Isotonic saline in elderly men: an open-labelled controlled infusion study of electrolyte balance, urine flow and kidney function

Isotonic saline causes greater volume overload than electrolyte-free irrigating fluids

OBJECTIVES

Systemic absorption of the irrigating fluid used to flush the operating site is a potentially serious complication in several types of endoscopic operations. To increase safety, many surgeons have changed from a monopolar to a bipolar resection technique because 0.9% saline can then be used instead of electrolyte-free fluid for irrigation. The present study examines whether the tendency for excessive plasma volume expansion is greater with saline than with electrolyte-free fluid.

METHODS

Pooled data were analyzed from four studies in which a mean of 1.25 L of either 0.9% saline or an electrolyte-free irrigating fluid containing glycine, mannitol, and sorbitol was given by intravenous infusion on 80 occasions to male volunteers and patients scheduled for transurethral prostatic surgery. The distribution of the infused fluid was analyzed with a population volume kinetic model based on frequently measured hemodilution and the urinary excretion.

RESULTS

Electrolyte-free fluid distributed almost twice as fast and was excreted four times faster than 0.9% saline. The distribution half-life was 6.5 and 10.6 min for the electrolyte-free fluid and saline, respectively, and the elimination half-lives (by urinary excretion) from the plasma volume were 21 and 87 min. Simulation showed that the plasma volume expansion was twice as great from 0.9% saline than from electrolyte-free fluid.

CONCLUSIONS

Isotonic (0.9%) saline expands the plasma volume by twice as much as occurs with electrolyte-free irrigating fluids. This difference might explain why signs of cardiovascular overload are the most commonly observed adverse effects when saline is absorbed during endoscopic surgery.

Concentrated urine, low urine flow, and postoperative elevation of plasma creatinine: A retrospective analysis of pooled data

Elevations of plasma creatinine are common after major surgery, but their pathophysiology is poorly understood. To identify possible contributing mechanisms, we pooled data from eight prospective studies performed in four different countries to study circumstances during which elevation of plasma creatinine occurs. We included 642 patients undergoing mixed major surgeries, mostly open gastrointestinal. Plasma and urinary creatinine and a composite index for renal fluid conservation (Fluid Retention Index, FRI) were measured just before surgery and on the first postoperative morning. Urine flow was measured during the surgery. The results show that patients with a postoperative increase in plasma creatinine by >25% had a high urinary creatinine concentration (11.0±5.9 vs. 8.3±5.6 mmol/L; P< 0001) and higher FRI value (3.2±1.0 vs. 2.9±1.1; P< 0.04) already before surgery was initiated. Progressive increase of plasma creatinine was associated with a gradually lower urine flow and larger blood loss during the surgery (Kruskal-Wallis test, P< 0.001). The patients with an elevation > 25% also showed higher creatinine and a higher FRI value on the first postoperative morning (P< 0.001). Elevations to > 50% of baseline were associated with slightly lower mean arterial pressure (73 ± 10 vs. 80 ± 12 mmHg; P< 0.005). We conclude that elevation of plasma creatinine in the perioperative period was associated with low urine flow and greater blood loss during surgery and with concentrated urine both before and after the surgery. Renal water conservation-related mechanisms seem to contribute to the development of increased plasma creatinine after surgery.

Trajectory of plasma syndecan-1 and heparan sulphate during major surgery: A retrospective observational study

BACKGROUND

Surgical trauma-induced inflammation during major surgery may disrupt endothelial integrity and affect plasma concentrations of glycocalyx constituents, such as syndecan-1 and heparan sulphate. To date, no studies have focused on their perioperative temporal changes.

METHODS

As part of a trial, we obtained plasma and urine specimens sampled during the perioperative period in 72 patients undergoing major abdominal surgery. The plasma concentration of syndecan-1 and heparan sulphate was measured on five occasions, from baseline to the second postoperative day. Plasma and urinary creatinine and urinary syndecan-1 concentrations were measured before surgery and on the first postoperative morning.

