Hypothermia and surgery: immunologic mechanisms for current practice

Contrasting seasonality of the incidence of incisional surgical site infection after general and gastroenterological surgery: an analysis of 8436 patients in a single institute

BACKGROUND

While seasonality of hospital-acquired infections, including incisional SSI after orthopaedic surgery, is recognized, the seasonality of incisional SSI after general and gastroenterological surgeries remains unclear.

AIM

To analyse the seasonality and risk factors of incisional SSI after general and gastroenterological surgeries.

METHODS

This was a retrospective, single-institute, observational study using univariate and multivariate analyses. The evaluated variables included age, sex, surgical approach, surgical urgency, operation time, wound classification, and the American Society of Anesthesiologists physical status (ASA-PS).

FINDINGS

A total of 8436 patients were enrolled. General surgeries (N = 2241) showed a pronounced SSI incidence in summer (3.9%; odds ratio (OR): 1.87; 95% confidence interval (CI): 1.05-3.27; P = 0.025) compared to other seasons (2.1%). Conversely, gastroenterological surgeries (N = 6195) showed a higher incidence in winter (8.3%; OR: 1.38; 95% CI: 1.10-1.73; P = 0.005) than in other seasons (6.1%). Summer for general surgery (OR: 1.90; 95% CI: 1.12-3.24; P = 0.018) and winter for gastroenterological surgery (1.46; 1.17-1.82; P = 0.001) emerged as independent risk factors for incisional SSI. Open surgery (OR: 2.72; 95% CI: 1.73-4.29; P < 0.001) and an ASA-PS score ≥3 (1.64; 1.08-2.50; P = 0.021) were independent risk factors for incisional SSI in patients undergoing gastroenterological surgery during winter.

CONCLUSION

Seasonality exists in the incisional SSI incidence following general and gastroenterological surgeries. Recognizing these trends may help enhance preventive strategies, highlighting the elevated risk in summer for general surgery and in winter for gastroenterological surgery.

Prewarming Parturients for Cesarean Section Does Not Raise Wound Temperature But Body Heat and Level of Comfort: A Randomized Trial

PURPOSE

Prewarming before cesarean section lowers the rates of surgical site infections (SSIs). We hypothesized that this effect is explained due to a higher core temperature resulting in a higher wound temperature.

DESIGN

We conducted an open-labeled randomized study with on-term parturients scheduled for elective cesarean section under spinal anesthesia. Participants were randomized into an intervention group (prewarming) and a control group.

METHODS

Core and wound temperature, comfort level, and examination results were taken at defined times until discharge from the postanesthesia care unit (PACU). There was a follow-up visit and interview 1 day after the procedure. The primary outcome was a difference in wound temperature. The secondary outcomes were differences in core temperature, patient comfort, blood loss, SSI, and neonatal outcome.

FINDINGS

We randomized a total of 60 patients, 30 per group. Prewarming lead to a significantly higher core temperature. Additionally, patient comfort was significantly higher in the prewarming group even after discharge from PACU. We did not find a difference in wound temperature, SSI, neonatal outcome, or blood loss.

CONCLUSIONS

Prewarming before cesarean section under spinal anesthesia maintains core temperature and improves patient comfort but does not affect wound temperature.

Escherichia coli-induced inflammatory responses are temperature-dependent in human whole blood ex vivo

Systemic inflammatory conditions are often associated with hypothermia or hyperthermia. Therapeutic hypothermia is used in post-cardiac arrest and some other acute diseases. There is a need for more knowledge concerning the effect of various temperatures on the acute inflammatory response. The complement system plays a crucial role in initiating the inflammatory response. We hypothesized that temperatures above and below the physiologic 37 °C affect complement activation and cytokine production ex vivo. Lepirudin-anticoagulated human whole blood from 10 healthy donors was incubated in the presence or absence of Escherichia coli at different temperatures (4 °C, 12 °C, 20 °C, 33 °C, 37 °C, 39 °C, and 41 °C). Complement activation was assessed by the terminal C5b-9 complement complex (TCC) and the alternative convertase C3bBbP using ELISA. Cytokines were measured using a 27-plex assay. Granulocyte and monocyte activation was evaluated by CD11b surface expression using flow cytometry. A consistent increase in complement activation was observed with rising temperature, reaching a maximum at 41 °C, both in the absence (C3bBbP p < 0.05) and presence (C3bBbP p < 0.05 and TCC p < 0.05) of E. coli. Temperature alone did not affect cytokine production, whereas incubation with E. coli significantly increased cytokine levels of IL-1β, IL-2, IL-6, IL-8, IFN-γ, and TNF at temperatures > 20 °C. Maximum increase occurred at 39 °C. However, a consistent decrease was observed at 41 °C, significant for IL-1β (p = 0.003). Granulocyte CD11b displayed the same temperature-dependent pattern as cytokines, with a corresponding increase in endothelial cell apoptosis and necrosis. Thus, blood temperature differentially determines the degree of complement activation and cytokine release.

Perioperative Hypothermia Is Associated With Increased 30-Day Mortality in Hip Fracture Patients in the United Kingdom: Α Systematic Review and Meta-analysis

OBJECTIVES

To undertake a systematic review and meta-analysis to determine the relationship between perioperative hypothermia and mortality after surgery for hip fracture.

DATA SOURCES

A systematic literature search of Medline, EMBASE, CINAHL, and Cochrane CENTRAL databases was performed using the Cochrane methodology for systematic reviews with no publication year limit. Only studies available in the English language were included.

STUDY SELECTION

Predetermined inclusion criteria were patients of any age with a hip fracture, exposure was their body temperature and outcome was mortality rate. Any comparative study design was eligible.

DATA EXTRACTION

The quality of selected studies was assessed according to each study design with the Methodological Index for Non-Randomised Studies (MINORS) used for all the retrospective comparative studies. The GRADE approach was used to assess the quality of evidence.

DATA SYNTHESIS

A meta-analysis was conducted using a random-effects model.

RESULTS

The literature search identified 1016 records. After removing duplicates and those not meeting inclusion criteria, 3 studies measuring 30-day mortality were included. All included studies were carried out in the United Kingdom. The mortality rate was higher in the hypothermic groups as compared with the normothermic group in all the studies, with the difference being significant in 2 of the studies (P < 0.0001). The meta-analysis showed that low body temperature was associated with an increased mortality risk (estimated odds ratio: 2.660; 95% confidence interval: 1.948-3.632; P < 0.001) in patients undergoing surgery for hip fracture.

CONCLUSIONS

This study shows that low body temperature in hip fracture patients is associated with an increased 30-day mortality risk in the United Kingdom. Randomized control trials are required to determine whether the association between perioperative hypothermia in hip fracture patients and mortality is causal. Nevertheless, based on this analysis, we urge the maintenance of normal body temperature in the perioperative period to be included in national hip fracture guidelines.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Risk Nomogram Does Not Predict Anastomotic Leakage After Colon Surgery Accurately: Results of the Multi-center LekCheck Study

PURPOSE

Anastomotic leakage (AL) is a dreaded complication after colorectal surgery. Preoperatively identifying high-risk patients can help to reduce the incidence of this complication. For this reason, AL risk nomograms have been developed. The objective of this study was to test the AL risk nomogram developed by Frasson, et al. for validity and to identify risk-factors for AL.

