Positioning in Thoracic Surgery




Positioning in Thoracic Surgery



Alessia Pedoto, Nicole Ginsberg



Abstract


Ideal position should facilitate surgical procedures and anesthesia management, without causing harm to patients and any involved personnel. The aim of this chapter is to describe the most common positions used during thoracic noncardiac surgery, highlighting the challenges and physiologic changes associated with each one, and how to prevent possible complications.


Keywords


position; thoracic noncardiac surgery; complications; nerve injury; compartment syndrome



Introduction


Adequate patient position is essential to facilitate surgical exposure. This in turn has direct consequence on the anesthetic management. In addition to providing best access to the patient, optimal position should minimize any potential harm and injuries, especially when positional changes occur during general anesthesia, because of lack of patient feedback. The anesthesiologist has a key role during the perioperative period as the person in charge for the safety of this task.


Ideally, patient position should facilitate both the performance of surgery by providing optimal access to the operative site and access to the patient for the anesthesiologist. Optimal position should not interfere with respiration or circulation or cause undue nerve pressure or muscular discomfort.


Common positions for thoracic surgery include supine, lateral, or prone, which can be modified by the addition of flexion or reverse Trendelenburg, usually while the patient is anesthetized. Preventing both long- and short-term damage requires careful planning, which should be implemented during the preoperative encounter. A meticulous evaluation and documentation of any preoperative neuropathy and limited range of motion should take place at this time. Unfortunately, a clear mechanism for positional injury can be recognized only in less than 10% of cases,1 therefore patients deemed at risk for positional injury, such as the elderly, diabetics, or those with an extreme body mass index (BMI) should be carefully evaluated. In the presence of significant limitations of the range of motion, the final surgical position should be checked while the patient is awake, to avoid significant or permanent damage when changing position following the induction of general anesthesia. In addition, any concerns or limitations should prompt an alternative position in cooperation with the surgeon.


The aims of this chapter are to describe the most common positions used during thoracic noncardiac surgery, highlighting the challenges and physiologic changes associated with each one, and to discuss how to prevent possible complications.



Positions for Thoracic NoncardiacSurgery


Thoracic noncardiac surgery involves multiple positions often assumed after the patient is anesthetized.



Supine Position


General anesthesia is usually induced in the supine position. The neck is placed in the sniffing position to facilitate intubation with the arms alongside the body. The use of video laryngoscopes and the availability of the fiberoptic bronchoscope in the room has made intubation less dependent on optimal positioning. Nevertheless, the presence of neck stiffness or any preoperative neck injury should be addressed before induction. Special attention should be given when the patient is placed in the final surgical position, commonly being the lateral decubitus with the bed flexed. The double-lumen tube (DLT) or the bronchial blocker (BB) should be correctly positioned before turning the patient and rechecked in the final operating position. Intravascular lines, endotracheal tubes, and urinary catheters should be secured and have enough length to be safely moved.


Thoracic noncardiac cases that are performed in the supine position include resection of the esophagogastric tract, mediastinal tumors, or tracheal disease. In the supine position, the arms may be either abducted, tucked, or secured above the head (“hands up”). When abducted, they should be at less than a 90-degree angle and secured to prevent sliding off the arm boards, especially in cases that require reverse Trendelenburg. All pressure points should be padded and protected, and any source of direct skin pressure removed. If the arms are tucked alongside the patient, they should be in a neutral position, with the thumbs up and the palms inward.2 They should be secured to prevent sliding without causing distal hypoperfusion. In addition, stopcocks on arterial or intravenous (IV) lines should be padded to prevent pressure injuries to the skin. The hands-up position (90 degrees flexion at the elbows, and 90 degrees abduction at the shoulder) can result in brachial plexus stretching, as observed in cadaveric studies.3 In sternotomies, a shoulder roll is usually placed at the level of the scapula to open the clavicles and facilitate the sternal split. The head should be secured and not overextended or rotated to prevent brachial plexus injury.4 Pillows or protective foam should be placed under the head for support and protection from contact pressure. Dangling of the head will apply pressure to the cervical spinal cord, which in turn could lead to postoperative neurologic injuries. Before prepping and draping the patient, all the IV lines should be checked to confirm a free flow. If an epidural catheter was inserted, access to the port should be ensured.



