Pulmonary and Extrapulmonary Effects of Increased Colloid Osmotic Pressure During Endotoxemia in Rats: Results

Pulmonary and Extrapulmonary Effects of Increased Colloid Osmotic Pressure During Endotoxemia in Rats:  ResultsGroup II
Experiments in this group were completed in 10 of 11 rats, the results showed stable gas-exchange and acid-base balances (Table 2). The infusion of the three single doses of 1 g/kg human albumin was associated with a gradual and significant increase in COP up to a maximum of 58% (Fig 1). In this group, decreases in the Hb concentration were larger than those in saline solution-treated animals (Fig 2). Consequently, arterial O2 content was significantly reduced by > 15% (Fig 3). There were no significant changes in P(A-a)O2 (Fig 4), MABP (Fig 5), or HR (Fig 6).

Group III
Ten of 11 rats in this group survived the 6-h experimental period following a single dose of 4 mg/kg endotoxin and saline solution infusions, Pa02 was significantly increased, as early as 2 h after endotoxin injection (Table 3), while PaC02 was decreased. Endotoxemia was associated with a further decrease in the COP compared to saline solution-treated rats (Fig 1; Tukey-Kramer multiple comparisons test). Starting 4 h after endotoxin injection, Hb and arterial O2 content were reduced significantly. These reductions were similar to those observed in the saline solution-treated rats (Figs 2, 3). The P(A-a)O2 did not change throughout the experiment (Fig 4). Unlike the results for group I, endotoxemia caused a > 20% reduction in MABP starting at 4 h following endotoxin injection (Fig 5), while HR was significantly increased starting at 2 h following endotoxin injection (Fig 6).
Group IV
Nine of 11 rats in this group survived the combined treatment of endotoxin and albumin. Pa02 was gradually reduced, reaching a significant level (18%) by 6 h. PaC02, however, was reduced significantly at 2 h and 6 h (28% and 39%, respectively; Table 4). COP gradually increased, becoming significant at 6 h (Fig 1). This rate of increase in COP was significantly less than that in the rats treated with albumin alone (Fig 1). Endotoxin-albumin treatment caused the highest degree of Hb reduction (Fig 2) and arterial O2 content (Fig 3). Plasma in these rats (tested in four cases) showed no free Hb, indicating a lack of hemolysis. Endotoxin-albumin-treated rats showed comparable reductions in MABP and increases in HR compared to those in the endotoxin-treated group (Figs 5, 6).
Table 2—Gas Exchange and Blood COP During 6 h of Maintained Anesthesia in 10 Spontaneously Breathing Albumin-Treated Rats

Variables Time
1Baseline (Time Zero) 2 h 4h 6h
PaO£, mm Hg 80.3 ± 8.7 88.4 ± 10.6 80.8 ± 12.5 83.2 ± 13.8
PacO2, mm Hg 39.8 ± 3.7 40.2 ± 5.5 38.3 ± 4.2 37.4 ± 4.3
pH 7.361 ± 0.02 7.337 ± 0.02t 7.356 ± 0.03 7.346 ± 0.01
(HCO3)a, mmol/L 21.8 ± 1.6 20.8 ± 2.2 20.9 ± 1.6 19.9 ± 2.4t
HbO2, % 93.4 ± 3.1 94.3 ± 2.0 93.5 ± 2.4 92.5 ± 5.4
COP, mm Hg 14.5 ± 1.9 18.2 ± 1.6t 20.4 ± 2.9t 22.9 ± 2.11

Table 3—Gas Exchange and Blood COP During 6 h of Maintained Anesthesia in 10 Spontaneously Breathing Endotoxin-Treated Rat

Variables Time
1Baseline (Time Zero) 2h 4h 6h
PaO2, mm Hg 80.3 ± 10.0 97.1 ± 14.2t 88.3 ± 11.8 98.4 ± 14.71
PacO2, mm Hg 39.0 ± 5.8 24.1 ± 6.4t 25.7 ± 4.1t 19.3 ± 3.8t
pH2 7.378 ± 0.04 7.347 ± 0.06 7.329 ± 0.07 7.305 ± 0.11
(HCO3)a, mmol/L 22.3 ± 2.1 12.9 ± 3.6t 13.3 ± 3.1t .5t
2.
±
.4
9.
HbO2, % 95.5 ± 2.8 95.6 ± 1.8 93.3 ± 3.8 93.8 ± 6.3
COP, mm Hg 14.1 ± 1.9 10.7 ± 1.6t 9.0 ± 1.1t .3t
±
.6
8.

Table 4 —Gas Exchange and Blood COP During 6 h of Maintained Anesthesia in Nine Spontaneously Breathing Endotoxemic Rats Treated With Three Boluses of 1 g/kg Human Albumin Every 2 h

Variables Time
1Baseline (Time Zero) 2h 4h 6h
Pa0£, mm Hg 82.1 ± 9.1 83.3 ± 10.7 74.9 ± 5.9 67.7 ± 10.7i
PaC0£, mm Hg 42.6 ± 3.5 30.5 ± 5.6i 29.5 ± 5.9i 25.8 ± 5.7i
pH 7.364 ± 0.03 7.365 ± 0.03 7.403 ± 0.04 7.358 ± 0.08
(HCO3)a, mmol/L 23.6 ± 1.9 16.9 ± 2.9i 18.0 ± 3.0i 14.3 ± 3.0i
HbO2, % 92.4 ± 2.3 92.9 ± 1.5 92.9 ± 2.0 89.3 ± 4.5
COP, mm Hg 14.2 ± 0.9 13.4 ± 1.1 15.4 ± 1.8 16.9 ± 2.3i
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