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Biomedical subjects

F Sjöberg

Publications and source records attributed to F Sjöberg.

At least 37 records · Page 2Linked to original sources
PubMed1999

The effects of human burn injury on urinary nitrate excretion.

Different studies have demonstrated both an increase and a decrease in the biosynthesis of nitric oxide (NO) during the first 2 days following experimental and human burn trauma. This study investigated changes in urinary nitrate excretion in humans following thermal injury in order to determine the temporal relationship between NO release and the initial injury. Urinary nitrate was measured in daily 24-h urine collections taken on days 1-7 following burn injury from 15 patients. The control group consisted of 11 healthy, age- and sex-matched patients who kept a nitrate-restricted diet for five days prior to collection of a single 24-h urine sample. The burns group had a mean age of 41.9 +/- 19.4 (mean +/- S.D.) years and a mean total burn surface area (TBSA) of 30.2 +/- 24.9% (mean +/- S.D.). In the burn injured patients, urinary nitrate levels peaked at day 4 and a 2-fold increase relative to day 1 was observed. Urinary nitrate levels were significantly higher in the burns group than the control group on days 4 and 5 only (p < 0.05 for both days). There was no correlation between TBSA and the measured urinary nitrate levels. This study confirms that the biosynthesis of NO is increased during the first week following burn trauma and establishes that the renal elimination of the by-products of NO metabolism is not increased during the first three days after injury. Notwithstanding the potential effects of burns on nitrate distribution, our findings may reflect a delay in the release of NO following the initial insult.

Adolescent↗
PubMed1999

Specific blood flow reducing effects of hyperoxaemia on high flow capillaries in the pig brain.

The mechanisms behind oxygen mediated changes in tissue blood flow remain unsettled. Today these are thought to (from experiments on separate vessels and other tissues than the brain) operate through the vessels themselves, probably by involvement of the endothelium in the distal parts of the vascular tree. The aim of this study was to investigate how hyperoxaemia affects the cerebrocortical capillary blood flow distribution in order to gain further knowledge of oxygen mediated blood flow regulating mechanisms. The experiments were performed on seven ventilated anaesthetized pigs. A multiwire Clark-type microelectrode, placed on the brain surface (motor cortex), was used for capillary blood flow (hydrogen clearance) and oxygen pressure measurements, both of which were made at normoxaemia (arterial PO2 14.4 kPa) and hyperoxaemia (arterial PO2 50.4 kPa)(the animals serving as their own control). Blood pressure, arterial PCO2 and pH remained unchanged throughout the experiments. During hyperoxaemia a 11% reduction in the cerebrocortical capillary blood flow was found (P < 0.001). This flow reduction was seen mainly in two capillary blood flow classes (6/7 animals). In parallel a heterogeneous increase in the cerebrocortical oxygen pressures from 4.5 to 10.1 kPa (mean) (P < 0.001) was found. These results show that hyperoxaemia causes a selective reduction in capillary blood flow affecting capillaries at specific flow levels. A finding that suggests, for the brain, that both the oxygen sensor and effect mechanism is situated distally, in the vascular tree.

Animals↗
PubMed1999

The effect of hypermetabolism induced by burn trauma on the ethanol-oxidizing capacity of the liver.

OBJECTIVE: To study the rate of elimination of ethanol after a major burn trauma. DESIGN: Prospective, controlled study. SETTING: National burns unit in a Swedish university hospital. PATIENTS AND SUBJECTS: Eight consecutive patients suffering from 18%-72% total burned surface area and nine healthy male control subjects. INTERVENTIONS: The patients received ethanol, 0.35-0.60 g/kg body weight intravenously, during 1 hr. This was repeated daily during the first week postburn. The control subjects received the same amount of ethanol once. MEASUREMENTS AND MAIN RESULTS: Blood samples were drawn at 20- to 30-min intervals during 5 hrs after the start of the infusion. Serum ethanol was determined by headspace gas chromatography. The rate of elimination of ethanol was calculated from the concentration time profile. In the control subjects, the median elimination rate was 0.074 g/kg/hr (range, 0.059-0.083 g/kg/hr). In the patients, it was already 0.138 g/kg/hr (range, 0.111-0.201 g/kg/hr) on the first day; this increased even further over the following 6 days, reaching 0.183 g/kg/hr (range, 0.150-0.218 g/kg/hr) on the seventh day. CONCLUSIONS: Ethanol elimination is augmented postburn. A more effective reoxidation of reduced nicotinamide adenine dinucleotide seems the most likely explanation for the increased rate of ethanol elimination in these hypermetabolic trauma patients. This finding suggests that the oxidative capacity of the liver may be assessed by studying the rate of ethanol elimination in burn victims.

