Biomedical subjects

E Kuusela

Publications and source records attributed to E Kuusela.

11 recordsLinked to original sources

PubMed2004

Sedimentation dynamics of spherical particles in confined geometries.

We study the steady-state dynamics of sedimenting non-Brownian particles in confined geometries with full hydrodynamic interactions at small but finite Reynolds numbers. We employ extensive computer simulations using a method where a continuum liquid phase is coupled through Stokesian friction to a discrete particle phase. In particular, we consider a sedimentation box which is otherwise periodic except that it is confined by two parallel walls parallel to gravity with a spacing Lx. By systematically varying Lx we explore the change in dynamics from a quasi-two-dimensional (2D) case to a three-dimensional case. We find that in such confined geometries there is a depletion of particle number density at the walls for small volume fractions, while for large volume fractions there is an excess number of particles at the walls. For the average sedimentation velocity, we find that the Richardson-Zaki law is well obeyed but the decrease of the velocity for dilute systems is slower for smaller values of Lx. We study the anisotropy of the velocity fluctuations and find that in the direction of gravity there is excellent agreement with the predicted scaling with respect to Lx. We also find that the behavior of the corresponding diffusion coefficients as a function of Lx is qualitatively different in the direction parallel to gravity and perpendicular to it. In the quasi-2D limit where particles block each other, the velocity fluctuations behave differently from the other confined systems.

Journal Article↗

PubMed2003

Collective effects in settling of spheroids under steady-state sedimentation.

We study the settling dynamics of non-Brownian prolate spheroids under steady-state sedimentation. We consider the case of moderate particle Reynolds numbers properly taking into account the hydrodynamic effects. For small volume fractions, we find an orientational transition of the spheroids, characterized by enhanced density fluctuations. Around the transition, the average settling velocity has a maximum which may even exceed the terminal velocity of a single spheroid, in accordance with experiments.

Journal Article↗

PubMed2003

A comparison of propofol infusion and propofol/isoflurane anaesthesia in dexmedetomidine premedicated dogs.

The effects of propofol infusion were compared with propofol/isoflurane anaesthesia in six beagles premedicated with 10 microg/kg intramuscular (i.m.) dexmedetomidine. The suitability of a cold pressor test (CPT) as a stress stimulus in dogs was also studied. Each dog received isoflurane (end tidal 1.0%, induction with propofol) with and without CPT; propofol (200 microg/kg/min, induction with propofol) with and without CPT; premedication alone with and without CPT in a randomized block study in six separate sessions. Heart rate and arterial blood pressures and gases were monitored. Plasma catecholamine, beta-endorphin and cortisol concentrations were measured. Recovery profile was observed. Blood pressures stayed within normal reference range but the dogs were bradycardic (mean heart rate < 70 bpm). PaCO2 concentration during anaesthesia was higher in the propofol group (mean > 57 mmHg) when compared with isoflurane (mean < 52 mmHg). Recovery times were longer with propofol than when compared with the other treatments. The mean extubation times were 8 +/- 3.4 and 23 +/- 6.3 min after propofol/isoflurane and propofol anaesthesia, respectively. The endocrine stress response was similar in all treatments except for lower adrenaline level after propofol infusion at the end of the recovery period. Cold pressor test produced variable responses and was not a reliable stress stimulus in the present study. Propofol/isoflurane anaesthesia was considered more useful than propofol infusion because of milder degree of respiratory depression and faster recovery.

Anesthesia↗

PubMed2002

Some factors influencing the level of clinical sedation induced by medetomidine in rabbits.

Rabbits (n=23) received intravenous bolus medetomidine at 100 mug/kg. Prior to medetomidine administration, heart and respiratory rates were measured, arterial blood was collected and analysed for plasma cortisol, glucose and albumin concentrations. Fifteen minutes after medetomidine administration, heart and respiratory rates were measured again and sedation was scored. The rabbit was afterwards anaesthetized with 20 mg/kg ketamine administered intravenously to enable spinal tap and heart puncture. Cerebrospinal fluid (CSF) was collected (this occurred 20 min post medetomidine administration) and analysed for medetomidine concentration. Blood was collected by heart puncture immediately after the spinal tap and analysed for serum medetomidine concentration. Cerebrospinal fluid medetomidine concentration correlated negatively with sedation. Serum medetomidine correlated positively with CSF medetomidine concentration. Cerebro-spinal fluid medetomidine was 17 +/- 13% of serum medetomidine concentration. Plasma cortisol and glucose concentrations correlated negatively with serum medetomidine. We conclude that after an intravenous bolus administration of a low sedative dose of medetomidine to rabbits; CSF concentration of the drug correlate negatively with sedation and that this may be because of the fact that only the free and unbound medetomidine may be available for detection in the CSF, the concentration of medetomidine detected in the CSF was much lower than that in blood and a positive correlation exists between CSF and serum medetomidine concentrations. Stress may have some effect on the distribution or metabolism of medetomidine in rabbits.

