Thrombotic microangiopathy in hematotoxic snakebites and its impact on the prognosis: an entity often overlooked

Redefining the role of therapeutic plasma exchange in complications of Echis carinatus sochureki envenomation refractory to anti-snake venom: A case series

INTRODUCTION

Saw-scaled viper (Echis carinatus) belongs to the Viperidae family. Its venom is hemotoxic and contains several small peptides and proteins affecting the coagulation system. Commonly used anti-snake venom (ASV) products in India are reported to be ineffective or less effective in cases with bites by Echis carinatus sochureki which are commonly found in desert areas in Rajasthan. Although therapeutic plasma exchange (TPE) has been successful in patients with snakebite envenomation in the past, American Society for Apheresis guidelines 2019 included this indication under category III with grade 2C recommendation.

AIM AND OBJECTIVES

To report the safety and efficacy of therapeutic plasma exchange procedures in the setting of ASV refractory E. c. sochureki envenomation.

MATERIALS AND METHODS

Four patients admitted to our institute in 2021 September with an alleged history of snake bites and who underwent at least one cycle of therapeutic plasma exchange were assessed for clinical outcome, laboratory parameters, and blood product consumption.

RESULTS

Three adult patients and one pediatric patient are included in this case series, all of them males. Indication for TPE in one case was suspected diffuse alveolar hemorrhage (DAH), while in all the other cases was thrombotic microangiopathy (TMA). All received a variable number of sessions from 2 to 5 and 1.3-1.5 plasma volume was removed on an average per cycle. The endpoint of TPE was the resolution of DAH in one while a reduction in lactate dehydrogenase and an increase in platelet count was in TMA cases. Consumption of blood products was drastically reduced in all four patients after starting the procedure. All the adult patients fared well on follow-up while the child had developed acute cortical necrosis and was dialysis-dependent. It has been noted in the previous studies too that a subset of snakebite-induced TMA cases was getting converted to chronic kidney disease and becoming dialysis dependent in the long run.

CONCLUSIONS

In regions where ASV treatment failure is very common, therapeutic plasma exchange is a safe and effective complementary treatment modality along with supportive care.

Therapeutic Plasma Exchange for Venom-Induced Thrombotic Microangiopathy Following Hump-Nosed Pit Viper (Genus: Hypnale) Bites: A Prospective Observational Study

INTRODUCTION

-Thrombotic microangiopathy (TMA), which is the triad of acute kidney injury (AKI), microangiopathic hemolytic anemia (MAHA), and thrombocytopenia, is a rare complication of snakebites, and in Sri Lanka, it is commonly seen with hump-nosed pit viper (HNPV) bites.

METHODS

-We conducted a prospective observational study of patients with AKI caused by HNPV bites in Teaching Hospital, Ratnapura, Sri Lanka for 6 y, commencing in June 2015. Some patients with TMA underwent therapeutic plasma exchange (TPE) and some did not. These 2 groups were compared. Statistical analysis was carried out using Minitab 18.1. Data were presented as median (IQR).

RESULTS

-There were 52 (8%) patients with TMA, of whom 21 (45%) were in the TPE group and 26 (55%) were in the non-TPE group. TPE improved time to platelet correction (4 d [IQR, 4-5 d] vs 7 d [IQR, 5-9 d]; P=0.009), time to MAHA correction (5 d [IQR, 3-4 d] vs 7 d [IQR, 6-9 d]; P=0.004), time to prothrombin time (PT)/international normalized ratio (INR) correction (1 d [IQR, 1-2 d] vs 3 d [IQR, 3-4 d]; P=0.003), and time to 20 min whole blood clotting test (WBCT20) correction (2 d [IQR, 1-2 d] vs 3 d [1QR 2-3 d]; P=0.020). Renal recovery was predicted by TPE (P=0.048) and highest creatinine level (P=0.001). There was no association between TPE and dialysis dependency at discharge (P=0.597), length of hospital stay (P=0.220), and the number of dialysis cycles prior to discharge (P=0.540). TPE did not improve the number of blood transfusions (5 packs [IQR, 3-8.5 packs] vs 4 packs [IQR, 0-9 packs]; P=0.290).

CONCLUSIONS

-TPE is effective for TMA in the early correction of platelet counts, MAHA, PT/INR, and WBCT20 in HNPV bites.

