Thrombotic microangiopathy from Australian brown snake (Pseudonaja) envenoming

Cortical Blindness and Thrombotic Microangiopathy Following a Hemotoxic Snake Envenomation: An Unusual Presentation

Snake envenomation leads to significant morbidity and mortality with local, hematological, renal, and neurological complications. Hemotoxic envenomation activates a hemorrhagic cascade, leading to many manifestations ranging from skin bleeds to major organ bleeds and fatal intracranial hemorrhage. Although rare, ischemic manifestations are possible following a hemotoxic envenomation, and they may present as cortical blindness, an unusual ocular symptom. Snake envenomation is also known to cause multifactorial acute kidney injury (AKI), precipitated by hemodynamic disturbances secondary to rhabdomyolysis, hemoglobinuria, direct tubular toxicity, and thrombotic microangiopathy. Thrombotic microangiopathy (TMA) is often overlooked in snake bites, as the hematological manifestations are often conveniently attributed to venom-induced consumptive coagulopathy (VICC). The distinct clinical entity of thrombotic microangiopathy should factor into one's differential diagnosis in patients presenting with microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury following a snake bite. We report a patient who developed cortical blindness and thrombotic microangiopathy following snake envenomation, which are uncommon sequelae.

Venom-induced consumptive coagulopathy leading to thrombotic microangiopathy following Echis carinatus sochureki bite: is snake antivenom effective?

The incidence of thrombotic microangiopathy (TMA) following snake bite is reported to be ranging from 3.6 to 15%. We report a 10-year-old boy who developed TMA and due to venom-induced consumptive coagulopathy (VICC) despite receiving adequate and timely doses of snake antivenom following a bite of saw-scaled viper (Echis carinatus sochureki). VICC was managed by plasmapheresis. Though snake bite envenomation-associated renal complications are not uncommon, possibility of TMA should be considered early during management. Our patient developed TMA with subsequent acute cortical necrosis after saw-scaled viper bite despite an adequate and timely dose of snake antivenom which emphasizes the ineffectiveness of antivenom against the venom of given snake species leading to long-term complications.

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.

Atypical Hemolytic Uremic Syndrome in a Patient With Bothrops asper Envenomation

Bothrops asper envenomation is common in Colombia and is characterized by local tissue injury and venom-induced consumption coagulopathy (VICC). Rarely, thrombotic microangiopathy is associated with envenomation by this species. The case of a 57-y-old man with B asper bite and envenomation on the left foot is presented. The patient was admitted 8 h after the event and progressively developed edema, hemorrhage at the site of the bite, and hemorrhagic blisters. His coagulation test results (prothrombin and partial thromboplastin times) were prolonged, and his fibrinogen levels were severely reduced. The diagnosis of VICC was made. Administration of Colombian polyvalent viper antivenom controlled the VICC within a few hours. Subsequently, the patient developed severe microangiopathic anemia, thrombocytopenia, and acute kidney injury. A diagnosis of thrombotic microangiopathy was made, and the patient met the criteria for hemolytic uremic syndrome. Management with hemodialysis in addition to therapeutic plasma exchange and replacement with fresh frozen plasma was indicated. The patient's condition resolved 14 d later. To the best of our knowledge, this is the first case of B asper envenomation in which the patient presented with hemolytic uremic syndrome after VICC. A proposal is made regarding the pathogenesis of this chain of events.

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.

Thrombotic microangiopathy following saw-scaled viper (Echis carinatus) envenoming in Sri Lanka

The saw-scaled viper (Echis carinatus) is considered as a highly venomous snake in Sri Lanka. The clinical manifestations are localized pain and swelling, coagulopathy and renal impairment. Thrombotic microangiopathy is rarely reported as a complication of saw-scaled viper envenoming. The clinical manifestations of thrombotic microangiopathy include thrombocytopenia, microangiopathic haemolytic anaemia and acute kidney injury. The consumption coagulopathy of post-envenoming could be followed by a syndrome consistent with thrombotic microangiopathy. We describe a patient with thrombotic microangiopathy following saw-scaled viper systemic envenoming which was managed with antivenom and supportive therapy. The dead snake which was brought by patient was identified by medical professional as saw-scaled viper (E. carinatus) based on morphological features. This case illustrates a rare manifestation thrombotic microangiopathy following saw-scaled viper envenoming.

