{'fraction_non_alphanumeric': 0.027275182284634082, 'fraction_numerical': 0.011612206319200648, 'mean_word_length': 5.299319727891157, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 2, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Extracorporeal Blood Purification for Acute Organophosphorus Pesticide Poisoning

We read with interest the paper by Altintop et al [1] describing the effect of hemoperfusion in acute anticholinesterase pesticide poisoning. This retrospective uncontrolled study describes a series of patients treated with extracorporeal blood purification. Clinical criteria were used to classify the severity of poisoning of eligible patients, and all patients with severe poisoning were treated with a single 3-hour session of hemoperfusion. We are also interested in the effect of hemoperfusion, and other extracorporeal techniques for blood purification, in the treatment of acute organophosphorus (OP) poisoning. This has prompted us to conduct a systematic review with the Cochrane Collaboration (protocol submitted) [2] to confirm whether further studies were needed and to obtain information to assist us to plan such a study. In that regard, we think it is worth explaining why we believe that this study’s outcomes are insufficient evidence of the benefit of hemoperfusion for this poisoning. The authors’ main outcome was changes in “plasma acetylcholinesterase.” This terminology may potentially mislead some readers. It seems certain from their previous publications, and the units reported in this paper, that this term refers to butyrylcholinesterase (BuChE, pseudocholinesterase, plasma cholinesterase or PChE; EC 3.1.1.8) [3]. In contrast, acetylcholinesterase (AChE; EC 3.1.1.7) is not found in human plasma (only erythrocytes) and is homologous with that found in the nervous system. Inhibition of synaptic AChE appears to be the primary toxicity from OP pesticides. A large increase in BuChE activity 24 hours after admission was reported in those patients who received hemoperfusion. However, inhibition of BuChE activity is not an important factor in the toxicity of OP, being probably a mere epiphenomenon. Therefore, use of changes in BuChE over 24 hours as the primary outcome in this study for determining the efficacy of hemoperfusion, renders the paper largely unhelpful in determining if this is a useful treatment strategy. The only basis on which hemoperfusion might be of benefit is if it enhances elimination of OP, and this was not measured. There is a relationship between the degree of BuChE inhibition by OP compounds and clinical severity, but it is inconsistent, and a causal relationship seems unlikely [3-9]. Different OPs have a different propensity to inhibit BuChE for the same degree of clinical severity and AChE inhibition [9]. Despite selecting patients with similar clinical severity who have taken different pesticides, the mean BuChE activity varied markedly. In patients with severe poisoning, the BuChE activity was 1211.4 ± 3066.3 mU/mL on admission, increasing to 2078.3 ± 2588.4 mU/mL at 24 hours. Although this increase was reported to be statistically significant (the statistical test is not stated nor is the magnitude of the P value), the data are obviously highly variable and skewed, and a nonparametric test should have been used. We also noted that different admission BuChE activities appear to have been reported in Table 1 and Table 2. However, even if this difference remained statistically significant, a benefit from hemoperfusion could only be assumed if there was a comparable control group indicating this was not simply an expected finding. Further, additional data From South Asian Clinical Toxicology Research Collaboration, Medical School, Australian National University, Australia; Department of Clinical Medicine, University of Colombo, Sri Lanka; and Department of Nephrology, Shanghai Tenth People’s Hospital of Tongji University, China.