Methemoglobinemia and organic acidemias are rare clinical situations that can be identified through arterial blood gas analysis. Two cases of methemoglobinemia are described, one in a child from playing with colored powder during Holi and another in an infant exposed to contaminated water. The document also summarizes the causes, pathophysiology, and pointers for identifying methemoglobinemia. Organic acidemias are inherited disorders that cause the buildup of harmful metabolites and features like developmental delay. A case example is provided of an infant presenting with respiratory failure and metabolic acidosis later diagnosed with methylmalonic acidemia.

1. Arterial Blood Gas
in
Rare Clinical Situations
Dr.Rittu Chandel
Junior Clinical Biochemist
Breach Candy Hospital Trust, Mumbai

2. OVERVIEW
• Methemoglobinemia
• Organic acidemias

3. Methemoglobinemia
Fugate Family Of Kentucky
Cawein M et al Arch Intern Med. 1964

4. Case 1
• 4-year-old unconscious boy brought to the EMS
• History- was playing Holi with his friends
• Examination reveals shallow and irregular respiration and
central cyanosis
Can Holi add colour to the blood?
Mauskar et al. J Trop Pediatr 2009
Arterial blood gas analysis
blood appeared chocolate brown in colour
Increased level of methemoglobin (60.9%)
normal partial pressure of oxygen (PaO2)

5. CASE 2
BLUE BABY SYNDROME
• 23 days old baby, suddenly turned blue
• Before admission the baby was well and healthy
• Mother was not on any medications
• O/E - baby was blue in colour
• Baby’s Methemoglobin level -67 % (normal of less
than 1 % )
• Milk-packaged formula milk mixed with underground
boring water
Saluja S ; Blue baby syndrome (methemoglobinemia ) in a
neonate due to water contamination

6. CAUSES
• Hereditary/ Congenital: Hemoglobin M, cytochrome
b5 reductase deficiency , NADPH deficiency of the
HMP shunt
• Acquired: multiple drugs and toxins including aniline
dyes, benzene, chloroquine, dapsone, local anesthetic
agents, naphthalene, nitrites (including NTG and
NO), primaquine, phenazopyridine, and sulfonamides

7. Pathophysiology of
Methemoglobinemia
• Methemoglobin is an altered state of hemoglobin in
which the ferrous (Fe++) irons of heme are oxidized
to the ferric (Fe+++) state
• The ferric heme of methemoglobin are unable to bind
oxygen
• In addition, the oxygen affinity of any accompanying
ferrous heme in the hemoglobin tetramer is increased
as a result, the oxygen dissociation curve is "left-
shifted" and oxygen delivery to the tissues is impaired

8. Pointers for early identification of
Methemoglobinemia
• High pO2 levels in the presence of Central Cyanosis
• As levels rise above 15%, neurologic and cardiac
symptoms arise as a consequence of hypoxia
• Levels higher than 70% are usually fatal
• Treatment
• iv methylene blue
• Exchange transfusion

9. ORGANIC ACIDEMIAS
• group of rare autosomal recessive inherited
disorders
• affect both males and females
• caused by enzymes that are deficient causing an
error in protein metabolism
• causes harmful metabolites to accumulate in
blood and excreted in urine
• These affect health, growth and learning of child
• The symptoms and treatment vary between
different organic acid disorders

10. Common lab findings
• ketones in the urine
• high levels of acidic substances in the blood,
causing metabolic acidosis
• high blood ammonia levels
• high levels of certain organic acids
• low platelets
• low white blood cells

11. CASE….
• 1 year girl child with developmental delay, came to
the EMS in critical state
• Respiratory intercurrent illness before admission
which rapidly progressed to respiratory failure
• Born at 44 weeks of gestation, with normal birth
weight- 3700g and Apgar score of 8
• Facial features- high forehead
broad nasal bridge
epicanthal folds
a long smooth filtrum
triangular mouth

12. • Laboratory studies
• Metabolic acidosis- pH 7.03
• High anion gap- 28.2
• Normal glycemic levels
• Normal blood lactate
• Recurrent episodes of metabolic acidosis with poor
response to treatment
• Intoxication ruled out and no sign of kidney disease
• Elevated levels of methylmalonic acid in urine and
Elevated levels of propyonilcarnitine in blood and
urine
Maria Gica; A Rare Case of High Anion
Gap Metabolic Acidosis

13. Take home message
• Methemoglobinemia is a medical emergency,
requiring prompt management
• Inborn errors of metabolism

14. THANK YOU