Patients undergoing abdominal surgery require a complete history and physical examination as outlined in Chapter 1. The following issues germane to abdominal surgery should be considered as well.

A. Preoperative Fluid Status. Surgical pathology may cause severe derangement in volume homeostasis, producing both hypovolemia and anemia. The main sources of fluid deficits are inadequate intake, sequestration of water and electrolytes into abdominal structures and fluid loss.

1. Assessment of volume status

a. Postural changes in vital signs (increased heart rate and decreased blood pressure) may reveal mild-to-moderate hypovolemia; severe hypovolemia will produce tachycardia and hypotension. Dry mucous membranes, decreased skin turgor and temperature, delayed capillary refill, and skin mottling indicate decreased peripheral perfusion secondary to hypovolemia.

b. Laboratory analysis including base excess, hematocrit, serum osmolality, BUN-creatinine ratio, serum and urine electrolyte concentrations, and urine output are helpful in estimating volume deficits.

c. If the intravascular volume status of a patient cannot be determined by clinical assessment alone, then invasive monitoring may be required. In addition to monitoring systemic pressures, an arterial line may be used to assess pulse pressure variation (PPV) and systolic pressure variation (SPV) that can aid in estimating volume status without the risks associated with central line placement. In general, a delta-down component of SPV of 5 mm Hg and a PPV of 13% to 15% indicates that a patient will be volume responsive. Central venous pressure (CVP) measurement that has been the customary way to estimate volume status has fallen out of favor for several reasons. A pulmonary artery catheter may be placed in patients who will have ongoing volume requirements to optimize cardiovascular performance (see Chapter 10). Esophageal Doppler monitors can also be used to assess.

a. Reduced Intake: NPO guidelines are reviewed in earlier chapters. Patients may have reduced or no oral intake before surgery. However, for elective cases, they may not be hypovolemic if following new NPO guidelines. Gastrointestinal tract obstruction may prevent adequate oral intake, and malabsorption may preclude absorption of adequate fluids. Despite IV hydration in the preoperative period, patients could arrive to the operating room with signs of hypovolemia and symptoms of dehydration.

b. Emesis or gastric drainage may produce significant fluid losses, particularly in patients with bowel obstruction. Quantity, quality (bloody), duration, and frequency of emesis should be assessed.

c. Diarrhea from intestinal disease, infection, or cathartic bowel preparation can cause significant extracellular fluid loss.

d. Bleeding from gastrointestinal sources includes ulcers, neoplasms, esophageal varices, diverticula, angiodysplasia, and hemorrhoids.

e. Sequestration of fluid may occur either into the bowel lumen from ileus or into the interstitium from peritonitis.

f. Fever increases insensible fluid loss.

B. Metabolic and hematologic derangements occur frequently in patients requiring emergency abdominal surgery. Hypokalemic metabolic alkalosis is common in patients with large gastric losses (emesis or nasogastric [NG] tube drainage). Severe hypovolemia or septicemia can cause metabolic acidosis. Sepsis can produce disseminated intravascular coagulopathy.

C. Length of surgery is influenced by the history of previous abdominal surgery, intra-abdominal infection, radiation therapy, steroid use, surgical technique, and surgeon experience. This is often unpredictable, particularly if the pathology is unclear preoperatively.

D. Anticipated postoperative course will determine the type of anesthetic, fluid administration, analgesic considerations, and immediate postoperative management.

E. All patients for emergency abdominal procedures are considered to have full stomachs. A rapid sequence induction (RSI), potentially with the use of cricoid pressure or an awake intubation technique, is indicated with the goal of minimizing aspiration risk. It is worth noting that cricoid pressure has not been shown to reduce the risk of aspiration on induction. Premedication with histamine (H₂) antagonist and oral nonparticulate antacid can decrease gastric acidity. Metoclopramide decreases gastric volume, though the efficacy to reduce the risk of aspiration has never been proven. Metoclopramide also should not be used in cases of bowel obstruction.

A. General anesthesia (GA) remains the most commonly employed technique.

1. Advantages include protection of the airway, assurance of adequate ventilation, and rapid induction of anesthesia with controlled depth and duration.

2. Disadvantages include loss of airway reflexes, which increases the risk of aspiration during routine or emergency surgery, potential adverse hemodynamic consequences of general anesthetics, and potentially increased time for recovery.

