| 1. |
- Broomé, Michael, et al.
(författare)
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Pressure-independent cardiac effects of angiotensin II in pigs.
- 2004
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Ingår i: Acta Anaesthesiol Scand. - 0001-6772 .- 1365-201X. ; 182:2, s. 111-9
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Angiotensin II (Ang II) is a potent vasoconstrictor with an important role in the development of cardiovascular disease. Earlier results have shown a positive acute inotropic effect of Ang II in anaesthetized pigs together with significant vasoconstriction. This investigation was designed to study cardiac effects of Ang II, when blood pressure was maintained constant by experimental means. METHODS: Ang II (200 microg h(-1)) was infused in anaesthetized pigs (n = 10) at two different arterial blood pressures, the first determined by the effects of Ang II alone, and the second maintained at baseline blood pressure with nitroprusside. Cardiac systolic and diastolic function was evaluated by analysis of left ventricular pressure-volume relationships. RESULTS: Heart rate, end-systolic elastance (Ees) and pre-load adjusted maximal power (PWRmax EDV(-2)) increased at both blood pressure levels, although less when blood pressure was kept constant with nitroprusside. The time constant for isovolumetric relaxation (tau(1/2)) was prolonged with Ang II alone and shortened with Ang II infused together with nitroprusside. CONCLUSION: Ang II infusion in the pig has inotropic and chronotropic properties independent of arterial blood pressure levels, although the effects seem to be blunted by pharmacological actions of the nitric oxide donor nitroprusside.
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| 2. |
- Osterlund, Barbro, et al.
(författare)
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Intracoronary beta2 receptor activation induces dynamic local t-PA release in the pig.
- 2003
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Ingår i: Thrombosis and haemostasis. - 0340-6245 .- 2567-689X. ; 90:5, s. 796-802
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Tidskriftsartikel (refereegranskat)abstract
- To investigate beta2 -adrenergic agonist-mediated effects on coronary fluxes of local fibrinolytic factors, healthy anaesthetised and instrumented pigs (n=10) were studied during infusion of isoprenaline (IPR) into the left main coronary artery. Coronary net fluxes of total t-PA antigen, active t-PA and total PAI-1 antigen were determined at baseline and at 3, 5, 7 and 10 minutes of IPR infusion. During IPR, net release of total t-PA increased in a biphasic pattern with transiently high levels at 3 (+440 %) and 7 minutes (+620%) and returned towards baseline at 10 minutes. Net coronary release of active t-PA increased with maximum levels at 3 minutes (+50%). Baseline coronary net flux of total PAI -1 showed a decrease which was most pronounced at 10 minutes. To conclude, a fast beta2 agonist-mediated local release of t-PA into the coronary vasculature was demonstrated. For total t-PA, this response was characterised by a biphasic release profile.
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| 3. |
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| 4. |
- Fröjse, R, et al.
(författare)
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Assessment of graded intestinal hypoperfusion and reperfusion using continuous saline tonometry in a porcine model.
- 2004
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Ingår i: Eur J Vasc Endovasc Surg. - : Elsevier BV. - 1078-5884 .- 1532-2165. ; 28:1, s. 79-88
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To evaluate effects of graded intestinal hypoperfusion and reperfusion on intestinal metabolic parameters as assessed by a modified continuous saline tonometry technique. MATERIALS: Twelve barbiturate-anaesthetized female pigs. METHODS: Measurements were performed prior to and during three predefined levels of superior mesenteric mean arterial blood pressure (P(SMA) 70, 50 and 30 mmHg, respectively, each 80 min long), obtained by an adjustable clamp around the origin of the superior mesenteric artery, and during reperfusion. We continuously measured jejunal mucosal perfusion (laser Doppler flowmetry), jejunal tissue oxygen tension (PO(2TISSUE); microoximetry) and intramucosal PCO(2) (continuous saline tonometry) and calculated net intestinal lactate production, mesenteric oxygenation, PCO(2) gap (jejunal mucosal PCO(2)-arterial PCO(2)) and pHi. RESULTS: At P(SMA) 70 and 50 mmHg mesenteric oxygen uptake and net lactate production remained unaltered, in spite of decreased oxygen delivery. At these P(SMA) levels PCO(2) gap increased, while pHi and PO(2TISSUE) decreased. At P(SMA) 30 mmHg pronounced increases in PCO(2) gap and mesenteric net lactate production as well as marked decreases in PO(2TISSUE) and pHi were demonstrated. Data indicate absence of anaerobic conditions at an intestinal perfusion pressure (IPP)> or =41 mmHg, a pHi> or =7.22 or PCO(2) gap< or =15.8 mmHg. CONCLUSIONS: Continuous saline tonometry detected intestinal ischemia as induced by graded reductions in IPP. A threshold could be defined above which intestinal ischemia does not occur.
