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Correspondence  |   March 2000
Hemodilution: Fewer Keystrokes, Greater Accuracy
Author Notes
  • Associate Professor of Anesthesiology
  • Baltimore Veterans Affairs Medical Center
  • Department of Anesthesiology
  • University of Maryland at Baltimore
  • Baltimore, Maryland 21201-1566
Article Information
Correspondence
Correspondence   |   March 2000
Hemodilution: Fewer Keystrokes, Greater Accuracy
Anesthesiology 3 2000, Vol.92, 902. doi:
Anesthesiology 3 2000, Vol.92, 902. doi:
To the Editor:—
I found the article by Monk et al.  1 a valuable contribution to the transfusion literature, especially because they included timely cost-effectiveness data. I am pleased to see the increasing interest in perioperative acute normovolemic hemodilution, evidenced by recent articles in ANESTHESIOLOGY 1 and elsewhere. 2,3 Perioperative acute normovolemic hemodilution can spare many surgical patients exposure to allogeneic blood. 4 Articles discussing hemodilution frequently refer to Gross’s formula for estimating allowable blood loss 5 :
Allowable blood loss = (Estimated blood volume)
×[(Hctstart− Hctfinal)/Hctaverage]
This formula was an ingenious approximation to the original formula described in 1974. 6 The original theoretical equation, which has been verified in several clinical studies, 4–7 involved the solution of a differential equation that resulted in a formula requiring the computation of natural logarithms:
Allowable blood loss = (Estimated blood volume)
×[ln(Hctstart/Hctfinal)]
In 1974, computing natural logs was inconvenient for the practicing clinician. However, now virtually everyone has access to inexpensive, solar-powered, lightweight, hand-held calculators that easily compute natural logs. Therefore, anyone can use the theoretical formula rather than an approximation. And it actually requires fewer keystrokes to compute a more accurate result.
References
Monk TG, Goodnough LT, Brecher ME, Colberg JW, Andriole GL, Catalona WJ: A prospective randomized comparison of three blood conservation strategies for radical prostatectomy. A NESTHESIOLOGY 1999; 91:24–33Monk, TG Goodnough, LT Brecher, ME Colberg, JW Andriole, GL Catalona, WJ
Habler OP, Kleen MS, Podtschaske AH, Hutter JW, Tiede M, Kemming GI, Welte MV, Corso CO, Messmer KF: The effect of acute normovolemic hemodilution (ANH) on myocardial contractility in anesthetized dogs. Anesth Analg 1996; 83:451–8Habler, OP Kleen, MS Podtschaske, AH Hutter, JW Tiede, M Kemming, GI Welte, MV Corso, CO Messmer, KF
McLoughlin TM, Fontana JL, Alving B, Mongan PD, Bunger R: Profound normovolemic hemodilution: Hemostatic effects in patients and in a porcine model. Anesth Analg 1996; 83:459–65McLoughlin, TM Fontana, JL Alving, B Mongan, PD Bunger, R
Ness PM, Bourke DL, Walsh PC: A randomized trial of perioperative hemodilution versus transfusion of preoperatively donated autologous blood in elective surgery. Transfusion 1992; 32:226–30Ness, PM Bourke, DL Walsh, PC
Gross JB: Estimating allowable blood loss: Corrected for dilution. A NESTHESIOLOGY 1983; 58:277–80Gross, JB
Bourke DL, Smith TC: Estimating allowable hemodilution. A NESTHESIOLOGY 1974; 41:609–12Bourke, DL Smith, TC
Ward CF, Meathe EA, Benumof JL, Trousdale F: A computer normogram for blood loss replacement. A NESTHESIOLOGY 1980; 53:S126Ward, CF Meathe, EA Benumof, JL Trousdale, F