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Biomedical subjects

F Sjöberg

Publications and source records attributed to F Sjöberg.

At least 55 records · Page 3Linked to original sources
PubMed1996

Effects on skeletal muscle oxygenation and capillary blood flow by adenosine-, sodium nitroprusside- and acetylcholine-induced hypotension.

BACKGROUND: Adenosine (ADO)-induced hypotension during diethyl ether anesthesia has been shown to increase skeletal muscle oxygenation. Whether this beneficial effect of ADO hypotension is present also during another anesthetic technique was tested in the present study using ketamine-xylazine anesthesia, and its actions were compared with sodium nitroprusside (SNP) and acetylcholine (ACh) induced hypotension in rabbits. METHODS: Local oxygen pressure and capillary blood flow were measured with a multiwire microelectrode which was placed on the surface of the left vastus medialis muscle. The experiments were performed in three groups, in which either ADO, SNP or ACh was infused into a central vein in a dose that produced a reduction of the mean arterial pressure by 20-25%, to approximately 60 mmHg. RESULTS: In the ADO group (60-170 micrograms kg-1 min-1) the tissue oxygen pressures increased by 23% while capillary blood flow decreased by 38%. During SNP administration (1-3 micrograms kg-1 min-1) the oxygen pressures decreased by 21% and an increase of 31% in capillary flows was seen. When ACh was infused (1-4 micrograms kg-1 min-1) the oxygen pressures decreased by 21% and, in parallel, capillary blood flow decreased by 50%. During hypotension no low tissue oxygen pressure values (< 1.5 kPa) were found in the ADO group, whereas they were present in both the SNP and ACh group. CONCLUSION: Compared to sodium nitroprusside and acetylcholine, adenosine appears to have an oxygen-sparing effect in the skeletal muscle during pharmacologically induced hypotension.

Acetylcholine↗
PubMed1996

Laser Doppler perfusion imager (LDPI)--for the assessment of skin blood flow changes following sympathetic blocks.

A laser Doppler perfusion imager (LDPI) for evaluation of skin blood flow is presented and its use illustrated in two cases with a presumptive diagnosis of reflex sympathetic dystrophy (RSD) treated with local anesthetic sympathetic blocks. Among the advantages are the good spatial resolution over the area measured (12 x 12 cm) and that measurements can be done without contact with the skin. Generating a complete image takes 4.5 min but if higher temporal resolution is needed continuous measurements at one point are possible by use of another software routine.

Adult↗
PubMed1995

Computerized thermistor technique for indirect studies of esophageal blood flow.

The aim of this study was to elaborate on a computerized microthermistor technique for indirect measurement of esophageal blood flow and to investigate if any changes in circulation could be found in patients who are provoked by esophageal acid perfusion of their acid-sensitive mucosa. A thermistor was mounted in a plastic catheter and placed in the esophagus 11 cm above the lower esophageal sphincter. The signal from the thermistor was transmitted to a personal computer. A 15 degrees C water bolus was injected into the catheter in order to cool the esophageal wall at the catheter side hole 1 cm above the thermistor. The reliability of the thermistor test was examined by repeating it in 29 patients. No statistical difference between the two test occasions was found. Twenty-five patients were provoked with an acid perfusion test, 14 of whom had a positive reaction with heartburn. Patients with a positive acid perfusion test had a shorter rewarming time before as well as after provocation than patients with a negative acid perfusion test. It is concluded that this thermistor technique is well suited for measuring intraluminal rewarming rate as an indirect sign of changes in esophageal blood flow. Furthermore, the results indicate that blood supply of the esophageal wall is increased in patients with a positive acid perfusion test.

Adult↗
PubMed1995

Variations in esophageal oxygen tension measured with intraluminal antimony electrodes.

Monocrystalline antimony electrodes (crystallographically oriented monocrystalline antimony; COMA) are known to be sensitive to oxygen and to pH. Accordingly, it has been shown that COMA electrodes can be used for the measurement of tissue oxygen tension provided the pH remains constant or is accounted for by the simultaneous use of a glass electrode. In this study the combination of a COMA together with a glass electrode was evaluated for measurement of esophageal oxygen tension in 5 patients. The COMA electrodes showed a mean value of 2.1 pH units higher than the glass electrodes, corresponding to a pO2 level in the esophagus of 10 kPa. As the more protracted oxygen effect on the COMA electrodes was easily recognized, especially in levels of the pH above 7.8 units, they were used for indirect evaluation of intraluminal oxygen tension in the esophagus in a further 57 patients, monitored over 24 h for gastroesophageal reflux disease. The intraluminal pO2 decreased in the supine position and with increase in age. An increase in pO2 was seen after eating and during reflux periods. The changes in pO2 are interpreted as being secondary to blood flow alterations in the esophagus.

