Acute change in extracellular fluids associated with major surgical procedures

The effect of restrictive compared to liberal intravenous fluid volume on hypotension in adults undergoing major abdominal surgery

In a cardiac output (CO) sub-study of the Restrictive versus Liberal Fluid Therapy in Major Abdominal Surgery (RELIEF) trial, it was shown that restrictive fluid management was associated with lower cardiac index at the end of surgery. However, the association of the fluid protocol with intraoperative blood pressure was less clear. This paper primarily compares rates of hypotension between the two fluid regimens. The haemodynamic effects of these protocols may increase our understanding of perioperative fluid prescription. Using a data set of arterial pressure and cardiac output measurements, this observational cohort study primarily compares intraoperative hypotension rates defined by a mean arterial pressure < 65 mmHg between liberal and restrictive fluid protocols. Secondary analyses explore predictors of invasive mean arterial pressure and doppler-derived cardiac output, including fluid volume regimens and surgical duration. 105 patients had a combined total of 835 haemodynamic data capture events from the beginning to the end of the surgery. Here we report that a restrictive regimen is not associated with a greater proportion of participants who experience at least one episode of hypotension than the liberal regimen 64.1% vs. 61.5% (mean difference 2.6%, 95% CI - 15.9% to 21%, p = 0.78). Duration of surgery was associated with an increased risk of hypotension (OR 1.05, 1 to 1.1, p = 0.038). A fluid restriction protocol compared to liberal fluid administration is not associated with lower blood pressure.

Risk factors for venous thrombosis after esophagectomy

BACKGROUND

Venous thrombosis (VT) after esophagectomy for esophageal cancer is an important complication, potentially leading to pulmonary embolism. However, there are few available information about the risk for the postsurgical VT.

METHODS

This study included 271 patients who underwent esophagectomy for esophageal cancer between 2006 and 2019. Contrast-enhanced computed tomography (CT) was performed for all patients on the seventh postoperative day to survey complications, including VT.

RESULTS

VT was radiologically visualized in 48 patients (17.7%), 8 of whom (16.7%) had pulmonary embolism. The thrombus disappeared in 42 patients, the thrombus size was unchanged in 5 patients, and 1 patient died. Multivariate analysis was performed on factors clinically considered to have a significant influence on thrombus formation. The analysis showed that CVC insertion via the femoral vein (odds ratio, 7.67; 95% CI, 2.64-22.27; P < 0.001), retrosternal reconstruction route (odds ratio, 3.94; 95% CI, 1.90-8.17; P < 0.001) and intraoperative fluid balance < 5 ml/kg/hr (odds ratio, 0.38; 95% CI, 0.17-0.85; P = 0.019) were independently related to VT.

CONCLUSIONS

Intraoperative fluid balance < 5 ml/kg/hr, along with CVC insertion via the femoral vein and retrosternal reconstruction may be potential risk factors for VT after esophagectomy.

Resuscitation and Care in the Trauma Bay

Start balanced resuscitation early (pre-hospital if possible), either in the form of whole blood or 1:1:1 ratio. Minimize resuscitation with crystalloid to minimize patient morbidity and mortality. Trauma-induced coagulopathy can be largely avoided with the use of balanced resuscitation, permissive hypotension, and minimized time to hemostasis. Using protocolized "triggers" for massive and ultramassive transfusion will assist in minimizing delays in transfusion of products, achieving balanced ratios, and avoiding trauma induced coagulopathy. Once "audible" bleeding has been addressed, further blood product resuscitation and adjunct replacement should be guided by viscoelastic testing. Early transfusion of whole blood can reduce patient morbidity, mortality, decreases donor exposure, and reduces nursing logistics during transfusions. Adjuncts to resuscitation should be guided by laboratory testing and carefully developed, institution-specific guidelines. These include empiric calcium replacement, tranexamic acid (or other anti-fibrinolytics), and fibrinogen supplementation.

Perioperative Fluid Management

The medical complexity of the geriatric patients has been steadily rising. Still, as outcomes of surgical procedures in the elderly are improving, centers are pushing boundaries. There is also a growing appreciation of the importance of perioperative fluid management on postoperative outcomes, especially in the elderly. Optimal fluid management in this cohort is challenging due to the combination of age-related physiological changes in organ function, increased comorbid burden, and larger fluid shifts during more complex surgical procedures. The current state-of-the-art approach to fluid management in the perioperative period is outlined.

The kinetics of isotonic and hypertonic resuscitation fluids is dependent on the sizes of the body fluid volumes

Background and Aims

The extracellular and intracellular fluid volumes (ECV and ICV) vary not only with age, gender, and body weight but also with the habitual intake of water. The present study examines whether the baseline variations in the ECV and ICV change the distribution and elimination of subsequently given infusion fluids.

Material and Methods

Twenty healthy male volunteers underwent 50 infusion experiments with crystalloid fluid for which the fluid volume kinetics was calculated based on frequent measurements of the hemodilution using mixed-effects modeling software. The results were compared with the ECV and ICV measured with multifrequency bioimpedance analysis before each infusion started. The fluids were given over 30 minutes and comprised 25 mL/kg Ringer's acetate (N = 20), Ringer's lactate, 5 mL/kg 7.5% saline, and 3 mL/kg 7.5% saline in 6% dextran 70 (these fluids, N = 10).

