Effects of nitrates on splanchnic and hepatic circulation.
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Animals↗
Biomedical subjects
L Irestedt
Publications and source records attributed to L Irestedt.
Effects of neurolept anaesthesia (NLA) on haemodynamics and oxygen consumption in the dog with special reference to the liver and preportal tissues.
The effects of neurolept anaesthesia (NLA) on central circulation, total oxygen uptake and splanchnic circulation and oxygen uptake were studied in 12 artificially ventilated dogs, basally anaesthetized with thiopental and nitrous oxide. Hepatic arterial, superior mesenteric arterial and portal venous blood flows were measured with electromagnetic flowmetry. Cardiac output was measured by thermodilution. Determinations of oxygen contents were made in arterial, pulmonary arterial, portal venous and hepatic venous blood. NLA was induced with droperidol 0.5 mg . kg-1 b.w. and fentanyl 0.01 mg . kg-1 b.w. Arterial blood pressure decreased to 63% of control value due to reductions of cardiac output to 78% and of total peripheral vascular resistance to 81% of control values. Hepatic arterial, superior mesenteric arterial and portal venous blood flows all diminished to 75% of control values. Hepatic arterial, superior mesenteric arterial and preportal tissue vascular resistances all decreased. Total oxygen uptake declined to the same extent as cardiac output, leaving the arterio-venous oxygen difference unchanged. Oxygen uptake of the preportal tissues was unaffected and hepatic oxygen uptake was not significantly reduced, although there were decreases of hepatic oxygen uptake in some of the individual dogs. It is suggested that the cardiovascular depression following NLA was due to adaptation to a lowered total oxygen uptake. It is further concluded that splanchnic circulation was well preserved due to decreases in splanchnic vascular resistances, and that splanchnic oxygen consumption was maintained by means of increased oxygen extraction.
Anesthetics↗
Effects of enflurane on haemodynamics and oxygen consumption in the dog with special reference to the liver and preportal tissues.
The effects of enflurane anaesthesia on central circulation, total oxygen uptake, splanchnic circulation and splanchnic oxygen uptake were studied in 10 artifically ventilated dogs, basally anaesthetized with thiopental and nitrous oxide. Hepatic arterial, superior mesenteric arterial and portal venous blood flows were measured with electromagnetic flowmetry. Cardiac output was measured by thermodilution. Determinations of oxygen contents were made in arterial, pulmonary arterial, portal venous and hepatic venous blood. The end-tidal enflurane concentration was kept at about 1 MAC (= 2.2%). Arterial blood pressure diminished 54% of control value due to decreases of cardiac output to 65% and of total peripheral vascular resistance to 81% of control values. Hepatic arterial, superior mesenteric arterial and portal venous blood flows decreased to 65-70% of control levels and the corresponding vascular resistances all declined to about 80-85% of control values. Total oxygen uptake decreased, but less than cardiac output, leading to an increased arterio-venous oxygen content difference. Oxygen uptake of the preportal tissues was unchanged and hepatic oxygen uptake was not significantly altered, although there were decreases in hepatic oxygen uptake in some of the individual experiments. It is suggested that the cardiovascular depression following enflurane anaesthesia in the dog was due, to a great extent, to a primary myocardial depression. It is further concluded that the splanchnic blood flows were relatively well preserved, due to decreases in splanchnic vascular resistances, and that hepatic and preportal tissue oxygen consumptions were maintained by increased oxygen extraction.
Anesthesia, General↗
Renal function and fluoride formation and excretion during enflurane anaesthesia.
