Effect of volume loading with 1 liter intravenous infusions of 0.9% saline, 4% succinylated gelatine (Gelofusine) and 6% hydroxyethyl starch (Voluven) on blood volume and endocrine responses: A randomized, three-way crossover study in healthy volunteers:

Fluids in acute respiratory distress syndrome: pros and cons

PURPOSE OF REVIEW

Fluid resuscitation in acute respiratory distress syndrome (ARDS) is not well documented. Clinical evidence comes from studies in critically ill patients, but these patients respond differently to fluids depending on the presence or absence of sepsis.

RECENT FINDINGS

Clinical trials have shown adverse effects on kidney and hemostatic functions and trends toward increased mortality after hydroxyethyl starch infusion. Although well conducted, the methodology deserves attention concerning the infused volume, hemodynamic goals and the presence of septic and nonseptic patients. Small single-center studies have shown beneficial results associated with colloidal molecules through innovative methodological apparatus. Ongoing clinical trials allied to retrospective and prospective trials may favor the introduction of albumin in the critically ill population.

SUMMARY

In order to evaluate the pros and cons of using fluids in ARDS patients, it is important to carefully analyze the latest trials. Recent studies have emphasized the importance of better understanding endothelial pathophysiology during fluid management in ARDS patients. Certainly, further studies analyzing fluid strategies in septic and nonseptic ARDS patients are needed.

The physiologic perspective in fluid management in vascular anesthesiology

Vascular surgery patients frequently suffer from atherosclerosis and peripheral arterial occlusive disease generating endothelial dysfunction. Furthermore, ischemia and reperfusion during surgery damage endothelial cells and, especially, the endothelial glycocalix. The damage of the glycocalix promotes an increase in permeability. Not only crystalloids, which freely diffuse between the intravascular and the interstitial compartment, but also colloidal fluids cross from the intravascular space in the interstitial space with the consequence of edema formation. Possible tissue edema may result in an impairment of tissue oxygenation, leading to wound healing disturbances and initiation of inflammatory responses up to tissue apoptosis. Particularly in vascular anesthesia, this possibly means that colloids only should be administered in acute volume resuscitation immediately after unclamping a big vessel for immediate volume restoration. Which colloidal fluid should be administered is still under intense discussion. From a theoretical physiologic point of view, iso-osmolar albumin is the best choice regarding volume effect, antioxidative properties, and protection against destruction of the glycocalix. Nonetheless, albumin experimentally has not lived up to its promise in the clinical setting. Thus, further well-conducted large randomized clinical trials are necessary to ascertain the optimal fluid therapy in vascular surgery patients.

Resuscitation speed affects brain injury in a large animal model of traumatic brain injury and shock

Background

Optimal fluid resuscitation strategy following combined traumatic brain injury (TBI) and hemorrhagic shock (HS) remain controversial and the effect of resuscitation infusion speed on outcome is not well known. We have previously reported that bolus infusion of fresh frozen plasma (FFP) protects the brain compared with bolus infusion of 0.9% normal saline (NS). We now hypothesize reducing resuscitation infusion speed through a stepwise infusion speed increment protocol using either FFP or NS would provide neuroprotection compared with a high speed resuscitation protocol.

Methods

23 Yorkshire swine underwent a protocol of computer controlled TBI and 40% hemorrhage. Animals were left in shock (mean arterial pressure of 35 mmHg) for two hours prior to resuscitation with bolus FFP (n = 5, 50 ml/min) or stepwise infusion speed increment FFP (n = 6), bolus NS (n = 5, 165 ml/min) or stepwise infusion speed increment NS (n = 7). Hemodynamic variables over a 6-hour observation phase were recorded. Following euthanasia, brains were harvested and lesion size as well as brain swelling was measured.

Results

Bolus FFP resuscitation resulted in greater brain swelling (22.36 ± 1.03% vs. 15.58 ± 2.52%, p = 0.04), but similar lesion size compared with stepwise resuscitation. This was associated with a lower cardiac output (CO: 4.81 ± 1.50 l/min vs. 5.45 ± 1.14 l/min, p = 0.03). In the NS groups, bolus infusion resulted in both increased brain swelling (37.24 ± 1.63% vs. 26.74 ± 1.33%, p = 0.05) as well as lesion size (3285.44 ± 130.81 mm³ vs. 2509.41 ± 297.44 mm³, p = 0.04). This was also associated with decreased cardiac output (NS: 4.37 ± 0.12 l/min vs. 6.35 ± 0.10 l/min, p < 0.01).

Conclusions

In this clinically relevant model of combined TBI and HS, stepwise resuscitation protected the brain compared with bolus resuscitation.