RESULTS

We observed three different temporal patterns of plasma syndecan-1 concentration. Group 1 'low' (64% of patients) showed only minor changes from baseline despite a median heparan sulphate increase of 67% (p < .005). Group 2 'increase' (21% of patients) showed a marked increase in median plasma syndecan-1 from 27 μg/L to 118 μg/L during the first postoperative day (p < .001) with a substantial (+670%; p < .005) increase in median plasma heparan sulphate from 279 to 2196 μg/L. Group 3 'high' (14% of patients) showed a constant elevation of plasma syndecan-1 to >100 μg/L, but low heparan sulphate levels. The plasma C-reactive protein concentration did not differ across the three groups and 90% of colon surgeries occurred in Group 1. Treatment with dexamethasone was similar across the three groups. Surgical blood loss, duration of surgery and liver resection were greatest in Group 2.

CONCLUSION

Changes in syndecan-1 and heparan sulphate after surgery appear to show three different patterns, with the greatest increases in those patients with greater blood loss, more liver surgery and longer operations. These observations suggest that increases in syndecan-1 and heparan sulphate reflect the degree of surgical injury.

Effects of rapid fluid infusion on hemoglobin concentration: a systematic review and meta-analysis

Background

Rapid fluid administration may decrease hemoglobin concentration (Hb) by a diluting effect, which could limit the increase in oxygen delivery (DO₂) expected with a positive response to fluid challenge in critically ill patients. Our aim was to quantify the decrease in Hb after rapid fluid administration.

Methods

Our protocol was registered in PROSPERO (CRD42020165146). We searched PubMed, the Cochrane Database, and Embase from inception until February 15, 2022. We selected studies that reported Hb before and after rapid fluid administration (bolus fluid given over less than 120 min) with crystalloids and/or colloids in adults. Exclusion criteria were studies that included bleeding patients, or used transfusions or extracorporeal circulation procedures. Studies were divided according to whether they involved non-acutely ill or acutely ill (surgical/trauma, sepsis, circulatory shock or severe hypovolemia, and mixed conditions) subjects. The mean Hb difference and, where reported, the DO₂ difference before and after fluid administration were extracted. Meta-analyses were conducted to assess differences in Hb before and after rapid fluid administration in all subjects and across subgroups. Random-effect models, meta-regressions and subgroup analyses were performed for meta-analyses. Risk of bias was assessed using the Cochrane Risk of Bias Assessment Tool. Inconsistency among trial results was assessed using the I² statistic.

Results

Sixty-five studies met our inclusion criteria (40 in non-acutely ill and 25 in acutely ill subjects), with a total of 2794 participants. Risk of bias was assessed as “low” for randomized controlled trials (RCTs) and ‘low to moderate’ for non-RCTs. Across 63 studies suitable for meta-analysis, the Hb decreased significantly by a mean of 1.33 g/dL [95% CI − 1.45 to − 1.12; p < 0.001; I² = 96.88] after fluid administration: in non-acutely ill subjects, the mean decrease was 1.56 g/dL [95% CI − 1.69 to − 1.42; p < 0.001; I² = 96.71] and in acutely ill patients 0.84 g/dL [95% CI − 1.03 to − 0.64; p = 0.033; I² = 92.91]. The decrease in Hb was less marked in patients with sepsis than in other acutely ill patients. The DO₂ decreased significantly in fluid non-responders with a significant decrease in Hb.

Conclusions

Hb decreased consistently after rapid fluid administration with moderate certainty of evidence. This effect may limit the positive effects of fluid challenges on DO₂ and thus on tissue oxygenation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-04191-x.

Renal water conservation and the volume kinetics of fluid-induced diuresis: A retrospective analysis of two cohorts of elderly men

Renal water conservation after an overnight fast mirrors the habitual intake of liquid. The hypothesis in the present study was that water conservation influences the diuretic response to infusion of two types of crystalloid fluid. Twenty-three elderly male patients (mean age 72 years) underwent a total of 46 intravenous infusions of 1.0 or 1.5 L of either hypotonic non-electrolyte fluid (glycine 1.5%) or isotonic electrolyte fluid (Ringer's acetate or 0.9% saline). Urine osmolality (used to indicate renal water conservation) and plasma creatinine were measured before the infusions started. A two-volume model was fitted to repeated measurements of the blood haemoglobin concentration and the urinary excretion, using mixed-effects modelling software. Urine osmolality was examined as a potential covariate to the fixed kinetic parameters. The results show that distribution and redistribution of infused fluid occurred twice as fast for the non-electrolyte fluids as for the electrolyte-containing fluids, while the urine flow showed less difference. For both types of fluid, high urine osmolality served as a statistically significant covariate to the rate constant describing urinary excretion. Simulations showed that a high pre-infusion urine osmolality doubled the time required for the kidneys to excrete 50% of a 30-minute infusion. High plasma creatinine independently prolonged the elimination of non-electrolyte fluid. The use of 0.9% saline instead of Ringer's prolonged the excretion of electrolyte-containing fluid. In conclusion, renal water conservation is a determinant of the diuretic response to crystalloid fluid, regardless of whether the fluid contains electrolytes, and it should be considered in fluid balance studies.

