Trying to stratify which patients with obstructive sleep apnoea merit an elective high dependency bed post-operatively can be difficult. The commonly used STOP BANG criteria is a validated screening tool but can lead to a high number of false positives – an issue when we have a finite resource of monitored post-operative beds.
An algorithm from Vancouver for stratifying patients thought to be at risk of OSA (based on STOPBANG Score), specifically for additional perioperative risk stratification. It suggests that patients at low perioperative risk may be appropriately managed by going ahead with surgery ‘expectantly’ and following up postoperatively with regard to sleep medicine consultation.
An Editorial discussing OSA was published in the Perioperative Medicine symposium issue of Anaesthesia in early 2016. The Author suggests a role for anaesthetists in dealing with OSA as a public health issue.
A useful reference outlining some of the evidence for recommendations is the ASA task force summary (ASA Task Force. Updated Practice Guidelines for the Perioperative Management of Patients with Obstructive Sleep Apnea. Anesthesiology 2014; 120:268-86 ). It can be found at:
A method to potentially increase the specificity of the STOPBANG screening process is suggested by Chung et al in:
Chung F, Yang Y, Brown R, Liao P. Alternative Scoring Models of STOP-Bang Questionnaire Improve Specificity To Detect Undiagnosed Obstructive Sleep Apnea. Journal of Clinical Sleep Medicine : JCSM : Official Publication of the American Academy of Sleep Medicine. 2014;10(9):951-958. doi:10.5664/jcsm.4022). The pubmed link to this article is at:-
A patient with STOPBANG Score of 5-6 has never been investigated for OSA. Should surgery be postponed for formal sleep studies? This may require considerable delay.
Discussion:- As generally used, the STOPBANG Score has high sensitivity but low specificity. Note that the criteria for positive scores are more severe than is commonly practiced. Note:- “S” requires loud snoring- (“loud enough to be heard through a closed door”). Similarly, “T” – is more than common tiredness and implies daytime somnolence (“such as falling asleep during driving or talking to someone”).
If positive, the outcome of sleep studies may be to recommend a trial of CPAP, however this requires 6 to 8 weeks if not longer to get full benefit in the case of pulmonary hypertension etc.
Frances Chung and her colleagues have established a comprehensive STOPBANG resource website, (www.stopbang.ca) which includes some pragmatic perioperative management guidelines developed in Vancouver. They suggest that for many patients it may be appropriate to use STOPBANG combined with clinical review to triage the patient, after consideration of surgical risk factors and urgency, proceed to surgery cautiously but without formal studies, with postoperative intervention as needed, using CPAP postoperatively if necessary.
For this patient. STOPBANG score should be combined with assessment using history & clinical signs. Consider echocardiogram looking for evidence of pulmonary hypertension or right heart failure or diastolic dysfunction. Note ‘hidden’ resting hypoxaemia due to sub-clinical Pickwickian syndromes, where saturation may be raised by voluntarily increasing ventilation. Check for HCO3 retention on biochemistry. Even if there is no time to start therapy, echo assessment may guide triage for HDU post operatively. Anaesthesia management should consider risk of OSA (i.e. optimize non-opiate analgesia etc). Postoperative reassessment in PACU.
What is the role of overnight oximetry as a screening/assessment tool? Is this a useful alternative to formal Sleep Medicine consultation and Polysomnography?
This was discussed with the Shyamala Pradeepan, JHH Department of Respiratory Medicine. She (and they) accept the limitations of STOPBANG, and the problem of access to formal sleep studies. They recommend that patients suspected at high risk of OSA in the perioperative clinic be referred immediately (i.e. prior to respiratory consultation) for overnight oximetry as a further screening test. Overnight oximetry can be organized on a “walk-in basis” through the respiratory laboratory, with next-day reporting. This can then be used as a triage tool for perioperative management, or for respiratory consultation, viz:-
- Normal:- Proceed with normal caution
- Abnormal:- Postpone elective surgery & refer for Respiratory or Sleep Medicine consult.
- Severely Abnormal:- expedited consult;
- Urgent Surgery & Abnormal Oximetry:- Use result to triage postoperative management, particularly to mandate HDU admission, and/or early CPAP.
Chung F1, Liao P, Elsaid H, Islam S, Shapiro CM, Sun Y. Oxygen desaturation index from nocturnal oximetry: a sensitive and specific tool to detect sleep-disordered breathing in surgical patients. Anesth Analg. 2012 May;114(5):993-1000. (Reference includes an introduction as follows:- “It is impractical to perform polysomnography (PSG) in all surgical patients suspected of having sleep disordered breathing (SDB). We investigated the role of nocturnal oximetry in diagnosing SDB in surgical patients.”)
Patel MR, Davidson TM. Home sleep testing in the diagnosis and treatment of sleep disordered breathing. Otolaryngol Clin North Am 2007;40:761-84.
Chung F, Liao P, Sun F, et al. Nocturnal oximeter: a sensitive and specific tool to detect the surgical patients with moderate and severe OSA. Anesthesiology 2009;111:A480
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