REVIEW CURRENT OPINION Anesthesia for transsphenoidal pituitary surgery Lauren K. Dunn and Edward C. Nemergut Purpose of review Pituitary tumors are commonly encountered in clinical practice. Patients with functioning adenomas frequently present with symptoms of hormone excess, whereas those with nonfunctioning adenomas often present later and have symptoms resulting from mass effect of the tumor. This article examines recent advancements in the preoperative assessment and anesthetic management of patients undergoing transsphenoidal pituitary surgery. Recent findings Endoscopic guidance has improved tumor visualization while minimizing the risk of nasal and dental complications and septal perforation. Computer-assisted navigation and intraoperative MRI has further improved surgical outcomes. Airway management may be particularly challenging in patients with acromegaly or Cushing’s disease. Both intravenous and volatile agents can be used for anesthetic maintenance. Although pituitary surgery can be intensely stimulating and associated with intraoperative hypertension, most patients require little postoperative analgesia. Postoperative diabetes insipidus is common after pituitary surgery and is typically self-limited. Some patients will require treatment with desmopressin and it is important to avoid ‘overshoot’ iatrogenic syndrome of inappropriate antidiuretic hormone SIADH and hyponatremia in these patients. Conclusion Anesthetic management for pituitary surgery requires thorough preanesthetic assessment of hormonal function and intraoperative management to facilitate surgical exposure while providing hemodynamic stability and allowing for rapid emergence. Keywords acromegaly, Cushing’s disease, diabetes insipidus, pituitary surgery, transsphenoidal surgery INTRODUCTION PREOPERATIVE ASSESSMENT Pituitary tumors are common in clinical practice, Pituitary adenomas can be classified by size at with radiologic and autopsy studies estimating that the time of diagnosis as either microadenomas as many as one in seven people have a pituitary (<10 mm) or macroadenomas (>10 mm), and as tumor; however, only one in 1000 are clinically either functioning or nonfunctioning, depending symptomatic [1&]. Treatment goals in the manage- on whether they are hormone-secreting. Patients ment of patients with pituitary tumors include sup- with functioning adenomas frequently present with pression of hormone hypersecretion, reduction of symptoms of hormone excess, whereas those with tumor mass, preservation of normal pituitary func- nonfunctioning adenomas often present later and tion, prevention of long-term effects from excess have symptoms resulting from mass effect of the hormone secretion, and prevention of tumor recur- tumor, such as headache, visual loss due to com- rence. Although medical therapy may suppress pression of the optic chiasm, or hypopituitarism due hyperfunctioning tumors, surgical resection has to compression of the anterior pituitary. Patients become the mainstay therapy with transsphenoidal may also be asymptomatic and report for surgery pituitary surgery being the most common approach used today. Transsphenoidal pituitary surgery Department of Anesthesiology, University of Virginia, Charlottesville, presents unique challenges for the neuroanesthesi- Virginia, USA ologist in the preoperative, intraoperative, and post- Correspondence to Edward Nemergut, MD, PO Box 800710, Charlot- operative management of patients undergoing tesville, VA 22908-0710, USA. Tel: +1 434 294 2283; fax: +1 434 982 tumor resection. Advances and challenges in the 0019; e-mail: [email protected] anesthetic management of these patients are pre- Curr Opin Anesthesiol 2013, 26:549–554 sented here. DOI:10.1097/01.aco.0000432521.01339.ab 0952-7907 ß 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins www.co-anesthesiology.com Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Neuroanesthesia Cushing’s disease, due to excess production of KEY POINTS adrenocorticotropic hormone, is associated with Preanesthetic assessment for transsphenoidal pituitary increased risk of cardiovascular disease, hyperten- surgery includes radiologic studies and evaluation of sion, and ischemic heart disease, which is a major hormone function. cause of perioperative mortality [6,9,10]. Hyperten- sion should be medically managed and patients Intravenous and volatile agents have been used should be assessed for cardiac risk factors preoper- successfully intraoperatively to provide hemodynamic stability and rapid emergence. atively. Diabetes mellitus is also common in patient’s with Cushing’s disease, and blood glucose Advances in computer-assisted navigation and should be controlled pre and intraoperatively. intraoperative