Effects of a phosphodiesterase III inhibitor on circulating blood volume after cardiopulmonary bypass

Capillary Leakage in Cardiac Surgery with Cardiopulmonary Bypass

Cardiopulmonary bypass causes a systemic inflammatory response, which can lead to capillary leak syndrome. In 15 adults undergoing elective cardiac surgery with cardiopulmonary bypass, we determined the volume and peak time of capillary leakage from the measurements of extracellular fluid volume and circulating blood volume taken preoperatively, at various intervals up to 24 hours after surgery, and on the 7th postoperative day. Extracellular fluid volume rose from 15.5 ± 2.7 Lpreoperatively to a peak 4 hours after surgery of 18.3 ± 3.2 L and remained elevated at 24 hours. Circulating blood volume fell from 4.10 ± 0.68 L preoperatively to 3.20 ± 0.58 L at the end of surgery. Fluid administered intraoperatively did not raise the circulating blood volume. Intraoperative fluid balance was positive at 2.62 ± 0.72 L but negative at all time points postoperatively. There was significant postoperative capillary leakage, increasing from 4.7% ± 2.3% of body weight at the end of surgery to a peak 4 hours later of 5.4% ± 2.0% and falling to 2.8% ± 3.3% at 24 hours. This knowledge of the pattern of change in capillary leakage after cardiac surgery with cardiopulmonary bypass might serve as a valuable guide for postoperative management.

Perioperative Circulating Blood Volume and Cardiac Function in Valve Disease

Circulating blood volume is important in managing fluid balance and cardiac function after surgery under cardiopulmonary bypass. Appropriate management differs among the valve disorders, but perioperative blood volume has not yet been considered. From February 2001 to March 2003, perioperative blood volume, fluid balance, cardiac index, and left ventricular stroke work index were measured in 31 patients: 10 with aortic stenosis, 9 with aortic regurgitation, 3 with mitral stenosis, and 9 with mitral regurgitation. All immediate postoperative blood volume measurements were less than preoperative values, and gradually returned to baseline. At all time points, blood volume in patients with aortic or mitral regurgitation was high, whereas it was low in those with stenosis, especially mitral stenosis. Fluid balance was positive in all patients. Postoperatively, there was a positive correlation between cardiac index and blood volume in all groups. The left ventricular stroke work index in the mitral regurgitation group was significantly higher than other groups, the aortic stenosis group was slightly lower, the mitral stenosis and mitral regurgitation groups were higher than the baseline, and the aortic regurgitation group was essentially unchanged. Thus, it is necessary to consider blood volume perioperatively in different valvular diseases to manage water balance.

Pivotal effects of phosphodiesterase inhibitors on myocyte contractility and viability in normal and ischemic hearts

Phosphodiesterases (PDEs) are enzymes that degrade cellular cAMP and cGMP and are thus essential for regulating the cyclic nucleotides. At least 11 families of PDEs have been identified, each with a distinctive structure, activity, expression, and tissue distribution. The PDE type-3, -4, and -5 (PDE3, PDE4, PDE5) are localized to specific regions of the cardiomyocyte, such as the sarcoplasmic reticulum and Z-disc, where they are likely to influence cAMP/cGMP signaling to the end effectors of contractility. Several PDE inhibitors exhibit remarkable hemodynamic and inotropic properties that may be valuable to clinical practice. In particular, PDE3 inhibitors have potent cardiotonic effects that can be used for short-term inotropic support, especially in situations where adrenergic stimulation is insufficient. Most relevant to this review, PDE inhibitors have also been found to have cytoprotective effects in the heart. For example, PDE3 inhibitors have been shown to be cardioprotective when given before ischemic attack, whereas PDE5 inhibitors, which include three widely used erectile dysfunction drugs (sildenafil, vardenafil and tadalafil), can induce remarkable cardioprotection when administered either prior to ischemia or upon reperfusion. This article provides an overview of the current laboratory and clinical evidence, as well as the cellular mechanisms by which the inhibitors of PDE3, PDE4 and PDE5 exert their beneficial effects on normal and ischemic hearts. It seems that PDE inhibitors hold great promise as clinically applicable agents that can improve cardiac performance and cell survival under critical situations, such as ischemic heart attack, cardiopulmonary bypass surgery, and heart failure.