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Effects of hypothermia 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.tb03718.x
Subject(s) - medicine , hypercapnia , hypoxemia , hypothermia , anesthesia , acidosis
Anesthetized, paralyzed and mechanically ventilated pigs were hypoventilated to extrene hypercapnia (Paco 2 ≅20 kPa) at Fio 2 0.5, and allotted to a hypothermic group (31.5 ±0.l°C, n = 6) or a control group (39.6±0.2°C, n = 6). Compared with the controls, the hypothermic animals had higher Pao 2 (19.2 vs 15.6 kPa, P >0.05), Sao 2 (97.2 vs 89.3%), Sv̈o 2 (78.7 vs 68.2%), end‐tidal 0 2 (34.5 vs 24.8 kPa) and arterial pH (7.01 vs 6.91), ( P >0.01), but lower Pv̈o 2 (7.0 vs. 10.2 kPa) and Paco 2 (13.2 vs 23.5 kPa), (P>0.01). Hypothermia reduced O 2 delivery (Do 2 ), O 2 consumption (Vo 2 ) and CO 2 production by 40–45% ( P > 0.05), but O 2 extraction ratio, i.e. VO 2 , Do 2 ‐ 1 . 100 (%), did not differ between groups. Hypothermic animals had lower heart rate (127 vs 223 beats.min‐ 1 , P >0.05) and cardiac output (2.5 vs 3.9 l.min‐ 1 , P>0.01). Subsequently, the inspired oxygen fraction (Fio 2 ) was decreased stepwise (0.3, 0.25, 0.21, 0.15, 0.10) at 30‐ min intervals. At Fio 2 0.3, the hypothermic group had higher Pao 2 (10.0 vs 5.7 kPa), Sao 2 (91.3 vs 28.5%), Pv̈o, (5.8 vs 3.4 kPa), Sv̈o 2 (70.7 vs 10.3%), end‐tidal O 2 (16.7 vs 8.5 kPa), O 2 delivery (344 vs 155 ml.min‐ 1 ), arterial pH (7.02 vs 6.94) and systemic vascular resistance (3850 vs 1652 dyn.s. cm‐ 5 (38500 vs 16520 μN. s. c m‐ 5 )) compared with the controls ( P >0.01), while Paco 2 was lower (12.4 vs 22.7 kPa), as well as O 2 extraction ratio (23 vs 63%) and O 2 half saturation tension (4.3 vs 8.0 kPa) ( P >0.01). Except for Pao 2 , all differences between groups remained significant at Fio 2 0.25. The control animals died during Fio 2 0.25 and 0.21, while all hypothermic animals remained circulatorily stable. One hypothermic animal died after 12 min at Fio 2 0.15 and the remainder after 6–39 min (mean 22 min) at Fio 2 0.10. We conclude that hypothermia markedly improves whole‐body oxygen balance, cardiovascular stability and survival in hypercapnic hypoxemia.