Anesthesiology

Congenital Diaphragmatic Hernia

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What the Anesthesiologist Should Know before the Operative Procedure

Congenital diaphragmatic hernia (CDH) is a condition that develops early in gestation whereby abdominal organs, which may include midgut along with the stomach, colon, left kidney, and left lobe of the liver are extruded into the thoracic cavity through a defect in the diaphragm. The left posterior-lateral foramen of Bochdalek is the most common place for this defect to occur. The herniation of abdominal contents prevents normal pulmonary maturation, the mediastinum shifts and the contralateral lung is compressed and also has abnormal development. Simple compression of the lungs does not explain the whole picture that includes fewer alveoli with thickened walls, smaller alveolar gas exchange surface areas, decreased vasculature with medial hyperplasia, and extension of the muscle layer into intra-acinar arterioles.

The incidence is 1:2500 to 1:3000 live births.

CDH is frequently associated with:

  1. Lung hypoplasia

  2. Pulmonary hypertension

  3. Congenital abnormalities involving the CV, GI, GU, and skeletal, neural, and trisomic systems.

Advances in neonatal care such as "gentle" ventilation strategies with small tidal volumes, moderate PEEP (5-7 cm H2O), permissive hypercapnia, high frequency jet ventilation (HFJV), extracorporeal membrane oxygenation (ECMO), and use of nitric oxide (NO) in addition to delaying surgery to stabilize the infant have all improved survival from 40% to 60% in the 1980s to 70% to 80% in the 1990s.

Pulmonary hypoplasia includes a reduction in size and number of respiratory units, alveoli, and bronchioles, with a corresponding decrease in the pulmonary vascular bed. Decreased number of alveoli are also present in the contralateral lung, but to a lesser extent than the affected lung. Limited alveolar development occurs postnatally but the number of airway generations remains constant after midgestation. Postnatal vascular remodeling is also limited and occurs over the first 2 to 4 weeks of life. Both hypoplastic lungs have extensive muscularization of peripheral small arteries leading to thickening of the medial and adventitial layers. Survival rates have not improved since the 1990s because there is no treatment for the major underlying factors, which include the degree of pulmonary hypoplasia and pulmonary hypertension present.

Predictors of a poor prognosis include:

  1. Severe respiratory distress at birth requiring immediate intubation

  2. Birth weight less than 1000 grams

  3. Prematurity less than 33 weeks

  4. P(A-a)O2 gradient greater than about 500

Infants with CDH have poor lung compliance and underdeveloped lungs; therefore, the risk of pneumothorax is high in the perioperative period and primarily occurs in the "good" lung rather than in the stiff hypoplastic lung that is compressed by the herniated abdominal contents. Persistent fetal circulation (PFC) now called persistent pulmonary hypertension (PPH) is also of great concern in this period.

Associated syndromes

CDH is a key feature in some syndromes, such as Beckwith-Wiedemann, CHARGE (coloboma, heart, imperforate anus, renal and radial problems, genital and ear), Cornelia de Lange, pentology of Cantrell, and Denys-Drash.

1. What is the urgency of the surgery?

Historically the reduction of the abdominal contents was considered a surgical emergency. Current management strategy is to avoid surgery if possible while the infant is unstable. Attempts are made to optimize the patient's cardiopulmonary status in the NICU. Early intubation and decompression of the stomach which is frequently in the left hemithorax may be necessary.

Surgery on the neonate in utero is not presently a successful or recommended option for diaphragmatic hernia due to the increased risk of pre-term labor and no increase in survival.

What is the risk of delay in order to obtain additional preoperative information?

CDH is frequently associated with other anomalies. A complete work up is indicated, with special attention to CV lesions.

Patients with CDH should be stabilized in the NICU prior to surgery since they have been shown to have higher survival.

Emergent: Not applicable since stabilization is recommended.

