Incidence and Risk Factors for Postoperative Hypothermia After Orthopaedic Surgery

John P. Kleimeyer, MD; Alex H. S. Harris, PhD; Joseph Sanford, MD; William J. Maloney, MD; Bassam Kadry, MD; Julius A. Bishop, MD

Disclosures

J Am Acad Orthop Surg. 2018;26(24):e497-e503. 

In This Article

Results

Across 3,822 procedures, mean age was 51.4 years (SD = 18.8), 52.5% (n = 2,006) were male, mean BMI was 27.9 kg/m2 (SD = 6.1), and mean BSA was 1.97 m2 (SD = 0.28). Of note, 75.7% (n = 2,881) of patients were ASA 1 or 2, 24.3% (n = 930) ASA 3, and 0.3% (n = 11) ASA 4; 73.4% (n = 2,805) of patients underwent general anesthesia, 22.7% (n = 868) underwent general anesthesia with regional anesthesia, and 3.9% (n = 149) underwent monitored anesthesia care with regional or local anesthesia. The mean preoperative temperature was 36.6°C (SD = 0.24), and the mean postoperative temperature was 36.4°C (SD = 0.51).

The incidence of intraoperative hypothermia was 72.5% (95% confidence interval [CI], 71.1% to 73.9%), whereas the incidence of postoperative hypothermia was 8.4% (95% CI, 7.5% to 9.3%). Stratified by subspecialty, the unadjusted incidence of postoperative hypothermia was highest in adult reconstruction at 14.9% (95% CI, 12.7% to 17.1%), followed by spine, arthroscopy, sports (excluding arthroscopy), tumor, foot and ankle, trauma, and hand (Table 1). Stratified by anatomic location, the unadjusted incidence of postoperative hypothermia was highest in hip procedures at 20.2% (95% CI, 17.1% to 23.2%), followed by shoulder, thigh, lumbar spine, cervical spine, knee, arm, calf, elbow, and ankle (Table 1). Postoperative hypothermia remained highest in the hip and pelvis region (Table 1). The intraclass correlation coefficient in the mixed-effect model predicting postoperative hypothermia was 0.058 (95% CI, 0.034 to 0.105), implying that 5.8% of the total variance was explained by providers (n = 39) rather than other factors.

Intraoperative hypothermia (odds ratio [OR], 2.72; 95% CI, 1.87 to 3.96), lower preoperative temperature (OR, 1.46; 95% CI, 1.11 to 1.93), female sex (OR, 1.42; 95% CI, 1.10 to 1.81), lower BMI (OR, 1.06 per kg/m2; 95% CI, 1.04 to 1.09), and older age (OR, 1.02 per year; 95% CI, 1.01 to 1.03) were found to markedly increase the risk for postoperative hypothermia (Table 2 and Figure 1, A). No relationship was found between case duration, ASA status, or anesthesia type and postoperative hypothermia. When hypothermia was treated as a continuous outcome, the case duration was also associated with lower postoperative temperature (P ≤ 0.003).

Figure 1.

AC, Forest plots represent odds ratios by variable. Bars represent 95% confidence intervals. Values are represented in logarithmic scale. A, Unstratified variables. ASA = American Society of Anesthesiology, MAC = monitored anesthesia care. B, Subspecialty model with trauma chosen as a reference category with the lowest rate of postoperative hypothermia. C, Anatomic region model with upper extremity chosen as a reference category with the lowest rate of postoperative hypothermia.

With trauma as the reference subspecialty category, a higher risk of postoperative hypothermia was associated with adult reconstruction (OR, 4.06; 95% CI, 1.75 to 9.40; Table 2; Figure 1, B). With upper extremity as the reference anatomic region category, hip and pelvis cases were associated with a higher risk of postoperative hypothermia (OR, 8.76; 95% CI, 2.41 to 31.93; Table 2; Figure 1, C). Longer case duration and arthroscopy were associated with lower postoperative temperature when hypothermia was treated as a continuous outcome (P's ≤ 0.0123). Postoperative hypothermia remained significantly associated with older age, female sex, lower BMI, lower preoperative temperature, and intraoperative hypothermia in separate models including subspecialty and anatomic region (P values ≤ 0.03).

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