D. Erni et al., Effects of epidural anaesthesia on microcirculatory blood flow in free flaps in patients under general anaesthesia, EUR J ANAES, 16(10), 1999, pp. 692-698
It has been suggested that epidural anaesthesia may increase blood flow in
free flaps on the lower extremity. The objective of the present study was t
o test this hypothesis in 21 patients undergoing reconstructive surgery of
the lower extremity with free muscle (n=8), fasciocutaneous (n=6) or muscul
ocutaneous (n=7) flaps. Microcirculatory blood flow was measured continuous
ly with a multichannel laser Doppler flowmetry, both in muscle and skin of
the free flap as well as in the intact skin and muscle on the same extremit
y. After completion of surgery, general anaesthesia was continued and the e
pidural block was induced by an injection of 2% lignocaine-hydrochloride in
to a pre-operatively inserted and tested epidural catheter. The epidural bl
ock caused no change in microcirculatory flow in the intact skin and muscle
, however, it resulted in a marked decrease in microcirculatory blood flow
in all the free flaps studied (20-30%; P < 0.05). The epidural block also c
aused a significant decrease in mean arterial blood pressure, from 85 (+/-
2.8) mmHg to 68 (+/- 2.8) mmHg (P < 0.01). It was concluded that epidural a
naesthesia may decrease microcirculatory blood flow in free flaps on the lo
wer extremity by diverting flow away from the flap to normal intact tissues
(a steal phenomenon).