Excessive fibrinolysis: the coagulopathy following Merrem's hump-nosed viper (Hypnale hypnale) bites

Diagnostic characteristics of the 20-minute whole blood clotting test in detecting venom-induced consumptive coagulopathy following carpet viper envenoming

INTRODUCTION

Envenoming by Echis spp. (carpet or saw-scaled vipers) causes haemorrhage and coagulopathy and represents a significant proportion of snakebites in the savannah regions of West Africa. Early diagnosis of envenoming is crucial in the management of these patients and there is limited evidence on the utility of the 20-minute whole blood clotting test (20WBCT) in diagnosing venom-induced consumptive coagulopathy (VICC) following envenoming by Echis ocellatus.

METHODS

A prospective observational cohort study was conducted at the Kaltungo General Hospital in North-eastern Nigeria from September 2019 to September 2021. Standardised 20WBCTs were conducted by trained hospital staff and citrated plasma samples were collected at numerous timepoints. Prothrombin time (PT) and international normalised ratio (INR) were determined using a semi-automated analyser and INR values were calculated using international sensitivity indices (ISI). The sensitivity, specificity, positive predictive values (PPV), negative predictive values (NPV), and likelihood ratios of the 20WBCT compared to an INR ≥ 1.4 were calculated, alongside 95% confidence intervals.

RESULTS

We enrolled 121 patients into our study, with a median age of 26 (18.0-35.0) years and a male predominance (75.2%). The 20WBCT was positive (abnormal) in 101 out of 121 patients at timepoint 0h, of which 95 had an INR ≥ 1.4, giving a sensitivity of 87.2% (95%CI 79.4-92.8). Among patients with a negative 20WBCT (normal), six had an INR < 1.4 giving a specificity of 50% (95%CI 21.1-78.9%). The positive and negative likelihood ratios were 1.7 (95%CI 1.6-1.9) and 0.3 (95%CI 0.1-0.4) respectively.

CONCLUSION

The 20WBCT is a simple, cheap, and easily accessible bedside test with a high sensitivity for the detection of patients with venom induced consumptive coagulopathy (VICC) following envenoming by E. ocellatus, although false positives do occur. Repeated 20WBCTs can identify patients with new, persistent, and rebound coagulopathy.

Venom induced consumption coagulopathy and performance of 20-min whole blood clotting test for its detection in viperid envenomation

Background:

Venom induced consumption coagulopathy (VICC) and its underlying mechanisms have not been fully elucidated in viperid envenomation (VE), especially among Indian patients. We evaluated for VICC in VE, assessed the performance of 20-min whole blood clotting test (20WBCT) for VICC detection and also studied predictors of VICC.

Methods:

This hospital-based observational study enrolled 103 consecutive patients (age ⩾ 12 years) of snakebite admitted within 24 h of bite, with features of VE. They underwent 20WBCT, prothrombin time (PT)/international normalised ratio (INR), plasma fibrinogen and D-dimer testing during first 24 h after enrolment. Overt VICC (defined by overt bleeding), subclinical VICC (INR ⩾ 1.4 and/or fibrinogen < 2g/L, without overt bleeding), disseminated intravascular coagulation (DIC) (overt/non-overt, defined based on International Society on Thrombosis and Haemostasis (ISTH) DIC score) and primary defibrination (PDF) were evaluated among patients.

Results:

VICC overall was noted in 77 (≈75%) and overt VICC in 52 (≈50%). DIC (overt/non-overt) was noted in 59 (≈77%) and PDF in 2 (2.6%) patients with VICC. Sensitivity, specificity, positive predictive value and negative predictive value of 20WBCT for VICC detection were 98.7% (95%CI: 92.9–99.9%), 65.4% (95%CI: 44.3–82.8%), 89.4% (95%CI: 83.3–93.5%) and 94.4% (95%CI: 70.4–99.2%) respectively. Severe cellulitis in bitten limb predicted reduced VICC risk.

Conclusion:

Majority (75%) of patients with VE had VICC and 68% with VICC had overt bleeding. DIC (overt/non-overt) was the predominant contributor to VICC. Though 20WBCT is a good screening test for VICC, false positive results should be kept in mind before deciding on snake antivenom treatment.