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.

Potential Role of Platelet-Activating C-Type Lectin-Like Proteins in Viper Envenomation Induced Thrombotic Microangiopathy Symptom

Envenomation by viperid snakes may lead to severe bleeding, consumption coagulopathy, and thrombotic microangiopathy symptoms. The exact etiology or toxins responsible for thrombotic microangiopathy symptoms after snake envenomation remain obscure. Snake C-type lectin-like proteins (snaclecs) are one of the main non-enzymatic protein constituents in viper venoms, of which a majority are considered as modulators of thrombosis and hemostasis. In this study, we demonstrated that two snaclecs (mucetin and stejnulxin), isolated and identified from Protobothrops mucrosquamatus and Trimeresurus stejnegeri venoms, directly induced platelet degranulation and clot-retraction in vitro, and microvascular thrombosis has been confirmed in various organs in vivo. These snaclecs reduced cerebral blood flow and impaired motor balance and spatial memories in mice, which partially represent the thrombotic microangiopathy symptoms in some snakebite patients. The functional blocking of these snaclecs with antibodies alleviated the viper venom induced platelet activation and thrombotic microangiopathy-like symptoms. Understanding the pathophysiology of thrombotic microangiopathy associated with snake envenoming may lead to emerging therapeutic strategies.

Thrombotic microangiopathy and acute kidney injury following Sri Lankan Daboia russelii and Hypnale species envenoming

Context: Thrombotic microangiopathy (TMA) resulting in acute kidney injury (AKI) is an important complication of venomous snakebites. We aimed to describe TMA secondary to Russell's viper (Daboia russelli) and hump-nosed viper (Hypnale spp.) bites and assess the effect of different treatments.Materials and methods: We undertook a prospective observational study of patients with AKI secondary to snakebite over a two-year period. Data recorded included: demographic details, clinical and laboratory features, treatment, complications and outcomes, until hospital discharge and at three months post-discharge. TMA was defined as the development of microangiopathic hemolytic anemia and thrombocytopenia along with AKI. Treatment with therapeutic plasma exchange (TPE; also known as plasmapheresis) and/or fresh frozen plasma (FFP) was determined by the treating clinician. Antivenom was given to all patients with evidence of systemic envenoming following Russell's viper bites.Results: Fifty-nine patients were included in the analysis. Thirty-three (56%) were males and median age was 56 years. Forty-five (76%) developed TMA while a further 11 and two developed isolated thrombocytopenia and microangiopathic hemolytic anemia, respectively. Presence of TMA was associated with increased dialysis requirements (5 vs. 3) and longer hospital stay (18 vs. 12 days). Of the patients with TMA, nine received TPE with or without FFP infusions. The use of TPE was not associated with improved outcomes in patients with TMA based on requirement for blood transfusion, recovery of thrombocytopenia, requirement of dialysis and duration of hospital stay. Patients who did not receive TPE had better renal function at three months compared to patients who received this treatment.Conclusion: Presence of TMA in patients with Daboia and Hypnale bites was associated with a more prolonged course of AKI. Patients with TMA who were treated with TPE did not have improved early or late outcomes compared to patients who were not treated with TPE.

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.

A case of acute hypogonadism following taipan (Oxyuranus scutellatus) envenomation

A previously well man developed acute, marked tender bilateral gynaecomastia two months after confirmed taipan (Oxyuranus scutellatus) envenomation. He had had laboratory evidence of thrombotic microangiopathy (TMA) including microangiopathic haemolytic anaemia, thrombocytopenia and acute kidney injury. Scrotal ultrasound revealed bilateral testicular atrophy, his serum testosterone was repeatedly low, while his luteinising and follicle stimulating hormone were elevated. It is hypothesised that TMA-related testicular ischaemia was responsible for his primary gonadal failure and dramatic clinical presentation.

