Skin preparation type and post-cesarean infection with use of adjunctive azithromycin prophylaxis

Objective: Surgical site infection (SSI) can markedly prolong postoperative hospital stay, aggravate the burden on patients and society, even endanger the life of patients. This study aims to investigate the national incidence of SSI following abdominal surgery and to analyze the related risk factors in order to provide reference for the control and prevention of SSI following abdominal surgery. Methods: A multicenter cross-sectional study was conducted. Clinical data of all the adult patients undergoing abdominal surgery in 68 hospitals across the country from June 1 to 30, 2020 were collected, including demographic characteristics, clinical parameters during the perioperative period, and the results of microbial culture of infected incisions. The primary outcome was the incidence of SSI within postoperative 30 days, and the secondary outcomes were ICU stay, postoperative hospital stay, cost of hospitalization and the mortality within postoperative 30-day. Multivariable logistic regression was used to analyze risk factors of SSI after abdominal surgery. Results: A total of 5560 patients undergoing abdominal surgery were included, and 163 cases (2.9%) developed SSI after surgery, including 98 cases (60.1%) with organ/space infections, 19 cases (11.7%) with deep incisional infections, and 46 cases (28.2%) with superficial incisional infections. The results from microbial culture showed that Escherichia coli was the main pathogen of SSI. Multivariate analysis revealed hypertension (OR=1.792, 95% CI: 1.194-2.687, P=0.005), small intestine as surgical site (OR=6.911, 95% CI: 1.846-25.878, P=0.004), surgical duration (OR=1.002, 95% CI: 1.001-1.003, P<0.001), and surgical incision grade (contaminated incision: OR=3.212, 95% CI: 1.495-6.903, P=0.003; Infection incision: OR=11.562, 95%CI: 3.777-35.391, P<0.001) were risk factors for SSI, while laparoscopic or robotic surgery (OR=0.564, 95%CI: 0.376-0.846, P=0.006) and increased preoperative albumin level (OR=0.920, 95%CI: 0.888-0.952, P<0.001) were protective factors for SSI. In addition, as compared to non-SSI patients, the SSI patients had significantly higher rate of ICU stay [26.4% (43/163) vs. 9.5% (514/5397), χ(2)=54.999, P<0.001] and mortality within postoperative 30-day [1.84% (3/163) vs.0.01% (5/5397), χ(2)=33.642, P<0.001], longer ICU stay (median: 0 vs. 0, U=518 414, P<0.001), postoperative hospital stay (median: 17 days vs. 7 days, U=656 386, P<0.001), and total duration of hospitalization (median: 25 days vs. 12 days, U=648 129, P<0.001), and higher hospitalization costs (median: 71 000 yuan vs. 39 000 yuan, U=557 966, P<0.001). Conclusions: The incidence of SSI after abdominal surgery is 2.9%. In order to reduce the incidence of postoperative SSI, hypoproteinemia should be corrected before surgery, laparoscopic or robotic surgery should be selected when feasible, and the operating time should be minimized. More attentions should be paid and nursing should be strengthened for those patients with hypertension, small bowel surgery and seriously contaminated incision during the perioperative period.

