Effect of reserpine in Raynaud's phenomenon

Raynaud's phenomenon and related vasospastic disorders

Raynaud's phenomenon, which is characterized by episodic digital pallor, cyanosis and rubor upon exposure to cold environment or to stress, is relatively common, although the prevalence depends on the climate. Still, it is under-diagnosed, under-treated, and often confused with other conditions. Primary Raynaud's phenomenon (i.e., Raynaud disease) must be distinguished from secondary Raynaud's phenomenon (i.e., Raynaud syndrome) as long-term morbidity and outcomes differ vastly between the two conditions. Additionally, the practitioner must differentiate between Raynaud's phenomenon and related vascular disorders, such as acrocyanosis, pernio, and livedo reticularis. In this article, we review differences between the conditions and suggest an approach to diagnosis and treatment strategy for these disorders.

Exaggerated local hand sympathetic but not renin-angiotensin system activation in patients with primary Raynaud's phenomenon

In Raynaud's disease (RD), an overactivity of sympathetic nervous system (SNS) was hypothesized but only indirect proofs were obtained. Complex interactions between the renin-angiotensin system (RAS) and SNS were reported without clear demonstrations of a RAS involvement. Recently, the use of ACE inhibitors and AT1 receptor antagonists in RD patients showed mixed results. The study of total and regional kinetics of tritiated noradrenaline (NA) and the measurements of local Angiotensin (Ang) I and II arterial-venous gradient were performed in 10 RD patients and 10 controls both in rest conditions and following a cold pressor test (CPT). Hand blood flow (HBF) was measured by strain-gauge plethysmography. Baseline HBF was slightly lower in patients than in controls, but during CPT, it significantly decreased only in RD patients (P < 0.01). Total (3H)-NA clearance and spillover were similar in the two groups throughout the study. On the contrary, baseline hand NA spillover was higher in RD patients than in controls and the difference further increased during CPT. Hand NA spillover was linearly related to HBF (P < 0.001). Arterial-venous Ang I and Ang II gradients were positive without difference between controls and patients throughout the study. In conclusion in RD patients, a pathological waste of NA from sympathetic nervous endings of the hand region, exaggerated by sympathetic stimulation, occurs but an enhanced local Ang II formation was not demonstrable.

Quantitative assessment of peripheral arterial obstruction in Raynaud's phenomenon: development of a predictive model of obstructive arterial cross-sectional area and validation with a Doppler blood flow study

The objective of this study was to develop a method for the analytical assessment of arterial obstruction in conditions of Raynaud's phenomenon capable of providing diagnostic criteria. Numerous attempts have been made to determine and quantify arterial obstruction in terms of Doppler ultrasound measurements of arterial blood velocity. Absent from these methods is a formulation that allows an assessment of arterial obstruction based on the obstructed area as derived from direct measurement. The authors used spectral analysis of velocity signals from a pulsed, range-gated Doppler ultrasonic instrument to make quantitative measurements of arterial blood flow velocity in hands of normal subjects and persons with Raynaud's phenomenon. They measured the peak and mean velocity during the cardiac cycle and the time integral of the velocity signal over the cardiac cycle. These measurements for two distinct hemodynamic states induced by temperature changes allowed them to calculate the fractional change in arterial cross-sectional area produced by the change in temperature through the application of a hydraulic model of digital arterial circulation. They found an equation expressing fractional obstructed area expressed as: dA/A = 2 (dD - taudv - vtau)/(D + vdtau), where D is the time integral of the velocity signal; tau is the blood flow interval, v is the blood velocity; and dD, dtau and dv are the differences in D, tau, and v at two different hemodynamic states produced by two different temperature states. Their findings suggest that over a temperature range of 35 degrees-25 degrees C, normal subjects experience 0.05/ degrees C reduction in cross-sectional area while Raynaud subjects experience a reduction of 5.8%/degrees C. The results, based on findings in 13 subjects, suggest that Doppler ultrasound can differentiate persons with Raynaud's phenomenon from normal subjects. Additionally, the hydraulic model appears to offer the potential of assessing relative stenotic area in other arterial obstructive diseases.

Raynaud's phenomenon in the emergency department

Raynaud's phenomenon manifests as triphasic color changes of the digits, induced by exposure to low temperature or emotional stress. It is a relatively common disorder, estimated to affect 5% to 10% of the general population and 25% to 30% of otherwise healthy women. Although usually self-limiting, it can be severely painful and debilitating, and complicated by ulcerations and tissue necrosis. For the emergency physician treating a patient with an acute presentation of the phenomenon, the main challenges are to achieve adequate pain control, reverse vasospasm, and maintain viable tissue. Emergency treatment can also extend to patient education and arrangement of appropriate referrals and follow-up care.

