Snakebite-induced Coagulopathy Ponlapat Rojnuckarin, MD, PhD Chulalongkorn University Elapid Viper Neurotoxin Hematotoxin Un-clotted blood Russell’s viper (Daboia siamensis) Rojnuckarin p Malayan Pit Viper (Calloselasma rhodostoma) Rojnuckarin p Green Pit Vipers in Bangkok Trimeresurus albolabris Trimeresurus macrops Rojnuckarin p Symptoms & signs of viper bites Local Systemic: –Systemic bleeding –Hemolysis –Renal failure Teeth Marks Fang Marks Non-venomous snake Venomous snake Mahasandana S Local effects I Ecchymosis Edema Mahasandana S Local effects II Blister Necrosis Mahasandana S Clinical syndromes 1. Consumptive coagulopathy Factor X/V activators: True vipers (Daboia russelli) Prothrombin activators: True vipers (Echis sp.), Australian elapids (Pseudonaja sp, Oxyurenus sp, Notechis sp), Colubrids (Rhabdophis sp.) Thrombin-like enzymes: most pit vipers 2. Anticoagulant syndrome: Australian elapids (Pseudoechis sp, Acanthophis sp., Austrelaps sp) 3. Thromboembolism: Bothrops lanceolatus, B. caribbaeus 4. Thrombotic microangiopathy: Doaboia russelli, Cerastes cerastes, Protheris superciliaris, Pseudonaja sp, Dispholidus typhus Rojnuckarin P. Toxins and Hemostasis: from Bench to Bedside 2010. Clotting factor activators Extrinsic Tenase TF FVIIa FIXa FVIIIa Intrinsic Tenase Prothrombinase Factor X Factor V activators FXa FVa activators PLASMINOGEN Plasminogen activators PROTHROMBIN THROMBIN Prothrombin PLASMIN activators Fibrinogenolysis FIBRINOGEN FIBRIN FDP Thrombin-like enzymes Rojnuckarin P. Toxins and Hemostasis: from Bench to Bedside 2010. Snake venoms activate the common pathway of coagulation. Russell’s viper Russell’s viper Pit vipers Red-necked Keelback Thrombin-like enzymes Fibrinopeptide A Fibrinopeptide B Fibrinogen Thrombin D E D D E D D E D D E D D E D Firm clot Thrombin-like enzymes Fibrinogen Fibrinopeptide A D E D Thrombin- like D E D D E D Mitrakul C, et al D E D D E D Am J Clin Path 1973 Friable clot Fibrinolysis Green pit viper bites (N = 46) Rojnuckarin et al. Toxicon 1999; 37: 743. Fibrinogenolysis Fibrinopeptide A Fibrinogenolysis Fibrinogen D E D Thrombin- like D E D D E D D E D D E D D E D Friable clot Fibrinolysis Fibrinolytic activation t-PA release Fibrin deposition PAI-1 Plasminogen Plasmin Venom Plasminogen Activator alborhagin Alboagg B Activators Alboagg A Gp VI Gp Ib/IX/V GpIIb/IIIa albolabrin Inhibitor Systemic bleeding from viper bites Hypofibrinogenemia – Thrombin-like enzymes clot fibrinogen in vitro – Activation of fibrinolysis in vivo – Defibrination syndrome Thrombocytopenia – Platelet activation and agglutination in vitro – Activated platelets are cleared from circulation. Metalloproteases damage vessel wall Toxicon 1999; 37: 743, Toxicon 2005; 45: 977 Laboratory – Thrombocytopenia – Hypofibrinogenemia causing prolonged Whole blood clotting time, thrombin time and prothrombin time – Elevated fibrin degradation products (FDPs): Usually not tested Whole blood clotting time Sribunruang S Partially clotted may be mistaken as un-clotted VCT. Slow recovery of fibrinogen (HL 4 days) Venous clotting time (VCT) Available in community hospitals Therapeutic laboratory – Not too sensitive – Require