This Month In: Anesthesiology

The purposes of these Guidelines are to improve the perioperative care and reduce the risk of adverse outcomes in patients with confirmed or suspected obstructive sleep apnea who receive sedation, analgesia, or anesthesia for diagnostic or therapeutic procedures under the care of an anesthesiologist. Recommendations made include those for preoperative evaluation and preparation, intraoperative and postoperative management, and criteria for discharge to unmonitored settings.

Sleep-disordered breathing and sleep architecture may be affected by anesthesia, surgery, and analgesia. In a prospective observational study, 38 patients with obstructive sleep apnea (OSA) and 20 without OSA underwent full night sleep studies preoperatively and on the first, third, fifth, and seventh nights after elective surgery. Polysomnography revealed the apnea-hypopnea index (AHI) increased and sleeping efficiency, rapid eye movement sleep, and slow wave sleep decreased postoperatively, more in OSA patients than in non-OSA patients. AHI increased most on day 3 whereas sleep architecture was most disturbed on day 1.

The increased incidence of postoperative adverse events in patients with obstructive sleep apnea (OSA) may be related to exacerbation of sleep-disordered breathing (SDB). Full night sleep studies were conducted preoperatively and on postoperative nights one and three; 376 patients completed preoperative and first night assessments and 242 patients completed all nights of polysomnography. The apnea-hypopnea index (AHI) increased in non-OSA and mild- and severe-OSA patients on night one and in all groups on night three. Preoperative SDB severity, age, and 72-h opioid dose were associated with postoperative AHI.

The recommended 20 cm H₂O peak airway pressure to avoid gastric insufflation during facemaskH₂Oventilation is based on detection of air entry using auscultation. Sixty-seven patients were randomlyH₂Oassigned to have applied inspiratory pressures of 10, 15, 20, and 25 cm H₂O. Gastric insufflation was determined byH₂Oreal-time ultrasonography of the antrum and auscultation for 2 min after induction of anesthesia. The highest probabilityH₂Oof successful facemask ventilation was observed at 15 cm H₂O peak airway pressure, for which the probability of gastricH₂Oinsufflation determined by real-time ultrasonography was 35%. See the accompanying Editorial View on page 263.

Extracorporeal carbon dioxide removal may provide support to enable lung healing and prevent ventilator-induced lung injury. Eight anesthetized pigs were connected to a low-flow (250 ml/min) venovenous extracorporeal circuit that included a membrane lung. Ventilatory parameters were set to achieve a Paco₂ of 50 mmHg before starting extracorporeal circulation and dead space was modified subsequently to maintain a constant Paco₂. Infusion of a concentrated lactic acid solution through a dialyzer in the circuit increased the volume of carbon dioxide removed by the membrane oxygenator by more than 60% for 48 h. See the accompanying Editorial View on page 266.

Because age is a risk factor for impaired pharyngeal function, elderly patients may be at increased risk for adverse effects of residual neuromuscular blockade. Pharyngeal function and coordination of breathing and swallowing were assessed by manometry and videoradiography in 17 healthy elderly volunteers at baseline, during partial neuromuscular blockade by rocuronium, and after recovery to a train-of-four ratio of more than 0.9. The incidence of pharyngeal dysfunction at baseline was 37% and increased to 71% during partial neuromuscular blockade, with no detectable effect on coordination of breathing and swallowing. See the accompanying Editorial View on page 260.

Quantitative neuromuscular monitoring may be difficult in patients with severe peripheral nervous system pathologies. The case of a patient with a 54-yr history of type I diabetes mellitus and diabetic peripheral polyneuropathy scheduled to undergo elective abdominal surgery is presented. Diabetic peripheral neuropathy and quantitative neuromuscular monitoring are reviewed. The importance of calibrating the neuromuscular monitoring device before administering a neuromuscular blocker is emphasized so poor stimulation can be recognized and improved upon by monitoring at alternate sites.

Acupuncture may be a useful adjunct to more commonly used pain relief strategies. The mechanisms of acupuncture in animal models of inflammatory pain, neuropathic pain, cancer pain, and visceral pain are reviewed. Evidence is provided that opioids play an important role in electroacupuncture inhibition of many kinds of pain by a variety of mechanisms at the peripheral, spinal, and supraspinal levels. The clinical implications of the animal studies and the rationale for combining Western medicine and acupuncture are also discussed.