arterial tourniquet and its anesthetic implication

1. Anesthetic concerns of tourniquet application
Dr. Muhammed Alif

2. Introduction
● Device which is used to control the flow of blood to and/or from an extremity.
● The word ‘’tourniquet’’ from the French verb ‘’tourner’’ (to turn).
● Louis Petit used screw-like device strapped to the thighs of patients undergoing leg
amputations.
● Arterial tourniquet – usually a pneumatic device consisting of an inflatable cuff connected to a
compressed gas supply.
● Allow controlled arterial compression and distal circulatory stasis.
● Most common – in surgical procedures on the extremities, creates bloodless surgical field.
● Examples include joint replacements and the repair of tendons, nerves, and blood vessels.
● Also used in Bier’s block

3. Components of pneumatic tourniquets
Five basic components
● An inflatable cuff (bladder)
● Compressed gas source
● Pressure display
● Pressure regulator
● Connection tubing.

4. Inflatable cuff
● Pressure – exerted on the circumference of extremity
● Different types of cuffs available
Following criteria considered while selecting a cuff:
• Cuff location
• Single vs double bladder design
• Cuff shape
• Cuff length
• Cuff width
• Disposable vs reusable
• Specialty application
• Limb protection

5. ● Length and width of the cuff – individualized considering the size and circumference of the pt’s
limb
● Cuff should overlap 3 inches but not more than 6 inches
● Too much overlap - ↑ pressure and rolling or wrinkling of underlying soft tissue
● Too small – compromise effective inflation, unexpected release or inadequate constriction
● Width of the cuff – wider than half the limb’s diameter.
● Wider cuff minimize the risk of injury to underlying tissue by dispersing pressure over a great
area.
● Wider cuff – consistently occlude the blood flow at lower pressure in adults and children
● Placed at point of the maximum circumference
● Soft padding kept around the limb – reduce wrinkling pinching, shearing of the tissues.
● Cuff tubing – positioned on or near the lateral aspect of the extremity to avoid pressure on
nerves and kinking of the tubing.

6. Tourniquet cuff pressure
● Depends on number of variables: age, skin, blood pressure, shape and size of
the extremity, dimensions of the cuff
● Optimal inflation pressure not established.
● Recommends cuff pressure of 200 – 300 mmHg
Various methods implemented to lower effective cuff pressure:
 Double tourniquet technique to change the point of compression
 Controlled hypotension to bring down the SBP
 Doppler technique and pulse oximetry to confirm the absence of arteria pulse
 Tourniquet inflation based on limb occlusion pressure
 Cuff pressure synchronization with systolic BP.

7. Limb occlusion pressure
● Minimum pressure required to stop the flow of arterial blood into the limb distal to the cuff.
● Determined by gradually increasing tourniquet pressure until distal blood flow interrupted
● Association of Perioperative Registered Nurses guideline:
● Cuff pressure should be adjusted by adding safety margin to LOP
1. Add 40 mmHg for LOP < 130mmHg
2. Add 60 mmHg for LOP 131 -190 mmHg
3. Add 80 mmHg for LOP >190 mmHg
4. For paediatric, adding 50 mmHg recommended
● LOP – should be measured during preop check up or when BP stabilized after induction
● Best practice – cuff pressure according to pt’s SBP or LOP.

8. ● Exsanguination before inflation – improves quality of bloodless surgical field
minimizes pain due to tourniquet
● Normally done by limb elevation or by elastic wrap around the limb.
● Elastic wrap should not be used in:
infection, malignant tumour, thrombi in extremity
● Exsanguination is done by limb elevation alone
● Exsanguination and tourniquet use – controversial in sickle cell disease

9. Inflation or occlusion time
● Kept minimum to minimize risk to the patient
● Safe inflation time – not been accurately determined
● Varies with patient’s age, physical status, vascular supply to extremity
● Safe time limit of 1-3 hours – described
● Recommended to assess the operative situation at 2 hours
● If anticipated >2.5 hours, deflation for 10 mins, and at subsequent 1 hr interval
● Pediatric patients inflation time <75 mins – recommended for lower extremities

10. Cuff deflation:
● Causes release of anaerobic metabolites into the systemic circulation
● Cause hypotension, metabolic acidosis, hyperkalemia, myoglobulinemia,
myoglobinuria and possible renal failure.
● Known as myonephropathic metabolic syndrome
● Depends on size of the extremity, duration of tourniquet time, overall
physiological status of the patient.