Results

A large ICV was associated with a small extravascular accumulation of infused fluid, which increased the plasma volume expansion and the urinary excretion. With hypertonic fluid, a large ECV greatly accelerated urinary excretion. The body weight did not serve as a covariate in the kinetic models. Albumin was recruited to the plasma during infusion of both types of fluid. The hypertonic fluids served as diuretics. The infused excess sodium and osmolality were distributed over a 35% larger space than the sum of the ECV and ICV.

Conclusion

A large ICV reduced the rate of distribution of Ringer's solution, whereas a large ECV accelerated the excretion of hypertonic saline.

Perioperative Hypertension Etiologies in Patients Undergoing Noncardiac Surgery in University Health Network Hospitals–Canada from 2015–2020

Introduction

Perioperative hypertension, defined as increased blood pressure around the surgery, is a known risk factor for perioperative complications, including cardiovascular events. Identifying reasons associated with hypertension in each period is of great help in preventing and better managing perioperative hypertension.

Objective

The aim of the study was to explore common etiologies of hypertension during the perioperative period (pre, intra, and post-operation) in patients who underwent noncardiac surgeries in University Health Network (UHN) hospitals, Canada, from 2015 to 2020.

Patients and Methods

We retrospectively analyzed the medical records of 174 patients undergoing noncardiac surgeries who experienced perioperative hypertension. We assessed the prevalence of 10 reasons for perioperative hypertension as a whole and also each period separately according to the physicians’ notes in patients’ medical records. Two-way measurements ANOVA was used to determine the change of mean hypertension among patients for specific etiology.

Results

The common etiologies of perioperative hypertension were poorly controlled hypertension (21.8%), excessive fluid therapy (19.5%), excessive vasopressor (18.4%), and medication withdrawal (13.7%). Regarding each period separately, the most common reasons were poorly controlled hypertension for pre (42.9%) and intraoperative period (22.7%) and fluid overload for the postoperative period (20.1%). Poor control of hypertension showed both within-subject statistical significance for systolic and between-subject statistical significance for diastolic blood pressure.

Conclusion

Poorly controlled hypertension is the most significant etiology of perioperative hypertension in patients undergoing noncardiac surgeries. Apart from poorly controlled hypertension, as a patient-related factor, iatrogenic factors such as excessive vasopressor therapy, aggressive fluid replacement and poor management of antihypertensive medications can also cause perioperative hypertension.

Postoperative fluid balance and outcomes after Pancreaticoduodenectomy: a retrospective study in 301 patients

BACKGROUND

The incidence of postoperative morbidity after pancreaticoduodenectomy (PD) is high; however, whether fluid management after surgery affects postoperative morbidity is unclear. This study aimed to determine whether fluid balance in patients undergoing PD is associated with postoperative complications and mortality.

METHODS

Data from a computer-based database of patients who underwent PD between 2016 and 2019 were retrospectively analyzed. Patients were stratified into four quartiles according to their fluid balance at 0-24, 24-48, 48-72, and 72-96 h after surgery. The predefined primary outcome measures were morbidity and mortality rates.

RESULTS

A total of 301 patients were included. The morbidity and mortality rates in the cohort were 56.5% and 3.7%, respectively. The most common complications after PD were postoperative pancreatic fistula (31.9%) and delayed gastric emptying (31.6%). Patients with a higher fluid balance in the 0-24-, 24-48-, and 48-72-h postoperative periods had a higher morbidity rate and longer hospital stay than those with a lower fluid balance (all P < 0.05). Patients with a fluid balance of 4212 mL during the postoperative 0-72 h were most likely to develop complications (P < 0.001). The area under the receiver operating characteristic curve was 0.71 (0.65-0.77), with a sensitivity of 58.24% and a specificity of 77.10%.

CONCLUSIONS

Higher postoperative fluid balance seems to be associated with increased morbidity after PD compared to lower fluid balance. Surgeons should pay close attention to the occurrence of complications in patients with a high fluid balance.

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.

Fluid escapes to the "third space" during anesthesia, a commentary

BACKGROUND

The "third fluid space" is a concept that has caused much confusion for more than half a century, dividing anesthesiologists into believers and non-believers.

AIM

To challenge the existence of the "third fluid space" based on analysis of crystalloid fluid kinetics.

METHODS

Data on hemodilution patterns from 157 infusion experiments performed in volunteers and from 85 patients undergoing surgery under general anesthesia were studied by population volume kinetic analysis. Elimination of infused crystalloid fluid from the kinetic model could occur either as urine or "third space" accumulation. The latter fluid volume remained in the body, but without equilibrating with the plasma within the 3-4 h of the experiment.

RESULTS

The rate constant for "third space" loss of fluid accounted for 20% of the elimination in conscious volunteers and for 75% during general anesthesia and surgery. The two elimination constants showed a reciprocal relationship, resulting in that "third-space" losses increase when urinary excretion is restricted. The effect on the plasma volume was smaller than indicated by these figures because fluid distributed to the extravascular space continuously redistributed to the plasma. Worked-out examples show that one-third of an infused crystalloid volume has been confined to the "third space" after 3 h of surgery. When equilibration with the plasma eventually occurs, which is necessary for excretion of the fluid, is not known.

CONCLUSION

During anesthesia and surgery one third of the infused crystalloid fluid is at least temporarily unavailable for excretion, which probably contributes to postoperative weight increase and edema.

Perioperative Fluid Restriction in Abdominal Surgery: A Systematic Review and Meta-analysis

BACKGROUND

Perioperative fluid management is a critical component in patients undergoing abdominal surgery. However, the benefit of restricted fluid regimen remains inconclusive. This systematic review aimed to explore potential factors causing these inconsistent findings.