Duration of hemodynamic effects of crystalloids in patients with circulatory shock after initial resuscitation

Background

In the later stages of circulatory shock, monitoring should help to avoid fluid overload. In this setting, volume expansion is ideally indicated only for patients in whom the cardiac index (CI) is expected to increase. Crystalloids are usually the choice for fluid replacement. As previous studies evaluating the hemodynamic effect of crystalloids have not distinguished responders from non-responders, the present study was designed to evaluate the duration of the hemodynamic effects of crystalloids according to the fluid responsiveness status.

Methods

This is a prospective observational study conducted after the initial resuscitation phase of circulatory shock (>6 h vasopressor use). Critically ill, sedated adult patients monitored with a pulmonary artery catheter who received a fluid challenge with crystalloids (500 mL infused over 30 min) were included. Hemodynamic variables were measured at baseline (T0) and at 30 min (T1), 60 min (T2), and 90 min (T3) after a fluid bolus, totaling 90 min of observation. The patients were analyzed according to their fluid responsiveness status (responders with CI increase >15% and non-responders ≤15% at T1). The data were analyzed by repeated measures of analysis of variance.

Results

Twenty patients were included, 14 of whom had septic shock. Overall, volume expansion significantly increased the CI: 3.03 ± 0.64 L/min/m² to 3.58 ± 0.66 L/min/m² (p < 0.05). From this period, there was a progressive decrease: 3.23 ± 0.65 L/min/m² (p < 0.05, T2 versus T1) and 3.12 ± 0.64 L/min/m² (p < 0.05, period T3 versus T1). Similar behavior was observed in responders (13 patients), 2.84 ± 0.61 L/min/m² to 3.57 ± 0.65 L/min/m² (p < 0.05) with volume expansion, followed by a decrease, 3.19 ± 0.69 L/min/m² (p < 0.05, T2 versus T1) and 3.06 ± 0.70 L/min/m² (p < 0.05, T3 versus T1). Blood pressure and cardiac filling pressures also decreased significantly after T1 with similar findings in both responders and non-responders.

Conclusions

The results suggest that volume expansion with crystalloids in patients with circulatory shock after the initial resuscitation has limited success, even in responders.

Consensus guidelines for enhanced recovery after gastrectomy: Enhanced Recovery After Surgery (ERAS®) Society recommendations

BACKGROUND

Application of evidence-based perioperative care protocols reduces complication rates, accelerates recovery and shortens hospital stay. Presently, there are no comprehensive guidelines for perioperative care for gastrectomy.

METHODS

An international working group within the Enhanced Recovery After Surgery (ERAS®) Society assembled an evidence-based comprehensive framework for optimal perioperative care for patients undergoing gastrectomy. Data were retrieved from standard databases and personal archives. Evidence and recommendations were classified according to the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system and were discussed until consensus was reached within the group. The quality of evidence was rated 'high', 'moderate', 'low' or 'very low'. Recommendations were graded as 'strong' or 'weak'.

RESULTS

The available evidence has been summarized and recommendations are given for 25 items, eight of which contain procedure-specific evidence. The quality of evidence varies substantially and further research is needed for many issues to improve the strength of evidence and grade of recommendations.

CONCLUSION

The present evidence-based framework provides comprehensive advice on optimal perioperative care for the patient undergoing gastrectomy and facilitates multi-institutional prospective cohort registries and adequately powered randomized trials for further research.

Perioperative use of crystalloids in patients undergoing open radical cystectomy: balanced Ringer's maleate versus a glucose 5%/potassium-based balanced solution: study protocol for a randomized controlled trial

Background

The optimal crystalloid solution to use perioperatively in patients undergoing open radical cystectomy remains unclear. Many of the fluids used for intravenous hydration contain supraphysiologic concentrations of chloride, which can induce hyperchloremia and metabolic acidosis, resulting in renal vasoconstriction and decreased renal function. In addition, patients receiving less fluid and less sodium show faster recovery of gastrointestinal (GI) function after colonic surgery.

Methods and design

This is an investigator-initiated, single-center, randomized, controlled, parallel group trial with assessor-blinded outcome assessment, in the Department of Urology, University Hospital Bern, Switzerland. The study will involve 44 patients with bladder cancer scheduled for radical cystectomy and urinary diversion. The primary outcome is the duration between the end of surgery and the return of the GI function (first defecation). Secondary outcomes are fluid balance (body weight difference postoperatively versus preoperatively) and the incidence of kidney function disorders according to the Risk – Injury – Failure – Loss - End Stage Renal Disease (RIFLE classification). An equal number of patients are allocated to receive Ringerfundin® solution or a glucose/potassium-based balanced crystalloid solution as baseline infusion during the entire time that intravenous administration of fluid is necessary during the perioperative period. The randomized crystalloid solution is infused at a rate of 1 ml/kg/h until the bladder has been removed, followed by 3 ml/kg/h until the end of surgery. Postoperative hydration is identical in both groups and consists of 1,500 ml of the randomized crystalloid solution per 24 hours. Postoperative patient care is identical in both groups; patients are allowed to drink clear fluids immediately after surgery, and liquid diet is started on postoperative day 1, as well as active mobilization and the use of chewing gum. Body weight is measured daily in the morning. Time of first flatus and first defecation are recorded.