Haemodynamic and hormonal response to a stream of cooled air

Many patients with angina note that their symptoms deteriorate in cold weather, although the precise physiological mechanism that explains this remains unclear. Exposure of the face to cool winds may be a contributory factor. The cardiovascular and hormonal response to a localised stream of room (22 degrees C) and cold (4 degrees C) air during submaximal treadmill exercise was therefore studied in nine normal subjects. Cardiac output and respiratory gases were measured with a mass spectrometer, using the indirect Fick principle. Blood samples were taken for plasma noradrenaline. A localised stream of air at 5 m.s-1 produced significant cardiovascular effects at rest, some of which persisted during exercise. In response to cold air, stroke volume, cardiac output, blood pressure and oxygen uptake increased (all P < 0.05). There was a trend towards a reduction in heart rate at rest and increase in plasma noradrenaline. Room air caused a reduction in blood pressure (P = 0.01) but stroke volumes and oxygen uptake were unchanged. The results of this study demonstrate significant cardiovascular effects of a cooled air facial stimulus at rest and during exercise. They may, in part, explain the effects of cold winds on patients with angina.

Effect of magnesium sulfate infusion on circulating levels of noradrenaline and neuropeptide-Y-like immunoreactivity in patients with primary Raynaud's phenomenon

The effect of a short-term magnesium sulfate (MgSO4) infusion on venous plasma concentration of noradrenaline (NA) and neuropeptide-Y-like immunoreactivity (NPY-LI) was investigated in 12 women with primary Raynaud's phenomenon (PRP) and in 12 healthy matched controls. The Raynaud's patients did not demonstrate any significant changes in mean basal plasma NA concentration (0.29 +/- 0.15 vs 0.37 +/- 0.09 ng/mL, ns) after MgSO4 infusion. However, in the controls there was more than twice the amount of circulating noradrenaline (cNA) (0.21 +/- 0.14 vs 0.54 +/- 0.22 ng/mL, P < 0.001) after MgSO4 infusion, compared with the preinfusion value. Measurements during the cold pressor test prior to the MgSO4 infusion showed a significant increase of cNA in both the PRP group and the control group (from 0.29 +/- 0.15 to 0.33 +/- 0.16 ng/mL, P < 0.05, and from 0.21 +/- 0.14 to 0.29 +/- 0.16 ng/mL, P < 0.005, respectively). After MgSO4 infusion the levels of cNA during the cold pressor test increased significantly only in the PRP group (from 0.37 +/- 0.09 to 0.41 +/- 0.11 ng/mL, P < 0.05). Circulating NPY-LI concentrations increased significantly during MgSO4 infusion in the Raynaud's patients as well as in the controls from 105 +/- 21 to 127 +/- 23 pmol/L, P < 0.05, and from 107 +/- 17 to 132 +/- 27 pmol/L, P < 0.01, respectively. There were no detectable changes during the cold pressor tests in either group.(ABSTRACT TRUNCATED AT 250 WORDS)

Cold-induced potentiation of alpha 2-adrenergic vasoconstriction in primary Raynaud's disease

OBJECTIVE

To determine the effects of local cooling on alpha-adrenergic responses in the fingers of patients with idiopathic Raynaud's disease.

METHODS

Clonidine HCl and phenylephrine HCl were administered through a brachial artery catheter while blood flow was measured by plethysmography in cooled and uncooled fingers.

RESULTS

Cooling potentiated alpha 2-adrenergic vasoconstriction in the patients but depressed this response in the controls. Vasoconstrictive responses to phenylephrine were not significantly affected by cooling but were significantly greater in the patients than in the controls.

CONCLUSION

Cold-induced sensitization of peripheral vascular alpha 2-adrenoceptors may be involved in the mechanism by which cooling triggers the vasospastic attacks of Raynaud's disease.

Radical microarteriolysis in the treatment of vasospastic disorders of the hand, especially scleroderma

Arterial spasm due to exaggerated sympathetic response is an important mechanism for Raynaud's phenomenon in scleroderma associated often with periadventitial scarring. The results of cervical sympathectomy have been unsatisfactory in the upper limb because of additional sympathetic pathways. Flatt therefore devised a distal sympathectomy by stripping the vessels of their adventitia over a short length of artery. The results of this operation were found by Wilgis in a large series to be poor in patients with scleroderma. A radical distal microarteriolysis including adventitia and surrounding scar is described and the results in 13 patients, 11 with scleroderma, are reported. Minimum follow-up is one year. All patients had relief from pain at rest and healing of painful ulceration. Mild recurrence of small ulcers was seen in only four patients.