B. Regional anesthetic techniques for abdominal surgery include neuraxial anesthetics (i.e., spinal, epidural, and caudal anesthesia) and peripheral nerve blocks performed on the trunk including rectus sheath, transverse abdominal plane (TAP), subcostal TAP, and ilioinguinal and iliohypogastric nerve blocks. The innervation of the abdominal wall is via the anterior divisions of the thoracolumbar nerves (T6-L1), and these blocks provide anesthesia and analgesia by blocking various divisions of these nerves. Thorough discussion of the risks and benefits of regional anesthesia are discussed in Chapter 18. Patients who undergo surgery via regional anesthesia typically require supplementation with anxiolytic/sedative medications to tolerate the operating room experience.

1. Lower abdominal procedures (e.g., inguinal hernia repair) can be performed with regional anesthesia techniques

a. Epidural anesthesia usually is performed with a continuous catheter technique. A “single-dose” technique is applicable for surgery of less than 3 hours but rarely used.

b. Spinal anesthesia usually is performed with a single-dose technique, although spinal catheters can be placed. The duration of block is determined by the choice of local anesthetic and adjuvants (see Chapter 17).

c. Peripheral nerve blocks (discussed below) can also provide adequate anesthesia for abdominal surgery but are more commonly used as adjuvant techniques for postoperative analgesia.

d. Blockade of the ilioinguinal, iliohypogastric, and genitofemoral nerves produces a satisfactory field block for herniorrhaphy. These nerve blocks are easily performed by the anesthesiologist but may require direct supplementation of spermatic cord structures by the surgeon.

2. Upper abdominal procedures (above the umbilicus, T10) are not well tolerated under regional anesthesia alone. Spinal or epidural anesthesia for upper abdominal procedures may require a sensory level to T2-T4. Paralysis of intercostal muscles from a high thoracic level impairs deep breathing. Although minute ventilation is maintained, patients often complain of dyspnea. Intraperitoneal air or upper abdominal exploration produces a dull pain referred to a C₅ distribution (usually over the shoulders) that is not prevented by regional anesthesia and may require supplementation with intravenous (IV) analgesics.

a. If awake for the procedure, patients maintain the ability to communicate symptoms (e.g., chest pain).

b. Airway reflexes are maintained.

c. Profound muscle relaxation and bowel contraction optimize surgical exposure.

d. Sympathectomy increases blood flow to bowel.

e. Continuous catheter techniques provide a ready means for postoperative analgesia.

f. Regional techniques are opioid sparing.

g. There is some evidence to support earlier return of bowel function in patients with prolonged postoperative ileus when epidural catheters are used for postoperative analgesia.

a. Local anesthetic toxicity from inadvertent IV injection or rapid absorption.

b. Patient cooperation is necessary for the institution of block and positioning during surgery.

c. Failure necessitates intraoperative conversion to GA.

d. Regional nerve blockade may be contraindicated in patients with abnormal bleeding profile or localized infection at the site of injection.

e. Sympathectomy with neuraxial techniques may lead to vaso/venodilation and bradycardia that can precipitate profound hypotension. Unopposed parasympathetic activity causes the bowel to contract and may make construction of bowel anastomoses more difficult; this can be reversed with glycopyrrolate, 0.2 to 0.4 mg IV, or 1 mg glucagon.

f. Blockade of upper thoracic nerves may compromise pulmonary function.

g. Awake patients often require frequent communication and reassurance; this may distract the anesthesiologist during complicated cases.

C. A combined technique makes use of a regional technique along with a general anesthetic. This technique is commonly used for extensive upper abdominal surgeries and may include an epidural or a nerve block + GA. Peripheral nerve blocks of the abdominal wall may be done awake, but more commonly immediately after induction or just prior to emergence (postprocedure) from GA. The nerve blocks can provide significant intraoperative and postoperative analgesia, creating an opioid-sparing technique. The blocks may be viable options when neuraxial techniques are contraindicated due to concerns for sepsis, severe spinal stenosis, severe peripheral nerve disease, or patient refusal. The common peripheral nerve blocks that are performed on the abdominal wall include the following:

1. TAP blocks can be used for most lower abdominal procedures, often as an alternative for epidural anesthesia. A regional needle is placed in the anterior axillary line, between the costal margin and the iliac crest. The local anesthetic spreads between the transversus abdominis and internal oblique muscle planes. Catheters are often used for TAP blocks to provide postoperative analgesia, providing a significant opioid-sparing effect.

2. Rectus sheath blocks are appropriate for midline procedures, particularly periumbilical procedures. Local anesthetic is deposited via a regional needle between the rectus muscle and posterior rectus sheath.

