Splanchnic Oxygen Transport Research Articles

Aortic atresia is associated with an inferior systemic, cerebral, and splanchnic oxygen-transport status in neonates after the Norwood procedure☆

Aortic atresia (AA) is a risk factor for mortality after the Norwood procedure. The mechanisms remain unknown. We compared the profiles of systemic, cerebral, and splanchnic oxygen transport in neonates with hypoplastic left-heart syndrome with AA or aortic stenosis (AS) after the Norwood procedure. Systemic oxygen consumption (VO(2)) was measured using respiratory mass spectrometry for 72 h in 17 neonates (nine in the AA group, eight in the AS group). Cardiac output (CO), systemic vascular resistance (SVR), oxygen delivery (DO(2)), and oxygen extraction ratio (ERO(2)) were calculated combining with blood gases and pressures at 2-4-h intervals. Cerebral (ScO(2)) and splanchnic (SsO(2)) oxygen saturations were measured by near-infrared spectroscopy. The doses of dopamine, milrinone, phenoxybenzamine, and vasopressin were recorded. Preoperative echocardiographic left-ventricular morphology and ejection fraction ratio were measured. Compared with the AS group, the AA group had lower CO (p = 0.03), higher SVR (p = 0.002), lower DO(2) (p = 0.07), VO(2) (p = 0.003), and ScO(2) (p = 0.07) during the first 40 h. SsO(2) was insignificantly lower. Despite a similar ERO(2), the AA group had higher lactate (p = 0.01). The AA group received higher doses of milrinone (p < 0.0001), vasopressin (p = 0.005), and phenoxybenzamine (p = 0.02), and lower higher doses of dopamine (p = 0.07). Vasopressin adversely correlated with systemic oxygen-transport variables and SsO(2) (p < 0.05). The AA group had thicker left-ventricular posterior wall (p = 0.05) that was negatively correlated with CO (p = 0.02). AA is associated with an inferior status of systemic, cerebral, and splanchnic oxygen transport after the Norwood procedure. Aggressive use of vasopressin may worsen systemic oxygen transport and decrease splanchnic perfusion.

Abstract 2597: Aortic Atresia Is Associated with an Inferior Postoperative Systemic, Cerebral and Splanchnic Oxygen Transport Status in Neonates with Hypoplastic Left Heart Syndrome after the Norwood Procedure

Aortic atresia (AA) has been identified as a risk factor for mortality after the Norwood procedure. We compared postoperative systemic and regional (cerebral and splanchnic) oxygen transport profiles in neonates with hypoplastic left heart syndrome with or without AA after the Norwood procedure. Systemic oxygen consumption (VO 2 ) was measured using respiratory mass spectrometry postoperatively for 72 hrs in 17 neonates (n=9 in AA group and 8 in non-AA group). Arterial, superior vena cava, and pulmonary venous blood gases and pressures were measured at 2– 4 hr intervals to calculate cardiac output (CO), systemic vascular resistance (SVR), oxygen delivery (DO 2 ) and oxygen extraction ratio (ERO 2 ). Cerebral (ScO 2 ) and splanchnic (SsO 2 ) oxygen saturations were measured using near infrared spectroscopy. The doses of dopamine, vasopressin (up to 0.0008 unit/kg/min), phenoxybenzamine and milrinone were noted. When compared to non-AA group, AA group had lower CO (p=0.03), higher systolic arterial blood pressure (p=0.01) and SVR (p=0.002), lower DO 2 (p=0.07), VO 2 (p=0.003) and ScO 2 during the first 30 to 40 hrs. There was no significant difference in SsO 2 (p=0.12, n=7 in AA group and 3 in non-AA group). Despite a similar ERO 2 (p=0.5), AA group had higher lactate over 72 hrs (p=0.01). AA group received higher doses of vasopressin (p=0.005) and milrinone (p&lt;0.0001), lower doses of dopamine (p=0.07), with similar use of phenoxybenzamine. Furthermore, VO 2 negatively correlated with vasopressin (p=0.05), positively correlated with milrinone (p=0.03) and dopamine (p&lt;0.0001). When including the drugs, the inferior status in all the oxygen transport variables remained, and additionally adversely correlated with vasopressin (p from &lt;0.0001 to 0.06), except for ScO 2 that positively correlated with dopamine, but not with other drugs. Aortic atresia is associated with an inferior status of systemic, cerebral and splanchnic oxygen transport in neonates after the Norwood procedure. Aggressive use of vasopressin worsens systemic and splanchnic oxygen transport status. Postoperative management strategies should be directed to improve both systemic and regional oxygen transport in this special group of patients.

