Evidence-based recommendations for haemodialysis in lithium-poisoned patients: Getting from where we are to where we want to be

Validation of a nomogram used to predict lithium concentration in overdose

INTRODUCTION

Extracorporeal Treatment (ECTR) is an essential component in management of severe lithium toxicity. The Extracorporeal Treatments in Poisoning (EXTRIP) group's suggested indications for ECTR include "if the expected time to obtain a [Li+] < 1.0mEq/L with optimal management is >36h". Buckley et al. developed a lithium nomogram which could help predict the fall in lithium concentrations for chronic poisoning. Our aim is to externally validate the lithium nomogram in a cohort of cases with chronic accumulation and acute on chronic lithium poisoning.

METHODS

A retrospective analysis of suspected cases of chronic accumulation and acute on chronic lithium poisoning referred to our Toxicology Unit from May 2013 to 2020 was performed.

RESULTS

Out of 51 cases, 29 cases of chronic accumulation and eight cases of acute on chronic poisoning were analysed after excluding 14 cases who required haemodialysis. In chronic accumulation cases, the nomogram correctly identified 10 out of 14 patients whose [Li+] failed to drop below 1.0 mmol/L by 36 h (sensitivity 71.4% [95% CI 42 - 92%]), and 8 out of 15 patients whose [Li+] dropped below 1.0 mmol/L by 36 h (specificity 53.3% [95% CI 27 - 78%]), resulting in the positive predictive value (PPV) of 58.8%, negative predictive value (NPV) of 66.7% and accuracy of 62.1%.

CONCLUSIONS

Our study shows that the lithium nomogram is moderately sensitive at identifying patients with chronic lithium accumulation who will have a serum lithium concentration >1 mmol/L at 36 h without ECTR.

Evaluation of the utilization of extracorporeal toxin removal in lithium poisoning patients in Hong Kong

Background:

Extracorporeal toxin removal is used for enhanced elimination in severe lithium poisoning. The Extracorporeal TReatments In Poisoning workgroup provides recommendations on the use of extracorporeal toxin removal in poisoning.

Objectives:

Our aim was to identify the pattern for using extracorporeal toxin removal in managing lithium poisoning in Hong Kong and compare the outcomes in extracorporeal toxin removal-treated patients and non-extracorporeal toxin removal-treated patients if indicated for treatment as defined by The Extracorporeal TReatments In Poisoning criteria.

Methods:

Lithium poisoning presented between year 2009 and 2019 in Hong Kong Poison Information Centre (HKPIC) database was categorized into extracorporeal toxin removal-treated group and non-extracorporeal toxin removal-treated group. Comparative analyses were performed.

Results:

Among 112 lithium-poisoned patients, 21% were treated with extracorporeal toxin removal. Larger proportion of patients had fulfilled at least one Extracorporeal TReatments In Poisoning criteria for extracorporeal toxin removal in the extracorporeal toxin removal-treated group (87% vs 18%, p < 0.005). The extracorporeal toxin removal-treat group patients were more commonly presented with impaired consciousness, seizure and dysrhythmia ( p < 0.05). They also got higher admission (3.62 mmol/L vs 2.18 mmol/L, p < 0.05) and peak (4.15 mmol/L vs 2.28 mmol/L, p < 0.05) serum lithium concentrations, as well as a significantly higher serum creatinine concentration upon presentation (263.74 µmol/L vs 98.66 µmol/L, p < 0.05). Extracorporeal toxin removal-treat group patients more frequently had a severe poisoning outcome (91.3% vs 9%, p < 0.05) and developed complications (69.6% vs 13.5%, p < 0.05). Logistic regression identified seizure, peak serum lithium concentration, and serum creatinine concentration upon presentation as risk factors for severe poisoning outcome. In subgroup analysis on patients with at least one indication for extracorporeal toxin removal as defined by Extracorporeal TReatments In Poisoning criteria, the proportion of severe poisoning remained higher in the extracorporeal toxin removal-treated group (90% vs 43.7%, p < 0.05). Complication rate was not significantly different between the two groups.

Conclusion:

Clinically severe lithium poisoning patients were treated with extracorporeal toxin removal in Hong Kong. Extracorporeal TReatments In Poisoning criteria can serve as a reference in considering extracorporeal toxin removal treatment for lithium poisoning patients. Nevertheless, Extracorporeal TReatments In Poisoning criteria recommend more extracorporeal toxin removal treatment than it was actually done. Lithium poisoning patients with positive Extracorporeal TReatments In Poisoning criteria have been managed without extracorporeal toxin removal. No statistically significant adverse outcome was observed in these cases.