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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
Patient Operation Post-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; 334:1209-15• 200 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; 334:1209-15• 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. 2001
• 290 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
Patient Operation Post-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 RoleAnesthesiology 2006; 105:413-21
• Hypothermia
• Hyperoxia
• Fluid Management
• Hyperglycemia
• Blood transfusion
• Antimicrobial Prophylaxis
CSI: Hypothermia
Complications and treatment of mild hypothermia
Anesthesiology 2001; 95:531-43
• Myocardial Ischemia Frank et al. JAMA 1997;277:1127-34 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 neutrophilsfunction
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 O2 40-50mmHg 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
Sugery Date
ProcedureProcedure
Yes NoIs Temperature >= 36 o on leaving OR
Yes NoIs Temperature >= 36 o on Arrival in PACU
OR TempTemperature
PACU TemoTemperature
Safer Healthcare Now! Campaign
Sunnybrook and Women's CollegeHealth Sciences CentreData Collection Record
SSI BUNDLE
Normothermia
OR
D D M M M Y Y Y YSugery Date Copy
BRADMA
Infection rates in colorectal
Infection No Infection Total
Hypothermic N=13
46.4%
N=15
53.6%
N=28
Normothermic N=2
12.5%
N=14
87.5%
N=16
Total N=15 N=29 N=44
P=0.022
Quarterly Incidence of InfectionsAmong Isolated ACB’s 2004-2005
0
5
10
15
20
1stQuarter2004
2ndQuarter3004
3rdQuarted
2004
4thQuarter2004
1stQuarter2005
2ndQuarter2005
3rdQuarter2005
4thQuarter2005
SS
I R
ate
(%
)
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?