Small-Dose Epoprostenol Decreases Systemic Oxygen Consumption and Splanchnic Oxygen Extraction During Normothermic Cardiopulmonary Bypass

Normothermic, nonpulsatile cardiopulmonary bypass (CPB) impairs systemic and splanchnic oxygen transport and increases gastrointestinal permeability. It is an important therapeutic goal to avoid splanchnic dysoxia during CPB. Small-dose prostacyclin therapy improves splanchnic oxygen transport and microcirculation in septic patients. In this study, we sought to determine if during cardiac surgery, the prostacyclin analog epoprostenol improves the balance of systemic and splanchnic oxygen transport. Eighteen patients undergoing cardiac valve replacement were randomized to receive either epoprostenol (3 ng x kg(-1) x min(-1)) or placebo during, and for 1 hour after, surgery. Systemic and splanchnic oxygen delivery, consumption, and extraction and arterial, mixed venous, and hepato-venous lactate concentrations were measured before, during, and after CPB. Gastrointestinal permeability was measured 1 day before and 1 day after surgery using the triple sugar permeability test. During CPB, the epoprostenol group had decreased systemic oxygen consumption and splanchnic oxygen extraction (P = 0.024). These effects were not present 1 hour after the end of epoprostenol infusion. The study was not adequately powered to determine whether epoprostenol altered the trend towards increased lactate metabolism and increased postoperative gastrointestinal permeability, nor could we demonstrate any differences between groups in clinically relevant end-points. In conclusion, these findings suggest that during normothermic CPB, small-dose epoprostenol therapy may reduce systemic oxygen consumption and splanchnic oxygen extraction.

Splanchnic oxygen transport, hepatic function and gastrointestinal barrier after normothermic cardiopulmonary bypass.

The effect of non-pulsatile, normothermic cardiopulmonary-bypass (CPB) on the splanchnic blood-flow and oxygen-transport, the hepatic function and the gastrointestinal barrier were observed in a prospective observational study in 31 adults undergoing cardiac valve replacement surgery. The splanchnic (i.e. hepatic) blood-flow (HBF) was measured by the constant infusion of indocyanine-green (ICG) using a hepatic-venous catheter. Liver function was examined by calculation of lactate uptake, ICG extraction and the monoethylglycinexylidide (MEGX) test. A day before and after surgery the gastrioduodenal and intestinal permeability was measured by determination of sucrose and lactulose/mannitol excretion. Splanchnic blood flow and oxygen delivery did not decrease during and after surgery while splanchnic oxygen consumption (P < 0.0125) and arterial lactate concentrations increased. The splanchnic lactate uptake paralleled the lactate concentration. After but not during CPB an increase of systemic oxygen consumption was observed. The MEGX test values decreased on the first day after surgery. The ICG extraction was attenuated during the operation. The gastroduodenal and the intestinal permeability increased significantly postoperatively (P < 0.002, respectively, P < 0.001). There was no correlation between these findings and the duration of CPB. There was a significant correlation of the intestinal permeability but not of the gastroduodenal permeability between the prior and after surgery values (P < 0.001). Increased oxygen consumption during CPB may indicate an inflammatory reaction due to the pump beginning in the splanchnic area or a redistribution of the splanchinc blood flow during the CPB. Normothermic CPB does not lead to a significant or prolonged reduction of liver function. Normothermic CPB causes an increase of gastrointestinal permeability. The intestinal barrier function prior to surgery was accountable for the degree of loss of intestinal barrier function following surgery.

Splanchnic oxygen transport and lactate metabolism during normothermic cardiopulmonary bypass in humans.

The effect of normothermic (36.2 degrees C +/- 0.6 degree C) nonpulsatile cardiopulmonary bypass (CPB) on splanchnic (hepatic) blood flow (SBF), splanchnic oxygen transport (DO2spl) and oxygen consumption (VO2spl), splanchnic lactate uptake and gastric mucosal pH (pHi, gastric tonometry) was studied in 12 adults (New York Heart Association class II, ejection fraction > or = 0.4) undergoing coronary artery surgery. SBF was estimated with the constant-infusion indocyanine green (ICG) technique using a hepatic venous catheter. DO2spl, VO2spl, and splanchnic lactate uptake were calculated using the Fick principle after the induction of anesthesia, during aortic cross-clamping, after CPB, and 2 and 7 h after admission to the intensive care unit (ICU). SBF, DO2spl, and VO2spl did not decrease during CPB but increased after ICU admission, whereas pHi decreased 7 h after ICU admission. Initial ICG extraction was 0.78, which decreased to 0.54 during aortic clamping and remained low thereafter. The increased arterial blood lactate concentrations were not associated with a decreased splanchnic lactate uptake. We conclude that normothermic CPB is not associated with deterioration in the global intestinal oxygen supply. The increase of blood lactate levels and the decrease in ICG extraction, as well as in pHi, are consistent with a systemic inflammatory response to CPB. This study demonstrated that normothermic cardiopulmonary bypass (at flows > 2.4 L.min-1.m-2) was not associated with deterioration in global intestinal oxygen delivery, which suggests that increased blood lactate concentrations and decreased gastric mucosal pH and indocyanine green extraction are manifestations of a systemic inflammatory response to cardiopulmonary bypass.

