Abstract

Due to smaller incisions, fewer wound injuries, and a shorter time of recovery, laparoscopic procedures are becoming increasingly popular in pediatric surgery, but the safety of their application in low-body-weight or premature infants should be a major concern. Here we present a case report of a 3-month-old premature infant, who developed a sudden change of hemodynamic instability while undergoing a laparoscopic Nissen's fundoplication for gastroesophageal reflex disease. This was thought to result from an accidental passage of massive insufflation of carbon dioxide gas across the diaphragm, leading to pneumomediastinum.

Keywords

infant; laparoscopy; mediastinal emphysema; premature;

1. Introduction

The clinical experiences of laparoscopic surgery in infants and children with congenital defects are limited in certain countries and hospitals; however, the evolving trend of laparoscopy, whether diagnostic or therapeutic, is going to gain in popularity in pediatric surgery.¹ Although the physical responses to abdominal insufflation are well documented in adult patients, the unique responses of pediatric patients to this change of abdominal cavity pressure may be underestimated by many anesthesiologists who are not familiar with the pediatric laparoscopy and its associated impact on respiratory and cardiac physiology. Currently, the safety of laparoscopic surgery application in low-body-weight or premature infants, and the ideal insufflation pressure for pneumoperitoneum, is still controversial.

Laparoscopic surgery has some detrimental side effects. Carbon dioxide (CO₂) pneumoperitoneum causes respiratory acidosis, presumably from absorption of the insufflated gas. The pneumoperitoneum required for laparoscopic surgery leads to several important hemodynamic alterations.² Due to a decrease in stroke volume, cardiac output decreases by up to 30% during laparoscopic surgery. Pneumoperitoneum also causes an increase in systemic vascular resistance. As a result, the mean arterial pressure remains unchanged or can increase up to 16%. Patients with marginal cardiac performance may warrant invasive cardiac monitoring, to assure they tolerate pneumoperitoneum. Joris et al³ demonstrated that these hemodynamic changes were, at least in part, due to intravascular volume status, and could be ameliorated by preloading patients with isotonic fluid and achieving pneumoperitoneum in the supine position, rather than the reverse-Trendelenberg position.

Pneumomediastinum, with a reported incidence of around 1.9%, is well tolerated in adult patients without any significant cardiovascular effects.⁴However, the impact of its external cardiac compression in premature, low-body-weight infants has not been recognized. We report a premature infant who encountered pneumomediastinum that resulted in severe cardiovascular deterioration during a laparoscopic Nissen fundoplication procedure.

2. Case report

The patient was a 3-month-old premature male infant, born via vaginal delivery at a gestational age of 27 weeks and 3 days with a birth weight of 1020 g. His Apgar scores were 8 and 9 at 1 and 5 minutes, respectively. Before the day of surgery, he weighed 2580 g, and had a body length reaching 42 cm. Aside from premature birth, he was relatively healthy. Gastroesophageal reflux was diagnosed, however, when he was observing repeatedly vomiting after feeding, and laparoscopic Nissen's fundoplication was scheduled to relieve this symptomatic reflux.

The patient arrived in the operating room without any premedication in the ward. Induction for general anesthesia commenced with inhaled sevoflurane, slowly increasing the concentration from 4% to 6% through a fitting mask. Before intubation, atropine 0.05 mg and ketamine 3 mg were administered intravenously. A 3.0 endotracheal tube was inserted into the trachea with the aid of a straight-blade laryngoscope and fixed periorally at the mark of 9.0 cm. Bilateral equal breath sounds were confirmed via a stethoscope and the ventilation was achieved by the Datex-Ohmeda Aestiva-5 anesthesia machine. To maintain an appropriate blood level of oxygen, a maximum inspiratory pressure of 15 cm H₂O and a respiratory rate of 25 times/minute were set accordingly. Anesthesia was maintained mainly with sevoflurane, to provide an adequate level of analgesia and muscle relaxation. The patient's vital signs and physical status were under close observation, by monitoring pulse oximetry, and using electrocardiography (EKG), non-invasive blood pressure monitoring, and capnography. The performance of the anesthesia machine was also confirmed by an anesthesia gas monitor.

