Test 4: PACU (pt 3/3) Hypothermia, PONV Flashcards
What is the definition of hypothermia?
A condition marked by an abnormally low internal body temperature (below 36°C), that occurs when systemic heat loss exceeds heat production.
The greatest amount of heat loss occurs during the _____ hour in the periop setting, and patients in rooms at a temperature of ____ degrees C will all develop hypothermia.
Reports suggest that the greatest amount of heat loss occurs during the first hour in the perioperative setting and that patients in rooms at a temperature of 21°C will all develop hypothermia.
What are the 4 Mechanisms for heat loss?
Radiation
Evaporation
Convection
Conduction
What is the mechanism responsible for the majority of heat loss?
Radiation
What is Radiation Heat Loss?
The loss of heat from a warm or hot surface (the body) to a cooler one (the environment).
-It does not require that the two surfaces be in direct contact with each other.
-Accounts for 40% to 60% of heat loss to the environment.
-Especially profound in the elderly, debilitated, and neonatal populations.
What is Convection Heat Loss?
-2nd most important contributor
-Convective heat loss depends on the existence of a temperature gradient between the body and the ambient air.
-This type of heat loss may occur in the OR, particularly in laminar flow rooms, and accounts for 25% to 50% of heat loss.
What is Conductive Heat Loss?
Loss of heat from a warm surface that comes into contact with a cooler one; it accounts for as much as 10% of heat loss in the OR, where patients lose heat to cooler OR tables, sheets, drapes, skin preparation fluids, and IV fluids or irrigants.
What is Evaporative Heat Loss?
Transfer of heat during the change from a liquid to a gas. Evaporative heat loss occurs via perspiration, respiration, or exposed viscera during surgery. Evaporation accounts for as much as 25% of heat loss in the OR.
What are other surgical related factors that cause hypothermia?
-Ambient room temperature
-Redistribution of lower-temp blood from the vasodilated, anesthetized periphery to the central compartment also accounts for significant heat loss.
-General and regional anesthesia inhibit thermoregulation and cause significant vasodilation such that temperature monitoring is warranted.
-Opioids and muscle relaxants depress shivering
-Any patient in whom a body cavity is entered will lose heat via convection/evaporation
-Irrigation solutions are cold
-During local anesthesia or sedation, temperature monitoring should be considered under circumstances in which the patient is at risk of hypothermia and should always be immediately available.
General anesthetics depress the _______________ center, with a usual temperature drop of ___°C to ____°C.
General anesthetics depress the thermoregulatory center, with a usual temperature drop of 1°C to 3°C.
Warming ____ induction can reduce redistribution hypothermia.
BEFORE induction
What are the physiologic consequences of Hypothermia?
-Increased O2 consumption 400-500% through shivering
-Increased risk CV events, MI, and sickling with sickle cell dz
-Impaired coagulation and cold-induced defect in platelet function (Increases surgical blood loss → increased transfusion rates)
-Decreased drug metabolism and elimination
-CNS depression
-Discomfort and decreased patient satisfaction
-Impaired wound healing, surgical site infection
-Prolonged PACU stay and increased hospital costs
____ of hypothermia is far superior to ______________________!!!
Prevention far superior to active rewarming!!!
What are strategies for Hypothermia Prevention?
-Assess every patient of the need for prewarming in preop
-Preoperative cutaneous warming: forced air warming blanket
-Airway heating and humidification (HME): More effective in pediatrics
-Warm IV fluids and fluid warmers (1U PRBC or 1 L crystalloid can decrease temp by 0.25oC )
-Warm ambient OR temperature (> 23oC required to maintain normothermia)
-Cutaneous heating: warm blankets, forced air warming systems
Postoperative nausea and vomiting (PONV) affects ___% to ___% of all surgical patients, and the chance for PONV can be as high as ___ to ___% for high-risk patients.
Postoperative nausea and vomiting (PONV) affects 20% to 30% of all surgical patients, and the chance for PONV can be as high as 70% to 80% for high-risk patients.
