Our numerous columns on the obstructive sleep apnea (OSA) in the perioperative period (see the list at the end of todays column) have emphasized that most cases of OSA are unrecognized and that such patients are at risk for complications and even death following surgery. In parallel with the obesity epidemic, the prevalence of OSA has been steadily increasing.
A new study sought to quantify outcomes and resource utilization in patients with known sleep apnea who underwent total hip or knee arthorplasty (Memtsoudis 2014). The authors reviewed data on over 500,000 patients from 2006 to 2010 in a large database. The prevalence of diagnosed sleep apnea was 8.4%. This actually increased from 6.2% to 10.3% over the course of the study period. Compared to those patients without sleep apnea diagnoses, patients with sleep apnea had a higher incidence of post-op complications, including a 47% increased risk of major postoperative morbidity. They also more frequently used critical care, telemetry, stepdown services, mechanical ventilation and noninvasive ventilator support, though they had less frequent blood transfusions. Patients with sleep apnea also had longer lengths of stay and consumed more economic resources (about 14% higher). Keep in mind that these were patients with diagnosed sleep apnea. As weve noted previously the vast majority of patients with sleep apnea are undiagnosed at the time they have surgery. It therefore is very likely that the impact of sleep apnea on both outcomes and resource utilization is actually much more substantial.
Interestingly, compared to other studies showing increased in-hospital mortality this study and some other recent ones have failed to demonstrate increased mortality in those patients with OSA undergoing surgery. In an accompanying editorial Chung and Mokhlesi (Chung 2014) speculate about this mortality issue. They suggest that the obesity paradox or ischemic preconditioning might play a protective role or that patients with known OSA simply have impending respiratory failure recognized and managed earlier. They stress that CPAP can be effective in the perioperative period, though compliance with CPAP is suboptimal (see our September 24, 2013 Patient Safety Tip of the Week Perioperative Use of CPAP in OSA).
Speaking of mortality and sleep apnea, a recent study has demonstrated an association between OSA and maternal mortality in pregnancy (Louis 2014). Because of a recent trend in increasing rates of severe maternal morbidity and mortality despite quality improvements, the authors sought to see if obstructive sleep apnea (OSA) in pregnant women was impacting pregnancy-related morbidities and in-hospital maternal mortality.
They looked at a nationally representative sample of 55,781,965 pregnancy-related inpatient hospital discharges from 1998-2009. The rate of OSA increased from 0.7 in 1998 to 7.3 in 2009, an average annual increase of 24%. After controlling for obesity and other potential confounders, OSA was associated with increased odds of preeclampsia, eclampsia, cardiomyopathy, and pulmonary embolism. Women with OSA experienced a more than fivefold increased odds of in-hospital mortality. The adverse effects of OSA on selected outcomes were exacerbated by obesity.
Back to OSA and surgery, another very interesting study provides some insight into sleep-disordered breathing in patients undergoing surgery (Roggenbach 2014). The authors looked at breathing patterns in 37 patients undergoing major surgery who had not already been diagnosed with OSA. They did polygraphic recordings on these patients the pre-op night and 6 consecutive nights following surgery. They did not have full polysomnograms. Rather, O2-saturation, pulse, nasal air flow and snoring were monitored. 59% of the patients had abnormal nocturnal breathing patterns (AHI = 5 or higher) on the pre-op night, with 22% having AHIs of 15 or higher. The median apnea-hypopnea index (AHI) was 6.0 for the group as a whole on the pre-op night. The AHI increased on the 6 nights following surgery, with the increases on the third through sixth nights being significant (median AHIs being 16.9, 11.6, 15.2, and 22.5 respectively for those subsequent nights). Previous observations had demonstrated a delayed increase in OSA after surgery, usually in conjunction with the return of REM sleep on the second or third post-op day. But this appears to be the first study to monitor for a longer duration and it shows a substantial increase in the risk of OSA in the late post-op period.
Those authors speculate that the surgery itself may have a modulating effect on nocturnal breathing patterns. Their patients underwent major prostate or abdominal surgeries. They note that such surgeries are regularly associated with substantial fluid accumulation and speculate that peripharyngeal soft tissue edema might contribute to reduced airway patency. They also speculate that some of the cytokines typically released with surgery may lead to the early REM suppression seen after surgery, with the subsequent REM rebound appearing later.
