Post-op MH
A 21 y/o, 72 kg, otherwise healthy male with no history of anesthetic problems in his family was brought to the OR for laproscopic removal of a ruptured appendix. After premedication, he was taken to the OR where he was given a rapid sequence induction and intubation using propofol 140 mg. and succinylcholine 80 mg. Anesthesia was maintained with O2, air and sevoflurane 2.5%, and he was later given rocuronium 20 mg. which was reversed at the end of the 35 minute procedure with neostigmine 2 mg and glycopyrrolate 0.35 mg. Throughout surgery, ventilation was controlled at a rate of 8 breaths per minute with a tidal volume of 700 ml. EtCO2 ranged from 33 to 39, and was 44 at the time of extubation in the OR. His esophageal temperature in the OR was 36.8 at the start of surgery and 37.1 just before extubation. No warming devices were used in the OR during the 35 minute operation.
His initial VS in the PACU were BP 140/85, HR 92, RR 16, temp 37.2, and he was awake, although sleepy.Fifteen minutes later he was more alert, but nurses noted his RR was 22, his HR was 110, his temp had increased to 37.4, his skin was pale and he was shivering. Ten minutes later he was still shivering, his RR was 25, HR was 116 and his temp was 37.6.
Questions:
1. At this point, you feel this is:
a. Definitely MH – give dantrolene immediately
b. Probably MH – call for the MH cart, but don’t open it.
c. Possibly MH – let’s first look into this more deeply
d. Unlikely MH – fever is probably not due to MH
e. Not MH – definitely not MH
2. While all of the following steps are of some value, the most useful at this point would be:
a. Stat ABG
b. CK level
c. Blood cultures
d. Ask the patient if he feels warm or cold
e. Give dantrolene, 2.5 mg/kg
3. If this patient was to receive dantrolene now, and had an immediate and substantial decrease in fever, this would be highly suggestive or confirmatory of a diagnosis of MH.
a. True
b. False
ANSWERS:
1. C or D
While this patient has some signs of MH (increasing post-op fever, increasing tachypnea and tachycardia) which cannot be ignored, the etiology of those signs must first be determined before proper therapy can begin. Thus, either answers C or D would be correct, depending upon ones level of optimism.
2. D
All these tests are useful, and could eventually be done in this patient, but the most diagnostically useful step would be to ask the patient if he feels warm or cold. In MH, the patients body becomes warmer than the normal temperature set by the hypothalamic temperature regulating area, and thus heat losing mechanisms are instituted by the brain, including vasodilatation and diaphoresis, as well as stimulating a subjective sensation of heat discomfort, such that the patient would feel hot and try to cool himself/herself. Conversely, an endotoxin response from the bacteria released from the ruptured appendix would trigger a fever, with the hypothalamic temperature regulating area instituting physiologic heat conserving and generating measures including cutaneous vasoconstriction and shivering, as in this case.
3. B – False
While dantrolene will decrease the fever and other signs of an MH reaction, it also has antipyretic effects on fevers from other causes. Thus, a decrease in a fever of unknown origin following dantrolene therapy cannot, by itself, be considered diagnostic of MH.
Michael Adragna
Dept of Anesthesiology
SUNY School of Medicine
Buffalo, NY
