 10 days, stopped on the day of surgery,
or intensive care unit (ICU) admission, and post–dural punc- and then restarted 6 hours after operation. Platelet transfu-
ture headache (PDPH). Previous anesthetic records may be sion can be considered if there is a very high potential for
requested. significant bleeding.5
The airway must be carefully examined to identify patients The increasing use of herbal and alternative medicines has
at risk for difficult ventilation or intubation [see Special led to significant morbidity and mortality as a consequence
Scenarios, Difficult Airway, below], with particular attention of unexpected interactions with traditional drugs. Because
paid to teeth, caps, crowns, dentures, and bridges. Patients many patients fail to mention such agents as part of their
must be informed about the risk of trauma associated with medication regimen during the preoperative assessment, it is
intubation and airway management. Anesthetic options [see advisable to question all patients directly about their use.
Choice of Anesthesia, below] should be discussed, including Particular attention should be given to Chinese herbal teas,
the likelihood of postoperative ventilation and admission to which include organic compounds and toxic contaminants
the hospital or ICU. When relevant, the possibility of blood that may produce renal fibrosis or failure, cholestasis, hepati-
product administration should be raised [see 1:4 Bleeding and tis, and thrombocytopenia. Specific recommendations exist
Transfusion], and the patient’s acceptance or refusal of trans- for the discontinuance of many of these agents [see Table 1].
fusion should be carefully documented. Postoperative pain Prophylactic administration of perioperative beta blockers
management [see 1:6 Postoperative Pain] should be addressed, in patients with or at risk for atherosclerotic disease under-
particularly when a major procedure is planned. The risks going noncardiac surgery is controversial and merits specific
DOI 10.2310/7800.S01C03
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1 BASIC SURGICAL AND PERIOPERATIVE CONSIDERATIONS 3 PERIOPERATIVE CONSIDERATIONS FOR
ANESTHESIA — 2
Table 1 Recommendations for Preoperative Discontinuance of Drugs and Medicine68–81
Type of Agent Pharmacologic Effects Adverse Effects Discontinuance Recommendations
Drug
MAOIs Isocarboxazid Irreversible inhibition of Potentiation of sympathomimetic Elective surgery: discontinue at least
Phenelzine monoamine oxidase amines, possible hypertensive crisis 2 wk in advance; consider potential
Pargyline with the resultant May prolong and intensify effects of for suicidal tendency—mental
Tranylcypromine increase in serotonin, other CNS depressants health specialist should be involved
Selegiline norepinephrine, Severe idiopathic hyperpyrexic Emergency surgery: avoid meperidine;
epinephrine, dopamine, reaction with meperidine and consider regional anesthesia
and octamine possibly other narcotics
neurotransmitters Potential catastrophic interaction
with tricyclic antidepressants,
characterized by high fever and
excessive cerebral excitation and
hypertension
Oral Warfarin Inhibition of vitamin K– Bleeding Elective surgery: discontinue 5–7 days
anticoagu- dependent clotting in advance; replace with heparin if
lants factors II, VII, IX, X necessary
Aspirin and Inhibition of May increase intraoperative and Primary hemostasis normalizes in
NSAIDs thromboxane A2 postoperative bleeding but not 48 hr in healthy persons; platelet
Aspirin 80% of platelets must be transfusion requirement activity fully recovered in 8–10 days
Fenoprofen inhibited for therapeutic Perioperative hemorrhagic complica- Patients on long-term aspirin therapy
Ibuprofen effect tions increase with increasing for coronary or cerebrovascular
Sodium Susceptibility to aspirin half-life of drug pathology should not discontinue
meclofenamate varies between patients drug in perioperative period unless
Tolmetin hemorrhagic complications of
Indomethacin procedure outweigh risk of acute
Ketoprofen thrombotic event
Diflunisal
Naproxen
Sulindac
Piroxicam
Antiplatelet Thienopyridines Inhibition of platelet Synergistic antithrombotic effect with Discontinue ticlopidine 2 wk in
agents Ticlopidine aggregation aspirin advance; discontinue clopidogrel
Clopidogrel Inhibition of platelet 7–10 days in advance
ADP–induced amplifi- Patients with coronary artery stents
cation may receive aspirin plus ticlopidine
for prolonged period after angio-
plasty; stopping therapy consider-
ably increases risk of coronary
thrombosis; elective surgery should
be delayed for 1–3 mo
Antiglycoprotein Competitive inhibition of Literature (mainly from cardiac Discontinue at least 12 hr in advance
agents GPIIb/IIIa receptors to surgery) shows increased hemor- Transfuse platelets only if needed to
Eptifibatide prevent platelet rhagic risk if surgery undertaken correct clinically significant bleeding
Tirofiban aggregation < 12 hr after discontinuance of
Abciximab Rapid onset of action abciximab
Short half-lives Individual variability in recovery time
Often combined with of platelet function
aspirin and/or heparin
Herbal Chaparral Used as an alternative Hepatotoxicity As soon as possible
medicines anticancer agent
This herbal agent should
be considered as
dangerous
Coltsfoot Used as an antitussive and Carcinogenic As soon as possible
demulcent agent
Considered dangerous
Comfrey Used as a general healing Hepatotoxicity, liver failure As soon as possible
agent
Considered dangerous
Ephedra/ma Noncatecholamine Dose-dependent increase in HR and Discontinue at least 24 hr in advance
huang sympathomimetic agent BP, with potential for serious
(Ephedra with a1, b1, and b2 cardiac and CNS complications
sinica) activity; both direct and Possible adverse drug reactions:
indirect release of MAOIs (life-threatening hyperten-
endogenous catechol- sion, hyperpyrexia, coma), oxytocin
amines (hypertension), digoxin and volatile
anesthetics (dysrhythmias),
guanethedine (hypertension,
tachycardia)
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Table 1 Continued
Type of Agent Pharmacologic Effects Adverse Effects Discontinuance Recommendations
Drug
Herbal Echinacea Immunostimulatory effect Hepatotoxicity Discontinue as far in advance as
medicines (Echinacea Allergic potential possible in any patient with hepatic
purpurea) dysfunction or surgery with possible
hepatic blood flow compromise
Feverfew May increase bleeding especially in At least 7 days
patients already on anticlotting
medications
Garlic (Allium Irreversible dose- Increased bleeding may potentiate Discontinue at least 7 days in advance
sativum) dependent inhibition of other platelet inhibitors
platelet aggregation
Germander Choleretic, antiseptic Hepatotoxicity As soon as possible
properties
Used in weight control
Considered dangerous
Ginkgo (Ginkgo Inhibition of platelet- Increased bleeding Discontinue at least 36 hr in advance
