Blood pressure and heart rate changes during apnoea testing with or without CO2 insufflation

To determine changes of blood pressure and heart rate during apnoea testing for brain death without (A) and with (B) artificial CO2 augmentation.

Prospective, consecutive study.

12 intensive care units in six towns in Northern Bavaria.

A total of 55 apnoea tests were performed on 55 consecutive patients as part of the determination of brain death, 27 without and 28 with CO2 augmentation.

Apnoea tests following oxygenation with 100% O2 either after reduction of ventilatory volume (A) or after insufflation of CO2 during normoventilation (B). In each case, an arterial partial CO2 pressure of at least 8 kPa was documented.

All apnoea tests were without serious adverse effects (hypoxia, newly induced cardiac arrhythmia, cardiac asystole). An increased dopamine infusion rate was deemed necessary in only one case of group (A) because of marked systolic hypotension (< 8 kPa). Individual variation of systolic and diastolic blood pressure (BP) did not exceed + 62 to -46% and + 49 to -52% respectively, in group (A) and + 35 to -57% and + 40 to -48% respectively, in group (B). Variation of heart rate (HR) remained within the range + 24 to -31% in group (A) and + 37 to -22% in group (B).

HR varied less than BP. The possibility of a marked relative rise of fall of BP in group (A) was equal; in group (B) there was a lower change of rising BP. The chances for a rise or fall in HR were equal for the two groups. There was a tendency for less variation of cardiovascular parameters in group (B).