METHODS

From the international multi-center LekCheck study database, patients who underwent colonic surgery with the formation of an anastomosis were included. Data were prospectively collected between 2016 and 2019 at 14 hospitals. Univariate and multivariable regression analyses, and area under receiver operating characteristic curve analysis (AUROC) were performed.

RESULTS

A total of 643 patients were included. The median age was 70 years and 51% were male. The majority underwent surgery for malignancies (80.7%). The overall AL rate was 9.2%. The risk nomogram was not predictive for AL in the population tested (AUROC 0.572). Low preoperative haemoglobin (p = 0.006), intraoperative hypothermia (p = 0.02), contamination of the operative field (p = 0.004), and use of epidural analgesia (p = 0.02) were independent risk-factors for AL.

CONCLUSION

The AL risk nomogram could not be validated using the international LekCheck study database. In the future, intraoperative predictive factors for AL, as identified in this study, should also be included in AL risk predictors.

Too Cool? Hip Fracture Care and Maintaining Body Temperature

Introduction:

Patients with hip fractures can become cold during the perioperative period despite measures applied to maintain warmth. Poor temperature control is linked with increasing complications and poorer functional outcomes. There is generic evidence for the benefits of maintaining normothermia, however this is sparse where specifically concerning hip fracture. We provide the first comprehensive review in this population.

Significance:

Large studies have revealed dramatic impact on wound infection, transfusion rates, increased morbidity and mortality. With very few studies relating to hip fracture patients, this review aimed to capture an overview of available literature regarding hypothermia and its impact on outcomes.

Results:

Increased mortality, readmission rates and surgical site infections are all associated with poor temperature control. This is more profound, and more common, in older frail patients. Increasing age and lower BMI were recognized as demographic factors that increase risk of hypothermia, which was routinely identified within modern day practice despite the use of active warming.

Conclusion:

There is a gap in research related to fragility fractures and how hypothermia impacts outcomes. Inadvertent intraoperative hypothermia still occurs routinely, even when active warming and cotton blankets are applied. No studies documented temperature readings postoperatively once patients had been returned to the ward. This is a point in the timeline where patients could be hypothermic. More studies need to be performed relating to this area of surgery.

American College of Surgeons National Surgical Quality Improvement Program as a Quality Improvement Tool: A Single Institution's Experience with Vascular Surgical Site Infections

Vascular surgical site infections (VSSIs) result in significant patient morbidity and hospital cost. The objective of this study is to report a single hospital's experience using the National Surgical Quality Improvement Program (NSQIP) as an instrument to decrease VSSIs. After review of initial NSQIP data, changes in antibiotic dosage and timing, surgical preparation, patient warming, and oxygenation were put into practice. Records of all patients undergoing vascular surgical operations during a two-year period were reviewed and VSSIs were identified. Statistical comparisons were made between groups before and after implementation of these changes. A total of 478 cases met our criteria. Practice changes were introduced in October 2009 and fully implemented by January 2010. Two hundred forty-three cases were performed in 2009 and 235 in 2010. When operations during the two time periods were compared, significantly fewer VSSIs were identified in 2010 than in 2009 ( P = 0.036). NSQIP enabled our institution to identify an unacceptably high level of VSSIs. By implementing changes in our clinical practice, we were able to significantly lower our rate of VSSI.

Intensive fever control using a therapeutic normothermia protocol in patients with febrile early septic shock: A randomized feasibility trial and exploration of the immunomodulatory effects

Objectives:

Fever control has been shown to reduce short-term mortality in patients with septic shock. This study aimed to explore the feasibility of early intensive fever control in patients with septic shock and to assess the immunomodulatory effects of this intervention.

Methods:

In this single-center, randomized, open-label trial, febrile patients with septic shock presenting to the emergency department were assigned to either a standard fever control or therapeutic normothermia group. Therapeutic normothermia involved intensive fever control in maintaining normothermia below 37°C. The primary outcome was the feasibility of fever control for 24 h. Secondary outcomes included changes in immunomodulatory biomarkers and adverse events.

Results:

Fifteen patients were enrolled and analyzed. Fever control was comparable in both groups, but significantly more patients in the therapeutic normothermia group experienced shivering (p = 0.007). Both groups demonstrated increased C-reactive protein and unchanged neutrophil chemotaxis and CD11b expression. The therapeutic normothermia group revealed significant decreased IL-6 and IL-10. The standard fever control group significantly expressed increased monocytic human leukocyte antigen. There were no significant differences between the groups in terms of immunomodulation.

Conclusions:

Therapeutic normothermia was feasible in patients with febrile septic shock but was not superior to standard fever control in terms of average body temperature and host defense function. Shivering was more frequent in the therapeutic normothermia group.

Trial registration:

Thai Clinical Trials Registry number: TCTR20160321001

The impact of warmed and humidified CO2 insufflation during robotic radical prostatectomy: Results of a randomized controlled trial

Background:

Cool and dry gas insufflation during laparoscopy induces hypothermia and cytokine increase, with significant perioperative morbidity. Our aim was to assess if warmed and humidified CO2 insufflation with HumiGard™ device can achieve significant benefits over standard insufflation in terms of risk of hypothermia, cytokine response, blood gases, and intra- and postoperative parameters, in the setting of robot-assisted radical prostatectomy (RARP).

Methods:

This was a prospective, randomized controlled clinical trial. Sixty-four patients with prostate cancer undergoing RARP were randomized to receive warmed and humidified CO2 insufflation with HumiGard device, plus hot air warming blanket (treatment group, H + WB), or standard CO2 insufflation, plus hot air warming blanket (control group, WB). Body core temperature (BCT), plasma levels of IL-6 and TNF-α, pain scores, and intraoperative parameters were recorded. The data were analyzed according to the Bayesian paradigm.

Results:

Intraoperative BCT increased in both groups during surgery, with a statistically significant difference favoring group H + WB, ending at 0.2°C higher on average than group WB. No difference across groups was shown for cytokine levels. Blood gas parameters were not affected by warmed CO2 insufflation. No statistical differences were noted for pain scores and the other intra- and postoperative parameters.

Conclusions:

During RARP, warm and humidified CO2 insufflation with the HumiGard device was more effective than the standard CO2 insufflation in maintaining the patient’s heat homeostasis, even if the difference was minimal. No imbalances were detected on blood gas analyses. No benefit could be shown in terms of cytokine levels and pain scores.

Consensus Bundle on Prevention of Surgical Site Infections After Major Gynecologic Surgery

Surgical site infections are the most common complication of surgery in the United States. Of surgeries in women of reproductive age, hysterectomy is one of the most frequently performed, second only to cesarean birth. Therefore, prevention of surgical site infections in women undergoing gynecologic surgery is an ideal topic for a patient safety bundle. The primary purpose of this safety bundle is to provide recommendations that can be implemented into any surgical environment in an effort to reduce the incidence of surgical site infection. This bundle was developed by a multidisciplinary team convened by the Council on Patient Safety in Women's Health Care. The bundle is organized into four domains: Readiness, Recognition and Prevention, Response, and Reporting and Systems Learning. In addition to recommendations for practice, each of the domains stresses communication and teamwork between all members of the surgical team. Although the bundle components are designed to be adaptable to work in a variety of clinical settings, standardization within institutions is encouraged.

