Utility of Red Blood Cell Acetylcholinesterase Measurement in Mechanically Ventilated Subjects After Organophosphate Poisoning

Organophosphate detoxification by membrane-engineered red blood cells

Biotherapeutics have achieved global economic success due to their high specificity towards their drug targets, providing exceptional safety and efficiency. The ongoing shift away from small molecule drugs towards biotherapeutics heightens the need to further improve the pharmacokinetics of these biological drugs. Three pervasive obstacles that limit the therapeutic capacity of biotherapeutics are proteolytic degradation, circulating half-life, and the development of anti-drug antibodies. These challenges can culminate in limited efficiency and consequently warrant the need for higher drug doses and more frequent administration. We have explored the coupling of biotherapeutics to long-lived and biocompatible red blood cells (RBCs) to address limited pharmacokinetics. Butyrylcholinesterase (BChE), for example, provides prophylactic protection against organophosphate nerve agents (OPNAs), yet the short circulation life of the drug requires extraordinary doses. Herein, we report the rapid and tunable chemical engineering of BChE to RBC membranes to create a cell-based delivery system that retains the enzyme activity and enhances stability. In a three-step process that first pre-modifies BChE with a cell-reactive polymer chain, primes the cells for engineering, and then grafts the conjugates to the cells, we attached over 2 million BChE molecules to the surface of each RBC without diminishing the bioscavenging capacity of the enzyme. Critically, this membrane-engineering approach was cell-tolerated with minimal hemolysis observed. These results provide strong evidence for the ability of engineered RBCs to serve as an enhanced biotherapeutic delivery vehicle. STATEMENT OF SIGNIFICANCE: Organophosphate nerve agents (OPNAs) are one of the most lethal forms of chemical warfare. After exposure to OPNAs, a patient is given life-saving therapeutics, such as atropine and oxime. However, these drugs are limited, and the patient can still suffer from irreparable injuries. Given the toxicity of OPNAs, access to a prophylactic is vital. We have created an enhanced delivery system for prophylactic butyrylcholinesterase (BChE) by engineering this biotherapeutic to the red blood cell (RBC) surface. In three simple steps that first pre-modifies BChE with a cell-reactive polymer, primes the cells for engineering, and then grafts the conjugates to the cells, we attached over 2 million BChE molecules to a single RBC while retaining the enzyme's activity and enhancing its stability.

Factors associated with time to successful weaning in mechanically ventilated organophosphate poisoned patients

We designed this study to identify the factors associated with time to successful weaning in mechanically ventilated organophosphate (OP)-poisoned patients as the primary outcomes while duration of mechanical ventilation (MV) support, intensive care unit (ICU), and hospital length of stay (LOS) and in-hospital mortality as the secondary outcomes. We conducted a retrospective study of mechanically ventilated OP-poisoned patients admitted to the ICU of Poison Control Center of Ain Shams, Cairo, Egypt, starting from January 2019 to December 2019. Weaning was considered successful if the patient succeeded in the first spontaneous breathing trial of weaning and did not need reinstitution of MV. We used Cox proportional hazards regression models to identify factors associated with time to successful weaning in the studied patients. A total of 55 patients were enrolled in the study. Thirty-eight patients were weaned successfully. Lower initial red cell distribution width (RDW) levels [adjusted hazard ratio (HR), 0.299, 95% confidence interval (CI) (0.184-0.486)] and lower initial doses of atropine [adjusted HR, 0.97, 95% CI (0.935-0.999)] were independently associated with shorter time to achieve successful weaning. Successfully weaned patients had significantly longer hospital LOS (p = 0.019) and no reported in-hospital mortality (p < 0.001) compared with patients who failed to wean. We concluded that initial RDW and initial doses of atropine were found to be the strongest factors associated with time to successful weaning in mechanically ventilated OP-poisoned patients. RDW and atropine can be used as simple risk assessment tools in OP poisoning.

Usefulness of serum lactate as a predictor of successful discontinuation of continuous atropine infusion in patients with severe acute organophosphate poisoning

Objective

In severe organophosphate (OP) poisoning, administration of atropine via continuous intravenous infusion is typically considered. To date, there have been no studies on predicting successful atropine discontinuation through plasma cholinesterase (PChE) and serum lactate levels, which are monitored during critical care in severe acute OP poisoning. Therefore, we retrospectively evaluated the usefulness of serum lactate and PChE as predictors of successful discontinuation of atropine infusion.

Methods

This retrospective observational study was performed on consecutive adult patients treated for severe acute OP poisoning between March 2011 and December 2016. We sequentially evaluated serum lactate and PChE levels on emergency department arrival and before a discontinuation trial of atropine infusion. Discontinuation of atropine intravenous infusion was attempted in patients after clearance of respiratory secretions and cessation of bronchoconstriction. Discontinuation of atropine infusion attempts were divided into successful and failed trials.

Results

A total of 95 trials were conducted in 62 patients. Serum lactate levels before trials were significantly different between patients with successful and failed trials. The area under the curve for prediction of successful atropine discontinuation using serum lactate levels before trial discontinuation were 0.742 (95% confidence interval, 0.638 to 0.846). PChE level was not significantly different between two groups.

Conclusion

Serum lactate levels before the discontinuation trial of atropine infusion served to predict successful discontinuation in severe acute OP poisoning.

