Hemodynamic and myocardial consequences of scorpion venom

Clinical features and prognosis of severe scorpion envenomation in children

BACKGROUND

Scorpionism is endemic and represents a real public health problem in Morocco. The most dangerous arthropod in the central area is Androctonus mauretanicus (Am) scorpion. Its venom can be lethal, especially for children. This study aimed to determine a clinico-epidemiological profile of severe scorpion envenomation among children and identify risk factors for mortality.

METHODS

This retrospective cohort study included 606 children admitted for severe scorpion envenomation (SSE) from January 2010 to July 2015 in the Pediatric Intensive Care Unit (PICU) of Mohammed VI Teaching Hospital.

RESULTS

The mean age of envenomed children was 6.3 ± 4.2 years. Seventy-four percent of them came from rural settings. Envenomation occurred mostly during the summer months and 78.4% of stings were nocturnal. The time between the sting and evaluation was greater than 2 h in 83% of cases. Bivariate analysis indicated that from 1 to 24 months of age (P = 0.001), hyperthermia (P = 0.022), episodes of diarrhea (P < 0.001), tachycardia (P < 0.001), abdominal distention (P < 0.001), skin marbling (P < 0.001), signs of respiratory distress (P < 0.001), irritability (P < 0.001), generalized seizures (P = 0.053), and Glasgow Coma Score (GCS) of 3 to 9 (P < 0.001) were significantly correlated with mortality. On multivariate analysis, diarrhea (P = 0.007), skin marbling (P = 0.006), and respiratory distress (P = 0.002), and GCS 3-9 (P = 0.007) were found to be independent risk factors for mortality in our patient population.

CONCLUSIONS

Children are at high risk of developing serious complications, even death, from severe scorpion envenomation. Here we identified multiple factors that appear to increase the mortality risk in children after scorpion envenomation, including previously described central nervous system alterations.

Involvement of the Endothelin Receptor Type A in the Cardiovascular Inflammatory Response Following Scorpion Envenomation

Elevated levels of endothelin-1 (ET-1) were recorded in sera of scorpion sting patients. However, no studies focused on the mechanism of ET-1 involvement in the pathogenesis of scorpion envenomation, particularly in the cardiovascular system which is seriously affected in severe cases of scorpion stings. Inflammation induced by Androctonus australis hector (Aah) scorpion venom in the heart together with the aorta was studied in mice pretreated with a specific endothelin A receptor (ETA-R) inhibitor. ETA-R inhibition resulted in the attenuation of the high amounts of cytokine (tumor necrosis factor alpha (TNF-α) and interleukin-17 (IL-17)) recorded in the sera of envenomed mice. The recovery of the oxidative stress marker balance and matrix metalloproteinase (MMP) expression were also observed, concomitantly with the reduction of tissular neutrophil infiltration. Additionally, the cardiac and the aortic tissue alterations, and the metabolic enzymes (creatine kinase (CK) and muscle–brain isoform creatine kinase (CK-MB)) overspread into sera were significantly attenuated. Obtained results suggest the implication of endothelin throughout its ETA receptors in the inflammatory response observed in the cardiovascular components during scorpion envenomation. Further knowledge is needed to better understand the implication of the endothelin axis and to improve the therapeutic management of severe scorpion sting cases.

Scorpion bite-induced ischaemic stroke

We report a 54-year-old woman with scorpion bite. After 3 hours of admission, the patient developed sudden onset tachycardia with hypotension. Cardiac evaluation showed raised creatine kinase MB isoenzyme was elevated; ECG and two-dimensional echocardiography findings were suggestive of myocarditis. Subsequently, she developed transient ventricular tachycardia before developing abrupt onset, right hemiplegia, global aphasia and progressive worsening of sensorium 12 hours after the bite. MRI of brain revealed massive left middle cerebral artery (MCA) territory infarct. The magnetic resonance angiography showed non-visualisation of left internal carotid artery (ICA) and MCA. Coagulation parameters were normal. Sudden complete occlusion of left ICA was probably secondary to cardioembolic phenomenon leading to massive infarct. Despite aggressive medical and supportive measures, she clinically worsened rapidly to Glasgow Coma Scale of 3/15 over next 6 hours and succumbed to her illness the next day.

Scorpion envenomation among children: clinical manifestations and outcome (analysis of 685 cases)

Our objective was to characterize both epidemiologically and clinically manifestations after severe scorpion envenomation and to define simple factors indicative of poor prognosis in children. We performed a retrospective study over 13 years (1990-2002) in the medical intensive care unit (ICU) of a university hospital (Sfax-Tunisia). The diagnosis of scorpion envenomation was based on a history of scorpion sting. The medical records of 685 children aged less than 16 years who were admitted for a scorpion sting were analyzed. There were 558 patients (81.5%) in the grade III group (with cardiogenic shock and/or pulmonary edema or severe neurological manifestation [coma and/or convulsion]) and 127 patients (18.5%) in the grade II group (with systemic manifestations). In this study, 434 patients (63.4%) had a pulmonary edema, and 80 patients had a cardiogenic shock; neurological manifestations were observed in 580 patients (84.7%), 555 patients (81%) developed systemic inflammatory response syndrome (SIRS), and 552 patients (80.6%) developed multi-organ failure. By the end of the stay in the ICU, evolution was marked by the death in 61 patients (8.9%). A multivariate analysis found the following factors to be correlated with a poor outcome: coma with Glasgow coma score ≤ 8/15 (odds ratio [OR] = 1.3), pulmonary edema (OR = 2.3), and cardiogenic shock (OR = 1.7). In addition, a significant association was found between the development of SIRS and heart failure. Moreover, a temperature > 39°C was associated with the presence of pulmonary edema, with a sensitivity at 20.6%, a specificity at 94.4%, and a positive predictive value at 91.7%. Finally, blood sugar levels above 15 mmol/L were significantly associated with a heart failure. In children admitted for severe scorpion envenomation, coma with Glasgow coma score ≤ 8/15, pulmonary edema, and cardiogenic shock were associated with a poor outcome. The presence of SIRS, a temperature > 39°C, and blood sugar levels above 15 mmol/L were associated with heart failure.

