The half-life of infusion fluids: An educational review

Anesthesia-induced Lymphatic Dysfunction

General anesthetics adversely alters the distribution of infused fluid between the plasma compartment and the extravascular space. This maldistribution occurs largely from the effects of anesthetic agents on lymphatic pumping, which can be demonstrated by macroscopic fluid kinetics studies in awake versus anesthetized patients. The magnitude of this effect can be appreciated as follows: a 30% reduction in lymph flow may result in a fivefold increase of fluid-induced volume expansion of the interstitial space relative to plasma volume. Anesthesia-induced lymphatic dysfunction is a key factor why anesthetized patients require greater than expected fluid administration than can be accounted for by blood loss, urine output, and insensible losses. Anesthesia also blunts the transvascular refill response to bleeding, an important compensatory mechanism during hemorrhagic hypovolemia, in part through lymphatic inhibition. Last, this study addresses how catecholamines and hypertonic and hyperoncotic fluids may mobilize interstitial fluid to mitigate anesthesia-induced lymphatic dysfunction.

Comparison of Continuous Albumin Infusion, Bolus Albumin, and Crystalloid Fluid Administration in Open-Abdomen Surgical-Trauma Patients

Background: The open abdomen (OA), an intentional lack of fascial closure following abdominal cavity opening, is utilized for various indications among surgical-trauma patients. Among intravenous fluid options, administration of albumin as a continuous infusion may improve outcomes in OA. The purpose of this study is to compare the time to abdomen closure among patients with OA according to type of fluid administration. Methods: We conducted a retrospective cohort study of adults with OA from 2012 through 2018 and stratified by intravenous fluid administration into one of three groups: continuous albumin infusion, intermittent bolus albumin, or crystalloid. The primary outcome was median time to abdomen closure. Secondary outcomes included hemodynamic parameters, length of stay (LOS), and mortality. Time to final abdomen closure was analyzed by Cox proportional hazards regression. Results: Eighty-four patients were included with 28 in each cohort. Compared to crystalloids (44.2 [interquartile range, IQR, 36.3-62.9] hours), median time to abdomen closure was significantly longer in bolus albumin (79.0 [IQR, 44.5-130.8] hours; P = .002) and continuous albumin groups (63.6 [IQR, 42.9-139.6] hours; P = .001) in Cox regression analysis. The incidence of hospital mortality was highest in the bolus albumin cohort (continuous albumin: 21.4% vs bolus albumin: 50.0% vs crystalloid: 25.0%; P = .044). All other secondary outcomes were similar between groups. Conclusions: Among patients with OA, administration of intravenous crystalloid was associated with the shortest time to abdomen closure compared to bolus or continuous albumin. Further evaluation of continuous albumin infusion in patients with OA is needed.

Early high-volume resuscitation with crystalloid solution combined with albumin improves survival of critically ill patients: A retrospective analysis from MIMIC-IV database

BACKGROUND

Volume resuscitation is often required in critically ill patients. However, we have no clear consensus on the choice between crystalloid solution and colloidal solution. This study aimed to explore the effect of albumin administration in massive fluid resuscitation.

METHODS

This was a retrospective cohort study based on the Medical Information Mart for Intensive Care IV (MIMIC-IV) database (2008 and 2019). The prognosis of patients receiving albumin in combination with crystalloids and those receiving crystalloids alone was compared to assess the benefits of albumin in fluid resuscitation.

RESULTS

4426 patients received crystalloids alone (crystalloids group), 692 patients received albumin in combination with crystalloids within the first 24 h of initiation of crystalloids (early albumin combination group), and 382 patients received albumin after the first 24 h (late albumin combination group). Patients in early albumin combination group were more severe than those in Crystalloids group. Nevertheless, we found no statistically significant difference in mortality between the two groups. Multivariate logistic regression analysis using the propensity-score matched cohort showed that the 28-day and 60-day mortality in the early albumin combination group were lower than those in the crystalloids group (odds ratio: 0.64 [95% CI 0.50-0.82; P < 0.001] and 0.71 [95% CI 0.56-0.90; P = 0.004], respectively. Patients in early albumin combination group lived, on average, 1.16 days (95% CI 0.33-2.00; P < 0.01) and 3.3 days (95% CI 1.15-5.44; P < 0.01) longer than the crystalloids group during 28-day follow-up and 60-day follow-up.

CONCLUSION

Administration of albumin within 24 h after the initiation of crystalloids was associated with a lower mortality and a longer restricted mean survival time during 28-day follow-up and 60-day follow-up compared with crystalloid infusion alone. However, administration of albumin 24 h after the initiation of crystalloids was not associated with better prognosis compared to crystalloid infusion alone.

Evaluating the efficacy of a standardized 4 mL/kg fluid bolus technique in critically ill patients with elevated PvaCO2: secondary analysis of two prospective studies

Background

Limiting the fluid bolus (FB) volume may attenuate side effects, including hemodilution and increased filling pressures, but it may also reduce hemodynamic responsiveness. The minimum volume to create hemodynamic effects is considered to be 4 mL/kg. In critically ill patients, the hemodynamic effects of FB with this volume have not been adequately investigated and compared to higher quantities. We hypothesized that a standardized FB approach using 4 mL/kg has comparable hemodynamic and metabolic effects to the common practice of physician-determined FB in critically ill patients.

Methods

We conducted post hoc analysis of two trials in non-selected critically ill patients with central venous-to-arterial CO2 tension (PvaCO2) >6 mmHg and no acute bleeding. All patients received crystalloids either at a physician-determined volume and rate or at 4 mL/kg pump-administered at 1.2 L/h. Cardiac index (CI) was calculated with transthoracic echocardiogram, and arterial and venous blood gas samples were assessed before and after FB. Endpoints were changes in CI and oxygen delivery (DO2) >15%.

Results

A total of 47 patients were eligible for the study, 15 of whom received physician-determined FB and 32 of whom received standardized FB. Patients in the physician-determined FB group received 16 (12-19) mL/kg at a fluid rate of 1.5 (1.5-1.9) L/h, compared to 4.1 (3.7-4.4) mL/kg at a fluid rate of 1.2 (1.2-1.2) L/h (p < 0.01) in the standardized FB group. The difference in CI elevations between the two groups was not statistically significant (8.8% [-0.1-19.9%] vs. 8.4% [0.3-23.2%], p = 0.76). Compared to physician-determined FB, the standardized FB technique had similar probabilities of increasing CI or DO2 by >15% (odds ratios: 1.3 [95% CI: 0.37-5.18], p = 0.66 and 1.83 [95% CI: 0.49-7.85], p = 0.38).

Conclusion

A standardized FB protocol (4 mL/kg at 1.2 L/h) effectively reduced the volume of fluid administered to critically ill patients without compromising hemodynamic or metabolic effects.

Physiological changes after fluid bolus therapy in cardiac surgery patients: A propensity score matched case-control study

Objective

Fluid bolus therapy (FBT) is ubiquitous in intensive care units (ICUs) after cardiac surgery. However, its physiological effects remain unclear.

Design

: We performed an electronic health record-based quasi-experimental ICU study after cardiac surgery. We applied propensity score matching and compared the physiological changes after FBT episodes to matched control episodes where despite equivalent physiology no fluid bolus was given.

Setting

The study was conducted in a multidisciplinary ICU of a tertiary-level academic hospital.

Participants

The study included 2,736 patients who underwent Coronary Artery Bypass Grafting and/or heart valve surgery.

Main Outcome Measures

Changes in cardiac output (CO) and mean arterial pressure (MAP) during the 60 minutes following FBT.

Results

We analysed 3572 matched fluid bolus (FB) episodes. After FBT, but not in control episodes, CO increased within 10 min, with a maximum increase of 0.2 l/min (95%CI 0.1 to 0.2) or 4% above baseline at 40 min (p < 0.0001 vs. controls). CO increased by > 10% from baseline in 60.6% of FBT and 49.1% of control episodes (p < 0.0001). MAP increased by > 10% in 51.7% of FB episodes compared to 53.4% of controls. Finally, FBT was not associated with changes in acid-base status or oxygen delivery.