Discussion

This trial assesses the benefits and harms of two different balanced crystalloid solutions for perioperative fluid management in patients undergoing open radical cystectomy with urinary diversion, with regard to return of GI function and effects on postoperative renal function.

Trial registration

Current Controlled Trials ISRCTN32976792 (registered on November 21 2013).

A randomized, controlled, double-blind crossover study on the effects of 1-L infusions of 6% hydroxyethyl starch suspended in 0.9% saline (voluven) and a balanced solution (Plasma Volume Redibag) on blood volume, renal blood flow velocity, and renal cortical tissue perfusion in healthy volunteers

OBJECTIVE

We compared the effects of intravenous administration of 6% hydroxyethyl starch (maize-derived) in 0.9% saline (Voluven; Fresenius Kabi, Runcorn, United Kingdom) and a "balanced" preparation of 6% hydroxyethyl starch (potato-derived) [Plasma Volume Redibag (PVR); Baxter Healthcare, Thetford, United Kingdom] on renal blood flow velocity and renal cortical tissue perfusion in humans using magnetic resonance imaging.

BACKGROUND

Hyperchloremia resulting from 0.9% saline infusion may adversely affect renal hemodynamics when compared with balanced crystalloids. This phenomenon has not been studied with colloids.

METHODS

Twelve healthy adult male subjects received 1-L intravenous infusions of Voluven or PVR over 30 minutes in a randomized, double-blind manner, with crossover studies 7 to 10 days later. Magnetic resonance imaging proceeded for 60 minutes after commencement of infusion to measure renal artery blood flow velocity and renal cortical perfusion. Blood was sampled, and weight was recorded at 0, 30, 60, 120, 180, and 240 minutes.

RESULTS

Mean peak serum chloride concentrations were 108 and 106 mmol/L, respectively, after Voluven and PVR infusion (P = 0.032). Changes in blood volume (P = 0.867), strong ion difference (P = 0.219), and mean renal artery flow velocity (P = 0.319) were similar. However, there was a significant increase in mean renal cortical tissue perfusion after PVR when compared with Voluven (P = 0.033). There was no difference in urinary neutrophil gelatinase-associated liopcalin to creatinine ratios after the infusion (P = 0.164).

CONCLUSIONS

There was no difference in the blood volume-expanding properties of the 2 preparations of 6% hydroxyethyl starch. The balanced starch produced an increase in renal cortical tissue perfusion, a phenomenon not seen with starch in 0.9% saline.

Diuretic response to colloid and crystalloid fluid loading in critically ill patients

AIMS

In the critically ill patient, fluid loading is commonly done to stabilise hemodynamics and increase diuresis, whereas the absence of diuresis may predispose to harmful overloading. The goal of the current study was to evaluate the diuretic response and determinants thereof upon crystalloid and colloid fluid loading.

SUBJECTS AND METHODS

This is a substudy on 42 clinically hypovolemic, septic or non-septic patients without acute kidney injury, who were randomly assigned, after stratification for sepsis, to a 90-min fluid loading protocol with either 0.9% saline or a colloid solution (gelatin, hydroxyethyl starch 200/0.5 or albumin). Hemodynamics, biochemical parameters and diuresis were recorded. A response was defined by an increase in diuresis of >10% during fluid loading.

RESULTS

Diuresis increased more during saline than colloid infusion, together with a decline in colloid osmotic pressure (COP) of plasma and less increase in plasma volume and global hemodynamics with saline, at similar fluid balance. Nine patients (82%) receiving saline had a diuretic response, compared to 13 patients (42%) receiving colloids (P = 0.04), and the response was not predicted by underlying condition, global hemodynamics, volume of fluid infused and COP.

CONCLUSION

In critically ill patients with clinical hypovolemia, diuresis increases more during saline than colloid fluid loading, only partly dependent of a fall in plasma COP.

National survey of fluid therapy in acute pancreatitis: current practice lacks a sound evidence base

BACKGROUND

Fluid therapy (FT) is a critical intervention in managing acute pancreatitis (AP). There is a paucity of evidence to guide FT and virtually no data on current prescribing practice. This survey aims to characterize current practice and opinion with regard to FT in AP throughout New Zealand.