Snakebite Associated Thrombotic Microangiopathy and Recommendations for Clinical Practice

Snakebite is a significant and under-resourced global public health issue. Snake venoms cause a variety of potentially fatal clinical toxin syndromes, including venom-induced consumption coagulopathy (VICC) which is associated with major haemorrhage. A subset of patients with VICC develop a thrombotic microangiopathy (TMA). This article reviews recent evidence regarding snakebite-associated TMA and its epidemiology, diagnosis, outcomes, and effectiveness of interventions including antivenom and therapeutic plasma-exchange. Snakebite-associated TMA presents with microangiopathic haemolytic anaemia (evidenced by schistocytes on the blood film), thrombocytopenia in almost all cases, and a spectrum of acute kidney injury (AKI). A proportion of patients require dialysis, most survive and achieve dialysis free survival. There is no evidence that antivenom prevents TMA specifically, but early antivenom remains the mainstay of treatment for snake envenoming. There is no evidence for therapeutic plasma-exchange being effective. We propose diagnostic criteria for snakebite-associated TMA as anaemia with >1.0% schistocytes on blood film examination, together with absolute thrombocytopenia (<150 × 10⁹/L) or a relative decrease in platelet count of >25% from baseline. Patients are at risk of long-term chronic kidney disease and long term follow up is recommended.

Snakebite-associated thrombotic microangiopathy: an Australian prospective cohort study [ASP30]

BACKGROUND

Snakebite-associated thrombotic microangiopathy (TMA) occurs in a subset of patients with venom-induced consumption coagulopathy (VICC) following snakebite. Acute kidney injury (AKI) is the commonest end-organ manifestation of TMA. The epidemiology, diagnostic features, outcomes, and effectiveness of interventions including therapeutic plasma-exchange (TPE), in snakebite-associated TMA are poorly understood.

METHODS

We reviewed all patients with suspected or confirmed snakebite recruited to the Australian Snakebite Project (2004-2018 inclusive), a prospective cohort study, from 202 participating Australian hospitals across the country. TMA was defined as anemia with schistocytosis.

RESULTS

2069 patients with suspected snakebite were enrolled, with 1158 (56.0%) systemically envenomed, of which 842 (72.7%) developed VICC, from which 104 (12.4%) developed TMA. Of those systemically envenomed, TMA occurred in 26% (13/50) taipan, 17% (60/351) brown, and 8% (16/197) tiger snakebites. Thrombocytopenia was present in 90% (94/104) of TMA cases, and a further eight (8%) had a > 25% decrease in platelets from the presentation. Patients with TMA were significantly older than non-TMA patients with VICC (53 [35-61] versus 41 [24-55] years, median [IQR], p < 0.0001). AKI developed in 94% (98/104) of TMA patients, with 34% (33/98) requiring dialysis (D-AKI). There were four deaths. In D-AKI TMA cases, eventual dialysis-free survival (DFS) was 97% (32/33). TPE was used in five D-AKI cases, with no significant difference in DFS or time to independence from dialysis. >90-day follow-up for 25 D-AKI cases (130 person-years) showed no end-stage kidney disease but 52% (13/25) had ≥ stage 3 chronic kidney disease (CKD).

CONCLUSION

Our findings support a definition of snakebite-associated TMA as anemia with schistocytosis and either thrombocytopenia or >25% drop in platelet count. AKI occurring with snakebite-associated TMA varied in severity, with most achieving DFS, but with a risk of long-term CKD in half. We found no evidence of benefit for TPE in D-AKI.

Schistocyte quantitation, thrombotic microangiopathy and acute kidney injury in Australian snakebite coagulopathy [ASP28]

INTRODUCTION

The major systemic manifestation of hemotoxicity in human snakebite envenoming is venom-induced consumption coagulopathy (VICC). A subset of patients with VICC develop thrombotic microangiopathy (TMA), in which acute kidney injury (AKI) occurs. We aimed to investigate the association between schistocytosis in snakebite patients with VICC and AKI, compared to non-envenomed patients.

METHODS

Serial blood films collected from a prospective cohort of snakebite patients (Australian Snakebite Project) were examined. Cases were classified a priori as non-envenomed snakebites (normal controls), envenomed without VICC, partial VICC without AKI, complete VICC without AKI, and VICC with AKI based on defined clinical and laboratory criteria. The percentage of schistocytes between groups was compared and correlated by Kendall's tau b test.

RESULTS

Seven hundred and eighty blood films from 234 snakebite cases were analyzed. There was a statistically significant correlation (τ = .69, SE .03, P < .001) for schistocytosis between the ordered groups of non-envenomed snakebites, envenomed without VICC, partial VICC without AKI, complete VICC without AKI, and VICC with AKI groups. Patients with VICC and AKI had a platelet nadir median of 42 × 10⁹ /L (interquartile range [IQR] :25-130 × 10⁹ /L), hemoglobin nadir of median 107 g/L (IQR 66-122 g/L), and maximum LDH median of 1128 U/L (IQR 474-3255 U/L). A 1.0% threshold for schistocytosis yielded 90% sensitivity (95% CI: 67%-98%) and 71% specificity (95% CI: 62%-79%) for predicting AKI in patients with VICC.

CONCLUSION

Schistocyte quantitation has good diagnostic utility in snakebite patients with VICC. A definition of snakebite TMA as MAHA with ≥1.0% schistocytes and thrombocytopenia, would appear to be appropriate.