Fatal Rattlesnake Envenomation in Northernmost Brazilian Amazon: A Case Report and Literature Overview

Snakebite envenomations are classified as Category A Neglected Tropical Diseases by the World Health Organization. In Brazil, 405 snake species are distributed among 11 families, with the genera Bothrops and Crotalus being the most studied and main responsible for severe and lethal envenomations. In the country, Crotalus genus (i.e., rattlesnakes) is represented by Crotalus durissus species, showing seven different subspecies distributed along the country, including Crotalus durissus ruruima, which inhabits Roraima, the Brazilian nothermost state from Amazon forest. Here, we report a fatal case of a severe envenomation following a rattlesnake bite. The patient presented classic crotalic neurological signs and symptoms such as ptosis, drooling of saliva, sluggishness, macroscopic hematuria, and oliguria, which evolved to acute kidney failure (AKF) and hemodynamic instability. Although the patient was treated with the specific antivenom therapy, the severe envenomation resulted in three cardiac arrests and death of the victim in less than 38 h. This study discusses the causes of the patient death, the features of rattlesnake venom-induced AKF, and shows evidences that the Brazilian crotalic antivenom should be improved to treat rattlesnake envenomations caused by C. d. ruruima venom in Roraima state.

Plasmapheresis for Pulmonary Hemorrhage Following Viperine Snakebite: A Case Report with Review of Literature

Introduction

Snakebites are one of the commonest occupational hazards in tropical countries and viperine bites are potential to cause systemic toxicity. Coagulopathies and acute kidney injury (AKI) have been documented and easily dealt with in past, but pulmonary hemorrhage has been rarely seen and plasmapheresis has shown promising result for the same. This case reports highlight the effective use of plasmapheresis for pulmonary hemorrhage post-snakebite.

Background

Viperine snakebite has been associated with high morbidity and mortality due to its toxic systemic envenomization. The important systemic manifestations are coagulopathy, neuromuscular paralysis, AKI, myotoxicity, and cardiovascular collapse. Antivenomization, renal replacement therapy, steroids, and other supportive care are considered to be the mainstay of treatment till date. Pulmonary hemorrhage has been an unusual manifestation of viper bite and rarely reported and steroids have been used in such scenario but with mixed results. Role of plasmapheresis has been documented in the management of snakebite but especially for hematological problems and in limb preservation/salvage strategies. The use of same, for pulmonary hemorrhage has not been studied yet. Here, we present a rare case of pulmonary hemorrhage along with renal failure following viper bite which was successfully treated with plasmapheresis. To the best of our knowledge, it is a rare presentation and has not been reported in the literature reviewed till date.

Case description

A previously healthy, 36-year-old man presented to our hospital 48 hours after a viper bite. He developed local as well systemic manifestations evident as hemolysis and renal failure. Gradually, he started having hemoptysis followed by respiratory failure requiring ventilatory support. CT chest done was s/o bilateral pulmonary hemorrhages correlating clinically with ongoing tracheal bleed. He had no other bleeding manifestations and had normal coagulation profile. He was initially treated with methylprednisolone therapy, but then did not show any improvement and finally plasmapheresis was done as rescue therapy. Following this, he had improvement in respiratory parameters and settling tracheal bleed with resolution of radiological changes. He was successfully weaned off from the ventilation and also his renal failure also improved with near normalization of pulmonary and renal functions.

Conclusion

This case highlights the unusual presentation of pulmonary hemorrhage in a patient with viperine bite with normal coagulation and was aggressively managed with plasmapheresis. Hence, plasmapheresis can be used as life-saving modality in patients with systemic envenomization post-viperine bit.

How to cite this article

Sampley S, Sakhuja V, Bhasin D, Singh K, Singh H. Plasmapheresis for Pulmonary Hemorrhage Following Viperine Snakebite: A Case Report with Review of Literature. Indian J Crit Care Med 2020;24(10):986-990.

Systemic bleeding including pulmonary haemorrhage following hump-nosed pit viper (Hypnale hypnale) envenoming: A case report from Sri Lanka

Out of seven venomous land snake species of Sri Lanka, hump-nosed pit viper (Hypnale spp.) causes the commonest venomous snakebites. It is widely distributed all over the country except in the peninsula of Jaffna. The genus has three species naming H. hypnale, H. zara and H. nepa. They frequently cause local envenoming and rarely cause coagulopathy and acute kidney injury. Systemic bleeding is the most trivial complication associated with coagulopathy caused by these snakes and pulmonary haemorrhages are one of them which are rarely reported. Antivenoms are currently not available for genus Hypnale bites in Sri Lanka. We describe a fatal case of pulmonary haemorrhage caused by a proven hump-nosed viper (Hypnale hypnale) bite associated with other systemic bleeding manifestations and thrombotic microangiopathy. This is the first known case of pulmonary and intracranial haemorrhages caused by hump-nosed viper bite.

