Intraoperative jet ventilation during aortic coarctation repair in an infant

Abstract

The patient was a 7-week-old, 1,930-g female triplet born at a gestational age of 32 and 3/7 weeks. The birth weight was 1,330 g. Immediately after birth, echocardiography revealed a large patent ductus arteriosus and an isolated short-segment aortic coarctation. Past surgical history included a colostomy shortly after birth for imperforate anus. Additional neonatal issues included ventilatory support for 2 to 3 days, grade I intraventricular hemorrhage, and occasional episodes of apnea and bradycardia. At 7 weeks of age and a weight of 1,930 g, elective repair of the coarctation and ligation of the patent ductus arteriosus were planned. An arterial blood gas obtained while breathing room air, 24 hours before coming to the operating room, revealed pH 7.38, PaCO2 49 mmHg, PaO2 86 mmHg, and bicarbonate 28.1 mEq/L with an oxygen saturation of 96%. The preoperative chest x-ray was negative for pulmonary infiltrates. For the case, an Ohmeda 210 SE anesthesia machine (Madison, WI) was used. The infant was held nil per os for 6 hours, and intravenous fluids of 5% dextrose in 1/2 normal saline were administered at a maintenance rate of 8 mL/h. After transport to the operating room, standard ASA monitors plus a transcutaneous CO2 monitor (TCM-3; Radiometer, Copenhagen, Denmark) were placed. The pulse oximeter probe was placed around the right hand. Glycopyrrolate (0.05 mg) was administered intravenously. Anesthetic induction consisted of fentanyl (incremental doses to a total of 10 g/kg) followed by neuromuscular blockade with cisatracurium to facilitate tracheal intubation with a 3.0-mm endotracheal tube (ETT). An audible airleak was noted at 18 cmH2O. The ETT was taped at 8 cm at the alveolar ridge. A right radial arterial catheter and a second peripheral intravenous catheter were placed. The patient was positioned in the right lateral decubitus position and prepared for surgery. The patient tolerated surgical incision without changes in her hemodynamic status. Anesthesia was supplemented as needed with isoflurane (expired concentration 0.2%-0.3%) and intermittent doses of cisatracurium administered to provide ongoing neuromuscular blockade. Initial ventilatory management included positive-pressure ventilation with a fraction of inspired oxygen concentration (FIO2) of 1.0, rate of 34 breaths/min, inspiratory-to-expiratory ratio of 1:2, and a peak inflating pressure (PIP) of 26 cmH2O, which provided adequate chest excursion. The oxygen saturation measured by pulse oximetry was 100%, and the transcutaneous CO2 was 32 to 36 mmHg. During surgical manipulation of the lung on the operative side to obtain surgical visualization of the coarctation, there were frequent episodes of oxygen desaturation into the 60% to 70% range, which resolved with discontinuation of lung retraction. During this time, the transcutaneous CO2 increased to 64 mmHg. Repeat arterial blood gas analysis revealed a pH of 7.23 and a PaCO2 of 62 mmHg. There were persistent episodes of oxygen desaturation despite hand ventilation with a PIP up to 36 to 38 cmH2O, several variations of surgical retractor placement, and assurance of correct ETT placement without inadvertent mainstem intubation. Because of the inability of the surgeon to gain appropriate visualization of the aorta without significant oxygen desaturation, HFJV was started using the Bunnell Life Pulse High-Frequency Ventilator (Bunnell Inc, Salt Lake City, UT) with initial settings of PIP of 30 cmH2O, rate of 420 breaths/min, inspiratory time of 0.02 seconds, and F IO2 of 1.0. Repeat arterial blood gas analysis revealed a pH of 7.57, a PaCO2 of 26 mmHg, PaO2 of 382 mmHg, and a bicarbonate of 24.4 mEq/L with an oxygen saturation of 100%. There were no further oxygen desaturations during lung retraction/compression. Aortic cross-clamp time was 14 minutes, and the aortic coarctation was repaired without difficulty. ABG analysis after release of the cross-clamp revealed a pH of 7.53, a PaCO2 of 26 mmHg, a PaO2 of 460 mmHg, and a bicarbonate of 22 mEq/L. After closure of the thoracotomy, the patient was returned to conventional mechanical ventilation without consequence. The infant’s trachea was extubated on the first postoperative day. The remainder of the postoperative course was unremarkable. DISCUSSION Thoracic surgical procedures may require alterations in ventilatory management to allow for adequate visualization. In the majority of cases, this is accomplished by using techniques of one-lung ventilation or merely retraction/compression of the lung to avoid interference with surgical visualization. Although, in most circumstances, these techniques are well tolerated without periods of hypoxemia; in rare instances, patients may not tolerate these alterations in respiratory mechanics. In the authors’ patient, retraction or compression of the lung on the operative side resulted in hypoxemia and hypercarbia, which necessitated re-expansion of the lung to allow for adequate ventilation and oxygenation. When several different maneuvers of conventional ventilation failed, HFJV provided adequate ventilation and oxygenation without impairing surgical visualization. In such circumstances, before using HFJV, appropriate maneuvers to rule out mainstem intubation are indicated as well as discontinuation of agents that interfere with hypoxic pulmonary vasoconstriction.