Metabolic stress modifies the thermogenic effect of dobutamine in man

The Effects of Dobutamine in Septic Shock: An Updated Narrative Review of Clinical and Experimental Studies

The key objective in the hemodynamic treatment of septic shock is the optimization of tissue perfusion and oxygenation. This is usually achieved by the utilization of fluids, vasopressors, and inotropes. Dobutamine is the inotrope most commonly recommended and used for this purpose. Despite the fact that dobutamine was introduced almost half a century ago in the treatment of septic shock, and there is widespread use of the drug, several aspects of its pharmacodynamics remain poorly understood. In normal subjects, dobutamine increases contractility and lacks a direct effect on vascular tone. This results in augmented cardiac output and blood pressure, with reflex reduction in systemic vascular resistance. In septic shock, some experimental and clinical research suggest beneficial effects on systemic and regional perfusion. Nevertheless, other studies found heterogeneous and unpredictable effects with frequent side effects. In this narrative review, we discuss the pharmacodynamic characteristics of dobutamine and its physiologic actions in different settings, with special reference to septic shock. We discuss studies showing that dobutamine frequently induces tachycardia and vasodilation, without positive actions on contractility. Since untoward effects are often found and therapeutic benefits are occasional, its profile of efficacy and safety seems low. Therefore, we recommend that the use of dobutamine in septic shock should be cautious. Before a final decision about its prescription, efficacy, and tolerance should be evaluated throughout a short period with narrow monitoring of its wanted and side effects.

Non-Hemodynamic Effects of Catecholamines

Circulatory shock is defined as an imbalance between tissue oxygen supply and demand, and mostly results from a loss of blood volume, cardiac pump failure, and/or reduction of vasomotor tone. The clinical hallmarks of circulatory shock are arterial hypotension and lactate acidosis. Since the degree and duration of hypotension are major determinants of outcome, vasopressor administration represents a cornerstone therapy to treat these patients. Current guidelines recommend the use of catecholamines as the drug of first choice. However, apart from their hemodynamic effects, which depend on the different receptor profile, receptor affinity, receptor density, and the relative potency of the individual molecule, catecholamines have numerous other biological effects as a result of the ubiquitous presence of their receptors. In shock states, catecholamines aggravate hypermetabolism by promoting hyperglycemia and hyperlactatemia, and further increase oxygen demands, which can contribute to further organ damage. In the mitochondria, catecholamines may promote mitochondrial uncoupling, and aggravate oxidative stress, thereby contributing to the progression of mitochondrial dysfunction. Immunological side effects have also gained specific attention. Although both pro- and anti-inflammatory effects have been described, current evidence strongly indicates an immunosuppressive effect, thereby making patients potentially vulnerable to secondary infections. Catecholamines may not only decrease splanchnic perfusion due to their vasoconstrictor properties, but can also directly impair gastrointestinal motility. This article reviews the non-hemodynamic effects of different catecholamines, both under physiologic and pathophysiologic conditions, with a special focus on energy metabolism, mitochondrial function, immune response, and the gastrointestinal system.

Time course of central venous-to-arterial carbon dioxide tension difference in septic shock patients receiving incremental doses of dobutamine

PURPOSE

To assess the time course of the central venous-arterial carbon dioxide tension difference (∆PCO2)-as an index of the carbon dioxide production (VCO2)/cardiac index (CI) ratio-in stable septic shock patients receiving incremental doses of dobutamine.

METHODS

Twenty-two hemodynamically stable septic shock patients with no signs of global tissue hypoxia, as testified by normal blood lactate levels, were prospectively included. A dobutamine infusion was administered at a dose of up to 15 μg/kg/min in increments of 5 μg/kg/min every 30 min. Complete hemodynamic and gas measurements were obtained at baseline, and at each dose of dobutamine.

RESULTS

Dobutamine induced a significant dose-dependent increase of CI from 0 to 15 μg/kg/min (P < 0.001). Oxygen consumption (VO2) and VCO2 were progressively increased by dobutamine. These increases were more marked between 10 and 15 μg/kg/min (8.3 and 8.6 %, respectively) than between the lower doses. ∆PCO2 and oxygen extraction (EO2) significantly decreased between 0 (8.0 ± 2.0 mmHg and 43.8 ± 13.4 %, respectively) and 10 μg/kg/min of dobutamine (4.2 ± 1.6 mmHg and 28.9 ± 7.9 %, respectively), but remained unchanged from 10 to 15 μg/kg/min (5.4 ± 2.4 mmHg and 29.5 ± 8.2 %, respectively). The central venous oxygen saturation significantly (ScvO2) increased from 0 to 10 μg/kg/min and remained unchanged from 10 to 15 μg/kg/min. Time courses of ∆PCO2, ScvO2, and EO2 were linked therefore to the biphasic changes of VO2 and VCO2.

