Pressure-Immobilization Bandages Delay Toxicity in a Porcine Model of Eastern Coral Snake (Micrurus fulvius fulvius) Envenomation

First aid and pre-hospital practices in snakebite victims: The persistent use of harmful interventions

First aid intervention and pre-hospital (FAPH) practices are common in patients suffering from snakebite envenomation (SBE). In this study, we have reviewed the literature concerning the use of these practices in various regions of the world in the period 1947-2023 based on published prospective studies. A total of 71 publications fulfilled the inclusion criteria. In terms of the total number of patients in all studies that used each FAPH intervention, the most common practice was the application of tourniquets (45.8%). Other FAPH practices described include cuts/incisions (6.7%), the application of a variety of natural or synthetic substances at the bite site (5.6%), and ingestion of natural, usually herbal, remedies (2.9%). Washing the site of the bite was described in 9.1% of patients. There were other less frequent FAPH practices, including suction, splinting-immobilization, pressure-bandage, ice packs, application of a snake/black stone, and administration of alcoholic beverages. There were differences in the extent of application of FAPH interventions in different continents. Tourniquets were highest (55.7%) in Asia. Topical application of various products was common in South America, while pressure-bandage was only reported in Australia. We did not find any statistically significant variations in the frequency of the most frequent FAPH interventions at three-time intervals (before 2006, between 2006 and 2015, and after 2015). Our findings highlight the use of FAPH interventions in patients suffering SBE, some of which are known to be harmful. It is necessary to study these practices to a higher level of geographic granularity, using community-based surveys. Programs tailored to local contexts should be promoted, aimed at avoiding the use of harmful FAPH practices. It is also necessary to assess the efficacy and safety of some interventions through robust preclinical and clinical studies.

Cardiac Effects of Micrurus corallinus and Micrurus dumerilii carinicauda (Elapidae) Venoms and Neutralization by Brazilian Coralsnake Antivenom and Varespladib

In this work, we examined the action of two South American coralsnake (Micrurus corallinus and Micrurus dumerilii carinicauda) venoms on rat heart function in the absence and presence of treatment with Brazilian coralsnake antivenom (CAV) and varespladib (VPL), a potent phospholipase A₂ inhibitor. Anesthetized male Wistar rats were injected with saline (control) or a single dose of venom (1.5 mg/kg, i.m.) and monitored for alterations in echocardiographic parameters, serum CK-MB levels and cardiac histomorphology, the latter using a combination of fractal dimension and histopathological methods. Neither of the venoms caused cardiac functional alterations 2 h after venom injection; however, M. corallinus venom caused tachycardia 2 h after venom injection, with CAV (given i.p. at an antivenom:venom ratio of 1:1.5, v/w), VPL (0.5 mg/kg, i.p.) and CAV + VPL preventing this increase. Both venoms increased the cardiac lesional score and serum CK-MB levels compared to saline-treated rats, but only the combination of CAV + VPL prevented these alterations, although VPL alone was able to attenuate the increase in CK-MB caused by M. corallinus venom. Micrurus corallinus venom increased the heart fractal dimension measurement, but none of the treatments prevented this alteration. In conclusion, M. corallinus and M. d. carinicauda venoms caused no major cardiac functional alterations at the dose tested, although M. corallinus venom caused transient tachycardia. Both venoms caused some cardiac morphological damage, as indicated by histomorphological analyses and the increase in circulating CK-MB levels. These alterations were consistently attenuated by a combination of CAV and VPL.

A retrospective evaluation of eastern coral snake envenomation and antivenom administration in cats: 30 cases (2012-2019)