METHODS

The literature searches were performed in three databases including PubMed, Embase, and the Cochrane library until August 30, 2018. Only randomized, controlled trials comparing the effect of restricted versus liberal regimen in abdominal surgery were included. The primary outcome was total postoperative complications. Subgroup analysis was performed according to between-group weight increase difference (≥ 2 kg and < 2 kg) and fluid intake ratio (≥ 1.8 and < 1.8).

RESULTS

Sixteen studies were finally included in this meta-analysis. The benefit of the restricted regimen in reducing postoperative complication was only significant in the subgroup with high weight increase difference (≥ 2 kg) (RR 0.67, 95% CI 0.57-0.79) and the subgroup with high fluid intake ratio (≥ 1.8) (RR 0.72, 95% CI 0.62-0.82). In the subgroup with low weight increase difference (< 2 kg) or low fluid intake ratio (< 1.8), the effect of the restricted regimen was not significant (RR 0.88, 95% CI 0.51-1.50, and RR 1.18, 95% CI 0.91-1.53, respectively).

CONCLUSIONS

The benefit of the restricted regimen was only significant in the subgroup with high weight increase difference (≥ 2 kg) or high fluid intake ratio (≥ 1.8).

Damage control resuscitation

The United States Navy originally utilized the concept of damage control to describe the process of prioritizing the critical repairs needed to return a ship safely to shore during a maritime emergency. To pursue a completed repair would detract from the goal of saving the ship. This concept of damage control management in crisis is well suited to the care of the critically ill trauma patient, and has evolved into the standard of care. Damage control resuscitation is not one technique, but, rather, a group of strategies which address the lethal triad of coagulopathy, acidosis, and hypothermia. In this article, we describe this approach to trauma resuscitation and the supporting evidence base.

[Perioperative fluid management]

An appropriate perioperative infusion management is pivotal for the perioperative outcome of the patient. Optimization of the perioperative fluid treatment often results in enhanced postoperative outcome, reduced perioperative complications and shortened hospitalization. Hypovolemia as well as hypervolemia can lead to an increased rate of perioperative complications. The main goal is to maintain perioperative euvolemia by goal-directed therapy (GDT), a combination of fluid management and inotropic medication, to optimize perfusion conditions in the perioperative period; however, perioperative fluid management should also include the preoperative and postoperative periods. This encompasses the preoperative administration of carbohydrate-rich drinks up to 2 h before surgery. In the postoperative period, patients should be encouraged to start per os hydration early and excessive i.v. fluid administration should be avoided. Implementation of a comprehensive multimodal, goal-directed fluid management within an enhanced recovery after surgery (ERAS) protocol is efficient but the exact status of indovodual items remains unclear at present.

Management of perioperative volume therapy - monitoring and pitfalls

Over 300 million surgical procedures are performed every year worldwide. Anesthesiologists play an important role in the perioperative process by assessing the overall risk of surgery and aim to reduce the risk of complications. Perioperative hemodynamic and volume management can help to improve outcomes in perioperative patients. There has been ongoing discussion about goal-directed therapy. However, there is a consensus that fluid overload and severe fluid depletion in the perioperative period are harmful and can lead to adverse outcomes. This article provides an overview of how to evaluate the fluid responsiveness of patients, details which parameters could be used, and what limitations should be noted.

Perioperative Acute Kidney Injury

Perioperative organ injury is among the leading causes of morbidity and mortality of surgical patients. Among different types of perioperative organ injury, acute kidney injury occurs particularly frequently and has an exceptionally detrimental effect on surgical outcomes. Currently, acute kidney injury is most commonly diagnosed by assessing increases in serum creatinine concentration or decreased urine output. Recently, novel biomarkers have become a focus of translational research for improving timely detection and prognosis for acute kidney injury. However, specificity and timing of biomarker release continue to present challenges to their integration into existing diagnostic regimens. Despite many clinical trials using various pharmacologic or nonpharmacologic interventions, reliable means to prevent or reverse acute kidney injury are still lacking. Nevertheless, several recent randomized multicenter trials provide new insights into renal replacement strategies, composition of intravenous fluid replacement, goal-directed fluid therapy, or remote ischemic preconditioning in their impact on perioperative acute kidney injury. This review provides an update on the latest progress toward the understanding of disease mechanism, diagnosis, and managing perioperative acute kidney injury, as well as highlights areas of ongoing research efforts for preventing and treating acute kidney injury in surgical patients.

The Effect of Adding Dopamine Infusion to Noradrenaline Infusion Combined With Restrictive Hydration on Renal Function and Tissue Perfusion during Open Abdominal Surgeries

Objectives

This study was designed to assess the effect of adding dopamine infusion in addition to restrictive hydration combined with noradrenaline infusion on intraoperative renal function and serum lactate levels in comparison to restrictive hydration combined with noradrenaline infusion only and standard hydration during open abdominal surgeries.

Patients and Methods

One hundred and twenty patients were randomly assigned into three equal groups undergoing major open abdominal procedures. In Group I, dopamine infusion in addition to norepinephrine infusion were administered with restrictive hydration. In Group II, norepinephrine infusion was started before the induction of anesthesia with restrictive hydration. In Groups I and II, Ringer's solution was infused at a fixed rate of 2 mL.kg^-1.h^-1 until the end of surgery. In Group III, the conventional fluid replacement was introduced according maintenance, fluid deficit and third space loss. The outcome to be assessed was serial measurements of creatinine and serum lactate levels preoperatively, intraoperatively, and just postoperatively in addition to after 24 h.