Adult↗
PubMed1998

Evaluation of enhanced high-resolution laser Doppler imaging in an in vitro tube model with the aim of assessing blood flow in separate microvessels.

An enhanced high-resolution laser Doppler imaging (EHR-LDI) technique intended for visualization of separate microvessels was evaluated by use of in vitro flow models. In EHR-LDI, a laser beam focused to a half-power diameter less than 40 microm successively scans the tissue under study in steps of 25 microm. Spatial blood flow variations within microvascular structures of 1.5 x 1.5 mm are rendered by 64 x 64 measurement sites. Individual microvessel diameters could be estimated and an average difference of 11 microm compared to microscopic measurements was obtained. For the flow algorithm used, the LDI output signal was found to scale linearly with average velocity (0-3.5 mm/s) when a plastic tube of inner diameter 175 microm was perfused with human blood (correlation coefficient 0.99). The LDI output signal was further found insensitive to hematocrit variations in the range 16-44%. Due to the limited laser light penetration in blood, a reduction in the LDI output signal was observed as the inner tube diameters were successively changed from 280 to 1400 microm.

Animals↗
PubMed1998

Non-invasive assessment of intercompartmental fluid shifts in burn victims.

Two non-invasive methods (the bioimpedance technique, BIA, and the impression method, IM) were studied, to find out whether they are sensitive enough to detect and chronicle the development of the oedema and fluid resuscitation effects (Parkland formula) that occur secondary to a major burn. Ten patients with a total burned body surface area (TBSA) of more than 10% were included in this prospective study. Total body water (TBW), as measured by the resistance (BIA) or F(0) variable (IM), reached a maximum on day 2. The tissue fluid translocation (INT) variable (IM) followed a different course, increasing slowly to reach a maximum on day 6, when it was 40% higher than the 12 h value. TBW and the interstitial translocatable fluid were still increased 1 week post-burn. The non-invasive measurements of TBW (resistance by BIA and F(0) by IM) reflected the anticipated changes in TBW. The phase angle (BIA) indicative of cellular membrane effects of burn and sepsis had its lowest values at day 1.5, and stayed significantly low until day 4. Interestingly, the phase angle was lowest in the two cases that died subsequently. The different time course of the INT value (IM), which reflected the translocatable interstitial fluid volume in skin, may be the result of resuscitation fluid remaining in this compartment, due to the excess sodium content together with a possible change in tissue compliance secondary to the early total water peak on day 2.

Adolescent↗
PubMed1998

Anaesthesia for videoarthroscopy of the knee. A comparison between desflurane and sevoflurane.

BACKGROUND: The newer inhalational agents desflurane and sevoflurane have a low blood-gas partition coefficient and are not very fat soluble, and consequently recovery is rapid and smooth. Very few studies have been published concerning adults where a direct comparison has been made between sevoflurane and desflurane in the ambulatory setting. METHODS: This study was done to assess aspects of recovery following minor ambulatory videoarthroscopic knee surgery in 50 ASA I-II patients. Baseline values were obtained on the following psychomotor tests: digit symbol substitution test (DSST), perceptive accuracy test (PAT) and simple reaction time (SRT). The patients were then randomly allocated to one of two groups according to an open (unblinded) study design: Group D (Desflurane) were maintained on desflurane while Group S (Sevoflurane) were maintained on sevoflurane. Propofol was used as the induction agent in all patients and the larynx mask was used to maintain a free airway. Oxygen and air (FiO2 0.33) were used as the carrier gases. The concentration of desflurane or sevoflurane was adjusted in order to maintain adequate anaesthesia and stable haemodynamics. Alfentanil was given at induction and every 15 min as an analgesic. At the end of the operation, the gases were turned off abruptly and 100% oxygen was delivered at 6 L/min until eye-opening. Early recovery was measured by the time to eye-opening, giving name and date of birth. Intermediate recovery was measured by psychomotor testing every 30 min, and the time to sitting up in bed, drinking fluids and discharge home by a nurse who was blinded to the anaesthetic technique. RESULTS: Early recovery was quicker in the desflurane compared to the sevoflurane group (P<0.001). Psychomotor recovery as measured by the PAT occurred significantly earlier in the desflurane compared to the sevoflurane group at 15 and 45 min (P<0.001) and as measured by the DSST at 30 min (P<0.05). The number of patients who could not perform the SRT test at 15 min was greater in the sevoflurane compared to the desflurane group (13 vs 0) (P<0.01). No differences were found in other recovery parameters, including home discharge, between the groups. The incidence of pain and other minor postoperative complications was similar between the groups except for sore throat which was higher in the desflurane group. CONCLUSION: Early and intermediate (psychomotor) recovery is quicker in the desflurane compared to the sevoflurane group, but there is no difference in discharge times between the groups.

