Trendelenburg Position - an overview (2023)

Pneumoperitoneum and the Trendelenburg Position

Carbon dioxide is the gas most commonly used to establish pneumoperitoneum. The high blood solubility of carbon dioxide facilitates absorption from the peritoneal cavity after laparoscopic surgery and may represent a life-saving property of the gas in the rare but potentially catastrophic event of gas embolization. For example, rapid intravenous injection of 5 to 10 mL/kg of carbon dioxide produces only transient (< 1 minute) hypotension in anesthetized dogs (Fig. 15.13),⁸³ whereas intravascular administration of a similar volume of a less soluble gas (e.g., helium, oxygen, nitrogen) is usually fatal.

Signs of embolization of large quantities of carbon dioxide (or any other gas) in anesthetized patients may include hypocapnia, hypotension, hypoxemia, ST-segment and T-wave changes, arrhythmias, and audible changes in heart sounds.⁸⁴ Initial treatment of carbon dioxide embolism should include release of the pneumoperitoneum and pharmacologic support of the circulation. If initial resuscitation efforts are unsuccessful, aspiration of gas from the right atrium (using a multi-orifice central venous catheter) should be considered. Although the use of the left lateral recumbent position (Durant's maneuver), with or without head-down positioning, has been suggested to facilitate removal of the postulated air lock from the right side of the heart,⁸⁵ laboratory evidence suggests that this maneuver may have a detrimental effect on cardiac function after venous gas embolism.⁸⁶

Nearly as soluble in blood as carbon dioxide, nitrous oxide is associated with less peritoneal and diaphragmatic irritation⁸⁷ and has been suggested for the establishment of pneumoperitoneum in awake patients undergoing laparoscopy. A major disadvantage of nitrous oxide is its ability to support combustion, which could increase the possibility of an explosion if the surgeon uses electrocautery.

GIFT and ZIFT procedures are often performed with the patient in the Trendelenburg position to facilitate visualization of the fallopian tubes and other pelvic structures. Positioning strategies to prevent the patient from moving cephalad on the operating table and to prevent brachial plexus damage should be used. The adduction of the patient's arms against her trunk has been suggested to reduce the risk for brachial plexus injury, but the efficacy of this precaution is unproven.

Both pneumoperitoneum and the Trendelenburg position produce physiologic changes. Hemodynamic effects of moderate pneumoperitoneum (< 20 mm Hg) in a patient in the Trendelenburg position include increased mean arterial and central venous pressures, increased systemic vascular resistance, and decreased stroke volume and cardiac output.⁸⁸ Heart rate usually does not change, but in some patients pneumoperitoneum may elicit sinus bradycardia, heart block, or even cardiac arrest. Finally, pneumoperitoneum aggravates the respiratory effects of the Trendelenburg position (e.g., reduced chest wall compliance, increased venous admixture). Overall, most healthy patients easily tolerate the cardiovascular and pulmonary effects of intra-abdominal pressures lower than 20 mm Hg.

7 What are the physiologic effects and risks associated with the Trendelenburg position?

Head down, or Trendelenburg position, further increases translocation of blood to the central compartment. Intracranial and intraocular pressure increase in the Trendelenburg position secondary to decreased cerebral venous drainage. Adverse outcomes in healthy patients have not been noted, although the Trendelenburg position is clearly contraindicated in patients with increased intracranial pressure. Lengthy procedures may result in significant facial and upper airway edema. The likelihood of postextubation airway obstruction should be considered, and the ability of the patient to breathe around the endotracheal tube with the cuff deflated is reassuring, although it does not completely ensure that postextubation airway obstruction will not occur. After prolonged surgery in the Trendelenburg position, particularly when there has been substantial intravenous fluid administration, it may be prudent to leave the patient intubated with the upper torso elevated, allowing time for fluid redistribution to take place. Decreases in pulmonary compliance and functional residual and vital capacity also occur in the Trendelenburg position. Peak airway pressures during mechanical ventilation are also noted. Shoulder braces used to keep the patient from sliding off the surgical table have been associated with brachial plexus injuries.

