The Science Journal of the American Association for Respiratory Care

1998 OPEN FORUM Abstracts

VENTILATOR STRATEGIES FOR FIRST STAGE NORWOOD PALLIATION

Douglas Eric Petsinger, Vincent Kam Hung Tam, Angel Raul Cuadrado, Frederick Konrad Emge, Pamela Louise Moreau, - Egleston Children's Hospital, Cardiac Intensive Care Unit, 1405 Clifton Road, NE, Atlanta, Georgia 30322

Introduction

Postoperative stabilization of First Stage Norwood palliation presents a challenging strategy battling unstable hemodynamics. Initially, when the patient population emerges from general anesthesia the clinician is faced with a reactive parallel circulation that must provide adequate tissue perfusion. The strategy developed from November 1994 has utilized a mixture of paralysis and sedation, inotropic support, ventilatory management with moderate mean airway pressure (Paw), mild permissive hypercapnia and delayed sternotomy closure.

Methods

Twenty-seven consecutive infants underwent First Stage Norwood operation from November 1994 to April 1996. Infants ranged from 1 to 45 days of age with weight range of 2.37± 0.57 kg. Surgical management included a modified Blalock-Taussig shunt of 3 to 4 mm diameter. A Gortex(r) graft was used exclusively. The graft was placed from the innominate or right subclavian artery to the right pulmonary artery or confluence of the branch pulmonary arteries. Veno-venous modified ultrahemofiltration was used immediately after separation from cardiopulmonary bypass. The sternotomy was left open and the incision covered with a silastic dam patch. Early postoperative management consisted of continuous sedation and paralysis. Inotropic support routinely included low dose dopamine (3 to 5 mcg/kg/min), dobutamine (5 to 10 mcg/kg/min) and/or epinephrine (0.01 to 0.1 mcg/kg/min). Despite using smaller systemic arterial to pulmonary arterial shunts, these infants generally have excessive pulmonary blood flow. Low dose continuous furosemide infusion is used to encourage diuresis and resolution of edema. Criteria for delayed sternotomy closure included satisfactory hemodynamics, minimal ventilatory requirement, and resolution of overall edema. The ventilation strategy is geared toward decreasing pulmonary blood flow through a variety of manipulations including mean airway pressure (5 to 13 cm H_{2}O), tidal volume (VT)(15 to 20 cc/kg), and peak inspiratory pressure (PIP) ( < =25 cm H_{2}O). All infants were ventilated with Siemens Servo 900C ventilators with Synchronized Intermittent Mandatory Ventilation (SIMV) or Pressure Control Ventilation (PCV). Target PaCO_{2}'s ranged from 40 to 60 torr, and arterial saturations from 65 to 80%. In cases of unrestricted excess pulmonary blood flow (PBF), Carbon Dioxide (CO_{2}) was added via the low pressure gas inlet of the Servo 900C, CO_{2} (1 to 5%) was measured via Novametrix 1260 End tidal Carbon Dioxide Monitor (ET CO_{2}) in instantaneous percentage monitoring mode. Thirteen of our 27 patients (48%) required CO_{2} ventilation. Parameters used to monitor systemic cardiac output (Qs) included distal peripheral cutaneous temperature, urine output (UOP), acid base status, and systemic and central pressures (Arterial, CVP and RAP). Target values for peripheral cutaneous temperatures were >= 30°C, UOP of 1 to 3 cc/kg/hr, and metabolic alkalosis. Blood pressures were generally maintained at > 65 mmHg systolic, > 35 mmHg diastolic. CVP and RAP ranged from 5 to 10 mmHg. Pulmonary to systemic flow ratio (Qp/Qs) of 0.8 to 1.0 were also desired.

Results

Twenty-four of 27 (88%) infants survived hospitalization. Hospital stay averaged 14.9 days. Patients underwent delayed sternotomy closure on day 2.1 (average) postoperatively with endotracheal extubation 4.5 days (average) after surgery. Three patients developed superficial wound infections.

Conclusions

This protocol of postoperative management has significantly improved outcome after First Stage Norwood procedure. Despite smaller systemic arterial to pulmonary arterial shunts, excessive pulmonary blood flow was predominant; maneuvers including ventilatory management and selective use of vasoactive medications were all directed toward limiting excessive pulmonary flow. This experience is in marked contrast to that reported by Mosca et al. This approach has encouraged the utilization of smaller systemic arterial to pulmonary arterial shunts. The survival of patients following the modified First Stage Norwood palliation continues to improve.

(See Original for Figure)

The 44th International Respiratory Congress Abstracts-On-Disk®, November 7 - 10, 1998, Atlanta, Georgia.

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