Minimum hematocrit at differing cardiopulmonary bypass temperatures in dogs

David J. Cook, Thomas A. Orszulak, Richard C. Daly

Research output: Contribution to journalArticle

50 Citations (Scopus)

Abstract

Background - The purpose of this study was to determine the minimum hematocrit (Hct) supporting cerebral oxygenation over the range clinically relevant cardiopulmonary bypass (CPB) temperatures in dogs. The effect of hemodilution on cerebral blood flow (CBF), cerebral metabolic rate (CMRO2), and cerebral oxygen delivery (CDO2) was determined over a range of Hcts during CPB at 38°C, 28°C, and 18°C. Methods and Results - Measurements were obtained at target CPB temperature and after progressive normovolemic hemodilution in 3 groups of 8 anesthetized animals. Dextran 70 (6%) was used as a diluent. CBF was measured by use of the sagittal sinus outflow technique. CMRO2 and CDO2 were calculated by the use of standard formulae. In each temperature group, hemodilution was associated with a reciprocal rise in CBF. As Hot was reduced to 0.10±0.02 at 38°C, 28°C, and 18°C, CBF increased 260%, 220%, and 160% of the control nonhemodiluted value. Increases in CBF helped compensate for decreased arterial oxygen content and maintain CDO2. With progressive temperature reduction, these compensatory flow increases were reduced and CDO2 was decreased at lesser degrees of hemodilution. Statistical analysis indicated that cerebral oxygen demand was maintained to an Hct of 0.14, 0.11, and ≤0.10 in the 38°C, 28°C, and 18°C groups; however, physiologically important changes in cerebral oxygen supply occur at Hcts of ≃0.18, 0.15, and 0.12, respectively, at those temperatures. Conclusions - This investigation systematically characterizes the critical Hct supporting cerebral oxygenation at differing CPB temperatures. Over a range of CPB temperatures, the curve describing the relationship between Hct and cerebral oxygen balance has a broad plateau, indicating cerebral tolerance for a wide range of Hcts. The minimum Hct that supports cerebral oxygenation is shifted leftward as temperature is reduced, but the reduction in critical Hct is not proportional to the reduction in CMRO2. Although we do not advocate hemodilution to these extreme values, we find that these data provide a physiological foundation for our hemodilution practice and may provide some guidance for management of Her as body temperature changes during CPB.

Original languageEnglish (US)
JournalCirculation
Volume98
Issue number19 SUPPL.
StatePublished - Nov 10 1998

Fingerprint

Cerebrovascular Circulation
Cardiopulmonary Bypass
Hematocrit
Hemodilution
Dogs
Temperature
Oxygen
Body Temperature Changes
Dextrans

Keywords

  • Blood flow
  • Brain
  • Cardiopulmonary bypass
  • Hemoglobin
  • Metabolism

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

Cite this

Cook, D. J., Orszulak, T. A., & Daly, R. C. (1998). Minimum hematocrit at differing cardiopulmonary bypass temperatures in dogs. Circulation, 98(19 SUPPL.).

Minimum hematocrit at differing cardiopulmonary bypass temperatures in dogs. / Cook, David J.; Orszulak, Thomas A.; Daly, Richard C.

In: Circulation, Vol. 98, No. 19 SUPPL., 10.11.1998.