A comparative cross-reactivity and paraspecific neutralization study on Hypnale hypnale, Echis carinatus, and Daboia russelii monovalent and therapeutic polyvalent anti-venoms

Envenoming by the hump-nosed pit viper (Hypnale hypnale) raises concern as it inflicts significant debilitation and death in the Western Ghats of India and in the adjacent island nation of Sri Lanka. In India, its medical significance was realized only during 2007 due to its misidentification as Echis carinatus and sometimes as Daboia russelii. Of late, several case reports have underlined the ineptness of the existing polyvalent anti-venom therapy against H. hypnale envenoming. Currently, H. hypnale bite has remained dreadful in India due to the lack of neutralizing anti-venom therapy. Hence, this study was undertaken to establish a systematic comparative, biochemical, pathological, and immunological properties of Sri Lankan H. hypnale venom alongside Indian E. carinatus, and D. russelii venoms. All three venoms differed markedly in the extent of biochemical activities including proteolytic, deoxyribonuclease, L-amino acid oxidase, 5'-nucleotidase, hyaluronidase, and indirect hemolytic activities. The venoms also differed markedly in their pathological properties such as edema, hemorrhage, myotoxic, cardiotoxic, and coagulant activities. The venoms showed stark differences in their protein banding pattern. Strikingly, the affinity-purified rabbit monovalent anti-venoms prepared against H. hypnale, E. carinatus, and D. russelii venoms readily reacted and neutralized the biochemical and pathological properties of their respective venoms, but they insignificantly cross-reacted with, and thus failed to show paraspecific neutralization of any of the effects of the other two venoms, demonstrating the large degree of variations between these venoms. Further, the Indian therapeutic polyvalent anti-venoms from VINS Bioproducts, and Bharath Serums and Vaccines failed to protect H. hypnale venom-induced lethal effects in mice.

Hypnale coagulopathy: snake envenomation of a different kind

Hypnale hypnale is a small pit viper that is known as the hump-nosed pit viper (HNV) or 'Merrem's hump-nosed pit viper' and is endemic to Sri Lanka and the Western Ghats of South India. Previously, it was thought that this viper bite would result in mild systemic or local envenomation, however, we now know that HNV bites could cause severe systemic toxicity and mortality. The most common systemic toxicity of this viper envenomation is coagulopathy, which is known as 'Hypnale coagulopathy'. Hypnale coagulopathy is quite different from the haemotoxicity caused by other vipers. In this paper, an effort has been made to discuss the unique and unpredictable nature of this coagulopathy due to Hypnale envenomation.

Hump-nosed pit viper (Hypnale hypnale and Hypnale zara) envenoming in Deniyaya, Sri Lanka: Epidemiological and clinical features from a prospective observational study

Hypnale hypnale, Hypnale zara and Hypnale nepa are the three species of Hump nosed pit vipers that are implicated in human bites in Sri Lanka. H. zara and H. nepa are two endemic species to the country. The objective of the study was to characterize epidemiology and clinical features after different Hump nosed pit viper species bites. A prospective observational study was conducted in Base Hospital Deniyaya from 2013 to 2015. Hump nosed pit viper as the offending snake was identified when the victims brought live or dead specimens. Species identification of dead specimen was done by a herpetologist. Clinical details were recorded during the hospital stay. 83 Hump nosed pit viper bite patients (19-81 years) were studied. Fifty two dead specimens were identified as 39 of H. zara and 13 of H. hypnale by the herpetologist. No H. nepa was identified. Thirty one live snakes were identified as Hump nosed pit vipers and released in to the wild. Envenoming was reported throughout the year. Eighty (96.4%) were daytime bites. Hands (43.4%), feet (55.4%) and arms (1.2%) were affected sites. Sixty two (74.7%) were bitten in tea plantations. All had pain over bite site. Overall, sixty nine (83.1%) had local swelling, seven (8.4%) extensive limb swelling, nineteen (22.9%) haemorrhagic blisters, and seven (8.4%) regional lymphadenopathy. Four (4.8%) patients had incoagulable blood by 20WBCT. H. zara bites had 28.2% haemorrhagic blisters, 7.7% extensive limb swelling and 2.6% coagulopathy. H. hypnale bites had 7.7% each extensive limb swelling and coagulopathy and 23.1% haemorrhagic blisters. None developed elevated serum creatinine. Neurotoxicity was not noted. Hump nosed pit viper bites caused substantial morbidity. Risk factors included day time outdoor activities and occupation. Pain, extensive limb swelling, bite site swelling, haemorrhagic blisters, regional lymphadenopathy and coagulopathy were prominent clinical features. Nephrotoxicity and neurotoxicity were notably absent. Clinical features varied depending on the species implicated.

