General anesthesia (GA) is the most commonly employed technique.

1. Advantages particularly relevant to abdominal surgery include airway protection, control of ventilation parameters, and use of neuromuscular blockade to relax abdominal wall musculature.

2. Disadvantages include loss of airway reflexes necessitating advanced airway management, which increases the risk of aspiration upon induction and emergence, and potential hemodynamic instability.

Monitored anesthesia care (MAC) describes a spectrum of anesthesia that ranges from anxiolysis to deep sedation without the need for advanced airway management. For abdominal surgeries, MAC is often employed with other analgesic modalities such as surgeon-administered local anesthetics. For example, various hernia repairs can be accomplished under this technique (local anesthetic with sedation).

Regional anesthetic techniques for abdominal surgery include neuraxial anesthetics and peripheral nerve blocks performed on the trunk. The abdominal wall is innervated via the anterior divisions of the thoracolumbar nerves (T6–L1). The abdominal viscera innervation arises from cervical, thoracic, lumbar, and sacral spinal levels. Regional techniques can be used as a primary anesthetic or as a complementary technique such as when an epidural or a nerve block is used as an adjuvant to GA. For example, umbilical and inguinal hernia repairs can be performed under neuraxial anesthesia with no additional sedation. Significant intraoperative and postoperative analgesia can be achieved by decreasing the need for opioids.

1. Neuraxial anesthesia involves the administration of local anesthetics and adjuvant medications into the epidural or intrathecal spaces via single injection or catheter placement for continuous infusion. These blocks have the benefit of providing muscle relaxation and profound analgesia to the abdominal wall and viscera. Neuraxial techniques are contraindicated due to concerns for infection, anticoagulation or coagulopathy, severe spinal stenosis, severe peripheral nerve disease, intracranial hypertension, expected hemodynamic instability after loss of sympathetic tone or patient refusal.

   1. Spinal anesthesia is usually performed with a single, lumbar, intrathecal injection. Block coverage and duration is determined by the choice of local anesthetic and adjuvants (see Chapter 20: Spinal, Epidural, and Caudal Anesthesia).

   2. Epidural anesthesia is usually performed with a continuous catheter technique.

   3. Paravertebral blocks are performed most commonly in the thoracic spine by injection into the paravertebral space to provide unilateral anesthesia to the dorsal and ventral rami of the spinal nerve and the sympathetic chain. Multiple unilateral and/or bilateral injections may be required.

   4. Caudal anesthesia is performed via single-dose injection or catheter placement through the sacral hiatus into the epidural space most commonly in infants. This technique provides analgesia for infraumbilical procedures.

2. Peripheral Nerve blocks primarily provide anesthesia to the abdominal wall and are most commonly used as adjuvant techniques for postoperative analgesia. They may be performed awake, or more commonly just prior to emergence (postprocedure) from GA. The nerve blocks can provide significant intraoperative and postoperative analgesia, creating an opioid-sparing technique. Peripheral nerve blocks can often be employed when neuraxial techniques are contraindicated due to bleeding, hemodynamic, or infectious concerns.

   1. Types

      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. Erector spinae plane (ESP) block is a paraspinal fascial plane block where local anesthetic is deposited between the erector spinae muscle and thoracic transverse process to anesthetize the dorsal and ventral rami of the spinal nerve providing somatic and visceral coverage. Local anesthetic spread of up to four spinal levels above and below the block location inside this facial plane can result in a unilateral, multidermatomal sensory blockade of the thoracic and abdominal walls.

   2. Advantages

      1. If awake for the procedure, patients maintain the ability to communicate symptoms (eg, chest pain).

      2. Airway reflexes are maintained.

      3. Profound muscle relaxation after neuraxial anesthesia optimizes surgical exposure.

      4. Sympathectomy after neuraxial anesthesia increases blood flow to the bowel.

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

      6. Regional techniques are opioid sparing.

      7. 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.

   3. Disadvantages

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

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

      3. Primary block failure necessitates intraoperative conversion to GA.

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

      5. Sympathectomy with neuraxial techniques may lead to vaso/venodilation and bradycardia that can precipitate profound hypotension, especially in patients who are hypovolemic. 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.

      6. Blockade of upper thoracic nerves may compromise pulmonary function in patients reliant on accessory muscles.

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

      8. Upper abdominal procedures (above the umbilicus at T10) are unlikely to be well tolerated under regional anesthesia alone. Spinal or epidural anesthesia for upper abdominal procedures may necessitate a sensory level of T2–T4. Although minute ventilation is maintained, paralysis of intercostal muscles from a high thoracic level impairs deep breathing, often resulting in an intolerable sensation of dyspnea. Intraperitoneal air or upper abdominal exploration commonly generates a dull pain referred to the C5 dermatomal distribution (usually over the shoulders) requiring supplemental intravenous (IV) analgesics.

A combined technique makes use of a regional technique along with a general anesthetic or MAC. This technique is often employed for extensive abdominal surgeries when an epidural and general anesthetic are used, or to avoid the need for GA such as an ESP or paravertebral block combined with MAC for a liver nodule microwave ablation. In either case, utilization of a regional technique will decrease intraoperative anesthetic requirements and postoperative pain.