Wound tissue oxygen tension predicts the risk of wound infection in surgical patients

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.

Identification of Various Perioperative Risk Factors Responsible for Development of Postoperative Hypoxaemia

Objective

Identification of risk factors that might be responsible for postoperative hypoxaemia, in view of changing profile of surgical patients and better but more complex perioperative care nowadays.

Methods

We conducted a prospective observational study that included patients aged 18-65 years, who underwent elective surgery and required general anaesthesia. Oxygen saturation was monitored before the induction in operating room and continued 72 hours post-surgery. Patients were maintained on room air if SpO₂ remained >94%. If SpO₂ was between 90% and 94%, then patients were provided oxygen therapy via face mask (flow rate at 5-6 litre min^-1). If SpO₂ was between 89%-85% despite oxygen therapy with face mask, the Bilevel Positive Airway Pressure (BiPAP) was applied. If SpO₂ was <85% despite therapy with face mask, or if patient was unable to maintain SpO₂>90% on BiPAP, then patient was intubated, and ventilatory support was provided.

Results

Out of 452 patients, 61 developed SpO₂ ≤94% requiring oxygen therapy (13.5%). Oxygen therapy by face mask was required in 51 patients, BiPAP in 8 and ventilatory support with endotracheal intubation in 2. Age, body mass index (BMI), smoking status, presence of preoperative respiratory disease, SPO₂ (on room air) at baseline and immediately after the transfer to the post-anaesthesia care unit (PACU) were independently associated with postoperative oxygen therapy.

Conclusion

The risk of postoperative hypoxaemia was highest in patients aged 51-65 years, BMI higher than 30, current and former smokers, pre-existing respiratory disease, chronic obstructive pulmonary disease, patients with 96% oxygen saturation or less at baseline or after shifting to PACU. The type of surgical incision, duration of surgery and dose of opioids administered were not independent risk factors.

Intermittent mild negative pressure applied to the lower limb in patients with spinal cord injury and chronic lower limb ulcers: a crossover pilot study

STUDY DESIGN

Randomized, assessor-blinded crossover pilot study.

OBJECTIVES

To explore the use of an intermittent negative pressure (INP) device for home use in addition to standard wound care (SWC) for patients with spinal cord injury (SCI) and chronic leg and foot ulcers before conducting a superiority trial.

SETTING

Patient homes and outpatient clinic.

METHODS

A 16-week crossover trial on 9 SCI patients (median age: 57 years, interquartile range [IQR] 52-66), with leg ulcers for 52 of weeks (IQR: 12-82) duration. At baseline, patients were allocated to treatment with INP + SWC or SWC alone. After 8 weeks, the ulcers were evaluated. To assess protocol adherence, the patients were then crossed over to the other group and were evaluated again after another 8 weeks. Lower limb INP treatment consisted of an airtight pressure chamber connected to an INP generator (alternating 10 s -40mmHg/7 s atmospheric pressure) used 2 h/day at home. Ulcer healing was assessed using a photographic wound assessment tool (PWAT) and by measuring changes in wound surface area (WSA).

RESULTS

Seven of nine recruited patients adhered to a median of 90% (IQR: 80-96) of the prescribed 8-week INP-protocol, and completed the study without side effects. PWAT improvement was observed in 4/4 patients for INP + SWC vs. 2/5 patients for SWC alone (P = 0.13). WSA improved in 3/4 patients allocated to INP + SWC vs. 3/5 patients in SWC alone (P = 0.72).

CONCLUSIONS

INP can be used as a home-based treatment for patients with SCI, and its efficacy should be tested in an adequately sized, preferably multicenter randomized trial.

Current evidence on the role of smoking in plastic surgery elective procedures: A systematic review and meta-analysis

BACKGROUND

Smoking is considered to be a significant risk factor for the development of postoperative complications after various surgical procedures, mainly by limiting oxygen delivery to tissues. Evidence on the collective impact of smoking in aesthetic procedure outcomes is scarce. The aim of this study is to evaluate the current evidence on the association between smoking and postoperative outcomes in patients who underwent common elective procedures in plastic surgery.

METHODS

PubMed and Cochrane bibliographical databases were searched from January 1950 to October 2016 for studies reporting on patients who underwent facelift, abdominoplasty, breast reduction and breast reconstruction and for studies with included data on smoking history of treated patients.

RESULTS

Fifty-three studies reporting on postoperative complications in tobacco users undergoing facelift, abdominoplasty, breast reduction and reconstruction were identified. Tobacco use is found to significantly increase the total number of postoperative complications as far as abdominoplasty (OR: 5.43; 95% CI = 2.92-10.10), breast reduction (OR: 2.36; 95% CI = 1.64-3.39) and breast reconstruction (OR: 1.91; 95% CI = 1.69-2.17) are concerned. Smoking history does not significantly affect total postoperative complications after facelift procedures (OR: 3.36; 95% CI = 0.92-12.30).

CONCLUSIONS

Smoking predisposes to surgical site infections, delayed wound healing and skin necrosis in patients undergoing the most common aesthetic procedures in plastic surgery. More rigorous and detailed reporting on the history of tobacco use and surgical outcomes following plastic surgery procedures is needed to better quantify the impact of smoking on the overall postoperative care for this patient population.

A perioperative care map improves outcomes in patients with morbid obesity undergoing major surgery

BACKGROUND

The surgical management of patients with morbid obesity (body mass index ≥ 40) is notable for a relatively high risk of complications. To address this problem, a perioperative care map was developed using precautions and best practices commonly employed in bariatric surgery. It requires additional medical assessments, sleep apnea surveillance, more stringent guidelines for anesthetic management, and readily available bariatric operating room equipment, among other items. This care map was implemented in 2013 at 4 major urban teaching hospitals for use in patients undergoing all types of nonambulatory surgery with a body mass index greater than 40 kg/m². The impact on patient outcomes was evaluated.

METHODS

The American College of Surgeons National Surgical Quality Improvement Program database was used to compare 30-day outcomes of morbidly obese patients before the year 2013 and after the years 2015 care-map implementation. In addition, trends in 30-day outcomes for morbidly obese patients were compared with those for non-obese patients.

