Cardiovascular responses to heat stress: implications in health and disease Craig Crandall, Ph.D Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas; Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas.
Integrative Physiology Course 2016
Human body can tolerate wide variations in environmental temperature, but only very small variations in internal temperature. During 1979--1999, a total of 8,015 deaths in the United States were associated with excessive heat exposure,present, 3,829 (48%) Several of the gentlemen as were "dueas tomyself, weatherwent conditions," 3,809 (48%) well into theand room were "of unspecified origin".
without shirts … when the thermometer Source: National Center for Health Statistics had risen much higher, almost to 260 ° F (127 ° C), … and found that we could Loss of life in heat waves in the US exceeds bear that very well, … all other weather related deaths combined
lightening, rain,Trans floods, hurricanes, C.(i.e., Blagden; Philos Royal Soc and tornadoes). (Lond) 65:111-123, 1775. Source: Klinenberg, 2002.
Incessant Indian heat wave leaves 1,800 dead Siddhant Mohan, Special for USA TODAY, 2:04 p.m. EDT May 29, 2015
Na#onal Oceanic and Atmospheric Administra#on: www.ncdc.noaa.gov/sotc
Semenza et al. N Engl J Med. 1996
Control 40.0
Heating
Temperatures, °C Tskin Tblood
35.0 13.0
6.4 1.5 0.9
24 Cardiac Output, L/min
4 Splanchnic Blood Flow, L/min
Renal Blood Flow, L/min
1.3 0.9 100
Arterial Mean Pressure, mmHg
80 5.4
Right Atrial Mean Pressure, mmHg
0 110
Where is the blood going?
Stroke Volume, ml
100 30 Rowell, Physiol Rev 1974
50 Minute
70
Vasoconstrictor
Vasodilator
Skin Blood Flow
Nerve activity
85-95%
5-15%
Hypothermia
Normothermia
Hyperthermia
What is the effect of heat stress on systemic vascular resistance?
Control 40.0
Heating
Nerve activity
Temperatures, °C Tskin
35.0 13.0
6.4 1.5 0.9
Skin Blood Flow
Tblood 24 Cardiac Output, L/min
+7.5 85-95% l/min 5-15%
4 Splanchnic Blood Flow, L/min
Hypothermia
Normothermia
Hyperthermia
Renal Blood Flow, L/min
1.3 0.9 100
Arterial Mean Pressure, mmHg
80 5.4
Right Atrial Mean Pressure, mmHg
0 110
Blood Pressure = C.O. x TPR
Stroke Volume, ml
100 30 Rowell, Physiol Rev 1974
50 Minute
70
Control 40.0
Heating
Nerve activity
Temperatures, °C Tskin
35.0 13.0
6.4 1.5 0.9
Skin Blood Flow
Tblood 24 Cardiac Output, L/min
+7.5 85-95% l/min 5-15%
4 Splanchnic Blood Flow, L/min
Hypothermia
Normothermia
Hyperthermia
Renal Blood Flow, L/min
1.3 0.9 100
Arterial Mean Pressure, mmHg
80 5.4
Right Atrial Mean Pressure, mmHg
Blood Pressure = C.O. x TPR
0 110
Stroke Volume, ml
C.O. = heart rate x stroke volume
100 30 Rowell, Physiol Rev 1974
50 Minute
70
110 38.15 (0.08)
100
Heart Rate (bpm)
90 37.40 (0.09)
38.21 (0.08)
37.65 (0.09)
80 70 60
36.96 (0.08)
50 40 Normothermia
Heating 1
Heating 2
Heating 3
Final
Jose et al. (Am Heart J 1970): 7-9 bpm / deg C increase in internal temperature; 1.25 deg C increase in temperature = 9 bpm increase in HR. But observe ~45 bpm increase in heart rate.
Control 40.0
Heating
12
Left ventricular
Temperatures, °C
Pulmonary Capillary filling Wedgepressure Pressure
Tskin
35.0 13.0
Pressure (mmHg)
Tblood 24 Cardiac Output, L/min
8
Central Venous Pressure
P
