Intraoperative Hypothermia and Surgical Site Infections in Patients with Class I/Clean Wounds: A Case-Control Study

Relationship between intraoperative hypothermia and hyperthermia with postoperative pulmonary infection and surgical site infection in major non-cardiac surgery

Background

Surgical patients often experience intraoperative hypothermia or hyperthermia. However, the relationship of intraoperative hypothermia and hyperthermia with postoperative pulmonary infection (PPI) and surgical site infection (SSI) is unclear. Here, we conducted a retrospective cohort study to address these issues.

Methods

Adult patients who underwent major non-cardiac surgery under general anesthesia were eligible for the study and were recruited. Three indices of core body temperature under hypothermia (<36°C) and hyperthermia (>37.3°C) were calculated as mentioned in the following: absolute value (0C), duration of exposure (min), and area under the curve (AUC,°C× min). The outcomes were in-hospital PPI and SSI. The risk-adjusted association of intraoperative hypothermia and hyperthermia with PPI and SSI was determined.

Results

The absolute value (the nadir value of hypothermia and the peak value of hyperthermia) was not associated with PPI and SSI. PPI was associated with (1) duration: hypothermia >90 min [adjusted odds ratio (aOR): 1.425, 95% confidence interval (CI): 1.131-1.796] and hyperthermia >75 min (aOR: 1.395, 95%CI: 1.208-1.612) and (2) AUC: hypothermia >3,198 (aOR: 1.390, 95%CI: 1.128-1.731) and hyperthermia >7,945 (aOR: 2.045, 95%CI: 1.138-3.676). SSI was associated with (1) duration: hypothermia > 195 min (aOR: 2.900, 95%CI: 1.703-4.937) and hyperthermia >75 min (aOR: 1.395, 95%CI: 1.208-1.612) and (2) AUC: hypothermia >6,946 (aOR: 2.665, 95%CI: 1.618-4.390), hyperthermia >7,945 (aOR: 2.619, 95%CI: 1.625-4.220). Interactions were not observed between hyperthermia and hypothermia on the outcomes.

Conclusions

It was observed that intraoperative hypothermia and hyperthermia are associated with postoperative pulmonary infection and surgical site infection in major non-cardiac surgery.

The relationship between intraoperative hypothermia and the ccurrence of surgical site infections: a meta-analysis of observational studies

Objective

Inconsistent evidence exists regarding the association between intraoperative hypothermia and incidence of surgical site infection (SSI). This study aimed to determine the association between intraoperative hypothermia and SSI.

Materials and methods

A systematic review was conducted using Embase, PubMed, and Web of Science to identify observational studies evaluating the risk of SSI in patients with intraoperative hypothermia. The primary outcome measure was the diagnosis of SSI within 30 days of surgery. The pooled risk ratio was estimated using a fixed- or random-effect meta-analysis. Sensitivity analyses were performed to examine the impact of the structural design of preoperative warming on the pooled risk of SSI.

Results

Five studies representing 6,002 patients were included in the present meta-analysis. Intraoperative hypothermia was not associated with SSI risk in patients (HR = 1.22, 95% CI: 0.95-2.24, P = 0.119). The pooled hazard ratio showed that intraoperative hypothermia did not result in a higher risk of SSI.

Conclusions

Intraoperative hypothermia was not associated with the risk of SSI. Further studies using objective exposure measurements are required to confirm these results.

The relationship between intraoperative hypothermia and postoperative delirium: The PNDRFAP study

OBJECTIVE

Our study aimed to investigate the correlation between intraoperative hypothermia and postoperative delirium (POD) in patients undergoing general anesthesia for gastrointestinal surgery.

