APPENDIX C: MANAGEMENT OF MALIGNANT HYPERTHERMIA

EMERGENCY THERAPY FOR MALIGNANT HYPERTHERMIA

MH Hotline 1-800-644-9737; website: WWW.MHAUS.ORG

Outside the US: 1-315-464-7079

DIAGNOSIS VS. ASSOCIATED PROBLEMS

Signs of MH

•  Increasing ETCO₂

•  Trunk or total body rigidity

•  Masseter spasm or trismus

•  Tachycardia/tachypnea

•  Mixed respiratory and metabolic acidosis

•  Increased temperature (may be a late sign)

•  Myoglobinuria

Sudden/Unexpected Cardiac Arrest in Young Patients

•  Presume hyperkalemia and initiate treatment (see #6 )

•  Measure CK, myoglobin,  ABGs, until normalized

•  Consider dantrolene

•  Usually secondary to occult myopathy (e.g., muscular dystrophy)

•  Resuscitation may be difficult and prolonged

Trismus or Masseter Spasm with Succinylcholine

•  Early sign of MH in many patients

•  If limb muscle rigid, begin treatment with dantrolene

•  For emergent procedures, continue with non-triggering agents, evaluate and monitor the patient, and consider dantrolene treatment

•  Follow CK and urine myoglobin for 36 hrs

•  Check CK immediately and at 6 hrs intervals until returning to normal. Observe for dark or cola-colored urine. If present, liberalize fluid intake and test for myoglobin

•  Observe in PACU or ICU for at least 12 hrs

ACUTE PHASE TREATMENT

1. GET HELP. GET DANTROLENE—Notify Surgeon

• Discontinue volatile agents and succinylcholine

• Hyperventilate with 100% oxygen at flows of 10 L/min or more

• Halt the procedure as soon as possible; if emergent, continue with non-triggering anesthetic technique

• Do not waste time changing the circle system and CO₂ absorbant

2. Dantrolene 2.5 mg/kg IV rapidly, through large-bore IV if possible

To convert kg to lb, for amount of dantrolene, give patients 1 mg/lb (2.5 mg/kg approximates 1 mg/lb)

• Dissolve the 20 mg in each vial with at least 60 mL sterile, preservative-free water for injection. Prewarming (not to exceed 39°C) the sterile water may expedite solublization of dantrolene. However, to date, there is no evidence that such warming improves clinical outcome

• Repeat until signs of MH are reversed

• Sometimes more than 10 mg/kg (up to 30 mg/kg) is necessary

• Each 20 mg bottle has 3 gm mannitol for isotonicity. The pH of the solution is 9

3. Bicarbonate for metabolic acidosis

• 1–2 mEq/kg if blood-gas values are not yet available

4. Cool the patient with core temperature >39°C. Lavage open body cavities, stomach, bladder, or rectum. Apply ice to surface. Infuse cold saline intravenously. Stop cooling if temp <38°C and falling to prevent drift <36°C

5. Dysrhythmias usually respond to treatment of acidosis and hyperkalemia

• Use standard drug therapy except calcium channel blockers, which may cause hyperkalemia or cardiac arrest in the presence of dantrolene

6. Hyperkalemia—treat with hyperventilation, bicarbonate, glucose/insulin, calcium

• Bicarbonate: 1–2 mEq/kg IV

• Insulin: For pediatric, 0.1 units insulin/kg and 1 mL/kg 50% glucose or for adults, 10 units regular insulin IV and 50 mL 50% glucose

• Calcium chloride 10 mg/kg or calcium gluconate 10–50 mg/kg for life-threatening hyperkalemia

• Check glucose levels hourly.

7. Follow ETCO₂, electrolytes, blood gases, CK, core temperature, urine output and color, coagulation studies. If CK and/or K+ rise more than transiently or urine output falls to less than 0.5 mL/kg/hr, induce diuresis to >1 mL/kg/hr and give bicarbonate to alkalinize urine to prevent myoglobinuria-induced renal failure (see D below)

• Venous blood gas (e.g., femoral vein) values may document hypermetabolism better than arterial values

• Central venous or PA monitoring as needed and record minute ventilation

• Place Foley catheter and monitor urine output

POST-ACUTE PHASE

A. Observe the patient in ICU for at least 24 hrs, due to risk of recrudescence

B. Dantrolene 1 mg/kg q4–6h or 0.25 mg/kg/hr by infusion for at least 24 hrs. Further doses may be indicated

C. Follow vitals and labs as above (see #7 above)

• Frequent ABG as per clinical signs

• CK every 8–12 hrs; less often as the values trend downward

D. Follow urine myoglobin and institute therapy to prevent myoglobin precipitation in renal tubules and the subsequent development of acute renal failure. CK levels above 10,000 IU/L is a presumptive sign of rhabdomyolysis and myoglobinuria. Follow standard intensive care therapy for acute rhabdomyolysis and myoglobinuria (urine output >2 mL/kg/hr by hydration and diuretics along with alkalinization of urine with Na-bicarbonate infusion with careful attention to both urine and serum pH values)

E. Counsel the patient and family regarding MH and further precautions; refer them to MHAUS. Fill out and send in the adverse metabolic reaction to anesthesia (AMRA) form (www.mhreg.org) and send a letter to the patient and her/his physician. Refer patient to the nearest biopsy center for follow-up