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Biomedical subjects

L Irestedt

Publications and source records attributed to L Irestedt.

At least 55 records · Page 3Linked to original sources
PubMed1984

Causes and consequences of maternal and fetal sympathoadrenal activation during parturition.

The sympathoadrenal system is activated in both the mother and fetus during parturition. The fetal plasma catecholamines may reach extremely high levels during deliveries complicated by asphyxia. Increased maternal sympathoadrenal activity during labour or caesarean section may negatively affect uteroplacental blood flow with possible adverse effects on the fetus. Such an increase may be avoided by adequate maternal pain relief and by the sympathetic blockade which follows epidural anaesthesia. Fetal sympathoadrenal activation during parturition seems on the contrary to be of positive functional importance both for fetal circulatory regulation in utero a well as for the neonatal adaptation in terms of pulmonary function and metabolic stimulation.

Adrenal Glands↗
PubMed1983

Haemodynamics and oxygen consumption in the dog during high epidural block with special reference to the splanchnic region.

High epidural block (Th I-IV) with bupivacaine was carried out in 16 dogs. Mean arterial blood pressure decreased to 52% of control value owing to nearly equal decreases in systemic vascular resistance and cardiac output. Portal venous blood flow decreased from 25.8 +/- 8.6 to 16.7 +/- 7.2 ml/kg b.w. X min-1 following epidural block, while hepatic arterial blood flow remained unchanged at 9.1 +/- 3.1 ml/kg b.w. X min-1 owing to a reduction in hepatic arterial resistance of 51%. Hepatic oxygen uptake was maintained during the epidural block through increased oxygen extraction. However, total oxygen uptake decreased by 18% and, in spite of this, arteriovenous oxygen content difference increased by 25%, indicating circulatory depression.

Anesthesia, Epidural↗
PubMed1983

Effects of dihydroergotamine on haemodynamics and oxygen consumption in the dog during high epidural block with special reference to the splanchnic region.

Dihydroergotamine (DHE) 0.02 mg X kg-1 was administered i.v. in 9 dogs with high epidural block. Mean arterial blood pressure was restored from 11.0 +/- 2.4 kPa to 18.8 +/- 2.5 kPa by DHE due to a near twofold increase in systemic vascular resistance while cardiac output was unchanged. Hepatic arterial blood flow was reduced by 50% by a marked increase in hepatic arterial resistance above the pre-epidural value, while portal venous blood flow remained unchanged. Hepatic oxygen consumption decreased following DHE in spite of an increase in total oxygen consumption, probably partly due to a reduction in hepatic arterial oxygen availability. The mechanism by which the arterial blood pressure is restored by DHE in dogs during high epidural block must be regarded as unfavourable, especially with respect to the liver.

Anesthesia, Epidural↗
PubMed1983

Catecholamine surge and lung function after delivery.

Lung function was measured at 30 minutes and again at 2 hours after birth in 12 infants delivered vaginally, in 15 infants delivered by elective caesarean section under general anaesthesia (GA), and in 15 delivered under epidural anesthesia (EDA). Umbilical arterial blood was analysed for pH and for concentrations of catecholamines and cortisol. No important differences in gestational age, birthweight, Apgar scores, or haematocrit were found among the three groups. Tidal volume and minute ventilation measured 30 minutes after birth were lower in infants delivered by caesarean section than in those delivered vaginally and at 2 hours the tidal volume was still lower in the babies delivered by caesarean section than in those delivered vaginally. Dynamic compliance was lower at 30 minutes in the group that had a caesarean section than in the vaginal group, and this difference was significant at two hours. Tidal volume, minute ventilation, and dynamic compliance in the GA and EDA groups did not differ. The catecholamine and cortisol concentrations at birth were higher in the vaginal group than in the group delivered by caesarean section. Two hours after birth there was a significant correlation (r = 0.84) between the catecholamine concentrations of the infants born vaginally and lung compliance. The lower dynamic lung compliance in infants delivered by elective caesarean section might be explained by delayed absorption of liquid in the lung due to lack of catecholamine surge.

Anesthesia, Epidural↗
PubMed1982

Fetal and maternal plasma catecholamine levels at elective cesarean section under general or epidural anesthesia versus vaginal delivery.

