Risk factors for postoperative hypothermia in the post-anesthetic care unit: a prospective prognostic pilot study

Mendonça, Fabrício Tavares; Lucena, Marcelo Cabral de; Quirino, Raul Silva; Govêia, Catia Sousa; Guimarães, Gabriel Magalhaes Nunes

doi:10.1016/j.bjane.2018.11.002

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Revista Brasileira de Anestesiologia

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Scientific Articles • Rev. Bras. Anestesiol. 69 (2) • Mar-Apr 2019 • https://doi.org/10.1016/j.bjane.2018.11.002 copy

Risk factors for postoperative hypothermia in the post-anesthetic care unit: a prospective prognostic pilot study

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Background:

Hypothermia occurs in up to 20% of perioperative patients. Systematic postoperative temperature monitoring is not a standard of care in Brazil and there are few publications about temperature recovery in the postoperative care unit.

Design and setting:

Multicenter, observational, cross-sectional study, at Hospital de Base do Distrito Federal and Hospital Materno Infantil de Brasília.

Methods:

At admission and discharge from postoperative care unit, patients undergoing elective or urgent surgical procedures were evaluated according to tympanic temperature, vital signs, perioperative adverse events, and length of stay in postoperative care unit and length of hospital stay.

Results:

78 patients, from 18 to 85 years old, were assessed. The incidence of temperatures <36 ºC at postoperative care unit admission was 69.2%. Spinal anesthesia (p < 0.0001), cesarean section (p = 0.03), and patients who received morphine (p = 0.005) and sufentanil (p = 0.003) had significantly lower temperatures through time. During postoperative care unit stay, the elderly presented a greater tendency to hypothermia and lower recovery ability from this condition when compared to young patients (p < 0.001). Combined anesthesia was also associated to higher rates of hypothermia, followed by regional and general anesthesia alone (p < 0.001).

Conclusion:

In conclusion, this pilot study showed that perioperative hypothermia is still a prevalent problem in our anesthetic practice. More than half of the analyzed patients presented hypothermia through postoperative care unit admission. We have demonstrated the feasibility of a large, multicenter, cross-sectional study of postoperative hypothermia in the post-anesthetic care unit.

KEYWORDS
Body temperature; Hypothermia; Anesthesia; Postoperative care

	Hypothermia (n = 54)	Normothermia (n = 24)	p-Value
Age (years)	38.4 ± 16.8	42.9 ± 18.8	0.305^a a Student's t test.
Weight (kg)	73.7 ± 14.5	69.7 ± 17.1	0.334^a a Student's t test.
Height (m)	1.62 ± 0.07	1.62 ± 0.08	0.764^a a Student's t test.
Gender (M/F)	13/39	9/16	0.317^b b Chi-square test.
ASA classification, n (%)
I	9 (16.7)	6 (25)	0.380^b b Chi-square test.
II	38 (70.3)	13 (54.2)
III	7 (13)	5 (20.8)
Elderly, n (%)	8 (14.8)	6 (25)	0.359^b b Chi-square test.
Hypertension, n (%)	17 (31.5)	8 (33.3)	0.952^b b Chi-square test.
Diabetes mellitus, n (%)	5 (9.2)	6 (25)	0.091^b b Chi-square test.
Obesity, n (%)	10 (18.5)	3 (12.5)	0.428^b b Chi-square test.
Hypothyroidism, n (%)	2 (3.7)	0 (0)	0.320^b b Chi-square test.
Anesthesia, n (%)
General	6 (11.1)	13 (54.2)	<0.001^b b Chi-square test. ,^e e p < 0.05 was considered significant.
Regional	46 (85.2)	9 (37.5)
Combined	1 (1.8)	2 (8.3)
Use of opioids, n (%)
Fentanyl	6 (11.1)	8 (33.3)
Sufentanil	4 (7.4)	1 (4.2)
Morphine	3 (5.6)	1 (4.2)	0.003^c c Fisher test. ,^e e p < 0.05 was considered significant.
Sufentanil + morphine	13 (24)	0 (0)
Fentanyl + morphine	2 (3.7)	2 (8.3)
Remifentanil + morphine	0 (0)	1 (4.2)
Fentanyl + remifentanil	0 (0)	1 (4.2)
Types of surgery, n (%)	4 (7.4)
Broncoesofagology	1 (1.85)	0 (0)
Oral and maxillofacial	0 (0)	1 (4.17)
Head and neck	1 (1.85)	0 (0)
General surgery	2 (3.7)	2 (8.33)
Oncology	2 (3.7)	0 (0)
Thoracic	2 (3.7)	3 (12.5)	0.612^b b Chi-square test.
Vascular	2 (3.7)	1 (4.17)
Gynecology	1 (1.85)	0 (0)
Obstetric	27 (50)	10 (41.7)
Neurosurgery	2 (1.85)	0 (0)
Orthopedia	5 (9.26)	3 (12.5)
Urology	9 (16.7)	4 (16.7)
Prolonged wakefulness, n (%)	(0)	(0)	-
Heating with air in OR, n (%)	8 (14.8)	1 (4.2)	0.194^b b Chi-square test.
Heating with mattress in OR, n (%)	3 (5.6)	0 (0)	0.251^b b Chi-square test.
Heated serum in OR, n (%)	17 (31.5)	8 (33.3)	0.700^b b Chi-square test.
Heating with air in PACU, n (%)	4 (7.4)	2 (8.3)	0.661^c c Fisher test.
Heating with mattress in PACU, n (%)	2 (3.7)	1 (4.2)	0.780^b b Chi-square test.
Heated serum in PACU, n (%)	4 (7.4)	42 (8.3)	0.655^c c Fisher test.
Length of stay in the PACU (min)	94.73 ± 34.4	78.1 ± 30.3	0.057^d d Mann-Whitney U test.
Length of hospital stay (hours)	103.5 ± 115.2	111.3 ± 153.5	0.248^d d Mann-Whitney U test.
Chills, n (%)	7 (13)	1 (4.2)	0.203^c c Fisher test.
Complications, n (%)	5 (9.3)	0 (0)	0.109^b b Chi-square test.

