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）：个体经常暴露于升高内部温度的条件下，导致皮肤血管电导增加，并伴随出汗导致的大量液体流失。处于这种情况的人通常会出现血压控制受损的情况，表现为站立时或类似重力应激源下的头晕、眩晕和恶心，这可能导致晕厥和高度受伤的可能性。该提案的目的是确定导致热应激期间直立不耐受的血压控制减弱的机制。具体目标 1：检验以下假设：热应激期间恢复中心血容量（以中心静脉压为指标）可改善血压控制和体位耐受性。具体而言，将检查容量恢复对以下方面的影响：1) SV 和肺毛细血管楔压之间的关系（即 Frank-Starling 曲线），以及 2) 重力应力期间左心室舒张末期容量。具体目标 2：检查热应激时直立挑战期间脑血流量 (CBF) 大幅减少的机制。具体来说，我们将检查：1）热应激和体位应激期间中心静脉压和心输出量下降对 CBF 的作用，2）动脉 CO2 张力 (PaCO2) 降低导致热应激期间观察到的 CBF 降低的相对贡献，以及 3) 热应激对脑血管系统对 PaCO2 变化的敏感性的影响。这些目标将通过评估 1) 正常体温、2) 热应激和 3) 热应激 + 通过葡聚糖/盐水输注恢复 CBV 期间的心血管和血流动力学变量来实现。一些方案将使用下半身负压来减少 CBV，从而模拟出血状态。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受损的重要信息。重要的是，这将为那些治疗内部温度升高的人提供见解，特别是当这种情况伴有出血性损伤时。这些人可能是在环境温度升高的条件下作战的士兵（例如中东）、在气候温暖的地方服役的消防员和警察，或任何其他事件（例如车祸），其中一个人大量流血，同时其内部温度升高。