Results

Serum lactate level was significantly low in Groups I and II than that in Group III intraoperatively and postoperatively. In addition, urine output was significantly more in Group I and Group III than in Group II. Creatinine level was higher with significance in Group II than in Group I and III 24 h postoperatively.

Conclusion

Dopamine infusion, when added to norepinephrine infusion combined with restricted hydration, improved urine output and creatinine level. Tissue perfusion as indicated by serum lactate level was more adequate in Groups I and II than that in Group III.

Restrictive Versus Liberal Fluid Regimens in Patients Undergoing Pancreaticoduodenectomy: a Systematic Review and Meta-Analysis

BACKGROUND

Pancreaticoduodenectomy is associated with significant morbidity and mortality which may be influenced by perioperative fluid management. It remains unclear whether liberal and restrictive fluid regimens impact mortality and morbidity in patients undergoing pancreaticoduodenectomy.

METHODS

Medline, EMBASE, Cochrane Library and clinicaltrials.gov were searched for studies comparing restrictive and liberal perioperative fluids in patients undergoing pancreaticoduodenectomy. Both prospective and retrospective studies in those undergoing pancreaticoduodenectomy were eligible for inclusion where the patient outcomes were stratified to restrictive and liberal perioperative fluid management regimens, with mortality as the primary outcome. Following study identification, a systematic review and meta-analysis with trial sequential analysis was completed.

RESULTS

Thirteen studies including five prospective trials and eight retrospective analyses totalling 3062 patients were included. Restrictive fluid regimens were associated with a significant reduction in mortality compared to liberal fluid regimens for the overall cohort (odds ratio 0.54; 95% CI 0.31-0.94, p = 0.03). There were no significant differences in complication profile. Subgroup analysis revealed this result was contributed to significantly by retrospective studies. The results of the trial sequential analysis suggest this mortality benefit may be due to a type I statistical error and that further patient numbers are required for definitive conclusions.

CONCLUSIONS

Restrictive fluid regimens are associated with a reduction in mortality following pancreaticoduodenectomy. The clinical relevance of this finding needs to be interpreted pragmatically given the lack of association with significant causes of morbidity and in considering the results of the recently published RELIEF study.

Supplemental perioperative intravenous crystalloids for postoperative nausea and vomiting

BACKGROUND

Postoperative nausea and vomiting (PONV) is a common complication following general anaesthesia. It may be associated with patient dissatisfaction, increased costs of treatment, and unintended admission to hospital.Supplemental intravenous crystalloid administration in the perioperative period may be a simple intervention to prevent PONV.

OBJECTIVES

To assess whether supplemental intravenous crystalloid administration prevents PONV in patients undergoing surgical procedures under general anaesthesia.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2018, Issue 7), MEDLINE (1946 to August 2018), Embase (1947 to August 2018), and the Cumulative Index of Nursing and Allied Health Literature (CINAHL; 1971 to August 2018). We searched clinical trials registers for ongoing or unpublished completed studies (August 2018), handsearched three major journals (British Journal of Anaesthesia, European Journal of Anaesthesiology, and Anesthesiology; August 2018), and conducted backward and forward citation searching of relevant articles.

SELECTION CRITERIA

We included randomized controlled trials of participants older than six months undergoing surgical procedures under general anaesthesia and given supplemental perioperative intravenous crystalloids, defined as a volume larger than that received by a comparator group, to prevent PONV.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures described by Cochrane.

MAIN RESULTS

We included 41 studies (4224 participants). Participants underwent ambulatory or short length of stay surgical procedures, and were predominantly American Society of Anesthesiology (ASA) class I or II. There is one study awaiting classification and three ongoing studies. All studies took place in surgical centres, and were conducted in geographically diverse settings. Risk of bias was generally unclear across all domains.Supplemental intravenous crystalloid administration probably reduces the cumulative risk of postoperative nausea (PON) (risk ratio (RR) 0.62, 95% confidence interval (CI) 0.51 to 0.75; 18 studies; 1766 participants; moderate-certainty evidence). When the postoperative period was divided into early (first six hours postoperatively) and late (at the time point closest to or including 24 hours postoperatively) time points, the intervention reduced the risk of early PON (RR 0.67, 95% CI 0.58 to 0.78; 20 studies; 2310 participants; moderate-certainty evidence) and late PON (RR 0.47, 95% CI 0.32 to 0.69; 17 studies; 1682 participants; moderate-certainty evidence).Supplemental intravenous crystalloid administration probably reduces the risk of postoperative vomiting (POV) (RR 0.50, 95% CI 0.40 to 0.63; 20 studies; 1970 participants; moderate-certainty evidence). The intervention specifically reduced both early POV (RR 0.56, 95% CI 0.41 to 0.76; 19 studies; 1998 participants; moderate-certainty evidence) and late POV (RR 0.48, 95% CI 0.29 to 0.79; 15 studies; 1403 participants; moderate-certainty evidence).Supplemental intravenous crystalloid administration probably reduces the need for pharmacologic treatment of PONV (RR 0.62, 95% CI 0.51 to 0.76; 23 studies; 2416 participants; moderate-certainty evidence).The effect of supplemental intravenous crystalloid administration on the risk of unplanned postoperative admission to hospital is unclear (RR 1.05, 95% CI 0.77 to 1.43; 3 studies; 235 participants; low-certainty evidence).No studies reported serious adverse events that may occur following supplemental perioperative intravenous crystalloid administration (i.e. admission to high-dependency unit, postoperative cardiac or respiratory complication, or death).