biloba) activating factor May potentiate other platelet
Modulation of neurotrans- inhibitors
mitter receptor activity
Ginger (Zingiber Potent inhibitor of Increased bleeding Discontinue at least 36 hr in advance
officinale) thromboxane synthase May potentiate effects of other
anticoagulants
Ginseng (Panax Inhibition of platelet Prolonged PT and PTT Discontinue at least 7 days in advance
ginseng) aggregation, possibly Hypoglycemia
irreversibly Reduced anticoagulation effect of
Antioxidant action warfarin
Antihyperglycemic action Possible additive effect with other
“Steroid hormone”–like stimulants, with resultant
activity hypertension and tachycardia
Goldenseal May worsen swelling and/or high BP At least 7 days
Kava (Piper Dose-dependent potentia- Potentiation of sedative anesthetics,
methysticum) tion of GABA- including barbiturates and
inhibitory neurotrans- benzodiazepines
mitter with sedative, Possible potentiation of ethanol
anxiolytic, and effects
antiepileptic effects
Licorice Hypertension
(Glycyrrhiza Hypokalemia
glabra) Edema
Contraindicated in chronic liver and
renal insufficiency
Lobelia Used as an antinausea and Respiratory depression, tachycardia, As soon as possible
mild expectorant hypotension, hallucinations, coma,
Considered dangerous death
Sassafras Stimulant, antispasmodic Carcinogenic As soon as possible
Considered dangerous
Saw palmetto May interfere with other hormone At least 7 days
therapies
St. John’s wort Inhibits reuptake of Possible interaction with MAOIs Discontinue on day of surgery; abrupt
(Hypericum serotonin, norepine- Evidence for reduced activity of withdrawal in physically dependent
perforatum) phrine, and dopamine cyclosporine, warfarin, calcium patients may produce benzodiaz-
by neurons Increases channel blockers, lidocaine, epine-like withdrawal syndrome
metabolism of some midazolam, alfentanil, and NSAIDs
P-450 isoforms
Valerian Dose-dependent Possible potentiation of sedative Discontinue at least 24 hr in advance
(Valeriana modulation of GABA anesthetics, including barbiturates
officinalis) neurotransmitter and and benzodiazepines
receptor function
Vitamin E May increase bleeding, especially in
patients taking anticlotting agents
May affect thyroid function in
otherwise healthy patients
In doses greater than 400 IU per day,
further increase in BP may be seen
in already hypertensive patients
Yohimbe Aphrodisiac, sexual Hypertension, tachycardia, paralysis, As soon as possible
stimulant death
Considered dangerous
ADP = adenosine diphosphate; BP = blood pressure; CNS = central nervous system; GABA = b-aminobutyric acid; GP = glycoprotein; HR = heart rate;
MAOIs = monoamine oxidase inhibitors; NSAIDs = nonsteroidal antiinflammatory drugs; PT = prothrombin time; PTT = partial thromboplastin time.
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consideration. Although a subgroup of patients may benefit Table 3 Fasting Recommendations* to Reduce Risk of
from such treatment with respect to decreased cardiac mor- Pulmonary Aspiration83
bidity, overall, an increased risk of death, stroke, and clini- Ingested Material Minimum Fasting Period† (hr)
cally significant hypotension and bradycardia has been
‡
reported.6 As such, it is anticipated that guidelines regarding Clear liquids 2
Breast milk 4
the role for beta blockers in the perioperative setting will con- Infant formula 6
tinue to evolve.7 Nonhuman milk§¤ 6
Light meal|| 8
Inpatient versus Outpatient Surgery *These recommendations apply to healthy patients undergoing elective proce-
dures; they are not intended for women in labor. Following the guidelines does
An ever-increasing number of operations are performed on not guarantee complete gastric emptying.
†
These fasting periods apply to all ages.
an ambulatory basis [see ECP:5 Patient Safety in Surgical Care: ‡
Examples of clear liquids include water, fruit juices without pulp, carbonated
A Systems Approach]. Operations considered appropriate for beverages, clear tea, and black coffee.
§
an ambulatory setting are associated with minimal physiologic Because nonhuman milk is similar to solids in gastric emptying time, the
amount ingested must be considered in determining the appropriate fasting
trespass, low anesthetic complexity, and uncomplicated period.
recovery.8,9 The design of the ambulatory facility may impose ||
A light meal typically consists of toast and clear liquids. Meals that include
limitations on the types of operations or patients that can be fried or fatty foods or meat may prolong gastric emptying time. Both
the amount and type of foods ingested must be considered in determining the
considered for ambulatory surgery. Such limitations may be appropriate fasting period.
secondary to availability of equipment, recovery room nursing
expertise and access to consultants, and availability of ICU or
hospital beds. Patients who are in class I or class II of the intraoperative and postoperative opioid requirements and
American Society of Anesthesiologists (ASA) physical status accelerate patient discharge. Use of a laryngeal mask airway
scale are ideally suited for ambulatory surgery; however, a rather than an endotracheal tube is ideal in the outpatient
subset of ASA class III patients may be at increased risk for setting because lower doses of induction agent are required
prolonged recovery and hospital admission [see Table 2]. to blunt the hypertension and tachycardia associated with its
Premedication to produce anxiolysis, sedation, analgesia, insertion; in addition, it is associated with a decreased inci-
amnesia, and reduction in PONV and aspiration may be dence of sore throat and does not require muscle paralysis for
considered for patients undergoing outpatient procedures, insertion. On the other hand, a laryngeal mask airway may
as it may for those undergoing inpatient procedures. Such not protect against aspiration.12,13
premedication should not delay discharge. Fasting guidelines The benefits of regional anesthesia [see Regional Anesthesia
[see Table 3] and intraoperative monitoring standards for Techniques, below] may include decreases in the incidence of
ambulatory surgery are identical to those for inpatient aspiration, nausea, dizziness, and disorientation. Spinal and
procedures [see Patient Monitoring, below]. epidural anesthesia may be associated with headache (dural
A number of currently used anesthetics (e.g., propofol, puncture) and backache. Compared with spinal anesthesia,
sevoflurane, desflurane), narcotics (e.g., alfentanil, fentanyl, epidural anesthesia takes more time to perform, has a slower
sufentanil, and remifentanil), and muscle relaxants (e.g., onset of action, and may not produce as profound a block;
succinylcholine, atracurium, mivacurium, and rocuronium) however, the duration of an epidural block can readily be
demonstrate rapid recovery profiles. Nitrous oxide also has extended intraoperatively or postoperatively if necessary.