CONCLUSION

∆PCO2 is a good indicator of the change of VCO2 induced by dobutamine. Measurement of ∆PCO2, along with ScvO2 and EO2, may be presented as a useful tool to assess the adequacy of oxygen supply versus metabolic and oxygen demand.

Glucose metabolism and catecholamines

Until now, catecholamines were the drugs of choice to treat hypotension during shock states. Catecholamines, however, also have marked metabolic effects, particularly on glucose metabolism, and the degree of this metabolic response is directly related to the beta2-adrenoceptor activity of the individual compound used. Under physiologic conditions, infusing catecholamine is associated with enhanced rates of aerobic glycolysis (resulting in adenosine triphosphate production), glucose release (both from glycogenolysis and gluconeogenesis), and inhibition of insulin-mediated glycogenesis. Consequently, hyperglycemia and hyperlactatemia are the hallmarks of this metabolic response. Under pathophysiologic conditions, the metabolic effects of catecholamines are less predictable because of changes in receptor affinity and density and in drug kinetics and the metabolic capacity of the major gluconeogenic organs, both resulting from the disease per se and the ongoing treatment. It is also well-established that shock states are characterized by a hypermetabolic condition with insulin resistance and increased oxygen demands, which coincide with both compromised tissue microcirculatory perfusion and mitochondrial dysfunction. This, in turn, causes impaired glucose utilization and may lead to inadequate glucose supply and, ultimately, metabolic failure. Based on the landmark studies on intensive insulin use, a crucial role is currently attributed to glucose homeostasis. This article reviews the effects of the various catecholamines on glucose utilization, both under physiologic conditions, as well as during shock states. Because, to date (to our knowledge), no patient data are available, results from relevant animal experiments are discussed. In addition, potential strategies are outlined to influence the catecholamine-induced effects on glucose homeostasis.

The cardiopulmonary effects of dobutamine and norepinephrine in isoflurane-anesthetized foals

OBJECTIVE

To evaluate the cardiovascular effects of norepinephrine (NE) and dobutamine (DB) in isoflurane-anesthetized foals.

STUDY DESIGN

Prospective laboratory study.

METHODS

Norepinephrine (0.05, 0.10, 0.20, and 0.40 microg kg(-1) minute(-1)) and dobutamine (2.5, 5.0, and 10 microg kg(-1) minute(-1)) were alternately administered to seven healthy, 1- to 2-week-old isoflurane-anesthetized foals. Arterial and pulmonary arterial blood pressure, right atrial pressure, pulmonary artery occlusion pressure, heart rate, body temperature, cardiac output, arterial and mixed venous blood pH, partial pressure of carbon dioxide, partial pressure of oxygen [arterial partial pressure of oxygen (PaO(2)) and mixed venous partial pressure of oxygen (PvO(2))], and packed cell volume were measured. Standard base excess, bicarbonate concentration, systemic and pulmonary vascular resistance, cardiac index (CI), stroke volume, left and right stroke work indices, oxygen delivery (DO(2)), consumption, and extraction were calculated. Results Norepinephrine infusion resulted in significant increases in arterial and pulmonary arterial pressure, systemic and pulmonary vascular resistance indices, and PaO(2); heart rate was decreased. Dobutamine infusion resulted in significant increases in heart rate, stroke volume index, CI, and arterial and pulmonary arterial blood pressure. Systemic and pulmonary vascular resistance indices were decreased while the ventricular stroke work indices increased. The PaO(2) decreased while DO(2) and oxygen consumption increased. Oxygen extraction decreased and PvO(2) increased.

CONCLUSIONS AND CLINICAL RELEVANCE

Norepinephrine primarily augments arterial blood pressure while decreasing CI. Dobutamine primarily augments CI with only modest increases in arterial blood pressure. Both NE and DB could be useful in the hemodynamic management of anesthetized foals.

