Table 3.
Demographic and pre-extracorporeal membrane oxygenation (ECMO) characteristics of patients, by dataset
| Variable | Derivation, 2008–2011 (n=3,139) | Validation, 2012–2013 (n=1,453) | p-value |
|---|---|---|---|
| Median (Interquartile Range) | |||
|
| |||
| pH† | 7.20 (7.08–7.30) | 7.17 (7.07–7.27) | <0.001 |
| PaCO2,† mm Hg | 59 (45–76) | 60 (47–79) | 0.04 |
| SaO2,† % | 68 (46–82) | 68 (47–82) | 0.36 |
| PF Ratio† | 37 (28–48) | 36 (28–46) | 0.49 |
| Oxygenation Index† | 47 (33–67) | 48 (35–67) | 0.19 |
| Apgar 1 minute of life | 5 (2–7) | 4 (2–7) | 0.11 |
| Mean Arterial Pressure,† mm Hg | 42 (35–50) | 43 (36–51) | 0.30 |
| Pre-ECMO hours of mechanical ventilation | 29 (14–58) | 30 (15–54) | 0.77 |
| Birth Weight, kilograms | 3.2 (2.8–3.6) | 3.2 (2.8–3.6) | 0.92 |
| Gestational Age, (weeks) | 39 (38–40) | 39 (37–40) | 0.03 |
| Age, days | 1 (1–3) | 1 (1–3) | 0.63 |
|
| |||
| Number (Percent) | |||
|
| |||
| Female | 1,291 (41.1) | 645 (44.4) | 0.03 |
| Primary Diagnosis | |||
| Meconium Aspiration Syndrome | 789 (25.1) | 346 (23.8) | 0.33 |
| Congenital Diaphragmatic Hernia | 920 (29.3) | 417 (28.7) | 0.67 |
| Respiratory Distress Syndrome | 62 (2.0) | 15 (1.0) | 0.02 |
| Persistent Pulmonary Hypertension | 650 (20.7) | 312 (21.5) | 0.55 |
| Sepsis | 235 (7.5) | 102 (7.0) | 0.58 |
| Other | 483 (15.4) | 261 (18.0) | 0.03 |
| Comorbidity‡ | 259 (8.3) | 151 (10.4) | 0.02 |
| Pre-ECMO Renal Failure* | 41 (1.3) | 17 (1.2) | 0.7 |
| Pre-ECMO Cardiac Arrest* | 43 (1.4) | 15 (1.0) | 0.34 |
| Ventilator Mode | |||
| Conventional Mechanical Ventilator | 826 (26.3) | 387 (26.6) | 0.82 |
| Oscillator | 1,832 (58.4) | 897 (61.7) | 0.03 |
| Other or missing | 481 (15.3) | 169 (11.6) | 0.01 |
| Inhaled Nitric Oxide | 2,739 (87.3) | 1,231 (84.7) | 0.02 |
| Surfactant | 894 (28.5) | 411 (28.3) | 0.89 |
| Neuromuscular Blockade | 1,801 (57.4) | 738 (50.8) | <0.001 |
| Vasoactive Infusions | 2,126 (67.7) | 697 (48) | <0.001 |
PaCO2=arterial partial pressure of carbon dioxide, SaO2 =percent oxygen saturation of hemoglobin in arterial blood, PF ratio=ratio of arterial partial pressure of oxygen to the fraction of inspired oxygen, and pre-ECMO hours of mechanical ventilation=number of hours of mechanical ventilation prior to ECMO. For p-values continuous, nonparametric variables were compared using Mann-Whitney U test, and categorical variables were compared using Pearson’s chi-square test.
Most abnormal value recorded within 6 hours of ECMO support.
Comorbidity is defined using Agency for Healthcare Research and Quality definitions (16).
Pre-ECMO renal failure and pre-ECMO cardiac arrest are defined by ICD-9-CM codes plus the respective absence of renal failure or cardiac arrest as an ECMO complication.