Cerebrovascular manifestations and alteration of coagulation profile in scorpion sting: a case series

Cerebrovascular manifestations are uncommon presentations of scorpion sting in the Indian subcontinent. A prospective study was carried out on 42 patients with scorpion sting in the intensive care unit (ICU) of the Institute of Medical Sciences, Banaras Hindu University, Varanasi-05, INDIA, during the period of May 2005 to October 2007. In all the patients detailed history, physical examination with a specific neurological examination and routine biochemical testing and fundus examination were done. Computerized tomography and magnetic resonance imaging were done in cases with neurological deficit. All these patients also underwent a complete hematological, rheumatologic and cardiovascular work-up for stroke. Cerebrovascular involvement was noted in three patients (7.15%). Hemorrhagic stroke was noted in two patients (4.77%) and thrombotic stroke was noted in one patient (2.39%). The mean time of presentation of neurological symptoms was 3 days. Contrary to world literature, there have been no reports of cranial nerve palsies or neuromuscular involvement in our series.

Scorpion toxin of Androctonus australis garzonii induces neuropeptide Y release via bradykinin stimulation in rat atria and kidneys

The ability of scorpion toxins to produce hemodynamic alterations is well documented but all mediators implied in cardiovascular disturbances are not known. In the present investigation we studied the effect of North African Androctonus australis garzonii scorpion toxin on neuropeptide Y (NPY) release from rat atria and kidneys by a perifusion system in vitro. To further understand the mechanisms of the scorpion toxin action on NPY release, the effects of icatibant (HOE 140, a selective bradykinin-B2 receptor antagonist), tetrodotoxin (TTX, a sodium channel antagonist) and diltiazem (a calcium channel antagonist), and the effect of the scorpion toxin on bradykinin (BK, a potent vasorelaxant peptide of the kinin group) release were studied in both tissues. We showed that the scorpion toxin (10(-6)M) increased the NPY release from both atria (35%) and kidneys (40%). This increase was significantly (p<0.001) inhibited by HOE 140 (10(-5)M). The scorpion toxin (10(-6)M) enhanced BK secretion in both atria (52%) and kidneys (55%). Diltiazem (10(-5)M) and TTX (10(-5)M) decreased by 45-75% NPY levels induced by scorpion toxin in both organs. The results show that A. australis garzonii scorpion toxin stimulates NPY release from both rat atria and kidneys, and suggest that the toxin induces NPY release via BK stimulation through B2 receptors. This effect appears to involve calcium and sodium channel activation.

Unusual presentations of scorpion envenomation

Scorpions are nocturnal arthropods that inject their venom through the victims’ skin by stingers. By the envenomation, clinical manifestations in a wide spectrum may occur, including pain at one side and death because of severe cardiopulmonary or neurological abnormalities. Sometimes the victim cannot describe the insect or does not remember even being stung after the event. We present two cases of scorpion envenomation with different and rare clinical situations with a short review of the literature.

A clinical score predicting the need for hospitalization in scorpion envenomation

OBJECTIVE

Predicting complications is a clinical challenge in the assessment of victims of scorpion envenomation (SE). We sought to develop a clinical score to predict need for hospitalization after scorpion sting.

METHODS

We prospectively collected data in patients attending the emergency department after SE in derivation (n = 868) and validation groups (n = 435). A score was derived from a multiple regression analyses using clinical variables as dependent variables and hospitalization as independent variable.

RESULTS

Discrimination power of the constructed score was good (area under the receiver operating characteristic curve, 0.85 and 0.83 in derivation and validation group, respectively). Goodness-of-fit tests indicated that the score performed well in the derivation and the validation groups (P = .88 and P = .67 respectively). The score has a good sensitivity and negative predictive value at cutoff value of 2.

CONCLUSION

Our clinical score could be used for efficient hospital admission decision in patient's victims of SE.

Scorpion venom increases mRNA expression of lung cytokines

Previous studies have demonstrated that scorpion toxins increase the serum levels of IL-1, IL-6, INF-gamma, and GM-CSF in patients with severe shock and pulmonary edema. Moreover, it has been shown that experimental models of scorpion envenomation presented an increase in serum levels of IL-1, IL-6, IFN-gamma and nitric oxide. Thus, it is possible that the cytokine release may contribute to the onset and maintenance of the pulmonary edema induced by scorpion venom. This study was designed to investigate whether inflammatory and non-inflammatory cytokines, contribute to the pulmonary injury induced by infusion of Tityus serrulatus scorpion toxin in rats. We show that scorpion venom not only increases the expression of mRNA pulmonary inflammatory cytokines but also non-inflammatory cytokines as well. Moreover, the expression of IL-1alpha, IL-1beta and IL-6 mRNA was shown to be higher among the remaining detectable cytokines. The findings of this study provide additional insight towards the understanding of the pathophysiology of the pulmonary edema induced by scorpion venom. The increased level of pulmonary cytokines observed during the pulmonary edema may be responsible for the exacerbation and maintenance of the inflammatory response to scorpion venom in the lungs.

Acute left ventricular dysfunction of severe scorpion envenomation is related to myocardial perfusion disturbance

BACKGROUND

Scorpion envenomation (SE) may present severe cardiac dysfunction with acute pulmonary edema and cardiogenic shock. The pathophysiology of this acute heart failure is still controversial. We aimed at assessing the contribution of the myocardial ischemia to the left ventricular dysfunction in SE by using 99mTc-Sestamibi myocardial perfusion scintigraphy (MPS).

METHODS

Twelve children (7 males, 1-12 years old) presenting severe Tityus serrulatus envenomation were prospectively submitted to MPS within 72 h (acute) and 15 days (follow-up) after the event. MPS images were interpreted using a visual semi-quantitative uptake score (0 = normal, 4 = absent). Echocardiography was used for the assessment of left ventricular (LV) ejection fraction (EF) and regional wall motion (WM) by using a semi-quantitative score (0 = normal, 4 = akinesia). A 16-segment LV model was used.

RESULTS

Initial echocardiography showed marked WM abnormalities with a mean score of 31.4+/-13.9, and a reduced EF (36+/-16%). All patients exhibited myocardial perfusion (MP) defects. The mean MP uptake score was 14.6+/-7.8. A significant topographic association between MP and WM changes was obtained (p<0.0001, Fischer exact test). A positive correlation was obtained between the summed WM and MP scores (R=0.68, p=0.016). Follow-up evaluation showed a significant improvement of LVEF (65+/-10%) and WM score (3.9+/-4.2), parallel to the normalization of MP.

CONCLUSIONS

These observations strongly support the participation of transitory myocardial ischemia in the mechanism of the acute cardiac dysfunction caused by severe scorpion envenoming. Micro vascular spasm related to the catecholamine over stimulation may be the pathophysiologic link triggering the myocardial perfusion disturbance in this syndrome.

