Hemodynamic and echocardiographic effects of hemofiltration performed during cardiopulmonary bypass

OBJECTIVE: To evaluate the effects of hemofiltration performed during rewarming before emergence from cardiopulmonary bypass on hemodynamic and echocardiographic parameters. DESIGN: Prospective randomized study; blind analysis of echocardiographic parameters and hemodynamic parameters. SETTING: Single-center study performed in a university hospital. PARTICIPANTS: Two groups of 13 adult patients undergoing coronary artery bypass graft surgery. INTERVENTION: Patients were randomized to conventional procedure or hemofiltration performed with a polysulfone hemofilter. Hemofiltration, started at the time of rewarming on cardiopulmonary bypass, was performed with a flow rate adjusted to achieve an ultrafiltrate volume of 15 mL/kg on completion of rewarming. MEASUREMENTS AND MAIN RESULTS: Hemodynamic (systemic mean arterial pressure, right atrial pressure, heart rate) and echocardiographic parameters (shortening fraction, segmental kinetic score, cardiac output, systemic vascular resistance) were measured before and after hemofiltration and on arrival in the intensive care unit. Heart rate and cardiac index were increased significantly in both groups during the postoperative period. In the control group, systemic vascular resistance was decreased significantly, and cardiac index was increased during the postoperative period, together with significant alterations of segmental kinetic score and shortening fraction. In the hemofiltration group, systemic vascular resistance remained unchanged, associated with a significantly improved segmental kinetic score compared with the control group. CONCLUSIONS: Hemofiltration performed during rewarming before emergence from cardiopulmonary bypass is associated with stability of hemodynamic parameters and improved segmental myocardial kinetics.     

Forced-air warming decreases vasodilator requirement after coronary artery bypass surgery

Postoperative hypothermia is common and associated with adverse hemodynamic consequences, including adrenergically mediated systemic vasoconstriction and hypertension. Hypothermia is also a known predictor of dysrhythmias and myocardial ischemia in high-risk patients. We describe a prospective, randomized trial designed to test the hypothesis that forced-air warming (FAW) provides improved hemodynamic variables after coronary artery bypass graft. After institutional review board approval and written informed consent, 149 patients undergoing coronary artery bypass graft were randomized to receive postoperative warming with either FAW (n = 81) or a circulating water mattress (n = 68). Core temperature was measured at the tympanic membrane. A weighted mean skin temperature was calculated. Heart rate, mean arterial blood pressure, central venous pressure, cardiac output, and systemic vascular resistance were monitored for 22 h postoperatively. Mean arterial blood pressure was maintained by protocol between 70 and 80 mm Hg by titration of nitroglycerin and sodium nitroprusside. The two groups had similar demographic characteristics. Tympanic and mean skin temperatures were similar between groups on intensive care unit admission. During postoperative rewarming, tympanic temperature was similar between groups, but mean skin temperature was significantly greater in the FAW group (P < 0.05). Heart rate, mean arterial pressure, central venous pressure, cardiac output, and systemic vascular resistance were similar for the two groups. The percent of patients requiring nitroprusside to achieve the hemodynamic goals was less (P < 0.05) in the FAW group. In conclusion, aggressive cutaneous warming with FAW results in a higher mean skin temperature and a decreased requirement for vasodilator therapy in hypothermic patients after cardiac surgery. This most likely reflects attenuation of the adrenergic response or opening of cutaneous vascular beds as a result of surface warming. IMPLICATIONS Forced-air warming after cardiac surgery decreases the requirement for vasodilator drugs and may be beneficial in maintaining hemodynamic variables within predefined limits.     

Temperature and ventilation after hypothermic cardiopulmonary bypass

Rewarming in the postoperative period after hypothermic cardiopulmonary bypass is often associated with hemodynamic and ventilatory instability. Temperature changes, PaCO2 values, and delivered mechanical ventilation were observed for the first 12 hr in the intensive care unit in 73 patients who had undergone cardiac surgery with hypothermic cardiopulmonary bypass. Mean rectal temperature increased from 34.7 to 38.3 degrees C over the first 8 hr after admission to the intensive care unit (P less than 0.001). The temperature curve was sigmoid rather than linear, and the most rapid rate of temperature increase occurred 2-4 hr after admission. During rewarming, the most common abnormality of PaCO2 on mechanical ventilation was acute respiratory acidosis (PaCO2 greater than 45 mm Hg, pH less than 7.35), which occurred in 42% of patients. This suggests that ventilatory management in the early postoperative period after hypothermic cardiopulmonary bypass should be carefully adjusted to the increased metabolic rate during rapid rewarming.     