Introducción: la incidencia de eventraciones oscila entre uno y 16% de las laparotomías, convirtiendo la eventrorrafia en un procedimiento muy común en los servicios quirúrgicos. El National Nosocomial Infection Surveillance Systems NNISS, mostró que la infección del sitio operatorio (ISO) es la tercera infección nosocomial más frecuente en pacientes hospitalizados, con una prevalencia del 14 al 16%.' Son muchos los factores que se han relacionado con la ISO en eventrorrafias que a su vez se identifica como factor de riesgo para la recidiva de las eventraciones. Objetivo: describir la frecuencia de presentación de ISO y los factores relacionados, en pacientes a quienes se les realizó eventrorrafia. Metodología: estudio descriptivo de corte transversal en el período de julio 1 de 2004 y julio 1 de 2006 en el Hospital de San José. Se analizaron variables demográficas, quirúrgicas, las propias de la eventración y del postoperatorio y las escalas de riesgo de infección. Resultados: de los 132 pacientes llevados a eventrorrafia, el 58.3% (77) fueron mujeres y 41.6% (55) hombres; el promedio de edad fue 50 años. La frecuencia de ISO global fue del 9% (12); la ISO superficial en diez casos (7.5%) y profunda en dos (1.5%). Los antecedentes patológicos identificados en la población con ISO fueron diabetes mellitus en 25%, enfermedad coronaria y EPOC en 8,3% y tabaquismo en 33%. En aquellos que no presentaron ISO se encontró 5%, 2,5%, 5.8% y 9% respectivamente. El tiempo promedio de cirugía fue 115 minutos en los pacientes con ISO y 86 minutos en aquellos sin ISO. El 33 % (4) con ISO requirió cirugía de urgencias por encarcelamiento. No se documentó ISO en los dos pacientes que requirieron resección intestinal. En los pacientes que no presentaron ISO, uno tuvo NNISS 3 y SENIC 4. Conclusiones: la frecuencia global de ISO y los factores de riesgo descritos en el estudio son similares a los reportes de la literatura médica. Se requiere de estudios futuros de tipo prospectivo con un adecuado seguimiento que permitan identificar factores de riesgo de ISO y hacer vigilancia sobre el comportamiento de la ISO secundaria a eventrorrafias en la institución. Abreviaturas: ISO, infección del sitio operatorio; EPOC, enfermedad pulmonar obstructiva crónica; NNISS, national nosocomial infection surveillonce systems; IPO, infección postoperatoria.

The level of microbial contamination is an important risk factor for surgical site infections. The aim of this study was to investigate the frequency of surgical site infections in regard to the level of microbial contamination at the Department of Orthopedic and Traumatologic Surgery of the Clinical Hospital Center in Kragujevac. This study included 474 patients who underwent surgery in the period from January 1, 2002 to December 31, 2002 at the Department of Orthopedic and Traumatologic Surgery of the Clinical Hospital Center in Kragujevac. Hospital infections were identified using CDC definitions, modified to fit our circumstances. The traditional classification of surgical sites in regard to the level of microbial contamination includes three categories: clean, contaminated and dirty. The incidence of surgical site infections was higher at the Orthopedic Surgery Ward (5.94%) compared to Traumatologic Surgery Ward (5.02%). Additionally, a significantly higher frequency of deep surgical site infections, which were classified as clean were established at the Orthopedic Surgery Ward, in regard to the level of microbial contamination, whereas the greatest frequency of surface infections in clean surgical sites (p=0. 000) were established at the Traumatologic Surgery Ward. Surgical site infections were more frequent in patients undergoing multiple surgeries at the Orthopedic Surgery Ward zhan in those treated at the Traumatologic Surgery Ward (p=0.037). It is of utmost importance to estimate the frequency of surgical stie infections and identify associated risk factors in order to undertake adequate measures for their prevention and control.

Objective: Surgical site infection (SSI) is a common health care-related infection after gastrointestinal surgery. Once SSI occurs after surgery, it can significantly prolong the postoperative hospital stay, increase the cost burden of patients and society, and even endanger the life safety of patients. The purpose of this study was to investigate the clinical phenotypes of gastrointestinal surgery, identify the clinical characteristics of SSI, and provide reference for the prevention of SSI after gastrointestinal surgery. Methods: This is a multicenter prospective cohort study that collected clinical data from all adult patients undergoing gastrointestinal surgery from March 2021 to February 2022 at 42 hospitals in China, including baseline and perioperative characteristics. Based on the variables associated with SSI, latent class analysis (LCA) was used to explore the population characteristics of SSI. Results: In total, 16 087 patients were included in the study, of whom 345 (2.1%) developed SSI. LCA analysis revealed that patients undergoing gastrointestinal surgery were classified into four clinical phenotypes, including α (3851), β (1538), γ (6387), and δ (4311). Type α had minimal abnormality on related system functions (ASA score > 2: 4.5% [173/3851]), and mainly underwent appendix surgery (98.9% [3808/3851]). The postoperative SSI incidence of type α was 0.4% (16/3,851), which belonged to the group of SSI low risk. The abnormality of system functions of type β (ASA score > 2: 17.4% [268/1538]) was worse than that of type α. Type β mainly underwent stomach surgery (72.4% [1113/1538]), and its incidence of postoperative SSI was 1.2% (18/1538), belonging to the group of SSI medium risk. The ASA score of type γ (ASA score > 2: 18.0% [1148/6387]) was comparable to that of type β. Type γ mainly received colorectal surgery (colon surgery: 40.1% [2562/6387]; rectal surgery: 33.6%[2143/6387]), and its incidence of postoperative SSI was 1.7% (106/6387), belonging to the group of SSI medium risk. Type δ (ASA score > 2: 23.5%[1015/4311]) was the most serious type with the highest proportion of open surgery. Type δ mainly underwent small intestine (54.0%[2327/4311]) and stomach surgery (32.3% [1392/4311]) and had the highest incidence of SSI (4.8% [205/4311]) and the highest mortality rate (0.6% [24/4311]), belonging to the group of SSI high risk. Compared with type α and β, the median length of hospital stay (α, β, γ, and δ: 5.0 days, 9.6 days, 13.0 days, and 16.0 days, P<0.001) and postoperative hospital stay (α, β, γ, and δ: 4.0days, 6.0days, 8.3 days, and 10.0 days, P<0.001) of type γ and δ were significantly increased, and the median medical costs (α, β, γ, and δ: 14 178.7 yuan, 39 514.2 yuan, 62 893.0 yuan and 57 266.6 yuan, P<0.001) were also significantly increased. Conclusion: LCA analysis elucidated four clinical phenotypes of patients undergoing gastrointestinal surgery. Type α had a low risk of SSI. Type β and γ had a medium risk of SSI, and type δ had a high risk of SSI.