Prediction of organophosphorus insecticide-induced intermediate syndrome with stimulated concentric needle single fibre electromyography

BACKGROUND

Deliberate self-poisoning (DSP) using organophosphorus (OP) insecticides are a common clinical problem in Asia. OPs inhibit acetylcholine esterase (AChE), leading to over-activity of muscarinic and nicotinic cholinergic circuits. Intermediate syndrome (IMS) is mediated via prolonged nicotinic receptor stimulation at the neuromuscular junction and its onset is between 24-96 hours post ingestion. The aims of the present study were 1) to investigate whether neuromuscular junction dysfunction within the first 24 hours following exposure, quantified by jitter in single fibre electromyography (SfEMG), can predict IMS, and 2) to compare the changes in SfEMG jitter over the course of the illness among patients who developed IMS (IMS+) and those who did not (IMS-).

METHODS AND FINDINGS

We conducted a prospective cohort study in a tertiary care hospital in Sri Lanka on 120 patients admitted between September 2014 and August 2016 following DSP by OP insecticides viz., profenofos 53, phenthoate 17, diazinon 13, chlorpyrifos 5, others 12, unknown 20. SfEMG was performed every second day during hospitalization. Exposure was confirmed based on the history and red blood cell AChE assays. IMS was diagnosed in patients who demonstrated at least three out of four of the standard IMS criteria: proximal muscle weakness, bulbar muscle weakness, neck muscle weakness, respiratory paralysis between 24-96 hours post ingestion. Respiratory failure requiring intubation occurred in 73 out of 120 patients; 64 of these were clinically diagnosed with IMS. Of the 120 patients, 96 had repeated SfEMG testing, 67 of them being tested within the first 24 hours. Prolonged jitter (>33.4μs) within the first 24 hours was associated with greatly increased risk of IMS (odds ratio = 8.9, 95% confidence intervals = 2.4-29.6, p = 0.0003; sensitivity 86%, specificity 58%). The differences in jitter between IMS+ and IMS- patients remained significant for 72 hours and increased jitter was observed in some patients for up to 216 hours. For intubated patients, the median time for jitter to normalize and median time to extubate were similar, and the two variables had a moderate positive correlation (r = 0.49, P = 0.001).

CONCLUSIONS

Prolonged jitter recorded with SfEMG <24 hours of ingestion of an OP strongly correlates with subsequent occurrence of IMS. The time course of electrophysiological recovery of the NMJ was similar to the time course of respiratory recovery in IMS patients.

Prognostic Factors Determining Morbidity and Mortality in Organophosphate Poisoning

Objective:

Our aim in this retrospective study was to determine the factors affecting poor prognosis and mortality of organophosphate (OP) poisoning by reviewing patient data. We also reviewed present knowledge to make conclusions on certain longstanding debates in light of the literature.

Methods:

In this retrospective descriptive study, patients who were admitted to and hospitalized in the emergency department (ED) or intensive care unit (ICU) of a university hospital with the diagnosis of OP poisoning between December 2010 and December 2015 were evaluated. All the data were obtained from electronic and manual patient files. A total of 80 patients were included in the study.

Results:

The mean age of the study patients was 32.4±15.0 (13-94). Forty-nine (61.2%) patients were female. Twenty-two (27.5%) patients were seriously poisoned and needed mechanical ventilation (MV) support. Low pseudocholinesterase (PChE), high creatinine (Cr), low Glasgow Coma Scale (GCS) scores and long hospitalization durations were all found to be poor prognostics in MV patients. Low PChE and high Cr levels were found to be independent predictors of the hospitalization duration and high Cr was found to be an independent predictor of the intubation duration of MV patients in regression analyses. Ten (45.5%) of the MV patients were unresponsive to medical treatment and Therapeutic plasma exchange (TPE) was performed. Seven patients were discharged healthy. Three patients with low PChE levels and comorbidities died.

Conclusions:

Prolongation of respiratory depression necessitating MV support, comorbidities, long hospital stay, elevated creatinine, low GCS scores and low PcHE levels without regeneration in the first 48 hours of admission are all found to be poor prognostic factors for organophosphate (OP) poisoning.

An exploratory study; the therapeutic effects of premixed activated charcoal-sorbitol administration in patients poisoned with organophosphate pesticide

OBJECTIVE

The effects of activated charcoal (AC) mixed with cathartics for gastric decontamination in the management of organophosphate (OP) poisoning remain unknown due to limited clinical evidence. This exploratory study assessed the effectiveness of premixed AC-sorbitol as a treatment for OP poisoning.

MATERIALS AND METHODS

This retrospective observational case study included patients who either did not receive AC-sorbitol or received a single dose of AC-sorbitol within 24 h after OP ingestion. The patients were divided into three groups: no AC-sorbitol treatment, patients who received AC-sorbitol within 1 h of OP ingestion, and patients who received AC-sorbitol more than 1 h after OP ingestion. Mortality, the development of respiratory failure, and the duration of mechanical ventilation were used as outcome measurements for effectiveness, whereas aspiration pneumonia and electrolyte imbalance were employed as safety measurements.

RESULT

Among 262 patients with OP poisoning, 198 were included. Of these, 133 patients did not receive AC-sorbitol, whereas 14 and 51 patients received AC-sorbitol within 1 h or more than 1 h after ingestion, respectively. The time from ingestion to hospital arrival and time from ingestion to administration of atropine and pralidoxime differed among the groups, whereas other characteristics, including age, amount ingested, and type of ingested OP, were similar among the groups. Univariate and multivariate analysis demonstrated that the administration of AC-sorbitol was not associated with outcome measures for effectiveness and did not significantly increase either aspiration pneumonia or electrolyte imbalances during hospitalization.

DISCUSSION AND CONCLUSION

The administration of AC-sorbitol exerted neither beneficial nor harmful effects on the outcomes of OP-poisoned patients regardless of the time from OP ingestion to administration, compared with those of patients who did not receive AC-sorbitol. However, this study enrolled a small number of patients who received AC-sorbitol; further qualified trials with a sufficient number of patients are therefore needed.