Consensus Bundle on Prevention of Surgical Site Infections After Major Gynecologic Surgery

Surgical site infections are the most common complication of surgery in the United States. Of surgeries in women of reproductive age, hysterectomy is one of the most frequently performed, second only to cesarean birth. Therefore, prevention of surgical site infections in women undergoing gynecologic surgery is an ideal topic for a patient safety bundle. The primary purpose of this safety bundle is to provide recommendations that can be implemented into any surgical environment in an effort to reduce the incidence of surgical site infection. This bundle was developed by a multidisciplinary team convened by the Council on Patient Safety in Women's Health Care. The bundle is organized into four domains: Readiness, Recognition and Prevention, Response, and Reporting and Systems Learning. In addition to recommendations for practice, each of the domains stresses communication and teamwork between all members of the surgical team. Although the bundle components are designed to be adaptable to work in a variety of clinical settings, standardization within institutions is encouraged.

Comparison of forced-air and water-circulating warming for prevention of hypothermia during transcatheter aortic valve replacement

Introduction

Transcatheter Aortic Valve Replacement (TAVR) procedures at our institution were complicated by perioperative hypothermia despite use of the standard of care forced-air convective warming device (the BairHugger, Augustine Medical Inc, Eden Prairie, MN, USA). To remedy this problem, we initiated a quality improvement process that investigated the use of a conductive warm water-circulating device (the Allon ThermoWrap, Menen Medical Corporation, Trevose, PA, USA), and hypothesized that it would decrease the incidence of perioperative hypothermia.

Methods

We compared two different intraoperative warming devices using a historic control. We retrospectively reviewed intraoperative records of 80 TAVRs between 6/2013 and 6/2015, 46 and 34 of which were done with the forced-air and water-circulating devices, respectively. Continuous temperature data obtained from pulmonary artery catheter, temperature upon arrival to cardiothoracic ICU (CTU), age, BSA, height, and BMI were compared.

Results

Patients warmed with both devices were similar in terms of demographic characteristics. First recorded intraoperative temperature (mean 36.26 ± SD 0.61 vs. 35.95 ± 0.46°C, p = 0.02), lowest intraoperative temperature (36.01 ± 0.58 vs. 34.89 ± 0.76°C, p<0.001), temperature at the end of the procedure (36.47 ± 0.51 vs. 35.17 ± 0.75°C, p<0.001), and temperature upon arrival to the CTU (36.35 ± 0.44 vs. 35.07 ± 0.78°C, p<0.001) were significantly higher in the water-circulating group as compared to the forced-air group.

Conclusion

A quality improvement process led to selection of a new warming device that virtually eliminated perioperative hypothermia at our institution. Patients warmed with the new device were significantly less likely to experience intraoperative hypothermia and were significantly more likely to be normothermic upon arrival to the CTU.

Evidence-Based Strategies to Reduce Postoperative Complications in Plastic Surgery

Reconstructive plastic surgery is vital in assisting patients with reintegration into society after events such as tumor extirpation, trauma, or infection have left them with a deficit of normal tissue. Apart from performing a technically sound operation, the plastic surgeon must stack the odds in the favor of the patient by optimizing them before and after surgery. The surgeon must look beyond the wound, at the entire patient, and apply fundamental principles of patient optimization. This article reviews the evidence behind the principles of patient optimization that are commonly used in reconstructive surgery patients.

Warmed, humidified CO2 insufflation benefits intraoperative core temperature during laparoscopic surgery: A meta-analysis

BACKGROUND

Intraoperative hypothermia is linked to postoperative adverse events. The use of warmed, humidified CO₂ to establish pneumoperitoneum during laparoscopy has been associated with reduced incidence of intraoperative hypothermia. However, the small number and variable quality of published studies have caused uncertainty about the potential benefit of this therapy. This meta-analysis was conducted to specifically evaluate the effects of warmed, humidified CO₂ during laparoscopy.

METHODS

An electronic database search identified randomized controlled trials performed on adults who underwent laparoscopic abdominal surgery under general anesthesia with either warmed, humidified CO₂ or cold, dry CO₂ . The main outcome measure of interest was change in intraoperative core body temperature.

RESULTS

The database search identified 320 studies as potentially relevant, and of these, 13 met the inclusion criteria and were included in the analysis. During laparoscopic surgery, use of warmed, humidified CO₂ is associated with a significant increase in intraoperative core temperature (mean temperature change, 0.3°C), when compared with cold, dry CO₂ insufflation_. CONCLUSION: Warmed, humidified CO₂ insufflation during laparoscopic abdominal surgery has been demonstrated to improve intraoperative maintenance of normothermia when compared with cold, dry CO_2.

Heated insufflation with or without humidification for laparoscopic abdominal surgery

BACKGROUND

Intraoperative hypothermia during both open and laparoscopic abdominal surgery may be associated with adverse events. For laparoscopic abdominal surgery, the use of heated insufflation systems for establishing pneumoperitoneum has been described to prevent hypothermia. Humidification of the insufflated gas is also possible. Past studies on heated insufflation have shown inconclusive results with regards to maintenance of core temperature and reduction of postoperative pain and recovery times.

OBJECTIVES

To determine the effect of heated gas insufflation compared to cold gas insufflation on maintaining intraoperative normothermia as well as patient outcomes following laparoscopic abdominal surgery.

SEARCH METHODS

We searched Cochrane Colorectal Cancer Specialised Register (September 2016), the Cochrane Central Register of Controlled Trials (CENTRAL; The Cochrane Library 2016, Issue 8), Ovid MEDLINE (1950 to September 2016), Ovid Embase (1974 to September 2016), International Pharmaceutical Abstracts (IPA) (September 2016), Web of Science (1985 to September 2016), Scopus, www.clinicaltrials.gov and the National Research Register (1956 to September 2016). We also searched grey literature and cross references. Searches were limited to human studies without language restriction.

SELECTION CRITERIA

Only randomised controlled trials comparing heated (with or without humidification) with cold gas insufflation in adult and paediatric populations undergoing laparoscopic abdominal procedures were included. We assessed study quality in regards to relevance, design, sequence generation, allocation concealment, blinding, possibility of incomplete data and selective reporting. Two review authors independently selected studies for the review, with any disagreement resolved in consensus with a third co-author.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed screening of eligible studies, data extraction and methodological quality assessment of the trials. We classified a study as low-risk of bias if all of the first six main criteria indicated in the 'Risk of Bias Assessment' table were assessed as low risk. We used data sheets to collect data from eligible studies. We presented results using mean differences for continuous outcomes and relative risks for dichotomous outcomes, with 95% confidence intervals. We used Review Manager (RevMan) 5.3 software to calculate the estimated effects. We took publication bias into consideration and compiled funnel plots.