METHODS

The study comprised 750 participants from the Perioperative Neurocognitive Disorder Risk Factor and Prognosis (PNDRFAP) study database, which ultimately screened 510 individuals in the final analysis. Preoperative cognitive function was evaluated using the Mini-Mental State Examination (MMSE). The occurrence of POD was determined using the Confusion Assessment Method, and the severity of POD was evaluated using the Memorial Delirium Assessment Scale. Logistic regression was employed to scrutinize the association between intraoperative hypothermia and the incidence of POD, and the sensitivity analysis was conducted by introducing adjusted confounding variables. Decision curves and a nomogram model were utilized to assess the predictive efficacy of intraoperative hypothermia for POD. Mediation analysis involving 10,000 bootstrapped iterations was employed to appraise the suggested mediating effect of numeric rating scale (NRS) scores at 24 and 48 h post-surgeries. The receiver-operating characteristic (ROC) was utilized to evaluate the effectiveness of intraoperative hypothermia in predicting POD.

RESULTS

In the PNDRFAP study, the occurrence of POD was notably higher in the intraoperative hypothermia group (62.2%) compared to the intraoperative normal body temperature group (9.8%), with an overall POD incidence of 17.6%. Logistic regression analysis, adjusted for various confounding factors (age [40-90], gender, education, MMSE, smoking history, drinking history, hypertension, diabetes, and the presence of cardiovascular heart disease), demonstrated that intraoperative hypothermia significantly increased the risk of POD (OR = 4.879, 95% CI = 3.020-7.882, p < .001). Mediation analyses revealed that the relationship between intraoperative hypothermia and POD was partially mediated by NRS 24 h after surgery, accounting for 14.09% of the association (p = .002). The area under the curve of the ROC curve was 0.685, which confirmed that intraoperative hypothermia could predict POD occurrence to a certain extent. Decision curve and nomogram analyses, conducted using the R package, further substantiated the predictive efficacy of intraoperative hypothermia on POD.

CONCLUSION

Intraoperative hypothermia may increase the risk of POD, and this association may be partially mediated by NRS scores 24 h after surgery.

Ability of minimally invasive surgery to decrease incisional surgical site infection occurrence in patients with colorectal cancer and other gastroenterological malignancies

Background

Surgical site infection (SSI) is one of the most important complications of surgery for gastroenterological malignancies because it leads to a prolonged postoperative hospital stay and increased inpatient costs. Furthermore, SSI can delay the initiation of postoperative treatments, including adjuvant chemotherapy, negatively affecting patient prognosis. Identifying the risk factors for SSI is important to improving intra- and postoperative wound management for at-risk patients.

Methods

Patients with gastroenterological malignancies who underwent surgery at our institution were retrospectively reviewed and categorized according to the presence or absence of incisional SSI. Clinicopathological characteristics such as age, sex, body mass index, malignancy location, postoperative blood examination results, operation time, and blood loss volume were compared between groups. The same analysis was repeated of only patients with colorectal malignancies.

Results

A total of 528 patients (330 men, 198 women; mean age, 68 ± 11 years at surgery) were enrolled. The number of patients with diseases of the esophagus, stomach, small intestine, colon and rectum, liver, gallbladder, and pancreas were 25, 150, seven, 255, 51, five, and 35, respectively. Open surgery was performed in 303 patients vs. laparoscopic surgery in 225 patients. An incisional SSI occurred in 46 patients (8.7%). Multivariate logistic regression analysis showed that postoperative hyperglycemia (serum glucose level ≥140 mg/dl within 24 h after surgery), colorectal malignancy, and open surgery were independent risk factors for incisional SSI. In a subgroup analysis of patients with colorectal malignancy, incisional SSI occurred in 27 (11%) patients. Open surgery was significantly correlated with the occurrence of incisional SSI (P = 0.024).

Conclusions

Postoperative hyperglycemia and open surgery were significant risk factors for SSI in patients with gastroenterological malignancies. Minimally invasive surgery could reduce the occurrence of incisional SSI.

Surgical Site Infection in Thoracic Surgery Is Not Associated With Perioperative Hypothermia

INTRODUCTION

The Surgical Care Improvement Project (SCIP) added the SCIP-Inf-10 measure to mandate that all surgical patients have perioperative temperature management to reduce surgical site infection. While the basis of this measure originated in colorectal surgery, we hypothesized that this would also apply to thoracic surgery patients.

