By: 20 May 2013

Nuraxial anaesthesia (spinal or epidural anaesthesia) is a highly underutilised technique, but one which improves outcomes in patients undergoing hip or knee replacement, according to a new study by researchers at Hospital for Special Surgery (HSS). The study, from the journal Anesthesiology, found that neuraxial anaesthesia reduced morbidity, mortality, length of hospital stay and costs when compared with general anaesthesia.

“The influence that the type of anaesthetic can have on perioperative outcomes has been vastly underestimated. Indeed, our study suggests that the type of anaesthesia chosen may have important impacts on all kinds of medical and economic outcomes in orthopaedic surgical patients,” said Stavros Memtsoudis, MD, PhD, director of Critical Care Services at HSS, New York City. “It is not something to be taken lightly.”

Using neuraxial anaesthesia over general anaesthesia reduced the risk of pulmonary compromise twofold in knee replacement patients and over threefold in hip replacement patients. “When one considers the modest decrease in risk of adverse outcomes associated with the use of a number of widely used medications such as anti-cholesterol drugs, the effect sizes seen in this study are really impressive,” said Dr Memtsoudis.

Neuraxial anaesthesia involves injecting medication into fatty tissue that surrounds the nerve roots in the spine or into the cerebrospinal fluid that surrounds the spinal cord. Anaesthetists at HSS, use regional anaesthesia for over 90 percent of hip and knee replacements. In the past, several small studies have shown that compared with general anaesthesia, regional anaesthesia reduces intraoperative blood loss and the need for blood transfusions.

In the new study, researchers at HSS conducted a retrospective review of hip and knee replacements performed between 2006 and 2010 in the United States using data collected by Premier Perspective. This administrative database contains discharge information from approximately 400 acute care hospitals located throughout the United States.

Information on the type of anaesthesia used was available in 71.4 percent of 528,495 patients. Eleven percent received neuraxial anaesthesia, 14.2 percent received combined neuraxial and general anaesthesia, and 74.8 percent received general anaesthesia. Thirty-day mortality was significantly higher in patients who received general anaesthesia, 0.18 percent, compared with those who received neuraxial, 0.10 percent, or neuraxial-general, 0.10 percent.

“Other studies have suggested some benefit of neuraxial over general anaesthesia, but they looked at very limited outcomes, primarily at risk of bleeding and blood transfusions. What this study does for the first time is really explore the impact of anaesthesia on a wider range of important outcomes,” said Dr Memtsoudis. “We found lower rates of complications including pulmonary compromise, pneumonia, infections, and acute renal failure when neuraxial anaesthesia is used. The choice of anaesthesia seemed to basically affect every organ system.”

When patients who received general anaesthesia were compared to patients who received neuraxial or a combination of neuraxial and general, they were found to have higher rates of pulmonary compromise (0.81 percent vs. 0.37 percent vs. 0.61 percent), infections (4.5 percent vs. 3.11 percent vs. 3.87 percent) and acute renal failure (1.75 percent vs. 1.1 percent vs. 1.43 percent).

Neuraxial anaesthesia was also associated with shorter hospital stays and lower healthcare costs. Patients were defined as having a prolonged hospital stay if they fell in the 75th percentile of the study cohort in terms of stay duration. The researcher found that more patients receiving general anaesthesia (35.4 percent) had a prolonged hospital stay than patients who received neuraxial (28.7 percent) or neuraxial and general (27.4 percent). Patients were less likely to fall into the upper 75th percentile in terms of health care costs if they received neuraxial anaesthesia (21.4 percent) or combined neuraxial-general (18.3 percent) than in the general anaesthesia group (23.4 percent). “Patients were 30 percent more likely to be in the group that had the highest costs if they received general anaesthesia alone,” said Dr Memtsoudis.

Anaesthesia medications used during surgeries are a small fraction of overall healthcare costs, and the costs of regional and general anaesthesia are similar.

Dr Memtsoudis pointed out that educating patients is key. “Some patients don’t like the idea of having an injection in their back and their legs being numb, but a thorough discussion of risks, benefits and alternatives can go a long way to help an educated patient make rational decisions,” he said. “For the anaesthetist, a number of factors come into play, including patient comorbidities and preferences as well as other practice-specific factors, such as the choice for anticoagulation, but regional anaesthesia should, at the very least, be considered in every patient.”

While randomised clinical trials are the gold standard of clinical research, such trials are not feasible for testing anaesthesia technique in joint replacement surgeries, because the low incidence outcomes would require a huge number of patients.