submitted on 13 December 2008
Dr LAU Chun Wing Arthur
Department of Intensive Care, Pamela Youde Nethersole Eastern Hospital
History of Present Illness
Known schizophrenia, poor compliance, frequent defaulter
History of multiple drug abuse: ICE, MDMA, weight reducing agents, etc; history of repeated suicidal attempt
Called police after taking >200 sleeping pills with alcohol, the drug was said to be ?dogmatil, ?zoloft, ?imovane; ? recently prescribed zoloft by GP
At AED: SpO2 at AED 94% in RA, Bp 75/33, P 130; Met-Hb 0.5%
After admission to ward, found further oxygen desaturation 89% in RA
CXR clear
ABG: pO2 28.38, pCO2 5.27, SaO2 99.4%
GCS full now
What would you do?
Met-Hb was repeated and was found to be 4.2% (normal 0 – 1.5%)
Drug history clarified by medical doctor: should have been Zopiclone (= ImovaneR) instead of ZoloftR (= Sertraline)
SpO2 gradually improved with supportive treatment only, no need for methylene blue
Met-Hb around 6 hrs later 1.1% only
Clinical pearls
- Zoplicone is a cause of Methemoglobinemia. Suspect Met-Hb when SpO2 is low or drifting towards 85% but SaO2 is normal
- Met-Hb may only rise on serial checking
- Important to clarify the drug history. Also don’t mix up generic and trade names which can create confustion if we are not familiar with these psychiatric drug names.