Thirty cats were identified to be have been suspected to have a potential coral snake envenomation after searching medical records from 2012 to 2019 at a university teaching hospital. The records were reviewed and evaluated for signalment, date and time of the snake encounter, elapsed time between encounter and hospital examination, presenting complaint, initial physical examination findings, initial laboratory findings, antivenom dose and duration of administration, adverse reactions to antivenom, additional treatments administered, progression of clinical signs, length of hospitalization, and outcome. Thirteen cats presented with clinical signs consistent with envenomation while 17 cats were treated for possible asymptomatic envenomation, as defined by the owner discovering a live or dead coral snake in their home or on their property. Initial physical examination findings included tachypnea with short shallow breaths and use of accessory muscles; tetraparesis with normal or decreased to absent spinal reflexes; cranial nerve deficits including decreased to absent gag, slow pupillary light reflexes, and absent physiologic nystagmus; and normal or altered mentation. Laboratory findings included hypercapnia, hyperglycemia, hypokalemia, increased aspartate aminotransferase activity, increased alanine aminotransferase activity, echinocytosis, leukocytosis, azotemia, and hyperlactatemia. Twenty-eight cats received antivenom; two cats received two vials while twenty-six cats received one vial. Antivenom reaction was suspected in one cat that developed facial swelling during administration of the drug. Average length of hospitalization was 1 day for cats without clinical signs and 3 days for cats with clinical signs. Twenty-nine cats survived to discharge. Due to the inclusion criteria of the study, cats euthanized on presentation or discharged without receiving antivenom may have been unintentionally excluded from the study. Diagnosis of eastern coral snake envenomation should be suspected in the cat that has acute onset of lower motor neuron neuropathy. Prognosis with treatment is considered good with 97% of cats surviving to discharge. Antivenom reaction occurred in 3.5% of administrations with none being fatal. Monitoring of hypercapnia was critical in making the decision to mechanically ventilate patients. Supportive care that includes antivenom administration, recumbency care, and mechanical ventilation if needed are the mainstays of therapy.

Delayed LY333013 (Oral) and LY315920 (Intravenous) Reverse Severe Neurotoxicity and Rescue Juvenile Pigs from Lethal Doses of Micrurus fulvius (Eastern Coral Snake) Venom

OBJECTIVE

There is a clear, unmet need for effective, lightweight, shelf-stable and economical snakebite envenoming therapies that can be given rapidly after the time of a snake's bite and as adjuncts to antivenom therapies in the hospital setting. The sPLA2 inhibitor, LY315920, and its orally bioavailable prodrug, LY333013, demonstrate surprising efficacy and have the characteristics of an antidote with potential for both field and hospital use.

METHODS

The efficacy of the active pharmaceutical ingredient (LY315920) and its prodrug (LY333013) to treat experimental, lethal envenoming by Micrurus fulvius (Eastern coral snake) venom was tested using a porcine model. Inhibitors were administered by either intravenous or oral routes at different time intervals after venom injection. In some experiments, antivenom was also administered alone or in conjunction with LY333013.

RESULTS

14 of 14 animals (100%) receiving either LY315920 (intravenous) and/or LY333013 (oral) survived to the 120 h endpoint despite, in some protocols, the presence of severe neurotoxic signs. The study drugs demonstrated the ability to treat, rescue, and re-rescue animals with advanced manifestations of envenoming.

CONCLUSIONS

Low molecular mass sPLA2 inhibitors were highly effective in preventing lethality following experimental envenoming by M. fulvius. These findings suggest the plausibility of a new therapeutic approach to snakebite envenoming, in this example, for the treatment of a coral snake species for which there are limitations in the availability of effective antivenom.

Anti-Ophidian Properties of Herbal Medicinal Plants: Could it be a Remedy for Snake Bite Envenomation?

Snake bite envenoming causes high rates of morbidity and mortality and is one of the serious health-related concerns all over the globe. Around 3200 species of snakes have been discovered till date. Amid these species, about 1300 species of snakes are venomous. On account of its severity, World Health Organization (WHO) recently included snakebite envenoming in the list of neglected tropical diseases. Immunotherapy has partially solved the issues related to snakebite envenomation. However, it is associated with numerous adverse effects, due to which alternative treatment strategies are required for the treatment of snakebite. Traditionally, a large repository of herbal medicinal plants is known to possess activity against snake venom. An exploration of the therapeutic benefits of these medicinal plants used for the treatment of snakebites reveals the presence of various potential phytochemicals. The aim of the present review is to provide an outline regarding poisonous snakes all over the world, various compositions of snake venom, adverse effects related to anti-snake venom and numerous medicinal plants used for the anti-ophidian activity.

First Aid and Pre-Hospital Management of Venomous Snakebites

BACKGROUND

Antivenom is the definitive treatment for venomous snakebites, but is expensive and not available in many rural and poorly developed regions. Timely transportation to facilities that stock and administer antivenom may not be available in rural areas with poorly developed emergency medical services. These factors have led to consideration of measures to delay onset of toxicity or alternatives to antivenom therapy.