desirable pharmacokinetic properties, but it may be associ- Care should be exercised in choosing a local anesthetic for
ated with increased PONV. Titration of anesthetics to indices neuraxial blockade: spinal lidocaine may be associated with
of CNS activity (e.g., the bispectral index) may result in a transient radicular irritation, and bupivacaine may be
decreased drug dosages, faster recovery from anesthesia, associated with prolonged motor block; narcotics may pro-
and fewer complications.10,11 Multimodal analgesia (involving duce pruritus, urinary retention, nausea and vomiting, and
the use of local anesthetics, ketamine, alpha2-adrenergic ago- respiratory depression. Various dosing regimens, including
nists, beta blockers, acetaminophen, or NSAIDs) may reduce minidose spinal techniques, have been proposed as means of
minimizing these side effects.14–17
Monitored anesthesia care [see Choice of Anesthesia, below]
Table 2 Association between Preexisting Medical achieves minimal CNS depression, so the airway and sponta-
Conditions and Adverse Outcomes82 neous ventilation are maintained and the patient is able
Medical Associated Adverse Outcome to respond to verbal commands. Meticulous attention to
Condition
monitoring is required to guard against airway obstruction,
Congestive heart 12% prolongation of postoperative stay arterial desaturation, and pulmonary aspiration.
failure
Hypertension Twofold increase in risk of intraoperative In the recovery room, the anesthetic plan is continued until
cardiovascular events discharge. Shorter-acting narcotics and NSAIDs are admin-
Asthma Fivefold increase in risk of postoperative istered for pain relief, and any of several agents may be given
respiratory events for control of nausea and vomiting. Criteria for discharge
Smoking Fourfold increase in risk of postoperative
respiratory events
from the recovery room have been established [see Table 4].
Obesity Fourfold increase in risk of intraoperative and Recovery of normal muscle strength and sensation (including
postoperative respiratory events proprioception of the lower extremity, autonomic function,
Reflux Eightfold increase in risk of intubation-related and ability to void) should be demonstrated after spinal or
adverse events epidural anesthesia. Delays in discharge are usually the result
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Table 4 Postanesthetic Discharge Scoring System definitive surgical treatment must not be unduly delayed by
(PADSS)84 attempts to “get a line.”
Category Score* Explanation
Vital signs 2 Within 20% of preoperative value Choice of Anesthesia
1 Within 20 to 40% of preoperative
Anesthesia may be classified into three broad categories:
value
0 Within 40% of preoperative value (1) general anesthesia, (2) regional anesthesia, and (3) moni-
tored anesthesia care. General anesthesia can be defined as a
Activity, mental 2 Oriented and steady gait
state of insensibility characterized by loss of consciousness,
status 1 Oriented or steady gait
0 Neither amnesia, analgesia, and muscle relaxation. This state may be
achieved either with a single anesthetic or, in a more balanced
Pain, nausea, 2 Minimal
fashion, with a combination of several drugs that specifically
vomiting 1 Moderate
0 Severe induce hypnosis, analgesia, amnesia, and paralysis.
There is, at present, no consensus as to which general
Surgical bleeding 2 Minimal
anesthetic regimen best preserves organ function. General
1 Moderate
0 Severe anesthesia is employed when contraindications to regional
anesthesia are present or when regional anesthesia or moni-
Intake/output 2 Oral fluid intake and voiding
1 Oral fluid intake or voiding
tored anesthesia care fails to provide adequate intraoperative
0 Neither analgesia. In addition, a few situations specifically mandate
general anesthesia and controlled ventilation: the need for
*Total possible score is 10; patients scoring g9 are considered fit for discharge
home.
abdominal muscle paralysis, lung isolation, and hyperventila-
tion; the presence of serious cardiorespiratory instability; and
the lack of sufficient time to perform regional anesthesia.
Alternatives to general anesthesia should be considered for
of pain, PONV, hypotension, dizziness, unsteady gait, or lack
patients who are susceptible to malignant hyperthermia
of an escort.18
(MH), for those in whom intubation is likely to prove difficult
or the risk of aspiration is high, and for those with pulmonary
Elective versus Emergency Surgery compromise that may worsen after intubation and positive
pressure ventilation.
Surgical procedures performed on an emergency basis may
Regional anesthesia is achieved by interfering with afferent
range from relatively low priority (e.g., a previously cancelled
or efferent neural signaling at the level either of the spinal
case that was originally elective) to highly urgent (e.g., a
cord (neuraxial blockade) or of the peripheral nerves. Neur-
case of impending airway obstruction). For trauma, specific
axial anesthesia (i.e., epidural or spinal administration of
evaluation and resuscitation sequences have been established
local anesthetics) is commonly employed as the sole anes-
to facilitate patient management [see 7:1 Initial Management
thetic technique for procedures involving the lower abdomen
of Life-Threatening Trauma]. The urgency of the situation
and the lower extremities; it also provides effective pain relief
dictates how much time can be allotted to preoperative patient
after intraperitoneal and intrathoracic procedures. Combin-
assessment and optimization. When it is not possible to ing regional and general anesthesia has become increasingly
communicate with the patient, information obtained from popular.19 Currently, some physicians are using neuraxial
family members and paramedics may be crucial. Information blockade as the sole anesthetic technique for procedures such
should be sought concerning allergies, current medications, as thoracotomy and coronary artery bypass grafting, which
significant past medical illnesses, nihil per os (NPO) status, are traditionally thought to require general anesthesia and
personal or family problems with anesthesia, and recent endotracheal intubation.20
ingestion of alcohol or drugs. Any factor that may complicate Neuraxial blockade has several advantages over general
airway management should be noted (e.g., trauma to the anesthesia, including better dynamic pain control, shorter
face or the neck, a beard, a short and thick neck, obesity, or duration of paralytic ileus, reduced risk of pulmonary
a full stomach). When appropriate, blood samples should be complications, and decreased transfusion requirements; it is
obtained as soon as possible for typing and cross-matching, also associated with a decreased incidence of renal failure
as well as routine blood chemistry, complete blood count, and myocardial infarction [see 1:6 Postoperative Pain].21–24
and toxin screen. Arrangements for postoperative ICU Contrary to conventional thinking, however, the type of anes-
monitoring, if appropriate, should be instituted early. thesia used (general or neuraxial) is not an independent risk
Clear communication must be established between the factor for long-term cognitive dysfunction.25 Neuraxial block-
surgical team and anesthesia personnel so that an appropriate ade is an essential component of multimodal rehabilitation
anesthetic management plan can be formulated and any programs aimed at optimization of perioperative care and
specialized equipment required can be mobilized in the oper- acceleration of recovery [see ECP:3 Perioperative Considerations
ating room (OR). The induction of anesthesia may coincide for Anesthesia].26,27
with resuscitation. Accordingly, the surgical team must be For short, superficial procedures, a variety of peripheral
immediately available to help with difficult intravenous nerve blocks may be considered.28 With procedures on the
(IV) access, emergency tracheostomy, and cardiopulmonary upper or lower extremity, an IV regional (Bier) block with
resuscitation. Patients in shock may not tolerate standard diluted lidocaine may be useful. Anesthesia of the upper
anesthetics, which characteristically blunt sympathetic extremity and shoulder may be achieved with the brachial
outflow. The anesthetic dose must be judiciously titrated, and plexus block. Anesthesia of the lower extremity may be
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achieved by blocking the femoral, obturator, and lateral fem- are advocated by some as measures of hypnosis to guide the
oral cutaneous nerves (knee surgery) or the ankle and popli- administration of anesthetics.32,33 However, their effectiveness
teal sciatic nerves (foot surgery). Anesthesia of the thorax in preventing intraoperative awareness remains controversial,
may be achieved with intercostal or intrapleural nerve blocks. particularly when anesthesia is maintained by inhalational
Anesthesia of the abdomen may be achieved with celiac drugs.34 CNS function may also be assessed by measurement
plexus and paravertebral blocks. Anesthesia of the head and of cerebral blood flow, using transcranial Doppler, jugular
neck may be achieved by blocking the trigeminal, supraor- bulb venous oxygen saturation, and cerebral oximetry
bital, supratrochlear, infraorbitral, and mental nerves and the monitoring techniques. Although there is growing clinical
cervical plexus. Local infiltration of the operative site may experience with these noninvasive intraoperative neurologic
provide intraoperative and postoperative analgesia. monitors, randomized, prospective, and adequately powered
Unlike the data on neuraxial blockade, the data on studies to support and guide their use are currently lacking.
