Thermoregulation during prolonged exercise in heat: alterations with beta-adrenergic blockade

Freund, B. J.; Joyner, M. J.; Jilka, S. M.; Kalis, J. K.; Nittolo, J.; Taylor, J. Andrew; Peters, Helmut; Feese, G.; Wilmore, Jack H.

doi:10.1152/jappl.1987.63.3.930

Cited by 42 publications

(34 citation statements)

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“…* P < 0.05 versus pre-valsalva, P < 0.05 versus previous phase alpha-2 receptor agonist DEX has a greater affinity for alpha-2 receptors, shorter duration of action, and a more transient adverse effect (sedation) when compared to the mixed alpha-1 and alpha-2 agonist clonidine. Finally, our data confirm findings from early studies, using beta-adrenergic receptor antagonists [10,27], which demonstrate a sympathetic component to resting heart rate. The tachycardia elicited by cardiovagal inhibition in the present study was reduced with the addition of DEX, suggesting inhibition of central sympathetic outflow to the heart.…”

Section: Discussionsupporting

confidence: 91%

Alternative to ganglionic blockade with anticholinergic and alpha-2 receptor agents

et al. 2006

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The ganglionic blocking agent trimethaphan (TMP) is no longer produced. Therefore, a need exists for alternative pharmacological approaches to investigate baroreflex control of the circulation. The aim of the present study was to examine baroreflex-mediated cardiovascular responses during the administration of a muscarinic receptor antagonist (glycopyrrolate; GLY: ) and a selective alpha-2 receptor agonist (dexmedetomidine; DEX: ) and to compare responses to ganglionic blockade with TMP. We hypothesized that combined GLY-: DEX: would inhibit the baroreflex similar to TMP. Ten volunteers participated in two study days and were instrumented with pulse oximeter, nasal cannula, ECG, continuous blood pressure monitoring (Finapres), and I.V. catheter for drug infusions. Each study day consisted of a control condition followed by either combined GLY: -DEX: or TMP on alternating days. A Valsalva maneuver was performed under each condition with every subject and six subjects received bolus phenylephrine (25 mug) during GLY: -DEX: and TMP. Combined GLY: -DEX: increased (P < 0.05) blood pressure (99 +/- 4 mmHg) and heart rate (99 +/- 3 bpm) relative to control condition (BP: 90 +/- 2 mmHg; HR: 64 +/- 3 bpm) and TMP infusion decreased (P < 0.05) blood pressure (79 +/- 3 mmHg) while increasing heart rate (88 +/- 3 bpm). Valsalva maneuver elicited a persistent drop in arterial pressure (no phase IIb recovery) with the absence of a phase IV overshoot during both GLY: -DEX: and TMP conditions. Phenylephrine increased systolic pressure 34 +/- 4 mmHg under GLY: -DEX: and 23 +/- 3 mmHg with TMP (P < 0.05). Heart rate only decreased 1 +/- 2 bpm during GLY: -DEX: and 1 +/- 1 bpm with TMP. Taken together, our results suggest that GLY: -DEX: is a reasonable alternative to TMP for baroreflex inhibition.

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Section: Discussionsupporting

confidence: 91%

Alternative to ganglionic blockade with anticholinergic and alpha-2 receptor agents

et al. 2006

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“…Consistent with this hypothesis, others have shown attenuated cutaneous vasodilation during exercise in healthy subjects taking ␤-blockers. 31,32 However, in the present study, the magnitude of cutaneous vasodilation in the patients taking ␤-blocking agents was not different from the subjects not taking a ␤-blocker. Nevertheless, it is difficult to identify whether altered cutaneous vasodilatory responses in patients with CHF was attributed to CHF, medications used to treat this illness, or a combination of both.…”

Section: Study Limitationscontrasting

confidence: 71%

Effects of Heat Stress on Thermoregulatory Responses in Congestive Heart Failure Patients

