Beta-adrenergic blockade in stress protection. Limited effect of metoprolol in psychological stress reaction

Physiological reactivity to acute mental stress in essential hypertension-a systematic review

Objective

Exaggerated physiological reactions to acute mental stress (AMS) are associated with hypertension (development) and have been proposed to play an important role in mediating the cardiovascular disease risk with hypertension. A variety of studies compared physiological reactivity to AMS between essential hypertensive (HT) and normotensive (NT) individuals. However, a systematic review of studies across stress-reactive physiological systems including intermediate biological risk factors for cardiovascular diseases is lacking.

Methods

We conducted a systematic literature search (PubMed) for original articles and short reports, published in English language in peer-reviewed journals in November and December 2022. We targeted studies comparing the reactivity between essential HT and NT to AMS in terms of cognitive tasks, public speaking tasks, or the combination of both, in at least one of the predefined stress-reactive physiological systems.

Results

We included a total of 58 publications. The majority of studies investigated physiological reactivity to mental stressors of mild or moderate intensity. Whereas HT seem to exhibit increased reactivity in response to mild or moderate AMS only under certain conditions (i.e., in response to mild mental stressors with specific characteristics, in an early hyperkinetic stage of HT, or with respect to certain stress systems), increased physiological reactivity in HT as compared to NT to AMS of strong intensity was observed across all investigated stress-reactive physiological systems.

Conclusion

Overall, this systematic review supports the proposed and expected generalized physiological hyperreactivity to AMS with essential hypertension, in particular to strong mental stress. Moreover, we discuss potential underlying mechanisms and highlight open questions for future research of importance for the comprehensive understanding of the observed hyperreactivity to AMS in essential hypertension.

Alpha-Adrenergic Mechanisms in the Cardiovascular Hyperreactivity to Norepinephrine-Infusion in Essential Hypertension

AIMS

Essential hypertension (EHT) is characterized by cardiovascular hyperreactivity to stress but underlying mechanism are not fully understood. Here, we investigated the role of α-adrenergic receptors (α-AR) in the cardiovascular reactivity to a norepinephrine (NE)-stress reactivity-mimicking NE-infusion in essential hypertensive individuals (HT) as compared to normotensive individuals (NT).

METHODS

24 male HT and 24 male NT participated in three experimental trials on three separate days with a 1-min infusion followed by a 15-min infusion. Trials varied in infusion-substances: placebo saline (Sal)-infusions (trial-1:Sal+Sal), NE-infusion without (trial-2:Sal+NE) or with non-selective α-AR blockade by phentolamine (PHE) (trial-3:PHE+NE). NE-infusion dosage (5µg/ml/min) and duration were chosen to mimic duration and physiological effects of NE-release in reaction to established stress induction protocols. We repeatedly measured systolic (SBP) and diastolic blood pressure (DBP) as well as heart rate before, during, and after infusions.

RESULTS

SBP and DBP reactivity to the three infusion-trials differed between HT and NT (p's≤.014). HT exhibited greater BP reactivity to NE-infusion alone compared to NT (trial-2-vs-trial-1: p's≤.033). Group differences in DBP reactivity to NE disappeared with prior PHE blockade (trial-3: p=.26), while SBP reactivity differences remained (trial-3: p=.016). Heart rate reactivity to infusion-trials did not differ between HT and NT (p=.73).

CONCLUSION

Our findings suggest a mediating role of α-AR in DBP hyperreactivity to NE-infusion in EHT. However, in SBP hyperreactivity to NE-infusion in EHT, the functioning of α-AR seems impaired suggesting that the SBP hyperreactivity in hypertension is not mediated by α-AR.

Talking effect and white coat phenomenon in hypertensive patients

Both white coat effect (the tendency of blood pressure to rise during a medical visit) and talking effect were analyzed in 42 patients with essential hypertension. Blood pressure was measured during the clinic visit and over the subsequent 24-hour ambulatory period, with the physician performing 49 +/- 4 measurements for each patient. Three silent periods and two talking periods (stress and relaxation) were randomly allocated in a crossover design and studied, using analysis of variance. During the initial 11-minute silent period, systolic/diastolic blood pressures increased by 6 mm Hg/5 mm Hg. During the subsequent talking periods, these variations were significantly greater: +22 mm Hg/+17 mm Hg. Measures of systolic/diastolic blood pressure were higher during stressful talking than during relaxed talking. The talking and its emotional contents seemed to explain 70% of the white coat phenomenon. To minimize the white coat phenomenon in the clinic, physicians, nurses, and clinicians are advised to measure blood pressure during an initial period of silence.

