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F Sjöberg

Publications and source records attributed to F Sjöberg.

71 records · Page 4Linked to original sources
PubMed1991

Extracellular muscle surface pO2 and pH heterogeneity during hypovolemia and after reperfusion.

Tissue pO2 (ptO2) and pH (ptH) in skeletal muscle are known to be affected at an early stage of hemorrhage. This study examines the effects of hypovolemia on the extracellular ptO2 and ptH distributions at multiple tissue sites using a recently developed multipoint microelectrode, that provides simultaneous measurements of ptO2 and ptH. The results show that the development of tissue acidosis occurs in spatially different patterns and that the magnitude of the acidosis at some tissue sites is larger and remains longer than previously known. The changes described are believed to be due to the heterogeneous blood flow seen during shock and after reperfusion. The degree of local acidosis was correlated to the relative decrease in oxygen tension at that particular site. These new findings can be of importance for the development of future resuscitative measures as well as in constructing patient monitoring systems.

Animals↗
PubMed1990

Assessment of peripheral blood flow using a pulse oximeter.

We investigated the bar graph on a pulse oximeter as an indicator of peripheral blood flow. Because blood flow is known to increase in the lower extremities during spinal analgesia, we chose patients receiving spinal analgesia as the experimental model. Although they are indirect indicators, we used laser Doppler readings and skin temperature to reflect peripheral blood flow. These measurements were made from each patient's foot and hand before and after spinal analgesia and were compared with the deflection on the pulse oximeter bar graph. After subarachnoid injection of bupivacaine, laser Doppler readings from the foot increased to 620 +/- 120% (P less than 0.05) of the control reading. The pulse oximeter signal amplitude increased from 5.2 +/- 0.4 to 9.4 +/- 0.3 bars (P less than 0.05) and mean skin temperature increased from 24.6 +/- 0.5 to 31.2 +/- 0.8 degrees C (P less than 0.05). No changes were noted in readings obtained from the hand. A Nellcor N-200 pulse oximeter may be used to evaluate the effect of sympathetic nerve block as indicated by an increase in peripheral blood flow.

Adult↗
PubMed1990

Effect of hyperoxemia and ritanserin on skeletal muscle microflow.

Serotonin2 (5-HT2) receptor antagonists (ketanserin, ritanserin) can normalize a hyperoxemia-induced disturbance in skeletal muscle oxygenation, presumably by local microflow changes. The purpose of this study was to develop equipment for local hydrogen clearance measurements with a modified eight-channel platinum electrode to assess changes in local skeletal muscle capillary blood flow induced by hyperoxemia and ritanserin (0.035 mg/kg) during hyperoxemia. Laser-Doppler flowmetry was used for regional microflow measurements. Two groups of six anesthetized and artificially ventilated rabbits were studied: group I with normoxemia and hyperoxemia [arterial PO2 (PaO2) 48 kPa; 360 Torr] and group II before and after ritanserin with hyperoxemia (PaO2 46 kPa; 345 Torr). In group I, hyperoxemia induced a mean local hydrogen clearance decrease of 22% while laser-Doppler flowmetry signal decreased 31%. In group II, ritanserin induced a 125% mean local hydrogen clearance increase compared with hyperoxemia (or 37% compared with group I normoxemia); laser-Doppler flowmetry signal increased 30%. The sum distribution of local hydrogen clearances shifted to the left during hyperoxemia and to the right after ritanserin. The conclusion from this study is that local and regional microflow changes can explain the effects of hyperoxemia and ritanserin on skeletal muscle oxygenation.

Animals↗
PubMed1990

The clinical value of the haemoglobin concentration analysis (g/L) and the calculation of oxyhaemoglobin saturation (%) in an automatic blood gas analyser (ABL2, Radiometer A/S, Denmark).

This study was aimed to evaluate the accuracy and thereby the clinical value of the haemoglobin concentration (g/L) analysis and of the calculation of oxyhaemoglobin saturation (%) in a commonly used automatic blood gas analyser (ABL2, Radiometer A/S, Denmark). The measured and calculated values (ABL2) were compared to the readings obtained in a last generation haemoximeter (OSM3, Radiometer A/S, Denmark), which served as reference. The haemoglobin concentration measurements performed in the ABL2 apparatus showed an increasing underestimation of the true haemoglobin value at larger haemoglobin concentration values. This together with a poor correlation makes the analysis unsuitable for clinical use. The oxyhaemoglobin saturation values (%) obtained using the ABL2, however, had a good correlation to the corresponding values measured in the OSM3. It is suggested that the oxyhaemoglobin saturation value obtained in the ABL2 can be used clinically, e.g., for invasive control of pulsoximeters.

