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Wednesday, January 09, 2008

Thiopentone doesn’t trigger malignant hyperthermia

Question

021. Which of the following anesthetic agents doesn’t trigger malignant hyperthermia?

1. Halothane

2. Isoflurane

3. Suxamethonium

4. Thiopentone

Answer

4. Thiopentone

Reference

KDTripathi 5th Edition Page 315

Quality

Spotter

Status

Repeat

QTDF

All Books

Discussion

  • Malignant Hyperthermia is the clinical syndrome observed during general anaesthesia associated with rapidly increasing temperatures as great as 1oC/5 minutes
  • It is due to abnormality of Ryanodine receptor, which is calcium releaseing channel of sarcopalsmic reticulum.

Explanation

The drugs causing malignant hyperthermia are

  1. Muscle relaxants
    1. Succinyl Choline is the most commonly implicated drug
  2. Inhalational agents
    1. Halothane is the most common inhalational agent
    2. Isoflurane
    3. Desflurane
    4. Sevoflurane
    5. Methoxyflurane
  3. Local Anaesthetics
    1. Lignocaine
  4. Others
    1. Tricyclic antidepressants
    2. Mono amine oxidase inhibitors
    3. Phenothiazines

Comments

· Clinical features

a. Hyperthermia 0 may be even 109oC

b. Increased end tidal CO2 (ETCO2). This may rise to more than 100 mm Hg (normal 32 to 42 mm Hg). Increase in ETCO2 is the most sensitive early sign of malignant hyperthermia

c. Hypoxia

d. Cyanosis

e. Tachycardia

f. Hypertension

g. Cardiac Arrhythmias

h. Severe metabolic acidosis (pH <>

i. Hyperkalemia, Muscle rigidity, Increased Creatine Phosphokinase, increased myoglobin.

j. Renal Failure, DIC, pulmonary and cerebral edema

k. Death

· Treatment

a. Stop anaesthetics

b. Hyperventilation with 100 % oxygen

c. Control temperature

d. Control Acidosis with Sodium bi carbonate 2 to 4 mEq/kg

e. Correct electrolyte imbalance(hyperkalemia)

f. Maintain Urine Output

g. Dantrolene 2mg/kg to be repeated every 5 minutes to a maximum of 10mg/kg

Tips

· Screening

a. High levels of Creatine Phosphokinase make an individual susceptible

b. Masseter spasm after Succinyl Choline

· Other causes of hyperthermia

a. Malignant Neurolept syndrome

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