	Elderly (n = 14)	Young patients (n = 64)	p-Value
Age (years)	70.29 ± 6.2	33.3 ± 10.6	<0.001^a a Student's t test. ,^d d p < 0.05 was considered significant.
Weight (kg)	79 ± 20.4	71 ± 14.9	0.325^a a Student's t test.
Height (m)	1.62 ± 0.1	1.62 ± 0.07	0.891^a a Student's t test.
Gender (M/F)	7/7	15/49	0.045^b b Chi-square test. ,^d d p < 0.05 was considered significant.
ASA classification, n (%)			0.006^b b Chi-square test. ,^d d p < 0.05 was considered significant.
I	1 (7.1)	14 (21.9)
II	7 (50)	44 (68.8)
III	6 (42.9)	6 (9.4)
Hypertension	11 (78.5)	14 (22)	<0.001^b b Chi-square test. ,^d d p < 0.05 was considered significant.
Diabetes mellitus	3 (21.4)	8 (12.5)	0.385^b b Chi-square test.
Obesity	1 (7.1)	12 (18.7)	0.291^b b Chi-square test.
Hypothyroidism	1 (7.1)	1 (1.6)	0.231^b b Chi-square test.
Anesthesia, n (%)
Inhalational	4 (28.6)	6 (9.4)	0.097^b b Chi-square test.
Total intravenous	1 (7.1)	10 (15.6)
Anesthesia, n (%)
General	3 (21.4)	16 (25)
Regional	8 (57.1)	47 (73.4)	0.009^b b Chi-square test. ,^d d p < 0.05 was considered significant.
Combined	3 (21.4)	1 (1.6)
Use of opioids, n (%)
Fentanyl	3 (21.4)	11 (17.2)
Sufentanil	1 (7.1)	4 (6.3)
Morphine	1 (7.1)	3 (4.7)	0.205^c c Fisher test.
Sufentanil + morphine	0 (0)	13 (20.3)
Fentanyl + morphine	2 (14.3)	2 (3.1)
Remifentanil + morphine	0 (0)	1 (1.6)
Fentanyl + remifentanil	0 (0)	1 (1.6)
Types of surgery, n (%)
Broncoesofagology	0 (0)	1 (1.6)
Oral and maxillofacial	0 (0)	1 (1.6)
Head and neck	0 (0)	1 (1.6)
General surgery	2 (14.3)	2 (3.13)
Oncology	0 (0)	2 (3.13)
Thoracic	0 (0)	4 (6.25)	0.004^c c Fisher test. ,^d d p < 0.05 was considered significant.
Vascular	1 (7.15)	2 (3.13)
Gynecology	0 (0)	1 (1.6)
Obstetric	0 (0)	37 (57.8)
Neurosurgery	1 (7.15)	1 (1.6)
Orthopedia	2 (14.3)	7 (11)
Urology	8 (57.15)	5 (7.8)
Prolonged wakefulness, n (%)	(0)	(0)	-
Heating with air in OR, n (%)	5 (35.7)	4 (6.3)	0.008^b b Chi-square test. ,^d d p < 0.05 was considered significant.
Heating with mattress in OR, n (%)	1 (7.1)	2 (3.1)	0.460^c c Fisher test.
Heated serum in OR, n (%)	10 (71.4)	15 (23.4)	0.001^b b Chi-square test. ,^d d p < 0.05 was considered significant.
Heating with air in PACU, n (%)	0 (0)	6 (9.4)	0.171^b b Chi-square test.
Heating with mattress in PACU, n (%)	0 (0)	3 (4.7)	0.309^b b Chi-square test.
Heated serum in PACU, n (%)	2 (14.3)	4 (6.3)	0.437^b b Chi-square test.
Chills, n (%)	1 (7.1)	7 (10.9)	0.672^b b Chi-square test.
Complications, n (%)	0 (0)	5 (7.8)	0.280^b b Chi-square test.
Hypothermia, n (%)	8 (57.1)	45 (70.3)	0.339^b b Chi-square test.