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| 5. |
- Fröjse, R, et al.
(författare)
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Local metabolic effects of dopexamine on the intestine during mesenteric hypoperfusion.
- 2004
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Ingår i: Shock. - : Ovid Technologies (Wolters Kluwer Health). - 1073-2322 .- 1540-0514. ; 21:3, s. 241-7
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Tidskriftsartikel (refereegranskat)abstract
- This self-controlled experimental study was designed to test the hypothesis that dopexamine, a synthetic catecholamine that activates dopaminergic (DA-1) and beta2-adrenergic receptors, improves oxygenation in the jejunal mucosa during intestinal hypotension. In six normoventilated barbiturate-anesthetized pigs, controlled reductions in superior mesenteric arterial pressure (PSMA) was obtained by an adjustable clamp around the artery. Dopexamine infusions (0.5 and 1.0 microg.kg(-1).min(-1)) were administered at a freely variable PSMA (i.e., with the perivascular clamp fully open) and at a PSMA of 50 mmHg and 30 mmHg. We continuously measured superior mesenteric venous blood flow (QMES; transit-time ultrasonic flowmetry), jejunal mucosal perfusion (laser Doppler flowmetry), and tissue oxygen tension (PO2TISSUE; microoximetry). Jejunal luminal microdialysate of lactate, pyruvate, and glucose were measured every 5 min. Measurements of mucosal PCO2 (air tonometry), together with blood sampling and end-tidal PCO2 measurements, enabled calculations of pHi and PCO2 gap. Dopexamine reduced mesenteric vascular resistance and increased QMES at a PSMA of 50 mmHg and 30 mmHg. At a PSMA of 30 mmHg, dopexamine increased mesenteric oxygen delivery but did not influence mesenteric oxygen uptake or extraction. In this situation, dopexamine had no beneficial effect on jejunal mucosal blood flow. On the contrary, dopexamine increased mesenteric net lactate production and PCO2 gap, whereas PO2TISSUE and pHi decreased. Jejunal luminal microdialysate data demonstrated an increased lactate concentration and a pattern of decreased glucose concentration and increased luminal lactate-pyruvate ratio. These negative metabolic effects of dopexamine should be taken into account in situations of low perfusion pressures.
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| 6. |
- Haney, Michael, et al.
(författare)
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Analysis of left ventricular systolic function during elevated external cardiac pressures : an examination of measured transmural left ventricular pressure during pressure-volume analysis
- 2001
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Ingår i: Acta Anaesthesiol Scand. ; 45:7, s. 868-74
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Variations or disturbances in intrathoracic and extracardiac pressures (ECP) occur in critically ill and anaesthetised patients. There are uncertainties concerning the analysis of left ventricular pressure-volume relationship (LVPVR) and the calculation of systolic function parameters when conducted without reference to transmural left ventricular pressure (LVPtm) in the setting of elevated ECP. METHODS: In 7 anaesthetised adult pigs, we measured LVPVR using conductance volumetry and tip manometry along with measurement of pericardial and other intrathoracic pressures. Experimental pericardial infusion and pleural insufflation were performed. Transient controlled preload reductions were accomplished using balloon occlusion of the inferior vena cava. Preload recruitable stroke work (PRSW) was calculated using both intracavitary left ventricular pressure (LVPic) and LVPtm, and differences were tested for using a paired t-test. RESULTS: The pericardial and pleural interventions produced significant elevations in ECP. No difference in PRSW calculated using LVPic and LVPtm was detected. CONCLUSION: These results suggest that LVPtm need not be measured and included in LVPVR analysis of systolic function when there is significant external cardiac pressure. To be able to employ LVPVR analysis of systolic function without reference to LVPtm is important for simplified application in the clinical setting, particularly when elevated extracardiac pressures are suspected, or have been therapeutically induced, as with continuous positive pressure ventilation.
