Z. Ovadiatirosh et al., AN INTEGRATED NONINVASIVE SYSTEM FOR MONITORING THE MICROCIRCULATORY EFFECTS OF VASOACTIVE DRUGS - AN EXPERIMENTAL-STUDY, Microvascular research, 53(1), 1997, pp. 14-21
Background: No information is available on the effects of vasoactive d
rugs on the microcirculation and on the correlation between their effe
cts on the capillary and the systemic circulation. Purpose: To charact
erize the effects of nitroglycerin (NTG), nitroprusside (NP), and meta
raminol infusion on microcirculatory variables using a noninvasive mon
itoring system. Methods: Increasing doses of NTG (5-40 mu g/kg/min) an
d NP (5-20 mu g/kg/min) were intravenously infused to eight rabbits. T
he microcirculatory parameters were monitored by a combined noninvasiv
e system which included laser Doppler flowmetry (LDF), photoplethysmog
raph (PPG), and transcutaneous oxygen tension (tc-PO2). Mean blood pre
ssure (MBP) was measured simultaneously. Results: At maximal rate of N
TG infusion, the values of LDF, PPG, tc-PO2, and MBP were 72.2 +/- 23.
9, 234.7 +/- 165.6, 103.5 +/- 37.4, and 82.7 +/- 7.4% of baseline, res
pectively. Following NP infusion the LDF, PPG, tc-PO2, and MBP reached
70.8 +/- 24.1, 190.5 +/- 68.9, 70.0 +/- 14.7, and 75.6 +/- 14.6% of b
aseline, respectively. The tissue oxygenation was significantly reduce
d during NP infusion compared to NTG (P < 0.05). The values gradually
returned to the baseline 10 min after termination of NP infusion, but
not after NTG. After injection of 1 mg metaraminol there was a steep d
ecline in LDF, PPG, and tc-PO2 parallel to a significant increase in M
BP. When metaraminol was administered after injection of 0.1 mg phenox
ybenzamine, these changes were abolished. Conclusions: This noninvasiv
e system effectively monitors microcirculatory hemodynamic changes ind
uced by vasoactive drugs. NTG and NP cause similar changes in the syst
emic and microcirculatory bed, with the exception of peripheral oxygen
ation, which is reduced only during infusion of NP. The changes in the
microcirculatory bed following metaraminol and phenoxybenzamine imply
that their effects on the arterioles are mediated by adrenegic alpha-
receptors. (C) 1997 Academic Press.