The treatment of the scorpion envenoming syndrome: the Saudi experience with serotherapy

Detection of scorpion venom by optical circular dichroism method

Various efforts have been made to detect minimum amounts of any toxic materials in water or the neurotoxic effect of venom (Odontobuthus Doriae Scorpion) in the human's blood serum nerve by high-sensitivity, accurate, and low-cost sensors in order to enhance life style. Therefore, the present study was done to investigate reliability of two-dimensional plasmonic structure and circular dichroism (CD) in toxic samples in order to measure and determine venom concentrations and its neurotoxic effect on humans҆ blood serum Neurotransmitter analytes. Our results confirmed dependency of CD signal to neurotoxic effect of venom concentrations and good sensitivity of this sensor with the help of achiral plasmonic structure.

Scorpions and scorpion sting envenoming (scorpionism) in the Arab Countries of the Middle East

The twelve Arab countries of the Middle East are inhabited by 117 species of scorpions of varying medical importance within six families. Scorpion stings are a very common occurrence throughout the region. Twenty-two scorpion species are considered to be dangerously venomous, causing potentially life threatening stings. Accessible literature in English and Arabic on scorpions, scorpion stings and available antivenoms was reviewed to document the scorpion fauna and scorpion stings in each country. Saudi Arabia, Iraq and Jordan report the highest numbers of stings and envenomings. Clinically, the most important toxins in Old World scorpion venoms are α-toxins that target voltage-gated sodium (Na_v) channels at neurotoxin binding site 3, causing sympathetic excitation and the endogenous release of catecholamines that is responsible for transient, but life-threatening myocardial damage. Most victims of scorpion stings suffer severe local pain, but a few, especially children, develop systemic envenoming which, in the case of most Middle Eastern buthid species, such as Androctonus and Leiurus species, is dominated by the cardiovascular and respiratory consequences of hypercatecholinaemic myocarditis. Other syndromes include paralysis (Parabuthus leiosoma), coagulopathy (Nebo hierichonticus and Hemiscorpius species), and local tissue damage, haemolysis and acute kidney injury (H. lepturus). Early antivenom treatment is recommended but its value remains controversial. However, intensive care, with the ancillary use of vasoactive drugs such as prazosin and dobutamine, has proved effective.

Complete neutralization of the lethality of Hemiscorpius lepturus crude venom by a novel anti-recombinant phospholipase D1 IgGs

Treatment of scorpion envenomation is a challenging issue since serotherapy is implemented by administration of polyvalent equine antisera. In our previous study we discovered that recombinant phospholipase D1 (Hl-RecPLD1) is responsible for the lethality of Hemiscorpius lepturus (H. lepturus) venom in mice. Accordingly, this study was aimed to investigate the protectivity of purified anti-Hl-RecPLD1 IgG against the lethality or major complications of H. lepturus venom. The neutralization efficiency of purified anti-Hl-RecPLD1 IgGs against sphingomyelinase activities of the crude venom and Hl-RecPLD1 was also assessed. Anti-Hl-RecPLD1 IgGs at optimum amount of 3.7 mg completely neutralized one Lethal Dose 100 (LD₁₀₀) of crude venom in mice. The anti-Hl-RecPLD1 IgGs remarkably reduced the necrosis area from 6.5 to 1 cm² in rabbit derma, induced by the crude venom. The anti-Hl-RecPLD1 IgGs remarkably reduced the sphingomyelinase and hemolytic activities of crude venom as well. In conclusion, a novel rabbit monovalent IgG against Hl-RecPLD1 was able to completely protect the mice against the lethality of H. lepturus crude venom and reduced its toxicity as well. Such monovalent anti-Hl-RecPLD1 IgGs may have potential applications in serotherapy of H. lepturus envenomation.

Study on Distribution of Scorpions to Provide Prevention and Interventions in Combating Scorpionism in Poldokhtar County, Lorestan Province, Iran

INTRODUCTION

Scorpions are arthropods of medical importance classified in the class Arachnida, inhabiting hot and dry environments. All scorpions have a venomous sting and several thousand people die each year from scorpion stings, but this mortality is due to the venom of about 25 species located in northern Africa, the Middle East, India, Mexico and parts of South America. Poldokhtar County belongs to one of the southern cities of Lorestan Province, providing suitable habitats for many different species of scorpions due to its specific climatic conditions.

AIM

To examine the fauna of scorpion and its distribution in the Poldokhtar County and to provide appropriate preventive and medical interventions in combating scorpionism.

MATERIALS AND METHODS

This present study was a descriptive and analytical cross-sectional study. This study was conducted from April 2014 to November 2014 in regions of Poldokhtar County, Lorestan Province, and west of Iran. Cluster sampling methodology was employed in the sampling and scorpion collection procedure. Sampling was undertaken for an eight-month period, in villages and districts, namely, Myankuhe sharqi, Jayedar, Jelogir and Malavi within the county. The Chi-square test and the Fisher-exact test for homogeneity of proportions were used to compare quantitative variables.

RESULTS

Totally, 393 specimens were captured entailing 193 (49.1%) males and 200 (50.9%) females. There were at least seven species of scorpions belonging to three families; BU= Buthidae, HE = Hemiscorpiidae, SCN = Scorpionidae in Poldokhtar. Out of 393 collected scorpions, seven species, Androctonus crassicauda, Hottentotta (Buthotus) saulcyi, Compsobuthus matthiesseni, Compsobuthus rugosulus, Orthochirus scrobiculosus, Scorpio maurus and Hemiscorpius lepturus were identified. The overall sex ratio of females to males was 1:1.03.

CONCLUSION

It is crucial to improve the knowledge of residents in this region regarding preventive methods towards scorpion stinging. All the known dangerous Iranian scorpions having medical importance, including Hemiscorpius lepturus and Androctonus crassicauda were found in the study area. Additionally, other complementary research detailing the fauna of scorpions and their morphological, ecological and molecular variety in this region is highly recommended to estimate the correlation between particular scorpions' species and ensuring clinical signs and symptoms.

Efficacy of scorpion antivenom plus prazosin versus prazosin alone for Mesobuthus tamulus scorpion sting envenomation in children: a randomised controlled trial

OBJECTIVE

To assess the efficacy of combined use of scorpion antivenom (SAV) with prazosin, compared with prazosin alone in children with Mesobuthus tamulus scorpion envenomation.

STUDY DESIGN

Randomised controlled trial.

SETTING

A tertiary care hospital in south India.

PATIENTS

50 children with definite history and/or systemic manifestations of scorpion envenomation were recruited from the paediatric emergency or outpatient department from February 2012 to July 2013.

INTERVENTIONS

The children were randomised into two groups. In 25 children, SAV was administrated as a slow intravenous bolus combined with prazosin (group A). Others received prazosin alone (group B). Results were analysed by Student t test and χ(2) test.

MAIN OUTCOME MEASURES

Time required for resolution of autonomic symptoms, total dose of prazosin, adverse events.

RESULTS

Children in group A recovered earlier than those in group B (mean difference 9.1 h, 95% CI 6.0 to 12.2). 23 children (92%) in group A were clear of autonomic symptoms within 10 h, compared with 10 children (40%) in group B (mean difference 52%, 95% CI 29% to 75%). The proportion of children deteriorating to clinical grade 3 or 4 was 8% in group A as against 44% in group B (p<0.01). The mean dose of prazosin required was 54 µg/kg versus 130.8 µg/kg in group A and B, respectively (p<0.01). SAV was not associated with severe adverse reactions.

