Circulating adrenaline and blood pressure: the metabolic effects and kinetics of infused adrenaline in man

Effect of Nasal Submucosal Injection of Low-concentration Epinephrine on Visual Field Visualization in Endoscopic Sinus Surgery: A Systematic Review and Meta-analysis

Objective: To determine whether nasal submucosal injection of low-concentration epinephrine improved the surgical field visualization and physician satisfaction compared to placebo or without intervention. Methods: A literature search of PubMed, Scopus, Web of Science, Cochrane library, China National Knowledge Infrastructure, and Wanfang Database was conducted from inception to January 10, 2023. This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Meta-analyses were performed using Review Manager (RevMan version 5.3; the Cochrane Collaboration). Quality was assessed by 2 reviewers using the Cochrane Risk of Bias Tool. And we used funnel plots to visually assess the risk of publication bias. Results: We included a total of 11 studies with 492 patients, all of which were randomized controlled trials. Among the studies, 4 had a low risk of bias, 4 had a moderate risk of bias, and 3 had a high risk of bias. Five studies reported visual bleeding grade in the surgical field (P = 0.07) and total blood loss (P = 0.16), 8 studies reported preoperative baseline heart rate (P = 0.58) and baseline mean arterial pressure (MAP) (P = 0.78), and 9 studies reported intraoperative heart rate (P = 0.27) and MAP (P = 0.56), which showed no significant differences in these parameters between the 2 groups. None of these outcomes were statistically significant between the epinephrine group and the control group. Conclusion: There is insufficient evidence to support the nasal submucosal application of low-concentration epinephrine to improve surgical field dryness and reduce total surgical bleeding.

Combination Topical Epinephrine and Non-steroidal Inflammatory Drugs in the Prevention of Post-ERCP Pancreatitis: A Systematic Review

BACKGROUND

The utility of combination rectal NSAID and topical epinephrine (EI) or rectal NSAID and normal saline (SI) sprayed on duodenal papilla in the prevention of post-ERCP pancreatitis (PEP) has been studied but results have been conflicting.

AIMS

To evaluate the benefit of using combination prophylaxis in preventing PEP.

METHODS

A literature search was performed using Scopus, PubMed/MEDLINE, and Cochrane databases in May 2021. Randomized controlled trials (RCTs) involving adults patients who underwent ERCP and received EI versus SI were eligible for inclusion. The pooled effect was expressed as odds ratio (OR) to assess the rate of PEP, severity of PEP, and specific adverse events. The results were pooled using Reviewer Manager 5.4 software.

RESULTS

Six RCTs involving 4016 patients were included in the final analysis. The EI group did not demonstrate any significant benefit over SI group in preventing PEP (OR = 1.00, 95% CI [0.68, 1.45], P = 0.98), irrespective of gender or the epinephrine concentration used. The tests for subgroup differences were not statistically significant with P-values of 0.66 and 0.28, respectively. The addition of topical epinephrine to rectal NSAID did not improve the rate of moderate to severe PEP (OR = 0.94, P = 0.86) or PEP in high-risk patients (OR = 1.14, 95%, P = 0.73). The rates of infection, including cholangitis and sepsis (OR = 0.63, P = 0.07), gastrointestinal bleeding (OR = 1.25, P = 0.56) and procedure-related death (OR = 0.71, P = 0.59) were similar between both groups.

CONCLUSION

The addition of topical epinephrine did not demonstrate any benefit over rectal NSAID alone in preventing PEP or reducing other procedure-related adverse events.

A Non-inferiority Trial: Safety and Efficacy of Topical 1:1000 versus 1:10 000 Epinephrine in Sino-nasal Surgeries

OBJECTIVE

This study aimed to test the non-inferiority of topical 1:1000 epinephrine compared to topical 1:10 000 with regard to intraoperative hemodynamic stability, and to determine whether it produced superior visibility conditions.

METHODS

A single-blinded, prospective, cross-over non-inferiority trial was performed. Topical 1:1000 or topical 1:10 000 was placed in 1 nasal passage. Hemodynamic parameters (heart rate, systolic and diastolic blood pressures, and mean arterial pressure) were measured prior to insertion then every minute for 10 minutes. This was repeated in the contralateral nasal passage of the same patient with the alternate concentration. The surgeon graded the visualization of each passage using the Boezaart Scale. The medians of the greatest absolute change in parameters were compared using a Wilcoxon Rank-Signed test and confidence intervals were calculated using a Hodges-Lehman test. The non-inferiority margin was pre-determined at 10 bpm for heart rate and 10 mmHg for blood pressures. A Wilcoxon Rank-Signed test was used to assess superiority in visualization.