Snakebite associated thrombotic microangiopathy: a protocol for the systematic review of clinical features, outcomes, and role of interventions

BACKGROUND

Thrombotic microangiopathy is an uncommon complication of snake envenoming associated with a subset of snakebite cases presenting with venom-induced consumption coagulopathy. It presents with microangiopathic haemolytic anaemia and thrombocytopenia. Available studies are predominantly small retrospective observational studies only. Renal end organ injury appears common. It has variably been likened to either thrombotic thrombocytopenic purpura or atypical haemolytic uraemic syndrome. Many studies report acute kidney injury, with dialysis required in a subset of patients. Some studies suggest a role for treatment with plasmapheresis. Interpretation of the literature is complicated by variable nomenclature and historically poor case definitions of both venom-induced consumption coagulopathy and thrombotic microangiopathy associated with snake envenoming.

METHODS

The main objective of this systematic review is to synthesise the worldwide experience of snakebite-associated thrombotic microangiopathy with respect to its features and outcomes, and collate any evidence for the role of plasmapheresis as treatment. A predetermined case definition of confirmed or suspected snakebite with either blood film evidence of microangiopathic haemolytic anaemia or histological evidence of thrombotic microangiopathy will be used. This case definition will determine the search terms and study inclusion criteria. Relevant studies will be identified by electronic database, published conference abstracts, and grey literature search. This systematic review will be performed and reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist. The quality of included studies will be assessed by a proposed tool for evaluating the methodological quality of case reports and case series. Results will be reported by a descriptive synthesis with a focus on the presenting features; outcomes of acute kidney injury, dialysis-free survival, other end organ damage, and overall survival; and any evidence of a role for treatment with plasmapheresis. The quality of accumulated evidence will be assessed via the Grading of Recommendations, Assessment, Development, and Evaluations framework.

DISCUSSION

It is anticipated that eligible studies will consist of small observational studies. Evidence gathered from this review will provide the first broader understanding of the clinical features, outcomes, prognosis, and management of snakebite-associated thrombotic microangiopathy.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42019121436.

Thrombotic Microangiopathy: An Under-Recognised Cause of Snake-bite-related Acute Kidney Injury

Introduction:

Thrombotic microangiopathy (TMA) as a cause of snake-bite-induced acute kidney injury (AKI) is rarely reported. Very little is known about the clinical course, optimal management, and prognosis of this entity. We describe a series of snake-bite-induced TMA and compare their outcomes with those without TMA.

Methods:

This was a single-center retrospective study of patients with AKI following snake envenomation admitted between January 2012 and December 2017. Demographic profile, clinical parameters, and outcomes were studied. TMA was diagnosed based on presence of triad of microangiopathic hemolytic anemia, thrombocytopenia, and AKI, and groups with and without TMA were compared.

Results:

Of 103 patients with AKI following snake bite, 19 (18.5%) had clinical evidence of TMA. All patients with TMA had advanced azotemia (mean peak serum creatinine 9.5 ± 3.0 mg/dL), with 18 (95%) requiring renal replacement therapy (RRT). Thirteen (68%) had either complete or partial recovery of renal functions, two (10%) progressed to end-stage renal disease, and one died (three patients were lost to follow-up). Age ≥50 years, presence of oliguria/anuria, anti-snake venom dose ≥10 vials, and urea ≥80 mg/dL at presentation were independently associated with TMA (P < 0.05). RRT requirement (95% vs. 57%), mean number of RRT sessions (18 vs. 4.5 sessions), and hospital stay ≥7 days (84% vs. 58%) were higher in patients with TMA (P < 0.05), but patient outcomes did not differ.

Conclusions:

In conclusion, TMA was seen in 18.5% of patients with snake-bite-related AKI in our study and was associated with almost universal need for RRT, longer duration on RRT, and hospital stay compared with patients without TMA.

Thrombotic microangiopathy following Bothrops jararaca snakebite: case report

CONTEXT

Thrombotic microangiopathy (TMA) is an uncommon and severe complication of snakebites, and is similar, in general, to hemolytic-uremic syndrome (HUS). We describe a case of TMA following envenomation by Bothrops jararaca.

