title: Effects of buffering in hypercapnia and hypercapnic hypoxemia.
abstract: Anesthetized, paralyzed and mechanically ventilated pigs were exposed to extreme hypercapnia (PaCO2 approximately 20 kPa) at FiO2 0.4 for 480 min, with (n = 6) or without (n = 6) continuous infusion of isotonic buffers (bicarbonate and trometamol). Arterial pH was higher in buffered animals than controls, 7.21 +/- 0.01 vs 7.01 +/- 0.01 (mean +/- s.e.mean, P < 0.01). Serum osmolality and PaCO2 did not differ between groups throughout the experiment. The hemodynamic response to hypercapnia was attenuated in the buffered group, who had lower heart rate, 133 +/- 6 vs 189 +/- 12 min-1 (P < 0.01), mean arterial pressure (MAP) 109 +/- 4 vs 124 +/- 4 mmHg (14.5 +/- 0.5 vs 16.5 +/- 0.5 kPa) (P < 0.05), mean pulmonary arterial pressure 16 +/- 1 vs 23 +/- 1 mmHg (2.1 +/- 0.1 vs 3.1 +/- 0.1 kPa) (P < 0.01), and pulmonary vascular resistance (PVR) 249 +/- 21 vs 343 +/- 20 dyn s.cm-5 (2490 +/- 210 vs 3430 +/- 200 microN.s.cm-5) (P < 0.01), compared with the control group. Subsequently, both groups were exposed to hypercapnic hypoxemia by stepwise increases in FiO2 (0.15, 0.10, 0.05) at 30-min intervals, while FiCO2 was kept at 0.2. PVR increased in both groups (P < 0.05) but, except for heart rate, all hemodynamic differences between the groups disappeared during hypoxia. At FiO2 0.15, buffered animals had higher arterial oxygen saturation (73 +/- 5%) than the controls (55 +/- 5%), (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Anesthesiology, University of Lund, Sweden.
authors.forename: T
authors.initials: T
authors.lastname: Wetterberg
authors.forename: T
authors.initials: T
authors.lastname: Sjöberg
authors.forename: S
authors.initials: S
authors.lastname: Steen
mesh_terms: D000137:Acid-Base Imbalance / Q000097:blood / Q000503:physiopathology; D000818:Animals; D001639:Bicarbonates / Q000627:therapeutic use*; D001794:Blood Pressure / Q000502:physiology; D002021:Buffers; D002245:Carbon Dioxide / Q000097:blood; D002302:Cardiac Output / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D006935:Hypercapnia / Q000097:blood* / Q000503:physiopathology; D000860:Hypoxia / Q000097:blood* / Q000503:physiopathology; D007552:Isotonic Solutions; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology; D011651:Pulmonary Artery; D012121:Respiration, Artificial; D013552:Swine; D014325:Tromethamine / Q000627:therapeutic use*; D014655:Vascular Resistance / Q000502:physiology
chemical_list: D001639:Bicarbonates; D002021:Buffers; D007552:Isotonic Solutions; D014325:Tromethamine; D002245:Carbon Dioxide; D010100:Oxygen