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  • 1
    Electronic Resource
    Electronic Resource
    Pharmacodynamic model of the haemodynamic effects of pinacidil in normotensive volunteers (1993)
    Springer
    European journal of clinical pharmacology 44 (1993), S. 177-182 
    Details
    ISSN: 1432-1041
    Keywords: Pinacidil ; Pharmacodynamic model ; effect-compartment model ; potassium channel activator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The concentration-effect relationships of pinacidil, a peripheral vasodilator, have been measured in 12 healthy adults who received placebo or pinacidil 25 mg daily for 1 week in a cross-over experiment. Diastolic blood pressure (DBP) and heart rate (HR) were recorded and blood samples were taken on days 1 and 7. Plasma drug concentration-time data were fitted by a biexponential function with zero-order input. The pharmacokinetic model was incorporated into a combined pharmacokinetic-dynamic model (PK-PD) using the Hill equation, which has three parameters: n, the sigmoidicity parameter, Emax the maximum effect and EC50 the concentration which gives 50% of Emax. For ΔDBP, the parameter medians were estimated as n=5, EC50=44.6 ng · ml−1 and Emax=13.5 mm Hg. A hysteresis loop was found when ΔHR was plotted against concentration, which could be fitted by a linear effect compartment model. Simulations showed that experimental ΔDBP points on Day 7 could be predicted from a simulated curve computed by the model using parameters estimated on Day 1. Using the simulation, it was possible to suggest an optimal dosage regimen for pinacidil tablets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00315477
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  • 2
    Electronic Resource
    Electronic Resource
    Hypotensive and peripheral vascular effects in healthy volunteers of repeated oral administration of pinacidil (1989)
    Springer
    European journal of clinical pharmacology 37 (1989), S. 527-529 
    Details
    ISSN: 1432-1041
    Keywords: pinacidil ; vasodilatation ; plethysmography ; calf blood flow ; hypotension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The hypotensive and peripheral vascular effects of two different oral formulations of pinacidil were investigated in twelve healthy male volunteers. Arterial blood pressure, heart rate and calf blood flow were measured on Days 1 and 7. The vasodilator activity of both formulations was confirmed by a significant increase in calf blood flow on both days, which was correlated with a significant decrease in diastolic blood pressure. There was no differences between the tablet and the pellet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00558137
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  • 3
    Electronic Resource
    Electronic Resource
    Changes in skin thermal clearance during anaesthesia (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 41 (1986), S. 0 
    Details
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Thermal and vascular side effects occuring during general anaesthesia are related to skin blood flow. A new, noninvasive probe which measures skin thermal clearance, a variable closely related to skin blood flow, was used in nine patients under phenoperidine, droperidol, propanidid anaesthesia. Statistically significant increases in skin thermal clearance clearly preceded the drop in mean arterial blood pressure and the rise in skin temperature. It is concluded that general anaesthesia induced an early increase in skin blood flow and that thermal clearance is a better technique than skin thermometry to monitor skin blood flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2044.1986.tb13223.x
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of thiopental on middle cerebral artery blood velocities: a transcranial Doppler study in children (1993)
    Springer
    Child's nervous system 9 (1993), S. 220-223 
    Details
    ISSN: 1433-0350
    Keywords: Intracranial pressure ; Middle cerebral artery ; Blood flow velocity ; Thiopental ; Transcranial pulsed ; Doppler ; Head injury
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of an intravenous injection of thiopental on middle cerebral artery blood velocities was assessed by transcranial pulsed Doppler monitoring in 20 children: ten head-injured patients and ten control subjects. Thiopental induced a moderate but immediate decrease of middle cerebral artery blood velocities in both groups; this variation was significant (P〈0.01) and more prolonged in the head-injured than in control patients. Transcranial Doppler ultrasonography thus appears to be suitable for monitoring children in intensive care units and could help to avoid the use of thiopental in patients with low cerebral artery blood flow velocity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00303573
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  • 5
    Electronic Resource
    Electronic Resource
    Simplified model of laser Doppler signals during reactive hyperaemia (2000)
    Springer
    Medical & biological engineering & computing 38 (2000), S. 80-87 
    Details
    ISSN: 1741-0444
