Fever and Rigidity not Responding to Dantrolene
66 y/o woman s/p mitral valve replacement who presented to the ICU with trachea intubated. Her ABG on ICU admission and FIO2 of 50% was as follows: PH: 7.12, PCO2: 61 mmHg, PO2: 210 mmHg, BE: -5 with vital signs stable except for temperature of 38.6°C. Half an hour following ICU admission, the nurse noted that the patient has rigid extremities and the temperature was still elevated despite acetaminophen administration. Patient was still sedated with HR of 115 b/min. Family history is negative for MH and this is the first general anesthetic the patient received in her life.
1) Do you think this is MH?
A) Definitely yes
B) Definitely no
C) Likely MH
D) Unlikely MH
2) Based on the above information, will you treat with dantrolene?
A) Dantrolene is contraindicated in this patient
B) I will start with 1 mg/kg and titrate to effect
C) Dantrolene 2.5 mg/kg is indicated immediately
3) The most sensitive and useful monitor for the early diagnosis of a hypermetabolic event is:
A) EKG
B) Temperature monitor
C) ETCO2
D) Pulse oximeter
E) Blood pressure monitor
4) Following administration of dantrolene (2.5 mg/kg), rigidity and elevated temperature did not improve. Can MH be ruled out?
A) Certainly yes
B) Certainly no
C) Another dose of dantrolene (2.5 mg/kg) should be administered
D) Another dose of dantrolene (1 mg/kg) should be administered
Answers and Narrative:
1) The symptoms of muscle rigidity and fever following general anesthetic with gas of succinycholine are high indication of MH and should be treated as so.
Answer C
2) When suspicious of MH episode, dantrolene could be a life saver. It is always recommended to start early treatment with dantrolene (2.5 mg/kg) that delaying the treatment waiting for more signs of MH to develop.
Answer C
3) MH is a hypermetabolic event and like most other hypermetabolic events it results in increased CO2 production and O2 extraction.
Answer C
4) Improvement in clinical signs (rigidity or temperature) following the administration of dantrolene indicates the likelihood of MH episode. However, if the clinical signs do not improve, it is still difficult to role out MH. Another dose of dantrolene (1 mg/kg) could be indicated in this case.
Answer D
Assistant Professor, Anesthesiology
Children’s
