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PubMedDate not supplied

Postprandial hemodynamic responses in patients with cirrhosis.

The hemodynamic response to a 800 kcal liquid meal was investigated in 24 patients (study group) with cirrhosis and two control groups. One control group of six cirrhotic patients (volume control) had a calorie-free equivolumic electrolyte solution. The second control group (normal control) of six patients with normal hepatic function had the same test meal. Cardiac index, mean arterial pressure, heart rate, hepatic venous pressures, hepatic blood flow and azygos blood flow (only measured in the study group) were measured before and 30 and 60 min after the meal. Systemic circulatory responses were generally absent. Hepatic blood flow and wedged hepatic venous pressure increased significantly in both cirrhotic patients and normal controls; however, cirrhotic patients tended to have a quicker response (peaks at 30 min) than normals (peaks at 60 min). Azygos blood flow showed large postprandial variability, but overall did not change significantly. These results demonstrate that the splanchnic circulation of the patient with cirrhosis reacts differently from normals to the physiologic stimulus of a meal, and in particular appears to have precocious vasoactive reactivity.

Alcoholism↗
PubMed2001

Effect of fenestration on the sub-diaphragmatic venous hemodynamics in the total-cavopulmonary connection.

OBJECTIVE: To understand differences in the sub-diaphragmatic venous physiology between patients with fenestrated and non-fenestrated total-cavopulmonary connections (TCPC). METHODS: We studied the effects of respiration, retrograde flow, and gravity on the sub-diaphragmatic venous flows in 20 normal healthy volunteers (control), 25 Fontan patients with non-fenestrated TCPC, and 21 with fenestrated TCPC. Subhepatic inferior vena cava (IVC), hepatic vein (HV), and portal vein (PV) flow rates were measured with Doppler ultrasonography during inspiration and expiration in both supine and upright positions. The supine inspiratory-to-expiratory flow rate ratio was calculated to reflect the effect of respiration, the supine-to-upright flow rate ratio was calculated to assess the effect of gravity, and the magnitude of retrograde flow was evaluated with respect to total antegrade flow. Mean IVC, HV, and wedged hepatic venous (WHV) pressures were measured during cardiac catheterization in four TCPC patients before and after fenestration closure. The transhepatic venous pressure gradient (TVPG) was calculated as the difference between the HV and WHV pressure. RESULTS: Compared with control, HV flow in TCPC was heavily dependent on respiration; this inspiratory capacity was greater in fenestrated than non-fenestrated subjects (inspiratory-to-expiratory flow ratio 1.7, 4.4, and 3.0, respectively P<0.001). Normal retrograde HV flow was diminished in TCPC patients, furthermore, fenestrated subjects had less flow reversal than non-fenestrated (retrograde as percent of antegrade flow 43, 19, and 30%, respectively P<0.001). Gravity decreased IVC and HV flows more in TCPC subjects than control, but this effect was not different between the two TCPC groups. Closure of the fenestration resulted in higher IVC and HV pressures (pre-closure versus post-closure pressures [mmHg]: 11.2 +/- 4.0 vs. 12.3 +/- 3.9, and 11.5 +/- 3.8 vs. 12.4 +/- 3.8, respectively P< or =0.001). The normal TVPG was reduced in fenestrated TCPC, and worsened after fenestration closure (0.9 +/- 0.3 and 0.7 +/- 0.4, respectively P < 0.04). CONCLUSIONS: Fenestration of the inferior venous connection has important influences on sub-diaphragmatic venous return in TCPC patients. Although fenestration lowers venous pressures and partially restores TVPG, its beneficial effects on flow in TCPC patients are mediated primarily by an increase in inspiration-derived forward HV flow and reduced flow reversal. These observations suggest fenestration results in a more efficient and less congested splanchnic circulation in TCPC patients, and may have important implications in the early and late management of Fontan patients.

Blood Flow Velocity↗
PubMed1986

The influence of a long-acting somatostatin analogue on splanchnic haemodynamics and metabolism in healthy subjects and patients with liver cirrhosis.