Background: Appendectomy is the most commonly performed emergency surgical procedure and has significant morbidity of surgical site infection (SSIs). Regarding this, there are conflicting reports and dilemma on use of optimal duration of antibiotics. The aim of this study was to evaluate the incidence of SSIs after three doses of perioperative prophylactic antibiot­ics (single dose before surgery and two doses postoperatively) after ap­pendectomy in acute non- perforated appendicitis (NPA).&#x0D; Methods: This cross sectional study was conducted in the department of General surgery, Chitwan Medical College Teaching Hospital, from May 2018 to April 2019. All the cases received single dose of antibiotics (cef­triaxone and metronidazole) during the induction of anesthesia and two doses of the same antibiotics postoperatively within 24 hours. SSIs was assessed on 2nd and followed up till 7th postoperative day. The data col­lected was analyzed using SPSS version 16.&#x0D; Results: In the study of 100 patients, who received perioperative three doses of antibiotics, the overall frequency of SSIs on 2nd and 3rd post-operative day were 2% (p=.840) and 6% (p=.539) respectively, which was statistically not significant. In follow up after 3rd postoperative day, there was no evidence of SSIs. Statistically there was no significant difference in the incidence and grade of SSIs between age group, sex and duration of operation.&#x0D; Conclusions: A combined three doses of perioperative antibiotics was ad­equate for SSIs prevention in patients of any age group and sex with acute NPA after appendectomy in usual operative time.

Background: Surgical Site Infections (SSIs) are infections of tissues, organs or spaces exposed by surgeons during performance of an invasive procedure and continue to be a major source of morbidity following operative procedures. Wound irrigation is the steady flow of a solution across an open wound surface meant to remove cellular debris and surface pathogens contained in wound exudates or residue from topically applied wound care products.Methods: This prospective comparative study was conducted to compare the effectiveness of Pressurized Pulse Irrigation (PPI) and Standard Irrigation Technique (SIT) in laparotomy wounds. Duration of the study was for a period of 12 months and included 100 consecutive patients undergoing laparotomy.Results: 13% of patients who underwent laparotomy had SSI out of which 9 patients had superficial infection only. 8% of 50 patients who had PPI developed SSI, whereas 18% of those who underwent SIT had SSI. Though PPI had less incidence of SSI, statistically it was insignificant.Conclusions: The study showed a decrease in the incidence of postoperative SSI in both elective and emergency laparotomy wounds irrigated with PPI compared to SIT, though the study was statistically insignificant since the p value was less than 0.005 with a odds ratio of 2.52. The study results suggested that there was decrease in the incidence of SSI in PPI patients and also that it decreases the postoperative stay, morbidity and cost.

