Biomedical subjects
G M Hall
Publications and source records attributed to G M Hall.
Effects of epidural analgesia on plasma calcitonin gene-related peptide.
The effects of epidural analgesia on plasma calcitonin gene-related peptide (CGRP) values during and after hysterectomy were investigated in 14 healthy patients. In seven patients who received general anaesthesia alone for pelvic surgery, there were no significant changes in plasma CGRP concentrations. In the remaining patients, who received extensive epidural blockade in addition to general anaesthesia, there were again no significant changes in plasma CGRP values. This was in spite of profound sympathetic blockade, as shown by marked hypotension and a significant decline in plasma catecholamines. The epidural group of patients showed the expected attenuation of the glucose, cortisol and growth hormone responses to surgery. The results show that circulating CGRP is unlikely to be involved in the modulation of peripheral vascular tone during pelvic surgery under either general or epidural anaesthesia.
The responses of the catecholamines and beta-endorphin to brief maximal exercise in man.
The responses to brief maximal exercise of 10 male subjects have been studied. During 30 s of exercise on a non-motorized treadmill, the mean power output (mean +/- SD) was 424.8 +/- 41.9 W, peak power 653.3 +/- 103.0 W and the distance covered was 167.3 +/- 9.7 m. In response to the exercise blood lactate concentrations increased from 0.60 +/- 0.26 to 13.46 +/- 1.71 mmol.l-1 (p less than 0.001) and blood glucose concentrations from 4.25 +/- 0.45 to 5.59 +/- 0.67 mmol.l-1 (p less than 0.001). The severe nature of the exercise is indicated by the fall in blood pH from 7.38 +/- 0.02 to 7.16 +/- 0.07 (p less than 0.001) and the estimated decrease in plasma volume of 11.5 +/- 3.4% (p less than 0.001). The plasma catecholamine concentrations increased from 2.2 +/- 0.6 to 13.4 +/- 6.4 nmol.l-1 (p less than 0.001) and 0.2 +/- 0.2 to 1.4 +/- 0.6 nmol.l-1 (p less than 0.001) for noradrenaline (NA) and adrenaline (AD) respectively. The plasma concentration of the opioid beta-endorphin increased in response to the exercise from less than 5.0 to 10.2 +/- 3.9 p mol.l-1. The post-exercise AD concentrations correlated with those for lactate as well as with changes in pH and the decrease in plasma volume. Post-exercise beta-endorphin levels correlated with the peak speed attained during the sprint and the subjects peak power to weight ratio. These results suggest that the increases in plasma adrenaline are related to those factors that reflect the stress of the exercise and the contribution of anaerobic metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)
Local analgesic techniques for upper abdominal surgery--endocrine and metabolic effects.
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Diabetes and anaesthesia--slow progress?
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Fentanyl and the beta-endorphin, ACTH and glucoregulatory hormonal response to surgery.
The effect of the supplementation of nitrous oxide-oxygen anaesthesia with either fentanyl 15 micrograms kg-1 or 0.5% halothane on the beta-endorphin, ACTH, glucoregulatory hormonal and metabolic response to pelvic surgery was investigated. Fentanyl inhibited the increases in circulating beta-endorphin, ACTH, growth hormone, cortisol and glucose concentrations found in the patients receiving halothane. Changes in circulating beta-endorphin concentrations during surgery probably reflect alterations in pituitary secretion and appear to have no major metabolic effects. The suppression of pituitary secretion persisted for at least 4 h after the start of surgery.
Effects of graded exercise on leg exchange of energy substrates in malignant hyperthermia susceptible subjects.
It has been speculated that, in malignant hyperthermia-susceptible (MHS) individuals, an abnormality of sympathetic activity is seen during stressful situations, such as exercise. The authors investigated whether muscle metabolism in eight MHS subjects, at rest and during moderate and heavy short-term exercise, is different then that in normals. Leg exchange of energy substrates (glucose, lactate, and glycerol) was quantified by measuring leg blood flow and arterial-venous concentration differences. Muscle biopsies were also performed, and ATP, glycogen, and lactate were analyzed. Catecholamines and oxygen uptake were also measured. The study was performed at rest with subjects in the supine position and during two periods (40% and 80% of the subjects maximal oxygen uptake, respectively) on a bicycle ergometer. The principal finding of the study was that there was no major difference in oxygen uptake or leg exchange of glucose, lactate, and glycerol between MHS-subjects and previously standard normals during different grades of exercise. Furthermore, muscle metabolites and plasma catecholamines did not differ between the groups. This study indicates a normal sympathetic activity and muscle metabolism in MHS subjects during rest, as well as during moderate and severe exercise. The authors' results do not support the opinion that persons with positive in vitro tests for MH should restrict their physical activity.
Beta-endorphin infusion fails to modulate the hormonal and metabolic response to surgery.
