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Microvascular hemoglobin oxygen saturation (SO 2 ) during prolonged hemorrhagic hypotension (HH)
Author(s) -
Torres Luciaeves,
Torres Ivo P,
Pittman Roland N
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a1150-b
Subject(s) - microcirculation , hemoglobin , hemodynamics , intravital microscopy , medicine , oxygenation , vascular resistance , respiratory system , blood flow , blood pressure , arteriole , oxygen saturation , mean arterial pressure , anesthesia , cardiology , hypoxia (environmental) , cardiac output , heart rate , chemistry , oxygen , organic chemistry
Since skeletal muscle represents up to 40% of body mass and suffers severe reductions in blood flow during HH, we examined the microcirculatory consequences of prolonged hypotension due to hemorrhage in the rat spinotrapezius muscle. An aortic transducer was implanted for continuous measurement of cardiac output. Systemic hemodynamic and respiratory variables were measured 7 days after the implantation. Functional capillary density, microvascular diameter, arteriolar SO 2 and hemoglobin concentration ([Hb]) were measured using intravital microscopy. Measurements were made before and up to 4 h after HH. Additional bleeding or lactated Ringer's infusion were used to maintain mean arterial pressure at 40 mmHg. Controls were subjected to the same procedures except HH. Fifty‐three percent of rats survived ≥ 3 h (S); others were considered nonsurvivors (NS). There was a positive correlation (r= 0.83, p ≤ 0.05) between microvascular SO 2 and respiratory rate in S. Significant differences between S and NS were obtained for arteriolar SO 2 (lower in S, p ≤ 0.05). Microvascular [Hb] was correlated with the systemic [Hb] (r= 0.93, p ≤ 0.001). Small arterioles constricted more in S than in NS, while large arterioles dilated in S. The diameter findings may explain why S showed higher total peripheral resistance levels for a longer period of time during HH. Our findings suggest that respiratory compensations and microvascular changes are essential for survival of prolonged HH. Support: DOD and NIH HL079087.