Splanchnic Oxygen Transport and Lactate Metabolism During Normothermic Cardiopulmonary Bypass in Humans

Splanchnic Oxygen Transport and Lactate Metabolism During Normothermic Cardiopulmonary Bypass in Humans

Gastric mucosal pH does not reflect changes in splanchnic blood flow after cardiac surgery

Despite the widespread use of gastric tonometry to assess splanchnic oxygen transport, no human data are available on the relationship between splanchnic blood flow, splanchnic oxygen delivery and gastric mucosal pH. We have studied the effect of splanchnic blood flow and oxygen delivery on gastric mucosal pHi after cardiac surgery. During the first postoperative hours of intensive care, dopexamine was infused to increase cardiac output in eight patients, while six patients served as controls. Gastric mucosal pH (gastric tonometry), splanchnic blood flow and splanchnic oxygen delivery and consumption (dye dilution) were measured. Dopexamine administration significantly increased splanchnic blood flow (0.72 vs 1.02 litre min-1 m-2) (P < 0.05) and oxygen delivery (117 vs 161 ml min-1 m-2) (P < 0.05) compared with baseline values. However, splanchnic oxygen consumption remained unchanged and gastric mucosal pH levels decreased (7.30 vs 7.25) (P < 0.05). The proportion of splanchnic blood flow of cardiac output did not change in response to infusion of dopexamine, that is dopexamine did not favour blood flow distribution to the splanchnic region. In the control group there were no changes in splanchnic blood flow and oxygen delivery, while splanchnic oxygen consumption increased (36 vs 39 ml min-1 m-2) (P < 0.05) and gastric mucosal pH tended to decrease (7.33 vs 7.29) (ns). We conclude that after cardiac surgery gastric mucosal pH did not reflect changes in splanchnic blood flow and oxygen delivery suggesting heterogeneous or inadequate blood flow distribution within the splanchnic region.

Effect of clonidine on liver oxygen extraction during alcohol withdrawal in man

Since catecholamines can alter splanchnic oxygen transport and extraction, the suppression of sympathetic overactivity during alcohol withdrawal might improve hepatic oxygen extraction. Therefore, this study investigated the effects of clonidine, a centrally-acting alpha 2-agonist which reduces sympathetic nervous outflow, on splanchnic oxygen transport and extraction in 13 patients with chronic alcoholism during alcohol withdrawal. All patients had elevated transaminases and steatosis at liver biopsy and were withdrawn from alcohol 51 +/- 15 h (mean +/- SD) before the study. Hepatic blood flow, cardiac output and the oxygen contents were measured in the radial and pulmonary arteries and in the hepatic veins before and 45 min after intravenous administration of clonidine, 150 micrograms. Basal hepatic blood flow was inversely correlated with norepinephrine plasma concentrations (r = -0.63, p < 0.025). After clonidine administration, the decrease in plasma norepinephrine correlated with the norepinephrine basal value (r = 0.889, p < 0.001), and splanchnic oxygen extraction increased (from 40 +/- 15 to 49 +/- 17%, p < 0.025). After clonidine administration, splanchnic oxygen extraction was correlated with the decrease in plasma norepinephrine (r = 0.72, p < 0.01). Arterial lactate concentration decreased (from 0.74 +/- 0.20 to 0.64 +/- 0.23 mmol/l, p < 0.01). These results suggest that defective liver oxygen extraction might occur during alcohol withdrawal as a result of sympathetic nervous hyperactivity. Alterations in the hepatic microcirculation during withdrawal might be related to catecholamine secretion and be controlled by pharmacological manipulation.

Oxygen transport-dependent splanchnic metabolism in the sepsis syndrome.

Total body oxygen consumption (VO2) may be pathologically oxygen delivery (DO2)-dependent in critically ill patients exhibiting the sepsis syndrome. This observation has been used to infer the presence of occult tissue or organ ischemia that potentially can be eradicated by augmenting DO2. We examined this hypothesis by determining the VO2-DO2 relationship and lactate metabolism in the splanchnic region. Before and after intervention trial. University-affiliated Veterans Affairs Medical Center, Allen Park, Mich. Eighteen surgical patients exhibiting the sepsis syndrome. Systemic and splanchnic oxygen exchange and lactate uptake measurements before and after augmentation of DO2 with blood transfusion. Changes in oxygen exchange and lactate metabolism. The splanchnic VO2 index rose 9% in association with a 26% regional DO2 index increase indicating an oxygen transport dependency (P < .05). Splanchnic O2 extraction (0.47 +/- 0.04) was significantly greater than the mean systemic level (0.31 +/- 0.02) and showed a greater decline following DO2 index augmentation (0.41 +/- 0.04 vs 0.28 +/- 0.03, respectively). However, splanchnic lactate uptake was not changed significantly in response to the increased DO2 index. Although splanchnic oxygen transport dependency and elevated extraction ratios suggest the presence of regional ischemia that should be relieved with an increased DO2 index, the observed changes in lactate uptake do not support this conclusion. The significance of the VO2-DO2 relationship, its role in the pathophysiology of the sepsis syndrome, and its place in the clinical care of the septic surgical patient are in doubt.