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Hahn R.G.,Sodertalje Hospital
Anesthesia and Analgesia | Year: 2017

Excretion of crystalloid fluid is slow during general anesthesia. The distribution and elimination of buffered Ringer's solution were analyzed to determine whether the rate of elimination correlates with a hemodynamic factor, consciousness, patient posture, or the type of general anesthesia. Data were derived from 4 separately published studies in which 30 volunteers and 48 anesthetized patients had received 0.833 (1 series 0.667) mL/kg/min of lactated or acetated Ringer's solution over 30 minutes. Frequent measurements of the blood hemoglobin and mean urinary excretion were used as input in a kinetic analysis according to a 2-volume model and covariates, using microconstants and mixed-effects modeling software. The results show that rate of elimination of crystalloid fluid decreased with the mean arterial pressure (MAP) and patient age, but was unaffected by consciousness and inhalational or intravenous anesthesia. The elimination rate constant was 6.5 (95% confidence interval, 5.2-7.9) × 10 -3 × (MAP/mean MAP) 5.2 × (Age/mean Age) -1.5. The mean MAP for the 2108 data points was 81.3 mm Hg and the mean age was 40 years. The central fluid space that was expanded by infused fluid (V c, plasma volume) increased with body weight but decreased with general anesthesia and with reductions of MAP. Simulations revealed a more than 10-fold difference in the excreted fluid volume after a theoretical 30-minute infusion, depending on whether the MAP was 50 or 100 mm Hg. In conclusion, the rate of elimination of crystalloid fluid decreased in proportion to MAP but was independent of general anesthesia and moderate-sized surgery. © Copyright 2017 International Anesthesia Research Society.

Background: The present study was undertaken to identify factors that correlate with the gain in body weight after surgery. Methods: Twenty-one patients (median age of 49 years) were randomized to receive either Ringer × s acetate or 6% dextran 70 as their first infusion fluid during cholecystectomy or hysterectomy. Each patient's body weight was measured before the surgery and on the first postoperative morning. Blood and urine samples were analyzed for signs of stress, inflammation, and kidney injury. The fluid retention index (FRI), which reflects how strongly the kidneys excrete or retain fluid, was also calculated. Results: The body weight increased by a median of 0.4 kg in the crystalloid fluid group and by 1.0 kg in the colloid fluid group (maximum 2.5 kg, P< 0.01). This difference was due to less urinary excretion after surgery in the colloid group (P < 0.03). The increase in body weight did not correlate with the infused fluid volume, the plasma concentrations of C-reactive protein or cortisol, or the urinary excretion of albumin, cortisol, or neutrophil gelatinase-associated lipocalin. However, the body weight increased with the postoperative FRI score (r = 0.64; P< 0.003) and with the surgery-induced change in FRI score (r = 0.72; P< 0.002). Conclusion: How strongly the kidneys excrete or retain fluid, which can be assessed by urine sampling, was the strongest indicator of the increase in body weight during the day of surgery. The amount of fluid alone did not correlate with the gain in body weight. © 2017 Saudi Journal of Anesthesia | Published by Wolters Kluwer - Medknow.

Bergek C.,Linköping University | Zdolsek J.H.,Linköping University | Hahn R.G.,Linköping University | Hahn R.G.,Sodertalje Hospital
British Journal of Anaesthesia | Year: 2015

Background: Plethysmographic measurement of haemoglobin concentration (SpHb), pleth variability index (PVI), and perfusion index (PI) with the Radical-7 apparatus is growing in popularity. Previous studies have indicated that SpHb has poor precision, particularly when PI is low. We wanted to study the effects of a sympathetic block on these measurements. Methods: Twenty patients underwent hand surgery under brachial plexus block with one Radical-7 applied to each arm. Measurements were taken up to 20 min after the block had been initiated. Venous blood samples were also drawn from the non-blocked arm. Results: During the last 10 min of the study, SpHb had increased by 8.6%. The PVI decreased by 54%, and PI increased by 188% in the blocked arm (median values). All these changes were statistically significant. In the non-blocked arm, these parameters did not change significantly. Conclusions: Brachial plexus block significantly altered SpHb, PVI, and PI, which indicates that regional nervous control of the arm greatly affects plethysmographic measurements obtained by the Radical-7. After the brachial plexus block, SpHb increased and PVI decreased. © The Author 2014. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved.

Hahn R.G.,Linköping University | Waldreus N.,Sodertalje Hospital
International Journal of Sport Nutrition and Exercise Metabolism | Year: 2013

Purpose: Urine sampling has previously been evaluated for detecting dehydration in young male athletes. The present study investigated whether urine analysis can serve as a measure of dehydration in men and women of a wide age span. Methods: Urine sampling and body weight measurement were undertaken before and after recreational physical exercise (median time: 90 min) in 57 volunteers age 17-69 years (mean age: 42). Urine analysis included urine color, osmolality, specific gravity, and creatinine. Results: The volunteers' body weight decreased 1.1% (mean) while they exercised. There were strong correlations between all 4 urinary markers of dehydration (r = .73-.84, p < .001). Researchers constructed a composite dehydration index graded from 1 to 6 based on these markers. This index changed from 2.70 before exercising to 3.55 after exercising, which corresponded to dehydration of 1.0% as given by a preliminary reference curve based on 7 previous studies in athletes. Men were slightly dehydrated at baseline (mean: 1.9%) compared with women (mean: 0.7%; p < .001), though age had no influence on the results. A final reference curve that considered both the present results and the 7 previous studies was constructed in which exercise-induced weight loss (x) was predicted by the exponential equation x = 0.20 dehydration index1.86. Conclusion: Urine sampling can be used to estimate weight loss due to dehydration in adults up to age 70. A robust dehydration index based on four indicators reduces the influence of confounders. © 2013 Human Kinetics, Inc.

