Combined neuraxial and general anaesthesia - a dangerous combination?
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Analgesia, Epidural↗
Biomedical subjects
F Sjöberg
Publications and source records attributed to F Sjöberg.
Acidosis in muscle tissue distal to vascular contusion despite unchanged global blood flow in rats: an uncoupling of microvascular blood flow and metabolism?
Studies using a contusion trauma model have shown that the femoral artery of the rat remains patent in 85% despite a severe vessel injury. A significant increase in tissue oxygenation (PtO2) has been found despite only a minor effect on blood flow (<20% decrease) on the muscle surface distal to the injury indicating a disturbed relationship between microvascular blood flow and metabolism. The aim of the present study was to further study the interplay between microvascular blood flow and metabolism within the distal muscle using an ethanol clearance technique (blood flow) in conjunction to the determination of an ischemia marker (lactate) by use of microdialysis. Although skeletal muscle blood flow remained unaltered as assessed by ethanol clearance, skeletal muscle lactate levels increased significantly (P<0.001) post-trauma in both legs. The increase was initially higher, faster and the increase over time larger in the trauma leg as compared to the control leg (P<0.001). These findings indicate a systemic effect of the trauma. Further, it suggests a functional impairment of the relationship between microvascular blood flow and/or muscle metabolic processes when the trauma is directed towards the supplying blood vessel. The reason for this anaerobic insult as found in this study compared to the presence of a local increase in PtO2 in the trauma leg as shown in our previous study is suggestive of an microvascular blood flow and tissue metabolism uncoupling.
Acidosis↗
Inhalation injury assessed by score does not contribute to the development of acute respiratory distress syndrome in burn victims.
OBJECTIVE: To establish the incidence, mortality, and time of onset of acute respiratory distress syndrome (ARDS) in relation to extent of burn and inhalation injury in patients who required mechanical ventilation. DESIGN: Data about burn and inhalation injury were recorded prospectively whereas ARDS and multiple organ dysfunction were assessed by review of patient charts. SETTING: National burn intensive care unit at Linkoping University Hospital, Sweden (a tertiary referral hospital). PATIENTS: Between 1993 and 1999, we studied all patients with thermal injury (n=553) who required mechanical ventilation for more than two days (n=91). MEASUREMENTS AND RESULTS: Out of the thirty-six burn victims who developed ARDS (40%), 25 (70%) did so early post burn (in less than 6 days). Patients with ARDS had higher multiple organ dysfunction scores (mean 10.5) than those who did not develop ARDS (mean 5.6) (p<0.01). The probable presence of inhalation injury as assessed by an inhalation lung injury score (ILIS) did not contribute to the development of ARDS. Mortality tended to be higher in patients who developed ARDS (14%) compared to those who did not (6%, p=0.2). CONCLUSIONS: In our burn patients the incidence of ARDS was high whereas mortality was low. We found no association between inhalation injury as assessed using the ILIS and development of ARDS. Our data support a multi-factorial origin of ARDS in burn victims as a part of a multiple organ failure event.
Adolescent↗
Acute hyperoxaemia-induced effects on regional blood flow, oxygen consumption and central circulation in man.