AUTHORS' CONCLUSIONS

There is moderate-certainty evidence that supplemental perioperative intravenous crystalloid administration reduces PON and POV, in ASA class I to II patients receiving general anaesthesia for ambulatory or short length of stay surgical procedures. The intervention probably also reduces the risk of pharmacologic treatment for PONV. The effect of the intervention on the risk of unintended postoperative admission to hospital is unclear. The risk of serious adverse events resulting from supplemental perioperative intravenous crystalloid administration is unknown as no studies reported this outcome. The one study awaiting classification may alter the conclusions of the review once assessed.

Restrictive versus Liberal Fluid Therapy for Major Abdominal Surgery

BACKGROUND

Guidelines to promote the early recovery of patients undergoing major surgery recommend a restrictive intravenous-fluid strategy for abdominal surgery. However, the supporting evidence is limited, and there is concern about impaired organ perfusion.

METHODS

In a pragmatic, international trial, we randomly assigned 3000 patients who had an increased risk of complications while undergoing major abdominal surgery to receive a restrictive or liberal intravenous-fluid regimen during and up to 24 hours after surgery. The primary outcome was disability-free survival at 1 year. Key secondary outcomes were acute kidney injury at 30 days, renal-replacement therapy at 90 days, and a composite of septic complications, surgical-site infection, or death.

RESULTS

During and up to 24 hours after surgery, 1490 patients in the restrictive fluid group had a median intravenous-fluid intake of 3.7 liters (interquartile range, 2.9 to 4.9), as compared with 6.1 liters (interquartile range, 5.0 to 7.4) in 1493 patients in the liberal fluid group (P<0.001). The rate of disability-free survival at 1 year was 81.9% in the restrictive fluid group and 82.3% in the liberal fluid group (hazard ratio for death or disability, 1.05; 95% confidence interval, 0.88 to 1.24; P=0.61). The rate of acute kidney injury was 8.6% in the restrictive fluid group and 5.0% in the liberal fluid group (P<0.001). The rate of septic complications or death was 21.8% in the restrictive fluid group and 19.8% in the liberal fluid group (P=0.19); rates of surgical-site infection (16.5% vs. 13.6%, P=0.02) and renal-replacement therapy (0.9% vs. 0.3%, P=0.048) were higher in the restrictive fluid group, but the between-group difference was not significant after adjustment for multiple testing.

CONCLUSIONS

Among patients at increased risk for complications during major abdominal surgery, a restrictive fluid regimen was not associated with a higher rate of disability-free survival than a liberal fluid regimen and was associated with a higher rate of acute kidney injury. (Funded by the Australian National Health and Medical Research Council and others; RELIEF ClinicalTrials.gov number, NCT01424150 .).

Randomized Comparison of Oral and Intravenous Fluid Regimens after Gallbladder Surgery

Numerous studies of post-operative fluid status have utilized sophisticated measurements of electrolyte distribution and fluid shift without relating results to clinical practice. The aim of this prospective randomized study was to investigate the response of patients undergoing abdominal surgery of moderate severity to conservative post-operative fluid administration. Forty-five patients undergoing open cholecystectomy were randomized to receive 2.51 of fluid (1 l normal saline and 1.51 5% dextrose), 1 l of normal saline, or free oral fluids (groups 1, 2, 3, respectively). Serum and urine osmolality and electrolytes were measured pre-operatively and at 24 and 48 h post-operatively. Patients remained in the study irrespective of the urine output. Plasma electrolytes and osmolality remained within normal limits in all three groups despite significant changes in urine electrolyte and osmolality in groups 2 and 3. This confirms that a conservative approach to fluid administration has no detrimental effect on hydration in fit patients with uncomplicated surgery.

R A Cowley, the “Golden Hour,” the “Momentary Pause,” and the “Third Space”

R Adams Cowley (1917–1991), the Baltimore thoracic and trauma surgeon, was an outstanding politician and promoter of emergency medical services. His skills included the effective use of language, for example, identifying the critical time immediately after injury as a “golden hour,” and describing shock as a “momentary pause in the act of death.” Conversely, Cowley avoided the tendency of some contemporaries to justify massive crystalloid infusion by invoking a “third space.” Cowley is often assumed to have originated the first two phrases, but, in fact, their histories go back at least to the 19th century and illustrate the development of surgical science. The “third space” is often assumed to have originated with Cowley's contemporary, Tom Shires (1925–2007), but, in fact, neither of them used the phrase to describe Shires’ controversial theories about an extracellular fluid deficit after trauma. Reviewing the actual etymology of these terms may help clarify the history of the underlying scientific ideas and enable more effective communication in the future.

Resuscitation for Hypovolemic Shock

Hemorrhage is the leading cause of preventable deaths in trauma patients. After presenting a brief history of hemorrhagic shock resuscitation, this article discusses damage control resuscitation and its adjuncts. Massively bleeding patients in hypovolemic shock should be treated with damage control resuscitation principles including limited crystalloid, whole blood or balance blood component transfusion to permissive hypotension, preventing hypothermia, and stopping bleeding as quickly as possible.

