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A Mellström

Publications and source records attributed to A Mellström.

At least 19 recordsLinked to original sources
PubMed1998

Comparison of tissue oxygen-tension measurements by different devices. An experimental study in pigs.

UNLABELLED: The aim of this study was to evaluate measurements of subcutaneous oxygen tension (PscO2) generated by three different monitors and to compare measurements obtained with and without the tonometer technique in a standardized animal model. Seven domestic pigs weighing 20-28 kg were anaesthetized and mechanically ventilated. A pulmonary artery catheter was inserted for haemodynamic monitoring and temperature measuring. An external carotid artery was cannulated for blood pressure monitoring and blood sampling. A peripheral venous line was used for fluid and drug infusion. The animals were then subjected to hyperoxia and hypoxia by varying the inspiratory oxygen fractions (FiO2) between 0.1 and 0.8. Arterial and central venous blood gases were analysed at each step of FiO2. Cardiac output was determined using a thermodilution technique. Central, subcutaneous and skin surface temperatures were measured. Three different devices for subcutaneous tissue oxygen-tension (PscO2) measurements were compared: (1) Biogenesis, (2) Continucath and (3) Paratrend 7. Continucath was used both with and without tonometer simultaneously. Inter Class Coefficient of Correlation between PscO2 values obtained by the two Continucath sensors was 76% and between Paratrend 7 and Biogenesis 88%. Absolute values generated by Biogenesis and Paratrend 7 were not different. PscO2 values obtained with the Continucath devices were on average 50% higher than those generated by Biogenesis and Paratrend 7 (p < 0.05). CONCLUSIONS: The new Paratrend 7 and the old Biogenesis sensors generate almost equal tissue oxygen-tension values in response to changes in arterial oxygen tension. The Continucath sensor generates almost 50% higher values compared with the Paratrend 7 and Biogenesis sensors, both with and without tonometer.

Animals↗
PubMed1995

Rectal versus intramuscular morphine-scopolamine as premedication in children.

Intramuscular morphine-scopolamine for premedication was compared with a hydrogel of the same drugs for rectal administration in 205 healthy children scheduled for minor ENT surgery. The intramuscular dose was 0.15 +/- 0.006 mg x kg-1 compared to 0.25 +/- 0.015 mg x kg-1 rectally. Reaction at administration and anaesthetic induction, incidence of intraoperative airway difficulties, Spo2, ECG changes, postoperative pain and incidence of nausea were recorded. The administration for the rectal hydrogel group worked better and resulted in less postoperative nausea and slightly more postoperative pain. The children's behaviour at anaesthesia induction and the frequency of perioperative complications were similar in both groups. We conclude that for minor ENT surgery on children, premedication with rectal hydrogel of morphine-scopolamine is a good alternative to intramuscular morphine-scopolamine.

Adenoidectomy↗
PubMed1991

Lysosomal activity at nodes of Ranvier in dorsal column and dorsal root axons of the cat after injection of horseradish peroxidase in the dorsal column nuclei.

The occurrence of acid phosphatase (AcPase)-positive bodies, i.e. lysosomes, in dorsal column and dorsal root axons of the spinal cord segments C8 and L7 in adult cats was analyzed by light and electron cytochemical methods after injection of horseradish peroxidase (HRP) in the dorsal column nuclei. Axonal lysosomes were, with few exceptions, concentrated at the nodes of Ranvier. We found no changes in nodal occurrence and distribution of lysosomes in axons of the HRP-injected sides, as compared to axons of the uninjected sides or of animals not exposed to HRP. Axonal lysosomes were very rare in the dorsal columns, where the frequency of nodes containing light microscopically detectable AcPase-positive bodies was 0-5% at the HRP-injected sides, 0-6% at the contralateral sides, and 0-3% in control animals. The corresponding values in the cervical and lumbar dorsal roots were 6-23%, 9-20%, 10-12% and 19-37%, 21-40%, 26-43%, respectively. In view of our recent observations in alpha-motor neurons, the results point at a noteworthy difference in local degradative ability between dorsal column axons and alpha-motor axons, the latter being able to accumulate intramuscularly injected and retrogradely transported HRP at their PNS nodes of Ranvier for 48-60 h, during which period the axoplasmic AcPase activity/concentration increases at some nodes. Such a degradative activity, which could protect the motor neurons by restricting axoplasmic transport of exogenous materials imbibed by their axon terminals outside the CNS, may not be of the same significance for neurons, e.g. dorsal root ganglion neurons, the axon terminals of which are located within the CNS.

Acid Phosphatase↗
PubMed1990

Observations on intracranial dynamics during respiratory physiotherapy in unconscious neurosurgical patients.

The effects of airway care procedures on intracranial dynamics were studied in 12 patients with intracranial lesions. The patients had controlled ventilation and were treated according to a standardized protocol with endotracheal suction and bag squeezing. Intracranial, arterial blood and airway pressures were recorded and cerebral perfusion pressure was calculated. Both methods used for airway care elicited marked changes in intracranial, arterial blood and cerebral perfusion pressures during the treatment session. However, within 1 min after termination of the procedure the different pressure levels returned to pretreatment values except for the intracranial and arterial blood pressure in endotracheal suction. Cerebral perfusion pressure, calculated at different time intervals: 1, 5 and 15 min after the treatment, showed only minor deviations from values before treatment. The mean values varied from 70 to 90 mmHg (9.3 to 12.0 kPa) and the lower limit of the 99% confidence interval of the means was never below 55 mmHg (7.3 kPa). At times complementary administration of sedatives during endotracheal suction was found to induce a drop in arterial blood pressure and cerebral perfusion pressure. In conclusion, patients with severe brain injuries treated on mechanical ventilation are exposed to equal risks when using bag squeezing for airway care as when using traditional endotracheal suction. Regardless of the method used, patients should be adequately sedated before starting the procedure in order to reduce the risk of adverse effects.

