An integrated noninvasive system for monitoring the microcirculatory effects of vasoactive drugs: an experimental study.
BACKGROUND
No information is available on the effects of vasoactive drugs on the microcirculation and on the correlation between their effects on the capillary and the systemic circulation.


OBJECTIVE
To characterize the effects of nitroglycerin (NTG), nitroprusside (NP), and metaraminol infusion on microcirculatory variables using a noninvasive monitoring system.


METHODS
Increasing doses of NTG (5-40 microg/kg/min) and NP (5-20 microg/kg/min) were intravenously infused to eight rabbits. The microcirculatory parameters were monitored by a combined noninvasive system which included laser Doppler flowmetry (LDF), photoplethysmograph (PPG), and transcutaneous oxygen tension (tc-PO2). Mean blood pressure (MBP) was measured simultaneously.


RESULTS
At maximal rate of NTG 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, respectively. 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 baseline, respectively. The tissue oxygenation was significantly reduced 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 decline in LDF, PPG, and tc-PO2 parallel to a significant increase in MBP. When metaraminol was administered after injection of 0.1 mg phenoxybenzamine, these changes were abolished.


CONCLUSIONS
This noninvasive system effectively monitors microcirculatory hemodynamic changes induced by vasoactive drugs. NTG and NP cause similar changes in the systemic and microcirculatory bed, with the exception of peripheral oxygenation, 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 adrenergic alpha-receptors.
Ovadia-Tirosh
Z
Z
Sackler School of Medicine, Tel-Aviv University, Tel Hashomer, 52621, Israel.
Kornowski
R
R
Walden
R
R
Chayen
D
D
Gavish
B
B
Battler
A
A
Eldar
M
M
D000704:Analysis of Variance; D000818:Animals; D016903:Drug Monitoring / Q000379:methods*; D005260:Female; D007262:Infusions, Intravenous; D007275:Injections, Intravenous; D008680:Metaraminol / Q000494:pharmacology; D008833:Microcirculation / Q000187:drug effects*; D005996:Nitroglycerin / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism; D010313:Partial Pressure; D011817:Rabbits; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D014665:Vasodilator Agents / Q000494:pharmacology*
D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009599:Nitroprusside; D008680:Metaraminol; D005996:Nitroglycerin; D010100:Oxygen