Biomedical subjects
Publications and source records attributed to L Ekström.
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The dynamic axial stiffness of the L2-3 motion segment subjected to vibratory loading under intact and injured states of the intervertebral disc was studied using an in vivo porcine model. Three groups of animals with the following states of the intervertebral discs were studied: intact disc, acutely injured disc, and degenerated disc. A miniaturized servo-hydraulic exciter was used to sinusoidally vibrate the motion segment from 0.05 to 25 Hz under a compressive load with a peak value of either 100 or 200 N. The dynamic axial stiffness of the intervertebral disc was calculated at 1-Hz intervals over the frequency range. The results showed that the dynamic axial stiffness was frequency dependent. A positive relationship was found between an increase in mean dynamic stiffness and load magnitude. An increase in mean stiffness with successive exposures at the same load magnitude was observed, despite the allowance of a recovery period between loading. The greatest difference was noted between the first and second load sets. No significant change in stiffness was found due to an acute disc injury, whereas a significant increase in mean stiffness was found for the degenerated disc group as compared with the intact group. The form of the frequency response curve, however, remained relatively unaltered regardless of the degenerated state of the disc. With heavier loads, repeated loading, and/or disc degeneration, the stiffness of the intervertebral disc increases. An increase in stiffness can mean a reduction in the amount of allowable motion within the motion segment or a potentially harmful increase in force to obtain the desired motion. This may locally result in greater stresses due to an altered ability of the disc to distribute loads.
In a cadaveric experiment, 16 functional spinal units (FSUs) obtained from 7 subjects with a mean age of 16.3 years were tested in compression to failure. The deformation rate was 5 mm/min. The bone mineral content (BMC) in the vertebrae was determined by using dual-photon absorptiometry (DPA). In 15 of the FSUs, traumatic changes were registered. Three different types of changes were seen. In nine vertebrae, there was a rupture in the cartilaginous end plate, in 12, a separation of the end plate from the vertebral body, and in three vertebrae, a compression fracture was registered. A close relation was found between BMC and the ultimate force (r2 = 0.63), the ultimate displacement (r2 = 0.73), and the energy absorption (r2 = 0.74). The weakest part of a spinal segment in this experimental situation is the growth plate.
Rat liver microsomal glutathione transferase is rapidly inactivated upon treatment with the arginine-selective reagent phenylglyoxal or the lysine-selective 1,3,5-trinitrobenzenesulfonate. Glutathione sulfonate, an inhibitor of the enzyme, gives nearly complete protection against inactivation and prevents modification, indicating that these residues form part of or reside close to the active site. Sequence analysis of peptides from peptic and tryptic digests of [7-14C]phenylglyoxal- and 1,3,5-trinitrobenzenesulfonate-treated microsomal glutathione transferase indicated arginine 107 and lysine 67 as the sites of modification. A set of mutant forms of microsomal glutathione transferase was constructed by site-directed mutagenesis and heterologously expressed in Escherichia coli BL21(DE3). Arginine 107 was exchanged for alanine and lysine residues. The alanine mutant (R107A) exhibited an activity and inhibition profile similar to that of the wild type enzyme but displayed a decreased thermostability. Thus, arginine 107 does not appear to participate in catalysis or substrate binding; instead, an important structural role is suggested for this residue. Lysine 67 was mutated to alanine and arginine with no effect on activity. All three histidines were replaced by glutamine, and the resulting mutant proteins had activities comparable with that of the wild type. It can thus be concluded that the chemical modification experiments indicating that arginine 107, lysine 67, and one of the histidines partake in catalysis can be disproved. However, protection from modification by a competitive inhibitor indicates that these residues could be close to the glutathione binding site. All tyrosine to phenylalanine substitutions resulted in mutants with activities similar to that of the wild type. Interestingly, the exchange of tyrosine 137 appears to result in activation of the enzyme. Thus, the microsomal glutathione transferase must display an alternate stabilization of the thiolate anion of glutathione other than through interaction with the phenolic hydroxyl group of a tyrosine residue. Substitution of cysteine 49 with alanine resulted in a semiactivated mutant enzyme with enzymatic properties partly resembling the activated form of microsomal glutathione transferase. The function of this mutant was not altered upon reaction with N-ethylmaleimide, and cysteine 49 is thus demonstrated as the site of modification that results in activation of microsomal glutathione transferase.
