Abdominal Wall Defects (omphalocele and gastroschisis)
Both present as extracorporeal abdominal contents, however they are significantly different in that omphaloceles are covered (less risk of infection or dehydration) and gastroschisis is not. Additionally, 20% of infants with omphalocele will have a congenital heart lesion, and many others will have other organ defects (ex. Beckwith-Wiedemann – cognitive deficits, hypoglycemia, CHD, large tongue, and omphalocele), whereas lesions associated with gastroschisis are usually abdominal in nature. Preoperative management should focus on fluid resuscitation (start with isotonic fluids, titrate to a UOP of 1-2 cc/kg/hr), minimizing heat loss, treating sepsis, and avoiding trauma. Preoperative respiratory failure in omphalocele is a risk factor for mortality [Tsakayannis DE et. al. J Pediatr Surg 31: 1088, 1996] Surgery can be delayed for several days, but when it occurs can have a dramatic impact on ventilation/oxygenation (i.e., placing extruded intestines back into the abdominal cavity) as well as cardiac output and SBP. Invasive arterial and central venous monitoring is often indicated, as is a pulse oximeter on the foot (allows one to assess distal circulation). Some authors advocate measuring nasogastric pressure through an NG tube to assess whether or not a staged closure is necessary – if P < 20 mm Hg, closure can proceed, otherwise a Dacron silo may be needed [Yaster M et. al. Anesthesiology 69: 84, 1988] Fluids generally average 10-100 cc/kg/hr and glucose should be given at 3-4 mg/kg/min. SpO2 should be maintained between 95 and 97%. Avoid N2O. High dose opiates are acceptable because almost all of these children will be ventilated post-operatively. During surgery, incision of the omphalocele covering can release vast amounts of fluid, which are lost and must be replaced. TPN is usually required postoperatively, so be sure to establish appropriate access while the patient is anesthetized. Neonates may remain intubated for up to 7 days. Renal perfusion is often decreased, leading to renin release and subsequent hypertension.
- Establish adequate IV access
- Place an arterial line for frequent labs and to monitor rapid hemodynamic shifts
- Beware of lung hypoplasia and/or abnormal thoracic development (common in large omphaloceles), as well as the difficult airway (common in Beckwith-Wiedemann syndrome)
- Minimize fluid losses, using isotonic fluids
- Muscle relaxation is often required to allow abdominal closure
- Place a pulse oximeter on the foot to evaluate lower extremity perfusion
Incidence 1:3000. 86% are type IIIB (esophageal atresia with a distal TEF), and 8% are type I (discontinuous esophagus with no fistula). 60-65% will have at least one other abnormality (VACTERL = vertebral, anal, cardiac, TE, renal, and limb abnormalities) and 15-25% of these infants will have a congenital heart defect [Greenwood RD et. al. Pediatrics 57: 87, 1976]. Preoperatively, the patient must be protected from aspiration (1. avoid feeding 2. upright position 3. intermittently suction the blind esophageal pouch 4. abx and physiotherapy if pneumonia does develop) and dehydration. Awake tracheal intubation is the safest approach in these patients, minimizing the risk of gastric distension and subsequent pulmonary compromise. Small doses of fentanyl (0.2-0.5 ucg/kg) or morphine (20 – 50 ucg/kg IV) prior to intubation may be helpful. An alternative to awake intubation is asleep induction, either via inhalation or intravenous agents. Inhalation induction is accomplished by first suctioning (blood clots and secretions often block the ETT, so frequent suctioning is often required), applying a facemask, spraying lidocaine, and intubating during spontaneous respiration. The IV induction / paralytic agent technique may lead to distension of the stomach and fistula, which can be dangerous. Thus, unless a gastrostomy tube is in place, an inhalational induction is the first choice after awake intubation. Once intubated, the endotracheal tube should ideally be placed between the fistula and the carina – to do this, intubate the bronchus, then pull back just enough to inflate both lungs. Beware of inadvertent entry into the fistula itself! If the TEF is of “H-type” (< 1%) the anesthesiologist may have to help locate it. The surgeon will use a bronchoscope to pass a wire into the distal esophagus. The neonate is then intubated, after which an esophagoscope is used to pull the proximal end of the wire into the mouth – this allows for localization of the fistula on imaging. Always place an arterial line prior to the start of the case. Repair is usually performed via a right extrapleural thoracotomy (lung is dropped, neonate in the left lateral position). A precordial stethoscope in the dependent axilla will help identify obstruction of the mainstem bronchus, which is common during surgical retraction. A fall in SpO2 may mean that the retracted lung needs to be reexpanded. Retraction/thoracotomy can compress the great vessels, trachea, heart, and vagus. These infants usually require 100% oxygen, despite the risk of the retinopathy of prematurity. Blood should be immediately available for transfusion. After the TEF is ligated, the anesthesiologist passes a catheter in to the blind esophageal pouch (surgeon from below), after anastamosis the distance from the mouth to the tip is noted and no catheter longer than this may be used. Most infants will be ventilated 24-48 hrs after surgery secondary to tracheomalacia. Esophageal dysmotility and reflux are common, as are long-term obstructive and restrictive forms of lung disease.
