Need For Inotropic Support Research Articles

Suppression of Shivering Decreases Oxygen Consumption and Improves Hemodynamic Stability during Postoperative Rewarming

Thirty-three patients undergoing elective myocardial revascularization were prospectively randomized into two study groups (Group S and Group P) to permit evaluation of the effects of shivering on oxygen consumption per minute ( Vo 2), carbon dioxide production per minute ( Vco 2), and hemodynamic performance. Group S was allowed to shiver during the postoperative rewarming period, and Group P received hourly injections of pancuronium bromide and Metubine (metocurine) sulfate with sedation to block the shivering response. Group S demonstrated significantly higher increases in Vo 2 and Vco 2, lower systolic blood pressure and mixed venous oxygen saturation, and a greater use of inotropic support than the patients in Group P. Suppression of the shivering response minimized increases in Vo 2 and Vco 2, improved hemodynamic stability, and resulted in a decreased need for inotropic support.

Determinants of Cardiac Failure after Coronary Bypass Surgery within 30 Days of Acute Myocardial Infarction

Timing of coronary artery bypass grafting after acute myocardial infarction (MI) is controversial, especially if myocardial function is depressed. Early coronary artery bypass grafting may result in reperfusion injury causing cardiac failure. Delay, however, may risk a second ischemic event. This study was performed to determine if four preoperative factors—time after MI, ejection fraction, ischemia (need for intravenous administration of nitroglycerin), and failure (need for inotropic support)—independently predict postoperative cardiac failure. Postoperative failure was defined as the need for inotropic support or intraaortic balloon pumping. The study group consisted of 145 patients who underwent isolated coronary artery bypass grafting between January, 1980, and July, 1985, within 4 weeks of an acute MI. Postoperatively 38 patients (26%) had cardiac failure. Five patients, all of whom had postoperative cardiac failure, died. Univariate and stepwise logistic regression analyses showed preoperative failure ( p = .0001), ejection fraction less than 45% ( p = .002), and preoperative ischemia ( p = .02) were predictors of postoperative cardiac failure. Time after MI was not found to be an independent predictor ( p = .96). We conclude that if ischemia or threatening coronary anatomy is present early after MI and clinical improvement is not occurring, operative intervention should be strongly considered at that time, as it does not appear that delay itself reduces the risk of cardiac failure and may risk a second ischemic event.

II. Assessment of adequacy of myocardial preservation

Intramyocardial pH and temperature were continuously measured in the anteroseptal region in 40 patients undergoing aortic cross-clamping during cardiac operations. Myocardial protection was achieved with systemic cooling (25 degrees C) and multidose potassium cardioplegia (4 degrees C). A clinical myocardial preservation score was devised based on intraoperative and postoperative need for inotropic support, postoperative creatine kinase isoenzyme (CK-MB) and electrocardiographic changes, and radionuclide ventriculography. The patients were divided into three groups according to their preservation scores. Group I (n = 17) with good preservation (scores 0 to 2), Group II (n = 15) with fair preservation (scores 3 to 8), and Group III (n = 8) with poor preservation (scores 9 to 15). Baseline intramyocardial pH was similar in all groups (mean +/- SEM = 6.77 +/- 0.03). With the administration of cold potassium cardioplegia, intramyocardial pH rose above baseline in all three groups. The magnitude of this rise related directly to the adequacy of preservation and to the duration of the cross-clamp period. Patients with lowest preservation scores and shortest cross-clamp periods had the highest intramyocardial pH. In contrast, there was no relationship between myocardial temperature during cross-clamp and either intramyocardial pH or the preservation score. The integrated mean intramyocardial pH during cross-clamp was found to be the parameter that correlated most with the adequacy of preservation. The correlation between intramyocardial pH and myocardial temperature during the period of cross-clamping related to the length of this period; it was good (r = 0.76, p less than 0.01) in periods of 40 minutes or less and very poor in periods exceeding 60 minutes (r = 0.27, p greater than 0.10). It is concluded that (1) the magnitude of rise in intramyocardial pH during the period of aortic cross-clamping is a good indicator of the adequacy of myocardial preservation; (2) during periods of aortic cross-clamping exceeding 40 minutes, myocardial temperature is a poor indicator of adequacy of preservation, since progressive tissue acidosis may occur despite low myocardial temperatures; and (3) techniques and solutions that can effectively reduce the progression of tissue acidosis will, in most likelihood, enhance our ability to protect the ischemic myocardium during cardioplegic arrest.

