Rising Ventilatory Need During Anesthesia: Is this MH?
An anesthesiologist called because he was having a problem while taking care of a 44 year-old, 88 kg woman who is having robot-assisted laparoscopic resection of uterine fibroids… The surgery is important because she had very heavy uterine bleeding because of the fibroids and is anemic. After induction of anesthesia with non-triggering anesthetic agents, propofol and rocuronium, she was intubated and given desflurane in oxygen and air. We immediately noticed a rising ventilation requirement as the end-tidal carbon dioxide level rose well before laparoscopy was started. Now that laparoscopy is underway, we need a very high minute ventilation to keep the CO2 in the high 40’s and, at the same time, we see the temperature rising from 37° to 38.1° esophageally. I asked our surgeon to stop the operation before it was very far underway, discontinued the desflurane, and sent laboratory tests. The arterial blood gasses were: pH 7.29, PaO2 513, and PaCO2 48. The potassium level was 4.9. Now that our call is being connected, I see the temperature has slowly returned to a more normal 37.1° and, with the high minute ventilation I’ve been giving, I see the end-tidal CO2 is down to 29. The heart rate and blood pressure are stable.
Questions:
1) Could this be Malignant Hyperthermia Crisis?
Yes
No
2) Should we give dantrolene?
Yes
No
3) What else should we do?
a. Monitor her temperature, vital signs, minute ventilation need and laboratory tests for evidence of Recurrant Hypermetabolism
b. Wean her ventilation and awaken her if the situation continues to stablilize
c. Serial Blood Gasses with decreasing frequency if more stable and can be extubated
d. Abort the surgery for now while we determine what’s happened
e. Serum CKs now and q 8 hours X 3 if abnormal or until values decline
f. Serial Electrolytes with decreasing frequency until stable
g. Blood and Urine for Myoglobin ASAP and in 2-4 hours
h. Maintain good urine flow, alkalinize by giving sodium bicarbonate until urinalysis demonstrates alkaline urine pH, if urine test strip is + for blood in the absence of grossly bloody urine
i. Obtain an Adverse Metabolic Reaction to Anesthesia report form from the MH Hotline Consultant so that this episode can be placed in a larger informational data base for professionals
4) When can we operate on her again?
a. Tomorrow morning.
b. Wait two weeks until things are stable
c. After you have referred the patient to a MH biopsy center for the definitive MH susceptibility CHCT muscle test, other neuromuscular evaluation, and genetic profile testing
d. When you see that there is no new morbidity and her laboratory findings and physical status are normal for her
Answers and Comments:
The patient’s vital signs continued to stabilize; she had no recurrent fever or evidence of hypermetabolism. Neither serum nor urine were positive for myoglobin. Urine volume was maintained at 2X normal for the next 24 hours by infusion of 2-3 X predicted her predicted hourly requirement of RL. Her initial serum CK was about 1000 and rose to a peak of 12,000 over the next 24 hours, after which it slowly normalized.
Correct Answers
1. Yes
2. Not necessarily
3. D
4. C
Charles Watson, MD
Bridgeport Hospital
Bridgeport, CT