RESULTS

Thirty-two patients were enrolled and after exclusions, nineteen were assessed (mean age = 35.63 ± 12.49). Differences in means of greatest absolute change between the 2 concentrations were calculated (heart rate = 2.49 ± 1.20; systolic = -1.51 ± 2.16; diastolic = 2.47 ± 1.47; mean arterial pressure = 0.07 ± 1.83). In analyses of medians, 1:1000 was non-inferior to the 1:10 000. There was a significant difference (-0.58 ± 0.84; P = .012) in visualization in favor of topical 1:1000.

CONCLUSION

Topical 1:1000 epinephrine provides no worse intraoperative hemodynamic stability compared to topical 1:10 000 but affords superior visualization and should be used to optimize surgical conditions.

Rectal Indomethacin and Spraying of Duodenal Papilla With Epinephrine Increases Risk of Pancreatitis Following Endoscopic Retrograde Cholangiopancreatography

BACKGROUND & AIMS

Rectal indomethacin and spraying of the duodenal papilla with epinephrine might reduce the incidence of pancreatitis after endoscopic retrograde cholangiopancreatography (ERCP). We performed a randomized trial to compare the effects of the combination of indomethacin and epinephrine (IE) vs indomethacin plus saline (IS) in prophylaxis of post-ERCP pancreatitis (PEP).

METHODS

We performed a double-blind trial at 10 centers in China, from February 2017 to October 2017, of 1158 patients with native papilla undergoing ERCP. The patients were assigned randomly to groups given IE (n = 576) or IS (n = 582). All patients received a single dose of rectal indomethacin within 30 minutes before ERCP; 20 mL of dilute epinephrine (IE group) or saline (IS group) then was sprayed on the duodenal papilla at the end of ERCP. The primary outcome was the incidence of overall PEP. Data were analyzed on an intention-to-treat principle.

RESULTS

The study was terminated at the interim analysis for safety concerns and futility. The groups had similar baseline characteristics. PEP developed in 49 patients in the IE group (8.5%) and in 31 patients in the IS group (5.3%) (relative risk, 1.60, 95% CI, 1.03-2.47; P = .033). There were no significant differences between groups in proportions of patients with postsphincterotomy bleeding (2.1% in the IE group and 1.5% in the IS group) and biliary infection (1.2% in the IE group and 2.2% in the IS group).

CONCLUSIONS

In a randomized trial, we found the combination of rectal indomethacin with papillary epinephrine spraying increased the risk of PEP compared with indomethacin alone. Spray epinephrine should not be used with rectal indomethacin for prevention of post-ERCP pancreatitis. ClincialTrials.gov no: NCT03057769.

Early Epinephrine Improves the Stabilization of Initial Post-resuscitation Hemodynamics in Children With Non-shockable Out-of-Hospital Cardiac Arrest

Background: In children with non-shockable out-of-hospital cardiac arrest, early epinephrine (EE) might help to establish the return of spontaneous circulation (ROSC) and be associated with survival. In the present study, we aimed to analyze the effects of EE on outcomes and post-resuscitation hemodynamics in children with non-shockable OHCA. Methods: This was a retrospective analysis of data from 216 children (<19 years) who had suffered non-traumatic and non-shockable OHCA and received epinephrine for resuscitation (Jan 1, 2006-Dec 31, 2014). Demographics, pre-/in-hospital information, and the time to the first dose of epinephrine were recorded. Early post-resuscitation hemodynamics (the first hour after sustained ROSC), survival and good neurological outcomes (Pediatric Cerebral Performance Category Scales 1 or 2) were analyzed by the time to epinephrine-classified as early (EE): <15 min, intermediate (IE): 15-30 min, or late (LE): >30 min. Results: Twenty-eight (13.0%) children survived to discharge, but only 17 (7.9%) had good neurological outcomes. In all, 41 (18.9%) children received EE; in comparison to IE and LE, this was significantly associated with tachycardia (73.9%) in the post-resuscitation period (p < 0.05). Tachycardia (OR: 7.41, 95% CI: 1.96-29.31) and hypertension (OR: 6.03, 95% CI: 1.85-13.77) were significantly associated with EE after adjusting for confounding factors. EE was also significantly associated with better overall outcomes than ME and LE (any ROSC, sustained ROSC, survival to the intensive care unit, admission, survival to discharge and good neurological outcomes, all p < 0.05). Conclusions: EE helped to establish ROSC but was also associated with more tachycardia and hypertension in the early post-resuscitation period. In children with non-traumatic and non-shockable OHCA, EE was associated with a higher survival rate and better neurological outcomes than were ME and LE.