peripheral nerve blockade neither support nor discourage its
use as a substitute for general anesthesia. Generally, however,
General Anesthesia Techniques
we favor regional techniques when appropriate: such
approaches maintain consciousness and spontaneous breath- An ever-expanding armamentarium of drugs is available
ing while causing only minimal depression of the CNS and for premedication and for induction and maintenance of
the cardiorespiratory systems, and they yield improved pain anesthesia. Selection of one agent over another is influenced
control in the immediate postoperative period. by the patient’s baseline condition, procedure, local standard
Monitored anesthesia care involves the use of IV drugs of practice, and predicted duration of hospitalization.
to reduce anxiety, provide analgesia, and alleviate the dis-
premedication
comfort of immobilization. This approach may be combined
with local infiltration analgesia provided by the surgeon.29 Preoperative medications are given primarily to decrease
Monitored anesthesia care requires monitoring of vital signs anxiety, to reduce the incidence of nausea and vomiting,
and the presence of an anesthesiologist who is prepared and to prevent aspiration. Other benefits include sedation,
to convert to general anesthesia if necessary. Its benefits amnesia, analgesia, drying of oral secretions, and blunting of
are substantially similar to those of regional anesthesia. These undesirable autonomic reflexes.
benefits are lost when attempts are made to overcome surgi-
Sedatives and Analgesics
cal pain with excessive doses of sedatives and analgesics.
Benzodiazepines produce anxiolysis, sedation, hypnosis,
amnesia, and muscle relaxation; they do not produce analge-
Patient Monitoring sia. They may be classified as short acting (midazolam), inter-
Patient monitoring is central to the practice of anesthesia. mediate acting (lorazepam), or long acting (diazepam).
A trained, experienced physician is the only truly indispens- Adverse effects [see Table 5] may be marked in debilitated
able monitor; mechanical and electronic monitors, although patients. Their central effects may be antagonized with
useful, are, at most, aids to vigilance. Wherever anesthesia is flumazenil.
administered, the proper equipment for pulse oximetry, blood Muscarinic antagonists (e.g., scopolamine and atropine)
pressure measurement, electrocardiography, and capnogra- were commonly administered at one time; this practice is not
phy should be available. At each anesthesia workstation, as popular today. They produce, to varying degrees, sedation,
equipment for measuring temperature, a peripheral nerve amnesia, lowered anesthetic requirements, diminished nausea
stimulator, a stethoscope, and appropriate lighting must and vomiting, reduced oral secretions, and decreased gastric
be immediately available. A spirometer must be available hydrogen ion secretion. They blunt the cardiac parasym-
without undue delay. pathetic reflex responses that may occur during certain
Additional monitoring may be indicated, depending on the procedures (e.g., ocular surgery, traction on the mesentery,
patient’s health, the type of procedure to be performed, and and manipulation of the carotid body). Adverse effects include
the characteristics of the practice setting. Cardiovascular
monitoring, including measurement of systemic arterial,
Table 5 Benzodiazepines: Doses and Duration of Action85
central venous, pulmonary arterial, and wedge pressures;
cardiac output; and continuous arterial and mixed venous Dose (for Elimination
Benzodiazepine Comments
Sedation) Half-Life
oximetry, is covered in detail elsewhere [see 8:3 Shock].
Additional information about the cardiovascular system may Midazolam 0.5–1.0 mg, 1.7–2.6 hr Respiratory
repeated depression,
be obtained by transesophageal echocardiography.30 Practice excessive
guidelines for this technique have been developed.31 It may sedation,
be particularly useful in patients who are undergoing valve hypotension,
repair or who have persistent severe hypotension of unknown bradycardia,
anticonvulsant
etiology. activity
The effects of anesthesia on the CNS may be assessed (withdrawal)
by monitoring electroencephalographic (EEG) activity that is Lorazepam 0.25 mg, 11–22 hr See midazolam
either spontaneous (raw or processed) or evoked (e.g., repeated Venous
somatosensory, auditory, or visual). Commercially available thrombosis
devices that employ spectral analysis of spontaneous EEG Diazepam 2.0 mg, 20–50 hr See midazolam
activity (e.g., bispectral index) are relatively easy to use and repeated and lorazepam
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tachycardia, heat intolerance, inhibition of gastrointestinal pharmacologic treatment may be helpful [see Table 7]. H2
(GI) motility and micturition, and mydriasis. receptor antagonists (e.g., cimetidine, ranitidine, and famoti-
Opioids are used when analgesia, in addition to sedation dine) and proton pump inhibitors (e.g., omeprazole) reduce
and anxiolysis, is required. With morphine and meperidine, gastric acid secretion, thereby raising gastric pH without
the time of onset of action and the peak effect are unpredict- affecting gastric volume or emptying time. Nonparticulate
able. Synthetic opioids (e.g., fentanyl) have a more rapid antacids (e.g., sodium citrate) neutralize the acidity of gastric
onset and a predictable time course, which make them contents. Metoclopramide promotes gastric emptying (by
more suitable for premedication immediately before surgery. stimulating propulsive GI motility) and decreases reflux (by
Adverse effects [see Table 6] can be reversed with full increasing the tone of the esophagogastric sphincter); it may
(naloxone) or partial (nalbuphine) antagonists. also possess antiemetic properties.
