Anesthesia for pyloromyotomy in infants

INTRODUCTION — Infantile hypertrophic pyloric stenosis is one of the most common conditions requiring surgery in infants. This topic will discuss the anesthetic management of pyloromyotomy. Epidemiology, diagnosis, treatment options, and preoperative medical management are discussed in detail separately. (See "Infantile hypertrophic pyloric stenosis".)

PREOPERATIVE EVALUATION AND MANAGEMENT — In addition to the usual preanesthesia evaluation, infants with pyloric stenosis should be evaluated specifically for dehydration and electrolyte abnormalities. Patients generally present at three to five weeks of age with a history of projectile nonbilious vomiting due to gastric outlet obstruction at the level of the pylorus. Depending on the duration of symptoms and degree of stenosis, the vomiting can result in hypochloremic, hypokalemic, metabolic alkalosis, and dehydration. Surgery should be delayed until these abnormalities are corrected. (See "Infantile hypertrophic pyloric stenosis", section on 'Preoperative fluid and electrolyte management'.)

For patients diagnosed with pyloric stenosis, feeding is halted and an intravenous (IV) catheter is typically placed for hydration and correction of any electrolyte abnormalities while awaiting surgery. Preoperative alkalosis has been associated with increased time to extubation at the end of surgery [1] and postoperative apnea. The primary stimulus for ventilation in infants is the partial pressure of carbon dioxide (PaCO₂) and its effect on the pH of cerebrospinal fluid; therefore, even mild to moderate alkalosis can lead to postoperative apnea.

Management in anticipation of surgery and goals for preoperative preparation are discussed separately. (See "Infantile hypertrophic pyloric stenosis", section on 'Preoperative fluid and electrolyte management'.)

Patients are typically otherwise healthy, although they may have a history of prematurity. (See "Infantile hypertrophic pyloric stenosis", section on 'Epidemiology'.)

ANESTHETIC MANAGEMENT — The risk of aspiration during induction of anesthesia is a primary concern for anesthetic management in patients with pyloric stenosis. The incidence of aspiration in these patients is unknown.

Surgery is brief (20 to 30 minutes) with either laparoscopic or open techniques. (See "Infantile hypertrophic pyloric stenosis", section on 'Pyloromyotomy'.)

Emptying the stomach — We suggest emptying the stomach with an orogastric or nasogastric tube in the operating room just prior to anesthesia (general or neuraxial anesthesia), to minimize residual gastric contents with the goal of reducing the risk of aspiration. We pass a 10 or 14 french catheter into the stomach, and apply suction to the catheter with the infant in each of the supine, left lateral decubitus, and right lateral decubitus positions, to maximize stomach emptying [2].

Some clinicians routinely administer an anticholinergic (glycopyrrolate or atropine) before aspirating the stomach and prior to induction of anesthesia, to reduce the risk of bradycardia. Others feel that this is unnecessary or administer an anticholinergic only if the infant has other risks for bradycardia (eg, prematurity).

Gastric volumes in patients with pyloric stenosis may be large, whether or not they are managed with preoperative gastric suction. Immediate preoperative suctioning may not completely empty the stomach, and though it likely decreases the risk, suctioning does not eliminate concerns for aspiration. In a prospective observational study of 75 infants with pyloric stenosis who had three position gastric suctioning immediately before induction of general anesthesia (GA) for pyloromyotomy, the average gastric volume was 4.8 ± 4.3 mL/kg, and 83 percent of patients had a gastric volume of >1.25 mL/kg [3]. Retrieved gastric volumes were similar in patients who had preoperative gastric suction, preoperative upper gastrointestinal barium studies, or neither. In a subset of 15 patients who had upper endoscopy after induction of anesthesia, 14 patients had a residual volume (after preoperative suctioning) of ≤1 mL, though one patient had 1.8 mL/kg of gastric fluid.

Gastric volume is a surrogate endpoint used in most clinical studies of aspiration risk. There is not a known gastric volume that either eliminates risk or places a particular child at undue risk. In most studies, "at risk," stomach volume has been defined as >0.4 mL/kg, but this is based on animal studies without clear relevance to humans. (See "Preoperative fasting in children and infants", section on 'Rationale for preoperative fasting'.)