Glucose and insulin supply before cardiopulmonary bypass in cardiac surgery: a double-blind study.

A double-blind study versus placebo was carried out to evaluate the effects of a 500-mL infusion of 30% glucose containing 300 units of ordinary insulin and 5 g of potassium chloride administered at a rate of 1.66 mL.kg-1.h-1 for 1 hour before cardiopulmonary bypass. The hemodynamic parameters measured before and after administration of the solution, after cardiopulmonary bypass, after administration of protamine, and 3 hours after leaving the operating room showed the beneficial effect of the glucose-insulin-potassium infusion on cardiac index (+23.6% after protamine infusion) and left (+16.3% 3 hours postoperatively) and right (+47.3% after cardiopulmonary bypass) ventricular workload index with a decrease in systemic vascular resistance. For patients with a cardiac index of less than 2.5 L.min-1.m-2 before administration of the glucose-insulin-potassium solution, the beneficial effect on the cardiac index was further increased 3 hours postoperatively (+33%). During the postoperative period, the requirements in inotropic drugs and disturbances of rhythm were not significantly different between the two groups, although they were twofold lower in patients receiving glucose-insulin-potassium. Laboratory tests showed that postoperative hypoglycemia was more common in the glucose-insulin-potassium group but had no detrimental effects; it no longer occurs since we began administering the glucose infusion at 15 g/h over 8 hours. The data reflect the beneficial effect associated with the action of glucose-insulin-potassium on myocardial protection during heart operations and were confirmed by the hemodynamic results. This argues in favor of the routine use of this technique, especially in patients with poor ventricular function.     

Effects of hypothermia and hemodilution on oxygen metabolism and hemodynamics in patients recovering from coronary artery bypass operations

The coexistence of hypothermia and hemodilution in patients in the intensive care unit immediately postoperatively after coronary artery bypass graft operations presents concerns regarding the adequacy of hemodynamics and oxygen metabolism. We evaluated the hemodynamic status and oxygen metabolism during the postoperative recovery period in six patients with moderate hemodilution (hematocrit value 34% +/- 3%) and in eight patients with marked hemodilution (hematocrit value 23% +/- 2%). All patients were well sedated and paralyzed with pancuronium bromide during the study period, during which their body temperature was slowly returning toward normal. In both groups, cardiac index at 34 degrees C was about 40% lower than at 37 degrees C. This was associated with 50% higher systemic vascular resistance and 30% lower oxygen availability to tissue. Oxygen consumption, however, was proportionally lower (45%) and coronary perfusion pressure was higher (28%) at 34 degrees C than at 37 degrees C; thus neither mixed venous nor coronary sinus blood oxygen saturation was compromised under hypothermic conditions. Although the trends in hemodynamic changes were similar in both groups, cardiac indices in patients with marked hemodilution were higher than cardiac indices in those with moderate hemodilution at all temperatures. This observation indicates that the hemodilution-induced rise in cardiac index remains intact even under hypothermic conditions. Under the conditions we studied, hypothermia with or without hemodilution had no significant adverse effects on hemodynamics and oxygen metabolisms of the whole body or of the heart.     

