Mechanisms of Cardiac Function and Cerebral Vascular Control during Heat Stress

热应激期间心脏功能和脑血管控制的机制

• 批准号: 7673062
• 负责人: Robert Matthew Brothers
• 金额: $ 5.01万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-05-01 至 2011-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7673062
• 关键词: Accidents; Activities of Daily Living; Adverse effects; Antihypertensive Agents; Attenuated; Baroreflex; Blood Pressure; Blood Vessels; Blood Volume; Carbon Dioxide; Cardiac; Cardiac Output; Cardiovascular system; Catecholamines; Central venous pressure; Cerebrovascular Circulation; Cerebrum; Climate; Cutaneous; Data; Dextrans; Event; Exercise; Heart Rate; Heat Stress Disorders; Heating; Hemorrhage; Human; Individual; Infusion procedures; Injury; Lead; Left; Lightheadedness; Liquid substance; Location; Lower Body Negative Pressure; Maintenance; Middle East; Military Personnel; Nausea; Nerve; Performance at work; Perfusion; Plasma; Police officer; Protocols documentation; Pulmonary Capillary Wedge Pressure; Regulation; Relative (related person); Restaurants; Role; Saline; Simulate; Soldier; Stress; Stroke Volume; Sturnus vulgaris; Sweat; Sweating; Symptoms; Syncope; Temperature; Testing; Time; Ventricular End-Diastolic Volumes; Vertigo; Work; blood pressure regulation; dextran; early onset; fighting; hemodynamics; improved; indexing; insight; interest; pressure; public health relevance; response; restoration; stressor

DESCRIPTION (provided by applicant): Individuals are frequently exposed to conditions that elevate internal temperature which results in increased cutaneous vascular conductance accompanied by significant fluid loss via sweating. It is common for individuals in this condition to have compromised blood pressure control evidenced by lightheadedness, vertigo, and nausea upon standing or similar gravitational stressors, which can lead to syncope and a high potential of injury. The objective of this proposal is to identify mechanisms responsible for attenuated blood pressure control leading to orthostatic intolerance during heat stress. Specific Aim 1: Tests the hypothesis that restoration of central blood volume (indexed by central venous pressure) during heat stress improves blood pressure control and orthostatic tolerance. Specifically the effects of volume restoration on: 1) the relationship between SV and pulmonary capillary wedge pressure (i.e., Frank-Starling curve), and 2) left ventricular end diastolic volume during gravitational stress, will be examined. Specific aim 2: Examine mechanisms of greater reductions in cerebral blood flow (CBF) during an orthostatic challenge while heat stressed. Specifically we will examine: 1) the role of decreased central venous pressure and cardiac output during combined heat and orthostatic stress on CBF, 2) the relative contributions of reduced arterial CO2 tensions (PaCO2) causing reduced CBF observed during heat stress and 3) the effect of heat stress on the sensitivity of the cerebral vasculature to changes in PaCO2 . These objectives will be accomplished by evaluating cardiovascular and hemodynamic variables during 1) normothermia, 2) heat stress, and 3) during heat stress + restoration of CBV via dextran/saline infusion. Some protocols will use lower body negative pressure to reduce CBV and thus mimic a state of hemorrhage. PUBLIC HEALTH RELEVANCE: Data obtained will provide important information regarding compromised blood pressure control during heat stress. Importantly, this will provide insight to those who treat individuals with an elevated internal temperature and particularly when this scenario is accompanied with a hemorrhagic injury. Such individuals may be soldiers fighting in conditions in which environmental temperature is elevated (e.g. Middle East), firefighters and police officers who serve in warmer climate locations, or any other incidents (e.g., car accident) in which an individual is profusely bleeding while at the same time their internal temperature is elevated.

描述（由申请人提供）：个人经常暴露于升高内部温度的条件，从而导致皮肤血管电导增加，并通过出汗而伴随着大量的液体损失。在这种情况下，个人常见的是，在站立或类似的重力压力源或类似的重力压力源时，会损害血压控制，这可能导致晕厥和高损伤潜力。该建议的目的是确定导致血压控制导致血压减弱的机制，导致热应激期间的体位不耐受。具体目的1：检验以下假设：在热应力期间，中枢血容量的恢复（由中央静脉压力索引）可以提高血压控制和体位耐受性。具体来说，将检查体积恢复对以下方面的影响：1）将检查SV和肺毛细管楔压之间的关系（即，坦率的延伸曲线），以及2）在重力应力期间左心室舒张体积。具体目标2：检查在热量压力的同时，在体位挑战期间，在脑血流（CBF）中较大减少的机制。具体而言，我们将研究：1）在热热和原位应力对CBF的组合压力期间中央静脉压力和心脏输出降低的作用，2）动脉二氧化碳张力降低（PACO2）的相对贡献（PACO2）在热应激和热应激中观察到的CBF降低和3）在热应激过程中降低了CBF，而3）3）3）对Paco2中脑体血管敏感性的效果对Pacoco2 carneco2的敏感性的影响。这些目标将通过评估1）近期热疗法期间的心血管和血液动力学变量来实现，以及3）在热应力 +通过葡萄糖/盐水输注中CBV恢复期间。某些方案将使用低身体负压减少CBV，从而模仿出血状态。公共卫生相关性：获得的数据将提供有关热应激期间血压控制损害的重要信息。重要的是，这将为那些治疗内部温度升高的人，尤其是在这种情况伴有出血性损伤时的洞察力。这样的人可能是在环境温度升高（例如中东），在温暖的气候地点服役的消防员和警察在环境温度升高的条件下战斗的士兵，或者在同一时间内部升高其内部温度的情况下，他们在温暖的气候地点或任何其他事件（例如，车祸）中会出现。