PREOPERATIVE ASSESSMENT

Positioning the patient

The modified lithotomy Trendelenburg position is used to facilitate synchronous combined excision of the rectum. The patient is catheterised, a soft sandbag or ‘wedge’ is placed under the buttocks and a tray is placed under the perineum and attached to the end of the table. A plastic sheet is inserted between the buttocks and the sandbag so that the towels will slide easily over the perineal tray and under the buttocks without a member of the theatre staff having to lift the patient and without the surgeon becoming contaminated during the towelling procedure. At this stage the patient should not be placed in the steep Trendelenburg tilt unless restraining supports have been fitted to the shoulders, for fear that he or she may slip cephalad. The optimum position will depend upon the size of the buttocks, the presence of hip disease or kyphoscoliosis and the build of the individual. In order not to compromise access by the abdominal surgeon, approximately 60–80° of hip flexion is used, with 40° of abduction at the hip and 100° of knee flexion (Figure 39.3). The position of the legs should be supervised by the surgeon and the Allan stirrups adjusted accordingly. Pneumatic leg bags are then placed around the calves and the skin preparation applied to the abdominal wall and perineum.

The first towel to be applied should be the one under the buttocks and over the perineal tray. Two leg bags are then placed over the lower limbs, to cover the penis and scrotum in the male. The leg bags and perineal towels are then sutured to the skin. The side towels and upper sheet are then placed around the abdomen and secured to the abdominal wall with a transparent adhesive drape. A covering sheet with two separate openings (for the abdomen and perineum) is placed over the existing towels and the Mayo table. Two side towels are attached to the Mayo table so as to exclude the anaesthetist from the sterile area.

For a synchronous combined proctocolectomy, one assistant and a scrub nurse are sufficient for the colectomy, but another surgeon and scrub nurse are needed for synchronous combined excision of the rectum.

Trendelenburg Position

Hypotensive patients are often placed in the Trendelenburg position while resuscitative efforts, such as establishing intravenous access and administering fluids, are initiated. The Trendelenburg position was thought to increase venous return and thereby augment cardiac output. This assumption is incorrect because of the capacitance of the venous circulation. The Trendelenburg position does not promote venous return or increase cardiac output. Hypotensive patients should not be put in the Trendelenburg position. This position serves only to increase the risk for aspiration.

Positioning

Positioning patients in the reverse Trendelenburg position can optimize respiratory function. However, lying in one position for prolonged periods increases the risk of pressure sore formation. Pressure ulcers result from prolonged pressure on soft tissue or compression of the skin between a bony prominence or hard surface (e.g., bed sides). Pressure-induced injury ranges from nonblanching, erythematous (but intact) skin to deep ulcers down to the bone. The risk of pressure sores in critically ill patients is reduced by repositioning patients regularly [39]. When positioning patients, it is important not to occlude blood flow, which could increase the risk of VTE.

7 Describe the external jugular vein approach

When the patient is in a Trendelenburg position, the external jugular vein frequently can be visualized where it crosses the sternocleidomastoid muscle. The needle is advanced in a direction paralleling the vessel and is introduced into the vein approximately two finger widths below the inferior border of the mandible. Difficulty may arise in advancing the catheter or guidewire into the central circulation from the external jugular vein approach because the patient's anatomy frequently directs the catheter into the subclavian rather than the innominate vein. It is also frequently difficult to pass the guidewire or catheter past the clavicle.