METHODS

This was a retrospective single-center pilot study reviewing two years of thoracic surgery cases for the incidence and duration of hypothermia during the operation and surgical site infection occurring within 30 days. Hypothermia was defined as a core temperature of < 36° C.  Results: A total of 317 patients were included in the study. Sixty-two percent of patients were identified as hypothermic. The average intraoperative temperature was 35.4°C ± 0.8°C in the hypothermic group and 36.4°C ± 0.3°C in the normothermic group. There were four surgical site infections in the study with three cases from the <36°C group (p = 1). There was no difference in average post-anesthesia care unit length of stay between the groups. The average hospital length of stay was 5.5 ± 5.2 days for the hypothermic group and 8.6 ± 12.8 days for the normothermic group (p=0.0024).

CONCLUSION

Perioperative hypothermia was common in thoracic surgery and did not have a negative impact on surgical site infection.

The Role of Perioperative Hypothermia in the Development of Surgical Site Infection: A Systematic Review

Surgical patients may experience inadvertent perioperative hypothermia, a condition that can cause a variety of complications, including surgical site infection (SSI). The authors of this systematic review used the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols guidelines to examine the role of perioperative hypothermia in the development of SSI. The authors searched the PubMed, Cumulative Index Nursing and Allied Health Literature, Cochrane, and ScienceDirect databases for eligible articles published between January 2008 and November 2018 and identified seven studies that met the inclusion criteria. The results of this review indicate that the relationship between hypothermia and SSI is closely related to the type of the surgical intervention performed (eg, emergent, colorectal), and that severe hypothermia (eg, <35.0° C [95.0° F]) can increase the risk of developing an SSI. Perioperative nurses should monitor patients for inadvertent hypothermia and prevent its occurrence when possible.

Surgical Infection Society Research Priorities: A Narrative Review of Fourteen Years of Progress

Background: In 2006, the Surgical Infection Society (SIS) utilized a modified Delphi approach to define 15 specific priority research questions that remained unanswered in the field of surgical infections. The aim of the current study was to evaluate the scientific progress achieved during the ensuing period in answering each of the 15 research questions and to determine if additional research in these fields is warranted. Methods: For each of the questions, a literature search using the National Center for Biotechnology Information (NCBI) was performed by the Scientific Studies Committee of the SIS to identify studies that attempted to address each of the defined questions. This literature was analyzed and summarized. The data on each question were evaluated by a surgical infections expert to determine if the question was answered definitively or remains unanswered. Results: All 15 priority research questions were studied in the last 14 years; six questions (40%) were definitively answered and 9 questions (60%) remain unanswered in whole or in part, mainly because of the low quality of the studies available on this topic. Several of the 9 unanswered questions were deemed to remain research priorities in 2020 and warrant further investigation. These included, for example, the role of empiric antimicrobial agents in nosocomial infections, the use of inotropes/vasopressors versus volume loading to raise the mean arterial pressure, and the role of increased antimicrobial dosing and frequency in the obese patient. Conclusions: Several surgical infection-related research questions prioritized in 2006 remain unanswered. Further high-quality research is required to provide a definitive answer to many of these priority knowledge gaps. An updated research agenda by the SIS is warranted at this time to define research priorities for the future.

Perioperative body temperature maintenance and occurrence of surgical site infection: A systematic review with meta-analysis

BACKGROUND

Current guidelines recommend perioperative warming as one of the strategies to prevent surgical site infection, although there are gaps in the knowledge produced on this issue.

AIM

Assess the efficacy of active warming methods to maintain perioperative patients' body temperature and its effect on the occurrence of surgical site infection.

METHODS

A systematic review with meta-analysis was carried out. PubMed, CINAHL, LiLACS, CENTRAL, and EMBASE databases were searched.