Adrenaline: insights into its metabolic roles in hypoglycaemia and diabetes

Adrenaline is a hormone that has profound actions on the cardiovascular system and is also a mediator of the fight-or-flight response. Adrenaline is now increasingly recognized as an important metabolic hormone that helps mobilize energy stores in the form of glucose and free fatty acids in preparation for physical activity or for recovery from hypoglycaemia. Recovery from hypoglycaemia is termed counter-regulation and involves the suppression of endogenous insulin secretion, activation of glucagon secretion from pancreatic α-cells and activation of adrenaline secretion. Secretion of adrenaline is controlled by presympathetic neurons in the rostroventrolateral medulla, which are, in turn, under the control of central and/or peripheral glucose-sensing neurons. Adrenaline is particularly important for counter-regulation in individuals with type 1 (insulin-dependent) diabetes because these patients do not produce endogenous insulin and also lose their ability to secrete glucagon soon after diagnosis. Type 1 diabetic patients are therefore critically dependent on adrenaline for restoration of normoglycaemia and attenuation or loss of this response in the hypoglycaemia unawareness condition can have serious, sometimes fatal, consequences. Understanding the neural control of hypoglycaemia-induced adrenaline secretion is likely to identify new therapeutic targets for treating this potentially life-threatening condition.

Vascular access and drug therapy in pediatric resuscitation

Using the evidence brought together through the 2005 International Liaison Committee on Resuscitation evidence evaluation process and the subsequent 2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care, the role for specific drug therapy in pediatric cardiac arrest is outlined. The drugs discussed include epinephrine, vasopressin, calcium, sodium bicarbonate, atropine, magnesium, and glucose. The literature addressing how best to deliver these drugs to the critically ill child is also presented, specifically looking at the use of intraosseous and endotracheal drug therapy.

Inhibitory effects of neuropeptide Y on splanchnic glycogenolysis and renin release in humans

Neuropeptide Y (NPY) is stored in sympathetic nerves and NPY levels increase several times during exercise. NPY administration during prolonged exercise causes reduced splanchnic glucose production. To elucidate the effects of NPY on adrenaline (Adr)-stimulated splanchnic glycogenolysis these substances were infused to seven healthy subjects in the post-absorptive state. Blood samples were drawn from an arterial and a central hepatic vein catheter for determination of splanchnic blood flow, exchanges of metabolites and arterial levels of NPY, catecholamines, insulin, glucagon and renin in the basal state and during 20 min Adr infusion (0.1-0.3 nmol kg-1 min-1). After basal values were reached a 60 min NPY infusion was initiated. At 40 min of NPY infusion the Adr infusion was repeated. Adr alone increased splanchnic blood flow (41%, P < 0.01), arterial glucose concentration (29%, P < 0.001) and splanchnic glucose production (102%, P < 0.01). During the NPY infusion both splanchnic blood flow and arterial glucose fell (P < 0.05). Although the combined NPY and Adr infusion caused the same proportional increases in splanchnic blood flow, arterial glucose and splanchnic glucose production as with Adr alone the absolute values were lower (all P < 0.05). Arterial insulin as well as Adr and noradrenaline increased with the combined NPY-and Adr infusion as with Adr alone. Arterial plasma renin activity was 12% lower with the combined NPY and Adr-infusion compared to Adr infusion alone. These results indicate further an inhibitory effect of NPY on splanchnic glycogenolysis and suggest that NPY inhibits Adr-stimulated renin release.

Ageing, late-onset asthma and the beta-adrenoceptor

Late-onset asthma in old age is a common clinical problem. There are similarities between receptor and post-receptor beta 2-adrenoceptor abnormalities reported in young asthmatics and in elderly normal subjects. Recent evidence lends some support to the idea of the 'aging' beta 2-adrenoceptor as a contributory factor in the development of late-onset asthma, although questions of the validity of the peripheral mononuclear cell model and of receptor tachyphylaxis to intrinsic and extrinsic beta-adrenoceptor agonists remain unresolved. Further work should focus on in vivo studies of airway receptor function and on beta 2-adrenoceptor-mediated pathways other than smooth muscle-related bronchoconstriction.

