Supplemental Postoperative Oxygen and Wound Infection in Morbidly Obese Patients

2014-07-23 21:45:16 | BioPortfolio


The investigators propose to test the hypothesis that the incidence of major complications related to infection or inadequate healing is reduced in morbidly obese patients given 80% inspired oxygen during, and for 12-18 hours after, surgery compared with patients given 80% oxygen only during surgery. The primary outcome will be a composite of major complications plausibly related to infection or healing.


Wound infection is a common and serious consequence of anesthesia and surgery. Infection is associated with major complications including intra-abdominal abscess, peritonitis without leakage, and sepsis. The average wound infection thus prolongs hospitalization by a week, doubles the need for ICU care, and doubles mortality.

The first few hours following bacterial contamination constitute a decisive period during which infection is established. Techniques aimed at improving resistance to surgical wound infections are thus most effective when implemented during the decisive period — even though infections are not detected clinically until five-to-ten days after surgery.

The primary defense against surgical pathogens is oxidative killing by neutrophils. This reaction critically depends on tissue oxygen tension. It is therefore unsurprising that subcutaneous tissue oxygen tension (PsqO2) is inversely correlated with the risk of surgical wound infection. As might be expected, supplemental perioperative oxygen administration increases tissue oxygen partial pressure (compared with an FIO2 of 30%) and decreases wound infection risk. While 100% oxygen is associated with atelectasis and pulmonary inflammation, we and others have shown that 80% oxygen is not.

Inadequate healing is also common. Scar formation starts with transcription of pro-collagen, which undergoes post-translational hydroxylation of the abundant proline and lysine residues. This promotes the cross-linking within and between collagen strands that provides tensile strength which begins the healing process. The prolyl and lysyl hydroxylases that catalyze this reaction depend on the substrate oxygen. The Km (substrate concentration at which the velocity of the reaction is half-maximal) for O2 of prolyl hydroxylase has been variously estimated at 20, 25, and 100 mmHg. Even using the most conservative estimate, these data suggest that proline hydroxylation of collagen (e.g., scar formation) will be PO2 dependent through the range of 0 to ≈200 mmHg, with 90% of the effect occurring by 90 mmHg. In vitro and in vivo animal evidence supports this theory. Inadequate healing is associated with anastomotic leakage, wound dehiscence, and bleeding.

In morbidly obese patients, the incidence of infection and major complications related to either infection or inadequate healing is 15-20% after gastric bypass based on our preliminary data and a review of records at Washington University. Roughly 30% of the American population is now obese with a body mass index (BMI) > 30 kg/m2; about 5% of the population is morbidly obese, with a BMI exceeding 40 kg/m2. These patients are at extraordinarily high risk of wound infection, and infections in these patients are especially severe.

Cardiac output, circulating blood volume, and resting oxygen consumption are all increased in the obese; however, total blood flow is sub-normal in relation to body weight. Obesity augments the size of individual fat cells without increasing blood flow. Specifically, fat tissue is hypoperfused and poorly oxygenated. Intraoperative tissue oxygenation is abnormally low in obese patients and postoperative tissue oxygenation is especially low — although it can be improved by oxygen administration. It thus seems likely that inadequate tissue oxygenation contributes to the observed extraordinary high wound infection risk in obese patients.

Although supplemental oxygen during surgery and for the first two-to-six hours after surgery halves the risk of surgical wound infection, it remains unknown whether prolonged supplemental postoperative oxygen significantly augments the benefits of intraoperative oxygen. There is some evidence suggesting that prolonged postoperative oxygen administration may be helpful. For example, experimental infections in guinea pigs are reduced by administration of supplemental oxygen for 45 h. In contrast, restricting oxygen for only 45 minutes after contamination reduces tensile wound strength in rabbits no more than restricting oxygen for 5 full days. No study in humans has evaluated the effects of supplemental postoperative oxygen on surgical wound infection or associated complications.

To the extent that supplemental oxygen after surgery is likely to reduce the incidence of major complications related to wound infection and healing, benefit is especially likely in morbidly obese patients because their baseline tissue oxygenation is usually sub-optimal and their risk is high. We thus propose to test the hypothesis that the incidence of major complications related to infection or inadequate healing are reduced in morbidly obese patients given 80% inspired oxygen during and for 12-18 hours after surgery compared with patients given 80% oxygen only during surgery.

Patients will be enrolled at two OUTCOMES RESEARCH Group sites: the University of Louisville and the Cleveland Clinic. Patients undergoing gastric bypass will all be given 80% intraoperative oxygen and then randomly assigned to 30% or 80% oxygen until the first postoperative morning. The primary outcome will be a composite of major complications plausibly related to infection or healing. A maximum of 1,276 patients will provide a 90% power to detect a 25% reduction in the proportion of patients with at least one major complication. Supplemental oxygen is safe and inexpensive, costing only a few dollars per patient. Confirming our hypothesis would indicate that clinicians can reduce the risk of serious complications by making an essentially trivial modification in postoperative patient care.

