Abstract:

This study was designed to examine the effect of nitroglycerine infusion in children hospitalized for scorpion sting with severe myocardial dysfunction and decompensated shock. Children satisfying the inclusion criteria were started on nitroglycerine infusion under hemodynamic monitoring and other supportive measures. The effects of nitroglycerine, including improvement in oxygenation and decrease in pulmonary congestion and liver size were recorded. Seven out of 11 children responded well to nitroglycerine therapy and the clinical response was evident within 30-60 minutes. The first parameter to improve was oxygen saturation, followed by an improvement in the blood pressure and respiratory rate. Heart rate was the last parameter to improve after nitroglycerine infusion. The average duration of nitroglycerine infusion was 25 hours (12-36 hours). It was seen that the non-survivors had significant tachycardia at admission, and a greater need for assisted ventilation compared to the survivors. We conclude that nitroglycerine therapy could bring about significant improvement in myocardial function and hemodynamic parameters with a potential for improved survival.

Key words: Nitroglycerine, Scorpion sting, Shock. 

Scorpion sting is a potential life-threatening medical emergency presenting to the children’s Accident and Emergency in southern India. Cardiac toxicity dominate the clinical picture in these children. The use-fulness of alpha blockade and additional carftableiac support with ionotropes and sodium nitroprusside for this condition have been earlier documented(1,2). Despite these measures, in some children myocardial dysfunction and hypotension persist. The usefulness of intravenous nitroglycerine along with ionotropes for adults with severe left ventricular failure has been reported by Loeb, et al.(3) and Edwards, et al.(4). There are hardly any studies to nitroglycerine usage in cases of children with scorpion sting. Hence, the present communication.

This interventional study was conducted prospectively in the Pediatric Intensive Care Unit of JIPMER Hospital, Pondicherry between May 2001 to March 2003. Children below 12 years of age with scorpion sting-induced myocardial dysfunction with decompensated shock were studied. Decompensated shock was defined as presence of persistent hypotension and tachycardia even after the standard protocol outlined below. In these children, myocardial dysfunction was evident by the presence of gallop rhythm, tachypnea, raised jugular venous pressure (JVP), and hepatomegaly. Electrocardiographic evidence of abnormal Q waves along with ST-T wave changes were taken as additional criteria for myocardial dysfunction. These children with scorpion sting envenomation had initially received in the High Dependency Unit of the department standard alpha blockade therapy with Prazosin (30 µg/Kg/dose 4-6 hourly). Heart rate, blood pressure, respiratory rate, liver size, peripheral perfusion, central venous pressure (ventilated children only), electrocardio-graph, oxygen saturation and blood gas were closely monitored in these children.

The children received inotropic support with dobutamine (5-15 µg/ Kg/min) as per the standard dosage schedule(5). Clinical response was assessed as given below: improvement in oxygenation (>5% improvement in oxygen saturation), blood pressure (increase in mean arterial pressure by 10%), work of breathing, reduction of heart rate (decrease by 10%), hepatomegaly and JVP.

Nitroglycerine(NTG) was used as a rescue therapy prior to transfer to Intensive care unit. Nitroglycerine was started at a dose of 0.5 µg/kg/min and titrated with clinical response with a maximum dose of 5 µg/kg/min. Children with type I respiratory failure with a FiO2 greater than 0.6 and not improving with nitroglycerine therapy and those with type II respiratory failure were ventilated. Nitroglycerine and inotropic support were continued during ventilation till the children recovered. The study protocol had the approval of the local ethical standards committee. Data from standardized study forms were entered into a computer database for analysis.