MAIN RESULTS

We included 22 studies in this updated analysis, including six new trials with 584 additional participants, resulting in a total of 1428 participants. The risk of bias was low in 11 studies, high in one study and unclear in the remaining studies, due primarily to failure to report methodology for randomisation, and allocation concealment or blinding, or both. Fourteen studies examined intraoperative core temperatures among heated and humidified insufflation cohorts and core temperatures were higher compared to cold gas insufflation (MD 0.31 °C, 95% CI, 0.09 to 0.53, I2 = 88%, P = 0.005) (low-quality evidence). If the analysis was limited to the eight studies at low risk of bias, this result became non-significant but remained heterogeneous (MD 0.18 °C, 95% CI, -0.04 to 0.39, I2= 81%, P = 0.10) (moderate-quality evidence).In comparison to the cold CO2 group, the meta-analysis of the heated, non-humidified group also showed no statistically significant difference between groups. Core temperature was statistically, significantly higher in the heated, humidified CO2 with external warming groups (MD 0.29 °C, 95% CI, 0.05 to 0.52, I2 = 84%, P = 0.02) (moderate-quality evidence). Despite the small difference in temperature of 0.31 °C with heated CO2, this is unlikely to be of clinical significance.For postoperative pain scores, there were no statistically significant differences between heated and cold CO2, either overall, or for any of the subgroups assessed. Interestingly, morphine-equivalent use was homogeneous and higher in heated, non-humidified insufflation compared to cold insufflation for postoperative day one (MD 11.93 mg, 95% CI 0.92 to 22.94, I2 = 0%, P = 0.03) (low-quality evidence) and day two (MD 9.79 mg, 95% CI 1.58 to 18.00, I2 = 0%, P = 0.02) (low-quality evidence). However, morphine use was not significantly different six hours postoperatively or in any humidified insufflation groups.There was no apparent effect on length of hospitalisation, lens fogging or length of operation with heated compared to cold gas insufflation, with or without humidification. Recovery room time was shorter in the heated cohort (MD -26.79 minutes, 95% CI -51.34 to -2.25, I2 = 95%, P = 0.03) (low-quality evidence). When the one and only unclear-risk study was removed from the analysis, the difference in recovery-room time became non-significant and the studies were statistically homogeneous (MD -1.22 minutes, 95% CI, -6.62 to 4.17, I2 = 12%, P = 0.66) (moderate-quality evidence).There were also no differences in the frequency of major adverse events that occurred in the cold or heated cohorts.These results should be interpreted with caution due to some limitations. Heterogeneity of core temperature remained significant despite subgroup analysis, likely due to variations in the study design of the individual trials, as the trials had variations in insufflation gas temperatures (35 ºC to 37 ºC), humidity ranges (88% to 100%), gas volumes and location of the temperature probes. Additionally, some of the trials lacked specific study design information making evaluation difficult.

AUTHORS' CONCLUSIONS

While heated, humidified gas leads to mildly smaller decreases in core body temperatures, clinically this does not account for improved patient outcomes, therefore, there is no clear evidence for the use of heated gas insufflation, with or without humidification, compared to cold gas insufflation in laparoscopic abdominal surgery.

Positive impact on heat loss and patient experience of preheated skin disinfection: a randomised controlled trial

AIMS AND OBJECTIVES

The aim of this study was to compare the effect of preheated (36 °C) and room-temperature (20 °C) skin disinfectant solution on skin temperature and patients' experience of the skin disinfection process.

BACKGROUND

To prevent surgical site infections, it is important to disinfect skin prior to invasive surgery. In clinical practice, conscious patients often comment on the coldness of the preoperative skin disinfection solution. Evidence is lacking, as to whether preheated skin disinfectant has any positive effects during preoperative skin disinfection.

DESIGN

Randomised controlled trial.

METHODS

A total of 220 patients undergoing pacemaker, implantable cardioverter-defibrillator, or cardiac resynchronisation therapy under local anaesthesia were included and randomly allocated to preheated or room-temperature skin disinfection. Skin temperature was assessed before and after skin disinfection at the planned incision site; in addition, three study-specific questions were used to assess how patients experienced the temperature.

RESULTS

Patients experienced the skin disinfection process with preheated disinfectant as significantly more pleasant. They felt less cold and reported increased satisfaction with the temperature of the solution compared to patients who were disinfected with room-temperature solution. Skin disinfection with preheated solution also yielded a significantly higher mean skin temperature compared to room-temperature solution.

CONCLUSIONS

Preoperative skin disinfection with preheated disinfectant may prevent heat loss and contributes to a more pleasant experience for patients.

RELEVANCE TO CLINICAL PRACTICE

Skin disinfection with preheated skin disinfectant is an easy and inexpensive nursing intervention that has a positive impact on heat loss and on patients' experience of the disinfection process.

The Involvement of Danger-Associated Molecular Patterns in the Development of Immunoparalysis in Cardiac Arrest Patients

OBJECTIVES

After cardiac arrest, patients are highly vulnerable toward infections, possibly due to a suppressed state of the immune system called "immunoparalysis." We investigated if immunoparalysis develops following cardiac arrest and whether the release of danger-associated molecular patterns could be involved.

DESIGN

Observational study.

SETTING

ICU of a university medical center.

PATIENTS

Fourteen post-cardiac arrest patients treated with mild therapeutic hypothermia for 24 hours and 11 control subjects.

MEASUREMENTS AND MAIN RESULTS

Plasma cytokines showed highest levels within 24 hours after cardiac arrest and decreased during the next 2 days. By contrast, ex vivo production of cytokines interleukin-6, tumor necrosis factor-α, and interleukin-10 by lipopolysaccharide-stimulated leukocytes was severely impaired compared with control subjects, with most profound effects observed at day 0, and only partially recovering afterward. Compared with incubation at 37°C, incubation at 32°C resulted in higher interleukin-6 and lower interleukin-10 production by lipopolysaccharide-stimulated leukocytes of control subjects, but not of patients. Plasma nuclear DNA, used as a marker for general danger-associated molecular pattern release, and the specific danger-associated molecular patterns (EN-RAGE and heat shock protein 70) were substantially higher in patients at days 0 and 1 compared with control subjects. Furthermore, plasma heat shock protein 70 levels were negatively correlated with ex vivo production of inflammatory mediators interleukin-6, tumor necrosis factor-α, and interleukin-10. Extracellular newly identified receptor for advanced glycation end products-binding protein levels only showed a significant negative correlation with ex vivo production of interleukin-6 and tumor necrosis factor-α and a borderline significant inverse correlation with interleukin-10. No significant correlations were observed between plasma nuclear DNA levels and ex vivo cytokine production.

INTERVENTIONS

None.

CONCLUSIONS

Release of danger-associated molecular patterns during the first days after cardiac arrest is associated with the development of immunoparalysis. This could explain the increased susceptibility toward infections in cardiac arrest patients.

Surgical trauma induces postoperative T-cell dysfunction in lung cancer patients through the programmed death-1 pathway

The programmed death-1 (PD-1) and programmed death ligand-1 (PD-L1) pathway have been shown to be involved in tumor-induced and sepsis-induced immunosuppression. However, whether this pathway is involved in the surgery-induced dysfunction of T lymphocytes is not known. Here, we analyzed expression of PD-1 and PD-L1 on human peripheral mononuclear cells during the perioperative period. We found that surgery increased PD-1/PD-L1 expression on immune cells, which was correlated with the severity of surgical trauma. The count of T lymphocytes and natural killer cells reduced after surgery, probably due to the increased activity of caspase-3. Caspase-3 level was positively correlated with PD-1 expression. Profile of perioperative cytokines and hormones in plasma showed a significantly increased level of interferon-α, as well as various inflammatory cytokines and stress hormones. In ex vivo experiments, administration of anti-PD-1 antibody significantly ameliorated T-cell proliferation and partially reversed the T-cell apoptosis induced by surgical trauma. We provide evidences that surgical trauma can induce immunosuppression through the PD-1/PD-L1 pathway. This pathway could be a target for preventing postoperative cellular immunosuppression.

