Malignant Hyperthermia Flashcards
% of MH cases that have been previously exposed to anesthesia
> 50%
States with higher MH rates
- Wisconsin
- Nebraska
- West Virginia
- Michigan
Main culprit of excessive release of intracellular Ca2+ in MH
ryanodine receptor type 1
Pathophysiology of MH
- genetic mutation of RYR receptor 1
- triggered by succs & volatiles
- ^ interact with RYR receptor causing excessive release and sequestration of Ca2+
- tetanic contraction of muscle
- hypermetabolic state (cellular hypoxia, acidosis, death)
RYR receptor 1 resides where? Why is this relevant?
resides on sarcoplasmic reticulum in skeletal muscle
important because interaction of this receptor + succs/volatiles = excessive Ca2+ release
MH triggering agent that works directly on the ryanodine receptor
volatiles
MH triggering agent that works INdirectly on the ryanodine receptor
succinylcholine
Volatile agents and their likelihood of triggering MH
Halothane > Iso > Sevo > Des
Severity of MH symptoms is dependent on…
amount of intracellular Ca2+ released
Manifestations of MH
*elevated EtCO2 out of proportion to minute ventilation
*masseter muscle rigidity
*tachycardia
*hyperthermia
later signs:
- decreased PaO2, increased PaCO2
- CV instability, arrhythmias
- hyperkalemia, elevated CK
- combined resp and metab acidosis
Incidence of hyperthermia in MH
first sign in 1/3 of patients, one of first 3 signs in 2/3 of patients
Consequences of increased intracellular Ca2+
- sustained muscle contraction
- hyper-metabolic rate
- increased O2 consumption
- increased heat production & CO2
- rapid depletion of ATP
- resp and metab acidosis
- ## breakdown of sarcolemma
3 earliest symptoms of MH
- elevated EtCO2
- tachycardia
- masseter spasm
+/- hyperthermia
Most sensitive MH indicator
EtCO2 that rises out of proportion to minute ventilation
Initial treatment of MH
- communicate
- administer Dantrolene
- stop volatiles
- switch to non-triggering anesthetic
- activated charcoal filters
- hyperventilate 100%, high Ve
Main advantage of Ryanodex over Dantrium
faster constitution & administration
Initial dose of Dantrolene
2.5mg/kg
MOA of Dantrolene
RYR1 antagonist
- halts Ca2+ release from RYR1
- prevents Ca2+ entry into myocyte
- reduces Ca2+ (+) feedback system
Describe the process of reconstituting Dantrium/Revonto
- each vial has 20mg Dantrolene/3000mg Mannitol
- reconstitute each vial in 60mL sterile H2O
- takes 86 sec to dissolve
- 12.5 vials needed
How many vials of Dantrium/Revonto does MHAUS recommend be available?
36
Dose range of Dantrolene
2.5 to max of 10 mg/kg
Final concentration of Dantrium/Revonto after reconstitution:
Final concentration of Ryanodex after reconstitution:
Dantrium/Revonto: 1mg/3mL
Ryanodex: 50mg/1mL
Describe the process of reconstituting Ryanodex
- each vial contains 250mg Dantrolene/125mg Mannitol
- reconstitute each vial in 5mL sterile H2O
- takes 20 sec to dissolve
-1 vial needed for patients up to 100kg
How many vials of Ryanodex does MHAUS recommend be available?
3
