CP24 Malignant Hyperthermia

Malignant HyperthermiaSpace 1

CP24  Malignant Hyperthermia

 

Definition

Hypermetabolic state causing increased cellular activity within the muscle, especially the skeletal muscle.  Hyperthermia doesn’t appear to affect the myocardium directly.

Mechanism

There becomes an increased amount of calcium levels in the myoplasmic reticulum, resulting in the escalated glycolytic pathway.  The increased calcium levels cause muscle contracture, resulting in depletion of adenosine triphosphate (ATP) stores and production of heat, carbon dioxide, pyruvate, and lactate.  The loss of calcium uptake is prevented due to the loss of ATP The sodium/calcium pump is driven via the ATPASE pump.  Therefore, the efflux has increased levels of potassium, magtnesium, phosphate, and enzymes myoblobin and calvcium move intracellularly.  Note that giving exogenous calcium intravenously will not work because the sodium/calcium pump is not able to function.

 

Triggering Factors

  1. Depolarizing muscle relaxants, i.e., succinylcholine chloride and Gallamine.
  2. Inhalation agents, i.e., all volatile anesthetics.

Agents that increase myoplasmic calcium levels include lidocaine, cardiac glycosides, caffeine, calcium salts, alpha agonists, and catecholamine.

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Anesthetic Considerations

  1. Disconnect vaporizers and change the tubing.
  2. Pretreament with Dantole4ne/Na oral preparation preoperatively.
  3. It has been shown that Dantrolene blood levels have decreased with CPB, but it is not known whether additional Dantrolene is needed.
  4. Drugs to use include-barbiturates, narcotics, benzodiazepines, and non-depolarizing muscle relaxants.
  5. Hypothermia blanket.

 

Clinical Signs of Malignant Hperthermia

1.Increased heart rate

  1. Dysrythmias
  2. Muscle rigidity (masseter muscle)
  3. Increased temperature
  4. Dissemmanated intravascular coagulation
  5. Tonic contracture of skeletal muscle.

 

Clinical Signs While on CPB with Aortic Cross Clamp On

  1. Decreased venous oxygen saturation
  2. Increased potassium and glucose
  3. Decreased calcium levels
  4. Increased temperature
  5. Blood gas results reveal metabolic/respiratory acidosis

 

Treatment for Malignant Hyperthermia on CPB

  1. Dantrolene/Na 1-10 mg/kg (2.5 mg/kg) immediately before muscle circulation is cut off; then increases the cardiac index
  2. Cool the patient
  3. Sodium bicarbonate administration for acidosis
  4. Glucose and insulin for increased potassium levels
  5. Mannitol and lasix for increased myoglobin levels to prevent acute renal failure
  6. Disconnect oxygen tubing from the vaporizer on the pump
  7. Avoid prime solutions with calcium

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