Adolescent↗
PubMed1988

Peroxidase activity at CNS nodes of Ranvier and in initial axon segments of lumbosacral alpha-motoneurons after intramuscular administration of horseradish peroxidase.

The occurrence of peroxidase activity in central (CNS) and peripheral nervous system (PNS) parts of alpha-motor axons was studied by light and electron microscopy in adult cats after injection of horseradish peroxidase (HRP) into the medial gastrocnemius muscle. The intrafunicular parts of the axons were virtually free of HRP-positive bodies except at a few nodes of Ranvier. Most of these nodes were weakly HRP-positive and contained, irrespective of a survival time between 25 and 48 h, only a few HRP-positive bodies randomly scattered in the nodal axoplasm. In contrast to this and as described elsewhere (J. Neurocytol., 15 [1986] 253-260), the nodal regions of alpha-motor axons at the level of the ventral root showed strong and characteristic accumulations of HRP-activity. The initial axon segments and adjoining axonal parts contained many HRP-positive bodies. We conclude that the CNS and the PNS parts of an alpha-motor axon differ with regard to the way nodal regions interact with retrogradely transported HRP. Possible mechanisms behind this difference are discussed.

Animals↗
PubMed1986

Peroxidase activity at nodes of ranvier in lumbosacral ventral spinal roots and in the PNS-CNS transitional region after intramuscular administration of horseradish peroxidase.

The axoplasm of nodes of Ranvier in feline lumbosacral ventral spinal roots was analysed by light and electron microscopy 18-168 h after the injection of horseradish peroxidase (HRP) into the medial gastrocnemius muscle. Three main HRP distribution patterns were distinguished at PNS nodes (bordered by Schwann cells only) of large fibres transporting HRP. The type A pattern, characterized by a distal accumulation of HRP-positive bodies and a proximal system of vesiculotubular membrane profiles. The incidence of this type of node was highest at relatively short survival times. The type B pattern, which appeared somewhat later, resembled the type A node with the addition of a disc-like, proximal accumulation of HRP activity. The type C pattern which contained scattered HRP-positive bodies and delicate strands of membraneous profiles, dominated 72 h after injection. The number of HRP-positive PNS-CNS borderline nodes (bordered by both Schwann cells and glial cells) was less than 5% of the corresponding value in the same fibres of the ventral root proper. A highly segregated state of the axoplasm of PNS-CNS borderline nodes was noted only in two cases. The observations indicate a functional difference between nodal axoplasm at the PNS-CNS borderline and nodal axoplasm in the PNS part of the alpha motor neuron.

Animals↗
PubMed1986

Peroxidase activity at consecutive nodes of Ranvier in the nerve to the medial gastrocnemius muscle after intramuscular administration of horseradish peroxidase.

The distribution of axoplasmic organelles at consecutive nodes of Ranvier was investigated light- and electronmicroscopically in horseradish peroxidase-transporting muscle nerve fibres of the adult cat. Three main and apparently temporally interrelated distribution patterns were noted. These patterns were referred to as A, B and C. The axoplasm of type-A and type-B nodes was highly segregated with regard to the proximodistal distribution of certain organelles. At type-A nodes horseradish peroxidase-positive membrane limited bodies and horseradish peroxidase-negative vesiculotubular membrane profiles were accumulated just distal and just proximal to the nodal mid-level, respectively. At B nodes a disc-like accumulation of enzyme activity, that was situated a few micron proximal to the mid-level, added to the type-A pattern. The type-C node showed a barely segregated axoplasm in which horseradish peroxidase-positive bodies were distributed randomly. We suggest, on the basis of the mutual order of the nodal types in a sequence of consecutive nodes and their appearance relative to the time after the administration of the HRP, that the different axoplasmic patterns reflect the operation of an ordered process that delays part of the retrogradely transported HRP for 2-3 days. The large number of lysosome-like HRP positive bodies that appeared at the nodes during this process indicates that the nodal axoplasm not only delays but also might take part in the degradation of the foreign protein.

Acid Phosphatase↗
PubMed1985

Peroxidase activity at nodes of Ranvier in some commonly used laboratory animals after intramuscular administration of horseradish peroxidase.

During retrograde transport of intramuscularly administrated horseradish peroxidase (HRP) nodal axon segments of rabbit, rat, and mouse peripheral nerve fibers became HRP-positive and showed a striking proximodistal segregation of certain axoplasmic organelles. HRP-positive bodies and HRP-negative vesiculotubular membrane profiles were seen just distal and proximal to the nodal midlevel, respectively. This appearance was similar to that found earlier in HRP-transporting feline muscle nerve fibers. Some mechanisms that might explain the segregated appearance are briefly discussed.

Animals↗
PubMed1981

Atlantoaxial instability in Marfan's syndrome. Diagnosis and treatment. A case report.

A case of Marfan's syndrome is described in which progressive neurological signs and symptoms were produced by flexion of the head. Radiological examinations revealed hypermotility between the atlas and axis, as well as compression of the medulla oblongata by the odontoid process on flexion, since low positioned cerebellar tonsils prevented dorsal shift of the oblongata. The signs and symptoms disappeared after occipitocervical internal transfixation.

Adult↗
PubMed1980

Atlantoaxial arthrography. A postmortem study.

The atlantoaxial joints of nine cadavers were examined with Amipaque. A lateral percutaneous approach was elaborated. Interarticular communications and pertinent anatomical features were analyzed.

Atlanto-Occipital Joint↗