Animals↗

PubMed2002

24-hour Holter-monitoring in the perianaesthetic period in dogs premedicated with dexmedetomidine.

Baseline and perianaesthetic 24-hour Holter recordings were carried out in six healthy beagles. After dexmedetomidine premedication anaesthesia was induced with propofol and maintained with propofol infusion or isoflurane for one hour. Dexmedetomidine alone was used as control. The recordings were analysed for ventricular premature complexes (VPC), atrioventricular (AV) blocks and mean heart rate/hour (HR). In most recordings, no ventricular arrhythmias were detected, the maximum frequency being two VPCs/24 h. VPCs were not seen during anaesthesia or during the recovery period. The development of second-degree AV-blocks varied from dog to dog. Most of the heart blocks were seen during the premedication period when bradycardia was most prominent. During the subsequent night, HR was similar between treatments and did not differ from that seen on the baseline recordings. In beagles treated with dexmedetomidine alone or combined with propofol or propofol/isoflurane, ventricular arrhythmias were not detected more frequently than those reported in healthy non-anaesthetised dogs.

Anesthesia, General↗

PubMed2001

Double-blind evaluation of implants of gold wire at acupuncture points in the dog as a treatment for osteoarthritis induced by hip dysplasia.

Thirty-eight dogs with hip dysplasia were studied to evaluate the use of gold wire implants at acupuncture points around the hip joints. They were assigned at random into two groups of 19. In the treated group, gold wire was inserted through hypodermic needles at electrically found acupuncture points around both hips. In the control group, the areas were prepared in the same way but had only the skin pierced at sites which were not acupuncture points, with a needle of the same size as that used in the treated group. Over a period of six months the dogs were studied repeatedly by two veterinarians and by the dogs' owners who were unaware of the treatments the dogs had received; they assessed the dogs' locomotion, hip function and signs of pain. Radiographs were taken at the beginning and end of the study. Although the data collected from both groups by the veterinarians and the owners showed a significant improvement of locomotion and reduction in signs of pain (P=0.036 for the veterinary evaluation and locomotion and P=0.0001 and P=0.0034 for the owners' evaluation of locomotion and pain, respectively), there were no statistically significant differences between the treated and control groups (P=0.19 and P=0.41, P=0.24, respectively).

Acupuncture Analgesia↗

PubMed2001

Velocity correlations and diffusion during sedimentation.

We study the dynamics of sedimenting non-Brownian particles under steady-state conditions in two-dimensional geometry. We concentrate on the autocorrelation functions of the velocity fluctuations and the corresponding memory functions and diffusion coefficients as functions of Phi(V) for small but finite Reynolds numbers. For the numerical simulations we have chosen the model of Schwarzer [Phys. Rev. E 52, 6461 (1995)] where a continuum liquid phase is coupled through Stokesian friction to a discrete particle phase with volume fraction Phi(V). We find that the steady-state velocity fluctuations are spatially highly anisotropic and the correlation functions parallel to gravity have nonexponential time dependence similar to that of purely dissipative systems with strong interactions. The corresponding memory functions also show nontrivial behavior. Diffusion along the direction of gravity is much faster than perpendicular to it, with the anisotropy decreasing as either the Reynolds number or the volume fraction increases.

Journal Article↗

PubMed2001

Comparison of medetomidine and dexmedetomidine as premedicants in dogs undergoing propofol-isoflurane anesthesia.

OBJECTIVE: To compare 3 dose levels of medetomidine and dexmedetomidine for use as premedicants in dogs undergoing propofol-isoflurane anesthesia. ANIMALS: 6 healthy Beagles. PROCEDURE: Dogs received medetomidine or dexmedetomidine intravenously at the following dose levels: 0.4 microg of medetomidine or 0.2 microg of dexmedetomidine/kg of body weight (M0.4/D0.2), 4.0 microg of medetomidine or 2.0 microg of dexmedetomidine/kg (M4/D2), and 40 microg of medetomidine or 20 microg of dexmedetomidine/kg (M40/D20). Sedation and analgesia were scored before induction. Anesthesia was induced with propofol and maintained with isoflurane. End-tidal isoflurane concentration, heart rate, and arterial blood pressures and gases were measured. RESULTS: Degrees of sedation and analgesia were significantly affected by dose level but not drug. Combined mean end-tidal isoflurane concentration for all dose levels was higher in dogs that received medetomidine, compared with dexmedetomidine. Recovery time was significantly prolonged in dogs treated at the M40/D20 dose level, compared with the other dose levels. After induction, blood pressure decreased below reference range and heart rate increased in dogs treated at the M0.4/D0.2 dose level, whereas blood pressure was preserved in dogs treated at the M40/D20 dose level. However, dogs in these latter groups developed profound bradycardia and mild metabolic acidosis during anesthesia. Treatment at the M4/D2 dose level resulted in more stable cardiovascular effects, compared with the other dose levels. In addition, PaCO2 was similar among dose levels. CONCLUSIONS AND CLINICAL RELEVANCE: Dexmedetomidine is at least as safe and effective as medetomidine for use as a premedicant in dogs undergoing propofol-isoflurane anesthesia.