Urgent: Not applicable since stabilization is recommended. Surgical repair causes a decrease of 10% in respiratory compliance. This suggests that pulmonary dynamics may deteriorate with early repair of the hernia. Therefore, delayed surgery is recommended in order to allow transition to a stable postnatal cardiorespiratory status.

Elective: Prenatal diagnosis of CDH occurs in 60% of cases. The common findings include displacement of the heart and a fluid-filled bowel in the thorax. Presently fetal endoscopic tracheal occlusion procedures remain investigational; survival rates for this operation are not better than conventional stabilization methods. Infants with CDH are referred to be delivered at centers with pediatric surgeons, anesthesiologists, and other advanced neonatal therapies including NO, HFJV, and ECMO. Signs and symptoms at birth include cyanosis, dyspnea, and apparent dextrocardia. Physical examination reveals a scaphoid abdomen with decreased breath sounds and bowel sounds in the chest. CXR shows bowel gas pattern in the chest, and mediastinal shift. All systems should be optimized prior to bringing the infant to the operating room.

2. Preoperative evaluation

Preoperative care should start in the delivery room with early intubation and decompression of the stomach. Minimizing volutrauma from positive ventilation is critical. Preductal oxygen saturations should be kept at 90% to 95%, PaCO2 is allowed to be 60 to 65 mmHg and a pH higher than 7.30.

Patients with congenital diaphragmatic hernia should have a transthoracic echocardiogram to identify any cardiac anomalies, and to estimate pulmonary artery pressures.

Increase in pulmonary vascular resistance, triggered by stress, acidosis, and hypoxia, can cause a return to a fetal circulatory pattern, called PPH. In this situation blood is shunted from right to left at both the patent foramen ovale and the patent ductus arteriosus. Patients should have preductal and postductal pulse oximetry measurements. Wide variance in values indicates persistent pulmonary hypertension with right-to-left shunting at the level of the ductus arteriosus. Trials of NO and HFJV are the first lines of treatment before escalating to ECMO.

Routine laboratory values should be reviewed and include, complete blood count, electrolyte panel, arterial blood gas measurements, serum glucose, and coagulation panel. Patients intubated in the NICU frequently have chest radiographs which should be reviewed. Placement of a right radial arterial line is important so that preductal oxygen levels can be measured. Arterial and venous access should be assessed. Blood products should be available for the surgery.

3. What are the implications of co-existing disease on perioperative care?

The degree of pulmonary hypoplasia as well as complications such as a pneumothorax will affect the timing of surgery as well as the time to extubation and/or decannulation from ECMO.

Surgery is often deferred until the patient is stable off ECMO. However, if surgery is undertaken while the patient is on ECMO, bleeding is a major concern.

b. Cardiovascular system:

Persistent fetal circulation/persistent pulmonary hypertension may be treated with volume (monitor CVP and urine output), NO, vasopressors, and ECMO. PPH is diagnosed when hypotension and/or acidosis have triggered an increase in PVR. A gradient is usually observed between preductal and postductal oxygen saturations. The degree of pulmonary hypertension can be measured on echocardiography. The cardinal echocardiographic features, if increased pulmonary artery pressure is present, are flattening of the intraventricular septum, development of tricuspid regurgitation, and right-to-left or bidirectional shunting at the ductal level. The presence of the tricuspid regurgitation jet allows one to estimate right ventricular pressure. Identification of the ductus is also important because as long as this is widely patent it allows the right ventricle to decompress and prevents right heart failure when the right ventricular pressure becomes suprasystemic.

A new finding of preductal desaturation in a previously stable infant might indicate that the ductus has closed or become restrictive and, if confirmed by echo, would warrant a trial of prostaglandin (PGE1) to open the ductus and prevent right ventricular heart failure. Right-to-left ductal shunting is not harmful as long as preductal saturations are maintained over 85%, as this reflects adequate cerebral oxygenation. Infants who demonstrate significant ductal shunting or elevated right ventricular pressure can be tried on inhaled nitric oxide. Ductal shunting with low systemic pressures can also be improved with the use of intravascular volume expansion and inotropic support.

