Monday, March 22, 2021

Pyloric Stenosis Case File

Posted By: Medical Group - 3/22/2021 Post Author : Medical Group Post Date : Monday, March 22, 2021 Post Time : 3/22/2021
Pyloric Stenosis Case File
Lydia Conlay, MD, PhD, MBA, Julia Pollock, MD, Mary Ann Vann, MD, Sheela Pai, MD, Eugene C. Toy, MD

Case 40
A 4-week-old male infant is brought to the emergency room by his parents. He has been vomiting after feeding for approximately 1 week, more frequently over the last 2 days. For the past 12 hours or so the baby has been sleepy. His diapers are no longer as heavy with urine. On physical examination, he is well nourished, but with dry mucous membranes, poor skin turgor, and sunken fontanelles. He appears lethargic. Palpation of the abdomen shows an olive-size mass just above the umbilicus, and beneath the liver’s edge. A basic metabolic panel lists the NA+ 131 mEq/L, K+ 3.0 mEq/L, Cl– 95 mEq/L, HCO3 – 29 mEq/L, BUN 12 mg/dL, and creatinine (Cr) 0.6 mg/dL. Ultrasound of the abdomen reveals a pyloric muscle greater than 4 mm and longer than 16 mm, leadingto a diagnosis of infantile hypertrophic pyloric stenosis. He is scheduled for a surgical correction for this problem.

➤ How should this patient be prepared for his surgery?

➤ What are the anesthetic concerns in a patient undergoing a pyloromyotomy?

➤ How is the airway in a neonate different from the airway in an adult?


ANSWERS TO CASE 40:
Pyloric Stenosis
Summary: A 4-week-old male infant presents with persistent vomiting due to hypertrophic pyloric stenosis.

Preparation for surgery: Pyloric stenosis is a medical—not surgical—emergency. This patient has a fluid deficit and electrolyte imbalances which must be corrected before surgical correction of the hypertrophic pylorus. Fluid resuscitation and correction of metabolic derangements may require 24 to 48 hours.

Anesthetic concerns: Any patient who is vomiting is considered to have a full stomach. In addition, pyloric stenosis is an obstruction; therefore this patient is at increased risk of aspiration. The anesthetic plan needs to include steps to protect the patient’s airway from this possibility. In addition, pyloric stenosis is a congenital anomaly and patients who have one such anomaly are at increased risk to have other anomalies, any or all of which may affect the anesthetic plan. During the period of fluid resuscitation, a workup to preclude other congenital anomalies can take place.

Neonatal airway: The neonate’s airway differs from an adult’s in size, shape of the airway, shape of the epiglottis position of the glottis, position of the narrowest point, slanting of the vocal cords, and fixation of the mucus membranes. These characteristics combine to make intubation of the neonate’s
trachea much more difficult than that of an adult. (see Table 40–1).


ANALYSIS

Objectives
1. Recognize the most urgent medical issues associated with pyloric stenosis and their initial treatment.
2. Understand the anesthetic implications when caring for a neonate.
3. Describe the implications in caring for an infant with pyloric stenosis.

Table 40–1 DIFFERENCES IN THE NEONATAL AIRWAY

• Large tongue.

• Larynx is higher in the neck (C3-C4 vs C6 in the adult).

• Epiglottis is short, stubby, and angled over laryngeal inlet.

• Vocal cords slant anterior (vs transverse or slightly posterior).

• Larynx is funnel-shaped (vs cylindrical).

• Narrowest point is below cords (vs at the cords).

• Mucus membranes are loose, and susceptible to swelling.


Considerations
This young patient has presented to the emergency room with clear signs of dehydration (lethargy and low urine output) and laboratory studies showing electrolyte abnormalities. He has metabolic alkalosis, consistent with the vomiting associated with pyloric stenosis. This is a medical—not surgical— emergency. Appropriate treatment includes volume resuscitation, and stabilization of electrolyte imbalances prior to any surgical correction.

While the patient is receiving fluids, he should be examined for the presence of other congenital anomalies. Two other syndromes (among others) commonly found in the presence of pyloric stenosis are tracheoesophageal fistula and eosinophilic gastroenteritis, both of which could complicate his anesthetic care.

