Perioperative Normothermia – a lesson
in how attention to detail matters
Addison K. May, MD, FACS, FCCM
Professor of Surgery and Anesthesiology
Division of Trauma and Surgical Critical Care
Objectives:
1. identify complications associated with
perioperative hypothermia
2. identify measures associated with intraoperative
normothermia
3. review standardized processes introduced for the
trauma/EGS services to maintain normothermia
What is normothermia?
• Definition: a condition of normal body temperature
– 37°C (36.5–37.5°C) or 98.6°F (98–100°F) core temperature
– Peripheral tissues may fall significantly below and before core
temperature falls
• Mild hypothermia: 32–35°C or 90–95°F
–
–
–
–
–
shivering
hypertension
tachycardia
tachypnea
vasoconstriction
–
–
–
–
cold diuresis
mental confusion
hyperglycemia
hepatic dysfunction
Why should we maintain normothermia?
• The World Health Organization standard: maintain patient core
temperature > 36°C throughout the perioperative period
• Perioperative hypothermia:
– Increases susceptibility to infections
• Decreased perfusion, decreased antibiotic penetration, altered phagocytic
function
– Increases blood loss
• Temperature induced coagulopathy, altered platelet function
– Decreases wound healing
– Increases cardiac morbidity
• Vasoconstriction, shivering, cardiac dysthymias
• Randomized studies demonstrate improved outcome with
normothermia
What factors contribute to perioperative hypothermia?
• anesthetic-induced impairment of thermoregulation
• altered distribution of body heat
• exposure
– body surface
– body cavities
• application of fluids to body surface
• low ambient room temperatures
• delivery of and exposure to hypothermic fluids
Perioperative normothermia to reduce the incidence of
surgical-wound infection and shorten hospitalization
Kurz A - N Engl J Med 1996; 334:1209-1215
• 200 patients
• elective colorectal surgery
• Interventions started at induction
• hypothermia vs normothermia
Normothermia
– Target temps: 36.5 ° C
– Fluids via warmer activated
– Forced air @ 40°C
Hypothermia
– Target temps: 34.5 ° C
– Fluids via warmer in-activated
– Forced air @ ambient temperature
Perioperative normothermia to reduce the incidence of
surgical-wound infection and shorten hospitalization
Kurz A - N Engl J Med 1996; 334:1209-1215
• Active warming resulted in significant
– reduction of infections, hospital length of stay
– improved wound healing and resolution of ileus
Postoperative Findings in the Two Study Groups
Multivariate Analysis of Risk Factors for
Surgical-Wound Infection
Effects of preoperative warming on the incidence of wound
infection after clean surgery: a randomized controlled trial
Melling AC . Lancet 2001; 358:876-880
• 421 patients
• clean (breast, varicose vein, or
hernia) surgery
• Intervention prior to OR
• Warming vs standard
Warming
Systemic warming: forced air 30 min prior to OR
Local warming: radiant heat dressing
Standard
No intervention
The effects of warming therapies compared with standard treatment
Randomized clinical trial of perioperative systemic
warming in major elective abdominal surgery
Wong PF. Br J Surg 2007; 94:421-426
• 103 patients
• All patients with
– Forced air @ 40°C intra-op
– Warmed fluids
• Treatment group
– Warming pad beneath
– 40°C - 2 hrs before and
throughout OR
• Control group
– Warming pad beneath
– Turned off



Core temp adm:
Core temp at start:
Core temp at study end:
treatment 36.5
treatment 36.4
treatment 36.3
control 36.5
control 36.0
control 36.2
Randomized clinical trial of perioperative systemic
warming in major elective abdominal surgery
Wong PF. Br J Surg 2007; 94:421-426
• Addition of warming blanket before and
through surgery improved outcomes
• Treatment group
fewer complications: 32 vs 54% (p=0.027)
less blood loss: 200 vs 400 ml (p=0.011)
How is VUMCs performance for normothermia?
Trauma/EGS cases for August 2008
Colorectal cases for August 2008
• 240 of 255 cases with temp values
•
All cases:
– 55% of cases - lowest temp < 360C
– 20% never get above 360C
Elective cases:
– 59% of elective cases - lowest temp < 360C
– 41% of elective cases - 1st temp < 36°C
111 of 131 cases with temp values
– 41% of colorectal cases 1st temp < 360C
– 52% of cases have either the first or last
temp recorded < 360C
Trauma/EGS normothermia initiative
Purpose/description:
• To improve maintenance of normothermia for the
Trauma/EGS patient population
• Target goals:
– > 90% patients with first and post-op temperature > 36°C.
– > 80% patients with minimum temperature > 36°C
Trauma/EGS Perioperative Process
Pre-operative:
•
Bear Paws:
– All elective cases should have Bear Paws placed on the patient in holding room and forced
warm air turned on to maintain temperature greater than 36.5°C at all times
Intra-operative:
•
Ambient room temperature:
– non-trauma cases: Room temperature should be set to 24°C (75°F)
– Room temperature to be recorded in VPIMS
– Adjust room temperature during case if core temp > 36.5°C
•
Peri-induction and intra-operative management:
– Bear Paws (if elective) / Bear Hugger applied, forced air @ 40°C prior to induction & prep
– Upper & lower forced air warming devices should be applied as allowed by the case
– Intraoperative fluids and irrigation should be warmed to 37°C
Post-operative management:
•
Patients immediately covered with either warm blankets and/or forced air device depending
on pt core temperature at completion of case
Percentage of patients with hypothermia
Trauma/EGS: % patients with temperature value < 36°C
VPIMS reported data: Min temp = lowest recorded intra-op temp, first temp = 1st after induction
Percentage of patients with hypothermia
Colorectal: % patients with temperature value < 36°C
VPIMS reported data: first temp = 1st after induction
My take home points:
• Strict attention to normothermia improves patient outcomes
• Attention to detail throughout the perioperative period required
to achieve high level compliance with normothermia
• Ability to measure and monitor compliance is important in
achieving our goals
• To maintain normothermia in the majority of patients, likely
need
– Pre-op active warming to maintain > 36.5°C
– Intra-op maintenance of ambient temp, active warming, and warm fluids