Perioperative hypothermia and incidence of surgical wound infection: a bibliographic study

The purpose of this review article was to understand and analyze the scientific production related to the occurrence of perioperative hypothermia and the incidence of infection on the surgical site. For this purpose, a search was conducted in the databases LILACS, MEDLINE, PubMed, CINAHL and Cochrane, using the health science descriptors DECS, from 2004 to 2009. A total of 91 articles were found. After eliminating duplicate items and using selection criteria for inclusion, six manuscripts remained for analysis. The studies were classified as retrospective, prospective, case studies, and clinical trials. After analysis, the majority of studies showed that hypothermia must be prevented during the perioperative period to reduce complications in the healing process of the surgical incision. Therefore, unadverted hypothermia directly influences in surgical site healing, increasing the incidence of infection in the surgical wound.

Thermoregulation and Risk of Surgical Site Infection

Surgical site infections (SSIs) occur in approximately 2%–5% of patients undergoing surgery in the acute care setting in the United States. These infections result in increased length of stay, higher risk of death, and increased cost of care compared with that in uninfected surgical patients. Given the inclusion of maintenance of perioperative normothermia for all major surgeries as a means of lowering the risk of infection in the Surgical Care Improvement Project 2009, we prepared a summary of the literature to determine the strength and quantity of the evidence underlying the performance measure. Although the data are generally supportive of perioperative normothermia as a means of reducing the risk of SSIs, a more rigorous approach using standard SSI definitions as well as standardized temperature measurements (and timing thereof) will further delineate the role played by temperature regulation in SSI development.

Does close temperature regulation affect surgical site infection rates?

The argument for close temperature control, to which regulatory bodies have held health systems in an effort to reduce the burden of hospital-acquired infections, is not fully supported by current evidence. The literature is complex on the topic, and overinterpretation of historical data supporting close temperature regulation does not preclude an important recognition of these early works' contribution to high-quality surgical care. Avoidance of hypothermia through the regular use of active rewarming should be a routine part of safe surgical care. The biochemical basis of emphasizing temperature regulation is sound, and ample evidence shows the frank physiologic derangements seen when biological processes occur at suboptimal temperature. It is also recognized that patients tend to do better when warmed during the perioperative period, suggesting that warming devices are an important and essential adjunct to good perioperative care. Clinicians, researchers, and policymakers must be careful in how they apply these well-supported findings to process metrics in an era of limited resources with increasingly stringent quality guidelines and outcomes measures. Discrete temperature targets in current measures are not supported by the existing literature. Not only do these targets artificially anchor clinicians to temperature values with an inadequate scientific basis but they demand intensive resources from health institutions that could potentially be better used on quality requirements with stronger evidence of their ultimate effect on patient care.

Cardiac arrest patients have an impaired immune response, which is not influenced by induced hypothermia

INTRODUCTION

Induced hypothermia is increasingly applied as a therapeutic intervention in ICUs. One of the underlying mechanisms of the beneficial effects of hypothermia is proposed to be reduction of the inflammatory response. However, a fear of reducing the inflammatory response is an increased infection risk. Therefore, we studied the effect of induced hypothermia on immune response after cardiac arrest.

METHODS

A prospective observational cohort study in a mixed surgical-medical ICU. Patients admitted at the ICU after surviving cardiac arrest were included and during 24 hours body temperature was strictly regulated at 33°C or 36°C. Blood was drawn at three time points: after reaching target temperature, at the end of the target temperature protocol and after rewarming to 37°C. Plasma cytokine levels and response of blood leucocytes to stimulation with toll-like receptor (TLR) ligands lipopolysaccharide (LPS) from Gram-negative bacteria and lipoteicoic acid (LTA) from Gram-positive bacteria were measured. Also, monocyte HLA-DR expression was determined.

RESULTS

In total, 20 patients were enrolled in the study. Compared to healthy controls, cardiac arrest patients kept at 36°C (n = 9) had increased plasma cytokines levels, which was not apparent in patients kept at 33°C (n = 11). Immune response to TLR ligands in patients after cardiac arrest was generally reduced and associated with lower HLA-DR expression. Patients kept at 33°C had preserved ability of immune cells to respond to LPS and LTA compared to patients kept at 36°C. These differences disappeared over time. HLA-DR expression did not differ between 33°C and 36°C.

CONCLUSIONS

Patients after cardiac arrest have a modest systemic inflammatory response compared to healthy controls, associated with lower HLA-DR expression and attenuated immune response to Gram-negative and Gram-positive antigens, the latter indicative of an impaired immune response to bacteria. Patients with a body temperature of 33°C did not differ from patients with a body temperature of 36°C, suggesting induced hypothermia does not affect immune response in patients with cardiac arrest.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01020916, registered 25 November 2009.

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

INTRODUCTION

Hypothermia occurs in as many as 7% of elective colorectal operations and is an underestimated risk factor for complications and death. Rewarming of hypothermic patients alone is not sufficient to prevent such adverse events. We investigated the outcomes of patients who became hypothermic (<35°C) after elective operations and compared them with closely matched, nonhypothermic operative patients to better define the impact of hypothermia on surgical outcomes, as well as to identify independent risk factors for hypothermia.

METHODS

We queried the University HealthSystem Consortium (UHC) database for elective operative patients who became unintentionally hypothermic from October 2008 to March 2012, and identified 707 patients. Exclusion criteria were deliberate hypothermia, age <18 years, or death on day of admission. Separately, to validate the accuracy of hypothermia coding, we reviewed the hospital charts of all University of Louisville Hospital patients with hypothermia whose data were submitted to UHC.

RESULTS

All patients from UHC with a code for hypothermia were indeed unintentionally hypothermic. Hypothermic patients undergoing elective operations experienced a 4-fold increase in mortality (17.0% vs 4.0%; P < .001) and a doubled complication rate (26.3% vs 13.9%; P < .001), in which sepsis and stroke increased the most. Several independent risk factors for hypothermia were amenable to preoperative improvement: anemia, chronic renal impairment, and unintended weight loss. Severity of illness on admission, age >65 years, male sex, and neurologic disorders also were risk factors.

CONCLUSION

Hypothermia is associated with an increased rate of mortality and complications. Preventive treatment of these risk factors before operation and aggressive warming measures in the "at risk" population may decrease hypothermia-related morbidity and mortality in elective operations. Randomized-controlled trials should be conducted to evaluate the impact of aggressive warming measures in the at-risk population.

Association between preoperative 25-hydroxyvitamin D level and hospital-acquired infections following Roux-en-Y gastric bypass surgery

IMPORTANCE

Postoperative hospital-acquired infections (HAIs) may result from disruption of natural barrier sites. Recent studies have linked vitamin D status and barrier site integrity.

OBJECTIVE

To investigate the association between preoperative vitamin D status and the risk for HAIs.

DESIGN, SETTING, AND PARTICIPANTS

A retrospective analysis was performed using propensity score methods to construct a matched-pairs cohort to reduce baseline differences between patients with 25-hydroxyvitamin D (25[OH]D) levels less than 30 ng/mL vs 30 ng/mL or greater. Multivariable logistic regression analysis was then performed to examine the association between 25(OH)D levels and HAIs while adjusting for additional perioperative factors. Locally weighted scatterplot smoothing was used to depict the relationship between increasing 25(OH)D levels and the risk for HAIs. This study was conducted in a single, teaching hospital in Boston, Massachusetts, and involved 770 gastric bypass surgery patients between January 1, 2007, and December 31, 2011.