Once the child is euvolemic and his electrolytes repleted, he is ready for the operating room. Although the infant will not have eaten during his resuscitation, he is still considered to have a full stomach because of his hypertrophic pylorus, and the resulting obstruction which may not even allow passage of gastric secretions. Prior to the induction, the patient’s stomach must be emptied. An orogastric tube is passed into the infant’s stomach while he is awake and gastric contents suctioned. This process is sometimes repeated three times, with the infant first on his back, then in left lateral and right lateral positions.

Immediately after suctioning, the patient is pre-oxygenated (and denitrogenated) with 100% oxygen given by face mask. Most patients with pyloric stenosis arrive in the operating room with an intravenous in place. He is induced by a rapid-sequence induction, with cricoid pressure (some advocate intubating these patients “awake,” and prior to induction). Correct placement of the endotracheal tube is confirmed by observing equal and symmetric rise of both sides of the chest when breaths are delivered. Once correct placement of the endotracheal tube has been confirmed, the cricoid pressure may be released.

Once the patient’s airway is secured, general anesthesia is maintained with an anesthetic gas, and an opiate is administered for postoperative pain relief. At the end of the surgery, when the child is vigorous and awake, the endotracheal tube is removed and he is taken to the recovery room. The patient will be watched carefully over the next 12 to 24 hours as infants post-pyloromyotomy are more prone to postoperative apnea than other infants.


APPROACH TO
Pyloric Stenosis

CLINICAL APPROACH
Anesthetizing a neonate is fraught with hazards and surprises, few of them pleasant. Meticulous attention to detail is imperative, since matters unimportant in the adult, such as minute amounts of air in the intravenous line, may be catastrophic in an infant. Warming devices and/or the operating room
itself becomes the incubator. The neonate’s airway differs significantly from the adult’s, predisposing these young patients to difficulty with intubation (Table 40–1). Auscultation of bilateral breath sounds is not very useful to verify position of the endotracheal tube, as breath sounds are easily transmitted across the small chest. Similarly, tissues surrounding the airway are not firmly bound to subcutaneous tissue, predisposing to airway edema. There should be a small air leak past the endotracheal tube to help prevent damage to the patient’s trachea, and no more than 15 to 20 cm of H2O-positive pressure delivered to the lungs when giving a breath. Oxygen saturation is maintained between 93% and 95% to reduce the risk of retinopathy of prematurity. Although narcotics are tolerated, the potent inhalation agents may well not be.

The presence of pyloric stenosis, if improperly managed, adds a level of complexity to the anesthetic management of the neonate. This congenital anomaly typically presents in the first weeks of life, and occurs with a fourfold predominance in males. It is characterized by persistent, projectile, nonbilious vomiting, and a palpable hypertrophic mass (or “olive”) pyloric region also visible on noninvasive imaging. Peristaltic waves are often visible in the gastrium.

The persistent vomiting that occurs in patients with pyloric stenosis leads to hypovolemia and electrolyte imbalances which progress with the degree of dehydration. The classic picture is one of dehydration with a hypokalemic, hypochloremic alkalosis, possibly accompanied by a compensatory respiratory acidosis from hypoventilation and even periods of apnea. As the child’s dehydration worsens, circulatory shock may ensue, resulting in an entirely different picture: metabolic acidosis with compensatory respiratory alkalosis. Thus, the acid-base findings associated with pyloric stenosis may vary considerably, depending on the duration of the patient’s vomiting. However, most patients present with hypokalemic, hypochloremic alkalosis.

Resuscitative fluids for an infant are most often 5% dextrose with either 0.9% or 0.45% normal saline. Half the patient’s deficit should be given over the first 8 hours, another quarter over the second 8 hours, and the final quarter over a third 8-hour period. Maintenance fluids must be given as well. Potassium may be added to fluids once the patient has started to urinate. The patient is not ready for surgery until his serum chloride level is at least 90 mmol/L and his serum bicarbonate, no more than 26 mmol/L.

Once resuscitative fluids have been administered and any electrolyte imbalances corrected, the patient with pyloric stenosis is no different than any other neonate, with the possible exception of having a “full” stomach. Nevertheless, neonates are at a higher risk for complications than other patients. Because of the special circumstances surrounding their care, neonatal anesthesia is best performed by individuals familiar and practiced with this type of anesthesia.