The alpha2-adrenergic agonists clonidine and dexmedeto- In all patients at risk for aspiration who require general
midine are sympatholytic drugs that also exert sedative, anesthesia, a rapid sequence induction is traditionally consid-
anxiolytic, and analgesic effects. They reduce intraoperative ered a standard of practice, although this has been recently
anesthetic requirements, thus allowing faster recovery, and questioned.37 A rapid sequence induction is achieved through
attenuate sympathetic activation secondary to intubation adequate preoxygenation, administration of drugs to produce
and surgery, thus improving intraoperative hemodynamic rapid loss of consciousness and paralysis, and exertion of
stability. Major drawbacks are hypotension and bradycardia; pressure on the cricoid cartilage (the Sellick maneuver) as
rebound hypertensive crises may be precipitated by their loss of consciousness occurs to occlude the esophagus and so
discontinuance.35,36 limit reflux of gastric contents into the pharynx. An alterna-
tive is the so-called modified rapid sequence induction, which
Prevention of Aspiration permits gentle mask ventilation during the application of
Aspiration of gastric contents is an extremely serious cricoid pressure (thereby potentially reducing or abolishing
complication that is associated with significant morbidity insufflation of gas into the stomach). The advantages of the
and mortality. Fasting helps reduce the risk of this complica- modified approach are that there is less risk of hypoxia and
tion [see Table 3]. When the likelihood of aspiration is high, more time to treat cardiovascular responses to induction
Table 6 Opioids: Doses and Duration of Action86
Agent Relative Dose Time to Duration of Comments
Induction Analgesic Peak Action
Potency Induction or Maintenance Effect
Maintenance Loading
Morphine 1 1 mg/kg 0.05–0.2 mg/kg/hr 5–20 min 2–7 hr Respiratory depression, nausea,
For perioperative vomiting, pruritus, constipa-
analgesia: tion, urinary retention, biliary
0.1 mg/kg IV, spasm, neuroexcitation
IM Pseizure, tolerance
Cough suppression, relief of
dyspnea-induced anxiety
(common to all opioids)
Histamine release, orthostatic
hypotension, prolonged
emergence
Meperidine 0.1 For perioperative NA 2 hr (oral); 2–4 hr See morphine
analgesia: 1 hr Orthostatic hypotension,
0.5–1.5 mg/kg (SC, myocardial depression, dry
IV, IM, SC IM) mouth, mild tachycardia,
mydriasis, histamine release
Attenuates shivering; to be
avoided with MAOIs
Local anesthetic–like effect
Remifentanil 250–300 1 µg/kg 0.25–0.4 µg/kg/min 3–5 min 5–10 min See morphine
Awareness, bradycardia, muscle
rigidity
Ideal for infusion; fast recovery,
no postoperative analgesia
Alfentanil 7.5–25 50–300 µg/kg 1.25–8.0 µg/kg/min 1–2 min 10–15 min See morphine
Awareness, bradycardia, muscle
rigidity
Fentanyl 75–125 5–30 µg/kg 0.25–0.5 µg/kg/min 5–15 min 30–60 min See morphine and alfentanil
Sufentanil 525–625 2–20 µg/kg 0.05–0.1 µg/kg/min 3–5 min 20–45 min See morphine and alfentanil
Ideal for prolonged infusion
IM = intramuscular; IV = intravenous; MAOI = monoamine oxidase inhibitor; NA = not applicable; SC = subcutaneous.
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Table 7 Pharmacologic Prevention of Aspiration87,88
Agent Dose Timing of Administration Comments
before Operation
H2 receptor antagonists 1–3 hr Hypotension, bradycardia, heart block, increased airway
Cimetidine 300 mg, PO resistance, CNS dysfunction, reduced hepatic metabolism
Ranitidine 50 mg IV of certain drugs
Famotidine 20 mg IV Bradycardia
Rare CNS dysfunction
Sodium citrate 30 mL PO 20–30 min Increased gastric fluid volume
Omeprazole 40 mg IV 40 min Possible alteration of GI drug absorption, hepatic metabolism
Metoclopramide 10 mg IV 15–30 min Extrapyramidal reactions, agitation, restlessness (large doses);
to be avoided with MAOIs, pheochromocytoma, bowel
obstruction
CNS = central nervous system; GI = gastrointestinal; IV = intravenous; MAOI = monoamine oxidase inhibitor; PO = oral.
agents before intubation. Regardless of which technique is hyperreactive airway disease). Inhalation induction is also
used, consideration should be given to emptying the stomach popular for ambulatory surgery when paralysis is not required.
via an orogastric or nasogastric tube before induction. Sevoflurane is well suited for this application because it is not
irritating on inhalation, as are most other volatile agents, and
induction it produces rapid loss of consciousness. Sevoflurane has
Induction of general anesthesia is achieved by administer- mostly replaced halothane as the agent of choice for inhala-
ing drugs to produce unconsciousness. It is one of the most tion induction because it is less likely to cause dysrhythmias
crucial and potentially dangerous moments for the patient and is not hepatotoxic.
during general anesthesia because of the precipitous depres-
sion of the cardiorespiratory systems and airway protective maintenance
mechanisms. Various agents can be used for this purpose; the Balanced general anesthesia is produced with a variety of
choice depends on the patient’s baseline medical condition drugs to maintain unconsciousness, prevent recall, and pro-
and fasting status, the state of the airway, the surgical proce- vide analgesia. Various combinations of volatile and IV agents
dure, and the expected length of the hospital stay. The agents may be employed to achieve these goals. The volatile agents
most commonly employed for induction are propofol, sodium isoflurane, desflurane, and sevoflurane are commonly used
thiopental, ketamine, and etomidate [see Table 8]. The opi- for maintenance [see Table 9]. Nitrous oxide is a strong anal-
oids alfentanil, fentanyl, sufentanil, and remifentanil may also gesic and a weak anesthetic agent that possesses favorable
be used for this purpose; they are associated with a very stable pharmacokinetic properties (fast onset, fast offset). Because
hemodynamic profile during induction and surgery but only of its relatively high blood:gas partition coefficient compared
invariably produce unconsciousness [see Table 6]. with nitrogen, nitrous oxide rapidly difuses into and expands
Volatile agents [see Table 9] may be employed for induction air-filled cavities. Thus, it should be avoided in situations in
of general anesthesia when maintenance of spontaneous ven- which expansion of such cavities is undesirable (e.g., pneu-
tilation is of paramount importance (e.g., with a difficult mothorax, air embolism, bowel obstruction, and middle ear
airway) or when bronchodilation is required (e.g., with severe surgery). It cannot be used as the sole anesthetic agent unless
Table 8 Induction Agents: Doses and Duration of Action85
Agent Induction Time to Duration Comments
Dose Peak of Action
(mg/kg) Effect (s) (min)
Propofol 1.0–2.5 90–100 5–10 Hypotension, apnea, antiemetic (low dose), sexual fantasies and hallucinations,
convulsions Pseizures (rare), pain on injection, thrombophlebitis
Thiopental 2.5–4.5 60 5–8 Hypotension, apnea, emergence delirium, prolonged somnolence,
anaphylactoid reaction, injection pain, hyperalgesia
Anticonvulsant effect
Contraindicated with porphyria
Ketamine 0.5–2 30 10–15 Analgesia; increased BP, HR, CO; lacrimation and salivation; bronchial
dilatation; elevated ICP
Dreaming, illusions, excitement
Preservation of respiration (apnea possible with high doses)
Etomidate 0.2–0.6 60 4–10 Minor effects on BP, HR, CO
Adrenocortical suppression, injection pain and thrombophlebitis, myoclonus,
nausea and vomiting
BP = blood pressure; CO = cardiac output; HR = heart rate; ICP = intracranial pressure.