Effects of hypertonic saline-dextran solution in cardiac valve surgery with cardiopulmonary bypass

BACKGROUND: Hypertonic saline-dextran (HSD) solution may be beneficial in patients undergoing coronary artery surgery with cardiopulmonary bypass. Valvular dysfunction is associated with high pulmonary wedge pressure, pulmonary hypertension, and ventricular dysfunction. Fluid overload or transient left ventricular failure may occur with HSD infusion in such patients. This study evaluates the cardiorespiratory effects and tolerance of HSD solution infusion in patients undergoing cardiac valve surgery. METHODS: This prospective, randomized, double-blind study compared clinical, laboratory, hemodynamic, and respiratory measurements, and fluid balance in 50 patients over a 48-hour period after cardiopulmonary bypass for cardiac valve surgery. Twenty-five patients received 4 mL/kg of HSD during 20 minutes before cardiopulmonary bypass (HSD group). The control group received the same volume of Ringer's solution (Ringer group). RESULTS: Hospital mortality was zero. The HSD patients had a near zero fluid balance (6.5 +/- 13.5 mL/Kg/48 hours), and the control patients had a positive balance (91.0 +/- 33.7 mL/Kg/48 hours). Hemoglobin was similar in both groups, but more blood transfusions were necessary in the Ringer group (1.21 +/- 1.28 vs 0.48 +/- 0.59 units per patients). The HSD solution induced a higher cardiac index and left ventricular systolic work index postoperatively, and a lower systemic vascular resistance index until 6, 24, and 48 hours. Right ventricular systolic work index increased and pulmonary vascular resistance index decreased after HSD infusion. A better Pao(2)/Fio(2) relation was observed at 1 and 6 hours postoperatively in the HSD group and was associated with a shorter extubation time (432.0 +/- 123.6 vs 520.8 +/- 130.2 minutes). Increased oxygen delivery index occurred in the HSD group. The HSD infusion was well tolerated as none of the patients experienced fluid overload or had left ventricular failure develop. No other complication attributable to the use of HSD solution was observed. CONCLUSIONS: The HSD solution infusion in patients during cardiac valve surgery with cardiopulmonary bypass was well tolerated. Hemodynamic and respiratory functions improved and fluid balance was near zero during the first 48 hours as compared with a large positive balance in the control group. We conclude that HSD infusion is advantageous for patients undergoing cardiac valve surgery.     

Clinical observation of hemodynamic changes during anaphylactic reaction]

Four cases of anaphylactic shock are reported. In two patients who underwent A-C bypass operation, we evaluated hemodynamic changes systemically when the anaphylactic reaction occurred. At that time it was observed that arterial pressure, central venus pressure, left atrial pressure and systemic vascular resistance decreased and that cardiac index increased. In other two patients it was not possible to evaluate hemodynamic changes during reaction. But one of these two patients developed coronary spasm accompanied with anaphylactic shock and the other patient who had depressed cardiac function and had developed cardiogenic shock, died of cardiac failure after 47 days. It is suggested that hemodynamic changes in anaphylactic reaction varies depending on different general conditions of the patient.     

Differences between aortic and radial artery pressure associated with cardiopulmonary bypass.

Previous investigators have identified an aortic-to-radial artery pressure gradient thought to develop during rewarming and discontinuation of cardiopulmonary bypass. The authors measured mean aortic and radial artery pressures before, during, and after cardiopulmonary bypass in 30 patients, to determine when the pressure gradient develops. The pressure gradient was also measured before and after intravenous injections of sodium nitroprusside (1 microgram/kg) and phenylephrine (7 micrograms/kg) to determine the effect of changes in systemic vascular resistance. A significant (P less than 0.05) pressure gradient (mean +/- SEM = 4.9 +/- 0.7 mmHg) developed upon initiation of cardiopulmonary bypass. This gradient did not change significantly during the middle of bypass (4.2 +/- 0.5 mmHg), with rewarming (4.8 +/- 0.7 mmHg), immediately prior to discontinuation of bypass (4.6 +/- 0.7), or 5 and 10 min following bypass (4.9 +/- 0.9 and 4.8 +/- 0.7 mmHg). Sodium nitroprusside significantly decreased systemic vascular resistance, by 15 +/- 2%, during the middle of bypass but did not affect the pressure gradient. Likewise, phenylephrine increased the systemic vascular resistance by 52 +/- 6% and 34 +/- 4% during the middle of bypass and rewarming, respectively, without affecting the pressure gradient. Although the exact mechanisms responsible for the pressure gradient remain unknown, these results suggest its etiology is associated with events occurring during initiation of cardiopulmonary bypass rather than with rewarming or discontinuation of cardiopulmonary bypass.     