MRI have improved surgical outcomes. Immunosuppression, fragile skin, and easy bruising may lead to poor wound healing, hemorrhage, and difficult intravenous cannulation. Airway manage- after the tumor found incidentally during intracra- ment may be challenging because of truncal obesity nial imaging. Rarely, pituitary tumors cause elevated or gastroesophageal reflux. In addition, Cushing’s intracranial pressure because of their size or obstruc- disease is associated with myopathy of proximal tion of the third ventricle, which may cause head- muscle groups. Although patients are not more ache, nausea, vomiting, and papilledema. susceptible to neuromuscular blockade due to myo- Preoperative management for transsphenoidal pathy, this may impair postoperative ventilation. pituitary surgery begins with a thorough preanes- Nonfunctioning tumors frequently present later thetic assessment, including laboratory and radio- with symptoms of mass effect and may cause pan- logic evaluation. Laboratory work-up includes a hypopituitarism due to compression of the anterior complete blood cell count to evaluate for anemia, pituitary. Thyroid hormone and glucocorticoid metabolic panel to evaluate for electrolyte abnormal- must be replaced preoperatively and patients are ities (hyponatremia in diabetes insipidus, hypercal- susceptible to water intoxication and hypoglycemia. cemia in patients with multiple endocrine neoplasia, They may also be sensitive to central nervous system type I, and hyperglycemia in patients with Cushing’s depressants, including general anesthetics and may disease), as well as a thorough endocrine evaluation. require blood pressure support intraoperatively. At a minimum, an endocrine assessment includes measurement of serum levels of prolactin, thyroid- PERIOPERATIVE MANAGEMENT stimulating hormone, free thyroxine, luteinizing Several comprehensive reviews of anesthesia for hormone, follicle-stimulating hormone, testosterone transsphenoidal pituitary surgery have been pre- (in men), adrenocorticotropic hormone, cortisol, and viously published [2,6,11]. Here, we review the insulin-like growth factor-1, a surrogate marker for intraoperative anesthetic goals and highlight advan- growth hormone in acromegaly [2,3]. Preoperative ces in surgical technique and anesthetic manage- MRI or, less frequently, computed tomography aids ment. Anesthetic goals for transsphenoidal pituitary in diagnosis and differentiation of pituitary adeno- surgery include optimizing cerebral oxygenation, mas from other disorders, such as other tumors, maintaining hemodynamic stability, providing autoimmune conditions, or vascular lesions, and & conditions to facilitate surgical exposure, prevent- for surgical planning [1 ]. ing and managing intraoperative complications, Several tumor types produce unique effects that and allowing for rapid smooth emergence. merit particular attention in the preoperative period. Patients with acromegaly are at increased risk for cardiovascular disease including hyperten- SURGICAL APPROACH AND OPTIMIZING sion, accelerated coronary artery disease, cardio- THE SURGICAL FIELD myopathy, congestive heart failure, and arrhythmias The direct endonasal approach is favored over the due to the effects of excess growth hormone sublabial transseptal approach by most surgeons secretion [4&,5]. Airway management may be because it requires less dissection and removal of challenging due to hypertrophy of the soft tissues bone; however, a sublabial approach may be necess- of the mouth, nose, tongue, soft palate, epiglottis and ary in children or in adults with very large tumors. aryepiglottic folds, and prognathism due to bony Endoscopic guidance has further improved tumor proliferation of the mandible and may present visualization while minimizing the risk of nasal and difficulty for airway management and intubation dental complications and septal perforation [1&]. [6]. Up to 70% of acromegalic patients may have One institution compared traditional microsurgery sleep apnea, which places them at increased risk versus endoscopic endonasal resection in a series for perioperative airway compromise [7,8]. of 60 consecutive patients and found improved 550 www.co-anesthesiology.com Volume 26 Number 5 October 2013 Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Anesthesia for transsphenoidal pituitary surgery Dunn and Nemergut remission rate in endoscopically resected tumors (78 secondary techniques readily available. There are versus 43%) but increased incidence of cerebrospi- no data available to specifically recommend one nal fluid (CSF) leak [12]. secondary technique (i.e., video laryngoscopy) over A recent meta-analysis compared short-term another. An oral airway