EXPOSURES

Preoperative 25(OH)D levels.

MAIN OUTCOMES AND MEASURES

Association between preoperative 25(OH)D levels and the risk for postoperative HAIs.

RESULTS

The risk for HAIs was 3-fold greater (adjusted odds ratio, 3.05; 95% CI, 1.34-6.94) in patients with 25(OH)D levels less than 30 ng/mL vs 30 ng/mL or greater. Further adjustment for additional perioperative factors did not materially change this association. Locally weighted scatterplot smoothing analysis depicted a near inverse linear relationship between vitamin D status and the risk for HAIs for 25(OH)D levels around 30 ng/mL.

CONCLUSIONS AND RELEVANCE

In our patient cohort, a significant inverse association was observed between preoperative 25(OH)D levels and the risk for HAIs. These results suggest that preoperative 25(OH)D levels may be a modifiable risk factor for postoperative nosocomial infections. Prospective studies must determine whether there is a potential benefit to preoperative optimization of vitamin D status.

[Prevention of surgical site infection in abdominal surgery. A critical review of the evidence]

Surgical site infection (SSI) is associated with prolonged hospital stay, increased morbidity, mortality and sanitary costs, and reduced patients quality of life. Many hospitals have adopted guidelines of scientifically-validated processes for prevention of surgical site and central-line catheter infections and sepsis. Most of these guidelines have resulted in an improvement in postoperative results. A review of the best available evidence on these measures in abdominal surgery is presented. The best measures are: avoidance of hair removal from the surgical field, skin decontamination with alcoholic antiseptic, correct use of antibiotic prophylaxis (administration within 30-60 min before incision, use of 1(st) or 2(nd) generation cephalosporins, single preoperative dosis, dosage adjustments based on body weight and renal function, intraoperative re-dosing if the duration of the procedure exceeds 2 half-lives of the drug or there is excessive blood loss), prevention of hypothermia, control of perioperative glucose levels, avoid blood transfusion and restrict intraoperative liquid infusion.

Moderate hypothermia inhibits brain inflammation and attenuates stroke-induced immunodepression in rats

AIMS

Stroke causes both brain inflammation and immunodepression. Mild-to-moderate hypothermia is known to attenuate brain inflammation, but its role in stroke-induced immunodepression (SIID) of the peripheral immune system remains unknown. This study investigated the effects in rats of moderate intra-ischemic hypothermia on SIID and brain inflammation.

METHODS

Stroke was induced in rats by permanent distal middle cerebral artery occlusion combined with transient bilateral common carotid artery occlusion, while body temperature was reduced to 30°C. Real-time PCR, flow cytometry, in vitro T-cell proliferation assays, in vivo delayed-type hypersensitivity (DTH) reaction and confocal microscopy were used to study SIID and brain inflammation.

RESULTS

Brief intra-ischemic hypothermia helped maintain certain leukocytes in the peripheral blood and spleen and enhanced T-cell proliferation in vitro and delayed-type hypersensitivity in vivo, suggesting that hypothermia reduces SIID. In contrast, in the brain, brief intra-Ischemic hypothermia inhibited mRNA expression of anti-inflammatory cytokine IL-10 and proinflammatory mediators INF-γ, TNF-α, IL-2, IL-1β and MIP-2. Brief intra-Ischemic hypothermia also attenuated the infiltration of lymphocytes, neutrophils (MPO(+) cells) and macrophages (CD68(+) cells) into the ischemic brain, suggesting that hypothermia inhibited brain inflammation.

CONCLUSIONS

Brief intra-ischemic hypothermia attenuated SIID and protected against acute brain inflammation.

Prospective evaluation of ambient operating room temperature on the core temperature of injured patients undergoing emergent surgery

BACKGROUND

Although uncomfortable for the operating team, trauma operating room (OR) temperatures have traditionally been kept warm in an attempt to mitigate intraoperative heat loss. The purpose of this study was to examine how ambient OR temperatures impact core temperature in patients undergoing emergent surgery for trauma.

METHODS

Injured adult patients requiring emergent surgery at a Level 1 trauma center were prospectively enrolled between July 2008 and January 2010. Standardized warming measures were used for all patients. Ambient OR temperature was recorded in 5-minute intervals with the Fourier Microlog EC600 temperature data logger. Intraoperative core patient temperatures were compared with ambient OR temperature. Patients experiencing intraoperative core temperature decreases were compared with those who did not, to examine the impact of ambient temperature changes on the risk of perioperative hypothermia.

RESULTS

During the 18-month study period, 118 patients requiring emergent surgery (73% laparotomy, 5% thoracotomy, 7% combined, 15% other) were enrolled. Incidence of hypothermia (<35°C) at admission to the OR was 29.7%. Crude mortality increased as the final patient core temperature achieved in the OR decreased (4.2% for temperatures >35°C and as high as 50% for temperatures ≤32°C). Overall, core temperature decreased in 46 patients (39.0%) but remained stable or increased by the end of the procedure in 72 (61%). There were no significant differences in the admission temperature, clinical demographics, or volume of fluids and blood products between the two groups. In a forward logistic regression analysis, a lower ambient OR temperature was not associated with a drop in the patient's core temperature.

CONCLUSION

In this prospective study, the ambient OR temperature did not affect the core temperature of injured patients undergoing emergent surgery.

LEVEL OF EVIDENCE

Prognostic study, level III; therapeutic study, level IV.

Preoperative risk reduction: strategies to optimize outcomes

The success of hernia repair is measured by absence of recurrence, appearance of the surgical scar, and perioperative morbidity. Perioperative surgical site occurrence (SSO), defined as infection, seroma, wound ischemia, and dehiscence, increases the risk of recurrent hernia by at least 3-fold. The surgeon should optimize all measures that promote healing, reduce infection, and enhance early postoperative recovery. In the population with ventral hernia, the most common complication in the immediate perioperative period is surgical site infection. This article reviews several preoperative measures that have been reported to decrease SSOs and shorten length of hospital stay.

[Risk factors of nasogastric tube placement after elective colorectal surgery included in a rehabilitation programme: a multivariate analysis]

OBJECTIVE

Nasogastric tube placement (NTP) is no more systematically recommended in patients scheduled for elective colorectal surgery but could be necessary in case of postoperative vomiting. The aim of this study was to determine independent risk factors for NTP after colorectal surgery.

PATIENTS AND METHODS

We performed an observational study including 290 patients scheduled for elective colorectal surgery included in an enhanced recovery programme: immunonutrition, thoracic epidural analgesia, antiemetic prophylaxis, respiratory physiotherapy, absence of NT and drainage, forced mobilization and oral nutrition. The main outcome was the occurrence of vomiting requiring NTP. Univariate analysis included: age, sex, BMI, American Society of Anesthesiologist Physical Status Classification System (ASA), duration of surgery, epidural analgesia, and mobilization, intraoperative fluid, temperature, laparotomy, use of droperidol, parenteral nutrition, stoma, diabetes, hypertension or coronary disease, COPD, type of surgery. A logistic regression was performed to determine independent risk factors of NTP.