Effects of chlorpromazine as a systemic vasodilator during cardiopulmonary bypass in neonates

OBJECTIVES: Vasodilator use during cardiopulmonary bypass is important in pediatric cardiac surgery, but the full range of their effects on hemodynamics remains to be clarified. We studied the effects of chlorpromazine, a potent alpha-blocking agent, in neonates. METHODS: Subjects were 60 neonates undergoing arterial switch operations for complete transposition of the great arteries with an intact ventricular septum. Of these, 37 received 2.1 to 6.5 mg/kg of chlorpromazine during cardiopulmonary bypass (CPZ group) and 23 received no vasodilator (control group). We then compared hemodynamic parameters between groups during and early after surgery. RESULTS: The systemic vascular resistance index and mean arterial pressure during cardiopulmonary bypass were significantly lower in the CPZ group (p < 0.05), but systolic pressure 15 minutes after cessation of cardiopulmonary bypass did not differ between groups. The rise in peripheral temperature during rewarming after hypothermia was significantly higher and the acid-base status 40 minutes after cardiopulmonary bypass less acidotic in the CPZ group. Urine output during cardiopulmonary bypass was higher in the CPZ group. CONCLUSIONS: Chlorpromazine effectively counteracts systemic vasoconstriction induced by cardiopulmonary bypass without serious side effects in neonatal cardiac surgery.     

Oxygen consumption following pediatric cardiac surgery

Metabolic responses during recovery from cardiac operations for various congenital heart defects were studied in 30 mechanically ventilated pediatric patients in two groups: infants 1 year or less (group I) and children more than 1 year old (group II). Oxygen consumption (VO₂) and carbon dioxide production (VCO₂) were measured using a pediatric metabolic monitor intermittently after induction of anesthesia, after skin closure, 2 to 4 hours postoperatively, and on the first postoperative morning in the pediatric intensive care unit. Energy expenditure and respiratory quotient were determined from respiratory gas measurements. Rectal and skin temperatures and hemodynamic variables were recorded at the same time. VO₂ increased during rewarming 2 to 4 hours after the operation by 12 ± 15% in group I and by 24 ± 19% in group II, while rectal temperature increased by 2.0 ± 1.2°C and 1.8 ± 1.4°C, respectively. No further increase in VO₂ occurred until the first postoperative morning. A hypermetabolic response was not seen in all cases despite marked thermal changes. High-dose fentanyl anesthesia partly explains the low responses. On the other hand, low cardiac output may also compromise oxygen supply. Sixty-three percent of infants were treated for cardiac failure before surgery and 75% needed inotropic support immediately after the operation. Low central venous oxyhemoglobin saturation values (S_CVO₂ < 60%) were observed during rewarming, indicating an increase in oxygen extraction secondary to an increased oxygen demand in the brain during recovery from anesthesia, and a low cardiac output or delayed restoration of cerebral blood flow after CPB and deep hypothermia.     

Clinical benefits of normothermic cardiopulmonary bypass on postoperative systemic metabolism

To evaluate the influence of body temperature during cardiopulmonary bypass (CPB) on postoperative systemic metabolism, 32 patients undergoing elective cardiac surgery were randomly assigned to either hypothermia (n = 16) or normothermia (n=16). Serial hemodynamic parameters and blood samples were obtained after surgery. CPB and operation times were significantly shorter and the platelet reduction ratio during CPB [= (platelets before CPB-platelets after CPB)/platelets before CPB] was significantly lower in normothermic patients than in hypothermic patients. The platelet reduction ratio was dependent on the minimum rectal temperature during CPB, the operation time, and the CPB time. In the early postoperative period, hypothermic patients had abnormally high systemic vascular resistance and a reduced cardiac index compared with the normothermic patients. There were no differences between 2 groups in postoperative hepatic and renal functions, changes in oxygen consumption, arterial-venous PCO₂ or arterial-venous pH gradient. This study suggested a beneficial influence of normothermic CPB on postoperative hemodynamics. Normothermic CPB was not associated with adverse effects on postoperative metabolic recovery.     

