Positioning of a morbidly obese patient during retinal surgery.

A body mass index (BMI) ≥35 kg/m2 is classified as obese, and a BMI ≥40 kg/m2 is classified as morbidly obese. Obese people are at a higher risk for developing cardiovascular complications like ischemic heart diseases, congestive cardiac failure, hypertension, type 2 diabetes mellitus and obstructive sleep apnea (OSA) among other health issues. Central obesity can also increase the pleural pressure and cardiac filling pressures, thus increasing the intracranial (ICP) and intraocular pressure (IOP). These clinical co-morbidities can make retina surgeries, which require patient in supine position for 45-90 minutes, a challenging task. We present our experience in the intraoperative positioning of such a patient who underwent surgery for retinal detachment.

The BMI is an important determinant of lung volumes, respiratory mechanics and oxygenation during anesthesia.[12] The central obesity increases intra-abdominal pressure and this leads to an increase in the pleural pressure and cardiac filling pressure.[3] Also, this can impede the venous return from the brain, leading to an increase in the ICP and IOP[45] [Fig. 1a]. When an organ is raised above the heart level it reduces the arterial and venous hydrostatic pressures in proportion to the height of elevation. The optimal anesthesia positioning for morbid obesity is 20-30° Reverse trendelenburg position (RTP).[2] The benefits of the RTP with neck extension for the patient include better oxygenation, decreased orthopnea (in case of topical anesthesia) and less vitreous pressure. However, the surgeon and the operating team should plan the surgical procedure to minimize the surgical time.

Figure 1

(a) shows the obese patient in a supine position which is the conventional position for retinal surgeries. Visceral fat accumulation leads to increased intra-abdominal pressure which in the supine position, pushes the diaphragm upwards thereby increasing the pleural pressure and cardiac filling pressure. Due to increased pressure on inferior vena cava, venous return from the brain is reduced, leading to increased ICP and IOP. (b) shows the obese patient in RTP (15-20°) with neck extension which leads to lowering of the diaphragm and thereby decreasing the intrapleural pressure and in turn decreased IOP. The neck extension allows the eyeball to be in primary position and the head parallel to the ground, making it easy for the surgeon to maneuver the eyeball for scleral buckling and continue further with vitrectomy and required retinal procedure

Care Report

A 57-year-old gentleman came to the eye hospital with a complaint of sudden blurring of vision in the left eye. He was diagnosed with total retinal detachment in the left eye, and urgent retinal surgery was advised. The procedure planned was implantation of a scleral encircling band with pars plana vitrectomy and silicone oil injection for endotamponade.

During the clinical examination, it was noted that the gentleman was extremely obese (height- 162 centimeters, weight- 130 kilograms) with a BMI of 49.6 kg/m2. He also had a short neck, wheezing, and dyspnea on exertion grade 3. He was on anti-hypertensive medications in addition to aspirin. The pulmonary function tests were within normal limits for his age. He had OSA which could get aggravated on lying down for a long time. Peribulbar anesthesia using a mixture of xylocaine and bupivacaine, without adrenaline was chosen for him.

Technique

The patient was placed in RTP with neck extension position [Fig. 1b]. Continuous oxygen was administered with the help of nasal prongs. The patient was given intravenous aminophylline for bronchodilation for wheezing noted before surgery. The SpO2 was continuously monitored with a pulse oximeter and sedatives were avoided in the patient. The patient was given injection glycopyrrolate to prevent sudden bradycardia. The surgeon tagged the recti muscles and passed a silicone band in an encircling manner. A 23-gauge suture less vitrectomy was performed to repair the retinal detachment. Silicone oil was injected for endotamponade. The procedure was completed uneventfully in 65 minutes.

Discussion

There have to be specific considerations when planning a retinal surgery in a morbidly obese patient. Positioning the patient in RTP reduces the risks of dropping SpO2 and also reduces the increased vitreous pressure in such individuals. Mansour et al. have described this as “Standing Phacoemulsification” as a modification over the conventional surgical positioning for cataract surgeries in morbidly obese patients.[5] Standing surgeries are also indicated in morbid obesity patients undergoing urologic endoscopy,[6] laryngoscopy[7] and laparoscopy.[8] Other positions for cataract surgery in patients with postural disorders and other medical issues are – face to face position described by Ang et al.,[9] phacoemulsification in the waiting room with the patient in a seated position with head extension described by Fine et al.[10]

As compared to that of cataract surgery even the retinal surgeries are more time consuming. Our patient required a vitrectomy along with scleral buckling. During this procedure, traction on the extraocular muscles along with pressure on the globe can cause bradycardia, hypotension or dysrhythmias and even cardiac arrest (the oculocardiac reflex). In morbidly obese patients, even those who are breathing spontaneously, oculocardiac reflexes can be exaggerated if the patient has hypoxia, acidosis or hypoventilation. Hence the patient's respiration and oxygen saturation must be monitored continuously even under local anesthesia and preferably be given injection glycopyrrolate to prevent sudden bradycardia.

Conclusion

The RTP allows retina surgery in a morbidly obese patient with fewer chances of systemic complications compared to supine position. Neck extension along with RTP provides good surgical access for scleral buckling, and the eye remains in a primary position which allows the retina surgery to proceed uneventfully. Such a modification can be used in case of a morbidly obese patient for retinal surgeries.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.