Unraveling the Contribution of Fluid Therapy to the Development of Augmented Renal Clearance in a Piglet Model

Augmented renal clearance (ARC) observed in the critically ill pediatric population has received an increased attention over the last years due to its major impact on the disposition and pharmacokinetics of mainly renally excreted drugs. Apart from an important inflammatory trigger, fluid administration has been suggested to contribute to the development of ARC. Therefore, the primary objective of this study was to evaluate the effect of continuous intravenous fluid administration on renal function using a conventional piglet animal model and to quantify the impact of fluid administration on the pharmacokinetics of renally excreted drugs. At baseline, twenty-four piglets (12 treatment/12 control; 7 weeks old, all ♂) received the marker drugs iohexol (64.7 mg/kg body weight (BW)) and para-aminohippuric acid (10 mg/kg BW) to quantify glomerular filtration rate and effective renal plasma flow, respectively. In addition, the hydrophilic antibiotic amikacin (7.5 mg/kg BW) was administered. Following this baseline measurement, the treatment group received fluid therapy as a constant rate infusion of 0.9% saline at 6 mL/kg/h over 36 h. After 24 h of fluid administration, the marker drugs and amikacin were administered again. When comparing both groups, a significant effect of fluid administration on the total body clearances of iohexol (p = 0.032) and amikacin (p = 0.0014) was observed. Clearances of iohexol and amikacin increased with on average 15 and 14%, although large interindividual variability was observed. This led to decreased systemic exposure to amikacin, which was manifested as decrease in area under the plasma concentration-time curve from time 0 h to infinity from 34,807 to 30,804 ng.h/mL. These results suggest that fluid therapy is a key factor involved in the development of ARC and should be taken into account when administering mainly renally excreted drugs. However, further research is necessary to confirm these results in children.

Effects of diet, habitual water intake and increased hydration on body fluid volumes and urinary analysis of renal fluid retention in healthy volunteers

Purpose

To increase our knowledge about the causes and physiological consequences of concentrated urine, the relevance of which in the general population is uncertain.

Methods

Twenty healthy volunteers (mean age 42 years) recorded all intake of food and water for 2 weeks. During the 2nd week, they increased their daily consumption of water by 716 mL (32%). The volunteers delivered a 24-h and a morning urine sample for analysis of osmolality and creatinine during the first 4 days of both weeks, and a sample each time they voided on the other days. The water content of food and liquid was calculated and the body fluid volumes were measured by bioimpedance. Haemodynamic stability was assessed with the passive leg-raising test.

Results

There was a curvilinear correlation between the daily intake of water and biomarkers measured in the 24-h collection of urine (coefficient of determination 0.37–0.70). Habitual low intake of water was associated with larger body fluid volumes. The increased fluid intake during the 2nd week was best reflected in the 24-h collection (−15 and −20% for the osmolality and creatinine, respectively, P < 0.002), while morning urine and body fluid volumes were unchanged. Increased fluid intake improved the haemodynamic stability in volunteers with a low intake of water (< median), but only in those who had minimally concentrated morning urine.

Conclusions

The 24-h collection reflected recent intake of fluid, whereas the morning urine seemed to mirror long-term corrections of the fluid balance. Concentrated urine was associated with larger body fluid volumes.

Plasma volume expansion and capillary leakage of 20% albumin in burned patients and volunteers

Background

Burn injury is associated with a long-standing inflammatory reaction. The use of albumin solutions for plasma volume support is controversial because of concerns of increased capillary leakage, which could aggravate the commonly seen interstitial oedema.

Methods

In the present open controlled clinical trial, an intravenous infusion of 20% albumin at 3 mL/kg was given over 30 min to 15 burn patients and 15 healthy volunteers. Blood samples and urine were collected for 5 h. Plasma dilution, plasma albumin and colloid osmotic pressure were compared. Mass balance calculations were used to estimate plasma volume expansion and capillary leakage of fluid and albumin.