CONCLUSIONS

Usage of SAV led to faster recovery and reduced the incidence of myocardial dysfunction. Combined therapy with SAV and prazosin is beneficial for children with M tamulus scorpion envenomation.

TRIAL REGISTRATION NUMBER

CTRI/2013/09/004002 (Clinical Trials Registry of India).

Comments on Environmental and Sanitary Aspects of the Scorpionism by Tityus trivittatus in Buenos Aires City, Argentina

Deaths by venomous animals are medical emergencies that can lead to death and thus constitute sanitary problems in some regions of the world. In the South of America, the accidents by these animals are a common sanitary problem especially in warm, tropical or subtropical regions, related with rural work in several countries. Argentina is located in the extreme South of South America and a minor part of the continental surface is in tropical or subtropical regions, where most of the accidents by venomous animals happen. However, in the big cities in the center and South of the country, with no relation to rural work, scorpionism, mostly due to the synanthropic and facultative parthenogenetic scorpion Tityus trivittatus, has become a sanitary problem in the last few decades. This scorpion is present in the biggest cities of Argentina and in the last decades has killed over 20 children in provinces of the center and north of the country, mostly in big cities. In addition, it seems that this species is growing and spreading in new regions of the cities. In this revision, some characteristics of this scorpion regarding its habitat, spreading in Buenos Aires city, combat measures and available treatments are discussed.

Neurological effects of venomous bites and stings: snakes, spiders, and scorpions

Snake and spider bites, as well as scorpion sting envenoming, are neglected diseases affecting millions of people all over the world. Neurological complications vary according to the offending animal, and are often directly related to toxic effects of the venom, affecting the central nervous system, the neuromuscular transmission, the cardiovascular system, or the coagulation cascade. Snake bite envenoming may result in stroke or muscle paralysis. Metalloproteinases and other substances (common in vipers and colubrids) have anticoagulant or procoagulant activity, and may induce ischemic or hemorrhagic strokes. The venom of elapids is rich in neurotoxins affecting the neuromuscular transmission at either presynaptic or postsynaptic levels. The clinical picture of scorpion sting envenoming is dominated by muscle weakness associated with arterial hypertension, cardiac arrythmias, myocarditis, or pulmonary edema. These manifestations occur as the result of release of catecholamines into the bloodstream or due to direct cardiac toxicity of the venom. Cerebrovascular complications have been reported after the sting of the Indian red scorpion. Intracranial hemorrhages occur in the setting of acute increases in arterial blood pressure related to sympathetic overstimulation, and cerebral infarctions are related to either cerebral hypoperfusion, consumption coagulopathy, vasculitis, or cardiogenic brain embolism. Three main syndromes result from spider bite envenoming: latrodectism, loxoscelism, and funnel-web spider envenoming. Latrodectism is related to neurotoxins present in the venom of widow spiders. Most cases present with headache, lethargy, irritability, myalgia, tremor, fasciculation, or ataxia. Loxoscelism is caused by envenoming by spiders of the family Sicariidae. It may present with a stroke due to a severe coagulopathy. The venom of funnel-web spiders also has neurotoxins that stimulate neurotransmitter release, resulting in sensory disturbances and muscle paralysis. Proper management of the envenomed patient, including prompt transport to the hospital, correction of the hemostatic disorder, ventilatory support, and administration of antivenom, significantly reduce the risk of neurological complications which, in turn, reduce the mortality and improve the functional outcome of survivors.

Emerging options for the management of scorpion stings

Scorpion stings are common in many tropical countries. Although most scorpion stings cause only localized pain without life-threatening envenoming, about one third of stings cause systemic envenoming which can result in death. Children are particularly sensitive to scorpion envenoming. The severity of scorpion stings is related to the presence of neurotoxins in the venom that cause a sudden release of neurotransmitters from the autonomic nervous system, predominantly sympathetic. There is also a strong inflammatory response that worsens symptoms, including those of a respiratory nature. Several vital functions may be directly affected, including the cardiovascular, respiratory, and neuromuscular systems. Hypertension is constant at the beginning of systemic envenoming and sometimes has a severe cardiac and respiratory impact. Although controversial, immunotherapy is the only etiological treatment. Administered early, it prevents many complications and improves the outcome. New antivenoms are highly purified immunoglobulin fragments, the efficacy and safety of which are excellent. As a consequence, adverse reactions to antivenoms are now very rare and usually mild, which should limit any reluctance regarding their routine use. Symptomatic treatment is still necessary to support immunotherapy, especially in cases of delayed arrival at hospital. A combination of both approaches should be considered, based on local resources and constraints.

An In Vitro Method for Assessing the Efficacy of Antivenom Against Hemiscorpius lepturus Venom

BACKGROUND

Hemolyis of red blood cells is a serious toxic effect commonly found among patients envenomed by Hemiscorpius lepturus scorpion.

OBJECTIVES

The aim of the present study was to evlaute the efficay of the avaible polyvalent antivneom in preventing this phenomena.

MATERIALS AND METHODS

Using a red blood cell fragility test, the anti-hemolytic effectiveness of a new antivenom serum against Hemiscorpius lepturus venom was investigated. Hemolysis was measured using spectrophotometry.

RESULTS

Addition of venom (2, 10, 20, and 40 µg/ml) to 0.5 ml of 5% washed red blood cell suspension produced concentration-dependent hemolysis. Both the pre-incubation of red blood cell suspensions with various concentrations of antivenom (4%, 10%, and 20% v/v) and the co-administration of antivenom with 20 µg/ml venom resulted in concentration-dependent protection against hemolysis. Both the methods resulted in protection against hemolysis at the antivenom concentration of 20% (v/v). However, the inhibition of hemolysis after 24 h was found to be greater for red blood cell suspensions preincubated with antivenom (75% inhibition) than for red blood cell suspensions that were co-administered with antivenom and venom (50% inhibition).

CONCLUSIONS

The results suggest that the antivenom against H. lepturus venom is useful in inhibiting hemolysis produced by the venom, but the duration of protection is relatively short and appropriate measures need to be taken, depending on the patients' clinical progress, to re-administer the antivenom at intervals less than 8 h. This proposed treatment method merits further clinical assessment.

Amelioration of cardio-respiratory perturbations following Mesobuthus eupeus envenomation in anesthetized rabbits with commercial polyvalent F(ab')2 antivenom

Immunotherapy is the only specific treatment for scorpion sting. In the present study, protective effects of polyvalent antivenom against hemodynamic disturbances, biomarkers (troponin T, creatinine kinase isoenzyme MB, Lactate dehydrogenase) changes, electrocardiogram abnormalities and histopathological complications in heart and lung induced by Mesobuthus eupeus scorpion venom was investigated in anesthetized rabbits. Twenty four rabbits were randomized into four equal groups: six rabbits in control group received 1 ml ultra-pure water subcutaneously (group 1). Group two received LD50 of venom (4.5 mg/kg). In the third and fourth groups, 5 ml of scorpion antivenom was administrated intravenously simultaneous with venom injection and 60 min following envenomation, respectively. Results of the present study indicate significant decrease in hemodynamic parameters following envenomation in the second group of animals. Venom injection caused edema, myocytolysis, coagulation necrosis, hemorrhage in heart as well as edema, hemorrhage and vascular thrombus in lungs. Although envenomed rabbits presented rises in LDH and TnT but no alteration in CK-MB was observed. Electrocardiogram monitoring of rabbits showed ST elevation and inverted T waves. Simultaneous administration of antivenom and venom prevented entirely the clinical signs, hemodynamic disturbances, markers changes, ECG abnormalities and histopathological damages. Delayed immunotherapy gradually ameliorated clinical signs, hemodynamic disturbances and markers changes related to envenomation. Histopathological evaluation showed slight alterations such as mild myocytolysis in heart and mild edema in lung following delayed immunotherapy. In conclusion, scorpion antivenom administration has preventive, neutralizing and curative properties for M. eupeus scorpion envenomation, if it would be applied at optimum time, dose and route.

