Publications (3)4.36 Total impact
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Article: Blood flow autoregulation in pedicled flaps.
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ABSTRACT: Clinical work on the blood perfusion in skin and muscle flaps has suggested that some degree of blood flow autoregulation exists in such flaps. An autoregulatory mechanism would enable the flap to protect itself from changes in the perfusion pressure. The purpose of the present study was to evaluate if, and to what extent, a tissue flap could compensate a reduction in blood flow due to an acute constriction of the feed artery. Further, we wanted to examine the possible role of smooth muscle L-type calcium channels in the autoregulatory mechanism by pharmacological intervention with the L-type calcium channel blocker nimodipine and the vasodilator papaverine. Pedicled flaps were raised in pigs. Flow in the pedicle was reduced by constriction of the feed artery (n=34). A transit time flow probe measured the effect on blood flow continuously. Following this, three different protocols were followed: (1) Time control (n=10): the procedure described above was repeated in the same flap to determine whether autoregulatory efficiency changed over time. (2) Nimodipine infusion (n=13): continuous intra-arterial infusion of nimodipine (0.2mg/ml, 0.5 ml/min) started when the flow had returned to the initial value. After stabilisation, the flow was reduced. When the flow had been stable for at least 5 min, the constriction was removed. (3) Nimodipine and papaverine (n=8): the infusion of nimodipine was followed by an intra-arterial bolus of papaverine (10mg). After stabilisation, the flow in the pedicle was reduced and the flow was recorded. The flaps showed a strong autoregulatory response with complete compensation for flow reductions of up to 70-80%. Infusion of nimodipine caused a 28+/-10% increase in blood flow and removed the autoregulation. Papaverine caused a further increase in blood flow by 61+/-19%. The time control experiments proved that the experimental procedure was reproducible and stable over time. A tissue flap can nearly completely compensate for repeated flow reductions of up to 70-80%. This is due to a decrease in the peripheral resistance, mediated by a local intrinsic mechanism. Nimodipine (a blocker of L-type voltage-activated calcium channels) abolishes the autoregulation, but a significant vasodilatory reserve exists, as an additional injection of papaverine (a smooth muscle relaxant) results in a further increase in the blood flow. This strongly suggests a direct role for voltage-activated calcium channels in the autoregulatory process.Journal of Plastic Reconstructive & Aesthetic Surgery 03/2009; 62(12):1671-6. · 1.49 Impact Factor -
Article: Evaluation of tissue oxygen measurements for flap monitoring in an animal model.
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ABSTRACT: Tissue oxygen tension (p(ti)O(2)) measurements are common in neurosurgery but uncommon in plastic surgery. We examined this technique as a monitoring method with probe placement in the subcutaneous tissue and addressed the importance of probe placement. Myocutaneous flaps were raised in an animal model and p(ti)O(2) measurements performed at different levels in the subcutaneous fat. Flap artery and vein were occluded until a 50% p(ti)O(2) reduction had occurred (T(1/2)). We found no significant effect of depth (P>0.10) on the level of p(ti)O(2). T(1/2)(arterial) was 7.2 minutes and T(1/2)(venous) was 18 minutes. We found no significant relation between initial levels of p(ti)O(2) and T(1/2). Location of the probe and absolute p(ti)O(2) value is of little relevance for flap monitoring. It is the relative change in p(ti)O(2) that is important. The p(ti)O(2) technique is well suited for monitoring in the subcutaneous tissue and is highly sensitive to changes in both arterial and venous blood flow.Journal of Reconstructive Microsurgery 08/2008; 24(6):391-6. · 1.43 Impact Factor -
Article: Validation of a 1-mm transit time flow probe and the potential for use in microsurgery.
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ABSTRACT: The objective of this study was to validate a prototype transit time ultrasound flow probe (Medi-Stim Butterfly Flowmeter BF 2004) of only 1 mm and to evaluate its potential for use in microsurgery. Knowledge of the ability of this kind of system to measure flow in small vessels and at small flow rates did not previously exist. The experimental design was an in vitro study using the median artery of 15-kg pigs. The vessel was perfused by the pigs' own heparinated blood, at a known flow rate, using a Gemini infusion pump. The infusion rate was increased stepwise, starting at 1 ml/min until 16 ml/min. Transit time flow was measured continuously. The results showed very accurate flow measurements at all flow rates when compared to the known infusion rate of the Gemini pump. However, at flow rates below 4 ml/min, variation became a problem.Journal of Reconstructive Microsurgery 11/2006; 22(7):519-24. · 1.43 Impact Factor