Baseline coronary artery disease or cardiac dysfunction – goals of management

Blood pressure, heart rate, O2 saturation, pH, and CVP should be normalized.

c. Pulmonary:

The hallmark of congenital diaphragmatic hernia is hypoplastic, poorly compliant lungs, and pulmonary artery hypertension. Early intubation and ventilation with ventilation strategies that minimize volutrauma have been shown to increase survival. Additionally inhaled NO is effective in treating pulmonary hypertension.

Every effort should be made to avoid factors known to contribute to pulmonary hypertension such as light anesthesia, hypothermia, hypoxia, acidosis, and excessive hypercapnia.

d. Renal-GI:

N/A

e. Neurologic:

Risk for intraventricular hemorrhage can be reduced with appropriate level of stress reduction with narcotics and close control of PT/PTT for the patient on ECMO. Ultrasound evaluation of the head may be performed to evaluate this complication of therapy. Sodium bicarbonate should be administered in half strength concentration in order to avoid IVH.

f. Endocrine:

N/A

g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (e.g., musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

Nondepolarizing neuromuscular blocking agents are part of the anesthetic plan. Neonates may have a prolonged response to long-acting neuromuscular blocking drugs such as rocuronium and pancuronium, so these drugs should be monitored with a peripheral nerve stimulator, even if the drug will be continued in the postoperative period, to avoid prolonged duration of action. Intermediate-acting agents such as vecuronium and cisatracurium are also acceptable.

4. What are the patient's medications and how should they be managed in the perioperative period?

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

Pulmonary hypertension is a hallmark of CDH. Inhaled NO is a vasodilator which can be administered exogenously in inhaled form. Due to its rapid scavenging and inactivation in the blood by hemoglobin, its location of action is limited to the pulmonary vasculature. NO also has bronchodilating properties, and has been suggested to improve V/Q matching. This drug is administered in doses starting at 10 to 20 ppm.

Extracorporeal membrane oxygenation is a means to oxygenate and ventilate that has been used in infants. The most common means to institute ECMO is via cannulae in the venous and arterial system (VA). Veno-venuos ECMO has also been described in CDH Infants. Intracranial hemorrhage is a complication of this treatment especially with severely preterm infants.

i. What should be recommended with regard to continuation of medications taken chronically?

Medications such a narcotic, NO, antibiotics, and pressors/ECMO should be continued.

j. How to modify care for patients with known allergies

No modification is necessary.

k. Latex allergy - If the patient has a sensitivity to latex (e.g., rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

N/A

l. Does the patient have any antibiotic allergies - Common antibiotic allergies and alternative antibiotics

N/A

m. Does the patient have a history of allergy to anesthesia?

Malignant hyperthermia (MH)

Documented: Avoid all trigger agents, such as succinylcholine and inhalational agents. Follow a proposed general anesthetic plan: total intravenous anesthesia with propofol ± opioid infusion Ensure that an MH cart is available [MH protocol].

5. What laboratory tests should be obtained and has everything been reviewed?

Routine laboratory values should be reviewed, and include complete blood count, electrolyte panel, arterial blood gas measurements, serum glucose, and coagulation panel.

Hemoglobin levels:Newborns have a high hemoglobin level.

Electrolytes:Electrolytes should be normalized prior to GA.

Coagulation panel:Clotting studies, PT, INR, and PTT as well as platelet count should be obtained.

Other tests: Evaluation of cardiac status with ECHO and chest radiography preoperatively is appropriate.

Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?

General Anesthesia

Due to the often severe pulmonary derangements present in patients with CDH, general anesthesia with controlled mechanical ventilation is the only practical mode of anesthesia. Both inhaled anesthetic agents and high-dose narcotics may be chosen. Neuromuscular blocking drugs are necessary

Monitored anesthesia care: Not applicable to repair of congenital diaphragmatic hernia.

