Preoperative Considerations in the AS Patient
1. Pulmonary Considerations: Significant spinal deformity in AS can result in restrictive respiratory physiology, with notable decreases in vital capacity and total lung capacity. The decrease in these values may make ventilation during surgery challenging, especially when prone position is anticipated. Pulmonary function testing and analysis of arterial blood gas are not routinely performed, but for some surgeries they may be need to be assessed, especially in situations involving one-lung ventilation (eg, lateral thoracotomy with a double-lumen endotracheal tube). In less-involved surgeries, restrictive respiratory physiology can influence timing and technique of extubation. For those patients with AS and severe restriction of chest excursion, aggressive pulmonary hygiene in the postoperative period can be encouraged.
2. Cardiovascular Considerations: AS is associated with increased risk of aortic regurgitation and abnormal aortic distensibility. A preoperative cardiac evaluation may be challenging as it is difficult to estimate a patient’s functional capacity and exercise tolerance if ambulation is restricted by pain or limited range of motion. The specific surgery should also be classified according to cardiac perioperative risk.
3. Neuromuscular Considerations: A thorough physical examination should be performed to document any preoperative sensory or motor deficits, especially in patients undergoing spinal surgery. Notation of any motor weakness is important as this may affect the choice of neuromuscular blocking drug or any intraoperative nerve monitoring that may be required in cases of spinal surgery.