Variability in adequacy of ventilation during transport of cardiac surgery patients: a cohort study

Inadequate ventilation of intubated patients during transport from the operating theatre to the intensive care unit with attendant hypercarbia may adversely affect haemodynamics. In a retrospective observational study, we assessed the incidence of inadequate ventilation during transport from the operating theatre to the intensive care unit in 99 consecutive cardiac surgery patients admitted to our university tertiary hospital. Demographic, clinical, arterial blood gas and haemodynamic measurements were made on arrival in the intensive care unit after cardiac surgery. The relationships between arterial carbon dioxide tension (P(a)CO2), mean pulmonary artery pressure (MPAP) and other relevant haemodynamic variables were explored. Overall, hypocarbia (P(a)CO2 < 35 mmHg) occurred in 18.2% of patients, while 28.3% of patients had hypercarbia (P(a)CO2 > 45 mmHg). Pulmonary hypertension was common, with nearly half of the cohort having MPAP > or = 25 mmHg and 17.2% > or = 30 mmHg. However there was no association between P(a)CO2 and MPAP (R2 = 0.0076, P = 0.39). Contrary to expectation, neither hypercarbia nor high MPAP were associated with measured adverse outcomes, although this may have been because we studied an insufficient number of patients with extreme values. Associations of higher MPAP, which would be expected to compromise cardiovascular status, included acidaemia, hypoxia and the requirement for noradrenaline. These factors define a group of high-risk patients who should receive particular attention and who should be the focus of future studies.