Comparison of 7.5% NaCl/6% dextran-70 resuscitation of hemorrhage between euhydrated and dehydrated sheep

Abstract

7.5% NaCl/6% dextran-70 (HSD) has been shown to be an effective, small volume resuscitation fluid following hemorrhage (HEM) in euhydrated (E) sheep. However, there is controversy whether hypertonic solutions would be effective in dehydrated (D) animals. Therefore, we used two groups (E and 4 days D) of chronically instrumented ewes to evaluate the responses to HSD following HEM. All sheep were bled and maintained at 50 mmHg mean arterial pressure (MAP) for 2 h, then resuscitated with a 4 mL/kg bolus of HSD. Dehydration did not affect baseline MAP, heart rate (HR), or total peripheral resistance (TPR), whereas cardiac output (CO: E, 5.28 +/- .31; D, 4.00 +/- .31 L/min), stroke volume (SV: E, 61 +/- 4; D, 44 +/- 4 mL/beat), urine flow rate (V: E, .51 +/- .11; D, .34 +/- .07 mL/min), and sodium excretion (UNa V: E, 22 +/- 8; D, 6 +/- 2 microEq/min) were reduced and plasma sodium (PNa: E, 150 +/- 3; D, 157 +/- 2 mEq/L) and protein (PTP E, 7.8 +/- .1; D, 8.8 +/- .6 g/dL) were elevated. The only difference between groups during HEM were HR (E, 98 +/- 8; D, 150 +/- 17 bpm), SV (E, 31 +/- 3; D, 14 +/- 2), and TPR (E, 23 +/- 2; D, 32 +/- 3). Resuscitation with HSD restored MAP (E, 92 +/- 3; D, 92 +/- 2), CO (E, 6.2 +/- .3; D, 4.2 +/- .2), and TPR (E, 15 +/- 1; D, 23 +/- 1) to baseline values. SV was increased above hemorrhage values but was not restored to baseline values in either group (E, 50 +/- 7; D, 27 +/- 3). HR increased further following HSD (E, 143 +/- 11; D, 158 +/- 5). PNa was raised 10 and 16 mEq/L in the E and D sheep, respectively, following HSD infusion, but no adverse effects associated with elevated PNa were observed in either group. Thus, HSD was effective in restoring MAP, CO, and TPR to baseline values in D sheep but it was at the expense of a lower SV and a higher HR than in E sheep.