Unintentional perioperative hypothermia is associated with severe complications and high mortality in elective operations

The incidence of mild hypothermia after total knee or hip arthroplasty: A study of 2600 patients

Hypothermia is associated with a higher risk of perioperative complications and occurs frequently after total joint arthroplasty (TJA). The incidence of hypothermia following total joint arthroplasty was assessed with its risk factors and its correlation with PJI. Correlation of hypothermia with age, gender, BMI, type of arthroplasty surgery, type of anesthesia, operation time, blood loss, date of surgery and PJI was evaluated in 2600 patients. Female gender and spinal anesthesia increased the risk for hypothermia whereas an increased BMI and surgery duration correlated decreased the risk of hypothermia. The incidence of hypothermia decreased over time without a correlation with PJI.

Cost-utility analysis of the insufflation of warmed humidified carbon dioxide during open and laparoscopic colorectal surgery

BACKGROUND

An evaluation was conducted to estimate the cost-effectiveness of insufflation of warmed humidified CO₂ during open and laparoscopic colorectal surgery compared with usual care from a UK NHS perspective.

METHODS

Decision analytic models were developed for open and laparoscopic surgery. Incremental costs per quality-adjusted life year (QALY) were estimated. The open surgery model used data on the incidence of intra-operative hypothermia and applied risks of complications for hypothermia and normothermia. The laparoscopic surgery model utilised data describing complications directly. Sensitivity analyses were conducted.

RESULTS

Compared with usual care, insufflation of warmed humidified CO₂ dominated. For open surgery, savings of £20 and incremental QALYs of 0.013 were estimated per patient. For laparoscopic surgery, savings of £345 and incremental QALYs of 0.001 per patient were estimated. Results were robust to most sensitivity analyses.

CONCLUSIONS

Considering the current evidence base, the intervention is likely to be cost-effective compared with usual care in patients undergoing colorectal surgery.

Efficacy of Prewarming With a Self-Warming Blanket for the Prevention of Unintended Perioperative Hypothermia in Patients Undergoing Hip or Knee Arthroplasty

PURPOSE

Unintended perioperative hypothermia (UPH) is a common and serious complication for patients undergoing anesthesia. The purpose of this study was to identify the incidence of UPH and evaluate the efficacy of a self-warming blanket on the drop in core temperature and risk of UPH in patients undergoing hip or knee arthroplasty.

DESIGN

A case-control study was used.

METHODS

Sixty patients were included. Thirty patients received prewarming with a self-warming blanket and forced-air warming intraoperatively; thirty patients received only forced-air warming intraoperatively.

FINDING

The incidence of UPH (<36°C) was identified in 13% of the patients in the prewarmed group and 43% of the patients in the control group. Mean core temperature in the prewarmed group was significantly higher and remained above 36°C in the perioperative period.

CONCLUSIONS

The study suggests that preoperative warming with a self-warming blanket reduces the incidence of UPH and decreases the drop in core temperature.

Novel Zero-Heat-Flux Deep Body Temperature Measurement in Lower Extremity Vascular and Cardiac Surgery

OBJECTIVE

The aim of this study was to compare deep body temperature obtained using a novel noninvasive continuous zero-heat-flux temperature measurement system with core temperatures obtained using conventional methods.

DESIGN

A prospective, observational study.

SETTING

Operating room of a university hospital.

PARTICIPANTS

The study comprised 15 patients undergoing vascular surgery of the lower extremities and 15 patients undergoing cardiac surgery with cardiopulmonary bypass.

INTERVENTIONS

Zero-heat-flux thermometry on the forehead and standard core temperature measurements.

MEASUREMENTS AND MAIN RESULTS

Body temperature was measured using a new thermometry system (SpotOn; 3M, St. Paul, MN) on the forehead and with conventional methods in the esophagus during vascular surgery (n = 15), and in the nasopharynx and pulmonary artery during cardiac surgery (n = 15). The agreement between SpotOn and the conventional methods was assessed using the Bland-Altman random-effects approach for repeated measures. The mean difference between SpotOn and the esophageal temperature during vascular surgery was+0.08°C (95% limit of agreement -0.25 to+0.40°C). During cardiac surgery, during off CPB, the mean difference between SpotOn and the pulmonary arterial temperature was -0.05°C (95% limits of agreement -0.56 to+0.47°C). Throughout cardiac surgery (on and off CPB), the mean difference between SpotOn and the nasopharyngeal temperature was -0.12°C (95% limits of agreement -0.94 to+0.71°C). Poor agreement between the SpotOn and nasopharyngeal temperatures was detected in hypothermia below approximately 32°C.

CONCLUSIONS

According to this preliminary study, the deep body temperature measured using the zero-heat-flux system was in good agreement with standard core temperatures during lower extremity vascular and cardiac surgery. However, agreement was questionable during hypothermia below 32°C.

Anesthesia for colorectal surgery

Anesthesiologists play a pivotal role in facilitating recovery of patients undergoing colorectal surgery, as many Enhanced Recovery After Surgery (ERAS) elements are under their direct control. Successful implementation of ERAS programs requires that anesthesiologists become more involved in perioperative care and more aware of the impact of anesthetic techniques on surgical outcomes and recovery. Key to achieving success is strict adherence to the principle of aggregation of marginal gains. This article reviews anesthetic and analgesic care of patients undergoing elective colorectal surgery in the context of an ERAS program, and also discusses anesthesia considerations for emergency colorectal surgery.