METHODS

Information was collected on fluid selection, administration, and goal-directed FT. The survey was distributed online and in print to all doctors employed in General Surgery Departments in New Zealand on 1 May 2012. Monthly email reminders were sent for 6 months.

RESULTS

The overall response rate was 47 % (n = 190/408). Crystalloids were the preferred initial fluid for all categories of severity; however, colloid use increased with severity (p < 0.001). Fluid volume also increased with severity (p = 0.001), with 74 % of respondents prescribing >4 L for AP with organ failure (OF). Clinicians treating 26-50 patients per year with AP were less likely to prescribe colloid for AP with OF (8 vs 43 %) (p = 0.001). Rate of fluid administration in AP with OF varied according to physicians' seniority (p = 0.004); consultants prescribed >4 L more than other groups (83 vs 68 %). Only 17 % of respondents reported the use of guidelines.

CONCLUSIONS

This survey reveals significant variation in prescription of FT for AP, and aggressive FT is commonly prescribed for AP with OF. There is little adherence to published guidelines or best available evidence.

Should chloride-rich crystalloids remain the mainstay of fluid resuscitation to prevent 'pre-renal' acute kidney injury?: con

The high chloride content of 0.9% saline leads to adverse pathophysiological effects in both animals and healthy human volunteers, changes not seen after balanced crystalloids. Small randomized trials confirm that the hyperchloremic acidosis induced by saline also occurs in patients, but no clinical outcome benefit was demonstrable when compared with balanced crystalloids, perhaps due to a type II error. A strong signal is emerging from recent large propensity-matched and cohort studies for the adverse effects that 0.9% saline has on the clinical outcome in surgical and critically ill patients when compared with balanced crystalloids. Major complications are the increased incidence of acute kidney injury and the need for renal replacement therapy, and that pathological hyperchloremia may increase postoperative mortality. However, there are no large-scale randomized trials comparing 0.9% saline with balanced crystalloids. Some balanced crystalloids are hypo-osmolar and may not be suitable for neurosurgical patients because of their propensity to cause brain edema. Saline may be the solution of choice used for the resuscitation of patients with alkalosis and hypochloremia. Nevertheless, there is evidence to suggest that balanced crystalloids cause less detriment to renal function than 0.9% saline, with perhaps better clinical outcome. Hence, we argue that chloride-rich crystalloids such as 0.9% saline should be replaced with balanced crystalloids as the mainstay of fluid resuscitation to prevent ‘pre-renal' acute kidney injury.

Pros and cons of tetrastarch solution for critically ill patients

Proper fluid management is crucial for the management of critically ill patients. However, there is a continuing debate about the choice of the fluid, i.e., crystalloid vs. colloid. Colloid solution is theoretically advantageous to the crystalloid because of larger volume effect and less interstitial fluid accumulation, and hydroxyethyl starch (HES) is most frequently used for perioperative setting. Nevertheless, application of HES solution is relatively limited due to its side effects including renal toxicity and coagulopathy. Since prolonged presence of large HES molecule is responsible for these side effects, rapidly degradable HES solution with low degree of substitution (tetrastarch) supposedly has less potential for negative effects. Thus, tetrastarch may be more frequently used in the ICU setting. However, several large-scale randomized trials reported that administration of tetrastarch solution to the patients with severe sepsis has negative effects on mortality and renal function. These results triggered further debate and regulatory responses around the world. This narrative review intended to describe the currently available evidence about the advantages and disadvantages of tetrastarch in the ICU setting.

Influence of goal-directed therapy with balanced crystalloid–colloid or unbalanced crystalloid solution on base excess

Objective

To investigate changes in standard base excess (SBE) when administering two different infusion regimens for elective hip replacement within a goal-directed haemodynamic algorithm.

Methods

This prospective, double-blind, randomized, controlled study enrolled patients scheduled for primary hip replacement surgery, who were randomized to receive either an unbalanced crystalloid (chloride: 155.5 mmol/l) or a 1 : 1 mixture of a balanced crystalloid and a balanced colloid (6% w/v hydroxyethyl starch 130/0.42; chloride: 98 and 112 mmol/l, respectively). Fluid management was goal-directed to optimize stroke volume using oesophageal Doppler.

Results

A total of 40 patients (19 female/21 male) participated in the study. After surgery, median (25–75% percentiles) SBE was significantly lower in the unbalanced group compared with the balanced group: −2.0 mmol/l (−3.1 to −1.1) versus −0.4 mmol/l (−1.2 to 0.7), respectively. This difference was mainly due to greater plasma chloride concentrations in the unbalanced group. The amount of study medication required to reach haemodynamic stability (median 1200 ml) did not differ between the two groups.