Heminecrolysin, a potential immunogen for monospecific antivenom production against Hemiscorpius lepturus scorpion

Serotherapy against Hemiscorpius (H.) lepturus scorpion sting is based on the administration of equine polyvalent antivenom prepared against a mixture of six venoms. In a previous study, we reported the identification of Heminecrolysin, a 33 kDa H. lepturus venom protein endowed with a sphingomyelinase D, hemolytic and dermonecrotic activities. We aimed herein to investigate the capacity of Heminecrolysin to generate antibodies able to neutralize the major physiopathological properties of H. lepturus envenomation, e.g. hemolysis and dermonecrosis. The efficiency of anti-Heminecrolysin antibodies was compared to that of anti-whole venom. Our results demonstrated that Heminecrolysin elicits high levels of specific IgGs. Anti-Heminecrolysin, similarly to anti-whole venom antibodies, totally inhibited H. lepturus hemolytic effect when up to 5 times the half maximal effective concentration of venom were used. Phosphatidylserine exposure on the external lipid monolayer of human red blood cells treated with whole venom was also fully blocked by both anti-sera. Experimental envenomation of rabbits showed that anti-Heminecrolysin antibodies were as potent as anti-H. lepturus antibodies to neutralize dermonecrotic effects when up to 4 times the minimal necrotic dose of venom were injected. However, inflammatory reaction was better controlled with anti-whole venom sera. In conclusion, Heminecrolysin elicits protective antibodies of comparable potency to those elicited by immunization with whole venom.

Scorpion envenomation and antivenom therapy

Scorpion envenomation is a dangerous and common global event that can result in a variety of toxic clinical effects. These are typically managed with supportive care or antivenom. Antivenom use is controversial because of conflicting evidence of effectiveness for adrenergic toxicity. However, both controlled and uncontrolled studies have shown that antivenom is effective in resolving neuromotor toxicity associated with envenomations by the scorpions of genus Centruroides.

Efficacy and safety of scorpion antivenom plus prazosin compared with prazosin alone for venomous scorpion (Mesobuthus tamulus) sting: randomised open label clinical trial

OBJECTIVE

Envenomation by Mesobuthus tamulus scorpion sting can result in serious cardiovascular effects. Scorpion antivenom is a specific treatment for scorpion sting. Evidence for the benefit of scorpion antivenom and its efficacy compared with that of commonly used vasodilators, such as prazosin, is scarce. We assessed the efficacy of prazosin combined with scorpion antivenom, compared with prazosin alone, in individuals with autonomic storm caused by scorpion sting.

DESIGN

Prospective, open label randomised controlled trial.

SETTING

General hospital inpatients (Bawaskar Hospital and Research Centre Mahad Dist-Raigad Maharashtra, India).

PARTICIPANTS

Seventy patients with grade 2 scorpion envenomation, older than six months, with no cardiorespiratory or central nervous system abnormalities.

INTERVENTION

Scorpion antivenom plus prazosin (n=35) or prazosin alone (n=35) assigned by block randomisation. Treatment was not masked. Analysis was by intention to treat.

MAIN OUTCOME MEASURES

The primary end point was the proportion of patients achieving resolution of the clinical syndrome (sweating, salivation, cool extremities, priapism, hypertension or hypotension, tachycardia) 10 hours after administration of study drugs. Secondary end points were time required for complete resolution of clinical syndrome, prevention of deterioration to higher grade, doses of prazosin required overall and within 10 hours, and adverse events. The study protocol was approved by the independent ethics committee of Mumbai.

RESULTS

Mean (SD) recovery times in hours for the prazosin plus scorpion antivenom group compared with the prazosin alone groups were: sweating 3 (1.1) v 6.6 (2.6); salivation 1.9 (0.9) v 3 (1.9); priapism 4.7 (1.5) v 9.4 (1.5). Mean (SD) doses of prazosin in the groups were 2 (2.3) and 4 (3.5), respectively. 32 patients (91.4%, 95% confidence interval 76.9% to 97.8%) in the prazosin plus antivenom group showed complete resolution of the clinical syndrome within 10 hours of administration of treatment compared with eight patients in the prazosin group (22.9%, 11.8% to 39.3%). Patients from the antivenom plus prazosin group recovered earlier (mean 8 hours, 95% CI 6.5 to 9.5) than those in the control group (17.7 hours, 15.4 to 19.9; mean difference -9.7 hours, -6.9 to -12.4). The number of patients whose condition deteriorated to a higher grade was similar in both groups (antivenom plus prazosin four of 35, prazosin alone five of 35). Hypotension was reported in fewer patients in the antivenom plus prazosin group (12 of 35, 34.3%) than in the prazosin group (19 of 35, 54.3%), but the difference was not statistically significant. No difference was noted in change in blood pressure and pulse rate over time between two groups.

CONCLUSION

Recovery from scorpion sting is hastened by simultaneous administration of scorpion antivenom plus prazosin compared with prazosin alone.

TRIAL REGISTRATION NUMBER

CTRI/2010/091/000584 (Clinical Trials Registry India).

Comparative study between the protective effects of Saudi and Egyptian antivenoms, alone or in combination with ion channel modulators, against deleterious actions of Leiurus quinquestriatus scorpion venom

This study compared efficacy of two polyvalent antivenoms (Saudi Arabian and Egyptian), against lethality and pathophysiological changes of Leiurus quinquestriatus quinquestriatus (LQQ) scorpion venom in mice. Additionally, the study examined whether treatment with selected ion channel modulators, lidocaine, nimodipine or amiodarone would be effective, alone or combined with the antivenoms. The protein concentration of the Saudi antivenom was 1/3 of Egyptian, indicating lesser immunogenicity, while both preservative contents were within limits. In immunodiffusion experiments, both exhibited prominent precipitin bands indicating high concentrations of specific antibodies. Neutralizing capacities (60-70 LD(50)) stated on labels were confirmed. Both antivenoms significantly (P < 0.001) prolonged survival time (from 26.9 +/- 1.18 min, 100% dead with venom to 224-300 min, 0-30% dead) of envenomed mice, whether injected iv before or 5 min after venom. Injection of either antivenom plus ion channel modulators, gave comparable results to that observed in mice treated with antivenoms alone. The Na(+) channel blocker lidocaine and the Ca(2+) channel blocker nimodipine on their own significantly protected the animals (P < 0.05), but to a lesser extent. The two antivenoms, significantly ameliorated the venom-evoked changes in serum LDH (P < 0.001) and CKMB (P < 0.01) plus cardiac TNFalpha and nitrate/nitrite levels (P < 0.001). When combined with lidocaine or nimodipine, the effects were not greater than antivenom alone. Moreover, the antivenoms ameliorated characteristic venom-evoked changes in the isolated perfused Langendorff hearts. Lidocaine and amiodarone were more effective than nimodipine. In Conclusion both Saudi and Egyptian antivenoms protected mice from the pathological and lethal effects of LQQ scorpion. Sodium and calcium channel blockers, lidocaine and nimodipine, may be useful when antivenoms are not available.