Central circulation, renal function, and fluoride formation and excretion were studied in nine patients during enflurane anaesthesia and surgery. Cardiac output and mean systemic arterial pressure remained unchanged compared with preoperative control values. During anaesthesia and surgery, urine flow rate, inulin clearance, PAH clearance and fractional sodium excretion were 60, 65, 55, and 45% of control values, respectively. Mean peak plasma level of fluoride was 20.0 microM. It was reached 4 hours after termination of anaesthesia. Fluoride clearance (CF) decreased from 23.9 ml . min-1 to 2.7 ml . min-1 during anaesthesia. Postoperative, CF increased to 41.6 and 76.0 ml . min-1, respectively, during two consecutive measurement periods. There was no correlation between plasma fluoride levels and depression of any renal function variable.
Adult↗
Fluoride kinetics and renal function during enflurane anaesthesia.
Renal function, fluoride formation and excretion were studied during and after enflurane anaesthesia in seven patients. During anaesthesia, urine flow rate, inulin clearance, PAH clearance and fractional sodium excretion were 13, 78, 65 and 49% of control values, respectively. Renal function was promptly restored postoperatively. Enflurane was metabolized to inorganic fluoride with a mean maximal serum level of 17.4 +/- 3.3 microM. Fractional fluoride excretion decreased during anaesthesia to 35% of the control value. Postoperatively, there was a highly significant correlation between the increase in fractional fluoride excretion and the rise in urinary pH during two consecutive 3-hour periods. It is suggested that tubular reabsorption of fluoride is inversely related to tubular fluid pH and that fluoride is reabsorbed by non-ionic diffusion.
Adult↗
Effects of enflurane on splanchnic circulation.
A brief summary of the anatomy and physiology of the splanchnic circulation is presented. The influence of 1 MAC enflurane anaesthesia on splanchnic circulation and oxygenation was studied in 10 dogs. Superior mesenteric arterial, portal venous and hepatic arterial blood flows decreased less than mean arterial blood pressure, due to reductions in superior mesenteric arterial, preportal vascular and hepatic arterial resistances. It is suggested that these reactions within the splanchnic circulation are mainly dependent on normal autoregulative responses elicited by the fall in blood pressure. Oxygen consumption of the preportal tissues and the liver was unchanged as a result of increased extraction of oxygen.
Anesthesia, Inhalation↗
Effects of enflurane on haemodynamics and oxygen uptake with special reference to the influence of surgical stress.
The influence on central haemodynamics of enflurane, in uniform anaesthetic concentration (1.5 MAC), was studied in 10 normocapnic patients undergoing upper abdominal surgery. The patients were studied awake, during anaesthesia prior to surgery, and during surgery. On institution of anaesthesia, cardiac output (QT) fell from 5.05 +/- 0.51 to 4.12 +/- 0.15 1/min and systemic vascular resistance (SVR) decreased from 2.36 +/- 0.22 to 1.93 +/- 0.18 kPa min. 1(-3). The arteriovenous oxygen content difference (AVD) did not change. On commencement of surgery, AVD diminished from 38.5 +/- 2.6 to 30.8 +/- 1.9 ml/min and QT rose to 5.82 +/- 0.46 1/min, while SVR remained unchanged. It is concluded that the fall in QT seen during enflurane anaesthesia is caused by a diminished tissue oxygen demand. It is also suggested that enflurane acts as an alpha-blocking agent.
Abdomen↗
The elimination of bupivacaine (Marcain) after short intravenous infusion in the dog: with special reference to the role played by the liver and lungs.
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Animals↗
Hepatic release of fluoride from halothane under hypoxic and non-hypoxic conditions in the dog.
Six dogs were subjected to halothane anaesthesia under hypoxic and non-hypoxic conditions. Plasma fluoride levels in hepatic venous and arterial blood, as well as blood flow to the liver, were measured during anaesthesia. The amount of fluoride released by the liver could thus be calculated. Release of fluoride took place in all animals during non-hypoxic halothane anaesthesia. The amount released varied between the individual animals and in three of them it rose further during hypoxic anaesthesia. The occurrence of defluorination of halothane, even under nonhypoxic conditions, may indicate a reductive metabolism in at least some parts of the liver. The significance of this hypothesis is discussed.