Conclusion

SBE decreased in the unbalanced group without influence on fluid requirements and haemodynamic stability.

The pathophysiology of fluid and electrolyte balance in the older adult surgical patient

BACKGROUND & AIMS

Age-related physiological changes predispose even the healthy older adult to fluid and electrolyte abnormalities which can cause morbidity and mortality. The aim of this narrative review is to highlight key aspects of age-related pathophysiological changes that affect fluid and electrolyte balance in older adults and underpin their importance in the perioperative period.

METHODS

The Web of Science, MEDLINE, PubMed and Google Scholar databases were searched using key terms for relevant studies published in English on fluid balance in older adults during the 15 years preceding June 2013. Randomised controlled trials and large cohort studies were sought; other studies were used when these were not available. The bibliographies of extracted papers were also searched for relevant articles.

RESULTS

Older adults are susceptible to dehydration and electrolyte abnormalities, with causes ranging from physical disability restricting access to fluid intake to iatrogenic causes including polypharmacy and unmonitored diuretic usage. Renal senescence, as well as physical and mental decline, increase this susceptibility. Older adults are also predisposed to water retention and related electrolyte abnormalities, exacerbated at times of physiological stress. Positive fluid balance has been shown to be an independent risk factor for morbidity and mortality in critically ill patients with acute kidney injury.

CONCLUSIONS

Age-related pathophysiological changes in the handling of fluid and electrolytes make older adults undergoing surgery a high-risk group and an understanding of these changes will enable better management of fluid and electrolyte therapy in the older adult.

Impact of intravascular volume replacement and transfusion on outcome: where are we now?

Intravenous fluid administration is often required to counteract haemodynamic instability during emergency and elective surgeries, as well as in the intensive care unit. However, the best type and the amount of fluid required are controversial. A recent meta-analysis suggested that there is no difference among different types of colloids on outcome. Furthermore, colloids and crystalloids seem to be comparable in terms of efficiency in reverting haemodynamic instability, as well as morbidity and mortality. The interpretation of the results of different randomised controlled trials is somewhat difficult - the context must be always kept in mind. For example, results may differ in septic as compared to non-septic patient populations. Another important aspect concerns the effects on the macro- versus microcirculation. More recent studies emphasise that the microcirculation has to be taken into account when studying and interpreting the interaction between fluid therapy and the underlying disease. Nevertheless, the macrocirculation and clinical parameters have to be considered as well. Given that red blood cells remain the most important oxygen carriers, recent evidence regarding blood age may stimulate new studies according to the actual range for blood storage. Artificial oxygen carriers may play a role in specific situations, where the transfusion is indicated but the access to blood is problematic, but there is doubt that they may replace blood transfusion.

Acid-base and electrolyte status during normovolemic hemodilution with succinylated gelatin or HES-containing volume replacement solutions in rats

Background

In the past, several studies have compared different colloidal replacement solutions, whereby the focus was usually on the respective colloid. We therefore systematically studied the influence of the carrier solution’s composition of five approved colloidal volume replacement solutions (Gelafundin, Gelafusal, Geloplasma, Voluven and Volulyte) on acid-base as well as electrolyte status during and following acute severe normovolemic hemodilution. The solutions differed in the colloid used (succinylated gelatin vs. HES) and in the presence and concentration of metabolizable anions as well as in their electrolyte composition.

Methods

Anesthetized Wistar rats were subjected to a stepwise normovolemic hemodilution with one of the solutions until a final hematocrit of 10%. Subsequent to dilution (162 min), animals were observed for an additional period (150 min). During dilution and observation time blood gas analyses were performed eight times in total. Additionally, in the Voluven and Volulyte groups as well as in 6 Gelafundin animals, electrolyte concentrations, glucose, pH and succinylated gelatin were measured in urine and histopathological evaluation of the kidney was performed.

Results

All animals survived without any indications of injury. Although the employed solutions differed in their respective composition, comparable results in all plasma acid-base and electrolyte parameters studied were obtained. Plasma pH increased from approximately 7.28 to 7.39, the plasma K⁺ concentration decreased from circa 5.20 mM to 4.80-3.90 mM and the plasma Cl⁻ concentration rose from approximately 105 mM to 111–120 mM. Urinary analysis revealed increased excretion of K⁺, H⁺ and Cl⁻.

Conclusions

The present data suggest that the carrier solution’s composition with regard to metabolizable anions as well as K⁺, Ca²⁺ only has a minor impact on acid-base and electrolyte status after application of succinylated gelatin or HES-containing colloidal volume replacement solutions.

