Effects of buffering in hypercapnia and hypercapnic hypoxemia

• 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).

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Anestesi och intensivvård (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Anesthesiology and Intensive Care (hsv//eng)

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