Identification of potent nanobodies to neutralize the most poisonous polypeptide from scorpion venom

Scorpion venom, containing highly toxic, small polypeptides that diffuse rapidly within the patient, causes serious medical problems. Nanobodies, single-domain antigen-binding fragments derived from dromedary heavy-chain antibodies, have a size that closely matches that of scorpion toxins. Therefore these nanobodies might be developed into potent immunotherapeutics to treat scorpion envenoming. Multiple nanobodies of sub-nanomolar affinity to AahII, the most toxic polypeptide within the Androctonus australis hector venom, were isolated from a dromedary immunized with AahII. These nanobodies neutralize the lethal effect of AahII to various extents without clear correlation with the kinetic rate constants kon or koff, or the equilibrium dissociation constant, KD. One particular nanobody, referred to as NbAahII10, which targets a unique epitope on AahII, neutralizes 7 LD50 of this toxin in mice, corresponding to a neutralizing capacity of approx. 37000 LD50 of AahII/mg of nanobody. Such high neutralizing potency has never been reached before by any other monoclonal antibody fragment.

VHH, bivalent domains and chimeric Heavy chain-only antibodies with high neutralizing efficacy for scorpion toxin AahI'

Many efforts aim at solving the serious problems encountered with immunotherapy against scorpion envenoming. The most attractive approach consists in generating single-chain antibody fragments (scFv) as their pharmaco-kinetic properties should match closely those of the scorpion toxins. Although high affinity scFv reagents have been generated in the past, their production level, stability, and toxin neutralizing capacity remain disappointingly poor. In the current study, we identified one Nanobody (Nb), a single-domain antigen-binding fragment of a dromedary Heavy-chain antibody (HCAb) that recognizes specifically the Androctonus australis hector AahI' toxin. This Nb has excellent production, stability and solubility characteristics. With this Nb we further manufactured a tandem linked bivalent construct and assembled a HCAb with improved antigen binding due to avidity effects. All these constructs were shown in mouse models to possess a scorpion toxin neutralization capacity that exceeds by far all previous attempts with scFv-based materials, even when used at lower doses. It is therefore clear that in the near future Nanobodies will be at the core of novel serotherapeutics as they combine multiple benefits over other reagents to treat scorpion envenomed patients.

Scorpion stings in Qassim, Saudi Arabia—A 5-year surveillance report

We reviewed and analyzed 5-year (1999-2003) surveillance data of scorpion stings in Qassim, Saudi Arabia. A total of 6465 scorpion sting cases were notified. Male-to-female ratio for scorpion stings was 1.9:1. The mean age for cases was 23+/-17 years and 3079 (47.8%) cases were between the ages of 11 and 30 years. The scorpion stings had a higher incidence in the months of May-October. This information is beneficial for health education and prevention of scorpion sting cases.

Toxin gamma from Tityus serrulatus scorpion venom plays an essential role in immunomodulation of macrophages

Fraction number II obtained from Sephadex G-50 gel filtration of the soluble venom from the Brazilian scorpion Tityus serrulatus (TSV) stimulates macrophage function in vitro. The aim of this study was to identify which one of the several components of this fraction was responsible for the main stimulatory activity on macrophages. This component was identified as sub-fraction II-11, also known by the name of gamma toxin or simply abbreviated Ts1, which stands for toxin 1 of T. serrulatus venom. The effect of Ts1 was analyzed by detection of inflammatory mediators. Several functional bioassays were performed: TNF activity was assayed by measuring its cytotoxicity on L929 cells, whereas IL-1, IL-6, IFN-gamma and IL-10 were assayed by enzyme-linked immunosorbent assay. The levels of NO were evaluated by Griess colorimetric reactions in supernatants of macrophages in culture exposed to Ts1 and compared with FII. Macrophages exposed to Ts1 increase the production of mediators. With respect to the pro-inflammatory cytokines, an increment of IL-1alpha, IL-1beta was observed after 12 h; the maximum levels of IL-6 and TNF were observed after 24 h; the highest levels of IFN-gamma and NO were observed after 72 h. In contrast, the highest levels of anti-inflammatory cytokines such as IL-10 were observed after 120 h. With respect to the balance of pro- and anti-inflammatory cytokines, IL-1alpha/IL-10 and IL-6/IL-10 ratios appear incremented between 12 and 48 h in macrophages exposed to Ts1. IL-1beta/IL-10 and TNF/IL-10 ratios were increased in macrophages exposed to Ts1 for 12 h. IFN-gamma/IL-10 ratios increased up to 48 h, decaying thereafter. Elevated IL-6/TNF ratios were observed up to 24 h. These ratios may possibly reflect the inflammatory status during exposition to the venom. In conclusion, these data indicate that Ts1 has an important immunomodulatory effect on macrophages, and add important knowledge for understanding scorpion envenomation. It also opens the field for further research about the intoxication phenomenon as it is discussed here.

Balance between pro- and anti-inflammatory cytokines in mice treated with Centruroides noxius scorpion venom

CSV consists of a very complex of molecules and demonstrates significant cellular activities capable of stimulating immune functions in vivo. The purpose of this study was to analyze the effects of CSV on sex, weight, route of injection and the balance of pro- and anti-inflammatory cytokines in mice. The susceptibility and route of injection were analyzed by lethal (LD(50)) determination. The effects of CSV were also analyzed in blood from immunized mice using detection by means of antibodies and mediators production. Several functional bioassays were employed: TNF activity was assayed by measuring its cytotoxic activity in L929 cells, and other cytokines were assayed by enzyme-linked immunosorbent assay, whereas nitric oxide levels were detected by Griess colorimetric reactions in sera from BALB/c mice. After injecting subcutaneously, the LD(50) presented an increase of the CSV correlation and similar levels of susceptibility were obtained for female and male from BALB/c mice. Significant differences were observed in the time-course of cytokine levels. The balance of pro- and anti-inflammatory cytokines TNF/IL-10 and IL-6/IL-10 ratios were significantly higher in injected mice group when compared with those obtained for non-injected group. The CSV is poor in antigenic composition and it is difficult to get antibodies specific to neutralizing the lethal factor. The effect of immunization with 0.5 LD(50) of CSV on the balance of pro- and anti-inflammatory cytokines was measured. The maximum levels of TNF and IL-6, IFN-gamma and NO were observed on days 7 and 21 after immunization, respectively. IL-10 levels peaked between days 21 and 28 after immunization with CSV. With respect, to balance of pro- and anti-inflammatory cytokines it was possible to observe that negative correlation between serum levels of IL-6/IL-10 and TNF/IL-10 exists. These ratios may possibly reflect the balance of pro- and anti-inflammatory cytokines in serum, which may by manifested in the inflammatory status during the envenoming processes. In conclusion, an increase in the serum levels of TNF and IL-6 may be a useful marker for scorpion envenomation.