Adrenergic alpha-Agonists↗

PubMed2001

Sedative, analgesic, and cardiovascular effects of levomedetomidine alone and in combination with dexmedetomidine in dogs.

OBJECTIVE: To determine whether a high dose of levomedetomidine had any pharmacologic activity or would antagonize the sedative and analgesic effects of dexmedetomidine in dogs. ANIMALS: 6 healthy Beagles. PROCEDURE: Each dog received the following treatments on separate days: a low dose of levomedetomidine (10 microg/kg), IV, as a bolus, followed by continuous infusion at a dose of 25 microg/kg/h; a high dose of levomedetomidine (80 microg/kg), IV, as a bolus, followed by continuous infusion at a dose of 200 microg/kg/h; and a dose of isotonic saline (0.9% NaCl) solution, IV, as a bolus, followed by continuous infusion (control). For all 3 treatments, the infusion was continued for 120 minutes. After 60 minutes, a single dose of dexmedetomidine (10 microg/kg) was administered IV. Sedation and analgesia were scored subjectively, and heart rate, blood pressure, respiratory rate, arterial blood gas partial pressures, and rectal temperatures were monitored. RESULTS: Administration of levomedetomidine did not cause any behavioral changes. However, administration of the higher dose of levomedetomidine enhanced the bradycardia and reduced the sedative and analgesic effects associated with administration of dexmedetomidine. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that administration of dexmedetomidine alone may have some cardiovascular benefits over administration of medetomidine, which contains both dexmedetomidine and levomedetomidine. Further studies are needed to confirm the clinical importance of the effects of levomedetomidine in dogs.

Adrenergic alpha-Agonists↗

PubMed2000

Clinical effects and pharmacokinetics of medetomidine and its enantiomers in dogs.

The clinical effects and pharmacokinetics of medetomidine (MED) and its enanti-omers, dexmedetomidine (DEX) and levomedetomidine (LEVO) were compared in a group of six beagle dogs. The dogs received intravenously (i.v.) a bolus of MED (40 microg/kg), DEX (20 and 10 microg/kg), LEVO (20 and 10 microg/kg), and saline placebo in a blinded, randomized block study in six separate sessions. Sedation and analgesia were scored subjectively, and the dogs were monitored for heart rate, ECG lead II, direct blood pressure, respiratory rate, arterial blood gases, and rectal body temperature. Blood samples for drug analysis were taken. Peak sedative and analgesic effects were observed at mean (+/- SD) plasma levels of 18.5 +/- 4.7 ng/mL for MED40, 14.0 +/- 4.5 ng/mL for DEX20, and 5.5 +/- 1.3 ng/mL for DEX10. The overall level of sedation and cardiorespiratory effects did not differ between MED40, DEX20 and DEX10 during the first hour, apparently due to a ceiling effect. However, the analgesic effect of DEX20 lasted longer than the effect of the corresponding dose of racemic medetomidine, suggesting greater potency for dexmedetomidine in dogs. Levomedetomidine had no effect on cardio-vascular parameters and caused no apparent sedation or analgesia. The pharmacokinetics of dexmedetomidine and racemic medetomidine were similar, but clearance of levomedetomidine was more rapid (4.07 +/- 0.69 L/h/kg for LEVO20 and 3.52 +/- 1.03 for LEVO10) than of the other drugs (1.26 +/- 0.44 L/h/kg for MED40, 1.24 +/- 0.48 for DEX20, and 0.97 +/- 0.33 for DEX10).

Analgesia↗

PubMedDate not supplied

Magnetic resonance imaging findings in Finnish Spitz dogs with focal epilepsy.

Eleven Finnish Spitz dogs with focal seizures and 3 healthy controls were evaluated. General clinical and neurological examinations, blood examination, urinalysis, cerebrospinal fluid examination, electroencephalography (EEG), and magnetic resonance imaging (MRI) of the brain were performed on all dogs. On EEG examination, focal epileptic activity was found in 7 of 11 dogs (64%), and generalized epileptic activity was observed in 4 of 11 dogs (36%). MRI (performed with 1.5 T equipment) detected changes in 1 epileptic dog. Mild contrast enhancement after gadolinium injection was identified in this dog's right parietal cortex. However, no such changes were observed in repeated magnetic resonance images. Special emphasis was given to seizure history to determine any correlations between seizure intervals and MRI findings. Our results indicate that Finnish Spitz dogs with focal seizures suffer from focal idiopathic epilepsy and have nondetectable findings on MRI or pathology. MRI showed poor sensitivity in detecting epileptogenic areas in our patients with focal seizures. Reversible MRI changes in 1 dog could have been caused by seizures.

Animals↗