METHODS

PubMed searches were conducted for articles on snakebite treatment, or that contained first aid, emergency medical services, tourniquets, pressure immobilization bandages, suction devices, and lymphatic flow inhibitors.

RESULTS

The reviewed articles describe how venoms spread after a venomous snakebite on an extremity, list the proposed first aid measures for delaying the spread of venoms, and evaluate the scientific studies that support or refute methods of snakebite first aid. The recommendations for field treatment of venomous snakebites will be discussed.

CONCLUSIONS

The evidence suggests that pressure immobilization bandages and related strategies are the best interventions to delay onset of systemic toxicity from venomous snakebites but may increase local toxicity for venoms that destroy tissue at the site of the bite, so their use should be individualized to the circumstances and nature of the venom.

North American Snake Envenomation

Native US snakes that produce clinically significant envenomation can be divided into 2 groups, crotalids and elapids. The crotalids include rattlesnakes, cottonmouths, and copperheads. Crotalid envenomation can result in significant local tissue damage as well as thrombocytopenia and coagulopathy. Rarely are bites fatal. Native US elapids are all coral snakes that possess neurotoxic venom that can cause weakness, respiratory paralysis, and rarely death. Treatment of both types of envenomation revolves around general supportive care and antivenom administration when indicated. Previously advocated treatments, such as tourniquets, venom extraction, and bite site excision are not recommended.

A Survey of Snakebite Knowledge among Field Forces in China

Background: A snakebite is a neglected extrinsic injury associated with high morbidity and global mortality. Members of Chinese field forces are at high risk of snakebites, and their perception and knowledge of snakebites are unknown. The aim of this study is to assess perception and knowledge of snakebites in field forces in southeast China; Methods: A cross-sectional questionnaire-based survey was conducted in July 2016. A total of 216 field force members participated in this study; Results: A total of 10.3% had experienced snakebites and 86.4% rated their demands for knowledge about snakebite as “high”. No significant correlation between the actual and perceived snakebite knowledge status was detected (κ = 0.0237, p = 0.3852). Ineffective and harmful traditional first-aid methods, such as the application of tourniquets, sucking the venom out of the wound, and making local incisions, were used by more than three quarters of the respondents. However, pressure immobilization bandages were applied by only 17.3% of members. The proportion of responses for each question was not significantly different among the respondents when considering separate demographic groups; Conclusions: Snakebite knowledge among Chinese field force members is inadequate and in some cases misleading, when focusing on manifestation, prevention, and first-aid. A pragmatic, intensive educational scheme should be undertaken in at-risk populations.

Efficacy of Trypsin in Treating Coral Snake Envenomation in the Porcine Model

Antivenom is the definitive treatment for venomous snakebites. Alternative treatments warrant investigation because antivenom is sometimes unavailable, expensive, and can have deleterious side effects. This study assesses the efficacy of trypsin to treat coral snake envenomation in an in vivo porcine model. A randomized, blinded study was conducted. Subjects were 13 pigs injected subcutaneously with 1 mL of eastern coral snake venom (10 mg/mL) in the right distal hind limb. After 1 min, subjects were randomized to have the envenomation site injected with either 1 mL of saline or 1 mL of trypsin (100 mg/mL) by a blinded investigator. Clinical endpoint was survival for 72 h or respiratory depression defined as respiratory rate <15 breaths per minute, falling pulse oximetry, or agonal respirations. Fisher's exact t test was used for between group comparisons. Average time to toxicity for the saline control was 263 min (191-305 min). The development of respiratory depression occurred more frequently in control pigs than treated pigs (p = 0.009). Four of the six pigs that received trypsin survived to the end of the 3-day study. No control pigs survived. Two of the trypsin treatment pigs died with times to toxicity of 718 and 971 min. Survival to 12 and 24 h was significantly greater in the trypsin treatment group (p = 0.002, p = 0.009, respectively). Local injection of trypsin, a proteolytic enzyme, at the site of envenomation decreased the toxicity of eastern coral snake venom and increased survival significantly. Further investigation is required before these results can be extended to human snakebites.