AIM: To describe the occurrence, characteristics and outcome among patients with out-of-hospital cardiac arrest who required continuation of cardiopulmonary resuscitation (CPR) on admission to the emergency department. PATIENTS: all patients in the municipality of Göteborg who suffered out-of-hospital cardiac arrest, were reached by the emergency medical service (EMS) system and in whom CPR was initiated. Period for inclusion in study: 1 Oct. 1980-31 Dec. 1992. RESULTS: of 334 out-of-hospital cardiac arrests, 2,319 (68%) were receiving on-going CPR at the time of admission to hospital. Of these, 137 patients (6%) were hospitalized alive and 28 (1.2%) could be discharged from hospital. Of these patients, 39% had a cerebral performance categories (CPC) score of 1 (no cerebral deficiency), 18% had a CPC score of 2 (moderate cerebral deficiency), 36% had a CPC score of 3 (severe cerebral deficiency) and 7% had a CPC score of 4 (coma) at discharge. Among patients discharged. 76% were alive after 1 year. CONCLUSION: among consecutive patients with out-of-hospital cardiac arrest, CPR was ongoing in 68% of them on admission to hospital. Among these patients, 6% were hospitalized alive and 1.2% were discharged from hospital. Thus, among patients with ongoing CPR on admission to hospital, survivors can be found but they are few in numbers and extensive cerebral damage is frequently present.
BACKGROUND: A large proportion of cardiac arrests outside hospital are caused by ventricular fibrillation. Although it is frequently used, the exact role for treatment with lidocaine in these patients remains to be determined. AIM: To describe the proportion of patients with witnessed out-of-hospital cardiac arrest found in ventricular fibrillation who survived and were discharged from hospital in relation to whether they were treated with lidocaine prior to hospital admission. PATIENTS AND TREATMENT: All the patients with out-of-hospital cardiac arrest found in ventricular fibrillation in Göteborg between 1980 and 1992 in whom cardiopulmonary resuscitation (CPR) was initiated by our emergency medical service (EMS). During the observation period, some of the EMS staff were authorized to give medication and some were not. RESULTS: In all, 1,360 patients were found in ventricular fibrillation, with detailed information being available in 1,212 cases (89%). Lidocaine was given in 405 of these cases (33%). Among patients with sustained ventricular fibrillation, those who received lidocaine had a return of spontaneous circulation (ROSC) more frequently (P < 0.001) and were hospitalized alive more frequently (38% vs. 18%, P < 0.01). However, the rate of discharge from hospital did not significantly differ between the two groups. Among patients who were converted to a pulse-generating rhythm, those who received lidocaine on that indication were more frequently alive than those who did not receive such treatment (94% vs. 84%; P < 0.05). However, the rate of discharge did not significantly differ between the two groups. CONCLUSION: In a retrospective analysis comparing patients who received lidocaine with those who did not in sustained ventricular fibrillation and after conversion to a pulse-generating rhythm, such treatment was associated with a higher rate at ROSC and hospitalization but was not associated with an increased rate of discharge from hospital.
This paper reports, consistent with Utstein Style definitions, 13 years experience observing out-of-hospital cardiac arrest survivors' prognosis, longevity and functional status. We report for all patients, available outcome information for out-of-hospital cardiac arrest survivors in Göteborg Sweden between 1980 and 1993. Patients were followed for at least 1 year and some for over 14 years. From 1980 to 1993 Göteborg EMS treated 3754 out-of-hospital cardiac arrests. 9% (n = 324) were discharged from the hospital alive. Survivors' median age was 67 and 21% (n = 67) were women. Mortality rate was: 21% (n = 61) at 1 year; 56% (n = 78) by 5 years; and 82% (n = 32) by 10 years following the arrest. During the first 3 years, 16% (n = 46) experienced another cardiac arrest, 19% (n = 53) had an acute myocardial infraction and a total of 81% (n = 232) were rehospitalized for various conditions. 14% (n = 40) returned to previous employment, and 74% (n = 229) had retired before their arrest occurred. Cerebral performance categories (CPC) scores were: At hospital discharge N = 324; Data available for 320-1 = 53% (n = 171), 2 = 21% (n = 66), 3 = 24% (n = 77), 4 = 2% (n = 6). One year post arrest N = 263; Data available for 212-1 = 73% (n = 156), 2 = 9% (n = 18), 3 = 17% (n = 36), 4 = 1% (n = 2). Overall, 21% (n = 61) of cardiac arrest survivors died during the first year, and an additional 16% (n = 46) experienced another arrest. 73% of those patients who were still alive after 1 year returned to pre-arrest function.