Endothelial Glycocalyx and Cardiopulmonary Bypass

On the outer surface of a human cell there is a dense layer of complex carbohydrates called glycocalyx, also referred to as glycans or the sugar coating on the cell surface, which is composed of a complex array of oligosaccharide and polysaccharide glucose chains that are covalently bonded to proteoglycans and lipids bound to the cell membrane surface. Studies of an intact endothelial glycocalyx layer (EGL) have revealed a number of critical functions that relate the importance of this protective layer to vascular integrity and permeability. These functions include the following: stabilization and maintenance of the vascular endothelium, an active reservoir of essential plasma proteins (i.e., albumin, antithrombin, heparan sulfate, and antioxidants), a buffer zone between the blood (formed elements) and the surface of the endothelium, and a mechanotransducer to detect changes in shear stress that facilitate vascular tone. There have been numerous review articles about the structure and function of endothelial glycocalyx over the past two decades, yet there still remains a significant knowledge gap in the perfusion literature around the importance of EGL. Perioperative fluid management and gaseous microemboli can both contribute to the damage/degradation of endothelial glycocalyx. A damaged EGL can result in systemic and myocardial edema, platelet and leukocyte adhesion, fluid extravasation, and contributes to microvascular perfusion heterogeneity. Knowledge of the importance of endothelial glycocalyx will enable clinicians to have a better understanding of the impact of gaseous microbubbles, hyperoxia, and ischemic reperfusion injury during cardiac surgery. The purpose of this article is to provide an in depth review of the EGL and how this protective barrier impacts the microcirculation, fluid homeostasis, inflammation, and edema during cardiac surgery.

Restrictive versus liberal fluid therapy in major abdominal surgery (RELIEF): rationale and design for a multicentre randomised trial

INTRODUCTION

The optimal intravenous fluid regimen for patients undergoing major abdominal surgery is unclear. However, results from many small studies suggest a restrictive regimen may lead to better outcomes. A large, definitive clinical trial evaluating perioperative fluid replacement in major abdominal surgery, therefore, is required.

METHODS/ANALYSIS

We designed a pragmatic, multicentre, randomised, controlled trial (the RELIEF trial). A total of 3000 patients were enrolled in this study and randomly allocated to a restrictive or liberal fluid regimen in a 1:1 ratio, stratified by centre and planned critical care admission. The expected fluid volumes in the first 24 hour from the start of surgery in restrictive and liberal groups were ≤3.0 L and ≥5.4 L, respectively. Patient enrolment is complete, and follow-up for the primary end point is ongoing. The primary outcome is disability-free survival at 1 year after surgery, with disability defined as a persistent (at least 6 months) reduction in functional status using the 12-item version of the World Health Organisation Disability Assessment Schedule.

ETHICS/DISSEMINATION

The RELIEF trial has been approved by the responsible ethics committees of all participating sites. Participant recruitment began in March 2013 and was completed in August 2016, and 1-year follow-up will conclude in August 2017. Publication of the results of the RELIEF trial is anticipated in early 2018.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov identifier NCT01424150.

Pancreatoduodenectomy and the risk of complications from perioperative fluid administration

BACKGROUND

The dogma of administering sufficient intravenous fluids aggressively to avoid under-resuscitation has recently been challenged. Evidence suggests that excessive perioperative fluid administration may be associated with negative clinical outcomes in gastrointestinal surgery. This study examines the impact of fluid administration on perioperative outcomes in patients undergoing pancreatoduodenectomy (PD).

METHODS

A retrospective analysis of 202 patients undergoing PD between January 2004 and August 2015 was performed. A cut-off value of 10 mL/kg/h was applied (low fluid group: <10 mL/kg/h versus high fluid group: ≥10 mL/kg/h).

RESULTS

There were 76 patients in the low fluid group and 126 patients in the high fluid group. Both groups had comparable age, American Society of Anesthesiologists score and preoperative morbidity rates. Patients in the high fluid group received significantly more total fluids, crystalloids and colloids intraoperatively (P < 0.0001, P < 0.0001 and P = 0.013, respectively) without a significant difference in estimated blood loss (P = 0.586). The net fluid balance on post-operative day 0 was also significantly higher in the high fluid group (P < 0.0001). The mortality rate was 0% in the cohort. Major morbidity rate was 46.1% and 44.4% in low and high fluid groups, respectively (P = 0.836). Reoperation rate was 5.3% for the low fluid group and 1.6% for the high fluid group (P = 0.136). There were no significant differences between the groups for any of the individual complications.

CONCLUSION

This study did not identify a difference in post-operative outcomes between the low and high fluid regime in patients undergoing PD.

Intraoperative fluid management

Evidence-based medicine has been slow to address the critically important issue of intraoperative fluid maintenance for surgical patients. A "rule" published by Holliday and colleagues in 1957 was the accepted practice for the initial calculation of fluid maintenance for nearly 50 years. Using this formula, the nil per os fluid deficit was based on how long it had been since the preoperative patient had last consumed anything by mouth, even water. New technology and monitoring modalities are being used to guide evidence-supported intraoperative care, leading to better outcomes for surgical patients.

