A mini volume loading test (mVLT) using 2.5-mLkg-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 Ringer's 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.

Different Stabilization Techniques for Type 62B3 Acetabular Fractures in Combination With Primary Total Hip Arthroplasty in Elderly Patients: A Biomechanical Comparison.

INTRODUCTION: The total hip arthroplasty (THA) as part of acute fracture management is used for acetabular fractures in elderly patients. Our objective was to assess the stability of osteosynthesis performed using 2 different techniques in combination with THA in an experimental model. MATERIALS AND METHODS: We conducted 20 experiments using the left-side hemipelves composite bone models. There were 2 testing groups: 1- and 2-stage osteosynthesis. The acetabular fractures of the anterior column and posterior hemitransverse were simulated. The same THA technique was used in both groups. The stability of osteosynthesis was explored and compared between the groups by measuring the fracture displacement of anterior and posterior columns under the standardized test load (1187 N) protocol. Load distance diagrams were generated. RESULTS: The 0.680-mm gap (0.518; 1.548) of the posterior column in the 1-stage group (n = 10) was higher than the 0.370-mm gap (0.255; 0.428) in the 2-stage group (n = 10; P = .002). There was no significant difference between the gap of the anterior column in the 1- and 2-stage groups (0.135 [0.078; 0.290] mm vs 0.160 [0.120; 0.210] mm; P = .579). CONCLUSION: The 2-stage osteosynthesis of the anterior and posterior columns in combination with THA provides better stability of posterior column when compared to 1-stage method in composite bone models.

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. 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.

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.

The efficacy comparison of on-demand boluses with and without basal infusion of 0.1 % bupivacaine via perineural femoral catheter after arthroscopic ACL reconstruction.

PURPOSE: Optimal postoperative analgesia after anterior cruciate ligament repair remains challenging. The objective of this prospective experimental clinical study was to compare the postoperative analgesic efficacy of two infusion regimens of 0.1 % bupivacaine administered via perineural femoral catheter. METHODS: Forty adult ASA I and II patients undergoing anterior cruciate ligament reconstruction were enrolled. Surgery was performed under spinal anesthesia combined with femoral nerve block. A perineural femoral catheter was connected to the patient controlled analgesia infusion pump filled with 0.1 % bupivacaine for postoperative pain control. Subjects were assigned to one of two groups according to the bupivacaine infusion regimen: (1) 5 mL/h basal infusion with on-demand 5 mL boluses and 30-min refractive periods, and (2) only on-demand 5 mL boluses and 15-min refractive periods. Quality of postoperative analgesia, adjunctive analgesic consumption, and overall patient satisfaction were recorded for 48 h. RESULTS: Pain control was better in Group I on the day of surgery (P = 0.001) and on the first postoperative day at rest and during mobilization (P = 0.02 and P = 0.009). On the second postoperative day, only pain control during mobilization was better in Group I (P = 0.047). Adjunctive analgesic consumption and patient satisfaction were similar. CONCLUSION: Perineural femoral infusion of on-demand 5 mL boluses of 0.1 % bupivacaine combined with 5 mL/h basal infusion was more efficient than on-demand regimen alone for postoperative pain management after reconstruction of anterior cruciate ligament of the knee. LEVEL OF EVIDENCE: II.

A randomized double-blind clinical trial of tourniquet application strategies for total knee arthroplasty.