Arteries↗
PubMed1988

Pulse oximetry during extradural analgesia for extracorporeal shock wave lithotripsy.

Exracorporeal shock wave lithotripsy (ESWL) may require immersion of the patient in water and extradural blockade for analgesia, which may both affect pulmonary and cardiovascular function and increase the likelihood of hypoxaemia. Twenty-four patients (ASA I-III) with extradural blockade and six healthy subjects were studied by pulse oximetry during immersion. Oxygen saturation (SaO2) tended to decrease after induction of extradural analgesia. Immersion decreased SaO2 further, by up to 2% in healthy volunteers (P less than 0.05) and 3% in patients (P less than 0.05). In two patients with arteriosclerosis, an SaO2 of 92% was accompanied by arrhythmias which resolved after administration of oxygen.

Adult↗
PubMed1987

The oxygen sensitivity of a multipoint antimony electrode for tissue pH measurements. A study of the sensitivity for in vivo PO2 variations below 6 kPa.

Monocrystalline micro antimony electrodes in a multipoint arrangement as described by Lund et al. were placed on the skeletal muscle surface of the rabbit. Tissue oxygen levels were measured simultaneously with the MDO (Mehrdraht Dortmund Oberfläche) oxygen electrode. The sensitivity for variations in tissue PO2 (PO2(t)) was evaluated for the antimony metal-metal oxide sensor. The sensitivity (delta E/delta log10 PO2)+/- SE was found to be 21.8 +/- 1.2 mV in the interval between 0.1 kPa and 1 kPa and 53 +/- 5 mV in the interval between 1 kPa and 6 kPa. These results are not consistent with the oxygen sensitivity of monocrystalline antimony described in vitro, but are in agreement with the findings of Nilsson & Edwall. A plausible explanation for the S-shaped oxygen sensitivity curve of antimony at oxygen levels below 10 kPa could be an interaction, at the electrode surface, between the dissolved oxygen and the oxygen bound to haemoglobin. If this is the case, the use of an antimony electrode would make possible the determination of the dissociation of oxyhaemoglobin in tissues.

Animals↗
PubMed1985

Acute coronary occlusion: oxygen pressure in the border zone studied in the pig.

The area between ischemic and normal myocardium after acute coronary occlusion-the border zone-is of great interest. It has been proposed that this area contains reversibly damaged myocardium subjectable to myocardial salvage. Twenty Swedish land race pigs were studied, 13 after acute occlusion of the left anterior descending coronary artery (LAD), while seven served as controls. We measured tissue oxygen pressures (ptO2) subepicardially with the MDO electrode. This is a multiwire surface electrode measuring ptO2 with eight individual platinum wires. Hundred and twenty values were collected in each measuring situation. The electrode was positioned on the lateral border zone, measurements were performed before and 5, 30 and 120 min after LAD occlusion. In five cases successful measurements were performed across the border zone. A mixture of normal and ischemic ptO2 values was found 5 min after occlusion. After 30 min of occlusion the number of ischemic values decreased and this was particularly the case after two hours of occlusion. The results support the view that the border zone was very narrow. The reduced number of ischemic values after two hours of permanent LAD occlusion also indicated that the border zone may be narrow but not necessarily fixed but instead dynamic. In this case there was a spontaneous decrease of the ischemic area.

Animals↗
PubMed1984

A multipoint micro antimony pH electrode for tissue surface measurements.

