Hypothermia and SSI Claude Laflamme MD, FRCPC Director Cardio-vascular anesthesia Assistant Professor U of Toronto

Surgical site infection (SSI) 30,000,000 operations/year in USA 2% = 600,000 have SSI Increases in mortality Increases readmission rates Increases LOS by an average of 7 days Increases cost to more than $30,000

Patient and operation characteristics that may influence the SSI rates Age Nutritional status Diabetes Smoking Obesity Steroid use Prolonged pre-op LOS PatientOperationPost-op care Antiseptic technique Surgical technique Wound classification Length of surgery Antimicrobial prophylaxis Hair removal, BG, Normothermia, Blood transfusion Wound care Discharge

Complications of mild hypothermia Increases duration of hospitalization Increases intra-operative blood loss Increases adverse cardiac event Increases patient shivering in PACU Increases SSI rates

Perioperative hypothermia GA alters central thermoregulation Thermoregulatory responses are triggered after 2-3ºC of hypothermia (±34ºC) Core temperature decreases by 1ºC within 30 minutes of induction Heat production decreases by 5%/ºC in the absence of shivering Enhanced heat loss

Normothermia for colorectal surgery A Kurz, NEJM 1996; 334: patients, double-blind study Followed for 2 weeks 34.7±0.6 Celsius VS 36.6±0.5 Celsius SSI 18.8% VS 5.8% (p=0.009) Sutures were removed one day later (p=0.002) Hospital LOS prolonged by 2.6 days (p=0.01)

Normothermia for colorectal surgery 1.9ºC core hypothermia triples the incidence of surgical wound infection after colon resection Hypothermia increases by 20% the duration of hospitalization

Normothermia for colorectal surgery A Kurz, NEJM 1996; 334: Intraoperative vasoconstriction was present in 74% vs 6% of patients and persisted throughout the 6 hr recovery period

Hypothermia and cholecystectomy Flores-Maldonado et al consecutive patients 30-day follow-up Patients that received blood transfusion were excluded 35.4º±0.4ºC vs 36.2º±0.2ºC 11.5% vs 2% SSI

What do I do now?

Realistic options Get the department of Anesthesiology on board Listen to their concerns about SSI Provide support to address their concerns Choose your battles Emphasize on the critical role they play on SSI

Patient and operation characteristics that may influence the SSI rates Age Nutritional status Diabetes Smoking Obesity Steroid use Prolonged pre-op LOS PatientOperationPost-op care Antiseptic technique Surgical technique Wound classification Length of surgery Antimicrobial prophylaxis Hair removal, BG, Normothermia, Blood transfusion Wound care Discharge

The Anesthesiologist’s Role Anesthesiology 2006; 105: Hypothermia Hyperoxia Fluid Management Hyperglycemia Blood transfusion Antimicrobial Prophylaxis

CSI: Hypothermia

Complications and treatment of mild hypothermia Anesthesiology 2001; 95: Myocardial Ischemia Frank et al. JAMA 1997;277: High risk patients assigned to 1.3ºC core hypothermia were three times as likely to experienced adverse cardiac outcome Cold-induced hypertension is associated with a threefold increase in plasma norepinephrine concentrations

Complications and treatment of mild hypothermia Coagulopathy Platelet dysfunction (reduction in the release of thromboxane A2 Clotting factor enzyme Fibrinolytic activity-TEG

Complications and treatment of mild hypothermia Hypothermia Impairs neutrophils function Vasoconstriction Tissue hypoxia

Hypothermia Vasoconstriction Decreases the partial pressure of oxygen in tissues which impairs the oxidative killing by neutrophils Reduces the deposition of collagen Impairs immunity Chemo taxis and phagocytosis of granulocytes motility of macrophages Production of antibody Reduces the production of super oxide radicals

Hypothermia Animal study Hypothermia increased levels of interleukin 10 and decreased levels of interleukin 2 This profile is similar to other proinfectious state as burn and hemorrhagic choc.

Hopf et al, Arch Surg 1997 Subcutaneous oxygen tension at surrogate wound inversely correlated with the risk of SSI S/C O mmHg had a SSI of 43% S/C O2 above 90 mmHg had no SSI

Complications and treatment of mild hypothermia Pharmacokinetics and Pharmacodynamics Reduces clearance during hypothermia Prolongs PACU stay

Minimizing hypothermia Anesthetics profoundly inhibits central thermoregulation decreasing the vasoconstriction threshold by 2-4ºC The second major factor is the magnitude of the core-to-peripheral temperature gradient Minimizing the core-to-peripheral temperature gradient and preoperative vasodilatation, is the basis to reduce heat redistribution Degree of adiposity, concurrent medication

Minimizing hypothermia Prewarming:Decreases core-to-peripheral temperature gradient Eventually provokes vasodilatation Pharmacologic vasodilatation

Cutaneous warming Passive insulation reduces heat loss by approximately 30% Active cutaneous heating: efficacy will be proportional to the skin surface warmed Circulating water, Forced air, Radiant warmers

Active cutaneous warming systems Forced-air systems Circulating-water mattresses Resistive heating systems (ICU,trauma) Carbon-fiber patient cover Circulating-water garments Water has a conductivity of heat 26 times higher than air Infrared radiation(neonats, pediatric Sx)

Core temperature monitoring Pulmonary artery Nasopharynx Tympanic membrane Aural thermocouples probe Infrared thermometer Distal Oesophagus Rectal temperature during neuraxial anesthesia

Fluid warming If more than 2 liters/hr One liter of crystalloid or 1 unit of refrigerated blood decreases core temperature by 0.25ºC

Infection rates in colorectal InfectionNo InfectionTotal HypothermicN= % N= % N=28 NormothermicN=2 12.5% N= % N=16 TotalN=15N=29N=44 P=0.022

Quarterly Incidence of Infections Among Isolated ACB’s SSI Rate (%)

Quiz Is prewarming useful? Is postoperative rewarming efficient? Do you believe that an open cholecystectomy carries approximately the same risk of hypothermia than a laparascopic cholecystectomy? What is the future of normothermia in your OR?

Quiz What is the definition of intraoperative hypothermia? Is intravenous fluid warming helpful? How do you mesure the temperature to reflect core temperature reliably?