Clinical physiology and functional imaging
-
Clin Physiol Funct Imaging · Mar 2004
Randomized Controlled Trial Clinical TrialDifferential effects of peripheral ketamine and lidocaine on skin flux and hyperalgesia induced by intradermal capsaicin in humans.
The capsaicin-induced flux in the primary and secondary hyperalgesic area after pretreating the capsaicin injection site with local ketamine, lidocaine or saline 10 min prior to injection was examined in this study. Twelve healthy volunteers participated in two randomized, double-blinded, placebo-controlled, cross-over experiments. In the first experiment, the skin on the volar forearm was pretreated with s.c. ketamine or saline, 10 min prior to capsaicin injection. ⋯ Only lidocaine reduced spontaneous pain, evoked pain and areas of hyperalgesia, whereas ketamine had no effect. Our results suggest that there is no simple and close relation between vascular and sensory reactions to pharmacological manipulation following intradermal capsaicin injection. We propose distinct mechanisms for local lidocaine and ketamine based on the differential effects of local lidocaine and ketamine on flux and pain.
-
Clin Physiol Funct Imaging · Nov 2003
Comparative Study Clinical Trial Controlled Clinical TrialQuantification of inspiratory-induced vasoconstrictive episodes: a comparison of laser Doppler fluxmetry and photoplethysmography.
Laser Doppler fluxmetry (LDF) or photoplethysmography (PPG) are frequently used as non-invasive tools to assess skin blood flow. They are both thought to be suitable and interchangeable methods for the detection of sympathetically activated vasoconstrictive episodes that can be provoked by a voluntary deep inspiration (DI), the so-called inspiratory gasp response (IGR). However, a rigorous comparison of the two methods has not been reported in the literature. ⋯ Overall correlation of IGR amplitude detected with LDF and PPG was significant (r=0.433). Surprisingly, there was a continuous increase of the correlation coefficient from the first (r=0.105) or second (r=-0.184) IGR to the fifth (r=0.727) IGR. This implies that experimental data obtained with PPG and LDF are not equivalent and that one has to be cautious regarding the comparison and interpretation of results obtained with these two different methods.
-
Clin Physiol Funct Imaging · Sep 2003
Assessment of adipose tissue metabolism by means of subcutaneous microdialysis in patients with sepsis or circulatory failure.
To evaluate the role of adipose tissue in the metabolic stress response of critically ill patients, the release of glycerol and lactate by subcutaneous adipose tissue was assessed by means of microdialysis in patients with sepsis or circulatory failure and in healthy subjects. Patients with sepsis had lower plasma free fatty acid concentrations and non-significant elevations of plasma glycerol concentrations, but higher adipose-systemic glycerol concentrations gradients than healthy subjects or patients with circulatory failure, indicating a stimulation of subcutaneous adipose lipolysis. They also had a higher lipid oxidation. ⋯ These observations highlight major differences in lipolysis and lipid utilization between patients with sepsis and circulatory failure. Hyperlactataemia was present in both groups of patients, but the adipose-systemic lactate concentration gradient was not increased, indicating that lactate production by adipose tissue was not involved. This speaks against a role of adipose tissue in the development of hyperlactataemia in critically ill patients.
-
Clin Physiol Funct Imaging · Jul 2003
Cerebral oxygenation monitor during head-up and -down tilt using near-infrared spatially resolved spectroscopy.
Reflectance near-infrared spectroscopy (NIRS) has become a suitable and easily manageable method to monitor cerebral oxygenation changes in presyncopal and syncopal symptoms caused by postural changing or standing. A new clinical tissue oxygenation monitor has been recently developed which measures absolute tissue haemoglobin saturation (Tissue Oxygenation Index, TOI) utilizing spatially resolved spectroscopy (SRS). The present study examined the effects of postural changes on cerebral oxygenation as reflected in SRS-NIRS findings. ⋯ A significant session effect was observed in the left forehead TOI during SUP, but not in the right. SRS-NIRS measurements confirmed sub-clinical alterations of cortical oxygenation during HUT. NIRS data from the left side of the forehead, which may vary with cognitive or emotional activation, were more variable than those from the right side.
-
Clin Physiol Funct Imaging · May 2003
Oxygen tension under hyperbaric conditions in healthy pig brain.
To investigate the effect of hyperbaric conditions on brain oxygenation, intracranial pressure and brain glucose/lactate levels in healthy non-brain-traumatized animals. ⋯ If there is a need for increased oxygenation in the brain, then one way to achieve this is to apply hyperbaric conditions at 100% oxygen. Compared with an atmospheric pressure with a FiO2 of 0.4, a nine-fold increase (900%) in PbrO2 values can be reached by increasing the FiO2 to 1.0 and the pressure to 2.8 bar. In this study, hyperbaric oxygen pressure in the brain did not lead to changes in intracranial pressure or in brain glucose/lactate levels.