Acid-Base Equilibrium↗
Delivery complicated by myasthenia gravis and epilepsy.
The literature on the possible risk of myasthenia gravis complicating pregnancy and delivery is sparse and partly contradictory but some of the reports on the number of perinatal and neonatal deaths are alarming. Epilepsy in pregnancy implies on approximately twofold risk of intervention in connection with labour. A pregnant patient with myasthenia gravis and epilepsy has recently been delivered. The case is reported and the considerations with regard to suitable anaesthesia and the two diseases are discussed.
Adult↗
General anaesthesia or lumbar epidural block for caesarean section? Effects on the foetal heart rate.
Caesarean section was performed in 10 patients under general anaesthesia and in 10 other patients under epidural block. The foetal heart rate was monitored continuously during anaesthesia and operation with a scalp electrode and a cardiotocograph. There was no major difference between the two anaesthetic techniques in their effect on the foetal heart rate. The most common finding was a reduction of the beat-to-beat variation. The operative time was longer in the epidural group than in the general anaesthesia group, due to a higher frequency of Pfannenstiel incisions and repeat caesarean sections in the epidural group. Clinically, all newborns seemed to be unaffected, with normal Apgar scores. Epidural block seems to be a good alternative to general anaesthesia for caesarean section, particularly when a long operative time is expected.
Anesthesia, Epidural↗
The different responses of the hepatic arterial bed to hypovolaemia and to halothane anaesthesia.
Ten dogs were subjected to a period of hypovolaemia (bleeding volume: 2% of body weight) and to a period of halothane anaesthesia (end-tidal halothane concentration: 1%). Mean arterial blood pressure decreased to 79% of control value during hypovolaemia and to 58% of control value during halothane anaesthesia. Mean total peripheral and preportal vascular resistances increased during hypovolaemia and were unchanged during halothane. Mean hepatic arterial and portal venous blood flows decreased to 82% and 55% of control values, respectively, during hypovolaemia, and to 41% and 56% of control value, respectively, during exposure to halothane. Mean hepatic arterial resistance was unchanged during hypovolaemia, but increased during halothane. Mean hepatic oxygen consumption did not change significantly during hypovolaemia, but decreased during halothane anaesthesia, in spite of an increased extraction of oxygen from both the hepatic arterial and the portal venous blood. Possible mechanisms which may maintain oxygen supply to the liver by increasing the hepatic arterial fraction of total liver blood flow when portal venous blood flow is reduced are discussed. It is concluded that this mechanism is upset or inhibited during halothane anaesthesia.
Anesthesia, Inhalation↗
Uptake of bupivacaine (Marcaine) in liver and lung after intramuscular administration in the dog.
The uptake of bupivacaine in the liver and lung of the dog was studied 10,20,30 and 60 min after intramuscular injection of the drug. It was possible to quantify this uptake by combining measurements of concentrations and flows. The administration of bupivacaine (0.75 mg/kg b.w.) did not result in any significant circulatory changes. Arterial bupivacaine concentrations showed major variations, indicating interindividual differences in absorption rate. Lung uptake after 10 min was high in two dogs with initially high blood concentrations of bupivacaine, but low after 20 min or longer. The other dogs showed little or no uptake. Mean hepatic bupivacaine uptake was about 50% of the total dose during the first hour after injection, this indicates the central role of the liver in eliminating bupivacaine even during the initial period following administration. The hepatic extraction ratio showed interindividual variations, but the mean value of about 55% was constant throughout the observation period. This is in agreement with earlier findings indicating a first-order elimination of bupivacaine.
Animals↗
Decrease of oxygen consumption in the dog liver during temporary arterial occlusion.