Low molecular weight pentastarch is more effective than crystalloid solution in goal-directed fluid management in patients undergoing major gastrointestinal surgery

BACKGROUND

This prospective observational study compared the volume effect between hydroxyethyl starch (HES) and crystalloid solution and its context dependency in intraoperative goal-directed fluid management.

METHODS

With institutional review board (IRB) approval, 35 patients undergoing major gastrointestinal surgery were enrolled. Fluid challenge consisting of 250 ml of either bicarbonate Ringer solution (BRS) or low molecular weight pentastarch (HES 70/0.5) was given to maintain stroke volume index >35 ml/m2. The context of fluid challenge was classified as related to either epidural block (EB) or blood loss (BL) or as nonspecific. The primary end point was the interval between index fluid challenge and the next fluid challenge, and the secondary end point was the hemodynamic parameter at the end of fluid challenge. Differences in these parameters in each clinical context were compared between BRS and HES 70/0.5. A p value <0.05 was considered statistically significant.

RESULTS

Eighty-eight, 77, and 127 fluid challenges were classified as related to EB and BL and as nonspecific, respectively. In the nonspecific condition, the median (range) interval after fluid challenge with HES 70/0.5 and BRS was 45 (11-162) min and 18 (8-44) min, respectively, and the difference was statistically significant. Also, mean arterial pressure and stroke volume index significantly increased, whereas stroke volume variation significantly decreased after fluid challenge with HES 70/0.5 compared with BRS. Such differences were not observed in the other situations.

CONCLUSIONS

HES 70/0.5 exerted larger volume effects than did crystalloid under nonspecific conditions. However, similar volume effects were observed during volume loss and extensive sympathetic blockade.

Dose and type of crystalloid fluid therapy in adult hospitalized patients

OBJECTIVE

In this narrative review, an overview is given of the pros and cons of various crystalloid fluids used for infusion during initial resuscitation or maintenance phases in adult hospitalized patients. Special emphasis is given on dose, composition of fluids, presence of buffers (in balanced solutions) and electrolytes, according to recent literature. We also review the use of hypertonic solutions.

METHODS

We extracted relevant clinical literature in English specifically examining patient-oriented outcomes related to fluid volume and type.

RESULTS

A restrictive fluid therapy prevents complications seen with liberal, large-volume therapy, even though restrictive fluid loading with crystalloids may not demonstrate large hemodynamic effects in surgical or septic patients. Hypertonic solutions may serve the purpose of small volume resuscitation but carry the disadvantage of hypernatremia. Hypotonic solutions are contraindicated in (impending) cerebral edema, whereas hypertonic solutions are probably more helpful in ameliorating than in preventing this condition and improving outcome. Balanced solutions offer a better approach for plasma composition than unbalanced ones, and the evidence for benefits in patient morbidity and mortality is increasing, particularly by helping to prevent acute kidney injury.

CONCLUSIONS

Isotonic and hypertonic crystalloid fluids are the fluids of choice for resuscitation from hypovolemia and shock. The evidence that balanced solutions are superior to unbalanced ones is increasing. Hypertonic saline is effective in mannitol-refractory intracranial hypertension, whereas hypotonic solutions are contraindicated in this condition.

Effects of Intravascular Volume Replacement on Lung and Kidney Function and Damage in Nonseptic Experimental Lung Injury

Background:

Intravascular volume replacement is often required in the presence of increased pulmonary capillary leakage, for example in patients with volutrauma with major hemorrhage. In the present study, the effects of Ringer’s acetate (RA), gelatin-polysuccinate (GEL), and a modern hydroxyethyl starch (HES, 6% 130/0.42) on lung and kidney function and damage were compared in a two-hit model of acute lung injury. The authors hypothesized that GEL and HES, compared to RA: (1) reduced lung histological damage, (2) impaired kidney morphology and function.

Methods:

Acute lung injury was induced in 30 anesthetized pigs by tidal volumes approximately 40 ml/kg, after saline lung lavage. Protective ventilation was initiated and approximately≈25% of estimated blood volume was drawn. Animals were randomly assigned to receive RA, GEL, or HES (n = 10/group) aimed at approximately 90% of intrathoracic blood volume before blood drainage.

Results:

Fluid volumes were higher with RA (2,250 ± 764 ml) than GEL (704 ± 159 ml) and HES (837 ± 82 ml) (P &lt; 0.05). Compared to RA, HES reduced diffuse alveolar damage overall, and GEL in nondependent zones only. GEL and HES yielded lower wet-to-dry ratios compared to RA (6.5 ± 0.5 and 6.5 ± 0.6 vs. 7.9 ± 0.9, respectively, P &lt; 0.05). HES and RA resulted in less kidney damage than GEL, but kidney function did not differ significantly among groups. Compared to GEL, HES yielded lower lung elastance (55 ± 12 vs. 45 ± 13 cm H2O/l, P &lt; 0.05) and intra-abdominal pressure (15 ± 5 vs. 11 ± 4 cm 14;H2O, P &lt; 0.05).

