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Biomedical subjects

J Pfitzner

Publications and source records attributed to J Pfitzner.

At least 55 records · Page 3Linked to original sources
PubMed1989

Radiosynthesis of [14C]acarbose.

Acarbose (O-4,6-dideoxy-4-[[(1S, 4R, 5S, 6S)-4,5,6-trihydroxy-3- (hydroxymethyl)-2-cyclohexen-1-yl]amino]-a-D-glucopyranosyl-(1---- 4)-O-a-D- glucopyranosyl-(1----4)-4-glucopyranose, Bay g 5421), an a-glucosidase inhibitor from Actinoplanes, has been developed for the treatment of diabetes mellitus. To investigate the pharmacokinetics and the biotransformation, 14C-labelled acarbose ([14C]Bay g 5421) was required. About 37 GBq (1 Ci) D-[U-14C]glucose was used as a precursor to obtain [14C]acarbose with a radiochemical yield of between 1.58 and 2.56%. For fermentation purposes resting cells of the Actinoplanes mutant SN 1667/47 were used under cometabolism conditions with a 10-fold excess of maltose. The specific radioactivities achieved in individual preparations were 7.77 MBq/mg (210 microCi/mg), 8.03 MBq/mg (217 microCi/mg), and 9.14 MBq/mg (247 microCi/mg), with a radiochemical purity of greater than 98% in each case. By hydrolysis and subsequent investigation of the hydrolysis products it was shown that [14C]carbon atoms originating from the radioactive glucose are present only in the core and not in the maltose unit of [14C]acarbose.

Acarbose↗
PubMed1988

Hypoxaemia following sustained low-volume venous air embolism in sheep.

In six upright (head above thorax) anaesthetised sheep, serial blood gas measurements were made over a 100-minute period during which repeated small-volume air emboli were injected intravenously to lower and maintain the end-tidal CO2 concentration approximately 0.5% below its initial baseline level. With constant volume ventilation and an inspired N2O:O2 ratio of 2:1, the arterial PCO2 progressively increased and the arterial PO2 progressively decreased with significant arterial hypoxaemia ensuing in three out of the six animals. It is suggested that during neurosurgery performed in the sitting position and with an inspired oxygen concentration of 33%, the degree of cardio-respiratory disturbance caused by venous air embolism should be assessed by continuous monitoring not only of end-tidal CO2 concentration but also of arterial oxygen saturation using pulse oximetry.

Animals↗
PubMed1987

Venous air embolism and active lung inflation at high and low CVP: a study in "upright" anesthetized sheep.

To assess the safety and efficacy of the maneuver of active lung inflation (ALI) after venous air embolism, measurements were made of pulmonary artery occlusion pressure (PAOP), central venous pressure (CVP), and superior jugular bulb pressure (JbP) as an index of cerebral venous sinus pressure in eight sheep before and after a 2-ml/kg air embolus and before and in the release phase of an ALI to a pressure of 4 kPa (30 mm Hg). (PAOP-CVP) difference decreased significantly after the air embolus with a further decrease after ALI (P less than 0.01). An increase in JbP occurred with ALI only when the CVP was elevated before the injection of air. After air embolism in neurosurgery, ALI may increase the likelihood of paradoxical embolism in patients at risk and may also fail to help in identifying the site of air entry.

Anesthesia↗
PubMed1987

Embolized air collection in the superior vena cava of "upright" sheep.

In 34 studies on six "upright" anesthetized sheep central venous pressure from sites in the upper and lower superior vena cava (SVC) was recorded before, during, and after the injection into a neck vein of 1-ml increments of air every minute for 15 min. After the injection of air, the pressure recorded from the upper site increased significantly. This increase was the result of air collecting in the SVC with a consequent loss or partial loss of the SVC hydrostatic pressure difference. The time of onset and the duration of collection were not influenced by hyper- or hypovolemia nor by 1 kPa positive end-expiratory pressure. The readily identifiable change in the venous pressure in the upper SVC provided an earlier and more reliable warning of these small-volume air emboli than did a Doppler probe directed at the right side of the heart.

Animals↗
PubMed1985

Controlled neck compression in neurosurgery. Studies on venous air embolism in upright sheep.

Bilateral compression of the jugular veins to raise temporarily cerebral venous pressure, is a manoeuvre recommended frequently in the immediate management of venous air embolism during neurosurgery. One method of compressing the neck veins is to inflate a pneumatic cuff secured around the neck with adhesive tape. This method of neck vein compression had been assessed in upright anaesthetised sheep and found to be an easily controlled and efficient way to raise the cerebral venous pressure. Advantages, dangers and potential problems associated with the use of an inflatable cuff in the clinical situation are discussed.