Effects of epinephrine and norepinephrine on hemodynamics, oxidative metabolism, and organ energetics in endotoxemic rats

OBJECTIVE

To determine whether epinephrine increases lactate concentration in sepsis through hypoxia or through a particular thermogenic or metabolic pathway.

DESIGN

Prospective, controlled experimental study in rats.

SETTING

Experimental laboratory in a university teaching hospital.

INTERVENTIONS

Three groups of anesthetized, mechanically ventilated male Wistar rats received an intravenous infusion of 15 mg/kg Escherichia coli O127:B8 endotoxin. Rats were treated after 90 min by epinephrine ( n=14), norepinephrine ( n=14), or hydroxyethyl starch ( n=14). Three groups of six rats served as time-matched control groups and received saline, epinephrine, or norepinephrine from 90 to 180 degrees min. Mean arterial pressure, aortic, renal, mesenteric and femoral blood flow, arterial blood gases, lactate, pyruvate, and nitrate were measured at baseline and 90 and 180 min after endotoxin challenge. At the end of experiments biopsy samples were taken from the liver, heart, muscle, kidney, and small intestine for tissue adenine nucleotide and lactate/pyruvate measurements.

MEASUREMENTS AND RESULTS

Endotoxin induced a decrease in mean arterial pressure and in aortic, mesenteric, and renal blood flow. Plasmatic and tissue lactate increased with a high lactate/pyruvate (L/P) ratio. ATP decreased in liver, kidney, and heart. The ATP/ADP ratio did not change, and phosphocreatinine decreased in all organs. Epinephrine and norepinephrine increased mean arterial pressure to baseline values. Epinephrine increased aortic blood flow while renal blood low decreased with both drugs. Plasmatic lactate increased with a stable L/P ratio with epinephrine and did not change with norepinephrine compared to endotoxin values. Nevertheless epinephrine and norepinephrine when compared to endotoxin values did not change tissue L/P ratios or ATP concentration in muscle, heart, gut, or liver. In kidney both drugs decreased ATP concentration.

CONCLUSIONS

Our data demonstrate in a rat model of endotoxemia that epinephrine-induced hyperlactatemia is not related to cellular hypoxia.

Metabolic changes after cardiac surgery

The metabolic changes that occur after cardiac surgery result from a complex interaction between the effects of surgery and extracorporeal circulation per se, the inflammatory response to surgical trauma and extracorporeal circulation, perioperative use of hypothermia, the cardiovascular and neuroendocrine responses characteristic to cardiac surgery, and the drugs and blood products used to support circulation during and after operation. These changes include among others increased oxygen consumption and energy expenditure and increased secretion of insulin, growth hormone, adrenocorticotrophic hormone, cortisol, epinephrine and norepinephrine. Other changes include decreased total-Trijodthyronine levels, hyperglycemia, hyperlactatemia, increased glutamate, aspartate and free fatty acid concentrations, hypokalemia, an increased production of inflammatory cytokines and increased consumption of complement and adhesion molecules. There is evidence that better control of metabolic abnormalities improves the patients' outcome.

Amrinone in pediatric refractory septic shock: An open-label pharmacodynamic study

OBJECTIVE: To investigate the short-term hemodynamic effects of amrinone in pediatric patients with refractory septic shock. DESIGN: Open-label, clinical trial. SETTING: Pediatric intensive care unit. PATIENTS: Nine patients admitted with a diagnosis of septic shock receiving stable doses of vasopressors and inotropes. INTERVENTIONS: Pediatric patients with septic shock and a pulmonary artery catheter were treated with amrinone in a stepwise fashion at 5, 10, and 15 &mgr;g/kg/min. MEASUREMENTS AND MAIN RESULTS: Heart rate, blood pressure, cardiac index, rate pressure product, systemic vascular resistance index, pulmonary vascular resistance, oxygen delivery, and oxygen consumption were measured at baseline and 90 mins after each amrinone dose. The addition of amrinone increased cardiac index (p <.05) and oxygen delivery (p <.05) without increasing the rate pressure product. Decreases were observed in systemic vascular resistance index (p <.05) and pulmonary vascular resistance (p <.05). No significant changes were seen in heart rate, blood pressure, or oxygen consumption. CONCLUSIONS: In this short-term, dose-response study in children with refractory septic shock, amrinone improved cardiac index and oxygen delivery in pediatric patients with refractory septic shock without increasing myocardial work.

