Case series on anesthesia for video-assisted thoracoscopic surgery for congenital diaphragmatic hernia in children.

Video-assisted thoracoscopic surgery (VATS) in the pediatric population is a challenging task for any anesthesiologist, moreover considering the high incidence of associated congenital anomalies which are individual predictors of poor prognosis. A thorough preoperative evaluation, knowledge of the physiology of one lung ventilation - pertaining to various methods of lung isolation, individualized meticulous planning, and continuous vigilance to detect any untoward event at the earliest with good communication between the anesthesiology and surgical teams contributes to a safe and successful surgery. We present a case series of anesthetic management of congenital diaphragmatic hernia with VATS.

INTRODUCTION

The incidence of congenital diaphragmatic hernia (CDH) is 1:2000 to 1:3000 with a male: female ratio of 1:1.[1] Failure of development of a portion of the fetal diaphragm allows abdominal contents to enter the thorax, interfering with normal lung growth. About 80% of cases are due to a defect in the development of a portion of left posterior diaphragm (foramen of Bochdalek). More than half of these cases are associated with other congenital anomalies such as cleft lip, cleft palate, and congenital heart disease; which are the independent predictors of outcome.[2] Over 50 different syndromic associations are reported[3] and mutation of chromosome 15q26 is frequent.[4] CDH cases have a variable degree of pulmonary hypoplasia, altered surfactant system, and pulmonary vasculature with or without pulmonary artery hypertension. Patients commonly present in the neonatal period with respiratory distress and in some cases cyanosis, however, 10% present later in life.[56] We present a case series of anesthetic management of CDH with video-assisted thoracoscopic surgery (VATS).

CASE REPORTS

Case 1

A 1-year-old child, weighing 6.8 kg, presented with loss of appetite, vomiting, breathlessness, and cough for past 1-month; and frequent episodes of chest infections. On examination, child was lean and thin; afebrile, and pale with a respiratory rate of 40/min. On respiratory system examination, there was decreased chest movement on the left-side. On auscultation, there was decreased air entry at the left posterior side of the chest and peristaltic sounds were heard on left hemithorax. The abdomen was scaphoid and nontender. Hematologic investigations were within normal limits.

Chest roentgenogram was suggestive of possible congenital left Bochdalek hernia with herniation of gut loops and passive collapse of left lower lobe. Mediastinum was displaced to the right. A diagnosis of late-onset left CDH was made and was posted for surgery.

Case 2

A 10-month-old male child, weighing 8.0 kg, presented with the complaints of regurgitation of milk, vomiting, and cough with a recurrent chest infection. Ultrasound scan showed bowel loops in the thoracic cavity and congenital absence of left kidney. Abdominal and thoracic magnetic resonance imaging confirmed the diagnosis of a left posterolateral CDH. The hernial sac was found to contain the left kidney, left colic angle, and the spleen. The surgical repair was performed using thoracoscopy.

Case 3

A 16-month-old child, weighing 12 kg, presented with repeated episodes of bronchopneumonia, from the age of 8 months. Chest X-ray revealed the presence of a left diaphragmatic anomaly consistent with a CDH. An upper gastrointestinal contrast barium swallow demonstrated herniation of stomach and spleen into the left hemithorax. The surgical repair was performed thoracoscopically.

Anesthetic management

All the patients were kept nil by mouth for 6 h. Informed consent was taken pertaining to anesthetic risk. Intravenous ranitidine 2 mg/kg and metoclopramide 1.5 mg/kg was administered at night and morning of the surgery. Anesthetic plan constituted of general anesthesia with controlled ventilation along with one-lung ventilation achieved by selective main stem bronchus intubation with standard endotracheal tube (ETT). Following premedication with glycopyrrolate (0.01 mg/kg) and midazolam (0.05 mg/kg) intravenously, the children were preoxygenated with 100% oxygen. Pulse oximeter and electrocardiographic monitors were attached and intravenous fluids were started. Suction was done through a nasogastric tube. Cricoid pressure was applied, and rapid sequence induction was performed using fentanyl 2 µ/kg, thiopentone 5 mg/kg, and rocuronium 1.0 mg/kg. They were intubated with a standard cuffed orotracheal tube appropriate for age. Anesthesia was maintained using sevoflurane in oxygen and air. Patients were then placed in a right lateral decubitus position with head elevated. Epidural analgesia was facilitated by a 20-gauge epidural catheter inserted through an epidural needle placed through the sacrococcygeal membrane. The epidural catheter was then advanced up to 14 to 18 cm (measured distance from caudal to midthoracic level) and analgesia maintained with bupivacaine 0.125% and 2 µg/ml fentanyl was given at a rate of 0.2 – 0.3 mg/kg/h of bupivacaine.

The surgical procedure was performed using three ports; two 3 mm and one 5 mm port for the telescope. The abdominal contents were reduced into the abdomen by CO2 insufflation, and the pressure was not allowed to exceed 5 mm Hg. The contents were reduced by the laparoscope and the defect was repaired thoracoscopically.

