Mechanism: Incompletely understood, but apparently hypermetabolic. It may be related to elevated serum thyroxine, which is common in patients with osteogenesis imperfecta.
Findings:
(1) hyperthermia, usually mild (maximum reported by Solomons and Myers was 102.5°F, or 39.2°C, but patients were being cooled)
(2) diaphoresis (excessive perspiration)
(3) tachycardia with high cardiac output
(4) tachypnea
(5) muscular rigidity is not prominent
(6) respiratory acidosis does not occur
(7) serum CPK values may be normal
Factors which may predict a hyperthermic episode (Libman. page 124):
(1) elevated CPK prior to surgery
(2) fever preoperative
(3) agitation preoperative
Prevention:
(1) Dantrolene sodium may help prevent (Libman, page 124) but probably should not be used routinely (Ryan, page 813). No controlled studies have been performed to document efficacy.
(2) Avoid atropine and other anticholinergics during surgery.
Management:
(1) The use of dantrolene sodium is controversial but the agent is relatively safe.
(2) Active cooling is usually sufficient to control the hyperthermia.
(3) Supplemental oxygen should be administered.
Differential diagnosis: A very rare patient may have both malignant hyperthermia and osteogenesis imperfecta, but this would occur perhaps once in 250 million people (frequency malignant hyperthermia is 1 in 12,000; osteogenesis imperfecta 1 in 20,000). The presence of marked hyperthermia, prominent muscular rigidity and respiratory acidosis would favor this diagnosis.