Animals↗
PubMed1984

Central venous and pulmonary artery occlusion pressures following air embolism in upright sheep.

A study on five upright (head above thorax) anaesthetised sheep demonstrated a statistically significant increase in central venous pressure and decrease in pulmonary artery occlusion pressure, following the injection of air 2 ml per kg into the pulmonary artery. In two out of the five sheep after air embolism, right-sided pressures equalled or exceeded those on the left, confirming their potential susceptibility to paradoxical air embolism.

Anesthesia↗
PubMed1983

Restricted spread of analgesia following epidural blood patch. Case report with a review of possible complications.

A complete restriction of upward spread of local analgesic solution in the epidural space is reported in a patient who three years earlier had received an epidural blood patch for post-spinal headache. Organisation of the blood clot with fibrous tethering of the dura to the wall of the spinal canal is suggested as the most likely cause of this apparent obstruction to spread. Other potential complications of epidural blood patch are presented. It is concluded from the literature on the subject that there is a need for a multi-centre analysis of the factors which might influence the incidence of inadvertent dural tap with an epidural needle.

Adult↗
PubMed1982

Hazards of anaesthetic scavenging: case reports and brief review.

Two cases are presented of misadventure occurring in association with the use of anaesthetic scavenging equipment. The first case demonstrates how easily the scavenging line linking the venting port of a mechanical ventilator to the scavenging interface can become accidentally obstructed. The second case suggests that the proper use of scavenging equipment will effectively eliminate any possibility of recognising by smell an accidental overdose of volatile anaesthetic agent. Previous reports of scavenging hazards are briefly reviewed. It is concluded from this review that scavenging suction should be 'low-vacuum', that a relief valve must be included in the scavenging pathway proximal to any site of potential obstruction, and that the appearance and function of a scavenging interface must be simple and immediately obvious.

Air Pollution↗
PubMed1981

Tourniquet failure and arterial calcification. Case report and theoretical dangers.

A patient with Mönckeberg's calcinosis is presented in whom a pneumatic limb tourniquet failed to be effective because of calcification of the femoral artery wall. Bleeding from the operation site was noticed to be appreciably greater while the tourniquet was inflated since the cuff, though not occluding the femoral artery, acted as a very effective venous tourniquet. Theoretical risks which might be associated with the use of tourniquets in the presence of arterial calcification are fracture of the calcified vessel wall and systemic overdose of local anaesthetic agent following attempted regional intravenous block. The problem of tourniquet failure in general, and the dangers which might be associated with the use of tourniquets in patients with incompressible arteries, are briefly discussed.

Arteriosclerosis↗
PubMed1977

Pneumotachography in intubated infants.

A new flat-bodied pneumotachograph head is described which can be readily interposed between a commercially available endotracheal tube connector on one side and a suitable low dead space attachment on the other. The head was designed to enable the respiratory flow of infants and neonates to be measured both easily and accurately, and without adding appreciably to the work of breathing. The method used to heat the head, and to heat and humidify the inspired gases are also detailed. The underlying aim has been to record inspiratory and expiratory flow as accurately as is possible within the bounds of practical clinical measurement.

Humans↗
PubMed1976

Poiseuille and his law.

Comparatively little is known of the life of Jean Leonard Marie Poiseuille (1797-1869) of Paris. He made important contributions to the experimental study of circulatory dynamics but it can hardly be said that Poiseuille knowingly described the law which governs laminar flow. He did however establish, in a series of meticulously executed experiments, that at a given temperature water flow through tubes of very fine bore is inversely proportional to the length of the tube and directly proportional to the pressure gradient and to the fourth power of the tube diameter.

Blood Circulation↗
PubMed1976

Continuous positive airway pressure. The collection of expired gases.

A low dead space, low resistance, non-rebreathing valve is described. When used with a constant pressure source it enables the expired gases of patients being managed on CPAP to be collected for physiological analysis. It also functions as a collect valve during normal spontaneous respiration and during IPPV.

Adult↗
PubMed1975

Measurement of cardiac output by thermal dilution in infants and children.

The accuracy of the thermal dilution technique for measuring cardiac output in infants and children has been assessed by comparison with the direct Fick technique. Satisfactory correlation between the two methods has been demonstrated, and it is concluded that a commercially available monitor can be used to determine cardiac output by thermal dilution in acutely sick infants and children. The volume of injectate should be selected according to the weight of the child, and the value displayed by the monitor should be adjusted by the appropriate fraction.

Acute Disease↗