Scorpion envenoming in two regions of Colombia: clinical, epidemiological and therapeutic aspects

To determine clinical and epidemiological features of scorpion stings in two departments of Colombia, a descriptive study was performed in the hospitals of 10 towns from Antioquia (2 256 071 inhabitants) and five from Tolima (630 424 inhabitants). One hundred and twenty-nine cases were admitted during one year, 51 in Antioquia, 78 in Tolima and 41 were children less than 15 years old. Most stings (70.5%) occurred inside the house; 27.9% were on the hands and 26.4% on the feet. The scorpion species involved were Tityus pachyurus (51), Centruroides gracilis (31), T. fuehrmanni (29), T. asthenes (7) and Chactas spp. (1). In 10 cases the scorpion involved was not identified. Systemic envenoming signs (e.g. vomiting, tachypnea) were significantly more frequent in children than in adults (P < 0.05). Four children had hypertension, but none developed pulmonary oedema. One 3-year-old girl, stung by T. asthenes, had acute oedematous pancreatitis. Ninety-eight patients had mild envenoming. Moderate (27 patients) and severe (four patients) envenoming was significantly more frequent in children than in adults (P = 0.003; relative risk = 2.97). A pepsin-digested anti-Centruroides spp. antivenom was administered to 19 of 31 patients presenting systemic envenoming signs. No adverse reactions to antivenom were observed.

Scorpion stings in Australia: five definite stings and a review

Despite scorpions being locally abundant in many parts of Australia, scorpion sting is a poorly defined clinical condition in Australia. Many health-care workers are unaware of the effects of their stings and scorpions are often feared based on their international reputation. Five scorpion stings that occurred in different parts of Australia where the scorpion was caught at the time of the sting and identified by a professional arachnologist are reported in the present paper. The spectrum of clinical effects of scorpion stings in Australia and the potential for significant effects are discussed. These cases and recent prospective case series demonstrate that in Australia scorpion stings cause only minor effects. The main effect is localized pain lasting for several hours, associated less commonly with systemic effects, local numbness and paraesthesia. Most stings are from smaller scorpions from the family Buthidae and often occur indoors at night. The stings from Australian buthid scorpions cause more severe effects than from the larger species in the families Urodacidae (genus Urodacus) and Liochelidae (genus Liocheles).

Quantitative variability in the biodistribution and in toxinokinetic studies of the three main alpha toxins from the Androctonus australis hector scorpion venom

Scorpion stings represent a medical problem in numerous countries. The scorpion Androctonus australis hector produces three alpha toxins (Aah I to III), which are responsible for most of the lethality in mammals. These toxins act on sodium channel and do not cross-react immunologically. We used RIA and ELISA to measure the concentrations of these three toxins in plasma, urine and different organs after i.v. and s.c. injections of water extracts of venoms in rabbits or mice. In both animals, the toxins rapidly appeared in plasma after s.c. injection as it was previously described for the whole venom. However, the toxins disappeared from the blood more quickly than did other main components of the venom. Thus, serotherapy must be initiated immediately to prevent the toxin from reaching its target. We also detected the toxins in urine, kidneys, heart and lungs, but not in the brain. However, the concentration of Aah II was always lower than that of Aah I. Analysis of five samples of venom collected in different areas of southern Tunisia showed that a large polymorphism exists for the three toxins. This is yet another difficulty for serotherapy as there is no cross-antigenicity between them.

Epidemiological data, clinical admission gradation and biological quantification by ELISA of scorpion envenomations in Algeria: effect of immunotherapy

An epidemiological and biological survey of scorpion envenomation was conducted in Algeria. Analysis of 182 medical files showed that 70% of the patients were stung by Androctonus australis. Most accidents occurred during the morning (40%) or the evening (30%). Two-thirds of the patients reached a hospital 1 hour after being stung. Their clinical symptoms classified 78% of them as Grade I (mild envenomation) and 17% of them as Grade II (moderate envenomation) on admission to hospital. No severe envenomation (Grade III) was reported. Most patients were treated with antivenom by the intramuscular route. Blood samples were collected before and after antivenom immunotherapy. A good correlation was observed between the grade of envenomation on admission and the blood venom concentrations measured by ELISA. The venom concentration decreased as function of the interval between the sting and blood collection (t1/2 = 2 h). Intramuscular injection of 10 ml of antivenom did not efficiently neutralize scorpion venom. Inflammation was followed by measuring IL6 concentration. IL6 peaked 1 h after scorpion envenomation. This study shows that optimization of the administration of antivenom is required to achieve clinical efficiency. In particular, intravenous injection of a larger dose of a more potent antivenom should be considered.

A canine study of immunotherapy in scorpion envenomation

OBJECTIVE

To evaluate the effects of scorpion venom and antivenom in experimental envenomation.

DESIGN

Prospective, controlled animal study.

SETTING

University research laboratory

SUBJECTS

Twenty-nine anesthetized and ventilated dogs.

INTERVENTIONS

The first group of animals had venom alone (0.05 mg/kg). Animals from the second group had simultaneous administration of 10 ml of scorpion antivenom (SAV). In the third and fourth groups, 10 ml and 40 ml SAV, respectively, were injected 10 min following venom.

MEASUREMENTS AND RESULTS

Hemodynamic parameters using right heart catheter were recorded and dosage of catecholamines, neuropeptide Y (NPY), endothelin-1, and atrial natriuretic peptide (ANP) were performed at baseline and during 60 min following envenomation. In the control group, at 5 min, there was a sharp increase in pulmonary artery occluded pressure (PAOP, from 2 mmHg to 23 mmHg), mean arterial pressure (MAP, from 125 mmHg to 212 mmHg) and systemic vascular resistance (SVR, from 2450 dyn sec(-1 )m(5) to 5775 dyn sec(-1 )m(5), P<0.05 for all). Heart rate, cardiac output, and stroke volume decreased. There was a 40-fold increase in epinephrine and norepinephrine plasma concentrations. Circulating NPY and ANP dosages increased too. PAOP and MAP decreased thereafter to reach baseline levels. Simultaneous administration of SAV with venom totally offset the hallmarks of scorpion envenomation. Delayed administration of SAV at any dosage failed to alter the features of scorpion envenomation.

CONCLUSION

While simultaneous administration of SAV and scorpion venom is effective in preventing scorpion envenomation-related manifestations, delayed administration of SAV, either at standard or elevated dosages, failed to alter any of the scorpion envenomation features.

Antivenom treatment in arachnidism

Envenomation by arachnids causes significant medical illness worldwide. Scorpion sting is the most important arachnid envenomation causing adult morbidity and pediatric mortality. Important groups of spiders include the widow spiders (Latrodectus spp.), the recluse spiders (Loxosceles spp.), and two spiders confined to single countries: the Australian funnel web spider (Atrax and Hadronyche spp.) and the armed spider (Phoneutria spp.) from Brazil. There are four widow spider antivenoms available, including the Australian redback spider antivenom and the American black widow antivenom. Despite good in vitro animal work demonstrating effective neutralization with these antivenoms, and cross-reactivity between many species, there continues to be a reluctance to use them in some countries. They are both associated with a relatively low rate of allergic reactions. Redback antivenom is routinely used by the intramuscular route, which may not be as effective as intravenous use based on clinical experience and animal studies. Antivenoms are available for Loxosceles spp., but there is little evidence to support their effectiveness, particularly against local effects. The Australian funnel web spider causes severe neurotoxic envenomation, and antivenom appears to be effective in reported cases. An antivenom exists for the Brazilian armed spider, but is used in only a minority of cases. Many scorpion antivenoms exist worldwide, but there remains significant controversy regarding their efficacy. Animal and human venom level studies demonstrate neutralization of circulating venom in systemic envenomation. Clinical experience in countries where antivenom has been introduced suggests it has reduced pediatric mortality. However, three controlled trials demonstrated that antivenom was not effective, but these included few severe cases. Until controlled trials of antivenom in systemically envenomated patients are undertaken, antivenom use appears justified in severe envenomation. Although envenomation from arthropods is common, no antivenoms exist for these, excepting Lonomia caterpillars in South America, and Ixodes paralysis ticks in Australia.

