Posttraumatic Period in Cardiac Contusion (Experimental Study)

Abstract

Objective: to study the efficiency of pre-administration of hypoxen in experimental cardiac contusion in order to lower the degree of posttraumatic myocardial dysfunction. Materials and methods: experiments were carried out on non-inbred albino male rats anesthetized with sodium thiopental. Cardiac contusion was reproduced by an original device that imitated a blow of the steering wheel to the anterior chest, as that observed when a moving car clashes against an obstacle. Some animals were traumatized after pre-administration of hypoxen. An electrocardiogram, left carotid blood pressure (BP), an integral rheogram, and the first derivative of a differential rheogram were recorded prior to cardiac contusion simulation and in different posttraumatic periods. Stroke volume (SV), cardiac output (CO), and total peripheral vascular resistance were calculated. Results. Preinjection of hypoxen completely prevented the development of sinus arrhythmia, paroxysmal ventricular tachycardia, and intraatrial and intraventricular conduction disturbances, irrespective of the baseline BP. In a subgroup of animals with a baseline low BP, the agent reduced the incidence of bradycardia by 1.5 times, heterotopic rhythms by 5.3 times, ventricular premature contractions by 6 times, atrioventricular (AV) block by 5.3 times and diminished the changes in the terminal of a ventricular complex by 6.3 times. In a subgroup of animals with baseline normal BP, bradycardia and heterotopic rhythms were recorded 2 and 7 times more infrequently recorded; ventricular premature beats, AV block, and ST-segment displacement were present in none case. Preinjection of hypoxen improved myocardial contractility, as evidenced by 17—25% SV increases within an hour posttraumatically. However, significant arterial hypotension and lowered CO due to bradycardia in most experimental animals during the preinjection of hypoxen before injury and throughout the posttraumatic period caused a ten-fold increase in mortality rates as compared with the non-hypoxen group. Conclusion. The hemodynamic effects of hypoxen can substantially limit the possibility of using the agent to diminish the degree of posttraumatic cardiac dysfunction. Key words: experimental cardiac contusion, central hemodynamics, hypoxen.