Adolescent↗
PubMed1997

New approach for elucidating the oxygen sensitivity and calibration of the antimony electrode.

The biomedical use of the polycrystalline antimony pH electrode is hampered by oxygen dependence and low pH resolution (0.1 pH). Although, the pH resolution is improved by using highly purified crystallographically oriented monocrystalline antimony (COMA), the oxygen effect on the electrode remains. In an in vitro examination of the COMA electrode it was found that the oxygen dependence is similar to that of polycrystalline antimony, i.e. nonlinear with an increase in sensitivity below 10 kPa. These findings imply that the oxygen tension in the vicinity of a COMA pH electrode, has to be known or controllable for the pH reading to be at all valid especially at low oxygen levels, such as is often seen in biomedical applications. A calibration procedure using a zero oxygen solution is used in order to obtain absolute pH readings in a measurement solution of pre-set or known oxygen levels. Furthermore, the nonlinear oxygen sensitivity of the antimony electrode suggests that the underlying electrochemical reactions are other than those described by corrosion theory.

Antimony↗
PubMed1997

Is there a need for antithrombin III substitution early after burn injury?

The changes in antithrombin III (AT-III) levels in the blood and restitution in coagulation parameters between patients receiving and not receiving AT-III substitution were examined early after burn injury. The study was divided into two parts with a total of 14 consecutive patients (per cent total body surface area (TBSA) > or = 20 per cent). The first six patients were given AT-III substitution when AT-III levels fell below 50 per cent. The second part examined the restitution of the coagulation parameters when the patients (n = 8) obtained AT-III substitution only at extremely low values of AT-III. The decline in AT-III observed occurred in parallel to the permeability changes and the haemodilution normally seen secondarily to the initial fluid rescucitation. The observed changes in the coagulation parameters were modest and no hepatic dysfunction was noted. In addition, no differences of the restitution in these coagulation parameters were noted between the substituted and non-substituted groups. These results suggest that changes in AT-III early after burn injury depend mainly on factors other than an ongoing disseminated coagulation process. Probable causes are increased capillary leak and haemodilution. Our results suggest that substitution of AT-III in the early postburn period, on the assumption that low levels alone indicate ongoing coagulation, is not warranted.

Adolescent↗
PubMed1997

Cerebral blood flow of the exposed brain surface measured by laser Doppler perfusion imaging.

A novel application of laser Doppler flowmetry (LDF) laser Doppler perfusion imaging (LDPI), was used to study cerebral cortical blood flow (CBFcortex). In contrast to the conventional laser Doppler perfusion monitor, LDPI creates two dimensional maps of the tissue perfusion in a well defined area of up to 120 x 120 mm comprising 4096 measurements points. Measurements of CBFcortex were made through an optically transparent polyester film applied to a cranial window preparation in ventilated anaesthetized pigs. Temporal and spatial heterogeneity in CBFcortex were visualized by LDPI during provocations which are known to alter CBF (varying arterial PCO2 or MABP, or infusion of adenosine at constant MABP (concomitant angiotensin administration) or by hyperoxemia). During hypercapnia the recorded CBFcortex increased homogeneously. The adenosine-mediated increase in recorded CBFcortex was concentrated on the lower flow interval, as was the hyperoxemia-caused decline. At decreasing MABP the autoregulatory threshold was found to vary locally within the cortex. The results suggest that LDPI, apart from detecting localized changes in CBFcortex' also visualizes flow changes within different vascular segments. Together with the practical advantages of the system, i.e. not necessitating direct contact with the tissues, this feature makes the technique suitable for studies of CBFcortex distributions.

Animals↗
PubMed1997

Heterogeneous blood flow response in the foot on dependency, assessed by laser Doppler perfusion imaging.

The exact nature of the decrease in foot skin blood flow seen after a change in posture remains unsettled. This mechanism has previously been examined by non-invasive techniques such as the laser Doppler perfusion monitor (laser Doppler flowmetry). Taking into account the shortcomings of laser Doppler perfusion monitoring when applied to the determination of skin blood flow, which normally shows substantial heterogeneity, we have applied an emerging technology, the laser Doppler perfusion imager (LDPI). This technique provides a more comprehensive picture of the blood flow distribution in the skin, as it maps skin blood flow over a surface area (120 x 120 mm, 4096 measurement sites). It was used to examine if the reduction in tissue perfusion or the alterations in flow distributions seen after a change in posture (supine to dependency) could be fully explained by an increase in venous pressure (venous stasis of 50 mmHg) or if the data suggest a complementary mechanism. Skin blood flow of the forefoot decreased from 0.60 V (volt) (median) during rest to 0.40 and 0.38 V during venous stasis and dependency, respectively. Although almost identical median values were obtained during stasis and dependency, the flow distributions were different with a loss of high flow values during venous stasis. Biological zero was 0.24 V. As the LDPI technique readily records skin perfusion during variations in venous stasis and posture, as well as information on flow distribution changes. It appears promising for future application in stimuli-response studies of skin blood flow. The difference in flow distribution seen between increased venous pressure and dependency suggests an additive regulatory mechanism to the veni-vasomotor reflex during a change in posture.

