Role of Perioperative Oxygen Unclear in Wound Infections

SAN DIEGO – The benefit of giving a high perioperative oxygen fraction during surgery to prevent wound infections is not clear cut, judging by conflicting data from several studies.

Surgical site infections occur in 2%-3% of surgical patients. "They’re serious – the average infected patient stays in the hospital longer than they would otherwise" and the risk of being admitted to the ICU or dying doubles if surgical sites become infected, said Dr. Daniel I. Sessler said at a meeting of the American Society of Anesthesiologists.

High tissue oxygenation reduces the risk of wound infection by improving the efficacy of neutrophils to kill bacteria, so surgical patients often receive extra inspired oxygen to boost tissue oxygen. However, different results were seen in four randomized, controlled studies comparing surgical patients given a high inspiratory oxygen fraction (80%) with those who received a more conventional, lower oxygen fraction (30%) during surgery and for 2 hours afterward, said Dr. Sessler, professor and chair of outcomes research at the Cleveland Clinic.

One study randomized 500 patients undergoing colorectal resection and found surgical wound infections in 5% of the 80% oxygen group, less than half the 11% infection rate in the 30% oxygen group (New Engl. J. Med. 2000;342:161-7).

A separate study of 165 surgical patients reported that the wound infection rate more than doubled in the 80% oxygen group, compared with the 30% oxygen group – 25% vs. 11%, respectively (JAMA 2004;291:79-87).

In a separate study of 291 patients undergoing colorectal surgery, the surgical wound infection rate was lower in the 80% oxygen group than in the 30% oxygen group – 15% vs. 24%, respectively (JAMA 2005;294:2035-42).

The differences between groups in those studies were statistically significant, but no significant difference in infection rates between groups was seen in the most recent study, the PROXI trial. Among 1,386 adult patients undergoing abdominal surgery (acute or elective laparotomy) wound infection rates were 19% in the 80% oxygen group and 20% in the 30% oxygen group (JAMA 2009;302:1543-50).

"There are differences among the trials" Dr. Sessler noted. In the PROXI trial, for example, the investigators gave very little fluid to patients, so patients may have been well oxygenated but not well perfused. Factors like this may help explain their conflicting results.

"But, basically, we don’t know why this difference exists, and clearly additional research is necessary," he added.

Improving postanesthesia outcomes such as wound infections is an important goal, especially since the risk of mortality is so rare, Dr. Sessler said. "Twenty-five years ago, when I was an anesthesiology resident, anesthetic mortality was about 1 in 10,000 people, making anesthesia more dangerous than surgery in most cases," he recalled. "Now, preventable anesthetic mortality is probably about 1 in 100,000 cases," thanks to improvements in equipment, drugs and training.

Dr. Sessler has had financial relationships with Arizant, Dynatherm, Aspect Medical System (Covidien), Hutchinson Technology, Merck Pharmaceuticals, Cardinal Health, King Systems, and Velomedix.

SAN DIEGO – The benefit of giving a high perioperative oxygen fraction during surgery to prevent wound infections is not clear cut, judging by conflicting data from several studies.

Surgical site infections occur in 2%-3% of surgical patients. "They’re serious – the average infected patient stays in the hospital longer than they would otherwise" and the risk of being admitted to the ICU or dying doubles if surgical sites become infected, said Dr. Daniel I. Sessler said at a meeting of the American Society of Anesthesiologists.

High tissue oxygenation reduces the risk of wound infection by improving the efficacy of neutrophils to kill bacteria, so surgical patients often receive extra inspired oxygen to boost tissue oxygen. However, different results were seen in four randomized, controlled studies comparing surgical patients given a high inspiratory oxygen fraction (80%) with those who received a more conventional, lower oxygen fraction (30%) during surgery and for 2 hours afterward, said Dr. Sessler, professor and chair of outcomes research at the Cleveland Clinic.

One study randomized 500 patients undergoing colorectal resection and found surgical wound infections in 5% of the 80% oxygen group, less than half the 11% infection rate in the 30% oxygen group (New Engl. J. Med. 2000;342:161-7).

A separate study of 165 surgical patients reported that the wound infection rate more than doubled in the 80% oxygen group, compared with the 30% oxygen group – 25% vs. 11%, respectively (JAMA 2004;291:79-87).