Adult↗
PubMed1994

Spinal anaesthesia for caesarean section following epidural analgesia in labour: a relative contraindication.

Three cases are described in which epidural analgesia was performed during labour using an infusion of bupivacaine 0.125-0.25%. When, in all 3 cases, caesarean section was required for failure to progress, hyperbaric bupivacaine was given in doses of 10 mg, 12.5 mg and 15 mg respectively. Within 2-4 min all 3 patients had a high block, complained of difficulty in breathing and subsequently developed apnoea. The trachea was intubated after administration of thiopentone and succinylcholine and the operation continued. Cardiovascular support was provided by the administration of ephedrine injected intermittently intravenously. The spinal block receded and the patients were able to return to the ward without any further complications. All three mothers remain in good health and do not regret having had spinal anaesthesia for caesarean section. In contrast to previously reported cases of high spinal anaesthesia following unsuccessful epidural anaesthesia for caesarean section, this report describes 3 cases of high spinal following the administration of spinal anaesthesia upon an ongoing epidural infusion of local anaesthetic during labour. As no guidelines are available as to the recommended dose of spinal anaesthetic under such circumstances and, in view of the several case reports describing a similar complication under different circumstances, we suggest that spinal anaesthesia is contraindicated upon ongoing epidural analgesia or following a failed epidural.

Journal Article↗
PubMed1994

Out-patient surgery--a survey of anaesthesia care in a university hospital.

This study was done at the Linköping University Hospital, Sweden, to assess the quality of care given to patients undergoing outpatient anaesthesia. A questionnaire was given to all adult patients (> 15 years old) immediately on admission to the outpatients' surgical ward and the patients were asked to answer all the questions, if necessary with the help of an attending nurse. Another questionnaire was given to the patients in the post-operative ward immediately prior to their being discharged home. Analyses of results indicate that although most patients were satisfied with the care offered at the outpatient surgical unit, 50% requested, but were not given, anxiolytic premedication before the operation. A majority of these were women undergoing gynaecological operations. Twenty per cent of the patients complained of post-operative pain that was poorly managed. Drowsiness (12%), headache (10%), and sore throat (8%) were common complications following general anaesthesia. In contrast, patients who had regional or local anaesthesia had an extremely low incidence of complications. Almost one-third of the patients were discharged without a responsible person accompanying them home and 25% were alone at home during the first 24 hours. Of the patients who went home alone, most either walked, cycled or took the bus, but 4% actually drove home after the operation. In our opinion more stress should be laid on patient information before the operation and better methods to relieve preoperative anxiety should be used whenever indicated.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Effect of hypoxic hypoxia and ritanserin on capillary flow and oxygenation in rabbit skeletal muscle.

This study examined capillary flow and oxygenation in rabbit skeletal muscle during hypoxic hypoxia (inspired oxygen fraction = 0.10) and after administration of ritanserin (highly selective 5-Hydroxytryptamine-2-receptor antagonist). Capillary flow (hydrogen clearance) or oxygen pressure was measured with a multiwire micro-electrode which was placed on the surface of the left vastus medialis muscle. For measurement of regional microcirculatory blood flow a laser-Doppler flowmeter probe was placed on the contralateral muscle. An experimental sequence with normoxaemia (arterial PO2 12.5 kPa), followed by hypoxaemia (arterial PO2 3.9 kPa) and thereafter sustained hypoxaemia (arterial PO2 4.0 kPa) during which ritanserin (0.035 mg kg-1 i.v.) was administered, was used. During hypoxaemia a decrease was seen in mean arterial pressure (MAP) by 27%, capillary flow by 25%, muscle oxygen pressure by 32% and laser-Doppler flowmetry (LDF) flow by 24%. After the administration of ritanserin the mean arterial pressure was further reduced by 7%, whereas the capillary flow increased by 59% and the muscle oxygen pressure by 31%. The LDF flow remained unchanged. These results demonstrate that, in this animal model, a decrease in skeletal muscle capillary flow and oxygenation during hypoxaemia can be reversed by the administration of ritanserin, despite a further reduction in blood pressure.

Animals↗
PubMed1993

Human postburn oedema measured with the impression method.