Lateral Decubitus


The lateral decubitus position is commonly used for most intrathoracic resections, with the patient being turned after induction of general anesthesia (Fig. 10.1). The anesthesia team should oversee the turning, to avoid displacement or loss of lines and airway devices. When in the lateral decubitus position, any unnatural positions that could cause injury to the patient, even if transient, should be avoided. The staff moving the patient should take precaution to prevent injuring themselves in the act of turning.5–7 Once in the lateral decubitus, all pressure points should be padded, and the patient secured to prevent potential sliding or falls. Periodic intraoperative checks should be frequently done, and adjustments made in case of shifts from the original position. During thoracic procedures in the lateral position it is essential to have at least two IV accesses before placing the patients in the lateral position. Placing an IV line in the lateral position may present a significant challenge, and is time consuming.


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• Fig. 10.1 Lateral decubitus with bed flexed and patient secured with tape. A sandbag is used to prevent lateral movements. The dependent lower extremity is slightly flexed, while the nondependent is straight, with a pillow placed between the knees to prevent common peroneal nerve compression.

Lower extremities (see Fig. 10.1): The dependent leg is slightly flexed with padding under the knee to avoid pressure on the common peroneal nerve. A pillow is placed in between the legs to decompress the common peroneal nerve of the nondependent leg, which is usually positioned straight. The saphenous nerve should be free of any compression. Vascular compression should be avoided because of the potential of ischemia, especially in patients with peripheral vascular disease. The hips are usually secured to the bed with tape or Velcro straps to prevent rotation and dislodgment, as well as distal hypoperfusion. Compartment syndrome has been reported in the lower extremities secondary to pressure of the dependent leg and decreased inguinal venous return.8–10 A combination of risk factors, such as long duration of surgery (>5 hours), BMI higher than 40 kg/m2,11 low venous return and hypoperfusion have been suggested as contributing factors. The gluteal area is also at risk, because the gluteus muscle is compartmentalized.8 Cases of gluteal compartment syndrome have been reported after prolonged lateral decubitus especially in young patients with high BMI.12,13


The upper extremities should be in a neutral position (Fig. 10.2).14 The dependent arm should rest on a padded arm board and abducted to less than 90 degrees. Padding under the elbows prevents ulnar nerve compression. The wrist should be in a neutral position to avoid radial nerve injury. An “axillary roll” is often placed under the axilla at the level of T4 to free the space, avoiding both brachial plexus injury and vascular compression.15 After its placement and before draping, the provider should check that the roll did not migrate cephalad, especially if the position is readjusted. Placing the pulse oximeter on the dependent arm can be used as an indicator of adequate perfusion.16 The nondependent arm can be suspended on a sling (see Fig. 10.2A) or rest on a board (see Fig. 10.2B). In both cases, extreme flexion at the elbow or stretch of the shoulder should be avoided to prevent brachial plexus or ulnar nerve injury.3 Resting the upper extremity on a pillow placed on top of the dependent arm can potentially cause compression injuries and make intraoperative access to the patient and lines difficult. If not well secured, the pillow and the arm can slide into unnatural positions. If the tape is placed too tight over the elbow, it can cause direct pressure on the ulnar nerve, leading to postoperative neuropathy. Finally, the upper extremity can be placed on the operating room (OR) table close to the face (see Fig. 10.2C), but only if there is enough space available to maintain neutral position and avoid falls during surgery. Access to the chest will be difficult, making intraoperative checks challenging.


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• Fig. 10.2 The upper extremities are placed in a neutral position. The dependent arm is secured on an arm board in a neutral position with padding at the elbow and wrist. The nondependent arm can be placed on a sling (A), on a board (B), or close to the face on the bed (C). In all cases, padding should be used, and neutrality maintained.

The neck should be neutral and supported by a gel or a foam pillow, as well as blankets or pillows when the bed is flexed. A careful evaluation of the cervical spine position should be done from the side before draping to confirm neutral positioning (Fig. 10.3). If the patient has any cervical spine limitation, extreme caution should be applied to keep the head in a neutral position. If commercially available devices are used to facilitate cervical spine neutrality, they should be of the appropriate size for the specific patient. Careful attention should be given to the dependent ear and eye to be free from compression. An increase in intraocular pressure has been reported while in the lateral decubitus, with values higher in the dependent eye, persisting until returning to the supine position17 and worse with the use of sevoflurane. Yamada et al.18 evaluated the intraocular pressure (IOP) in 28 patients undergoing surgery in the lateral position, randomly allocating them to either a sevoflurane or propofol group. IOP in both eyes was recorded and compared between the groups at several points during the procedure. In the sevoflurane group, IOP was significantly increased in both the dependent and nondependent eye 1 hour after changing to the lateral position. The number of patients in whom IOP increased to 28 mm Hg or higher was greater in the sevoflurane group than in the propofol group. The authors concluded that propofol may be better than sevoflurane for the maintenance of anesthesia in the lateral position.


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• Fig. 10.3 The neck should be neutral and checked from the side.

