Long-term effects of unilateral carotid endarterectomy on arterial baroreflex function

Abstract.Background and purpose: Carotid endarterectomy (CE) may be complicated by the clinical syndrome of baroreflex failure. Alterations of baroreflex function may also account for the frequently observed blood pressure lability in the first hours following surgery. We investigated the long-term effects of unilateral CE on baroreflex control of function and blood pressure.Methods: We investigated 14 patients after unilateral CE (13m:1f, 64.8 ± 6.5 years), 9 patients with a surgically untreated uni-/bilateral carotid stenosis (CS, 7m:2f, 57.6 ± 10.7 years) and 12 healthy controls (HC, 11m:1f, 60.9 ± 7.9 years) by means of Valsalva maneuver, active standing, forced breathing, cold face test, cold pressor test and mental arithmetic. Ambulatory blood pressure level and variability were determined from 24-hour Spacelabs and 5-hour beat-to-beat Portapres recordings.Results: Baroreflex sensitivity (derived from phase IV Valsalva maneuver) was significantly lower in CE (1.53 ± 0.83 ms/mmHg) than in CS (4.39 ± 2.27, p = 0.002) and HC (5.34 ± 3.78, p = 0.003). CE patients exhibited a decreased reflex control of heart rate in response to Valsalvas maneuver and active standing without orthostatic hypotension. Office blood pressure levels before and after endarterectomy were similar, as were ambulatory blood pressure levels in the three groups. Ambulatory blood pressure variability was higher in CE and CS than in HC, but not different between CE and CS.Conclusions: Unilateral CE causes a long-term impairment of baroreflex function, resulting in an attenuated reflex control of heart rate, but no hypertension or blood pressure lability.     

Both body and arm position significantly influence blood pressure measurement

The position of both the body and the arm during indirect blood pressure (BP) measurement is often neglected. The aim of the present study was to test the influence of the position of the patient on BP readings: (1) sitting with the arms supported precisely at the right atrium level and (2) supine: (a) with the arms precisely at the right atrium level and (b) with the arms on the examination bed. In a first group of 57 hypertensive patients, two sessions of BP and heart rate (HR) measurements were performed in two positions: sitting and supine with the arms supported precisely at right atrium level in both positions. BP was measured simultaneously at both arms, with a Hawksley Random Zero sphygmomanometer at the right arm, and with an automated oscillometric device (Bosomat) at the left arm. BP and HR readings obtained in the two positions were then compared. In a second group of 25 normo- and hypertensive persons, two sessions of BP and HR readings were performed in supine with the arms in two different arm positions: (a) the arm placed precisely at right atrium level and (b) the other arm on the examination bed. The measurements were performed at both arms with two automated devices (Bosomat). The readings taken in the two positions were compared. Both systolic BP (SBP; by 9.5 +/- 9.0 (standard deviation, s.d.); right arm) and diastolic BP (DBP; by 4.8 +/- 6.0 mmHg; right arm) were significantly higher in the supine than in the sitting position. When the two different arm positions (body continously supine) were compared in the second part of the study, significantly higher SBP (by 4.6 +/- 6.1 mmHg) and DBP (by 3.9 +/- 2.8 mmHg) were obtained when the arm of the patient was placed on the bed (below the right atrium level), than when the arm was placed at the level of the right atrium. BP readings in sitting and supine positions are not the same. When according to guidelines the arm of the patient is meticulously placed at the right atrium level in both positions, the difference is even greater than when the arm rests on the desk or on the arm support of the chair. Moreover, in the supine position small but significant differences in BP are measured between arm on a 5 cm-high pillow and arm on the bed. In every study reporting BP values, the position of both the body and especially the arm should be precisely mentioned.     

Baroreflex and chemoreflex function after bilateral carotid body tumor resection

OBJECTIVE: To investigate whether bilateral carotid body tumor resection invariably and chronically affects arterial baroreflex or peripheral chemoreflex function. METHODS: We studied eight consecutive patients (two men and six women; ages 48.1 +/- 11.8 years), a median time of 3.4 years (range 1.3-20.6 years) after bilateral carotid body tumor resection, and 12 healthy control individuals (eight men and four women; ages 53.7 +/- 10.1 years). Baroreflex sensitivity (phenylephrine), blood pressure and its variability (24 h Spacelabs and 5 h Portapres recordings), responses to standard cardiovascular reflex tests and the ventilatory responses to normocapnic and hypercapnic hypoxia were assessed. RESULTS: Baroreflex sensitivity was lower in patients (6.4 +/- 7.2 ms/mmHg) than in controls (14.7 +/- 6.6 ms/mmHg; P +/- 0.011). Mean office blood pressure and heart rate were normal in patients (123.3 +/- 11.9/79.0 +/- 7.3 mmHg and 67.5 +/- 9.4 beats/min, respectively) and controls (117.8 +/- 10.6/74.0 +/- 6.8 mmHg and 61.1 +/- 9.2 beats/min, respectively). Blood pressure variability was increased during ambulatory measurements. Three patients exhibited orthostatic hypotension. The Valsalva ratio, an index of baroreflex-mediated cardiovagal innervation, was lower in patients (1.4 +/- 0.2) than in controls (1.8 +/- 0.5; P +/- 0.008). The normocapnic ventilatory response to hypoxia was absent in all patients, whereas a small residual response to hypoxia was observed under hypercapnic conditions in two patients. CONCLUSIONS: Bilateral carotid body tumor resection results in heterogeneous expression of arterial baroreflex dysfunction, whereas the normocapnic hypoxic drive is invariably abolished as a result of peripheral chemoreflex failure.     

