Severe OSA ups risk of cardiovascular complications after major noncardiac surgery

Unrecognized severe obstructive sleep apnoea (OSA) intensifies the risk of postoperative cardiovascular complications among at-risk adults receiving major noncardiac surgery, according to a new study presented at the recently concluded 2019 International Conference of the American Thoracic Society (ATS 2019).

“In the general population, OSA is associated with higher risk of cardiovascular complications such as hypertension, myocardial ischaemia, heart failure, arrhythmias, stroke and sudden cardiac death,” said one of the study authors Dr Frances Chung from the University of Toronto in Ontario, Canada. The aim then of the present study was to investigate whether these risks extended to patients who had undergone major noncardiac surgery.

The study included 1,218 patients, most of whom (67.6 percent) had unrecognized OSA. In comparison, 30.5 percent had moderate OSA while 11.2 percent had severe OSA. The primary outcome – a composite of myocardial injury, heart failure, stroke, thromboembolism, cardiac death and atrial fibrillation within 30 days of the procedure – occurred in 235 participants (19.3 percent).

Stratifying the analysis according to OSA severity showed that the primary outcome occurred more frequently in in those with severe (30.1 percent) than in those with moderate (22.1 percent) or mild (19.0 percent) OSA. Only 14.2 percent of those without OSA experienced the composite endpoint.

Cox proportional hazards analysis showed that relative to the no-OSA controls, those with the condition were significantly more likely to develop the primary outcome (adjusted hazard ratio [HR], 1.49, 95 percent CI, 1.19–2.01; p=0.01).

However, further investigation revealed that this trend was statistically significant in patients with severe OSA (adjusted HR, 2.23, 1.49–3.34; p=0.001) but not in those with moderate (adjusted HR, 1.47, 0.98–2.09; p=0.07) or mild (adjusted HR, 1.36, 0.97–1.91; p=0.08) condition (p-interaction=0.01).

“Despite a substantial decrease in [oxygen desaturation index] with oxygen therapy in patients with OSA during the first 3 postoperative nights, supplemental oxygen did not modify the association between OSA and postoperative cardiovascular event,” Chung and her team pointed out in the paper.

“Given that these [cardiovascular] events were associated with longer duration of severe oxyhaemoglobin desaturation, more aggressive interventions may be required,” they added.

In terms of secondary outcomes, OSA also significantly increased the likelihood of unplanned admission or readmission into the ICU, regardless of condition severity (severe, odds ratio [OR], 6.60, 2.61–16.70; p<0.001; moderate: OR, 4.99, 2.06–12.06; p<0.001; mild: OR, 3.55, 1.52–8.13; p=0.005).

The same was true for unplanned tracheal intubation or postoperative ventilation (severe: OR, 6.16, 2.51–15.16; p<0.001; moderate: OR, 6.26, 2.85–13.75; p<0.001; mild: OR, 2.28, 1.04–5.03; p=0.04). On the other hand, only severe (OR, 2.31, 1.03–5.18; p<0.04) and moderate (OR, 2.68, 1.34–5.36; p<0.005) OSA increased the risk of postoperative infections.

Important limitations of the present study included the failure to record electroencephalograms and potential underestimation of OSA severity, Chung noted. Other areas of improvement include controlling for perioperative medication and differences in ethnicity

“Further research would be needed to assess whether interventions can modify this risk,” the team said.