Basal sympathetic activity to the microcirculation in tetraplegic man revealed by wavelet transform of laser Doppler flowmetry.

BACKGROUND: The 1984/86 published neurogram results showing only rare sympathetic nerve activity (SNA) to the muscles and skin in tetraplegia are still accepted. The present study by a different method attempted to confirm or deny those findings. METHODS AND RESULTS: The effect of basal SNA to the microcirculation of the feet and calf in 10 complete (AIS A) traumatic tetraplegic and 10 healthy age matched subjects were evaluated by wavelet transform of laser Doppler flowmetry (LDF) recordings. The results clearly indicated there is significant basal SNA from the decentralized spinal cord in tetraplegia. In addition, wavelet analysis allowed a study of other influences on the microcirculation besides SNA. Collectively, in tetraplegia compared with controls, the powers of the low frequency oscillations in blood flow were reduced; in that the endothelium caused less vasodilatation while the SNA and intrinsic vascular smooth muscles induced smaller degrees of vasoconstriction. However, the high frequency and especially the cardiac powers were greater. The latter presenting an obvious important factor for the preservation of blood flow in the microcirculation. CONCLUSIONS: It is suggested that basal SNA to the cutaneous microcirculation occurs in complete tetraplegia, and the significant levels of circulating noradrenaline reported by others indicate this is also true in other parts of the body. This may explain the usual absence of severe, incapacitating, autonomic deficiency in this condition.

Renal distribution volumes of indocyanine green, ( 51 Cr)EDTA, and 24 Na in man during acute renal failure after shock. Implications for the pathogenesis of anuria.

The mechanism responsible for the anuria in acute renal failure after shock is still controversial. Suppressed glomerular filtration and/or tubular back-diffusion of the filtrate are major possible causes. In the present investigation, seven patients with acute anuria, three of these seven again in the polyuric phase, six patients with moderate renal impairment, four patients with chronic renal failure, and eight subjects with normal renal function were studied by a multiple indicator-dilution method in which the total renal blood flow and renal distribution volumes of indocyanine green, [(51)Cr]EDTA, and (24)Na were determined. In normal subjects the average values for one kidney were 582 ml/min, 42 ml, 92 ml, and 139 ml, respectively. The measurements in the patients with moderate renal impairment were similar to those in the normal subjects, but were decreased in chronic renal failure. In acute anuria, the average values were 269 ml/min, 40 ml, 101 ml, and 114 ml and the kidney volume, estimated radiographically, was increased by 40%. When expressed as milliliters per milliliters kidney, the average distribution volume of (24)Na was decreased from 0.64 to 0.38. This decrease is consistent with the hypothesis that suppressed filtration is largely responsible for the anuria and that back-diffusion is, at most, a contributory factor. The apparent contradiction between the relatively well-preserved total blood flow and the suppressed filtration may be due to a combination of afferent vasoconstriction and efferent vasodilatation. This view is supported by the observation that low filtration fractions were found in clearance measurements performed during the polyuric phase.

Serial measurements of total blood volume in patients on maintenance hemodialysis.

In 10 patients on maintenance dialysis red cell and plasma volumes (PV) were measured before and after dialysis and several times during the next 3 days in order to establish the usual pattern of intravascular variation associated with this treatment and to determine whether there was a correlation with dialysis induced untoward effects. PV decreased from 23.7 +/- 1.5 before to 20.7 +/- 1.5 ml/cm body height immediately after dialysis. Unexpectedly it was even significantly lower 16 h after (20.1 +/- 1.4 ml/cm). Nevertheless, undesired dialysis symptoms had disappeared by that time indicating that they had not been caused by a reduction in PV or that the patients had adapted to it. Changes in PV correlated better with changes in hematocrit (r = 0.89) than with changes in body weight (r = 0.60). Therefore careful determination of the large vessel hematocrit offers a reliable estimation of blood volume variations over short periods.

Intactness of the home and behavioural problems in children.

Referral problems for children in out-patient psychiatric clinics were compared for intact homes and for broken homes in which parents were widowed, divorced, separated, unmarried or "other". All varieties of broken homes were over-represented in the clinic population compared to the general population; intact homes were under-represented. Type of home was significantly differentiated by four referral problems: anxiety and neurotic symptoms, aggression, anti-social behaviour, and problems of habit formation. The evidence suggests that the broken home should not be treated as a unitary concept.

Orthostatic vasomotor response in spinal man.

The cardiovascular adaptation of tetraplegics to the upright position has been previously demonstrated to be deficient. Presumably this is due to the interruption of the spinal pathways linking supraspinal control centres with the peripheral sympathetic motor neurons. Review of previous studies of this phenomenon reveals that vasomotor responses have been determined primarily from blood flow measurements in the extremities. Contradictory conclusions have been drawn. Study of the visceral circulation, in particular renal blood flow, could shed more light on this poorly understood area. Renal clearance tests were carried out on seven healthy controls and eight chronic, clinically complete tetraplegic patients. Renal blood flow, mean arterial pressure, and total renal vascular resistance in both supine and passive head-up tilt positions were calculated from collected data. Renal blood flow and total renal vascular resistance showed significant decrease and increase respectively during tilting in controls and tetraplegic subjects. Although the renal circulation is autoregulated, postural change causes profound alteration of the renal blood flow mediated through the haemodynamic effects of the renal nerves. Sympathetic renal vasoconstriction is mediated by the carotid sinus reflex through the vasomotor centre in the brainstem. In the absence of supraspinal influence the renal vasculature is shown to respond to an orthostatic stimulus with a vigorous vasoconstriction. The adaptation of spinal man to the upright position may involve the recovery of a spinal vasomotor reflex involving the splanchnic circulation.