AIM: Despite numerous in vitro and animal studies, circulatory effects and mechanisms responsible for the vasoconstriction seen during hyperoxaemia are yet to be ascertained. The present study set out to: (i) set up a non-invasive human model for the study of hyperoxia-induced cardiovascular effects, (ii) describe the dynamics of this effect and (iii) determine whether hyperoxaemia also, by vasoconstriction alters oxygen consumption (O(2)). METHODS: The study comprised four experiments (A, B, C and D) on healthy volunteers examined before, during and after 100% oxygen breathing. A: Blood flow (mL min(-1).100 mL(-1) tissue), venous occlusion plethysmography was assessed (n = 12). B: Blood flow was recorded with increasing transcutaneous oxygen tension (P(tc)O(2)) levels (dose-response) (n = 8). C: Heart rate (HR), stroke volume, cardiac output (CO) and systemic vascular resistance (SVR) was assessed using echocardiography (n = 8). D: O(2) was measured using an open circuit technique when breathing an air-O(2) mix (fraction of inhaled oxygen: F(i)O(2) = 0.58) (n = 8). RESULTS: Calf blood flow decreased 30% during O(2) breathing. The decrease in calf blood flow was found to be oxygen dose dependent. A similar magnitude, as for the peripheral circulation, of the effect on central parameters (HR/CO and SVR) and in the time relationship was noted. Hyperoxia did not change O(2). An average of 207 (93) mL O(2) per subject was washed in during the experiments. CONCLUSION: This model appears suitable for the investigation of O(2)-related effects on the central and peripheral circulation in man. Our findings, based on a more comprehensive (central/peripheral circulation examination) evaluation than earlier made, suggest significant circulatory effects of hyperoxia. Further studies are warranted to elucidate the underlying mechanisms.
Adult↗
Computed tomography--a possible aid in the diagnosis of smoke inhalation injury?
Inhalation injury is an important contributor to morbidity and mortality in burn victims and can trigger acute lung injury and acute respiratory distress syndrome (ARDS) (1-3). Early diagnosis and treatment of inhalation injury are important, but a major problem in planning treatment and evaluating the prognosis has been the lack of consensus about diagnostic criteria (4). Chest radiographs on admission are often non-specific (5, 6), but indicators include indoor fires, facial burns, bronchoscopic findings of soot in the airways, and detection of carbon monoxide or cyanide in the blood (7). Changes in the lungs may be detected by bronchoscopy with biopsy, xenon imaging, or measurement of pulmonary extracellular fluid (4, 5, 8). These methods have, however, been associated with low sensitivity and specificity, as exemplified by the 50% predictive value in the study of Masanes et al. (8). Computed tomographs (CTs) are better than normal chest radiographs in the detection of other pulmonary lesions such as pulmonary contusion (9, 10). The importance of CT scans in patients with ARDS has been reviewed recently (9), but unfortunately there has been no experience of CT in patients with smoke inhalation injury. To our knowledge, there are only two animal studies reporting that smoke inhalation injury can be detected by CT (4, 11); specific changes in human CT scans have not yet been described. Therefore, confronted with a patient with severe respiratory failure after a burn who from the history and physical examination showed the classic risk factors for inhalation injury, we decided to request a CT.
Catheterization, Swan-Ganz↗
Moderate hypothermia for 359 operations to clip cerebral aneurysms.
BACKGROUND: Experimental data have suggested that hypothermia (32-34 degrees C) may improve outcome after cerebral ischaemia, but its efficacy has not yet been established conclusively in humans. In this study we examined the feasibility and safety of deliberate moderate perioperative hypothermia during operations for subarachnoid aneurysms. METHODS: A total of 359 operations for intracranial cerebral aneurysms were included in this prospective study. By using cold intravenous infusions (4 degrees C) and convective cooling our aim was to reduce the patient's core temperature to more than 34 degrees C within 1 h before operation. The protocol assessed postoperative complications such as infections, prolonged mechanical ventilation, pulmonary complications and coagulopathies. RESULTS: During surgery, the body temperature was reduced to a mean of 32.5 (SD 0.4) degrees C. Cooling was accomplished at a rate of 4.0 (SD 0.4) degrees C h(-1). All patients were normothermic at 5 (sd 2) h postoperatively. Peri/postoperative complications included circulatory instability (n=36, 10%), arrhythmias (n=17, 5%) coagulation abnormalities and blood transfusion (n=169, 47%), infections (n=29, 8%) and pulmonary complications (infiltrate or oedema while on ventilatory support) (n=97, 27%). Eighteen patients died within 30 days (5%). There was no significant correlation between the extent of hypothermia and any of the complications. However, there was a strong correlation between the occurrence of complications and the severity of the underlying neurological disease as assessed by the Hunt and Hess score. CONCLUSION: Moderate hypothermia accomplished within 1 h of induction of anaesthesia and maintained during surgery for subarachnoid aneurysms appears to be a safe method as far as the risks of peri/postoperative complications such as circulatory instability, coagulation abnormalities and infections are concerned.