Clinical toxinology--where are we now?

Clinical toxinology encompasses a broad range of medical conditions resulting from envenomation by venomous terrestrial and marine organisms, and also poisoning from ingestion of animal and plant toxins. Toxin-related disease is an important cause of morbidity and mortality worldwide, particularly in the tropical and subtropical continents. Snake bite is the single most important toxin-related disease, causing substantial mortality in many parts of Africa, Asia, and the Americas. The most important snake families are Viperidae and Elapidae, causing a range of clinical effects including local necrosis, neurotoxicity, coagulopathy and hemorrhage, myotoxicity and renal toxicity. These effects vary according to geography and group of snake. Arachnid envenomation results mainly in morbidity, particularly scorpion stings which can cause severe systemic envenomation. Spider bite is far less of a problem, and the majority of medically important cases can be attributed to widow spiders (Latrodectus spp.) and recluse spiders (Loxosceles spp.). Marine-related envenomations are common, but severe effects are less so. Plant and mushroom poisoning occur in most parts of the world, but the types and methods of poisoning vary considerably between continents. Management of toxin-related disease is often difficult, and in many cases meticulous supportive care is all that is available. The mainstay of treatment is the use of antivenoms for many envenomations and poisoning, although these do not exist for all dangerous organisms. Unfortunately antivenoms are not an economically viable product, so development and manufacture of these agents have been limited. This is now further worsened by a current shortage of antivenom. There is a need for improvement in the preventionand management of toxin-related disease. This will require well-designed studies to define the extent of the problem, initiatives to improve the prevention and management of these conditions, and development of new, and continuation of current, antivenom supplies.

Antivenom serotherapy and volume resuscitation partially improve peripheral organ ischemia in dogs injected with scorpion venom

We tested the hypothesis that fluid resuscitation combined with antivenom serotherapy given after injection of scorpion venom may increase cardiac output (CO) and blood pressure (BP) and prevent the decline in bicarbonate, pH and gastric perfusion. Seventeen anesthetized, mechanically ventilated dogs were given 0.1 mg/kg i.v. venom of the scorpion Leiurus quinquestriatus. The dogs were randomized into three groups: six dogs were given venom alone; three dogs were given 6 ml of antivenom 1 minute before venom injection; eight dogs were given 6 ml of antivenom and 20 ml/kg of synthetic colloid solution, 20 min after venom injection. Parameters reflecting respiratory and circulatory functions were determined at baseline and 120 min after venom injection. Scorpion venom caused a decrease in CO, BP, pH and HCO3-. Gastric mucosal perfusion was severely affected as assessed by mucosal pH (pHi) and the gradient between mucosal and arterial pCO2 (delta pCO2). Antivenom given before venom injection prevented all the effects induced by the venom. Antivenom and fluid given 20 min after venom injection caused a marked increase in CO and BP, but had no effect on pH and HCO3- decline (compared with venom alone). Gastric perfusion slightly improved as the increase in delta pCO2 was attenuated. The combination therapy of antivenom and fluid in this dog model is superior to the therapy of each of them alone. The marked and long-standing improvement of CO is promising and may suggest improvement in HCO3- and pH with time.

Epidemiological and clinical aspects of scorpionism by Tityus trivittatus in Argentina

This is a descriptive study of epidemiological and clinical aspects of stings caused by the scorpion Tityus trivittatus in Argentina. We analyzed 511 cases recorded from different health centers in 22 provinces. Most accidents took place during the period November-April (76%), in or nearby houses (86%). Over 50% of the accidents involved children and teenagers. Envenomation by T. trivittatus was mainly characterized by local symptoms: pain (85%), edema (26.6%), burning sensation (24.7%), erythema (20.7%), local hyperthermia (13.1%), paresthesia (9.8%) and general manifestations such as vomiting (25%), paleness (18.8%), headache (11.4%) and sweating (8.2%). Neurological, cardiovascular and respiratory disorders were uncommon. Almost 90% of the injured people got treated with specific antivenom within 2 h, 6% were treated 2-h after the accident and only 2 people were treated 12 or more hours after being stung. The global mortality recorded was 6 per 1000 cases. Scorpionism in Argentina is a public health problem under control due to the relatively low incidence and the accessibility of specific antivenom.

Australian scorpion stings: a prospective study of definite stings

There is little information on scorpion stings in Australia. The aim of this study is to describe the circumstances and clinical effects of stings by Australian scorpions. Cases of scorpion stings were collected prospectively from calls and presentations to Australian poison information centres and emergency departments from February 2000 to April 2002. Only definite scorpion stings where the scorpion was immediately collected and expertly identified were included. There were 95 patients, 33 males and 62 females, with a mean age of 32 (SD 19.5; range 1-71) and 23 children (age<15 years). Three families of scorpions caused all stings: Buthidae (79), Bothruiridae (11, all Cercophonius spp.) and Urodacidae (five, all Urodacus spp.). The majority of stings (76%) were by one genus of scorpion Lychas spp. Seventy one percent of stings occurred between 6pm and 8am and 82 (86%) occurred indoors. Sixty percent of stings occurred on distal limbs. The median duration of effects was 6 h (interquartile range (IQR): 1-24 h). Immediate localised pain occurred in all cases and was severe in 76 cases (80%). Other local effects included red mark/redness (66%), tenderness (35%), numbness (12%) and paraesthesia (11%). Minor systemic effects (nausea, headache and malaise) occurred in 11% of cases. There were no deaths or major systemic envenoming. Less severe effects were observed for the larger Urodacus species, compared to Lychas spp. Scorpion stings in Australia do not appear to cause severe or life-threatening effects, even in children. This differs from other parts of the world, where severe envenoming is reported. The major clinical effect is severe pain, consistent with other scorpion stings. Most stings occurred indoors and at night.

Analysis of the immune response induced by a scorpion venom sub-fraction, a pure peptide and a recombinant peptide, against toxin Cn2 of Centruroides noxius Hoffmann

Three different immunogens from the venom of the Mexican scorpion Centruroides noxius Hoffmann were used to study protective antibody response in mice and rabbits, challenged with toxin Cn2, one of the most abundant toxic peptide of this venom. The immunogens were: Cn5, a crustacean specific toxin; a recombinant protein containing the peptide Cn5 linked to the maltose transporter and a sub-fraction (F.II.5) containing 25 distinct peptides, among which is Cn5. Mice immunized with these three preparations, when directly challenged with Cn2 presented no apparent protection, whereas anti-sera produced in rabbits with these three immunogens were capable of partially neutralizing the effect of Cn2, when injected into naive mice. Cn5 rabbit anti-serum showed a better protective effect on mice, than the rabbit sera obtained against the two other antigens. The subcutaneous route of challenging mice was shown to be better than intraperitoneal injections. Comparative structural analysis of Cn5 with other toxins of this venom showed that our results are important to be taken into consideration, when choosing appropriate immunogens aimed at the production of better anti-venoms or for the rational design of possible vaccines.