Bedside Coagulation Tests in Diagnosing Venom-Induced Consumption Coagulopathy in Snakebite

Venom-induced consumption coagulopathy is the most important systemic effect of snake envenoming. Coagulation tests are helpful to accurately and promptly diagnose venom-induced consumption coagulopathy and administer antivenom, which is the only specific treatment available. However, bedside clotting tests play a major role in diagnosing coagulopathy in low-income settings, where the majority of snakebites occur. We conducted a literature search in MEDLINE^® from 1946 to 30 November 2019, looking for research articles describing clinical studies on bedside coagulation tests in snakebite patients. Out of 442 articles identified, 147 articles describing bedside clotting assays were included in the review. Three main bedside clotting tests were identified, namely the Lee–White clotting test, 20-min whole blood clotting time and venous clotting time. Although the original Lee–White clotting test has never been validated for snake envenoming, a recently validated version has been used in some South American countries. The 20-min whole blood clotting time test is the most commonly used test in a wide range of settings and for taxonomically diverse snake species. Venous clotting time is almost exclusively used in Thailand. Many validation studies have methodological limitations, including small sample size, lack of case-authentication, the inclusion of a heterogeneous mix of snakebites and inappropriate uses of gold standard tests. The observation times for bedside clotting tests were arbitrary, without proper scientific justification. Future research needs to focus on improving the existing 20-min whole blood clotting test, and also on looking for alternative bedside coagulation tests which are cheap, reliable and quicker.

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.

Venom-Induced Consumption Coagulopathy Following Hump-Nosed Pit Viper (Genus: Hypnale) Envenoming in Sri Lanka: Uncertain Efficacy of Fresh Frozen Plasma

INTRODUCTION

Hump-nosed pit vipers (Hypnale spp) cause the highest number of venomous snakebites in Sri Lanka. Bites commonly cause local envenoming leading to local pain, swelling, and necrosis of the site of the bite. Acute kidney injury is the most common systemic manifestation, and some patients develop venom-induced consumption coagulopathy (VICC). Genus Hypnale comprises 3 species. Of them, H hypnale is found in Sri Lanka and the Western Ghats region of India. The other 2 (H nepa and H zara) are endemic species in Sri Lanka.

METHODS

This study included 500 patients with hump-nosed viper bites studied prospectively over 4.5 y starting June 2014. All patients were assessed and the data were collected by the principal investigator (primary data). A subgroup of patients who developed VICC is described. There were 2 groups, including proven (patients with the specimen of the snake) and probable (specimen of snake not available) bites.

RESULTS

Thirty (n=500; 6%) patients developed VICC; of them, 17 (3%) were proven cases, and 13 (2%) were probable cases. In both groups, 24 (80%) recovered, 2 (7%) progressed to chronic kidney disease, 1 (3%) died of severe hemostatic dysfunction, and 3 (10%) were lost to follow-up. Systemic bleeding was observed in 16 patients (53%), including hematuria (microscopic and gross) in 8 (27%) and venipuncture bleeding in 5 (17%). Eleven (37%) developed local bleeding at the site of the bite. Fresh frozen plasma was administered to 20 patients (67%), among whom only 11 (55%) experienced early correction of VICC. In both groups, 15 (50%) developed acute kidney injury, and 2 (7%) progressed to chronic kidney disease. Microangiopathic hemolysis was observed in 18 patients (60%) and thrombocytopenia in 16 (53%). Thrombotic microangiopathy was detected in 13 patients (43%), of whom 10 (33%) developed hemolytic uremic syndrome and 2 (7%) had thrombotic thrombocytopenic purpura. Of patients with VICC in the proven group, 94% (n=16) was caused by H hypnale and 1 (6%) was caused by H zara. In the proven group, median international normalized ratio was 3.7 (interquartile range 1.6-5.0); in the probable group, it was 5.0 (interquartile range 2.1-5.4).

CONCLUSIONS

We found that 6% of patients develop hemostatic dysfunction after hump-nosed viper bites. However, which patients will develop coagulopathy or die of envenoming is unpredictable. Reliable and accessible treatments are unmet essential needs because antivenoms for these bites are currently not available in the country. Therapy with fresh frozen plasma has doubtful efficacy in early correction of VICC and needs further evaluation.

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.