INVESTIGATION OF THE MICROCIRCULATION AND THE STATE OF OXIDATIVE STRESS IN THE RAT AFTER SCORPION ENVENOMATION

1. Severe cases of scorpion envenomation (SE) generally show both respiratory and cardiocirculatory dysfunction. However, the pathophysiology of SE remains controversial. In the present study, we tried to explain the pathophysiology of the haemodynamic perturbations and cardiac failure in rats poisoned by the venom of Buthus occitanus tunetanus through a histomorphometric study of myocardial and muscular skeletal microcirculation and analysis of the oxidative stress state in order to evaluate the implication of the inflammatory process in the pathogenesis of SE. 2. Experiments were performed on 96 rats divided into 16 groups (n = 6 in each group). Two groups were used to determine the optimum conditions of venom administration and times when to measure haemodynamic parameters. The B. occitanus tunetanus venom was administered at a dose of 800 microg/kg and tissues were removed 5 and 20 min after envenomation. Six groups were used for histomorphometric study: two control groups, two poisoned groups an two melatonin-pretreated and poisoned groups. The histomorphometric study was performed on isolated hearts and skeletal muscles. The final eight groups of rats (two control groups, two envenomated groups, two control groups pretreated with melatonin and two groups pretreated and envenomated) were used to investigate the state of tissue oxidative stress during SE and to evaluate the anti-oxidant effect of melatonin on rats poisoned with B. occitanus tunetanus venom. This study was based on the determination of tissue malondialdehyde in isolated organs as an indicator of thiobarbituric acid-reactive substances (TBARS). Melatonin was injected at a dose of 5 mg/kg, i.v., 15 min before the administration of serum or venom. Data were compared using analysis of variance and Tukey's test for multiple pair-wise comparisons. 3. Five minutes after venom injection, a significant reduction in the mean relative volume of venules and arterioles in the heart and skeletal muscles of poisoned rats was noted. Twenty minutes after venom injection, these volumes were significantly increased in the heart and skeletal muscles of poisoned rats. Pretreatment of envenomated rats with melatonin resulted in a significant decrease in the mean relative volume of the venules and arterioles in the heart and skeletal muscles 5 and 20 min after venom injection compared with untreated envenomated rats. Investigation of the oxidative stress state showed a highly significant increase in TBARS in poisoned rats compared with control groups 5 and 20 min after venom injection. Melatonin pretreatment of rats poisoned with B. occitanus tunetanus venom resulted in an important and highly significant reduction of TBARS compared with untreated envenomated rats. 4. It appears from the results of the present study that administration of B. occitanus tunetanus venom engendered an excessive myocardial and skeletal muscular vasoconstriction attributed to massive catecholamine release followed by arteriolar and venular vasodilatation. This venous stasis at the muscular microcirculation could be due to myocardiac failure. However, the concomitant presence of arteriolar vasodilatation suggests an inflammatory process in the pathophysiology of SE. This process was suggested by the genesis of a state of oxidative stress in relation to the important lipoperoxidation, which was inhibited by administration of the anti-oxidant melatonin. Thus, melatonin pretreatment seemed to accentuate the first phase of vascular reactivity in envenomed rats and inhibit the second vasodilator phase observed 20 min after administration of the venom.

Neurohormonal activation in severe scorpion envenomation: correlation with hemodynamics and circulating toxin

We studied the effects of scorpion (Androctonus australis hector) venom on hemodynamics and on the release of catecholamines, neuropeptide Y (NPY), endothelin-1 (ET-1) and atrial natriuretic peptide (ANP) in dog model of severe scorpion envenomation. Nine mongrel anesthetized dogs were submitted to mechanical ventilation through intubation and were administered intravenously purified dried scorpion venom (Androctonus autstralis) 0.05 mg/kg. Measurements including pulmonary artery catheter derived parameters, serum toxin levels and humoral variables were performed at baseline (before venom injection) and 5, 15, 30 and 60 min after venom injection. Humoral variables included: serum lactate, epinephrine (EP), norepinephrine (NE), NPY, ET-1 and ANP plasma concentrations. Scorpion venom caused rapid and transient increase of mean arterial pressure (MAP) and PAOP associated with a marked and sustained decline in cardiac output (-55% at 60 min; P < 0.001). Hemodynamic changes were associated with a rapid and significant increase of all measured hormones. The highest increase was for NE (28-fold) and EP (25-fold). MAP was closely correlated with NE and less significantly correlated with toxin levels. Similarly, significant correlation was observed between PAPO and ANP plasma levels. These findings support the implication of excessive catecholamines release in hemodynamic disturbances of severe SE and suggest that NPY and ET-1 could be involved in this process. Serum toxin does not appear to consistently contribute to these effects. Through its correlation with PAOP, ANP could be a reliable and useful marker of cardiac dysfunction in SE.

Dose-dependent serum biochemical alterations in Wistar albino rats after Palamneus gravimanus (Indian black scorpion) envenomation

Palamneus gravimanus envenomated rats showed dose-dependent alterations in serum biochemical parameters. Sub lethal doses of 100, 200, and 400 microg/kg of P. gravimanus venom were injected intramuscularly into rats. Blood samples were collected by heart puncture before and 4 h after crude venom administration. Serum was analyzed for glucose, blood urea nitrogen (BUN), uric acid, total protein, cholesterol, sodium, potassium, inorganic phosphorus, alkaline phosphatase, aspartate aminotransferase (AST-SGOT), alanine amino-transferase (ALT-SGPT), lactate dehydrogenase (LDH), and creatinine phosphokinase (CPK). Statistically significant increases in serum levels of glucose, creatinine, AST, ALT, BUN, CPK, and LDH and significant decreases in serum levels of total protein, uric acid, cholesterol, calcium, and potassium 4 h after venom administration could be due to the toxic action of P. gravimanus venom on certain organs in rats.

[Cardiovascular dysfunction following severe scorpion envenomation. Mechanisms and physiopathology]

The seriousness of scorpion envenomation results essentially from left cardiac function with pulmonary oedema and/or a state of shock. Adrenergic myocarditis, toxic myocarditis and myocardial ischemia are the 3 mechanisms that explain the cardiac dysfunction. Myocardial ischemia is not only due to the release of catecolamines but also the effect of the cytokines and/or neuropeptide Y on the coronary vessels. The cardiac damage can be due or enhanced by the depressive effect of the cytokines on the myocardial cells. The frequently observed hyperglycaemia only enhances the state of the already damaged myocardium.