6. What is the author's preferred method of anesthesia technique and why?

An infant with CDH is stabilized when O2 saturations are greater than 90% on as low an inspired oxygen delivery system as possible (preferably less than 50% FiO2) with pH of 7.35 to 7.45 and PCO2 of 35 to 55 with conventional or high frequency oscillation or, if need be, on ECMO. Cardiovascular evaluation and support include normovolemia as per CVP between 5 to 5 cm as well as minimal pressor support to maintain mean blood pressure 35 to 45 mmHg for term infant.

Emergency medications epinephrine (1-10 mcg/kg doses), sodium bicarbonate (0.5-1 mEq/kg), calcium gluconate and chloride, milrinone, dopamine and epinephrine infusions, and nitric oxide are prepared. Blood products are available.

Temperature control to avoid the stress of hypothermia (<35ºC) is important. For an open abdominal approach, the infant is positioned on the operating table with Bair Hugger in place, warming lights on, and elevated room temperature. Two IV, a CVP, and an right radial arterial catheter are inserted. If persistent pulmonary hypertension occurs with shunting, the right radial artery value will give the preductal oxygen value, which reflects cerebral oxygenation. Routine monitors including NIBP and a precordial stethoscope should be used. When the stethoscope is placed on the right chest and decreased breath sounds are noticed, a main stem intubation or a pneumothorax may be present.

The airway is evaluated, a newborn will take a 3.0 to 3.5 ET, preferably with a cuff so that PEEP of 4 to 5 mmHg may be used. The ET depth should be evaluated with chest radiography to see that the ET tip is appropriate and bilateral breath sounds are present. A term newborn with a 3.0 cuffed ET should be placed at 9 cm. The tube may be suctioned with a 6 French suction catheter and the baby's head positioned so that the ET does not kink or move either in or out. Care should be taken to record and use the smallest peak inspiratory pressure to produce tidal volumes of 5 mL/kg with a respiratory rate of 20 to 40 in order to attain as end-tidal PCO2, 35 to 55.

When the abdominal incision is made and retractors are used, the PIP may need to be increased to maintain tidal volume and prevent acidosis. Hypoxia (oxygen saturation <85-90%), acidosis (pH <7.25), hypothermia (<34ºC), and an increase in catecholamine release due to inadequate anesthesia can all contribute to persistent pulmonary hypertension, which may result in right-to-left shunting of blood through the patent foramen ovale or patent ductus arteriosus, bypassing the pulmonary circulation and continuing the cycle of hypoxia and hypotension.

Treatment includes increased oxygen delivery (100% oxygen), decreasing the PCO2 and treating acidosis with sodium bicarbonate (0.5-1 mEq/kg) for a base deficit of –5 or greater, calcium gluconate (20-30 mg/kg) for peripheral administration, and 10 to 20 mg/kg calcium chloride for central administration to increase the systemic vascular resistance. Inhaled nitric oxide should be available to be delivered in the operating room in 10 to 20 ppm to treat pulmonary hypertension. Relaxation of pulmonary pressures will allow for an increase in pulmonary blood flow, a decrease in right-to-left shunt, increased systemic perfusion, and an increase in preductal O2 saturations.

Therefore, the other serious event that may occur is pneumothorax, primarily in the healthier right lung. One is tempted to use higher peak inspiratory pressures since the hypoplastic (usually left) lung is more stiff. Pneumothorax is diagnosed with a high level of suspicion, sudden desaturation, equal change in preductal and postductal O2 saturation, decreased breath sounds on the right side not due to change in endotracheal tube placement, and chest radiographic evidence. Treatment is with placement of a chest tube.

Normovolemia is maintained utilizing the CVP (5-15) and urine output (0.5-1 mL/kg/hr) as guides.

Electrolytes, hemoglobin, and ABGs should be monitored frequently.

Considerations that are different if the surgical approach is thoracoscopic/laparoscopic

Insufflation with CO2 will increase the PCO2, so increased peak inspiratory pressures, respiratory rates, and tidal volumes are necessary to maintain normal pH and oxygenation. This may be enough to preclude using these approaches successfully.