RESULTS

Morbidly obese patients, between 2013 and 2015, saw an adjusted decrease in the rate of unplanned return to the operating room (OR = 0.49; P = .039), unplanned readmission (OR = 0.57; P = .006), total duration of stay (-0.87 days; P = .009), and postoperative duration of stay (-0.69 days; P = .007). Of these, total duration of stay (-0.86 days; P = .015), and postoperative duration of stay (-0.69 days; P = .012) improved significantly more for morbidly obese patients than for nonmorbidly obese patients.

CONCLUSION

Outcomes in morbidly obese patients improved from 2013 to 2015. Implementation of a perioperative care map may have contributed to these improvements. The care map should be further investigated and considered for more widespread use.

Infection prevention in pediatric anesthesia practice

Healthcare-associated infections are an important source of morbidity and mortality in pediatric patients. Anesthesiologists have a unique role in infection prevention. Hand hygiene and anesthesia workspace decontamination decrease infection rates in surgical patients. Standard protocols exist for insertion and handling of central lines, arterial lines, and regional procedures, which should be strictly adhered to in order to prevent infectious complications. Temperature control and timely administration of antibiotics contribute to the prevention of surgical site infections. Education, culture shift, staff engagement, and effective change management are necessary for successful implementation of infection prevention strategies.

Surgical Site Infection Research Opportunities

Much has been done to identify measures and modify risk factors to decrease the rate of surgical site infection (SSI). Development of the Centers for Disease Control and Prevention (CDC) Core recommendations for the prevention of SSI revealed evidence gaps in six areas: Parenteral antimicrobial prophylaxis, glycemic control, normothermia, oxygenation, antiseptic prophylaxis, and non-parenteral antimicrobial prophylaxis. Using a modified Delphi process, seven SSI content experts identified nutritional status, smoking, obesity, surgical technique, and anemia as additional areas for SSI prevention research. Post-modified Delphi process Staphylococcus aureus colonization and SSI definition and surveillance were also deemed important topic areas for inclusion. For each topic, research questions were developed, and 10 were selected as the final SSI research questions.

Association Between Obesity and Wound Infection Following Colorectal Surgery: Systematic Review and Meta-Analysis

BACKGROUND

The aim of this meta-analysis is to comprehensively review and quantify the excess risk of surgical site infections (SSI) in obese patients following colorectal surgery.

METHODS

A systematic electronic search of the MEDLINE and EMBASE databases identified studies that investigated the association of obesity, defined by body mass index (BMI) with SSI among colorectal surgery patients.

RESULTS

Twelve studies were included in the final analysis. Patients with BMI ≥30 kg/m² were at 1.5 times (pooled OR 1.51, 95% CI: 1.39, 1.63, p < 0.001) higher odds of developing SSI after colorectal surgery when compared to BMI <30 kg/m². Subgroup analysis of the eight studies that investigated only elective procedures showed that the odds of developing SSI when BMI ≥30 kg/m² is 1.6 times that of those with BMI <30 kg/m² (pooled OR 1.60; 95% CI 1.34, 1.86; p < 0.001). The odds of having SSI when BMI is 25-29.9 kg/m² are 1.2 times than those with BMI <25 kg/m² (pooled OR 1.17; 95% CI 1.07, 1.28; p < 0.001).

CONCLUSION

Overweight and obese patients carry at least 20% and 50% higher odds of developing SSI after colorectal surgery compared to normal weight patients, respectively.

Phenylephrine infusion impact on surgical site infections after lower extremity bypass surgery

OBJECTIVE

Lower extremity bypass (LEB) operations have high rates of surgical site infections (SSI). Phenylephrine is a commonly used vasoconstrictor which may reduce skin blood flow and increase the likelihood of SSI in these patients. We studied the potential effect of phenylephrine infusion during LEB surgery on SSI.

METHODS

LEB cases and their demographic data were identified through the Vascular Quality Initiative registry. SSI in this population was identified using the hospital epidemiology surveillance database. Phenylephrine use in this population was identified through chart review.

RESULTS

We identified 699 patients who underwent LEB; 82 (11.7%) developed an SSI, and 244 of 698 (35.0%) were treated with phenylephrine infusion. In bivariate analysis, higher body mass index (28.8 kg/m² vs 27.3 kg/m²; P = .034), diabetes (14.6% vs 9.4%; P = .035), hypertension (12.6% vs 4.7%; P = .038), groin incision (13.2 vs 5.4%; P = .013) and longer procedure times (17.1% for >220 minutes and 8.9% for ≤220 minutes; P = .003) were associated with higher rates of SSI. Whereas phenylephrine infusion exhibited a trend toward a higher rate (14.8% vs 9.9%; P = .057). In the logistic regression model, diabetes (odds ratio [OR], 1.8; 95% confidence interval [CI], 1.0-3.2; P = .032), total procedure time (OR, 1.85; 95% CI, 1.1-3.1; P = .026) and vertical groin incision (OR, 2.6; 95% CI, 1.1-6.5; P = .035) were independent predictors of increased SSI rates, whereas body mass index (OR, 1.04; 95% CI, 0.99-1.08; P = .09), hypertension (OR, 2.5; 95% CI, 0.6-10.9; P = .22), and phenylephrine infusion (OR, 1.08; 95% CI, 0.63-1.85; P = .78) were not independent predictors of increased SSI rates.

CONCLUSIONS

Phenylephrine infusion did not increase the risk of SSI in patients who underwent LEB.

Association Between Smoking Status, Preoperative Exhaled Carbon Monoxide Levels, and Postoperative Surgical Site Infection in Patients Undergoing Elective Surgery

Importance

Cigarette smoking is a risk factor for many perioperative complications, including surgical site infection (SSI). The duration of abstinence from smoking required to reduce this risk is unknown.

Objectives

To evaluate if abstinence from smoking on the day of surgery is associated with a decreased frequency of SSI in patients who smoke cigarettes and to confirm that smoking is significantly independently associated with SSI when adjustment is made for potentially relevant covariates, such as body mass index.