Clinical evaluation of a newly designed fluid warming kit on fluid warming and hypothermia during spinal surgery

BACKGROUND

The Mega Acer Kit® (MAK) is a newly designed heated and humidified breathing circuit that warms fluid passing through the circuit lumen. In this study, we investigated the system's efficacy for the perioperative prevention of hypothermia and fluid warming.

METHODS

Ninety patients undergoing spinal surgery were enrolled in this study and randomly assigned to 3 groups based on the fluid warming device used: no fluid warming system (Group C, n = 30), via a Standard Ranger (Group R, n = 30), or via the MAK (Group M, n = 30). Distal esophageal temperatures (Teso) and infusion fluid temperature (TF) were recorded at 15 min intervals for duration of 180 min during surgery. If Teso was < 35.0℃, a forced-air convective warming device was used.

RESULTS

Final Teso values were 34.8 ± 0.3℃, 35.1 ± 0.1℃, and 35.8 ± 0.3℃ in groups C, R, and M, respectively (P < 0.01). Teso was significantly higher in group M when compared with that in groups C and R throughout the study period (P < 0.05). The number of patients requiring a forced-air convective warming device was significantly lower in group M (n = 0) when compared with that in groups R (n = 17) and C (n = 30) (P < 0.05). The final infusion fluid temperature was higher in group M when compared with that in groups C and R throughout the study period (35.4 ± 1.0 vs. 23.0 ± 0.3 and 32.8 ± 0.6℃; P < 0.01).

CONCLUSIONS

The MAK is more effective for preventing hypothermia and for warming fluid than the Standard Ranger.

TRPA1 mediates the effects of hypothermia on the monocyte inflammatory response

INTRODUCTION

Hypothermia is a well-known risk factor for postoperative complications because it prolongs the monocyte inflammatory response. The purpose of this study was to investigate whether temperature-activated ion channels (transient receptor protein channels [TRP] A1 and V1) mediate the effects of temperature on monocytes.

METHODS

Primary human monocytes were isolated and stimulated with lipopolysaccharide at 32°C or 39°C. RNA was isolated for analysis of microRNA (miR)-155 expression, and cytokines in the supernatant were measured with an enzyme-linked immunosorbent assay. Specific inhibitors of TRPA1 (HC- 030031) and a specific activator of TRPV1 (capsaicin) were used to block or activate TRPA1 and TRPV1, respectively. Statistical analysis was performed using the Wilcoxon signed-rank test.

RESULTS

TRPM8 mRNA was not expressed in primary human monocytes, whereas TRPA1 and TRPV1 were expressed. TRPV1 mRNA expression was suppressed at 32°C but not at 39°C. TRPA1 was induced strongly at 32°C and 39°C. Immunofluorescence microscopy confirmed that monocytes express TRPA1 and TRPV1 on their cell surface. Interleukin-10 secretion was increased by blocking TRPA1 (77.8 ± 3 2.8 pg/mL) and activating TRPA1 (79.4 ± 16.1 pg/mL) after 24 hours at 32°C (control 37.4 ± 17.1 pg/mL, P < .05). At 36 hours, tumor necrosis factor secretion was decreased after TRPA1 blockade (2,321 ± 439 pg/mL) and TRPV1 activation (2,137 ± 411 pg/mL) compared with control (2,567 ± 495 pg/mL, P < .05). Furthermore, miR-155 expression also was suppressed at 24 hours by TRPA1 blockade and TRPV1 activation (both P < .05). Silencing of TRPA1 normalized monocyte IL-10 secretion at 32°C.

CONCLUSION

These results demonstrate that hypothermia mediates its effects on monocytes through TRPA1. Blockade of TRPA1 or activation of TRPV1 may be used to modify the effects of hypothermia on the monocyte inflammatory response.

MicroRNA-155 potentiates the inflammatory response in hypothermia by suppressing IL-10 production

Therapeutic hypothermia is commonly used to improve neurological outcomes in patients after cardiac arrest. However, therapeutic hypothermia increases sepsis risk and unintentional hypothermia in surgical patients increases infectious complications. Nonetheless, the molecular mechanisms by which hypothermia dysregulates innate immunity are incompletely understood. We found that exposure of human monocytes to cold (32°C) potentiated LPS-induced production of TNF and IL-6, while blunting IL-10 production. This dysregulation was associated with increased expression of microRNA-155 (miR-155), which potentiates Toll-like receptor (TLR) signaling by negatively regulating Ship1 and Socs1. Indeed, Ship1 and Socs1 were suppressed at 32°C and miR-155 antagomirs increased Ship1 and Socs1 and reversed the alterations in cytokine production in cold-exposed monocytes. In contrast, miR-155 mimics phenocopied the effects of cold exposure, reducing Ship1 and Socs1 and altering TNF and IL-10 production. In a murine model of LPS-induced peritonitis, cold exposure potentiated hypothermia and decreased survival (10 vs. 50%; P < 0.05), effects that were associated with increased miR-155, suppression of Ship1 and Socs1, and alterations in TNF and IL-10. Importantly, miR-155-deficiency reduced hypothermia and improved survival (78 vs. 32%, P < 0.05), which was associated with increased Ship1, Socs1, and IL-10. These results establish a causal role of miR-155 in the dysregulation of the inflammatory response to hypothermia.