Before extubation, the bed should be unflexed or even seated to facilitate spontaneous ventilation. If flexible bronchoscopy is needed before awakening, it should be done in the supine or semi-sitting position and the DLT (if used) exchanged to either a single-lumen tube (preferable in case of esophagectomy to avoid possible aspiration) or a supraglottic airway device, to accommodate the 6.0 mm fiberoptic bronchoscope. In cases of prolonged lateral decubitus, the face may be edematous because of decreased venous return. All precautions should be used when exchanging the DLT, starting with placing the patient in an optimal sniffing position. Strict extubation criteria should be met because reintubation may be difficult in such instance. If a BB was used to provide lung separation, flexible bronchoscopy can be performed following its removal.



Flexion


The goal of the bed flexion is to move the hips away from the chest and facilitate the opening of the spaces between the ribs. This is usually achieved by using the kidney rest or flexing the table (see Fig. 10.1). The flexion point should be at the level of the iliac crest, avoiding direct compression of the bony structures of the hip to prevent ischemia or necrosis, especially in elderly or cachectic patients. Protective foam or a gel pad is placed under the dependent iliac crest.16 Flexion at the flank can cause compression of the abdominal organs and the inferior vena cava with hypotension from reduced venous return. Obese patients may be difficult to secure to the table because of their body habitus. Falls from the OR table may occur if the patient is not secured properly. A vacuumed sandbag or gel rolls properly placed and secured to the table are used to stabilize the patient and avoid potential disaster. All pressure points should be padded to avoid compression injury,16 while avoiding distal ischemia secondary to tight straps.



Reverse Trendelenburg


This position is commonly used for surgery in the upper abdomen, such as minimally invasive esophagectomy, Nissen fundoplication, or Heller myotomy, because it facilitates organ exposure by displacing the abdominal content in a caudal direction (Fig. 10.4). Great care needs to be taken in preventing the patient from sliding off the table. Nonslip gel mattresses, chest and pelvic straps, as well as padded foot boards can be used for this purpose.16 Independently from the device chosen to secure the patient, excessive pressure that could cause harm should be avoided at all times.16 Significant hypotension can occur secondary to venous pooling in the lower extremities because of the additional use of pneumoperitoneum. Frequent blood pressure measurements are required, either via noninvasive or invasive monitors. Because the head is positioned above the heart, there is potential risk of cerebral hypoperfusion. This should be considered when managing the mean arterial pressure (MAP). For every 2.5 cm in vertical height, there is a 2 mm Hg decrease in MAP.19


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• Fig. 10.4 Reverse Trendelenburg. The arms are neutral, padded, and secured. The feet are protected by foam crates and secured to the foot board to prevent sliding.


Prone


The prone position is sometimes advocated for the thoracic dissection and reconstruction of the esophagus during minimally invasive surgery because of its posterior location,20,21 offering the advantages of superior surgical ergonomics and physiologic benefits22 when compared with other approaches.


The greatest challenge of turning the patient prone is to avoid loss of monitors, lines, and the endotracheal tube. A single lumen tube is often adequate because gravity facilitates the displacement of the lungs anteriorly, which is expedited by using insufflation. If lung isolation is required, a BB may be preferred to a DLT because maintaining proper position without kinks or dislodgment may be difficult, because of its shape and stiffness.23 The head is usually placed on a soft foam molded facial mask or a commercial device (Proneview™, Mizuho OSI, Tokyo, Japan), with the eyes, the nose, and the chin free from compression and resting in the proper cutouts. Mirrors can be used for periodic checks during the procedure.16 The face should be resting above the heart to avoid facial edema, which has been associated with devastating postoperative visual loss, especially when paired with high volumes of intravenous fluids.14 The head should still be in a neutral position because rotation above 60 to 80 degrees has been associated with compression of the carotid and vertebral arteries.14 The arms are placed to accommodate the surgeon and the instruments, usually with the left side tucked along the body and the right elevated above the head (90–100 degrees abduction). The shoulders and elbows should be flexed to less than 90 degrees, and the cervical spine kept neutral. The chest and the abdomen are held in place by gel bolsters that extend from the clavicles to the iliac crests, to alleviate the pressure on the chest.14 Abdominal compression with secondary cephalad dislodgment of the diaphragm and decreased functional residual capacity (FRC) should be avoided. The breasts, iliac crests, and genitalia should be free of compression. The Foley catheter should be secured to avoid pulling on the genitalia. A dedicated stretcher should also be readily available for rapid turning to the supine position in case of emergency.

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Oct 6, 2021 | Posted by in ANESTHESIA | Comments Off on Positioning in Thoracic Surgery
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