Clinical implications of differential antivenom efficacy in neutralising coagulotoxicity produced by venoms from species within the arboreal viperid snake genus Trimeresurus

Snake envenomation globally is attributed to an ever-increasing human population encroaching into snake territories. Responsible for many bites in Asia is the widespread genus Trimeresurus. While bites lead to haemorrhage, only a few species have had their venoms examined in detail. We found that Trimeresurus venom causes haemorrhaging by cleaving fibrinogen in a pseudo-procoagulation manner to produce weak, unstable, short-lived fibrin clots ultimately resulting in an overall anticoagulant effect due to fibrinogen depletion. The monovalent antivenom 'Thai Red Cross Green Pit Viper antivenin', varied in efficacy ranging from excellent neutralisation of T. albolabris venom through to T. gumprechti and T. mcgregori being poorly neutralised and T. hageni being unrecognised by the antivenom. While the results showing excellent neutralisation of some non-T. albolabris venoms (such as T. flavomaculaturs, T. fucatus, and T. macrops) needs to be confirmed with in vivo tests, conversely the antivenom failure T. hageni, and the very poor results against T. gumprechti and T. mcgregori, despite being conducted in the ideal scenario of preincubation of antivenom:venom, indicates that the likelihood of clinically relevant cross-reactivity for these species is low (T. gumprechti and T. mcgregori) to non-existent (T. hageni). These same latter three species were also not inhibited by the serine protease inhibitor AEBSF, suggesting that the toxins leading to a coagulotoxic effect in these species are non-serine proteases while in contrast T. albolabris coagulotoxicity was completely impeded by AEBSF, and thus driven by kallikrein-type serine proteases. There was a conspicuous lack of phylogenetic pattern in venom variation, with the most potent venoms (T. albolabris and T. hageni) being distant to each other on the organismal tree, and with the three most divergent and poorly neutralised venoms (T. gumprechti, T. hageni, and T. mcgregori) were also not each others closest relatives. This reinforces the paradigm that the fundamental dynamic evolution of venom results in organismal phylogeny being a poor predictor of venom potency or antivenom efficacy. This study provides a robust investigation on the differential venom effects from a wide range of Trimeresurus species on coagulation, highlighting differential fibrinogenolytic effects, while also investigating the relative antivenom neutralisation capabilities of the widely available Thai Red Cross Green Pit Viper antivenom. These results therefore have immediate, real-world implications for patients envenomed by Trimeresurus species.

Basal but divergent: Clinical implications of differential coagulotoxicity in a clade of Asian vipers

Envenomations by Asian pitvipers can induce multiple clinical complications resulting from coagulopathic and neuropathic effects. While intense research has been undertaken for some species, functional coagulopathic effects have been neglected. As these species' venoms affect the blood coagulation cascade we investigated their effects upon the human clotting cascade using venoms of species from the Azemiops, Calloselasma, Deinagkistrodon and Hypnale genera. Calloselasma rhodostoma, Deinagkistrodon acutus, and Hypnale hypnale produced net anticoagulant effects through pseudo-procoagulant clotting of fibrinogen, resulting in weak, unstable, transient fibrin clots. Tropidolaemus wagleri was only weakly pseudo-procoagulant, clotting fibrinogen with only a negligible net anticoagulant effect. Azemiops feae and Tropidolaemus subannulatus did not affect clotting. This is the first study to examine in a phylogenetic context the coagulotoxic effects of related genera of basal Asiatic pit-vipers. The results reveal substantial variation between sister genera, providing crucial information about clinical effects and implications for antivenom cross-reactivity.

Cardiac arrest and atrial fibrillation in a patient after hump-nosed pit viper (Hypnale hypnale) bite

A 42-year-old previously healthy male patient died 16 days after a proven hump-nosed pit viper (Hypnale hypnale) envenoming due to multi-organ failure. On admission he had cardiac arrest that recovered from cardiopulmonary resuscitation then developed atrial fibrillation which was reverted to normal rhythm by application of synchronized electrical cardioversion. He also had persistent coagulopathy and thrombotic microangiopathy comprising the triad of microangiopathic haemolysis, acute kidney injury and thrombocytopenia. This is the second reported case with cardiac complications following hump-nosed pit viper bites in Sri Lanka.