Results

The patients were studied between 4 and 14 (median, 7) days after the burn injury, which spread over 7–48% (median, 15%) of the total body surface area. The albumin solution expanded the plasma volume by almost 15%, equivalent to twice the infused volume, in both groups. The urinary excretion exceeded the infused volume by a factor of 2.5. Capillary leakage of albumin occurred at a rate of 3.4 ± 1.5 g/h in burn patients and 3.7 ± 1.6 g/h in the volunteers (P = 0.61), which corresponded to 2.4 ± 1.0% and 2.5 ± 1.2% per hour of the intravascular pool (P = 0.85). The median half-life of the plasma volume expansion was 5.9 (25th–75th percentiles 2.7–11.7) h in the burn patients and 6.9 (3.4–8.5) h in the volunteers (P = 0.56).

Conclusions

Albumin 20% was an effective volume expander in patients at 1 week post-burn. No relevant differences were found between burn patients and healthy volunteers.

Trial registration

EudraCT 2016-000996-26 on May 31, 2016.

Understanding volume kinetics

The distribution and elimination kinetics of the water volume in infusion fluids can be studied by volume kinetics. The approach is a modification of drug pharmacokinetics and uses repeated measurements of blood hemoglobin and urinary excretion as input variables in (usually) a two-compartment model with expandable walls. Study results show that crystalloid fluid has a distribution phase that gives these fluids a plasma volume expansion amounting to 50%-60% of the infused volume as long as the infusion lasts, while the fraction is reduced to 15%-20% within 30 minutes after the infusion ends. Small volumes of crystalloid barely distribute to the interstitium, whereas rapid infusions tend to cause edema. Fluid elimination is very slow during general anesthesia due to the vasodilatation-induced reduction of the arterial pressure, whereas elimination is less affected by hemorrhage. The half-life is twice as long for saline than for Ringer solutions. Elimination is slower in conscious males than conscious females, and high red blood cell and thrombocyte counts retard both distribution and re-distribution. Children have faster turnover than adults. Plasma volume expansions are similar for glucose solutions and Ringer's, but the expansion duration is shorter for glucose. Concentrated urine before and during infusion slows down the elimination of crystalloid fluid. Colloid fluids have no distribution phase, an intravascular persistence half-life of 2-3 hours, and-at least for hydroxyethyl starch-the ability to reduce the effect of subsequently infused crystalloids. Accelerated distribution due to degradation of the endothelial glycocalyx layer has not yet been demonstrated.

Volume kinetic analysis of fluid retention after induction of general anesthesia

Background

Induction of general anesthesia increases the hemodilution resulting from infusion of crystalloid fluid, which is believed to be due to slower distribution caused by arterial hypotension. When normal distribution returns is not known.

Methods

An intravenous infusion of 25 mL kg^− 1 of Ringer’s lactate was infused over 30 min to 25 volunteers just after induction of general anesthesia for open abdominal hysterectomy. A two-volume model was fitted to the repeated measurements of the blood hemoglobin concentration and the urinary excretion using mixed-effects modelling software. Individual-specific covariates were added in sequence.

Results

Distribution of infused fluid was interrupted during the first 20 min of the infusions. During this time 16.6 mL kg^− 1 of lactated Ringer’s had been infused, of which virtually all remained in the circulating blood. Thereafter, the fluid kinetics was similar to that previously been found in awake volunteers except for the elimination rate constant (k₁₀), which remained to be very low (0.86 × 10^− 3 min^− 1). Redistribution of infused fluid from the interstitium to the plasma occurred faster (higher k₂₁) when the arterial pressure was low. No covariance was found between the fixed parameters and preoperatively concentrated urine, the use of sevoflurane or propofol to maintain the anesthesia, or the plasma concentrations of two degradation products of the endothelial glycocalyx, syndecan-1 and heparan sulfate.

Conclusions

Induction of general anesthesia interrupted the distribution of lactated Ringer’s solution up to when 16.6 mL kg^− 1 of crystalloid fluid had been infused. Plasma volume expansion during this period of time was pronounced.

Trial registration

Controlled-trials.com (ISRCTN81005631) on May 17, 2016 (retrospectively registered).

Fluid volume kinetics of 20% albumin

AIMS

A population kinetic model was developed for the body fluid shifts occurring when 20% albumin is given by intravenous infusion. The aim was to study whether its efficacy to expand the plasma volume is impaired after major surgery.