Different response of oxygen consumption and cardiac output to various endogenous and synthetic catecholamines in awake dogs

OBJECTIVE

To determine whether catecholamines with different adrenergic receptor affinities are characterized by individual relationships between cardiac output (Q) and oxygen consumption (VO2).

DESIGN

Comparison of the dose-effect relationships and Q/VO2 relationships of four different catecholamines in the same awake dogs.

SETTING

University research department of experimental anesthesiology.

SUBJECTS

Ten trained, healthy dogs in the basal metabolic state with chronically implanted ultrasonic flow transducers around the pulmonary artery for the continuous measurement of cardiac output.

INTERVENTIONS

Increasing doses of norepinephrine, epinephrine, dobutamine, or dopexamine were infused in a randomly varied sequence on separate days until VO2 and Q reached a maximum.

MEASUREMENTS AND MAIN RESULTS

VO2 was measured by indirect calorimetry, and Q was measured via the pulmonary artery by ultrasonic flowmetry. In healthy dogs, catecholamines increased both VO2 and Q in a dose-dependent manner until a plateau was reached when VO2 had doubled and Q had quadrupled compared with baseline conditions. Regardless of the catecholamine, the resulting Q/VO2 relationships were linear up to the maximal effects, but their slopes (s) differed significantly between agents (p < .05, paired sign test) and increased approximately three-fold in the order norepinephrine (s = 34), epinephrine (s = 54), dobutamine (s = 86), and dopexamine (s = 105). Except for norepinephrine, the catecholamines also increased oxygen delivery more than VO2, so that O2 extraction decreased to 40% below baseline.

CONCLUSIONS

Catecholamines are characterized by linear Q/VO2 relationships with drug-specific slopes. All agents (except norepinephrine) increased oxygen delivery more than oxygen demand. For the practice of catecholamine therapy, our experiments imply that synthetic agents such as dobutamine and particularly dopexamine may be preferred in the treatment of low cardiac output states because they increase Q with the least metabolic effects.

Evaluation of oxygen consumption and resting energy expenditure in critically ill patients with systemic inflammatory response syndrome

OBJECTIVE

To determine whether oxygen consumption VO2), CO2 production, and resting energy expenditure (REE) in critically ill patients differ in varying grades of systemic inflammatory response syndrome (SIRS).

DESIGN

Prospective, clinical study.

SETTING

Intensive care unit at a university hospital.

PATIENTS

Twenty-six critically ill patients requiring mechanical ventilation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A total of 100 metabolic measurements were performed. The grade of SIRS and the Acute Physiology and Chronic Health Evaluation II score were evaluated at the time of the metabolic cart study. VO2 and REE differed among the groups inadequate for SIRS (non-SIRS), with SIRS without infection (nonseptic SIRS), and with SIRS with infection (septic SIRS) (125 +/- 37 mL/min/m2 and 855 +/- 204 kcal/day/m2, 135 +/- 33 mL/min/m2 and 948 +/- 214 kcal/day/m2, and 166 +/- 55 mL/min/m2 and 1149 +/- 339 kcal/day/m2, respectively; p < .005). Patients with septic SIRS had higher VO2 and REE than patients with non-SIRS and nonseptic SIRS.

CONCLUSION

VO2 and REE differ among groups of patients with non-SIRS, nonseptic SIRS, and septic SIRS. Patients with septic SIRS have higher VO2 and REE than patients with non-SIRS or nonseptic SIRS. The present study shows that classifying patients into three grades (non-SIRS, nonseptic SIRS, and septic SIRS) is a valid predictor of metabolic stress in critically ill patients.

Is there occult tissue ischemia in chronic end-stage liver disease?

Whether pathological oxygen supply dependency exists in patients with chronic end-stage liver disease (CESLD) is unknown, although the frequently occurring multiorgan dysfunction seen in these patients may be the result of occult tissue ischemia. In this study, 15 adult patients with CESLD were evaluated for the presence of pathological oxygen supply dependency and, thus, occult tissue ischemia before undergoing orthotopic liver transplantation. Whole-body oxygen consumption (VO2) was measured using indirect calorimetry at baseline, at reduced oxygen delivery (DO2) using positive end-expiratory pressure, and at increased DO2 using volume infusion. As a group, no significant increase or decrease in VO2 was observed with changes in DO2. However, 4 patients showed increases in VO2 of 14%, 10.8%, 9.6%, and 8.2% when DO2 was increased. The study results suggest that pathological oxygen supply dependency is present in a subset of patients with CESLD, and the existence of occult tissue ischemia is speculated.