- Minimize preoperative risk of aspiration
- Prevent dehydration
- Awake intubation (vs. inhalation induction)
- Note that 20-25% have cardiac abnormalities
- Frequent ETT suctioning (blood clots, secretions)
- Place an a-line preoperatively
- If SpO2 falls during thoracotomy, the non-dependent lung may need to be re-inflated
- Anesthesiologist will pass and measure catheter into esophagus
- Long-term effects: esophageal dysmotility, reflux, obstructive and restrictive lung disease
Congenital Diaphragmatic Hernia
Incidence is 1:4000. 70% occur on the left, although pulmonary hypoplasia is often present on both sides of the thorax. The lungs are often hyperreactive. Goal of initial management is to avoid surgery when the infant is hypoxic and acidotic (mortality has improved to ~ 40% with a trend towards permissive hypercapnea [avoids barotrauma – keep preductal SpO2 > 85% using peak pressures < 25 cm H2O] and delaying surgery. Some neonates, however, have no chance of survival). Infants may have normal APGARs at 1 minute, but will deteriorate in minutes/hours. Signs and symptoms include scaphoid abdomen, unilateral breath sounds, apparent dextrocardia, respiratory distress, and rarely bowel sounds in the thorax. PPV with facemask is very risky because the lungs are noncompliant and distension of the stomach and intestines can further compress the thoracic contents. Early intubation and gastric decompression are key. Do not be fooled by the “honeymoon period” many of these infants experience – most will suddenly return to a state of pulmonary hypertension and clinical deterioration, and attempts to lower PVR are often futile. Consider high-frequency oscillatory support (although it has not been shown to improve survival [Katz AL et. al. Clin Perinatol 25: 219, 1998]), inhaled nitric oxide (also not shown to help [NINOS. Pediatrics 99: 838, 1997], except possibly after ECMO), or even ECMO (which may be effective in patients with an a priori mortality or > 80% [CDH Study Group. J Pediatr Surg 34: 720, 1999]). Also consider prophylactic surfactant [Katz AL et. al. Clin Perinatol 25: 219, 1998] Virtually all of these infants require intubation prior to surgery as well as NMJ blockade. If sudden deterioration does occur, always consider a contralateral pneumonthorax. Avoid nitrous oxide during surgery. Key point: 25-30% of these infants will have a cardiac anomaly [Greenwood RD et. al. Pediatrics 57: 92, 1976]
- Avoid surgery in the hypoxic/acidotic infant
- Avoid PPV and facemask (stomach inflation highly dangerous)
- Important initial steps include tracheal intubation and gastric decompression (often before surgery)
- Preductal SpO2 > 85%, peak pressure < 25 cm H2O, pCO2 < 55 mm Hg
- Consider prophylactic surfactant
- Do not be fooled by the pre-surgical “honeymoon period”
- Always keep pneumothorax on the differential
- Volatile anesthesia with opiates and NMBD is ideal, although surgery can be performed on ECMO with opiates and NMBD alone
- Arterial catheter is indicated due to the need for frequent laboratory measurements
Multiple causes, including duodenal obstruction, imperforate anus, malrotation, etc. Patients will often be sodium and potassium deficient. Those with malrotation or volvulus are at high risk for pulmonary aspiration (awake intubation or RSI may need to be employed). Volvulus patients are often acidotic and may not tolerate volatile anesthesia, thus consider using ketamine. The preferred technique is caudal + light volatile GA, as this leads to earlier extubation. Adequate paralysis is essential. That said, some neonates, either because of their preoperative state or the extent of surgery, will remain intubated postoperatively.