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Table 9 Volatile Drugs89,90 hydrolysis of remifentanil, its administration may be labor
†
intensive, necessitating frequent administration of boluses
Agent Oil/Gas MAC Blood/Gas Rank
Coefficient* (atm) Coefficient‡ Order
and constant vigilance. Its short half-life also limits its useful-
(FA/FI)§ ness as an analgesic in the postoperative period and may even
contribute to acute opioid intolerance. To help circumvent
Halothane 224 0.0074 2.5 6
these problems, various dosing regimens have been proposed
Enflurane 96.5 0.0168 1.8 5 in which the patient is switched from remifentanil to a
Isoflurane 90.8 0.0115 1.4 4 longer-acting narcotic.
Desflurane 18.7 0.060 0.45 2 neuromuscular blockade
Sevoflurane 47.2 0.0236 0.65 3 The reversible paralysis produced by neuromuscular block-
Nitrous 1.4 1.04 0.47 1 ade improves conditions for endotracheal intubation and
oxide facilitates surgery. Neuromuscular blocking agents are classi-
FA/FI = alveolar concentration of gas/inspired concentration; MAC = mini- fied as either depolarizing (succinylcholine) or nondepolariz-
mum alveolar concentration to abolish purposeful movement in response to ing (pancuronium, rocuronium, vecuronium, atracurium,
noxious stimulation in 50% of patients.
*Lipid solubility correlates closely with anesthetic potency (Meyer-Overton
cisatracurium, and mivacurium) and may be further differen-
rule). tiated on the basis of chemical structure and duration of
†
Correlates closely with lipid solubility. action [see Table 10]. The blocking effect of nondepolarizing
‡
Relative affinity of an anesthetic for blood compared to gas at equilibrium.
The larger the coefficient, the greater the affinity of the drug for blood and muscle relaxants is enhanced by volatile drugs, hypothermia,
hence the greater the quantity of drug contained in the blood. acidosis, certain antibiotics, magnesium sulfate, and local
§
Rise in alveolar anesthetic concentration toward the inspired concentration is anesthetics and is reduced by phenytoin and carbamazepine.
most rapid with the least soluble drugs and slowest with the most soluble.
Patients with weakness secondary to neuromuscular disorders
(e.g., myasthenia gravis and Eaton-Lambert syndrome) may
it is administered in a hyperbaric chamber; it is usually be particularly sensitive to nondepolarizing muscle relax-
administered with at least 30% oxygen to prevent hypoxia. ants.
Nitrous oxide is commonly used in combination with other
volatile agents. Potent volatile agents can trigger malignant emergence
hyperthermia in susceptible patients. General anesthesia is terminated by cessation of drug
The IV drugs currently used to maintain general anesthesia, administration, reversal of muscle paralysis, and extubation
whether partially or entirely, feature a short, context- (or removal of an upper airway device). During this poten-
sensitive elimination half-life; thus, pharmacologically signifi- tially dangerous period, close scrutiny of the patient is essen-
cant drug accumulation during prolonged infusion is avoided. tial, and all OR personnel must coordinate their efforts to
Such agents (including propofol, midazolam, sufentanil, help ensure a smooth and safe emergence from general anes-
and remifentanil) are typically administered via computer- thesia. In this phase, patients may demonstrate hemodynamic
controlled infusion pumps that use population-based instability, retching and vomiting, respiratory compromise
pharmacokinetic data to establish stable plasma (and CNS (including laryngospasm), and, occasionally, uncooperative
effector site) concentrations. Because of the extremely rapid or aggressive behavior.38
Table 10 Neuromuscular Blocking Agents: Doses and Duration of Action91
Agent Dose Duration of Metabolism Elimination Comments
(mg/kg) Action (min)
Succinylcholine 0.7–2.5 5–10 Plasma cholinesterase Renal < 2%, Fasciculations, elevation of serum potassium,
chloride hepatic 0% increased ICP, bradycardia, MH trigger;
prolonged effect in presence of atypical
pseudocholinesterase
Pancuronium 0.04–0.1 60–120 Hepatic 10–20% Renal 85%, Muscarinic antagonist (vagolytic), prolonged
hepatic 15% paralysis (long-term use)
Rocuronium 0.6–1.2 35–75 None Renal < 10%, Minimal histamine release
hepatic > 70%
Vecuronium 0.08–0.1 45–90 Hepatic 30–40% Renal 40%, Prolonged paralysis (long-term use)
hepatic 60%
Atracurium 0.3–0.5 30–45 Hoffman elimination, Renal 10–40%, Histamine release; laudanosine metabolite (a
nonspecific ester hepatic 0% CNS stimulant)
hydrolysis
Cisatracurium 0.15–0.2 40–75 Hoffman elimination Renal 16%, Negligible histamine release; laudanosine
hepatic 0% metabolite
Mivacurium 0.15–0.2 15–20 Plasma cholinesterase Renal < 5%, Histamine release; prolonged effect in presence
hepatic 0% of atypical pseudocholinesterase
CNS = central nervous system; ICP = intracranial pressure; MH = malignant hyperthermia.
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Reversal of neuromuscular blockade is achieved by admin- the headrest used in the prone position.41 The relationship
istering anticholinesterases such as neostigmine or edropho- between postoperative cognitive dysfunction (POCD) and
nium. These drugs should be given in conjunction with a anesthesia per se remains unclear and may occur in patients
muscarinic antagonist (atropine or glycopyrrolate) to block who receive general (intravenous or inhalational) or regional
their unwanted parasympathomimetic side effects. Neostig- anesthesia. POCD does not seem to be associated with intra-
mine is more potent than edrophonium in reversing profound operative hypoxemia, hypotension, or acid-base disturbances.
neuromuscular blockade. It is imperative that paralysis be Certain procedures, such as cardiac and orthopedic surgery,
sufficiently reversed before extubation to ensure that sponta- have been associated with this disorder, and a common
neous respiration is adequate and that the airway can be etiology (air, particulate, or fat microemboli) is implicated.