Neuropsychological consequences of antihypertensive medication use

A growing proportion of the general population is being prescribed antihypertensive medications for the long-term treatment of essential hypertension. Untreated hypertensive individuals exhibit some neuropsychological performance decrements, and numerous researchers have sought to determine whether drug therapy for hypertension worsens, improves, or leaves unaltered objectively measured cognitive skills. These issues may be especially important in the elderly, among whom both high blood pressure and compromised cognitive function are common. In this review, we collate the findings of more than 50 clinical studies according to class of antihypertensive medication studied and domains of neuropsychological performance assessed. Special attention is given to investigations of elderly subjects, and a critical summary is provided.

Cardiovascular reactivity to psychosocial stressors. A review of the effects of beta-blockade

Fifty-nine studies examining the effects of beta-blockers on cardiovascular reactivity to psychosocial stressors are reviewed. Across all classifications of beta-blockers, heart rate reactivity was reduced (p less than 0.0001), while there were no significant changes in either systolic or diastolic blood pressure reactivity. Nonselective beta-blockers were more often associated with a reduction in heart rate reactivity than selective blockers (p less than 0.05). There was no evidence that drug lipophilicity or intrinsic sympathomimetic activity differentially affected blood pressure or heart rate reactivity; nor was there evidence that the reactivity of hypertensive subjects was differentially affected by blockade compared to the reactivity of normotensive subjects. While beta-blockers are effective in reducing resting blood pressure, they are not effective agents in reducing blood pressure reactivity to mild psychosocial stressors.

Behavioral performance effects of antihypertensive drugs: human and animal studies

Antihypertensive drug treatments have been reported in clinical investigations to produce adverse effects to a degree that causes hypertensive patients to discontinue medication. Many of the debilitating effects reported by patients appear to be of central nervous system origin, such as sedation, fatigue, memory loss and sensorimotor disturbances. Human and animal laboratory studies in the past two decades have been characterizing the psychotropic effects of antihypertensive medications with use of a wide range of behavioral techniques. Antihypertensive drug classes covered in this review are beta-adrenergic blocking agents, alpha-adrenergic agonists, diuretics, angiotensin-converting enzyme inhibitors and calcium channel blockers. While findings in animal studies show generally greater behavioral impairments after administration of alpha-adrenergic agonists in comparison with other drug classes, the few laboratory studies conducted with hypertensive subjects present a confusing picture. A need for further laboratory research with hypertensive subjects and, study of antihypertensive drug combinations is discussed.

Assay of catecholamines and dihydroxyphenylethyleneglycol in human plasma and its application in orthostasis and mental stress

A high performance liquid chromatographic method involving electrochemical detection is described which permits the assay of noradrenaline (NA), adrenaline (A), dopamine (DA), and dihydroxyphenylethyleneglycol (DOPEG) in human plasma and brings about analytical recoveries of 70% and more. This method was used to assess the effects of graded orthostasis and mental stress on the plasma levels of these catechols. Orthostasis elicited increases in plasma NA and DOPEG, but did not cause any change in plasma A and DA. The increases in NA and DOPEG were dependent on the degree of orthostasis and correlated closely (rs = 0.724; n = 30, P less than 0.001). Pretreatment with desipramine abolished the DOPEG response to standing, indicating that orthostasis - induced increases in plasma DOPEG are presynaptic in origin. Mental stress evoked pronounced increases in plasma A, less pronounced increases in plasma NA and no changes in plasma DA and DOPEG. Hence, the simultaneous measurement of plasma NA and DOPEG may help to distinguish between various types of activation of the sympathetic nervous system.

