The Effect of 7.2% Hypertonic Saline Solution with 6% Dextran 70 on Cardiac Contractility as Observed by an Echocardiography in Normovolemic and Anesthetized Dogs

Abstract

ABSTRACT. We studied the effect of a small volume of 7.2% hypertonic saline solution (HSS) or HSS with 6% dextran 70 (HSD) on hemodynamic status, especially on cardiac contractility, in anesthetized dogs using the left ventricular end-systolic volume index (ESVI) and ejection fraction (EF), which can be obtained in noninvasive echocardiography. In the present study, the mean values of ESVI were unaffected by HSS and HSD infusion, whereas the left ventricular end-diastolic volume index (EDVI) was markedly and significant increased. As a result of the changes in EDVI but not in ESVI, EF increased transiently and significantly in the HSS and HSD group, whereas no such significant change was observed in the dogs that received isotonic saline solution. In addition, as a result of the increases in cardiac index but not arterial pressure, system vascular resistances (SVR) decreased transiently and significantly in the HSS and HSD groups, whereas no such significant change was observed in the ISS group. Therefore, the positive inotropic effects of HSS and HSD may be attributable to the increase in left ventricular preload and decreases in SVR rather than direct changes in myocardial contractility. KEY WORDS: canine, cardiac contractility, cardiac index, echocardiography, hypertonic saline.J. Vet. Med. Sci. 70(1): 89-94, 2008 Recent clinical data supports the concept that early restitution of the circulation in severe sepsis and septic shock patients improves oxygenation and increases the survival rate [22]. It is therefore of great importance to restore the intravascular volume and thereby maintain adequate cardiac output (CO) and oxygen delivery. Hypovolemic shock resuscitation with colloids is preferred over crystalloids because colloids result in better regional and microcirculatory blood flow [24]. Small-volume hypertonic saline solution (HSS) has been successfully used to resuscitate dogs with experimentally induced hypovolemic shock [13,28,29]. The beneficial hemodynamic effects of HSS have been attributed to rapid plasma volume expansion caused by body fluid shift from intracellular space [2,7], transient decrease in systemic and pulmonary vascular resistance [27], a vagally mediated reflex dependent stimulation of pulmonary osmoreceptors [13,30] and increased cardiac contractility [29]. These beneficial effects most likely result from an increase in preload and/or decrease in afterload [27].Some studies have found a positive inotropic effect after HSS infusion [9,10,15,17]. HSS induces cellular dehydration through an osmotic effect, thus decreasing cellular water content and directly increasing the calcium level [32]. This could produce a positive inotropic effect of HSS because the increase in intracellular calcium concentration ([Ca 2+ ]in) results in increased cardiac contractility. Myocardial oxygen consumption increases at the end of HSS infusion without significant change in coronary venous oxygen tension and content [15]. However, many in vitro studies have demonstrated that a sudden increase in the ...

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