Case history
Case history #1
An 8-year-old boy develops breathing difficulties when given sevoflurane. He does not react to placement of an intravenous catheter. His arms are stiff, which is not uncommon during mask anaesthetic induction. The anaesthetist notes a high exhaled carbon dioxide value and tries increasing ventilation to normalise the exhaled carbon dioxide level. After giving a non-depolarising neuromuscular blocker and placing a breathing tube in the trachea, the exhaled carbon dioxide partial pressure is >65 mmHg. There is no response to a train-of-4 stimuli to the ulnar nerve (a method in which the response to electrical nerve stimulation is used to assess the degree of neuromuscular blockade). Blood gas analysis shows a mixed respiratory and metabolic acidosis, potassium of 5 mmol/L, and lactate of 3 mmol/L.
Case history #2
A 68-year-old man is undergoing laparoscopic surgery. In the third hour of isoflurane anaesthesia, the surgeon notes that the man's abdomen is stiff. The anaesthetist had recently given a non-depolarising neuromuscular blocker and no movement can be seen after facial train-of-4 stimulation of a motor nerve. An intravenous beta-blocker fails to keep the heart rate below 80 beats/minute. Doubling the minute ventilation fails to achieve an exhaled carbon dioxide partial pressure of <45 mmHg. The forced air warming device was turned off after the oesophageal temperature had reached 37°C (98.6°F), but the temperature continues to rise. Inhalation anaesthesia is stopped.
Other presentations
MH often presents without muscle rigidity or metabolic acidosis, and treatment before these signs appear may abort the syndrome without complications. It can also present post-anaesthesia in the recovery room.[4] Physical signs and laboratory data will be similar to those found during inhalation anaesthesia, but it can be more difficult to document changes in minute ventilation and carbon dioxide levels in a spontaneously breathing patient. MH can also present as rhabdomyolysis without metabolic changes. This has been observed in patients who received succinylcholine (suxamethonium) without exposure to potent inhalation anaesthetics and in some who received inhalation anaesthesia of short duration.[5] MH can also appear during general anaesthesia without exposure to triggering agents (potent inhalation anaesthetics and/or succinylcholine).[6] Rarely MH can occur without exposure to anaesthetics.[3][7] In most of these cases, there was either intense physical activity, exercise-induced rhabdomyolysis, febrile illness, or repeated episodes of heat-related illness prior to fatal MH events.[8][9][10][11][12][13][14] MH is also known to occur in infants.[15]
Use of this content is subject to our disclaimer