Glucocorticoid with cyclophosphamide for oral paraquat poisoning

BACKGROUND

This an update of a Cochrane Review. Paraquat is a widely used herbicide, but is also a lethal poison. In some low- and middle-income countries (LMICs) paraquat is commonly available and inexpensive, making poisoning prevention difficult. Most of the people poisoned by paraquat have taken it as a means of self-poisoning. Standard treatment for paraquat poisoning prevents further absorption and reduces the load of paraquat in the blood through haemoperfusion or haemodialysis. The effectiveness of standard treatments is extremely limited. The immune system plays an important role in exacerbating paraquat-induced lung fibrosis. Immunosuppressive treatment using glucocorticoid and cyclophosphamide in combination has been developed and studied as an intervention for paraquat poisoning.

OBJECTIVES

To assess the effects of glucocorticoid with cyclophosphamide for moderate to severe oral paraquat poisoning.

SEARCH METHODS

The most recent searches were run in September 2020. We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Injuries Trials Register), Ovid MEDLINE(R), Ovid MEDLINE In-Process & Other Non-Indexed Citations, Ovid MEDLINE Daily and Ovid OLDMEDLINE, Embase Classic + Embase (Ovid), ISI WOS (SCI-EXPANDED, SSCI, CPCI-S, and CPSI-SSH), and trials registries. We also searched the following three resources: China National Knowledge Infrastructure database (CNKI ); Wanfang Data (); and VIP () on 12 November 2020. We examined the reference lists of included studies and review papers.

SELECTION CRITERIA

We included randomised controlled trials (RCTs). For this update, in accordance with Cochrane Injuries' Group policy (2015), we included only prospectively registered RCTs for trials published after 2010. We included trials which assessed the effects of glucocorticoid with cyclophosphamide delivered in combination. Eligible comparators were standard care (with or without a placebo), or any other therapy in addition to standard care. Outcomes of interest included mortality and infections.

DATA COLLECTION AND ANALYSIS

We calculated the mortality risk ratio (RR) and 95% confidence interval (CI). Where possible, we summarised data for all-cause mortality at relevant time periods (from hospital discharge to three months after discharge) in meta-analysis, using a fixed-effect model. We conducted sensitivity analyses based on factors including whether participants were assessed at baseline for plasma paraquat levels. We also reported data on infections within one week after initiation of treatment.

MAIN RESULTS

We included four trials with a total of 463 participants. The included studies were conducted in Taiwan (Republic of China), Iran, and Sri Lanka. Most participants were male. The mean age of participants was 28 years. We judged two of the four included studies, including the largest and most recently conducted study (n = 299), to be at low risk of bias for key domains including sequence generation. We assessed one study to be at high risk of selection bias and another at unclear risk, since allocation concealment was either not mentioned in the trial report or explicitly not undertaken. We assessed three of the four studies to be at unclear risk of selective reporting, as no protocols could be identified. An important source of heterogeneity amongst the included studies was the method of assessment of participants' baseline severity using analysis of plasma levels (two studies employed this method, whilst the other two did not). No studies assessed the outcome of mortality at 30 days following ingestion of paraquat. Low-certainty evidence from two studies indicates that glucocorticoids with cyclophosphamide in addition to standard care may slightly reduce the risk of death in hospital compared to standard care alone ((RR 0.82, 95% CI 0.68 to 0.99; participants = 322); results come from sensitivity analysis excluding studies not assessing plasma at baseline). However, we have limited confidence in this finding as heterogeneity was high (I2 = 77%) and studies varied in terms of size and comparators. A single large study provided data showing that there may be little or no effect of treatment at three months post discharge from hospital (RR 0.98, 95% CI 0.85 to 1.13; 1 study, 293 participants; low-certainty evidence); however, analysis of long-term results amongst participants whose injuries arose from self-poisoning must be interpreted with caution. We remain uncertain of the effect of glucocorticoids with cyclophosphamide on infection within one week after initiation of the treatment; this outcome was assessed by two small studies only (31 participants, very low-certainty evidence) that considered leukopenia as a proxy or risk factor for infection. Neither study reported infections in any participants.

AUTHORS' CONCLUSIONS

Low-certainly evidence suggests that glucocorticoids with cyclophosphamide in addition to standard care may slightly reduce mortality in hospitalised people with oral paraquat poisoning. However, we have limited confidence in this finding because of substantial heterogeneity and concerns about imprecision. Glucocorticoids with cyclophosphamide in addition to standard care may have little or no effect on mortality at three months after hospital discharge. We are uncertain whether glucocorticoid with cyclophosphamide puts patients at an increased risk of infection due to the limited evidence available for this outcome. Future research should be prospectively registered and CONSORT-compliant. Investigators should attempt to ensure an adequate sample size, screen participants for inclusion rigorously, and seek long-term follow-up of participants. Investigators may wish to research the effects of glucocorticoid in combination with other treatments.

Ventilator settings and outcome of respiratory failure in paraquat-induced pulmonary injury

Paraquat is a nonselective contact herbicide that has significant importance in clinical toxicology due to its high mortality rate. The cause of mortality in the acute phase of poisoning is a multi-organ failure while in the sub-acute phase is alveolar injury and lung fibrosis. The aim of this study was to evaluate the advantages and drawbacks of mechanical ventilation (MV) in paraquat-induced pulmonary injury and its consequential respiratory failure (PIPI-CRF). This retrospective descriptive analytical study was done to investigate the outcome of patients who had developed PIPI-CRF and underwent conventional treatments with invasive MV in three teaching hospitals in Shiraz, Iran, from March 2010 to February 2015. In total, 44 patients (mean age of 27.9 ± 9.98 years) had undergone MV due to PIPI-CRF. None of the patients had a successful wean off from the ventilator. Although all the patients’ were on aggressive life support and full efforts to resuscitate were carried out in case of cardiac arrest, all of them expired. We suggest that in the case of conventional treatment of paraquat poisoning, only noninvasive ventilation should be applied. However, considering the chance of patient’s survival performing novel treatments, such as extracorporeal membrane oxygenation (ECMO), lung protective ventilation with optimal positive end-expiratory pressure (PEEP) could be applied only in such circumstances.

Systematic review and meta-analysis of the efficacy and safety of immunosuppressive pulse therapy in the treatment of paraquat poisoning

Paraquat (PQ), a highly effective herbicide, is widely used worldwide. PQ poisoning can cause multiple organ failure, in which the lung is the primary target organ. After PQ poisoning, the patient mortality rate is as high as 90%, and there is currently no specific antidote. The main clinical treatment is the use of glucocorticoids and cyclophosphamide for pulse therapy, but its effectiveness and safety are still uncertain. We investigated the effectiveness and safety of immunosuppressive pulse therapy with glucocorticoids and cyclophosphamide to evaluate the treatment value in patients with acute PQ poisoning. This meta-analysis, combined with seven trials that enrolled a total of 426 patients, showed that immunosuppressive pulse therapy with glucocorticoids and cyclophosphamide for PQ poisoning significantly reduced mortality of the study group (59.3%, 134/226) compared with the control group (81.0%, 162/200). There was no significant difference of hepatitis or renal failure between the control and study groups, indicating that immunosuppressive pulse therapy was relatively safe. Several patients were reported to have leukopenia and returned to normal after 1-2 weeks without any abnormalities. Two cases of non-fatal sepsis were reported and considered to be a side effect of the immunosuppressive pulse therapy. Thus, immunosuppressive pulse therapy can efficiently reduce the mortality of PQ poisoning and it is relatively safe.