The influence of a long-acting somatostatin octapeptide analogue (SMS 201-995) on splanchnic circulation and metabolism has been studied in healthy subjects and in patients with liver cirrhosis. In healthy subjects doses of 5, 10, 50, or 100 micrograms SMS and in the cirrhotic patients 25 micrograms SMS were infused intravenously during 1 h. Measurements were obtained before, during, and for 1 h after SMS infusion. SMS infusion in healthy subjects resulted in a 25-35% reduction in hepatic blood flow. This effect was largely independent of the dose used. Splanchnic oxygen uptake was unchanged before and during SMS infusion. Insulin and glucagon levels fell markedly in response to SMS administration, and the blood concentration and splanchnic output of glucose decreased transiently. Patients with liver cirrhosis responded to SMS infusion similarly to the healthy subjects. Hepatic blood flow decreased by 25-35% and remained suppressed for at least 1 h after infusion. Wedge hepatic venous pressure was 18 +/- 2 mm Hg in the basal state and decreased progressively during and after SMS infusion (60 min after infusion, 15 +/- 2 mm Hg; P less than 0.01). The marked hyperinsulinaemia and hyperglucagonaemia seen in the basal state decreased significantly during SMS administration. As in the case of the controls, blood concentration and splanchnic output of glucose fell transiently during and after SMS infusion. It is concluded that SMS exerts a marked and prolonged suppressive effect on hepatic blood flow in both healthy subjects and patients with liver cirrhosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1983

Mesenteric blood flow response to dopamine infusion during myocardial infarction in the awake dog.

This study was designed to determine the effects of dopamine on the superior mesenteric arterial circulation of conscious dogs subjected to experimental myocardial infarction. Electromagnetic blood flow transducers were implanted on the superior mesenteric artery in 10 dogs. Direct infusion into the superior mesenteric artery of dopamine (2.5 micrograms/kg/min) after induction of acute myocardial infarction (AMI) revealed a steadily decreasing ability of dopamine to produce mesenteric vasodilation; 4 hr after AMI, infusion of dopamine decreased mesenteric resistance only 14 +/- 0.05%, which was significantly less (P less than 0.001) than during the control period when it decreased resistance 41 +/- 1.0%. Isoproterenol (N = 3) produced substantial increases in flow, despite the reduction in effectiveness of dopamine. Treatment of the 10 dogs with phenoxybenzamine, 5 mg directly into the superior mesenteric artery, restored the ability of dopamine to dilate the mesenteric bed. Beta-adrenergic blockage did not affect the dopaminergic vasodilation after alpha-blockade. The results of this study question the efficacy of dopamine to produce mesenteric vasodilation in the face of increased resistance in the splanchnic circulation during the acute myocardial infarction complicated by hypotension.

Animals↗
PubMedDate not supplied

Beneficial hemodynamic effects of ketanserin in patients with cirrhosis: possible role of serotonergic mechanisms in portal hypertension.

We studied the acute effects of ketanserin, a serotonin S2 antagonist, on systemic and splanchnic hemodynamics in 11 patients with cirrhosis. Mean arterial pressure decreased moderately but significantly after ketanserin. This effect was maximal at 5 min and correlated to the severity of cirrhosis. Cardiac index and systemic vascular resistance were not significantly changed. The hepatic venous pressure gradient, used as an index of portal pressure, significantly decreased after ketanserin (-23%). Azygos blood flow, a reflection of superior portosystemic collateral blood flow, also significantly decreased (-26%), but this effect was delayed, progressive and not correlated to the arterial pressure decrease. Hepatic blood flow was unchanged. These findings suggest that the systemic and splanchnic circulations may be hypersensitive to ketanserin in cirrhotic patients, and that serotonergic mechanisms may contribute to maintain portal hypertension. New specific antiserotonergic drugs deserve further evaluation for potential therapeutic implications in portal hypertension.

