Skin blood flow. Laser Doppler flowmetry provides
continuous real-time qualitative measurement of cutaneous
microvascular blood flow (14,18). An estimate of SKBF
was obtained via a Perimed Periflux 4001 Master Multichannel
Laser Doppler system (Perimed Ltd., Ja¨rfa¨lla,
Sweden). Previous laser Doppler flow studies have shown
that the maximum depth of penetration of the signal ranges
from 1 mm (23) to 0.4 mm (26). Thus, the derived results
will be purely based at the cutaneous or skin level and would
be unaffected by deeper underlying muscle (21). The laser
Doppler power spectrum density operates in a frequency
range of 0–8.2 Hz representative of the skin blood flow
(15). Two skin probes were employed in this study. Both
were placed on the anterior aspect of the subject’s right
thigh. Site 1 was placed at the mid line of the thigh half way
between the anterior superior iliac spine and the tibial tuberosity.
Site 2 was placed 5 cm distal to the site of lignocaine
injection and hence muscle thermistor insertion. At
both sites the probes were placed in areas where visually
noted blood vessels were absent in order to obtain SKBF
from cutaneous capillaries rather than major vessel readings.
Such precise positioning allowed reproduction of the site
both within and between trials