Physiological implications of hyperbaric oxygen tensions in isolated limb perfusion using melphalan: a pilot study.

Controversy exists concerning the optimal pO2 of the perfusate during isolated limb perfusion (ILP) with melphalan. Therefore we studied the implications of hyperbaric oxygen tensions in the perfusate. In 12 consecutive patients, subcutaneous pO2 (Continucath 1000), tissue and tumor pH, and blood gas values were monitored throughout the ILP procedure. ILP started with an oxygen flow through the bubble oxygenator which was set routinely at one half of the flow of the perfusate; 30 min before the end of ILP, the oxygen flow was tripled. Mean arterial pO2 before and during ILP (before and after increasing the oxygen supply) was 19.4, 25.5 and 49.4 kPa, respectively. Mean subcutaneous pO2 values before, during (before and after increasing the oxygen supply), and post-ILP, were 7.4, 10.1, 16.3, and 9.1 kPa, respectively. Tissue pH values in the subcutis and muscle decreased during routine oxygen supply (p = 0.001); muscle pH moved towards starting values after increase of the oxygen supply (p = 0.011). In 4 patients, tumor pH was recorded showing a rise after increasing the oxygen supply (from 7.10 to 7.22; p = 0.11). In conclusion, high pO2 in the perfusate improves muscle pH during ILP. However, a concomitant rise in tumor pH may unfavorably influence the therapeutic effect of ILP, as it has been shown that low pH increases the cytotoxicity of melphalan.