Development of a new polyspecific antivenom for snakebite envenoming in Sri Lanka: Analysis of its preclinical efficacy as compared to a currently available antivenom

A new whole IgG, freeze-dried, polyspecific antivenom was prepared from the plasma of horses immunized with the venoms of the snakes Daboia russelii, Echis carinatus, Hypnale hypnale, and Naja naja from Sri Lanka. The preclinical neutralizing ability of this antivenom against several toxic and enzymatic activities of these four venoms was analyzed, and compared with that of a batch of VINS antivenom (India) being currently used in Sri Lanka. The activities tested were: lethality, hemorrhagic, in vitro coagulant, proteinase and phospholipase A₂. Both antivenoms neutralized, to a different extent, these activities of the venom of D. russelii, E. carinatus, and N. naja. In general, the polyspecific Sri Lankan antivenom was more effective than the Indian antivenom in the neutralization of the venoms of D. russelii and E. carinatus, whereas the Indian antivenom showed a higher efficacy against the venom of N. naja. Regarding H. hypnale, the new Sri Lankan antivenom was effective in the neutralization of all activities tested, whereas the Indian antivenom neutralized lethality but not hemorrhagic, coagulant, proteinase and PLA₂ activities, in agreement with the fact that this venom is not included in the immunization mixture for this antivenom. Results suggest that the new polyspecific Sri Lankan antivenom has a satisfactory preclinical neutralizing profile and compares favorably with the Indian antivenom. This is ready to be tested in a clinical trial to evaluate its efficacy and safety in human victims of snakebite envenomings by D. russelii, E. carinatus and H. hypnale in Sri Lanka.

Proteomic investigation of Sri Lankan hump-nosed pit viper (Hypnale hypnale) venom

The hump-nosed pit viper, Hypanle hypnale, contributes to snakebite mortality and morbidity in Sri Lanka. Studies showed that the venom is hemotoxic and nephrotoxic, with some biochemical and antigenic properties similar to the venom of Calloselasma rhodostoma (Malayan pit viper). To further characterize the complexity composition of the venom, we investigated the proteome of a pooled venom sample from >10 Sri Lankan H. hypnale with reverse-phase high performance liquid chromatography (rp-HPLC), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and peptide sequencing (tandem mass-spectrometry and/or N-terminal sequencing). The findings ascertained that two phospholipase A2 subtypes (E6-PLA2, W6-PLA2) dominate the toxin composition by 40.1%, followed by snake venom metalloproteases (36.9%), l-amino acid oxidase (11.9%), C-type lectins (5.5%), serine proteases (3.3%) and others (2.3%). The presence of the major toxins correlates with the venom's major pathogenic effects, indicating these to be the principal target toxins for antivenom neutralization. This study supports the previous finding of PLA2 dominance in the venom but diverges from the view that H. hypnale venom has low expression of large enzymatic toxins. The knowledge of the composition and abundance of toxins is essential to elucidate the pathophysiology of H. hypnale envenomation and to optimize antivenom formulation in the future.

Presumptive thrombotic thrombocytopenic purpura following a hump-nosed viper (Hypnale hypnale) bite: a case report

Hump-nosed viper bites are frequent in southern India and Sri Lanka. However, the published literature on this snakebite is limited and its venom composition is not well characterized. In this case, we report a patient with thrombotic thrombocytopenic purpura-like syndrome following envenoming which, to the best of our knowledge, has not been reported in the literature before. A 55-year-old woman from southern Sri Lanka presented to the local hospital 12 hours after a hump-nosed viper (Hypnale hypnale) bite. Five days later, she developed a syndrome that was characteristic of thrombotic thrombocytopenic purpura with fever, thrombocytopenia, microangiopathic hemolysis, renal impairment and neurological dysfunction in the form of confusion and coma. Her clinical syndrome and relevant laboratory parameters improved after she was treated with therapeutic plasma exchange. We compared our observations on this patient with the current literature and concluded that thrombotic thrombocytopenic purpura is a theoretically plausible yet unreported manifestation of hump-nosed viper bite up to this moment. This study also provides an important message for clinicians to look out for this complication in hump-nosed viper bites since timely treatment can be lifesaving.

Hump-nosed viper bite: an important but under-recognized cause of systemic envenoming

Hump-nosed viper bites are common in the Indian subcontinent. In the past, hump-nosed vipers (Hypnale species) were considered moderately venomous snakes whose bites result mainly in local envenoming. However, a variety of severe local effects, hemostatic dysfunction, microangiopathic hemolysis, kidney injury and death have been reported following envenoming by Hypnale species. We systematically reviewed the medical literature on the epidemiology, toxin profile, diagnosis, and clinical, laboratory and postmortem features of hump-nosed viper envenoming, and highlight the need for development of an effective antivenom.

Hump-nosed pit viper (Hypnale hypnale) envenoming causes mild coagulopathy with incomplete clotting factor consumption

CONTEXT

Limited information exists on the coagulopathy caused by hump-nosed pit viper (Hypnale hypnale) envenoming.