Conclusions:

In this model of acute lung injury, intravascular volume expansion after major hemorrhage with HES yielded less lung damage than RA and less kidney damage than GEL.

Intraoperative fluid management in open gastrointestinal surgery: goal-directed versus restrictive

OBJECTIVE

The optimal strategy for fluid management during gastrointestinal surgery remains unclear. Minimizing the variation in arterial pulse pressure, which is induced by mechanical ventilation, is a potential strategy to improve postoperative outcomes. We tested this hypothesis in a prospective, randomized study with lactated Ringer's solution and 6% hydroxyethyl starch solution.

METHOD

A total of 60 patients who were undergoing gastrointestinal surgery were randomized into a restrictive lactated Ringer's group (n = 20), a goal-directed lactated Ringer's group (n = 20) and a goal-directed hydroxyethyl starch group (n = 20). The goal-directed fluid treatment was guided by pulse pressure variation, which was recorded during surgery using a simple manual method with a Datex Ohmeda S/5 Monitor and minimized to 11% or less by volume loading with either lactated Ringer's solution or 6% hydroxyethyl starch solution (130/0.4). The postoperative flatus time, the length of hospital stay and the incidence of complications were recorded as endpoints.

RESULTS

The goal-directed lactated Ringer's group received the greatest amount of total operative fluid compared with the two other groups. The flatus time and the length of hospital stay in the goal-directed hydroxyethyl starch group were shorter than those in the goal-directed lactated Ringer's group and the restrictive lactated Ringer's group. No significant differences were found in the postoperative complications among the three groups.

CONCLUSION

Monitoring and minimizing pulse pressure variation by 6% hydroxyethyl starch solution (130/0.4) loading during gastrointestinal surgery improves postoperative outcomes and decreases the discharge time of patients who are graded American Society of Anesthesiologists physical status I/II.

The intravascular volume effect of Ringer's lactate is below 20%: a prospective study in humans

Introduction

Isotonic crystalloids play a central role in perioperative fluid management. Isooncotic preparations of colloids (for example, human albumin or hydroxyethyl starch) remain nearly completely intravascular when infused to compensate for acute blood losses. Recent data were interpreted to indicate a comparable intravascular volume effect for crystalloids, challenging the occasionally suggested advantage of using colloids to treat hypovolemia. General physiological knowledge and clinical experience, however, suggest otherwise.

Methods

In a prospective study, double-tracer blood volume measurements were performed before and after intended normovolemic hemodilution in ten female adults, simultaneously substituting the three-fold amount of withdrawn blood with Ringer's lactate. Any originated deficits were substituted with half the volume of 20% human albumin, followed by a further assessment of blood volume. To assess significance between the measurements, repeated measures analysis of variance (ANOVA) according to Fisher were performed. If significant results were shown, paired t tests (according to Student) for the singular measurements were taken. P < 0.05 was considered to be significant.

Results

A total of 1,097 ± 285 ml of whole blood were withdrawn (641 ± 155 ml/m² body surface area) and simultaneously replaced by 3,430 ± 806 ml of Ringer's lactate. All patients showed a significant decrease in blood volume after hemodilution (-459 ± 185 ml; P < 0.05) that did not involve relevant hemodynamical changes, and a significant increase in interstitial water content (+2,157 ± 606 ml; P < 0.05). The volume effect of Ringer's lactate was 17 ± 10%. The infusion of 245 ± 64 ml of 20% human albumin in this situation restored blood volume back to baseline values, the volume effect being 184 ± 63%.

Conclusions

Substitution of isolated intravascular deficits in cardiopulmonary healthy adults with the three-fold amount of Ringer's lactate impedes maintenance of intravascular normovolemia. The main side effect was an impressive interstitial fluid accumulation, which was partly restored by the intravenous infusion of 20% human albumin. We recommend to substitute the five-fold amount of crystalloids or to use an isooncotic preparation in the face of acute bleeding in patients where edema prevention might be advantageous.