Conclusion

In this quasi-experimental comparative ICU study in cardiac surgery patients, FBT was associated with statistically significant but numerically small increases in CO. Nearly half of FBT failed to induce a positive CO or MAP response.

Capillary leak and endothelial permeability in critically ill patients: a current overview

Capillary leak syndrome (CLS) represents a phenotype of increased fluid extravasation, resulting in intravascular hypovolemia, extravascular edema formation and ultimately hypoperfusion. While endothelial permeability is an evolutionary preserved physiological process needed to sustain life, excessive fluid leak-often caused by systemic inflammation-can have detrimental effects on patients' outcomes. This article delves into the current understanding of CLS pathophysiology, diagnosis and potential treatments. Systemic inflammation leading to a compromise of endothelial cell interactions through various signaling cues (e.g., the angiopoietin-Tie2 pathway), and shedding of the glycocalyx collectively contribute to the manifestation of CLS. Capillary permeability subsequently leads to the seepage of protein-rich fluid into the interstitial space. Recent insights into the importance of the sub-glycocalyx space and preserving lymphatic flow are highlighted for an in-depth understanding. While no established diagnostic criteria exist and CLS is frequently diagnosed by clinical characteristics only, we highlight more objective serological and (non)-invasive measurements that hint towards a CLS phenotype. While currently available treatment options are limited, we further review understanding of fluid resuscitation and experimental approaches to target endothelial permeability. Despite the improved understanding of CLS pathophysiology, efforts are needed to develop uniform diagnostic criteria, associate clinical consequences to these criteria, and delineate treatment options.

Changes in respiratory mechanics in response to crystalloid infusions in extremely premature infants

Extremely premature infants are at a higher risk of developing respiratory distress syndrome and circulatory impairments in the first few weeks of life. Administration of normal saline boluses to manage hypotension is a common practice in preterm infants. As a crystalloid, a substantial proportion might leak into the interstitium; most consequently the lungs in the preterm cohorts, putatively affecting ventilation. We downloaded and analyzed ventilator mechanics data in infants managed by conventional mechanical ventilation and administered normal saline bolus for clinical reasons. Data were downloaded for 30 min prebolus, 60 min during the bolus followed by 30 min postbolus. Sixteen infants (mean gestational age 25.2 ± 1 wk and birth weight 620 ± 60 g) were administered 10 mL/kg normal saline over 60 min. The most common clinical indication for saline was hypotension. No significant increase was noted in mean blood pressure after the saline bolus. A significant reduction in pulmonary compliance (mL/cmH2O/kg) was noted (0.43 ± 0.07 vs. 0.38 ± 0.07 vs. 0.33 ± 0.07, P = 0.003, ANOVA). This was accompanied by an elevation in the required peak inspiratory pressure to deliver set volume-guarantee (19 ± 2 vs. 22 ± 2 vs. 22 ± 3 mmHg, P < 0.0001, ANOVA), resulting in a higher respiratory severity score. Normal saline infusion therapy was associated with adverse pulmonary mechanics. Relevant pathophysiologic mechanisms might include translocation of fluid across pulmonary capillaries affected by low vascular tone and heightened permeability in extremes of prematurity, back-pressure effects from raised left atrial volume due to immature left-ventricular myocardium; complemented by the effect of cytokine release from positive pressure ventilation.NEW & NOTEWORTHY Administration of saline boluses is common in premature infants although hypovolemia is an uncommon underlying cause of hypotension. This crystalloid can redistribute into pulmonary interstitial space. In the presence of an immature myocardium and diastolic dysfunction, excess fluid can also be "edemagenic." This study on extremely premature infants (25 wk gestation) noted adverse influence on respiratory physiology after saline infusion. Clinicians need to choose judiciously and reconsider routine use of saline boluses in premature infants.

Sepsis Management in the Cardiac Intensive Care Unit

Septic shock management in the cardiac intensive care unit (CICU) is challenging due to the complex interaction of pathophysiology between vasodilatory and cardiogenic shock, complicating how to optimally deploy fluid resuscitation, vasopressors, and mechanical circulatory support devices. Because mixed shock portends high mortality and morbidity, familiarity with quality, contemporary clinical evidence surrounding available therapeutic tools is needed to address the resultant wide range of complications that can arise. This review integrates pathophysiology principles and clinical recommendations to provide an organized, topic-based review of the nuanced intricacies of managing sepsis in the CICU.

Continuous fluid infusion per rectum compared with intravenous fluid infusion in pigs

BACKGROUND

Peripheral blood vessels in pigs are not easily accessible, making placement of intravenous catheters difficult. Alternative methods to intravenous administration of fluids, such as administering fluids via the rectum (proctoclysis), are warranted in pigs.

HYPOTHESIS

Administration of polyionic crystalloid fluids via proctoclysis results in hemodilution changes similar to intravenous administration. The objectives of this study were to evaluate the tolerance for proctoclysis in pigs and compare analytes before and after intravenous or proctoclysis therapy.

ANIMALS

Six healthy, growing, academic institution-owned pigs.

METHODS

Randomized, cross-over design clinical trial, with 3 treatments (control, intravenous, and proctoclysis) with a 3-day washout period. The pigs were anesthetized and jugular catheters were placed. A polyionic fluid (Plasma-Lyte A 148) was administered at 4.4 mL/kg/h during the intravenous and proctoclysis treatments. Laboratory analytes, including PCV, plasma, and serum total solids, albumin, and electrolytes were measured over 12 h at T0 , T3 , T6 , T9 , and T12 . Effects of treatment and time on analytes were determined by analysis of variance.

RESULTS

Proctoclysis was tolerated by pigs. Albumin concentrations decreased during the IV treatment between T0 and T6 (least square mean of 4.2 vs 3.9 g/dL; 95% CI of mean difference = -0.42, -0.06; P = .03). Proctoclysis did not significantly affect any laboratory analytes at any time points (P > .05).

CONCLUSIONS AND CLINICAL IMPORTANCE

Proctoclysis did not demonstrate hemodilution similar to intravenous administration of polyionic fluids. Proctoclysis might not be an effective alternative to the intravenous administration of polyionic fluids in healthy euvolemic pigs.

Advances in the Physiology of Transvascular Exchange and A New Look At Rational Fluid Prescription

The Starling principle is a model that explains the transvascular distribution of fluids essentially governed by hydrostatic and oncotic forces, which dynamically allow vascular refilling according to the characteristics of the blood vessel. However, careful analysis of fluid physiology has shown that the principle, while correct, is not complete. The revised Starling principle (Michel-Weinbaum model) provides relevant information on fluid kinetics. Special emphasis has been placed on the endothelial glycocalyx, whose subendothelial area allows a restricted oncotic pressure that limits the reabsorption of fluid from the interstitial space, so that transvascular refilling occurs mainly from the lymphatic vessels. The close correlation between pathological states of the endothelium (eg: sepsis, acute inflammation, or chronic kidney disease) and the prescription of fluids forces the physician to understand the dynamics of fluids in the organism; this will allow rational fluid prescriptions. A theory that integrates the physiology of exchange and transvascular refilling is the "microconstant model", whose variables include dynamic mechanisms that can explain edematous states, management of acute resuscitation, and type of fluids for common clinical conditions. The clinical-physiological integration of the concepts will be the hinges that allow a rational and dynamic prescription of fluids.

Hypovolemia with peripheral edema: What is wrong?

Fluid normally exchanges freely between the plasma and interstitial space and is returned primarily via the lymphatic system. This balance can be disturbed by diseases and medications. In inflammatory disease states, such as sepsis, the return flow of fluid from the interstitial space to the plasma seems to be very slow, which promotes the well-known triad of hypovolemia, hypoalbuminemia, and peripheral edema. Similarly, general anesthesia, for example, even without mechanical ventilation, increases accumulation of infused crystalloid fluid in a slowly equilibrating fraction of the extravascular compartment. Herein, we have combined data from fluid kinetic trials with previously unconnected mechanisms of inflammation, interstitial fluid physiology and lymphatic pathology to synthesize a novel explanation for common and clinically relevant examples of circulatory dysregulation. Experimental studies suggest that two key mechanisms contribute to the combination of hypovolemia, hypoalbuminemia and edema; (1) acute lowering of the interstitial pressure by inflammatory mediators such as TNFα, IL-1β, and IL-6 and, (2) nitric oxide-induced inhibition of intrinsic lymphatic pumping.