FINDINGS

Of the 956 publications identified, 9 studies were selected for quantitative synthesis and 6 for the meta-analysis. The forced-air warming system was investigated in 8 studies. The generated evidence indicated that the use of an active warming method could maintain higher average body temperature as well as could decrease the surgical site infection incidence. Exposure of the patient to temperatures below 36°C in the perioperative period increased the chances of developing this type of infection. The meta-analysis indicated that the association between perioperative active warming methods compared with others to reduce the chances of developing surgical site infection remains unclear (odds ratio = e^-3.59 = 2.718^-0.59 = 0.552, 95% confidence interval (odds ratio) = (0.269-1.135), P = 0.106 I² = 54.34%).

CONCLUSIONS

The employment of an active warming method is effective to maintain higher averages of body temperature. However, more randomized clinical trials are needed to assess the efficacy of that intervention to prevent surgical site infection.

Current Strategies in Prevention of Postoperative Infections in Spine Surgery

STUDY DESIGN

Narrative review.

OBJECTIVES

Postoperative surgical site infections (SSIs) are among the most common acute complications in spine surgery and have a devastating impact on outcomes. They can lead to increased morbidity and mortality as well as greater economic burden. Hence, preventive strategies to reduce the rate of SSIs after spine surgery have become vitally important. The purpose of this article was to summarize and critically analyze the available evidence related to current strategies in the prevention of SSIs after spine surgery.

METHODS

A literature search utilizing Medline database was performed. Relevant studies from all the evidence levels have been included. Recommendations to decrease the risk of SSIs have been provided based on the results from studies with the highest level of evidence.

RESULTS

SSI prevention occurs at each phase of care including the preoperative, intraoperative, and postoperative periods. Meticulous patient selection, tight glycemic control in diabetics, smoking cessation, and screening/eradication of Staphylococcus aureus are some of the main preoperative patient-related preventive strategies. Currently used intraoperative measures include alcohol-based skin preparation, topical vancomycin powder, and betadine irrigation of the surgical site before closure. Postoperative infection prophylaxis can be performed by administration of silver-impregnated or vacuum dressings, extended intravenous antibiotics, and supplemental oxygen therapy.

CONCLUSIONS

Although preventive strategies are already in use alone or in combination, further high-level research is required to prove their efficacy in reducing the rate of SSIs in spine surgery before evidence-based standard infection prophylaxis guidelines can be built.

Effects of intraoperative temperatures on postoperative infections in infants and neonates

BACKGROUND

Perioperative hypothermia has been shown to increase surgical site infection (SSI) rates in adults. We sought to characterize whether intraoperative hypothermia or hyperthermia is associated with postoperative infections in infants.

METHODS

We conducted a retrospective review of patients ≤6 months old who underwent surgical procedures from November 2013 to October 2015 at a Level I ACS Children's Surgical Center. The outcome was infections within 30 days after operation, with particular attention to SSI. Data obtained included weight and age at surgery, American Society of Anesthesiologists (ASA) physiologic status, wound class, case length, blood transfusion within 72 h of surgery, and administration of prophylactic antibiotics. Temperatures were classified as hypothermia (T < 36 °C), normothermia (T = 36.0 to 37.9 °C), and hyperthermia (T ≥ 38 °C).

RESULTS

The 885 patients had 25 SSIs (2.8%) and 11 nonsurgical site infections (1.2%). On univariate analysis, weight at surgery, higher ASA, perioperative transfusions, and longer case length were associated with higher rate of SSI. Higher median T_high, higher median T _low, and any hyperthermia were associated with higher rate of SSI. On multivariable logistic regression adjusted analyses, hyperthermia at any time during the case was associated with SSI (OR 3.47, [95% CI 1.34, 9.04], p = 0.011). Transfusions were also associated with higher SSI rates (OR 3.60 [95% CI, 1.28, 10.3], p = 0.016).

CONCLUSIONS

Intraoperative hyperthermia is associated with increased SSI rates in infants.