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| 7. |
- Haney, Michael, et al.
(författare)
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Heart-lung interactions during positive pressure ventilation : left ventricular pressure-volume momentary response to airway pressure elevation
- 2001
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Ingår i: Acta Anaesthesiologica Scandinavica. - : Wiley. - 0001-5172 .- 1399-6576. ; 45:6, s. 702-709
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Left ventricular (LV) pressure and volume changes are known to occur in response to positive airway pressure (PAP). We aimed to further describe the immediate LV response to increased PAP as demonstrated in successive heart cycles with LV pressure and volume alterations. We postulated that these acute systematic LV events during institution of PAP can follow a distinct pattern that would allow calculation of parameters of systolic function, including end-systolic elastance (Ees) and preload recruitable stroke work (PRSW). We also aimed to examine the relationship of PAP-derived Ees and PRSW to the same parameters derived from vascular occlusion. METHODS: Eight anesthetized adult pigs were studied with invasive circulatory measurements including LV pressure and volume (conductance). The PAP intervention was an airway pressure plateau of 15 cm H2O for 6 s (APP). Venous occlusion was performed by transient balloon inflation in the inferior vena cava (IVCO). Ees and PRSW were derived for each APP and IVCO intervention. RESULTS: Central circulatory variables during APP and IVCO are reported. LV systolic function parameters could be derived from each of the heart-lung interactions during APP sequences. Ees and PRSW derived from APP showed a significant positive bias in relation to those derived from the IVCO sequence. CONCLUSIONS: We conclude that the heart-lung interactions during APP of the magnitude and duration shown here can allow derivation of Ees and PRSW. These parameters are not interchangeable with Ees and PRSW derived from IVCO.
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| 8. |
- Haney, Michael, et al.
(författare)
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Method of preload reduction during LVPVR analysis of systolic function : airway pressure elevation and vena cava occlusion
- 2002
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Ingår i: Anesthesiology. ; 97:2, s. 436-46
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: A graded preload reduction during analysis of the left ventricular pressure-volume relationship (LVPVR) is required for derivation of end-systolic elastance (Ees) and preload recruitable stroke work (PRSW). The authors aimed to measure serial changes in these systolic function parameters before and during planned circulatory interventions using two different methods of preload alteration: a positive airway pressure plateau (APP) and inferior vena cava occlusion (IVCO). METHODS: In eight animals, measurements were made at 38 degrees, 30 degrees, 32 degrees, 34 degrees, and posthypothermia 38 degrees C. In an additional eight animals, isoflurane, adrenaline, and aorta occlusion (balloon catheter occluder) were administered in series, each with a preintervention control measurement. Left ventricular volume was measured by conductance. Paired measurements of the systolic function parameters Ees and PRSW, each derived with two preload methods, were analyzed for bias. RESULTS: Circulatory alterations were achieved with the temperature, isoflurane, adrenaline, and aorta occlusion interventions. Measured changes in Ees and PRSW from control to intervention showed a strong correlation and no significant bias for APP in relation to IVCO. The APP-derived absolute values for Ees and PRSW demonstrated a consistent positive bias compared with IVCO. CONCLUSION: The APP method for preload reduction during LVPVR analysis detected changes in Ees and PRSW during the circulatory interventions in this model that were not different than those detected using another preload reduction method, IVCO. APP and IVCO are not interchangeable methods for preload reductions during LVPVR absolute quantitation of systolic function, and each needs to be used serially.
