An easy mnemonic to remember anesthetic considerations during transsphenoidal surgeries
The endonasal approach for pituitary surgeries is a very popular approach in view of better cosmesis, lesser incidence of diabetes insipidus, and lesser incidence of dental and nasal complications., Intraoperative management of these surgeries has various special considerations and can prove to be challenging for anesthesiologists.,,
Mnemonics are simple techniques to help us remember things and have been applied in many domains of life. LEMON [L: Look externally (facial trauma, large incisors, beard or moustache, large tongue; E: Evaluate the 3-3-2 rule, that is, incisor distance: 3 finger breaths (FB), hyoid-mental distance: 3 FB, and thyroid-to-mouth distance: 2 FB; M: Mallampati score > 3; O: Obstruction, that is, the presence of any condition like epiglotitis, peritonsillar abscess, trauma; N: Neck mobility (limited neck mobility)] for airway assessment and MOANS (M: Mask seal difficult due to receding mandible, syndrome with facial anomalies, burns, strictures, etc. O: Obesity, upper airway Obstruction; A: Advanced age; N: No teeth; S: Snorer) to predict difficult facemask ventilation, are examples of mnemonics used in anesthesia on a routine basis.
We propose the mnemonic “SPHENOIDAL” as a guide for anesthetic management for transsphenoidal pituitary surgeries, guiding the anesthesiologist intraoperatively during the important steps of surgery. This is just meant to be a guide to remind the anaesthesiologist intraoperatively about special considerations at various steps of surgery and definitely not a replacement for a well-performed preanesthetic evaluation. Also, there are various manifestations of pituitary tumors that affect the intraoperative management in addition to the considerations described below:
1. S – Steroid supplementation
Explanation: Intraoperatively, the anaesthesiologist must know about the need to administer steroids. Historically, these patients were administered “stress doses” of steroids perioperatively. Presently, different institutions have developed local protocols about the need to administer steroids to these patients perioperatively. For patients with proven adrenocorticotropic hormone (ACTH) deficiency preoperatively [usually based on the response to a short ACTH 1–24 (Synacthen) test], 48 h of supraphysiological glucocorticoid therapy should be administered perioperatively (e.g., hydrocortisone 50 mg every 8 h on day 0, 25 mg every 8 h on day 1, and 25 mg at 08.00 h on day 2). For patients with an intact hypothalamo-pituitary function preoperatively, and in whom selective adenomectomy is possible, perioperative glucocorticoids are not necessary.
2. P – Packing of the oropharynx
Explanation: A pharyngeal pack is inserted after intubation to prevent blood and debris from entering the stomach to prevent nausea, vomiting, and aspiration in the postoperative period.
3. H – Hormone levels/hypercarbia
Explanation: These patients must be euthyroid before they undergo surgery. In addition, the levels of other pituitary hormones must also be determined. The patients on preoperative hormone supplementation should continue the same perioperatively. Also, controlled hypercarbia up to 60 mmHg has been described as an effective measure to lower the tumor into the surgical field intraoperatively without any ill effects.
4. E – Endotracheal tube to be fixed to the opposite side
Explanation: The endotracheal tube and the anesthesia circuit should be on the opposite side to that of the surgeon's dominant hand.
5. N – Normothermia
Since early awakening is the norm in most of these patients, these patients must be kept normothermic intraoperatively.
6. O – Observe for hemodynamic changes during tumor dissection
Explanation: Activation of the trigeminocardiac reflex during the dissection of tumor can precipitate bradycardia and even asystole.
7. I – Infiltration of nasal mucosa
Explanation: Performed by the surgeon to achieve a bloodless field, this evokes a very strong sympathetic response and can result in a hypertensive crisis and myocardial infarction. The anesthesiologist must be aware of this complication, and drugs to deal with it must be ready.
8. D – Diabetes insipidus
Explanation: Pituitary surgeries are associated with a high incidence of water and electrolyte abnormalities. One must keep an eye on the intraoperative urine output, and sodium levels must be checked at regular levels.
9. A – Airway
Explanation: Patients with acromegaly and Cushing's disease can prove to be difficult to mask-ventilate and intubate.
10. L – Lumbar drain
Explanation: It is used to manipulate the cerebrospinal fluid (CSF) pressure by the injection of saline or removal of CSF. Sometimes, air is inserted intrathecally through a lumbar drain, to increase the CSF pressure and push the tumor down into the surgical field. Nitrous oxide should be discontinued at this time to prevent expansion of the intracranial air space.
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