During the study period of twenty two months, 80 children brought for scorpion sting envenomation were triaged according to the criteria of Abrough, et al.(6). Thirty of these children developed pulmonary edema due to myocardial dysfunction and received standard alpha blockade therapy and inotropic support with dobutamine. Eleven of these children who developed decompensated shock were the subjects for this study. Six of them were girls and the rest were boys. Their mean (SD) age was 8.3 (3.8) years, the youngest being 18 months of age. The clinical characteristics of these patients are shown in Table I. The mean (SD) time delay at presentation was 14.7 (4.9) hours for survivors and 12.8 (10.1) hours for non-survivors. The mean respiratory rate, mean arterial pressure and oxygen saturation among survivors was 34/min, 68 mm Hg and 92% and among non-survivors was 44/min , 60 mm Hg and 85% respectively. Four patients had no evidence of myocardial involvement at admission, but developed clinical features of myocardial dysfunction 6-24 hours after admission while on standard alpha blockade therapy.

Eleven children were started on nitro-glycerine infusion, and the mean duration of infusion was 25 hours (12-36 hours). Five children improved with the nitroglycerine infusion only and did not require ventilation. The clinical response to NTG infusion was evident within 30-60 minutes. The parameters which showed improvement were in the following order: oxygen saturation, liver size, blood pressure respiratory rate heart rate and ECG. Two children showed marked improvement in ECG changes 1-2 hours after commencement of NTG infusion. Out of the remaining six children who required ventilation due to worsening respiratory status, two recovered well without any further complication. The seven survivors were discharged after mean (SD) hospital stay of 5.6 (3.1) days. No adverse reaction to NTG was noted in them.

Among the four fatal cases, one child developed sudden unexplained ventricular arrhythmia 6 hours after initial improvement. The others did not show consistent improvement in oxygenation even after ventilatory support due to ventilation perfusion mismatch. None of these four fatal cases had received prazosin prior to reaching our hospital.

Cardiovascular involvement remains the major cause of mortality in scorpion envenomation(7). Ancillary pharmacological therapy with prazosin and dobutamine support with close monitoring resulted in favourable outcome in majority (86.25%) of the children admitted with scorpion envenomation.

Only a small subset (13.75%) of children had developed persistent hypotension inspite of myocardial supportive measures and were potential candidates for ventilatory support. Nitroglycerine was used as a rescue measure in these sick children and the response was evident within 30-60 minutes. Of the eleven children who received nitroglycerine, five had sufficient improvement in oxygenation and work of breathing so as to avoid the need for mechanical ventilation. This beneficial effect can be explained by the predominant venodilator action of nitroglycerine decreasing venous return to the heart, thereby reducing left ventricular end-diastolic pressure (preload). In addition, nitroglycerin improves intra-pulmonary shunting thus bringing down ventilation perfusion mismatch(8,9). Nitrates also dilate epicardial coronary arteries and coronary collateral vessels, thereby increasing coronary blood flow(8). These beneficial effects on coronary circulation could explain the improvement in ECG among the survivors. The usefulness of nitroglycerine in left ventricular failure and pulmonary edema in adults is well established. However, its use in scorpion sting, where the hemodynamic instability is contributed by autonomic storm resulting in intense vasoconstriction and myocardial injury was not reported earlier.

Four of our children did not have favorable outcome in spite of all the myocardial supportive measures. Continuing absorption of venom from depot sites can be hypothesized for late deterioration in such cases. Early administration of prazosin after the sting even in peripheral health facility could have favorably influenced the outcome in the non-survivors.

In our pilot study with NTG, the intervention and its measured effects appear clinically significant. Only an open controlled trial done in large number of patients will be able to conclude the benefits of NTG over other drugs. Such a study in the future can validate the magnitude and precision of treatment effects with NTG.

We would like to thank Dr. Pragnya Shenoy, Senior Resident and Dr. Ashish Pradhan, Postgraduate of JIPMER for their help in collecting the data for this study.

Contributors: SM conceptualized and designed the study and critically reviewed the manuscript. SM will act as guarantor. NP was involved in collection of data, managing the patients and helped in preparing the manuscript. TSV was involved in management of patients.

Competing interests: None.

Funding: None.

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