LEVEL OF EVIDENCE

III.

Mild hypothermia is associated with improved outcomes in patients undergoing microvascular head and neck reconstruction

OBJECTIVE

Microvascular free tissue transfer has become the standard for reconstruction for large defects. With long operative times and an increased surface area exposed, transient hypothermia is common, but it is unclear how this impacts surgical outcomes. This study evaluated the impact of core body temperature on free tissue flap outcomes in patients undergoing microvascular reconstruction.

STUDY DESIGN

Retrospective data analysis.

SETTING

Mount Sinai Hospital; NYC, NY; 2007-2016.

SUBJECTS AND METHODS

Demographic information, mean/minimum/maximum body temperatures, and the presence of flap complications (venous thrombosis, arterial insufficiency, flap death, wound infection/dehiscence, fistula, chyle leak, hematoma/seroma) of 519 free tissue transfer patients were documented. Binomial logistic regression was used to examine associations between the presence of flap complications and mean temperature. Statistical analysis used SPSS, with p-values ≤0.05 deemed statistically significant.

RESULTS

393 soft-tissue and 125 osteocutaneous flaps were included. 19.8% (n = 103) patients had the presence of ≥1 flap complication, while 80.2% (n = 416) did not. Average temperature for all patients was 36.12 ± 0.84 °C, with minimum at 34.43 ± 0.97 °C and maximum at 37.24 ± 1.23 °C. After controlling for several factors including: tumor stage, radiation, diabetes, BMI, age, sex, and flap type, there was a significant association between flap complications and mean intraoperative temperature (Exp(B) = 1.559, p = 0.004).

CONCLUSION

Higher intraoperative temperatures were associated with worse outcomes. A mild relative hypothermia may improve flap outcomes in this population. This represents the largest study to date evaluating the impact of intraoperative temperature on free tissue transfer outcomes.

Effects of a multifaceted individualized pneumoperitoneum strategy in elderly patients undergoing laparoscopic colorectal surgery: A retrospective study

BACKGROUND

Laparoscopic colorectal surgery may adversely affect respiration, circulation, and acid-base balance in elderly patients, owing to the relatively long duration of CO2 absorption. We conducted this retrospective study to determine the safety and efficacy of warmed, humidified CO2 pneumoperitoneum in elderly patients undergoing laparoscopic colorectal surgery.

METHODS

We enrolled 245 patients between January 2016 and August 2018.The experimental group (warming and humidification group [WH]) received warmed (37°C), humidified (98%) insufflation of CO2, and the control group (cold, dry CO2/control group [CD]) received standard CO2 (19°C, 0%). All other aspects of patient care were standardized. Intraoperative hemodynamic data, arterial blood pH, and lactic acid levels were recorded. We also recorded intra-abdominal pressure, incidence of shivering 1 hour after surgery, satisfaction scores of patients and surgeons 24 hours after surgery, times to first flatus/defecation, first bowel movement, and tolerance of semiliquid food, discharge time, and incidence of vomiting, diarrhea, and surgical site infections.

RESULTS

Compared with the WH group, heart rate and mean arterial pressure were significantly higher from T3 to T8 (P < .05), lactic acid levels were significantly higher from T4 to T9 (P < .05), and recovery time in the post-anesthesia care unit (PACU) was significantly longer in the CD group (P < .05). Patient and surgeon satisfaction scores were significantly higher in the WH group than the CD group (P < .05). In addition, the times to first flatus/defecation and bowel movement were significantly longer in the CD group (P < .05). No significant differences were noted between the groups in the time to tolerance of semiliquid food and time of discharge (P > .05). The incidence of vomiting, diarrhea, and shivering was significantly lower in the WH group (P < .05). The number of patients with a shivering grade of 0 was significantly higher in the WH group, whereas the number with a shivering grade of 3 was significantly higher in the CD group (P < .05).