Dobutamine increases heart rate more than epinephrine in patients recovering from aortocoronary bypass surgery

To determine whether epinephrine might prove to be a cost-effective substitute for dobutamine, two 8-minute infusions of either epinephrine (10 and 30 ng/kg/min, n = 28) or dobutamine (2.5 and 5 micrograms/kg/min, n = 24) were administered to 52 patients recovering in the intensive care unit (ICU) after aortocoronary bypass (CABG) surgery. At the higher dose, both drugs significantly (P < .05) increased cardiac index (CI), epinephrine from 2.8 +/- 0.1 at baseline to 3.3 +/- 0.1 L/min/m2, and dobutamine from 3.2 +/- 0.1 at baseline to 4.1 +/- 0.2 L/min/m2. Epinephrine increased CI significantly less than dobutamine. Both drugs significantly increased stroke volume index (SVI), epinephrine from 32 +/- 1 at baseline to 36 +/- 1 mL/beat/m2, and dobutamine from 36 +/- 1 at baseline to 40 +/- 2 mL/beat/m2. At the higher dose, the effects of the two drugs on SVI were indistinguishable. On the other hand, while the higher dose of both drugs significantly increased heart rate (HR), epinephrine from 88 +/- 2 at baseline to 90 +/- 2 beats/min and dobutamine from 89 +/- 2 at baseline to 105 +/- 3 beats/min, the increase following the higher dose of dobutamine was significantly greater than that seen after epinephrine. Effects of the two drugs on mean arterial pressure, central venous pressure, pulmonary artery occlusion pressure, systemic vascular resistance, pulmonary vascular resistance, and left-ventricular stroke work did not significantly differ. Similar results were obtained in the subset of patients with baseline CI less than 3 L/min/m2 who more closely resembled patients who might acutely require inotropic drug administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between arterial and peripheral venous catecholamine plasma catecholamine concentrations during infusion of noradrenaline and adrenaline in healthy volunteers

Noradrenaline and adrenaline were infused IV at 5 different rates (0.01-0.2 micrograms.kg.min-1) for 30 min to volunteers. The plasma catecholamine concentrations were determined by HPLC and electro-chemical detection. At the highest infusion rate, the arterial and venous plasma concentrations of noradrenaline increased from 1.18 to 44.1 nmol.l-1 and from 1.14 to 31.9 nmol.l-1, respectively, and of adrenaline from 0.29 to 23.9 nmol.l-1 and from 0.28 to 19.3 nmol.l-1, respectively. The peripheral venous plasma concentration of noradrenaline averaged 76% of the arterial concentration, and of adrenaline it was 73%. There was a linear relationship between the peripheral venous and arterial plasma noradrenaline and adrenaline concentrations at therapeutic doses.

Accumulation and release of adrenaline, and the modulation by adrenaline of noradrenaline release from rabbit blood vessels in vitro

The accumulation of (-)-3H-adrenaline (3H-A) by rabbit isolated aorta was studied. In all experiments, monoamine oxidase and catechol-O-methyltransferase were inhibited by treatment with pargyline and 3',4'-dihydroxy-2-methyl-propiophenone, respectively. The relationship between the accumulation of 3H derived from 3H-A and the duration of incubation was linear. The 3H-accumulation after 3 h incubation was 22.5 ml/g. In reserpine-treated tissue, the 3H-accumulation levelled off after 30 min and was 8.5 ml/g after 3 h. The concentration of 3H-A or (-)-3H-noradrenaline (3H-NA) and the 3H-accumulation (ml/g) were inversely related. At 10(-8) M, the 1-hour accumulation of 3H derived from 3H-A and 3H-NA was 7.8 and 15.2 ml/g, respectively. With increasing concentrations the accumulation values approached each other. The accumulation of 3H derived from 3H-A by reserpine-treated tissue also showed an inverse relationship with concentration. The accumulation of 3H derived from 3H-A was dependent on the bath temperature. Storage of tissue (0-5 days in salt solution without equilibration with 95% O2/5% CO2; 4 degrees C) did not affect the accumulation of 3H derived from 3H-A. Thereafter (7-14 days), the accumulation decreased. The inhibitory potency (IC50; -log M) of desipramine, cocaine, propranolol, isoprenaline, and normetanephrine on accumulation of 3H derived from 3H-A was found to be 8.26; 6.50; 5.48; 4.88, and 4.02, respectively. The maximal degree of inhibition was almost the same for these drugs, while that of clonidine and corticosterone was 50 and 20%, respectively. In the presence of desipramine, either clonidine, corticosterone or isoprenaline reduces the accumulation of 3H derived from 3H-A. Ouabain and iodoacetic acid, but not sodium cyanide and 2,4-dinitrophenol, reduced the accumulation of 3H derived from 3H-A. Anoxia (95% N2/5% CO2; 37 degrees C; 1-24 h) did not alter the accumulation of 3H derived from 3H-A. Glucose deprivation alone or combined with anoxia markedly reduced the 3H-accumulation. The release of 3H-A from rabbit isolated aorta was studied. This release was compared with that of 3H-NA. The stimulation-evoked 3H-overflow from aorta preloaded with 3H-A decreased with repeated stimulation. In contrast, prestimulation enhanced subsequent stimulation-evoked 3H-overflows. For both 3H-amines, the 3H-overflow increased concomitantly to the same degree with the number of pulses. The time course of 3H-overflows with either 3H-A or 3H-NA was compared.(ABSTRACT TRUNCATED AT 400 WORDS)