Design, Setting, and Participants

In this observational, nested, matched case-control study, 2 analyses were performed at an academic referral center in the upper Midwest. Cases included all patients undergoing elective surgical procedures at Mayo Clinic, Rochester, Minnesota, between January 1, 2009, and July 31, 2014 (inclusive) who subsequently developed an SSI. Controls for both analyses were matched on age, sex, and type of surgery.

Exposures

Smoking status and preoperative exhaled carbon monoxide level, assessed by nurses in the preoperative holding area. Patients were classified as smoking on the day of surgery if they self-reported smoking or if their preoperative exhaled carbon monoxide level was 10 ppm or higher.

Main Outcomes and Measures

Surgical site infection after a surgical procedure at Mayo Clinic, Rochester, as identified by routine clinical surveillance using National Healthcare Safety Network criteria.

Results

Of the 6919 patients in the first analysis, 3282 (47%) were men and 3637 (53%) were women; median age (interquartile range) for control and SSI cases was 60 (48-70). Of the 392 patients in the second analysis, 182 (46%) were men and 210 (54%) were women; median age (interquartile range) for controls was 53 (45-49) and for SSI cases was 51 (45-60). During the study period, approximately 2% of surgical patients developed SSI annually. Available for the first analysis (evaluating the influence of current smoking status) were 2452 SSI cases matched to 4467 controls. The odds ratio for smoking and SSI was 1.51 (95% CI, 1.20-1.90; P < .001), which remained statistically significant after adjusting for covariates. In the second analysis (evaluating the influence of smoking on the day of surgery), there were 137 SSI cases matched to 255 controls. The odds ratio for smoking on the day of surgery and SSI was 1.96 (95% CI, 1.23-3.13; P < .001), which remained statistically significant after adjusting for covariates. Preoperative exhaled carbon monoxide level was not associated with the frequency of SSI, suggesting that the association between smoking on the day of surgery and SSI was not related to preoperative exhaled carbon monoxide levels.

Conclusions and Relevance

Current smoking is associated with the development of SSI, and smoking on the day of surgery is independently associated with the development of SSI. These data cannot distinguish whether abstinence per se reduces risk or whether it is associated with other factors that may be causative.

WHO Needs High FIO2?

World Health Organization and the United States Center for Disease Control have recently recommended the use of 0.8 FIO₂ in all adult surgical patients undergoing general anaesthesia, to prevent surgical site infections. This recommendation has arisen several discussions: As a matter of fact, there are numerous studies with different results about the effect of FIO₂ on surgical site infection. Moreover, the clinical effects of FIO₂ are not limited to infection control. We asked some prominent authors about their comments regarding the recent recommendations.

Fat Thickness as a Risk Factor for Infection in Lumbar Spine Surgery

Body mass index does not account for body mass distribution. This study tested the hypothesis that subcutaneous fat thickness is a better indicator than body mass index of the risk of surgical site infection in lumbar spine procedures performed through a midline posterior approach. Charts were reviewed for previously identified risk factors for surgical site infection (age, diabetes, smoking, obesity, albumin level, multilevel procedures, previous surgery, and operative time) in 149 adult patients who underwent lumbar spine procedures through a midline posterior approach. Subcutaneous fat thickness was measured with a novel automated technique. Regression analysis was used to determine associations between risk factors and fat thickness with surgical site infection. In the study group, 15 surgical site infections occurred (10.1%). Bivariate analysis showed a significant association between surgical site infection and body mass index (P=.01), obesity (P=.02), and fat thickness (P=.002). With multivariate analysis, body mass index and obesity did not show significance, but fat thickness remained significant (P=.026). For every 1-mm thickness of subcutaneous fat there was a 6% (odds ratio, 1.06; 95% confidence interval, 1.02-1.10) increase in the odds of surgical site infection, and patients with fat thickness of greater than 50 mm had a 4-fold increase in the odds of surgical site infection compared with those with fat thickness of less than 50 mm. Body mass index and fat thickness were moderately correlated (r²=0.44). These results confirm the hypothesis that local subcutaneous fat thickness is a better indicator than body mass index of the risk of surgical site infection in lumbar spine procedures. [Orthopedics. 2016; 39(6):e1124-e1128.].

Postoperative hypothermia and surgical site infection following peritoneal insufflation with warm, humidified carbon dioxide during laparoscopic colorectal surgery: a cohort study with cost-effectiveness analysis

Background

Surgical Site Infection (SSI) occurs in 9 % of laparoscopic colorectal surgery. Warming and humidifying carbon dioxide (CO₂) used for peritoneal insufflation may protect against SSI by avoiding postoperative hypothermia (itself a risk factor for SSI). This study aimed to assess the impact of CO₂ conditioning on postoperative hypothermia and SSI and to perform a cost-effectiveness analysis.

Methods

A retrospective cohort study of patients undergoing elective laparoscopic colorectal resection was performed at a single UK specialist centre. The control group (n = 123) received peritoneal insufflation with room temperature, dry CO₂, whereas the intervention group (n = 123) received warm, humidified CO₂ (using HumiGard™, Fisher & Paykel Healthcare). The outcomes were postoperative hypothermia, SSI and costs. Multivariate analysis was performed.

Results

A total of 246 patients were included in the study. The mean age was 68 (20–87) and mean BMI 28 (15–51). The primary diagnosis was cancer (n = 173), and there were no baseline differences between the groups. CO₂ conditioning significantly decreased the incidence of postoperative hypothermia (odds ratio 0.10, 95 % CI 0.04–0.23), with hypothermic patients found to be at increased risk of SSI (odds ratio 4.0, 95 % CI 1.25–12.9). Use of conditioned CO₂ significantly decreased the incidence of SSI by 66 % (p = 0.04). The intervention group incurred costs of £155 less per patient. The incremental cost-effectiveness ratio was negative.

Conclusion

CO₂ conditioning during laparoscopic colorectal surgery is a safe, feasible and a cost-effective intervention. It improves the quality of surgical care relating to SSI and postoperative hypothermia.