The effects of an i.v. infusion of synthetic human beta-endorphin on the hormonal, metabolic and cardiovascular responses to surgery were investigated in female patients undergoing pelvic surgery. A beta-endorphin infusion (2 micrograms/kg as a bolus at induction of anaesthesia + 10 micrograms/kg/h for the first hour of surgery) increased plasma beta-endorphin immunoreactivity to values at least 100-fold greater than those seen during surgery in a control group of patients. In spite of this massive increase the only significant findings were a transient augmentation of the expected hyperglycaemic response and increased plasma glucagon values. There were no significant changes in ACTH, GH, insulin and cortisol secretion, in blood concentrations of lactate or glycerol, or in cardiovascular variables. Complete dissociation between plasma and cerebrospinal fluid concentrations of beta-endorphin was found even when plasma values exceeded 10,000 pmol/l in the presence of anaesthesia and surgery. These results show that the increase in circulating beta-endorphin immunoreactivity associated with clinical stress states are unlikely to modulate the associated hormonal, metabolic and cardiovascular changes.
Hormonal and metabolic responses to cardiac surgery with sufentanil-oxygen anaesthesia.
The effects of sufentanil, 10 and 20 micrograms kg-1 on the hormonal and metabolic responses to coronary artery surgery were compared in 20 patients. The most important finding was that the changes in circulating beta-endorphin, ACTH, cortisol, GH, glucose, lactate and glycerol concentrations during and after cardiac surgery were similar with both doses of sufentanil. Although sufentanil prevented a significant increase in plasma beta-endorphin, ACTH and cortisol values until 6 h after cardiopulmonary bypass (CPB), a significant increase in GH secretion occurred with the onset of CPB. Plasma insulin concentrations declined significantly after 30 min CPB, but recovered after 60 min CPB with the restoration of normothermia. Blood glucose values did not change during surgery before CPB, but started to rise with the onset of CPB and continued to increase significantly in the postoperative period. Changes in blood lactate and plasma glycerol concentrations primarily reflected the load of CPB and the effects of heparin, respectively. The results show that increasing the dose of sufentanil up to 20 micrograms kg-1 does not result in better suppression of the endocrine and metabolic changes associated with cardiac surgery.
The effects of cortisol supplementation on the metabolic and hormonal response to surgery.
The role of cortisol in determining the metabolic and hormonal changes associated with a standardized surgical operation was investigated. Twelve patients undergoing pelvic surgery were studied. Six received steroid supplementation with an infusion of hydrocortisone sodium succinate at a rate of 8 mg/h for 24 h, together with 1.5 g hydrocortisone acetate intraperitoneally at the completion of surgery, while the remainder acted as a control group. Steroid supplementation resulted in plasma cortisol values in the range 1913-2265 nmol/l from 4 to 24 h after the start of surgery. However, this marked hypercortisolaemia had no significant effects on circulating metabolites other than glucose, and did not alter plasma ACTH, GH and insulin values. The usual glycaemic response to surgery was significantly augmented by 1.0-1.5 mmol/l in the cortisol group. We conclude that changes in substrate mobilization observed after cortisol administration in normal volunteers may not accurately predict the effects found after surgery, when catabolic hormones and other modulators such as interleukin-1 may influence metabolism.
Effects of enflurane and halothane on carbohydrate metabolism in isolated perfused rabbit lungs.
Isolated, perfused rabbit lungs were used to investigate the effects of enflurane and halothane on pulmonary carbohydrate metabolism. The development of oedema in the preparation was assessed by continuous measurement of pulmonary artery pressure, airway pressure and lung weight. Ventilation of the lungs with 2% enflurane for 3 h had no effect on the rates of glucose utilization and lactate production and there were only small changes in the indices of oedema. Likewise, ventilation with 1% halothane for 1 h had no effect on the rates of glucose utilization and lactate production, and did not change significantly the concentrations of glycogen, glucose, glycolytic intermediates and high-energy phosphate compounds in lung tissue. Enflurane and halothane, at clinically relevant concentrations, probably do not influence carbohydrate metabolism in the lung.
Effects of two differing halothane concentrations on the metabolic and endocrine responses to surgery.
The effects of two differing concentrations of halothane, 2.1 MAC or 1.2 MAC, on the metabolic and endocrine responses to abdominal hysterectomy were investigated. The changes in blood glucose and lactate values, and plasma glycerol, cortisol, insulin and catecholamine concentrations were similar in both groups. We conclude that high concentrations of halothane do not suppress the responses to pelvic surgery, and that accurate quantification of the dose of halothane, within the concentration range of 1.2 to 2.1 MAC, is not essential in studies of metabolic changes associated with surgery.
Effects of cortisol suppression by etomidate on changes in circulating metabolites associated with pelvic surgery.