Plethysmographic evaluation of the vascular effects of human calcitonin gene-related peptide in man

Calcitonin gene-related peptide (CGRP) is a neuropeptide with potent cardiovascular effects that include positive inotropic and chronotropic actions systemic vasodilation, and hypotension in animals and in man. The mechanism of action of CGRP is still, however, not clear, and in particular it is not known whether vasodilation by CGRP occurs by changes in cutaneous or in muscular blood flow, or both. The aim of the study was, therefore, to evaluate the cutaneous and muscular blood flow, at rest and after ischemic test, induced by an IV bolus 25 micrograms human CGRP infusion in 5 healthy normotensive volunteers, using a strain gauge plethysmographic procedure with venous occlusion. Human CGRP provoked a transient but significant decrease in systolic and diastolic blood pressure, associated with tachycardia, marked flushing, a significant increase in plasma noradrenaline, adrenaline, and cyclic AMP levels, and a slight, but significant, decrease in serum total calcium. Moreover, a significant increase in the carpal cutaneous blood flow at rest was observed, with no significant change in the lower extremity muscular blood flow at rest and after ischemic test. Finally human CGRP produced a significant increase in the venous partial O2 pressure and in the hematocrit and a significant decrease in the venous partial CO2 pressure. The results of the present study confirm the acute cardiovascular and metabolic effects of CGRP. In fact, hypotension, tachycardia, flushing, and the increased cutaneous blood flow indicate a systemic vasodilation by the neuropeptide, with a secondary sympathetic response, as documented by the augmented catecholamine and cyclic AMP plasma levels.

Platelet activation in nocturnal asthma

Platelet activation may be a factor in the bronchial hyperresponsiveness that characterises asthma. As hyperresponsiveness is increased at night, changes in platelet activation over 24 hours were related to the diurnal changes in peak expiratory flow and plasma catecholamine concentrations in five subjects with asthma and five normal subjects. The effect of muscarinic receptor blockade with intravenous atropine at 0400 hours on these measurements was also studied. Platelet activation, assessed as the ration of beta thromboglobulin to platelet factor 4, was highest when the peak expiratory flow rate was at its lowest in the asthmatic subjects. There was no correlation between platelet activation and plasma catecholamine concentrations. Intravenous atropine did not alter the ratio of beta thromboglobulin to platelet factor 4, suggesting that parasympathetic activity is not the cause of the increased platelet activation at night.

Adrenaline and nocturnal asthma

OBJECTIVE

To determine whether the nocturnal fall in plasma adrenaline is a cause of nocturnal asthma.

DESIGN

Double blind placebo controlled cross-over study. In the first experiment the nocturnal fall in plasma adrenaline at 4 am was corrected in 10 asthmatic subjects with an infusion of adrenaline after parasympathetic blockade with 30 micrograms/kg intravenous atropine. In the second experiment 11 asthmatic subjects showing similar variations in peak expiratory flow rate had the nocturnal fall in plasma adrenaline corrected by infusion before atropine was given.

PATIENTS

Asthmatic subjects with a diurnal variation in home peak expiratory flow rate of greater than 20% for at least 75% of the time in the two weeks before the study.

MAIN OUTCOME MEASURES

Peak expiratory flow rate and plasma adrenaline.

RESULTS

Correction of the nocturnal fall in plasma adrenaline at 4 am to resting 4 pm levels did not alter peak expiratory flow rate either before or after parasympathetic blockade with atropine.

CONCLUSION

A nighttime fall in plasma adrenaline is not a cause of nocturnal asthma.