Can a urine dipstick test be used to assess smoking status in patients undergoing planned orthopaedic surgery? a prospective cohort study

AIMS

Smoking is associated with post-operative complications but smokers often under-report the amount they smoke. Our objective was to determine whether a urine dipstick test could be used as a substitute for quantitative cotinine assays to determine smoking status in patients.

PATIENTS AND METHODS

Between September 2013 and July 2014 we conducted a prospective cohort study in which 127 consecutive patients undergoing a planned foot and ankle arthrodesis or osteotomy were included. Patients self-reported their smoking status and were classified as: 'never smoked' (61 patients), 'ex-smoker' (46 patients), or 'current smoker' (20 patients). Urine samples were analysed with cotinine assays and cotinine dipstick tests.

RESULTS

There was a high degree of concordance between dipstick and assay results (Kappa coefficient = 0.842, p < 0.001). Compared with the quantitative assay, the dipstick had a sensitivity of 88.9% and a specificity of 97.3%. Patients claiming to have stopped smoking just before surgery had the highest rate of disagreement between reported smoking status and urine testing.

CONCLUSION

Urine cotinine dipstick testing is cheap, fast, reliable, and easy to use. It may be used in place of a quantitative assay as a screening tool for detecting patients who may be smoking. A positive test may be used as a trigger for further assessment and counselling. Cite this article: Bone Joint J 2016;98-B:1418-24.

The Effect of Early Postoperative Physical Activity on Tissue Oxygen and Wound Healing

Background. Supplemented postoperative activity was compared to standard activity for effects on wound healing, subcutaneous tissue perfusion, and oxygen (PscO2 ) following hip replacement (THR).

Methods. 58 patients were randomized to standard post-THR activity (N = 27) or supplemental activity (N = 31) (arm and leg exercises, walking protocol). PscO2 was measured with a microelectrode/tonometer system and perfusion determined by oxygen response. Healing was evaluated by (1) tissue cellularity, (2) mRNA for pro collagen, (3) hydroxyproline, and (4) DNA content obtained from a subcutaneous implant removed on the 7th postoperative day.

Results. Activity significantly increased DNA levels, but did not increase PscO2 , perfusion, cellularity, or collagen measures.

Conclusions. Healing measures were not improved with increased activity levels. However, activity did not reduce PscO2 or wound healing. The majority of patients adhered to additional activity and tolerated the protocol well. Increased activity was associated with earlier discharge, suggesting other recovery-related benefits.

Treatment of Acute Purulent Dacryocystitis by Early Bicanalicular Silicone Intubation: Safety, Efficacy, and Outcomes

PURPOSE

To evaluate the safety, efficacy, and outcomes of early bicanalicular silicone intubation in the treatment of acute purulent dacryocystitis.

METHODS

This prospective interventional case series focused on acute purulent dacryocystitis from February 2010 to March 2014. Of the 21 cases, 16 cases were treated at the Fujian Provincial Hospital, and five cases were treated at the Lianjiang Hospital. Bicanalicular silicone intubation was inserted in the original lacrimal duct within 10 days after abscess decompression by pus aspiration method and systemic antibiotic application. Data collection included demographic profiles, perioperative and postoperative complications, and revision surgery. Resolution of signs and symptoms of acute purulent dacryocystitis, as well as successful anatomical patency assessed by irrigation, was evaluated. Follow-up times were more than 12 months, and ranged from 14 to 63 months.

RESULTS

All patients showed remarkable improvement of pain and swelling within 48 hours. Resolution of the erythema and edema was observed within one week after bicanalicular silicone intubation combined with topical antibiotic lavage. No intraoperative and postoperative complications were observed. After initial bicanalicular silicone intubation, anatomical success was observed in 66.7% (14/21) of the patients. Of the remaining seven patients who presented with severe reflux in irrigation, two patients chose re-intubation and five patients underwent standard external dacryocystorhinostomy. All patients had anatomical success at last follow-up.

CONCLUSION

Early bicanalicular silicone intubation appears to be a safe, effective, and simple procedure, which offers a reasonable option in the treatment of acute purulent dacryocystitis, especially for those developing and underdeveloped areas.

Optical Measurement of Tissue Oxygen Saturation

Advances in opto-electronic systems have meant that optical spectroscopy can now be used for noninvasive measurements in tissue in patients. A number of techniques have evolved over the last 15 years that make use of the characteristic differences in the absorption spectrum of deoxygenated and oxygenated hemoglobin to measure oxygen saturation. This article summarizes, in particular, those techniques that may prove to be applicable to measurements relating to lower extremity wounds. A short introduction is given about existing electrode methods before describing applications of near infrared and visible wavelength spectroscopy to measurements in tissue. The advantages and limitations of these methods are discussed. An example of an area where tissue spectroscopy is now in routine clinical use for tissue healing viability assessment is presented.

Heat for wounds - water-filtered infrared-A (wIRA) for wound healing - a review

Background: Water-filtered infrared-A (wIRA) is a special form of heat radiation with high tissue penetration and a low thermal load to the skin surface. wIRA corresponds to the major part of the sun’s heat radiation, which reaches the surface of the Earth in moderate climatic zones filtered by water and water vapour of the atmosphere. wIRA promotes healing of acute and chronic wounds both by thermal and thermic as well as by non-thermal and non-thermic cellular effects.

Methods: This publication includes a literature review with search in PubMed/Medline for “water-filtered infrared-A” and “wound”/”ulcus” or “wassergefiltertes Infrarot A” and “Wunde”/”Ulkus”, respectively (publications in English and German), and additional analysis of study data. Seven prospective clinical studies (of these six randomized controlled trials (RCT), the largest study with n=400 patients) were identified and included. All randomized controlled clinical trials compare a combination of high standard care plus wIRA treatment vs. high standard care alone. The results below marked with “vs.” present these comparisons.