    Keywords: Laser Doppler flowmetry ; Model ; Reactive hyperaemia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Laser Doppler flowmetry (LDF) is a non-invasive method to measure tissue blood flow. During reactive hyperaemia, the LDF signal increases to a peak and then returns to a resting value. A simplified model is developed to explain these variations. The emphasis is on simulating the effects occurring rather than on trying to mimic the anatomical structure of the microcirculation. A single blood vessel is therefore analysed. The increasing value of blood velocity is studied, and vasodilatation as well as vasoconstriction are taken into account. The model parameters are calculated using wavelets. For a 2-min occlusion on a healthy subject, the radius of the vessel is initially 15 μm, increasing to 24.6 μm at the peak, reached 14 s after the release of the occlusion. The model shows that the high value of the LDF signal during the initial phase of reactive hyperaemia is produced by an increasing number of erythrocytes in a cross-section, due to vasodilatation rather than an increase in moving blood cell velocities. Moreover, the rapidity of the vasodilatation and vasoconstriction effects determine the rapidity of the signal variations. The paper aims to give a basic solution to develop a numerical model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02344693
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of posture, hypotension and locally applied vasoconstriction on the middle ear microcirculation in anaesthetized humans (1994)
    Springer
    European journal of applied physiology 69 (1994), S. 414-420 
    Details
    ISSN: 1439-6327
    Keywords: Middle ear blood flow regulation ; Laser ; Doppler flowmetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Studies by laser-Doppler flowmetry of middle ear microcirculation changes induced by physical and chemical stimuli in the animal have only recently been made. This prospective study, performed in humans, was designed to compare the effects of a postural manoeuvre (headup tilt 30°), hypotension and locally applied vasoconstriction on middle ear blood flow during anaesthesia. Circulatory changes provoked by a headup tilt of 30°, and successive intravenous boluses of potent vasodilators, were compared with circulatory changes provoked by locally applied adrenaline, in ten healthy patients in good physical states undergoing middle ear surgical repair. Heart rate and direct arterial pressure were continuously recorded via a radial artery cannula. Middle ear blood flow was continuously recorded via a laser-Doppler probe placed on the promontorium cavi tympani. Metabolic parameters (partial pressure of O2 and CO2 in arterial blood, pH, arterial lactate concentrations) and arterial concentrations of propofol were measured just before and just after the experiment. Headup tilt did not modify heart rate, mean arterial pressure or middle ear blood flow. Vasodilators (nicardipine, nitroprusside, nitroglycerin) provoked a fall in arterial pressure (P〈0.0001,P〈0.0001,P〈0.019, respectively), but did not induce any significant variations in heart rate; variations occurred in middle ear blood flow (P〉0.05, not significant) which were different according to patients and agents. Locally applied adrenaline provoked a fall in the middle ear blood flow (P〈0.0012), with no effect on heart rate and arterial pressure. There were no significant changes in metabolic values, or propofol serum concentrations. The behaviour of the middle ear blood flow submitted to hypotension, posture, or to vasoconstriction could be related to counteracting regulatory responses and/or to direct vascular effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00865405
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  • 7
    Electronic Resource
    Electronic Resource
    Skin blood flow changes in anaesthetized humans: comparison between skin thermal clearance and finger pulse amplitude measurement (1986)
    Springer
    European journal of applied physiology 54 (1986), S. 574-577 
    Details
    ISSN: 1439-6327
    Keywords: Cutaneous microcirculation ; Skin temperature ; Hypotension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of general anaesthesia on skin blood flow in the left hand, measured by a new non-invasive probe using the thermal clearance method was examined. A mercury silastic gauge was placed around the third left finger and the plethysmographic wave amplitude was recorded to measure changes in finger pulse amplitude. Heart rate (HR), mean arterial blood pressure (MABP) and skin temperature were also recorded. General anaesthesia was induced by droperidol and phenoperidine injection and propanidid infusion in eight female patients. Skin thermal clearance, plethysmographic wave amplitude, HR, MABP and skin temperature were 0.40±0.02 w · m−1
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00943343
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  • 8
    Electronic Resource
    Electronic Resource
    Finger and forearm vasodilatatory changes after local cold acclimation (1990)
    Springer
    European journal of applied physiology 60 (1990), S. 49-53 
    Details
    ISSN: 1439-6327
    Keywords: Cold acclimation ; Ischaemia ; Exercise ; Peripheral