Abdominal Wall Thickness Predicts Surgical Site Infection in Emergency Colon Operations

Surgical site infections are the third most frequently reported hospital acquired infection. Women who give birth by caesarean section are exposed to the possibility of infection from their own, and external or environmental, sources of infection. Preventing infection by properly preparing the skin before incision is thus a vital part of the overall care given to women prior to caesarean birth. An antiseptic is applied to remove or reduce bacteria. These antiseptics include iodine or povidone-iodine, alcohol, chlorhexidine and parachlorometaxylenol and can be applied as liquids or powders, scrubs, paints, swabs or on impregnated drapes. The available evidence from the randomised trials identified for this review (five trials involving 1462 women) is not sufficient to guide the best type of skin preparation for preventing wound or surgery site infection following caesarean section. Comparing different antiseptic procedures, no difference was found in wound infection (four trials) or uterine infection including of the lining (endometritis) (two trials). The five included trials studied different forms, concentrations and methods of applying skin preparations for surgery. Of the five trials, two were reasonably large and the other three involved only small numbers of women. Guidance about preparation is needed for women, particularly those at higher risk of surgical site infection, such as malnourished women, women with diabetes mellitus or obesity, or those who have an established infection before caesarean section.

Objective: This study aims to survey the incidence of surgical site infection (SSI) in China and to analyze its risk factors, so as to prevent and control SSI after colorectal surgery. Methods: An observative study was conducted. Based on a program of Chinese SSI Surveillance from 2018 to 2020, the clinical data of all adult patients undergoing colorectal surgery during this time period were extracted. These included demographic characteristics and perioperative clinical parameters. Minors, pregnant women, obstetric or gynecological surgery, urological system surgery, retroperitoneal surgery, resection of superficial soft tissue masses, and mesh or other implants were excluded. A total of 2122 patients undergoing colorectal surgery from 50 hospitals were included, including 1252 males and 870 females. The median age was 63 (16) years and the median BMI was 23 (4.58) kg/m2. The primary outcome was the incidence of SSI within 30 days after colorectal surgery. The secondary outcomes were mortality within 30 days postoperatively, length of ICU stays and postoperative hospital stays, and cost of hospitalization. Patients were divided into the SSI group and non-SSI group based on the occurrence of SSI. Multivariable logistic regression was performed to analyze risk factors of SSI after colorectal surgery, and subgroup analysis was conducted for open and laparoscopic surgery. Results: The incidence of SSI after colorectal surgery was 5.6% (119/2122), including 47 cases (47/119, 39.5%) with superficial incisional infections, 24 cases (24/119, 20.2%) with deep incisional infections, and 48 cases (48/119, 40.3%) with organ/space infections. The occurrence of SSI significantly increased mortality [2.5% (3/119) vs. 0.1%(3/2003), χ2=22.400, P=0.003], the length of ICU stay [0 (1) day vs. 0(0) day, U=131 339, P<0.001], postoperative hospital stay [18.5 (12.8) days vs. 9.0 (6.0) days, U=167 902, P<0.001], and medical expenses [75 000 (49 000) yuan vs. 60 000 (31 000) yuan, U=126 189, P<0.001] (P<0.05). Multivariate analysis revealed that hypertension (OR=1.782, 95%CI: 1.173-2.709, P=0.007), preoperative albumin level (OR=1.680, 95%CI: 1.089-2.592, P=0.019), a contaminated or infected incision (OR= 1.993, 95%CI: 1.076-3.689, P=0.028), emergency surgery (OR=2.067, 95%CI: 1.076-3.972, P=0.029), open surgery (OR=2.132, 95%CI: 1.396-3.255, P<0.001), and surgical duration (OR=1.804, 95%CI: 1.188-2.740, P=0.006) were risk factors for SSI, while preoperative skin preparation (OR=0.478, 95%CI: 0.310-0.737, P=0.001) was a protective factor for SSI. Subgroup analysis was performed on patients undergoing open or laparoscopic surgery. The incidence of SSI in the open surgery group was 10.2%, which was significantly higher than that in the laparoscopic or robotic group (3.5%, χ2=39.816, P<0.001). Subgroup analysis identified that a contaminated or infected incision (OR=2.168, 95%CI: 1.042-4.510, P=0.038) and surgical duration (OR=2.072, 95%CI: 1.171-3.664, P=0.012) were risk factors for SSI after open surgery, while mechanical bowel preparation (OR=0.428, 95%CI: 0.227-0.807, P=0.009) and preoperative skin preparation (OR=0.356, 95%CI: 0.199-0.634, P<0.001) were protective factors for SSI after open surgery. In laparoscopic surgery, diabetes mellitus (OR= 2.292, 95%CI: 1.138-4.617, P=0.020) and hypertension (OR=2.265, 95%CI: 1.234-4.159, P=0.008) were risk factors for SSI. Conclusions: The incidence of SSI after colorectal surgery is 5.6%. Minimally invasive surgery should be selected to reduce the occurrence of postoperative SSI. To prevent the occurrence of SSI after open surgery, skin preparation and mechanical bowel preparation should be performed before the operation, and the duration of the operation should be shortened as much as possible. In the perioperative period, care of patients with hypertension, diabetes, and contaminated or infected incisions should be given particular attention.

