Anesthetic Technique for Endoscopic Orbital Surgery

Henry P. Barham and Raymond Sacks

Keywords: endoscopic, sinus, rhinology, orbit, dacryocystorhinostomy, anesthesia, orbit

19.1 Introduction

In recent years, there has been a growing trend toward the use of minimally invasive techniques in surgery. This is a result of trying to achieve a better cosmetic outcome combined with reducing the morbidity of extensive tissue dissection. Endoscopic surgery exemplifies these attempts and has been enthusiastically adopted by general surgeons, gynecologists, and ear, nose, and throat (ENT) surgeons.

Endoscopic orbital surgery, however, is in its infancy and is performed primarily via sinonasal approaches by ENT surgeons. Transnasal endoscopic approaches are well established for orbital decompression, orbital medial wall fracture repair, and optic canal decompression. The use of a transmaxillary or transnasal endoscopic approach has also been described for repair of orbital floor fractures. The ophthalmologists are familiar with the endoscope primarily in the context of endoscopic dacryocystorhinostomy (DCR) and endoscopic brow lift. Nasal endoscopy has also been proven useful in the perioperative assessment for lacrimal surgery and probing of the nasolacrimal duct. Additional applications in oculoplastic surgery include transcanalicular endoscopy and endoscopic assistance in facelifts and in harvesting fascia lata.

Adverse events are rare, most of which relate to the proximity of the paranasal sinuses to the orbits and brain. Major complications include dura puncture, cerebrospinal fluid leak, meningitis, orbital and optic nerve trauma, and extensive hemorrhage. ^{1,​ 2} As such, the option for the procedure to be done under general anesthesia offers numerous advantages and the role of the anesthetist in these procedures is undoubtedly significant.

19.2 Discussion

The classic endoscopic sinonasal procedure was initially done under topical anesthesia with sedation. In this manner, patients would be conscious and able to signal any kind of pain or discomfort, alerting and allowing the surgeon to minimize trauma and complications. ^{3,​ 4} In current times, the evolution of surgical technique has allowed surgeons to become much more aggressive with the extent of their resection.

A general anesthetic will allow immobile surgical field, effective airway protection, adequate analgesia, and patient comfort. Currently, local anesthesia is still considered suitable for minor procedures in selected patients, but general anesthesia is preferred for most cases to meet more challenging surgical needs. ⁵ Maintenance of normothermia is vital for the function of platelets and coagulation factors essential in hemostasis. ^{6,​ 7}

Depth of anesthesia is important in avoiding any coughing or straining by the patient during a light anesthetic plane, which will result in an increase in intrathoracic pressure and hence impair venous drainage from the head and increase surgical bleeding. The use of muscle relaxants will also effectively prevent such occurrences during the procedure. Intermittent positive pressure ventilation should be adjusted such that the airway pressures are kept to a minimum. Avoidance of the use of positive end expiratory pressure is also helpful via preventing higher intrathoracic pressure. ^{8,​ 9}

Volatile anesthetic agents cause smooth muscle relaxation and decreases systemic vascular resistance. Tissue perfusion is increased due to vasodilation and may also contribute to surgical bleeding.

Initial studies have suggested that the intraoperative blood loss was reduced with propofol total intravenous anesthesia (TIVA) compared to volatile agents. ^{10,​ 11,​ 12,​ 13} However, more recent studies do not show significant difference after excluding the effect of concomitant use of remifentanil. ^{14,​ 15,​ 16} The use of propofol has the advantage of reducing systolic blood pressure via a lesser decrease in systemic vascular resistance.

Hemostasis, both during and after endoscopic procedures, is critical for successful outcomes. ^{1,​ 17} Intraoperative bleeding, especially in the setting of highly vascular sinonasal tumors and polyposis, remains a common pitfall in performing endoscopic sinus, orbital, and skull base surgery. Although endoscopic bipolar forceps, suction cautery, and newer technologies, such as radiofrequency coblation, are indispensable for producing intraoperative hemostasis, various topical agents are also effective in controlling diffuse bleeding and, in some cases, also provide postoperative benefits.