METHODS

An intravenous infusion of 3 mL/kg 20% albumin over 30 minutes was given to 15 volunteers and to 15 patients on the 1^st day after major open abdominal surgery. Blood samples and urine were collected during 5 hours. Mixed-effect modelling software was used to develop a fluid volume kinetic model, using blood haemoglobin and urine excretion the estimate body fluid shifts, to which individual-specific covariates were added in sequence.

RESULTS

The rise in plasma albumin expanded the plasma volume in excess of the infused volume by relocating noncirculating fluid (rate constant k₂₁ ), but it also increased losses of fluid from the kinetic system (k_b ). The balance between k₂₁ and k_b maintained the rise in plasma albumin and plasma volume at a virtual steady-state for almost 2 hours. The rate constant for urinary excretion (k₁₀ ) was slightly reduced by the preceding surgery, by a marked rise in plasma albumin, and by a high preinfusion urinary concentration of creatinine. The arterial pressure, body weight, and plasma concentrations of C-reactive protein and shedding products of the endothelial glycocalyx layer (syndecan-1, heparan sulfate, and hyaluronic acid) did not serve as statistically significant covariates.

CONCLUSIONS

There were no clinically relevant differences in the kinetics of 20% albumin between postoperative patients and volunteers.

Effect of isotonic versus hypotonic maintenance fluid therapy on urine output, fluid balance, and electrolyte homeostasis: a crossover study in fasting adult volunteers

Background. Daily and globally, millions of adult hospitalized patients are exposed to maintenance i.v. fluid solutions supported by limited scientific evidence. In particular, it remains unclear whether fluid tonicity contributes to the recently established detrimental effects of fluid, sodium, and chloride overload.

Methods. This crossover study consisted of two 48 h study periods, during which 12 fasting healthy adults were treated with a frequently prescribed solution (NaCl 0.9% in glucose 5% supplemented by 40 mmol litre⁻¹ of potassium chloride) and a premixed hypotonic fluid (NaCl 0.32% in glucose 5% containing 26 mmol litre⁻¹ of potassium) at a daily rate of 25 ml kg⁻¹ of body weight. The primary end point was cumulative urine volume; fluid balance was thus calculated. We also explored the physiological mechanisms behind our findings and assessed electrolyte concentrations.

Results. After 48 h, 595 ml (95% CI: 454–735) less urine was voided with isotonic fluids than hypotonic fluids (P<0.001), or 803 ml (95% CI: 692–915) after excluding an outlier with ‘exaggerated natriuresis of hypertension’. The isotonic treatment was characterized by a significant decrease in aldosterone (P<0.001). Sodium concentrations were higher in the isotonic arm (P<0.001), but all measurements remained within the normal range. Potassium concentrations did not differ between the two solutions (P=0.45). Chloride concentrations were higher with the isotonic treatment (P<0.001), even causing hyperchloraemia.

Conclusions. Even at maintenance rate, isotonic solutions caused lower urine output, characterized by decreased aldosterone concentrations indicating (unintentional) volume expansion, than hypotonic solutions and were associated with hyperchloraemia. Despite their lower sodium and potassium content, hypotonic fluids were not associated with hyponatraemia or hypokalaemia.

Clinical trial registration. ClinicalTrials.gov (NCT02822898) and EudraCT (2016-001846-24).

Recruitment of extravascular fluid by hyperoncotic albumin

BACKGROUND

Although hyperoncotic albumin may be used to recruit oedema, its effectiveness remains unclear. Therefore, this issue was studied during infusion experiments in healthy volunteers.

METHOD

Fifteen healthy volunteers (mean age 31 years) received an infusion of 3 mL/kg of 20% albumin over 30 minutes. Their urinary excretion was recorded, and venous blood samples were taken to measure blood haemoglobin (Hb), haematocrit, colloid osmotic pressure as well as plasma albumin and sodium concentrations on 15 occasions over a period of 300 minutes. Plasma volume expansion was taken as the inverse of the fluid-induced dilution of venous plasma, as given by the blood Hb concentration. Mass balance calculations were used to estimate the mobilisation of fluid from the tissues.

RESULTS

Maximum plasma volume expansion was reached 20 minutes after completing an infusion of 20% albumin. Urinary excretion was effectively increased, and the mobilised fluid from the tissues at 300 minutes amounted to 3.4 ± 1.2 mL for each infused mL of 20% albumin, of which 19% was of intracellular origin. The urinary excretion correlated strongly with the amount of recruited fluid (R²  = 0.87) and inversely with the plasma volume expansion (R²  = 0.53).

