Alkalinisation for organophosphorus pesticide poisoning

Poisoning with organophosphorus pesticides (OPs) is an important cause of morbidity and mortality in all parts of the world, particularly developing countries. The case-fatality ratio for pesticide intentional self-poisoning is around 10-20% even when the standard antidotes (atropine, oximes and benzodiazepines) are used. Alternative treatments have been trialled in an attempt to improve outcomes from acute OP poisoning, one of which is plasma alkalinisation. Animal and preliminary human research has suggested benefit from plasma alkalinisation with sodium bicarbonate (NaHCO3) as a treatment for acute OP poisoning.

To determine the efficacy of alkalinisation, in particular NaHCO3, for the treatment of acute OP poisoning.

We searched MEDLINE (1966-2004), EMBASE (1980-2004), the Controlled Trials Register of the Cochrane Collaboration, Current Awareness in Clinical Toxicology, Info Trac, http://www.google.com.au, and Science Citation Index of studies identified by the previous searches. We also manually reviewed the bibliographies of identified articles and personally contacted experts in the field.

Randomised controlled trials and controlled clinical trials of symptomatic patients following acute OP poisoning treated with alkalinisation. The quality of studies and eligibility for inclusion was assessed using criteria by Jadad and Schulz.

Studies were identified and both authors independently extracted data which was recorded on a pre-designed form. Study design, including the method of randomisation, participant characteristics, type of intervention and outcomes were recorded. Outcomes were discussed, but unfortunately specific analyses could not be performed, given the poor quality of the studies identified.

Five studies were identified but none satisfied inclusion criteria. NaHCO3 was used in each of these to induce alkalinisation. Two studies were uncontrolled, two studies were historically controlled and one study was randomised but poorly concealed. Marked heterogeneity between subjects and treatments was noted - for example, a different regimen of NaHCO3 was used in each study. While there may have been a trend towards improved outcomes (lower total dose of atropine and shorter length of stay), these were not statistically significant.

There is insufficient evidence to support the routine use of plasma alkalinisation for treatment of OP poisoning. Further research is required to determine the method of alkalinisation that will optimise outcomes, and the regimen which will produce the target arterial pH of 7.50 (range 7.45-7.55). This should be followed by a well-designed randomised controlled trial to determine efficacy.