Azygos Vein↗
PubMed1990

Duplex scanning for assessment of mesenteric ischemia.

The accurate diagnosis of mesenteric arterial occlusive disease has in the past required invasive examination, primarily arteriography. Recent innovations in duplex ultrasound scan technology have for the first time provided a method for the noninvasive assessment of the splanchnic circulation in man. Mesenteric duplex scanning has been used successfully to measure postprandial changes in celiac and superior mesenteric arterial blood flow as well as changes in visceral flow produced by other pharmacologic stimuli.

Arteriovenous Shunt, Surgical↗
PubMedDate not supplied

The 2003 Carl A Moyer Award: real-time metabolic monitors, ischemia-reperfusion, titration endpoints, and ultraprecise burn resuscitation.

Real-time metabolic monitoring of varied vascular beds provides the raw data necessary to conduct ultraprecise burn shock resuscitation based on second-by-second assessment of regional tissue perfusion. It also illustrates shortcomings of current clinical practices. Arterial base deficit was continuously monitored during 11 clinical resuscitations of patients suffering burn shock using a Paratrend monitor. Separately, in a 30% TBSA rat burn model (N = 70), three Paratrend monitors simultaneously recorded arterial blood gas and tissue pCO2 of the burn wound and colonic mucosa during resuscitation at 0, 2, 4, 6, and 8 ml/kg/%TBSA. Paratrend data were analyzed in conjunction with previously reported laser Doppler images of actual burn wound capillary perfusion. With current clinical therapy, continuous monitoring of arterial base deficit revealed repetitive cycles of resolution/worsening/resolution during burn shock resuscitation. In the rat model, tissue pCO2 in both burn wounds and splanchnic circulation differed depending on the rate of fluid resuscitation (P <.01 between sham and 0 ml/kg/%TBSA and between 2 ml/kg/%TBSA and 4 ml/kg/%TBSA). Burn wound pCO2 values correlated well with laser Doppler determination of actual capillary perfusion (rho = -.48, P <.01). The following conclusions were reached: 1). Gratuitous and repetitive ischemia-reperfusion-ischemia cycles plague current clinical therapy as demonstrated by numerous "false starts" in the resolution of arterial base deficit; 2). in a rat model, real-time monitoring of burn wound and splanchnic pCO2 demonstrate a dose-response relationship with rate of fluid administration; and 3). burn wound and splanchnic pCO2 are highly correlated with direct measurement of burn wound capillary perfusion by laser Doppler imager. Either technique can serve as a resuscitation endpoint for real-time feedback-controlled ultraprecise resuscitation.

Acid-Base Equilibrium↗
PubMed2001

Monitoring tissue oxygenation during resuscitation of major burns.

BACKGROUND: Because subcutaneous and splanchnic oxygenation indices are sensitive indicators of evolving hemorrhagic shock and adequacy of resuscitation, we postulated that these indices might have an equivalent role in the monitoring of severely burned patients. This observational study was undertaken to examine changes in tissue oxygenation indices during burn resuscitation. METHODS: Seven patients with major burns (54 +/- 21% total body surface area) were studied during the first 36 hours of fluid resuscitation. Silastic tubing was placed in the subcutaneous tissue just beneath both normal skin and deep partial thickness burn. Fiberoptic sensors inserted into the tubing measured subcutaneous oxygen and carbon dioxide tensions in the burnt skin (PO2scb and PCO2scb) and normal skin (PO2scn and PCO2scn) continuously. Gastric intramucosal pH (pHi) and the mucosal CO2 (PCO2m) gap were calculated using gastric tonometers. Mean arterial pressure, arterial pH, lactate, and pHi measurements were obtained for 36 hours. RESULTS: There were no significant differences in mean arterial pressure, arterial pH, or lactate concentrations throughout the study period, whereas indices of tissue oxygenation showed deterioration: pHi decreased from 7.2 +/- 0.1 to 6.7 +/- 0.3 (p = 0.06), the PCO2m gap increased from 12 +/- 17 to 108 +/- 123 mm Hg (p < 0.01), PO2scn decreased from 112 +/- 18 to 50 +/- 11 mm Hg (p < 0.01), PO2scb decreased from 62 +/- 23 to 29 +/- 16 mm Hg (p < 0.01), PCO2scn increased from 42 +/- 4 to 46 +/- 10 mm Hg (p = 0.2), and PCO2scb increased from 42 +/- 10 to 52 +/- 5 mm Hg (p = 0.05). CONCLUSION: Despite adequate global indices of tissue perfusion after 36 hours of resuscitation, tissue monitoring indicated significant deterioration in the splanchnic circulation and in the normal and burnt skin.

