What is the anesthetic plan, and what are the intra-operative and postoperative concerns in this patient?
The patient should be transported to the operating room in a warmed isolette and placed on a forced-air warming blanket. Gastric decompression should be done if it has not already been performed. Monitors should be placed before preoxygenation. The pulse oximeter probe should be placed on the right hand in order to monitor preductal oxygen saturations. If post-ductal oxygen satura-tions are measured, you may be delivering a higher con-centration of oxygen than necessary, increasing the risk of retinopathy of prematurity. Premedication with atropine will help to reduce secretions and prevent the bradycardia sometimes seen in infants during laryngoscopy. A rapid sequence intravenous induction with cricoid pressure fol-lowed by endotracheal intubation should be performed. An awake intubation may cause further extrusion of abdominal contents. A mixture of air and oxygen is used, maintaining the oxygen saturation between 90% and 95%. A balanced technique using a volatile anesthetic and intravenous opioid, such as morphine or fentanyl, may be used for the anesthetic maintenance. In order to avoid distention of the gastro-intestinal tract, nitrous oxide is avoided. Maximal muscle relaxation should be provided in order to facilitate the sur-geon’s attempt to replace the bowel in the abdomen.
The decision whether a primary closure will be tolerated or whether a gradual reduction of the hernia will be neces-sary is determined intraoperatively. A primary closure can lead to multiple organ system dysfunctions, including the pulmonary, circulatory, renal and gastrointestinal systems, if there is excessive intra-abdominal pressure. Intra-abdom-inal pressures of up to 20 mmHg are usually well tolerated. Visualizing the lower extremities as well as measuring pulse oximetry and blood pressure in the lower extremities may help determine whether primary closure will be tolerated. Monitoring peak airway pressures during the closure will also provide information about the appropriateness of the primary closure. Alternatively, intra-abdominal pressures can be indi-rectly measured through either the nasogastric tube or the Foley catheter. If central venous pressure is monitored, increases greater than 4 mmHg are associated with compro-mised venous return and a decrease in cardiac index.
Ventilation and fluid management are the major concerns both intraoperatively and postoperatively. Ventilatory requirements may change during the surgical procedure as the bowel is returned to the abdomen. Large amounts of balanced salt solutions are often necessary to replace losses from the exposed bowel. Peripheral circulation, urine output, blood pressure, and acid-base measurements are helpful in assessing the adequacy of fluid resuscitation.
If a primary closure is performed in a patient with a large defect, the patient is kept intubated and muscle relax-ation is continued until the intra-abdominal pressure has decreased to an acceptable level. If a silon chimney is used for a gradual reduction and closure, the patient’s trachea can usually be extubated. A daily reduction is done without anesthesia in the neonatal intensive care unit. The patient is returned to the operating room for final closure of the abdominal defect.