CONCLUSION

The infusion of 20% albumin significantly increases the plasma volume by recruiting interstitial fluid. After completing the infusion, there is a delay of 20 minutes until maximum plasma dilution is reached, and the duration of the plasma volume expansion lasts far beyond 5 hours.

Crystalloid fluid choice in the critically ill : Current knowledge and critical appraisal

Intravenous infusion of crystalloid solutions is one of the most frequently administered medications worldwide. Available crystalloid infusion solutions have a variety of compositions and have a major impact on body systems; however, administration of crystalloid fluids currently follows a "one fluid for all" approach than a patient-centered fluid prescription. Normal saline is associated with hyperchloremic metabolic acidosis, increased rates of acute kidney injury, increased hemodynamic instability and potentially mortality. Regarding balanced infusates, evidence remains less clear since most studies compared normal saline to buffered infusion solutes.; however, buffered solutes are not homogeneous. The term "buffered solutes" only refers to the concept of acid-buffering in infusion fluids but this does not necessarily imply that the solutes have similar physiological impacts. The currently available data indicate that balanced infusates might have some advantages; however, evidence still is inconclusive. Taking the available evidence together, there is no single fluid that is superior for all patients and settings, because all currently available infusates have distinct differences, advantages and disadvantages; therefore, it seems inevitable to abandon the "one fluid for all" strategy towards a more differentiated and patient-centered approach to fluid therapy in the critically ill.

Preoperative fluid retention increases blood loss during major open abdominal surgery

BACKGROUND

Quantification of renal fluid conservation is possible by urine analysis, and the results can indicate dehydration. The present report sought to determine whether this fluid retention correlates with fluid requirements during major abdominal surgeries that have estimated operating times ≥ 2 h.

METHODS

Urine colour, specific weight, osmolality and creatinine concentration were used to calculate a composite "fluid retention index" (FRI) in 97 patients prior to major abdominal surgery. Goal-directed fluid volume optimization, with hydroxyethyl starch supplemented with a background administration of crystalloid fluid, was used.

RESULTS

The median preoperative FRI was 3.0. Fluid retention, considered as present when FRI ≥ 3.5, was found in 37% of the patients. Fluid retention was followed by a significantly larger blood loss (+ 125%; 450 vs. 200 ml), higher haemorrhage rate (+ 41%; 123 vs. 87 ml/h) and greater need for both colloid (+ 43%; 1.43 vs. 1.00 l) and crystalloid (+ 18%; 1.28 vs. 1.08 l) fluids. Despite the larger blood loss, the total fluid balance was more positive after surgery in the dehydrated patients (+ 26%; 1.91 vs. 1.51 l; P < 0.02).

CONCLUSIONS

Preoperative fluid retention, as detected in a urine sample, was associated with a greater blood loss and a more positive fluid balance during major abdominal surgery.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01458678.

Minimal shedding of the glycocalyx layer during abdominal hysterectomy

Background

Surgery with and without hypervolaemia may cause shedding (breakdown) of the endothelial glycocalyx layer, but the severity of this problem is unclear.

Methods

In this preliminary report of a larger clinical trial, the plasma and urine concentrations of three biomarkers of glycocalyx shedding (syndecan-1, hyaluronic acid and heparan sulfate) were measured in seven patients before, during, and after open hysterectomy. The fluid therapy consisted of 25 ml/kg (approximately 2 l) of Ringer’s lactate, which was infused over 30 min when the surgery started. The resulting plasma volume expansion at the end of the infusion was estimated from the haemodilution.

Results

The mean plasma concentration of syndecan-1 was 21.7 ng/ml before surgery and averaged 19.7 ng/ml during and after the surgery. The plasma concentration of hyaluronic acid decreased from 38.0 to 27.7 ng/ml (P < 0.05), while heparan sulfate increased from 3.4 to 5.5 μg/ml (P < 0.05). The urine concentrations of syndecan-1 decreased significantly, while they increased for hyaluronic acid and heparan sulfate. Despite the vigorous fluid load, the urine flow did not exceed 1 ml/min.

Conclusions

No clear evidence was found for shedding of the endothelial glycocalyx layer when 2 l of Ringer’s lactate was infused over 30 min during abdominal hysterectomy. Urine analyses yielded patterns of changes that differed from those in plasma.

