A bolus dose of 1.5 mg/kg amrinone effectively improves low cardiac output state following separation from cardiopulmonary bypass in cardiac surgical patients

Intraoperative Hemodynamic Instability During and After Separation From Cardiopulmonary Bypass

Every year, more than 1 million patients worldwide undergo cardiac surgery. Because of the aging of the population, cardiac surgery will increasingly be offered to patients at a higher risk of complications. The consequence is a reduced physiological reserve and hence an increased risk of mortality. These issues will have a significant impact on future health care costs because the population undergoing cardiac surgery will be older and more likely to develop postoperative complications. One of the most dreaded complications in cardiac surgery is difficult separation from cardiopulmonary bypass (CPB). When separation from CPB is associated with right-ventricular failure, the mortality rate will range from 44% to 86%. Therefore, the diagnosis and the preoperative prediction of difficult separation from CPB will be crucial to improve the selection and care of patients and to prevent complications for this high-risk patient population.

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.

Milrinone enhances systolic, but not diastolic function during coronary artery bypass grafting surgery

PURPOSE

To evaluate the effect of milrinone on diastolic function during coronary artery bypass grafting surgery (CABG).

METHODS

Fifty patients undergoing CABG were randomized to receive a bolus and infusion of milrinone or placebo before cardiopulmonary bypass (CPB) until skin closure. Hemodynamic and transesophageal echocardiographic measurements of systolic and diastolic function were obtained. Pulsed wave Doppler measurements of the early (E wave) and atrial components (A wave) of the transmitral (TMF) and transtricuspid (TTF) flows, and systolic (S wave), diastolic (D wave) and atrial components (Ar) of the pulmonary (PVF) and hepatic venous blood flow (HVF) velocities were performed. Early and atrial components of the mitral (Em and Am waves) and tricuspid annulus velocities (Et and At waves) were assessed by tissue Doppler imaging (TDI). Assessment of diastolic dysfunction was graded from normal to severe using a scale score.

RESULTS

Cardiac index and heart rate were higher in the milrinone group compared to placebo after the administration of study drug (2.8 +/- 0.6 vs 2.1 +/- 0.5 L.min(-1)m(-2)) (P < 0.0001) and (67 +/- 8 vs 60 +/- 12 beats.min(-1)) (P < 0.05) respectively. There were no changes in left and right ventricular diastolic dysfunction scores between study groups. Higher PVF S wave, HVF S wave, TTF A wave and At measured by TDI in the milrinone group compared with placebo suggested an improvement in ventricular systolic and atrial contraction.

CONCLUSION

Distinct from its effects on systolic function, milrinone administered before CPB is not with associated improved biventricular diastolic function in patients undergoing CABG.

Milrinone Facilitates Resuscitation From Cardiac Arrest and Attenuates Postresuscitation Myocardial Dysfunction

Background— Left ventricular (LV) dysfunction with a low cardiac index after successful CPR contributes to early death attributable to multiorgan failure, and an effective treatment has not been identified. The purpose of this study was to investigate the use of milrinone, a selective phosphodiesterase III inhibitor, as treatment for LV dysfunction after resuscitation.

Methods and Results— Ventricular fibrillation (VF) was induced electrically in 32 swine. After 5 minutes of VF, CPR was initiated and animals were randomized to receive either saline (control group, n=16) as a bolus and infusion or milrinone 50 μg/kg as a bolus and then 0.5 μg/kg per min for 60 minutes (treatment group, n=16). After 2 minutes of CPR (total VF time, 7 minutes), countershocks were given. Coronary perfusion pressures during CPR were similar for the groups (24±2 versus 21±4 mm Hg). All animals were defibrillated; 6 of 16 control animals developed refractory postcountershock pulseless electrical activity compared with 0 of 16 treated animals ( P =0.018). At 30 minutes after restoration of spontaneous circulation, stroke volume (16±3 versus 26±7 mL, P <0.01) and LV dp/dt (793±197 versus 1108±316 mm Hg/s, P <0.02) were higher in the treatment group. Similar differences were observed 60 minutes after restoration of spontaneous circulation. Significant differences in heart rates between groups were not observed, and peripheral vascular resistance was significantly greater in the control group 30 and 60 minutes after resuscitation.