11. Physiological effects of tourniquet application
Local effects
● Result of tissue ischemia distal to the inflated tourniquet and a combination of ischemia and
compression of the tissues beneath it.
Muscle
● Progressive decrease in Po2 and an increase in Pco2 within muscle cells.
● Energy stores steadily decline with time and intracellular stores of ATP and creatine phosphate are
exhausted after 2 and 3 h, respectively.
● Lactate concentration increases with the switch to anaerobic metabolism
● Changes to the histological appearances of muscle fibres - Marked changes in mitochondrial
morphology are visible after 1 h.
● Muscle underlying the tourniquet  subjected to both ischemia and compression
● Prone to develop changes such as local fibre necrosis after inflation times as short as 2 h.
● Microvascular injury occurs in muscle after ischaemia of greater than 2 h duration.

12. ● After tourniquet release  increased vascular permeability results in:
Interstitial and intracellular oedema  frequently leads to the ‘post
tourniquet syndrome’,
Patient has a swollen, pale, stiff limb with weakness but no paralysis.
Typically lasts 1–6 weeks.
Nerve
● Physiological conduction block develops between 15 and 45 min
● Conduction block affects both motor and sensory modalities
● Reversible after deflation of the cuff
● Rate of development of this conduction block is the same with cuff pressures of 150 and 300
mm Hg.
● suggests – ischaemia rather than direct compression is the cause

13. ● Direct mechanical compression of nerves  responsible for a second, longer lasting nerve
conduction block called ‘tourniquet paralysis’.
● Higher cuff pressures (e.g. 1000 mm Hg maintained for >1 h) can cause morphological changes
within the larger myelinated nerves
● Most marked at the sites where the pressure gradient between compressed and
uncompressed nerve is greatest
● At the proximal and distal edges of the tourniquet.
● The pressure gradient  results in displacement of the nodes of Ranvier, stretching and
degeneration of paranodal myelin and impaired nerve conduction
● Lasts up to 6 months.

14. Systemic effects
Cardiovascular effects
● ↑ in systemic vascular resistance and an effective ↑ in circulating blood volume – after exsanguination
and tourniquet inflation
● Transient ↑ in CVP and SBP
● b/l thigh tourniquet – can ↑ effective circulating blood volume by 15% (~750mL in adult)
● ↑ in CVP and circulatory overload
● Cardiac failure and cardiac arrest have been reported after the application of bilateral thigh
tourniquets.
● ↑ BP after transient rise  tourniquet pain –
● The rise in arterial pressure can be attenuated by the addition of ketamine (0.25 mg/kg)
● This may also help with tourniquet pain.

15. Tourniquet deflation,
● Post-ischaemic reactive hyperaemia is seen.
● Causes a transient increase in the volume of blood in the limb compared
with baseline levels.
● Metabolites from the ischaemic limb are released into the systemic
circulation.
● In combination with the redistribution of blood flow  causes a decrease
in both central venous and systolic pressures
● Temporary but can be dramatic.

16. Respiratory effects
● Deflation of the tourniquet  increase in end-tidal carbon dioxide concentration which usually peaks
within 1 min.
● The increase in Etco2 occurs for two reasons:
○ mixed venous PCO2 increases (after release of hypercapnic blood from the ischaemic area distal to the tourniquet into the
systemic circulation)
○ cardiac output increases after tourniquet deflation (in response to the decrease in arterial pressure).
● The peak increase in Etco2 concentration is greater with deflation of lower limb tourniquets (0.7–2.4
kPa) than with upper limb tourniquets (0.1–1.6 kPa).
● The duration of the increase in Etco2 depends on the ventilatory characteristics of the patient.
● In spontaneously breathing patients, minute ventilation increases rapidly  Etco2 returns to baseline
values within 3–5 min.
● In patients undergoing controlled ventilation, the Etco2 will typically remain raised for >6 min unless
minute ventilation is deliberately increased.

17. Central nervous system effects
● The increase in PaCO2 after deflation of the tourniquet causes an
increase in cerebral blood flow.
● Measurements of middle cerebral artery blood flow velocity show an
increase of up to 50%.
● In patients with head injuries  can cause an increase in intracranial
pressure.
● Hyperventilation after tourniquet deflation can prevent increases in
intracranial pressure by maintaining normocapnia.