Comprehension Questions
40.1. A 56-year-old man is brought to the emergency room with severe stomach pains. He has vomited four times in the last 12 hours and has had no bowel movement for 3 days. The surgeon determines that the patient needs an emergent laparotomy for a bowel obstruction. Which of the following is most appropriate to include in your anesthetic plan?
A. Medical management first with fluid resuscitation.
B. Standard induction of anesthesia with continued oxygenation after induction by delivery of positive pressure breaths before intubation.
C. Rapid-sequence induction of anesthesia.
D. Empty the patient’s stomach prior to induction of anesthesia.

40.2. A 2-year-old boy is brought to the pediatrician by his parents because although he is talking, his parents cannot understand him and have noticed that his tongue doesn’t move normally in his mouth. The pediatrician finds that the patient has a short frenulum which needs surgical correction. Which of the following should be included in your anesthetic plan?
A. A rapid-sequence induction because the patient had breakfast before seeing the pediatrician.
B. Ensuring that the patient has had a thorough examination for possible additional congential anomalies prior to the needed surgery.
C. Fluid resuscitation before surgery because the patient may not have been able to drink well with the restricted movement of his tongue.
D. Assume that the patient has other anomalies of the gastrointestinal tract and plan a rapid-sequence induction when surgery is scheduled.

40.3. A female neonate previously diagnosed in utero with gastroschisis is born early in the morning. Gastroschisis is a defect of the abdominal wall that results in exposure of the viscera which are not covered by peritoneum. The viscera are covered sterilely and the surgeon schedules surgery for the next morning. You consider your anesthetic plan and decide on which of the following?
A. The patient will need fluid resuscitation and maintenance over the next 24 hours to optimize her status in preparation for surgery.
B. She will need her stomach emptied prior to a rapid-sequence intubation.
C. The patient’s surgery should be postponed for more than 24 hours in order to have time to thoroughly examine the neonate for other congenital abnormalities.
D. You approach the surgeon because you believe that the patient needs surgery more urgently by the next morning.


ANSWERS
40.1. C. The management of an adult with a bowel obstruction usually differs from the management of a neonate with pyloric stenosis. This patient is likely somewhat (as opposed to severely) dehydrated, but because of the possibility of perforation, his need for surgery is emergent and there is little time for fluid resuscitation. This patient has a bowel obstruction and therefore a “full stomach,” and will need a rapid-sequence induction. A standard induction of anesthesia will pose a greater risk of aspirating gastric contents into his lungs before placement of the endotracheal tube. While emptying his stomach before induction of anesthesia would be optimal, adults do not tolerate this procedure as well as infants, and it is not usually done.

40.2. B. The patient has a problem which needs correction soon, but is definitely not emergent or urgent. His short frenulum is a congenital anomaly and the physicians caring for him have plenty of time to thoroughly examine for other anomalies prior to his surgery. Unless an anomaly of the GI tract is discovered (unlikely at this point as the patient is 2 years old), the patient can have a standard induction of anesthesia, which for a child of his age, will most likely be an inhalational induction using anesthetic gas.

40.3. A. Correction of gastroschisis is urgent. The viscera are exposed and severe dehydration and infection are constant threats to the life of this neonate. She needs to be euvolemic before this major surgery, and this can be accomplished over the 24 hour period before her surgery. Gastroschisis is not a bowel obstruction, and there is no need to empty the patient’s stomach before induction and intubation. While this congenital anomaly should prompt a search for other anomalies in this patient, her surgery should not be postponed until such examinations are complete.


Clinical Pearls
➤ Pyloric stenosis is a medical emergency, not a surgical emergency. The patient is often dehydrated and has a metabolic alkalosis, both of which need correction prior to pyloromyotomy.
➤ The neonate’s airway differs significantly from an adult’s, in ways that may make intubation difficult and predispose to airway edema.
➤ Neonatal anesthesia is fraught with hazards and unpleasant surprises, and is best left to individuals with special expertise in this type of anesthesia.

References

Bingham R. Hatchard Sumner’s Textbook of Paediatric Anaesthesia. 3rd ed. London, UK: Hadder Arnold; 2008: 75-76. 

Gregory George A, ed. Pediatric Anesthesia. 3rd ed. New York, NY: Churchill Livingston; 2001: 557-558. 

Kissin I. General anesthetic action: an obsolete notion. Anesth Analg. 1993;76:215. 

Kliegman RM, Behrman RE, Jenson HB, et al. Nelson’s Textbook of Pediatrics. 18th ed. Philadelphia, PA: Saunders Elsevier; 2007: 1555-1557.

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