Management of a Pediatric Snake Envenomation After Presentation With a Tight Tourniquet

We describe an illustrative case of pediatric snake envenomation presenting with a tightly wound tourniquet. A 10-year-old boy presented after a snake bite to the right calf. A tourniquet was in place just below the right knee. The species of snake was unknown. The patient was hemodynamically stable, but the entirety of the right leg distal to the tourniquet was discolored. Over concern for a potential venom bolus effect upon tourniquet removal, the decision was made to start a crotaline Fab antivenom infusion and gradually loosen the tourniquet. The patient tolerated the infusion and removal of the tourniquet without signs of anaphylaxis or decompensation. Dynamic improvements were observed in the right leg and wound site that appeared to be the result of vascular congestion. Tourniquets are generally not recommended for snakebites; however, if a tourniquet is already placed, we avoid removal until prepared to manage acute toxicity or immediate hypersensitivity.

Long-term efficacy of pressure immobilization bandages in a porcine model of coral snake envenomation

BACKGROUND

Pressure immobilization bandages delay mortality for 8 hours after coral snake envenomation, but long-term efficacy has not been established.

OBJECTIVE

The objective of this study is to determine the long-term efficacy of pressure immobilization bandages after coral snake envenomation in the absence of antivenom therapy.

METHODS

A randomized, observational pilot study was conducted. Ten pigs (17.3-25.6 kg) were sedated, intubated for 5 hours, and injected subcutaneously with 10 mg of lyophilized Micrurus fulvius venom resuspended in water. Pigs were randomly assigned to a control group (no treatment) or a treatment group (compression bandage and splint) approximately 1 minute after envenomation. Bandage pressure was not controlled. Pigs were monitored daily for 21 days for signs of respiratory depression, decreased oxygen saturations, and paralysis. In case of respiratory depression, pigs were humanely euthanized and time to death recorded. Statistical analysis was performed with Fisher exact test, Mann-Whitney U test, and Kaplan-Meier survival curve as appropriate.

RESULTS

Median survival time of control animals was 307 minutes compared with 1172 minutes in treated animals (P = .10). Sixty percent of pigs in the treatment group survived to 24 hours vs 0% of control pigs (P = .08). Two of the treatment pigs survived to the end point of 21 days but showed necrosis of the distal lower extremity.

CONCLUSIONS

Long-term survival after coral snake envenomation is possible in the absence of antivenom with the use of pressure immobilization bandages. The applied pressure of the bandage is critical to allowing survival without necrosis. Future studies should be designed to accurately monitor the pressures applied.

Treating venomous snakebites in the United States: a guide for nurse practitioners

This article discusses the current, evidence-based guidelines for managing venomous snakebites indigenous to the United States. A review of common varieties of venomous snakes, venom effects, risk factors for snakebites, and management strategies are presented to assist nurse practitioners in caring for snakebite victims.

Reality bites: a case of severe rattlesnake envenomation

Rattlesnake venoms can cause a wide range of adverse human health effects. However, with the availability of modern antivenin, toxicity can generally be minimized and controlled. We present a rare case of rattlesnake envenomation resulting in severe systemic effects and syndrome relapse. Management considerations and patient course are described in the context of the current literature.

A localizing circumferential compression device delayed death after artificial eastern diamondback rattlesnake envenomation to the torso of an animal model in a pilot study

Nearly all prior studies to delay onset of systemic toxicity and death after snake bite use a model of distal extremity envenomation. In the first of a series of planned studies using snake venoms with different toxicity profiles, the application of a novel device in a new model of torso envenomation in the setting of Eastern Coral Snake (Micrurus fulvius) venom (a potent neurotoxin) envenomation showed promise by delaying systemic intoxication. In this pilot study, we investigated this novel localizing circumferential compression (LoCC) device's ability to delay onset of life threatening systemic toxicity after Eastern Diamondback Rattlesnake (Crotalus adamanteus) envenomation, a potent hemotoxic and myotoxic venom. With university approval, four juvenile female pigs (22-25 kg) were anesthetized, sedated, and intubated but not paralyzed to allow for spontaneous respirations. Each animal was injected subcutaneously with 50 mg of C. adamanteus venom in identical preselected areas of the trunk. After 1 min, two treatment animals had the LoCC device applied; two control animals had no intervention. Vital signs were recorded every 10 min for the first 2 h and every 30 min thereafter. Endpoints included cardiovascular collapse (fatal arrhythmia, loss of mean arterial pressure, or pulse) or respiratory arrest (<3 breaths/min, saturation < 80%) or survival to 7 h. The pigs in the treatment group reached an endpoint at an average time of 355 (+/-65) min compared with control 32 (+/-3.5) min (p < 0.04). In this pilot study, the LoCC device significantly delayed onset of systemic symptoms and death after torso envenomation with Eastern Diamondback Rattlesnake venom in this model.