Outcome	Median (interquartile range)	Average difference (95% CI)	p-Value
Tympanic temperature in the OR
Admission	36.3 (35.8-36.6)	0.9 (0.514-0.799)	<0.0001^a a p < 0.05 was considered significant. Data were analyzed by Wilcoxon test.
Discharge	35.6 (35.0-36.1)
Tympanic temperature in the PACU
Admission	35.6 (34.9-36.1)	0.4 (-0.657 to 0.206)	0.0001^a a p < 0.05 was considered significant. Data were analyzed by Wilcoxon test.
Discharge	36.0 (35.6-36.5)

Temperatures	Elderly (n = 14)	Young (n = 64)	p-Value
Arrival on OR	36.2 ± 0.4	36.4 ± 0.5	0.854
Exit from OR	35.7 ± 0.7	35.7 ± 0.55	0.384
Arrival on PACU	35.4 ± 0.6	35.8 ± 0.57	0.134
15 min	35.6 ± 0.9	35.5 ± 0.68	0.650
30 min	35.2 ± 0.6	35.7 ± 0.61	0.101
45 min	35.3 ± 0.7	35.9 ± 0.79	0.033^a a p < 0.05 was considered significant. Data were analyzed by Mann-Whitney U test.
1 h	35.2 ± 0.8	36.0 ± 0.65	0.004^a a p < 0.05 was considered significant. Data were analyzed by Mann-Whitney U test.
1 h 15 min	35.2 ± 0.7	36.1 ± 0.49	<0.001^a a p < 0.05 was considered significant. Data were analyzed by Mann-Whitney U test.
1 h 30 min	34.8 ± 0.8	36.1 ± 0.5	0.001^a a p < 0.05 was considered significant. Data were analyzed by Mann-Whitney U test.
1 h 45 min	35.1 ± 0.5	36.1 ± 0.58	0.010^a a p < 0.05 was considered significant. Data were analyzed by Mann-Whitney U test.
2 h	35.5 ± 0.4	36.1 ± 0.6	0.202
2 h 15 min	35.6 ± 0.7	35.9 ± 0.59	0.643
Exit from PACU	35.6 ± 0.7	36.1 ± 0.59	0.018^a a p < 0.05 was considered significant. Data were analyzed by Mann-Whitney U test.

Independent variable	Chi-square	Pr (>Chi-square)
Spinal anesthesia
Temperature	63.0562	<0.0001^a a p < 0.05 was considered significant.
Spinal	17.9251	<0.0001^a a p < 0.05 was considered significant.
Temperature: Spinal	5.6002	0.01796^a a p < 0.05 was considered significant.
Cesarea considering use of spinal anesthesia
Temperature	86.7207	<0.000^a a p < 0.05 was considered significant.
Spinal	0.1661	0.68357
Temperature: Spinal	5.0752	0.02427^a a p < 0.05 was considered significant.
Hot air convection
Temperature	86.1308	<0.0001^a a p < 0.05 was considered significant.
Hot air convection	0.9452	0.3309
Temperature: Hot air convection	25.8577	<0.0001^a a p < 0.05 was considered significant.
Age (years)
Temperature	66.4415	<0.0001^a a p < 0.05 was considered significant.
Age	1.9894	0.1584
Temperature: Age	28.8965	<0.0001^a a p < 0.05 was considered significant.
Gender
Temperature	62.5628	<0.0001^a a p < 0.05 was considered significant.
Gender	0.0932	0.760136
Temperature: Gender	8.3174	0.0033927^a a p < 0.05 was considered significant.
OR temperature
Temperature	14.0678	0.0001763^a a p < 0.05 was considered significant.
OR temperature	4.6765	0.03057^a a p < 0.05 was considered significant.
Opioid use
Temperature	18.566	<0.0001^a a p < 0.05 was considered significant.
Opioid use	17.084	0.008981^a a p < 0.05 was considered significant.
Temperature: Opioid use	33.810	<0.0001^a a p < 0.05 was considered significant.

	Odds ratio	95% CI	p-Value
Diabetes mellitus (Yes^a a Reference category. /No)	3.032	0.826-11.127	0.095
Type of anesthesia
Regional^a a Reference category.	1	-
General	0.119	0.035-0.397	0.001^b b p < 0.05 was considered significant.
Combined	1.091	0.081-14.664	0.948
Use of opioids
Sufentanil + morphine^a a Reference category.	1	-	-
Fentanyl	0.159	0.038-0.657	0.011^b b p < 0.05 was considered significant.
Sufentanil	2.545	0.257	0.424
Morphine	1.826	0.173	0.617
Fentanyl + morphine	1.846	0.232	0.562
Heating with air in OR (Yes^a a Reference category. /No)	4.200	0.492-35.873	0.190
Length of stay in the PACU (hours)	0.985	0.967-1.003	0.102
Complications (Yes^a a Reference category. /No)	0.906	0.830-0.988	0.112

Sociedade Brasileira de Anestesiologia R. Professor Alfredo Gomes, 36, 22251-080 Botafogo RJ Brasil, Tel: +55 21 2537-8100, Fax: +55 21 2537-8188 - Campinas - SP - Brazil
E-mail: bjan@sbahq.org

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[1] * Corresponding author. E-mail:fabricio.tavares@me.com (F.T. Mendonça).