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Biomedical subjects

A Hedlund

Publications and source records attributed to A Hedlund.

15 recordsLinked to original sources
PubMed2001

Effects of sustained pressure application on compliance and blood gases in healthy porcine lungs.

BACKGROUND: Short periods of sustained increase in airway pressures (Press(up)) are believed to re-open lung areas that collapsed upon induction of anaesthesia. Recruitment of alveolar surface is usually assessed in terms of changes in the pressure-volume (PV) curve. The purpose of this study was to analyse PV-curves before and after a Press(up) and to ascertain whether such changes are compatible with the concept of recruitment of lung volume. METHODS: During ketamine anaesthesia, 12 healthy piglets were subjected to a Press(up) with end-expiratory pressure (PEEP) of 12 cmH2O and end-inspiratory pressure of 40 cmH2O. Before and after Press(up), PV-curves were obtained from a slow insufflation of 630 ml at zero PEEP (ZEEP). RESULTS: Compliance was non-linear both before and after Press(up) increasing up to 300 ml and sharply decreasing thereafter. After Press(up), the entire compliance curve was shifted to a higher absolute level. Up to 100 ml and a pressure level corresponding to the lower inflection point on the PV-curve (LIP), compliance was higher before Press(up). No effects on blood gases could be observed. CONCLUSION: If the similar shape of the compliance curve corresponds to a similar chain of re-opening and overdistension events, this would imply that all volume gained by Press(up) is lost within 10 min, without explaining the higher absolute compliance following Press(up). We speculate that a) re-opening of rapidly collapsing small airways determines the initial compliance increase; b) the lower compliance after Press(up) until LIP indicates reduced intratidal re-opening of lung regions; and c) changes in bronchomotor tone induced by Press(up) raise the absolute compliance, with a similar scenario of alveolar and small airway recruitment now taking place but at different degrees of airway stiffness.

Airway Resistance↗
PubMed2000

Static versus dynamic respiratory mechanics for setting the ventilator.

The lower inflection point (LIP) of the inspiratory limb of a static pressure-volume (PV) loop is assumed to indicate the pressure at which most lung units are recruited. The LIP is determined by a static manoeuvre with a PV-history that is different from the PV-history of the actual ventilation. In nine surfactant-deficient piglets, information to allow setting PEEP and VT was obtained, both from the PV-curve and also during ongoing ventilation from the dynamic compliance relationship. According to LIP, PEEP was set at 20 (95% confidence interval 17-22) cm H2O. Volume-dependent dynamic compliance suggested a PEEP reduction (to 15 (13-18) cm H2O). Pulmonary gas exchange remained satisfactory and this change resulted in reduced mechanical stress on the respiratory system, indirectly indicated by volume-dependent compliance being consistently great during the entire inspiration.

Animals↗
PubMed2000

Impact of different inspiratory flow patterns on arterial C02-tension.

Ventilation with decelerating inspiratory flow is known to reduce the dead space fraction and to decrease PaCO2. Constant inspiratory flow with an end-inspiratory pause (EIP) is also known to increase the removal of CO2. The aim of the study was to elucidate the effect of the pause/no-flow period while both the pattern and rate of inspiratory flow was unchanged, and when the lung was ventilated with sufficient PEEP to prevent end-expiratory collapse. Surfactant depleted piglets were assigned to decelerating or constant inspiratory flow with 24 breaths per minute (bpm) or 12 bpm, or to constant flow, without and with an end-inspiratory pause of 25%. By adding an EIP the total time without active inspiratory flow of the respiratory cycle was kept unchanged. Gas exchange, airway pressures, functional residual capacity (using sulfurhexafluoride) and haemodynamics (thermo-dye indicator dilution technique) were measured. Irrespective of ventilatory frequency, PaCO2 was lower and serial dead space reduced with decelerating flow, compared with constant inspiratory flow. With an end-inspiratory pause added to constant inspiratory flow, serial dead space was reduced but did not decrease PaCO2. The results of this study corroborate the assumption that total time without active inspiratory flow is important for arterial CO2-tension.

Animals↗
PubMed1998

Addition of etoposide to CHOP chemotherapy in untreated patients with high-grade non-Hodgkin's lymphoma.