As point of care ultrasound is increasingly used in the operating room for a variety of purposes, gastric ultrasound has been used in clinical trials to assess gastric volume and contents in infants and children, including in infants with pyloric stenosis [4]. Gastric ultrasound is noninvasive, and in experienced hands can be performed quickly. However, similar to other methods for assessing gastric residual volume, results have not been correlated with the risk of aspiration, and further study is required before using gastric ultrasound to guide clinical decisions. (See "Overview of perioperative uses of ultrasound", section on 'Gastric ultrasound'.)

General versus neuraxial anesthesia — At the author's institution, we use GA for pyloromyotomy. Spinal anesthesia is possible, with theoretical advantages of reduced operating room time, and if sedation is avoided, reduced risk of postoperative apnea. However, spinal anesthesia has a relatively high rate of failure and the need for sedation in infants [5,6]; aspiration is a concern if supplementation with intravenous (IV) or inhaled anesthesia is required in a patient without a secured airway. Epidural and caudal anesthesia are not generally used because the large volumes and doses of local anesthetics required can approach the toxic range for infants.

●Open pyloromyotomy – A retrospective study compared outcomes for over 200 pyloromyotomies at each of two institutions, one of which used exclusively GA, while the other used almost exclusively spinal anesthesia [5]. Open pyloromyotomy was used for all patients at the institution that used spinal anesthesia, and in approximately one-half of the patients at the institution that used GA, with the remainder done laparoscopically. Spinal anesthesia was associated with shorter operating room times (17.5 minutes, 95% CI 13.5-21.4 minutes), and shorter postoperative length of stay, including in analysis restricted to open pyloromyotomies. However, 36 percent of patients who had spinal anesthesia required either supplemental anesthesia for incomplete block or conversion to GA for failed block. The incidence of adverse events was similar in the two groups.

●Laparoscopic pyloromyotomy – Although there are case reports of infants undergoing laparoscopic pyloromyotomy with spinal anesthesia, there currently are not enough data to conclude that spinal anesthesia provides reliable and adequate anesthesia for a laparoscopic approach. In a small retrospective study that compared spinal anesthesia with GA in 24 patients, spinal anesthesia had to be converted to GA in 3 of 12 patients who initially had spinals [7]. Time from the end of surgery to leaving the operating room was shorter after spinal anesthesia, though wake up time may have been prolonged by the large induction dose of propofol (6 to 7 mg/kg) used for GA.

Use of epidural and caudal anesthesia for open pyloromyotomy has been reported [8-10]. However, in all of these cases sedation or GA was used without protecting the airway with intubation. Though aspiration was not reported to have occurred, these studies were too small to assess the risk of aspiration.

There is increasing interest in alternatives to GA in young children because of concerns about potential for anesthesia-related neurotoxicity. However, the best available evidence suggests that a single brief exposure to anesthesia does not have detrimental long-term neurodevelopmental or cognitive outcomes in young children. These issues are discussed in detail separately. (See "Neurotoxic effects of anesthetics on the developing brain".)

General anesthesia

Choice of induction and intubation technique — A primary goal for induction of anesthesia is avoidance of aspiration. We suggest using a modified rapid sequence induction and intubation (RSII) for patients who undergo pyloromyotomy, to minimize the risk of aspiration while preventing oxygen desaturation. We induce anesthesia with propofol and rocuronium, and use low pressure mask ventilation with 100 percent oxygen until neuromuscular block is complete, followed by intubation with a cuffed endotracheal tube.

RSII, modified RSII, and awake intubation have been used, though inhalation induction is used by some. Awake intubation has historically been used, but has fallen out of favor. Since patients are typically resuscitated with IV fluid preoperatively, they come to the operating room with an IV catheter in place, which negates the advantage of an inhalation induction for most pediatric patients. (See "General anesthesia in neonates and children: Agents and techniques", section on 'Choice of induction technique'.)

In a single institution retrospective review that compared RSII with modified RSII in approximately 300 infants who underwent pyloromyotomy, hypoxemia was more common in patients who had RSII [11]. Hypoxemia (PaO₂ <90 percent) occurred in 30 percent of patients in the RSII cohort, compared with 17 percent of patients in the modified RSII cohort (adjusted odds ratio 2.8, 95% CI 1.5-5.3). Patients 30 days of age had a higher absolute risk of hypoxemia, and a higher relative risk with RSI compared with modified RSII (adjusted OR 6.5, 95% CI 2.0-22.2). There were no cases of aspiration.