Adult↗
PubMed1996

Magnetic resonance imaging: a new diagnostic aid in the care of high-voltage electrical burns.

Magnetic resonance imaging (MRI) can detect and delineate alterations in the hydration properties of tissues such as oedema and necrosis. The distinction between living tissue oedema and frank necrosis is also possible with MRI, by use of a spin-echo (SE) sequence and a fast spin-echo (FSE) sequence with a 1.5 T imager. With this background, the aim of this study was to examine the ability of MRI for early detection of concealed tissue injuries caused by high-voltage electrical burns, an entity not previously explored. Clinical use of MRI examinations in patients with high-voltage injuries admitted to the Burn Unit at Linköping University Hospital, has resulted in the significant elucidation of the deeper tissue injuries that occur. The T2-weighted images provided substantial information about the localization and amount of muscle necrosis, thus enabling increased surgical precision in the treatment of these high-voltage injury victims. FSE sequences produce T2-weighted images with increased speed of acquisition and/or increased image resolution compared to conventional SE sequence. Two illustrative examples are provided.

Adult↗
PubMed1996

Adverse effects of hyperoxemia during cardiopulmonary bypass.

OBJECTIVE: Aiming at elucidating the effects on capillary blood flow and tissue oxygenation of hyperoxemia during cardiopulmonary bypass, we studied skeletal muscle surface oxygen tensions in 10 patients undergoing elective cardiac operations. METHODS: In a prospective investigation each patient was exposed to normoxemia (arterial oxygen tension 75 to 115 mm Hg) and hyperoxemia (arterial oxygen tension > 185 mm Hg, inspired oxygen fraction = 1.00) during normal anesthetized conditions before and after cardiopulmonary bypass, as well as during normothermic and hypothermic continuous-flow bypass. In each state hemodynamic variables and arterial and mixed venous blood gas and acid base values were measured. From these data oxygen transport variables were calculated. Tissue oxygenation was studied with the use of a multiple-point polarographic oxygen microelectrode, known to provide measures of oxygen tensions at the capillary level. The oxygen distribution profile of such a sample is also indicative of capillary blood flow distribution changes. RESULTS: In all patients and at each occasion of the investigation markedly low mean surface oxygen tensions in skeletal muscle were registered. When hyperoxemia was instituted, a significant decrease in these surface oxygen tensions together with an increase in distribution heterogeneity was seen during all stages. Contrary to prebypass, postbypass, and hypothermic bypass, where vascular resistance, oxygen delivery, and oxygen consumption remained similar during hyperoxemia and normoxemia, a significant (p < 0.05) increase in vascular resistance together with a decline in oxygen consumption was seen during hyperoxemic normothermic (35 degrees to 36 degrees C) cardiopulmonary bypass. CONCLUSION: These findings show that the microcirculatory response to hyperoxemia, seen under other circumstances, persists during continuous-flow cardiopulmonary bypass, normothermic as well as hypothermic. If these adverse effects on tissue oxygenation by hyperoxemia can be further verified and shown to be valid for other organs than skeletal muscle, we would suggest that hyperoxemia should be avoided, especially during normothermic cardiopulmonary bypass.

Acid-Base Equilibrium↗
PubMed1996

Psoralens used for cosmetic sun tanning: an unusual cause of extensive burn injury.

Psoralen combined with long-wave ultraviolt radiation (UV-A) has become a standard method of psoriasis treatment. A well-known and often appreciated 'side-effect' is the hyperpigmentation caused by this treatment. Three patients demonstrating a novel cause of severe skin loss, 'psoralen burn', are presented. No patient was afflicted by psoriasis and all three had used psoralen and ultraviolet exposure with the intent to enhance sun tanning. In the case histories presented, it is notable that two of the patients share an alarmingly extensive skin injury (90-95 per cent body surface area), while the third had an extensive but rather superficial injury. In addition, a very similar time-table for the development of the injury could be observed, with a maximum distribution of skin loss not reached until 7 or 8 days after exposure. Psorelen-UV-A can cause life-threatening skin losses when used in an erratic manner. Early recognition of the nature and knowledge of the time-course in the development of these lesions is necessary for optimal treatment. Some principles of treatment are discussed. Dermatologists prescribing PUVA treatment should further increase their warnings of uncontrolled use of psoralens in non-psoriatrics.

Adult↗