In order to reduce mortality and the need for hospital care for patients suffering from acute asthma, an emergency programme was set up. An ambulance crew, trained in coronary-pulmonary resuscitation was instructed in dealing with acute asthma and delegated to give 24 h treatment with bronchodilators (inhaled salbutamol and ipratropium bromide). If there was no, or only slight, improvement with this therapy, nurses (daytime) were delegated to give injections with corticosteroids (terbutaline and theophylline). Over a period of 2 years, 240 patients, 115 women and 125 men, were treated on 367 occasions. In 127 patients (53%), two or more treatments were given. The number of times treatment was given, as well as the proportion of females to males, increased the younger the patients were. Out of all the cases, more than 70% improved after treatment. On arrival, 21 patients (6%) were unconscious. After therapy, 15/21 patients (71%) survived. This may correspond to a similar reduction in mortality (population about 350,000 inhabitants), as it is unlikely that unconscious patients can survive without intensive care.
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Rat liver microsomal glutathione transferase is a mammalian membrane protein that can be successfully expressed in Escherichia coli in an enzymatically active form. The protein does not form inclusion bodies and is recovered in the membrane fraction. The membrane topology of recombinant rat liver microsomal glutathione transferase expressed in E. coli was investigated by comparing the proteolytic cleavage products from intact and permeabilized spheroplasts. It was shown that lysine-4 of microsomal glutathione transferase is directed towards the outside, whereas lysine-41 faces the inside of the E. coli inner membrane. This shows that microsomal glutathione transferase has an inside-out orientation in E. coli spheroplasts as compared to liver microsomes. This fact enables us to make topology experiments that were previously not possible. Intact spheroplasts treated with pronase yielded a cleavage pattern consistent with two additional exposed segments closer to the C-terminus. Thus a polytopic model is suggested for the membrane association of microsomal glutathione transferase.
AIM: To describe the prognosis of patients with out-of-hospital cardiac arrest judged to be caused by the deterioration of obstructive pulmonary disease. PATIENTS: All patients in the community of Göteborg Sweden who suffered out-of-hospital cardiac arrest between 1980 and 1992 attended by our emergency medical service and in whom cardiopulmonary resuscitation was initiated. METHODS: The etiology of cardiac arrest was determined according to clinical history, observations at resuscitation and findings at autopsy. RESULTS: There were 3434 cardiac arrests of which 130 (4%) were judged to have been caused by deterioration of obstructive pulmonary disease. Of these patients 50% were found in asystole, 40% in pulseless electrical activity, and only 7% in ventricular fibrillation. Among patients with cardiac arrest caused by obstructive pulmonary disease 21 (16%) were hospitalized alive and six (5%) were discharged from hospital. Among patients who developed cardiac arrest after arrival of the ambulance, 16% were discharged from hospital versus 0% among patients who had arrest prior to arrival of the ambulance. CONCLUSION: Among patients with out-of-hospital cardiac arrest caused by deterioration of obstructive pulmonary disease, half were found in asystole. Overall, the survival rate was low. This highlights the importance of effective treatment early in the course of deterioration of obstructive pulmonary disease in order to avoid cardiac arrest.
At present there are about 1 million trained cardiopulmonary resuscitation (CPR) rescuers in Sweden. CPR out-of-hospital is initiated about 2000 times a year in Sweden. However, very little is known about the bystanders' experiences and reactions. The aim of this study was to describe bystander-initiated CPR, the circumstances, the bystander and his experiences. All CPR bystanders in Sweden who reported their resuscitation attempts between 1990 and 1994 were approached with a phone interview and a postal questionnaire, resulting in 742 questionnaires. Bystander-initiated CPR most frequently took place in public places such as the street. The rescuer most frequently had problems with mouth-to-mouth ventilation (20%) and vomiting (18%). More than half (53%) of the rescuers experienced CPR without problems. Ninety-two percent of the bystanders had no hesitation because of fear of contracting the acquired immunodeficiency syndrome (AIDS) virus. Ninety-three percent of the rescuers regarded their intervention as a mainly positive experience. Of 425 interviewed rescuers, 99.5% were prepared to start CPR again.
Outcome after cardiac arrest is strongly related to whether the patient has ventricular fibrillation at the time the emergency medical service (EMS) arrives on the scene. The occurrence of various arrhythmias at the time of EMS arrival among patients with out-of-hospital cardiac arrest was studied in relation to the interval from collapse and whether cardiopulmonary resuscitation (CPR) was initiated by a bystander. The patients studied were all those with out-of-hospital cardiac arrest in Goteborg, Sweden, between 1980 and 1992 in whom CPR was attempted by the arriving EMS and for whom the interval between collapse and the arrival of EMS was known. In all, information on the time of collapse and the arrival of EMS was available for 1,737 patients. Among patients for whom EMS arrived within 4 minutes of collapse, 53% were found in ventricular fibrillation/tachycardia. There was a successive decline in occurrence of such arrhythmias with time. However, when the interval exceeded 20 minutes, ventricular fibrillation/tachycardia was still observed in 27% of cases. Bystander CPR increased the occurrence of such arrhythmias regardless of the interval between collapse and EMS arrival.