Evidence that free radical generation occurs during scorpion envenomation

Although it is well established that symptomatology, morbidity and death following scorpion envenomation are due to increases in neurotransmitter release secondary to toxins binding to voltage-sensitive sodium channels, the mechanism by which venom action is involved in damaging heart, liver, lungs and kidneys remains unclear. We hypothesized that scorpion toxins could induce the generation of high levels of free radicals responsible for membrane damage in organs targeted by venom action. We have investigated lipid peroxidation in different organs, through the evaluation of thiobarbituric acid reactive substances (TBARS), after experimental envenomation of rats by toxic fractions of Androctonus australis Hector venom. We have shown that scorpion toxins cause considerable lipid peroxidation in most vital organs. We also evaluated the protective effects of antioxidants in mice injected with lethal doses of toxins. Among the drugs tested, N-acetylcysteine (NAC) was effective in protecting the mice when injected prior to toxin application. However, the free radical scavenging properties of NAC seem less implicated in these protective effects than its ability to increase the fluidity of bronchial secretions. We therefore conclude that free radical generation only plays a minor role in the toxicity of scorpion venom.

Lung compliance, plasma electrolyte levels and acid-base balance are affected by scorpion envenomation in anesthetized rats under mechanical ventilation

To determine the effects of Tityus serrulatus scorpion toxin on lung compliance and resistance, ionic equilibrium and acid-base balance over time in anesthetized and mechanically ventilated rats, we measured air flow, tracheal and esophageal pressure. Lung volume was obtained by electronic integration of airflow signal. Arterial blood samples were collected through a catheter at baseline (before) and 5, 15, 30 and 60 min after scorpion toxin injection for arterial blood gases, bicarbonate, and alkali reserve levels as well as for, sodium, potassium, magnesium, glucose, lactate, hematocrit, and osmolality analysis. Injection of the gamma fraction of the T. serrulatus scorpion venom in rats under mechanical ventilatory support leads to a continuous decrease in lung compliance secondary to pulmonary edema, but no change in airway resistance. The changes in arterial blood gases characterizing metabolic acidosis were accompanied by an increase in arterial lactate and glucose values, suggesting a scorpion toxin-induced lactic acidosis, in association with poor tissue perfusion (hypotension and low cardiac output). Moreover, scorpion toxin injection resulted in hyperosmolality, hyperkalemia, hypermagnesemia and an increase in hematocrit. The experiments have shown a clinically relevant animal model to study severe scorpion envenoming and may help to better understand the scorpion envenoming syndrome.

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.

Scorpion venom decreases lung liquid clearance in rats

It has been reported that scorpion venom causes respiratory failure and pulmonary edema. However, the effects of this toxin on lung edema clearance have not been previously studied. We examined the effects of scorpion (Tityus serrulatus) venom on the ability of the lung to clear fluid and on alveolar epithelial Na,K-ATPase. The wet-to-dry lung weight ratio was increased in anesthetized rats injected intraperitonally with scorpion venom. Lung edema clearance decreased by up to approximately 60% in rats injected with the venom. Na,K-ATPase alpha1- and beta1-subunit protein abundance and activity decreased at the basolateral membranes of alveolar epithelial type II cells incubated with scorpion venom as compared with that of control animals. There was no difference in cell injury in alveolar epithelial type II cells incubated with scorpion venom for 60 minutes compared with that of control animals. We provide here the first evidence that scorpion venom decreases lung liquid clearance, probably by downregulating Na,K-ATPase in the alveolar epithelium.

Significance of assessment of serum cardiac troponin I and interleukin-8 in scorpion envenomed children

In the present study, 41 children in Upper Egypt were admitted to Pediatric Intensive Care Unit, Assiut University Hospital, for scorpion envenomation. They were compared with 15 apparently healthy children of matching age as controls. The victims and controls were subjected to complete clinical examination, full blood count and arterial blood gases analysis. According to severity of scorpion envenomation, 17 children had manifestations of severe envenomation and clinical signs of toxic myocarditis (severe cases), 14 children had moderate manifestations of envenomation without clinical evidence of carditis (moderate cases) and 10 cases showing only mild symptoms of envenomation (mild cases). The serum levels of cardiac troponin I (cTnI) and interleukin-8 (IL-8) beside the enzymatic activities of creatine phosphokinase (CPK), CPK-isoenzyme-MB (CPK-MB) and lactate dehydrogenase (LDH) were determined once for mild cases and controls on admission and twice for severe and moderate cases on admission and after 24. Electrocardiography and measurements of echocardiographic (Echo) of % fractional shortening of left ventricule (% SF), left ventricular ejection fraction (LVEF) and cardiac chambers dilatation were done for severe and moderate cases. All the envenomed victims showed significantly higher mean values of CPK, CPK-MB, LDH, and IL-8 on admission in comparison to control group. cTnI was not detectable in the sera of control group as well as patients of mild envenomation. The mean values of CPK, CPK-MB, LDH, and IL-8 were significantly higher in severe cases while only IL-8 and CPK-MB were significantly higher in moderate cases in comparison with mild cases. The mean values of IL-8, cTnI, CPK, CPK-MB and LDH were significantly higher in severe cases both on admission and on follow-up comparing with moderate cases. The case fatality rate was 12.5% and all were from severe cases with toxic myocarditis. The non-survivors victims showed significant higher mean values of only cTnI on admission and both cTnI and IL-8 on follow up in comparison to the survivors. Significant reduction of % SF and LVEF were noticed among the non-survivors in comparison to survivors. The cTnI showed 100% specificity and sensitivity for diagnosis of myocardial injury in relation to Echo finding in the envenomed victims. In severe cases, cTnI was positively correlated with IL-8 while negatively correlated with %SF and LVEF. In conclusion, cTnI is a specific marker for diagnosis of myocardial injury in scorpion envenomation while other biochemical markers did not show such specificity. Also, IL-8 may be involved in the pathogenesis of myocardial injury of scorpion envenomation. Both cTnI and IL-8 may be useful to forecast the fatal outcome in scorpion envenomation.

