Last week, I gave a lecture to our residents about the risks of medical complications after surgery in patients with obstructive sleep apnea. It brought back memories of some studies about the risks of surgery in which I was involved and highlighted two recent studies of the risks of surgery published last month in journals from the field of anesthesiology. There are a number of small studies out there about medical complications, but many of them focus on trivial issues like a 5-second drop in the oxygen level to 85% while someone is in the recovery room immediately after surgery. That is not really relevant to anyone, so I prefer to focus on complications that have potential health implications, from as relatively minor as having the patient remain intubated (leaving in the breathing tube during placed during surgery for another day, for example) to more-substantial (pneumonia or emergency need for placement of a breathing tube). I will describe findings that have been shown in two groups of patients with potential risks: those undergoing surgery for sleep apnea and those who have sleep apnea but are undergoing surgery unrelated to sleep apnea.
Risks for sleep apnea surgery
About 10 years ago, I had the chance to work with Edward Weaver, MD, MPH at the University of Washington to determine the risks of complications in patients undergoing sleep apnea surgery. Relying on a database on serious surgical complications in the Veterans Administration health care system, we were able to analyze data on 3130 patients who had sleep apnea surgery (mainly soft palate surgery) at over 100 hospitals from 1991-2001. We showed that the risk of serious complication after sleep apnea surgery was 1.6% and the mortality risk was 0.2%, both of which were lower than many smaller studies suggested. The most likely complications were related to breathing, ranging from being as minor as We then followed this up with a second study that showed, perhaps not surprisingly, that the most important risk factor for complication was having serious medical conditions prior to surgery; this is true for almost any surgery. Other risk factors were having worse sleep apnea (higher apnea-hypopnea index) and higher body mass index (a ratio of a person’s weight to their height). In addition to being the largest study of its kind, the important thing is that the results were generalizable, meaning that they reflected the broad experience of patients because they came from many surgeons performing surgery at hospitals across the entire country. Of course, the data came only from patients who had surgery in Veterans Administration medical centers, but the results overall were probably more realistic than from studies that are limited to individual surgeons or individual hospitals.
Risks of other surgeries in sleep apnea patients
Patients with sleep apnea who are undergoing surgery are at increased risk of complication if they are not treating their sleep apnea. The best initial study showing this came from the Mayo Clinic, examining the risk of complication after knee or hip arthroplasty (joint replacement). Interestingly, they started with 101 patients who underwent knee or hip replacement within 3 years before or after a diagnosis of sleep apnea and showed that the risks of complications were higher than in similar patients who did not have sleep apnea. They then looked at patients who had sleep apnea diagnosed before the surgery, who received CPAP, and who were actually wearing their CPAP. They showed that wearing CPAP prior to surgery reduced the risks of complication to the same level as in patients who did not have sleep apnea at all.
Society of Anesthesia and Sleep Medicine
In November, I was alerted to two new studies about risks of hip and knee replacement in sleep apnea patients by a newsletter from the Society of Anesthesia and Sleep Medicine. This group was formed to advance the understanding of problems common to anesthesiology and sleep medicine, and these risks certainly fit in that category. As a surgeon and sleep specialist, I am drawn to these concerns and have joined the SASM. Professor David Hillman, an anesthesiologist and sleep specialist with whom I collaborate in research, encouraged me to join, and I now serve on its Clinical Committee. SASM generates their own monthly Literature Updates and Featured Articles, which identified these two studies. The first used high-quality databases from hospitals across the entire United States to show that patients with sleep apnea had a greater odds of serious complication (both pulmonary and cardiac) after knee or hip arthroplasty, in addition to having higher costs. The second came from Manitoba and showed that sleep apnea was associated with serious complication, although treatment with CPAP (they could not determine whether patients were using it) did lower the risk.
There have been a number of other studies that have explored the risks of other surgeries in sleep apnea patients, and the research overall has shown similar findings. This has led to the development of screening questionnaires that can be used in all patients scheduled for surgery in order to determine the risks of sleep apnea and, if needed, to proceed with testing and treatment before surgery. The Society for Anesthesia and Sleep Medicine is one of a few groups dedicated to improving patient safety, and I have been excited to be a part of their efforts. The SASM website has more information about the unique challenges of anesthesia in patients with sleep apnea, and I encourage anyone interested to explore it.