INTRODUCTION. Both hypocapnia and hypercapnia can be deleterious to brain injured
patients. Strict PaCO2 control is difficult to achieve because of patient's instability and
unpredictable effects of ventilator settings changes.
OBJECTIVE. The aim of this study was to evaluate our ability to comply with a protocol
of controlled mechanical ventilation (CMV) aiming at a PaCO2 between 35 and 40 mmHg
in patients requiring neuro-resuscitation.
METHODS. Retrospective analysis of consecutive patients (2005-2011) requiring intracranial
pressure (ICP) monitoring for traumatic brain injury (TBI), subarachnoid
haemorrhage (SAH), intracranial haemorrhage (ICH) or ischemic stroke (IS). Demographic
data, GCS, SAPS II, hospital mortality, PaCO2 and ICP values were recorded. During CMV
in the first 48 h after admission, we analyzed the time spent within the PaCO2 target in
relation to the presence or absence of intracranial hypertension (ICP[20 mmHg, by
periods of 30 min) (Table 1). We also compared the fraction of time (determined by linear
interpolation) spent with normal, low or high PaCO2 in hospital survivors and non-survivors
(Wilcoxon, Bonferroni correction, p\0.05) (Table 2). PaCO2 samples collected during and
after apnoea tests were excluded. Results given as median [IQR].
RESULTS. 436 patients were included (TBI: 51.2 %, SAH: 20.6 %, ICH: 23.2 %, IS:
5.0 %), age: 54 [39-64], SAPS II score: 52 [41-62], GCS: 5 [3-8]. 8744 PaCO2 samples
were collected during 150611 h of CMV.
CONCLUSIONS. Despite a high number of PaCO2 samples collected (in average one
sample every 107 min), our results show that patients undergoing CMV for neuro- resuscitation
spent less than half of the time within the pre-defined PaCO2 range. During
documented intracranial hypertension, hypercapnia was observed in 17.4 % of the time.
Since non-survivors spent more time with hypocapnia, further analysis is required to
determine whether hypocapnia was detrimental per se, or merely reflects increased severity
of brain insult.