G.M. Hall

The hormonal responses to repetitive brief maximal exercise in humans

SummaryThe responses of nine men and nine women to brief repetitive maximal exercise have been studied. The exercise involved a 6-s sprint on a non-motorised treadmill repeated 10 times with 30 s recovery between each sprint. The total work done during the ten sprints was 37,693±3,956 J by the men and 26,555±4,589 J by the women (M > F,P<0.01). This difference in performance was not associated with higher blood lactate concentrations in the men (13.96± 1.70 mmol·−1) than the women (13.09±3.04 mmol·l−1). An 18-fold increase in plasma adrenaline (AD) occurred with the peak concentration observed after five sprints. The peak AD concentration in the men was larger than that seen in the women (9.2 +- 7.3 and 3.7 ± 2.4 nmol · l−1 respectively,P<0.05). The maximum noradrenaline (NA) concentration occurred after ten sprints in the men (31.6±10.9 nmol·l−1) and after five sprints in the women (27.4 ± 20.8 nmol · l−1). Plasma cardiodilatin (CDN) and atrial natriuretic peptide (ANP) concentrations were elevated in response to the exercise. The peak ANP concentration occurred immediately postexercise and the response of the women (10.8 ± 4.5 pmol · l−1 was greater than that of the men (5.1 ± 2.6 pmol · l−1,P<0.05). The peak CDN concentrations were 163 ± 61 pmol · l−1 for the women and 135 ± 61 pmol · l−1 for the men. No increases in calcitonin gene related peptide (CGRP) were detected in response to the exercise. These results indicate differences between men and women in performance and hormonal responses. There was no evidence for a role of CGRP in the control of the cardiovascular system after brief intermittent maximal exercise.

The responses of the catecholamines and β-endorphin to brief maximal exercise in man

SummaryThe responses to brief maximal exercise of 10 male subjects have been studied. During 30 s of exercise on a non-motorised 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<0.001) and blood glucose concentrations from 4.25±0.45 to 5.59±0.67 mmol·l−1 (p<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<0.001) and the estimated decrease in plasma volume of 11.5±3.4% (p<0.001). The plasma catecholamine concentrations increased from 2.2±0.6 to 13.4±6.4 nmol·l−1 (p<0.001) and 0.2±0.2 to 1.4±0.6 nmol·l−1 (p<0.001) for noradrenaline (NA) and adrenaline (AD) respectively. The plasma concentration of the opioidβ-endorphin increased in response to the exercise from <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-exerciseβ-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. In common with other situations that impose stress,β-endorphin concentrations are also increased in response to brief maximal exercise.

Plasma catecholamine response to cataract surgery: a comparison between general and local anaesthesia

We studied the plasma catecholamine, plasma glucose and cardiovascular responses to cataract surgery in 20 elderly patients allocated randomly to receive either general anaesthesia or local anaesthesia by retrobulbar block. Local anaesthesia prevented the increase in plasma noradrenaline, adrenaline and glucose concentrations found in those patients who received general anaesthesia and also improved cardiovascular stability. The results show the beneficial effects of local anaesthesia in preventing the hormonal, metabolic and cardiovascular changes found when cataract surgery is conducted under general anaesthesia.

Effects of high‐dose fentanyl anaesthesia on the established metabolic and endocrine response to surgery

The effect of the administration of fentanyl 50 μg/kg body weight on the established metabolic response to pelvic surgery was investigated. In comparison with a control group of patients in whom anaesthesia was supplemented with halothane, fentanyl was associated with a significant decrease in only blood lactate concentrations and heart rate. There were no significant differences in blood glucose, plasma non‐esterified fatty acids, and plasma cortisol values between the two anaesthetic techniques. It is concluded that the administration of high‐dose fentanyl has little effect on the established metabolic response to surgery, compared with the marked changes observed when the same dose is given before the onset of surgical stimulation.