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| 9. |
- Lehtipalo, Stefan, et al.
(författare)
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Cutaneous sympathetic vasoconstrictor reflexes for the evaluation of interscalene brachial plexus block
- 2000
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Ingår i: Acta Anaesthesiologica Scandinavica. - : Wiley. - 0001-5172 .- 1399-6576. ; 44:8, s. 946-952
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Tidskriftsartikel (refereegranskat)abstract
- Background: Although signs of sympathetic blockade following interscalene brachial plexus block include Horner’s syndrome, increased skin temperature and vasodilatation, the degree of sympathetic blockade is not easily determined. The aim of this study was, therefore, to use activation of cutaneous finger pad vasoconstrictor reflexes for description and quantification of the degree of sympathetic blockade following unilateral interscalene brachial plexus block.Methods: Eight patients scheduled for acromioplasty under general anesthesia were studied. An interscalene plexus catheter was inserted preoperatively on the side to be operated upon and used postoperatively for administration of bupivacaine, given as a bolus (1.25 mg kg−1) followed by a continuous infusion (0.25 mg kg−1 h−1). Skin blood flow (SBF) in the pad of the index finger was assessed by the laser Doppler technique, and regional skin vascular resistance (RVR) was calculated. The inspiratory gasp test (apnea at end‐inspiration) or a local heat provocation were used as provocations of the cutaneous microcirculation.Results: Interscalene brachial plexus block increased SBF and decreased RVR at rest, and produced satisfactory sensory and motor block. The inspiratory gasp test decreased SBF and increased RVR in the unblocked arm, while the opposite, increased SBF and decreased RVR, were observed during local heat provocation. In the blocked arm, these gasp‐induced cutaneous vasoconstrictor and heat‐induced vasodilator responses were attenuated.Conclusions: Interscalene brachial plexus block reduces regional sympathetic nervous activity, illustrated by increases in skin blood flow, skin temperature and attenuated vasoconstrictor responses to an inspiratory gasp. The inspiratory gasp vasoconstrictive response is a powerful and sensitive indicator for monitoring the sympathetic blockade following interscalene brachial plexus block.
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| 10. |
- Lehtipalo, Stefan, et al.
(författare)
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Does dopexamine influence regional vascular tone and oxygenation during intestinal hypotension?
- 2002
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Ingår i: Acta Anaesthesiol Scand. ; 46:10, s. 1217-26
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Local effects of dopexamine on intestinal vascular tone and oxygenation were investigated during intestinal hypotension. To this end, we employed an experimental model, in which the superior mesenteric arterial pressure (PSMA) was controlled by an adjustable perivascular clamp. This approach enabled us to keep the intestinal perfusion pressure (IPP) constant in the face of any systemic circulatory alterations. METHODS: In 11 barbiturate-anesthetized pigs, we instrumented the superior mesenteric circulation for assessments of vascular resistance (RMES), IPP, jejunal mucosal perfusion (Laser Doppler) and intestinal tissue oxygenation (microoximetry). Measurements were carried out before and during dopexamine infusions (0.5 and 1.0 micro g.kg-1.min-1) at a freely variable PSMA (i.e. the perivascular clamp fully open) and at a PSMA of 50 mmHg and 30 mmHg. RESULTS: At a constant PSMA of 50 mmHg, dopexamine had no significant intestinal vascular effects. However, at a constant PSMA of 30 mmHg, both doses of dopexamine were associated with decreases in RMES. Effects of dopexamine on intestinal oxygen delivery and extraction were minimal during these procedures, while a minor decrease in intestinal tissue oxygen tension was observed during dopexamine administration at the lowest IPP level. CONCLUSION: At very low intestinal perfusion pressures (approximately 30 mmHg) dopexamine produces intestinal vasodilation in excess of what is produced by intrinsic autoregulation. This suggests that there is a vasodilatory reserve in the intestine under such conditions and that a pharmacological vasodilator like dopexamine may improve intestinal circulation during regional severe hypotension.
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