18. Temperature effects
● Inflation of arterial tourniquets  associated with a gradual increase in
core body temperature.
● Caused by reduced heat transfer to and heat loss from the ischaemic
limb.
● The magnitude of this increase is small, ~0.5oC after 2 h of inflation.
● Tourniquet deflation causes a transient decrease in core temperature,
● Caused by redistribution of body heat.
● Associated with the return, of a small amount of hypothermic blood from
the ischaemic limb

19. Haematological effects
● Effects  complicated.
● Associated with a global hypercoagulable state.
● increased platelet aggregation caused by catecholamines released in response to pain - from surgery and the
tourniquet itself.
● After deflation of the tourniquet, there is a brief period of increased fibrinolytic activity.
● Maximal at 15 min and returns to preoperative levels within 30 min.
● But may nevertheless cause increased bleeding.
● The increase in fibrinolysis is caused by release of tissue plasminogen activator.
● Produced by the vasa vasorum in the affected limb in response to the acidosis and hypoxemia associated with
tourniquet application.

20. Metabolic effects
● Deflation of the tourniquet after 1–2 h  associated with small increases in plasma concentrations of
potassium and lactate.
● Peak increases of 0.3 and 2 mmol/litre, respectively, occur 3 min after deflation.
● Lactate and carbon dioxide returning to the systemic circulation from the ischaemic limb cause a
reduction in arterial pH.
● Reperfusion of the ischaemic limb and the other haemodynamic changes associated with tourniquet
deflation can cause brief increases in oxygen consumption and carbon dioxide production.
● The magnitude of these changes correlates with the duration of ischaemia.
● All of these changes are fully reversed within 30 min of tourniquet deflation.

21. Pharmacological effects:
● Isolates the limb from rest of the body.
● Can alter the Vd of some medications alteration in the pharmacokinetics
of anaesthetic drugs
● time interval between antibiotic administration and tourniquet inflation –
important for antibiotic prophylaxis.
● Clinical evidence – 5-10 mins before inflation – good tissue penitration

22. Complications associated with the use of arterial tourniquets
Nerve injury
● The most common complication and
can be the most devastating.
● Lower limb tourniquets
● Lower limb – sciatic nerve, upper limb –
radial nerve
● Esmarch bandage associated with
higher incidence of nerve inury
● Large diameter nerve fibres are more
susceptible to pressure
Muscle injury
● The post-tourniquet syndrome results in
a swollen, stiff, weak limb.
● Very rarely the post-ischaemic swelling
and oedema, in combination with
reperfusion hyperaemia, may lead to
the development of a compartment
syndrome.
● Rhabdomyolysis has been reported, but
is extremely rare.
○ associated with unusually long
ischaemic times or high cuff inflation
pressures.

23. Skin injury
● Chemical burns – most common form of
skin injury
● occur when alcohol-based solutions used
for skin preparation.
● Friction burns resulting from movement of
poorly applied tourniquets.
Intraoperative bleeding
● Incomplete exsanguination of the limb
● A poorly fitting or underpressurized cuff.
● May also be caused by blood entering
through the intramedullary vessels of long
bones.
Vascular injury
● uncommon, but can be catastrophic.
● 7 in >5000 sx
● Acute vascular insufficiency – may occur
mechanical pressure from the tourniquet
damages atheromatous vessels, causing
plaque rupture.
● Recommend avoiding the use in patients with
peripheral vascular disease.

24. Tourniquet pain
● Poorly localized, dull tight aching pain
● During GA, manifests as ↑ HR , MAP
● More common ↓ GA (53 -67%), more common lower limb Sx’s
● Etiology – unclear, thought to be by unmyelinated, slow conducting c fibres
that are usually inhibited by Aδ fibres.
● Aδ fibres – blocked by mechanical compression in 30 mins while C fibre
continue functioning
● Release PG’s  ↑ pain perception by sensitizing and exciting the pain
receptors.
● Limb ischemia – central sensitization via NMDA receptors due to repeated
nociceptive stimulus

25. • Has important impacts in anesthesia.
• Application of EMLA cream
• Infiltration with local anaesthetics.
• Use of wider cuff with low cuff pressure
• Addition of opioids, clonidine, epinephrine along with LA’s in spinal block
• None has attained complete success in pain relief.
• IV drugs, Ketamine, dexmedetomidine, MgSO4, also been studied
• Only thing reliably works – tourniquet deflation.

26. Tourniquet-induced hypertension
● Gradual increase in arterial pressure is frequently observed after a
variable time after tourniquet inflation.
● The exact mechanism - not known.
● Suggested - represents activation of the sympathetic nervous system in
response to the development of tourniquet pain.
● Plasma norepinephrine concentrations increase in parallel with arterial
pressure during tourniquet inflation.
● Clonidine attenuates sympathetic activity and, if given preoperatively,
blunts the hypertensive response.

27. Contraindications
● No absolute C/I
● Adequate care should be taken in
○ Severe peripheral vascular diseases.
○ Sickle cell disease
○ Sever crush injury’
○ Diabetic neuropathy
○ Patients with h/o DVT and PE.

28. Thank you…