Conclusions— Milrinone facilitates resuscitation from prolonged VF and attenuates LV dysfunction after resuscitation without worsening major determinants of myocardial oxygen demand.

Survey of observer variation in transesophageal echocardiography: comparison of anesthesiology and cardiology literature

OBJECTIVE

Transesophageal echocardiographic examination tends to be somewhat observer and experience dependent, and observer bias can arise easily when data are calculated and interpreted by unskilled, nonblinded, or single observers. The study plan was to see whether authors have adequately described how observer bias is minimized in their studies. Thus, a study was conducted systematically reviewing methods reported in transesophageal echocardio graphy articles in peer-reviewed anesthesiology journals versus those reported in peer-reviewed cardiology journals.

INTERVENTIONS

After MEDLINE searches of the literature published from 1997 through 1999, the authors investigated 56 anesthesiology reports and 56 randomly selected, year-matched cardiology reports. An 8-item questionnaire was developed that examined several factors: the number of observers and their experience levels, whether observers were blind to clinical data, whether low-quality images were excluded, the use of on-line or off-line analysis, and observer variability.

MAIN RESULTS

The analysis revealed inadequacies in reporting of important information that relates to bias and quality in 91.1% of anesthesiology and 98.2% of cardiology articles. Observer variability was not reported in 50.0% of the anesthesiology reports and 67.9% of the cardiology reports; however, difference between the 2 bodies of literature was not significant. The journal impact factor was significantly higher for the cardiology literature than for the anesthesiology literature (2.42 [0.386-10.893] v 1.07 [0.664-3.439]; median [range], p < 0.001).

CONCLUSION

Articles reviewed had at least some inadequacies in reporting the methods to minimize observer bias in both the anesthesiology and cardiology literature. Reporting methodology standards in TEE examinations remain to be established.

The efficacy of preemptive Milrinone or Amrinone therapy in patients undergoing coronary artery bypass grafting

Acute deterioration in ventricular function and oxygen transport is common after cardiac surgery. We hypothesized that milrinone or amrinone may reduce their occurrence and catecholamine requirements and increase cellular enzyme levels in patients undergoing coronary artery bypass. In 45 patients, we randomly administered milrinone 50 microg/kg plus 0.5 microg x kg(-1) x min(-1) infusion for 10 h, amrinone 1.5 mg/kg plus 10 microg x kg(-1) x min(-1) infusion for 10 h, or placebo at release of aortic cross-clamp. Hemodynamic variables, dopamine requirement, and laboratory values were recorded. At the postoperative nadir, stroke volume index was higher in the Milrinone and Amrinone groups (mean +/- SD, 27.8 +/- 4.0 and 26.1 +/- 3.2 vs. 20.4 +/- 5.1 mL x min (-1) x m(-2) per beat, P < 0.0001), and oxygen transport index was higher (354.7 +/- 57.8 and 353.7 +/- 91.2 vs 283.0 +/- 83.9 mL. min(-1) x m(-2), P = 0.009). The postoperative dopamine requirement was less (6.6 +/- 2.7 and 6.8 +/- 2.6 vs 10.4 +/- 2.0 mg/kg, P < 0.008), and postoperative serum lactate, alanine and aspartate aminotransferase, lactate dehydrogenase, creatinine kinase, C-reactive protein, and glucose levels were less (P < 0.01). The mean postoperative heart rate was faster in the Milrinone group than in the Amrinone and Placebo groups (96.8 +/- 10.3 vs. 86.9 +/- 9.5 and 87.8 +/- 10.8 bpm, P < 0.01). Milrinone and amrinone administered preemptively reduce postoperative deterioration in cardiac function and oxygen transport, dopamine requirement, and increases in serum lactate, glucose, and enzyme levels, although milrinone may increase heart rate.

