SUBCUTANEOUS TISSUE OXYGEN-PRESSURE - A RELIABLE INDEX OF PERIPHERAL PERFUSION IN HUMANS AFTER INJURY

The usual initial life-threatening effect of injury is hypovolemic sho ck. In the hierarchial physiologic response to hypovolemia, perfusion of peripheral tissues is sacrificed early and restored late. But the u sual hemodynamic and metabolic measurements of blood pressure, urine o utput, and base deficit are not reliable indices of peripheral perfusi on. Although the Clark electrode can quantitate tissue oxygen pressure and thereby serve as an index of perfusion, its use is compromised by several technical deficiencies. Recently, an optical method (optode) using fluorescent technology has been developed for measurement of oxy gen tension in subcutaneous tissue (P(sg)0(2)). Our studies compared t his device with the Clark electrode in the laboratory and tested its v alue in both animal and clinical studies of hypovolemic shock. The res ults of these several studies demonstrated that: (1) the new oximeter tracked a rapid fall or rapid rise of oxygen tension between room air (150 mm Hg) and 0 mm Hg (a glucose oxidase/catalase solution) as well as the Clark electrode without encountering its technical problems; (2 ) with an acute hemorrhage to 20% of base line, the P(sg)0(2) was foun d to decline rapidly in parallel with the decline of mean arterial pre ssure (MAP). Although the MAP rapidly returned to normal after immedia te complete return of all shed blood, the P(sg)0(2) did not reach norm al levels for at least 2 hours, suggesting persistent peripheral vasoc onstriction. (3) Studies in progress suggest that between 35 and 78% o f trauma patients (n = 18) adequately resuscitated for hypovolemia by customary criteria have a decreased level of P(sg)0(2) for as long as 60 hours after resuscitation for injury. If care is taken to prevent o ther causes of catecholamine induced vasoconstriction such as pain, fe ar, cold, and arterial hypoxia, these several results suggest that a c ertain number of injured patients are inadequately resuscitated despit e the return to normal of conventional hemodynamic measurements. The s erial analysis of P(sg)0(2) may assist in managing patients and promot e better understanding of the responses to injury.