The maintenance and monitoring of perioperative blood volume

The assessment and maintenance of perioperative blood volume is important because fluid therapy is a routine part of intraoperative care. In the past, patients undergoing major surgery were given large amounts of fluids because health-care providers were concerned about preoperative dehydration and intraoperative losses to a third space. In the last decade it has become clear that fluid therapy has to be more individualized. Because the exact determination of blood volume is not clinically possible at every timepoint, there have been different approaches to assess fluid requirements, such as goal-directed protocols guided by invasive and less invasive devices. This article focuses on laboratory volume determination, capillary dynamics, aspects of different fluids and how to clinically assess and monitor perioperative blood volume

Modelling of Peripheral Fluid Accumulation after a Crystalloid Bolus in Female Volunteers – A Mathematical Study

Objective. To simultaneously model plasma dilution and urinary output in female volunteers

Fluid therapy in the intensive care unit, with a special focus on sepsis

This chapter deals with fluid therapy in the ICU with particular focus on septic patients.SCOPUS: ch.binfo:eu-repo/semantics/publishe

Evaluation of hydration status calculated from differences in venous and capillary plasma dilution during stepwise crystalloid infusions: A randomized crossover study in healthy volunteers

Background and objective: A mini volume loading test (mVLT) was proposed for estimating hydration status and interstitial fluid accumulation during stepwise infusion of crystalloids. The method is based on both the transcapillary reflux model and the hypothesis that when subjects are dehydrated, venous plasma dilution induced by a fluid challenge is higher than in the capillaries, and that difference is diminished when the fluid challenge is given to more hydrated individuals. Our objective was to test that hypothesis by evaluating the veno-capillary dilution difference during mVLT in subjects with different hydration status. Materials and methods: In a prospective randomized crossover study, three mini fluid challenges were given to 12 healthy volunteers on two occasions. The subjects were either dehydrated or hydrated before the experiments. Results: In dehydrated subjects only, capillary plasma dilution was significantly lower than venous (P = 0.015, 0.005 and 0.006) after each mini fluid challenge. Conclusions: Veno-capillary dilution difference during mVLT depends on the hydration status. The mVLT method could possibly discriminate between the different states of hydration

End-tidal carbon dioxide monitoring during bag valve ventilation: the use of a new portable device

<p>Abstract</p> <p>Background</p> <p>For healthcare providers in the prehospital setting, bag-valve mask (BVM) ventilation could be as efficacious and safe as endotracheal intubation. To facilitate the evaluation of efficacious ventilation, capnographs have been further developed into small and convenient devices able to provide end- tidal carbon dioxide (ETCO₂). The aim of this study was to investigate whether a new portable device (EMMA™) attached to a ventilation mask would provide ETCO₂values accurate enough to confirm proper BVM ventilation.</p> <p>Methods</p> <p>A prospective observational trial was conducted in a single level-2 centre. Twenty-two patients under general anaesthesia were manually ventilated. ETCO₂was measured every five minutes with the study device and venous PCO₂(PvCO₂) was simultaneously measured for comparison. Bland- Altman plots were used to compare ETCO_2,and PvCO₂.</p> <p>Results</p> <p>The patients were all hemodynamically and respiratory stable during anaesthesia. End-tidal carbon dioxide values were corresponding to venous gases during BVM ventilation under optimal conditions. The bias, the mean of the differences between the two methods (device versus venous blood gases), for time points 1-4 ranges from -1.37 to -1.62.</p> <p>Conclusion</p> <p>The portable device, EMMA™ is suitable for determining carbon dioxide in expired air (kPa) as compared to simultaneous samples of PvCO₂. It could therefore, be a supportive tool to asses the BVM ventilation in the demanding prehospital and emergency setting.</p

Modelling of peripheral fluid accumulation after a crystalloid bolus in female volunteers -a mathematical study

Objective. To simultaneously model plasma dilution and urinary output in female volunteers. Methods. Ten healthy female non-pregnant volunteers, aged 21 -39 years (mean 29), with a bodyweight of 58 -67 kg (mean 62.5 kg) participated. No oral fluid or food was allowed between midnight and completion of the experiment. The protocol included an infusion of acetated Ringer&apos;s solution, 25 ml/kg over 30 min. Blood samples (4 ml) were taken every 5 min during the first 120 min, and thereafter the sampling rate was every 10 min until the end of the experiment at 240 min. A standard bladder catheter connected to a drip counter to monitor urine excretion continuously was used. The data were analysed by empirical calculations as well as by a mathematical model. Results. Maximum urinary output rate was found to be 19 (13 -31) ml/min. The subjects were likely to accumulate three times as much of the infused fluid peripherally as centrally; 1/m ¼ 2.7 (2.0-5.7). Elimination efficacy, E eff , was 24 (5 -35), and the basal elimination k b was 1.11 (0.28-2.90). The total time delay T tot of urinary output was estimated as 17 (11 -31) min. Conclusion. The experimental results showed a large variability in spite of a homogenous volunteer group. It was possible to compute the infusion amount, plasma dilution and simultaneous urinary output for each consecutive time point and thereby the empirical peripheral fluid accumulation. The variability between individuals may be explained by differences in tissue and hormonal responses to fluid boluses, which needs to be further explored

A Mini volume loading test for indication of preoperative dehydration in surgical patients

Background and objective: Previously, a mini volume loading test (mVLT) detected signs of dehydration in healthy volunteers after an overnight fast. Our objective was to investigate whether mVLT could indicate preoperative dehydration in patients after an overnight fast. Materials and methods: The mVLT was performed in 36 elective primary total knee arthroplasty patients. Each subject received three fluid challenges before anesthesia induction. These consisted of 5 mL/kg boluses of Ringer's acetate infused over 3–5 min and followed by a 5-min period without fluids. Invasive (arterial, venous) and noninvasive (capillary) measurements of hemoglobin concentration were performed before and after each fluid challenge, as well as after a 20-min period without fluids which followed the last bolus. Arterial, venous and capillary plasma dilutions were calculated in every data point. Dilution values were used to calculate the plasma dilution efficacy of each fluid challenge. Results: Venous dilution was higher than capillary after the first fluid challenge (P = 0.030), but lower than capillary after 20 min period following the last bolus (P = 0.009). Arterial dilution was lower than capillary (P = 0.005) after 20 min following the last bolus. Venocapillary and arterio-capillary plasma dilution efficacy differences decreased (P = 0.004 and P = 0.033, respectively) from positive to negative during mVLT. These are signs of re-hydration from pre-existing dehydration according to a transcapillary reflux model