Responses to mental stress and physical provocations before and during long term treatment of hypertensive patients with beta-adrenoceptor blockers or hydrochlorothiazide

1 Cardiovascular and sympatho-adrenal responsiveness to mental stress (CWT; a colour word test), orthostatic testing (ORT) and a cold pressor test (CPT) were examined in three groups of hypertensive patients (n = 14-16) before and after 6 months treatment with metoprolol (243 +/- 26 mg daily), propranolol (149 +/- 16 mg daily) or hydrochlorothiazide (50 +/- 8 mg daily) in an open trial design. 2 Treatment reduced outpatient blood pressures in the three groups similarly (from approximately 155/102 to 135/90 mm Hg). During treatment resting blood pressures in the laboratory were clearly reduced by beta-adrenoceptor blockade but not by thiazide treatment. Metoprolol and propranolol caused similar reductions of basal heart rates and plasma glycerol levels, whereas only propranolol reduced cyclic AMP concentrations in plasma. 3 Before treatment CWT and CPT increased systolic and diastolic blood pressures by about 30%. Heart rate increased by about 30 beats min-1 during CWT and 10-15 beats min-1 during CPT and ORT. Small venous plasma adrenaline responses were evoked by all tests, whereas noradrenaline was elevated mainly by CPT and ORT. Dopamine levels did not change. 4 Heart rate responses to all stressors were markedly and similarly reduced, whereas blood pressure responses were essentially unchanged during metoprolol or propranolol treatment. In the thiazide group circulatory responses to CWT were slightly attenuated, whereas responses to ORT and CPT were unchanged. 5 The systolic blood pressure levels were reduced throughout the test session in all three groups, although less so in the hydrochlorothiazide group. Both beta-adrenoceptor antagonists clearly reduced diastolic blood pressure and heart rate levels at rest and during stress, whereas thiazide treatment caused no significant changes in these respects. 6 The rate pressure product, which increased by 80-100% in response to CWT before treatment, was more markedly reduced by beta-adrenoceptor blockade than by thiazide treatment both at rest and during stress. 7 Self ratings (visual analogue scales) of stress and irritation were increased by CWT in a similar fashion before and during treatment in all groups. beta-adrenoceptor blockade was associated with higher subjective ratings of tiredness at rest, but not after CWT. Performance in the CWT increased slightly more in the thiazide group. The physiological responses to CWT were not correlated to the subjective responses.(ABSTRACT TRUNCATED AT 400 WORDS)

Pharmacologic aspects of cardioselectivity in a beta-blocking drug

Beta 2 adrenoceptors have been subdivided into beta 1 and beta 2 receptors, both by the varying response of different tissues to sympathomimetic amines and, more recently, by radioligand-binding techniques. It would appear that beta 1 receptors occur predominantly in the heart, whereas beta 2 receptors are found in lungs, peripheral blood vessels and uterus, and are also involved with glycogenolysis and glucagon and insulin secretion. In addition, the distribution of beta 1 receptors appears to relate to the density of sympathetic innervation of an organ or tissue, but tissues without sympathetic innervation are found to contain beta 2 receptors. Thus, beta 1 adrenoceptors may be considered as physiologically innervated receptors mediating responses to neuronally released norepinephrine, and beta 2 receptors as mediating responses to circulating catecholamines, particularly epinephrine. Radioligand-binding studies have also shown that the heart contains beta 2 receptors and the lung beta 1 receptors, but these are in the minority, and their role has not been identified. For many years, cardioselective beta 1-adrenoceptor antagonists have been available. This was considered to be a dose-dependent phenomenon but recent evidence has cast doubt on the concept that cardioselectivity is lost during dose increases within the therapeutic range. Nevertheless, even small doses of cardioselective drugs may show some beta 2-receptor antagonism, and may have adverse effects on patients with obstructive airways disease. Finally, nonselective drugs may result in a diastolic pressor effect in the presence of circulating catecholamines in contrast to the "vascular sparing" seen with cardioselective drugs.

Multicenter clinical evaluation of long-term efficacy and safety of labetalol in treatment of hypertension

The long-term efficacy and safety of labetalol, an antihypertensive agent with combined beta- and alpha-blocking activity, were evaluated alone (number = 193) and in combination with a diuretic (number = 144) in an open-label multicenter trial of 337 hypertensive patients aged 21 to 75 years, including initially 205 (61 percent) men and 219 (65 percent) Caucasians. There were 219 (65 percent) mild, 85 (25 percent) moderate, and 33 (10 percent) severe hypertensive patients. Labetalol (100 to 1,200 mg twice a day) alone or in combination with a diuretic reduced the mean standing blood pressure by 13/11 and 25/16 mm Hg to 135/88 and 130/91 mm Hg, respectively (p less than 0.01), and supine blood pressure by 6/7 and 18/13 mm Hg to 141/86 and 138/90 mm Hg (p less than 0.01), respectively. Blood pressure reductions observed at one month were maintained after one year; 206 (62 percent) patients had 10 mm Hg or greater reductions and 184 (56 percent) patients were maintained at diastolic blood pressures less than 90 mm Hg. Most frequently reported drug-related side effects included fatigue (14 percent), dizziness (12 percent), nausea (11 percent), nasal stuffiness (8 percent), headache (4 percent), and male sexual dysfunction (14 percent). Side effects were generally of mild to moderate intensity and often transient. In addition, in 27 (8 percent) patients reversible asymptomatic transaminase elevations to greater than twice normal developed at some time during the study. In 13 (4 percent) patients these alterations resolved during continued labetalol therapy, but in five (2 percent) patients these marked elevations led to discontinuation of the drug. A total of 32 (9.5 percent) patients were terminated prematurely due to side effects (most commonly genitourinary or gastrointestinal) possibly attributable to the drug. These findings indicate that labetalol with or without a diuretic is a potentially effective, safe, and relatively well-tolerated long-term antihypertensive therapy.