A localizing circumferential compression device increases survival after coral snake envenomation to the torso of an animal model

BACKGROUND

Pressure immobilization bandages have been shown to delay onset of systemic toxicity after Eastern coral snake (Micrurus fulvius) envenomation to the distal extremity.

OBJECTIVES

To assess the efficacy of a novel compression device in delaying onset of systemic toxicity after truncal envenomations with Eastern coral snake (Micrurus fulvius) venom in a porcine model.

METHODS

With University approval, nine juvenile pigs (11 kg to 22 kg) were sedated, anesthetized, and intubated but not paralyzed to ensure continuous spontaneous respirations in a university animal laboratory. Each animal was injected subcutaneously with 10 mg of M. fulvius venom in a pre-selected area of the trunk. After 1 min, six animals had the application of a novel, localizing circumferential compression (LoCC) device applied to the bite site (treatment group) and three animals had no treatment (control group). The device was composed of a rigid polymer clay form molded into a hollow fusiform shape with an internal dimension of 8 × 5 × 3 cm and an elastic belt wrapped around the animal securing the device in place. Vital signs were recorded at 30-min intervals. End points included a respiratory rate below 3 breaths/min, oxygen saturation < 80%, or survival to 8 h. Survival to 8 h was analyzed using Fisher's exact test, with p < 0.05 indicating significance. Survival analysis was performed using the Mantel-Cox test to assess time to death with outcomes represented in a Kaplan-Meier Cumulative survival plot.

RESULTS

Five of the six pigs in the treatment group survived 8 h (293-480 min). None of the control pigs survived to 8 h (Fisher's exact p = 0.04), with mean time of respiratory failure 322 min (272-382 min). Survival analysis showed a significant delay in time to event in the treatment group compared to the control group (p = 0.04).

CONCLUSIONS

The LoCC device used in this study delayed the onset of systemic toxicity and significantly increased survival time after artificial truncal envenomation by Eastern coral snake venom.

Pilot studies of pressure-immobilization bandages for rattlesnake envenomations

STUDY OBJECTIVE

Pressure-immobilization bandages sequester venom in extremities and are recommended for snakebites without local toxicity. Pilot studies were performed to determine the time of onset of toxicity and efficacy of pressure-immobilizations bandages in a porcine model of rattlesnake envenomation.

METHODS

After IACUC approval, anesthetized pigs were injected subcutaneously in a distal hind leg with 200 mg of Crotalus atrox venom. After 1 min, pigs received either a pressure-immobilization bandage (N = 3) or no treatment (N = 3). At 24 h, surviving pigs received antivenin and then the pressure-immobilization bandages were removed. Surviving subjects were followed for 1 week. Chi-square analysis and paired t-test were used.

RESULTS

Pigs with pressure-immobilization bandages survived for 24 h, whereas untreated pigs died at 13.68 +/- 3.42 h (p = 0.014). Surviving pigs walked on the extremity at 7 days. Potassium rose from 4.033 +/- 0.252 at baseline to 17.767 +/- 5.218 mEq/L (p < 0.0001) at time of death in untreated pigs but was normal at 24 h in treated subjects. Widespread tissue necrosis was seen in the untreated group but only local necrosis in the treatment group.

CONCLUSIONS

Pressure-immobilization bandages prevented death from severe C. atrox envenomations with a 24 h delay to treatment. Surviving pigs had recovery of limb use at 1 week.

Death following coral snake bite in the United States--first documented case (with ELISA confirmation of envenomation) in over 40 years

We report the first documented death due to a coral snake (Micrurus species) in the United States (U.S.) in over 40 years. The victim failed to seek medical care following the bite of an eastern coral snake (Micrurus fulvius) and succumbed within hours. Post-mortem proof of envenomation was obtained using an ELISA (enzyme-linked immunosorbent assay) developed specifically for this investigation. U.S. coral snakes are briefly reviewed in terms of their venom compositions, their clinical effects, and proper pre-hospital and hospital management. The clinical significance of the impending absence of commercially available antivenom for coral snake bites in the U.S. is highlighted.