The author and some other UpToDate contributors use video laryngoscopy for all RSIIs in infants to maximize the chance of first attempt success. This is discussed separately. (See "Airway management for pediatric anesthesia", section on 'Choice of intubation technique'.)

Some clinicians use apneic oxygenation during intubation for all neonates (<1 month of age), since they are at high risk of rapid desaturation during apnea, and have a higher incidence of unrecognized difficult intubation than older infants and children. This issue is discussed separately. (See "Management of the difficult airway for pediatric anesthesia".)

RSII — Rapid sequence induction and intubation (RSII) is a technique designed to intubate as rapidly as possible to protect the airway from aspiration. RSII entails preoxygenation, followed by simultaneous administration of an IV induction agent and a neuromuscular blocking agent (NMBA), avoidance of mask ventilation, and intubation as soon as neuromuscular block is established. Use of cricoid pressure to decrease the risk of passive regurgitation is controversial (see "Rapid sequence induction and intubation (RSII) for anesthesia"). Mask ventilation is avoided during RSII to prevent gastric insufflation and the associated increase in the risk of regurgitation. However, this classic RSII can be problematic in infants for several reasons:

●Faster onset of hypoxemia – Infants have increased chest wall elasticity and large abdomens, resulting in a decreased functional residual capacity compared with older children and adults. They also have a significantly higher oxygen consumption. These factors can cause profound oxygen desaturation even with short periods of apnea, despite adequate preoxygenation. (See "Emergency airway management in children: Unique pediatric considerations", section on 'Physiologic considerations' and "Complications of pediatric airway management for anesthesia", section on 'Hypoxemia'.)

●Difficulty with cricoid pressure – Identification of the cricoid ring and appropriate depth of cricoid pressure is more challenging in infants. Cricoid pressure may deform the compressible infant airway, leading to difficult intubation and even mask ventilation [12,13].

Modified RSII — We use a modified rapid sequence induction and intubation (RSII) for patients who undergo pyloromyotomy. Though there is not a standard definition of a modified RSII, in this setting we use the term to mean using low pressure ventilation (peak pressure <12 cm H₂O), after induction and while waiting for neuromuscular blockade, and avoidance of cricoid pressure. Low pressure mask ventilation is used to prevent oxygen desaturation, while minimizing the risk of gastric insufflation. We do not use cricoid pressure, as its benefit is unclear, and cricoid pressure can compress the infant trachea and make mask ventilation more difficult. [11,12,14,15].

Awake intubation — The proposed advantages of awake intubation include preservation of airway reflexes, decreased risk of aspiration, and safety in the setting of potentially undiagnosed airway abnormalities. However, awake intubation has been associated with soft tissue trauma, bradycardia, breath-holding, hypoxemia, and laryngospasm [15-17]. In addition, anesthesiologists may be reluctant to subject infants to awake laryngoscopy, without clear evidence of benefit.

In a single institution prospective observational study of 76 infants who underwent pyloromyotomy with awake intubation, RSII, or modified RSII, awake intubation was associated with higher need for multiple intubation attempts, and longer time to intubation; incidences of oxygen desaturation, bradycardia, and other complications were similar among groups [17].

Inhalation induction — Although it is uncommon practice in the United States, many anesthesiologists in other countries preferentially use inhalation induction for pyloromyotomy [14,18]. Reasons cited for this choice include the low overall risk of perioperative aspiration in pediatric patients, the absence of good outcome data to suggest that one type of induction is superior to any other, as well as a perceived high rate of airway complications supervising trainees in the performance of RSII. In a single institution retrospective review of 269 patients who underwent pyloromyotomy (94 percent with inhalation induction after nasogastric suction), there were no cases of aspiration, vomiting or severe hypoxemia during induction, though this study is likely too small to assess the risk of aspiration [18]. The benefit of an inhalation induction in a patient who already has an IV catheter in place is unclear.

Induction medications — During induction of anesthesia for pyloromyotomy, it is critical to achieve adequate depth of anesthesia and neuromuscular block prior to intubation. Vomiting and aspiration may be associated with inadequate anesthesia and paralysis [19,20].

