Anesthetic Management and Surgical Site Infections In Total Hip or Knee Replacement

Anesthesiology 2010;113:279-284

Chang C-C, Lin H-C, Lin H-W, Lin H-C

Abstract

Purpose The purpose of this study was to determine if subarachnoid block and epidural block were associated with lower rates of Surgical Site Infections than general anesthesia in patients who had total joint replacements.

Background Surgical site infections (SSIs) have been estimated to occur after about 5% of surgeries overall in the USA. Often resulting in additional hospital inpatient days or hospital readmission, SSIs reportedly add four days following breast surgery and 32 days following cardiothoracic surgery. With increased inpatient days comes increased cost, an average of $1,157 per surgical infection. The cost of care following discharge may be even greater.

Surgical site infections develop during the initial hours immediately postoperatively. Risk factors for the development of SSIs include: smoking, obesity, surgical duration, and hyperglycemia. Tissue oxygenation and leukocyte tissue perfusion are thought to be critical factors in whether or not an SSI develops postoperatively. General anesthesia does not block the surgical stress response as completely as can regional anesthesia. Surgical pain also results in sympathetic activation. Sympathetic stimulation and increased circulating catecholamines result in vasoconstriction, reducing circulation to the wound. Reduced wound circulation results in reduced tissue oxygenation and locally reduced leukocyte activity. Furthermore, potent inhaled anesthetics and opioids have been shown to impair neutrophils and other cellular elements of the blood that defend against infection. Subarachnoid and epidural anesthesia typically block sympathetic activation more completely than does general anesthesia, improving tissue perfusion, oxygenation, and leukocyte perfusion. In patients who had major upper abdominal surgery, combined general - epidural anesthesia has been shown to increase tissue oxygenation with an associated reduction in SSIs compared to general anesthesia alone.

Methodology This was a retrospective study of a systematically collected “Longitudinal Health Insurance Database,” available to Taiwanese researchers. A randomly selected subset of the database was used for this study. The investigators identified 3,081 patients who had either total hip (n=951) or total knee (n=2,130) replacements during a five year period. Of these surgical patients, 1,191 received general anesthesia and 1,890 either subarachnoid block (n=1,281) or epidural block (n=609). A postoperative SSI included infections, cellulitis, and abscesses either during hospitalization or after discharge but within 30 days of hospital admission.

Result The mean age of all patients was 62.6 years. On average, patients who received regional anesthesia were about 2 years older than general anesthesia patients. Regional anesthesia patients were also more likely to have hypertension, diabetes, hyperlipidemia, and coronary artery disease. Those who received general anesthesia were more likely to have had surgery at a teaching hospital. Patients who had a general anesthetic for their total joint replacement were 2.21 times more likely (95% CI 1.25 – 3.90) to have an SSI compared to patients who had a subarachnoid block or epidural block. (Adjusted for comorbidities; the unadjusted risk for general anesthesia patients was 2.31.)

Data from Anesthesiology 2010;113:279 table 2. * P = 0.002 compared to general anesthesia.

Comment

This very simple study has a lot to teach us. While it does have limitations, from a common sense point of view, they were unlikely to have blurred the overall outcome and the study was reasonably adjusted for many of them. This is a big picture sort of study, not a bunch of minutia. And the big picture is that a spinal or epidural alone for your total hip or knee replacement cuts your risk of a surgical site infection in half.

There are lots of reasons we donʼt do more total joints with regional anesthesia but, in my opinion, the reasons we donʼt arenʼt nearly as good as the reasons we should. Iʼm not going to address each one of them, but I am going to make my case for a patient care reason and a financial reason we should make regional anesthesia our first choice for total knee and total hip replacements. First, these patients have much better pain control and better surgical recovery when their total joint is done with a regional anesthetic. This is good patient care. Second, while regional anesthesia is often not used because “it takes too long” we must look at the total cost of care, not just the time to get the case started. In addition to the morbidity caused by postoperative infections, wound infections dramatically increase the cost of a total joint. If a regional anesthetic costs a little bit more for a few additional minutes of anesthesia time, it will, overall, be more than made up for by the lower cost of not having to treat twice as many infections. That is good financial management in a time of shrinking healthcare dollars (good patient care too).

While it would be easy to criticize this study for being retrospective, a prospective version would be hard to conduct for many reasons. One big reason is that most patients, and surgeons, have a strong idea of whether they want regional or general anesthesia and getting all to agree to have their anesthetic randomize might prove difficult.

This study is just one reason why all anesthesia providers need to be skilled in regional anesthesia and sedation techniques. And why anesthesia practice needs to be based upon evidence rather than simple surgeonʼs preference, anesthesia provider convenience, an OR that is behind schedule, or the inability to coordinate care between services.

Michael Fiedler, PhD, CRNA

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 6, June 30, 2010