Hemodynamic effects of prostacyclin infusions in healthy volunteers

Remodelling of the superficial vascular network of skin flaps in rats, following a vasodilatory cream application, before elevation

Flap necrosis on random pattern skin flaps continues to be a challenge. In this study, we evaluated whether topical application of a vasodilator substance (the prostaglandin PGI₂ analogue, Iloprost^®, in cream form) as pre-treatment, would increase blood flow and improve flap viability. Wistar rats randomly allocated into four groups with 7 rats per group and two flaps 4cm × 2cm in the same rat i.e. 56 flaps were developed. Flaps on the wright side received pre-treatment with Cream in different drug concentrations, 2.5μgr/gr, 5 μgr/gr, and 10μgr/gr and 20 μgr/gr containing the active factor Iloprost^®® ZK 36,374(M. W 360.5) prepared with white petrolatum as a base. Flaps on the left side received placebo cream (white petrolatum). After 10 days of flap pre-treatment, evaluation of blood flow by laser Doppler flowmetry (LDF) were recorded, then flap elevation and re suturing back were performed. After 7 days we estimated flap viability on digital imaging and the percentages of flap survival estimated. Means and standard deviations were used to describe blood flow measurements and survival percentages. The significance was set at 0.05 in all cases and the analysis were carried out with the use of the SPSS v23.0. Furthermore, we performed dynamic analyses of circulation using the radioisotope 99mTc which confirmed hyperaemia of the treated areas relative to that observed in control areas. These findings demonstrated that pretreatment of skin flaps with Iloprost^® cream for 10 days prior to elevation increased blood flow in the flap and improved their overall survival rate.

Effects of intravenous administration of prostacyclin on regional blood circulation in awake rats

1. The effects of intravenous infusion of prostacyclin (PGI2, 0.1, 0.2, 0.3 and 1.0 microg kg(-1) min(-1) lasting 5 min) on regional blood flow and regional vascular resistance have been studied in awake rats using the radioactive microsphere method. 2. The control values of blood flow to the heart, kidney, small intestine, hind limb muscle, pericranial skin and brain as well as the corresponding vascular resistance were not modified by an i.v. infusion (0.1 ml min(-1)) of Tris-buffer (the vehicle of PGI2). 3. The i.v. infusion of PGI2 produced graded dose-dependent decreases of MAP (r=0.87, P<0.001; ED20=0.73 [0.13-2.55] microg kg(-1) min(-1)) as well as decreases of vascular resistance in the heart (r=0.83, P<0.001; ED30=0.17 [0.09-0.31] microg kg(-1) min(-1)), pericranial skin (r=0.88, P<0.001; ED30=0.28 [0.18-0.43] microg kg(-1) min(-1)) and small intestine (r=0.74, P<0.001; ED30=0.21 [0.11-0.39] microg kg(-1) min(-1)), which led to dose-related increases of blood flow to these territories. 4. On the contrary, PGI2 increased vascular resistance in skeletal muscle (r=0.73, P<0.001; ED30=0.20 [0.10-0.39] microg kg(-1) min(-1)) with corresponding reductions in blood flow. The low doses reduced renal blood flow but there were no significant changes during the high ones. Cerebral vessels did not dilate during any infusion of PGI2 and cerebral blood flow decreased as MAP fell (r=0.56, P<0.01). 5. We conclude that, in awake rats, the coronary vessels are extremely sensitive to the vasodilating effect of PGI2 and that the mesenteric vessels and those of the pericranial skin are very responsive too. Moreover, autoregulation is inefficient to maintain cerebral blood flow during infusion of PGI2.