Liberal or restrictive fluid management during elective surgery: a systematic review and meta-analysis

This article reviews if a restrictive fluid management policy reduces the complication rate if compared to liberal fluid management policy during elective surgery. The PubMed database was explored by 2 independent researchers. We used the following search terms: "Blood transfusion (MESH); transfusion need; fluid therapy (MESH); permissive hypotension; fluid management; resuscitation; restrictive fluid management; liberal fluid management; elective surgery; damage control resuscitation; surgical procedures, operative (MESH); wounds (MESH); injuries (MESH); surgery; trauma patients." A secondary search in the Medline, EMBASE, Web of Science, and Cochrane library revealed no additional results. We selected randomized controlled trials performed during elective surgeries. Patients were randomly assigned to a restrictive fluid management policy or to a liberal fluid management policy during elective surgery. The patient characteristics and the type of surgery varied. All but 3 studies reported American Society of Anaesthesiologists groups 1 to 3 as the inclusion criterion. The primary outcome of interest is total number of patients with a complication and the complication rate. Secondary outcome measures are infection rate, transfusion need, postoperative rebleeding, hospital stay, and renal function. In total, 1397 patients were analyzed (693 restrictive protocol, 704 liberal protocol). Meta-analysis showed that in the restrictive group as compared with the liberal group, fewer patients experienced a complication (relative risk [RR], 0.65; 95% confidence interval [CI], 0.55-0.78). The total complication rate (RR, 0.57; 95% CI, 0.52-0.64), risk of infection (RR, 0.62; 95% CI, 0.48-0.79), and transfusion rate (RR, 0.81; 95% CI, 0.66-0.99) were also lower. The postoperative rebleeding did not differ in both groups: RR, 0.76 (95% CI, 0.28-2.06). We conclude that compared with a liberal fluid policy, a restrictive fluid policy in elective surgery results in a 35% reduction in patients with a complication and should be advised as the preferred fluid management policy.

Goal-directed fluid therapy for microvascular free flap reconstruction following mastectomy: A pilot study

BACKGROUND

Fluid management of the surgical patient has undergone a paradigm shift over the past decade. A change from 'wet' to 'dry' to a 'goal-directed' approach has been witnessed. The fluid management of patients undergoing free flap reconstruction is particularly challenging. This is typically a long operation with minimal surgical stimulation, and hypotension often ensues. The use of vasopressors in these cases is contraindicated to maintain adequate flow to the flap. Hypotension is often treated with intravenous fluid boluses. However, aggressive fluid administration to maintain adequate blood pressure can result in flap edema, venous engorgement and, ultimately, flap loss.

OBJECTIVE

The primary objective of the present study was to determine whether goal-directed fluid therapy, titrated to maintain stroke volume variation ≤13%, with the use of an arterial pulse contour device results in improved postoperative cardiac index (CI) and stroke volume index (SVI) with reduced amounts of intravenous fluid. The primary end points studied were CI, SVI and cumulative crystalloid/colloid administration.

METHODS

Twenty female patients undergoing simultaneous microvascular free flap reconstruction immediately following mastectomy were studied. Preoperative and intraoperative care were standardized. Each patient received intra-arterial blood pressure monitoring. In all patients, cardiac output measurement occurred throughout the intraoperative period using the arterial pulse contour device. Control patients had their fluid administered at the discretion of the anesthesiologist (blinded to results from the cardiac output device). Patients in the intervention group had a baseline crystalloid infusion of 5 mL/kg/h, with intravenous colloid boluses to maintain a stroke volume variation ≤13%.

RESULTS

There was no difference in heart rate or mean arterial pressure between groups at the end of the operation. However, at the end of the operation, the intervention group had significantly higher mean (± SD) CI (3.8±0.8 L/min/m(2) versus 3.0±0.5 L/min/m(2); P=0.02) and SVI (51.4±2.4 mL/m(2) versus 43.3±2.3 mL/m(2); P=0.03). This improved CI and SVI was achieved with similar amounts of administered intraoperative fluid (5.8±0.5 mL/kg/h versus 5.0±0.7 mL/kg/h, control versus intervention). The intervention group required less postoperative fluid resuscitation during the early postoperative period (total fluid administered from end of operation to midnight of the operative day, 6.4±1.9 mL/kg/h versus 10.2±3.3 mL/kg/h, intervention versus control, respectively, P<0.01).

DISCUSSION

Goal-directed fluid therapy using minimally invasive cardiac output monitoring resulted in improved end-operative hemodynamics, with less 'rescue' fluid administration during the perioperative period.

Fluid management in abdominal surgery: what, when, and when not to administer

The entire team (including anesthesiologists, surgeons, and intensive care physicians) must work together (before, during, and after abdominal surgery) to determine the optimal amount (quantity) and type (quality) of fluid necessary in the perioperative period. The authors present an overview of the basic principles that underlie fluid management, including evidence-based recommendations (where tenable) and a rational approach for when and what to administer.

Goal-directed fluid therapy for microvascular free flap reconstruction following mastectomy: a pilot study

Background

Fluid management of the surgical patient has undergone a paradigm shift over the past decade. A change from ‘wet’ to ‘dry’ to a ‘goal-directed’ approach has been witnessed. The fluid management of patients undergoing free flap reconstruction is particularly challenging. This is typically a long operation with minimal surgical stimulation, and hypotension often ensues. The use of vasopressors in these cases is contra-indicated to maintain adequate flow to the flap. Hypotension is often treated with intravenous fluid boluses. However, aggressive fluid administration to maintain adequate blood pressure can result in flap edema, venous engorgement and, ultimately, flap loss.

Objective

The primary objective of the present study was to determine whether goal-directed fluid therapy, titrated to maintain stroke volume variation ≤13%, with the use of an arterial pulse contour device results in improved postoperative cardiac index (CI) and stroke volume index (SVI) with reduced amounts of intravenous fluid. The primary end points studied were CI, SVI and cumulative crystalloid/colloid administration.

