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Correspondence  |   February 2002
Extrapolating beyond the Data
Author Notes
  • DURECT Corporation, Cupertino, California.
Article Information
Correspondence
Correspondence   |   February 2002
Extrapolating beyond the Data
Anesthesiology 2 2002, Vol.96, 515-516. doi:
Anesthesiology 2 2002, Vol.96, 515-516. doi:
To the Editor:—
In my years as an editor of Anesthesiology and a reviewer for numerous journals, I frequently encountered submissions in which figures contained fitted curves (linear regression or other nonlinear functions) extrapolated beyond the range of measured X  values. Authors were often resistant to changing these figures to limit their predictions to the observed range of X  values. The folly of extrapolating beyond the observed range is seen in figure 4 in a recent review article in Anesthesiology 1 . The fitted function indicates that a decrease in blood volume increases cardiac output, certainly an unexpected and unphysiologic finding (and not supported by the data). Fortunately, the authors limited their extrapolation; had they extended their curve further, it would suggest that profound hypovolemia was desirable, certainly not the authors’ intention.
Reference
Reference
Liu S, McDonald SB: Current issues in spinal anesthesia. A nesthesiology 2001; 94: 888–906Liu, S McDonald, SB