Perioperative fluid management for lung transplantation is challenging

Lung transplantation is the definitive end-stage treatment for many lung diseases, and postoperative pulmonary oedema severely affects survival after lung transplantation. Optimizing perioperative fluid management can reduce the incidence of postoperative pulmonary oedema and improve the prognosis of lung transplant patients by removing the influence of patient, donor's lung and ECMO factors. Therefore, this article reviews seven aspects of lung transplant patients' pathophysiological characteristics, physiological characteristics of fluids, the influence of the donor lung on pulmonary oedema as well as current fluid rehydration concepts, advantages or disadvantages of intraoperative monitoring tools or types of fluids on postoperative pulmonary oedema, while showing the existing challenges in section 7. The aim is to show the specificity of perioperative fluid management in lung transplant patients and to provide new ideas for individualised fluid management in lung transplantation.

Individualizing Fluid Management in Patients with Acute Respiratory Distress Syndrome and with Reduced Lung Tissue Due to Surgery—A Narrative Review

Fluids are the cornerstone of therapy in all critically ill patients. During the last decades, we have made many steps to get fluid therapy personalized and based on individual needs. In patients with lung involvement—acute respiratory distress syndrome—finding the right amount of fluids after lung surgery may be extremely important because lung tissue is one of the most vulnerable to fluid accumulation. In the current narrative review, we focus on the actual perspectives of fluid therapy with the aim of showing the possibilities to tailor the treatment to a patient’s individual needs using fluid responsiveness parameters and other therapeutic modalities.

Protocolised reduction of non-resuscitation fluids versus usual care in patients with septic shock (REDUSE): a protocol for a multicentre feasibility trial

INTRODUCTION

Administration of large volumes of fluids is associated with poor outcome in septic shock. Recent data suggest that non-resuscitation fluids are the major source of fluids in the intensive care unit (ICU) patients suffering from septic shock. The present trial is designed to test the hypothesis that a protocol targeting this source of fluids can reduce fluid administration compared with usual care.

METHODS AND ANALYSIS

The design will be a multicentre, randomised, feasibility trial. Adult patients admitted to ICUs with septic shock will be randomised within 12 hours of admission to receive non-resuscitation fluids either according to a restrictive protocol or to receive usual care. The healthcare providers involved in the care of participants will not be blinded. The participants, outcome assessors at the 6-month follow-up and statisticians will be blinded. Primary outcome will be litres of fluids administered within 3 days of randomisation. Secondary outcomes will be proportion of randomised participants with outcome data on all-cause mortality; days alive and free of mechanical ventilation within 90 days of inclusion; any acute kidney injury and ischaemic events in the ICU (cerebral, cardiac, intestinal or limb ischaemia); proportion of surviving randomised patients who were assessed by European Quality of Life 5-Dimensions 5-Level questionnaire and Montreal Cognitive Assessment; proportion of all eligible patients who were randomised and proportion of participants experiencing at least one protocol violation.

ETHICS AND DISSEMINATION

Ethics approval has been obtained in Sweden. Results of the primary and secondary outcomes will be submitted for publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT05249088.

Analysis of the estimation of bleeding using several proposed haematometric equations

PURPOSE

Among various methods for estimating blood loss, the gravimetric method is the most accurate; however, its use in routine practice is complicated. Although several equations have been proposed for this purpose, there is no consensus on the most suitable.

METHODS

A cross-sectional study was conducted in seven secondary and tertiary hospitals between March and July 2018 including all patients undergoing total hip arthroplasty or hip prosthesis replacement under general or regional anaesthesia. We compared blood loss estimates obtained using the gravimetric method (weighing gauzes and pads and measuring volumes of blood collected by suction during surgery) and using three different equations, two of which considered intravenous fluids (CRYS 3.5 and 1.5) and a third which did not (the traditional equation). Additionally, intraclass correlation coefficients (ICCs) and Bland-Altman plots were used.

RESULTS

The mean blood loss estimated using the gravimetric method was 513.7 ± 421.7 mL, while estimates calculated using the CRYS 3.5, CRYS 1.5 and traditional equations were 737.2 ± 627.4, 420.8 ± 636.2 and 603.4 ± 386.3 mL, respectively. Comparing these results, we found low levels of agreement (based on ICCs), except when using the traditional equation (ICC: 0.517). The limits of agreement comparing external blood loss with the estimates from the equations ranged from - 1655.6 to 1459.2 in the case of the CRYS 1.5 equation to - 839.6 to 1008.4 in the case of the traditional equation.

CONCLUSIONS

For use in clinical practice, haematological index-based equations, regardless of whether they consider fluids administered, do not show sufficiently strong correlations with gravimetric estimates of intraoperative blood loss.

Review of Burn Resuscitation: Is Plasmalyte® a Comparable Alternative to Ringer's Lactate?

Ringer's lactate has been the most widely used fluid for burn resuscitation for decades. Plasmalyte® (PL), a newer balanced crystalloid, is gaining popularity for use in the critically ill, including patients with burns. This popularity is partly due to the fact that PL theoretically offers a favorable metabolic profile, but may also be attributed to its relatively lower cost. Patients who are critically ill with large burns receive enormous volumes of fluids, especially during the resuscitation period. The choice of balanced crystalloid solution used is likely to have an impact on the metabolic status of patients and their overall outcomes. The choice of fluid for burn resuscitation has been one of the most researched topics in burn care and various types of fluids have been superseded based on research findings. This narrative review examines the evidence guiding fluid management in burns and explores the data supporting the use of balanced crystalloid solutions, in particular PL for burn resuscitation. Our literature search revealed only one study that focused on a direct comparison between PL and standard Ringer's Lactate for burn resuscitation. Based on the limited literature on the use of PL in burns, it is difficult to draw meaningful conclusions. Further research, into the suitability of PL for use in burns, is needed before formulary changes are instituted widely.

A retrospective comparison of albumin versus mannitol priming fluid with relation to postoperative atrial fibrillation

BACKGROUND AND AIM OF THE STUDY

Postoperative atrial fibrillation (POAF) is a common complication following cardiac surgery which can result in increased mortality and increased healthcare costs. During Hurricane Maria (2017), a nationwide shortage of mannitol occurred, and our institution switched to the utilization of albumin as a priming fluid solution. We observed decreased rates of POAF during that time and began alternating albumin and mannitol priming fluid solutions. We hypothesized this observation may be from altered perinexal conduction from albumin utilization.

METHODS

A retrospective chart review of all patients from January 2020 through December 2020 who underwent cardiac surgery was performed, to determine if albumin was associated with reduced POAF rates. Two hundred and thirteen patients were identified and 4 were excluded. Two hundred and nine patients (110 albumin priming fluid and 99 mannitol priming fluid) were included in our final analysis.

RESULTS

Analysis was performed for all patients with POAF and in patients with new-onset AF (without a history of prior AF) after surgery. POAF rates showed no statistically significant difference between cohorts. For all patients, POAF occurred in 43% of the albumin subgroup and 47% of the mannitol subgroup (p = .53) and for patients with new-onset AF, POAF occurred in 35% of the albumin subgroup versus 42% of the mannitol subgroup (p = .36). Logistic regression revealed that age, ejection fraction and cardiopulmonary bypass time was associated with POAF, in our cohort.

CONCLUSIONS

The use of albumin compared to mannitol as priming fluid solutions was not associated with statistically significant reductions in POAF rate, in our population.

The Volume-Cost Relationship: How Does Surgical Volume Affect Cost and Value in AIS Surgery

STUDY DESIGN

Retrospective review.

OBJECTIVE

The objective of this study was to evaluate and compare distribution of hospital and operating room charges and outcomes during posterior spinal fusion for adolescent idiopathic scoliosis (AIS) patients by high-volume (HV) and standard-volume (SV) surgeons at one institution and examine potential cost savings.

SUMMARY OF BACKGROUND DATA

Increased surgical volume has been associated with improved perioperative outcomes after spinal deformity correction. However, there is a lack of information on how this may affect hospital costs.