OBJECTIVES

This study aimed to characterise the coagulopathy in hump-nosed pit viper bites by measuring laboratory clotting times and factor studies.

MATERIALS AND METHODS

Cases of hump-nosed pit viper envenoming were included from a prospective cohort study of Sri Lankan snake-bite patients. Patient age, sex, snake identification, time of bite and clinical effects were recorded. Patients did not receive anti-venom because no specific anti-venom to hump-nosed vipers exists. All patients received supportive care and serial 20-min whole blood clotting tests (WBCT20). The prothrombin time (PT), international normalised ratio (INR), activated partial thromboplastin time (aPTT), coagulation factors I, II, V, VII, VIII, IX and X, von Willebrand factor (vWF) antigen and D-Dimer concentrations were measured. The median of highest or lowest test result for each patient was reported with interquartile range (IQR). Results. There were 80 hump-nosed pit viper bites, median age was 37 years (IQR: 26-51 years) and 48 were male. The WBCT20 was positive in one patient. The median highest INR was 1.9 (1.5-2.2; Range: 1.3 to > 12) and median highest aPTT was 54 s (46-72 s; Range: 35-170 s). There was low fibrinogen [median: 1.3 g/L;1, -1.8 g/L; Range: < 0.2-2.9], low factor VIII levels [median: 23%; 16-37%] and low factor V levels [median: 43%; 23-74%]. D-Dimer concentrations [median: 3.4 mg/L; 2-7.4 mg/L] were slightly elevated. Factors II, VII and X and vWF antigen concentrations were normal.

DISCUSSION AND CONCLUSIONS

Hump-nosed pit viper bites result in a mild coagulopathy which is usually not detected by a WBCT20. It is characterised by mild elevation of INR, low fibrinogen and Factors V and VIII which may be consistent with the venom containing a thrombin-like enzyme.

Type IV renal tubular acidosis following resolution of acute kidney injury and disseminated intravascular coagulation due to hump-nosed viper bite

Hump-nosed viper bite can cause acute kidney injury (AKI) and disseminated intravascular coagulation. In some patients, it can cause chronic kidney disease necessitating life-long renal replacement therapy. Lack of effective antivenom makes the management of these patients difficult. A 51-year-old Sri Lankan male was admitted with AKI and disseminated intravascular coagulation following a hump-nosed viper bite. He made a complete recovery with blood product support and hemodialysis. Renal biopsy was performed as his renal recovery was prolonged which revealed patchy tubular atrophy and interstitial inflammation suggestive of subacute interstitial nephritis. Later, he presented with hyperkalemic paralysis and acidosis. A diagnosis of late onset type 4 renal tubular acidosis was made and he responded well to a course of fludrocortisone.

Acute ischemic stroke following Hump-nosed viper envenoming; first authenticated case

Hump-nosed pit viper (Genus Hypnale) is a medically important venomous snake in Sri Lanka and Southwestern India which causes significant morbidity and mortality. Envenoming of this snake results in hemostastic dysfunction, thrombotic microangiopathy, acute kidney injury and death. This case describes an authenticated first case of ischemic stroke in a 65 year old male following envenoming by H.hypnale in Sri Lanka.

Haemolytic uremic syndrome a hitherto unreported complication of humpnosed viper envenomation

Merrem's humpnosed viper bite is known to cause incoagulable blood, acute renal failure, acute respiratory distress syndrome, Raynaud's phenomenon and gangrene of the distal limb. Venom-induced consumptive coagulopathy (VICC) is the commonest coagulopathy that occurs following snake envenomation which is characterised by prolonged clotting times. In a small proportion of patients with VICC, microangiopathy is also seen. The authors report a novel case of haemolytic uraemic syndrome following a merrem's humpnosed viper bite, which highlights the need for comprehensive and serial haematological evaluation to detect the condition and initiate timely plasma exchange. The authors recommend screening of all victims of humpnosed viper bite for haemolytic uremic syndrome which might otherwise be overlooked and stress the need for further studies to see the role of haemolytic uremic syndrome following humpnosed viper bite.

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.

Chronic kidney disease in snake envenomed patients with acute kidney injury in Sri Lanka: a descriptive study

BACKGROUND

Data on the long-term outcomes of acute kidney injury (AKI) in envenomed patients leading to chronic kidney disease (CKD) are scarce. The aim of the study was to investigate this issue and to determine the predictive factors in developing CKD.