Adult↗
PubMed2001

Effects of haemoglobin-based oxygen carrier hemoglobin glutamer-200 (bovine) on intestinal perfusion and oxygenation in a canine hypovolaemia model.

The objective of this investigation was to study the effects of the first marketed haemoglobin-based oxygen carrier, Hemoglobin glutamer-200 (bovine) (Hb-200) (Oxyglobin) on splanchnic perfusion and oxygenation in a canine model of acute hypovolaemia. Twelve anaesthetized dogs [mean weight 30.8 (S.D. 1.4) kg] were instrumented for recordings of heart rate (HR), mean arterial pressure (MAP), central venous pressure (CVP), cardiac output and cranial mesenteric arterial (CMA) and venous blood flows (CMV). Total and plasma haemoglobin (Hb), oxygen content and saturation, lactate concentration, pH and blood gases were analysed in arterial, mixed venous and mesenteric venous blood samples. Measurements were made before (baseline) and after 1 h of haemorrhage, after which animals were resuscitated with either shed blood (controls) or Hb-200 until HR, MAP and CVP returned to prehaemorrhage levels. Recordings were repeated immediately and 3 h after termination of fluid resuscitation, after which organ specimens were obtained for microscopic examination. Haemorrhage (average 32 ml kg(-1)) reduced MAP to 50 mm Hg, increased HR and systemic vascular resistance (SVR), and was accompanied in both the systemic and the splanchnic circulation by significant decreases in blood flow, Hb content and oxygen delivery (DO2), and lactic acidosis. In controls, all variables recovered to baseline after isovolaemic resuscitation with shed blood. In dogs resuscitated with a small volume of Hb-200 (10 ml kg(-1)), HR, MAP, CVP and CMA and CMV blood flows returned to baseline. However, cardiac output, total Hb, oxygen content and systemic and mesenteric DO2 remained depressed while SVR increased further. Mesenteric and systemic acid-base status recovered in both groups, and there was no difference in microscopic tissue damage between groups. Thus, Hb-200 reconstituted splanchnic perfusion and oxidative metabolism in spite of pronounced systemic vasoconstriction and insufficient restoration of CO and DO2; it may improve diffusive oxygen transport in the microvasculature by virtue of haemodilution and its high efficiency in the uptake and release of oxygen.

Acid-Base Equilibrium↗
PubMed1993

Beta-adrenergic-dependent and -independent actions of naloxone on perfusion during endotoxin shock.

