A unitary system incorporates an upper reservoir container having a blood gas separator, a cardiotomy reservoir and a venous reservoir. The upper container is positioned directly above a lower mass transfer container coupled with the venous reservoir by means of a check valve and having a spirally wound flattened tubular transfer membrane. A vacuum is drawn upon an upper portion of the reservoir container which carries a blood gas separator into which aspirated wound site blood is drawn for filtering and collection of blood in the cardiotomy reservoir. The latter is automatically drained via a pressure responsive valve into a venous blood reservoir at the lower portion of the reservoir container and into which venous blood flows for mixing with the filtered cardiotomy blood. A bladder pump within the mass transfer container above the tubular membrane alternately increases and decreases pressure within the lower container to help draw venous blood from the venous reservoir and to force blood between adjacent windings of the tubular membrane and outwardly from the mass transfer container to an arterialized blood return. The tubular membrane itself is used as a heat exchanger to lower the blood temperature below body temperature and to raise it above body temperature by controlling temperature and increasing thermal conductivity of gaseous oxygen flowing through the tubular membrane and by causing the oxygen to flow at a very high velocity.