METHODS

The records of a series of 54 patients who had AKI following a snakebite during the period 2004-2009 and who had been followed up were reviewed in the nephrology unit, Kandy, Sri Lanka. The primary outcome measure was the failure of renal functions to return to normal within 1 year. The renal histology was studied in seven patients.

RESULTS

The mean age of the group was 50 years (SD 13 years) and 39 (72%) patients were men. The offending snakes were Russell's viper and hump-nosed viper in 15 (28%) and 13 (24%) patients, respectively. At 1 year, 20 patients (37%) had developed CKD (CKD group) and the rest (63%) had recovered (recovered group). The acute stage serum creatinine was high in both groups with no difference (on admission, p=0.134; on discharge, p=0.323), but the CKD group showed significantly high serum creatinine at 2 months after AKI (p=0.004). Mean duration of renal replacement therapy (RRT) of the recovered group and CKD group were 7 (SD 5) and 16 (SD 12) days, respectively (p=0.015). Renal histology of six CKD patients showed predominant glomerular sclerosis and interstitial nephritis.

CONCLUSIONS

CKD is an outcome of severe AKI following snake envenoming probably predicted by the length of RRT.

Inadequacy of present polyspecific anti snakevenom - a study from central Kerala

OBJECTIVES

To study the cause for prolonged coagulation profile and death in properly treated hemotoxic snake envenomation and the bad prognostic indicators in snake envenomation.

METHODS

This was a hospital based prospective analytical study. All snake bites with envenomation from 2006 through 2009 were clinically analysed at the time of admission. They were treated with standard treatment protocol. Snakes brought were preserved, identified and correlated with clinical details.

RESULTS

Of the 73 envenomation patients registered, 66 (90.4%) were hemotoxic envenomation, in which 14 (19.2%) had late recovery and 11 (15.1%) expired mainly due to hemorrhagic complication. The incidence of late recovery and mortality is higher compared to other Indian studies. Ten snakes were brought during the period along with the victims. Three of them were identified as hump nosed pit vipers, of which two victims had late recovery and one expired.

CONCLUSIONS

Hump nosed pit viper envenomation is not rare in Kerala and can cause death, unlike the earlier belief. Available anti snake venoms does not cover pit viper. So, antivenom for this snake is urgently required.

Parallels between Russell's viper (Daboia russelii) and hump-nosed viper (Hypnale species) bites in the central hills of Sri Lanka amidst the heavy burden of unidentified snake bites

OBJECTIVE

To describe the epidemiology of snake bite in the region and attempt to compare proven Russell's viper with hump-nosed viper bites.

METHODS

All snake bite admissions to the Toxicology Unit of Teaching Hospital Peradeniya over three year from 2006 were included.

RESULTS

Of the 776 snakebites, 665(86%) were unidentified and non-envenomed. Hump-nosed viper and Russell's viper accounted for 55(7%) and 40(5%) bites respectively, of them, incriminated snakes were found in 36(65%) and 19(48%) cases. The cobra bites-5, krait bites-0. The median ages: Russell's viper bites-41(range 16-66), hump-nosed viper bites-42(range 15-75). The gender incidence, time of bite (>58% daytime) were similar. In hump-nosed viper bite; upper limb involved in 13(36%), happened at home garden in 22(61%), none in paddy fields. In Russell's viper bite; 6(33%) occurred in paddy fields. Dry bites were similar at 5%. In hump-nosed viper bite: local effects 94%, coagulopathy 3%, acute renal failure 3% and one patient died. In Russell's viper bite; local effects 84%, coagulopathy 53%, neurotoxicity 21%. Abdominal pain occurred only in Russell's viper bites 10(53%).

CONCLUSIONS

Overwhelming numbers of unidentified, non-envenomed snakebites are common in the central hills. Some distinctive differences were observed between Russell's viper and hump-nosed viper bites.

