pH 6.68--surviving severe metformin intoxication

Continuous extracorporeal clearance in metformin-associated lactic acidosis and metformin-induced lactic acidosis: a systematic review

INTRODUCTION

Metformin poisoning with lactic acidosis is an uncommon yet clinically serious condition related to the inhibition of normal aerobic metabolism. Toxicity may occur after an acute overdose although it is much more common after a systemic insult, such as acute kidney injury, in the setting of chronic use. Hemodialysis is currently the preferred extracorporeal treatment modality (Grade 1D evidence) although some patients may be too hemodynamically unstable to tolerate it. Continuous renal replacement therapy is considered an alternative if hemodialysis is unavailable but an evaluation of survival amongst this specific treatment class is lacking.

OBJECTIVES

To assess overall survival and provide an updated review of the toxicokinetic elimination parameters of patients receiving continuous renal replacement therapy for metformin poisoning.

METHODS

A comprehensive search was performed using the EMBASE and MEDLINE libraries from inception until November 30, 2021. Data was extracted and findings were summarized. Toxicokinetic parameters were analyzed and confirmed for accuracy when data permitted.

RESULTS

Eighty-three reports met inclusion criteria. These consisted of only low-quality evidence including 75 case reports, four case series, and four descriptive retrospective reviews. Overall survival among patients suffering from metformin toxicity who received continuous extracorporeal treatment was 85.8%. When stratified between metformin-induced lactic acidosis and metformin-associated lactic acidosis, survival was 75.0% and 87.4%, respectively. Available continuous renal replacement therapy toxicokinetic parameters were quite heterogeneous. Errors in previously published toxicokinetic calculations were noted in only two instances. The overall average and median peak metformin concentrations were 70.5 mg/L and 41.9 mg/L, respectively. The average and median extracorporeal clearance rates were 39.0 mL/min and 42.1 mL/min (range 9.0-58.7 mL/min). The average and median elimination half-life parameters were 27.5 h and median 23.0 h. Elimination half-life ranged from seven to 74 h. There was no meaningful relationship between peak metformin concentration and continuous extracorporeal treatment half-life at lower concentrations, though at very high concentrations (over 200 mg/L), there was a trend towards a half-life below 20 h. There is insufficient data to robustly evaluate overall survival in relation to the extracorporeal clearance rate. Finally, there was no relevant relationship between maximal lactate concentration and survival, nor nadir pH and survival, for patients with either type of metformin toxicity.

CONCLUSIONS

This retrospective systematic analysis of published cases treating metformin related lactic acidosis with continuous renal replacement therapy notes an overall slightly greater survival percentage compared to previous publications of individuals requiring any modality of renal replacement therapy. Because of publication bias, these results should be interpreted with caution and serve as hypothesis generating for future research. Prospective study focusing on the most clinically meaningful endpoint - survival - will help elucidate if continuous modalities are non-inferior to intermittent hemodialysis in metformin toxicity.

The Association between Metformin Therapy and Lactic Acidosis

INTRODUCTION AND OBJECTIVES

There is increasing evidence to suggest that therapeutic doses of metformin are unlikely to cause lactic acidosis. The aims of this research were (1) to formally evaluate the association between metformin therapy and lactic acidosis in published case reports using two causality scoring systems, (2) to determine the frequency of pre-existing independent risk factors in published metformin-associated lactic acidosis cases, (3) to investigate the association between risk factors and mortality in metformin-associated lactic acidosis cases, and (4) to explore the relationship between prescribed metformin doses, elevated metformin plasma concentrations and the development of lactic acidosis in cases with chronic renal impairment.

METHODS

A systematic review was conducted to identify metformin-associated lactic acidosis cases. Causality was assessed using the World Health Organisation-Uppsala Monitoring Centre system and the Naranjo adverse drug reaction probability scale. Compliance to dosing guidelines was investigated for cases with chronic renal impairment as well as the association between steady-state plasma metformin concentrations prior to admission.

RESULTS

We identified 559 metformin-associated lactic acidosis cases. Almost all cases reviewed (97%) presented with independent risk factors for lactic acidosis. The prescribed metformin dose exceeded published guidelines in 60% of cases in patients with impaired kidney function. Metformin steady-state plasma concentrations prior to admission were predicted to be below the proposed upper limit of the therapeutic range of 5 mg/L.

CONCLUSIONS

Almost all cases of metformin-associated lactic acidosis reviewed presented with independent risk factors for lactic acidosis, supporting the suggestion that metformin plays a contributory role. The prescribed metformin dose, on average, exceeded the dosing recommendations by 1000 mg/day in patients with varying degrees of renal impairment but the predicted pre-admission plasma concentrations did not exceed the therapeutic range.

A Rare Outcome Induced by Metformin Intoxication: Severe Lactic Acidosis and Hepatotoxicity

Metformin is a widely used oral anti-diabetic agent that decreases insulin resistance. Lactic acidosis rarely develops with this medication. Metformin-induced hepatotoxicity has been rarely reported in the literature. We describe a patient, who presented with lactic acidosis and hepatotoxicity after ingestion of 40 pills of metformin in order to commit suicide. The most important treatment step in patients with metformin-associated lactic acidosis (MALA) is high-volume hemodialysis and hemofiltration.

Severe acidosis does not predict fatal outcomes in intensive care unit patients: a retrospective analysis

PURPOSE

Severe acidosis is a potentially life-threatening acid-base imbalance. The outcome of patients with severe acidosis has only been anecdotally described. We therefore assessed the discharge rate of such patients from the intensive care unit (ICU) and survival time after the event.

METHODS

A retrospective evaluation of medical records of patients admitted to the ICU of Tel Aviv Medical Center between 2005 and 2010, in whom arterial blood pH less than 6.8 was documented during their ICU stay, was performed.

RESULTS

Twenty-eight patients were suitable for study entry. Septic shock was the most common underlying medical condition (33%). Nine (32.1%) patients were either discharged alive or survived for at least 30 days in the ICU after their arterial blood pH measurement was less than 6.8. More than a quarter of the patients with life-threatening acidosis (n = 8; 28.6%) were discharged home and returned to their prehospitalization daily activity. Mean follow-up period for these patients was 132 ± 111 weeks. Multivariate analysis identified hyperkalemia, Acute Physiology and Chronic Health Evaluation II score, and Glasgow Coma Scale as determinants for ICU death after severe acidosis.

CONCLUSIONS

A significant number of patients can outlast severe acidosis and return to their prehospitalization status. Larger studies are needed to define the patient population most likely to benefit from aggressive resuscitation efforts during severe acidosis.