RESULTS

Among the 290 patients included, 277 were analyzed. The incidence of NTP was 10.5% (95%CI [7.4-14.6%]). Univariate analysis documented BMI, low temperature in PACU (<35°C), ASA scores, duration of surgery and epidural analgesia, rectal and sigmoid resections, diabetes, transfusion, no use of droperidol, duration of mobilization, conversion to laparotomy. Three independent risk factors were associated with NTP: temperature in SSPI<35.5°C (OR: 14.49; IC95% [4.52-45.45], P<0.0001), BMI<21kg/m(2) (8.40; [1.99-35.71], P=0.0038) and lack of postoperative droperidol administration (3.37 [1.02-11.39], P=0.04).

CONCLUSIONS

After colorectal surgery tolerance to rapid oral feeding is impaired by denutrition and postoperative hypothermia. The combined used of postoperative droperidol should also be considered to avoid postoperative NTP.

Anesthesia in patients with cancer disorders

PURPOSE OF REVIEW

Along with the increasing population of elderly people in developed countries, anesthesiologists have increasing opportunities to anesthetize cancer patients in their routine work. However, no guideline of anesthesia procedures for cancer patients is available even though guidelines of operative procedures have been formulated for different types of cancer. This review provides recent findings related to the optimal choice of anesthetics and adequate anesthesia management for cancer patients.

RECENT FINDINGS

The intrinsic weapon fighting cancer cells is competent immune cells, particularly CD4+ T helper 1-type cells, CD8+ cytotoxic T cells, and natural killer cells. However, surgical inflammation, some anesthetics, and inadvertent anesthesia management suppress these effector cells and induce suppressive immune cells, which render cancer patients susceptible to tumor recurrence and metastasis after surgery.

SUMMARY

Accumulated basic and clinical data suggest that total intravenous anesthesia with propofol, cyclooxygenase antagonists, and regional anesthesia can decrease negative consequences associated with perioperative immunosuppression. Volatile anesthesia, systemic morphine administration, unnecessary blood transfusions, intraoperative hypoxia, hypotension, hypothermia, and hyperglycemia should be avoided.

Does clinically relevant temperature change miRNA and cytokine expression in whole blood?

Unintentional hypothermia is a well-described risk factor for death and complications after elective and emergency surgery. The molecular mechanisms by which hypothermia exerts its detrimental effects are not well understood. Differences in cytokine production and the overall cell function have been reported under hypothermic conditions. We investigated the effect of a range of clinically relevant temperatures on cytokine production and microRNA (miRNA) expression in a whole-blood model. We found that there was a wide variation in tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and IL-10 production among different subjects, ranging from low to high TNF-α producers. The intersubject variation can also be found on the transcriptional level: high producers had higher upregulation of TNF-α messenger RNA than intermediate and low producers. This variation in TNF-α was reproducible in each individual. Temperature seems to modulate TNF-α production among these different groups. miRNA expression was modulated by temperature. miRNA-181a might control, or be a part of the mechanism which controls, TNF-α production. However, an analysis of whole-leukocyte RNA does not allow the investigation of mechanisms in a specific leukocyte subpopulation such as monocytes, because these changes may be concealed by miRNA expression changes in the other leukocyte subsets. In conclusion, TNF-α, IL-6, and IL-10 production is highly variable among different persons, but temperature affects the expression of miRNAs, which may consequently alter the production of TNF-α.

[Management of peri-operative hypothermia]

Hypothermia (body temperature under 36°C) is the thermal disorder most frequently found in surgical patients, but should be avoided as a means of reducing morbidity and costs. Temperature should be considered as a vital sign and all staff involved in the care of surgical patients must be aware that it has to be maintained within normal limits. Maintaining body temperature is the result, as in any other system, of the balance between heat production and heat loss. Temperature regulation takes place through a system of positive and negative feedback in the central nervous system, being developed in three phases: thermal afferent, central regulation and efferent response. Prevention is the best way to ensure a normal temperature. The active warming of the patient during surgery is mandatory. Using warm air is the most effective, simple and cheap way to prevent and treat hypothermia.

The effects of intraoperative hypothermia on surgical site infection: an analysis of 524 trauma laparotomies

OBJECTIVES

Our primary study objective was to determine whether intraoperative hypothermia predisposes patients to postoperative surgical site infections (SSI) after trauma laparotomy.

BACKGROUND

Although intraoperative normothermia is an important quality performance measure for patients undergoing colorectal surgery, the effects of intraoperative hypothermia on SSI remain unstudied in trauma.

METHODS

A review of all patients (July 2003-June 2008) who survived 4 days or more after urgent trauma laparotomy at a level I trauma center revealed 524 patients. Patient characteristics, along with preoperative and intraoperative care focusing on SSI risk factors, including the depth and duration of intraoperative hypothermia, were evaluated. The primary outcome measure was the diagnosis of SSI within 30 days of surgery. Cut-point analysis of the entire range of lowest intraoperative temperature measurements established the temperature nadir that best predicted SSI development. Single and multiple variable logistic regression determined SSI predictors.

RESULTS

The mean intraoperative temperature nadir of the study population (n = 524) was 35.2°C ± 1.1°C and 30.5% had at least 1 temperature measurement less than 35°C. Patients who developed SSI (36.1%) had a lower mean intraoperative temperature nadir (P = 0.009) and had a greater number of intraoperative temperature measurements <35°C (P < 0.001) than those who did not. Cut-point analysis revealed an intraoperative temperature of 35°C as the nadir temperature most predictive of SSI development. Multivariate analysis determined that a single intraoperative temperature measurement less than 35°C independently increased the site infection risk 221% per degree below 35°C (OR: 2.21; 95% CI: 1.24-3.92, P = 0.007).

CONCLUSIONS

Just as intraoperative hypothermia is an SSI risk factor in patients undergoing elective colorectal procedures, intraoperative hypothermia less than 35°C adversely affects SSI rates after trauma laparotomy. Our results suggest that intraoperative normothermia should be strictly maintained in patients undergoing operative trauma procedures.

Effect of anesthetic breathing circuit type on thermal loss in cats during inhalation anesthesia for ovariohysterectomy

OBJECTIVE

To compare the effects of a nonrebreathing circuit versus a reduced volume circle anesthetic breathing circuit on body temperature change in cats during inhalation anesthesia for ovariohysterectomy.

DESIGN

Randomized, controlled clinical trial.

ANIMALS

141 female domestic cats hospitalized for routine ovariohysterectomy.

PROCEDURES

Cats were randomly assigned to receive inhalation anesthetics from either a nonrebreathing circuit or a reduced volume circle system with oxygen flow rates of 200 and 30 mL/kg/min (90.9 and 13.6 mL/lb/min), respectively. Body temperatures were monitored throughout the anesthetic period via an intrathoracic esophageal probe placed orally into the esophagus to the level of the heart base.

RESULTS

No difference in body temperature was found between the 2 treatment groups at any measurement time. The duration of procedure had a significant effect on body temperature regardless of the type of anesthetic circuit used.

CONCLUSIONS AND CLINICAL RELEVANCE

Duration of the procedure rather than the type of anesthetic circuit used for inhalation anesthesia was more influential on thermal loss in cats undergoing ovariohysterectomy.