Adolescent↗
Hyperoxaemia does not change concentrations of serotonin and beta-thromboglobulin in blood of healthy humans.
BACKGROUND: The mechanisms of oxygen-induced effects on blood vessels (vasoconstriction in hyperoxaemia and vasodilatation during hypoxaemia) are uncertain. Many investigators have suggested that the vasoconstriction seen during hyperoxia/hyperoxaemia is mediated through the endothelium as a result of either increased release or activity of vasoconstrictors (oxygen radicals, endothelin, norepinephrine, angiotensin II, or serotonin (5-HT)), or reduced activity of vasodilators (prostaglandin E2 and nitric oxide). Serotonin has been assumed to have a central role. METHODS: Eight healthy volunteers were exposed to FiO2 of 1.0 for 20 min and serum concentrations of serotonin and activated platelets were measured (indicated by concentrations of beta-thromboglobulin (beta-TG)). RESULTS: During hyperoxaemia in humans, serum concentrations of scrotonin and beta-TG remained unchanged. CONCLUSION: If serotonin is involved in oxygen-induced vasoconstriction, the mechanism is more likely to be either a potentiating effect of serotonin on other vasoconstrictors or increased activity of serotonin on its receptor.
Adult↗
Nonspecific vasodilatation during transdermal iontophoresis-the effect of voltage over the skin.
We used laser Doppler perfusion imaging (LDPI) to study nonspecific vasodilatation during iontophoresis. In iontophoresis studies, nonspecific vasodilatation occurs as a result either of galvanic currents or of the applied voltage over the skin. We made dose-response measurements to study the effect of ionic strength of the vehicle on the nonspecific vasodilatation during iontophoresis of sodium chloride and deionized water, while we monitored the voltage over the skin. We found that anodal and cathodal ionotophoresis induced a voltage over the skin that was dependent on the ionic strength of the test solution. The nonspecific vasodilatation during anodal iontophoresis was less pronounced than during cathodal iontophoresis, and was independent of the voltage over the skin. The nonspecific vasodilatation in cathodal iontophoresis was related to the voltage over the skin, and was possibly mediated by depolarization of local sensory nerves. In experiments using cathodal iontophoresis, therefore, the ionic strengths of the vehicle and the drug are important when vasoactive drugs are examined, as the nonspecific vasodilatation needs to be controlled for. As the vasodilatation that we observed was heterogeneously distributed within the area of iontophoresis, LDPI may provide more accurate measurements than conventional laser Doppler perfusion monitoring.
Administration, Cutaneous↗
Cortical blood flow autoregulation revisited using laser Doppler perfusion imaging.
Methods of laser Doppler perfusion monitoring (LDPM) and imaging (LDPI) have been validated and found useful for measurements of brain blood flow in several studies. The present work was undertaken to examine the cortical blood flow autoregulatory phenomenon as it has lately been questioned and claimed to be method-dependent and related to sample volume. Spatial variations in cerebral cortical blood flow (CBF(cortex)) in the pressure range 20-140 mmHg (static cerebral autoregulation; caval block/angiotensin infusion) were studied in six mechanically ventilated (hypocapnic, normocapnic and hypercapnic) pigs anaesthetized with propofol and fentanyl. Although the cortical blood flow values sampled were highly heterogeneously distributed, they were strongly pressure-dependent as well as CO2-dependent (P < 0.001). A cumulative cerebral blood flow (CBF)-pressure (MAP) plot comprising all values obtained indicated a pressure range between 70 and 120 mmHg where CBF remained almost constant. However, at the local level in the cortex (mm2) the same type of 'classic' autoregulatory flow : pressure graphs (FPG) were found in only a few of the cases of the cortical areas examined (n = 96). Alterations in blood P(a)CO2 saturation did not affect the pressure : flow relationship at low perfusion pressures, whereas at normal or above normal values, and as anticipated, hypercapnia considerably increased CBF (P < 0.001). 'Classic' autoregulatory FPGs were found only when all values sampled were clustered together, whereas, as a new finding, data are presented indicating that autoregulatory capacity is lacking at the local level at some cortical surface areas.
