Central Sleep Apnea (CSA)

Find the driver - CSA is a symptom of something else, and the something else is what you actually have to anesthetize. Echocardiogram for heart failure and ejection fraction, brain and brainstem MRI when a lesion or stroke is suspected, a documented opioid history, and the nocturnal polysomnogram itself. Atrial fibrillation, heart failure with preserved or reduced EF, ischemic stroke, cervical spinal cord injury, and renal failure are the usual company.

Opioids are causal, not just additive - Chronic opioid use is an established cause of CSA through suppression of the brainstem respiratory rhythm generator. Build a regional and non-opioid plan where the case allows, and titrate what is left against respiratory rate.

Skip the premed - Standing guidance for CSA is to avoid sedative medications. A benzodiazepine before the block or on the way to the room removes drive you cannot get back until they wake up.

Do not hyperventilate them - Their apnea threshold sits a few mmHg below resting PaCO2, and narrower still in heart failure. Blowing off CO2 during controlled ventilation sets up central apnea the moment you hand breathing back; let PaCO2 drift toward their baseline before planning on spontaneous ventilation.

Bring their device - Positive airway pressure is the mainstay, delivered as CPAP, BPAP, or adaptive servo-ventilation. CPAP and BPAP are the more effective options in heart-failure and opioid-associated CSA. Have the home machine and mask in PACU.

They do not look like OSA - Snoring is often absent and these patients are relatively less obese, so the usual visual cues fail. What flags them is the history: witnessed apneas, nocturnal awakening, morning headache, and daytime somnolence in a heart-failure or chronic-opioid patient. Heart failure patients often deny sleepiness despite objective evidence of it, so fatigue alone in an older patient is enough to raise it.

Position - Cheyne-Stokes breathing is worse supine and worsens on the move from supine to lateral. Head up in PACU where the surgery allows.

Watch them after - Once the cycle starts it perpetuates itself into repetitive hypoxia and irregular breathing. Continuous pulse oximetry, not spot checks.

Central sleep apnea (CSA) is repetitive cessation of airflow with no respiratory effort - the pontomedullary rhythm generator briefly stops sending the signal. An event is at least 10 seconds of absent flow without effort.

Two routes get there. Hyperventilation drops PaCO2 below the apnea threshold, which normally sits only 4 to 6 mmHg under the awake PaCO2 and much closer in heart failure, where the carbon dioxide reserve narrows to 1.3 to 3 mmHg; the apnea is followed by a CO2 rise, hyperpnea, and another overshoot - high loop gain. Alternatively, hypoventilation from opioids, brainstem stroke, cervical cord injury, or kyphoscoliosis simply removes drive. Either way the upper airway narrows at the retropalatal level during the central event, so CSA and obstructive sleep apnea overlap more than the names suggest.