Oxygen saturation and haemodynamic changes prior to circulatory arrest: Implications for transplantation and...

To describe the progression of oxygen saturations and blood pressure observations prior to death.

The progression of physiological changes around death is unknown. This has important implications in organ donation and resuscitation. Donated organs have a maximal warm ischaemic threshold. In hypoxic cardiac arrest, an understanding of pre-cardiac arrest physiology is important in prognosticating and will allow earlier identification of terminal states.

Data were examined for all regional patients over a two-year period offering organ donation after circulatory death. Frequent observations were taken contemporaneously by the organ donation nurse at the time of and after withdrawal of intensive care.

In all, 82 case notes were examined of patients aged 0 to 76 (median 52, 4 < 18 years). From withdrawal of intensive care to death took a mean of 28.5 min (range 4 to 185). A terminal deterioration in saturations (from an already low baseline) commenced 14 min prior to circulatory arrest, followed by a blood pressure fall commencing 8 min prior to circulatory arrest, and finally a rapid fall in heart rate commencing 4 min prior to circulatory arrest. Two patients had a warm ischaemic time of greater than 30 min; 15 patients had a warm ischaemia time of 10 min or greater; and 53 patients had a warm ischaemia time of 5 min or less. It was observed that 0/82 patients had saturations of less than 40% for more than 3 min prior to cardiac arrest and 74/82 for more than 2 min.

There is a perimortem sequence of hypoxia, then hypotension, and then bradycardia. The heart is extremely resistant to hypoxia. A warm ischaemic time of over 30 min is rare.