IMPLICATIONS

Preemptive milrinone or amrinone administration before separation from cardiopulmonary bypass in cardiac surgical patients not only ameliorates postoperative deterioration in cardiac function and oxygen transport, but also reduces dopamine requirement and increases serum lactate, glucose, and cellular enzyme levels, although milrinone may increase heart rate.

Diastolic dysfunction is predictive of difficult weaning from cardiopulmonary bypass

Diastolic function is receiving more attention since echocardiographic measurements were developed and have become widely available. The importance and significance of diastolic dysfunction (DD) observed before cardiac surgery and its relationship with adverse outcomes, such as difficult separation from cardiopulmonary bypass (CPB), have not been fully explored. In this study, we hypothesize that DD can be a predictor for the need of inotropic support to successfully separate from CPB. Ninety-two consecutive patients underwent surgery during the study period. Twenty-six patients were excluded. From the remaining 66 patients, 52 had coronary artery bypass grafting alone and 14 combined procedures, valvular surgery, and reoperations (redo). Systolic and diastolic function was evaluated by two experts blinded as to the clinical data except for the age. The evaluation of diastolic function was done according to published guidelines. The demographic, echocardiographic, and hemodynamic variables were entered in a logistic regression analysis to determine which variables were independent predictors of difficult separation from CPB and the need for postoperative vasoactive support. DD was present in 20 patients (30%). Patients with DD had lower weight (P = 0.046), less frequent coronary artery bypass grafting alone (P = 0.0004), more myocardial infarction before surgery (P = 0.02), higher regional wall motion score index (P = 0.0002), and larger left ventricle (P = 0.03). Total CPB time (P = 0.004) and ischemic time (P = 0.007) were longer in the DD group. Patients with DD required more frequent inotropic support at the end of surgery (P = 0.006) and up to 12 h after surgery (P = 0.003). Multivariate logistic regression identified female sex, DD, and total CPB time as predictive of difficult weaning and inotropic requirements up to 12 h after surgery.

Diastolic dysfunction is predictive of difficult weaning from cardiopulmonary bypass

Diastolic function is receiving more attention since echocardiographic measurements were developed and have become widely available. The importance and significance of diastolic dysfunction (DD) observed before cardiac surgery and its relationship with adverse outcomes, such as difficult separation from cardiopulmonary bypass (CPB), have not been fully explored. In this study, we hypothesize that DD can be a predictor for the need of inotropic support to successfully separate from CPB. Ninety-two consecutive patients underwent surgery during the study period. Twenty-six patients were excluded. From the remaining 66 patients, 52 had coronary artery bypass grafting alone and 14 combined procedures, valvular surgery, and reoperations (redo). Systolic and diastolic function was evaluated by two experts blinded as to the clinical data except for the age. The evaluation of diastolic function was done according to published guidelines. The demographic, echocardiographic, and hemodynamic variables were entered in a logistic regression analysis to determine which variables were independent predictors of difficult separation from CPB and the need for postoperative vasoactive support. DD was present in 20 patients (30%). Patients with DD had lower weight (P = 0.046), less frequent coronary artery bypass grafting alone (P = 0.0004), more myocardial infarction before surgery (P = 0.02), higher regional wall motion score index (P = 0.0002), and larger left ventricle (P = 0.03). Total CPB time (P = 0.004) and ischemic time (P = 0.007) were longer in the DD group. Patients with DD required more frequent inotropic support at the end of surgery (P = 0.006) and up to 12 h after surgery (P = 0.003). Multivariate logistic regression identified female sex, DD, and total CPB time as predictive of difficult weaning and inotropic requirements up to 12 h after surgery.

Management of perioperative ventricular dysfunction

With the recognition of the clinical importance of the right ventricle; the development of new techniques for the perioperative evaluation of RV function, particularly transesophageal echocardiography; and new treatment modalities (pharmacologic and mechanical), clinicians will be able to more accurately diagnose and precisely manage patients who have sustained RV injury.