How is MH treated?

How is MH treated?

A suspected case of MH must be treated promptly, because full-blown episodes proceed rapidly to death.

Triggering agents must be discontinued immediately. It is no longer recommended that the anesthesia machine be changed to a “clean” machine (one which has never been used to administer potent inhaled agents) nor does the breathing circuit have to be changed during an acute episode of MH. Dantrolene is the only drug that effectively treats MH. Each vial of dantrolene contains 20 mg of dantrolene and 3 g of mannitol, which must be dissolved in 60 mL of sterile water. The initial dose is 2.5 mg/kg intra-venously, which may be repeated every 5 minutes until signs abate.

In addition to treating the cause of MH, its effects must be quickly dealt with. The increase in core temperature must be treated with cold intravenous fluids, cold irrigation fluids poured into open body cavities, as well as cold water lavage of the stomach and urinary bladder. Arterial blood gases should be monitored closely, preferably from an arte-rial catheter, and the patient should be vigorously ventilated with 100% oxygen to correct hypercarbia and hypoxemia. Sodium bicarbonate should be used to treat profound base deficits. Central venous catheters and urinary bladder drainage catheters help monitor intravascular volume and renal status. Maintaining renal blood flow is important to prevent renal damage. Intravenous sodium bicarbonate and acetazolamide alkalinize the urine and prevent precipita-tion of myoglobin in renal tubules. Diuretics should be given to maintain urine output, and examination of the urine for myoglobin should be carried out.

Hyperkalemia should be treated with insulin and 50% dextrose solutions, while cardiac dysrhythmias are treated according to standard protocols. Calcium-channel blockers are contraindicated because of their interaction with dantrolene, possibly resulting in significant hyperkalemia. Following an episode of proven or suspected MH, the patient should be monitored for 24–36 hours. Recognized complications of MH include re-emergence, disseminated intravascular coagulation, and myoglobinuric renal failure. Recommended treatments are given in Table 28.3.