Alkalinisation for organophosphorus pesticide poisoning
Poisoning with organophosphorus pesticides (OPs) is an important cause of morbidity and mortality worldwide, particularly in developing countries. The case‐fatality for intentional self‐poisoning is around 10 to 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 blood alkalinisation. Animal and preliminary human research has suggested benefit from blood 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 Cochrane Central Register of Controlled Trials (The Cochrane Library 2010, issue 4), MEDLINE, EMBASE, ISI Web of Science: Science Citation Index Expanded (SCI‐EXPANDED) and ISI Web of Science: Conference Proceedings Citation Index‐ Science (CPCI‐S), LILACS, Current Awareness in Clinical Toxicology and The Internet using Google. We also carried out a citation search and manually reviewed the bibliographies of identified articles. The searches were last conducted in October 2010.
Randomised controlled trials of symptomatic patients following acute OP poisoning treated with alkalinisation. The quality of studies and eligibility for inclusion was assessed using criteria of the Cochrane Collaboration risk of bias tool.
Data collection and analysis
Studies were identified and both authors independently extracted data which were recorded on a pre‐designed form. Study design, including the method of randomisation, participant characteristics, type of intervention and outcomes were recorded. The Relative Risk (RR) for death and Weighted Mean Difference (WMD) for the total dose of atropine were determined.
Two small randomised controlled trials were located, one with higher dose NaHCO3 and alternating allocation, the other with lower dose NaHCO3 was presented in abstract form only. In the higher dose study, the RR of death in patients receiving NaHCO3 compared to controls was 0.52 (95% CI 0.05 to 5.39) and the WMD for total dose of atropine was ‐36.1 (95% CI ‐68.43 to ‐3.77). No clinical benefits from lower dose NaHCO3 were noted. Six other studies were identified but none satisfied inclusion criteria; three studies were uncontrolled and three were controlled. NaHCO3 was used in each study to induce alkalinisation. Marked heterogeneity between subjects and treatments was noted ‐ for example, varying regimens of NaHCO3.
Preliminary studies suggest benefit from blood alkalinisation with NaHCO3 in OP poisoning, but there is insufficient evidence to support its routine clinical use. 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 to 7.55). This should be followed by a well‐designed randomised controlled trial to determine efficacy.
Darren M Roberts, Nick Buckley
Plain language summary
Use of sodium bicarbonate to treat organophosphorus pesticide poisoning
Many people, particularly in developing countries, are poisoned by organophosphorus pesticides (OPs) used in agriculture or for killing insects in the home. Poisoning may be accidental or intentional. Even when the usual antidotes are given, 10 to 20% of those poisoned still die. Research in animals has suggested that use of sodium bicarbonate (baking soda) or similar chemicals which make the blood alkaline might save people poisoned by OPs.
The review authors looked for studies in which such chemicals were given to OP poisoned patients, to see how effective the treatment is. They sought randomised controlled trials, a type of research study in which one group of patients is given one treatment, while a similar group (the control group) is given a different treatment.
The authors found eight studies but only two small randomised controlled trials, one using higher dose sodium bicarbonate and the other a lower dose. Only the trial using higher dose sodium bicarbonate, which included 53 participants, showed a slight benefit from using sodium bicarbonate in conjunction with standard treatment for OP poisoning. This study does not provide enough evidence to recommend routine clinical use of sodium bicarbonate. There are hundreds of different kinds of OPs so treatment may vary based on the type of poisoning as well as the severity of the poisoning. More research needs to be done to determine the best treatment for poisoning with OPs in various situations.
Darren M Roberts, Nick Buckley
Implications for practice
Clinical studies suggest benefit from blood alkalinisation with higher doses of NaHCO3 in acute OP poisoning, but there is insufficient evidence to support its routine use.
Implications for research
Formal dose‐optimisation studies of NaHCO3 in acute OP poisoning should be conducted to determine the regimen that will rapidly, reliably and safely produce a target arterial pH of 7.50 (range 7.45 to 7.55). This should be followed by a randomised controlled trial to determine efficacy. To minimise the effect of heterogeneity, this requires the study of a large cohort of patients who have been poisoned by particular OPs which are common and problematic.