Physiological mechanisms of temperature biofeedback

Research on the physiological mechanisms of finger temperature biofeedback with normal subjects and Raynaud's disease patients is reviewed. Studies conducted in the author's laboratory have shown that feedback-induced vasodilation is mediated through a non-neural, beta-adrenergic mechanism rather than through reductions in sympathetic nervous system activation. In contrast, feedback-induced vasoconstriction is mediated through the traditional, sympathetic nervous pathway. When used with primary Raynaud's disease patients, feedback-induced vasodilation has achieved reductions in reported symptom frequency ranging from 66% to 92% in controlled investigations. Future research directions are discussed.

Raynaud's phenomenon. An update

The pathogenesis of primary Raynaud's phenomenon remains an enigma. Most evidence favors a local abnormality in the digital arteries as opposed to an increased activity of the sympathetic nervous system. The local fault may involve the alpha 2-adrenergic receptors, which are most important in reflex sympathetic vasoconstriction. Cooling blood vessels increase the sensitivity of alpha 2-adrenergic receptors, increased levels of alpha 2-adrenergic receptors are present in primary Raynaud's disease, and patients show an increased sensitivity to alpha 2-adrenergic receptor agonists on finger blood flow. Serotonin has also been implicated, but the evidence is not compelling. In secondary Raynaud's phenomenon, vasospastic attacks can often be explained by a low arterial distending pressure, a thickened vessel wall, or absence of beta-adrenergic receptor activity. Diagnosis of primary Raynaud's disease relies on a typical history and normal physical examination, laboratory studies, and nailfold capillaroscopy. Finger systolic blood pressures during local cooling with ischemia may be helpful to document vasospastic attacks but does not distinguish primary from secondary Raynaud's phenomenon. The treatment of Raynaud's phenomenon is usually conservative. Pavlovian conditioning or biofeedback may be beneficial. When drug therapy is necessary, the calcium channel entry blocker nifedipine or sympatholytic agents have been shown to decrease the frequency and duration of vasospastic attacks in about two thirds of patients, although subjective improvement does not usually correlate with objective testing. Direct-acting vasodilators have not been shown to be of definite benefit. New therapies include prostaglandins, captopril, and the serotonergic antagonist ketanserin. Surgical sympathectomy has not been beneficial.

Cold-induced changes in plasma norepinephrine, epinephrine and dopamine concentrations in patients with Raynaud's phenomenon

To investigate the role of the sympathetic system in Raynaud's phenomenon, which has not yet been elucidated, we measured the levels of norepinephrine, epinephrine and dopamine before, immediately and 30 min after the cold pressor test in plasma from 17 patients with primary, 6 with secondary Raynaud's phenomenon and 19 volunteers, matched for age and sex. Patients had significantly low baseline epinephrine (0.13 +/- 0.02 vs 0.37 +/- 0.04, nmol/l, p less than 0.001, mean +/- S.E.), but normal norepinephrine and dopamine (norepinephrine: 1.77 +/- 0.16 and 2.06 +/- 0.18; dopamine: 0.10 +/- 0.01 and 0.11 +/- 0.02, patients and controls). Immediately after the cold test norepinephrine significantly increased (p less than 0.001) in patients (2.42 +/- 0.22) and controls (3.24 +/- 0.28); epinephrine increased in patients (0.18 +/- 0.02, p less than 0.02); dopamine did not show any significant change (0.13 +/- 0.01 and 0.13 +/- 0.02, patients and controls). In the recovery period, while norepinephrine and epinephrine returned to baseline in both groups, dopamine increased in controls (0.21 +/- 0.04, p less than 0.005) but remained unchanged in patients (0.11 +/- 0.01). We conclude that there is no sympathetic overactivity in Raynaud's phenomenon and propose a role for circulating dopamine in post-ischaemic vasodilatation as an explanation for the particular behaviour of dopamine.