Fentanyl and the metabolic response to gastric surgery

The effect of the supplementation of nitrous oxide‐oxygen anaesthesia with either 50 μg fentanyl/kg body weight or 0·5–1·0% halothane on the metabolic and hormonal response to gastric surgery was investigated in 16 patients. Those patients who received fentanyl showed a significant decrease (p<0·05) in the hyperglycaemic response to surgery after 30 and 90 minutes and a significant decrease (p<0·05) in the plasma cortisol response after 30 minutes. Profound respiratory depression occurred at the end of surgery in all patients who were given fentanyl. This required the intravenous administration of naloxone and careful supervision in the early postoperative period. It is concluded that the transient metabolic and endocrine benefits produced by fentanyl do not compensate for the severe respiratory problems postoperatively and thus ‘high‐dose fentanyl’ cannot be recommended for upper abdominal surgery.

Postoperative morbidity following cataract surgery : A comparison of local and general anaesthesia

Two hundred and thirty‐one patients were questioned the day following their cataract surgery to ascertain the incidence of postoperative morbidity. One hundred and nineteen patients received local anaesthesia (LA) and 112 received general anaesthesia (GA). There was a significant difference in the incidence of nausea (21% in G A group, 3% in LA group, p < 0.01), sore throat (41% G A group, 3% LA group, p < 0.01), and bruising of the eye (15% G A group, 39% LA group, p < 0.01). There was no significant difference in the incidence of vomiting, headache, double vision, the severity of postoperative pain, or the need for analgesia. The time before the patients drank and ate postoperatively was significantly shorter in the local anaesthetic group (1.3 h and 1.8 h LA group, 4.1 h and 6.7 h GA group respectively, p < 0.01).

Modification of the hormonal and metabolic response to surgery by narcotics and general anaesthesia

Summary The last decade has seen increasing interest in attempts to modify the hormonal and metabolic response to surgery by the newer opioids fentanyl, alfentanil and sufentanil. This work followed classical endocrinological studies that showed the ability of clinical doses of morphine to prevent stress-induced ACTH secretion in man. High-dose fentanyl anaesthesia (50–100 μg/kg) can prevent the hormonal and metabolic responses to pelvic and upper abdominal surgery, but the most appropriate use of this technique is for cardiac surgery. There is widespread agreement that it is possible to abolish completely the hormonal and metabolic changes associated with cardiac surgery until the start of cardiopulmonary bypass. However, the profound physiological changes associated with bypass appear to exacerbate further the endocrine response which cannot be completely attenuated by high doses of fentanyl, alfentanil or sufentanil. In particular, the catecholamine response to bypass proceeds inexorably. Inhalational agents have little effect on the hormonal and metabolic response to surgery. Isolated reports that high concentrations of a volatile anaesthetic may attenuate some aspects of the response have not been confirmed. The effects of potent opioids on the endocrine and metabolic changes associated with surgery are short lived, about 6–8h, and there is no evidence of any long-term benefit to the patient in terms of a decrease in post-operative morbidity and mortality.

Treatment of porcine malignant hyperthermia. A review based on experimental studies.

The metabolic and endocrine changes in porcine malignant hyperthermia are described and the importance of the catecholamine response emphasised. The relative effectiveness of several different therapeutic agents in the treatment of this syndrome in the Pietrain pig are described and the importance of a common link with the catecholamine response discussed.

The stress response to surgery: An essential mechanism for survival or an evolutionary remnant?

The stress response refers to the endocrine and metabolic changes which occur with surgery, resulting in substrate mobilisation, a negative nitrogen balance, potassium loss and sodium and water retention. Surgery is associated with an increase in pituitary hormone secretion namely adrenocorticotrophic hormone (ACTH), [3 endorphin, growth hormone (GH), prolactin and arginine vasopressin (AVP). Stimulation of the sympathetic nervous system causes an increase in circulating adrenaline and noradrenaline concentrations. Plasma cortisol rises as a result of increased secretion of ACTH. Simultaneous with the increased production of catabolic hormones, there is a decrease in the secretion of the anabolic hormones insulin and testosterone. These hormonal changes, and the ensuing metabolic effects have been described in detail previously. 1 Blood glucose may increase up to 10 mmol 1 i during surgery. This occurs as a result of an imbalance between glucose production and utilisation. The mechanism of this is multifactorial and not completely elucidated, but essentially it results from increased production of glucose by glycogenolysis and gluconeogenesis in the liver, together with impaired uptake peripherally. Fat metabolism is not grossly affected by surgery unless other factors such as starvation are an important influence. The production of free fatty acids (FFA) and glycerol from lipids is stimulated by catecholamines and inhibited by insulin. Amino acids are produced by the breakdown

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.