NORMOVOLEMIC HEMODILUTION AND HYPEROXIA HAVE NO EFFECT ON FRACTAL DIMENSION OF REGIONAL MYOCARDIAL PERFUSION IN DOGS

Hypervolaemic haemodilution makes myocardial perfusion more homogenous as reflected by reduced fractal dimension of regional myocardial perf usion. The clinically more commonly performed acute normovolaemic haem odilution, however, has not yet been studied in this respect. Hyperoxi c ventilation with 100% oxygen is used in conjunction with haemodiluti on to compensate for low oxygen content by increasing physically disso lved oxygen in plasma. Since hyperoxia is known to cause disturbance i n microcirculatory regulation we studied the effects of acute normovol aemic haemodilution to haematocrit (hct) 20 +/- 1% and hyperoxia on re gional myocardial perfusion heterogeneity in 22 anaesthetized dogs usi ng fractal and correlation analysis. Regional myocardial perfusion was assessed with radioactive microspheres. The results of the study were that heart rate, blood volume and arterial pressure were unchanged du ring haemodilution. Cardiac index was 3.6 +/- 0.7 L min(-1) m(-2) befo re and 4.6 +/- 0.7 L min(-1) m(-2) after haemodilution (P < 0.05). Fra ctal dimension (D) of regional myocardial perfusion was 1.17 +/- 0.10 at baseline. Neither haemodilution (D = 1.19 +/- 0.10) nor hyperoxia ( D = 1.17 +/- 0.10) altered fractal properties of regional myocardial p erfusion. Spatial correlation of blood flow to adjacent tissue samples before haemodilution was 0.58 +/- 0.15. Haemodilution and hyperoxia d id not significantly influence spatial correlation (0.57 +/- 0.12 vs. 0.60 +/- 0.09; ns). We conclude that neither acute normovolaemic haemo dilution nor haemodilution in combination with hyperoxic ventilation a lter physiological myocardial perfusion heterogeneity.