Haemodynamic response to a small intravenous bolus injection of epinephrine in cardiac surgical patients

BACKGROUND AND OBJECTIVE: The aim was to study the rapid changes in cardiac output and systemic vascular resistance produced by intravenous epinephrine (5 microg) on a beat-by-beat basis. METHODS: Ten patients were studied during cardiac surgery. Radial or brachial arterial pressure was recorded continuously during intravenous administration of epinephrine (5 microg). Cardiac output and systemic vascular resistance were derived for each beat using arterial pulse contour analysis calibrated by lithium indicator dilution. In each patient a further dose of epinephrine (5 microg) was administered during cardiopulmonary bypass with the blood flow kept constant so that changes in arterial pressure corresponded to changes in systemic vascular resistance. RESULTS: When the patients were not on cardiopulmonary bypass, the epinephrine produced an initial increase in systemic vascular resistance to 129 +/- 15% (mean +/- SD) of control, followed by a more prolonged reduction to 57 +/- 13% of control. Cardiac output showed a small initial reduction coincident with the increase in systemic vascular resistance, followed by an increase to 152 +/- 24% of control. During cardiopulmonary bypass, the changes produced by epinephrine on systemic vascular resistance were qualitatively similar but smaller in amplitude, probably because of a greater volume of dilution in the bypass circuit. CONCLUSIONS: Small bolus doses of epinephrine produce an initial increase in systemic vascular resistance followed by a much greater reduction that may cause hypotension.     

Normobaric hyperoxia reduces cardiac index in patients after coronary artery bypass surgery

OBJECTIVE: The purpose of this study was to assess the hemodynamic changes in response to normobaric hyperoxia in patients immediately after coronary artery bypass surgery. DESIGN: Observational study. SETTING: Single-center university hospital. PARTICIPANTS: Patients immediately after coronary artery bypass surgery. INTERVENTION: Change of fractional inspired oxygen concentration from baseline (< or =0.60) to 1.0 and return to baseline. MEASUREMENTS AND MAIN RESULTS: Cardiovascular changes were assessed with a lithium dilution technique. Cardiac index decreased from 2.82 to 2.52 L/min/m2 (10.6%). Heart rate decreased from 85.9 to 82.5 beats/min (4.0%), and the systemic vascular resistance index increased from 1,858 to 2,304 dyne/s/cm5/m2 (24.1%). Stroke index or mean arterial pressure did not change significantly. On reducing the FIO2 from 1.0 to the baseline FIO2 , there was significant reversal of the previous changes in heart rate and systemic vascular resistance. Heart rate increased from 82.5 to 84.0 beats/min (1.8%), and the systemic vascular index decreased from 2304 to 1932 dyne/s/cm5/m2 (16.1%). The cardiac output did not return to baseline, and the mean arterial pressure decreased from 69.6 to 64.4 mmHg (7.6%). CONCLUSIONS: Exposing patients after coronary artery surgery to hyperoxia induces significant hemodynamic changes.     

Cardiovascular responses to verapamil during coronary artery bypass graft surgery

The cardiovascular effects of verapamil administration during coronary artery bypass graft surgery were studied in patients with normal left ventricular function. Anesthesia consisted of morphine, diazepam, and nitrous oxide. Before atrial cannulation for cardiopulmonary bypass, 16 patients received either verapamil (N = 8) 0.075 mg X kg-1 or an equal volume of its solvent (N = 8) administered intravenous over 1 min. Hemodynamic functions and serum verapamil levels were measured over the succeeding 10 min. Verapamil produced rapid reductions in systemic vascular resistance, systemic arterial blood pressure, and left ventricular stroke work index. The PR interval increased slightly and two of the patients who had a baseline PR interval of 200 msec developed a mild first degree heart block. Heart rate, cardiac index, pulmonary capillary wedge pressure, central venous pressure, and right ventricular stroke work index did not significantly change. No measured cardiovascular functions changed in the control group. Serum verapamil levels peaked at 346.4 +/- 143.5 ng X ml-1 0.5 min after drug administration and then rapidly declined. Both groups of patients tolerated surgery and the immediate postoperative recovery period without hemodynamic compromise. Verapamil can be safely administered before cardiopulmonary bypass in patient with good left ventricular function during narcotic-based anesthesia.     