Naloxone, an opioid antagonist, has been shown to improve cardiovascular status during endotoxin shock, including splanchnic perfusion. Enhancement of adrenergic action has been implicated as a physiological path by which naloxone effects changes in cardiac function during endotoxin shock, but the mechanism for changes in various splanchnic vascular beds has not been examined. In this study, we examined the role of beta-adrenergic actions in cardiovascular performance and the splanchnic perfusion changes caused by naloxone during endotoxin shock. Rats were instrumented with catheters in the tail artery, left cardiac ventricle, and jugular vein. Twenty-four hours later, rats received saline or endotoxin (2 mg/kg) challenge intravenously over 30 min, followed at 40 min by i.v. naloxone (or saline) treatment (4 mg/kg + 2 mg/kg.hr) in the presence or absence of propranolol (1 mg/kg + 1 mg/kg.hr). Radiolabelled microspheres were used to determine cardiac outputs and blood flows at 0, 30, 60, and 120 min after beginning endotoxin infusion. Blood pressure was not affected by endotoxin challenge, but cardiac output and most organ blood flows fell over time. beta-Adrenergic blockade did not alter this response. Naloxone improved cardiac output and blood flow to the stomach, small intestine, colon, and spleen but not to other splanchnic organs. Naloxone also increased renal and coronary blood flows. The improvements in cardiac output with naloxone were ablated in the presence of propranolol, as were the increases in gastric, colonic, splenic, coronary, and renal blood flows. However, the beneficial effect of naloxone on small bowel blood flow was not diminished by blockage of beta receptors. These results suggest that the effects of opioid antagonism are mediated, in part, by enhancing endogenous beta-adrenergic actions in vivo. Improvements in the splanchnic circulation are selectively altered by naloxone during endotoxin shock, some independent of beta-adrenergic actions. Understanding this phenomenon can lead to the appropriate use of opioid antagonism, should it prove clinically useful in the treatment of septic shock.

Animals↗
PubMed1987

Effect of synthetic neuromedin-N, a novel neurotensin-like peptide, on exocrine pancreatic secretion and splanchnic blood flow in dogs.

Neuromedin-N, a novel neurotensin-like peptide, has recently been identified from porcine spinal cord by using a bioassay for a stimulatory effect on guinea pig ileum. The amino acid sequence of the peptide has been determined to be Lys-Ile-Pro-Tyr-Ile-Leu, which is quite homologous to the COOH-terminal sequence of neurotensin. In this study, the effect of neuromedin-N on pancreas and splanchnic blood flow was investigated in eight dogs. Intravenous injections of graded doses of synthetic neuromedin-N caused a dose-dependent decrease of systemic arterial pressure and a dose-dependent increase in both portal and superior mesenteric arterial blood flow, which were measured with transit time ultrasonic flow meter. Volume and protein output of the pancreatic juice were also increased significantly by Neuromedin-N. Pancreatic capillary blood flow measured with laser Doppler flowmetry was increased in a dose-related manner. The present study first demonstrated that neuromedin-N retains a potent stimulatory effect on the pancreas and splanchnic circulation, indicating that this peptide is one of the biological active forms of neurotensin-like peptide in mammals. This study also leads to the suggestion that this peptide possesses physiological significance as a novel neuropeptide.

Animals↗
PubMed2006

The role of ultrasonography in patients with celiac disease.

The aim of the present review was to summarize the current evidence on the role of ultrasonography (US) and doppler-US in the diagnosis of celiac disease. Several ultrasonographic signs have been reported in the association with celiac disease in studies using real-time US. Firstly, case control studies identified some of these US signs and then in a prospective series some of these parameters, due to their high specificity, have been shown to be of value in confirming CD diagnosis, whereas others, due to their high sensitivity, have been demonstrated to be useful in excluding the presence of the disease. The pattern of splanchnic circulation in CD have extensively been investigated by several studies all of which reported similar results and identified a hyperdynamic mesenteric circulation that reverts to normal values after successful a gluten-free regimen. The last part of this review will deal with the possible role of US in identifying the most severe and common intestinal complication of CD, i.e. the enteropathy-associated T cell non-Hodgkin lymphoma.

Abdomen↗
PubMed1994

Intraoperative evaluation of big-endothelin plasma levels during liver transplantation in different vascular compartments.