METHODS

Retrospective study of AIS patients undergoing posterior spinal fusion between 2013 and 2019. Demographic, x-ray, chart review and hospital costs were collected and compared between HV surgeons (≥50 AIS cases/y) and SV surgeons (<50/y). Comparative analyses were computed using Wilcoxon rank-sum, Kruskal-Wallis, and the Fisher exact tests. Average values with corresponding minimum-maximum rages were reported.

RESULTS

A total of 407 patients (HV: 232, SV: 175) operated by 4 surgeons (1 HV, 3 SV). Radiographic parameters were similar between the groups. HV surgeons had significantly lower estimated blood loss (385.3 vs. 655.6 mL, P <0.001), fewer intraoperative transfusions (10.8% vs. 25.1%, P <0.001), shorter surgery time (221.6 vs. 324.9 min, P <0.001), and lower radiation from intraoperative fluoroscopy (4.4 vs. 6.4 mGy, P <0.001). HV patients had a significantly lower length of stay (4.3 vs. 5.3, P <0.001) and complication rate (0.4% vs. 4%, P =0.04).HV surgeons had significantly lower total costs ($61,716.24 vs. $72,745.93, P <0.001). This included lower transfusion costs ( P <0.001), operative time costs ( P <0.001), screw costs ( P <0.001), hospital stay costs ( P <0.001), and costs associated with 30-day emergency department returns ( P <0.001).

CONCLUSION

HV surgeons had significantly lower operative times, lower estimated blood loss and transfusion rates and lower perioperative complications requiring readmission or return to emergency department resulting in lower health care costs.

LEVEL OF EVIDENCE

Level III.

Fast versus slow infusion of 20% albumin: a randomized controlled cross-over trial in volunteers

BACKGROUND

We investigated whether plasma volume (PV) expansion of 20% albumin is larger when the fluid is administered rapidly compared with a slow infusion.

METHODS

In this open-labeled randomized interventional controlled trial, 12 volunteers (mean age, 28 years) received 3 mL/kg of 20% albumin (approximately 225 mL) over 30 min (fast) and 120 min (slow) in a cross-over fashion. Blood hemoglobin and plasma albumin were measured on 15 occasions during 6 h to estimate the PV expansion and the capillary leakage of albumin and fluid.

RESULTS

The largest PV expansion was 16.1% ± 6.5% (mean ± SD) for fast infusion and 12.8% ± 4.0% for slow infusion (p = 0.52). The median area under the curve for the PV expansion was 69% larger for the fast infusion during the first 2 h (p = 0.034), but was then similar for both infusions. The half-life of the PV expansion did not differ significantly (median, 5.6 h versus 5.4 h, p = 0.345), whereas the intravascular half-life of the excess albumin was 8.0 h for fast infusion and 6.3 h for slow infusion (p = 0.028). The measured urine output was almost three times larger than the infused volume. The plasma concentration of atrial natriuretic peptide (MR-proANP) accelerated the capillary leakage of albumin and the urine flow.

CONCLUSIONS

The intravascular persistence of albumin was longer, but the fluid kinetics was the same, when 20% albumin was infused over 30 min compared with 120 min. We found no disadvantages of administering the albumin at the higher rate. Trial registration EU Clinical Trials Register, EudraCT2017-003687-12, registered September 22, 2017, https://www.clinicaltrialsregister.eu/ctr-search/trial/2017-003687-12/SE.

Assessment of fluid unresponsiveness guided by lung ultrasound in abdominal surgery: a prospective cohort study

A fluid challenge can generate an infraclinical interstitial syndrome that may be detected by the appearance of B-lines by lung ultrasound. Our objective was to evaluate the appearance of B-lines as a diagnostic marker of preload unresponsiveness and postoperative complications in the operating theater. We conducted a prospective, bicentric, observational study. Adult patients undergoing abdominal surgery were included. Stroke volume (SV) was determined before and after a fluid challenge with 250 mL crystalloids (Delta-SV) using esophageal Doppler monitoring. Responders were defined by an increase of Delta-SV > 10% after fluid challenge. B-lines were collected at four bilateral predefined zones (right and left anterior and lateral). Delta-B-line was defined as the number of newly appearing B-lines after a fluid challenge. Postoperative pulmonary complications were prospectively recorded according to European guidelines. In total, 197 patients were analyzed. After a first fluid challenge, 67% of patients were responders and 33% were non-responders. Delta-B-line was significantly higher in non-responders than responders [4 (2–7) vs 1 (0–3), p < 0.0001]. Delta-B-line was able to diagnose fluid non-responders with an area under the curve of 0.74 (95% CI 0.67–0.80, p < 0.0001). The best threshold was two B-lines with a sensitivity of 80% and a specificity of 57%. The final Delta-B-line could predict postoperative pulmonary complications with an area under the curve of 0.74 (95% CI 0.67–0.80, p = 0.0004). Delta-B-line of two or more detected in four lung ultrasound zones can be considered to be a marker of preload unresponsiveness after a fluid challenge in abdominal surgery.

The objectives and procedures of the study were registered at Clinicaltrials.gov (NCT03502460; Principal investigator: Stéphane BAR, date of registration: April 18, 2018).

Feasibility to estimate mean systemic filling pressure with inspiratory holds at the bedside

Background: A decade ago, it became possible to derive mean systemic filling pressure (MSFP) at the bedside using the inspiratory hold maneuver. MSFP has the potential to help guide hemodynamic care, but the estimation is not yet implemented in common clinical practice. In this study, we assessed the ability of MSFP, vascular compliance (Csys), and stressed volume (Vs) to track fluid boluses. Second, we assessed the feasibility of implementation of MSFP in the intensive care unit (ICU). Exploratory, a potential difference in MSFP response between colloids and crystalloids was assessed. Methods: This was a prospective cohort study in adult patients admitted to the ICU after cardiac surgery. The MSFP was determined using 3-4 inspiratory holds with incremental pressures (maximum 35 cm H₂O) to construct a venous return curve. Two fluid boluses were administered: 100 and 500 ml, enabling to calculate Vs and Csys. Patients were randomized to crystalloid or colloid fluid administration. Trained ICU consultants acted as study supervisors, and protocol deviations were recorded. Results: A total of 20 patients completed the trial. MSFP was able to track the 500 ml bolus (p < 0.001). In 16 patients (80%), Vs and Csys could be determined. Vs had a median of 2029 ml (IQR 1605-3164), and Csys had a median of 73 ml mmHg^-1 (IQR 56-133). A difference in response between crystalloids and colloids was present for the 100 ml fluid bolus (p = 0.019) and in a post hoc analysis, also for the 500 ml bolus (p = 0.010). Conclusion: MSFP can be measured at the bedside and provides insights into the hemodynamic status of a patient that are currently missing. The clinical feasibility of Vs and Csys was judged ambiguously based on the lack of required hemodynamic stability. Future studies should address the clinical obstacles found in this study, and less-invasive alternatives to determine MSFP should be further explored. Clinical Trial Registration: ClinicalTrials.gov Identifier NCT03139929.

Existing fluid responsiveness studies using the mini-fluid challenge may be misleading: Methodological considerations and simulations

BACKGROUND

The mini-fluid challenge (MFC) is a clinical concept of predicting fluid responsiveness by rapidly infusing a small amount of intravenous fluids, typically 100 ml, and systematically assessing its haemodynamic effect. The MFC method is meant to predict if a patient will respond to a subsequent, larger fluid challenge, typically another 400 ml, with a significant increase in stroke volume.

METHODS

We critically evaluated the general methodology of MFC studies, with statistical considerations, secondary analysis of an existing study and simulations.

RESULTS

Secondary analysis of an existing study showed that the MFC could predict the total fluid response (MFC + 400 ml) with an area under the receiver operator characteristic curve (AUROC) of 0.92, but that the prediction was worse than random for the response to the remaining 400 ml (AUROC = 0.33). In a null simulation with no response to both the MFC and the subsequent fluid challenge, the commonly used analysis could predict fluid responsiveness with an AUROC of 0.73.

CONCLUSION

Many existing MFC studies are likely overestimating the classification accuracy of the MFC. This should be considered before adopting the MFC into clinical practice. A better study design includes a second, independent measurement of stroke volume after the MFC. This measurement serves as reference for the response to the subsequent fluid challenge.

