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Measurement of Dead Space Fraction Upon ICU Admission Predicts Length of Stay and Clinical Outcomes Following Bidirectional Cavopulmonary Anastomosis*

Cigarroa, Claire L. MD1,2; van den Bosch, Sarah J. MS1; Tang, Xiaoqi MS1; Gauvreau, Kimberlee ScD1,2; Baird, Christopher W. MD3,4; DiNardo, James A. MD5,6; Kheir, John Nagi MD1,2

Pediatric Critical Care Medicine: January 2018 - Volume 19 - Issue 1 - p 23-31
doi: 10.1097/PCC.0000000000001378
Cardiac Intensive Care

Objectives: Increased alveolar dead space fraction has been associated with prolonged mechanical ventilation and increased mortality in pediatric patients with respiratory failure. The association of alveolar dead space fraction with clinical outcomes in patients undergoing bidirectional cavopulmonary anastomosis for single ventricle congenital heart disease has not been reported. We describe an association of alveolar dead space fraction with postoperative outcomes in patients undergoing bidirectional cavopulmonary anastomosis.

Design: In a retrospective case-control study, we examined for associations between alveolar dead space fraction ([Paco2 – end-tidal Co2]/Paco2), arterial oxyhemoglobin saturation, and transpulmonary gradient upon postoperative ICU admission with a composite primary outcome (requirement for surgical or catheter-based intervention, death, or transplant prior to hospital discharge, defining cases) and several secondary endpoints in infants following bidirectional cavopulmonary anastomosis.

Settings: Cardiac ICU in a tertiary care pediatric hospital.

Patients: Patients undergoing bidirectional cavopulmonary anastomosis at our institution between 2011 and 2016.

Interventions: None.

Measurements and Main Results: Of 191 patients undergoing bidirectional cavopulmonary anastomosis, 28 patients were cases and 163 were controls. Alveolar dead space fraction was significantly higher in the case (0.26 ± 0.09) versus control group (0.17 ± 0.09; p < 0.001); alveolar dead space fraction at admission was less than 0.12 in 0% of cases and was greater than 0.28 in 35% of cases. Admission arterial oxyhemoglobin saturation was significantly lower in the case (77% ± 12%) versus control group (83% ± 9%; p < 0.05). Sensitivity and specificity for future case versus control assignment was best when prebidirectional cavopulmonary anastomosis risk factors, admission alveolar dead space fraction (AUC, 0.74), and arterial oxyhemoglobin saturation (AUC, 0.65) were combined in a summarial model (AUC, 0.83). For a given arterial oxyhemoglobin saturation, the odds of becoming a case increased on average by 181% for every 0.1 unit increase in alveolar dead space fraction. Admission alveolar dead space fraction and arterial oxyhemoglobin saturation were linearly associated with prolonged ICU length of stay, hospital length of stay, duration of mechanical ventilation, and duration of thoracic drainage (p < 0.001 for all).

Conclusions: Following bidirectional cavopulmonary anastomosis, alveolar dead space fraction in excess of 0.28 or arterial oxyhemoglobin saturation less than 78% upon ICU admission indicates an increased likelihood of requiring intervention prior to hospital discharge. Increasing alveolar dead space fraction and decreasing arterial oxyhemoglobin saturation are associated with increased lengths of stay.

1Department of Cardiology, Boston Children’s Hospital, Boston, MA.

2Department of Pediatrics, Harvard Medical School, Boston, MA.

3Department of Cardiovascular Surgery, Boston Children’s Hospital, Boston, MA.

4Department of Surgery, Harvard Medical School, Boston, MA.

5Department of Anesthesia, Perioperative and Pain Medicine, Boston Children’s Hospital, Boston, MA.

6Department of Anaesthesia, Harvard Medical School, Boston, MA.

*See also p. 81.

Supported, in part, by the Hess Family Philanthropic Fund, the Gerber Foundation, and the Boston Children’s Hospital Heart Center Strategic Investment Fund.

The authors have disclosed that they do not have any potential conflicts of interest.

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Copyright © 2017 by the Society of Critical Care Medicine and the World Federation of Pediatric Intensive and Critical Care Societies