The course of tissue swelling in human non-injured skin after burn injury was investigated with a non-invasive impression method that measures force and tissue fluid translocation during mechanical compression of the skin. Time-dependent changes in the fluid translocation and the interstitial-pressure related to impression force were measured on 11 occasions, during 3 weeks, in seven patients postburn. A mathematical model was fitted to the impression force curves and the parameters of the model depicted the time-dependent compartmental fluid shift in the postburn generalized oedema. Tissue fluid translocation increased significantly (P < 0.05) up to a maximum value after 6 days postburn and declined thereafter. This indicated a continuous increase in the generalized postburn oedema for the first 6 days postburn. Impression force at 3 weeks postburn was significantly lower (P < 0.001) as compared with the half-day postburn value, indicating an increased tissue pressure during the first days postburn. Parameter analysis indicated a flux of water-like fluid from the vasculature to the interstitial space during the first 6 days postburn. The spread of the values registered between different measurement sites was, however, large.

Adolescent↗
PubMed1993

Cardiac arrest during caesarean section.

A case is described of a previously healthy obese woman in her fourth pregnancy who presented for caesarean section due to cephalopelvic disproportion (CPD). Forty minutes after a spinal anaesthetic a healthy child was delivered. Shortly after the injection of ergometrine and Syntocinon into the uterus, the patient described a general feeling of discomfort which was followed by convulsions and cardiac arrest. Resuscitation was successful and the circulation was restored. However, it was difficult to maintain oxygenation and the patient was mechanically ventilated for 24 hours and subsequently supplementary oxygen therapy was given for three days. A pulmonary scintigram on the fourth day after delivery showed large uptake defects indicative of pulmonary embolism. The patient recovered completely and was discharged home after two weeks. Differential diagnosis and measures to reduce the risk of deep vein thrombosis (DVT) are discussed.

Journal Article↗
PubMed1993

Effect of systemic adenosine infusion on capillary flow and oxygen pressure distributions in skeletal muscle of the rabbit.

The aim of this study was to investigate the effect of systemic adenosine (ADO) infusion on blood flow and oxygenation at the capillary level in skeletal muscle in order to estimate oxygen demand. In anesthetized rabbits, a multiwire microelectrode was placed on the left vastus medialis muscle surface, and was used for capillary flow (determined by hydrogen clearance) as well as for oxygen pressure (PtO2) measurements. Laser Doppler flowmetry (LDF) was also used on the contralateral muscle surface for regional microcirculatory blood flow measurements. ADO infusion (50-100 micrograms/kg/min) was given in a central vein. During the ADO infusion the mean arterial blood pressure decreased from 81 +/- 5 (mean +/- SD) to 64 +/- 4 mmHg (a 21% decrease) (p < 0.001), while capillary flow decreased by 37% from a mean value (relative units) of 1.0 +/- 0.84 during control to 0.63 +/- 0.72 (p < 0.001). During ADO infusion there was an increased flow heterogeneity. The mean PtO2 increased by 29% from 5.6 +/- 2.3 to 7.2 +/- 2.2 kPa (p < 0.001) associated with decreased oxygen heterogeneity. A 43% reduction of the relative calculated local oxygen consumption was found during ADO infusion (p < 0.05). The LDF flux decreased by 7% (p < 0.05). We conclude from these results that systemic adenosine infusion decreases skeletal muscle capillary blood flow and in parallel increases the oxygen pressures. This can be explained by a redistribution of the capillary blood flow as well as a reduction in skeletal muscle oxygen demand.

Adenosine↗
PubMed1993

The effect of hypocapnia on skeletal muscle microcirculatory blood flow, oxygenation and pH.

Hypocapnia is known to decrease blood flow and tissue oxygen tension in the brain and the splanchnic organs, but there are few and contradictory results in skeletal muscle. The aim of the present study was to investigate the effect of hypocapnia on microcirculatory blood flow, local skeletal muscle PO2 (PtO2) and pH (pHt). Blood flow was measured using laser-Doppler flowmetry (LDF) and a multichannel antimony microelectrode served for PtO2 and pHt measurements. These parameters were studied in six anesthetized and mechanically ventilated rabbits during normocapnia (arterial PCO2 4.4 kPa), hypocapnia (PCO2 2.3 kPa) and finally a second period of normocapnia (PCO2 4.5 kPa). During normocapnia the relative LDF flux was 100 +/- 53% (mean +/- SD), decreased to 80 +/- 48% (p < 0.01) during hypocapnia and returned to 103 +/- 51% during the second period of normocapnia (N.S.). The PtO2 was 3.2 +/- 1.2 kPa, 2.9 +/- 0.8 kPa (p < 0.05) and 3.2 +/- 1.0 kPa (N.S.), respectively. pHt remained unchanged, although there was a significant arterial alkalosis (pH increased 0.10 units, p < 0.01). These results show that hypocapnia induces a 20% decrease in LDF flow and a 9% reduction in PtO2 with an unchanged pHt level. In this skeletal muscle model, the decrease in microcirculatory blood flow due to vasoconstriction leads to a reduction in both tissue oxygenation and in the removal of acid metabolites, which counteract a developing tissue alkalosis.