Methods

Twenty female patients undergoing simultaneous microvascular free flap reconstruction immediately following mastectomy were studied. Preoperative and intraoperative care were standardized. Each patient received intra-arterial blood pressure monitoring. In all patients, cardiac output measurement occurred throughout the intraoperative period using the arterial pulse contour device. Control patients had their fluid administered at the discretion of the anesthesiologist (blinded to results from the cardiac output device). Patients in the intervention group had a baseline crystalloid infusion of 5 mL/kg/h, with intravenous colloid boluses to maintain a stroke volume variation ≤13%.

Results

There was no difference in heart rate or mean arterial pressure between groups at the end of the operation. However, at the end of the operation, the intervention group had significantly higher mean (± SD) CI (3.8±0.8 L/min/m2 versus 3.0±0.5 L/min/m2; P=0.02) and SVI (51.4±2.4 mL/m2 versus 43.3±2.3 mL/m2; P=0.03). This improved CI and SVI was achieved with similar amounts of administered intraoperative fluid (5.8±0.5 mL/kg/h versus 5.0±0.7 mL/kg/h, control versus intervention). The intervention group required less postoperative fluid resuscitation during the early postoperative period (total fluid administered from end of operation to midnight of the operative day, 6.4±1.9 mL/kg/h versus 10.2±3.3 mL/kg/h, intervention versus control, respectively, P<0.01).

Discussion

Goal-directed fluid therapy using minimally invasive cardiac output monitoring resulted in improved end-operative hemodynamics, with less ‘rescue’ fluid administration during the perioperative period.

A randomized controlled trial on the effects of goal-directed therapy on the inflammatory response open abdominal aortic aneurysm repair

Introduction

Goal-directed therapy (GDT) has been shown in numerous studies to decrease perioperative morbidity and mortality. The mechanism of benefit of GDT, however, has not been clearly elucidated. Targeted resuscitation of the vascular endothelium with GDT might alter the postoperative inflammatory response and be responsible for the decreased complications with this therapy.

Methods

This trial was registered at ClinicalTrials.gov as NCT01681251. Forty patients undergoing elective open repair of their abdominal aortic aneurysm, 18 years of age and older, were randomized to an interventional arm with GDT targeting stroke volume variation with an arterial pulse contour cardiac output monitor, or control, where fluid therapy was administered at the discretion of the attending anesthesiologist. We measured levels of several inflammatory cytokines (C-reactive protein, Pentraxin 3, suppressor of tumorgenicity--2, interleukin-1 receptor antagonist, and tumor necrosis factor receptor-III) preoperatively and at several postoperative time points to determine if there was a difference in inflammatory response. We also assessed each group for a composite of postoperative complications.

Results

Twenty patients were randomized to GDT and twenty were randomized to control. Length of stay was not different between groups. Intervention patients received less crystalloid and more colloid. At the end of the study, intervention patients had a higher cardiac index (3.4 ± 0.5 vs. 2.5 ± 0.7 l/minute per m², p < 0.01) and stroke volume index (50.1 ± 7.4 vs. 38.1 ± 9.8 ml/m², p < 0.01) than controls. There were significantly fewer complications in the intervention than control group (28 vs. 12, p = 0.02). The length of hospital and ICU stay did not differ between groups. There was no difference in the levels of inflammatory cytokines between groups.

Conclusions

Despite being associated with fewer complications and improved hemodynamics, there was no difference in the inflammatory response of patients treated with GDT. This suggests that the clinical benefit of GDT occurs in spite of a similar inflammatory burden. Further work needs to be performed to delineate the mechanism of benefit of GDT.

Trial registration

ClinicalTrials.gov Identifier: NCT01681251. Registered 18 May 2011.

The relationship of perioperative fluid administration to outcomes in colorectal and pancreatic surgery: a review of the literature

Optimal perioperative fluid administration in major gastrointestinal surgery remains a challenging clinical problem. Traditional dogma of a liberal approach to fluid administration in order to counteract potential hypovolemia and decreased end-organ perfusion can often result in fluid overload, perhaps negatively impacting perioperative outcomes. This hypothesis has been investigated in several types of gastrointestinal surgery. We discuss the current literature on perioperative fluid administration in colorectal and pancreatic surgery and highlight the controversies that still exist.

Fluid management in the cardiothoracic intensive care unit: diuresis--diuretics and hemofiltration

PURPOSE OF REVIEW

The present review discusses the current concepts of fluid management in cardiothoracic surgery, and its clinical implications with special reference to organ-related complications and their prevention.

RECENT FINDINGS

Current strategies in fluid management for cardiothoracic patients, various fluid formulation, and the preventive strategies for minimizing fluid-related complications are described, with particular reference to new discoveries and controversies that have arisen from recent literature.

SUMMARY

The optimal fluid management in cardiothoracic patients has not been settled. Results of recent clinical published trials highlight the need for minimizing fluid administration and attempting to use diuretics to achieve a negative fluid, although hypovolemia and hypoperfusion should be carefully considered. An individualized optimization of fluid status, using goal-directed therapy, has emerged as a possible preferable approach. The old debate between crystalloid and colloid solutions has been partially solved, as some colloids have demonstrated deleterious effect on renal function and coagulation system. Various preventive strategies have also emerged for minimizing fluid-related complications.