Hahn R.G.,Sodertalje Hospital
Anaesthesiology Intensive Therapy | Year: 2015

Anaesthetists are cautioned to avoid hypervolaemia in their patients. The most cited reason is that hypervolaemia elicits the release of atrial natriuretic peptides that damage the endothelial glycocalyx layer. Although shedding of the glycocalyx causes extravasation of protein in inflammatory disorders, it is more uncertain whether hypervolaemia alone is enough to cause clinically important shedding. This review scrutinises the methodology used in two key papers that propose such a link. The most cited one reports that hydroxyethyl starch and 5% albumin, when creating a hypervolaemic state, only expands the plasma by 40% of the infused volume. This result was obtained by comparing measurements of the plasma volume performed with the indocyanine green (ICG) dye method before and after the infusion. However, the transit time of the dye, as well as inequality in the concentration between vascular beds, both act to underestimate the plasma volume, particularly as times were extrapolated backwards to time zero instead of to (the more correct) 1 minute. A re-calculation based on theoretical ICG data, taking account of the transit time, shows the plasma volume expansion was closer to 100% than to 40% of the infused volume. This figure is supported by the dilution of the reported blood haemoglobin and plasma protein concentrations, as well as by other sources. In conclusion, only weak evidence supports a fluid-induced release of atrial peptides of sufficient size to alter the kinetics of colloid fluid by shedding of the endothelial glycocalyx layer.

Hahn R.G.,Linköping University | Hahn R.G.,Sodertalje Hospital
Acta Anaesthesiologica Scandinavica | Year: 2013

Intravenous fluid is life-saving in hypovolemic shock, but fluid sometimes aggravates the bleeding. During the past 25 years, animal models have helped our understanding of the mechanisms involved in this unexpected effect. A key issue is that vasoconstriction is insufficient to arrest the bleeding when damage is made to a major blood vessel. "Uncontrolled hemorrhage" is rather stopped by a blood clot formed at the outside surface of the vessel, and the immature clot is sensitive to mechanical and chemical interactions. The mortality increases if rebleeding occurs. In the aortic tear model in swine, hemorrhage volume and the mortality increase from effective restoration of the arterial pressure. The mortality vs. amount of fluid curve is U-shaped with higher mortality at either end. Without any fluid at all, irreversible shock causes death provided the hemorrhage is sufficiently large. Crystalloid fluid administered in a 3:1 proportion to the amount of lost blood initiates serious rebleeding. Hypertonic saline 7.5% in 6% dextran 70 (HSD) also provokes rebleeding resulting in higher mortality in the recommended dosage of 4ml/kg. Uncontrolled hemorrhage models in rats, except for the "cut-tail" model, confirm the results from swine. To avoid rebleeding, fluid programs should not aim to fully restore the arterial pressure, blood flow rates, or blood volume. For a hemorrhage of 1000ml, computer simulations show that deliberate hypovolemia (-300ml) would be achieved by infusing 600-750ml crystalloid fluid over 20-30min or 100ml of HSD over 10-20min in an adult male. © 2012 The Authors. Acta Anaesthesiologica Scandinavica © 2012 The Acta Anaesthesiologica Scandinavica Foundation.

Hahn R.G.,Sodertalje Hospital | Drobin D.,Central Hospital | Zdolsek J.,Linköping University
Acta Anaesthesiologica Scandinavica | Year: 2016

Background Crystalloid fluid requires 30 min for complete distribution throughout the extracellular fluid space and tends to cause long-standing peripheral edema. A kinetic analysis of the distribution of Ringer′s acetate with increasing infusion rates was performed to obtain a better understanding of these characteristics of crystalloids. Methods Data were retrieved from six studies in which 76 volunteers and preoperative patients had received between 300 ml and 2375 ml of Ringer's acetate solution at a rate of 20-80 ml/min (0.33-0.83 ml/min/kg). Serial measurements of the blood hemoglobin concentration were used as inputs in a kinetic analysis based on a two-volume model with micro-constants, using software for nonlinear mixed effects. Results The micro-constants describing distribution (k12) and elimination (k10) were unchanged when the rate of infusion increased, with half-times of 16 and 26 min, respectively. In contrast, the micro-constant describing how rapidly the already distributed fluid left the peripheral space (k21) decreased by 90% when the fluid was infused more rapidly, corresponding to an increase in the half-time from 3 to 30 min. The central volume of distribution (Vc) doubled. Conclusion The return of Ringer′s acetate from the peripheral fluid compartment to the plasma was slower with high than with low infusion rates. Edema is a normal consequence of plasma volume expansion with this fluid, even in healthy volunteers. The results are consistent with the view that the viscoelastic properties of the interstitial matrix are responsible for the distribution and redistribution characteristics of crystalloid fluid. © 2016 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Fagerstrom T.,Karolinska Institutet | Nyman C.R.,Karolinska Institutet | Hahn R.G.,Sodertalje Hospital
BJU International | Year: 2010