Perioperative Core Body Temperatures Effect on Outcome after Colorectal Resections

The World Health Organization has set a standard of maintaining a core body temperature above 36°C in the perioperative period. The purpose of this study was to examine the relationship between both intraoperative temperature (IOT) and immediate postop core body temperature as it relates to postop complications. A retrospective analysis of a prospective database of patients who underwent an elective segmental colectomy without a stoma, for 3 diagnoses was performed. Six postoperative outcomes were examined: length of stay (LOS), placement of a nasogastric tube, return to the operating room, placement of an interventional drain, diagnosed leak, and surgical site infection (SSI). Statistics were calculated using a two-sample Wilcoxon rank-sum (Mann-Whitney) test. Seventy-nine patients met the inclusion criteria and there were no preoperative differences between the groups (those with a postop complication vs without). LOS > 9 days (36.64°C vs 35.98°C; P = 0.011) and clinical leak (37.06°C vs 35.99°C; P = 0.005) both had a statistically higher average IOT than those who did not. Patients with SSI trended to a higher IOT (36.44°C vs 35.99°C; P = 0.062). When the last IOT recorded was compared with the six outcomes, again length of stay and leak both were statistically significant ( P = 0.018, P = 0.012) showing a higher temperature related to a higher complication rate. No other complications were related to IOT, nor did postop temperature relate to complication. In our data, relatively lower IOTs were protective for LOS and clinical leaks, with a trend of lower SSI rates. Further research is needed to fully endorse or refute the absolute recommendations for core body temperature.

Moderate temperature alterations affect Gram-negative immune signalling in ex vivo whole blood

BACKGROUND

Alterations in body temperature may influence immune system function and consequently affect the risk of infection and inflammatory diseases. Lipopolysaccharide (LPS) from gram-negative bacteria induces production of inflammatory cytokines after ligand binding to Toll-like receptor 4 (TLR4) on immune cells (especially monocytes/ macrophages). Our aim was to explore how clinically relevant hypo- and hyperthermia affect this signalling in an ex vivo whole blood model, and investigate if the cytokine response was correlated with monocyte TLR4 expression level.

METHODS

Blood from 11 healthy volunteers was incubated with LPS 10 ng/ml for 6 h at 33, 37 or 40°C. The concentrations of selected pro-inflammatory (tumour necrosis factor-α (TNF-α) and interleukin (IL)-1β) and anti-inflammatory (IL-10) cytokines were measured in plasma, and the surface expression of TLR4 was quantified on CD14 + monocytes.

RESULTS

Monocyte TLR4 expression and plasma IL-1β were inversely related to temperature. The TNF-α production was unaffected by hypothermia but increased significantly during hyperthermia, whereas plasma IL-10 was significantly reduced during both hypo- and hyperthermic incubation. No correlation was found between TLR4 expression and cytokine concentrations. During hypothermia, the TNF-α/IL-10 and IL-1β/IL-10 ratios increased seven and nine times, respectively. Hyperthermia increased the TNF-α/IL-10 ratio, but to a lesser extent (doubling), whereas the IL-1β/IL-10 ratio remained unchanged.

CONCLUSION

Hypothermia significantly changed the cytokine ratios in the pro-inflammatory direction. In comparison, the effect of hyperthermia was sparse, with a modest increase in the TNF-α/IL-10 ratio only. No association was found between LPS-stimulated cytokine production and TLR4 expression on CD14 + monocytes.

Bedside prediction rule for infections after pediatric cardiac surgery

Purpose

Infections after pediatric cardiac surgery are a common complication, occurring in up to 30% of cases. The purpose of this study was to develop a bedside prediction rule to estimate the risk of a postoperative infection.

Methods

All consecutive pediatric cardiac surgery procedures between April 2006 and May 2009 were retrospectively analyzed. The primary outcome variable was any postoperative infection, as defined by the Center of Disease Control (2008). All variables known to the clinician at the bedside at 48 h post cardiac surgery were included in the primary analysis, and multivariable logistic regression was used to construct a prediction rule.

Results

A total of 412 procedures were included, of which 102 (25%) were followed by an infection. Most infections were surgical site infections (26% of all infections) and bloodstream infections (25%). Three variables proved to be most predictive of an infection: age less than 6 months, postoperative pediatric intensive care unit (PICU) stay longer than 48 h, and open sternum for longer than 48 h. Translation into prediction rule points yielded 1, 4, and 1 point for each variable, respectively. Patients with a score of 0 had 6.6% risk of an infection, whereas those with a maximal score of 6 had a risk of 57%. The area under the receiver operating characteristic curve was 0.78 (95% confidence interval 0.72–0.83).

Conclusions

A simple bedside prediction rule designed for use at 48 h post cardiac surgery can discriminate between children at high and low risk for a subsequent infection.

[Systemic and immunomodulatory effects of whole body therapeutic hypothermia]

Several neurobiological mechanisms contribute to the development of ischemic-reperfusion damage of the central nervous system that may be modulated by hypothermia. Nowadays hypothermia is a therapeutic tool for the treatment of stroke and perinatal asphyxia. Hypothermia does not only affect the central nervous system, but also has systemic effects. It influences the muscular and cardiovascular system, the systematic metabolism, induces electrolyte changes, and decreases inflammation. This review summarizes the effects of therapeutic hypothermia on the immune system. Experiments on cell lines and in animals along with human experience indicate that short term (2-4 hours) hypothermia increases the levels of anti-inflammatory cytokines and decreases that of proinflammatory cytokines. Long term (>24 hours) hypothermia, however, increases proinflammatory cytokine levels. Furthermore, hypothermia inhibits lymphocyte proliferation and decreases HLA-DR expression associated with cell activation. These results suggest that therapeutic hypothermia has a systemic immunomodulatory effect. Further research is required to determine the contribution of immunomodulation to the defense of the central nervous system.

Active core rewarming avoids bioelectrical impedance changes in postanesthetic patients

Background

Postoperative hypothermia is a common cause of complications in patients who underwent laparoscopic cholecystectomy. Hypothermia is known to elicit electrophysiological, biochemical, and cellular alterations thus leading to changes in the active and passive membrane properties. These changes might influence the bioelectrical impedance (BI). Our aim was to determine whether the BI depends on the core temperature.

Methods

We studied 60 patients (52 female and 8 male) age 40 to 80 years with an ASA I-II classification that had undergone laparoscopic cholecystectomy under balanced inhalation anesthesia. The experimental group (n = 30) received active core rewarming during the transanesthetic and postanesthesic periods. The control group (n = 30) received passive external rewarming. The BI was recorded by using a 4-contact electrode system to collect dual sets of measurements in the deltoid muscle. The body temperature, hemodynamic variables, respiratory rate, blood-gas levels, biochemical parameters, and shivering were also measured. The Mann-Whitney unpaired t-test was used to determine the differences in shivering between each group at each measurement period. Measurements of body temperature, hemodynamics variables, respiratory rate, and BI were analyzed using the two-way repeated-measures ANOVA.

Results

The gradual decrease in the body temperature was followed by the BI increase over time. The highest BI values (95 ± 11 Ω) appeared when the lowest values of the temperature (35.5 ± 0.5°C) were reached. The active core rewarming kept the body temperature within the physiological range (over 36.5°C). This effect was accompanied by low stable values (68 ± 3 Ω) of BI. A significant decrease over time in the hemodynamic values, respiratory rate, and shivering was seen in the active core-rewarming group when compared with the controls. The temporal course of shivering was different from those of body temperatue and BI. The control patients showed a significant increase in the serum-potassium levels, which were not seen in the active-core rewarming group.

Conclusions

The BI analysis changed as a function of the changes of core temperature and independently of the shivering. In addition, our results support the beneficial use of active core rewarming to prevent accidental hypothermia.