PURPOSE: The optimal timing of pneumatic lower limb tourniquet application during primary elective total knee arthroplasty surgery (TKA) is a matter of debate. Most previous reports have failed to show significant differences between different tourniquet timings. The aim of the work was to determine how three strategies of lower limb pneumatic tourniquet application affect the outcome for TKA patients. METHODS: Forty-three patients who undergo TKA were randomized into one of the three groups, and 36 of these patients completed the study. The tourniquet was inflated just before incision and deflated after the hardening of the cement for twelve patients (Group 1), it was inflated just before cement application and deflated after its hardening for another twelve patients (Group 2), and it was inflated before incision and deflated after the last suture of the skin for a further twelve patients (Group 3). Fit-to-discharge criteria and six methods for calculating estimated blood loss were used. RESULTS: The estimated blood loss in Group 1 was lower than in Group 2, as determined by six methods of calculation (p < 0.05). Estimated blood loss in Group 3 was lower than in Group 2, as determined by one method (p = 0.050). The mobilization performance in Group 1 was better than in Group 2 (p = 0.023) and in Group 3 (p = 0.033). Group 1 was better fit to discharge than Group 3 (p = 0.030). CONCLUSIONS: Inflation of an automatic pneumatic lower limb tourniquet before skin incision and its deflation after hardening of cement tends to give better outcomes in TKA patients during six postoperative days. The estimated blood loss was highest when the tourniquet was inflated just before cement application and deflated after its hardening.

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.

A volume loading test for the detection of hypovolemia and dehydration.

BACKGROUND AND OBJECTIVES: There is a need for simple method allowing detection of dehydration and hypovolemia. Based on a new theory of homeostatic blood states, we hypothesized that hemodilution following standardized crystalloid fluid bolus can be used to discriminate between baseline normohydration and dehydration, also normovolemia and hypovolemia. METHODS: Computer simulations based on previously published kinetic data were used to define the best time points for discrimination between baseline normohydration and dehydration, also normovolemia and hypovolemia. Hemodilution was compared at the proposed timing in 20 volunteers who received 40 infusions of Ringer's solution of 25 mL/kg during 30 minutes. RESULTS: Simulations indicated that preexisting hypovolemia could be best detected at the end of infusion, while dehydration 20-30 min later. In baseline hypovolemia, the peak reduction of hemoglobin concentration was 16.0% at the end of infusion, while it was only 11.8%, when participants were normovolemic (P<0.004). In baseline dehydration, the residual hemodilution was 8.6%, when measured 30 min after the end of infusion. It was only 3.1% in baseline normohydration (P<0.006). CONCLUSIONS: In response to fluid load, the baseline dehydration exaggerates the lowering of residual hemoglobin in respect to baseline. Meanwhile, baseline hypovolemia exaggerates the lowering of peak hemoglobin concentration. The volume loading test that deploys interpretation of hemoglobin dynamics in response to the test volume load could possibly serve as an easily available guide to indicate an individual patient's baseline hydration state and volemia. The introduction of continuous noninvasive monitoring of hemoglobin concentration would expand the applicability of the new method.

New method of tracing blood hemoglobin concentration to hematocrit ratio for monitoring plasma dilution and osmotic origin shifts in blood.

Blood hemoglobin concentration and hematocrit are probably the most widely used parameters for outpatient and inpatient examination. In addition to their inherent significance for evaluation of blood viscosity and oxygen carrying capacity, these parameters are traditionally used as tracers of plasma dilution. Blood test derived results are conventionally recorded on multiple pages in patient's medical records making dynamical investigations tedious and time-consuming. In addition, research results describing plasma dilution by means of hemoglobin or hematocrit are presented in a clinically unpractical way. A new method, referred to as HBS Graphics (patent pending--USA serial # 60/712809) is introduced for the first time in this article. This method of evaluation of dynamical hemoglobin concentration, hematocrit and mean corpuscular hemoglobin concentration value deploys interfering parameter shifts for the evaluation of plasma dilution in relation to osmotic dynamics. The HBS Graphics complements two coordinate systems--hemoglobin concentration and hematocrit--with incorporated mean corpuscular hemoglobin concentration value specific trends referred to as radiating lines. Isosmotic plasma dilution and erythrocyte volume shifts follow radiating lines, while osmotic shifts induce intertrend shifts. This article also reviews other methods of tracing plasma dilution by means of blood hemoglobin concentration and hematocrit dynamics.