Mitral valve replacement with preservation of papillary muscles and chordae tendineae - revival of a seemingly forgotten concept. I. Preliminary clinical report.

In 45 consecutive patients mitral valve replacement was performed leaving the posterior mitral leaflet and its chordal attachment to both papillary muscles intact (Lillehei's technique). Most patients showed moderate to severe pulmonary hypertension before surgery, 15 of the patients had double valve operations and 4 had a triple valve procedure. All patients survived and were discharged, the postoperative courses being remarkably uneventful with only very limited need of inotropic support in 3 patients and resumption of spontaneous respiration within the first 20 hours after the operation. The clinical courses in these patients seem to indicate that preserving the continuity between papillary muscles and mitral annulus in mitral valve replacement may improve left ventricular function at least early after surgery.

Multicentre investigation of myocardial protection with cold cardioplegia.

In order to analyze factors of importance for the efficiency of myocardial protection during open-heart surgery, a study was made of 144 patients undergoing isolated aortic valve replacement with various cardioplegic techniques. The cardioplegia was of Bretschneider type in 54 cases, St Thomas in 31 and Ringer-potassium type in 11 cases. Single or multi-dose blood cardioplegia was used in 11 cases and continuous blood cardioplegia in 30 cases. Local cardiac hypothermia was additionally employed in all patients. The efficiency of myocardial protection was assessed mainly from the incidence of postoperative conduction disturbances, myocardial enzyme release and need for inotropic support. All patients survived the operation. In 20% surgery was followed by transient or persistent disturbance of conduction, in 9% by abnormally increased CK-MB release and in 5% by requirement for inotropic support. Preoperative risk factors such as high age or severe left ventricular (LV) hypertrophy or dysfunction had little influence on the results. Patients in whom aortic stenosis (AS) was dominant in the complex with aortic insufficiency (AS + AI) showed 20-hour postoperative CK-MB enzyme activity twice as high as those with pure aortic insufficiency. The most important factors in myocardial protection were the duration of aortic occlusion and the myocardial temperature during cardioplegia. When the aortic occlusion lasted more than 80 min there was a 32% incidence of conduction disturbances and 20-hour CK-MB activity thrice as high as after shorter occlusion. Patients with mean myocardial temperature below 18 degrees C during cardioplegia invariably had low enzyme activities, which indicated good myocardial protection. The best overall results were obtained in patients operated on during hypothermia at 25-27 degrees C, with single or multi-dose blood cardioplegia and with efficient local cooling of the heart.

Perioperative echocardiographic evaluation of cardiovascular function: assessment of changing hemodynamic state.

To evaluate echocardiographic assessment of ventricular function in a changing hemodynamic situation, 20 infants and children undergoing open heart surgery were examined preoperatively and 1,4 and 24 hours postoperatively by this technique. Clinical evaluation and measurements of cardiac output were obtained simultaneously with each echocardiogram. On the basis of their clinical course and cardiac output, the patients were divided into two groups: group 1 - cardiac index > 2.3 1/min/m2 without inotropic support (n = 9); and group 2 - cardiac index less than or equal to 2.3 1/min/m2 and/or need for inotropic support (n = 11). Of the echocardiographic measurements obtained, the left ventricular systolic time interval ratio (left ventricular preejection period/left ventricular ejection time ([LVPEP/LVET] correlated significantly with the clinical course, separating the two groups of patients completely at each determination. The aortic root velocity (AoV), a new index defined as the anterior excursion (in degrees) of the aortic root from the horizontal plane with systole, also correlated with the clinical course, although this was not statistically significant. Serial change in LVPEP/LVET and AoV crrrelated with changes in clinical status and cardiac output for individual patients. Using a formula based on the opening slope of the mitral valve, echocardiographic estimations of cardiac output correlated well with those determined by dye dilution. The results indicate that selected echocardiographic indexes can be used for serial assessment of cardiac performance in patients with a changing hemodynamic state.