CASE DETAILS

A 56-y-old-woman with controlled hypertension was transferred from a primary hospital to our ER ∼7 h after being bitten by B. jararaca in the distal left leg. She developed edema extending from the bite site to the proximal thigh, associated with intense radiating local pain, local paresthesia and ecchymosis at the bite site. Laboratory features upon admission revealed coagulopathy (20 min whole blood clotting time - WBCT20 > 20 min), thrombocytopenia (76,000 platelets/mm³) and slight increase in serum creatinine (1.58 mg/dL; RV < 1.2 mg/dL). Upon admission, the patient was treated with bothropic antivenom and fluids replacement. During evolution, her thrombocytopenia and anemia worsened, with blood films showing fragmented red cells, haptoglobin consumption, increase in serum lactate dehydrogenase, and progressive increase of serum creatinine (KDIGO stage = 3). No RBC transfusion, renal replacement therapy or plasmapheresis was done. The patient showed progressive improvement from day nine (D9) onwards and was discharged on D20; there was complete recovery of hemoglobin levels at follow-up (D50). ADAMTS-13 activity, assayed 10 months post-bite, was within reference values.

DISCUSSION

TMA following snakebite has been reported mainly in India, Sri Lanka and Australia, with several patients needing renal replacement therapy. Although controversial, plasmapheresis has also been used in some cases. Our patient developed microangiopathic hemolytic anemia, thrombocytopenia and acute kidney injury, a triad of features compatible with TMA similar to HUS. Despite the severity, the outcome following conservative treatment was good, with complete recovery.

Acute kidney injury induced by thrombotic microangiopathy in two cases of Bothrops envenomation

CONTEXT

Bothrops snakes are the most frequent agents of snakebites in South and Central America. Acute kidney injury (AKI) is one of its complications and has multifactorial origin. Thrombotic microangiopathy (TMA)-induced AKI in snakebites is uncommon and is not described in Bothrops envenomation.

CASE DETAILS

We report two cases of patients bitten by young Bothrops jararaca who developed AKI induced by TMA. Both patients evolved with mild envenomation and received the specific antivenom within 4 h after the snakebite. None of them had hypotension or shock, bleeding or secondary infection. Patient 1 (P1) was diabetic and using oral hypoglycemic drugs, and patient 2 (P2) was hypertensive without regular use of medication. On admission, both patients had levels of fibrinogen lower than 35 mg/dL, D-dimer higher than 10,000 ng/mL. They evolved with AKI, thrombocytopenia, normal coagulation assays, anemia, lactate dehydrogenase (LDH) elevation, low haptoglobin levels, negative direct antiglobulin test, and presence of schizocytes in peripheral blood. Only P1 required renal replacement therapy, and plasmapheresis was not required. Both patients were discharged and did not require outpatient dialysis, and subsequently had normal creatinine levels.

DISCUSSION

TMA may occur in Bothrops jararaca envenomation, even in mild cases that received early specific antivenom.

Therapeutic plasma exchange for pediatric nonrenal disease indications and outcomes: A single-center experience

INTRODUCTION

Outcome data in pediatric plasma exchange, especially in nonrenal indications are scarce. We aimed to evaluate its role and outcome in our patients.

SUBJECTS AND METHODS

A retrospective study of children admitted in the year 2016 to the Pediatric Intensive Care Unit requiring plasma exchange for nonrenal indications was undertaken. Plasma exchange was given as adjunctive therapy along with primary treatment for the disease concerned. Demographic and clinical data were studied, and descriptive statistical analysis was carried out.

RESULTS

Ten children underwent plasma exchange during this 1-year period with a male: female ratio of 3:2 and a mean age of 10 years (range 3-16 years). The indications were acute disseminated encephalomyelitis (n = 2), acute neuromyelitis optica (n = 1), catastrophic antiphospholipid antibody syndrome secondary to systemic lupus erythematosus (SLE) (n = 1), severe SLE with cerebritis/hemophagocytic lymphohistiocytosis (HLH) (n = 2), severe dengue sepsis with HLH/multi-organ dysfunction syndrome (n = 2), and thrombotic microangiopathy secondary to snake bite envenomation (n = 2). All received either 1.5 or 2 times plasma volume exchange (mean sessions - 4, range = 1-6). The mean duration of stay in hospital was 17.2 days (range = 3-40 days), and follow-up was 78 days (range = 3-180 days), with the majority of children (8/10, 80%) survived from the catastrophic illness at the time of discharge. Two children (2/10, 20%) succumbed due to the disease per se in severe dengue sepsis in one and enterobacteriaceae sepsis (hospital-acquired pneumonia) in another.

