Postoperative outcomes in obstructive sleep apnea

Patients with undiagnosed obstructive sleep apnea (OSA) are thought to be at higher risk after an operation than those who have already been diagnosed and are being treated with CPAP therapy. Current practice guidelines recommend screening for obstructive sleep apnea before an operation, and starting CPAP therapy prior to surgery if feasible. Routine monitoring of patients with OSA is recommended after many types of surgery.

This study looked at historical outcomes after surgery that occurred before the implementation of the current practice guidelines. The study included data on adults and compared them to controls at low risk of having sleep apnea. The control patients were matched for the type of surgery, indication for the surgery, and date of the surgery.

The results showed that the risk of cardiovascular complications, primarily cardiac arrest and shock, was increased in undiagnosed obstructive sleep apnea but not diagnosed obstructive sleep apnea. However the risk of respiratory complications, primarily Acute Respiratory Distress Syndrome (ARDS) and acute respiratory failure was increased in both groups without significant difference in risk between them. Also, the results showed that increasing severity of obstructive sleep apnea, age, comorbid disease, and the type of surgery were also important risk predictors for postoperative complications.

The study was not designed to determine whether reduction in cardiovascular complications in those patients diagnosed with OSA was due to CPAP use as usage of CPAP was not measured immediately after surgery.

Salt water infusion and sleep apnea

Sleep researchers have not worked out exactly how we develop obstructive sleep apnea (OSA). There are several risk factors and anatomical reasons involved. Some researchers have postulated that OSA may be worsened by fluid shifting from the legs to the neck area overnight. In other words, because the legs are generally at the level of the heart while in bed, fluid from the legs moves into the neck area, causing swelling in the upper airway. This narrows the upper airway enough to restrict airflow.

In this article in the Journal Sleep, researchers studied older and younger men to see if giving them IV salt water impacted the level of sleep apnea. The study was limited to men who were not obese and had either no or non-severe OSA. They did sleep studies after giving them the IV salt water. The results showed that the IV salt water worsened OSA significantly in older men, but not younger men. The reason for this was not clear from the study. However, the results have important implications for older men undergoing surgery, since IV fluids are commonly given during and right after surgery.

OSA and Perioperative Complications in Bariatric Patients

Article in the British Journal of Anaesthesia about OSA and complications around the time of surgery in obese patients. Obese patients, with and without OSA, are at higher surgical risk. It's assumed that OSA is an independent risk factor for perioperative complications, but the article says there is not much objective data to support that.

Currently, bariatric surgeons typically have their patients have a sleep study prior to weight loss surgery. If there is significant OSA, than the patient is treated for several weeks to months with CPAP prior and upto the weight loss surgery.

The authors of this study studied patients that had a pre-op sleep study. Ninety-three percent of the patients with OSA received perioperative positive airway pressure therapy. All patients were closely monitored after operation. The overall complication rate was increased with open procedures compared with laparoscopic. In addition, increased BMI and age were associated with increased likelihood of pulmonary and other complications. Complication rates were not associated with OSA severity.

The authors concluded that in obese patients evaluated by sleep study before bariatric surgery and managed accordingly, the severity of OSA (the AHI), was not associated with the rate of perioperative complications. Thus, either OSA is not an independent risk factor for complications or the recognition and management of OSA in the perioperative period mitigates this risk. These results cannot determine whether unrecognized and untreated OSA increases risk.

Sleep Deprivation, Elective Surgical Procedures, and Informed Consent

There was an article in the December 30th edition of the New England Journal of Medicine about sleep-deprived surgeons. The authors propose that surgeons awake 22-24 hours be required by law to disclose that to patients about to undergo elective surgery so that the patient can reschedule if they want. Apparently, complication risk goes up 83% for elective surgeries when the surgeon has less than a six hour opportunity to sleep between procedures when on call the night before.

Organized medicine, such as the surgery specialty societies are not happy about this proposal. They feel that surgeons should be able to judge for themselves if they are capable of proceeding with an elective surgery. Also, telling a patient that you are "sleep-deprived" could set up a surgeon for a lawsuit. Surgeons fear that next they will be forced to reveal any financial or even marital problems they are having to their patients, because such personal problems could affect operating room performance.

Unfortunately, sleep deprivation decreases your ability to recognize if you are impaired from the sleep loss. Thus, one solution is educating surgeons (and all other medical specialties) how to recognize fatigue and how fatigue degrades cognitive and physical performance.

Already, the FAA restricts pilots from flying if they haven't had a certain number of hours of sleep. And residents (physicians in training) have their work hours limited to improve patient safety and reduce resident health problems.

I am not convinced federal regulation is the answer to sleep deprived surgeons, but I can see both sides of the argument. More data is needed and more education of all involved might a good first step.

Sleep Apnea Increases Pulmonary Complications After Surgery

There is an article in the January issue of Anesthesia & Analgesia that warns that patients with sleep apnea have more frequent pulmonary complications after orthopedic and general surgery. I am not sure if this included sleep apnea patients that were treated. The risk of being intubated and put on a mechanical ventilator went up five-fold after orthopedic surgery and two-fold after general surgery. Other complications that were increased after these surgeries included aspiration pneumonia (lung infection after stomach contents are inhaled) and pulmonary embolus (lung clots).

This study points to the importance of pre-surgical screening for sleep apnea, so that anesthesiologists and surgeons are aware of the risk. Also, it would be interesting to know if treating sleep apnea reduces these pulmonary risks.