The viscoelastic response of a lumbar motion segment loaded in cyclic compression was studied in an in vivo porcine model (N = 7). Using surgical techniques, a miniaturized servohydraulic exciter was attached to the L2-L3 motion segment via pedicle fixation. A dynamic loading scheme was implemented, which consisted of one hour of sinusoidal vibration at 5 Hz, 50 N peak load, followed by one hour of restitution at zero load and one hour of sinusoidal vibration at 5 Hz, 100 N peak load. The force and displacement responses of the motion segment were sampled at 25 Hz. The experimental data were used for evaluating the parameters of two viscoelastic models: a standard linear solid model (three-parameter) and a linear Burger's fluid model (four-parameter). In this study, the creep behaviour under sinusoidal vibration at 5 Hz closely resembled the creep behaviour under static loading observed in previous studies. Expanding the three-parameter solid model into a four-parameter fluid model made it possible to separate out a progressive linear displacement term. This deformation was not fully recovered during restitution and is therefore an indication of a specific effect caused by the cyclic loading. High variability was observed in the parameters determined from the 50 N experimental data, particularly for the elastic modulus E1. However, at the 100 N load level, significant differences between the models were found. Both models accurately predicted the creep response under the first 800 s of 100 N loading, as displayed by mean absolute errors for the calculated deformation data from the experimental data of 1.26 and 0.97 percent for the solid and fluid models respectively. The linear Burger's fluid model, however, yielded superior predictions particularly for the initial elastic response.
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The aim of this study was to describe factors associated with in-hospital mortality among patients being hospitalised after out-of-hospital cardiac arrest and who were found in ventricular fibrillation. The study was set in the community of Göteborg, Sweden. The subjects consisted of all patients who were hospitalised alive after out-of-hospital cardiac arrest, being reached by our mobile coronary care unit and who were found in ventricular fibrillation, between 1981 and 1992. In all, 488 patients fulfilled the inclusion criteria of which 262 (54%) died during initial hospitalization. In a multivariate analysis including age, sex, history of cardiovascular disease, chronic medication prior to arrest and circumstances at the time of arrest, the following appeared as independent predictors of hospital mortality: (1) interval between collapse and first defibrillation (P < 0.001); (2) on chronic medication with diuretics (P < 0.01); (3) age (P < 0.01); (4) bystander initiated CPR (P < 0.05); and (5) a history of diabetes (P < 0.05). In a multivariate analysis considering various aspects of status on admission to hospital, the following were independently associated with death: (1) degree of consciousness (P < 0.001) and (2) systolic blood pressure (P < 0.05). In conclusion, among patients with out of hospital cardiac arrest found in ventricular fibrillation and being hospitalised alive, 54% died in hospital. The in-hospital mortality was related to patient characteristics before the cardiac arrest as well as to factors at the resuscitation itself.
BACKGROUND: A large proportion of cardiac arrests outside hospital are caused by ventricular fibrillation. Although it is frequently used, the exact role of treatment with adrenaline in these patients remains to be determined. AIM: To describe the proportion of patients with witnessed out-of-hospital cardiac arrest found in ventricular fibrillation who survived and were discharged from hospital in relation to whether they were treated with adrenaline prior to hospital admission. PATIENTS AND TREATMENT: All the patients with out-of-hospital cardiac arrest found in ventricular fibrillation in Göteborg between 1981 and 1992 in whom cardiopulmonary resuscitation (CPR) was initiated by our emergency medical service (EMS). During the observation period, some of the EMS staff were authorized to give medication and some were not. RESULTS: In all, 1360 patients were found in ventricular fibrillation and detailed information was available in 1203 cases (88%). Adrenaline was given in 417 cases (35%). Among patients with sustained ventricular fibrillation, those who received adrenaline experienced the return of spontaneous circulation more frequently (P < 0.001) and were hospitalized alive more frequently (P < 0.01). However, the rate of discharge from hospital did not differ significantly between the 2 groups. Among patients who converted to asystole or electromechanical dissociation, those who received adrenaline experienced the return of spontaneous circulation more frequently (P < 0.001) and were hospitalised alive more frequently (P < 0.001). However, the rate of discharge from hospital did not differ significantly between the 2 groups. CONCLUSIONS: On the basis of 2 treatment regimens during a 12-year survey, we explored the usefulness of adrenaline in out-of-hospital ventricular fibrillation. Both patients with sustained ventricular fibrillation and those who converted to asystole or electromechanical dissociation had an initially more favourable outcome if treated with adrenaline. However, the final outcome was not significantly affected. This study does not confirm the hypothesis that adrenaline increases survival among patients with out-of-hospital cardiac arrest who are found in ventricular fibrillation.