Plasma Volume Expansion and Fluid Kinetics of 20% Albumin During General Anesthesia and Surgery Lasting for More Than 5 Hours

BACKGROUND

Intraoperative administration of crystalloid for plasma volume expansion may be reduced by use of hyperoncotic albumin. However, the degree of plasma volume expansion with administration of 20% albumin is poorly quantitated. We estimated the amount of volume expansion attributable to 20% albumin administration in patients undergoing surgery for more than 5 hours.

METHODS

Twenty percent albumin was delivered at 3 mL/kg by intravenous infusion during 30 minutes to 15 patients (mean ± standard deviation [SD] age; 46 ± 15 years) undergoing surgery. Blood samples and urine were collected for 5 hours. Mass balance calculations and volume kinetics were used to estimate plasma volume expansion and capillary leakage of albumin and fluid.

RESULTS

Administration of 20% albumin was associated with an increase in plasma volume amounting to 1.7 times the infused volume. After correction for hemorrhage, the median (and 25th to 75th percentiles) intravascular half-life for the administered albumin mass was 20.4 (14.2-34.7) hours. The plasma volume decreased with a half-life of 21.7 (16.1-26.8) hours. Urinary excretion was 3 times greater than the infused volume of albumin, but kinetic analysis suggested that other flows of fluid to and from the plasma occurred more slowly than previously found in volunteers. Hemodynamic support with norepinephrine increased urinary excretion and contracted the plasma volume.

CONCLUSIONS

Albumin (20%) increased the plasma volume by 1.7 times the infused volume. Our results do not support that the transcapillary leakage of albumin is accelerated by anesthesia and surgery.

Restricted, optimized or liberal fluid strategy in thoracic surgery: A narrative review

Perioperative fluid balance has a major impact on clinical and functional outcome, regardless of the type of interventions. In thoracic surgery, patients are more vulnerable to intravenous fluid overload and to develop acute respiratory distress syndrome and other complications. New insight has been gained on the mechanisms causing pulmonary complications and the role of the endothelial glycocalix layer to control fluid transfer from the intravascular to the interstitial spaces and to promote tissue blood flow. With the implementation of standardized processes of care, the preoperative fasting period has become shorter, surgical approaches are less invasive and patients are allowed to resume oral intake shortly after surgery. Intraoperatively, body fluid homeostasis and adequate tissue oxygen delivery can be achieved using a normovolemic therapy targeting a “near-zero fluid balance” or a goal-directed hemodynamic therapy to maximize stroke volume and oxygen delivery according to the Franck–Starling relationship. In both fluid strategies, the use of cardiovascular drugs is advocated to counteract the anesthetic-induced vasorelaxation and maintain arterial pressure whereas fluid intake is limited to avoid cumulative fluid balance exceeding 1 liter and body weight gain (~1-1.5 kg). Modern hemodynamic monitors provide valuable physiological parameters to assess patient volume responsiveness and circulatory flow while guiding fluid administration and cardiovascular drug therapy. Given the lack of randomized clinical trials, controversial debate still surrounds the issues of the optimal fluid strategy and the type of fluids (crystalloids versus colloids). To avoid the risk of lung hydrostatic or inflammatory edema and to enhance the postoperative recovery process, fluid administration should be prescribed as any drug, adapted to the patient's requirement and the context of thoracic intervention.

Model-predicted capillary leakage in graded hypotension: Extended analysis of experimental spinal anesthesia

BACKGROUND

Crystalloid fluid infused during the induction of spinal anesthesia is involved in a complex set of physiological responses, including vasodilatation, reactive vasoconstriction, and changes in mean arterial pressure (MAP). The present evaluation compares the modeled capillary leakage in anesthetized versus nonanesthetized body regions.

METHODS

Ten female volunteers (mean age, 29 years) received 25 ml/kg of Ringer's acetate over 60 min during experimental spinal anesthesia. Blood hemoglobin was measured repeatedly in the radial artery (reference), arm (cubital) vein, and leg (femoral) vein for 240 min. Each pattern of data served as a dependent variable in volume kinetic analyses that used mixed models software and MAP as covariate.

RESULTS

The capillary leakage of fluid from the plasma to the extravascular space peaked at 17 ml/min when MAP was 100 mmHg, and the two venous curves were virtually identical. At MAP 60 mmHg, the rate was reduced to 10-12 ml/min when assessed in arterial blood and leg vein blood, but only 5 mmHg in blood collected from the arm vein. The distribution half-life of infused fluid was then 40 min in the leg and 80 min in the arm. These results suggest that vasoconstriction in nonanesthetized body regions halves the capillary leakage that is observed in vasodilated, anesthetized body regions.

CONCLUSION

Graded hypotension during spinal anesthesia reduced the capillary filtration of fluid as determined by volume kinetic analysis. The effect was twice as great when venous blood was sampled from a nonanesthetized body region than from an anesthetized body region.

Effect of Intra- and Post-Operative Fluid and Blood Volume on Postoperative Pulmonary Edema in Patients with Intraoperative Massive Bleeding

In patients with intraoperative massive bleeding, the effects of fluid and blood volume on postoperative pulmonary edema are uncertain. Patients with intraoperative massive bleeding who had undergone a non-cardiac surgery in five hospitals were enrolled in this study. We evaluated the association of postoperative pulmonary edema risk and intra- and post-operatively administered fluid and blood volumes in patients with intraoperative massive bleeding. In total, 2090 patients were included in the postoperative pulmonary edema analysis, and 300 patients developed pulmonary edema within 72 h of the surgery. The postoperative pulmonary edema with hypoxemia analysis included 1660 patients, and the condition occurred in 161 patients. An increase in the amount of red blood cells transfused per hour after surgery increased the risk of pulmonary edema (hazard ratio: 1.03; 95% confidence interval: 1.01–1.05; p = 0.013) and the risk of pulmonary edema with hypoxemia (hazard ratio: 1.04; 95% confidence interval: 1.01–1.07; p = 0.024). An increase in the red blood cells transfused per hour after surgery increased the risk of developing pulmonary edema. This increase can be considered as a risk factor for pulmonary edema.

Pharmacodynamic analysis of a fluid challenge with 4 ml kg-1 over 10 or 20 min: a multicenter cross-over randomized clinical trial

Purpose

A number of studies performed in the operating room evaluated the hemodynamic effects of the fluid challenge (FC), solely considering the effect before and after the infusion. Few studies have investigated the pharmacodynamic effect of the FC on hemodynamic flow and pressure variables. We designed this trial aiming at describing the pharmacodynamic profile of two different FC infusion times, of a fixed dose of 4 ml kg⁻¹.

Methods

Forty-nine elective neurosurgical patients received two consecutive FCs of 4 ml kg⁻¹ of crystalloids in 10 (FC₁₀) or 20 (FC₂₀) minutes, in a random order. Fluid responsiveness was defined as stroke volume index increase ≥ 10%. We assessed the net area under the curve (AUC), the maximal percentage difference from baseline (d_max), time when the d_max was observed (t_max), change from baseline at 1-min (d₁) and 5-min (d₅) after FC end.

Results

After FC₁₀ and FC_20, 25 (51%) and 14 (29%) of 49 patients were classified as fluid responders (p = 0.001). With the exception of the AUCs of SAP and MAP, the AUCs of all the considered hemodynamic variables were comparable. The d_max and the t_max were overall comparable. In both groups, the hemodynamic effects on flow variables were dissipated within 5 min after FC end.

Conclusions

The infusion time of FC administration affects fluid responsiveness, being higher for FC₁₀ as compared to FC₂₀. The effect on flow variables of either FCs fades 5 min after the end of infusion.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10877-021-00756-3.

Interstitial washdown and vascular albumin refill during fluid infusion: novel kinetic analysis from three clinical trials

BACKGROUND AND AIMS

Increased capillary filtration may paradoxically accelerate vascular refill of both fluid and albumin from the interstitial space, which is claimed to be edema-preventing. We characterized this proposed mechanism, called "interstitial washdown", by kinetic analyses of the hemodilution induced by intravenous infusion of crystalloid fluid during 3 distinct physiological states.