Autonomic effects of some scorpion venoms and toxins

1. The autonomic effects of venoms and toxins from several species of scorpions, including the Indian red scorpion Mesobuthus tamulus, the Chinese scorpion Buthus martensi Karsch and the Israeli scorpion Leiurus quinquestriatus quinquestriatus, all belonging to Buthidae, and the Asian black scorpions Heterometrus longimanus and Heterometrus spinifer, belonging to Scorpionidae, are reviewed. 2. The effects of the venoms of M. tamulus and L. q. quinquestriatus on noradrenergic and nitrergic transmission in the rat isolated anococcygeus muscle revealed that both venoms mediated their pharmacological effects via a prejunctional mechanism involving the activation of voltage-sensitive sodium channels with consequent release of neurotransmitters that mediate target organ responses, similar to the effects mediated by other alpha-scorpion toxins. 3. Two new toxins, Makatoxin I and Bukatoxin, were purified to homogeneity from the venom of B. martensi Karsch. Determination of their complete amino acid sequences confirmed that both toxins belonged to the class of alpha-scorpion toxins. The effects of both toxins on noradrenergic and nitrergic transmission in the rat anococcygeus muscle provided firm evidence that their pharmacological actions also closely resembled those mediated by other alpha-scorpion toxins on neuronal voltage-sensitive sodium channels. 4. The venoms of H. longimanus and H. spinifer were found to have high concentrations of noradrenaline (1.8 +/- 0.3 mmol/L) and relatively high concentrations of acetylcholine (79.8 +/- 1.7 micromol/L) together with noradrenaline (146.7 +/- 19.8 micromol/L), respectively, which can account for their potent direct cholinergic and noradrenergic agonist actions in the rat anococcygeus muscle. 5. Our studies confirmed that the rat anococcygeus muscle is an excellent nerve-smooth muscle preparation for investigating the effects of bioactive agents on noradrenergic and nitrergic transmission, as well as the direct agonist actions of these agents on post-synaptic alpha-adrenoceptors and M3 muscarinic cholinoceptors. Although many studies, including our own, have documented that scorpion venoms and toxins mediate their primary effects via a prejunctional mechanism that leads to the marked release of various autonomic neurotransmitters, our studies have shown that there are exceptions to this generally accepted phenomenon. In particular, we have provided firm evidence to show that the venoms from H. longimanus and H. spinifer do not have such a prejunctional site of action but, instead, the venoms mediate their autonomic effects through direct agonist actions on post-junctional muscarinic M3 cholinoceptors and alpha-adrenoceptors.

Cardiac troponin I release after severe scorpion envenoming by Tityus serrulatus

Eight children aged 2-9 years, with signs and symptoms of severe scorpion envenoming by Tityus serrulatus were studied. All patients showed clinical manifestations of cardiac dysfunction, with ECG and echocardiographic alteration and five developed pulmonary edema. Troponin I levels were normal in all patients on admission, except for two who arrived later, and increased thereafter, with maximum values being observed 24-36 h after the sting. The detection of TnI in patients with severe scorpion envenoming, and the observed temporal pattern and serum levels meet the criteria established for the diagnosis of acute myocardial infarction. The rapid reversibility of cardiac dysfunction, together with the normalization of the enzymatic, ECG and echocardiographic data, indicates the occurrence of an acute myocardial lesion without underlying or associated coronary disease.

Biochemical and pharmacological characterization of the venom of the black scorpion Heterometrus spinifer

The sting of the black scorpion Heterometrus spinifer, which can cause intense localized pain, has not been reported to produce lethal cardiovascular complications, which are well known to result from scorpion envenomation as a consequence of a massive release of catecholamines. Therefore, we have undertaken a biochemical and pharmacological characterization of the venom of H. spinifer. Pharmacologically, the venom (0.125 microL/mL) produced a marked, reversible contracture in the chick biventer cervicis muscle that was blocked by d-tubocurarine (2 microM) but not by tetrodotoxin (5 microM) and omega-conotoxin GVIA (3 microM). The anticholinesterase neostigmine (1 microM) potentiated the contracture by 5.3-fold. An ultra-filtrate fraction of MW < 3000 (F3K) of the venom produced a similar contracture in the biventer muscle, whereas the retentate of MW > 3000 did not. In the rat anococcygeus muscle, the venom produced a contractile response that was partially (37.4 +/- 1.6%) blocked by atropine (5 microM); phentolamine (5 microM) blocked the remaining response. Tetrodotoxin (5 microM) did not block the contractile response of the venom on the anococcygeus muscle. Electrospray ionization-mass spectrometry/mass spectrometry confirmed the presence of high concentrations of acetylcholine (79.8 +/- 1.7 microM) and norepinephrine (146.7 +/- 19.8 microM) in H. spinifer venom, which can fully account for the observed cholinergic and adrenergic effects. In contrast to scorpion venoms that selectively target neuronal ion channels in mediating transmitter release, our data show that H. spinifer venom does not possess such activity, which likely explains the apparent lack of lethality of black scorpion envenomation.

Evidence for a direct action of Tityus serrulatus scorpion venom on the cardiac muscle

The ability of toxins to activate the cardiovascular system plays an important role in the morbidity and lethality of the Tityus serrulatus scorpion envenoming. Most of the actions of the scorpion toxins are indirect and due to the release of adrenergic and cholinergic neurotransmitters. Accordingly, treatment following envenoming is targeted towards inhibition of adrenergic and cholinergic receptors. Here, we have sought evidence for a direct action of T. serrulatus venom on the isolated rat heart (Langendorff's method). We show that the bradycardia induced by T. serrulatus venom was completely blocked by atropine, a muscarinic receptor antagonist. Similarly, the increase in heart rate that follows the venom-induced bradycardia was totally inhibited by a beta(1)-adrenoceptor antagonist or by chemical sympathetic denervation with 6-hydroxydopamine. In contrast to these findings, the venom-induced increase in contractile force was not modified by beta(1)-adrenoceptor blockade or by chemical sympathetic denervation. The results clearly demonstrate that the chronotropic effects of T. serrulatus are dependent on neurotransmitter release, but the inotropic effects are not. The neurotransmitter-independent increase in contractility seems to be a direct action of the venom on cardiomyocytes. We suggest that this direct effect on cardiac fibers may play a role in the development of cardiac arrhythmias and contractility defects following envenoming with T. serrulatus scorpion.

