Question

On the day of Mr Jackson’s surgery, anaesthesia was induced with a sedative drug and suxamethonium. He was then ventilated with oxygen and halothane. Around ten minutes after the beginning of the surgery, an anaesthesiologist found that end-tidal CO2 gradually rose to 80 mmHg during the course of the operation. There was an associated rise in body temperature with a maximum reading of 40˚C. These high CO2 and temperature conditions disappeared after cessation of general anaesthesia. NSAIDs failed to alleviate these conditions. He had not previously received general anaesthesia. Answer the following sub-questions separately.

1) Is infection suspected in this clinical condition? Please answer ‘YES’ or ‘NO’ and explain the reason. (1 mark)

2) What is the clinical name for this high temperature condition in Mr Jackson’s case? (1 mark)

3) This clinical condition is due to a mutation of a certain receptor. What is the name of the receptor? (1 mark)

4) What is the function of this receptor? (1 mark)

5) Briefly describe how the mutant receptor led to the high body temperature in Mr Jackson’s case. (3 marks)

6) What is the primary drug for treatment of high temperature? (1 mark)

7) Briefly describe how action of this drug contributes to alleviating the high temperature condition. (2 marks)

Answer 1

1)No infection is not suspected because the increase in bofy temperature is associated with increased end tidal CO2 ; it disappeared after cessation of the general anesthesia and NSAIDs failed to alleviate the conditions.

2)The clinical name is Malignant hyperthermia.

3)The receptor name is RyR1 (Ryanodine).

4)The ryanodine receptors are responsible for release of calcium ions from the sarcoplasmic reticulum when the muscle is stimulated by an action potential.

5)Due to the mutant receptor ; large amount of Ca2+ ions were released into the cytoplasm without stimulation ; which led to sustained contraction of the muscle and the rise in temperature.

6)The primary drug used is dantrolene.

7)Dantrolene acts as an antagonist for the ryanodine receptor.Due to the presence of antagonist ; the receptor cant be activated and calcium cant be released into the cytoplasm.