Based on monocrystalline antimony we have developed a multipoint tissue surface pH electrode. The six electrodes were produced by spark cutting from a large antimony single crystal. The electrodes were then cast in epoxy resin in a ring shaped structure which fitted around the MDO oxygen electrode. The antimony electrode was ground and polished to expose an undisturbed closely packed crystal plane of antimony to the measuring solution. Before and after monitoring periods standardization was performed in TRIS buffers of pH 6.72, 7.32 and 7.74 at 37 degrees C. Antimony electrode potential is influenced by oxygen. Therefore, mean tissue oxygen pressure was registered simultaneously with an MDO electrode. The oxygen sensitivity factor used in this study was 18mV/logpO2. The correction factor for the antimony electrode oxygen dependence, measured in vitro, seemed to be correct also for the in vivo state. This, however, needs further investigation. To illustrate the usefulness of the multipoint pH electrode seven normal state rabbits were studied, and thereafter four - one each in a hypoxic, hypocarbic, hypovolemic or hyperoxic situation. In the normal state tissue pH measured on a skeletal muscle surface varied from 7.0 to 7.4. In the case of tissue microcirculation shutdown (in the hypocarbic or the hypovolemic situations), the initial reaction was a scattering of the pH values, and then the development of tissue acidosis. Our conclusion is that the use of a multipoint pH sensor enables improved and more detailed monitoring of the tissue acid-base status.

Animals↗
PubMedDate not supplied

Buses as fire hazards: a Swedish problem only? Suggestions for fire-prevention measures.

In Sweden, approximately 6% of all human transportation is made via buses. The Swedish Board of Accident Investigation and the Swedish Rescue Services Agency have pointed out repeatedly that buses are potential fire and burn hazards, not only when involved in collisions but also in other circumstances. The number of fire incidents is increasing, especially in newer buses. In conjunction with the Swedish Rescue Services Agency, we examined some of the recent bus fires in Sweden. We did not find any casualties, but the results of our study suggest that casualties as a result of bus fires are imminent unless preventive measures are taken. We also studied experiences from previous bus fires and suggest preventive measures.

Burns↗
PubMedDate not supplied

Influence of pentobarbital, propofol and ketamine on skeletal muscle capillary perfusion during hemorrhage: a comparative study in the rabbit.

Anesthetics affect tissue blood flow, which is of importance especially in situations of inadequate perfusion, as in hemorrhage. The present study compared the effect of three commonly used anesthetic agents on skeletal muscle capillary and regional blood flow during and after recovery from hemorrhage. Three groups of rabbits were anesthetized randomly with either pentobarbital, propofol or ketamine, chosen such that the anesthetic level, blood pressure and withdrawn blood volume were comparable in all groups. Capillary blood flow was measured using a local hydrogen clearance technique with a multi-wire microelectrode, placed on the left vastus medialis muscle surface, and the contralateral site served for regional microcirculatory blood flow measurements using laser-Doppler flowmetry. Hemorrhage was induced by withdrawal of blood to a mean arterial pressure of 40 mm Hg and monitoring was continued during the subsequent spontaneous recovery period of 120 min. Both capillary and regional blood flow decreased significantly during hemorrhage in all groups. The flow values in the pentobarbital group were given a mean value of 100% and the other two groups were compared with this. Local hydrogen clearance flow decreased from a relative baseline level of 100 to 64% during hemorrhage with pentobarbital, from 87 to 43% with propofol and from 146 to 70% with ketamine. Laser-Doppler flowmetry flow decreased from relative baseline levels of 100, 96 and 139%, to 71, 77 and 103%, respectively, during hemorrhage, whereas the percentage of zero capillary flow values increased from 4 to 34, 19 to 50 and 5 to 27% in the three groups, respectively. The results of the present study indicate that capillary perfusion is best maintained in the ketamine group followed by pentobarbital and propofol last. Furthermore, the flow distribution shapes for each anesthetic indicate a more pronounced deregulation of capillary blood flow in the propofol group than in the others, even at baseline.

Anesthetics↗
PubMedDate not supplied

Serotonin--one possible link between oxygen metabolism and the regulation of blood flow in the brain?

Hyperoxemia is known to alter tissue oxygenation, which in the brain results in a scattered and an uneven distribution of cerebrocortical tissue oxygen pressures (PtO2). This study examined the effect of ritanserin (a highly specific serotonin receptor antagonist, 5-HT2) on the PtO2 distribution during hyperoxemia. The measurements of brain oxygenation were performed on the motor cortex in anesthetized pigs with a multiwire Clark-type microelectrode. Ritanserin was administered (0.035 mg/kg i.v.) during hyperoxemia (inspired oxygen fraction = 0.70). In 4 of 5 animals, the disturbed oxygenation that was registered during hyperoxemia was normalized after the ritanserin injection. These results indicate that serotonin may be involved in the regulation of brain oxygenation during hyperoxemia, and they also suggest that serotonin may be a link in the coupling between the oxygen metabolism and the regulation of blood flow in the brain.