CONCLUSION

Plasma exchange was found to be beneficial as complementary therapy in a critical care setting, especially for nonrenal indications.

Snakebite Induced Thrombotic Microangiopathy Leading to Renal Cortical Necrosis

Renal complications from snakebite result in high mortality and morbidity. Acute kidney injury (AKI) occurs in 5–30% of cases. Renal manifestation could include acute tubular necrosis, cortical necrosis, interstitial nephritis, glomerulonephritis, and vasculitis. We present a case of thrombotic microangiopathy (TMA) resulting in renal cortical necrosis. Renal biopsy showed fibrin thrombi in glomeruli and arterioles with cortical necrosis. Our patient progressed to end-stage renal disease.

Thrombotic microangiopathy due to Viperidae bite: Two case reports

Snake bite is mainly an occupational hazard and causes serious health problems in rural India. Acute kidney injury (AKI) occurs in 5-30% cases. Renal pathologic findings include acute tubular necrosis, cortical necrosis, interstitial nephritis, glomerulonephritis, and vasculitis. Thrombotic microangiopathy (TMA) occurrence after a snake bite is reported rarely. Here, we present two patients who developed TMA after viper bite treated with hemodialysis and plasmapheresis. Renal biopsy showed fibrin thrombi in glomeruli and arterioles with cortical necrosis. One patient progressed to end-stage renal disease and other was lost to follow-up. TMA should be considered as a possible pathogenesis of AKI after snake bite. The role of plasma exchanges in snake bite TMA is yet to be defined.

Hematologic effects and complications of snake envenoming

Hematologic abnormalities are the most common effects of snake envenoming globally. Venom-induced consumption coagulopathy (VICC) is the commonest and most important. Other hematologic abnormalities are an anticoagulant coagulopathy and thrombotic microangiopathy. Venom-induced consumption coagulopathy is a venom-induced activation of the clotting pathway by procoagulant toxins, resulting in clotting factor consumption and coagulopathy. The type of procoagulant toxin differs between snakes and can activate prothrombin, factor X, and factor V or consume fibrinogen. The most useful investigation in VICC is a prothrombin time/international normalized ratio. The d-dimer may assist in early diagnosis, but fibrinogen levels often add little in the clinical setting. Bedside investigations would be ideal, but point-of-care testing international normalized ratio and whole blood clotting tests have been shown to be unreliable in VICC. The major complication of VICC is hemorrhage, including intracranial hemorrhage which is often fatal. The role of antivenom in VICC is controversial and may only be beneficial for some types of snakes including Echis spp where the duration of abnormal clotting is reduced from more than a week to 24 to 48 hours. In contrast, antivenom does not appear to speed the recovery of VICC in Australian snake envenoming. Other treatments for VICC include factor replacement, observation and prevention of trauma, and heparin. An Australian study showed that fresh-frozen plasma speeds recovery of VICC, but early use may increase consumption. There is no evidence to support heparin.

Effect of Australian elapid venoms on blood coagulation: Australian Snakebite Project (ASP-17)

Snake venoms contain toxins that activate the coagulation network and cause venom-induced consumption coagulopathy. A previously developed mathematical model of the coagulation network was refined and used to describe and predict the time course of changes in the coagulation factors following envenomation by Brown snake (Pseudonaja spp.), Tiger snake (Notechis scutatus), Rough-scaled snake (Tropidechis carinatus) and Hoplocephalus spp. (Stephens banded, Pale headed and Broad headed). Simulations of the time course of the change in coagulation factors were compared to data obtained from a large prospective study of Australian snake bites - the Australian Snakebite Project. The model predictions were also compared against data for partial and complete VICC obtained from the same study. The model simulations were used to understand the differences in consumption and recovery of clotting factors in partial versus complete VICC as well as among bites from different snake types. The model suggested that the venoms were absorbed almost instantaneously and provided a reasonable prediction of the observed concentration of clotting factors over time in patients bitten by Australian elapid snakes. The model predictions suggested a higher consumption of factors (fibrinogen, II and IX in particular) in patients with complete VICC compared to those with partial VICC. The model also predicted that snakes with "Xa-like" venoms may produce a less severe VICC than snakes with "Xa:Va-like" venoms.

