Perioperative Normothermia – a lesson in how attention to detail matters

Addison K. May, MD, FACS, FCCMProfessor 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

• 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

Why should we maintain 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

• 200 patients

• elective colorectal surgery

• Interventions started at induction

• hypothermia vs normothermiaNormothermia– 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

Kurz A - N Engl J Med 1996; 334:1209-1215

Perioperative normothermia to reduce the incidence of surgical-wound infection and shorten hospitalizationKurz A - N Engl J Med 1996; 334:1209-1215

Postoperative Findings in the Two Study Groups Multivariate Analysis of Risk Factors for Surgical-Wound Infection

• Active warming resulted in significant– reduction of infections, hospital length of stay– improved wound healing and resolution of ileus

Effects of preoperative warming on the incidence of wound infection after clean surgery: a randomized controlled trial

• 421 patients

• clean (breast, varicose vein, or hernia) surgery

• Intervention prior to OR

Melling AC . Lancet 2001; 358:876-880

• Warming vs standardWarmingSystemic warming: forced air 30 min prior to ORLocal warming: radiant heat dressingStandardNo intervention

The effects of warming therapies compared with standard treatment

Randomized clinical trial of perioperative systemic warming in major elective abdominal surgeryWong 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: treatment 36.5 control 36.5 Core temp at start: treatment 36.4 control 36.0 Core temp at study end: treatment 36.3 control 36.2

Randomized clinical trial of perioperative systemic warming in major elective abdominal surgeryWong 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

• 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

Colorectal cases for August 2008• 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

Trauma/EGS: % patients with temperature value < 36°CPe

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VPIMS reported data: Min temp = lowest recorded intra-op temp, first temp = 1st after induction

Colorectal: % patients with temperature value < 36°CPe

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of p

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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