2017 Update in perioperative medicine: 6 questions answered
ABSTRACT
The authors performed a MEDLINE search to identify articles published between January 2016 and April 2017 that had significant impact on perioperative care. They identified 6 topics for discussion.
KEY POINTS
- Noncardiac surgery after drug-eluting stent placement can be considered after 3 to 6 months for those with greater surgical need and lower risk of stent thrombosis.
- Perioperative statin use continues to show benefits with minimal risk in large cohort studies, but significant randomized controlled trial data are lacking.
- Patients should be screened for obstructive sleep apnea before surgery, and further cardiopulmonary testing should be performed if the patient has evidence of significant sequelae from obstructive sleep apnea.
- For patients with atrial fibrillation on vitamin K antagonists, bridging can be considered for those with a CHA2DS2-VASc score of 5 or 6 and a history of stroke, transient ischemic attack, or systemic thromboembolism. Direct oral anticoagulation should not be bridged.
- Frailty carries significant perioperative mortality risk; systems-based changes to minimize these patients’ risks can be beneficial and warrant further study.
LOAD trial: No benefit from starting statins
Both London et al5 and the VISION investigators4 called for a large randomized controlled trial of perioperative statin initiation. The Lowering the Risk of Operative Complications Using Atorvastatin Loading Dose (LOAD) trial attempted to answer this call.6
This trial randomized 648 statin-naïve Brazilian patients at high risk of perioperative cardiac events to receive either atorvastatin or placebo before surgery and then continuously for another 7 days. The primary outcomes were the rates of death, nonfatal myocardial injury after noncardiac surgery, and cerebrovascular accident at 30 days.6
The investigators found no significant difference in outcomes between the two groups and estimated that the sample size would need to be approximately 7,000 patients to demonstrate a significant benefit. Nonetheless, this trial established that a prospective perioperative statin trial is feasible.
When to continue or start statins
Although we cannot recommend starting statins for all perioperative patients, perioperative statins clearly can carry significant benefit and should be continued in all patients who have been taking them. It is also likely beneficial to initiate statins in those patients who would otherwise warrant therapy based on the American College of Cardiology/American Heart Association Pooled Cohort Equations Risk calculator.19
HOW SHOULD WE MANAGE SLEEP APNEA RISK PERIOPERATIVELY?
From 20% to 30% of US men and 10% to 15% of US women have obstructive sleep apnea, and many are undiagnosed. Obstructive sleep apnea increases the risk of perioperative respiratory failure, unplanned reintubation, unplanned transfer to the intensive care unit, and death.20 Sentinel events (unexpected respiratory arrest after surgery on general surgical wards) have prompted the development of guidelines that aim to identify patients with previously undiagnosed obstructive sleep apnea before surgery and to develop approaches to reduce perioperative morbidity and mortality.
Kaw et al: Beware obesity hypoventilation syndrome
A 2016 study suggested that patients with obstructive sleep apnea and obesity hypoventilation syndrome may be at particularly high risk of perioperative complications.21
Kaw et al21 queried a database of patients with obstructive sleep apnea undergoing elective noncardiac surgery at Cleveland Clinic. All patients (N = 519) had obstructive sleep apnea confirmed by polysomnography, and a body mass index greater than 30 kg/m2. The authors considered a patient to have obesity hypoventilation syndrome (n = 194) if he or she also had hypercapnia (Paco2 ≥ 45 mm Hg) on at least 2 occasions before or after surgery.
In an adjusted analysis, the odds ratios and 95% CIs for adverse outcomes in patients with obesity hypoventilation syndrome were:
- 10.9 (3.7–32.3) for respiratory failure
- 5.4 (1.9–15.7) for heart failure
- 10.9 (3.7–32.3) for intensive care unit transfer.
The absolute increases in risk in the presence of obesity hypoventilation syndrome were:
- 19% (21% vs 2%) for respiratory failure
- 8% (8% vs 0) for heart failure
- 15% (21% vs 6%) for intensive care unit transfer.
There was no difference in rates of perioperative mortality.21
The authors proposed an algorithm to identify patients with possible obesity hypoventilation syndrome before surgery that included prior sleep study results, STOP-BANG score (Table 2),22 and serum bicarbonate level.
Important limitations of the study were that most patients with obesity hypoventilation syndrome were undiagnosed at the time of surgery. Still, the study does offer a tool to potentially identify patients at high risk for perioperative morbidity due to obesity hypoventilation syndrome. Clinicians could then choose to cancel nonessential surgery, propose a lower-risk alternative procedure, or maximize the use of strategies known to reduce perioperative risk for patients with obstructive sleep apnea in general.
Two guidelines on obstructive sleep apnea
Two professional societies have issued guidelines aiming to improve detection of previously undiagnosed obstructive sleep apnea and perioperative outcomes in patients known to have it or suspected of having it:
- The American Society of Anesthesiologists in 201423
- The Society of Anesthesia and Sleep Medicine in 2016.7
Both guidelines recommend that each institution develop a local protocol to screen patients for possible obstructive sleep apnea before elective surgery. The American Society of Anesthesiologists does not recommend any particular tool, but does recommend taking a history and performing a focused examination that includes evaluation of the airway, nasopharyngeal characteristics, neck circumference, and tonsil and tongue size. The Society of Anesthesia and Sleep Medicine recommends using a validated tool such as the STOP-BANG score to estimate the risk of obstructive sleep apnea.
If this screening suggests that a patient has obstructive sleep apnea, should surgery be delayed until a formal sleep study can be done? Or should the patient be treated empirically as if he or she has obstructive sleep apnea? Both professional societies recommend shared decision-making with the patient in this situation, with the Society of Anesthesia and Sleep Medicine recommending additional cardiopulmonary evaluation for patients with hypoventilation, severe pulmonary hypertension, or resting hypoxemia.
Both recommend using continuous positive airway pressure (CPAP) after surgery in patients with known obstructive sleep apnea, although there is not enough evidence to determine if empiric CPAP for screening-positive patients (without polysomnography-diagnosed obstructive sleep apnea) is beneficial. The Society of Anesthesia and Sleep Medicine advises that it is safe to proceed to surgery if obstructive sleep apnea is suspected as long as monitoring and risk-reduction strategies are implemented after surgery to reduce complication rates.
During surgery, the American Society of Anesthesiologists advises peripheral nerve blocks when appropriate, general anesthesia with a secure airway rather than deep sedation, capnography when using moderate sedation, awake extubation, and full reversal of neuromuscular blockade before extubation. After surgery, they recommend reducing opioid use, minimizing postoperative sedatives, supplemental oxygen, and continuous pulse oximetry. The Society of Anesthesia and Sleep Medicine guideline addresses preoperative assessment and therefore makes no recommendations regarding postoperative care.
In conclusion, use of pertinent findings from the history and physical examination and a validated obstructive sleep apnea screening tool such as STOP-BANG before surgery are recommended, with joint decision-making as to proceeding with surgery with empiric CPAP vs a formal sleep study for patients who screen as high risk. The Society of Anesthesia and Sleep Medicine recommends further cardiopulmonary evaluation if there is evidence of hypoventilation, hypoxemia, or pulmonary hypertension in addition to likely obstructive sleep apnea.