Thrombotic microangiopathy and acute kidney injury in hump-nosed viper (Hypnale species) envenoming: a descriptive study in Sri Lanka

Hump-nosed viper (Hypnale species) bites are common in Sri Lanka and a proportion of these bites lead to coagulation abnormalities and acute kidney injury (AKI). We observed thrombotic microangiopathy (TMA) among some of these patients, but its contribution to severity of AKI and other morbidities remains unknown. Thus, we report a case series of TMA following hump-nosed viper bite addressing the complications and renal out comes in Sri Lanka. This was a prospective observational study carried out at the nephrology unit, Kandy in Sri Lanka from October 2010 to October 2011 and included 11 patients with AKI following hump-nosed viper bites. All eleven cases needed renal replacement therapy (RRT) with intermittent haemodialysis for a period of 1-5 weeks. Of them, 7 patients developed TMA with evidence of microangiopathic haemolytic anaemia (MAHA), thrombocytopenia and severe anaemia needing multiple blood transfusions. They needed longer duration of RRT (range 2-5 weeks); 2 patients developed chronic kidney disease and two died during acute stage. Autopsy study found thrombosis of micro-vessels. Thrombotic microangiopathy could be a causative pathology of AKI in hump-nosed viper bite carrying poor outcome.

The role of therapeutic plasma exchange in poisonings and intoxications

Poisonings, intoxications, and drug overdoses are common occurrences and rapid lowering of the toxin level is a cornerstone of all effective therapies. Therapeutic plasma exchange (TPE) has several unique characteristics that allow it to be a potentially effective therapy in rapidly achieving this goal. Specifically, TPE allows for the removal of large molecular weight, protein-bound molecules that have a small volume of distribution. Due to the nature of poisonings, intoxications, and drug overdoses, no randomized controlled trials studying the efficacy of TPE in these situations exist. Thus, careful interpretation and analysis of case reports and series are required to assess the potential efficacy of this therapy. Recent data suggest that TPE may also be effective in the therapy of patients receiving biologic treatments who develop life-threatening complications due to therapy.

Thrombotic microangiopathy in two tiger snake envenomations

Thrombotic microangiopathies are a rare group of disorders with features such as microangiopathic haemolytic anaemia, thrombocytopenia and renal failure. Thrombotic microangiopathy has been previously reported in association with envenomation from a number of snake species. We present the first two reported cases of thrombotic microangiopathy caused by envenomation from the common tiger snake (Notechis scutatus). Both patients had classical features of thrombotic microangiopathy with microangiopathic haemolytic anaemia, thrombocytopenia and renal failure commencing in the first 48 hours after envenomation. The presentations and recovery were similar to case presentations of other snakebite envenomation associated thrombotic microangiopathies. Normal ADAMTS13 activity suggests that plasmapharesis may not be beneficial, although this needs further investigation.

Changes in serial laboratory test results in snakebite patients: when can we safely exclude envenoming?

OBJECTIVES

To determine which laboratory tests are first associated with severe envenoming after a snakebite, when (ie, how long after the bite) the test results become abnormal, and whether this can determine a safe observation period after suspected snakebite.

DESIGN, PATIENTS AND SETTING

Prospective cohort study of 478 patients with suspected or confirmed snakebite recruited to the Australian Snakebite Project from January 2002 to April 2009, who had at least three sets of laboratory test results and at least 12 hours of observation in hospital after the bite. Severe envenoming was defined as venom-induced consumption coagulopathy (VICC), myotoxicity, neurotoxicity or thrombotic microangiopathy.

MAIN OUTCOME MEASURES

International normalised ratio (INR), activated partial thromboplastin time (aPTT), creatine kinase (CK) level, and neurological examination.