The effects of lignocaine on actions of the venom from the yellow scorpion "Leiurus quinquestriatus" in vivo and in vitro

Many toxins from scorpion venoms activate sodium channels, thereby enhancing neurotransmitter release. The aim of the present work was to determine if the in vivo and in vitro effects of Leiurus quinquestriatus venom (LQQ) could be ameliorated by lignocaine, a sodium channel blocker. In urethane anaesthetised rabbits, LQQ venom (0.5 mg kg(-1), i.v.) caused initial hypotension and bradycardia followed by hypertension, pulmonary oedema, electrocardiographic changes indicating conduction defects, ischaemia, infarction, and then hypotension and death. Lignocaine (1 mg kg(-1) i.v. bolus initially, followed by i.v. infusion of 50 microg kg(-1) min(-1)) significantly attenuated the majority of the venom-evoked effects and reduced mortality. Addition of LQQ venom (1, 3 and 10 microg ml(-1)) to chick biventer cervicis, guinea pig ileum, and rat vas deferens preparations, increased the height of electrically-induced twitches, elevated resting tension, and caused autorhythmic oscillations. Lignocaine (3 x 10(-4)-1.2 x 10(-3) M) greatly attenuated these venom-evoked actions in the three preparations. Antagonists of appropriate neurotransmitters were also tested to determine the contribution of released transmitters to LQQ effects. Atropine significantly decreased the venom-elicited effects on guinea pig ileum preparations, while prazosin and guanethidine significantly reduced the venom's actions on rat vas deferens. In chick biventer cervicis preparations, tubocurarine and hexamethonium significantly attenuated the venom-induced effects. This study supports the hypothesis that many effects of LQQ venom involve the release of neurotransmitters and may be ameliorated by treatment with lignocaine.

Characterization and mechanisms of the cardiovascular and haemodynamic alterations induced by scorpion venom in rats

The scope of this work was to investigate the nature, chronology and mechanisms of the cardiovascular disorders induced by scorpion envenomation. Anaesthetized rats were instrumented for measurement of cardiac output (CO), renal (RBF) and muscular (HBF) blood flows (pulsed Doppler flowmetry), blood pressure, heart rate and dP/dt. Buthus occitanus venom (BO) was administered intravenously in the absence/presence of different pre-treatments. BO dose-dependently (150-300 microg/kg) increased blood pressure, dP/dt, total peripheral (TPR), renal (RVR) and muscular (HVR) vascular resistances, and decreased CO, RBF and HBF. Recovery occurred after 150 but not after 300 microg/kg. BO, 600 microg/kg, produced qualitatively similar effects but arrhythmias developed and mortality increased. Pre-treatment with phentolamine prevented the rises in TPR, RVR, HVR and blood pressure and the decreases in CO, RBF and HBF induced by BO, 300 microg/kg. Pre-treatment with propranolol prevented the rise in dP/dt and the occurrence of arrhythmias and limited the rise in RVR and the drop in RBF induced by BO, 300 microg/kg. Phentolamine, propranolol and their combination also prevented BO, 600 microg/kg-induced mortality. Other pre-treatments (bosentan, losartan, diltiazem, mepyramine) were almost ineffective vs. BO effects. Finally, BO, 300 microg/kg, induced a 30-40-fold increase in plasma epinephrine and norepinephrine levels, but no change in plasma endothelin-1 levels. Thus in anaesthetized rats, the pattern of the cardiac and systemic and regional haemodynamic effects of BO is typically that of and results from catecholamine outpouring-induced alpha- and beta-adrenoceptor stimulation.

Acid-base balance following Tityus serrulatus scorpion envenoming in anaesthetized rats

In the present work the pH and arterial blood gases were measured in fasted and fed male albino rats, weighing 297 +/- 13 g, anaesthetized with urethane (1.4 g/kg, i.p.) before and after injection of T1 fraction from Titys serrulatus scorpion venom, during 60 min. Arterial blood samples were collected at 0, 5, 15, 30 and 60 min for pH, pCO2, pO2, bicarbonate and base-excess analysis. The data showed that the scorpion toxin induced a continuous drop in the blood pH along the time. Hypercapnia and hypoxemia peaking at 30 min and followed by a recovery towards normal values at 60 min were also observed. A pronounced decrease in the blood bicarbonate levels at 60 min and negative base-excess values along with time were evident at 60 min. The comparisons between fasted and fed animals have shown that in the last group the effects of scorpion toxin on the arterial blood gases were less pronounced. We conclude that T1 fraction of Tityus serrulatus scorpion venom induces in anaesthetized rats an acute respiratory acidosis followed by metabolic acidosis.

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.

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.

Acute myocarditis following Tityus trinitatis envenoming: morphological and pathophysiological characteristics

The clinicopathological features of four cases of scorpion envenoming by Tityus trinitatis are presented. The cardiac histopathology is recorded in the two fatal cases. The pathology of the acute myocarditis was a mixed picture of a toxic myocarditis and coagulative myocytolysis. These cardiac lesions are also seen in catecholamine induced cardiotoxicity and lend support to the theory that an adrenergic surge follows scorpion envenoming. A brief review of scorpion envenoming syndrome is undertaken in the light of these findings.

Spider bite envenomation in Al Baha Region, Saudi Arabia

BACKGROUND

The purpose of this study was to highlight the clinical features of spider bite envenomation, a subject which has not, to our knowledge, been previously published in Saudi Arabia.

PATIENTS AND METHODS

Ten patients (8 males and 2 females) aged between 13 and 75 years (mean 36.8) were hospitalized at King Fahad Hospital, Al Baha, with the diagnosis of spider bites during the 9-year period from June 1988 to May 1997.

RESULTS

One of the patients was bitten on the right hand by a brown spider, causing severe cellulitis and tissue necrosis, and requiring surgical debridement and pedicle skin flap graft. The nine other patients (90%) had bites from black spiders identified as black widow spiders. Two of the nine (22.2%) suffered only local reactions in the form of pain, erythema and swelling at the site of bite. The remaining seven (77.8%), had varying symptoms of systemic envenomation, including pulmonary edema, myocardial dysfunction with elevated creatinine kinase, electrocardiographic and echocardiographic abnormalities, progressive paresthesia, generalized body ache, etc. Therapy included analgesics, muscle relaxants, intravenous infusion of calcium gluconate and oxygen where indicated. Specific antivenin therapy was available for only four of the nine patients (44%) with black widow spider bite. Antivenin therapy still produced dramatic relief of the symptoms in the patient with pulmonary edema, even after a delay of 30 hours.

CONCLUSION

Spider bite envenomation should be considered in the differential diagnosis of acute surgical abdomen and myocardial infarction.

