Prevention of Perioperative Hypothermia

Kelly Mayson, MD, FRCPCDirector of Quality Assurance

Department of AnesthesiaVancouver Acute and UBC Hospitals

“Warm is the new Norm”

No financial disclosures

Neil Ramsay, Clinical Anesthesia Fellow

SQAN Dan Werry, Medical

Student Nursing staff-PCC,

PACU, NSQIP nurse reviewers

Objectives

1) Rational for promoting normothermia in the perioperative period

2) Understand the reasons for hypothermia

3) Local experience on the incidence of hypothermia in non-cardiac surgery

4) Review methods to maintain normothermia

5) Share our local QA project, and some of the culture of changing the status quo

Perioperative Hypothermia

Definition: as a temperature <36.0 C at any point in the perioperative period.

Mild hypothermia – 34-36o C is associated with an increased risk of complications

Increased risk of Surgical Site Infections (SSI)

Kurz NEJM 1996. Colorectal surgery N=200. 6% vs 19%. RR 0.31

Melling Lancet 2001. Clean general surgery. N=421 Systemic SSI 6% vs 14% RR 0.42, Local SSI 4% vs 14% RR 0.27

Wong Br J Surg 2007. Major abdominal cases N=103 13% vs 27% RR 0.48

Seamons Ann Surg 2012 Trauma laparotomiesN=524 . Significant increase risk of SSI if temp <

35o C Level 1 evidence, grade B recommendation

Pathophysiology

Leukocyte migration and oxidative killing impaired

Neutrophil phagocytosis Cytokine and antibody production Hypothermia-induced vasoconstriction

reduces skin perfusion and hence decreased tissue oxygen tension

INC

REA

SE B

LO

OD

LO

SS

AN

D

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F T

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SIO

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Meta-analysis 24 RCT Normothermia was associated with a 22%

less risk of transfusion 16% less blood loss Hypothermia impairs platelet function—

release of thromoxane A2. Impairs enzymes in the coagulation cascade Decrease clot formation Level 1 evidence.

Increases the risk of morbid myocardial outcomes

Frank . JAMA 1997. High risk vascular, abdominal & thoracic cases N=300. 1% vs 6%, RR 0.22

Level 1 evidence, grade B recommendation

Pathophysiology

Increase in circulating catecholamines› Cold induced HT, 3X fold in norepinephrine

Increase in systemic vasoconstriction Increase in cardiac demand

Inadvertent Hypothermia and Mortality in ICU

Retrospective study 5050 OR cases (cardiac and non-cardiac surgery)

35% were hypothermic on arrival to ICU 6% severely hypothermic <35o C.

› In-hospital mortality 5.6% normothermic› 8.9% for all hypothermic patients› 14.7% for severely hypothermic patients

› Karalapillai et al Anaesth 2009;64:968-972

Prevention of Hypothermia as Standard of Care

Surgical Care Improvement Project (SCIP) in the US, initiated a pay for performance for efforts to reduce surgical complications in July 2006› 1st step with colorectal surgery 2006› Oct 2009. SCIP Infection 10. “At least one body

temperature to be recorded within 30 minutes immediately before or in the 15 minutes immediately after anesthesia end time” for all patients regardless of age under going general or neuroaxial anesthesia one hour or longer.

UK—NICE Guidelines 2008Management of Perioperative Hypothermia

Patient temp measured and recorded every 30 minutes.

Induction should not commence until patient temp >36.

Intravenous fluids >500mls warmed with a fluid warming device.

High risk patients warmed with forced air warming devices for anesthesia <30 minutes.

All patients warmed with a forced air warmer for anesthesia >30 minutes.

pre-warming—high risk patients

Guid

elin

es

Core temperature <36O degree at end of case is a “failure”

Similar statements as NICE guideline Pre-warming should be initiated

between 30 minutes to 2 hours prior to major surgery

Frequency/incidence??

2001-2008

Hypothermia< 35.5 1.6%

Sample size 86,000 cases

How common is PACU hypothermia?

2001-2008

2011-2012

Hypothermia <35.5 1.6% Hypothermia <36.0 21%

Sample size N=86,000

Sample size N=870

Why?

Cold environment—what is your OR temp?› Suggested temperature 20-22O degree› Frequent air exchanges

Exposed patient Intraoperative fluids

› Actively warmed vs warmed solution Anesthesia effect on Thermoregulation

Thermoregulation

Anesthesia effect on Thermoregulation

Thermoregulatory Physiology

Two component model Core 2/3 of body heat

(trunk organs, brain) Peripheral 1/3—skin,

subcutaneous tissue Vasodilation results in

a core-to-peripheral temperature gradient and redistribution of body heat

Heat loss during anesthesia

Shivering Postoperatively

5-60% of patients having GA 33-50% of patients having epidurals & spinals Thermal pain— cold sensation can be worse

than surgical pain & shivering aggravates pain Increased oxygen consumption

› Vigorous shivering up to 600%, however 200% increase is all that can be sustained over long period

Increased catecholamine release Tachycardia and Hypertension

How to measure temperature?

Gold standard Pulmonary Artery Catheter Tympanic membrane probe-not typically used Esophageal and oral –level II-2 evidence, grade B

recommendation Bladder temperature for regional procedures. Or

axillary( in contact with artery, arm at side) IR tympanic thermometry—least reliable device—

Grade D Temporal artery thermometer—inferior to oral.

