Effects of hypothermia with and without buffering in hypercapnia and hypercapnic hypoxemia.
Anesthetized, paralyzed and mechanically ventilated pigs were hypoventilated to extreme hypercapnia (PaCO2 approximately 20 kPa) at FiO2 0.5, and allotted to receive hypothermia (approximately 31.5 degrees C) and buffer infusion, (HB-group, n = 6) or to a hypothermic control group (H-group, n = 6). The HB-group had higher arterial pH (7.34 vs 7.09, P < 0.01) and plasma bicarbonate (58.8 vs 35.4 mmol.l-1, P < 0.01) than the controls, but lower mean pulmonary arterial pressure (MPAP), (16 vs 23 mmHg (2.1 vs 3.1 kPa), P < 0.01) and pulmonary vascular resistance (PVR), (512 vs 699 dyn.s.cm-5 (5120 vs 6990 microN.s.cm-5), P < 0.05). Mixed venous PO2 (PVO2) was lower in the HB-group (5.1 vs 6.8 kPa, P < 0.01), as well as serum potassium (2.8 vs 3.7 mmol.l-1, P < 0.01) and ionized calcium (1.01 vs 1.29 mmol.l-1, P < 0.01). Subsequently, the inspired oxygen fraction (FiO2) was decreased stepwise (0.3, 0.25, 0.21, 0.15, 0.10) at 30 min intervals. At FiO2 0.3, the HB-group had lower PVO2 (6.6 vs 7.8 kPa, P < 0.01), O2 half saturation tension (3.6 vs 4.2 kPa, P < 0.01), MPAP (17 vs 25 mmHg (2.3 vs 3.3 kPa, P < 0.01) and PVR (598 vs 793 dyn.s.cm-5 (5980 vs 7930 microN.s.cm-5, P < 0.05) compared with the controls, but higher arterial O2 saturation (95.3 vs. 88.6%, P < 0.01) and O2 content (17.7 vs 15.7 ml.100 ml-1, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Wetterberg
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Department of Anaesthesiology, University of Lund, Sweden.
Sjöberg
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Steen
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S
D000818:Animals; D001639:Bicarbonates / Q000097:blood / Q000627:therapeutic use*; D001794:Blood Pressure / Q000502:physiology; D002021:Buffers; D002118:Calcium / Q000097:blood; D002245:Carbon Dioxide / Q000032:analysis / Q000097:blood; D002496:Central Venous Pressure / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D006935:Hypercapnia / Q000097:blood / Q000503:physiopathology / Q000628:therapy*; D007036:Hypothermia, Induced; D000860:Hypoxia / Q000097:blood / Q000503:physiopathology / Q000628:therapy*; D010100:Oxygen / Q000032:analysis / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology*; D011188:Potassium / Q000097:blood; D011651:Pulmonary Artery; D011669:Pulmonary Wedge Pressure / Q000502:physiology; D012964:Sodium / Q000097:blood; D013552:Swine; D013990:Tidal Volume; D014655:Vascular Resistance / Q000502:physiology
D001639:Bicarbonates; D002021:Buffers; D002245:Carbon Dioxide; D012964:Sodium; D011188:Potassium; D010100:Oxygen; D002118:Calcium