The sitting position in neurosurgery: a critical appraisal

Abstract

The potential for serious complications after venous air embolism and successful malpractice liability claims are the principle reasons for the dramatic decline in the use of the sitting position in neurosurgical practice. Although there have been several studies substantiating the relative safety compared with the prone or park bench positions, its use will continue to decline as neurosurgeons abandon its application and trainees in neurosurgery are not exposed to its relative merits. How can individual surgeons continue to use this position? Will individual, difficult surgical access cases be denied the obvious technical advantages of the sitting position? Limited use of the sitting position should remain in the neurosurgeon's armamentarium. However, several caveats must be emphasized. Assessment of the relative risk-benefit, based on the individual patient's physical status and surgical implications for the particular intracranial pathology, is of paramount importance. The patient should be informed of the specific risks of venous air embolism, quadriparesis and peripheral nerve palsies. Appropriate charting of patient information provided and special consent issues are essential. An anaesthetic input into the decision to use the sitting position is a sine qua non. The presence of a patient foramen ovale is an absolute contraindication. Preoperative contrast echocardiography should be used as a screening technique to detect the population at risk of paradoxical air embolism caused by the presence of a patent foramen ovale. The technique involves i.v. injection of saline agitated with air and a Valsalva manoeuvre is applied and released. Use of this position necessitates supplementary monitoring to promptly detect and treat venous air embolism. Doppler ultrasonography is the most sensitive of the generally available monitors to detect intracardiac air. The use of a central venous catheter is recommended, with the tip positioned close to the superior vena cava junction with the right atrium, to aspirate intravascular gas. Measures to minimize hypotension associated with the sitting position include a slow, staged positioning over 5-10 min and use of the 'G suit' inflated with compressed air applied to the lower extremities and pelvis. Use of the sitting or upright position for patients undergoing posterior fossa and cervical spine surgery presents unique challenges for the anaesthetist. With appropriate patient selection and preparation, and using prudent intraoperative monitoring and anaesthetic techniques, selected patients should still benefit from the optimum access to mid-line lesions, improved cerebral venous decompression, lower intracranial pressure and enhanced gravity drainage of blood and CSF associated with the sitting position.

Cerebral tissue oxygen saturation values in volunteers and patients in the lateral decubitus and beach chair positions: a prospective observational study

“…19 With 57% of our patients under general anesthesia revealing SctO 2 values \ 55% and a decrease of C 20% from baseline in the BCP, we confirm previous results on the frequent occurrence of cerebral tissue oxygen desaturation in patients undergoing arthroscopic shoulder surgery in the BCP. [6][7][8][9][10][11] The combination of general anesthesia and controlled hypotension resulted in a median decrease in blood pressure of 45 mmHg in both of our patient groups.…”

A case of intrapulmonary transmission of air while transitioning a patient from a sitting to a supine position after venous air embolism during a craniotomy

“…Careful examination of this patient preoperatively excluded evidence of intracardiac functional shunts, deliberately considered due to the known risks of neurosurgery in the sitting position. 12 Cases of paradoxical emboli without presence of an intracardiac shunt are rare with but a few isolated case reports. 13,14 The terms intrapulmonary shunting or shunts have been deliberately avoided throughout this article because this case does not take into account whether these arteriovenous anastomoses contribute to gas exchange, a fact still being debated.…”

Anesthetic management of bronchopleurocutaneous fistula - an alternate approach

“…The hazard of air embolism can be monitored with TEE and treated with a triple lumen central venous catheter. 2 When conventional methods of pulmonary isolation fail, anesthesia and surgery pose unusual challenges during the operative management of BPCF. 3,4 Careful planning and meticulous anesthetic management can transform a difficult case into a manageable one.…”