What do I need to know about the surgical technique to optimize my anesthetic care?

The left thoracoscopic approach is common for left-sided lesions. When the abdominal organs are pushed back into the abdomen, there is adequate room in the thorax for the surgeon to repair the diaphragm. However, this approach is not recommended if decreased ventilation will tip the balance in a stable infant to trigger persistent pulmonary hypertension. When an open procedure is chosen, the most common approach is abdominal, and gastrointestinal anomalies can be corrected with this approach. A patch may be necessary to repair the diaphragm. Avoiding excessive inspiratory pressures and maintenance of oxygenation are the primary intraoperative challenges. As in all neonatal procedures, positioning of the ET tube, as well as its obstruction with blood or secretions or due to kinking, needs to be observed. High suspicion for signs of pneumothorax and persistent pulmonary hypertension with right-to-left shunting should be observed.

The diagnosis of pneumothorax (often on the right "good" lung) is made when decreased breath sounds on the right along with an increase in peak inspiratory pressures accompanied by hypotension and hypoxia. High suspicion, physical findings, CXR if possible, and immediate treatment with insertion of a chest tube are indicated. Signs of persistent pulmonary hypertension also can be a sudden onset of hypoxia and hypotension, where stress, hypoxia, or acidosis has caused an increase in pulmonary vascular resistance with resultant shunting of blood from right to left through the patent foramen ovale. This is diagnosed when the preductal O2 saturation falls, and breath sounds are unchanged.

Treatment is increased FiO2, treatment of acidosis and hypercarbia, increased depth of anesthesia, increased systemic vascular resistance with inotropes and vasopressors, and the addition of inhaled nitric oxide.

What can I do intraoperatively to assist the surgeon and optimize patient care?

Small tidal volumes will assist the surgeon in both an abdominal or a thoracoscopic approach. Keeping the infant warm and continuing BP and HR control as preoperative are important.

What are the most common intraoperative complications and how can they be avoided/treated?

Pneumothorax and persistent pulmonary hypertension are the most common intraoperative complications. Small to moderate tidal volumes with permissive hypercarbia should be maintained. Vigilance in observing changes in ventilatory parameters is important as well as attention to ABG, glucose, volume status, and temperature.

Complications

Cardiac: Persistent pulmonary hypertension may occur and is triggered by light anesthesia, stress, hypoxia, and acidosis. Treatment includes increasing FiO2, sodium bicarbonate for acidosis, blood pressure support with fluids and inotropes, and reducing PVR with NO.

Pulmonary:Hypoxia and pneumothorax (in the "good" lung) may occur.

a. Neurologic:

IVH may occur when patient has abnormal coagulation and is hypertensive.

b. If the patient is intubated, are there any special criteria for extubation?

Patients with CDH typically arrive in the operating theater intubated on full ventilatory support. It is unusual to extubate the patient immediately after hernia reduction.

c. Postoperative management

These patients typically return to the NICU, where they are often maintained with advanced monitoring and advanced ventilatory techniques. Long-term outcome includes pulmonary, gastrointestinal, nutritional, and neurocognitive disorders. Approximately half of survivors require bronchodilators and inhaled steroids for their ventilator-induced and disease-related lung injury, of which some do improve over time. Additional issues include growth failure, oral aversion, GER, neurocognitive delay, and behavioral disorders.

What's the Evidence?

Boloker, J, Bateman, DA, Wung, JT, Stolar, CJ. "Congenital diaphragmatic hernia in 120 infants treated consecutively with permissive hypercapnea/spontaneous respiration/elective repair". J Pediatr Surg. vol. 37. 2002. pp. 357-66.

(The majority of infants with life-threatening CDH treated with permissive hypercapnea/spontaneous respiration/elective surgery survive to discharge with minimal pulmonary morbidity.)

"Estimating disease severity of congenital diaphragmatic hernia in the first 5 minutes of life". J Pediatr Surg . vol. 36. 2001. pp. 141-5.