Intraoperatively, patients were hyperventilated with 100% oxygen. Normal body temperature, intravascular volume, and acid-base status were maintained. Intraoperative course was uneventful. Postoperative analgesia was maintained with epidural infusion. All patients were electively ventilated postoperatively and extubated on the second postoperative day.

DISCUSSION

The anesthetic concerns in CDH for VATS are age of the patient, physiologically immature organ systems, restrictive lung disease, pulmonary hypoplasia, pulmonary vascular hypertension, associated congenital defects, and requirement of one-lung ventilation intraoperatively. Pulmonary complications such as hypoxemia, hypercarbia, impaired hypoxic pulmonary vasoconstriction, re-expansion pulmonary edema, atelectasis, and pneumonia are common in the perioperative period. Cardiac deformities, preoperative alveolar-to-arterial oxygen gradient >500 mm Hg, or severe hypercarbia despite vigorous ventilation are the forerunners of poor prognosis. There is always the possibility of some major vessel injury and torrential bleed. It is also difficult to assess the blood loss during thoracoscopy.[7] VATS can be performed while both lungs are being ventilated using carbon dioxide insufflation and placement of a retractor to displace lung tissue in the operative field, however, single lung ventilation (SLV) is extremely desirable.

Patients presenting for thoracoscopic surgery should undergo a similar preoperative evaluation to those presenting for open thoracotomy with special emphasis on the degree of pulmonary and cardiac dysfunction. It is customary to obtain a complete history, physical examination along with hemoglobin, serum electrolytes, arterial blood gases, chest roentgenogram, and a pediatric physician opinion to rule out other congenital anomalies. Chest physiotherapy, good nutrition, bronchodilator/antibiotic therapy and steroid supplementation, helps in optimizing the patient's condition prior to surgery.

In otherwise healthy patients, without airway compromise; intranasal midazolam 0.3 mg/kg or oral midazolam 0.5–0.75 mg/kg in children without intravenous access administered 15 to 20 min prior to anesthesia induction, provides anxiolysis. Blood loss during a diagnostic thoracoscopy is usually minimal, however, there is always a possibility of conversion to open thoracotomy, and therefore, advisable to have two venous accesses prior to the start of the procedure. In patients where severe cardiac instability and major hemodynamic fluctuations are expected, invasive arterial blood pressure monitoring is used. This facilitates monitoring of arterial blood pressure during manipulation of the lungs and mediastinum as well as arterial blood gas tensions during SLV. Atropine is administered as a vagolytic and antisialogogue. Antiemetics and H2 antagonists are administered in patients at risk for aspiration.

General anesthetic considerations are hyperventilation, minimizing inflating pressures, and avoidance of N2O. Hyperventilation to induce a respiratory alkalosis and 100% oxygen should be administered to decrease pulmonary vascular resistance. Sympathetic surges precipitating pulmonary hypertension should be avoided. Infants should be ventilated with small tidal volumes and low inflating pressures to avoid pneumothorax on the contralateral (usually right) side. A high index of suspicion of right-sided pneumothorax should be maintained, and a thoracostomy tube should be placed in the event of acute deterioration of respiratory or circulatory function. It is also imperative that normal body temperature, intravascular volume, and acid-base status be maintained. Mechanical ventilation is continued postoperatively in nearly all cases.

General anesthesia without lung separation can be contemplated on a case wise selection basis. CO2 insufflation into the operative hemithorax to facilitate collapse of the lung on the operative side is useful in smaller patients where lung isolation is not possible. Meticulous cardiopulmonary monitoring is mandatory as the displacement of intrathoracic contents and creation of an excessive pneumothorax can lead to significant cardiovascular compromise from decreased venous return or high left ventricular afterload. The effects of the artificial pneumothorax can be minimized by slowly adding the CO2 (flow rate 1 L/min) and limiting the inflating pressure from 4 to 6 mm Hg. Direct insufflations of CO2 into the lung parenchyma can cause a rise in etCO2 more than PaCO2. Subcutaneous emphysema and CO2 embolism are the other documented complications.

General anesthesia with one-lung ventilation is the standard practice.[8] Lung movement with general anesthesia can make intrathoracic surgical access difficult. This problem can be resolved with one-lung ventilation. This allows the lung on the operative side to be collapsed and motionless, facilitating exposure and surgical instrumentation.

Selective mainstem intubation is the simplest and quickly achieved means of one-lung ventilation in children. When the left bronchus is to be intubated, the bevel of the ETT is rotated 180° and the head turned to the right and advanced till breath sound disappear on the operative side.[9] This can be facilitated by fiberoptic bronchoscopy through or alongside the ETT. When a cuffed ETT is used, the distance from the tip of the tube to the distal cuff must be shorter than the length of the bronchus, so the cuff is not entirely in the bronchus. Cuffed ETTs tailored for age were used in our case as uncuffed tubes, might not be totally occlusive to avoid soilage and inadvertent ventilation of the operative side. Problems with this technique are that surgeon is unable to suction the operative lung, and hypoxemia may occur because of the obstruction of the upper lobe bronchus, especially when the short right mainstem bronchus is intubated.