Research output: Contribution to journalArticle

Cook, DJ, Orszulak, TA & Daly, RC 1998, 'Minimum hematocrit at differing cardiopulmonary bypass temperatures in dogs', Circulation, vol. 98, no. 19 SUPPL..
Cook DJ, Orszulak TA, Daly RC. Minimum hematocrit at differing cardiopulmonary bypass temperatures in dogs. Circulation. 1998 Nov 10;98(19 SUPPL.).
Cook, David J. ; Orszulak, Thomas A. ; Daly, Richard C. / Minimum hematocrit at differing cardiopulmonary bypass temperatures in dogs. In: Circulation. 1998 ; Vol. 98, No. 19 SUPPL.
@article{db0734a66d2849a58dff2f1f54f17aae,
title = "Minimum hematocrit at differing cardiopulmonary bypass temperatures in dogs",
abstract = "Background - The purpose of this study was to determine the minimum hematocrit (Hct) supporting cerebral oxygenation over the range clinically relevant cardiopulmonary bypass (CPB) temperatures in dogs. The effect of hemodilution on cerebral blood flow (CBF), cerebral metabolic rate (CMRO2), and cerebral oxygen delivery (CDO2) was determined over a range of Hcts during CPB at 38°C, 28°C, and 18°C. Methods and Results - Measurements were obtained at target CPB temperature and after progressive normovolemic hemodilution in 3 groups of 8 anesthetized animals. Dextran 70 (6{\%}) was used as a diluent. CBF was measured by use of the sagittal sinus outflow technique. CMRO2 and CDO2 were calculated by the use of standard formulae. In each temperature group, hemodilution was associated with a reciprocal rise in CBF. As Hot was reduced to 0.10±0.02 at 38°C, 28°C, and 18°C, CBF increased 260{\%}, 220{\%}, and 160{\%} of the control nonhemodiluted value. Increases in CBF helped compensate for decreased arterial oxygen content and maintain CDO2. With progressive temperature reduction, these compensatory flow increases were reduced and CDO2 was decreased at lesser degrees of hemodilution. Statistical analysis indicated that cerebral oxygen demand was maintained to an Hct of 0.14, 0.11, and ≤0.10 in the 38°C, 28°C, and 18°C groups; however, physiologically important changes in cerebral oxygen supply occur at Hcts of ≃0.18, 0.15, and 0.12, respectively, at those temperatures. Conclusions - This investigation systematically characterizes the critical Hct supporting cerebral oxygenation at differing CPB temperatures. Over a range of CPB temperatures, the curve describing the relationship between Hct and cerebral oxygen balance has a broad plateau, indicating cerebral tolerance for a wide range of Hcts. The minimum Hct that supports cerebral oxygenation is shifted leftward as temperature is reduced, but the reduction in critical Hct is not proportional to the reduction in CMRO2. Although we do not advocate hemodilution to these extreme values, we find that these data provide a physiological foundation for our hemodilution practice and may provide some guidance for management of Her as body temperature changes during CPB.",
keywords = "Blood flow, Brain, Cardiopulmonary bypass, Hemoglobin, Metabolism",
author = "Cook, {David J.} and Orszulak, {Thomas A.} and Daly, {Richard C.}",
year = "1998",
month = "11",
day = "10",
language = "English (US)",
volume = "98",
journal = "Circulation",
issn = "0009-7322",
publisher = "Lippincott Williams and Wilkins",
number = "19 SUPPL.",

}

TY - JOUR

T1 - Minimum hematocrit at differing cardiopulmonary bypass temperatures in dogs

AU - Cook, David J.

AU - Orszulak, Thomas A.

AU - Daly, Richard C.