Transanal Mucosectomy: Operative Technique

The table is positioned in the Trendelenburg position, and the hips are placed in flexion to adequately expose the anus. A self-retaining anal retractor is used to evert the anus and expose the dentate line. A circumferential incision is made through the mucosa at the dentate line, and the more proximal submucosal plane is infiltrated with a solution of 1 : 100,000 epinephrine. The mucosa is dissected off the underlying rectal wall with scissors or cautery, with the dissection continued to a level above the anorectal ring, at which point the rectal wall is incised and the proctectomy is completed. The specimen is either transabdominally or transanally removed, and the apex of the pouch is delivered to the level of the sphincter. Prior to delivering the pouch into the anal canal, four or more full-thickness sutures incorporating the anal mucosa and internal sphincter are placed at regular intervals around the circumference of the canal to begin the anastomosis. A ring or atraumatic clamp is passed through the anal canal into the pelvis to grasp the pouch in proper orientation (small bowel mesenteric edge to the patient's right, body of pouch in curve of sacrum) and deliver it to the distal canal. The previously placed sutures are passed through the full thickness of the pouch wall to secure the pouch into place. Finally, the anastomosis is completed with interrupted, full-thickness sutures such that no defects are identified. The spacing between each suture and the total number of sutures is at the surgeon's discretion (Fig. 162.16).

3 Creation of the Gastric Pouch

Placement of the patient in reverse Trendelenburg position facilitates exposure to the supramesocolic abdomen. Dissection is begun at the phrenoesophageal ligament using the surgeon's choice of energy source. Dissection at this location helps identify the presence of a hiatal hernia, which should be reduced and possibly repaired prior to pouch creation, and facilitates identifying the proper aiming point and passage for linear staplers. The energy source can then be used to divide the typically transparent area in the gastrohepatic ligament over the caudate lobe of the liver. This helps the surgeon identify the right crus, esophagogastric junction, left gastric vascular trunk, body of the pancreas, and posterior wall of the stomach. On occasion, it may be necessary to divide the avascular adhesions of the posterior wall of the stomach to the anterior body of the pancreas to free up the lesser sac posterior to the stomach. The lesser curvature vascular arcade approximately 3 to 6cm below the esophagogastric junction is then divided with the energy source. Care should be taken to preserve the left gastric trunk arising from superior to the body of the pancreas. All tubes and monitors are confirmed to be removed from the stomach before stapling (Figure 64-1).

In general, 45- or 60-mm linear stapler loads are used to create the gastric pouch. Most authors are reporting use of 3.5- to 4.8-mm staple heights, and current data demonstrate that use of staple line reinforcement reduces staple line leaks and postoperative complications.²⁰ With use of 60-mm stapler loads, the pouch can usually be completed in three to five stapler fires, resulting in a 15- to 30-mL pouch totally divided from the gastric remnant. The manner and sequence in which the gastric pouch is completed varies based on the technique being used to perform the gastrojejunostomy. For example, if the gastrojejunostomy is being completed with an end-to-end anastomotic (EEA) circular stapler with transoral passage of the anvil, the pouch can be completed in its entirety as the initial steps. If the EEA anvil is being introduced through the abdominal wall for transgastric passage, the anvil may be placed initially with the anvil spike presented through the anterior gastric wall followed by completion of the gastric pouch around it, or an initial transverse staple line may be fired with transgastric passage of the anvil through the end of the staple line. Recently, authors have described a technique whereby the initial staple lines of the pouch are created, followed by completion of a totally linear stapled gastrojejunostomy, and the pouch itself is only completed after the anastomosis has been created.²¹

The pouch can be sized by introducing a transoral Baker tube with a 30-mL balloon and retracting the inflated balloon to the esophagogastric junction. Alternatively, a transoral flexible dilator or bougie, typically 34 French (34F) in size, can be introduced transorally to help size the pouch for uniformity from patient to patient and can also help prevent inadvertent division of the superior stomach with a linear stapler. The use of a bougie is not necessary and is entirely at the discretion of the surgeon. Some surgeons prefer not to use these devices to prevent inadvertent inclusion of these objects in the staple lines. As the surgeon gains more experience with laparoscopic gastric bypass, gastric pouches with fairly consistent size from patient to patient can be created based on visual cues alone.

E. REDUCTION OF INCARCERATED HERNIA