Study Type - Therapy (RCT) Level of Evidence 1b Objective To compare bipolar with the conventional monopolar transurethral resection of the prostate (TURP) for blood loss and speed of resection. Patients and Methods In all, 202 consecutive patients from the hospital waiting list were randomized to undergo TURP using either a bipolar system (Surgmaster TURis, Olympus, Tokyo, Japan) or a monopolar system (24 F, Storz, Tübingen, Germany). The blood loss during and after surgery was measured using a photometer. Other variables compared included indices of resection speed and transfusion rate. Results There were no statistically significant differences in operative duration, resection weight, resection speed or radicality of resection. However, the median blood loss was 235 mL for the bipolar and 350 mL for monopolar TURP (P < 0.001). The decrease in blood haemoglobin concentration during the day of surgery was smaller in the bipolar group (5.5% vs 9.6% P < 0.001). Fewer patients were transfused with erythrocytes (4% vs 11%, P < 0.01), which can be explained by the much lower 75th percentile for blood loss in the bipolar group (at 472 vs 855 mL, respectively). Conclusions Bipolar TURP using the TURis system was performed with the same speed as monopolar TURP but caused 34% less bleeding, the difference being greatest (81%) for the largest blood losses. Bipolar TURP also required fewer erythrocyte transfusions than the conventional monopolar technique. © 2009 BJU INTERNATIONAL.

Hahn R.G.,Sodertalje Hospital | Hahn R.G.,Linköping University
Anaesthesiology Intensive Therapy | Year: 2014

The current trend in anaesthesia is to choose crystalloid over colloid fluids for volume replacement in the operating room. Outcome-oriented studies and kinetic analyses have recently provided more insight into how crystalloid infusions should be managed. These fluids have a much better short-term effect on the plasma volume than previously believed. Their efficiency (i.e. the plasma volume expansion divided by the infused volume) is 50-80% as long as an infusion continues, while this fraction increases to 100% when the arterial pressure has dropped. Elimination is very slow during surgery, and amounts to only 10% of that recorded in conscious volunteers. Capillary refill further reduces the need for crystalloid fluid when bleeding occurs. These four factors limit the need for large volumes of crystalloid fluid during surgery. Adverse effects associated with crystalloid fluids mainly include prolonged gastrointestinal recovery time, which occurs when > 3 L has been infused. Clinicians who do not want to prolong the length of the hospital stay by 1-2 days due to such problems may use colloid fluid selectively, but calculations show that the therapeutic window for colloids is quite narrow. Inflammation is likely to decrease the fluid efficiency of colloid fluids, while its effect on crystalloids is unclear. However, some recent evidence suggests that inflammation accelerates the turnover of crystalloid fluid as well.

Hahn R.G.,Linköping University | Hahn R.G.,Sodertalje Hospital | Bergek C.,Linköping University | Geback T.,Chalmers University of Technology | Zdolsek J.,Linköping University
Critical Care | Year: 2013

Introduction: The turnover of Ringeŕs solutions is greatly dependent on the physiological situation, such as the presence of dehydration or anaesthesia. The present study evaluates whether the kinetics is affected by previous infusion of colloid fluid.Methods: Ten male volunteers with a mean age of 22 years underwent three infusion experiments, on separate days and in random order. The experiments included 10 mL/kg of 6% hydroxyethyl starch 130/0.4 (Voluven™), 20 mL/kg of Ringer's acetate, and a combination of both, where Ringeŕs was administered 75 minutes after the starch infusion ended. The kinetics of the volume expansion was analysed by non-linear least- squares regression, based on urinary excretion and serial measurement of blood haemoglobin concentration for up to 420 minutes.Results: The mean volume of distribution of the starch was 3.12 L which agreed well with the plasma volume (3.14 L) estimated by anthropometry. The volume expansion following the infusion of starch showed monoexponential elimination kinetics with a half-life of two hours. Two interaction effects were found when Ringeŕs acetate was infused after the starch. First, there was a higher tendency for Ringeŕs acetate to distribute to a peripheral compartment at the expense of the plasma volume expansion. The translocated amount of Ringeŕs was 70% higher when HES had been infused earlier. Second, the elimination half-life of Ringeŕs acetate was five times longer when administered after the starch (88 versus 497 minutes, P <0.02).Conclusions: Starch promoted peripheral accumulation of the later infused Ringeŕs acetate solution and markedly prolonged the elimination half-life.Trial registration: NCT01195025. © 2013 Hahn et al.; licensee BioMed Central Ltd.

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