Study Design

Allocation: Randomized, Control: Active Control, Endpoint Classification: Safety/Efficacy Study, Intervention Model: Parallel Assignment, Masking: Double Blind (Subject, Investigator, Outcomes Assessor), Primary Purpose: Prevention


Surgical Wound Infection




University of Louisville
United States




Outcomes Research Consortium

Results (where available)

View Results


Published on BioPortfolio: 2014-07-23T21:45:16-0400

Clinical Trials [1948 Associated Clinical Trials listed on BioPortfolio]

Supplemental Oxygen Reduces Surgical Infection

Supplemental perioperative oxygen has been reported to halve or double the risk of surgical wound infection. We tested the hypothesis that supplemental oxygen reduces infection risk follow...

Supplemental Oxygen and Complications After Abdominal Surgery (The PROXI-trial)

Aim: To investigate the effect of high intra- and postoperative oxygen concentration (80%, as opposed to normally 30%) on surgical wound infection and pulmonary complications after abdomin...

Effect of Peri-operative Supplemental Oxygen in Wound Infection After Appendectomy

The study evaluates the role of supplemental hyper-oxygenation given perioperatively on wound site infection after appendectomy. Half of the patients received ≥50% oxygen and half of the...

Oxygen for Vascular Incisional Healing

The purpose of this clinical trial is to evaluate Transdermal Continuous Oxygen Therapy (TCOT) as an adjunct to surgical wound healing in subjects undergoing vascular surgery for lower ext...

Supplemental Oxygen in Vascular Surgery

The purpose of this study was to test the hypothesis that supplemental postoperative oxygen reduces the risk of surgical wound infection in patients following lower limb vascular surgery.

PubMed Articles [15809 Associated PubMed Articles listed on BioPortfolio]

Prevention of deep sternal wound infection in cardiac surgery, review of literature.

Deep sternal wound infection is a dreaded complication of cardiac surgery with considerable consequences in terms of mortality, morbidity and treatment costs. Multiple specific measures in the prevent...

Cost-effectiveness analysis of single use negative pressure wound therapy dressings (sNPWT) compared to standard of care in reducing surgical site complications (SSC) in patients undergoing coronary artery bypass grafting surgery.

There is a growing interest in using negative pressure wound therapy in closed surgical incision to prevent wound complications which continue to persist following surgery despite advances in infectio...

Negative Pressure Wound Therapy for Surgical-site Infections: A Randomized Trial.

This study seeks to evaluate the efficacy of negative pressure wound therapy for surgical-site infection (SSI) after open pancreaticoduodenectomy.

The Safety of Negative-Pressure Wound Therapy on Surgical Wounds: An Updated Meta-analysis of 17 Randomized Controlled Trials.

To assess whether negative-pressure wound therapy (NPWT) reduced complications such as wound infection, dehiscence, seroma/hematoma, skin necrosis/blistering, and bleeding compared with non-NPWT treat...

Culture results from wound biopsy versus wound swab: does it matter for the assessment of wound infection?

The aim of this study was to determine whether assessment of wound infection differs when culture results from wound biopsy versus wound swab are available in clinical practice.

Medical and Biotech [MESH] Definitions

Infection occurring at the site of a surgical incision.

Pathologic process consisting of a partial or complete disruption of the layers of a surgical wound.

Intraocular infection caused mainly by pus-producing bacteria and rarely by fungi. The infection may be caused by an injury or surgical wound (exogenous) or by endogenous septic emboli in such diseases as bacterial endocarditis or meningococcemia.

The application of a vacuum across the surface of a wound through a foam dressing cut to fit the wound. This removes wound exudates, reduces build-up of inflammatory mediators, and increases the flow of nutrients to the wound thus promoting healing.

Removal of degenerated and necrotic epithelium and underlying connective tissue of a periodontal pocket in an effort to convert a chronic ulcerated wound to an acute surgical wound, thereby insuring wound healing and attachment or epithelial adhesion, and shrinkage of the marginal gingiva. The term is sometimes used in connection with smoothing of a root surface or ROOT PLANING. (Jablonski; Illustrated Dictionary of Dentistry, 1982)

More From BioPortfolio on "Supplemental Postoperative Oxygen and Wound Infection in Morbidly Obese Patients"

Quick Search


Relevant Topics

Antiretroviral Therapy Clostridium Difficile Ebola HIV & AIDS Infectious Diseases Influenza Malaria Measles Sepsis Swine Flu Tropical Medicine Tuberculosis Infectious diseases are caused by pathogenic...

Obesity is the condition in which excess fat has accumulated in the body (mostly in subcutaneous tissues). clinical obesity is considered to be present when a person has a BMI of over 30 (Oxford Dictionary of Medicine). It is becoming increasing common i...

Surgical treatments
Surgery is a technology consisting of a physical intervention on tissues. All forms of surgery are considered invasive procedures; so-called "noninvasive surgery" usually refers to an excision that does not penetrate the structure being exci...

Searches Linking to this Trial