Incidence 1:1000. The majority of these patients will have a Chiari II malformation, and 90% of myelomeningocele patients will require a shunt. In most cases, these children go to the OR within 24 hours of birth, almost always within 72 hours. These children will usually need multiple surgeries over the course of their lives, thus latex precautions should be initiated [Shah S et. al. J Allergy Clin Immunol 101: 741, 1998] Patients should be intubated either supine lying on a donut or lateral. Avoid paralytics as neuromonitoring may be required. Spinal anesthesia has been used successfully with no anesthetic neurologic complications, at least in one case series of 14 patients [Viscomi CM et al. Anesth Analg 81: 492, 1995]. Postoperatively, these patients may have respiratory complications as 20% will have lower brainstem dysfunction from Chiari II, and thus may suffer from apneic episodes, stridor, bradycardia, aspiration, or vocal cord paralysis.
- Latex precautions
- Intubate supine on a donut (or lateral position)
- Avoid paralytics
- Consider a central neuraxial technique
Late Neonate (< 1 month)
Primarily effects infants < 32 weeks gestational age, incidence in very low birth weight infants is 5-15%. Produces a coagulative/ischemic necrosis (platelets 50-75,000/mm3) with prominent inflammatory response, usually occurring subsequent to perinatal asphyxia or cardiopulmonary instability. NEC is non-operative (normal treatment is NPO, antibiotics, fluids/electrolytes, and insertion of a peritoneal drain) unless there is evidence of necrosis or perforation. Patients usually require NG decompression, parenteral nutrition, and correction of hematologic abnormalities. From an anesthetic standpoint, understanding the preoperative status of these children is paramount. They must be monitored for signs of ductus arteriosus and/or congestive heart failure. Sepsis, acidosis, and hypovolemia must be addressed. Often they are already intubated, but do NOT tolerate volatile agents. Consider 0.5 – 1.0 ucg/kg ketamine every 20-30 minutes, adding fentanyl at 2-3 ucg/kg if tolerated. If surgery is needed, they often require arterial and CVP monitoring with frequent blood gases. In preterm infants, inspired oxygen should be titrated to SpO2 of 90-95% (not higher: retrolenticular dysplasia?), and N2O should be avoided. Volatile anesthetics are poorly tolerated, and should only be used in low concentrations to supplement IV anesthesia. Fluid losses can be enormous and should be replaced with isotonic solutions. Transfuse if hematocrit drops below 30%. Parenteral nutrition is essential after infection and metabolic instability are addressed.
- Address sepsis, acidosis, hypovolemia, and coagulopathies preoperatively if possible
- Place an arterial line for frequent labs and to monitor rapid hemodynamic shifts
- Avoid volatile anesthetics if possible
- Use isotonic solutions
The biggest concern is coexisting conditions – Rescorla’s study of 100 infants < 2 months of age undergoing this repair showed that 42% had a history of respiratory distress syndrome, 31% had incarcerated hernias, 30% were premature, and 19% had congenital heart disease [Rescorla FJ et al. J Pediatr Surg 19: 832, 1984]. The recent movement towards earlier surgery will likely dilute these coexisting pathologies, as healthier infants are no longer waiting 12 months for surgery. Inguinal repair is amenable to general or regional anesthesia (or both). Consider an ilioinguinal/iliohypogastric block or simply local infiltration.
Fluid and electrolyte imbalances are the most significant preoperative considerations in these patients (ex. hypokalemic hypochloremic metabolic acidosis, dehydration). IV fluids can usually correct these within 6-12 hours, after which surgery is acceptable. Pyloric stenosis is a medical emergency, not a surgical emergency, this it is critical to resuscitate the infant prior to surgery. Some anesthesiologists treat these infants as though they had a full stomach and recommend NG tube followed by RSI, others believe that inhalational or non-RSI IV induction is acceptable. A barium swallow is sometimes helpful in this regard. Many of these procedures are now being performed laparoscopically. Regardless, paralysis is required in two separate instances – once to deliver the pylorus, and once to return it to the abdomen. Consider a caudal block in these patients as it provides muscle relaxation, reduces anesthetic requirements, and provides post-operative analgesia.