The effect of local temperature versus sympathetic tone on digital perfusion in Raynaud's phenomenon

Matched groups of 7 to 8 patients with primary Raynaud's phenomenon, systemic sclerosis, and undifferentiated connective tissue disease and cold-tolerant normal control subjects were studied by simultaneous digital strain gauge plethysmography and laser Doppler capillary velocimetry during two controlled cycles of hand warming and cooling with and without addition of central cooling and during clinical maneuvers to evoke sympathetic tone. Transient vasoconstrictor responses of comparable degree could be evoked in all patient groups and in both the arterial and microvascular beds. While the addition of central cooling had little influence on arterial flow, patients with systemic sclerosis manifested a failure to maintain nutritive perfusion at finger temperatures associated with Raynaud's phenomenon. Linear regression and multivariate analysis suggested that finger temperature was the principal determinant of arterial flow in systemic sclerosis and that arterial flow was the principal determinant of microvascular perfusion. The inability of patients with systemic sclerosis to maintain nutritive flow in the face of either reflex or cold-induced proximal arterial constriction is consistent with their clinical propensity to ischemic tissue injury and separates these patients physiologically from other forms of Raynaud's phenomenon.

Pathogenesis and treatment of Raynaud's phenomenon

The pathogenetic theories and treatment of Raynaud's phenomenon are reviewed. In primary Raynaud's disease, most evidence supports a local defect at the digital artery level, with vasoconstriction or vasospasm of the digital arteries inducing the color changes. Normal sympathetic activity, low transmural arterial distending forces, and serotonin may be associated factors in the production of vasospastic attacks. In Raynaud's phenomenon, persistent vasoconstriction, thickened vessel walls, increased blood viscosity, and low digital artery blood pressure distal to obstructions may lead to vasospastic attacks with normal sympathetic nerve stimuli. Since the underlying cause of primary Raynaud's disease is unknown, treatment involves the use of agents to reduce sympathetic nerve activity or to prevent vascular smooth muscle contraction. Most patients will respond to conservative measures, but if they fail nifedipine is the drug of choice and alleviates the syndrome in about two thirds of patients. Reserpine and guanethidine may be as effective, but well-controlled studies have not been performed. The beneficial response to prazosin is moderate and dissipates with time. Side effects with these drugs prevent their use in many patients. Diltiazem and nitroglycerin ointments are of questionable value. Ketanserin, a serotonergic S2-receptor antagonist, which has been shown to decrease the frequency of vasospastic attacks, and parenteral prostacyclin are among the new promising therapies.

Induction of vasospastic attacks despite digital nerve block in Raynaud's disease and phenomenon

Using a combination of environmental and local cooling, we induced vasospastic attacks of Raynaud's phenomenon in nine of 11 patients with idiopathic Raynaud's disease and in eight of 10 patients with scleroderma. Attacks were defined as occurring if two of the possible three color changes (pallor, cyanosis, and rubor) occurred, and serial photographs were scored by three independent raters. Two fingers on one hand were anesthetized by local injection of lidocaine, and the effectiveness of nerve blocks was verified by plethysmography. The frequency of vasospastic attacks in nerve-blocked fingers was not significantly different from that in the corresponding intact fingers on the contralateral hand. These findings show that the vasospastic attacks of Raynaud's disease and phenomenon can occur without the involvement of efferent digital nerves and argue against the etiologic role of sympathetic hyperactivity.

Increased alpha-adrenergic responsiveness in idiopathic Raynaud's disease

In our study of 28 patients with idiopathic Raynaud's disease, the patients had significantly greater digital blood flow responses to intraarterial phenylephrine and clonidine than did normal control subjects. There were no group differences in finger blood flow responses to body heating, reflex cooling, digital ischemia, or to intraarterial tyramine or isoproterenol. There were also no group differences in blood pressure or heart rate during any procedure. These results suggest that patients with idiopathic Raynaud's disease have increased peripheral vascular alpha-adrenergic receptor sensitivity and/or density compared with normal persons.

Hand warming as a treatment for Raynaud's phenomenon in systemic sclerosis

Twelve patients with Raynaud's phenomenon (RP) due to systemic sclerosis (SS) warmed their hands for 5 min in hand hot water every 4 h throughout the day during alternate weeks of a 6-week study. There was a statistically significant decrease in the number and duration of Raynaud's attacks in the weeks in which warming was performed compared with the intervening weeks. An increase in blood flow as measured by laser-Doppler flowmetry accompanied clinical improvement. Simple hand warming appears to be effective in the management of RP in patients with SS.