Potassium-induced cardioplegia

Potassium-induced cardioplegia during anoxic arrest was utilized in a study of 190 consecutive patients undergoing revascularization (average 2.8 grafts per patient) from August, 1975, through August, 1976. Surgical technique, moderate systemic hypothermia with intermittent anoxic arrest, and the surgeon were the same for all patients. One hundred thirty-five patients (KC1-treated) received a bolus (150 ml.) of potassium solution injected into the proximal aortic root whenever the aortic cross-clamp was applied; 55 others served as control subjects. The mortality rate was 2.2% (three of 135) in the KCl-treated group and one of 55 in the control group. New Q waves appeared in 5.9% (eight of 135) of the KCl-treated patients and 11% (6 of 55) of control subjects (p = N.S.). Catecholamine drips were required after bypass in 4.4% (six of 135) of patients given potassium and 18% (10 of 55) of control patients (p less than 0.05). Profound myocardial relaxation was of added technical value with potassium. It is our impression that hearts treated with potassium exhibited more prompt cardioversion, separated from cardiopulmonary bypass with less need for inotropic support, and exhibited less myocardial injury during the revascularization procedure.

Comparison of myocardial preservation techniques for aortocoronary bypass surgery

The myocardial properties of three different techniques for cardiac arrest during aortocoronary bypass surgery were analyzed. Ventricular fibrillation and moderate total body hypothermia (30–33°C) (Group I) was found to be an insecure method of preservation. It produced a high incidence of focal irreversible ultrastructural changes (7 of 10 patients), high post-bypass CK-MB levels (mean 85.54 U/liter) indicative of myocardial damage, and impaired clinical and physiologic recovery courses. Six out of ten patients needed inotropic support, three had prolonged stay in ICU, and three patients showed Type III (unacceptable) recovery trajectories, one of whom died of myocardial decompensation four weeks after surgery. This method, which was the most common one used in our institution, was completely abandoned as a result of these studies. Potassium induced cardioplegia combined with methylprednisolone sodium succinate, hypertonic glucose and intermittent moderate topical cooling (25–27°C) of the heart (Group III) offered a generally acceptable form of myocardial protection, as only one patient showed irreversible ultrastructural changes. The mean post-bypass CK-MB level was only moderately elevated (mean 22.32 U/liter), but seven of ten patients needed inotropic support. There were no Type III recovery trajectories and two patients showed an optimal Type I recovery. Only one patient had a prolonged stay in ICU, and another patient exhibited electrocardiographic evidence of a perioperative myocardial injury pattern. Selective intracavitary profound hypothermic arrest (15–18°C) (SIPHA) offered the best myocardial protection as evidenced by remarkably well preserved ultrastructure and significantly ( P< 0.005) lower post-bypass CK-MB levels (mean 7.85 U/L). All SIPHA patients had acceptable physiologic recovery trajectories of the Type I or Type II with minimal need for inotropic support (one patient), and none had a Type III recovery. These data also suggest that the major determinant of a successful myocardial preservation is the level of myocardial layer temperature, being best at the lowest temperature (15–18°C), worst at the highest temperature (30–33°C) and intermediate at 25–27°C. Additional injury may also be induced by ventricular fibrillation which by itself increases myocardial metabolic demands.

Coronary revascularization in "high" versus "low-risk" patients: The role of myocardial protection.

Postoperative mortality, infarction, and need for inotropic support are reportedly increased following myocardial revascularization in "high-risk" patients. We believe these complications result from inadequate protection of the compromised myocardium and should not occur with greater frequency in "high-risk" than "Low-risk" patients if the heart is optimally protected during the entire course of the operative procedure. Results following revascularization in 50 consecutive "low-risk" and 50 consecutive "high-risk" patients were analyzed. One or more of the followin factors were present in the "high-risk" group: ventricular dysfunction--ejection fraction less than 0.4, preinfarction angina, evolving infarction, recent infarction (less than 2 weeks), and refractory ventricular tachyarrhythmia. The following principles were used in all patients to minimize ischemic injury: 1) avoidance of pre-bypass hypo- or hypertension, 2) limitation of ischemic arrest to less than 12 minutes, 3) avoidance of ventricular fibrillation, and 4) prolongation of total bypass as necessary to repay the myocardial oxygen debt. Postoperative inotropic support was required in 10% of "high" and 10% of "low-risk" patients, new postoperative infarction developed in 10% of "high" vs. 10% "low-risk" patients; death occurred in 2% of "high" vs. 4% "low-risk" patients. These results are comparable and indicate that optimum myocardial protection allows safe revascularization in the "high-risk" patient.