Anaesthesia in the fourth dimension. Is biological scaling relevant to veterinary anaesthesia?

Abstract

Fundamental laws, such as gravity and thermodynamics, are in common use in the physical sciences but are less applicable to biology. However, although there are fewer biological laws relative to other disciplines, the ones that exist are of great importance, e.g. natural selection. Another example may be a new law of biological network design which explains observations on how metabolic rate changes as organisms change size. It has been known for some time that as animal size increases its metabolic rate falls ( Rubner, 1883 Rubner M Ueber den Einfluss der Körpergrösse auf Stoffund. Kraftwechsel Z Biol. 1883; 19: 535-562 Google Scholar ; Kleiber, 1932 Kleiber M Body size and metabolism. Hilgardia. 1932; 6: 315-353 Crossref Google Scholar ; Adolph, 1949 Adolph EF Quantitative relations in the physiological constitutions of mammals. Science. 1949; 109: 579-585 Crossref PubMed Scopus (368) Google Scholar ; Schmidt-Nielsen, 1984 Schmidt-Nielsen K Why Is Animal Size So Important? Cambridge University Press, Cambridge, UK1984: 56-74 Google Scholar ; Calabrese, 1991 Calabrese EJ Scaling: An attempt to find a common denominator. in: Principles of Animal Extrapolation Lewis. 1991: 449-527 Google Scholar ). This has developed from a physiological curiosity to a tool that is used extensively to predict drug effects across species ( Lave et al., 1999 Lave T Portmann R Schenker G Gianni A Guenzi A Girometta M-A Schmitt M Interspecies pharmacokinetic comparisons and allometric scaling of Napsagatran, a low molecular weight thrombin inhibitor. J Pharm Pharmacol. 1999; 51: 85-91 Crossref PubMed Scopus (55) Google Scholar ). The function of this article is to review the development of this concept, and to examine its application in veterinary anaesthesia.