Influence of caloric restriction on the development of atherosclerosis in nonhuman primates: progress to date

Caloric restriction (CR) has been observed to retard aging processes and extend the maximum life span in rodents. In an effort to evaluate the effect of this nutritional intervention on physiologic variables in higher species, several nonhuman primate trials are ongoing. In particular, a study evaluating the independent effect of CR on the extent of atherosclerosis was initiated in 1993 in 32 adult cynomolgus monkeys. Therefore, the trial was designed to achieve identical cholesterol intake after animals were randomized to a control group or a calorie-restricted group (30% reduction from baseline caloric intake). The animals were routinely evaluated for glycated proteins, plasma insulin and glucose levels, insulin sensitivity, and specific measures for abdominal fat distribution by CT scans over a 4-year interval. The results from 4 years of intervention demonstrate that CR improves cardiovascular risk factors (such as visceral fat accumulation) and improves insulin sensitivity. In contrast to other primate studies with normolipidemic animals, CR had no independent effects on plasma lipid levels and composition in the presence of equivalent amounts of dietary cholesterol intake. Preliminary analysis of atherosclerotic lesion extent in the abdominal aorta has failed to demonstrate differences between control animals and CR animals. Follow- up studies are being conducted to determine the effect of CR on atherosclerosis extent in coronary and carotid arteries.      

Inherited disorders of 3-methylcrotonyl CoA carboxylation

The clinical course of 4 patients who had reduced activities of 3-methylcrotonyl CoA carboxylase (also called 3-methylcrotonylglycinuria) is described. Two children presented with a metabolic acidosis, one in the neonatal period and the other with episodes of acidosis that started in the second year of life. In the other 2 children neurological symptoms were prominent, one having infantile spasms and the other developmental regression with a skin rash and alopecia. Three of the children responded well to oral biotin and dietary protein restriction but the fourth, despite a biochemical response to biotin, has a severe neurological handicap. The clinical presentation of inborn errors of 3-methylcrotonyl CoA carboxylase is variable. Metabolic acidosis may not be conspicuous and instead neurological features may predominate.     

Suspected poisoning in children. Study of the incidence of true poisoning and poisoning scare in a defined population in North East Bristol

The distinction between true and suspected poisoning in children has not been made clear in previous work on childhood poisoning. A study of suspected poisoning in children under 15 years of age in a defined population of North East Bristol from November 1970 to July 1973 carried out by the Health Education Council Medical Research Division included 53,000 child-years at risk. The number of suspected poisonings was 3-4/1000 population aged under 15 years per year, with a higher incidence in younger age groups. Detailed investigation of the circumstances of the accidents carried out by a multidisciplinary team showed that at least 65%, and possibly as many as 78% were poisoning scares and not true poisoning. The evidence used by the casualty doctor and by the parents to diagnose poisoning was explored, and in many cases was circumstantial. Children with fathers in nonmanual occupations were over-represented. This may reflect differences in patterns of utilization behaviour rather than true differences in incidence.     

Sympathoadrenal activation and the dumping syndrome after gastric surgery

Dumping symptoms suggest concomitant sympathoadrenal activation. To evaluate the relation between dumping symptoms and postprandial plasma catecholamine changes, standardized dumping-provocation tests with use of oral glucose were performed for 16 gastric surgery patients with dumping, for 14 gastric surgery patients without dumping, and for 14 healthy control patients. Early dumping symptoms were present for all patients with dumping, and late symptoms developed in three patients with dumping after glucose ingestion. Patients without dumping and healthy control patients had slight complaints or no complains. Systolic and diastolic blood pressure remained unaffected for the three groups. Positive breath-hydrogen tests, heart rate increments, and reactive plasma glucose decrements were present for patients with dumping and for patients without dumping, but not for control patients. Plasma noradrenaline and adrenaline increased for patients with dumping and for patients without dumping, but not for control patients. The noradrenaline increment was higher for patients with dumping (98%) than for patients without dumping (78%; p<0.05). The noradrenaline increment was related to the dumping score and to the heart rate increment for the first hour after glucose ingestion, whereas the adrenaline increment was related to the plasma glucose decrement for the third hour. Therefore, dumping symptoms clearly are accompanied by postprandial sympathoadrenal activation, but sympathoadrenal activation cannot account completely for development of dumping symptoms.     

Exogenous lung surfactant: effect on radiographic appearance in premature infants

At birth, premature infants of 25-29 weeks gestation, at high risk for development of neonatal respiratory distress syndrome (RDS), were given a single dose (90 mg) of calf lung surfactant extract (CLSE) by intratracheal instillation. The frequency and severity of RDS were assessed with use of a simple radiographic scoring system in which pulmonary parenchymal densities and the prominence of the air-bronchogram effect were used as indicators of widespread atelectasis. Radiographs were obtained in surfactant-treated and control infants within the first 90 minutes of life as part of an initial evaluation of their pulmonary status. Subsequent examinations were performed at less than 24 hours and less than 48 hours of age. Radiographic assessment of lung disease compared consistently with coordinated data on oxygen and mean airway pressure requirements of the infants. Both indicated a significantly decreased frequency and severity of RDS in the infants treated with surfactant. The results provide supporting evidence of the effectiveness of exogenous lung surfactant replacement in mitigating RDS in very premature infants.