Bronchial blockade can be facilitated with one of the Fogarty embolectomy catheter (it has stylete but no end-hole),[10] or an end-hole, balloon wedge catheter like arrow balloon wedge catheter; Cook bronchial blocker; or Arndt bronchial blocker; placed under flexible bronchoscopic (FOB) guidance. Those devices with a central channel provide the advantage of allowing some degree of suctioning through the channel, to deflate the operative lung, or for the application of positive airway pressure. The potential problem with this technique is dislodgement of the blocker balloon into the trachea. The inflated balloons will then block ventilation to both the lungs or prevent the collapse of the operative lung. The balloons of most catheters used for bronchial blockade have low-volume, high-pressure properties, and overdistention can damage or even rupture the airway. The use of this technique is generally limited to children between the age of 18 months and 2 years, as, even with the use of a smallest diameter FOB with a diameter of 2.2 mm, the indwelling ETT must be of at least 5 mm internal diameter to allow passage of the bronchial blocker and FOB.

The Univent tube (Fuji Systems, Tokyo, Japan) is a conventional ETT with a second lumen containing a small tube that can be advanced into a bronchus. Univent tubes are available in sizes as small as a 3.5 and 4.5 mm ID for use in children over 6 years of age.[11] A disadvantage of the Univent tube is the large amount of cross-sectional area occupied by the blocker channel, especially in the smaller size tubes. Smaller Univent tubes have a disproportionately high resistance to gas flow. The Univent tube's blocker balloon has low-volume, high-pressure characteristics so mucosal injuries can occur during normal inflation.

Placement of double lumen ETT in patients weighing <30–35 kg or younger than 8–10 years of age is questionable.

Once successful separation of the nonoperative and operative lung has been accomplished, anesthesia is maintained with a combination of intravenous and inhalational anesthetics. During thoracic surgery, several factors act to increase ventilation perfusion (V/Q) mismatch. General anesthesia, neuromuscular blockade, and mechanical ventilation cause decreases in the functional residual capacities of both the lungs. Surgical retraction or SLV results in the collapse of the operative lung. Hypoxic pulmonary vasoconstriction, which acts to divert blood flow away from the underventilated lung, thereby minimizing V/Q mismatch, may be diminished by inhalational anesthetic agents and other vasodilating drugs. These factors apply equally to infants, children, and adults. Lateral decubitus position has a variable effect on V/Q mismatch in infants compared with older children and adults.

Postoperative analgesia is particularly desirable for thoracotomy, but may also be beneficial for VATS, especially when thoracostomy tube drainage, a source of significant postoperative pain, is anticipated. A variety of regional anesthetic techniques have been described for intraoperative anesthesia and postoperative analgesia, including intercostal, intrapleural infusions, and epidural anesthesia as inadequate postoperative pain relief can cause rapid shallow breathing, thus, leading to atelectasis, retention of secretions, decrease in functional residual capacity, and increase in V/Q mismatching all of which contribute to hypoxemia.[12] Of the regional anesthesia techniques described, only epidural anesthesia facilitates excellent intraoperative anesthesia, a low risk of local anesthetic toxicity, and “titratable” postoperative analgesia. A 20-gauge epidural catheter can be passed indirectly via caudal route to midthoracic level in infants, and in older children, an epidural can be placed directly at thoracic level T4-T8. Though the safety of placing epidural catheters in anesthetized patients has been questioned, this technique is widely used by pediatric anesthesia practitioners.[13] The incidence of neurologic sequelae, related to epidural catheterization in pediatric patients, is unknown. Flandin-Bléty et al.[14] reported five cases of serious neurologic injury in a retrospective review of 24,005 regional anesthetics performed in France and Belgium over a 10-year period. All these patients were infants under 3 months of age, and the causes of neurologic injuries and associations with epidural anesthesia were unknown. In a separate retrospective survey of 119 pediatric hospitals, including more than 150,000 epidural blocks, there were no reports of permanent neurologic injuries, epidural hematomas, infections, or deaths.[15] The authors concluded that the risk of a major complication was less than approximately 1:10,000. This complication rate is consistent with that observed in adult patients who are usually awake and able to report pain or paresthesias during needle and catheter placement.

CONCLUSION

VATS in the pediatric population is a challenging task for any anesthesiologist. A thorough preoperative evaluation, knowledge of the physiology of one-lung ventilation, individualized meticulous planning, and continuous vigilance to detect any untoward event at the earliest with good communication between the anesthesiology and surgical teams contributes to a safe and successful surgery.