Snakebite associated thrombotic microangiopathy: a systematic review of clinical features, outcomes, and evidence for interventions including plasmapheresis

Snakebite is a neglected tropical disease with significant morbidity and mortality. Thrombotic microangiopathy (TMA) is an important but poorly understood complication of snakebite associated with acute kidney injury (AKI). Numerous treatments have been attempted based on limited evidence. We conducted a systematic review of TMA following snakebite using a pre-determined case definition of blood film red cell schistocytes or histologically diagnosed TMA. The search strategy included major electronic databases and grey literature. We present a descriptive synthesis for the outcomes of AKI, dialysis free survival (DFS), other end-organ damage, overall survival, and interventions with antivenom and therapeutic plasmapheresis (TPE). This study was prospectively registered with PROSPERO (CRD42019121436). Seventy-two studies reporting 351 cases were included, predominantly small observational studies. Heterogeneity for study selection, design, reporting and outcomes were observed. The commonest envenoming species were hump-nosed vipers (Hypnale spp.), Russell's viper (Daboia russelii) and Australian brown snakes (Pseudechis spp.). The prevalence of TMA was at least 5.4% in proven and probable Hypnale bites, and 10-15% of Australian elapid envenomings, AKI occurred in 94% (293/312) of TMA cases, excluding case reports. The majority of cases with AKI required dialysis. Included prospective and retrospective cohort studies reporting interventions and renal outcomes showed no evidence for benefit from antivenom or TPE with respect to DFS in dialysis dependant AKI. The Grading of Recommendations, Assessment, Development and Evaluations (GRADE) assessment for quality of accumulated evidence for interventions was low. The major complication of TMA following snakebite is AKI. AKI improves in most cases. We found no evidence to support benefit from antivenom in snakebite associated TMA, but antivenom remains the standard of care for snake envenoming. There was no evidence for benefit of TPE in snakebite associated TMA, so TPE cannot be recommended. The quality of accumulated evidence was low, highlighting a need for high quality larger studies.

Severe acute kidney injury following Sri Lankan Hypnale spp. envenoming is associated with thrombotic microangiopathy

CONTEXT

Acute kidney injury (AKI) is the most serious clinical manifestation of the Sri Lankan hump-nosed pit viper (Hypnale spp.) bites. Thrombotic microangiopathy (TMA) is increasingly recognized in association with AKI in cases of Hypnale spp envenomation. We investigated AKI in a cohort of cases of Hypnale envenomation, its association with TMA and the early diagnostic value of common biomarkers for AKI occurring.

MATERIALS AND METHODS

We conducted a prospective observational study of suspected viper bites and included 103 confirmed cases of Hypnale envenomation, based on venom specific enzyme immunoassay of blood. AKI was defined using the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Thrombotic microangiopathy was diagnosed based on thrombocytopenia (platelet count < 150,000 × 10³/μL) and microangiopathic haemolytic anaemia (MAHA). We investigated the diagnostic performance of creatinine, platelet count and INR for AKI within 4 h and 8 h post-bite by area under the receiver operator characteristic curve (AUC-ROC).

RESULTS

Ten patients developed AKI: seven AKI stage 1 and three AKI stage 3. Ten patients (10%) developed thrombocytopaenia while 11 (11%) had MAHA. All three AKI stage 3 had thrombocytopaenia and MAHA fulfilling the criteria for TMA. Two of them presented with oliguria/anuria and all three required haemodialysis. Serum creatinine within 4 h post-bite was the best predictor of AKI with AUC-ROC of 0.83 (95% CI: 0.67-0.99) and was no better within 8 h of the bite.

CONCLUSIONS

We found that AKI is uncommon in Hypnale spp. envenomation, but an important serious complication. Severe AKI was associated with TMA. A creatinine within 4 h post-bite was the best predictor of AKI.

Thrombotic microangiopathy due to Bothrops erythromelas: a case report in Northeast Brazil

Bothrops erythromelas are serpents that belong to the Viperidae family, which are the main species responsible for human snakebites in Ceara State, Northeast Brazil. Thrombotic microangiopathy (TMA) is an uncommon group of disorders characterized by microangiopathic hemolytic anemia (MAHA), thrombocytopenia and acute kidney injury (AKI), and occurrence after snakebites have been rarely reported. In this report, we described the case of a 57 year-old-man without comorbidities who was bitten by a Bothrops erythromelas on his right ankle. He presented with pain, edema and local bleeding. Symptomatology and laboratory tests were compatible with the diagnosis of TMA. He received specific antivenom and fluids replacement without any anaphylactic reaction. The conservative treatment was effective and there was no need for red blood cells transfusion or plasmapheresis. The aim of this report was to describe the first case of thrombotic microangiopathy following Bothrops erythromelas envenoming in the Northeast Brazil, providing insights about important mechanistic pathways of Bothrops snakebite-associated TMA and how to change the prognosis of the disease.