Effects of antivenom serotherapy on hemodynamic pathophysiology in dogs injected with L. quinquestriatus scorpion venom

In dogs, scorpion venom causes an immediate increase in cardiac output that declines below baseline values within one hour. We tested the hypotheses that antivenom given before venom injection may prevent changes in cardiac output, while antivenom given after the inotropic stage of envenomation cannot reverse cardiac output decline. Twenty-five anesthetized, mechanically ventilated dogs were given 0.1 mg/kg i.v. venom of the scorpion Leiurus quinquestriatus. The dogs were randomized into 4 groups: 5 dogs were given venom alone (control group) and 6 dogs were given 6 ml of antivenom one minute before venom injection while 8 and 6 dogs were given 6 ml of antivenom 20 and 60 min after venom injection, respectively. Parameters reflecting respiratory and circulatory functions were measured for 180 min after venom injection. Scorpion venom caused a gradual decrease in heart rate, an initial elevation of systemic and pulmonary blood pressure and cardiac output followed by a decline in these parameters. PO2, pH and HCO3- gradually decreased, while PCO2 gradually increased from baseline. Antivenom given before venom injection prevented all the effects induced by the venom. Antivenom given at 20 and 60 min after venom injection had no effect on cardiac output and HCO3- decline, but caused an increase in heart rate, PO2 and pH and a decrease in PCO2. We assume that antivenom clears free toxins from the circulation, and since cardiac output and HCO3- did not improve after this clearance, we conclude that following intravenous venom injection, heart and circulation are rapidly affected by the toxins or by other substances released by the venom which do not respond to antivenom. Improvements in respiration and heart rate with antivenom given after venom injection may be secondary to reversion of cholinergic effects of the venom. Improvement in respiration may be also explained by reversion of the toxic effects on Ca2+ activated K+ channels of bronchial smooth muscle. All these effects may be secondary to clearance of toxins by the antivenom.

Haemodynamic patterns in patients with scorpion envenomation

OBJECTIVE

To study cardiovascular haemodynamics following scorpion envenomation.

SETTING

Intensive care unit of a university hospital.

PATIENTS

Eight patients with Indian red scorpion (Mesobuthus tamulus) stings.

INTERVENTION

Captopril (6.25 to 12.5 mg orally) every 30 minutes until pulmonary oedema resolved.

MAIN OUTCOME MEASURES

Haemodynamic data obtained by pulmonary artery catheterisation.

RESULTS

Two haemodynamic patterns were seen. There was a predominant vascular effect in one patient, with severe hypertension, tachycardia, increased systemic vascular resistance index (SVRI = 5893 dyn.s.cm-5), and normal cardiac index (2.73 l/m2). A predominant myocardial effect with left ventricular dysfunction and normal right ventricular function was seen in the other seven patients, with tachycardia, pulmonary oedema, mild hypotension, reduced stroke volume (mean (SD), 25.9 (8.3) ml/m2), normal SVRI (1812 (831) dyn.s.cm-5), and increased pulmonary artery wedge pressure (PAWP = 25 (4.4) mm Hg). Following mild dehydration pulmonary oedema subsided (PAWP = 14 (8.5) mm Hg) in three of these patients, but hypovolaemic shock developed (right atrial pressure (RAP) = 1.3 (2.1) mm Hg); pulmonary oedema recurred with rehydration. One patient developed fatal cardiogenic shock with raised PAWP (27 mm Hg) and RAP (11 mm Hg), and vasodilatation (SVRI = 1129 dyn.s.cm-5). Stroke volume (30.5 (8.7) ml/m2) and cardiac output (4.3 (1.5) 1/m2) improved with resolution of pulmonary oedema (PAWP = 14.4 (4.2) mm Hg) following afterload reduction with captopril.

CONCLUSIONS

Mild envenomation causes severe vasoconstriction and hypertension. Severe envenomation produces predominant left ventricular dysfunction with normal systemic vascular resistance manifesting as pulmonary oedema or severe hypotension depending on the fluid balance. Shock due to biventricular dysfunction and vasodilatation occurs terminally.

Lung oedema induced by Tityus serrulatus scorpion venom in the rat

The effects of drugs were investigated on the induction of acute lung oedema by scorpion Tityus serrulatus venom in male Wistar rats (200-230 g) anaesthetized with sodium pentobarbital (40 mg/kg, i.p.). Intravenous (i.v.) injection of scorpion venom (0.5 mg/kg) into 12 rats induced arterial hypertension and severe lung oedema, whereas i.v. injection of scorpion venom into 16 rats previously injected with commercial heparin induced arterial hypertension, but only a slight lung oedema. It is suggested that the inhibitory effect of commercial heparin on the genesis of lung oedema may be due to a decrease in vascular permeability in the lungs. Previous i.v. injection of aprotinin did not prevent the arterial hypertension and the lung oedema induced by scorpion venom. Previous injections of platelet-activating factor antagonists (BN-52021 and WEB-2170) or of an inhibitor of lipo- and cyclooxygenase (Nordihydroguaiaretic acid) did not prevent the arterial hypertension induced by scorpion venom, but decreased the magnitude of the lung oedema elicited by the venom. Previous injections of inhibitors of 5-lipoxygenase (MK-886) or cyclooxygenase (aspirin or indomethacin) significantly decreased the magnitude of the lung oedema induced by scorpion venom. It is concluded that the release of vascular permeability factors, such as platelet-activating factors, leukotrienes, and prostaglandins may play a role in the induction of acute lung oedema by scorpion venom in rats.

High-dose hydrocortisone hemisuccinate in scorpion envenomation

STUDY OBJECTIVE

Scorpion envenomation is a common life-threatening hazard in tropical and subtropical countries. Standard treatment is not clearly defined. Many therapies, such as steroids, are prescribed without experimental justification. We sought to assess the efficacy of systematic administration of intravenous hydrocortisone hemisuccinate (50 mg/kg) in scorpion envenomation.

METHODS

Six hundred consecutive envenomated patients older than 10 years who presented to the ED of a nonteaching secondary hospital in an area of Tunisia endemic for scorpion envenomation were randomly assigned to receive hydrocortisone hemisuccinate 50 mg/kg (n = 305) or placebo (n = 295) in addition to standard medical care. Patients in the two groups had similar clinical characteristics on initial clinical evaluation. Each was categorized as grade 1 (absence of systemic symptoms) or grade 2 (systemic symptoms of scorpion envenomation). Patients were treated in the ED for up to 4 hours or in the ICU, depending on clinical severity. Steroid and placebo groups were compared according to mortality rate, change of severity grade 4 hours after presentation and treatment, and duration of hospital stay.

RESULTS

Distribution of patients with respect to severity grade was similar in the two groups at the 4-hour clinical evaluation. We detected no significant difference at the time of discharge between steroid-and placebo-treated patients with respect to mortality (one patient in each group) or duration of hospital stay. Extra costs incurred through steroid administration totaled US $989,000.

CONCLUSION

Our findings do not support the use of intravenous high-dose steroids in scorpion-envenomated patients. The discontinuation of this practice would reduce costs substantially.