CONCLUSION

Warmed, humidified insufflation of CO2 in elderly patients undergoing laparoscopic colorectal surgery could stabilize hemodynamics, and reduce lactic acid levels, recovery time in the PACU, and the incidence of acute gastrointestinal injury-related symptoms.

Risk Factors for Surgical Site Infections Following Vertical Expandable Prosthetic Titanium Rib (VEPTR) Surgery in Children

STUDY DESIGN

Case-control study.

OBJECTIVES

To identify risk factors for surgical site infections (SSIs) following vertical expandable prosthetic titanium rib (VEPTR) surgery in children.

SUMMARY OF BACKGROUND DATA

VEPTR surgery is a growth-sparing approach for early-onset scoliosis and chest or rib abnormalities. SSIs are an important complication following VEPTR surgery. We aimed to identify modifiable risk factors for SSIs following VEPTR surgery.

METHODS

Children who underwent VEPTR surgery at a tertiary-care children's hospital from January 2010 through November 2014 were included. SSIs following VEPTR implant or revision surgeries were identified. For each case patient, three control subjects matched by procedure type were randomly selected among those without infection. Patient and surgery-related risk factors were analyzed using conditional logistic regression.

RESULTS

Twenty-six infections occurred in 22 subjects following 326 VEPTR surgeries (SSI rate: 8.0%). The infection rate was greater among implant than revision surgeries (15.5% vs. 4.5%; p<.001). Methicillin-susceptible Staphylococcus aureus was the most common pathogen (50% of infections). On multivariate analysis, VEPTR SSI infections were associated with male gender (OR 3.5, 95% CI 0.9-13.2), assisted feeding (OR 4.5, 95% CI 1.0-20.3), administration of preoperative antibiotics more than 30 minutes before surgery (or >60 minutes for vancomycin) (OR 6.9, 95% CI 1.2-39.0), and an intraoperative temperature less than 35.0°C (OR 4.3, 95% CI 0.8-23.7).

CONCLUSIONS

Administration of preoperative antibiotics closer to the time of surgery may reduce the risk of SSI in children undergoing VEPTR surgery. Further study is needed to determine the optimal timing of antibiotic prophylaxis for children undergoing spinal surgery.

LEVEL OF EVIDENCE

Level III.

Association between perioperative hypothermia and surgical site infection: A meta-analysis

BACKGROUND

A majority of reports in the past decade have demonstrated that perioperative hypothermia increases susceptibility to surgical site infection (SSI). However, in recent years, an increasing number of studies did not find an association between hypothermia and the risk of SSI. These contradictory results have given rise to a conflicting issue on whether perioperative hypothermia is associated with SSI risk in surgical patients.

METHODS

We examined the association between perioperative hypothermia and SSI incidence and then integrated available evidence by searching the databases, such as PubMed, Web of Science, Embase, and Cochrane library for potential papers from inception to April 2018. We included studies that reported original data or odds ratio (OR) with 95% confidence intervals (CIs) of the associations. Using fixed-effects models combined the OR with 95% CIs, randomized controlled trials and observational studies were analyzed, respectively, and cohort studies were further analyzed. Sensitivity analyses were performed by omitting each study iteratively, and publication bias was detected using Begg's tests.

RESULTS

We screened 384 studies, and identified 8 eligible studies, including 2 randomized controlled trials and 6 observational studies (1 case-control study and 5 cohort studies). The pooled OR results in the randomized controlled studies showed that perioperative hypothermia could increase the risk of SSI without heterogeneity (OR, 1.60; 95% CI, 1.14-2.23; I = 0.0%, P = .845). The fixed-effect meta-analysis indicated no association between perioperative hypothermia and SSI risk in observational studies (OR, 0.98; 95% CI, 0.96-1.01; I = 53.2%, P = .058). Furthermore, cohort studies were performed to pool OR by using the fixed-effect model, and the incorporated results also suggested a similar relationship (OR, 1.13; 95% CI, 0.97-1.33; I = 46.4%, P = .113).