3. Subcostal TAP blocks are similar to the TAP block described above but the needle is placed more superiorly and laterally, below the costal margin. The upper nerve fibers, in particular T8-T10, are more likely anesthetized with this modification of the TAP block.

A. Standard monitors are used as described in Chapter 10.

1. Restoration of volume deficits before induction should be considered (discussed below).

2. RSI or awake intubation is required for all patients considered with full stomachs. Indications include conditions in which gastric emptying is delayed, intra-abdominal pressure is increased, or lower esophageal tone is compromised. Examples include trauma, bowel obstruction or ileus, hiatal hernia, gastroesophageal reflux disease, pregnancy beyond the first trimester, significant obesity, ascites, and diabetes with gastroparesis and autonomic dysfunction.

1. Fluid replacement is guided by clinical judgment and/or invasive monitoring. Traditionally, very long cases with significant bowel exposure and preoperative hypovolemia required fluid replacement of up to 10 to 15 mL/kg/h. New evidence, however, suggests that a more restrictive approach may be associated with faster recovery and fewer complications.

2. Using a “protocol-based” strategy for fluid administration appears to reduce impairment of bowel motility, cardiopulmonary complications, and bowel edema; improve anastomosis healing; and reduce hospital stay time. There is not a strict definition of fluid restriction, nor is there agreed-upon protocol for fluid restriction. Literature has been published using differing protocols based on a variety of measured parameters including volume of fluid administered, perioperative weight gain, and volume based on hemodynamic responsiveness. The key point is
that more restrictive administration of intraoperative fluids in a deliberate, planned manner appears to improve outcomes. Patients with severe burns, severe hypotension, or major fluid shifts should not be significantly fluid restricted.

a. Bleeding should be estimated both by direct observation of the surgical field and suction traps and by weighing sponges. Blood loss may be concealed (e.g., beneath drapes or within the patient). Labs should be checked appropriately.

b. Insensible losses likely range from 0.5 mL/kg/h to 1 mL/kg/h for larger abdominal cases, much less than many anesthesia providers believe.

c. After an overnight NPO period, blood volume is likely near normal in most patients and may not require IV fluid to make up for the fluid deficit. Clinical judgment will guide the need for resuscitation prior to starting the case.

d. Abrupt drainage of ascitic fluid with surgical entry into the peritoneum can produce acute hypotension from sudden decreases of intra-abdominal pressure and pooling of blood in mesenteric vessels, thus reducing venous return to the right heart. Postoperative reaccumulation of ascitic fluid can produce significant intravascular fluid losses.

e. NG and other enteric drainage should be quantified and replaced appropriately.

3. Fluid losses should be replaced with crystalloids, colloids, or blood products.

a. Initially, fluid should be replaced by administration of an isotonic salt solution. When an isotonic crystalloid solution is used to replace blood loss, goal directed therapy and fluid response probably is better than traditional 3:1 replacement. Growing evidence shows aggressive normal saline use may cause non-anion gap metabolic acidosis.

b. Colloids are fluids containing particles large enough to exert oncotic pressure. They remain in the intravascular space longer than crystalloids. Multiple studies comparing fluid resuscitation with crystalloids to colloids have reported no benefit with colloids. Colloid solutions are more expensive than crystalloids, and their routine use may not be justified. Albumin may be superior to crystalloid in patients with significant burns, hepatorenal disease, or acute lung injury. Hydroxyethyl starch solutions (e.g., Hextend or Hespan) are non-blood-derived colloids that may also be used as methods of volume expansion but are falling out of favor due to deleterious effects on renal function, coagulation, and potentially all-cause mortality.

4. Muscle relaxation is required for all but the most superficial intraabdominal procedures. Sufficient relaxation is critical during abdominal closure because bowel distention, edema, and organ transplantation can increase the volume of abdominal contents.

a. Titrating relaxants to obtain a single twitch by train-of-four monitoring should provide enough relaxation for surgical closure yet allow for reversal of muscle relaxants for extubation.

b. Potent inhalational agents block neuromuscular conduction and are synergistic with relaxants.

c. Neuraxial blockade with local anesthetics provides excellent abdominal muscle relaxation.

d. Flexing the operating table may decrease tension on transverse abdominal and subcostal incisions and facilitate surgical closure without need for profound muscular relaxation which is often requested by the surgeons.