Animals↗
[Burn injuries in Sweden 1987-1996. The number of hospitalized patients has been reduced and the mortality lowered by 70 per cent].
Continuous improvement in burn trauma care has led to decreasing mortality, morbidity, and length of hospital stay. Current data from the Swedish population is lacking, which was the reason for this investigation. Data was gathered from the Swedish database for medical care (based on ICD-9). All Swedish care providers are enrolled and assumed to report data. Hence, the quality of the database is considered reasonably good, although data from individual patients may be incorrectly recorded due to clerical errors. Available data indicate that the number of burn victims seeking medical care has decreased by 16% during the past decade, whereas mortality has decreased by 70%! The demographic data is otherwise similar to what has previously been reported in the international literature.
Adolescent↗
Albumin supplementation during the first week after a burn does not mobilise tissue oedema in humans.
OBJECTIVE: To measure water balance and changes in distribution, and the effect of giving supplementary albumin, early after a burn injury. DESIGN: Consecutive patients (matched groups) and healthy controls. SETTING: National burn unit in a Swedish university hospital. PATIENTS AND SUBJECTS: Eighteen patients with 18%-90% total burned surface area and 16 healthy male control subjects. INTERVENTIONS: The patients were given an intravenous infusion of ethanol over 1 h, 0.35-0.60 g/kg body weight, and a bolus of 3.3 to 6.5 g of iohexol. The control subjects were given the same amounts of either ethanol or iohexol. Patients were subdivided into two groups according to whether or not they received supplementary albumin starting 12 h post-burn. MEASUREMENTS AND RESULTS: Blood samples were drawn at 20-30 min intervals over 4 h after the start of the infusion. Serum ethanol was measured by headspace gas chromatography, and iohexol with high-pressure liquid chromatography (HPLC). Distribution volume was calculated from the concentration-time profiles. Total body water (TBW) was measured by the ethanol tracer and bioelectric impedance (BIA) techniques, and estimated extracellular water (ECWest) by iohexol tracer. They were all significantly increased after a burn. Excess water was accumulated mainly in the extracellular compartment. It declined towards normal values (those of volunteers) at the end of the week. Albumin supplementation did not influence the amount or distribution of the excess fluid. CONCLUSION: Body water increases after a burn. Excess water is mainly deposited in the extracellular space. Tissue oedema fluid is not mobilised by albumin supplementation.
Adult↗
Measurement of depth of burns by laser Doppler perfusion imaging.
Laser Doppler perfusion imaging (LDPI), is a further development in laser Doppler flowmetry (LDF). Its advantage is that it enables assessment of microvascular blood flow in a predefined skin area rather than, as for LDF, in one place. In many ways this method seems to be more promising than LDF in the assessment of burn wounds. However, several methodological issues that are inherent in the LDPI technique, and are relevant for the assessment of burn depth, must be clarified. These include the effect of scanning distance, curvature of the tissue, thickness of topical wound dressings, and pathophysiological effects of skin colour, blisters, and wound fluids. Furthermore, we soon realised that to examine the perfusion image generated by LDPI adequately the process of analysis was appreciably improved by the simultaneous use of digital photography. In the present investigation we used both in vitro and in vivo models and also examined burned patients, and found that the listed factors all significantly affected the LDPI output signal. However, if these factors are known to the examiner, most of them can be adjusted for. If the technique is further improved by minimizing such effects and by reducing the practical difficulties of applying it to a burned patient in the burns unit, the technique may find uses in everyday clinical decision-making.
Adolescent↗
Utility of an intervention scoring system in documenting effects of changes in burn treatment.