The effects of occlusion of the hepatic artery on total and regional splanchnic oxygen consumption were studied in lightly anaesthetized dogs. Mean whole body oxygen uptake (+/- S.D.) was 4.72 +/- 0.55 ml/kg b.w. min-1, mean liver oxygen uptake (+/- S.D.) 1.18 +/- 0.42 ml/kg b.w. min-1 and mean oxygen uptake of the portally-drained tissues (+/- S.D.) was 0.80 +/- 0.54 ml/kg b.w. min-1 during the control period. The hepatic artery contributed 45 +/- 24% of the total liver oxygen uptake. The duration of occlusion was 45 min. Mean liver oxygen uptake was found to decrease to 64% of control values. The extraction of oxygen from the portal blood increased slightly. Mean whole body oxygen uptake and mean oxygen uptake of the portally-drained tissues were unchanged. 45 min after release of the hepatic artery occlusion, liver oxygen consumption had returned to control values. It is concluded that oxygen uptake in the liver is correlated to oxygen tension.
Animals↗
Blood circulation in the kidney of the cat under methoxyflurane (penthrane) anaesthesia.
In order to establish whether methoxyflurane causes any change in renal vascular resistance, the renal venous flow was measured by means of a drop recording technique in six cats under methoxyflurane anaesthesia. Arterial pressure was recorded simultaneously, and the renal vascular resistance was calculated. Methoxyflurane caused a significant reduction of the renal vascular resistance to about 85% of control value at an anaesthetic depth characterised by loss of the corneal reflex. At a deeper anaesthetic stage characterised by steady state circulation and absence of any reflexes, no further significant fall in renal vascular resistance occurred. Autoregulation and depression of the sympathetic activity are assumed to explain the reduction of the renal vascular resistance.
Anesthesia, Inhalation↗
Concentration of bupivacaine in arterial and venous plasma after epidural anaesthesia in man and after intramuscular administration in dog.
The arteriovenous concentration difference of bupivacaine in plasma after epidural injection in man and after intramuscular injection in dog was studied. In man, arterial concentration was higher than peripheral venous ocncentration during an initial period of about 30 min, after which time period venous and arterial concentrations became fairly similar. Comparable results were obtained in the animal experiments. In addition, the experiments in dog indicated that the concentration of bupivacaine was fairly similar in central venous plasma and arterial plasma, but higher than the peripheral venous plasma concentration. These factors have to be taken into consideration when toxicological studies of local anaesthetic drugs are made.
Adult↗
Effect of controlled halothane anaesthesia on splanchnic blood flow and cardiac output in the dog.
Effects of halothane anaesthesia on aplanchnic blood flow and cardiac output were studied in six dogs. Blood flows in the hepatic artery, the superior mesenteric artery and the portal vein were measured electromagnetically. Cardiac output was measured by thermodilution. Depth of anaesthesia, ventilation, acid-base state and body temperature were controlled. Cardiac output and blood flows in the hepatic artery, the superior mesenteric artery and the portal vein decreased significantly to 73%, 54%, 59% and 60% of control values, respectively. Total peripheral vascular resistance decreased significantly, while mesenteric and portal resistance remained essentially unchanged and hepatic arterial resistance showed a significant increase. It is suggested that the difference between the various vascular responses may be caused by a differentiated release from baroreceptor inhibition in various parts of the bulbar vasomotor center.
Anesthesia, General↗
The effect of controlled halothane anaesthesia on splanchnic oxygen consumption in the dog.
The influence of halothane ansesthesia on splanchnic oxygen flow and oxygen uptake was studied in seven dogs. Mean oxygen supply to the liver and the portally-drained tissues decreased significantly to 44% and 53% of control values, respectively, while mena oxygen consumption diminished insignificantly to 68% and 82% of control values, respectively. There was a fall in the oxygen flow/oxygen consumption ratio in all animals following halothane. The relatively unimpaired oxygen uptake, in spite of a diminished oxygen supply, led to an increased extraction of oxygen by the tissues. Some factors affecting oxygen utilisation during halothane anaesthesia are discussed.
Abdomen↗