Animals↗
PubMedDate not supplied

pH heterogeneity in skeletal muscle extracellular fluid.

Oxygen and carbon dioxide are known to be heterogeneously distributed in tissues. Extracellular skeletal muscle tissue pH (pHt) also exhibits a spatial variability in vitro, but this has not been examined in vivo. pHt distributions in resting skeletal muscle and the effect of the dispersion of pHt on ischemia and normoxic hypercarbia was therefore studied in an animal model with a multichannel pH microelectrode. Under resting conditions and spontaneous breathing, local pHt (from all animals, n = 10) was found to vary between 6.96 and 7.68 (range), and 70% of the values were within a pH of 7.00-7.32. In each animal the maximum pHt differences (maximum range between the 6 channels of the microelectrode) found were 0.32 +/- 0.11 pH units (mean +/- SD). During tissue acidosis, induced by ischemia, no significant change in the local pHt differences in each animal was seen. During normoxic hypercarbia a 2-fold increase in pHt variability within each animal was noticed (p < 0.01), which suggests that carbon dioxide and buffering effects of the blood are significant factors for the pHt distribution. The pHt distribution range found is of similar magnitude as previously described in in vitro studies on skeletal muscle. Locally varying pHt levels may be of importance as they will affect cellular H+ extrusion, membrane potential and volume control of different cell populations differently.

Acidosis↗
PubMedDate not supplied

Oxygen sensitivity of a multichannel antimony microelectrode for tissue surface oxygen pressure measurements.

The measuring properties of antimony electrodes were improved by the introduction of highly purified crystallographically oriented monocrystalline antimony (COMA). COMA electrodes are sensitive to pH and pO2. For measurements of either pH, pO2, or both, the pH and the pO2 sensitivities must be known and the components of the composite electrode signal must be separable. The oxygen sensitivity of COMA electrodes in vivo have been shown to be higher than in vitro in the pO2 range below 10 kPa. The present study was performed in an animal model to investigate the oxygen sensitivity and to further evaluate the tissue pO2 measuring properties of a miniaturized six channel COMA microelectrode. The results show that the COMA microelectrode has negligible drift, a response time of less than 5 s and high sensitivity and reproducibility for tissue pO2 measurements when the pH part of the electrode signal is eliminated. The oxygen sensitivity found (8.5 +/- 0.4 (mV/pO2) (mean +/- SEM)), is described by a direct linear function in the oxygen tension range studied. It is concluded that tissue pO2 can be calculated after elimination of the pH part of the electrode signal. A multichannel COMA microelectrode possess characteristics suitable for in vivo oxygen measurements and is therefore an interesting complement to traditional tissue oxygen sensors.

Animals↗
PubMedDate not supplied

Lack of peripheral analgesic effect of low-dose morphine during intravenous regional anesthesia.

OBJECTIVE: To determine whether 1 mg morphine injected intravenously in conjunction with prilocaine has any effect on postoperative pain and analgesic requirement during intravenous regional anesthesia. METHODS: This was a randomized, double-blind study that included 37 patients undergoing carpal tunnel operations of the hand under intravenous regional anesthesia. Either 1 ml of morphine or 1 ml of physiologic saline diluted to 5 ml with 5% glucose was injected into the isolated exsanguinated arm. This was followed by 3 mg/kg of 0.5% prilocaine (total volume, 30-50 ml). Pain was assessed at 30, 60, 90, and 120 minutes, and 8, 24, and 48 hours after the end of the operation using a linear visual analog scale (VAS). The total number of analgesic tablets consumed in the first 48 hours were also counted. RESULTS: No difference was found in the VAS pain scores between the groups at any of the time periods studied. The postoperative analgesic requirement was similar in both groups. CONCLUSION: The authors conclude that 1 mg morphine showed no effect on postoperative pain or analgesic requirements when given in conjunction with prilocaine during intravenous regional anesthesia.

Adult↗