The consequences of the introduction of a program of consistent use of topical antimicrobials and early aggressive excision of deep burn wounds by utilizing a comprehensive, computerized patient registry/therapeutic intervention scoring system, were investigated. Prospectively, the clinical course, mortality, outcome and hospital costs were compared for the year preceding (89 patients) and the 4 years following (226 patients) the introduction of the new treatment program. It was found that mortality decreased from 10.1 to 4.6% after change in therapy (P<0.001), despite an increase in mean burn extent. The length of hospital stay per % burn surface area declined from 1.2 to 1.0 days (P<0.001). The number and complexity of therapeutic interventions and the associated costs, also declined. Patients in the new treatment program had a better level of physical and psychosocial function at follow up. In conclusion, the introduction of a program of consistent use of topical antimicrobials and early, aggressive surgical excision was associated with an improved outcome at lesser cost. The combined registry-intervention scoring system permits ready analysis of results using data entered on a daily, near-real time basis.
Adult↗
Dual mode antimony electrode for simultaneous measurements of PO2 and pH.
BACKGROUND: In biomedical research and clinical medicine there is a demand for potent sensors to measure the components that make up blood gas analyses. Today, as when the electrochemical PO2, PCO2 and pH electrodes were first introduced, these measurements are usually made with the same type of sensor technology. The aims of the present study were, firstly, to find out whether the platinum cathode in the Clark electrode can be replaced by antimony for oxygen measurements (amperometry (A)); secondly, whether, during oxygen measurements, the inherent corrosion potential of the antimony metal can be used for measurement of pH in the same measurement area (potentiometry (P)). METHODS: An electrode of purified, crystallographically orientated monocrystalline antimony (COMA) connected to a reference electrode (silver-silver chloride) was used for the P measurements. Measurements of A (at -900 mV) and P were made in an aqueous environment regulated for oxygen, pH, and temperature. RESULTS: Reproducible oxygen sensitivities of 0.925 nA/% oxygen (2% CV (coefficient of variation)) (A), 10.7 mV/% (P), and 0.7 mV/% (P) were found in the oxygen range: 0-21%, <5%, and above 5%, respectively. The pH sensitivity was 57 mV/pH unit (P). Oxygen and pH measurements were less accurate at oxygen concentrations close to 0%. CONCLUSIONS: Both the oxygen and pH part of the composite electrode signal can be identified by this dual mode technique (A and P). The sensor seems to be promising as it provides measurements of two separate variables (oxygen and pH) and also has the desirable characteristics of a solid state sensor.
Antimony↗
Non-invasive assessment of fluid volume status in the interstitium after haemodialysis.
During dialysis excess fluid is removed from uraemic patients. The excess fluid is mainly located in the skin and subcutaneous tissues. In this study we wished, with two noninvasive techniques, the IM (impression method) and BIA (bioimpedance analysis), to study what mechanical (IM) and electrical cellular membrane (BIA) effects the fluid withdrawal has on these tissues. The IM measures the resistive force of the tissues when mechanically compressed. From the force curve two parameters are calculated, the F(0), indicative of interstitial tissue pressure and the FT corresponding to the translocation of tissue fluid (interstitial movable water). The BIA phase angle shift (phi), i.e. geometrical angular transformation of the ratio between reactance and resistance, which has been associated with cellular membrane function, was used as a measurement of electrical cellular membrane effects. Twenty patients were studied before and after haemodialysis measuring the F(0), FT and phi. Theresults showed that the patients lost a median of 3.7 kg during the haemodialysis. F(0) increased until after dialysis, but did not reach significant values, whereas FT increased significantly after dialysis, p < 0.001, as compared with before. After a peak at one hour postdialysis the FT value returned to predialysis values at four hours after termination of dialysis. Also phi increased from before to after dialysis, p < 0.001, but already after one hour it returned to predialysis values. It is common knowledge that dialysis alters the dynamics of fluid in the interstitium of the skin and subcutis. We conclude that the impression method is sensitive enough to detect and chronicle these changes. Furthermore, with the BIA, (phase angle) signs of changes in the electrical properties of the tissues, possibly reflecting cellular membrane function, could be detected.