Overall, their findings would certainly have implications about the duration of monitoring of patients with suspected OSA post-operatively. It would also seem to challenge performance of surgery in the ambulatory setting. But keep in mind that these were cases of major surgery. It would probably not be appropriate to generalize these findings to cases of more minor surgery. Note that Society for Ambulatory Anesthesia Consensus Statement on Preoperative Selection of Adult Patients with Obstructive Sleep Apnea Scheduled for Ambulatory Surgery (Joshi 2012) emphasizes the need for opioids and control of comorbidities as the most important considerations in deciding whether someone with suspected OSA should have their surgery as an inpatient or outpatient. But even that consensus statement emphasizes to patients and their families that the risks related to OSA persist for several days after surgery.
Reggenbach and colleagues also found little difference in self-reported snoring or daytime drowsiness in their patients who had sleep-disordered breathing compared to those who did not, but the small number of cases makes that difficult to interpret. While the small numbers would not suggest we need to stop using screening tools such as the STOP-Bang questionnaire, the observation does warn us that some patients will have abnormal AHIs in the post-op period even in the absence of pre-existing symptoms. They also surprisingly found no correlation between AHI values and daily opioid dosing but, again, the numbers were small.
Speaking of screening tools, another recent study found a screening tool for OSA to be of little value in children (Wild 2014). The authors found that, though identifying 85% of children with moderate to severe OSA, the American Society of Anesthesiologists screening tool for moderate to severe OSA (MSOSA) had a 78% false positive rate.
And, speaking of children, dont forget that the recent warnings about use of codeine in children first originated after deaths of pediatric patients receiving codeine after adenotonsillectomy for OSA (see our Whats New in the Patient Safety World columns for September 2012 FDA Warning on Codeine Use in Children Following Tonsillectomy and March 2013 Further Warning on Codeine in Children Following Tonsillectomy and our May 2014 Pediatric Codeine Prescriptions in the ER). And a study done last year focusing on death and neurological injuries following tonsillectomy (Cote 2013) concluded that at least 16 children could have been rescued had respiratory monitoring been continued throughout first- and second-stage recovery, as well as on the ward during the first postoperative night. Those authors also stress the need for a validated pediatric-specific risk assessment scoring system to assist with identifying children at risk for OSA. That might help determine which children are not appropriate to be cared for on an outpatient basis.
Our prior columns on obstructive sleep apnea in the perioperative period:
Patient Safety Tips of the Week:
June 10, 2008 Monitoring the Postoperative COPD Patient
August 18, 2009
August 17, 2010
July 13, 2010 Postoperative Opioid-Induced Respiratory Depression
February 22, 2011 Rethinking Alarms
November 22, 2011 Perioperative Management of Sleep Apnea Disappointing
May 22, 2012 Update on Preoperative Screening for Sleep Apnea
February 12, 2013 CDPH: Lessons Learned from PCA Incident
February 19, 2013 Practical Postoperative Pain Management
March 26, 2013 Failure to Recognize Sleep Apnea Before Surgery
September 24, 2013 Perioperative Use of CPAP in OSA
Whats New in the Patient Safety World columns:
November 2010 More on Preoperative Screening for Obstructive Sleep Apnea
Memtsoudis SG, Stundner O, Rasul R, et al. The Impact of Sleep Apnea on Postoperative Utilization of Resources and Adverse Outcomes. Anesth Analg 2014; 118: 407-418
Chung F, Mokhlesi B. Postoperative complications associated with obstructive sleep apnea: time to wake up! Anesth Analg 2014; 118: 251253
Louis JM, Mogos MF, Salemi JL, et al. Obstructive sleep apnea and severe maternal-infant morbidity/mortality in the United States, 1998-2009. Sleep 2014; 37(5): 843-849
Joshi GP, Ankichetty SP, Gan TJ, Chung F. Society for Ambulatory Anesthesia Consensus Statement on Preoperative Selection of Adult Patients with Obstructive Sleep Apnea Scheduled for Ambulatory Surgery. Anesthesia & Analgesia 2012; 115(5): 1060-1068
Wild D. OSA Screener of Limited Clinical Use in Children, Study Finds. Anesthesiology News 2014; 40:4 April 2014
Cote CJ, Posner KL, Domino KB. Death or Neurologic Injury After Tonsillectomy in Children with a Focus on Obstructive Sleep Apnea: Houston, We Have a Problem! Anesth Analg 2013; Published Ahead-of-Print 10 July 2013
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