Scorpion venom leads to gastrointestinal ischemia despite increased oxygen delivery in pigs

OBJECTIVES

Scorpion envenomation may be accompanied by metabolic acidosis even in the absence of hypoxia and cardiovascular derangement. We tested the hypothesis that venom causes ischemia of the gastrointestinal tract rather than failure of delivery of oxygen to the periphery.

DESIGN

Repeated measures, prospective study in experimental animals.

SETTING

University-affiliated hospital research laboratory.

INTERVENTIONS

In ten spontaneously breathing, intubated, sedated pigs, purified dried venom (Leiurus quinquestriatus), 0.05 mg/kg, was administered intravenously. Measurements were obtained before (baseline), and 5, 15, 30, 60, 120, 180, and 240 mins after injection.

MEASUREMENTS AND MAIN RESULTS

Variables measured included: mean arterial pressure (MAP), heart rate (HR), mean pulmonary arterial pressure, pulmonary artery occlusion pressure, cardiac output, stroke volume, right ventricular ejection fraction (rapid thermistor), left ventricular dimensions (echocardiography), arterial gas tensions, lactate and catecholamine concentrations, gastric interstitial mucosal pH (tonometry), as well as systemic and pulmonary vascular resistances. Within 5 mins after venom injection, there was a hyperdynamic state accompanied by significantly increased MAP (97 +/- 18 to 136 +/- 47 mm Hg, p < .0003), HR (70 +/- 12 to 121 +/- 24 beats/min, p < .00006), and cardiac output (1.88 +/- 0.35 to 2.95 +/- 0.53 L/min, p < .0003), with no change in stroke volume, or pulmonary artery occlusion pressure. Right ventricular ejection fraction increased from 38.1 +/- 4.3 to 48.6 +/- 9.0% (p < .0009) by 15 mins. No change in left ventricular function was observed. There were significant decreases in systemic vascular resistance and pulmonary vascular resistance following envenomation. Arterial and gastric mucosal pH significantly decreased from 7.40 +/- 0.04 to 7.25 +/- 0.07 (p < .0001) for arterial pH, and 7.33 +/- 0.08 to 7.17 +/- 0.13 (p < .00001) for gastric mucosal pH by 30 mins after envenomation. The decrease in arterial pH was not sufficient to account for the change in gastric mucosal pH, indicating gastric mucosal ischemia. Arterial lactate increased from 2.6 +/- 1.4 to 7.4 +/- 1.9 (p < .05 x 10(-8)). There were significant increases in serum epinephrine and norepinephrine values by 5 mins. All hemodynamic variables and catecholamine concentrations returned to baseline by 4 hrs. However, there was persistent arterial and gastric mucosal acidosis and increased lactate concentrations even at 4 hrs. Oxygen delivery remained normal or supernormal for 4 hrs following envenomation. However, despite this finding, systemic and gastric mucosal pH changes indicate impaired gastrointestinal oxygen delivery.

CONCLUSIONS

Despite increased peripheral oxygen delivery, scorpion envenomation was associated with evidence of ischemia of the gastrointestinal tract. This association could be due to shunting of blood from metabolically active areas, possibly associated with massive catecholamine release, or a direct toxic effect of the venom on regional oxygen transport at the cellular level.

Clinical description of Parabuthus transvaalicus scorpionism in Zimbabwe

An epidemiological and clinical study of Parabuthus transvaalicus scorpionism was conducted in Zimbabwe. Ten per cent of stings resulted in severe scorpionism. The clinical features of 17 patients with severe envenomation were primarily neuromuscular, with significant parasympathetic nervous system and cardiac involvement. The clinical course was prolonged compared to other scorpion syndromes, and significant therapeutic benefit was demonstrated in terms of hospital stay in response to species specific antivenom. The case fatality rate was 0.3%, with deaths in children below 10 years and adults above 50 years. The mortality rate in the district was 2.8 per 100,000 per year. This syndrome from a buthid scorpion resembles in many respects buthid scorpionism described elsewhere in the world, but shows important differences, notably cardiac involvement in the absence of clinical evidence of circulating catecholamines. The relevance of these findings to buthid scorpionism generally are presented as a hypothesis, in which it is postulated that the cardiac effects of the toxins are direct and primary, and autonomic effects secondary but synergistic, determining the ultimate clinical picture.

Right ventricular dysfunction following severe scorpion envenomation

OBJECTIVE

Evaluation of right ventricular (RV) performance in patients presenting with pulmonary edema following scorpion envenomation.

DESIGN

Cohort study.

SETTING

Medical intensive care unit of a teaching hospital.

PATIENTS

Eight consecutive adult patients stung by yellow scorpion Androctonus australis and presenting with pulmonary edema at hospital admission.

INTERVENTIONS

In all patients, standard hemodynamic parameters and RV volumes were measured using a pulmonary artery catheter equipped with a rapid responding thermistor enabling measurement of RV ejection fraction (RVEF).

MEASUREMENTS

Hemodynamic evaluation was performed at the time of hospital admission prior to any therapeutic intervention and just before the removal of the pulmonary catheter (2.3 +/- 0.5 days after admission) in the surviving patients (n = 7).

RESULTS

All patients had a decreased RVEF (24 +/- 7%) and cardiac index (2.44 +/- 0.5 L/min/m2) and increased pulmonary artery occlusion pressure (23 +/- 6 mm Hg). Right ventricular end-systolic pressure/volume ratio was decreased (.56 +/- .19 mm Hg/mL/m2), suggesting an altered RV contractility. Follow-up evaluation performed in survivors, without any inotropic support, showed hemodynamic changes reflecting a trend toward full recovery. Right ventricular ejection fraction and cardiac index improved markedly (from 24 +/- 7% to 39 +/- 10% and from 2.44 +/- 0.5 to 4 +/- .3 L/min/m2, respectively). Pulmonary artery occlusion pressure, peak systolic pulmonary artery pressure, and mean pulmonary artery pressure decreased significantly from baseline values (12 +/- 3 mm Hg, 29 +/- 5 mm Hg, and 20 +/- 4 mm Hg, respectively). Right ventricular end systolic pressure/volume ratio remained almost constant, suggesting that afterload enhancement accounted predominantly for RVEF improvement.

CONCLUSION

These data show that RV function impairment is associated with left ventricular dysfunction, suggesting similarities between left ventricular and RV alterations following severe scorpion envenomation providing further arguments to the hypothesis of scorpionic myocarditis.