The primary modality to achieve hemostasis in surgery is the prevention of bleeding. The three steps to improve one’s ability to prevent bleeding are patient positioning, proper surgical technique with avoidance of stripped mucosa, and vasoconstriction. The patient’s head should be placed in the neutral anatomic position and the operative bed placed in 15- to 20-degree reverse Trendelenburg with total intravenous anesthesia. ² Proper surgical technique cannot be overemphasized to avoid nuisance bleeding. The stripping of mucosa will cause oozing, which will decrease visualization and is not amenable to topical vasoconstrictors. If persistent bleeding occurs in the absence of mucosal stripping, vasoconstrictors have a significant role in endoscopic sinus, orbital, and skull base surgery.

Epinephrine has been used as a hemostatic agent in various surgical procedures for many years both in topical and injectable preparations. It is inexpensive and has excellent hemostatic properties. ³ The major drawback to its use is the potential for cardiac complications including tachycardia, arrhythmias, hypotension, or hypertension. ⁴ Hypertension and tachycardia historically are the most commonly observed complications. ⁵ Recently, use of topical epinephrine in endoscopic sinus and skull base surgery has experienced resurgence as topical preparations provide excellent hemostasis while greatly decreasing the potential for cardiac complications.

The authors’ practice routinely uses epinephrine with Naropin (anesthetic benefit) soaked cotton pledgets to aid with hemostasis. Their preferred concentration is 1:2,000, which provides excellent hemostasis with limited side effects. A prospective study evaluating varying concentrations of topical adrenaline including 1:2,000, 1:10,000, and 1:50,000 showed that the 1:2,000 group had a statistically significant decrease in blood loss and shorter operative times. ¹⁸

Hemorrhage decreases visibility of the surgical field during the functional endoscopic sinus surgery (FESS) procedure and is directly related to risk of vascular, orbital, and intracranial complications as well as procedural failure. ^{18,​ 19} Hence, it is of vital importance to the surgeon as well as anesthetist to minimize surgical bleeding for this operation. ⁸ Marked hypotension is proven to be induced in a predictable manner, lasting no longer than 4 minutes after local infiltration with epinephrine-containing local anesthetics. ²⁰ Considering the potential for adverse side effects, the effect of topical application of epinephrine 1:100,000 has been studied and it may be able to provide a similar hemostatic effect as intranasal injection during FESS. ⁶ In a recent study, Cohen-Kerem et al ²⁰ compared the effectiveness of topical 1:1,000 epinephrine versus injected local anesthetic containing 1:100,000 epinephrine during FESS. In this study, it was reported that submucosal injection of local anesthetic with epinephrine facilitated improved surgical condition; however, increased hemodynamic fluctuations were noted after infiltrations.

Bleeding may be difficult to control surgically due to the extensive vascular supply in the sinus region and pathophysiological changes in the patient. Capillary bleeding is the most fundamental problem of note in this procedure, barring any inadvertent trauma to the feeding arterial and venous vessels. ²¹ Fortunately, bleeding from the capillary circulation may be greatly reduced by decreasing the patient’s mean arterial pressure and by local vasoconstriction.

The reverse Trendelenburg 15-degree head up allows for venous decongestion of the upper part of the body by increasing venous pooling of blood in the lower extremities. Every 2.5 cm above the heart correlates to a decrease of 2 mm Hg in arterial blood pressure supply. ^{22,​ 23} This has been shown to improve the endoscopic field of view. ²⁴

Injected and topical local anesthetics and vasoconstrictors can help relieve postoperative pain and decrease blood loss and mucosal congestion. Commonly used vasoconstrictors include cocaine, epinephrine, and phenylephrine. ²⁵

Cocaine has local anesthetic and vasoconstrictor properties. Systemic absorption of these agents may cause hypertension, tachycardia, and other arrhythmias; hence, they should be used with great caution in patients with coronary heart disease, congestive heart failure, malignant arrhythmias, poorly controlled hypertension, and in those taking monoamine oxidase inhibitors. ²⁶

Hypotension induced by epinephrine under general anesthesia is seldom mentioned, but temporarily able to quickly blunt the sympathetic response to endotracheal tube (ETT) insertion and periods of surgical stimulation. Propofol also decreases cerebral metabolism and hence cerebral blood flow is reduced by autoregulation. This reduces flow via the ethmoidal and the supraorbital arteries, which supply the ethmoid, sphenoid, and frontal sinuses, improving surgical visibility. ²⁷

Multiple reviews have compared surgical field and blood loss during FESS. Amorocho and Sordillo ²⁸ found propofol general anesthesia improved the surgical field and reduced blood loss, whereas Baker and Baker ²⁹

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