Medroxalol combined with hydrochlorothiazide in the treatment of hypertension

The antihypertensive effect and safety of hydrochlorothiazide administration as a single drug and together with medroxalol were determined in 20 patients with primary hypertension. Following two biweekly intervals on placebo and hydrochlorothiazide, medroxalol was started at 100 mg three times a day and titrated against blood pressure response up to a maximum of 300 mg three times a day. In nine patients the effect of the single and the combined drug therapy on blood pressure during isometric handgrip exercise, on plasma renin activity, and on plasma catecholamines and their deaminated metabolites was investigated. The administration of hydrochlorothiazide was associated with a significant decrease in blood pressure, but heart rate did not change. The addition of medroxalol produced a substantial decrease in blood pressure and heart rate in both the recumbent and upright positions (P less than 0.001). Due to careful titration of medroxalol, orthostatic hypotension was observed only in one patient. Neither hydrochlorothiazide alone nor the combined drug regimen prevented or diminished the rise in blood pressure with exercise. Although plasma renin activity decreased during the combined drug therapy, there was no correlation between the initial levels or the change in plasma renin activity and the extent of decrease in blood pressure. The concentration of plasma epinephrine increased during the combined drug period, whereas catecholamine metabolites increased significantly during both periods of the study. It is concluded that medroxalol combined with hydrochlorothiazide constituted a potent and safe antihypertensive therapy for the duration of the present study.

Effect of diuretics and calcium antagonists on circulatory parameters and plasma catecholamines during mental stress

In a model of mental stress the influence of nifedipine and hydrochlorothiazide on stress-induced changes in blood pressure, heart rate, and plasma catecholamines was studied in normal persons. The drugs were used to investigate whether substances with antihypertensive but no particular sympatholytic properties were capable of suppressing emotionally induced stress reactions. In all subjects blood pressure and heart rate increased significantly during mental stress, and this effect was not inhibited either by nifedipine or hydrochlorothiazide. In the hydrochlorothiazide group plasma noradrenaline levels were significantly higher than in controls in the resting state and during the stress reaction, whereas in the nifedipine group no difference was observed. It is concluded that nifedipine or hydrochlorothiazide do not inhibit emotional stress reactions in normotensive persons.

Circulatory changes during mental stress in tetraplegic and paraplegic man

In ten patients suffering from complete chronic cervical spinal cord lesion, the effect of mental stress was studied. Before, during and after stress, variations of blood pressure, heart rate and plasma catecholamines were tested. The study showed a loss of hemodynamic reactions under mental stress in tetraplegics, namely the pressure response, the typical increase in heart rate and in plasma noradrenaline and adrenaline. It is concluded, that changes in sympathectomized man interfere with the acute hemodynamic stress reaction and impair the blood pressure homeostasis.

Effect of guanfacine on vigilance

1. In 20 patients suffering from mild hypertension (WHO classification I-II) the effect on vigilance was studied under double-blind conditions. Ten patients were given guanfacine 2 mg daily and ten others a placebo preparation. 2. Before the study and following 2 weeks' medication a battery of tests was applied in which the reaction time and attention were subjected to comparative analysis. The variation in blood pressure and heart rate under mental stress conditions was also tested. 3. The study shows a non-significant reduction in blood pressure in the guanfacine group without the parameters of vigilance being affected. Under mental stress, there was no impairment of haemodynamic reactions. 4. It is concluded that guanfacine, at the selected dose of 2 mg daily, has no apparent effect on the vigilance of hypertensive patients.