METHODS

Greater plasma dilution of hemoglobin as compared to albumin during fluid therapy indicated recruitment of albumin, which was compared to the flow of interstitial fluid to the plasma as indicated by population volume kinetic analysis. Data for the comparison were derived from 24 infusions of crystalloid fluid in conscious volunteers, 30 in anesthetized patients, and 31 in patients with ketoacidosis from hyperglycemia.

RESULTS

"Interstitial washdown" increased the plasma albumin concentration by between 0.3 and 1.0 g/L in the three series of infusions. The initial albumin concentration in the interstitial fluid returning to the plasma was estimated to between 22 g/L and 29 g/L, which decreased to an average of 50-75% lower during the subsequent 2-3 h. Kinetic simulations show that pronounced washdown was associated with increased capillary filtration (high k₁₂) and, in conscious subjects, with greater plasma and interstitial volume expansion and restricted urine flow. During anesthesia, the main effect was an increase in the non-exchangeable fluid volume ("third-spacing").

CONCLUSIONS

Crystalloid fluid accelerates lymphatic flow that moderately increases plasma albumin, but more clearly helps to maintain the intravascular volume. This "interstitial washdown" mechanism becomes exhausted after a few hours.

Early Albumin Exposure After Cardiac Surgery

OBJECTIVES

To determine whether the early use of albumin after cardiac surgery in the first 24 hours in the intensive care unit (ICU) is associated with reduced mortality.

DESIGN

A single-center nonrandomized retrospective cohort study using the Medical Information Mart in Intensive Care IV database.

SETTING

A single cardiothoracic ICU in the United States during a period between 2008 to 2019.

PARTICIPANTS

Patients undergoing valvular and/or cardiac bypass graft surgeries.

INTERVENTIONS

Albumin administered during the first 24 hours of the ICU admission.

MEASUREMENTS AND MAIN RESULTS

A total of 8,136 patients were included in this study, of whom 4,444 (54.6%) received albumin at any stage during the first 24 hours of ICU admission, and 69 (1.6%) of those patients died. The patient population exposed to albumin had higher comorbidities and illness severity compared to the no-albumin group. Patients exposed to albumin during the first 24 hours of ICU admission had a statistically significant reduction in mortality (odds ratio [OR], 0.68; 95% confidence interval [CI], 0.48-0.97, p < 0.05) after adjustment for age, the Oxford Acute Severity of Illness Score, and the Charlson comorbidity index. A sensitivity analysis of patients who received albumin at any stage during ICU admission showed increased mortality (OR, 1.93; 95% CI, 1.26-3.07, p < 0.01). Patients exposed to albumin had a significant increase in adjusted ICU length of stay (LOS) (geometric mean ratio 1.09; 95% CI, 1.05-1.10, p = < 0.001) and hospital LOS (geometric mean ratio 1.08; 95% CI, 1.05-1.10, p < 0.001).

CONCLUSIONS

Exposure to albumin in the first 24 hours after cardiac surgery is associated with a reduction in adjusted hospital mortality and an increase in both hospital and ICU lengths of stay.

Colloids Yes or No? - a "Gretchen Question" Answered

Colloid solutions, both natural and synthetic, had been widely accepted as having superior volume expanding effects than crystalloids. Synthetic colloid solutions were previously considered at least as effective as natural colloids, as well as being cheaper and easily available. As a result, synthetic colloids (and HES in particular) were the preferred resuscitation fluid in many countries. In the past decade, several cascading events have called into question their efficacy and revealed their harmful effects. In 2013, the medicines authorities placed substantial restrictions on HES administration in people which has resulted in an overall decrease in their use. Whether natural colloids (such as albumin-containing solutions) should replace synthetic colloids remains inconclusive based on the current evidence. Albumin seems to be safer than synthetic colloids in people, but clear evidence of a positive effect on survival is still lacking. Furthermore, species-specific albumin is not widely available, while xenotransfusions with human serum albumin have known side effects. Veterinary data on the safety and efficacy of synthetic and natural colloids is limited to mostly retrospective evaluations or experimental studies with small numbers of patients (mainly dogs). Large, prospective, randomized, long-term outcome-oriented studies are lacking. This review focuses on advantages and disadvantages of synthetic and natural colloids in veterinary medicine. Adopting human guidelines is weighed against the particularities of our specific patient populations, including the risk-benefit ratio and lack of alternatives available in human medicine.

Passive Immunity Should and Will Work for COVID-19 for Some Patients

In the absence of effective antiviral chemotherapy and still in the context of emerging vaccines for severe acute respiratory syndrome-CoV-2 infections, passive immunotherapy remains a key treatment and possible prevention strategy. What might initially be conceived as a simplified donor-recipient process, the intricacies of donor plasma, IV immunoglobulins, and monoclonal antibody modality applications are becoming more apparent. Key targets of such treatment have largely focused on virus neutralization and the specific viral components of the attachment Spike protein and its constituents (e.g., receptor binding domain, N-terminal domain). The cumulative laboratory and clinical experience suggests that beneficial protective and treatment outcomes are possible. Both a dose- and a time-dependency emerge. Lesser understood are the concepts of bioavailability and distribution. Apart from direct antigen binding from protective immunoglobulins, antibody effector functions have potential roles in outcome. In attempting to mimic the natural but variable response to infection or vaccination, a strong functional polyclonal approach attracts the potential benefits of attacking antigen diversity, high antibody avidity, antibody persistence, and protection against escape viral mutation. The availability and ease of administration for any passive immunotherapy product must be considered in the current climate of need. There is never a perfect product, but yet there is considerable room for improving patient outcomes. Given the variability of human genetics, immunity, and disease, and given the nuances of the virus and its potential for change, passive immunotherapy can be developed that will be effective for some but not all patients. An understanding of such patient variability and limitations is just as important as the understanding of the direct interactions between immunotherapy and virus.

New Trends in the Utilization of Intravenous Fluids

Intravenous fluids (IVFs) are the most commonly used drugs in hospitalized patients. Knowledge of the indications and pharmacokinetics of IVFs is critical for all medical disciplines. Isotonic saline (normal saline, 0.9% NS) is the most utilized intravenous solution. Isotonic saline effectively expands the intravascular compartment, as one-quarter of the infusate goes intravascularly, while the remaining three-quarters go into the interstitial space. The proper use of IVFs in different clinical scenarios is paramount. IVFs differ with regard to their half-life, intravascular volume expansion, preparation, and cost. Crystalloids are more commonly utilized due to their relatively low cost and availability. Colloids are very advantageous in cases of shock or hemorrhage, as they remain in the intravascular space, thus facilitating an increase in blood pressure (BP) prior to blood administration. Colloids are also advantageous in cases of burns and severe hypoglobulinemia. Human albumin (5%, 20%, and 25%) is the most used colloid solution. It remains intravascularly provided and there is no capillary leak as in systematic inflammation. The goal in hospitalized patients is timely and adequate intravenous fluid resuscitation. Utilization of a large volume of isotonic saline may lead to hypervolemia, hypernatremia, hyperchloremia, metabolic acidosis, and hypokalemia. The use of balanced intravenous solutions has been advocated to avoid these complications.

Mortality benefit of crystalloids administered in 1-6 hours in septic adults in the ED: systematic review with narrative synthesis

BACKGROUND

Based on the 2018 update of the Surviving Sepsis Campaign, the Committee for Quality Improvement of the NHSs of England recommended the instigation of the elements of the 'Sepsis-6 bundle' within 1 hour to adult patients screened positive for sepsis. This bundle includes a bolus infusion of 30 mL/kg crystalloids in the ED. Besides the UK, both in the USA and Australia, compliance with similar 1-hour targets became an important quality indicator. However, the supporting evidence may neither be contemporaneous nor necessarily valid for emergency medicine settings.

METHOD

A systematic review was designed and registered at PROSPERO to assess available emergency medicine/prehospital evidence published between 2012 and 2020, investigating the clinical benefits associated with a bolus infusion of a minimum 30 mL/kg crystalloids within 1 hour to adult patients screened positive for sepsis. Due to the small number of papers that addressed this volume of fluids in 1 hour, we expanded the search to include studies looking at 1-6 hours.