BACKGROUND: Second- and third-generation chemotherapy protocols for the treatment of aggressive non-Hodgkin's lymphomas (NHL) have considerable, and age-related, toxic effects. In addition, they do not seem to prolong overall survival in comparison to standard CHOP chemotherapy. In this phase II study we investigated the feasibility and efficacy of the addition of etoposide to the conventional CHOP regimen. PATIENTS AND METHODS: Toxicity and clinical efficacy were determined in 132 patients with previously untreated high-grade NHL. There were 51 patients in clinical stage I and II and 81 patients in stage III and IV, with a median age of 54 years (range 17-85). Patients received standard-dose CHOP plus etoposide 100 mg/m2 i.v. on day 1 and 200 mg/m2 p.o. on days 2-3. RESULTS: The overall response rate was 84%, with 70% complete and 14% partial responses. The predicted three- and five-year survivals for the group as a whole were 60% and 53%, respectively, and the corresponding disease-free survivals for patients achieving complete remissions were 65% and 56%, respectively. Outcome was not different from that of CHOP-treated patients in a recently completed Nordic study performed during the same time period. Myelosuppression (WHO grade 3-4), observed in 87% of patients and infectious complications (WHO grade 3-4) in 33%, dominated the toxicity profile of this regimen. Fifty-seven of 92 complete responders (62%) received 6-8 CHOP-E cycles with no reductions in planned dose intensity. LDH level higher than normal, extranodal sites = 2, stage III-IV at diagnosis were all indicators of a poor survival. CONCLUSIONS: We conclude that CHOP-E treatment is effective in high-grade NHL. However, mainly due to severe myelosuppression frequent schedule modifications were required and the results are not obviously superior to those of conventional CHOP.

Adolescent↗
PubMed1991

INFORM: integrated support for decisions and activities in intensive care.

Many medical decision support systems that have been developed in the past have failed to enter routine clinical practice. Often this is because the developers have failed to analyse in sufficient detail the precise user requirements, because they have produced a system which takes too narrow a view of the patient, or because the decision support facilities have not been sufficiently well integrated into the routine clinical data handling activities. In this paper we discuss how the AIM-INFORM project is setting out to deal with these issues, in the context of the provision of decision support in the intensive care unit.

Artificial Intelligence↗
PubMed1990

Angiographic findings and need for amputation in high tension electrical injuries.

Because it is difficult to estimate the extent of deep tissue injury clinically, angiography was carried out in 28 patients with signs of damage from current flow through the body. Eight of the arteriograms showed normal extremities, 6 showed changes of small arteries, and 38 showed injury to the main arteries. In the latter group there were 24 total arterial occlusions, narrow irregular lumens in 10, and 4 had occlusion and distal refilling. Changes in the main arteries were most often seen near major joints where the internal body resistance as well as the density of the current are higher. Injury to the main arteries resulted in severe neuromuscular damage or amputation of the limb, whereas injury to small arteries resulted in little functional deficit. Of the 25 amputations 19 were at the level of the arterial occlusion. Spasmolytic drugs did not increase filling. We conclude that early angiography is valuable for the detection of deep injury and often indicates the level of adequate amputation or the need for immediate exploration. In some patients it indicates the necessity for arterial reconstruction.

Adolescent↗
PubMed1989

Methicillin-resistant Staphylococcus aureus in two burn units: clinical significance and epidemiological control.

Routine isolation adequately controlled MRSA strains in two burns units with a restrictive antibiotic policy. Ventilation control and more rigorous change of clothing offered no further advantage. No carriers among staff were found, but some suffered minor skin lesions that were the source of further MRSA spread. Spread of MRSA from the unit to other parts of the hospital was prevented by early identification of colonized patients and by restricting patient and staff movement.

Burn Units↗
PubMed1984

Potential use of computer simulation in treatment of burns with special regard to oedema formation.

The potential usefulness of computer-based 'patient-simulators' in burn care is discussed and illustrated in the special case of oedema formation in three patients with severe thermal injuries. The present model was derived from a model by Wiederhielm (1978), and modified to be applicable to thermal injuries. The model seems to describe accurately the oedema formation as well as the distribution and composition of local and general oedema. Following thermal injuries the general oedema is characterized by typical disturbances in the circulatory state variables such as capillary pressure and plasma colloid osmotic pressure. The net water flow is increased because of an increase in filtration rate and a decrease in reabsorption rate. The resulting interstitial oedema leads to dilution of the free water proteins and a decrease in interstitial colloid osmotic pressure. The elevation of interstitial pressure leads to an increase in lymph flow. The local oedema is caused by changes in both the circulatory system and the interstitial space. There is an increase in both water and protein net flows. The latter is due to increased protein leakage to the interstitium. This results in an interstitial oedema with a higher protein concentration in free water than in general oedema. Because of the higher protein concentration in free water, the interstitial colloid osmotic pressure is at all times larger than the corresponding pressure in general oedema. In all three patients the general shape of the simulated and measured oedema curve were the same, but with minor differences in numerical values. It is interesting to note that the general oedema was larger than the local oedema in all three extensively burned patients. The results from the present investigation indicate the importance of monitoring either the total plasma protein concentration or the plasma colloid osmotic pressure and small vein pressure for guidance of a proper fluid resuscitation. The steady state 'oedema vs. venous pressure'-diagram obtained may also be used for evaluating the dynamic effects on general oedema formation due to changes in venous pressure and plasma protein concentration. It thus turned out that for a typical thermal injury with a decreased small vein pressure a continuous colloid infusion is to be preferred instead of an intermittent model of administration.

Blood Proteins↗
PubMed1984

Primary treatment of 50 patients with high-tension electrical injuries. I. Fluid resuscitation.