Neutralization of two North American coral snake venoms with United States and Mexican antivenoms

Elapid snakes throughout the world are considered very lethal, containing neurotoxic venoms that affect the nervous system. When humans are envenomated it is considered a serious medical emergency, and antivenom is the main form of treatment considered, in spite of the fact that some patients may only survive under intensive therapy treatment such as respiratory support. Coral snakes are part of the family Elapidae and envenomations by these snakes are very low (<2% of total snakebites) in most countries from southeastern United States to Argentina. In the United States, there are only two species of coral snakes of medical importance that belong to the Micrurus genera: Micrurus fulvius fulvius (Eastern coral snake) and Micrurus tener tener (Texas coral snake). In 2006, Wyeth pharmaceutical notified customers that the production of the North American coral snake antivenin (NACSA) in the US was discontinued and adequate supplies were available to meet historical needs through the end of October 2008; and therefore, it is of utmost important to consider other antivenoms as alternatives for the treatment of coral snake envenoming. One logical alternative is the coral snake antivenom, Coralmyn, produced by the Mexican company, Bioclon. In order to compare neutralization between NACSA and Coralmyn antivenoms with the North American coral snake venoms, the venom lethal doses (LD(50)) and antivenom effective doses (ED(50)) were determined in 18-20 g, female, BALB/c mice. Additionally, venom comparisons were determined through a non-reduced SDS-PAGE for M.f.fulvius, M.t.tener and the Mexican coral snake venom, Micrurus nigrocinctus nigrocinctus. Coralmyn antivenom was able to effectively neutralize three LD(50) doses of all venom from both M.t.tener and M.f.fulvius, while Wyeth antivenom only neutralized M.f.fulvius venom and was not effective in neutralizing three LD(50) doses of M.t.tener venom. Coralmyn is effective in the neutralization of both clinically important coral snake venoms in the US.

Texas coral snake (Micrurus tener) bites

BACKGROUND

The clinical features of bites from Texas coral snakes (Micrurus tener) have not been well studied. Our goal was to review the largest number of victims of Texas coral snakebites to determine their characteristics, effects, treatment, and outcome.

METHODS

Retrospective case series of Micrurus tener exposures reported to the Texas Poison Center Network from 2000 to 2004.

RESULTS

Eighty-two patients were included in the analysis. Most (57.3%) were 18 to 49-year-old men. Almost 90% had local swelling, pain, erythema, or paresthesias. Only 7.3% had systemic effects, and none of these were severe. Over half received coral snake antivenin, and 15.9% were given opioids for pain. No patient died and no patient required mechanical ventilation due to hypoventilation from the snakebite.

CONCLUSIONS

There were more local findings and less severe systemic effects than previously reported. Antivenin is not needed for most of these patients, and opioids may be administered safely.

Bites by coral snakes (Micrurus spp.) in Campinas, State of São Paulo, Southeastern Brazil

Coral snakes (Micrurus spp.) are the main representatives of the Elapidae in South America. However, bites by these snakes are uncommon. We retrospectively reviewed the data from 11 individuals bitten by coral snakes over a 20-year period; four were confirmed (snake brought for identification) and seven were highly suspected (neuromuscular manifestations) cases of elapid envenoming. The cases were classified as dry-bite (n = 1, caused by M. lemniscatus; did not receive antivenom), mild (n = 2, local manifestations with no acute myasthenic syndrome; M. frontalis and Micrurus spp.), moderate (n = 5, mild myasthenia) or severe (n = 3, important myasthenia; one of them caused by M. frontalis). The main clinical features upon admission were paresthesia (local, n = 9; generalized, n = 2), local pain (n = 8), palpebral ptosis (n = 8), weakness (n = 4) and inability to stand up (n = 3). No patient developed respiratory failure. Antivenom was used in ten cases, with mild early reactions occurring in three. An anticholinesterase drug was administered in the three severe cases, with a good response in two. No deaths were observed. Despite the high toxicity of coral snake venoms, the prognosis following envenoming is good. In serious bites by M. frontalis or M. lemniscatus, the venom of which acts postsynaptically, anticholinesterases may be useful as an ancillary measure if antivenom is unavailable, if there is a delay in obtaining a sufficient amount, or in those patients given the highest recommended doses of antivenom without improvement of the paralysis or with delayed recovery.