Animals↗
PubMed1992

Thiopentone or propofol for induction of isoflurane-based anaesthesia for ambulatory surgery?

This study compares psychomotor recovery following induction of anaesthesia with either thiopentone or propofol in 30 healthy, unpremedicated patients undergoing outpatient arthroscopic procedures of the knee. A battery of tests including simple reaction time (SRT), choice reaction time (CRT), perceptive accuracy test (PAT) and digit symbol substitution test (DSST) were done before anaesthesia. The patients were randomly divided into two groups: Group 1 was induced with thiopentone 5-6 mg/kg while Group 2 was induced with propofol 2-3 mg/kg. Anaesthesia was then maintained with isoflurane (0.5-2%) in oxygen and air, and supplements of alfentanil were given for analgesia during spontaneous respiration with a face mask. Psychomotor recovery assessed every 30 min postoperatively for 120 min showed that patients in Group 1 had not returned to baseline values until 120 min after the operation on the PAT, while those in Group 2 had returned to baseline values at 60 min. No patient had any significant side effects. The SRT, CRT and DSST proved to be relatively insensitive in the detection of residual effects of anaesthesia and had a significant learning effect. This study suggests that induction of anaesthesia with propofol followed by maintenance with isoflurane in oxygen and air during spontaneous ventilation is associated with rapid psychomotor recovery and is a suitable method for ambulatory surgery. The PAT is sensitive and not associated with some of the problems found with other commonly used tests.

Adult↗
PubMed1992

Alkaline oesophageal reflux--an artefact due to oxygen corrosion of antimony pH electrodes.

Antimony electrodes are widely used for gastro-oesophageal pH monitoring. They are also sensitive to oxygen, however, especially at low PO2 levels, which are known to shift recorded values in the alkaline direction. This study, which compares antimony and glass electrodes for oesophageal pH monitoring in six adults, shows that values recorded by antimony electrodes are 2.1 +/- 0.8 pH units (mean +/- SD) higher than by glass electrodes (p < 0.001; n = 7642). A further 52 patients with suspected gastro-oesophageal reflux were investigated by 24-h pH monitoring by means of antimony electrodes. In these patients the oesophageal pH was higher than 8.0 for 7% of the time (range, 0-60%). The alkaline periods recorded with antimony electrodes were all protracted in time, smoothly increasing from a neutral pH, and did not correspond to a sudden increase in pH, which would be expected if alkaline reflux had occurred. It is concluded that high pH values obtained by antimony electrodes are due to the oxygen sensitivity of the electrodes. The diagnosis of alkaline reflux seems to be valid only when pH monitoring is performed with glass electrodes or when values obtained with antimony electrodes are adjusted for the influence of the oxygen tension in the oesophagus.

Adult↗
PubMed1991

Basic studies of pulse oximetry in a rabbit model.

We have developed an animal model for the evaluation of pulse oximetry during severe hypoxaemia. Twelve rabbits were anaesthetized and mechanically ventilated via a tracheostomy tube. Increasing fractions of nitrogen were added to the gas mixture they inhaled to obtain severe hypoxaemia (saturation range 26%-100%). On 412 occasions, simultaneous pulse oximeter (SpO2) and invasive haemoximeter (SaO2) measurements were compared. The regression analysis of the data gave the equation: y = 0.7 x + 26.7, r = 0.90. In the SaO2 range less than or equal to 85%, the bias (mean value of SaO2-SpO2) was higher when compared with SaO2 greater than 85%. In an in vitro study the light absorption characteristics of rabbit haemoglobin (Hb) were compared to human Hb. The millimolar extinction coefficients of both reduced and oxygenated Hb from rabbits were found to be similar to human Hb. We consider the animal model (rabbit) suitable for studies of pulse oximetry during physiological and pathophysiological conditions.

Animals↗