To aim of this study was to determine the frequency of surgical site infections and to identify the associated risk factors in general surgery ward of a tertiary care hospital of Karachi. This was a one year cross sectional study conducted in a surgical ward of Jinnah Postgraduate Medical Centre, Karachi. During the study period data was collected on a predesigned questionnaire for all the patients who underwent surgery in the general surgery ward of JPMC and patients were followed for up to 30 days for developments of surgical site infection. Infected cases were identified using CDC, USA definition for Surgical site infections. In total of 1139 patients surgical procedures were performed in the selected ward during the study period, of which 19 dropped out from the study; of the remaining 1120 patients 82 (7.3%) patients developed surgical site infection. Incidence of surgical site infections was higher in emergency procedures (13.1%) as compared to elective procedures (2.9%). Incidence related to clean, clean contaminated, contaminated and dirty procedures was 1.5%, 2.5%, 6.5% and 21.5% respectively. Age, wound class, electivity of procedure and diabetes were identified as the main contributing factors towards the development of surgical site infections. Ten patients were readmitted in the hospital after discharge due to SSI. Frequency of SSI in surgical ward of JPMC was lower than other public sector hospitals reported from Pakistan but was much higher as compared to developed countries.

Laparoscopic appendectomy (LA) has been rapidly applied worldwide recently. The issue of surgical site infection (SSI) after appendectomy needs to be re-investigated and analyzed along with this trend. This study aimed to identify risk factors of SSI after appendectomy in recent years. This retrospective study was conducted among patients with acute appendicitis who underwent either laparoscopic or open appendectomy (OA) at 7 general hospitals in China from 2010 to 2013. The incidence of SSI, classified as incisional SSI and organ/space SSI, was investigated. A multivariate logistic regression model was used to assess independent risk factors associated with overall, incisional, and organ/space SSI, respectively. Among 16,263 consecutive patients, 3,422 (21.0 %) and 12,841 (79.0 %) patients underwent LA and OA, respectively. The incidences of overall, incisional, and organ/space SSI were 6.2, 3.7, and 3.0 %, respectively. The proportion of LAs among both procedures increased yearly from 5.3 to 46.5 %, while the incidences of overall and incisional SSI after appendectomy simultaneously decreased yearly from 9.6 to 4.5 % and from 6.7 to 2.2 %, respectively. In comparison with OA, LA was associated with lower incidences of overall and incisional SSI (4.5 vs 6.7 %, P < 0.001; and 1.9 vs 4.2 %, P < 0.001), but a similar incidence of organ/space SSI (3.0 vs 3.0 %, P = 0.995). After multivariate logistic regression analyses were performed, LA was found to be independently associated with a decrease in development of overall SSI [odds ratio (95 % confidence interval) OR (95 % CI), 1.24 (1.03-1.70); P = 0.04] or incisional SSI [OR (95 % CI), 1.32 (1.10-1.68); P = 0.01]. With the increasing application trends of laparoscopic procedure, the incidence of SSI after appendectomy declined accordingly. Compared with OA, LA was independently associated with a significantly lower incidence of incisional SSI, but a similar incidence of organ/space SSI.