Parasympathetic nervous system in nocturnal asthma

To investigate the effect of vagal blockade with atropine on nocturnal fall in peak expiratory flow rate 10 patients with asthma who had a diurnal variation in peak expiratory flow rate of greater than 20% were given 30 micrograms/kg of intravenous atropine or a placebo at 4 am and 4 pm. Vagal blockade caused significant bronchodilatation at 4 am and 4 pm (peak expiratory flow rate rose from 260 to 390 l/min at 4 am and 400 to 440 l/min at 4 pm) and significantly increased the pulse rate from 60 to 121 beats/minute at 4 am and from 76 to 122 beats/minute at 4 pm. Nocturnal asthma was almost totally reversed, implying that vagal mechanisms are fundamental in its pathophysiology. Other mechanisms--diurnal changes in plasma adrenaline concentration, the activity of non-adrenergic non-cholinergic nerves, and circadian rhythms of inflammatory mediator activity--may also be implicated.

Investigation of adrenomedullary function in atopic dermatitis

Adrenomedullary function in patients with atopic dermatitis was assessed by measurement of plasma levels of catecholamines (adrenalin and noradrenalin) and cyclic AMP in response to the stimuli of standing after lying supine, and a 5-min infusion of histamine in the standing position (i.e. histamine plus standing). Plasma clearance of adrenalin was examined by measurement of plasma catecholamine and cyclic AMP levels following a 15-min intravenous infusion of adrenalin in the supine position. Resting plasma levels of adrenalin, cyclic AMP and noradrenalin were not statistically different in atopic patients and normal controls. Standing or intravenous infusion of histamine in the standing position caused a rise in plasma catecholamine levels. Plasma adrenalin, cyclic AMP and noradrenalin levels in response to these stimuli and the rate of clearance of exogenous adrenalin from the plasma were not significantly different in patients with atopic dermatitis and in normal subjects.

Day-night patterns in bronchial patency and dyspnea: basis for once-daily and unequally divided twice-daily theophylline dosing schedules

Asthma typically worsens overnight. Although 24-hr variation in environmental conditions may contribute to the worsening of dyspnea at night, this does not fully explain day-night patterns of this disease. Circadian (about 24-hr) rhythms in bioprocesses which influence airways patency constitute major contributory factors. The nighttime exacerbation of asthma may represent the influence of circadian bioperiodicities in bronchial patency, airways hyperreactivity to acetylcholine, histamine and house dust, and altered levels of several plasma constituents such as cortisol, epinephrine, histamine and cyclic AMP.

Chronobiology and asthma. I. Day-night differences in bronchial patency and dyspnea and circadian rhythm dependencies

The symptoms of allergic asthmatic patients typically worsen during the night, especially during the early morning hours. Although 24-hour variations in the environment contribute to the intensification of the asthmatic condition nocturnally, environmental changes themselves do not fully explain the temporal aspects of this disease. Circadian (about 24-hour) rhythms in critical bioprocesses constitute significant contributory factors. The exacerbation of asthma during the night represents the changing status of biological functioning due to circadian rhythms in bronchial patency; airways hyperreactivity to acetylcholine, histamine, and house dust; and plasma cortisol, epinephrine, histamine, and cyclic AMP, among others.

Effects of exogenous catecholamines and exercise on plasma magnesium concentrations

Catecholamines and physical exercise are known to influence the metabolism of several minerals in man, but the effects on magnesium (Mg) have been scarcely investigated. In the present study, infusion of adrenaline (5 micrograms/min for 30 min followed by 10 micrograms/min for 30 minutes) significantly reduced the plasma Mg levels in healthy males. This effect was abolished by simultaneous infusion of propranolol. Noradrenaline had no such effect. In order to stimulate endogenous catecholamine release healthy males carried out physical exercise in four different ways: ergometer bicycling at maximum load until exhaustion with and without oral beta-blockade, ergometer bicycling with stepwise increasing load until exhaustion, isokinetic maximal exercise with one leg, with blood sampling both from the venous effluent of the exercising leg and the opposite resting arm and long-term (60 min) steady state ergometer bicycling at approximately 65% of estimated maximum capacity. During short-term (less than 20 min) intense exercise (i.e. experiments 1-3) the plasma Mg concentrations were increased. This was probably due to a reduction of plasma volume and to an influx of Mg to the vascular pool. During long-term steady state exercise (experiment 4) the Mg levels were not significantly affected but decreased during the first hour of recovery. These results suggest that both the beta-adrenergic system and muscular activity by itself affect Mg homeostasis.