protected. Reversal can be clinically verified by confirming There is a growing appreciation that even with other types of
the patient’s ability to lift the head for 5 seconds. Reversal can surgery, POCD can occur, with elderly patients (more than
also be assessed by muscle contraction response to electrical 60 years) being at particular risk during the first week after
nerve stimulation. the procedure. Presently, there is little evidence that POCD
Causes of failure to emerge from anesthesia include persists longer than 6 months.42
residual neuromuscular blockade, a benzodiazepine or opioid
overdose, the central anticholinergic syndrome, an intraop-
Regional Anesthesia Techniques
erative cerebrovascular accident, preexisting pathophysiologic
conditions (e.g., CNS disorders, hepatic insufficiency, and Neuraxial (central) anesthesia techniques involve continu-
drug or alcohol ingestion), electrolyte abnormalities, acidosis, ous or intermittent injection of drugs into the epidural or
hypercarbia, hypoxia, hypothermia, and hypothyroidism. intrathecal space to produce sensory analgesia, motor block-
As noted, the effects of narcotics and benzodiazepines can ade, and inhibition of sympathetic outflow. Peripheral nerve
be reversed with naloxone and flumazenil, respectively. blockade involves inhibition of conduction in fibers of a single
Physostigmine may be given to reverse the reduction in peripheral nerve or plexus (cervical, brachial, or lumbar) in
consciousness level produced by general anesthetics. Electro- the periphery. Intravenous regional anesthesia involves IV
lyte, glucose, blood urea nitrogen, and creatinine levels should administration of a local anesthetic into a tourniquet-occluded
be measured; liver and thyroid function tests should be extremity. Perioperative pain control may be facilitated
performed; and arterial blood gas values should be obtained. by administering local anesthetics, either infiltrated into the
Patients should be normothermic. Unexplained failure wound or sprayed into the wound cavity. Procedures per-
to emerge from general anesthesia warrants immediate formed solely under infiltration may be associated with patient
consultation with a neurologist. dissatisfaction caused by intraoperative anxiety and pain.43,44
contraindications
Risk and General Anesthesia Strong contraindications to regional (particularly neurax-
Determining the risk(s) attributed solely to anesthesia is ial) anesthesia include patient refusal or inability to cooperate
difficult because of the confounding variables of patient during the procedure, elevated intracranial pressure, antico-
characteristics, concurrent medications, and the surgical agulation, vascular malformation or infection at the needle
procedure itself, including context (e.g., elective versus emer- insertion site, severe hemodynamic instability, and sepsis.
gency). Prospective, unbiased studies sufficiently powered to Preexisting neurologic disease is a relative contraindication.
reveal the frequency of rare events are lacking, and reliance
on self-reporting of negative outcomes likely results in an anticoagulation and bleeding risk
underestimation of risk. Given these limitations, attempts Although hemorrhagic complications can occur after any
have been made to define the risks associated with anesthesia, regional technique, bleeding associated with neuraxial block-
based on extensive and critical literature reviews [see ade is the most serious possibility because of its devastating
Table 11].39 Perioperative mortality associated with consequences. Spinal hematoma may occur as a result of
anesthesia increases with age, ASA status, and emergency vascular trauma from placement of a needle or catheter into
procedures. Factors contributing to anesthesia-related the subarachnoid or epidural space. Spinal hematoma may
mortality include inadequate assessment, preparation and also occur spontaneously, even in the absence of antiplatelet
resuscitation, inappropriate anesthetic technique, inadequate or anticoagulant therapy. The actual incidence of spinal cord
perioperative monitoring, lack of supervision, and poor post- injury resulting from hemorrhagic complications is unknown;
operative care. Morbidity ranges from major permanent the reported incidence is estimated to be less than 1 in
disability to relatively minor events without long-term conse- 150,000 for epidural anesthesia and 1 in 200,000 for spinal
quence. Peripheral nerve injury, although rare, may have seri- anesthesia [see Table 12].45 With such low incidences, it is
ous disability. The etiology includes direct injury from nee- difficult to determine whether any increased risk can be
dles, instruments, suturing, injection of toxic substances, and attributed to anticoagulant use [see Table 13] without data
thermal insults. Less obvious but more frequent events involve from millions of patients, which are not currently available.
mechanical factors such as nerve compression or stretch. Much of our clinical practice is based on small surveys and
Ischemia associated with a low cardiac output state is often expert opinion.
implicated.40 Great caution must be used during patient posi-
tioning, with careful attention to proper padding. Loss of Antiplatelet Agents
vision is a rare but catastrophic event that may be associated There is no universally accepted test that can guide
with compression of the eye by a facemask or by padding of antiplatelet therapy. Antiplatelet agents can be divided into
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Table 11 Predicted Incidence of Complications of Anesthesia39
Mortality and Morbidity Approximate Incidence Rate per 10,000 Remarks
Population
Total perioperative deaths 1:200 (elective surgery) 50
(within 30 days) 1:40 (emergency surgery) 250
x2 (60–79 yr)
x5 (80–89 yr)
x7 (> 90 yr)
Death related to anesthesia 1:50,000 (anesthesia related) 0.2
1:100,000 (ASA physical status I and II) 0.1
Cardiac arrest 1:10,000–1:20,000 (general anesthesia) 0.5–1.0 Mortality ≈ 1:15,000–1:150,000
1:3,000 (local anesthesia) 3
1:1,500 (spinal: 25% fatal) 7
Myocardial reinfarction 1:20 (0–3 mo after myocardial infarction 500
1:40 (4–6 mo after myocardial
infarction) 250
Respiratory complications
Aspiration during general 1:3,000 3 x4 in emergencies
anesthesia 1:60,000 (death) 0.16 x3 in obstetrics
Difficult intubation 1:50 200
Failure to intubate 1:500 20 Obstetrics ≈ 1:250
Failure to intubate and 1:5,000 2
ventilate
Postoperative cognitive 1:4 at 1 wk 2,500 Regional anesthesia
dysfunction 1:10 at 3 mo 1,000 General anesthesia
(> 60 yr) 1:100 permanent 100
Postoperative delirium 1:7 (general surgery) 1,400 x3 >75 yr
Up to 1:2 for elderly fractures of neck 5,000 x3 if requiring intensive care
or femur
Drowsiness 1:2 5,000 Day surgery
Dizziness 1:5 2,000 Day surgery
Headache 1:5 2,000
Cerebrovascular accident 1:50 if previous stroke 200 46% mortality
(CVA) 1:100 general surgery 100 60% mortality if previous CVA
(≈ 1:700 in the nonsurgical
population)
Carotid endarterectomy (CVA 1:15 if symptomatic 700
+ death) 1:25 if asymptomatic 400
Disabling CVA + death
Awareness
With pain 1:3,000 3 2/3 with neuromuscular blockade
Without pain 1:300 30 1/3 without neuromuscular blockade
Total intravenous 1:500 20
anesthesia 1:10,000 1
Anaphylaxis 1:10,000 1
Deafness
“Idiopathic” (general 1:10,000 1 ≈ 1:1,000 cardiac surgery
anesthesia)
Transient after spinal 1:7 1,500
anesthesia
Loss of vision 1:125,000 0.08
1:100 (cardiac surgery) 100
Pain ~1:3 (moderate) 3,000
After major surgery 1:10 (severe) 1,000
Day surgery 1:2 5,000
Postoperative nausea and 1:4 2,500 2/3 nausea and 1/3 vomiting
vomiting Female:male 3:1
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Table 11 Continued
Mortality and Morbidity Approximate Incidence Rate per 10,000 Remarks
Population
Sore throat 1:2 (if tracheal tube) 5,000
1:5 (if laryngeal mask) 2,000
1:10 (if facemask only) 1,000
Dental damage
Requiring intervention 1:5,000 2
All dental damage 1:100 100
All oral trauma after tracheal 1:20 500
intubation
Peripheral nerve injury 1:300 ulnar neuropathy 30
General anesthesia 1:1,000 (other nerves) 10
Thrombophlebitis 1–2:20 (water-soluble drugs) 500–1,000
1:4 (propylene glycol based) 2,500
Arterial cannulation <1:100 (permanent) < 100
complication
Pulmonary artery perforation 1:2,000 5
Arterial puncture (during central venous cannulation)
Internal jugular vein 1:35 350
cannulation
Subclavian vein cannulation 1:200 50
ASA = American Society of Anesthesiologists.
