Table 1.
Changes in blood gas chemistry and Alveolar-arterial (A-a) gradient elicited by injections of morphine
| Time (minutes) post-vehicle or morphine (10 mg/kg, i.v.) |
||||||||
|---|---|---|---|---|---|---|---|---|
| Parameter | Group | Pre | +5 | +15 | +30 | +45 | +60 | +75 |
| pH | Vehicle | 7.46 ± 0.02 | 7.46 ± 0.02 | 7.44 ± 0.01 | 7.44 ± 0.02 | 7.46 ± 0.02 | 7.46 ± 0.01 | 7.48 ± 0.02 |
| Morphine | 7.47 ± 0.01 | 7.26 ± 0.02* | 7.31 ± 0.01* | 7.33 ± 0.02* | 7.38 ± 0.02* | 7.42 ± 0.03* | 7.45 ± 0.02 | |
| pCO2, mmHg | Vehicle | 33.5 ± 0.8 | 33.7 ± 0.5 | 33.5 ± 0.6 | 34.5 ± 0.8 | 34.9 ± 0.4 | 34.1 ± 0.9 | 34.1 ± 0.8 |
| Morphine | 32.8 ± 0.9 | 51.3 ± 1.8* | 48.7 ± 1.9* | 48.5 ± 1.6* | 45.8 ± 2.1* | 39.9 ± 1.3* | 34.6 ± 1.3 | |
| pO2, mmHg | Vehicle | 92.5 ± 1.3 | 92.9 ± 1.2 | 91.8 ± 0.9 | 92.9 ± 1.4 | 92.7 ± 1.4 | 93.2 ± 1.3 | 93.1 ± 1.0 |
| Morphine | 91.8 ± 0.9 | 53.7 ± 3.1* | 58.0 ± 3.2* | 63.7 ± 2.2* | 70.3 ± 3.4* | 79.6 ± 3.4* | 89.5 ± 2.6 | |
| sO2 (%) | Vehicle | 96.1 ± 1.6 | 97.6 ± 2.2 | 96.5 ± 2.0 | 97.5 ± 1.0 | 97.3 ± 1.3 | 96.0 ± 0.6 | 96.3 ± 1.2 |
| Morphine | 96.7 ± 2.0 | 63.3 ± 3.8* | 67.1 ± 4.2* | 72.9 ± 3.2* | 78.8 ± 3.1* | 87.2 ± 2.4* | 94.6 ± 1.4 | |
| A-a gradient, mmHg | Vehicle | 15.4 ± 1.8 | 14.7 ± 1.1 | 16.0 ± 1.4 | 13.7 ± 2.0 | 13.4 ± 1.4 | 13.9 ± 2.0 | 14.0 ± 0.7 |
| Morphine | 16.9 ± 1.6 | 32.0 ± 2.4* | 30.8 ± 4.5* | 25.3 ± 3.0* | 22.2 ± 4.5 | 20.3 ± 3.7 | 17.0 ± 1.8 | |
The data are presented as mean ± SEM. There were 5 rats in each group.
P < 0.05, significant change from pre-values.
A-a gradient = PAO2 - PaO2, where PAO2 is the partial pressure of alveolar O2 (calculated from the alveolar gas equation) and PaO2 is the partial pressure of O2 in arterial blood. PAO2 is determined by the formula, PAO2 = [(FiO2 × (Patm-PH2O) - (PaCO2/respiratory quotient)], where FiO2 is the fraction of O2 in inspired air; Patm is atmospheric pressure; PH2O is the partial pressure of water in inspired air; and PaCO2 is the partial pressure of CO2 in arterial blood. We took FiO2 of room-air to be 21% = 0.21; respiratory quotient to be 0.8; Patm to be 760 mmHg; and PH2O to be 47 mmHg [see 20,21].