Cross neutralization of Hypnale hypnale (hump-nosed pit viper) venom by polyvalent and monovalent Malayan pit viper antivenoms in vitro and in a rodent model

Hypnale hypnale (hump-nosed pit viper) is a medically important venomous snake in Sri Lanka and Southwestern India. Bite of this snake may result in hemostatic dysfunction, acute kidney injury and death. Clinical studies indicated that the locally available polyvalent antivenoms produced in India are not effective against hump-nosed pit viper envenoming. Hence, there is an urgent need to search for effective antivenom. In this paper, we examined the ability of Calloselasma rhodostoma (Malayan pit viper) monovalent antivenom and the Hemato polyvalent antivenom (both produced by Thai Red Cross Society, TRCS) to neutralize the lethality and toxic effects of H. hypnale venom, as C. rhodostoma is considered a sister taxon of H. hypnale. In vitro neutralization studies showed that the Hemato polyvalent antivenom effectively neutralized the lethality of H. hypnale venom (1.52mgvenom/mL antivenom) as well as the hemorrhagic, procoagulant and necrotic activities of the venom. The monovalent C. rhodostoma antivenom could also neutralize the lethality and toxic activities of the venom, but the potency was lower. The Hemato polyvalent antivenom also effectively protected mice from the lethal and local effects of H. hypnale venom in an in vivo rodent model of envenoming. Furthermore, the polyvalent antivenom could also effectively neutralize the venom of Daboia russelii (2.50mgvenom/mL antivenom), another common cause of snake bites in Sri Lanka and South India. These findings suggested that the Hemato polyvalent antivenom may be beneficial in the antivenom treatment of H. hypnale envenoming.

Snake bite in South Asia: a review

Snake bite is one of the most neglected public health issues in poor rural communities living in the tropics. Because of serious misreporting, the true worldwide burden of snake bite is not known. South Asia is the world's most heavily affected region, due to its high population density, widespread agricultural activities, numerous venomous snake species and lack of functional snake bite control programs. Despite increasing knowledge of snake venoms' composition and mode of action, good understanding of clinical features of envenoming and sufficient production of antivenom by Indian manufacturers, snake bite management remains unsatisfactory in this region. Field diagnostic tests for snake species identification do not exist and treatment mainly relies on the administration of antivenoms that do not cover all of the important venomous snakes of the region. Care-givers need better training and supervision, and national guidelines should be fed by evidence-based data generated by well-designed research studies. Poorly informed rural populations often apply inappropriate first-aid measures and vital time is lost before the victim is transported to a treatment centre, where cost of treatment can constitute an additional hurdle. The deficiency of snake bite management in South Asia is multi-causal and requires joint collaborative efforts from researchers, antivenom manufacturers, policy makers, public health authorities and international funders.

First authenticated cases of life-threatening envenoming by the hump-nosed pit viper (Hypnale hypnale) in India

In Kerala, south-western India, five patients developed systemic envenoming after bites by hump-nosed pit vipers (Hypnale hypnale), proved by identification of the snakes responsible. Two of the dead snakes had been misidentified as saw-scaled vipers (Echis carinatus), while three had remained unidentified. Symptoms of local envenoming were pain, swelling, haemorrhagic blistering, bruising and regional lymphadenopathy. Systemic symptoms included headache, nausea, vomiting and abdominal and chest pain. There was evidence of haemostatic dysfunction (coagulopathy, fibrinolysis, thrombocytopenia or spontaneous systemic haemorrhage) in all cases and of microangiopathic haemolysis in two. Two patients were haemodialysed for acute renal failure, one of whom developed pulmonary oedema requiring mechanical ventilation. In India, H. hypnale has not previously been regarded as a cause of frequent or potentially dangerous envenoming. Its medical importance has been overlooked throughout its geographical range, probably because of confusion with other small species. No specific antivenom exists, yet most patients are treated with non-specific antivenoms, risking reactions without hope of benefit. An effective antivenom is urgently needed in south India and in Sri Lanka, where this species is also a common cause of bites.

Identifying the biting species in snakebite by clinical features: an epidemiological tool for community surveys

The outcome of snakebite is related to the biting species but it is often difficult to identify the biting snake, particularly in community settings. We have developed a clinical scoring system suitable for use in epidemiological surveys, with the main aim of identifying the presumed biting species in those with systemic envenoming who require treatment. The score took into account ten features relating to bites of the five medically important snakes in Sri Lanka, and an algorithm was developed applying different weightings for each feature for different species. A systematically developed artificial data set was used to fine tune the score and to develop criteria for definitive identification. The score was prospectively validated using 134 species-confirmed snakebites. It correctly differentiated the bites caused by the three snakes that commonly cause major clinical problems (Russell's viper (RV), kraits and cobra) from other snakes (hump-nosed viper (HNV) and saw-scaled viper (SSV)) with 80% sensitivity and 100% specificity. For individual species, sensitivity and specificity were, respectively: cobra 76%, 99%; kraits 85%, 99%; and RV 70%, 99%. As anticipated, the score was insensitive in the identification of bites due to HNV and SSV.