In a separate study of 291 patients undergoing colorectal surgery, the surgical wound infection rate was lower in the 80% oxygen group than in the 30% oxygen group – 15% vs. 24%, respectively (JAMA 2005;294:2035-42).

The differences between groups in those studies were statistically significant, but no significant difference in infection rates between groups was seen in the most recent study, the PROXI trial. Among 1,386 adult patients undergoing abdominal surgery (acute or elective laparotomy) wound infection rates were 19% in the 80% oxygen group and 20% in the 30% oxygen group (JAMA 2009;302:1543-50).

"There are differences among the trials" Dr. Sessler noted. In the PROXI trial, for example, the investigators gave very little fluid to patients, so patients may have been well oxygenated but not well perfused. Factors like this may help explain their conflicting results.

"But, basically, we don’t know why this difference exists, and clearly additional research is necessary," he added.

Improving postanesthesia outcomes such as wound infections is an important goal, especially since the risk of mortality is so rare, Dr. Sessler said. "Twenty-five years ago, when I was an anesthesiology resident, anesthetic mortality was about 1 in 10,000 people, making anesthesia more dangerous than surgery in most cases," he recalled. "Now, preventable anesthetic mortality is probably about 1 in 100,000 cases," thanks to improvements in equipment, drugs and training.

Dr. Sessler has had financial relationships with Arizant, Dynatherm, Aspect Medical System (Covidien), Hutchinson Technology, Merck Pharmaceuticals, Cardinal Health, King Systems, and Velomedix.

SAN DIEGO – The benefit of giving a high perioperative oxygen fraction during surgery to prevent wound infections is not clear cut, judging by conflicting data from several studies.

Surgical site infections occur in 2%-3% of surgical patients. "They’re serious – the average infected patient stays in the hospital longer than they would otherwise" and the risk of being admitted to the ICU or dying doubles if surgical sites become infected, said Dr. Daniel I. Sessler said at a meeting of the American Society of Anesthesiologists.

High tissue oxygenation reduces the risk of wound infection by improving the efficacy of neutrophils to kill bacteria, so surgical patients often receive extra inspired oxygen to boost tissue oxygen. However, different results were seen in four randomized, controlled studies comparing surgical patients given a high inspiratory oxygen fraction (80%) with those who received a more conventional, lower oxygen fraction (30%) during surgery and for 2 hours afterward, said Dr. Sessler, professor and chair of outcomes research at the Cleveland Clinic.

One study randomized 500 patients undergoing colorectal resection and found surgical wound infections in 5% of the 80% oxygen group, less than half the 11% infection rate in the 30% oxygen group (New Engl. J. Med. 2000;342:161-7).

A separate study of 165 surgical patients reported that the wound infection rate more than doubled in the 80% oxygen group, compared with the 30% oxygen group – 25% vs. 11%, respectively (JAMA 2004;291:79-87).

In a separate study of 291 patients undergoing colorectal surgery, the surgical wound infection rate was lower in the 80% oxygen group than in the 30% oxygen group – 15% vs. 24%, respectively (JAMA 2005;294:2035-42).

The differences between groups in those studies were statistically significant, but no significant difference in infection rates between groups was seen in the most recent study, the PROXI trial. Among 1,386 adult patients undergoing abdominal surgery (acute or elective laparotomy) wound infection rates were 19% in the 80% oxygen group and 20% in the 30% oxygen group (JAMA 2009;302:1543-50).

"There are differences among the trials" Dr. Sessler noted. In the PROXI trial, for example, the investigators gave very little fluid to patients, so patients may have been well oxygenated but not well perfused. Factors like this may help explain their conflicting results.

"But, basically, we don’t know why this difference exists, and clearly additional research is necessary," he added.

Improving postanesthesia outcomes such as wound infections is an important goal, especially since the risk of mortality is so rare, Dr. Sessler said. "Twenty-five years ago, when I was an anesthesiology resident, anesthetic mortality was about 1 in 10,000 people, making anesthesia more dangerous than surgery in most cases," he recalled. "Now, preventable anesthetic mortality is probably about 1 in 100,000 cases," thanks to improvements in equipment, drugs and training.

Dr. Sessler has had financial relationships with Arizant, Dynatherm, Aspect Medical System (Covidien), Hutchinson Technology, Merck Pharmaceuticals, Cardinal Health, King Systems, and Velomedix.