Registry of laparoscopic cholecystectomy and new and evolving laparoscopic techniques

Endoscopic skull base surgery II: a new animal model for surgery of the posterior fossa

The field of skull base surgery has been influenced by a general philosophy that currently exists in modern surgical practice favoring less invasive means of managing surgical disease. Adapting techniques developed by general surgeons and other surgical subspecialists, skull base surgeons are now experimenting with endoscopy to resect tumors, manage vascular lesions, and manipulate critical intracranial structures. Lesions formerly requiring significant soft tissue dissection and craniotomy for exposure are now potentially amenable to treatment via a keyhole approach. As in other surgical specialties, however, a reliable animal model is necessary for experimentation with and development of new endoscopic techniques in the skull base. The swine provides just such a model, primarily due to craniofacial and skull base relationships that are analogous to humans. We have focused on the posterior skull base of the swine in this experiment: Via a retrosigmoid craniotomy we opened the dura of the posterior fossa and used endoscopes to visualize and manipulate the critical structures in this area. The cerebellum and midbrain were appreciated, as were cranial nerves V, VII, VIII, IX, X, and XI. Blood vessels on the surface of the midbrain were also identified. This experience further supports the use of the swine as an appropriate animal model for endoscopic skull base surgery.

Endoscopic skull base surgery I: a new animal model for pituitary surgery

Endoscopy has emerged as a new means to perform minimally invasive surgery of the skull base. Specifically, endoscopic techniques and instruments can be used to safely and effectively approach and resect tumors of the pituitary gland in humans. No animal model currently exists to serve as a template upon which to refine and develop endoscopic surgical technique in this region of the anatomy. We operated on two purpose-bred Hampshire-Yorkshire-Duroc hybrid swine to demonstrate the application of endoscopy to pituitary surgery. Based upon similar anatomical relationships in humans and swine between the oropharynx, nasopharynx, and skull base, we used a transoral, transpalatal approach to access the vomer of the swine. Under endoscopic exposure, we resected the vomer, entered the sphenoid sinus, and then resected the sphenoid septum, sella turcica, and adenohypophysis. Clear visualization of the pituitary, hypophyseal stalk, cavernous sinuses, and carotid prominences was achieved and documented with digital photography. Benefits and limitations of the technique were noted. These results have pertinent implications both for the study of the surgical anatomy of the swine craniofacial skeleton, and for future development of endoscopic surgical manipulation of the skull base.

Respiratory mechanics during laparoscopic cholecystectomy: the effects of the abdominal wall lift

The abdominal wall lift (AWL) has been proposed for laparoscopic cholecystectomy to reduce hemodynamic effects caused by carbon dioxide (CO2) and high intraabdominal pressures (IAP). Data concerning effects of AWL on respiratory mechanics are scant. We therefore used a noninvasive method to evaluate whether the AWL could offset these effects. The PETCO2, airflow, and airway pressure were continuously measured in nine patients undergoing laparoscopic cholecystectomy using an AWL with minimal CO2 insufflation. We used a least-squares method to calculate maximal airway pressure (Pmax), elastance (Ers), and resistances (Rrs) of the respiratory system. After CO2 insufflation, the initiation of AWL resulted in a significantly decreased IAP (from 13 to 6 mm Hg; P < 0.001) and Rrs (from 20.6 to 17.8 cm H2O.L(-1).s(-1); P = 0.029), whereas Ers was partly modified (34.0 to 33.3 cm H2O/L; not significantly different). With AWL, we hypothesized that the diaphragm remained flat and stiff, outweighing the beneficial effect of the decrease of IAP on Ers. PETCO2 significantly increased after AWL and at the end of the procedure. We conclude that AWL partly reverses the impairment of the respiratory mechanics induced by CO2 insufflation during laparoscopic surgery.

IMPLICATIONS

The abdominal wall lift (AWL), acting on the abdominal chest wall, had some benefits during laparoscopic surgery by limiting CO2 peritoneal insufflation and several side effects, such as hemodynamics. We examined the consequences of this technique on respiratory mechanics in nine patients undergoing laparoscopic cholecystectomy. Our findings suggest that the AWL decreases intraabdominal pressure and respiratory resistances without a significant effect on respiratory elastance.