Myocardial Performance Early After Aorto-Coronary Bypass Surgery Cardioplegic Arrest Versus Coronary Perfusion

Haemodynamic adaptation was studied during the first 10 h after aorto-coronary bypass surgery. In a control group of 12 patients the heart was fibrillating and perfused during cardiopulmonary bypass (at 30 degrees C), and in 11 patients cold cardioplegic arrest was used. The first 4--5 h were characterized by rewarming, with increasing oesophageal temperature, cutaneous vasoconstriction and elevated systemic vascular resistance (SVR). A phase of vasodilation followed. In the control group the oxygen uptake index increased by 57% during rewarming, but the cardiac index (CI) was constant (about 2.9 l . min-1.m-2). The arterio-venous oxygen content difference (AVDo2) therefore increased (max. 3.0 mmol . l-1). The postoperative left ventricular performance was better and the serum levels of aspartate aminotransferase (ASAT) during the first 2 days postoperatively were lower in the cardioplegic patients than in the controls, indicating more efficient myocardial preservation. In the cardioplegic-hypothermic group, CI was constant at about 3.2 l . min-1.m-2 (significantly higher than in the control group) and AVDo2 remained normal during the rewarming period. The heart rate was lower initially in the cardioplegic patients than in the controls, implying a favourable influence on myocardial oxygen consumption. The better myocardial function in the cardioplegic-hypothermic group was associated with an only moderately increased SVR. This suggests that the elevated SVR in the control group could have been due to myocardial depression.     

Low systemic vascular resistance after cardiopulmonary bypass: incidence, etiology, and clinical importance

BACKGROUND: Low systemic vascular resistance during and immediately after cardiac surgery in which cardiopulmonary bypass is utilized is a well-known phenomenon, characterized as vasoplegia, which appears with an incidence ranging between 5% and 15%. The etiology is not completely elucidated and the clinical importance remains speculative. METHODS: In this prospective clinical trial, we assessed the incidence of postoperative low systemic vascular resistance in 800 consecutive patients undergoing elective coronary artery bypass grafting and/or valve replacement. We have attempted to identify the predictive factors responsible for the presence of low systemic vascular resistance and we have examined the subsequent postoperative outcome of those patients who developed early postoperative vasoplegia. The severity of vasoplegia was divided into three groups according either to the value of systemic resistance and/or the dose of vasoconstrictive agents necessary to correct the hemodynamic. RESULTS: Six hundred twenty-five patients (78.1%) did not develop vasoplegia, 115 patients (14.4%) developed a mild vasoplegia, and 60 patients (7.5%) suffered from severe vasoplegia. Low systemic vascular resistance did not affect hospital mortality but was the cause for delayed extubation and prolonged stay on the intensive care unit (ICU). Logistic regression analysis identified temperature and duration of cardiopulmonary bypass, total cardioplegic volume infused, reduced left ventricular function, and preoperative treatment with angiotensin-converting enzyme (ACE)-inhibitors, out of 25 parameters, as predictive factors for early postoperative vasoplegia. CONCLUSION: The occurrence of low systemic vascular resistance following cardiopulmonary bypass is as high as 21.8%. The etiology of this clinical condition is most probably multifactorial. Mortality is not affected by vasoplegia, but there is a trend to higher morbidity and prolonged stay in the ICU.     

Prolonged infusion of varied doses of dopexamine hydrochloride for low cardiac output after cardiac surgery.