When indomethacin fails, as it often does in very premature neonates, the PDA must be ligated surgically. The traditional means was accomplished with open surgical ligation, and anesthesia was best provided with high-dose fentanyl (20-25 ucg/kg), pancuronium, and fluid resuscitation (10-15 cc/kg). Duration of action was not a concern as these infants often remained intubated post-operatively. Recently, however, a video-assisted procedure was developed, which uses smaller incisions and no rib splitting [Burke RR et al. Pediatrics 104: 227, 1999]
Central Venous Catheterization
Done under general anesthesia with endotracheal intubation. Major complications are due to 1) airway management 2) bleeding 3) pneumothorax.
Tonsillectomy and Adenoidectomy
Upper airway lymphoid hyperplasia can lead to obstructive sleep apnea, increased infections, and, although rare, pulmonary hypertension and subsequent cor pulmonale. Note that a recent study of 300 children (excluding those with frequent infections or OSA) aged 2-8 showed that tonsillectomy and adenoidectomy was not justified on a cost-benefit basis [Buskens E et al. Arch Otolaryngol Head Neck Surg. 133: 1083, 2007] Because of their potentially altered anatomy, children undergoing tonsillectomy and/or adenoidectomy are at increased risk for airway complications. Anticholinergics can be used to decrease pharyngeal secretions. Do not paralyze patients with a history of airway obstruction or apnea – instead, use an inhalational induction without paralysis. Consider a reinforced or RAE tube. Beware occult blood loss, and ensure through suctioning of the pharynx prior to extubation. Deep extubation decreases the chance of laryngospasm and may prevent blood clot dislodgment from coughing, however most anesthesiologists prefer an awake extubation to reduce the risk of aspiration. PONV is common. Post-operative bleeding is rare but possible, and may produce restlessness, pallor, tachycardia, or hypotension. If reoperation is necessary, replete volume, place an NG tube, and induce via rapid-sequence induction with cricoid pressure. Because of the possibility of bleeding and airway obstruction, children younger than 3 years old may be hospitalized for the first postoperative night.
- Consider patients at high risk for airway complications
- Avoid paralysis if a history of obstruction or apnea is present
- Consider glycopyrrolate to reduce secretions
- Consider a reinforced or RAE tube
- Suction adequately before extubation (awake preferred by most)
Myringotomy and Insertion of Tympanostomy Tubes
Usually undertaken to relieve pediatric patients from repeated upper respiratory infections/otitis media. The myringotomy is simply a radial incision in the tympanic membrane, which releases fluid that may be present – tympanostomy tubes provide a long-term benefit. Unfortunately, these patients often have URI symptoms on the day of scheduled surgery. The procedure itself usually takes < 15 minutes, thus inhalational induction with N2O, oxygen, and sevoflurane is acceptable. N2O can be used because there is not enough time for this expansive gas to accumulate in the middle ear prior to the myringotomy. IV access is often not necessary, assuming the patient is otherwise healthy, and ventilation with a facemask or LMA (as opposed to endotracheal intubation) can minimize the risk of perioperative respiratory complications.
In addition to obvious cosmetic considerations, scoliosis can also affect cardiac and respiratory function (and even produce RVH secondary to prolonged PVR from chronic hypoxia) – standard respiratory abnormalities include reduced lung volumes and chest wall compliance. SpO2 is reduced due to V/Q mismatching, whereas pCO2 is usually normal (an increase in pCO2 is a sign of severe disease). Pulmonary function tests should be considered prior to surgery, as should arterial blood gases (to check pCO2), and electrocardiography (to check for RVH). Complications of corrective surgery include significant blood loss, prone positioning, and the remote possibility of paraplegia and/or postoperative blindness. SSEPs and MEPs are recommended. Patients often remain intubated postoperatively, overnight. The patient population to be particularly aware of are young males with scoliosis secondary to muscular dystrophy, as they are at increased risk for malignant hyperthermia, arrhythmias, and adverse reactions to succinylcholine (hyperkalemia, myoglobinuria, and sustained muscular contractures).