●Induction agents – Induction agents (eg, propofol, ketamine) should be based on patient factors. Since most infants with pyloric stenosis are healthy and hemodynamically stable, we usually induce with propofol 3 mg/kg IV. (See "General anesthesia in neonates and children: Agents and techniques", section on 'Intravenous induction medications'.)

●Neuromuscular blocking agents – Either succinylcholine or rocuronium can be used for RSII in children.

•Succinylcholine 1 to 2 mg IV is often used for RSII because of its rapid onset and brief duration of action. However, the US Food and Drug Administration (FDA) has issued a boxed warning for succinylcholine for children, except for emergency airway management, over concerns for acute rhabdomyolysis and hyperkalemia in children with undiagnosed muscular dystrophies. Succinylcholine can be used for RSII, but appropriate screening is critical.

•Rocuronium 0.4 to 1 mg/kg IV can be used for RSII as well, though the duration of action of an intubating dose will generally outlast the surgical time for pyloromyotomy. Sugammadex can be used to reverse deeper levels of block from rocuronium than neostigmine. Dosing is similar to adults, based on the number of twitches with train of four neuromuscular monitoring (4 mg/kg IV if any twitches are present, with or without tetanus, 16 mg/kg if there are no twitches with or without tetanus) (see "Clinical use of neuromuscular blocking agents in anesthesia", section on 'Sugammadex'). Although sugammadex is FDA approved only for children >2 years of age, some clinicians use sugammadex "off label," in younger children, and it appears safe to do so [21-24].

Maintenance of anesthesia — Choice of agents for maintenance of GA should be based on patient factors.

●Maintenance anesthetics – Volatile inhaled anesthetics (eg, sevoflurane, desflurane) are used most commonly for children, though total IV anesthesia may be used for specific indications. (See "General anesthesia in neonates and children: Agents and techniques", section on 'Maintenance of anesthesia'.)

Nitrous oxide is usually avoided, particularly for laparoscopic procedures, because of its propensity to expand bowel gas (see "Inhalation anesthetic agents: Clinical effects and uses", section on 'Disadvantages and adverse effects'), particularly for laparoscopic procedures. If the surgery is done laparoscopically, to prevent expansion of bowel gas.

●Opioids – The author does not administer opioids during anesthesia for pyloromyotomy, though others do. Opioids are not required for postoperative pain for pyloromyotomy, and may increase the risk of apnea, delay feeding, and increase postoperative length of stay. (See 'Postoperative analgesia' below.)

Ultrashort-acting remifentanil may reduce the required dose of inhaled anesthetic without prolonging wake up or increasing risk of postoperative apnea [25].

●NMBA – If succinylcholine was used for intubation, administration of another NMBA may be required to facilitate surgery.

Antibiotics are not normally required.

Emergence from anesthesia — The patient should be extubated awake and able to protect the airway after pyloromyotomy.

POSTOPERATIVE ANALGESIA — Pyloromyotomy is a brief procedure with a small incision for open procedures, and small port incisions for laparoscopy. Multimodal analgesia (ie, acetaminophen along with local/regional anesthesia) without opioids is typically adequate for postoperative pain [26,27]. At the author's institution, patients receive intravenous (IV) acetaminophen during surgery, the surgeons infiltrate the incisions with local anesthetic, and the infants typically wake up comfortable. (See "Approach to the management of acute perioperative pain in infants and children", section on 'General approach to acute pediatric pain management'.)

With the above regimen and as needed postoperative acetaminophen, opioids are rarely necessary. Opioids may augment the risk of postoperative apnea in patients who already may be at increased risk due to prematurity or residual metabolic alkalosis. (See 'Preoperative evaluation and management' above.)

Opioids can also cause decreased gut motility, leading to feeding intolerance and potentially increased length of stay [28,29]. Use of perioperative opioids for pyloromyotomy varies widely. In a retrospective database study of over 25,700 infantile pyloromyotomies from the Pediatric Information Database in the United States over a 10 year period, 26.7 percent of infants received opioids during hospitalization [28]. Opioid use varied from 0 to 81 percent of cases by hospital; most opioids were administered intraoperatively. Infants who received postoperative opioids (but not infants who received only intraoperative opioids) had increased odds of prolonged hospital length of stay.

●Nonopioid analgesics – We suggest using perioperative acetaminophen for postoperative analgesia for children who are without severe liver disease. (See "Pharmacologic management of acute perioperative pain in infants and children", section on 'Acetaminophen'.)

