It is, again, the time of year when the temperatures drop precipitously – and, so, it is again the time of year to expand the differential for atraumatic headache to include carbon monoxide poisoning. With records already being broken in Southern states unused to such temperatures in November, this message comes earlier than usual.
And, as a reminder, there is essentially no usable evidence describing the use of hyperbaric oxygen therapy for acute CO poisoning.
The most recent Cochrane Review, from 2011, covers six studies regarding the efficacy of HBOT as compared to normobaric oxygen therapy. And, regrettably, all have serious methodologic flaws and potential for bias. Four of these trials are absolutely negative, with trivial differences in outcomes between the two arms. Two trials favor HBOT – a 60-patient trial published by Thom in 1995, and the seminal 152-patient trial presented by Weaver in the NEJM in 2002. All told, the pooled effect of HBOT on short-term neurologic sequelae provides a protective effect with an OR of 0.78 – but with a confidence interval crossing unity (0.54 to 1.12).
Thus, these data neither support nor refute the utility of HBOT for treatment acute carbon monoxide poisoning – and provide no insight into appropriate patient selection. What is most likely, given these results, is there is a cohort of patients for whom some benefit is observed. Probably the most reasonable patients to select for treatment include those with the most severe poisoning and who can receive treatment immediately – but, otherwise, expect extraordinarily low-yield resource utilization to attempt treatment in the remainder.
“Hyperbaric oxygen for carbon monoxide poisoning (Review)”
http://www.ncbi.nlm.nih.gov/pubmed/21491385