RESULTS

Seven full-text articles were identified, which investigated various aspects of the fluid resuscitation in adult sepsis. However, none answered completely to the original research question aimed to determine either the effect of time-to-crystalloids or the optimal fluid volume of resuscitation. Our findings demonstrated that in the USA/UK/Australia/Canada, adult ED septic patients receive 23-43 mL/kg of crystalloids during the first 6 hours of resuscitation without significant differences either in mortality or in adverse effects.

CONCLUSION

This systematic review did not find high-quality evidence supporting the administration of 30 mL/kg crystalloid bolus to adult septic patients within 1 hour of presentation in the ED. Future research must investigate both the benefits and the potential harms of the recommended intervention.

Crystalloid and Colloid Compositions and Their Impact

This manuscript will review crystalloid (hypo-, iso-, and hyper-tonic) and colloid (synthetic and natural) fluids that are available for intravenous administration with a focus on their electrolyte, acid-base, colligative, and rheological effects as they relate to each solution's efficacy and safety. The goal is for the reader to better understand the differences between each fluid and the influence on plasma composition, key organ systems, and their implications when used therapeutically in animals with critical illness.

Effects of 5% Albumin Plus Saline Versus Saline Alone on Outcomes From Large-Volume Resuscitation in Critically Ill Patients

OBJECTIVES

To compare 5% albumin with 0.9% saline for large-volume resuscitation (> 60 mL/Kg within 24 hr), on mortality and development of acute kidney injury.

DESIGN

Retrospective cohort study.

SETTING

Patients admitted to ICUs in 13 hospitals across Western Pennsylvania. We analyzed two independent cohorts, the High-Density Intensive Care databases: High-Density Intensive Care-08 (July 2000 to October 2008, H08) and High-Density Intensive Care-15 (October 2008 to December 2014, H15).

PATIENTS

Total of 18,629 critically ill patients requiring large-volume resuscitation.

INTERVENTIONS

Five percent of albumin in addition to saline versus 0.9% saline.

MEASUREMENTS AND MAIN RESULTS

After excluding patients with acute kidney injury prior to large-volume resuscitation, 673 of 2,428 patients (27.7%) and 1,814 of 16,201 patients (11.2%) received 5% albumin in H08 and H15, respectively. Use of 5% albumin was associated with decreased 30-day mortality by multivariate regression in H08 (odds ratio 0.65; 95% CI 0.49-0.85; p = 0.002) and in H15 (0.52; 95% CI 0.44-0.62; p < 0.0001) but was associated with increased acute kidney injury in H08 (odds ratio 1.98; 95% CI 1.56-2.51; p < 0.001) and in H15 (odds ratio 1.75; 95% CI 1.58-1.95; p < 0.001). However, 5% albumin was not associated with persistent acute kidney injury and resulted in decreased major adverse kidney event at 30, 90, and 365 days. Propensity matched analysis confirmed similar associations with mortality and acute kidney injury.

CONCLUSIONS

During large-volume resuscitation, 5% albumin was associated with reduced mortality and major adverse kidney event at 30, 90, and 365 days. However, a higher rate of acute kidney injury of any stage was observed that did not translate into persistent renal dysfunction.

Comparison of the Efficacy of Different Arterial Waveform-derived Variables (Pulse Pressure Variation, Stroke Volume Variation, Systolic Pressure Variation) for Fluid Responsiveness in Hemodynamically Unstable Mechanically Ventilated Critically Ill Patients

Introduction

This study was conducted to assess fluid responsiveness in critically ill patients to avoid various complications of fluid overload.

Material and methods

This study was done in an ICU of a tertiary care hospital after approval from the institute ethical committee over 18 months. A total of 54 consenting adult patients were included in the study. Patients were hemodynamically unstable requiring mechanical ventilation, had acute circulatory failure, or those with at least one clinical sign of inadequate tissue perfusion. All patients were ventilated using tidal volume of 6–8 mL/kg, RR—12–15/minutes, positive end expiratory pressure (PEEP)—5 cm of water, and plateau pressure was kept below 30 cm water. They were sedated throughout the study. The arterial line and the central venous catheter were placed and connected to Vigileo-FloTrac transducer (Edward Lifesciences). Patients were classified into responder and nonresponder groups on the basis of the cardiac index (CI) after fluid challenge of 10 mL/kg of normal saline over 30 minutes. Pulse pressure variation (PPV), stroke volume variation (SVV), and systolic pressure variation (SPV) were assessed and compared at baseline, 30 minutes, and 60 minutes.

Results

In our study we found that PPV and SVV were significantly lower among responders than nonresponders at 30 minutes and insignificant at 60 minutes. Stroke volume variation was 10.28 ± 1.76 in the responder compared to 12.28 ± 4.42 (p = 0.02) at 30 minutes and PPV was 15.28 ± 6.94 in responders while it was 20.03 ± 4.35 in nonresponders (p = 0.01). We found SPV was insignificant at all time periods among both groups.

Conclusion

We can conclude that initial assessment for fluid responsiveness in critically ill mechanically ventilated patients should be based on PPV and SVV to prevent complications of fluid overload and their consequences.

How to cite this article

Kumar N, Malviya D, Nath SS, Rastogi S, Upadhyay V. Comparison of the Efficacy of Different Arterial Waveform-derived Variables (Pulse Pressure Variation, Stroke Volume Variation, Systolic Pressure Variation) for Fluid Responsiveness in Hemodynamically Unstable Mechanically Ventilated Critically Ill Patients. Indian J Crit Care Med 2021;25(1):48–53.

Fluids in ARDS: more pros than cons

In acute respiratory distress syndrome (ARDS), increased pulmonary vascular permeability makes the lung vulnerable to edema. The use of conservative as compared to liberal fluid strategies may increase the number of ventilator-free days and survival, as well as reduce organ dysfunction. Monitoring the effects of fluid administration is of the utmost importance; dynamic indexes, such as stroke volume and pulse pressure variations, outperform static ones, such as the central venous pressure. The passive leg raise and end-expiratory occlusion tests are recommended for guiding fluid management decisions. The type of intravenous fluids should also be taken into consideration: crystalloids, colloids, and human albumin have all been used for fluid resuscitation. Recent studies have also shown differences in outcome between balanced and non-balanced intravenous solutions. In preclinical studies, infusion of albumin promotes maintenance of the glycocalyx layer, reduces inflammation, and improves alveolar-capillary membrane permeability. Fluids in ARDS must be administered cautiously, considering hemodynamic and perfusion status, oncotic and hydrostatic pressures, ARDS severity, fluid type, volume and infusion rate, and cardiac and renal function. Of note, no guideline to date has recommended a specific fluid composition for use in ARDS; most physicians currently follow recommendations for sepsis.

Understanding Volume Kinetics: The Role of Pharmacokinetic Modeling and Analysis in Fluid Therapy

Fluid therapy is a rapidly evolving yet imprecise clinical practice based upon broad assumptions, species-to-species extrapolations, obsolete experimental evidence, and individual preferences. Although widely recognized as a mainstay therapy in human and veterinary medicine, fluid therapy is not always benign and can cause significant harm through fluid overload, which increases patient morbidity and mortality. As with other pharmaceutical substances, fluids exert physiological effects when introduced into the body and therefore should be considered as "drugs." In human medicine, an innovative adaptation of pharmacokinetic analysis for intravenous fluids known as volume kinetics using serial hemoglobin dilution and urine output has been developed, refined, and investigated extensively for over two decades. Intravenous fluids can now be studied like pharmaceutical drugs, leading to improved understanding of their distribution, elimination, volume effect, efficacy, and half-life (duration of effect) under various physiologic conditions, making evidence-based approaches to fluid therapy possible. This review article introduces the basic concepts of volume kinetics, its current use in human and animal research, as well as its potential and limitations as a research tool for fluid therapy research in veterinary medicine. With limited evidence to support our current fluid administration practices in veterinary medicine, a greater understanding of volume kinetics and body water physiology in veterinary species would ideally provide some evidence-based support for safer and more effective intravenous fluid prescriptions in veterinary patients.

Crystalloids and colloids

Administration of intravenous fluid is like giving drugs, in that they have both beneficial and harmful effects. The composition of intravenous crystalloid and colloid fluids used for resuscitation is described in detail. The use of fluids for intravascular volume replacement is discussed as well as some of the controversies of this in haemorrhagic shock and septic shock.

