Unreliability of pulse contour-derived cardiac output in piglets simulating acute hemorrhagic shock and rapid volume expansion.
BACKGROUND
Pulse contour-derived cardiac output for continuous hemodynamic monitoring is becoming popular in critical care. However, the data regarding its reliability during acute hemodynamic instability are inconsistent. This study was conducted to determine whether pulse contour-derived cardiac output truly reflects rapid hemodynamic changes.


METHODS
Hemorrhagic shock was created in seven anesthetized piglets by continuous blood withdrawal at a rate of 1 mL . kg . min for 20 minutes. Volume expansion with 10% hydroxyethyl starch 8 mL . kg was then administered for 5 minutes. Pulse contour-derived and thermodilution- derived hemodynamic parameters were compared.


RESULTS
Baseline thermodilution-derived cardiac index was 3.2 +/- 0.4 L . min . M. After exsanguination, it decreased to 2.1 +/- 0.3 L . min . M while pulse contour-derived cardiac index increased to 4.4 +/- 0.4 L . min . M (p value <0.001). Thermodilution-derived systemic vascular resistance index (SVRI) increased to 2463 +/- 474 dyne . sec . cm . M while pulse contour-derived SVRI paradoxically decreased to 1047 +/- 368 dyne . sec . cm . M (p value <0.001). Following rapid volume expansion, thermodilution-derived cardiac index increased to 3.5 +/- 0.2 L . min . M while pulse contour-derived cardiac index decreased to 1.8 +/- 0.4 L . min . M (p value <0.001). Thermodilution-derived SVRI decreased to 2215 +/- 323 dyne . sec . cm . M while pulse contour-derived SVRI increased to 4105 +/- 1097 dyne . sec . cm . M (p value = 0.001).


CONCLUSIONS
Pulse contour-derived hemodynamic parameters do not accurately reflect rapid hemodynamic changes, and the trend may be misleading in piglets. Physicians are advised to interpret pulse contour-derived hemodynamic parameters with caution or to use invasive monitoring to guide treatment strategy therapy.
Department of Internal Medicine, Buddhist Tzu Chi General Hospital, Taipei Branch, Taipei, Taiwan.
Chih-Hsin
CH
Lee
Jann-Yuan
JY
Wang
Kuo-Liang
KL
Huang
Hung-Wen
HW
Chiu
Tsung-Ching
TC
Fei
Tsui-Shia
TS
Chen
Hung
H
Chang
D000465:Algorithms; D000704:Analysis of Variance; D000818:Animals; D001802:Blood Substitutes / Q000494:pharmacology; D002302:Cardiac Output; D004195:Disease Models, Animal; D006339:Heart Rate; D006439:Hemodynamics; D006895:Hydroxyethyl Starch Derivatives / Q000494:pharmacology; D008991:Monitoring, Physiologic / Q000379:methods*; D012771:Shock, Hemorrhagic / Q000503:physiopathology* / Q000628:therapy; D013552:Swine; D013815:Thermodilution / Q000379:methods
D001802:Blood Substitutes; D006895:Hydroxyethyl Starch Derivatives