Results:

wIRA increases tissue temperature (+2.7°C at a tissue depth of 2 cm), tissue oxygen partial pressure (+32% at a tissue depth of 2 cm) and tissue perfusion (effect sizes within the wIRA group).

wIRA promotes normal as well as disturbed wound healing by diminishing inflammation and exudation, by promotion of infection defense and regeneration, and by alleviation of pain (with respect to alleviation of pain, without any exception during 230 irradiations, 13.4 vs. 0.0 on a visual analogue scale (VAS 0–100), median difference between groups 13.8, 95% confidence interval (CI) 12.3/16.7, p<0.000001) with a substantially reduced need for analgesics (52–69% less in the three groups with wIRA compared to the three control groups in visceral surgery, p=0.000020 and 0.00037 and 0.0045, respectively; total of 6 vs. 14.5 analgesic tablets on 6 surveyed days (of weeks 1–6) in chronic venous stasis ulcers, median difference –8, 95% CI –10/–5, p=0.000002).

Further effects are:

Faster reduction of wound area (in severely burned children: 90% reduction of wound size after 9 vs. 13 days, after 9 days 89.2% vs. 49.5% reduction in wound area, median difference 39.5% wound area reduction, 95% CI 36.7%/42.2%, p=0.000011; complete wound closure of chronic venous stasis ulcers after 14 vs. 42 days, median difference –21 days, 95% CI –28/–10, p=0.000005).

Better overall evaluation of wound healing (surgical wounds: 88.6 vs. 78.5 on a VAS 0–100, median difference 8.9, 95% CI 6.1/12.0, p<0.000001).

Better overall evaluation of the effect of irradiation (79.0 vs. 46.8 on a VAS 0–100 with 50 as neutral point, median difference 27.9, 95% CI 19.8/34.6, p<0.000001).

Higher tissue oxygen partial pressure during irradiation with wIRA (at a tissue depth of 2 cm 41.6 vs. 30.2 mmHg, median difference 11.9 mmHg, 95% CI 9.6/14.2 mmHg, p<0.000001).

Higher tissue temperature during irradiation with wIRA (at a tissue depth of 2 cm 38.9 vs. 36.4°C, median difference 2.6°C, 95% CI 2.2/2.9°C, p<0.000001).

Better cosmetic result (84.5 vs. 76.5 on a VAS 0–100, median difference 7.9, 95% CI 3.7/12.0, p=0.00027).

Lower wound infection rate (single preoperative irradiation: 5.1% vs. 12.1% wound infections in total, difference –7.0%, 95% CI –12.8%/–1.3%, p=0.017, of these: late wound infections (postoperative days 9-30) 1.7% vs. 7.7%, difference –6.0%, 95% CI –10.3%/–1.7%, p=0.007).

Shorter hospital stay (9 vs. 11 postoperative days, median difference –2 days, 95% CI –3/0 days, p=0.022).

Most of the effects have been proven with an evidence level of 1a or 1b.

Conclusion: Water-filtered infrared-A is a useful complement for the treatment of acute and chronic wounds.

Perioperative high inspired oxygen fraction therapy reduces surgical site infection with Pseudomonas aeruginosa in rats

Surgical site infection (SSI) remains one of the most important causes of healthcare-associated infections, accounting for ~17 % of all hospital-acquired infections. Although short-term perioperative treatment with high fraction of inspired oxygen (FiO2) has shown clinical benefits in reducing SSI in colorectal resection surgeries, the true clinical benefits of FiO2 therapy in reducing SSI remain unclear because randomized controlled trials on this topic have yielded disparate results and inconsistent conclusions. To date, no animal study has been conducted to determine the efficacy of short-term perioperative treatments with high (FiO2>60 %) versus low (FiO2<40 %) oxygen in reducing SSI. In this report, we designed a rat model for muscle surgery to compare the effectiveness of short-term perioperative treatments with high (FiO2=80 %) versus a standard low (FiO2=30 %) oxygen in reducing SSI with Pseudomonas aeruginosa - one of the most prevalent Gram-negative pathogens, responsible for nosocomial SSIs. Our data demonstrate that 5 h perioperative treatment with 80 % FiO2 is significantly more effective in reducing SSI with P. aeruginosa compared to 30 % FiO2 treatment. We further show that whilst 80 % FiO2 treatment does not affect neutrophil infiltration into P. aeruginosa-infected muscles, neutrophils in the 80 % FiO2-treated and infected animal group are significantly more activated than neutrophils in the 30 % FiO2-treated and infected animal group, suggesting that high oxygen perioperative treatment reduces SSI with P. aeruginosa by enhancing neutrophil activation in infected wounds.

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.

Fluid therapy in the perioperative setting-a clinical review

BACKGROUND

Perioperative hypovolemia and fluid overload have effects on both complications following surgery and on patient survival. Therefore, the administration of intravenous fluids before, during, and after surgery at the right time and in the right amounts is of great importance. This review aims to analyze the literature concerning perioperative fluid therapy in abdominal surgery and to provide evidence-based recommendations for clinical practice.

RESULTS

Preoperative oral or intravenous administration of carbohydrate containing fluids has been shown to improve postoperative well-being and muscular strength and to reduce insulin resistance. Hence, the intake of fluid (preferably containing carbohydrates) should be encouraged up to 2 h prior to surgery in order to avoid dehydration. Excessive intravenous fluid administration adds to tissue inflammation and edema formation, thereby compromising tissue healing. During major abdominal surgery a "zero-balance" intraoperative fluid strategy aims at avoiding fluid overload (and comparable to the so-called restrictive approach) as well as goal-directed fluid therapy (GDT). Both proved to significantly reduce postoperative complications when compared to "standard fluid therapy". Trials comparing "restrictive" or zero-balance and GDT have shown equal results, as long as fluid overload is avoided in the GDT group as well (categorized as "zero-balance GDT"). It is possible that high-risk surgical patients, such as those undergoing acute surgery, may benefit from the continuous monitoring of circulatory status that the GDT provides. Data on this group of patients is not available at present, but trials are ongoing.

CONCLUSION

In elective surgery, the zero-balance approach has shown to reduce postoperative complications and is easily applied for most patients. It is less expensive and simpler than the zero-balance GDT approach and therefore recommended in this review. In outpatient surgery, 1-2 L of balanced crystalloids reduces postoperative nausea and vomiting and improves well-being.