The effects of cortisol suppression by etomidate on the changes in circulating metabolites associated with pelvic surgery were investigated in healthy female patients. The use of etomidate resulted in the inhibition of cortisol secretion for 24 h compared with a control group of patients. However, the inhibition of steroidogenesis was not associated with a significant effect on blood glucose, blood lactate and plasma nonesterified fatty acid values, although the glycaemic response to surgery was consistently less in those patients who received etomidate. Heart rate and arterial pressure were significantly decreased during surgery in the etomidate group compared with the control group, but were similar in the postoperative period when the difference in plasma cortisol between the groups was greatest. The results suggest that cortisol has only a minor role in determining changes in circulating metabolites associated with surgery.
Peptide YY kinetics and effects on blood pressure and circulating pancreatic and gastrointestinal hormones and metabolites in man.
Peptide YY (PYY) is a 36 amino acid peptide produced by mucosal endocrine cells of the ileum and colon which inhibits acid secretion and intestinal transit in man. To assess its effects on metabolites and digestive hormones PYY was infused into 18 fasting normal subjects at three dose levels (0.06, 0.19, and 0.57 pmol kg-1 min-1), each for a period of 1 h. During the infusions mean plasma PYY levels increased by 8, 25, and 73 pmol/liter, respectively. The mean disappearance half-time on stopping the infusions was 9.2 +/- 0.4 (SEM) min. The mean MCR was 7.3 +/- 0.7 ml kg-1 min-1 and the apparent volume of distribution was calculated to be 94 +/- 9 ml kg-1. During the highest dose infusion there was a significant increase in both systolic and diastolic blood pressure, of 8.6 +/- 3.7 mmHg (P less than 0.05) and 10.9 +/- 3.0 mmHg (P less than 0.01), respectively. PYY caused a significant 50% reduction in plasma pancreatic polypeptide concentrations (P less than 0.05) and a 55% reduction in circulating motilin levels (P less than 0.05). PYY had no significant effect on circulating concentrations of insulin, glucagon, gastrin, gastric inhibitory peptide, neurotensin, enteroglucagon, or vasoactive intestinal peptide. PYY also had no significant effect on circulating concentrations of glucose, lactate, glycerol, or nonesterified fatty acids. This recently discovered human intestinal hormonal peptide thus has significant effects both on gastrointestinal hormones (motilin and pancreatic polypeptide) and blood pressure in man, but appears not to influence glucose or lipid metabolism.
Simple enzymatic method for plasma branched-chain amino acids.
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Epidural diamorphine and the metabolic response to upper abdominal surgery.
The effect of the administration of diamorphine 10 mg epidurally on the metabolic response to cholecystectomy was investigated and compared with a control group of patients given intravenous papaveretum. There were no significant differences in blood glucose, lactate and pyruvate, and plasma nonesterified fatty acid values between the epidural diamorphine group and the control group. Plasma cortisol concentrations were significantly lower in the epidural diamorphine group postoperatively and this was associated with a marked improvement in pain relief. We conclude that epidural opiates do not directly influence the metabolic response to surgery, but decrease the cortisol response postoperatively secondary to improved analgesia.
The anaesthetic modification of the endocrine and metabolic response to surgery.
The metabolic and endocrine response to surgery has been investigated in detail for many years. The current view is that the response is detrimental to the patient and that the prevention or reduction of the changes may be beneficial in aiding recovery from surgery. Three main methods are available at present for modifying the response. First, the use of afferent neuronal blockage, by epidural or spinal analgesia, to inhibit the transmission of impulses from the site of trauma. Secondly, the intravenous administration of large doses of potent opiate analgesics to block hypothalamic-pituitary function. Thirdly, the hormonal status of the patient may be changed, either by the use of agents to inhibit the secretion or action of the catabolic hormones, or by the infusion of anabolic hormones such as insulin.
Metabolic, endocrine, and reproductive changes of a woman channel swimmer.
We report the coordinated metabolic, hormonal, and reproductive data of a female channel swimmer during the pre-swim training period, immediately post-swim, and in the post-swim untrained state. Urine and blood samples collected at these times were assayed for diurnal urinary catecholamines, urinary C-peptide and 3-methylhistidine, total blood ketone bodies, glycerol, the reproductive hormones, adrenal androgens, and thyroid hormones. Subcutaneous fat was measured by ultrasonography. All of the metabolic and hormonal data post-swim except cortisol reflected the severe physiological stress. Urinary catecholamines returned to near-normal levels by 12 hours post-swim. The metabolic changes were associated with reproductive changes, including a shortened luteal phase, absence of ovulation, and increased LH secretion relative to FSH. The swimmer maintained high levels of body fat; she did not become amenorrheic. Metabolic and reproductive hormone levels returned to normal by 2 months post-swim.