Cardiovascular autonomic dysfunction in normotensive awake subjects with obstructive sleep apnoea syndrome

Cardiovascular autonomic function in normotensive awake patients with obstructive sleep apnoea syndrome was studied in 21 normotensive (mean age 48 ± 14 years), drug-free men with obstructive sleep apnoea syndrome. Cardiovascular reflex tests with continuous blood pressure monitoring and biochemical indices were performed the morning after a standard polygraphic sleep recording. A group of 20 agematched (mean age 49 ± 19 years) normal subjects was used as controls. The obstructive sleep apnoea syndrome patients showed higher heart rate and noradrenaline plasma levels (p < 0.05) at rest and a higher blood pressure response to head-up tilt (p < 0.01), suggesting sympathetic overactivity. Respiratory arrhythmia, baroreflex sensitivity index and Valsalva ratio were significantly lower in the obstructive sleep apnoea syndrome group (p < 0.01) whereas the decrease in heart rate induced by the cold face test was significantly higher (p < 0.05) showing a blunting of reflexes dependent on baroreceptor or pulmonary afferents with normal or increased cardiac vagal efferent activity. These abnormalities in autonomic regulation may predispose obstructive sleep apnoea syndrome patients to cardiovascular complications like hypertension and cardiac arrhythmias.     

Physiological Effects of Mental Stress and Orthostasis in Young Insulin-Dependent Diabetic Patients

ABSTRACT. The effects of procedures which stimulate sympathetic activity, viz. mental stress induced by a colour-word conflict test (CWT) for 20 min, and orthostasis (ORT) for 8 min were studied in 8 young (16-20 yr) insulin-dependent diabetes mellitus (IDDM) patients and 9 age and sex-matched healthy controls. The IDDM patients showed no signs of neuropathy or retinopathy and their mean HbA_1c value was 8.4 ±0.6% (normal value < 5.0 %). Blood pressure and heart rate increased significantly during CWT and ORT in both groups. The changes in systolic blood pressure and heart rate were comparable in both groups during CWT; the IDDM group showed a higher ( p < 0.05) heart rate after 8 min of orthostasis, however. CWT and ORT elicited equivalent increases in noradrenaline in venous plasma in both groups ( p < 0.05), but the IDDM patients had 50% lower values ( p < 0.01) at rest, during CWT and at rest after CWT than controls. CWT and ORT evoked equivalent plasma adrenaline increases in both groups. The lipolysis marker, plasma glycerol, was about 40 % lower ( p < 0.05) in the IDDM group before and after CWT. Yet, mental stress evoked equivalent increases in glycerol levels ( p < 0.01) in both groups. These findings indicate that sympathetic activity in the young diabetic patients without signs of neuropathy may be blunted.     

Natural killer cell activity and CSF monoamine metabolites in suicide attempters

The aim of this study was to investigate markers of serotonin and immune function in suicidal patients. Cytotoxic activity of natural killer cells (NK) and CD16 lymphocytes were studied in 28 suicide attempters and 26 healthy controls, and related in patients to 5-hydroxyindoleacetic acid (5-HIAA) in cerebrospinal fluid (CSF). Patients with CSF 5-HIAA below the median had significantly lower NK cell activity than other patients. CD16 cell frequency was significantly lower in patients than in controls, and patients also tended to have lower NK cell cytotoxicity than healthy controls. There were no statistically significant correlations between 4-hydroxy-3methoxyphenyl glycol (HMPG), homovanillic acid (HVA), CSF cortisol and NK cell activity. The results support the hypothesis of compromised immune function in suicidal patients with evidence of disordered serotonin function.     

Effects of synchronization in the pacemaker during high-frequency atrial stimulation

I. M. Sechenov Medical Academy, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR A. D. Ado.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 111, No. 5, pp. 454–456, May, 1991.     