A systematic review of human and veterinary applications of noninvasive tissue oxygen monitoring

OBJECTIVE

To describe the methodology for and utilization of tissue oxygen monitoring by near infrared spectroscopy, and to review the current literature on the use of this monitoring modality in human and veterinary settings.

DATA SOURCES

Scientific reviews and original research found using the PubMed and CAB Abstract search engines with the following keywords: "tissue oxygen monitoring," "near-infrared tissue spectroscopy," and "tissue oxygen saturation (StO2 )."

HUMAN DATA SYNTHESIS

Tissue oxygen monitors have been evaluated in a wide variety of human clinical applications including trauma and triage, surgery, sepsis, and septic shock, and early goal-directed therapy. StO2 more rapidly identifies occult shock in human patients compared to traditional methods, which can lead to earlier intervention in these patients.

VETERINARY DATA SYNTHESIS

Veterinary studies involving tissue oxygen monitoring are limited, but the technology may have utility for identification of hemorrhagic shock earlier than changes in base excess, blood lactate concentration, or other traditional perfusion parameters.

CONCLUSION

Tissue oxygen monitoring is most commonly performed utilizing a noninvasive, portable monitor, which provides real-time, continuous, repeatable StO2 measurements. A decline in StO2 is an early indicator of shock in both human and veterinary patients. Low StO2 values in human patients are associated with increased morbidity, mortality, and length of hospitalization, as well as the development of multiple organ system dysfunction and surgical site infections.

Smoking, chronic wound healing, and implications for evidence-based practice

Chronic wounds are rising in prevalence and creating significant socioeconomic burdens for patients and healthcare systems worldwide. Therefore, it is now more important than ever that clinicians follow evidence-based guidelines for wound care when developing personalized treatment plans for their patients with chronic wounds. Evidence-based guidelines for treating venous leg ulcers, diabetic foot ulcers, and pressure ulcers, the 3 main categories of chronic wounds, focus primarily on biologic therapies. However, there are also evidence-based guidelines for treating behavioral risks to poor healing, such as smoking, which should be incorporated into treatment plans when appropriate. The purpose of this article was to review the mechanisms through which smoking adversely impacts the wound healing process, and propose strategies for incorporating evidence-based guidelines for treating tobacco dependence into treatment plans for patients with chronic wounds who smoke.

Microsensor and transcriptomic signatures of oxygen depletion in biofilms associated with chronic wounds

Biofilms have been implicated in delayed wound healing, although the mechanisms by which biofilms impair wound healing are poorly understood. Many species of bacteria produce exotoxins and exoenzymes that may inhibit healing. In addition, oxygen consumption by biofilms and by the responding leukocytes, may impede wound healing by depleting the oxygen that is required for healing. In this study, oxygen microsensors to measure oxygen transects through in vitro cultured biofilms, biofilms formed in vivo within scabs from a diabetic (db/db) mouse wound model, and ex vivo human chronic wound specimens was used. The results showed that oxygen levels within mouse scabs had steep gradients that reached minima ranging from 17 to 72 mmHg on live mice and from 6.4 to 1.1 mmHg on euthanized mice. The oxygen gradients in the mouse scabs were similar to those observed for clinical isolates cultured in vitro and for human ex vivo specimens. To characterize the metabolic activities of the bacteria in the mouse scabs, transcriptomics analyses of Pseudomonas aeruginosa biofilms associated with the db/db mice wounds was performed. The results demonstrated that the bacteria expressed genes for metabolic activities associated with cell growth. Interestingly, the transcriptome results also indicated that the bacteria within the wounds experienced oxygen-limitation stress. Among the bacterial genes that were expressed in vivo were genes associated with the Anr-mediated hypoxia-stress response. Other bacterial stress response genes highly expressed in vivo were genes associated with stationary-phase growth, osmotic stress, and RpoH-mediated heat shock stress. Overall, the results supported the hypothesis that bacterial biofilms in chronic wounds promote chronicity by contributing to the maintenance of localized low oxygen tensions, through their metabolic activities and through their recruitment of cells that consume oxygen for host defensive processes.

Effectiveness and safety of continuous wound infiltration for postoperative pain management after open gastrectomy

AIM: To prospectively evaluate the effectiveness and safety of continuous wound infiltration (CWI) for pain management after open gastrectomy.

METHODS: Seventy-five adult patients with American Society of Anesthesiologists (ASA) Physical Status Classification System (ASA) grade 1-3 undergoing open gastrectomy were randomized to three groups. Group 1 patients received CWI with 0.3% ropivacaine (group CWI). Group 2 patients received 0.5 mg/mL morphine intravenously by a patient-controlled analgesia pump (PCIA) (group PCIA). Group 3 patients received epidural analgesia (EA) with 0.12% ropivacaine and 20 µg/mL morphine with an infusion at 6-8 mL/h for 48 h (group EA). A standard general anesthetic technique was used for all three groups. Rescue analgesia (2 mg bolus of morphine, intravenous) was given when the visual analogue scale (VAS) score was ≥ 4. The outcomes measured over 48 h after the operation were VAS scores both at rest and during mobilization, total morphine consumption, relative side effects, and basic vital signs. Further results including time to extubation, recovery of bowel function, surgical wound healing, mean length of hospitalization after surgery, and the patient’s satisfaction were also recorded.

RESULTS: All three groups had similar VAS scores during the first 48 h after surgery. Group CWI and group EA, compared with group PCIA, had lower morphine consumption (P < 0.001), less postoperative nausea and vomiting (1.20 ± 0.41 vs 1.96 ± 0.67, 1.32 ± 0.56 vs 1.96 ± 0.67, respectively, P < 0.001), earlier extubation (16.56 ± 5.24 min vs 19.76 ± 5.75 min, P < 0.05, 15.48 ± 4.59 min vs 19.76 ± 5.75 min, P < 0.01), and earlier recovery of bowel function (2.96 ± 1.17 d vs 3.60 ± 1.04 d, 2.80 ± 1.38 d vs 3.60 ± 1.04 d, respectively, P < 0.05). The mean length of hospitalization after surgery was reduced in groups CWI (8.20 ± 2.58 d vs 10.08 ± 3.15 d, P < 0.05) and EA (7.96 ± 2.30 d vs 10.08 ± 3.15 d, P < 0.01) compared with group PCIA. All three groups had similar patient satisfaction and wound healing, but group PCIA was prone to higher sedation scores when compared with groups CWI and EA, especially during the first 12 h after surgery. Group EA had a lower mean arterial pressure within the first postoperative 12 h compared with the other two groups.