Assessment of alpha- and beta-adrenoceptor blocking actions of labetalol.

Isoprenaline dose-response curves plotting increases in heart rate before and after labetalol are suggestive of competitive antagonism at beta-adrenoceptor sites. Phenylephrine dose-response curves using increases in systolic pressure before and after labetalol are suggestive of competitive antagonism at alpha-adrenoceptor sites. The ratio of alpha:beta-adrenoceptor antagonism induced by labetalol is approximately 1:3. Peak pharmacological responses after a single oral dose of labetalol (400 mg) occurred between 90-120 min after administration.

Multiple suicide attempts.

A sample of 157 persons who attempted suicide from 2 to 6 times was compared with a sample of 1,045 single attempted suicides on a number of personal and social characteristics and other factors related to the act itself. Suicide death rates, obtained through a follow-up of both groups for a year following the last attempt, were also compared. It is concluded (1) that the two groups are essentially similar in their general characteristics and in their risk of suicide and (2) that, among multiples, little change occurs from first to second attempt. However, it is pointed out that both groups are at considerably higher risk of suicide than those who have not made attempts.

Pharmacological basis for antihypertensive effects of intravenous labetalol.

Labetalol 1-5 mg/kg administered intravenously to normal subjects in the supine position produced an immediate mean fall in systolic (16%) and diastolic (25%) blood pressure with a concomitant increase in heart rate (12%). After graded exercise, intravenous labetalol inhibited increases in heart rate and blood pressure. Isoprenaline log dose response curves of increase in heart rate and reduction in diastolic pressure after intravenous labetalol shifted to the right in a parallel manner compared with pre-labetalol response curves suggestive of competitive antagonism at beta-adrenoceptor sites. Similarly, phenylephrine dose response curves of increase in systolic pressure before and after intravenous labetalol were suggestive of competitive antagonism at alpha-adrenoceptor sites. The ratio of relative potency alpha: beta adrenoceptor antagonism after intravenous labetalol was approximately 1:7, whereas in the same subjects after oral labetalol the ratio was approximately 1:3 as previously reported. Using the inhibition of isoprenaline tachycardia to estimate the potency of the beta-adrenoceptor antagonism of labetalol relative to that of propranolol the potency ratio was 1:6. However, using inhibition of Valsalva tachycardia as the index, the estimated ratio was approximately 1:3. Estimates of relative potency using inhibition of tilt tachycardia were complicated by the additional effects upon blood pressure after labetalol not seen after propranolol. Labetalol produced adrenoceptor blockade at both alpha and beta sites in man sufficient to explain its therapeutic antihypertensive effect.

Hypertensive crises in quadriplegic patients. Changes in cardiac output, blood volume, serum dopamine-beta-hydroxylase activity, and arterial prostaglandin PGE2.

The syndrome of autonomic dysreflexia often occurs in quadriplegic subjects and is characterized by paroxysmal hypertension, headache, vasoconstriction below and flushing of the skin above the level of transection, and bradycardia. These attacks may cause hypertnesive encephalopathy, cerebral vascular accidents, and death. In five patients during crises, the mean arterial pressure changed from 95 to 154 mm Hg, heart rate 72 to 45 beats/min, cardiac output 4.76 to 4.70 L/min, and peripheral resistance 1650 to 2660 dynes.sec.cm-5. In eight subjects the control plasma, red cell, and total blood volumes were 19.1, 10.5, and 29.6 ml/cm body height, respectively, and when hypertensive, the plasma protein concentration increased by 9.9% and the hematocrit by 9.5%. Plasma volume was only reduced by an estimated 10-15%. At that time, arterial dopamine-beta-hydroxylase (DbetaH) activity increased 65% and prostaglandin E2 concentration by 68%. Thus, the augmented DbetaH activity presented primarily an elevated sympathetic tone and not hemoconcentration of that protein. The rise in prostaglandin may contribute to the severe headaches during hypertensive episodes.

Head-up tilt effect on glomerular filtration rate, renal plasma flow, and mean arterial pressure in spinal man.

Changes in glomerular filtration rate (GRF), renal plasma flow (RPF), and mean arterial pressure (MAP) were measured in subjects tested in supine and head-up tilt positions with various levels of spinal cord lesion and thus with different degrees of supraspinal sympathetic vasomotor control. Responses of paraplegic subjects to head-up tilt were not significantly different from those of normal controls but GFR and RPF were significantly lower in quadriplegics in the supine position. With tilt, MAP and RPF decreased significantly, but the fall in GFR was not significant. In all 3 groups, the GFR during head-up tilt was similar, indicating that in spite of the great loss of supraspinal sympathetic control, quadriplegic subjects apparently equally-constrict their afferent and efferent renal arterioles during orthostatic stress and thus prevent excessive fall of GFR.