Endothelin-1 (ET) is derived from its precursor big-ET, secreted by endothelial cells of multiple origin. The role of ET peptides in the physiological responses after orthotopic liver transplantation (OLT) was investigated. Venous big-ET plasma levels were analysed by RIA in 28 patients before and after OLT. Samples for analysis were taken intraoperatively from 12 patients from the caval, portal and hepatic veins and the radial artery at multiple time points. Highest caval levels were found during the anhepatic period and 60 min after reperfusion, followed by a drop and subsequent increase postoperatively. Highest levels in the hepatic and portal veins were detected during explanation and reperfusion. A different pattern was found in the radial artery. Values during rejection and infection were elevated compared with preoperative and postoperative levels. The heterogeneity of the kinetics points to different sites of ET generation, including liver and splanchnic circulation. It suggests a predominant paracrine secretion mode of ET peptides with various stimuli involved. Big-ET levels could reflect endothelial cell damage, as big-ET is generated intracellularly and biological activity is rather weak.

Adult↗
PubMed1989

Labetalol does not decrease placental perfusion in the hypertensive term-pregnant rat.

The acute effect of labetalol hydrochloride, a combined nonspecific beta-adrenergic and postsynaptic alpha 1-adrenergic blocker, on maternal hemodynamics and organ perfusion was investigated in 10 hypertensive, term-pregnant, spontaneously hypertensive rats with the use of the radioactive-labeled microsphere technique. The normal fall in blood pressure during pregnancy was prevented by the reduction of litter size to two conceptuses on day 7 of gestation. Labetalol (1 to 6 mg/kg) effectively lowered mean arterial pressure 22% by decreasing cardiac output 16%; total peripheral resistance was not significantly decreased. Thus, the blood pressure lowering effect of labetalol was due primarily to its beta-adrenergic blocking effect. Regional flows to the carcass and splanchnic circulation were decreased 19% and 15%, respectively, after labetalol administration. Uterine wall and ovarian perfusion were significantly reduced, but placental perfusion was not significantly altered. Because labetalol lowers blood pressure without reducing placental perfusion, it may be a useful alternative to hydralazine for the treatment of hypertensive emergencies in pregnancy.

Animals↗
PubMed2000

Splanchnic haemodynamic disturbances in perinatal sepsis.

AIM: To determine the effect of perinatal bacterial infection on the neonatal splanchnic circulation. SUBJECTS/SETTING: 76 premature infants with appropriate birth weight for gestation admitted for neonatal intensive care. METHODS: Doppler ultrasound was used to measure blood flow velocity and pulsatility index in the superior mesenteric artery and coeliac axis during the first 24 hours of life. Babies were classified according to the results of blood and surface cultures, as well as the presence or absence of maternal prolonged membrane rupture. RESULTS: Infection status had a significant effect on pulsatility index in both arteries, with that in the coeliac axis being reduced from 1.27 to 0.80 in babies with infection (p < 0.0001). Coeliac axis blood flow velocity was significantly increased in those with infection (from 34.6 to 46.5 cm/s; p < 0.05). CONCLUSION: As early as the first day of postnatal life, infected neonates show a pattern of splanchnic hyperaemia similar to that found in adult systemic inflammatory response syndrome.

Bacterial Infections↗
PubMed1993

Postburn gastrointestinal vasoconstriction increases bacterial and endotoxin translocation.

Splanchnic ischemia has been associated with bacterial translocation and increased endotoxin absorption from the gut. To study the effects of major burn on splanchnic circulation, minipigs were randomized to receive 40% flame burn and Parkland resuscitation or sham burn and maintenance fluids. Total and fractionated blood flow, O2 delivery and consumption, mucosal pH of the intestine, and endotoxin levels in the superior mesenteric vein were measured for 48 h, and then abdominal organs were harvested for bacteriological culture and histopathological analysis. Total mesenteric blood flow and fractionated blood flow to the mucosa-submucosa of the jejunum, cecum, and colon decreased 2 and 4 h postburn. Although mesenteric O2 consumption was unchanged, mesenteric O2 delivery and intestinal mucosal pH were decreased during the early postburn period. Concomitantly, endotoxin levels in the superior mesenteric vein were significantly elevated during the first 8 h postburn. The bacteriological cultures of the systemic tissue samples showed increased bacterial translocation in the burn group. After major burns, there is a transient selective splanchnic vasoconstriction, which is associated with intestinal mucosal acidosis and increased incidence of bacterial translocation and endotoxin absorption from the gut.