Circulatory failure after cardiac surgery often calls for active hemodynamic management with fluids, inotropes, and vasodilators. Dopexamine hydrochloride is a new combined beta 2-adrenergic and DA1-dopaminergic receptor agonist and an inhibitor of the uptake-1 mechanism of endogenous catecholamines. As a result, it exerts inotropic and vasodilator effects on the heart and systemic vasculature. The effects were examined over a mean of 22 hours, using 1 to 4 micrograms/kg/min of dopexamine to treat low cardiac output states following coronary bypass and valvular/ventricular repair surgery. In 8 out of 14 patients, low cardiac output was readily reversed by 1 microgram/kg/min of dopexamine. Six patients required higher doses (2 to 4 micrograms/kg/min) to achieve a satisfactory cardiac index. Significant changes from control values were observed throughout the infusion for heart rate (67 to 102 beats/min), cardiac index (2.0 to 3.4 L/min/m2), and systemic vascular resistance (1,545 to 914 dyne.s.cm-5). Pulmonary vascular resistance, pulmonary artery wedge pressure, and right atrial pressure were also significantly reduced during the infusion. Most of these changes reversed when dopexamine was discontinued, suggesting a drug-specific effect and a lack of tolerance. Nausea was a frequent complaint, but was no more frequent than in a random sample of similar patients. Titration of dopexamine, 1 to 4 micrograms/kg/min, was efficacious in producing circulatory improvement in patients with a low cardiac output after cardiac surgery.     

Effects of systemic morphine and epidural bupivacaine on postoperative oxygen consumption during rewarming

The alterations in hemodynamics and oxygen consumption as a consequence of continuous epidural infusions of bupivacaine at room temperature and conventionally administered morphine were studied during recovery from general anesthesia for total hip replacement. Twenty-four patients were randomized to receive either bupivacaine or morphine in the recovery room. The bupivacaine group received from 6 to 12 ml per hour of 0.25% bupivacaine epidurally. Patients in the morphine group received 0.1 mg/kg of morphine intramuscularly no more frequently than every 4 hours. A pulmonary artery flotation catheter was inserted into each patient to determine hemodynamics and oxygen consumption at three instances: before analgesia, when pulmonary artery blood temperature reached 36 degrees C, and when it reached 37 degrees C. During the rewarming there was a decrease in mean arterial blood pressure and the systemic vascular resistance index and an increase in heart rate. The whole body oxygen consumption index increased in the bupivacaine group at the last measuring point but was stable in the morphine group. There was no effect on the arterial-venous oxygen content difference in either group. At 37 degrees C, the cardiac index and oxygen consumption index were significantly higher in the bupivacaine group than in the morphine group. In contrast to regional analgesia, systemic morphine administration can partially antagonize cardiovascular response to postoperative rewarming because it induces a stable oxygen demand.     

The hemodynamic effects of intravenous norepinephrine versus epinephrine and phenylephrine in patients with ischemic heart disease

The hemodynamic effects of an intravenous bolus of norepinephrine 10 micrograms, phenylephrine 100 micrograms and epinephrine 10 micrograms were investigated in 30 patients scheduled for coronary artery bypass grafting. The hemodynamic changes following norepinephrine were similar to those achieved by phenylephrine. Both drugs increased the mean blood pressure and systemic vascular resistance without any significant change of cardiac output. In contrast, epinephrine increased the mean arterial pressure and cardiac output without a significant change of systemic vascular resistance. The results suggest that intravenous norepinephrine acts similar to phenylephrine as an alpha-adrenergic agonist, while epinephrine acts predominantly as a beta-adrenergic agonist.     

Hemodynamic effects of combined digoxin and dopamine administration in postoperative patients with cardiac dysfunction

In 10 patients with postoperative cardiac dysfunction which required dopamine for inotropic and hemodynamic support, we observed the cardiovascular effects of short-term digoxin administration. The average dosage of dopamine was 7.45 micrograms/kg per minute and was maintained while the patients were given 1 mg of digoxin over 8 hours. The dosage of dopamine was then tapered over the next 4 hours. We observed a significant increase in the cardiac index (4 hours) and a reduction in the heart rate (8 hours) before the dopamine dosage was reduced. After a reduction in dopamine dosage to 2.28 micrograms/kg per minute, these effects persisted. No significant changes were noted in systemic vascular resistance or pulmonary artery diastolic pressure during digoxin administration. These results indicate that the inotropic effects of dopamine and digoxin are additive when given in combination and that digoxin can be used to significantly reduce the dopamine dosage in patients with postoperative cardiac failure. Thus, the combination of an acute inotropic agent, dopamine, and a chronic inotropic agent, digoxin, appears to be clinically useful in postoperative cardiac dysfunction.