Slow-wave flowmotion in rabbit skeletal muscle after acute fixed-volume hemorrhage.

Laser Doppler flux (LDF) was used to detect flowmotion (regular cyclic alterations in red blood cell flux) in the left gastrocnemius muscle of 14 rabbits that were bled 30% of their blood volume and let to recover spontaneously for 30 min. Only rabbits that met stated inclusion criteria during control conditions were used in the study. During control conditions when femoral artery pressure averaged 68 mm Hg (range 60-80), no animal displayed regular flowmotion. After the end of the acute hemorrhage, arterial pressure was 35 mm Hg (20-51) and slow wave flowmotion appeared instantaneously in 13 of the 14 animals. The maximum relative amplitude of the induced flowmotion was 31% (7-100) and the frequency was 1.8 cycles per minute (cpm) (1.4-4.0). Flowmotion persisted throughout the 30 min observation period in 11 animals, during which time arterial pressure recovered to 46 mm Hg (42-50). Fast-wave flowmotion was not detected in the present study. These results suggest that slow-wave flowmotion as measured with LDF is not a phenomenon characteristic of normal regulation of blood flow in skeletal muscle. After a 30% fixed-volume hemorrhage, slow-wave flowmotion is induced as arterial pressure drops below a certain threshold.