Treatment of the scorpion envenoming syndrome: 12-years experience with serotherapy

The pathophysiology of the scorpion envenoming syndrome is described with emphasis on the body systems commonly affected. Concepts of the mechanisms underlying venom action, as can be explained by the recently discovered effects on ionic channels, are discussed. A protocol for the treatment of scorpion stings based mainly on antivenom therapy was applied nationwide in Saudi Arabia. A list of drugs with alternatives was specified to be used in adjunctive therapy, when required. Analysis of the outcome from 1,033 cases at Al-Baha region, 791 cases at Al-Qassim region and more than 2,000 cases from 12 central and specialist hospitals in the Central Province, Saudi Arabia gave impressive results. The incidence of severe venom toxicity following antivenom administration was almost negligible. The period of stay in the hospital was reduced. The early reaction to antivenom administration was lower than expected the severity of the reaction consisting mainly of skin rashes, urticaria, wheezing and bronchial hypersensitivity, but no anaphylaxis. About 13.8% of the victims had been previously treated with antivenom but only 1.7% of the patients showed positive skin tests. This might be due to the low protein content of the antivenom and the action of the venom in releasing massive amounts of catecholamines.

Intraspecific variability and pharmacokinetic characteristics of Androctonus mauretanicus mauretanicus scorpion venom

We evaluated the degree of venom toxicity and protein content of several specimens of Androctonus mauretanicus mauretanicus. The quantity of protein of individual venom obtained after manual extraction from 31 different scorpions varied from a minimum of 0.15 mg to a maximum of 1.53 mg. We determined the venom toxicity, in mice, by estimating the number of LD(50)s of 20 scorpions chosen randomly among the 31 scorpions. It ranged from less than 40 LD(50)s to a maximum of 272 LD(50)s. The correlation between protein content and venom lethality is not systematic. We also determined the pharmacokinetics of the venom and its specific anti-venom in rabbits to compare their distribution and elimination properties. After a subcutaneous injection, high concentrations of venom were measured by ELISA in the vascular space rapidly after the injection (T(max) = 0.5 h). The terminal half-life was 2.8 h, close the one determined after intravenous injection (t(1/2beta) = 3.2 h). The total volume of distribution (Vd(ss) or Vd(beta)) was between 317 and 380 ml/kg. The total body clearance was 82 ml/kg/h. For scorpion anti-venom, the terminal half-life, after intravenous injection, was 20.25 h; the volume of distribution was 83 ml/kg and the total body clearance was 3 ml/kg/h. After intramuscular administration, T(max) was reached at 36 h. The results show that venom lethality varies from specimen to specimen and that pharmacokinetic parameters of venom and anti-venom are totally different. This must be taken under consideration in anti-venom production (anti-venom titre) as well as in therapeutic protocols (dose, injection route) to improve serotherapy.

Sympathetic nervous system activation, antivenin administration and cardiovascular manifestations of scorpion envenomation

We performed two-dimensional echocardiograms and determined plasma norepinephrine levels on admission and at 24h after hospitalization, in 16 children with scorpion envenomation. All patients came from areas where scorpions have been identified as Tityus zulianus and received antivenin at the site of the accident or upon admission. Based on the presence or absence of cardiovascular manifestations, patients were divided into two groups.

GROUP A

10 patients had cardiovascular manifestations of pulmonary edema. Four patients had mild pulmonary edema (Left ventricular ejection fraction: 0.43+/-0.19) and six had moderate to severe pulmonary edema (Ejection fraction: 0.31+/-0.09. p=NS, M+/-SD). Plasma norepinephrine was elevated on admission (1279+/-824) and decreased at 24h in seven of eight patients (474+/-140 pg/ml, p<0.03).

GROUP B

Six patients had no cardiovascular manifestations. These patients had normal chest X-rays and normal echocardiograms. Plasma norepinephrine was not elevated (188+/-180 pg/ml). Time interval from the accident to antivenin administration was significantly longer in Group A compared to Group B (4.5+/-3.3 vs 1.2+/-0.4h, p<0.03) and correlated directly with the absolute change in plasma norepinephrine (r=0.76, p<001). Consequently, we strongly recommend very early administration of antivenin in the medical management of scorpion envenomation by T. zulianus.

Evaluation of antivenom therapy in children severely envenomed by Androctonus australis garzonii (Aag) and Buthus occitanus tunetanus (Bot) scorpions

One hundred and forty-seven cases of envenomed children under 15 years old presenting local and general symptoms without failure in vital functions (clinical grade II) or presenting serious general symptoms with failure in vital functions (clinical grade III) were collected during the summer seasons of 1993-1997. They were classified in six groups according to the use or not of antivenom, the route and the frequency of antivenom administration. The determination, by a sensitive ELISA, of blood venom concentration before and until 6 h after antivenom therapy, allowed the establishment of the venom toxicokinetic curve for each group. The intramuscular administration of antivenom did not show significant effects on venom toxicokinetic curves and on patients recovery time. However, the same amount of antivenom administered by intravenous route clear rapidly the blood free venom toxins. Also, the patient recovery time was significantly shortened. These data are in favor of intravenous application of an adequate dose of an efficient antivenom in order to treat successfully severe scorpion envenoming cases.

Serotherapy in scorpion envenomation: a randomised controlled trial

BACKGROUND

Evidence for the benefit of scorpion antivenom, the only specific treatment for scorpion envenomation, is scarce, despite its common use. We did a prospective, randomised, controlled trial to assess the efficacy of routine administration of scorpion antivenom to scorpion-stung patients, irrespective of clinical severity.

METHODS

We included 825 consecutive patients older than 10 years, who presented to the accident and emergency department of the hospital in Tozeur, Tunisia. We graded severity by absence (grade I) or presence (grade II) of systemic manifestations of scorpion envenomation. Patients were randomly assigned placebo (n=413) or 20 mL bivalent intraveneous scorpion antivenom (n=412). All patients were observed for 4 h. Patients who developed life-threatening symptoms were admitted to the intensive-care unit. At the end of 4 h observation we reassessed grade and discharged grade II patients and admitted grade II patients. We assessed the preventive and curative effects of scorpion antivenom by prevention of worsening grade or by improvement from grade II to grade I.

FINDINGS

Distribution of severity grades was similar in the two groups at baseline, as were the cure rates (55% scorpion antivenom, 66% placebo, absolute difference, 11% [95% CI -4.8 to 26.8]; p=0.234). Preventive effects were seen in 94% and 96% of patients in the scorpion antivenom and placebo groups, respectively, who were initially grade I and who remained symptom-free (absolute difference, 2% [-1.27 to 5.27]; p=0.377). Time from scorpion sting to administration of scorpion antivenom did not affect curative and preventive effects.

INTERPRETATION

We found no benefit in routine administration of scorpion antivenom after scorpion sting, irrespective of clinical severity. Future studies should focus on patients with the most severe symptoms and signs.

Dobutamine in severe scorpion envenomation: effects on standard hemodynamics, right ventricular performance, and tissue oxygenation

OBJECTIVES

To document the effects of dobutamine on standard hemodynamics and right ventricular (RV) performance in patients exhibiting pulmonary edema following severe scorpion envenomation, and to characterize the tissue oxygenation profile in patients sustaining scorpion envenomation-related shock.

DESIGN

Prospective cohort study.

SETTING

An ICU in a university hospital.

PATIENTS

Nineteen consecutive patients were admitted to the ICU for severe scorpion envenomation; all 19 patients exhibited hemodynamic pulmonary edema, and 10 patients had peripheral shock.

INTERVENTIONS

All patients underwent a hemodynamic study with a Swan-Ganz catheter. In 8 of 19 patients, the thermodilution catheter was equipped with a fast-response thermistor.