RESULTS

There were 240 patients with severe envenoming, 75 with minor envenoming and 163 non-envenomed patients. Of 206 patients with VICC, 178 had an INR > 1.2 (abnormal) on admission, and the remaining 28 had an INR > 1.2 within 12 hours of the bite. Of 33 patients with myotoxicity, a combination of CK > 250 U/L and an abnormal aPTT identified all but two cases by 12 hours; one of these two was identified within 12 hours by leukocytosis. Nine cases of isolated neurotoxicity had a median time of onset after the bite of 4 hours (range, 35 min - 12 h). The combination of serial INR, aPTT and CK tests and repeated neurological examination identified 213 of 222 severe envenoming cases (96%) by 6 hours and 238 of 240 (99%) by 12 hours.

CONCLUSION

Laboratory parameters (INR, aPTT and CK) and neurological reassessments identified nearly all severe envenoming cases within 12 hours of the bite, even in this conservative analysis that assumed normal test results if the test was not done.

Development of a sensitive enzyme immunoassay for measuring taipan venom in serum

The detection and measurement of snake venom in blood is important for confirming snake identification, determining when sufficient antivenom has been given, detecting recurrence of envenoming, and in forensic investigation. Venom enzyme immunoassays (EIA) have had persistent problems with poor sensitivity and high background absorbance leading to false positive results. This is particularly problematic with Australasian snakes where small amounts of highly potent venom are injected, resulting in low concentrations being associated with severe clinical effects. We aimed to develop a venom EIA with a limit of detection (LoD) sufficient to accurately distinguish mild envenoming from background absorbance at picogram concentrations of venom in blood. Serum samples were obtained from patients with taipan bites (Oxyuranus spp.) before and after antivenom, and from rats given known venom doses. A sandwich EIA was developed using biotinylated rabbit anti-snake venom antibodies for detection. For low venom concentrations (i.e. <1 ng/mL) the assay was done before and after addition of antivenom to the sample (antivenom difference method). The LoD was 0.15 ng/mL for the standard assay and 0.1 ng/mL for the antivenom difference method. In 11 pre-antivenom samples the median venom concentration was 10 ng/mL (Range: 0.3-3212 ng/mL). In four patients with incomplete venom-induced consumption coagulopathy the median venom concentration was 2.4 ng/mL compared to 30 ng/mL in seven patients with complete venom-induced consumption coagulopathy. No venom was detected in any post-antivenom sample and the median antivenom dose prior to this first post-antivenom sample was 1.5 vials (1-3 vials), including 7 patients administered only 1 vial. In rats the assay distinguished a 3-fold difference in venom dose administered and there was small inter-individual variability. There was small but measurable cross-reactivity with black snake (Pseudechis), tiger snake (Notechis) and rough-scale snake (Tropidechis carinatus) venoms with the assay for low venom concentrations (<1 ng/mL). The use of biotinylation and the antivenom difference method in venom EIA produces a highly sensitive assay that will be useful for determining antivenom dose, forensic and clinical diagnosis.

Antivenom efficacy or effectiveness: the Australian experience

Despite widespread use of antivenoms, many questions remain about their effectiveness in the clinical setting. The almost universal acceptance of their value is based mainly on in vitro studies, animal studies and human observational studies. Numerous examples exist where they demonstrate clear benefit, such as consumption coagulopathy in viper envenoming, prevention of neurotoxicity in Australasian elapid bites, systemic effects in scorpion and funnel-web spider envenoming. There are also concerns about the quality and efficacy of some antivenoms. However, it is important not to confuse the efficacy of antivenom, defined as its ability to bind and neutralise venom-mediated effects under ideal conditions, and the effectiveness of antivenom, defined as its ability to reverse or prevent envenoming in human cases. There are numerous potential reasons for antivenom failure in human envenoming, of which antivenom inefficacy is only one. Other important reasons include venom-mediated effects being irreversible, antivenom being unable to reach the site of toxin-mediated injury, or the rapidity of onset of venom-mediated effects. A number of recent studies in Australia bring into question the effectiveness of some antivenoms, including snake antivenom for coagulopathy, redback spider and box jellyfish antivenoms. Despite brown snake antivenom being able to neutralise venom induced clotting in vitro, use of the antivenom in human envenoming does not appear to change the time course of coagulopathy. However, it is important that apparent antivenom ineffectiveness in specific cases is correctly interpreted and does not lead to a universal belief that antivenom is ineffective. It should rather encourage further studies to investigate the underlying pathophysiology of envenoming, the pharmacokinetics of venoms and antivenoms, and ultimately the effectiveness of antivenom based on snake type, clinical effects and timing of administration.