Evaluation of the Distribution and Elimination of Balanced Isotonic Crystalloid, 5% Hypertonic Saline, and 6% Tetrastarch 130/0.4 Using Volume Kinetic Modeling and Analysis in Healthy Conscious Cats

This prospective, randomized, blinded, interventional cross-over study investigated the distribution, elimination, plasma volume expansion, half-life, comparative potency, and ideal fluid prescription of three commonly prescribed intravenous (IV) fluids in 10 healthy conscious cats using volume kinetic analysis that is novel to veterinary medicine. Each cat received 20 mL/kg of balanced isotonic crystalloid (PLA), 3.3 mL/kg of 5% hypertonic saline (HS), and 5 mL/kg of 6% tetrastarch 130/0.4 (HES) over 15 min on separate occasions. Hemoglobin concentration, red blood cell count, hematocrit, heart rate, and blood pressure were measured at baseline, 5, 10, 15, 20, 30, 40, 50, 60, and every 15 min until 180 min. Urine output was estimated every 30 min using point-of-care bladder ultrasonography. Plasma dilution derived from serial hemoglobin concentration and red blood cell count served as input variables for group and individual fluid volume kinetic analyses using a non-linear mixed effects model. In general, the distribution of all IV fluids was rapid, while elimination was slow. The half-lives of PLA, HS, and HES were 49, 319, and 104 min, respectively. The prescribed fluid doses for PLA, HS, and HES resulted in similar peak plasma volume expansion of 27–30%. The potency of HS was 6 times higher than PLA and 1.7 times greater than HES, while HES was 3.5 times more potent than PLA. Simulation of ideal fluid prescriptions to achieve and maintain 15 or 30% plasma volume expansion revealed the importance of a substantial reduction in infusion rates following initial IV fluid bolus. In conclusion, volume kinetic analysis is a feasible research tool that can provide data on IV fluid kinetics and body water physiology in cats. The rapid distribution but slow elimination of IV fluids in healthy conscious cats is consistent with anecdotal reports of fluid overload susceptibility in cats and warrants further investigation.

Iso-Oncotic Albumin Mitigates Brain and Kidney Injury in Experimental Focal Ischemic Stroke

Background: There is widespread debate regarding the use of albumin in ischemic stroke. We tested the hypothesis that an iso-oncotic solution of albumin (5%), administered earlier after acute ischemic stroke (3 h), could provide neuroprotection without causing kidney damage, compared to a hyper-oncotic albumin (20%) and saline.

Objective: To compare the effects of saline, iso-oncotic albumin, and hyper-oncotic albumin, all titrated to similar hemodynamic targets, on the brain and kidney.

Methods: Ischemic stroke was induced in anesthetized male Wistar rats (n = 30; weight 437 ± 68 g) by thermocoagulation of pial blood vessels of the primary somatosensory, motor, and sensorimotor cortices. After 3 h, animals were anesthetized and randomly assigned (n = 8) to receive 0.9% NaCl (Saline), iso-oncotic albumin (5% ALB), and hyper-oncotic albumin (20% ALB), aiming to maintain hemodynamic stability (defined as distensibility index of inferior vena cava <25%, mean arterial pressure >80 mmHg). Rats were then ventilated using protective strategies for 2 h. Of these 30 animals, 6 were used as controls (focal ischemic stroke/no fluid).

Results: The total fluid volume infused was higher in the Saline group than in the 5% ALB and 20% ALB groups (mean ± SD, 4.3 ± 1.6 vs. 2.7 ± 0.6 and 2.6 ± 0.5 mL, p = 0.03 and p = 0.02, respectively). The total albumin volume infused (g/kg) was higher in the 20% ALB group than in the 5% ALB group (1.4 ± 0.6 vs. 0.4 ± 0.2, p < 0.001). Saline increased neurodegeneration (Fluoro-Jade C staining), brain inflammation in the penumbra (higher tumor necrosis factor-alpha expression), and blood-brain barrier damage (lower gene expressions of claudin-1 and zona occludens-1) compared to both iso-oncotic and hyper-oncotic albumins, whereas it reduced the expression of brain-derived neurotrophic factor (a marker of neuroregeneration) compared only to iso-oncotic albumin. In the kidney, hyper-oncotic albumin led to greater damage as well as higher gene expressions of kidney injury molecule-1 and interleukin-6 than 5% ALB (p < 0.001).

Conclusions: In this model of focal ischemic stroke, only iso-oncotic albumin had a protective effect against brain and kidney damage. Fluid therapy thus requires careful analysis of impact not only on the brain but also on the kidney.

All-Polysaccharide, Self-Healing Injectable Hydrogels Based on Chitosan and Oxidized Hydroxypropyl Polysaccharides

Polysaccharide-based hydrogels are attractive materials for biomedical applications for reasons that include their polyfunctionality, generally benign nature, and biodegradability. However, the use of polysaccharide-based hydrogels may be limited by toxicity arising from small-molecule crosslinkers, or may involve undesired chemical modification [Hennink, W. E.; et al. Adv. Drug Delivery Rev. 2012, 64, 223-236]. Here, we report a green, simple, efficient strategy for the preparation of polysaccharide-based, in situ forming hydrogels. The Edgar group reports in the accompanying manuscript that chemoselective oxidation of oligo(hydroxypropyl)-substituted polysaccharides introduces ketone groups at the termini of the side chains [Nichols, B. L. B.; et al]. Amine-containing moieties can condense with ketones to form imines. The imine linkage is dynamic in the presence of water, providing the potential for self-healing [Wei, Z.; et al. Adv. Funct. Mater. 2015, 25, 1352-1359], injectability [Wei, Z.; et al. Adv. Funct. Mater. 2015, 25, 1352-1359], and pH responsiveness [Yao, K.; et al. J. Appl. Polym. Sci. 1993, 48, 343-354]. In this work, we designed and prepared two different types of hydrogels, oxidized hydroxypropyl cellulose/chitosan (Ox-HPC-Chitosan) and oxidized hydroxypropyl dextran/chitosan (Ox-HPD-Chitosan), each cross-linked by imine bonds. The mechanical properties of these hydrogels were characterized by rheometry, revealing that hydrogel storage modulus could be tuned from 300 Pa to 13 kPa simply by controlling the degree of substitution (DS) of ketone groups. Rheological characterization also illustrated the rapid self-healing property of these all-polysaccharide hydrogels. Moreover, these hydrogels exhibited high swelling rates and facile injectability. Therefore, this work reveals a potential strategy for the construction of hydrogels that require no small-molecule crosslinkers and are therefore highly attractive for biomedical, agricultural, controlled release, and other applications.

Systemic and microvascular comparison of Lactated Ringer's solution, VIR-HBOC, and alpha-alpha crosslinked haemoglobin-based oxygen carrier in a rat 10% topload model

Medical support for traumatic haemorrhage is lacking for far-forward combat units. VIR-HBOC (haemoglobin-based oxygen carrier) is a novel biological therapeutic under development as a field-stable resuscitation fluid. HBOCs have a long history of complications, chief among them is vasoconstrictive hypertension, which must be resolved before efficacy testing. As such, VIR-HBOC was compared against Lactated Ringers (LRS; vehicle) and a cross-linked haemoglobin (ααHb; a known vasoactive HBOC) in a rat topload model. Twenty-three male, Sprague Dawley rats were randomly assigned to receive a 10% infusion (estimated total blood volume) of one test article while normotensive and under anaesthesia. Cardiovascular, blood chemistry and oximetry, microvascular arteriolar diameters, and interstitial tissue oxygenation parameters were measured. Circulatory half-life was calculated by plasma total haemoglobin. Treatment with ααHb caused immediate increases in mean arterial pressure compared to LRS and VIR-HBOC groups, and corresponding arteriolar vasoconstriction (p < .05), which did not occur for LRS or VIR-HBOC. Circulatory half-lives for VIR-HBOC and ααHb were calculated as 340 and 157 min, respectively. This first report of VIR-HBOC showed no evidence of a hypertensive or vasoactive effect. It was well-tolerated over the eight-hour time course of this topload model, which warrants further investigation in studies of haemorrhagic shock.