Aminophylline Infusion Rate Can Affect the Cardiac Rate and Electrocardiographic Findings in Neonate Rats

Background: Cardiac arrhythmias are identified as the major cause of mortality and morbidity in neonates. Most term and preterm infants admitted to the neonatal intensive care unit (NICU) suffer from respiratory diseases, and generally aminophylline as a nonselective phosphodiesterase inhibitor is used. Although aminophylline has several physiological effects on the heart tissue, it has been recognized to have some side effects. Neonates are more prone to its cardiac side effects, notably arrhythmias. Objectives: This study aimed to evaluate and compare the effects of fast and slow aminophylline injections on electrocardiographic parameters and arrhythmias in neonate rats. Methods: Thirty-two male Sprague-Dawley rats (10 days old, 50 g) were divided into 4 groups (8 in each): Group I and Group II were treated with 5 mg/kg of normal saline intravenously for 3 and 20 minutes, correspondingly, and Group III and Group IV were treated with a 5-mg/kg bolus of aminophylline intravenously for 3 and 20 minutes, respectively. On the experiment day, the rats were anesthetized with a mixture of ketamine (50 mg/kg) and xylazine (10 mg/kg) with intraperitoneal injection, and lead II electrocardiograms were recorded. The femoral vein was cannulated using polyethylene catheters (PE50) for the intravenous injection of aminophylline (5 mg/kg) or normal saline. Results: The rats receiving aminophylline showed a dramatic reduction in the heart rate. Additionally, the PR interval and QTc significantly increased in the rats receiving aminophylline for 3 minutes. Moreover, complete heart blocks, premature ventricular beats, atrioventricular blocks (Mobitz I and Mobitz П), sustained and nonsustained ventricular tachycardias, and AV dissociations were observed. Conclusions: The results of the current study indicated that a slow infusion rate could prevent the cardiac complications of aminophylline, particularly arrhythmias, in neonate rats.(Iranian Heart Journal 2020; 21(4): 33-42)