CONCLUSION: CWI with ropivacaine yields a satisfactory analgesic effect within the first 48 h after open gastrectomy, with lower morphine consumption and accelerated recovery.

Effects of topical oxygen therapy on ischemic wound healing

[Purpose] This study evaluated the effects of topical oxygen therapy on the hind limb wounds of rats under ischemic conditions. [Subjects and Methods] Twelve injured rats were treated with topical oxygen on skin wounds located on the hind limb and compared with twelve injured control rats. Indexes including gross morphology of the wound, wound healing time, wound healing rate, and histological and immunohistochemical staining of sections of wound tissue were examined at different time points after intervention. [Results] The wound healing time was shorter in the topical oxygen therapy group than the control group. The wound healing rate and granulation tissue formation in the topical oxygen therapy group showed significant improvement on days 3, 7, and 14. Through van Gieson staining, the accumulation of collagen fiber in the topical oxygen therapy group was found to have improved when compared with the control group on day 7. Through semiquantitative immunohistochemical staining, many more new vessels were found in the topical oxygen therapy group compared with the model control group on day 7. [Conclusion] The results of the experiment showed that topical oxygen therapy improved ischemic wound healing.

Subcutaneous perfusion before and during surgery in obese and nonobese patients

Hypoxia at the surgical site impairs wound healing and oxidative killing of microbes. Surgical site infections are more common in obese patients. We hypothesized that subcutaneous oxygen tension (Psq O2) would decrease substantially in both obese and non-obese patients following induction of anesthesia and after surgical incision. We performed a prospective observational study that enrolled obese and non-obese surgical patients and measured serial Psq O2 before and during surgery. Seven morbidly obese and seven non-obese patients were enrolled. At baseline breathing room air, Psq O2 values were not significantly different (p = 0.66) between obese (6.8 kPa) and non-obese (6.5 kPa) patients. The targeted arterial oxygen tension (40 kPa) was successfully achieved in both groups with an expected significant increase in Psq O2 (obese 16.1 kPa and non-obese 13.4 kPa; p = 0.001). After induction of anesthesia and endotracheal intubation, Psq O2 did not change significantly in either cohort in comparison to levels right before induction (obese 15.5, non-obese 13.5 kPa; p = 0.95), but decreased significantly during surgery (obese 10.1, non-obese 9.3 kPa; p = 0.01). In both morbidly obese and non-obese patients, Psq O2 does not decrease appreciably following induction of anesthesia, but decreases markedly (∼33%) after commencement of surgery. Given the theoretical risks associated with low Psq O2 , future research should investigate how Psq O2 can be maintained after surgical incision.

High inspired oxygen versus low inspired oxygen for reducing surgical site infection: a meta-analysis

To perform a meta-analysis of published literature to assess the role of high-concentration inspired oxygen in reducing the incidence of surgical site infections (SSIs) following all types of surgery, a comprehensive search for published randomized controlled trials (RCTs) comparing high- with low-concentration inspired oxygen for SSIs was performed. The related data were extracted by two independent authors. The fixed and random effects methods were used to combine data. Twelve RCTs involving 6750 patients were included. Our pooled result found that no significant difference in the incidence of SSIs was observed between the two groups, but there was high statistic heterogeneity across the studies [risk ratio (RR): 0·91; 95% confidence interval (CI): 0·72-1·14; P = 0·40; I² = 54%]. The sensitivity analysis revealed the superiority of high-concentration oxygen in decreasing the SSI rate (RR: 0·86; 95% CI: 0·75-0·98; P = 0·02). Moreover, a subgroup analysis of studies with intestinal tract surgery showed that patients experienced less SSI when high-concentration inspired oxygen was administrated (RR: 0·53; 95% CI: 0·37-0·74; P = 0·0003). Our study provided no direct support for high-concentration inspired oxygen in reducing the incidence of SSIs in patients undergoing all types of surgery.

The National Neurosurgery Quality and Outcomes Database Qualified Clinical Data Registry: 2015 measure specifications and rationale

Meaningful quality measurement and public reporting have the potential to facilitate targeted outcome improvement, practice-based learning, shared decision making, and effective resource utilization. Recent developments in national quality reporting programs, such as the Centers for Medicare & Medicaid Services Qualified Clinical Data Registry (QCDR) reporting option, have enhanced the ability of specialty groups to develop relevant quality measures of the care they deliver. QCDRs will complete the collection and submission of Physician Quality Reporting System (PQRS) quality measures data on behalf of individual eligible professionals. The National Neurosurgery Quality and Outcomes Database (N2QOD) offers 21 non-PQRS measures, initially focused on spine procedures, which are the first specialty-specific measures for neurosurgery. Securing QCDR status for N2QOD is a tremendously important accomplishment for our specialty. This program will ensure that data collected through our registries and used for PQRS is meaningful for neurosurgeons, related spine care practitioners, their patients, and other stakeholders. The 2015 N2QOD QCDR is further evidence of neurosurgery’s commitment to substantively advancing the health care quality paradigm. The following manuscript outlines the measures now approved for use in the 2015 N2QOD QCDR. Measure specifications (measure type and descriptions, related measures, if any, as well as relevant National Quality Strategy domain[s]) along with rationale are provided for each measure.