Preoperative metoprolol improves cardiovascular stability and reduces oxygen consumption after thoracotomy

Background : Increased sympathetic activity perioperatively and associated cardiovascular effects play a central role in cardiovascular complications. High thoracic epidural blockade attenuates the sympathetic response, but even with complete pain relief, haemodynamic and endocrine responses are still present. Beta–adrenoceptor blockade is effective in situations with increased sympathetic activity. This study was designed to evaluate the perioperative haemodynamic effect of preoperative βblockade and its influence on the haemodynamic aspects of the surgical stress response.
Methods : Thirty–six otherwise healthy patients undergoing elective thoracotomy for lung resection were randomised doubleblinded to receive either 100 mg metoprolol or placebo preoperatively. Anaesthesia was combined high thoracic epidural block and general anaesthesia. The epidural analgesia was continued during recovery. Patients were monitored with ECG, pulse oximetry, invasive haemodynamic monitoring, arterial blood gases and electrolytes.
Results : After induction of anaesthesia the mean arterial pressure (MAP) decreased in both groups, and decreased further in the placebo group after initiation of the epidural block. The heart rate (HR) was slightly less throughout the observation period after metoprolol. Peroperatively, the only difference in measured haemodynamics was a marginally higher MAP after metoprolol. Postoperative cardiac index (CI) was lower with a lower variability and cardiac filling pressures were slightly higher in the metoprolol group. The oxygen consumption index was higher after placebo throughout the observation period, with no difference in the oxygen delivery.
Conclusion. We found that preoperative β–blockade during combined general anaesthesia and high thoracic epidural blockade stabilised perioperative HR and CI and decreased total oxygen consumption.     

Acetylcholinesterase Adaptation to Voluntary Wheel Running is Proportional to the Volume of Activity in Fast, but not Slow, Rat Hindlimb Muscles

Chronic enhancement of neuromuscular activity by forced exercise training programmes results in selective adaptation of the G₄ acetylcholinesterase (AChE) molecular form in hindlimb fast muscles of the rat, with only minor and non-selective AChE changes in the soleus. In order to shed further light on the physiological significance of this G₄ adaptation to training, we turned to a voluntary exercise model. The impact of 5 days and 4 weeks of voluntary wheel cage running on AChE molecular forms was examined in four hindlimb fast muscles and the slow-twitch soleus from two rat strains. Inbred Fisher and Sprague– Dawley rats, placed in live-in wheel cages, exercised spontaneously for distances which progressively increased up to an average of ∼3 and 18 km/day, respectively, by the end of week 4. Fast muscles responded to this voluntary activity by massive G₄ increases (up to 420%) with almost no changes in A₁₂, so that by week 4 the tetramer became the main AChE component of these muscles. The additional G₄ was composed primarily of amphiphilic molecules, suggesting a membrane-bound state. The G₄ content of fast muscles was highly correlated with the distance covered by the rats during the 5 days before they were killed ( r = 0.850-0.879, P < 0.001 in three muscles). The soleus muscle, in turn, responded to wheel cage activity by a marked selective reduction of its asymmetric forms—up to 45% for A₁₂. This A₁₂ decline, already maximal by day 5 of wheel cage running, showed no relationship with the distance covered. The present results constitute strong new evidence suggesting that the role of AChE in neuromuscular transmission is not limited solely to the rapid inactivation of just-released acetylcholine.     

Low peripheral plasma renin activity as a critical marker in pediatric hypertension

In evaluating hypertensive children and adolescents, the etiological considerations should include a set of inherited disorders that share very low plasma renin activity (PRA) as a common feature. In particular among these disorders, glucocorticoid remediable aldosteronism (GRA) appears to be emerging as an important etiology of hypertension in the pediatric population. We report the evaluation of a 9-year-old Caucasian girl who presented with severe hypertension and a strong family history of early-onset hypertension. Her suppressed PRA, her family history, and her failure to respond to conventional antihypertensive therapy raised GRA as a potential etiology. The diagnosis was confirmed by an elevated ratio of urinary 18-oxotetrahydrocortisol to urinary tetrahydroaldosterone and genetic testing, which demonstrated the chimeric gene duplication. The molecular pathogenesis of GRA and the clinical implications are reviewed. Received May 15, 1996; received in revised form and accepted September 16, 1996