The effects of epinephrine on norepinephrine release in essential hypertension

The effects of endogenous epinephrine (E), released by glucagon injection, and exogenously infused E on plasma norepinephrine (NE) and cardiovascular responses before and after beta-blockade were studied in patients with essential hypertension and in age-matched normotensive controls. The resting plasma NE and E levels were significantly higher in the borderline hypertensive subjects (NE: 251 +/- 21 pg/ml [SEM], p less than 0.005; E: 57 +/- 5, p less than 0.05, n = 18) than in controls (NE: 129 +/- 12; E: 39 +/- 5, n = 18). An intravenous injection of glucagon (1.0 mg) induced a transient rise of both plasma catecholamine levels and blood pressure in every subject studied. Plasma E levels rose transiently and returned to the basal levels by 20 minutes after the injection, whereas plasma NE levels showed a more prolonged rise over 20 minutes. beta-Blockade with propranolol did not affect the plasma E response to glucagon, but inhibited the prolonged rise of plasma NE levels. An intravenous infusion of exogenous E (1.25-1.50 micrograms/min) for 30 minutes caused an apparent rise of both plasma NE levels and blood pressure, which lasted more than 60 minutes after stopping the E infusion. Propranolol did not affect the time course of plasma E but again inhibited the prolonged rise of both plasma NE levels and blood pressure. No significant differences could be observed in the cardiovascular or plasma NE responses to glucagon or to E infusion between normal and hypertensive subjects. These findings lend support to the view that plasma E can act physiologically as a sustained stimulator of presynaptic beta-adrenergic receptors, which leads to an enhanced NE release from peripheral sympathetic nerve terminals and a rise of blood pressure in humans.

Circulating catecholamines in acute asthma

Plasma catecholamine concentrations were measured in 15 patients (six male) aged 14-63 years attending the casualty department with acute severe asthma (peak expiratory flow 27% (SEM 3%) of predicted). Nine patients were admitted and six were not. The plasma noradrenaline concentration, reflecting sympathetic nervous discharge, was two to three times normal in all patients and was significantly higher in those who required admission compared with those discharged home (mean 7.7 (SEM 0.6) v 4.7 (0.5) nmol/l (1.3 (SEM 0.1) v 0.8 (0.08) ng/ml); p less than 0.001). Plasma adrenaline concentration, however, was not increased in any patient. This surprising failure of the plasma adrenaline concentration to increase during the stress of an acute attack of asthma was unexplained and contrasts with the pronounced rise in plasma adrenaline and noradrenaline concentrations in acute myocardial infarction, heart failure, and septicaemia. The failure of plasma adrenaline concentration to increase in acute asthma is unlikely to be explained by adrenal exhaustion, but it may be another example of impaired adrenaline secretion in asthma.

Mechanisms of catecholamine effects on ketogenesis

Ketogenesis may be controlled at several sites. Lipolysis with release of plasma nonesterified fatty acid (NEFA) substrate is the first step. Plasma NEFA are taken up by the liver in a concentration-dependent fashion and, after conversion to the acyl-CoA derivative, may either be reesterified or enter the mitochondria via the carnitine shuttle. After beta-oxidation the resultant acetyl-CoA may either be converted to ketone bodies that are then released into the circulation or be condensed with oxaloacetate and enter the tricarboxylic acid cycle, the third potential control point. In humans, infusion of epinephrine causes a transient two- to threefold increase in fatty acids, glycerol, and ketone bodies. Insulin levels show a small absolute increase. Norepinephrine has similar effects, although insulin levels tend to be suppressed and glucagon levels rise somewhat. If somatostatin is added simultaneously, the lipolytic and ketogenic effects are accentuated and prolonged. Dopamine, in a high dose, has no effect on ketone bodies alone but shows small increases in NEFA and ketone bodies in the presence of somatostatin and may play a modulatory role in ketogenesis. The ketogenic effect of catecholamines could thus be in the adipocyte or in the liver. Studies with perfused liver or hepatocytes showed only trivial effects on ketogenesis even with supraphysiological doses of catecholamines. Furthermore infusion studies in rats showed decreased rather than increased ketogenesis with no change in NEFA levels. The data suggest that a) there are species differences, and b) in humans epinephrine- and norepinephrine-induced increases in ketogenesis are secondary to increases in NEFA substrate supply.

