Giedrius Kvederas

Goal Directed Fluid Therapy Revised: Indirect Monitoring of Interstitial Fluid Accumulation During Mini Fluid Challenges with Crystalloids

Goal directed fluid therapy (GDT) implies administration of fluid boluses with the aim of optimizing cardiac performance. There is a major concern that maximization of cardiovascular performance can be achieved in expense of deterioration in body hydration processes. Also, these methods require semi invasive devices. However, monitoring of the whole body hydration status and interstitial fluid accumulation during fluid loading is not possible in everyday clinical practice. A new method, minimum Volume Loading Test (mVLT), uses evaluation of plasma dilution efficacy in small fluid boluses (2.5 - 5.0 ml kg -1 ) of isoosmotic crystalloid solutions followed by 5 min periods without fluids. The inva- sively measured arterial and venous hemoglobins, and simultaneous non-invasively measured hemoglobin (SpHb TM from Radical-7, Masimo inc., Irvine, USA) are used for estimation of plasma dilution which serves as an indication of plasma volume expansion. The objective of this paper was to discuss plasmadilution as a target parameter for goal directed therapy. Could plasma di- lution also indicate a degree of interstitial fluid accumulation?

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 Ringers 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. Veno-capillary 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. CONCLUSIONS Signs of dehydration were observed during mVLT in patients after pre-operative overnight fast. A revised transcapillary reflux model was proposed to explain the results.

A mini volume loading test (mVLT) using 2.5-mL kg−1 boluses of crystalloid for indication of perioperative changes in hydration status

BACKGROUND AND OBJECTIVE A mini volume loading test (mVLT) evaluating hemodilution during step-wise crystalloid infusion has established that the arterio-capillary plasma dilution difference is inversely correlated to the body hydration level of subjects. This observational study aimed to test whether this can be replicated in a perioperative setting using a 2.5-mLkg-1 boluses. MATERIALS AND METHODS The mVLT was performed before induction of regional anesthesia and 24h later. Step-wise infusion implied six mini fluid challenges. These consisted of 2.5-mLkg-1 boluses of Ringers acetate infused during 2-3min and followed by 5-min periods with no fluids. Invasive (arterial) and noninvasive (capillary) measurements of hemoglobin were performed before and after each mini fluid challenge, as well as after a 20-min period without fluid following the last bolus. Hemoglobins were used to calculate the arterio-capillary plasma dilution difference which is used as an indication of changes in body hydration level. The 24-h fluid balance was calculated. RESULTS Subjects were 69.5 (6.0) years old, their height was 1.62m (1.56-1.65), weight was 87.0kg (75.5-97.5) and body mass index (BMI) was 33.5kg/m2 (31.0-35.1). Preoperative arterio-capillary plasma dilution difference was significantly higher than postoperative (0.085 [0.012-0.141] vs. 0.006 [-0.059 to 0.101], P=0.000). The perioperative 24-h fluid balance was 1976mL (870-2545). CONCLUSIONS The mVLT using 2.5-mLkg-1 boluses of crystalloid was able to detect the higher postoperative body hydration level in total knee arthroplasty patients.