PEDIATRIC ANESTHESIA SOCIETY FOR PEDIATRIC ANESTHESIA SECTION EDITOR WILLIAM J. GREELEY The Effect of Transesophageal Echocardiography on Ventilation in Small Infants Undergoing Cardiac Surgery Dean B. Andropoulos, MD*, Nancy A. Ayres, MD†, Stephen A. Stayer, MD*, Sabrina T. Bent, MD*, Carlos J. Campos, MD*, and Charles D. Fraser, MD‡ Divisions of *Pediatric Cardiovascular Anesthesiology, †Pediatric Cardiology, and ‡Congenital Heart Surgery, Texas Children’s Hospital and Baylor College of Medicine, Houston, Texas Transesophageal echocardiography (TEE) is frequently used during congenital cardiac surgery. Complications are infrequent, but interference with ventilation has been reported, especially in small infants. Ventilation variables were measured prospectively in 22 infants, 2–5 kg, undergoing heart surgery with TEE. Measure- ments were made preoperatively before and after TEE probe insertion and postoperatively before and after TEE probe removal. The variables measured included arterial blood gases, expired tidal volume, peak inspira- tory pressure, positive end-expiratory pressure, minute ventilation, airway resistance, dynamic compliance, and peak inspiratory and expiratory flow rates. No sig- nificant change in any ventilatory variable at either time period was noted in the infants. Implications: Ventila- tory compromise is infrequent in small infants under- going transesophageal echocardiography (TEE) exami- nation. Careful ventilatory monitoring rapidly detects changes in ventilation during TEE examination. Small infants who benefit from TEE during heart surgery should not be excluded from receiving a TEE examina- tion because of concern of ventilatory compromise. (Anesth Analg 2000;90:47–9) I ntraoperative transesophageal echocardiography (TEE) has become an important monitoring modality for patients undergoing repair or palliation of congen- ital heart disease. TEE is used to assess pre- and postop- erative anatomy, ventricular volume and function, intra- cardiac air (1), and recently has been used to guide central venous catheter placement (2). Complications from TEE are infrequent, but interference with ventila- tion from direct compression of the endotracheal tube, distal trachea, or mainstem bronchi have been reported (3–7). Despite the development of newer small TEE probes, small infants remain at greatest risk of experiencing im- paired ventilation (4). However, this group of patients often realizes significant benefits from the information provided by TEE. Fear of compromised ventilation has led some surgical or anesthesia teams to limit TEE use in small infants. This study assesses the effect of TEE ex- amination on multiple pulmonary function variables and gas exchange in small infants undergoing cardiac surgery. Methods After institutional review board approval and informed consent from parents, we studied infants weighing 2–5 kg scheduled for cardiac surgery and a TEE ex- amination. Patients with preexisting anatomic airway obstruction were excluded. General anesthesia was in- duced with midazolam 0.1– 0.2 mg/kg, fentanyl 10 – 30 g/kg, and pancuronium 0.2 mg/kg, and in 7 of 22 patients, isoflurane (always less than 0.8% end-tidal con- centration), and a nasotracheal tube and an arterial cath- eter were placed. After 10 min of steady-state volume- controlled ventilation using a Siemens 900C ventilator (Siemens-Elema AB, Solna, Sweden), an arterial blood gas (ABG) and baseline pulmonary function tests (PFT) were measured with a sensor at the proximal end of the endotracheal tube (BiCore CP-100 Neonatal, BiCore Monitoring Systems, Irvine, CA). This device directly measures airway pressure and flow and continuously calculates and displays the following vari- ables: expired tidal volume in mL (Vtexp), peak inspiratory pressure in cm H 2 O, positive end-expiratory pressure in cm H 2 O, minute ventilation in L/min, airway resistance in cm H 2 O  L -1  s -1 , dynamic com- pliance in mL/cm H 2 O, peak inspiratory flow rate in mL/s, and peak expiratory flow rate in mL/s. A pedi- atric biplane TEE probe with external dimensions 9 mm  8 mm (Acuson V705B, Mountain View, CA), Accepted for publication August 30, 1999. Address correspondence and reprint requests to Dean B. Andropoulos, MD, Department of Anesthesiology, Texas Children’s Hospital, 6621 Fannin, Ste. 310, MC 2-1495, Houston, TX 77030-2399. Address e-mail to dra@bcm.tmc.edu. ©2000 by the International Anesthesia Research Society 0003-2999/00 Anesth Analg 2000;90:47–9 47