The effect of posture on the sympathoadrenal response to theophylline infusion

We studied the effect of posture on the sympathoadrenal response to intravenous theophylline in six normal subjects. On three separate occasions they received an intravenous infusion of either theophylline (6 mg/kg) while supine, theophylline (6 mg/kg) while standing or saline as placebo while standing. With the subjects standing theophylline caused tremor, a peak heart rate of 99 +/- 6 beats/min, and an elevation of plasma cyclic AMP from 9.3 +/- 0.7 to 15.1 +/- 1.7 nmol/1 (mean +/- s.e. mean). There was a small, but significant, elevation of plasma adrenaline, noradrenaline and glucose. The elevation in plasma catecholamines was insufficient to explain either the sympathomimetic effects of theophylline or the rise in plasma cyclic AMP. Theophylline had little or no effect with the subjects supine. The mean peak theophylline concentration following infusion was significantly higher with the subjects upright than when supine (18.3 c.f. 12.4 mg/l, P less than 0.025). However, adequate plasma levels of theophylline were obtained in all subjects when lying or supine. Analysis of individual data suggests that differences in plasma levels of theophylline are unlikely to account for the increased effects seen on standing. The mechanism of action of theophylline cannot be explained by increased secretion of catecholamines alone. Theophylline appears to amplify the increased sympathetic activity associated with standing and this is probably by phosphodiesterase inhibition.

Relationship between plasma norepinephrine and sympathetic neural activity

For circulating norepinephrine (NE) to reflect sympathetic activity validly, plasma NE should show an intensity-dependent increase during sympathetic stimulation and decrease during sympathetic inhibition, and circulating NE should correlate with more directly obtained measures of sympathetic activity. Review of published evidence indicates that NE in peripheral plasma satisfies these criteria. However, models used to explain the relationship between circulating NE and sympathetic activity must take into account processes intervening between the synaptic cleft and free NE in the circulation and, since sympathetic outflow is regionalized, the contributions of specific vascular beds to circulating NE. In this report a model is presented where removal processes for NE are viewed as acting in series to produce a gradient in NE concentrations from synapse to plasma, and where the relative contributions of specific vascular beds are calculated from the arteriovenous difference in plasma NE across those beds and the percentage of cardiac output distributed to them. In general, venous plasma NE provides a useful estimation of average sympathetic outflow.

Metabolic and haemodynamic responses to adrenaline in normal dogs

The metabolic and haemodynamic effects of adrenaline were investigated in 6 intact anaesthetized dogs, which were subjected to an infusion of adrenaline. The dose given was similar to the endogenous production rate of adrenaline in experimental myocardial infarction. Adrenaline infusion (0.8, 1.17 ot 1.05 micrograms . kg-1 . min-1) over two hours led to a variable rise in blood level of this amine, regardless of the rate of infusion. Dogs with high blood adrenaline (over 3.5 ng . ml-1) exhibited haemodynamic deterioration, i.e. a rise in peripheral vascular resistance together with a fall in cardiac output and external cardiac work. Dogs with low blood adrenaline showed little change in peripheral vascular resistance, a rise in cardiac output and external cardiac work. The myocardial consumption of each of the substrates lactate, pyruvate, glucose and FFA was measured, and its equivalent oxygen consumption expressed as a percentage of the total myocardial oxygen consumption. No relationship was found between myocardial utilisation of individual substrates and the type of haemodynamic response. Thus in intact dogs exposed to adrenaline excess, similar to that found in acute myocardial infarction, the different types of haemodynamic response cannot be attributed to the type of substrate utilization by the myocardium, but to different rates of clearance of adrenaline. Low clearance rates lead to high blood adrenaline levels and an unfavourable response of the cardiovascular system.

Sodium intake alters the effects of norepinephrine on the renin system and the kidney

To examine the interactions between sodium intake and the sympathetic nervous system and their influences on the blood pressure control system we studied eight normotensive men after high (800 mEq/d) and low (10 mEq/d) sodium intake. We measured blood pressure, arterial, venous and urinary norepinephrine (NE), glomerular filtration rate (GFR), renal blood flow (RBF), plasma renin activity (PRA) and aldosterone (PA), and the fractional excretion of sodium (FENa) and potassium (FEK) before and during incremental infusion of norepinephrine. High salt intake influenced the sensitivity to NE as well as subsequent pressor responses. The NE-induced decrease in RBF and GFR was not different on high and low sodium intakes. A significant decrease in FENa (p less than 0.05) with NE infusion could only be seen during high sodium intake. A significant increase in PRA (p less than 0.01) and PA (p less than 0.05) was induced by NE only during the low sodium period. These observations reveal previously unrecognized qualitative and quantitative interactions between sodium homeostasis and norepinephrine which are capable of influencing blood pressure in man.