malignant hyperthermia

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Aborted case due to anesthetic concerns: 

Aborted case due to anesthetic concerns Michael Chao, MD June 22, 2006

Case History: 

Case History 47 yo male with a history of OSA. Patient could not tolerate CPAP and was therefore referred for surgical management of sleep apnea The patient was scheduled for septoplasty, turbinate reduction, and Uvulopalato-pharyngoplasty At the pre-operative appointment the patient reported a family history of malignant hyperthermia.

Case History: 

Case History The family history was documented and the patient was documented and surgery scheduled for the next day Upon review of the record by the anesthesiologist on the day of surgery, the strong family history was noted and the case was cancelled for lack of properly serviced anesthesia machines.

What could have been done?: 

What could have been done? Lack of communication between surgeon and anesthesiologist Need for pre-operative evaluation prior to day of surgery by anesthesia

Malignant Hyperthermia: 

Malignant Hyperthermia Background First described in 1960 by Denborough in a series of familial anesthetic related deaths Incidence is 1/15,000 children to 1/50,000 adults

Skeletal Muscle Physiology: 

Skeletal Muscle Physiology Sarcoplasmic reticulum-stores and releases Ca2+ Ca2+ pump keeps intracellular Ca2+ low Ryanodine receptor releases Ca2+ Ca2+ necessary for coupling of actin and myosin Decrease in Ca2+ necessary to end contraction

Skeletal Muscle Physiology: 

Skeletal Muscle Physiology

Pathophysiology of MH: 

Pathophysiology of MH Increased calcium release from the sarcoplasmic reticulum Excessive muscle contracture Resultant hypermetabolic state leads to acidosis and hyperthermia Reuptake of calcium is inhibited leading to increasing serum calcium levels Muscle necrosis due to membrane damage and cell lysis Increase in myoglobin and CK can lead to renal failure

Inheritance: 

Inheritance

High risk patients: 

High risk patients What makes a patient higher risk for MH Family history Muscular dystrophy Carnitine palmitoyl transferase deficiency King-Denborough syndrome Central Core disease Glycogen storgae myopathies

Clinical Presentation: 

Clinical Presentation Unexplained rise in end tidal CO2 Masseter (or other muscle) rigidity Increase in temperature Acidosis Hyperkalemia Myoglobinuria Tachypnea, tachycardia, arrhythmia

Clinical Presentation: 

Clinical Presentation

Triggering Agents: 

Triggering Agents Inhalation agents Halothane Enflurane Isoflurane Desflurane sevoflurane Depolarizing agents Succinylcholine Decamethonium Suxamethonium Controversial Ketamine Catecholamines Calcium salts MAO inhibitors

Safe Agents: 

Safe Agents Nitrous oxide Barbituates Narcotics Local anesthetics Non depolarizing muscle relaxants Propofol Benzodiazepines

Initial Treatment: 

Initial Treatment Discontinue all anesthetic agents and hyperventilate with 100% oxygen. Dantrolene Bicarbonate (2 to 4 mEq/kg). Control fever by iced fluids Monitor urinary output Continue to monitor blood gases, electrolytes, temperature, arrhythmia, muscle tone, and urinary output. Analyze electrolytes

Post Acute Phase Care: 

Post Acute Phase Care observation in ICU for at least 24 hours IV dantrolene for at least 24 hours frequent blood gas to monitor pH foley catheter to monitor UOP/myoglobin serial electrolytes

Preventive Measures: 

Preventive Measures Use non-triggering agents Anesthesia machine Remove/disable vaporizors Clean circuit by flow 10L/min x 20 min or for 10min if gas hose replaced Change bag, circuit

References: 

References Board Review Series - Physiology 2nd edition, Costanzo, LS. Williams & Wilkins 1998 Baltimore, MD Bertorini TE, Perisurgical management of patients with neuromuscular disorders. Neurologic Clinics, 2004;22(2)L 293-313 Brandom, BW, The genetics of malignant hyperthermia. Anesthiol Clin North America, 2005;23(4):615-619 http://www.mhaus.org