●Nonsteroidal antiinflammatory drugs (NSAIDs) – NSAIDs such as ketorolac are generally avoided in infants due to uncertainty over benefits and potential adverse effects (eg, bleeding and renal dysfunction). (See "Pharmacologic management of acute perioperative pain in infants and children", section on 'Nonsteroidal antiinflammatory drugs'.)

●Local and regional anesthesia – Local anesthesia infiltrated at the surgical site (ie, incision or laparoscopy port sites) has become routine for many operations, including pyloromyotomy. infiltration of the surgical site with a long-acting local anesthetic (eg, bupivacaine or ropivacaine) by the surgeon can provide effective postoperative analgesia for several hours after surgery.

Single injection rectus sheath or transversus abdominus nerve blocks have also been used, primarily for open procedures [30,31]. Their value for laparoscopic procedures is uncertain. When the block is performed prior to skin incision, it can decrease or even eliminate the need for intraoperative opioids [27], and may reduce the required concentration of volatile anesthetic.

POSTOPERATIVE MONITORING FOR APNEA — Patients should be monitored for postoperative apnea for at least 24 hours after surgery, usually with continuous pulse oximetry. Postoperative care is discussed separately. (See "Infantile hypertrophic pyloric stenosis", section on 'Pyloromyotomy'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Pediatric anesthesia".)

SUMMARY AND RECOMMENDATIONS

●Preoperative evaluation and management – Infants with pyloric stenosis are at risk for dehydration, electrolyte abnormalities, and metabolic alkalosis, all of which should be corrected preoperatively. Metabolic acidosis is associated with postoperative apnea after pyloromyotomy. (See 'Preoperative evaluation and management' above.)

●Anesthetic management

•Empty the stomach – We suggest emptying the stomach with an orogastric or nasogastric tube in the operating room just prior to anesthesia (general or neuraxial anesthesia) to minimize residual gastric contents and reduce the risk of aspiration (Grade 2C). (See 'Emptying the stomach' above.)

•Induction and intubation – A primary goal for induction of anesthesia is to rapidly protect the airway from aspiration. For patients who undergo pyloromyotomy, we suggest performing a modified rapid sequence induction and intubation (RSII), rather than classic RSII, standard induction, or inhalation induction, to minimize the risk of aspiration while preventing oxygen desaturation. (Grade 2C) We use the term modified RSII to mean using low pressure ventilation (peak pressure <12 cm H₂O) after induction to prevent desaturation while waiting for neuromuscular blockade, and avoidance of cricoid pressure, which can make mask ventilation more difficult in infants. (See 'Choice of induction and intubation technique' above.)

The author and some UpToDate contributors use video laryngoscopy for the first attempt at intubation during RSII in neonates and infants. We use apneic oxygenation during induction and intubation in all neonates <1 month of age, since they are at high risk of rapid desaturation during apnea and have a higher incidence of unrecognized difficult intubation than older infants and children. (See 'Choice of induction and intubation technique' above and "Management of the difficult airway for pediatric anesthesia", section on 'Apneic oxygenation'.)

Adequate depth of anesthesia and neuromuscular blockade should be achieved prior to intubation to reduce the risk of vomiting and aspiration. (See 'Induction medications' above.)

•Maintenance of anesthesia – Intravenous or inhaled anesthesia can be used, based on patient factors. Nitrous oxide is usually avoided during pyloromyotomy due to its propensity to expand bowel gas. (See 'Maintenance of anesthesia' above.)

•Emergence from anesthesia – Patients should be extubated awake and able to protect the airway after pyloromyotomy. (See 'Emergence from anesthesia' above.)

●Plan for postop analgesia – Pyloromyotomy involves a small incision for open procedures, and small port incisions for laparoscopy. Multimodal analgesia (ie, acetaminophen along with local/regional anesthesia) without opioids is typically adequate for postoperative pain. (See 'Postoperative analgesia' above.)

●Postoperative apnea monitoring – Patients should be monitored for postoperative apnea for at least 24 hours after surgery, usually with continuous pulse oximetry. (See 'Postoperative monitoring for apnea' above and "Infantile hypertrophic pyloric stenosis", section on 'Pyloromyotomy'.)