Impact of exogenous beta-adrenergic receptor stimulation on hepatosplanchnic oxygen kinetics and metabolic activity in septic shock

OBJECTIVE

To investigate the impact of exogenous beta-adrenergic receptor stimulation on splanchnic blood flow, oxygen kinetics, glucose-precursor flux, and liver metabolism in septic shock.

DESIGN

Prospective trial.

SETTING

University hospital intensive care unit.

PATIENTS

Six patients with hyperdynamic (cardiac index >4.0 L/min/m2) septic shock, all requiring norepinephrine to maintain blood pressure >65 mm Hg.

INTERVENTIONS

We compared norepinephrine and phenylephrine titrated to achieve similar systemic hemodynamics and gas exchange. Splanchnic hemodynamics, oxygen kinetics, and metabolic parameters were measured before, during, and after replacing norepinephrine with phenylephrine.

MEASUREMENTS AND MAIN RESULTS

Splanchnic blood flow and oxygen kinetics were derived from the steady-state indocyanine-green clearance based on hepatic dye extraction and arterial and hepatic venous blood gases. Endogenous glucose production rate was derived from the plasma appearance rate of stable-isotope-labeled glucose using a primed-constant infusion. Splanchnic lactate, alanine (high-performance liquid chromatography) uptake, and hepatic monoethylglycinexylidide (MEGX) (fluorescence polarization immunoassay) formation rates were calculated from splanchnic blood flow and arterial-hepatic venous concentration differences. Replacing norepinephrine with phenylephrine induced no change in systemic hemodynamics or gas exchange. While splanchnic oxygen consumption and alanine uptake rate remained unaffected, splanchnic blood flow, oxygen delivery, and lactate uptake rate were significantly decreased. Glucose production rate also decreased significantly. A return to norepinephrine restored splanchnic blood flow, oxygen delivery, and lactate uptake rate to baseline values, while glucose production rate remained depressed. Hepatic MEGX formation rate was not influenced during the investigation.

CONCLUSIONS

Exogenous beta-adrenergic receptor stimulation determines splanchnic blood flow, oxygen delivery, and glucose precursor flux but not splanchnic oxygen utilization in septic shock. Gluconeogenesis is not directly affiliated to hepatosplanchnic oxygen kinetics. The different response of glucose and MEGX production rates, metabolic pathways of the periportal and perivenous region, may document intrahepatic heterogeneity associated with hepatocellular metabolic compartmentation.

Value of the venous-arterial PCO2 gradient to reflect the oxygen supply to demand in humans: effects of dobutamine

OBJECTIVE

To test the value of venous-arterial PCO2 gradient (deltaPCO2) measurements to reflect the adequacy of cardiac index (CI) to oxygen demand in patients submitted to rapid changes of CI and oxygen demand.

DESIGN

Prospective, comparative study.

SETTING

Medical intensive care unit of a university hospital.

PATIENTS

Ten patients with congestive heart failure exhibiting low baseline CI (< or =2.5 L/min/m2) but no evidence of global tissue hypoxia, as attested by the absence of clinical signs of shock and by normal blood lactate concentrations.

INTERVENTIONS

Infusion of incremental doses of dobutamine: 0 (D0), 5 (D5), 10 (D10), and 15 (D15) microg/kg/min.

MEASUREMENTS AND MAIN RESULTS

The CI increased by a linear fashion from D0 (1.6+/-0.1 L/min/m2) to D15 (2.4+/-0.2 L/min/m2) (p< .05). The mixed venous oxygen saturation (SVO2) increased from D0 (49+/-2%) to D10 (61+/-2%) (p < .05) and remained unchanged from D10 to D15 (60+/-2%). The oxygen extraction ratio (O2 ER) and the deltaPCO2 decreased from D0 (48+/-2% and 9+/-1 torr [1.2+/-0.3 kPa], respectively) to D10 (36+/-2% and 5+/-1 torr [0.7+/-0.1 kPa], respectively) (p < .05 for both comparisons) and remained unchanged from D10 to D15 (36+/-2% and 6+/-1 torr [0.8+/-0.1 kPa], respectively). The biphasic courses of SVO2, O2 ER, and deltaPCO2 were related to the course of oxygen consumption that remained constant from D0 (113+/-9 mL/min/m2) to D10 (112+/-8 mL/min/m2) and significantly increased from D10 to D15 (127+/-10 mL/min/m2) (p <.05).