et al. 2005

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Background-Clinical observations suggest that tolerance to heat stress may be impaired in patients with cardiovascular diseases, particularly those associated with impaired ventricular function and congestive heart failure (CHF). However, thermoregulatory function during a controlled heat stress challenge in patients with CHF has not been studied. Methods and Results-To test the hypothesis that thermoregulatory responses are attenuated in such patients, we assessed cutaneous vasodilation and sweat rate in patients with stable class II-III CHF and in matched healthy subjects during passive whole-body heating. Whole-body heating induced a similar increase in internal temperature (Ϸ0.85°C) in both groups. The sweating responses in patients with CHF were not significantly different from that in control subjects. In contrast, the elevation in forearm cutaneous vascular conductance in patients with CHF was reduced by nearly 50% relative to the control subjects (3.8Ϯ0.8 versus 6.9Ϯ1.0 mL/100 mL tissue per minute per 100 mm Hg, Pϭ0.04). Moreover, maximal cutaneous vasodilator capacity to direct local heating in patients with CHF was also significantly lower than in control subjects, suggesting that vascular remodeling may be limiting cutaneous vasodilation during hyperthermia. Conclusions-These observations suggest that patients with CHF exhibit attenuated cutaneous vasodilator responses to both whole-body and local heating, whereas sweating responses are preserved. Attenuated cutaneous vasodilation may be a potential mechanism for heat intolerance in patients with CHF.

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“…Athletes who take certain medications or drugs, particularly medications with a dehydrating effect, are at an increased risk for a heat illness. [101][102][103][104][105][106][125][126][127][128][129][130][131][132][133][134][135][136] Alcohol, caffeine, and theophylline at certain doses are mild diuretics. 106,137,138 Caffeine is found in coffee, tea, soft drinks, chocolate, and several over-the-counter and prescription medications.…”

Section: Lack Of Acclimatization Tomentioning

confidence: 99%

National Athletic Trainers' Association Position Statement: Exertional Heat Illnesses

Casa¹,

DeMartini²,

Bergeron³

et al. 2015

Journal of Athletic Training

168

338

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Objective: To present recommendations for the prevention, recognition, and treatment of exertional heat illnesses and to describe the relevant physiology of thermoregulation.Background: Certified athletic trainers evaluate and treat heat-related injuries during athletic activity in ''safe'' and highrisk environments. While the recognition of heat illness has improved, the subtle signs and symptoms associated with heat illness are often overlooked, resulting in more serious problems for affected athletes. The recommendations presented here provide athletic trainers and allied health providers with an integrated scientific and practical approach to the prevention, recognition, and treatment of heat illnesses. These recommendations can be modified based on the environmental conditions of the site, the specific sport, and individual considerations to maximize safety and performance.Recommendations: Certified athletic trainers and other allied health providers should use these recommendations to establish on-site emergency plans for their venues and athletes. The primary goal of athlete safety is addressed through the prevention and recognition of heat-related illnesses and a welldeveloped plan to evaluate and treat affected athletes. Even with a heat-illness prevention plan that includes medical screening, acclimatization, conditioning, environmental monitoring, and suitable practice adjustments, heat illness can and does occur. Athletic trainers and other allied health providers must be prepared to respond in an expedient manner to alleviate symptoms and minimize morbidity and mortality.Key Words: heat cramps, heat syncope, heat exhaustion, heat stroke, hyponatremia, dehydration, exercise, heat tolerance H eat illness is inherent to physical activity and its incidence increases with rising ambient temperature and relative humidity. Athletes who begin training in the late summer (eg, football, soccer, and cross-country athletes) experience exertional heat-related illness more often than athletes who begin training during the winter and spring. [1][2][3][4][5] Although the hot conditions associated with late summer provide a simple explanation for this difference, we need to understand what makes certain athletes more susceptible and how these illnesses can be prevented. PURPOSEThis position statement provides recommendations that will enable certified athletic trainers (ATCs) and other allied health providers to (1) identify and implement preventive strategies that can reduce heat-related illnesses in sports, (2) characterize factors associated with the early detection of heat illness, (3) provide on-site first aid and emergency management of athletes with heat illnesses, (4) determine appropriate return-toplay procedures, (5) understand thermoregulation and physiologic responses to heat, and (6) recognize groups with special concerns related to heat exposure. ORGANIZATIONThis position statement is organized as follows:1. Definitions of exertional heat illnesses, including exerciseassociated muscle (heat) cramps, he...

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Thermoregulation during prolonged exercise in heat: alterations with beta-adrenergic blockade

Cited by 42 publications

References 0 publications

Alternative to ganglionic blockade with anticholinergic and alpha-2 receptor agents

Alternative to ganglionic blockade with anticholinergic and alpha-2 receptor agents

Effects of Heat Stress on Thermoregulatory Responses in Congestive Heart Failure Patients

National Athletic Trainers' Association Position Statement: Exertional Heat Illnesses

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