To evaluate the impact of restrictive prophylactic antibiotic guidelines on the incidence of surgical site infections (SSIs) following elective spinal surgery using nationwide quality assessment data from South Korea. Nationwide retrospective cohort study comparing SSI rates between unrestricted (seventh and eighth quality assessment waves) and restricted (ninth wave) prophylactic antibiotic guideline periods using multivariable logistic regression. All healthcare institutions performing elective spinal surgery and participating in the Health Insurance Review and Assessment Service (HIRA) quality assessment programme in South Korea. A total of 58 829 adult patients who underwent elective spinal surgery during the seventh (2015), eighth (2017) and ninth (2020) HIRA quality assessment waves were included. None. The primary outcome was the incidence of post-operative SSIs. Secondary outcomes included non-surgical site infections and factors associated with SSI occurrence. The overall post-operative infection rate was 5.79%. The incidence of SSIs was significantly higher in the restricted antibiotic group than in the unrestricted group (2.41% vs 0.84%). In multivariable logistic regression analysis, restrictive prophylactic antibiotic use was independently associated with an increased risk of SSIs (adjusted OR, 2.48; 95% CI 2.13 to 2.89; p<0.001). When stratified by hospital type, patients treated in tertiary hospitals had the highest SSI risk (adjusted OR, 4.47; 95% CI 3.65 to 5.47), followed by those treated in general hospitals (adjusted OR, 3.03; 95% CI 2.55 to 3.60) (all p<0.001). Non-surgical site infections were also more frequent in the restricted group. Restrictive prophylactic antibiotic guidelines were associated with a higher incidence of post-operative infections following elective spinal surgery. These findings suggest that prophylactic antibiotic strategies may need to consider patient risk profiles and surgical complexity rather than applying a uniform approach.