Scans skin temperature, detects the highest temperature, at 3 different points. “inferior to all devices” ( A & A 2002)

Pre-heat OR table/Forced Air warmers intraoperatively

Fluid warmers

Warming cupboard/warm flannels

Pre-Warming

Increase heat content in peripheral compartment before induction

Minimize temperature gradient between core and peripheral temperature

Attenuate the impact of heat redistribution

Pre-warming studies

Bock, BJA 1998-- 30 minutes prior to major laparotomy. Reduced transfusion, PACU stays, increased PACU temperature N=40

Melling, Lancet 2001—30 minutes FAW for clean procedures (breast, hernia, VV), SSI 5% vs 14% N=416

Horn, Anaesthesia 2012. FAW 10,20,30 min preop for OR lasting 30-90 minutes. N=200. PACU hypothermia 69% versus 13, 7 and 6%› BJA 1998;80:159-163 Lancet 2001;358:876-80

Anaesth 2012;67:612

VH Summer Project

Major non-cardiac procedures > 60 minutes were selected.

Forced air warming of patients using Bair Paws gowns.

Pre and post temperatures were taken in PCC (oral temp)

Length of warming was tracked Patients were allow to adjust temperature

in preoperative care unit (PCC)

Pre-op

Prewarming PreOR36.60

36.65

36.70

36.75

36.80Avg 68 min Pre-OR warming

Tem

per

atu

reoC

Intraoperative/Postoperative

Lowest temperature –esophageal, NP Duration of anesthesia Duration of hypothermia Temperature in the last 30 minutes of

OR Temperature on admission to PACU Did the gown make it to PACU PACU Length of Stay and complications NSQIP 30 day outcomes

Intraoperative Hypothermia

T>36C T<36

C Not Monitered

0

10

20

30

40

50

% P

atie

nts

Temperature Not Monitored

Spinal GA GA+ThEp0

20

40

60

80

100

% T

emp

no

t ch

arte

d

Percentage of OR Hypothermic

0% <25% 25-50% >50%0

10

20

30

40

50

% p

atie

nts % OR time spent hypothermic

Failure to achieve Normothermia

No pre-warming Pre-warming0

5

10

15

20

25

% H

ypo

ther

mic

in

PA

CU

Accuracy of temperature monitoring

-1.6 -1.2 -0.8 -0.4 0.0 0.4 0.8 1.2 1.60

20

40

60

PACU temp - last OR temp (oC)

# p

atie

nts

The OR Questionnaire

63 nurse and 67 Anesthesiologist interviews in the OR over a 7 week period.

What has been done to reduce the patient’s risk of developing hypothermia?

What do you think of the forced air warming gowns (“Bair Paws”)?

Is this patient at risk for developing hypothermia?

Nurses Anesthesiologists0

20

40

60

80

Patients reported to be at mod-severe risk

% P

atie

nts

1. ASA grade II-IV2. Pre-op temp < 363. Combined general and regional anesthesia4. Intermediate – major surgery5. Risk of cardiovascular complications

NICE criteria for high risk of hypothermia: 3 or more of the following…

Nurses Anesthesiologists NICE0

20

40

60

80

Patients reported to be at mod-severe risk

% P

atie

nts

What has been done to reduce the patient’s risk of

hypothermia?

Incr

ease

room

tem

p

Pre-w

arm

bed

Bair H

ugger

War

m IV

fluid

s

Extra

Fla

nnels

Activ

e Flu

id W

arm

er

Monito

r Tem

p?0

20

40

60

80

100Anesthesiologists

Nurses

% P

ati

en

ts

Mean OR temperature = 19.9 +/- 0.1 0C

Thoughts on the gowns?

Forced Air Warming Gowns: Bair Paws

Do you think Bair Paws are useful?

Nurses = 63 Anesthesiologists = n=67

yes

nodepends

yes

nodepends

What do you mean, the gowns are not “useful”?

- Not necessary

- Can get soiled

- Hard to use

What do you mean, the gowns are sometimes “useful”?

- Only for high risk patients

- Patient Position

- Not as upper air warmer

Nurses (n=63) Anesthesiologists (n=67)

yes

no

yes

no

Do you feel comfortable converting the gown to a blanket?

Why are you not comfortable converting the gowns to blankets?

- Not user friendly

- Need more practice

What did we learn?

1. Staff appropriately recognize the risk of hypothermia but do not necessarily act on the risk

2. Risk reduction strategies rarely used include increasing OR temperature

3. The Bair Paw gowns had mixed reviews and so we may want to consider alternatives

Complaints of Forced Air Warmers (FAW)

Noisy Costly disposables “blows bacteria” into surgical site—no

evidence Effects laminar airflow near surgical site—

could this effect the ability to remove airborne contaminants?

Dasari et al Anaesth 2012;67:244-249Belani et al Anesth Analg 2013;117:406-11

Air-free Conductive Fabric

No evidence

Warm Flannels—heat capacity is trivial› cutaneous heat loss identical with warmed

and unwarmed blankets Heated CO2 for MIS procedures

› Cochrane Systemic Review Jan 2011› No effect on postoperative pain, or change

in core temperature

SUMMARY--preop

Should be assessed for risk: High risk if more than 2

ASA 2-5Preoperative temp <36°CCombined GA and regionalIntermediate to major surgeryAt risk for cardiovascular

complications Pre-warm patients

SUMMARY--intraoperatively

Temperature should be monitored in most pts undergoing GA >30 minutes, and in all patients whose surgery > 60 minutes

Use esophageal and oral thermometry in anesthesized and awake patients , respectively

Use IV fluid warmers for abdominal procedures > 1 hr duration.

OR temperature. Ideally 22o C. But ideally at the start and end of case.

Use FAW intraoperatively when procedures are expected to last > 30 minutes

SUMMARY--postop

Patients temperature should be monitored every 15 minutes

Discharge criteria that patient temperature is greater than or equal 36o C.

Actively warm patients with FAW whose temperature is less than 36o C

Quality is not an act, it is a habit

Aristotle