antivenom, if prolonged WHO recommends 20 min WBCT – One tube and tilted only once at 20 min Prothrombin time Automated and Better standardized Study in Green pit viper bite (N=97) Fibrinogen < 100 mg/dL (Gold standard) Sensitivity Specificity INR>1.2 85.7% 95.6% WBCT 20 85.7% 95.8% (N=55) VCT> 30 57.0% 94.4% Pongpit and Limpawittayakul, et al. TRSTMH 2012; 106; 415 20min WBCT is not sensitive in Russell viper bites •Compared with INR > 1.5 •WBCT has only 40% sensitivity Sensitive to fibrinogen •INR prolongation due to Common pathway defects? •PT is better than WBCT. Isbister GK et al. QJM 2013 20min WBCT done by trained personnel is still not sensitive. •RV and Hump nose viper •N = 987 •8% Coagulopathy •Compared with INR > 1.4 •WBCT had 82% sensitivity 98% specificity Thromb Haemost 2017; 117: 500 POC-INR is not useful in Australian snakebites (N = 15). False Negative False Positive 3 = Afibrinogenemia Thromb Res 2013; 132: 610 Slow Onset of Toxicity (n=213) 54.9% 84% 94.4% 95.8% 98.6% 100% 120 100 80 >90% 60 within 3 days 40 20 0 24 48 72 96 120 144 Hours Rojnuckarin P, et al. J Hematology Trans Med 1996 GPV venom kinetics (Individual patients, n = 27) ng/ml Rojnuckarin & Bunchongkit Trop Doct 2007; 37: 207 18 16 14 Long half life 12 Some Detectable venom on d14 Wait for spontaneous recovery: Not recommended 10 8 6 Venom4 levels 2 0 0 1 2 3 4 5 6 7 8 Tim e after bites ( d a y ) SYSTEMIC BLEEDING (GPV; n=37) GUM HEMATEMESIS HEMATURIA PETECHIAE HEMOPTYSIS PER VAGINA MELENA HEMATOCHEZIA SUBCONJUNCTIVA EPISTAXIS Multiple sites 54.1% Rojnuckarin P, et al. Thai J Hematology Trans Med 1996 Hemolysis in Russell’s viper bites from Phospholipases J Nat toxins 1998; 7: 73-85, Toxin and Hemostasis 2010 Russell’s viper venom: Nephrotoxicity Decreased renal blood flow (hypotension, renal vasoconstriction) Thamaree, et al. Nephron 1994;67:209 Tungthanathanich, et al. Toxicon 1986;24:365 Thamaree, et al. J Nat Toxins 2000;9:43 Microthrombi in glomerulus Suntravat et al. Toxicon 2011; 58: 230 Direct nephrotoxicity Ratcliffe, et al. Am J Trop Med Hyg 1989;40:312 Interstitial nephritis Sitprija V, et al. Am J Trop Med Hyg 1982;31:408 Geographical variations of Russell’s viper bites Sri Lanka India Myanmar Thailand Coagulation + ++ ++ ++ Renal failure ++ + ++ + Pituitary - + ++ - infarction Hemolysis ++ + - + Neurotoxicity ++ + - - Edema - - ++ - Shock - + ++ - Variations of preys Trans Royal Soc Trop Med Hyg 1989; 83: 732 First Aids: Pressure immobilization Not practical for general uses. Do if not delay transportation to hospitals Sribunruang S Management (Viper) Initial evaluation – Physical exam: local & systemic effect – WBCT or PT, platelet count If normal: Follow-up coagulopathy for 3 days (At least twice on the first day) Russell’s Viper : Hydration & force diuresis to prevent renal failure Antivenom is the key treatment . Antivenom to all patients – For rapidly fatal toxin or irreversible damages – Cost and side effects – Only for Malayan kraits Antivenom only to symptomatic patients – 50% are dried bites. – Coagulopathy is promptly reversed. – Antivenom is not helpful for local tissue damages. – All other snakes QSMI Polyvalent