Evaluation of microangiopathy of the skin in patients with non-insulin-dependent diabetes mellitus by laser Doppler flowmetry; microvasodilatory responses to beraprost sodium

To determine the relationship of skin microangiopathy and other diabetic microvascular complications, we measured changes in skin blood flow after the administration of the prostacyclin (PGI2) analogue, beraprost sodium (BPS), in 82 patients with non-insulin-dependent diabetes mellitus and 20 healthy subjects. The diabetic patients had various degrees of retinopathy and nephropathy. Using laser Doppler flowmetry we measured skin blood flow at the dorsum of the right big toe at various times after the administration of 40 micrograms BPS and calculated the blood flow change (delta flux = peak flux--basal flux). We also determined the ankle pressure index (API), an ankle/brachial systolic pressure ratio. The basal blood flow was higher in healthy subjects than in diabetic patients (P < 0.001). BPS significantly increased blood flow in both diabetic patients and healthy subjects (P < 0.001). In all 102 subjects delta flux was positively correlated with the API (R = 0.40, P < 0.001). Despite no differences in API among the diabetic retinopathy and nephropathy subgroups, the delta flux in diabetic patients with progressive retinopathy and macroalbuminuria was significantly lower than in healthy subjects or in diabetic patients with less severe retinopathy and nephropathy (P < 0.05). The results suggested that BPS increases skin blood flow and the flow increase induced by BPS is related partly to the levels of API. The effect of BPS on skin blood flow decreased with an increases in the severity of retinopathy and nephropathy. Diabetic skin microangiopathy appears to coexist with other microvascular diabetic complications and may be proportional to their severity.

Peripheral macro- and microcirculation in short-term insulin-dependent diabetes mellitus: the role of prostaglandins in early haemodynamic changes

To determine whether vasodilator prostaglandins are involved in the peripheral hyperperfusion observed in patients with short-term insulin-dependent diabetes mellitus (IDDM), forearm and skin blood flow were studied before and after cyclooxygenase inhibition. Skin nutritive (CBV: capillary blood-cell velocity) and thermoregulatory (LDF: laser-Doppler fluxmetry), and forearm (muscle) blood flow (FBF) were measured before and after 500 mg acetylsalicylic acid (ASA) infused intravenously in 14 short-term IDDM patients and 22 healthy control subjects. In the IDDM patients, baseline LDF (median: 27 (19-35); interquartile range) vs. 17 (15-23) pu) and FBF (3.4 (2.5-4.1) vs. 2.6 (2.2-2.9) ml 100 ml-1 min-1) were increased, while CBV (0.70 (0.40-1.33) vs. 0.69 (0.41-0.96) mm s-1) was unchanged compared to healthy controls. ASA infusion had similar effects on baseline CBV, LDF, and FBF in patients and controls. In eight of the control subjects the role of prostaglandins in the regulation of basal peripheral blood flow was studied before and after ASA and placebo infusion. The changes in baseline CBV, LDF, and FBF were similar after ASA and placebo infusion in healthy controls. In conclusion, in short-term IDDM patients, increased skin thermoregulatory and forearm (muscle) blood flow are probably not related to vasodilator prostaglandins. Furthermore, prostaglandins are not likely to be involved in regulating basal peripheral blood flow in healthy man.

Effects of prostacyclin infusion on blood pressure and plasma renin activity in patients with essential hypertension

The effects of prostacyclin infusion (6.7 +/- 2.7 ng/kg/min, 3 to 10 ng/kg/min) on blood pressure, plasma renin activity (PRA), and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) were studied in 7 patients with essential hypertension (4 men and 3 women) with a mean age of fifty-eight +/- eleven years (forty-six to seventy-four years). The baseline value of 6-keto-PGF1 alpha for patients with essential hypertension was not lower than in healthy subjects. Blood pressure immediately dropped following prostacyclin infusion. Systolic blood pressure returned to the baseline value after prostacyclin infusion was discontinued. However, diastolic blood pressure and mean arterial blood pressure were still significantly decreased thirty minutes after termination of infusion. Heart rate did not change during prostacyclin infusion but decreased significantly when infusion was terminated. PRA was not significantly affected by prostacyclin infusion. The 6-keto-PGF1 alpha level was about 8 times higher than the baseline value thirty minutes after initiation of prostacyclin infusion and approximately twice as high as the baseline value thirty minutes after termination of infusion. The decrease in mean arterial blood pressure coincided with the increase in 6-keto-PGF1 alpha. There was no correlation between mean arterial blood pressure and PRA, nor between PRA and 6-keto-PGF1 alpha. These results demonstrate that production of prostacyclin is not reduced in patients with essential hypertension, and heart rate and PRA are not changed by prostacyclin infusion, although prostacyclin decreases blood pressure.