Patient-related medical risk factors for periprosthetic joint infection of the hip and knee

Despite advancements and improvements in methods for preventing infection, periprosthetic joint infection (PJI) is a significant complication following total joint arthroplasty (TJA). Prevention is the most important strategy to deal with this disabling complication, and prevention should begin with identifying patient-related risk factors. Medical risk factors, such as morbid obesity, malnutrition, hyperglycemia, uncontrolled diabetes mellitus, rheumatoid arthritis (RA), preoperative anemia, cardiovascular disorders, chronic renal failure, smoking, alcohol abuse and depression, should be evaluated and optimized prior to surgery. Treating patients to get laboratory values under a specified threshold or cessation of certain modifiable risk factors can decrease the risk of PJI. Although significant advances have been made in past decades to identify these risk factors, there remains some uncertainty regarding the risk factors predisposing TJA patients to PJI. Through a review of the current literature, this paper aims to comprehensively evaluate and provide a better understanding of known medical risk factors for PJI after TJA.

Safety and Efficacy of Nicotine Replacement Therapy in the Perioperative Period: A Narrative Review

Patients who smoke cigarettes are at increased risk for development of complications both during and after surgical procedures, including respiratory, cardiac, and healing-related complications. Abstinence from smoking can considerably reduce these risks. Pharmacotherapy, including nicotine replacement therapy (NRT), is an important component of efficacious tobacco use interventions. However, the use of NRT in the perioperative period is controversial. In this narrative review, we discuss the current evidence for the efficacy and safety of NRT in patients scheduled for surgical procedures, with emphasis on evidence from human studies. We performed a literature search for articles published from January 1, 1990, through May 1, 2015, in the PubMed online database using various permutations of the Medical Subject Headings terms surgery; surgical procedures, operative; nicotine; and smoking cessation. Studies were selected for inclusion according to their relevance to the preclinical and clinical evidence pertaining to how NRT affects surgical outcome and long-term rates of abstinence from tobacco. There is strong evidence that NRT enhances the efficacy of tobacco use interventions. Some preclinical studies suggest that nicotine in high doses that exceed those produced by NRT decreases the viability of skin flaps. Although the available data are limited, there is no evidence from human studies that NRT increases the risk of healing-related or cardiovascular complications. Individual clinical trials of tobacco use interventions that include NRT have revealed either no effect or a reduction in complication rates. Therefore, given the benefits of smoking abstinence to both perioperative outcomes and long-term health and the efficacy of NRT in achieving and maintaining abstinence, any policies that prohibit the use of NRT in surgical patients should be reexamined.

Rational Hyperoxia in the Perioperative Period: a Safe and Effective Tool in the Reduction of SSI

Oxygen supplemented at a concentration higher than 40-50 % for at least 2 h perioperatively is expected to reduce surgical site infections (SSI). Although supplementation of 80 % of oxygen perioperatively has shown to reduce SSI in various studies, this concentration is known to be associated with airway complications. This study was taken up to assess the efficacy of 60 %, i.e. <80 and >50 %, inspired oxygen supplemented perioperatively in reducing SSI. One hundred and eighty-eight patients who underwent elective class I and II surgeries were studied. Patients were divided equally into two groups and subgroups and matched for age, sex, type of surgeries, etc. The control group received 30 % and the study group received 60 % oxygen supplementation perioperatively for 2 h. Wounds were observed for the development of SSI. 8/94 patients in the study group and 13/94 patients in the control group developed SSI (p < 0.01). The results indicate a relative risk of 1.62, risk difference of 0.0531 and attributable risk of 38.42 %. Hence, it may be concluded that perioperative oxygen supplementation at 60 % concentration reduces SSI.

Evidence-Based Approach to Advanced Wound Care Products

There is increasing pressure from industry to use advanced wound care products and technologies. Many are very expensive but promise to reduce overall costs associated with wound care. Compelling anecdotal evidence is provided that inevitably shows wounds that failed all other treatments but responded positively to the subject product. Evidence-based medicine is the standard by which physician-scientists must make their clinical care decisions. In an attempt to provide policy makers with the most current evidence on advanced wound care products, the Department of Veteran Affairs conducted an Evidence-based Synthesis Program review of advanced wound care products. This paper suggests how to take this information and apply it to policy to drive evidence-based care to improve outcomes and fiduciary responsibility.

Diffusive transport through a model host-biofilm system

Free-living biofilms have been subject to considerable attention, and basic physical principles for them are generally accepted. Many host-biofilm systems, however, consist of heterogeneous mixtures of aggregates of microbes intermixed with host material and are much less studied. Here we analyze a key property, namely reactive depletion, in such systems and argue that two regimes are possible: (1) a homogenizable mixture of biofilm and host that in important ways acts effectively like a homogeneous macrobiofilm and (2) a distribution of separated microbiofilms within the host with independent local microenvironments.

Obesity--a risk factor for postoperative complications in general surgery?

Background

Obesity is generally believed to be a risk factor for the development of postoperative complications. Although being obese is associated with medical hazards, recent literature shows no convincing data to support this assumption. Moreover a paradox between body mass index and survival is described. This study was designed to determine influence of body mass index on postoperative complications and long-term survival after surgery.

Methods

A single-centre prospective analysis of postoperative complications in 4293 patients undergoing general surgery was conducted, with a median follow-up time of 6.3 years. We analyzed the impact of bodyweight on postoperative morbidity and mortality, using univariate and multivariate regression models.

Results

The obese had more concomitant diseases, increased risk of wound infection, greater intraoperative blood loss and a longer operation time. Being underweight was associated with a higher risk of complications, although not significant in adjusted analysis. Multivariate regression analysis demonstrated that underweight patients had worse outcome (HR 2.1; 95 % CI 1.4-3.0), whereas being overweight (HR 0.6; 95 % CI 0.5–0.8) or obese (HR 0.7; 95 % CI 0.6–0.9) was associated with improved survival.

Conclusion

Obesity alone is a significant risk factor for wound infection, more surgical blood loss and a longer operation time. Being obese is associated with improved long-term survival, validating the obesity paradox. We also found that complication and mortality rates are significantly worse for underweight patients. Our findings suggest that a tendency to regard obesity as a major risk factor in general surgery is not justified. It is the underweight patient who is most at risk of major postoperative complications, including long-term mortality.

Electronic supplementary material

The online version of this article (doi:10.1186/s12871-015-0096-7) contains supplementary material, which is available to authorized users.