PY - 1998/11/10

Y1 - 1998/11/10

N2 - Background - The purpose of this study was to determine the minimum hematocrit (Hct) supporting cerebral oxygenation over the range clinically relevant cardiopulmonary bypass (CPB) temperatures in dogs. The effect of hemodilution on cerebral blood flow (CBF), cerebral metabolic rate (CMRO2), and cerebral oxygen delivery (CDO2) was determined over a range of Hcts during CPB at 38°C, 28°C, and 18°C. Methods and Results - Measurements were obtained at target CPB temperature and after progressive normovolemic hemodilution in 3 groups of 8 anesthetized animals. Dextran 70 (6%) was used as a diluent. CBF was measured by use of the sagittal sinus outflow technique. CMRO2 and CDO2 were calculated by the use of standard formulae. In each temperature group, hemodilution was associated with a reciprocal rise in CBF. As Hot was reduced to 0.10±0.02 at 38°C, 28°C, and 18°C, CBF increased 260%, 220%, and 160% of the control nonhemodiluted value. Increases in CBF helped compensate for decreased arterial oxygen content and maintain CDO2. With progressive temperature reduction, these compensatory flow increases were reduced and CDO2 was decreased at lesser degrees of hemodilution. Statistical analysis indicated that cerebral oxygen demand was maintained to an Hct of 0.14, 0.11, and ≤0.10 in the 38°C, 28°C, and 18°C groups; however, physiologically important changes in cerebral oxygen supply occur at Hcts of ≃0.18, 0.15, and 0.12, respectively, at those temperatures. Conclusions - This investigation systematically characterizes the critical Hct supporting cerebral oxygenation at differing CPB temperatures. Over a range of CPB temperatures, the curve describing the relationship between Hct and cerebral oxygen balance has a broad plateau, indicating cerebral tolerance for a wide range of Hcts. The minimum Hct that supports cerebral oxygenation is shifted leftward as temperature is reduced, but the reduction in critical Hct is not proportional to the reduction in CMRO2. Although we do not advocate hemodilution to these extreme values, we find that these data provide a physiological foundation for our hemodilution practice and may provide some guidance for management of Her as body temperature changes during CPB.

AB - Background - The purpose of this study was to determine the minimum hematocrit (Hct) supporting cerebral oxygenation over the range clinically relevant cardiopulmonary bypass (CPB) temperatures in dogs. The effect of hemodilution on cerebral blood flow (CBF), cerebral metabolic rate (CMRO2), and cerebral oxygen delivery (CDO2) was determined over a range of Hcts during CPB at 38°C, 28°C, and 18°C. Methods and Results - Measurements were obtained at target CPB temperature and after progressive normovolemic hemodilution in 3 groups of 8 anesthetized animals. Dextran 70 (6%) was used as a diluent. CBF was measured by use of the sagittal sinus outflow technique. CMRO2 and CDO2 were calculated by the use of standard formulae. In each temperature group, hemodilution was associated with a reciprocal rise in CBF. As Hot was reduced to 0.10±0.02 at 38°C, 28°C, and 18°C, CBF increased 260%, 220%, and 160% of the control nonhemodiluted value. Increases in CBF helped compensate for decreased arterial oxygen content and maintain CDO2. With progressive temperature reduction, these compensatory flow increases were reduced and CDO2 was decreased at lesser degrees of hemodilution. Statistical analysis indicated that cerebral oxygen demand was maintained to an Hct of 0.14, 0.11, and ≤0.10 in the 38°C, 28°C, and 18°C groups; however, physiologically important changes in cerebral oxygen supply occur at Hcts of ≃0.18, 0.15, and 0.12, respectively, at those temperatures. Conclusions - This investigation systematically characterizes the critical Hct supporting cerebral oxygenation at differing CPB temperatures. Over a range of CPB temperatures, the curve describing the relationship between Hct and cerebral oxygen balance has a broad plateau, indicating cerebral tolerance for a wide range of Hcts. The minimum Hct that supports cerebral oxygenation is shifted leftward as temperature is reduced, but the reduction in critical Hct is not proportional to the reduction in CMRO2. Although we do not advocate hemodilution to these extreme values, we find that these data provide a physiological foundation for our hemodilution practice and may provide some guidance for management of Her as body temperature changes during CPB.

KW - Blood flow

KW - Brain

KW - Cardiopulmonary bypass

KW - Hemoglobin

KW - Metabolism

UR - http://www.scopus.com/inward/record.url?scp=0345563278&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0345563278&partnerID=8YFLogxK

M3 - Article

C2 - 9852900

AN - SCOPUS:0345563278

VL - 98

JO - Circulation

JF - Circulation

SN - 0009-7322

IS - 19 SUPPL.

ER -