Fifty patients with high-tension electrical injuries referred for primary treatment to the Burn Center at the University of Uppsala, Sweden during the period 1969 to 1982, have been investigated with special regard to the resuscitation and early complications from internal organs. Seven patients (14%) died, five of them prior to 1974, one in cardiac infarction and four in renal failure. Two died after 1974, one in cardiac infarction and the other in severe shock (98% burn). In 1974 an acute intensive prevention of renal failure was instituted based on forced fluid resuscitation, vasodilators, and supply of alkaline solutions in order to avoid myoglobin and hemoglobin casts in the kidneys. Some degree of renal dysfunction (diminished GFR, a lowered concentration capacity, and an increased fractionate excretion of sodium) was often seen but could usually be reversed without problems. Three patients who developed anuria were successfully treated with hemodialysis. During the years 1974-1982, when the "prevention scheme of renal failure" was applied, all patients with high-tension electrical injury combined with severe myoglobinuria (13 patients) have been successfully treated. 60% of the patients had normal ECG. Five of the seven fatal cases had ST-T abnormalities and two of these patients showed cardiac infarction at autopsy. Early angiography was performed in 20 patients (40%). Obliterated arteries were diagnosed on different levels in 18 extremities in ten patients. The arteriography very precisely indicated the level of amputation of the seriously injured extremities.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Kidney Injury↗
PubMed1984

Hemodynamic results of perorally administered converting enzyme inhibitors in congestive heart failure.

The acute hemodynamic response to captopril (8 patients) and enalapril (8 patients) was evaluated in congestive heart failure patients in NYHA functional class III. All patients had a history of congestive heart failure for more than six months. The results show marked interindividual variations but average values for cardiac output increase and decrease in filling pressures agree with findings in the literature. 6 patients in the captopril group and five in the enalapril group were started on maintenance therapy. One patient in the captopril group deteriorated and underwent a successful heart transplantation and one patient in the enalapril group returned with arrhythmias and hypertension (probably not drug-related) after 48 h of therapy. Our data indicate that activation of the renin-angiotensin system through excessive administration of loop-diuretics is associated with a risk of hypovolemia and thus drug-induced hypotension that deserves special attention when considering converting enzyme inhibitor therapy in congestive heart failure.

Administration, Oral↗
PubMedDate not supplied

Computer simulation of fluid resuscitation in trauma. I. Description of an extensive pathophysiological model and its first validation.

Computer-based 'patient simulators' are of a potential value in diagnosis, monitoring and therapy of the severely ill patient with trauma. An extensive pathophysiological model is described and documented in full detail. The model makes it possible to calculate and predict clinically important state variables on the basis of fluid input and fluid losses. Sample runs are presented for illustrations in hemorrhage, fluid and salt loading.

Animals↗
PubMedDate not supplied

KBSIM/FLUIDTHERAPY: a system for optimized design of fluid resuscitation in trauma.

An application of the KBSIM (Knowledge-Based SIMulation) system to the improved design of fluid resuscitation is described. The system integrates knowledge from three domains, viz. the pathophysiology of traumatized patients represented in a quantitative biodynamic model, the heuristics of fluid resuscitation of such patients as represented in 'production rules', and some 'metaknowledge' reflected in the design of a multi-window user interface. This technique of combining numerical simulation with symbolic reasoning has obvious advantages during the design process and in training, by giving the user a possibility to evaluate his measures by direct feedback from the system. This feature of the system to assist in evaluation of alternative resuscitation procedures should also be useful as a means for decision support.

Artificial Intelligence↗
PubMedDate not supplied

Computer simulation of fluid resuscitation in trauma. First pragmatic validation in thermal injury.

A comprehensive pathophysiologic model has been designed to describe the fluid shifts and hemodynamics in connection with fluid therapy for patients who have had trauma. The model is used to simulate treatment of a patient with burn injury, and these results are compared with measured physiologic and biochemical variables. Various formulas for resuscitation of patients with thermal injuries are also simulated to illustrate the potential use of the "patient simulator" for designing fluid resuscitation programs.

Burns↗
PubMedDate not supplied

A knowledge-based information system for advice in the crisis management of the patient with burns.

A knowledge-based information system that has been designed to be used as an electronic advisor to guide in fluid resuscitation and in the management of the most frequently occurring complications during the first 48 hours after burn injury is described. The system was also developed for training physicians and nurses and may eventually be used for peer review of the management of patients in the burn unit. Ten data screens are used for entry of the administrative data, the clinical background, and the monitored data. The latter include tables for recording fluid therapy and laboratory results. The knowledge base consists of a series of heuristic decision rules that were formulated by a burn care expert and that express the Uppsala fluid resuscitation program to prevent burn shock. The data recorded for a patient are compared with the data in the knowledge base, and the appropriate conclusions are generated. The system's conclusions, the fluid and ventilation prescription, and other required patient management measures are then displayed as a report. The underlying reasoning for each case may be explored by means of the system's explanation facility. The system has been successfully validated by 125 hypothetic cases that represent typical situations of patients with severe burns.

Adult↗