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Lower body impedance for the evaluation of venovenous bypass flow
Author(s) -
Ejlersen E,
Sode P,
Skak C,
Rasmussen A,
Espersen K,
Kirkegaard P,
Secher N H
Publication year - 1997
Publication title -
liver transplantation and surgery
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.814
H-Index - 150
eISSN - 1527-6473
pISSN - 1074-3022
DOI - 10.1002/lt.500030208
Subject(s) - medicine , splanchnic , inferior vena cava , derivation , cardiology , anesthesia , cardiac output , surgery , blood flow , hemodynamics , artery
Inferior vena cava (IVC) clamping during liver transplantation causes venous congestion in the splanchnic and IVC beds. A venovenous bypass relieves congestion and improves cardiac output (CO), but the bypass flow required for adequate drainage of the vascular beds is controversial. In this study we evaluated the bypass flow necessary to compensate for the IVC clamping. Lower body impedance (BI) is inversely related to tissue fluid content and was used to reflect congestion. A venovenous bypass was successfully applied to 59 of 62 patients. BI was measured across the left buttock and related to bypass flow, CO, bypass flow ratio (bypass flow/CO before IVC clamping; n = 62), and right femoral venous pressure (n = 8). The bypass flow was 1.7 (0.0‐3.0) L.min −1 (median and range). BI decreased (Δ BI; ‐2.2 [(−10.3‐1.1)] Ω) as the femoral venous pressure increased (29 [21‐49] mm Hg; r = ‐ 0.81; P < .05), and the femoral venous pressure correlated inversely to bypass flow ( r = ‐0.35; P < .01). The change in CO at IVC clamping (Δ CO; ‐2.3 [‐6.3‐1.6] L.min −1 ) related to bypass flow ratio (0.25 [0‐0.51]; r = 0.57, P < .01), whereas Δ BI related only minimally to bypass flow or bypass flow ratio ( r = 0.37; P < .05). In conclusion the median bypass flow of 1.7 L.min −1 was too small to prevent fluid accumulation in the lower caval region, and extrapolation of data suggests that bypass flow should have approached 3.5 L.min −1 or 50% of CO in order to prevent fluid accumulation in the lower caval region. However the minimal correlation between lower BI and bypass flow indicates that bypass flow per se is not the only determinant of lower body fluid accumulation.