No abstract

One hundred consecutive patients undergoing neurosurgical procedures in the seated position were monitored for venous air embolism with a Swan-Ganz pulmonary artery (PA) catheter, precordial Doppler ultrasound device, and continuous end-tidal CO2 (FETCO2) analysis. Simultaneous determinations of right atrial and pulmonary capillary wedge pressures were also performed during each operation. Although 80 episodes of air embolism were detected by changes in Doppler sounds, only 36 were associated with increased PA pressure, and only 30 developed a decrease in FETCO2. Changes in PA pressure and FETCO2 agreed closely (r = 0.86), and only marked changes were associated with systemic hypotension. Air was recovered from the right atrium and PA only in small amounts (2 to 20 ml) during air embolism, although it was possible to aspirate large quantities of blood. Twenty-nine patients were found to have right atrial pressures that were higher than pulmonary capillary wedge pressures. Paradoxical air embolism from a probe-patent foramen ovale was possible in these patients, and one developed signs and symptoms of systemic air embolism postoperatively. We conclude that noninvasive monitoring with the combination of a precordial Doppler device and end-tidal CO2 analysis is satisfactory for rapid detection of clinically significant venous air embolism. The unique advantage of Swan-Ganz monitoring, however, is that it permits identification of patients who may sustain paradoxical air embolism, and that it differentiates the hemodynamic effects of brain-stem manipulation from those caused by air embolism.

The potassium titanyl phosphate (KTP-532) laser has been applied to otologic surgery with a proven record of both safety and efficacy. The aim of this study was to demonstrate the use, safety, and advantages of laser dissection in the surgical treatment of acoustic neuromas. The authors' experience with 111 patients in whom laser surgery was used in acoustic neuroma is presented, with emphasis on surgical technique employed and facial nerve functional outcome. The method of laser dissection did not result in deleterious neurologic sequelae or laser-specific complications. In addition, laser dissection afforded certain advantages to traditional techniques, especially in larger tumors. The facial nerve functional outcome as assessed by the House-Brackmann grading system revealed that 90.2% of small tumors, 72.2% of medium tumors, and 75.0% of large tumors achieved satisfactory (grades I and II) functional results. These results compare favorably with the literature describing nonlaser dissection techniques. The observations and results reported in this article demonstrate the safety of the KTP-532 laser in the posterior cranial fossa, and specific advantages that this technology may offer to the surgical armamentarium of the neuro-otologist are outlined.

Preserving the function of the facial nerve remains a paramount objective in acoustic neuroma surgery. This study was undertaken to determine the influence of four independent variables on facial nerve outcome by means of a retrospective review of 111 surgical cases: 1) tumor size; 2) use of intraoperative facial nerve monitoring (IFNM); 3) completeness of tumor resection; and 4) surgical approach used. Partial tumor resection appeared to result in improved facial nerve outcome for patients with large tumors. Results indicated that tumor size did not correlate with facial nerve functional outcome, with no statistically significant differences observed among the three size categories. Facial nerve function was not found to depend on selection of either a translabyrinthine (n=47) or a suboccipital (n—55) surgical approach in that results were similar for both groups. Outcome data showed a trend in support of the use of IFNM, especially for large tumors, even though the differences between monitored and unmonitored groups were not statistically significant. This study describes the independent impact of the four factors generally thought to affect facial nerve outcome and, in addition, recommends the use of data stratification in reporting facial nerve function results.