Body Weight↗
Severe contusion of the femoral vessels in rats alters tissue oxygenation and microvascular blood flow regulation in the skeletal muscles of the limb.
BACKGROUND: Severe contusion of an artery often presents clinical problems in that it affects flow distal to the injury. However, the effect of a contusion on the microvascular flow regulation in the distal part of the limb is still largely unknown. METHODS: A multipoint microelectrode technique was used to assess both tissue oxygenation (PtO2) and microflow (hydrogen clearance) on the skeletal muscle surface in a standard contusion injury to the femoral vessels in rats. RESULTS: A significant increase in and an altered distribution of (PtO2) as well as a reduction in and altered distribution of microflow on the muscle surface distal to the injury was found in all animals (n = 27) compared with the uninjured control leg. These findings could not be reproduced experimentally by sympathectomy or when the adjacent skeletal muscle alone was injured. CONCLUSION: The results suggest that the changes observed distal to the injury are of vascular origin, possibly as a result of endothelial damage at the site of the contusion.
Animals↗
Red blood cell velocity and volumetric flow assessment by enhanced high-resolution laser Doppler imaging in separate vessels of the hamster cheek pouch microcirculation.
An enhanced high-resolution laser Doppler imager (EHR-LDI), configured to fit the demands of a measurement area containing separate microvessels, was evaluated for perfusion measurements in hamster cheek pouch preparations during ischemia, reperfusion, and pharmacologically induced vasodilation and vasoconstriction. Measurements in separate microvessels where the laser beam was smaller than the vessel diameter were referred to as red blood cell (RBC) velocity estimates, as previously validated in vitro, whereas a relative flow index, RFI (mean RBC velocity/tissue area), was introduced as a volumetric flow measure. Microvessel diameter and RBC velocity changes during ischemia, reperfusion, as well as during vasoconstriction and vasodilation correlated to the data obtained from the microscope. Correspondingly, during the described provocations anticipated volumetric flow changes were registered as changes in the RFI. When data on intravessel RBC velocity profiles are presented they reflect a parabolic flow profile usually seen in this size microvessel. The EHR-LDI appears a promising tool for investigation of the microvasculature, as it almost simultaneously provides information on relative changes of both in vivo RBC velocity and volumetric flow (RFI), although the latter estimate needs to be further refined.
Adenosine↗
Lack of significant treatment effect of plasma exchange in the treatment of drug-induced toxic epidermal necrolysis?
OBJECTIVE: Comparison of outcome in patients with toxic epidermal necrolysis (TEN) in patients who received plasma exchange (PE) compared with the results in two other centres that used almost identical treatment protocols but without PE. DESIGN: Retrospective comparative case series with two recently published case series serving as controls. SETTING: National burns intensive care unit (ICU) and Department of Transfusion Medicine at Linköping University Hospital, Sweden. PATIENTS: 8 consecutive patients admitted with TEN who received PE during 1987-1997. INTERVENTIONS: Neither prophylactic antibiotics nor cortisone were used. The patients were given a median of 5.5 PE treatments (range 1-8). RESULTS: Eight patients with a median (range) age of 45 years (5-89) and with a median skin involvement total body surface area (TBSA) of 38% (12-100) were treated. The length of stay in the burns ICU was 15 (13-25) days and the time from onset of the cutaneous signs until complete re-epithelialisation was 24 days (13-55) for the seven survivors. Five patients fulfilled the diagnostic criteria of sepsis. One patient with extensive ischaemic cardiac disease developed septic shock and died (mortality 12.5%). Two patients developed side effects from PE. CONCLUSIONS: To our knowledge, this is the largest series yet presented using PE in the treatment of TEN. Our results, in patients with less cutaneous involvement, similar causative agents, and similar demographic data as in the other two studies (controls), were no different as far as mortality, length of stay, or time to re-epithelialisation were concerned. This finding does not support the use of PE in the treatment of TEN.
Adolescent↗