four major classes: (1) aspirin and related cyclooxygenase during a 5-year period. LMWH should be stopped at least 24
inhibitors (NSAIDs); (2) ticlopidine and selective adenosine hours before regional blockade, and the first postoperative
diphosphate antagonists; (3) direct thrombin inhibitors (e.g., dose should be given no sooner than 24 hours afterward.47
hirudin); and (4) glycoprotein IIb/IIIa inhibitors. Only with
aspirin is there sufficient experience to suggest that it does complications
not increase the risk of spinal hematoma when given at clini- Drug Toxicity
cal dosages.46 Caution should, however, be exercised when
Systemic toxic reactions to local anesthetics primarily
aspirin is used in conjunction with other anticoagulants.47
involve the CNS and the cardiovascular system [see Table 14].
Oral Anticoagulants The initial symptoms are light-headedness and dizziness,
followed by visual and auditory disturbances. Convulsions
Therapeutic anticoagulation with warfarin is a contraindi-
and respiratory arrest may ensue and necessitate treatment
cation to regional anesthesia.48 If regional anesthesia is
and resuscitation.
planned, oral warfarin can be replaced with IV heparin (see
The use of neuraxial analgesic adjuncts (e.g., opioids,
below).
clonidine, epinephrine, and neostigmine) decreases the dose
Heparin of local anesthetic required, speeds recovery, and improves
the quality of analgesia. The side effects of such adjuncts
There does not seem to be an increased risk of spinal bleed-
include respiratory depression (opiods), urinary retention
ing in patients receiving subcutaneous low-dose (5,000 U)
(opiods), tachycardia (epinephrine), hypotension (clonidine),
unfractionated heparin [see 6:6 Venous Thromboembolism] if
and nausea and vomiting (neostigmine, opioids).
the interval between administration of the drug and initiation
of the procedure is greater than 4 hours.49 Higher doses, Neurologic Complications
however, are associated with increased risk. If neuraxial The incidence of neurologic complications ranges from 2
anesthesia or epidural catheter removal is planned, heparin in 10,000 to 12 in 10,000 with epidural anesthesia and from
infusion must be discontinued for at least 6 hours, and 0.3 in 10,000 to 70 in 10,000 with spinal anesthesia.49,50 The
the partial thromboplastin time should be measured. Recom- most common serious complication is neuropathy, followed
mendations for standard heparin cannot be extrapolated to by cranial nerve palsy, epidural abscess, epidural hematoma,
low-molecular-weight heparin (LMWH), because the bio- anterior spinal artery syndrome, and cranial subdural hema-
logic actions of LMWH are different and the effects cannot toma [see Table 12]. Vigilance and routine neurologic testing
be monitored by conventional coagulation measurements. of sensory and motor function are of paramount importance
After the release of LMWH for general use in the United for early detection and treatment of these potentially disas-
States in 1993, more than 40 spinal hematomas were reported trous complications.
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Table 12 Predicted Incidence of Complications of Regional Anesthesia39
Complication Incidence Rate per 10,000 Remarks
Population
Paraplegia ≈ 1:100,000 0.1
Permanent nerve injury
Spinal 1–3:10,000 1–3
Epidural 0.3–10:10,000 0.03–10
Peripheral nerve block ≈ 1:5,000 2 2% brachial plexus neuropraxia lasting
> 3 mo
Epidural hematoma ≈ 1:150,000 (epidural) 0.07 ≈ 1:1,000,000 (spontaneous)
≈ 1:14,000 (USA)
≈ 1:200,000 (spinal) 0.05 ≈ 1:2,250,000 (Europe)
≈ 1:10,000 (spontaneous)
Epidural abscess 1:2,000–1:7,500 0.7–5.0
Transient neural complications 1:1,000–1:10,000 (epidural) 1–10 (epidural)
1:125–1:2,500 (spinal) 4-80 (spinal)
Transient radicular irritation Up to 1:3 (heavy lidocaine and 3,000
(spinal) mepivacaine)
Cardiac arrest ≈ 1:1,500 (spinal) 5 (spinal)
≈ 1:3,000 (local anesthesia) 3 (local anesthesia)
≈ 1:10,000 (epidural) 1 (epidural)
≈ 1:10,000 (regional blocks) 1 (regional)
Post–dural puncture headache ≈ 1:100 100 80% following inadvertent dural tap
≈ 1:10 (day surgery) 1,000 Blood patch 70–100%
Immediate success, but headaches
recur in 30–50%
Backache < 1 hr surgery ≈ 20% 2,000 GA = LA
> 4 hr surgery ≈ 50% 5,000
Urinary dysfunction ≈ 1:50 200
Pneumothorax ≈ 1:20 (supraclavicular blocks) 500
Systemic LA toxicity ≈ 1:10,000 (epidural) 1
≈ 1:1,500 (regional blocks) 7
Cerebral seizures ≈ 1:4,000 (intravenous regional 2.5 Axillary ≈ 1:1,000
anesthesia)
≈ 1:500 (brachial plexus) 20 Supraclavicular ≈ 1:125
Eye blocks
Retrobulbar hemorrhage 1:250–1:20,000 0.5–40
Brainstem anesthesia ≈ 1:700 15
Globe perforation ≈ 1:10,000 1
Ptosis—transient after eye ≈ 1:2 at 24 hr 5,000
block
≈ 1:5 at 1 mo 2,000
Diplopia—transient after eye 8–70% 800–7,000
block
GA = general anesthesia; LA = local anesthesia.
Transient Neurologic Symptoms described after intrathecal use of all local anesthetics but
The term transient neurologic symptoms (TNSs) refers to are most commonly noted after administration of lidocaine,
backache with pain radiating into the buttocks or the lower in the ambulatory surgical setting, and with the patient in
extremities after spinal anesthesia. It occurs in 4 to 33% of the lithotomy position during operation. Discomfort from
patients, typically 12 to 36 hours after the resolution of spinal TNSs is self-limited and can be effectively treated with
anesthesia, and lasts for 2 to 3 days.51 TNSs have been NSAIDs.
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