Fetal and maternal plasma levels of catecholamines were measured at birth in 40 women with normal term pregnancies who underwent elective cesarean section. Twenty women were operated on under general anesthesia, and 20 under epidural anesthesia. For comparison, the same measurements were also made in 10 women who underwent vaginal delivery without signs of intrapartum fetal distress. Maternal venous levels of catecholamines were elevated in all three groups as compared to values in the resting adult. The highest levels were found in the vaginal delivery group (norepinephrine and epinephrine, 3.9 +/- 2.1 and 1.1 +/- 1.0 nmoles/L, respectively), and the lowest in the epidural cesarean section group. Fetal outcomes were similar in all three groups, as judged by Apgar scores and by measurements of umbilical arterial blood gases. In spite of that, neonates delivered vaginally showed a markedly higher sympathoadrenal activation (norepinephrine and epinephrine, 31.8 +/- 24.1 and 5.1 +/- 7.6 nmoles/L, respectively) than those born by elective cesarean section. In the latter group, however, it was found that the type of maternal anesthesia influenced fetal sympathoadrenal activation, since neonatal levels of catecholamines were higher in the epidural section group (norepinephrine and epinephrine, 9.5 +/- 6.4 and 4.0 +/- 4.5 nmoles/L, respectively) than in the general anesthesia group (norepinephrine and epinephrine, 3.2 +/- 2.7 and 1.0 +/- 1.4 nmoles/L, respectively). These results may have a certain clinical relevance since fetal sympathoadrenal activation is thought to promote extrauterine adaptation.

Anesthesia, Epidural↗
PubMed1981

Renal fluoride excretion and plasma fluoride levels during and after enflurane anesthesia are dependent on urinary pH.

To determine the effects of urinary pH on fluoride ion excretion and the resulting plasma fluoride concentration during and after enflurane anesthesia, renal function, plasma inorganic fluoride levels, and fluoride excretion were studied in two groups of patients pretreated with either NH4Cl or acetazolamide to produce acidic or alkaline urine, respectively. During anesthesia, urinary flow rate, inulin clearance (Cin) and para-aminohippurate (PAH) clearance (CPAH) were 7, 61, and 43 per cent of control values in the acidic-urine group and 22, 74, and 57 per cent of control values in the alkaline-urine group, respectively. Fractional fluoride clearances (CF/CIN) during anesthesia and operation were 0.06 +/- 0.05 in the acidic-urine group (urinary pH 5.08) and 0.68 +/- 0.23 in the alkaline-urine group (urinary pH 8.16). Values of total fluoride excretion during the same period were 0.06 +/- 0.04 mg and 0.87 +/- 0.29 mg, respectively. Mean maximal plasma levels of fluoride were 26.3 +/- 7.3 microM in the acidic-urine group and 13.5 +/- 2.4 microM in the alkaline-urine group. The differences between groups in fluoride clearance, fluoride excretion, and plasma fluoride levels were all statistically significant. The data clearly show that renal fluoride clearance is closely related to urinary pH.

Acetazolamide↗
PubMed1981

Neonatal depression after obstetrical analgesia with pethidine. The role of the injection-delivery time interval and of the plasma concentrations of pethidine and norpethidine.

Pethidine (100 mg) was administered i.m. to women in labor at different times before delivery. The interval before respiration in the newborn became sustained was shorter if pethidine was given less than one hour before delivery. The respiratory rate of the newborn increased after naloxone injection in 40 per cent of the cases, mostly when intrauterine exposure to pethidine exceeded one hour. The plasma concentrations of pethidine and norpethidine were measured in mother and newborn. The concentrations in the umbilical vein and artery indicted a continuous net transfer of pethidine from mother to fetus for approximately two hours. This correlated with the clinical finding of maximal neonatal depression 2-3 hours after maternal injection. The concentrations of norpethidine increased with a longer time interval between injection and delivery, but were probably too low to have any effect on the newborn. Neonatal depression seems to be related to the amount of unmetabolized pethidine that has been transferred from mother to fetus but not to norpethidine as had been suspected earlier.

Anesthesia, Obstetrical↗
PubMed1980

Renal fluoride excretion during and after enflurane anaesthesia: dependency on spontaneous urinary pH-variations.

Renal function, fluoride formation and excretion were studied in seven patients during and after enflurane anaesthesia and surgery. The mean maximal plasma level of fluoride was 17.4 microM. It was reached 2 h after termination of anaesthesia. Pre-operatively, fraction fluoride clearance (CF/CIn) was 0.31. During anaesthesia and surgery it decreased to 0.10 and postoperatively rose to 0.55 and 0.77 during two consecutive measurement periods. There was a highly significant correlation (P less than 0.001) between this increase in CF/CIn and the simultaneous rise in urinary pH between the two periods (r = 0.91).

Adult↗
PubMed1979

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↗
PubMed1979

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↗
PubMed1979

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↗
PubMed1979

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↗
PubMed1979

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↗
PubMed1978

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↗
PubMed1978

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↗
PubMed1978

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↗
PubMed1977

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↗