Prolonged steep Trendelenburg position: risk of postoperative upper airway obstruction

Abstract

Robot-assisted laparoscopic radical prostatectomy (RALRP) is the procedure of choice for the surgical treatment of prostatic cancer. Following induction of anesthesia, the patient is placed in a steep Trendelenburg position (40 – 45 ) in combination with a CO2 pneumoperitoneum. The steep Trendelenburg position is required for an optimal surgical exposure and to utilize the technical advantages of the robot. Besides the physiological effect of this position on the cardiovascular, respiratory and central nervous system, complications such as brachial plexus injuries, corneal abrasions and ischemic optic neuropathy have also been reported [1]. In our experience with RALRP over the last 8 years, upper airway obstruction in the postoperative period is another complication of RALRP which has not been widely reported. Some patients develop an obstructed breathing pattern after extubation associated with agitation and sometimes desaturation despite an adequate reversal of neuromuscular blockade. This is more common in patients who have had prolonged head-down position of more than 3 h or over-enthusiastic fluid therapy exceeding 3 L. Patients who have a large neck circumference or suffer from chronic obstructive airway disease (COPD) are also more prone to develop a similar obstruction. Although there is a report of laryngeal edema following RALRP [2], none of our patients has developed laryngeal edema. The upper airway obstruction usually resolves either with the insertion of a nasopharyngeal airway or with the application of continuous positive airway pressure. In the postanaesthesia care unit, these patients are then nursed in a head-up position and the symptoms resolve in 1–2 h. It has been reported that, in the 45 Trendelenburg position, central venous pressure increases almost threefold compared with the initial value [3]. The head-down position along with pneumoperitoneum also increases the abdominal pressure, which impedes the venous return from the head and neck. This increase in the capillary hydrostatic pressure leads to interstitial accumulation of fluid in the dependent tissues. This is most apparent in the form of periorbital and conjunctival edema. However, edema also forms in the neck and peripharyngeal tissues, which causes constriction of the upper airway lumen. Chiu et al. [4] showed that displacement of a small amount of fluid (340 ml) from the legs is sufficient to cause a 102 % increase in pharyngeal resistance in healthy, non-obese subjects. The degree of fluid accumulation is often directly proportional to the amount of fluid transfused and the length of the surgery. This theory is also corroborated by the fact that fluid overload in fluid-retension states such as heart and renal failure is responsible for the increased incidence of obstructive sleep apnea in these patients [4]. The effect of dependent edema in the upper airway would logically be exaggerated in obese patients with increased neck circumference who already have a compromised upper airway lumen due to fat deposition. In patients with COPD, it has been postulated that cigarette smoking may affect the upper-airway dilator muscles or that treatment with inhaled corticosteroids may cause local pharyngeal muscle myopathy which could lead to obstructive sleep apnea [5]. Therefore, a small amount of edema formation in the upper airway in these patients would make them V. Rewari (&) R. Ramachandran Department of Anaesthesiology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India e-mail: vimirewari@gmail.com; vimirewari@hotmail.com