Trial registration

ISRCTN81005631. Registered May 17, 2016.

Comparison between normal saline and Ringer's acetate in bipolar transurethral resection of the prostate

OBJECTIVE

The standard surgical treatment for benign prostatic hypertrophy (BPH) is transurethral resection of the prostate (TURP). The aim of this study was to compare normal saline (NS) (0.9% sodium chloride) and Ringer's acetate (RA) as irrigation fluid with regard to visibility, resection feasibility, coagulation and bleeding in bipolar TURP.

MATERIALS AND METHODS

Twenty patients (mean age 70 years) who were diagnosed with BPH were recruited to the study. The first three 3 liter bags of irrigation fluid contained either NS or RA and were administered in a randomized fashion. The surgeon assessed visibility, bleeding, coagulation, resection efficacy and overall outcome after each 3 liter bag on a scale of 1-10.

RESULTS

The results disclosed only marginal differences between the two fluids with regard to the recorded parameters. All of the differences lacked statistical significance (p > .05).

CONCLUSION

RA can be used as an irrigation fluid in bipolar TURP with no obvious difference in comparison with NS.

Renal water conservation determines the increase in body weight after surgery: A randomized, controlled trial

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.

Urinary Analysis of Fluid Retention in the General Population: A Cross-Sectional Study

OBJECTIVE

Renal conservation (retention) of fluid might affect the outcome of hospital care and can be indicated by increased urinary concentrations of metabolic waste products. We obtained a reference material for further studies by exploring the prevalence of fluid retention in a healthy population.

METHODS

Spot urine sampling was performed in 300 healthy hospital workers. A previously validated algorithm summarized the urine-specific gravity, osmolality, creatinine, and color to a fluid retention index (FRI), where 4.0 is the cut-off for fluid retention consistent with dehydration. In 50 of the volunteers, we also studied the relationships between FRI, plasma osmolality, and water-retaining hormones.

RESULTS

The cut-off for fluid retention (FRI ≥ 4.0) was reached by 38% of the population. No correlation was found between the FRI and the time of the day of urine sample collection, and the FRI was only marginally correlated with the time period spent without fluid intake. Volunteers with fluid retention were younger, generally men, and more often had albuminuria (88% vs. 34%, P < 0.001). Plasma osmolality and plasma sodium were somewhat higher in those with a high FRI (mean 294.8 vs. 293.4 mosmol/kg and 140.3 vs. 139.9 mmol/l). Plasma vasopressin was consistently below the limit of detection, and the plasma cortisol, aldosterone, and renin concentrations were similar in subjects with a high or low FRI. The very highest FRI values (≥ 5.0, N = 61) were always accompanied by albuminuria.

CONCLUSION

Fluid retention consistent with moderate dehydration is common in healthy staff working in a Swedish hospital.

Acetate-buffered crystalloid fluids: Current knowledge, a systematic review

INTRODUCTION

The concept of fluid resuscitation with balanced solutions containing acetate is relatively new. The knowledge about acetate mostly originates from nephrological research, as acetate was primarily used as a dialysis buffer where much higher doses of acetate are infused. The aim of this review is to give an overview of the advantages and disadvantages of an acetate-buffered crystalloid fluid when compared with other crystalloid infusates.

METHODS

We report trials with the primary object of comparing an acetate-buffered infusion solute to another crystalloid infusate. A systematic literature search of MEDLINE and the Cochrane Controlled Clinical trials register was conducted to identify suitable studies.

RESULTS

The search strategy used produced 1205 potential titles. After eliminating doubles, 312 titles and abstracts were screened, and 31 references were retrieved for full-text analysis. A total of 27 scientific studies were included in the study.

CONCLUSION

Acetate-buffered crystalloid solutes do have a favorable influence on microcirculation. To what extent the acetate-buffered crystalloids influence kidney function is controversially discussed and not yet clear. Metabolic alkalosis did not occur in a single study in humans after an acetate-buffered infusate; potassium levels stayed stable in all studies. Cardiac output and contractility seem to be positively influenced; nonetheless, data on maintenance of a target blood pressure remain inconclusive. Whether acetate-buffered crystalloid fluids lead to lower rates of acute kidney injury and increased survival when compared with normal saline is yet unclear and may depend on the amount of fluid administered.