SKELETAL-MUSCLE PO2, PCO2, AND PH IN HEMORRHAGE, SHOCK, AND RESUSCITATION IN DOGS

Objective: To test fiber-optic Po-2, Pco(2), and pH sensors placed in skeletal muscle as monitors of hemorrhage, shock, and resuscitation, c ompared with mean arterial blood pressure, cardiac output, and blood g as variables. Design: Observational study in physiology laboratory, us ing a canine controlled hemorrhagic shock model. Materials and Methods : Mongrel dogs (20-35 kg; n = 10) were monitored with arterial, venous , and pulmonary artery catheters. A probe (0.5 mm in diameter) with fi ber-optic Po-2, Pco(2), and pH sensors was placed percutaneously in th e adductor muscle of the right medial thigh. Mean arterial blood press ure of 45 to 50 mm Hg was maintained for 1 hour with controlled hemorr hage, after which shed blood was reinfused. The animals were monitored for 4 hours after reinfusion. Measurements and Main Results: Skeletal muscle Po-2 (Pmo(2)) decreased from 31 +/- 9 to 5 +/- 4 mm Hg during shock and recovered with reinfusion. Skeletal muscle pH (pHm) decrease d from 7.24 +/- 0.10 to 6.94 +/- 0.12 during shock, to 6.90 +/- 0.13 w ith reinfusion, and recovered to near baseline 2 hours after reinfusio n. Pmco(2) increased from 48 +/- 14 to 134 +/- 86 mm Hg during shock, to 138 +/- 92 mm Hg with a time course inverse to pHm, and recovered t o near baseline 30 minutes after reinfusion. On average, skeletal musc le Pco(2) (Pmco(2)) and pHm did not recover to baseline, possibly indi cating persistent anaerobic metabolic effects. O-2 delivery, mixed ven ous Po-2, mixed venous O-2 saturation and Pmo(2) responded with simila r time courses. Conclusion: Pmo(2), Pmco(2), and pHm can be monitored simultaneously for several hours with fiber-optic sensors in a single, small probe. Pmo(2) may provide information comparable to O-2 deliver y. Pmco(2) may reflect adequacy of perfusion. pHm may indicate success of resuscitation. This technology may offer new insight into the exte nt of injury and refinement of shock resuscitation and monitoring.