Digital and radial artery blood flow in patients with Raynaud's phenomenon in response to nifedipine

The effect of nifedipine on haemodynamic changes in the hand after cooling in 10 patients with Raynaud's phenomenon is assessed. Nifedipine reduced the fall in digit blood flow induced by cooling and limited the increase in pulsatility index (a measure of peripheral resistance). There was good correlation between digital arterial inflow (measured by strain gauge plethysmography) and radial artery pulsatility index (measured by Doppler waveform analysis).

Influence of vasospasm on visual function

In a number of patients with etiologically unexplained visual field loss, a vasospastic syndrome could be found with the help of a capillaroscopic local cooling test on the fingers. In the patients with proven vasospastic syndrome, the visual field defects were increased after a cold water test and decreased after a therapy with calcium entry blockers. General aspects of the physiology and pathophysiology of the circulation and especially of the circulation in the eye are presented.

Cold-induced Raynaud's phenomenon ameliorated by intravenous administration of ketanserin: a double-blind cross-over study

Fifteen patients suffering from Raynaud's phenomenon (RP) were examined. They were placed in a "climate chamber" (a small room in which the temperature and humidity could be varied). The temperature was gradually decreased, while the humidity was kept constant. After 60-90 min, distinct RP was induced and intravenous medication was administered. The whole trial was performed in a double-blind, cross-over fashion. Every patient participated in two experiments performed 2 days apart. Either ketanserin or placebo was given during the first experiment. In the second experiment, the medication (or placebo) which had not been given was administered. The effects of ketanserin were highly significant: the bluish pallor changed into bright erythema and the skin temperature rose significantly. This was interpreted as a spasmolytic effect. Intravenously administered ketanserin has a place in the clinical treatment of acutely deteriorating RP of diverse etiologies.

Epidural electrical stimulation in severe limb ischemia. Pain relief, increased blood flow, and a possible limb-saving effect

Peripheral vascular disease of the extremities causes ischemic pain and, at times, skin ulcerations and gangrene. It has been suggested that epidural spinal electrical stimulation (ESES) could improve peripheral circulation. Since 1978 we have used ESES in 34 patients with severe limb ischemia; all had resting pain and most had ischemic ulcers. Arterial surgery was technically impossible. Twenty-six patients had arteriosclerotic disease, one had Buerger's disease, and seven had severe vasospastic disorders. Ninety-four per cent of the patients experienced pain relief. ESES healed ulcers in 50% of those with preoperative nonhealing skin ulcerations. Seventy per cent of the patients showed improved skin temperature recordings. Only 38% of the stimulated arteriosclerotic patients underwent amputations during a mean followup period of 16 months, as compared to 90% of a comparable group of unstimulated patients. ESES is very promising in severe limb ischemia where reconstructive surgery is impossible or has failed.

Effect of the cold pressor test on diffusing capacity. Comparison of normal subjects and those with Raynaud's disease and progressive systemic sclerosis

Single-breath carbon monoxide diffusing capacity (Dsb) was measured before and during immersion of one hand in ice water (cold pressor test) in the following three groups of subjects: (1) normal subjects; (2) patients with isolated Raynaud's disease; and (3) patients with Raynaud's phenomenon and progressive systemic sclerosis. No change in Dsb was found in normal subjects or patients with progressive systemic sclerosis. Patients with isolated Raynaud's disease showed a rise in Dsb during cold pressor testing, the mean increase being 8 percent. These results suggest that a rise in Dsb during exposure to cold is a response unique to patients with isolated Raynaud's disease or Raynaud's phenomenon without progressive systemic sclerosis, and not a normal physiologic response to cold. The lack of change in Dsb in response to cold in progressive systemic sclerosis, interpreted by other authors as an indicator of pulmonary vascular disease, resembles the normal response to a challenge with cold.

Neuroendocrine response to cold in Raynaud's syndrome

Eleven patients with Raynaud's syndrome accompanied by monospecific IgG ANA, nine patients with Raynaud's syndrome in the absence of ANA, and nine normal volunteers were exposed to an ambient cold challenge during which time venous blood was continuously sampled. ANA negative patients were shown to have significantly higher levels of cortisol during a cold challenge than either ANA positive patients or normal controls, and exhibited significantly lower levels of plasma norepinephrine compared with normal controls. ANA positive patients did not differ significantly from normals in their neuroendocrine response to cold. It is suggested that the high plasma cortisol found in Raynaud's syndrome in the absence of ANA may be responsible for the vasospasticity in this group of patients.