Surgical site infection of scrotal and inguinal lesions after urologic surgery

IN this issue of Anesthesiology, Stæhr et al. 1report the lack of effect of perioperative hyperoxia on preventing surgical site infection (SSI) in obese patients undergoing laparotomy. The study was a secondary analysis of data from the PROXI Trial, a Danish multicenter study of 1,400 patients undergoing elective or emergency laparotomy who were randomized to receive a 30% or 80% oxygen concentration intraoperatively and for the first 2 h after surgery.2Although no significant reduction in the frequency of SSI was observed in the high-concentration group in that trial, it was hypothesized that the results for the subpopulation of 213 obese patients (body mass index ≥30 kg/m2, 15% of the sample) might be different. However, on reanalysis the researchers again found no significant differences in the rates of SSI or pulmonary complications.Surgical site infection, which accounts for 15–20% of all healthcare-associated infections, is the second most common preventable adverse outcome of major surgery.3The incidence of SSI, which differs according to surgical procedure, is highest for gastrointestinal interventions.4If we are to decrease the SSI rates in the various surgical settings and attenuate the consequences, it will be necessary to identify risk factors as a first step. Age, duration of surgery, hypoalbuminemia, obesity, diabetes mellitus, and a history of chronic obstructive pulmonary disease are some of the predictors that have been linked with SSI.4,5Obesity is associated with a higher incidence of SSI.6Glance et al. 7recently studied a population of 310,208 patients in the American College of Surgeons National Surgical Quality Improvement Program database, more than 95,000 of whom were overweight. Obese and morbidly obese patients with metabolic syndrome (obesity, hypertension, and diabetes), who accounted for 19% of all the obese patients in the study, had higher risk of postoperative complications, including death and SSI, in comparison with normal-weight and obese patients without metabolic syndrome. In addition, percentage of body fat8and thickness of subcutaneous fat9have been shown to be better predictors of SSI than body mass index, suggesting that obesity is not a homogeneous clinical state and body mass index may be too simplistic a measure for this complex illness. In other words, individuals classified as obese may be more or less healthy and have different levels of risk.In recent years, interest has grown in identifying factors amenable to management to reduce the risk of SSI, and anesthesiologists may have partial control over some of them.3Measures such as the avoidance of hypothermia10and the careful timing and selection of antibiotics11seem to be effective in preventing SSI.The rationale for proposing hyperoxia as another manageable factor for preventing SSI is well established.3Neutrophils safeguard against infection through nonspecific phagocytosis and elimination of bacteria from wounds; the oxygen tension in subcutaneous tissue is critical for these functions. Tissue oxygen tension12and concentration13have been shown to predict SSI after colorectal surgery, and supplemental oxygen (e.g. , 80%) can double oxygen partial pressure in tissue.14In vitro studies have shown that hyperoxia exerts significant influence on multiple cellular and immune system parameters, improving the functional capacity of the innate immune response as reflected by increasing concentrations of reactive oxygen species, a major component of the bactericidal defense.15Adequate wound oxygen tension is also important in the development of collagen and epithelium required for healing.3Hyperoxia increases the availability of molecular oxygen to tissues by increasing oxygen dissolved in plasma and enhancing the driving force between capillary blood and cells.16Achieving a subcutaneous oxygen tension greater than 90 mmHg seems to protect against infection,12and at least 40 mmHg would be needed to support the leukocyte-mediated oxidative burst and collagen formation. Good capillary perfusion of tissue also determines cell oxygenation, and helpful actions that can be managed by anesthesiologists are fluid replacement and the avoidance of vasoconstriction triggered by activation of the sympathetic nervous system by hypothermia and pain.3However, all actions intended to increase cell oxygen tension can be offset if tissue perfusion is compromised (e.g. , in diabetes or peripheral vascular disease) or when the oxygen pressure gradient along the axial capillary drops rapidly.16The results of the clinical translation of this rationale, in controlled trials testing perioperative hyperoxia, have been mixed. Two randomized trials comparing 30% and 80% oxygen in a total of almost 800 patients undergoing colorectal surgery reported significant reductions in the rate of SSI.14,17A large trial to test the effect of nitrous oxide on events after major surgery indirectly compared high (80%) and low (30%) oxygen concentrations and found significantly fewer cases of SSI in patients breathing the high concentration.18In contrast, 165 patients undergoing major abdominal surgery, including laparoscopically assisted procedures, were randomized to breathe 35% or 80% oxygen, and no improvement in SSI outcome was observed.19Finally, the multicenter PROXI Trial likewise found no significant reduction in risk of SSI with hyperoxia; however, the study included many different elective and emergency surgical procedures, ranging from high-risk colorectal interventions (fewer than 50% of all patients) to cholecystectomies, appendectomies, and hernia repair.2This heterogeneity could partly explain the negative findings.The secondary analysis of data for the PROXI Trial's high-risk subgroup of obese patients in this issue1is therefore welcome. It was hypothesized that the subcutaneous oxygen tension might be reduced in this subpopulation because of their anatomic, histologic, functional, and immune status. We know that in obese patients tissue oxygen tension is significantly increased when 80% oxygen is given,20favoring the defense mechanisms against an SSI. However, the authors observed no reduction in the incidence of SSI. Two sampling characteristics could have created bias leading to this negative result. First, the mean body mass index of the obese patients in this trial was relatively low (33.5 kg/m2), and hypertension was present in fewer than half the patients, suggesting that a large proportion did not have metabolic syndrome and probably had less risk. Second, the patients had undergone a large variety of procedures, and only 45% were operations such as colorectal surgery, which is associated with high risk for SSI.Thus, the issue of a clinical role for hyperoxia remains unsettled. Should we routinely administer high oxygen concentration perioperatively in the hope of reducing the risk of SSI? This intervention is attractive because oxygen therapy does not significantly increase costs, and the potential benefits might be great. But SSIs develop as the result of very complex circumstances, and prevention does not appear to be possible by taking a single step because a variety of other surgical, anesthetic, functional, and immune factors also play important roles. Even genetic factors seem to increase risk for severe infections.21Our poor understanding of those factors probably explains the conflicting results of trials to date. The answer to the question posed above seems to be that hyperoxia should not be provided routinely and individualized clinical vigilance is essential. Probably in some patients who are theoretically at high risk of infection (e.g. , in colorectal surgery) but whose tissue perfusion is well preserved, hyperoxia with 80% oxygen concentration may be beneficial. Additional research with high-risk patients undergoing high-risk procedures is needed. New studies on general populations probably will yield negative results because the beneficial effect of hyperoxia by itself can be marginal, or at least not comparable to antibiotic prophylaxis.11Thus, to reduce risk of SSI, we would argue in favor of a multimodal approach, including several surgical and anesthetic factors amenable to management. In such an approach, hyperoxia might well be one of the tools to select.*Department of Anesthesiology and Postoperative Care, Hospital Universitari Germans Trias i Pujol, Barcelona, Spain. jcanet.germanstrias@gencat.cat. †Department of Anesthesia and Critical Care, Hospital Clínico Universitario, Valencia, Spain.

Closed Incision Negative Pressure Therapy to Reduce Surgical Site Infection in High-Risk Gastrointestinal Surgery: A Randomized Controlled Trial.