MEASUREMENTS AND RESULTS

Standard hemodynamic parameters were recorded on admission and following the infusion of dobutamine in all patients at a dosage, from 7 to 20 microg/kg/min, intended to achieve the best hemodynamic and tissue oxygenation compromise. RV ejection fraction (RVEF) and RV volumes were simultaneously recorded in 8 patients, and tissue oxygenation parameters were assessed in the 10 patients with peripheral shock. The clinical signs of tissue hypoperfusion improved, and optimal hemodynamic parameters were achieved at a mean +/- SD dobutamine dosage of 17 +/- 7 microg/kg/min. Dobutamine infusion evoked statistically significant increases in cardiac index, from 2.3 +/- 0.6 to 3.6 +/- 0.7 L/min/m2; stroke volume index, from 18 +/- 5 to 31 +/- 10 mL/m2; and systemic arterial pressure, from 64 +/- 12 to 78 +/- 14 mm Hg. Pulmonary artery occlusion pressure (PAOP) and venous admixture decreased significantly: from 23 +/- 4 to 15 +/- 6 mm Hg and from 29 +/- 7% to 20 +/- 5%, respectively. With respect to RV function, dobutamine infusion significantly increased the RVEF, from 24 +/- 7% to 42 +/- 9%, without significantly changing the RV end-diastolic volume index, reflecting an enhanced RV contractility. In patients with peripheral circulatory failure, the baseline tissue oxygenation profile was consistent with cardiogenic shock, showing increased oxygen extraction as a consequence of a striking depression in oxygen delivery (DO2). After dobutamine infusion, DO2 improved significantly, from 386 +/- 104 to 676 +/- 156 mL/min/m2, with a significant decrease in oxygen extraction, from 34 +/- 8% to 24 +/- 6%.

CONCLUSIONS

In severe scorpion envenomation, dobutamine infusion improves impaired heart function. The effects involve both left ventricular and RV dysfunction. Impaired tissue oxygenation is also improved.

Efficacy of serotherapy in scorpion sting: a matched-pair study

BACKGROUND/OBJECTIVE

Although evidence of scorpion antivenin effectiveness in the clinical setting is lacking, scorpion antivenin is generally considered the only specific treatment for scorpion sting irrespective of its clinical severity. We conducted a matched-pair study to assess the efficacy of systematic administration of scorpion antivenin.

METHODS

Among 600 stung patients who participated in a study on the efficacy of high-dose hydrocortisone after scorpion sting, 135 (cases) had been treated with 10 to 20 mL intravenous scorpion antivenin (neutralizing 10 LD50 venom/mL). Controls were matched on disease severity on arrival to the emergency department. The severity of envenomation was graded I or II according to the absence (grade I) or the presence (grade II) of systemic manifestations of scorpion envenomation. Assessment of scorpion antivenin efficacy was based on the rate of changing severity grade in both groups (clinical improvement or worsening during an observation period of at least 4 hours).

RESULTS

Both groups were similar with respect to clinical severity (36 patients were graded II in each group), age, sex, time-lapse between scorpion sting and ED arrival, and the administration of adjunctive therapy such as hydrocortisone. By the 4-hour evaluation, 50% and 64% of patients initially graded II exhibited a substantial clinical improvement in cases and controls, respectively, suggesting similar effects in cases and controls. There was no difference in preventive effects: 13% and 10% of cases and controls developed systemic manifestations of scorpion envenomation during the 4-hour observation period; 23% of cases and 17% controls were hospitalized by this time. There was no difference in the duration of hospitalization. Three cases developed anaphylactic shock as a consequence of scorpion antivenin administration, while 1 scorpion antivenin-untreated patient died from refractory shock.

CONCLUSION

Systematic administration of scorpion antivenin irrespective of clinical severity did not alter the clinical course of scorpion sting. A prospective study is needed concerning the response of the more severe scorpion envenomations.

Effects of adrenergic-receptor blockade and ligation of spleen vessels on the hemodynamics of dogs injected with scorpion venom

OBJECTIVE

In dogs, scorpion venom evokes a rapid increase in cardiac output (CO) that decreases below baseline level in 1 hr. The changes in CO have recently been shown to be related to the effect of the venom on venous return. In the present study, we tested the hypothesis that changes in determinants of venous return are secondary to sympathoadrenal stimulation evoked by the venom, which causes splenic contracture in the first stage of envenomation leading to increased mean circulatory pressure (MCP) and CO. Persistence of adrenergic response is the main factor leading to the second stage of envenomation, characterized by an increase in resistance to venous return (Rv) and a decrease in CO.

DESIGN

Repeated measures, prospective study in dogs.

SETTING

University-affiliated research laboratory.

SUBJECTS

Mixed-breed dogs injected with scorpion venom.

INTERVENTIONS

The effects of alpha- and beta-adrenergic-receptor blockade (blockade group, n = 9 dogs) and effects of ligation of spleen vessels (spleen ligation group, n = 11 dogs) following intravenous injection of scorpion venom from Leiurus quinquestriatus (0.05 mg/kg) were tested on the determinants of venous return and compared with the effects of scorpion venom alone (control group, n = 6 dogs).

MEASUREMENTS AND MAIN RESULTS

Scorpion venom in the control group caused a marked increase in CO from 2.9+/-0.2 SD L/min to 6.5+/-2.2 L/min (p<.001) and MCP from 8.7+/-2.7 torr (1.2+/-0.35 kPa) to 21.6+/-1.4 torr (2.9+/-0.19 kPa) (p<.001) within 5 mins after venom injection. Cardiac output and MCP markedly decreased at 60 mins to 1.8+/-0.3 L/min (p<.001) and 7.3+/-3.8 torr (1.0+/-0.5 kPa) (p<.05), respectively. Rv did not change at 5 mins but increased from 196+/-50 dyne x sec/cm5 to 335+/-102 dyne x sec/cm5 (p<.01) at 60 mins. Adrenergic-receptor blockade attenuated the increase of CO and MCP at 5 mins, from 2.1+/-0.5 L/min to 2.7+/-1 L/min (p<.001) and from 5.6+/-2.0 torr (0.8+/-0.27 kPa) to 7.5+/-2.3 torr (1.0+/-0.31 kPa) (p<.05), respectively. By 60 mins, both CO and MCP returned to baseline, while Rv was not affected and was maintained at 204+/-158 dyne x sec/cm5. Ligation of spleen vessels prevented a CO increase at 5 mins and it was maintained at baseline value (2.5+/-0.6 L/min). However, MCP increased from 7.9+/-0.5 torr to 12+/-1.3 torr (p<.05). At 60 mins, CO decreased to 1.6+/-0.7 L/min (p<.01) while MCP returned to baseline. The changes in MCP were accompanied by significant increases of Rv from 152+/-24 dyne x sec/cm5 to 383+/-93 dyne x sec/cm5 (p<.001) at 5 mins, and 510+/-175 dyne x sec/cm5 (p<.01) at 60 mins.

CONCLUSIONS

The changes in CO and MCP following scorpion venom injection in dogs are in part related to sympathetic stimulation. Adrenergic-receptor blockade attenuated the initial inotropic effect of the venom and completely prevented a late decrease in CO and MCP. The increase in Rv is the most important factor for late decrease in CO, and results from persistent adrenergic-receptor stimulation. In addition, an Rv increase apparently expresses vasoconstriction and redistribution of blood flow. The initial increase in CO and MCP is explained mainly by adrenergic-receptor effects on the spleen leading to augmented circulatory blood volume.