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To determine the vascular changes induced by local cold acclimation, post-ischaemia and exercise vasodilatation were studied in the finger and the forearm of five subjects cold-acclimated locally and five non-acclimated subjects. Peak blood flow was measured by venous occlusion plethysmography after 5 min of arterial occlusion (PBFisc), after 5 min of sustained handgrip at 10% maximal voluntary contraction (PBFexe), and after 5 min of both treatments simultaneously (PBFisc+exe). Each test was performed at room temperature (25° C, SE 1 C) (non-cooled condition) and after 5 min of 5'C cold water immersion (cooled condition). After the cold acclimation period, the decrease in skin temperature was more limited in the cold-acclimated compared to the non-acclimated (P〈0.01). The PBFisc was significantly reduced in the cooled condition only in the cold-acclimated subjects (finger: 8.4 ml · 100 ml−1 · min−1, SE 1.1,P〈0.01; forearm: 5.8 ml · 100 ml−1 · min−1, SE 1.5,P〈0.01) compared to the non-cooled condition. Forearm PBFexe was significantly decreased in the cooled condition only in the cold-acclimated subjects (non-cooled: 7.4 ml · 100 ml−1 · min−1, SE 1.2; cooled: 3.9 ml · 100 ml−1 ·min−1, SE 2.6,P〈0.05) indicating that muscle blood flow was also reduced. The application of PBFisc+exe elicited an increase in peak blood flow only in the forearm of the non-acclimated subjects (non-cooled: 10.4 ml· 100 ml−1 · min−1, SE 2.0; cooled: 14.3 ml · 100 ml−1 · min−1, SE 2.6,P〈0.05) and conversely only in the finger of the cold-acclimated (non-cooled finger: 25.7 ml · 100 ml−1 · min−1, SE 4.4; cooled finger: 19.2 ml · 100 ml−1 · min−1, SE 3.3,P〈0.01). Therefore, subjects cold-acclimated locally showed decreased vasodilatatory responses only when exposed to cold.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00572185
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of hypotension on cutaneous and subcutaneous blood flow in anaesthetized humans (1991)
    Springer
    European journal of applied physiology 63 (1991), S. 205-209 
    Details
    ISSN: 1439-6327
    Keywords: Hypotension ; Nitroglycerin ; Sodium nitroprusside ; Cutaneous and subcutaneous blood flow ; Heat clearance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The aim of this study was to determine the effect of controlled hypotension on subcutaneous and cutaneous haemodynamics in humans. Moderate hypotension was achieved with nitroglycerin (NTG) and sodium nitroprusside (SNP) infusion during narconeuroleptanalgesia in seven patients. Subcutaneous and cutaneous blood flow were measured by a superficial and deep heat clearance (HC) technique. The mean arterial pressure ( $$\overline {BP} _a $$ ) decreased by 23%–30% and heart rate (f c) increased but only during NTG infusion (+22%; P 〈 0.02). Subcutaneous and cutaneous blood flows remained unchanged despite a significant decrease in calculated cutaneous resistance (NTG: −26%, P 〈 0.01; SNP: −34%, P 〈 0.02)) and subcutaneous vascular resistance changed only with SNP (−31%, P 〈 0.02). After hypotension was discontinued the subcutaneous blood flow decreased (−13%, P = 0.05), whereas subcutaneous vascular resistance returned to its control values. An inverse relationship was found between f c and $$\overline {BP} _a $$ (NTG: r = −0.525, P 〈 0.01; SNP: r = −0.622, P 〈 0.01) as well as with subcutaneous blood flow (NTG: r = −0.653, P 〈 0.001; SNP: r = −0.573, P 〈 0.01). In addition, we found oscillatory changes in deep HC values which differed in magnitudes (NTG 0.22 (SEM 0.09) W · m−1 · °C−1 vs SNP 0.42 (SEM 0.1) W · mt−1 · °C−1, P〈 0.01) and frequencies (NTG 0.02 (SEM 0.006) Hz vs SNP 0.01 (SEM 0.002) Hz, P 〈 0.01). Despite unchanged blood flow, the effects of controlled hypotension on cutaneous and subcutaneous haemodynamics were different depending on the type of drug. These differences may have been related to counterregulatory responses and/or to direct vascular effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233849
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  • 10
    Electronic Resource
    Electronic Resource
    Cutaneous and subcutaneous blood flow during general anaesthesia (1988)
    Springer
    European journal of applied physiology 57 (1988), S. 601-605 
    Details
    ISSN: 1439-6327
    Keywords: Heat clearance ; Skin blood flow ; Subcutaneous blood flow ; Anaesthesia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The vasodilator effect of anaesthetic agents on cutaneous vessels has often been investigated. In contrast, although subcutaneous tissue is concerned with metabolism and thermoregulation, the effects of anaesthesia on subcutaneous blood flow have not been well documented. The purpose of this study was to determine the magnitude of changes in cutaneous and subcutaneous blood flow during general anaesthesia in Man. Anaesthesia was induced with flunitrazepam in 15 patients before facial plastic surgery. Blood flow was estimated using heat thermal clearance (HC). Two HC sensors in different areas allowed the measurement of superficial and deep HC. Systolic (SABP), diastolic (DABP) and mean arterial blood pressure (MABP), heart rate (HR), and rectal and mean skin temperature were also recorded. After induction of anaesthesia, HR increased significantly (p〈0.05) whereas SABP, DABP and MABP remained unchanged. The rectal-toe temperature gradient fell from 6.3±4.1° C to 3.4±1.1° C (p〈0.01) suggesting a reduction in vasomotor tone. Superficial HC increased from 0.37±0.06 to 0.42±0.08 W · m−1 · ° C−1 (p〈0.05) whereas deep HC decreased from 0.33±0.07 to 0.31±0.09 W · m−1 · ° C−1 (NS) and returned to the control value thereafter. Rectal temperature and mean skin temperature were unchanged. The changes in deep HC are similar to those previously observed in muscle during induction of anaesthesia. Our results show that anaesthesia mainly affects cutaneous blood flow, without any significant change in subcutaneous blood flow during the early phase of anaesthesia in human beings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418469
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