Glycolate Causes the Acidosis in Ethylene Glycol Poisoning and is Effectively Removed by Hemodialysis

Multicenter Long-Term Real World Data on Treatment With Lumasiran in Patients With Primary Hyperoxaluria Type 1

Introduction

The RNA interference (RNAi) medication lumasiran reduces hepatic oxalate production in primary hyperoxaluria type 1 (PH1). Data outside clinical trials are scarce.

Methods

We report on retrospectively and observationally obtained data in 33 patients with PH1 (20 with preserved kidney function, 13 on dialysis) treated with lumasiran for a median of 18 months.

Results

Among those with preserved kidney function, mean urine oxalate (Uox) decreased from 1.88 (baseline) to 0.73 mmol/1.73 m2 per 24h after 3 months, to 0.72 at 12 months, and to 0.65 at 18 months, but differed according to vitamin B6 (VB6) medication. The highest response was at month 4 (0.55, -70.8%). Plasma oxalate (Pox) remained stable over time. Glomerular filtration rate increased significantly by 10.5% at month 18. Nephrolithiasis continued active in 6 patients, nephrocalcinosis ameliorated or progressed in 1 patient each. At last follow-up, Uox remained above 1.5 upper limit of normal (>0.75 mmol/1.73 m2 per 24h) in 6 patients. Urinary glycolate (Uglyc) and plasma glycolate (Pglyc) significantly increased in all, urine citrate decreased, and alkali medication needed adaptation. Among those on dialysis, mean Pox and Pglyc significantly decreased and increased, respectively after monthly dosing (Pox: 78-37.2, Pglyc: 216.4-337.4 μmol/l). At quarterly dosing, neither Pox nor Pglyc were significantly different from baseline levels. An acid state was buffered by an increased dialysis regimen. Systemic oxalosis remained unchanged.

Conclusion

Lumasiran treatment is safe and efficient. Dosage (interval) adjustment necessities need clarification. In dialysis, lack of Pox reduction may relate to dissolving systemic oxalate deposits. Pglyc increment may be a considerable acid load requiring careful consideration, which definitively needs further investigation.

Calcium Oxalate Monohydrate is Associated with Endothelial Cell Toxicity But Not with Reactive Oxygen Species Accumulation

One characteristic of ethylene glycol overdose is a cardiopulmonary syndrome including hypertension and pulmonary edema with pathology indicating damage to the endothelium of heart, lung and brain vessels. The mechanism of the cardiopulmonary toxicity is unknown, but has been linked with accumulation of the metabolite calcium oxalate monohydrate (COM) in the endothelium. These studies have evaluated the hypothesis that COM or the oxalate ion produces endothelial damage in vitro and that damage is linked with induction of reactive oxygen species (ROS). In cultured human umbilical vein endothelial cells (HUVEC), COM, but not the oxalate ion, produced cytotoxicity in a dose- and time-dependent manner. Using three ROS-sensitive dyes, HUVEC exposed to COM did not significantly increase ROS production. Additionally, co-treatment with three antioxidants that operate by different mechanisms did not reduce COM cytotoxicity. As such, an increase in ROS production does not explain cell death in endothelial cells. Aluminum citrate, uniquely among citrate compounds, significantly reduced COM cytotoxicity to endothelial cells and thus may act as an adjunct therapy for ethylene glycol poisoning to reduce endothelial damage. These results imply that accumulation of COM in endothelial cells is an important aspect of the cardiopulmonary toxicity from ethylene glycol.

Serum Calcium Concentration in Ethylene Glycol Poisoning

INTRODUCTION

The diagnosis of ethylene glycol intoxication can be challenging. Definitive testing for ethylene glycol is not readily available and clinical decisions are often based on clinical suspicion and the results of more readily available tests. One of these findings is hypocalcemia, presumable through complexation with the ethylene glycol metabolite oxalate.

METHODS

We performed a retrospective review of all patients admitted to a tertiary care hospital between 2005 and 2013 with laboratory confirmed ethylene glycol intoxication. Serum calcium on presentation was compared to blood gas pH on presentation as well as presentation serum bicarbonate.

RESULTS

We did not find any relationship between calcium and serum pH either by linear regression or when dichotomized by pH ≥ or <7.3. We did observe an inverse relationship between serum calcium and bicarbonate.

CONCLUSIONS

Hypocalcemia is not commonly observed following ethylene glycol poisoning, even in acidotic patients.

Ethylene glycol induces hyperoxaluria without metabolic acidosis in rats

Ethylene glycol (EG) consumption is commonly employed as an experimental regimen to induce hyperoxaluria in animal models of calcium oxalate nephrolithiasis. This approach has, however, been criticized because EG overdose induces metabolic acidosis in humans. We tested the hypothesis that EG consumption (0.75% in drinking water for 4 wk) induces metabolic acidosis by comparing arterial blood gases, serum electrolytes, and urinary chemistries in five groups of Sprague-Dawley rats: normal controls (CON), those made hyperoxaluric (HYP) with EG administration, unilaterally nephrectomized controls (UNI), unilaterally nephrectomized rats fed EG (HRF), and a metabolic acidosis (MA) reference group imbibing sweetened drinking water (5% sucrose) containing 0.28 M NH4Cl. Arterial pH, plasma bicarbonate concentrations, anion gap, urinary pH, and the excretion of titratable acid, ammonium, phosphate, citrate, and calcium in HYP rats were not significantly different from CON rats, indicating that metabolic acidosis did not develop in HYP rats with two kidneys. Unilateral nephrectomy alone (UNI group) did not significantly affect arterial pH, plasma bicarbonate, anion gap, or urinary pH compared with CON rats; however, HRF rats exhibited some signs of a nascent acidosis in having an elevated anion gap, higher phosphate excretion, lower urinary pH, and an increase in titratable acid. Frank metabolic acidosis was observed in the MA rats: decreased arterial pH and plasma HCO3−concentration with lower urinary pH and citrate excretion with elevated excretion of ammonium, phosphate and, hence, titratable acid. We conclude that metabolic acidosis does not develop in conventional EG treatments but may ensue with renal insufficiency resulting from an oxalate load.