CONCLUSIONS

deltaPCO2 can be reliably used at the bedside for informing on the adequacy of CI with respect to a given metabolic condition, and particularly for detecting changes in oxygen demand (e.g., the changes accompanying drug-induced changes in CI). In this regard, deltaPCO2, together with O2 ER and SVO2, can help to assess the adequacy of CI to global oxygen demand.

The relationship of oxygen consumption measured by indirect calorimetry to oxygen delivery in critically ill patients

OBJECTIVE

The existence of oxygen supply dependency, defined as oxygen consumption (VO2) limited by oxygen delivery (DO2), is still questioned. This study examined the relationship between VO2 and DO2 in two groups of critically ill surgical patients 50 years and older in the first 24 hours of resuscitation after pulmonary artery catheter insertion. Group 1 patients had systemic inflammatory response syndrome (SIRS), sepsis, severe sepsis, septic shock, and adult respiratory distress syndrome (ARDS). Group 2 patients had hemorrhagic shock.

METHODOLOGY

Study methodology included (1) augmenting DO2 with fluids, blood, and vasopressors, (2) measuring VO2 by indirect calorimetry to avoid the problem of mathematical coupling with DO2 calculation, and (3) analyzing data during steady states of temperature, sedation, paralyzing agents, and vasopressors.

RESULTS

Six to 18 measurements collected on all study patients during a period within the first 24 hours were analyzed using a linear regression analysis. Statistical significance was set at p < or = 0.05. Seven of nine patients in group 1 demonstrated positive, statistically significant relationships between VO2 and DO2. Of six patients in group 2, one patient demonstrated a positive, significant relationship of VO2 and DO2, three demonstrated inverse relationships, and two patients did not show a DO2/VO2 relationship. Supply dependency did not exist in all patients but was present in seven out of nine patients with systemic inflammatory response syndrome, sepsis, severe sepsis, septic shock, and adult respiratory distress syndrome in the first 24 hours of treatment.

Splanchnic oxygen transport after cardiac surgery: evidence for inadequate tissue perfusion after stabilization of hemodynamics

OBJECTIVE

To evaluate the adequacy of visceral oxygen transport and gastric pHi after open heart surgery in patients with stable hemodynamics.

DESIGN

Nonrandomized control trial.

SETTING

A general intensive care unit in a tertiary care center.

PATIENTS

Sixteen postoperative cardiac surgery patients were studied after stabilization of systemic hemodynamics.

INTERVENTIONS

The effect of dobutamine infusion (6 mu g kg-1 min-1) on systemic and regional oxygen transport was studied in ten patients, with six patients serving as controls. Systemic oxygen consumption was measured by indirect calorimetry and splanchnic and femoral blood flow, by continuous infusion of indocyanine green using regional catheters and gastric mucosal pHi by gastric tonometer.

MEASUREMENTS AND RESULTS

Gastric mucosal acidosis was observed in half of the patients. Dobutamine increased cardiac output (3.2 +/- 0.6 vs 4.4 +/- 0.7 l x min-1 x min-2; P <0.05), splanchnic blood flow (0.68 +/- 0.28 vs 0.91 +/- 0.28 l x min-1 x m-2; p <0.05) and femoral blood flow (0.25 +/- 0.08 vs 0.32 +/- 0.11 l x min-1 x m-2; p <0.05). Changes in splanchnic oxygen delivery and consumption were parallel in the two study groups. In response to dobutamine, gastric pHi did not change (7.30 +/- 0.08 vs 7.31 +/- 0.06; NS), while in the control group, gastric pHi tended to decrease (7.32 +/- 0.04 vs 7.28 +/- 0.06; NS). Systemic oxygen consumption increased in response to dobutamine (141 +/- 11 vs 149 +/- 11 ml x min-1 x m-2; P <0.05) but did not change in the control group.

CONCLUSIONS

We conclude that a mismatch between splanchnic oxygen delivery and demand may be present despite stabilization of systemic hemodynamics after cardiac surgery. This is suggested by the parallel changes in splanchnic oxygen delivery and consumption. Dobutamine is likely to improve splanchnic tissue perfusion at this phase.