5. Use of nitrous oxide (N₂O) may cause bowel distention because N₂O diffuses into the bowel lumen faster than nitrogen can diffuse out with the amount of distention depending on the concentration of N₂O delivered, the blood flow to the bowel, and the duration of N₂O administration. Under normal conditions, the initial volume of bowel gas is small; doubling or tripling of this volume does not pose a significant problem. Studies have shown that N₂O may be used in shorter (<3 hours) open and laparoscopic surgeries, without causing clinically significant bowel distention. Use of N₂O is relatively contraindicated in bowel obstruction because the initial volume of bowel gas may be large. Most recent ENIGMA trial did not prove nitrous oxide related to any significant adverse outcomes.

6. NG tubes are frequently placed in the perioperative period.

a. Preoperative placement is indicated for decompression of the stomach, especially in trauma victims and patients with obstructed bowel. Although suction via a large-bore NG tube can reduce the volume of gastric contents, it does not completely evacuate the stomach and may facilitate aspiration by stenting open the lower esophageal sphincter. NG tubes may also compromise mask fit. Before induction, suction should be applied to NG tubes. During induction, tubes should be allowed to drain. Cricoid pressure may help to prevent passive reflux when an NG tube is present.

b. Intraoperative placement is required to drain gastric fluid and air during abdominal surgery. NG and orogastric tubes should never be placed with excessive force; lubrication and head flexion facilitate insertion. Tubes can be directed into the esophagus by using a finger within the oropharynx or using Magill forceps under direct visualization with a laryngoscope.

c. Complications of NG tube insertion include bleeding, submucosal dissection of the retropharynx, and placement in the trachea. Intracranial placement has been described in patients with basilar skull fracture. The NG tube should be secured carefully to avoid excessive pressure on the nasal septum or nares, as this may cause ischemic necrosis.

d. As discussed above, the need for a gastric tube should be discussed with the surgeon as placement for elective procedures is not recommended in many cases.

7. Common intraoperative problems associated with abdominal surgery include the following:

a. Pulmonary compromise can be caused by surgical retraction of abdominal viscera to improve exposure, insufflation of gas during laparoscopy, or Trendelenburg positioning. These maneuvers may elevate the diaphragm, decrease functional residual capacity (FRC), and produce hypoxemia. Application of positive end-expiratory pressure (PEEP) may counter these effects.

b. Temperature control. Heat loss in open abdominal procedures is common. Potential sources and treatment are discussed in Chapter 19.

c. Hemodynamic changes as a result of bowel manipulation (i.e., hypotension, tachycardia, and facial flushing) and abdomen inflation.

d. Fecal contamination from perforation of the gastrointestinal tract can cause infection and sepsis.

e. Ischemic bowel patients can have intractable hypotension from SIRS and sepsis.

f. Hemodynamic instability and difficult ventilation during abdomen closures may be early warnings for postoperative abdominal compartment syndrome.

Popularized in Europe and now growing in use in the United States, patients are optimized to allow the fastest recovery and discharge postoperatively. The basic tenets include frequent use of epidurals and other regional techniques (regardless of open vs. laparoscopic), multimodal analgesia, goal-directed fluid therapy, reduced NPO times, and early feeding and early ambulation postoperatively. Many of the recommendations challenge the traditional approaches to perioperative management, both from an anesthetic and surgical standpoint.

1. With the ERAS protocols, there is enhanced recovery of bowel function, earlier feeding, reduced overall minor complication rates and reduced length of stay. Readmission rates and mortality are similar.

2. Guidelines have been published for many of the major types of abdominal surgery.

3. Notable highlights of ERAS protocols for elective colonic surgery

a. Premedications are generally not given.

b. Mechanical bowel preparations (MBPs) should not routinely be used as there is no clear evidence of benefit, but they may increase bowel spillage.

c. Clear fluids containing significant carbohydrate content are given 2 to 3 hours before surgery. and NPO times for solids are generally 6 hours. Modifications based on disease state are taken into consideration.

d. NG tubes should not be routinely used for elective colonic surgery.

4. Goal-directed therapy with respect to intraoperative fluid management is based on objective measurements of fluid status, often making use of an esophageal Doppler in many of the published studies. Fluid challenges are given to increase stroke volume until the patient is no longer volume responsive. The arterial waveform can potentially be used in a similar manner.

5. Postoperative fluids are minimized, and total perioperative fluids are significantly reduced.

6. Balanced solutions (i.e., lactated Ringers, Plasmalyte) are preferred to NS, which causes a metabolic acidosis.