CONCLUSION

The meta-analysis suggests that perioperative hypothermia is not associated with SSI in surgical patients. However, the 8 eligible studies were mostly cohort studies. Thus, further randomized controlled trials are required to confirm this finding.

Perioperative hypothermia during colectomy: when do patients get cold?

BACKGROUND

Hypothermia has been associated with an increase in the rate of infectious complications following colectomy. We hypothesized that a substantial fraction of temperature loss in patients undergoing elective colectomy occurs prior to operation.

METHODS

Temperature data were collected from 105 consecutive patients undergoing elective colectomy at a single institution.

RESULTS

The study population consisted of 105 patients; 67(64%) male, median age 59 years (range 17-95 years), median body mass index 27 kg/m² (range 15-48 kg/m²). Median preoperative temperature was 36.7 °C (range 35.2-39.2 °C), dropping to 35.7 °C (range 34.0-37.3 °C) immediately following intubation and then rising to 36.2 °C (range 34.0-38.0 °C) prior to leaving the operating room. The median first postoperative temperature was 36.3 °C (range 34.4-37.7 °C). Temperatures were significantly different from one another (p < 0.05, ANOVA), except for the last operative and first postoperative temperature. A first postoperative temperature of ≥ 36.0 °C (meeting Surgical Care Improvement criteria Inf-10) was achieved in 78 (74%) of patients. A preoperative temperature of ≥ 36.5 °C was associated with a first postoperative temperature of ≥ 36.0 °C, but operative approach (laparoscopic versus open) was not.

CONCLUSIONS

Most temperature loss occurs prior to operation in patients undergoing colectomy. Patients are rewarmed during the operative procedure. The time period prior to operation should be the focus of efforts designed to ensure normothermia.

Intra-Operative Inspired Fraction of Oxygen and the Risk of Surgical Site Infections in Patients with Type 1 Surgical Incisions

BACKGROUND

Whether the fraction of inspired oxygen (F_IO₂) influences the risk of surgical site infection (SSI) is controversial. The World Health Organization and the World Federation of Societies of Anesthesiologists offer conflicting recommendations. In this study, we evaluate simultaneously three different definitions of F_IO₂ exposure and the risk of SSI in a large surgical population.

PATIENTS AND METHODS

Patients with clean (type 1) surgical incisions who developed superficial and deep organ/space SSI within 30 days after surgery from January 2003 through December 2012 in five surgical specialties were matched to specialty-specific controls. Fraction of inspired oxygen exposure was defined as (1) nadir F_IO₂, (2) percentage of operative time with F_IO₂ greater than 50%, and (3) cumulative hyperoxia exposure, calculated as the area under the curve (AUC) of F_IO₂ by time for the duration in which F_IO₂ greater than 50%. Stratified univariable and multivariable logistic regression models tested associations between F_IO₂ and SSI.

RESULTS

One thousand two hundred fifty cases of SSI were matched to 3,248 controls. Increased oxygen exposure, by any of the three measures, was not associated with the outcome of any SSI in a multivariable logistic regression model. Elevated body mass index (BMI; 35+ vs. <25, odds ratio [OR] 1.78, 95% confidence interval [CI] 1.43-2.24), surgical duration (250+ min vs. <100 min, OR 1.93, 95% CI 1.48-2.52), diabetes mellitus (OR 1.37, 95% CI 1.13-1.65), peripheral vascular disease (OR 1.52, 95% CI 1.10-2.10), and liver cirrhosis (OR 2.48, 95% CI 1.53-4.02) were statistically significantly associated with greater odds of any SSI. Surgical sub-group analyses found higher intra-operative oxygen exposure was associated with higher odds of SSI in the neurosurgical and spine populations.

CONCLUSION

Increased intra-operative inspired fraction of oxygen was not associated with a reduction in SSI. These findings do not support the practice of increasing F_IO₂ for the purpose of SSI reduction in patients with clean surgical incisions.