Myocardial injury in scorpion envenomed children: significance of assessment of serum troponin I and interleukin-8.

OBJECTIVES: (1) To investigate the significance of assessment of serum levels of cardiac troponin I (cTnI) and interleukin-8 (IL-8) beside other biomarkers of myocardial injury in scorpion envenomed children. (2) To find the correlation between these biochemical indices with clinical status, prognosis and outcome of these cases.

METHODS: Forty-one children in Upper Egypt were admitted to Pediatric Intensive Care Unit, Assiut University Hospital, for scorpion envenomation. They were compared with fifteen 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 cTnI and IL-8 beside the enzymatic activities of creatine phosphokinase (CPK), CPK-MB isoenzyme (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 hrs. The measurements of electrocardiography (ECG), echocardiographic measurement of % fractional shortening of left ventricule (%SF), left ventricular ejection fraction (LVEF) and cardiac chambers dilatation were done for severe and moderate cases.

RESULTS: 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 with 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 (5/41=12.5%). 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.

CONCLUSION: it may be suggested that cTnI is the most specific marker for diagnosis of myocardial injury in scorpion envenomation, which is almost associated with skeletal muscle injury. 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.