Topical glyceryl trinitrate as adjunctive treatment in Raynaud's disease

The effects of topical glyceryl trinitrate in Raynaud's disease were compared with those of placebo in a double-blind, crossover trial in 17 patients with bilateral Raynaud's disease and an associated collagen disease, who were receiving oral sympatholytic agents at the maximum levels they could tolerate. 1% glyceryl trinitrate ointment or a placebo of lanolin was applied to one hand only for 6 weeks, then patients changed to the other preparation for 6 weeks. The results were evaluated every 2 weeks. The frequency of attacks, severity of attacks, and size of ulcers in the treated hand were significantly lower when the patients were using glyceryl trinitrate ointment than when they were using placebo. The treatment of Raynaud's disease may be improved by using topical glyceryl trinitrate ointment as an adjunct to a basic regimen of oral sympatholytic agents. Glyceryl trinitrate ointment may obviate the need for more aggressive treatment, such as intraarterial reserpine, in selected patients.

A 1-year follow-up of Raynaud's patients treated with behavioral therapy techniques

The purpose of this study was to assess to what degree learned control of digital temperature and vasospastic attacks can be retained by Raynaud's patients over a full year period. Subjects were 19 patients suffering from diagnosed idiopathic Raynaud's disease who had undergone behavioral training. These patients had been trained to increase digital temperature using either autogenic training, biofeedback, or a combination of autogenic training and temperature biofeedback. Results indicated that the mean number of vasospastic attacks per day occurring 1 year after training was approximately equal to the number occurring at the end of the initial training (1.2-1.3 per day). Patient satisfaction with the treatment program was above average (3.5 on a 5-point scale). The patients' ability to maintain digital temperature during the cold stress challenge was imparied, however. At 1-year follow-up, digital temperature readings taken in the laboratory were identical to baseline levels.

Vasospastic disorders

Acute digital ischemia not due to thromboembolism may be the result of either a primary vasospastic disorder (Raynaud's disease, acrocyanosis, livedo reticularis) or vasospasm associated with a systemic, regional, or traumatic disorder (Raynaud's syndrome, cold injury). Raynaud's disease versus syndrome is distinguishable up to 95% of the time from clinical criteria.

Raynaud's disease: reduced hand blood flows with normal blood viscosity

Hand blood flows and the blood and plasma viscosities were measured in patients with Raynaud's disease in an attempt to identify the mechanism of the episodic vascular insufficiency. Using venous occlusion plethysmography the following observations were made: (1) the hand blood flows were significantly less than in normals at 32 degrees, 27 degrees and 20 degrees C; (2) the percentage decrease in flow with cooling was greater in normals and (3) cooling of one hand from 32 degrees to 27 degrees C caused an abnormal decrease in flow through the contralateral hand. Using a rotational viscometer the blood and plasma viscosities were found to be normal at both high and low shear rates. The percentage increase in the blood viscosity with cooling from 35 degrees to 25 degrees was also normal. These studies demonstrate an increased constrictive response of the cutaneous vasculature of the hand to both local and reflex stimulation, and exclude a rheological abnormality, under conditions similar to those of the present study.

Effect of low dose intra-arterial reserpine on vascular wall norepinephrine content

A number of reports in recent years have indicated that the administration of low dose intra-arterial reserpine has resulted in significant clinical improvement in patients with symptomatic vasospasm, with the benefits presumably resulting from regional vascular wall norepinephrine depletion with resultant vasodilatation. However, to date, there has been no evidence that such low dose reserpine actually alters vascular wall norepinephrine content. This study was performed to determine both regional and systemic effects of low dose intra-arterial reserpine on vascular-wall norepinephrine content, and the duration of any alterations. Twenty-four mongrel dogs had vascular segments excised and assayed for norepinephrine content, before and for up to 4 weeks following a single injection of reserpine, 0.01 mgm/kg, into one femoral artery. The results indicate a pronounced norepinephrine depletion in the injected femoral arterial system, with the reduction persisting for 2-4 weeks, at which time complete norepinephrine recovery occurred. The visceral vessels sampled also showed considerable norepinephrine depletion, indicating systemic spill-over of the drug from the injected peripheral arterial tree. The visceral vessels, however, showed maximal depletion at 24 hours, with recovery by 7 days.

Radial artery cannulation

The status of radial artery cannulation is reviewed. The technique of percutaneous puncture, equipment in use, and known complications are discussed. Recommendations are made for precautionary measures to reduce the complication rate. It is concluded that radial artery cannulation is a safe and useful procedure in certain anaesthetic and intensive care situations.