Animals↗
PubMed2004

Dobutamine compensates deleterious hemodynamic and metabolic effects of vasopressin in the splanchnic region in endotoxin shock.

BACKGROUND: Vasopressin is a potent vasopressor in septic shock, but it may impair splanchnic perfusion. We compared the effects of vasopressin alone and in combination with dobutamine on systemic and splanchnic circulation and metabolism in porcine endotoxin shock. METHODS: Twelve pigs were randomized to receive either vasopressin (VASO, n = 6) or vasopressin in combination with dobutamine (DOBU, n = 6) during endotoxin shock (E. coli endotoxin infusion). Endotoxin infusion rate was increased to induce hypotension after which vasoactive drugs were started. We aimed to keep systemic mean arterial pressure (MAP) >70 mmHg by vasopressin; the goal of dobutamine infusion was to prevent decrease in cardiac output often associated with vasopressin infusion. Regional blood flows, oxygen delivery and consumption, arterial and regional lactate concentrations were measured. RESULTS: Mean arterial pressure >70 mmHg was achieved in both the VASO and DOBU groups. After the primary decrease of cardiac output by vasopressin, systemic blood flow remained stable in vasopressin-treated animals. However, vasopressin as a monotherapy decreased portal venous blood flow. This was prevented by dobutamine. Vasopressin also induced splanchnic lactate release and arterial hyperlactatemia, which were not observed when dobutamine was combined with vasopressin. CONCLUSION: Dobutamine prevents adverse hemodynamic and metabolic effects of vasopressin in septic shock.

Adrenergic beta-Agonists↗
PubMed1993

Splanchnic lactate production in cardiac surgery patients.

OBJECTIVE: To review the pathophysiology of lactic acidosis in patients undergoing open-heart surgery, with special reference to the splanchnic circulation. DATA SOURCE: MEDLINE search of pertinent experimental and clinical research studies. RESULTS: Lactate is an end-product of anaerobic metabolism and is in dynamic equilibrium with its precursor, pyruvate. The ratio of serum lactate to pyruvate concentrations in arterial blood is normally < or = 10:1. In patients with lactic acidemia, measurement of serum pyruvate concentrations may yield valuable clinical information. Lactate/pyruvate ratios > 10:1 suggest that oxygen delivery (DO2) is inadequate to meet metabolic demand, whereas increases in both lactate and pyruvate values with preservation of normal lactate/pyruvate ratios suggest a defect in oxidative utilization (e.g., a fractional increase in the inactive form of the pyruvate dehydrogenase enzyme complex) despite adequate DO2. Meaningful changes in regional oxygen kinetics occur during extracorporeal circulation. Increased production of endogenous vasoconstrictors in response to nonpulsatile flow, together with a decrease in arterial oxygen content resulting from the addition of 2 L of pump prime to the patient's circulation at the beginning of cardiopulmonary bypass, decrease DO2 to the gastrointestinal tract. The effect of this reduction is mitigated, in part, by lowering core temperature and reducing tissue oxygen demand. CONCLUSIONS: The abdominal organs tolerate reductions in DO2 when they are cold (25 degrees C), since gastric intramucosal pH (a marker of inadequate DO2), and hepatic venous lactate/pyruvate ratios and oxygen saturation during the first half of cardiopulmonary bypass are normal. As surgery nears completion and core temperature is increased, tissue oxygen demands escalate. The presence of gastric mucosal acidosis, coupled with lactic acidemia and oxygen desaturation of hepatic venous blood, suggest that delivery of oxygen to the abdominal organs at the conclusion of cardiopulmonary bypass is insufficient to meet demand. A growing proportion of cardiac surgery patients are older and many have concomitant medical problems that can impair their recovery. Useful strategies are needed to reduce the occurrence of splanchnic ischemia in these and other high-risk populations if surgical outcome is to improve in the future.

Coronary Artery Bypass↗