Antivenoms Immunize single horse with multiple venoms. For patients with weakness or coagulopathy, respectively Equally effective as monovalent antivenoms but more difficult to produced If not available, may combine multiple monovalent antivenom (More protein load) Queen Soavabha Memorial Institute (QSMI), Thai Red Cross Society Cross-neutralization QSMI Hemato-polyvalent antivenom – C. rhodostoma (Malaysia and Indonesia) – C. purpureomaculatus – D. siamensis (Myanmar) – NOT Tropidolaemus wagleri QSMI Neuro-polyvalent antivenom – Effectively neutralized venoms from many Southeast Asian cobras, kraits and king cobra but less effective for Indian cobra venoms Polyvalent antivenom may recognize common epitopes? Acta Trop 2014; 132: 7. PLOS Neglect Trop Dis 2012; 6: e1672. INDICATIONS for VIPER ANTIVENOM 1. Whole blood clotting time > 20 min. or PT INR > 1.2 2. Systemic Bleeding 3. Severe thrombocytopenia (?50x 109/L) 4. Impending compartment syndrome Repeat q 6 hours until WBCT or PT normal or bleeding stopped Effects on renal failure after RV bites: Still unknown Antivenom Dose Requirement (N=212) Doses 1 Dose = adequate to neutralize a simulated bite 1 dose every 6 h until normal coagulation time Thiansookon & Rojnuckarin. Acta Trop 2008; 105 203-5 Treatment of local effects Corticosteroid has no benefit (Nuchprayoon I) Antibiotic prophylaxis is not recommended (5% infection rate*) Pt with blister: higher risk Tetanus toxoid when normal coagulogram Antivenom – Helpful for severe edema – Not helpful to prevent/treat necrosis *Rojnuckarin P, et al. Am J Trop Hyg 1998 Antivenom can reduce edema. Chuntawibun & Rojnuckarin, TRSTMH 2006; 100: 879 Compartment syndrome Correct coagulopathy with antivenom Consider fasciotomy ? Conservative treatment may be helpful (limb elevation). Characteristics No Antivenom Antivenom P-values (N=163) (N=80) Hours after bite 4.2 7.7 7.6 10 0.004 Edema over 2 joints 18.9% 56.4% 0.000 Ecchymosis 12.2% 37.2% 0.000 Blister 7.9% 21.8% 0.040 Systemic bleeding 0.6% 10% 0.001 Un-clotted VCT 1.8% 98.7% 0.000 Platelet count (x109/L) 264.8 94.2 160.6 96.3 0.135 Necrosis 7.3% 8.9% 0.895 Chotenimitkun and Rojnuckarin, Clin Toxicol 2008; 46:122 Adverse reactions Early adverse reactions (within hrs) – Incidence 3.5-85% – Rash, fever, urticaria, bronchospasm, hypotension, may be fatal. – Major limitation of antivenom Late adverse reactions (Days-wk) – Incidence 4.9-56% – Serum sickness Clin Toxicol 2016; 54: 27 Incidence of early adverse reactions Saovabha F(ab’)2/Caprylic antivenom – 3.5% (9/254) reactions – 2.3 in vipers vs. 12.5% in cobras (p=0.016) ? Related to higher protein load in cobra antivenom (10 vs. 3 vials) 1.2% Hypotention All were skin test negative. Thiansookon & Rojnuckarin. Acta Trop 2008; 105 203-5 CURRENT ANTIVENOM Reactions: Nonspecific protein aggregation Skin test is NOT recommended, but patient observation is required. Pre-medication depends on the incidence. More liberal uses of antivenom Thiansookon & Rojnuckarin Acta Trop 2008; 105 203-5 Conclusion/Future direction PT should be used for viper bites 20-min WBCT when PT is not available. Polyvalent antivenoms are available. Due to lower incidence