Biomedical subjects
Publications and source records attributed to M Nattrass.
The effects of venestasis and hand exercise on antecubital vein blood lactate and pyruvate concentrations have been re-examined. The results show that venestasis for up to 5 min has no effect, while hand exercise for as little as 20 s causes a marked increase in blood lactate and pyruvate concentrations. The implications of these findings are discussed.
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It has been postulated that sympathetic denervation due to autonomic neuropathy may protect against the development of diabetic ketoacidosis in patients with insulin-dependent diabetes. We tested this hypothesis by withdrawing exogenous insulin from five men with established insulin-dependent diabetes and severe symptomatic autonomic neuropathy. Six men also with insulin-dependent diabetes of more than 5-years duration but no clinical evidence of neuropathy served as controls. Normoglycemia was maintained during the night before the study using a variable intravenous insulin infusion that was terminated at 0800 h the following morning (time 0 min). During a 600-min observation period following termination of the insulin infusion the rise (mean +/- SEM) in blood glucose concentration between 0 min and 600 min was comparable between the autonomic neuropathy and control groups (8.2 +/- 1.3 versus 8.3 +/- 1.1 mmol/L; p > 0.1). The rise in plasma nonesterified fatty acids was significantly less for the autonomic neuropathy patients (0.96 +/- 0.06 versus 1.65 +/- 0.14 mmol/L; p < 0.01) with a similar trend for the rise in total ketone body concentration (2.74 +/- 0.85 versus 3.72 +/- 0.38 mmol/L). Capillary pH at 600 min, however, was not significantly different between the groups (23 +/- 2 versus 20 +/- 1 mmol/L). In conclusion, plasma fatty acids and ketone body concentrations rise less rapidly following withdrawal of insulin in patients with insulin-dependent diabetes and autonomic neuropathy suggesting that such patients may have a degree of protection against the development of diabetic ketoacidosis.
Nine diabetic patients (age range 23-67y) with autonomic neuropathy and symptomatic postural hypotension were studied. The time course of the postural drop in blood pressure (BP) was documented firstly at 0900h, prior to breakfast and insulin, and secondly in the afternoon. Seven patients were symptomatic in the morning but only one in the afternoon. The systolic nadir in the morning was lower (p less than 0.02) than in the afternoon. The mean systolic pressure in the first 3 min after standing was no different in the afternoon but it was lower in the 2nd (p less than 0.05), 3rd (p less than 0.02), and 4th (p less than 0.02) 3-min intervals in the afternoon. The time taken to reach the systolic nadir was variable, ranging from 1-12 min. It is concluded that the assessment of the postural fall in BP may be underestimated if measured immediately after standing or if it is measured in the afternoon.
During the treatment of diabetic ketoacidosis intravenous glucose is infused when blood glucose has fallen to around 14 mmol l-1. The use of hypertonic (10%) glucose has been recommended in order to hasten the clearance of blood ketone bodies. In a randomized controlled study 17 patients presenting with severe diabetic ketoacidosis were allocated to one of two regimens of intravenous glucose and insulin when blood glucose had fallen to less than 14 mmol l-1. Nine patients were given 5% glucose containing 10 U l-1 insulin and 8 patients received 10% glucose with 40 U l-1 insulin. Fluid was infused at a rate of 250 ml h-1 for 6 h. At the start of the infusions blood glucose had fallen from levels at presentation to 12.8 +/- 1.1 mmol l-1 (mean +/- SE) in the group which subsequently received the low infusion rate and to 13.7 +/- 0.9 mmol l-1 in the subsequent high infusion rate group. With glucose/insulin infusion blood glucose after 6 h was 11.5 +/- 0.9 mmol l-1 (low infusion rate group) and 15.7 +/- 1.3 mmol l-1 (high infusion rate group). This difference between groups at 6 h was significant (p less than 0.05). Over the 6 h of infusion the fall in blood total ketone bodies was significantly greater in the group receiving the higher rate of glucose/insulin infusion (7.34 +/- 0.57 vs 5.18 +/- 0.57 mmol l-1; p less than 0.05). Despite the greater fall in total ketone bodies in this group there was no difference in the improvement in capillary blood pH or bicarbonate.(ABSTRACT TRUNCATED AT 250 WORDS)
Two hundred and fourteen patients with prima-facie evidence of symptomatic diabetic neuropathy were considered for inclusion in a clinical trial. Only 50 patients (24%) fulfilled all the clinical and electrophysiological criteria for entry. One hundred and nine patients (51%) were excluded on clinical grounds alone. Reasons for exclusion included the presence of alternative causes of neuropathy (15%), peripheral vascular disease (10%), proximal or asymmetrical neuropathies (11%), renal impairment (5%), nerve entrapment (4%), cerebrovascular disease (2%) and amputations (2%) with miscellaneous conditions accounting for the remaining 2%. Of the 105 patients who satisfied the clinical entry requirements another 55 patients (26%) were excluded by electrophysiological criteria. Peroneal motor nerve conduction velocity was unrecordable or unacceptably reduced (less than 30 m/s) in 42% of these patients, sensory nerve potentials were unrecordable in 8% and median nerve compression was evident in another 3%. The selection of cohorts for clinical trials in diabetic neuropathy involves careful consideration of clinical and electrophysiological features of the patients and exclusion of alternative causes of neuropathy.
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