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Effects of buffering in hypercapnia and hypercapnic hypoxemia
Author(s) -
WETTERBERG T.,
SJÖBERG T.,
STEEN S.
Publication year - 1993
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.1399-6576.1993.tb03726.x
Subject(s) - hypercapnia , medicine , hypoxemia , hemodynamics , anesthesia , vascular resistance , mean arterial pressure , cardiac output , heart rate , hypoxia (environmental) , blood pressure , acidosis , oxygen , chemistry , organic chemistry
Anesthetized, paralyzed and mechanically ventilated pigs were exposed to extreme hypercapnia (Paco 2‐ 20 kPa) at Fio 2 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 Paco 2 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 μN‐s‐cm ‐5 ) ( P < 0.01), compared with the control group. Subsequently, both groups were exposed to hypercapnic hypoxemia by stepwise increases in Fio 2 (0.15, 0.10, 0.05) at 30‐min intervals, while Fico 2 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 Fio 2 0.15, buffered animals had higher arterial oxygen saturation (73 ± 5%) than the controls (55 ± 5%), ( P < 0.05). The control animals died after 1–29 min (mean 14 min) at Fio 2 0.10, while all buffered animals survived Fio 2 0.10 with stable MAP (122 ± 14 mmHg (16.3 ± 1.9 kPa). The buffered animals died after 4–22 min (mean 15 min) at Fio 2 0.05. We conclude that buffering to a pH of 7.21 attenuates the observed hemodynamic response in extreme hypercapnia and improves survival in hypercapnic hypoxemia.