The laparoscopic procedure began with the insertion of surgical trocars; pneumoperitonium was achieved from abdominal insufflation with CO₂ and the intra-abdominal pressure was maintained around 10 mmHg. To better visualize the surgical field, the patient was placed in a steep reversed Trendelenburg's position. At the beginning, the operation proceeded uneventfully, but 15 minutes into the surgery after CO₂ insufflation, we found that both the pulse oximeter and the blood pressure were unrecordable, and the heart rate decreased gradually from 140 to 125 beats per minute. Moreover, the end-tidal carbon dioxide also suddenly dropped from 34 mmHg down to 18 mmHg, and the EKG monitor showed a widened QRS change, premature atrial contractions, and severe ST segment elevation in long lead II (Fig. 1). Physical examination showed weak carotid artery pulsations, and subcutaneous emphysema around the neck and anterior chest area, and auscultation revealed a significant decrease of bilateral breath sounds, thereby further confirming systemic hypotension. To immediately correct the hypotension, 3 mg of titrated ephedrine was given intravenously; however, there was no improvement in stabilizing the patient's hemodynamic status. We then turned the surgical table back to the neutral position, turned off the sevoflurane and gave the patient full oxygen support. To increase myocardial contractility and systemic vascular resistance, dopamine infusion was administered according to the patient's response. The surgery was promptly stopped and pneumoperitonium was quickly deflated, in order to reduce the intra-abdominal pressure and increase venous return. A portable chest X-ray examination was ordered straight away.

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Fig. 1. Intraoperative lead II electrocardiography (EKG) revealed widened QRS change, premature atrial contractions and severe ST segment elevation.

The chest X-ray did not show a pneumothorax; however, the distinct heart border and the gas extending from the mediastinum that separated the pleura (extrapleural air sign)⁵ implied the possibility of pneumomediastinum (Fig. 2). The patient's vital signs returned to acceptable ranges after the management described above. The resumed surgery was converted to the traditional open method, and was completed uneventfully, without any further respiratory abnormality or hemodynamic disturbance. The duration of the whole procedure lasted 3 hours and 10 minutes and the anesthesia time was 4 hours. After the surgery, the patient was transferred directly to the PICU for further therapy without extubation.

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Fig. 2. Intraoperative immediate portable chest X-ray revealed distinct heart border and gas extending from the mediastinum and separating the pleura (extrapleural air sign).

3. Discussion

Laparoscopy seems to be a safer and more superior method than open surgery, even for patients in the neonatal age group. The abdominal wall in infants and children is more pliable and the peritoneal cavity is smaller than in adults. The volume of gas insufflation necessary to maintain pneumoperitoneum in adults is typically 2.5–5.0 L of CO₂, while a 10 kg patient requires only 0.9 L.⁶ The insufflation pressure used in adults is 15 mmHg; however, intra-abdominal pressure should be limited to 5–10 mmHg in neonates and infants and 10–12 mmHg in older children.7, 8Gas flow rates in infants are as low as 2–3 L/min, while up to 40 L/min is used in larger adult patients and in situations where gas leakage must be overcome to maintain adequate abdominal distention.

The unique responses to abdominal insufflation in pediatric patients underscore the important role of anesthesiologists in pediatric laparoscopy and its associated impact on respiratory and cardiac physiology. Firstly, hypercapnia is more evidently noted in pediatric laparoscopy, because insufflated CO₂ gas is more readily absorbed across the peritoneum than in adults.⁹ CO₂ uptake is more efficient, given the shorter distance between capillaries and the peritoneum, as well as an increased absorptive area of peritoneum in relation to body weight. Hypercapnia can be overcome by increasing minute ventilation and sometimes by giving postoperative ventilation support. Secondly, abdominal distension will induce a significant increase in vagal tone and associated bradycardia, which may require subsequent abdominal desufflation.¹⁰ Finally, these patients may develop hypotension and bradycardia during the reverse Trendelenburg position. Volume loading and administration of vagolytic drugs help to prevent this problem.

Fundoplication involves surgical dissection and manipulation at the esophageal hiatus under continuous intra-abdominal insufflation with CO₂. At high intra-abdominal pressure levels, dissection of an esophageal hiatus may even permit the passage of insufflated gas across the diaphragm, occasionally causing pneumothorax and pnemomediastinum.¹¹Thangathurai et al¹² noted the development of intraoperative crepitation at the sternal notch, which was most often correlated with the presence of pneumomediastinum on immediate postoperative chest radiography. Some institutions even require a routine postoperative chest X-ray exam.

The pneumoperitoneum required for laparoscopic surgery leads to several important hemodynamic alterations in pediatric patients. In certain circumstances, decreasing the inflation pressure slightly may be enough to safely continue a laparoscopic approach. However, the ideal insufflation pressure during laparoscopic surgery in low body weight or premature infants is still controversial. When the laparoscopic approach is accompanying severe complications or hemodynamic derangements, surgeons must be willing to convert to open surgery, rather than risking further iatrogenic damages. Anesthesiologists also play an important role in the immediate diagnosis and prompt treatment.