(A total of 1,054 patients with CDH were evaluated from 1995 to 1999 with an overall survival rate of 64%. For the first 322 patients, factors associated with outcome included birth weight, Apgar scores, gestational age, race, immediate distress, presence of cardiac anomaly, and prenatal diagnosis. Multivariate analysis showed that birth weight and 5-minute Apgar scores were most useful in a predictive equation. A logistic equation using these 2 variables could separate the next 673 patients into high, intermediate, and low risk of death, and this correlated closely with the actual outcome. Stratifying neonates with CDH into broad risk groups should allow better comparison of outcomes data from different centers, reserving novel and high-risk strategies for patients with a high likelihood of dying.)

Dillon, PW, Cilley, RE, Mauger, D, Zachary, C, Meier, A. "The relationship of pulmonary artery pressure and survival in congenital diaphragmatic hernia". J Pediatr Surg. vol. 39. 2004. pp. 307-12.

(The evolution of pulmonary hypertension is a critical determinant of survival in CDH patients with current treatment strategies. Three groups can be modeled with markedly different clinical performance patterns. Using serial cardiac ECHO examinations, pulmonary artery pressure estimations can be used to predict clinical outcome.)

Nakayama, DK, Mutich, R, Motoyama, EK. "Pulmonary dysfunction in surgical conditions of the newborn infant". Crit Care Med. vol. 29. 1991. pp. 926-33.

(Preoperative ECMO was associated with an increase in respiratory system compliance of more than 60% for 1 week, a significant difference from respiratory system compliance among patients undergoing emergency CDH repair (p < .05). These observations provide physiologic evidence of possible benefits of preoperative stabilization before repair of CDH.)

Stege, G, Fenton, A, Jaffray, B. "Nihilism in the 1990s: the true mortality of congenital diaphragmatic hernia". Pediatrics. vol. 12. 2003. pp. 532-5.

(The mortality of CDH when complete case ascertainment is achieved is unaffected by new therapies. The survival rate is principally determined by the rate of antenatal termination and the incidence of associated anomalies. Reports of improved survival of CDH should be interpreted with caution, as variations in outcome are more likely to be explained by case selection artifact.)

Azarow, K, Messineo, A, Pearl, R, Filler, R, Barker, G, Bohn, D. "Congenital diaphragmatic hernia: a tale of two cities: the Toronto experience". J Pediatr Surg. vol. 32. 1997. pp. 395-400.

(Conventional ventilation with HFOV produced equal survival to conventional ventilation with ECMO in two comparable series. Pulmonary hypoplasia was the principal cause of death. This continued high mortality at both centers suggests that new therapies are required to improve outcomes.)

Mugford, M, Elbourne, D, Field, D. "Extracorporeal membrane oxygenation for severe respiratory failure in newborn infants". Cochrane Database Syst Rev. vol. 16. 2008. pp. CD001340.

(Apolicy of using ECMO in mature infants (without DH) with severe butpotentially reversible respiratory failure results in significantlyimproved survival without increased risk of severe disability. However,the benefit of ECMO for babies with diaphragmatic hernia is unclear.)

Shah, SR, Wishnew, J, Barsness, K, Gaines, BA, Potoka, DA, Gittes, GK, Kane, TD. "Minimally invasive congenital diaphragmatic hernia repair: a 7-year review of one institution's experience". Surg Endosc. vol. 23. 2009. pp. 1265-71.

(Minimally invasive surgery has been described for the repair of congenital diaphragmatic hernias (CDHs) in neonates, infants, and children. This report evaluates patient selection, operative technique, and clinical outcomes for minimally invasive surgery repair of CDHs from a single center's experience.)

Bohn, D. "Congenital diaphragmatic hernia". Am J Resp Crit Care Med. vol. 166. 2002. pp. 911-5.

Brett, C, Davis, PJ, Davis, PJ, Cladis, FP, Motoyama, EK. "Smith’s anesthesia for infants and children". Elsevier. 2011. pp. 554-8.

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