Revised Starling equation and the glycocalyx model of transvascular fluid exchange: an improved paradigm for prescribing intravenous fluid therapy

I.V. fluid therapy does not result in the extracellular volume distribution expected from Starling's original model of semi-permeable capillaries subject to hydrostatic and oncotic pressure gradients within the extracellular fluid. Fluid therapy to support the circulation relies on applying a physiological paradigm that better explains clinical and research observations. The revised Starling equation based on recent research considers the contributions of the endothelial glycocalyx layer (EGL), the endothelial basement membrane, and the extracellular matrix. The characteristics of capillaries in various tissues are reviewed and some clinical corollaries considered. The oncotic pressure difference across the EGL opposes, but does not reverse, the filtration rate (the 'no absorption' rule) and is an important feature of the revised paradigm and highlights the limitations of attempting to prevent or treat oedema by transfusing colloids. Filtered fluid returns to the circulation as lymph. The EGL excludes larger molecules and occupies a substantial volume of the intravascular space and therefore requires a new interpretation of dilution studies of blood volume and the speculation that protection or restoration of the EGL might be an important therapeutic goal. An explanation for the phenomenon of context sensitivity of fluid volume kinetics is offered, and the proposal that crystalloid resuscitation from low capillary pressures is rational. Any potential advantage of plasma or plasma substitutes over crystalloids for volume expansion only manifests itself at higher capillary pressures.

Fluids and gastrointestinal function

PURPOSE OF REVIEW

To highlight recent developments relating perioperative fluid therapy to gastrointestinal function by reviewing clinically pertinent English language articles mainly from January 2010 to March 2011.

RECENT FINDINGS

The control of fluid and electrolyte balance involves multiple processes in which the gastrointestinal tract plays an integral role. Diseases affecting the gastrointestinal tract commonly cause fluid and electrolyte disturbance. Similarly, intravenous fluid therapy in the perioperative period can affect gastrointestinal function and have a bearing on postoperative outcome. Striking a balance, in terms of both fluid composition and volume, is likely to reduce the morbidity associated with interstitial edema, a frequently observed occurrence with contemporary perioperative fluid regimens. This balance may be best achieved using individualized and goal-directed approaches to fluid therapy, in order to provide fluid when it is needed and in the correct quantities.

SUMMARY

In planning strategies of fluid therapy, the possibility of adverse effects on the gastrointestinal tract should be considered, as this is likely to have an impact on fluid and electrolyte balance and postoperative outcome.

Prediction, prevention and management of postresection liver failure

Background

Postresection liver failure (PLF) is the major cause of death following liver resection. However, there is no unified definition, the pathophysiology is understood poorly and there are few controlled trials to optimize its management. The aim of this review article is to present strategies to predict, prevent and manage PLF.

Methods

The Web of Science, MEDLINE, PubMed, Google Scholar and Cochrane Library databases were searched for studies using the terms ‘liver resection’, ‘partial hepatectomy’, ‘liver dysfunction’ and ‘liver failure’ for relevant studies from the 15 years preceding May 2011. Key papers published more than 15 years ago were included if more recent data were not available. Papers published in languages other than English were excluded.

Results

The incidence of PLF ranges from 0 to 13 per cent. The absence of a unified definition prevents direct comparison between studies. The major risk factors are the extent of resection and the presence of underlying parenchymal disease. Small-for-size syndrome, sepsis and ischaemia–reperfusion injury are key mechanisms in the pathophysiology of PLF. Jaundice is the most sensitive predictor of outcome. An evidence-based approach to the prevention and management of PLF is presented.

Conclusion

PLF is the major cause of morbidity and mortality after liver resection. There is a need for a unified definition and improved strategies to treat it.

Seventy-five percent of National Football League teams use pregame hyperhydration with intravenous fluid

OBJECTIVE

To determine the number of National Football League (NFL) teams using pregame hyperhydration with intravenous fluid (IVF), the most common protocols for using the IVF, the complications from this routine, and the perceived efficacy of this treatment.

DESIGN

Cross-sectional survey study.

SETTING

National Football League.

PARTICIPANTS

The head athletic trainer from all 32 NFL teams received and completed the survey.

INTERVENTION

A survey designed to answer the aforementioned topics.

MAIN OUTCOME MEASURES

Number of teams using IVF to hyperhydrate euvolemic players before NFL games.

RESULTS

All teams (100%, 32 of 32) responded. Seventy-five percent (24 of 32) of NFL teams used pregame hyperhydration with IVF. On average, 5 to 7 players per team per game received IVF. Players received an average of 1.5 L of fluid, an average of 2.5 hours before the game. When the athletic trainers were asked to mark all the reasons why they use pregame hyperhydration with IVF, the most commonly cited reason was muscle cramps (23 of 24). However, player request was the number one answer (10 of 24) when the athletic trainers were asked to mark only the primary reason for giving IVF. Of the 27 head athletic trainers who had used pregame hyperhydration with IVF in the past, 13 (48%) reported complications.

CONCLUSIONS

Pregame hyperhydration is a common practice in the NFL. Because pregame hyperhydration with IVF is often a player- driven routine and has potential complications, more scientific studies are needed to determine its true efficacy.

Hydration status after overnight fasting as measured by urine osmolality does not alter the magnitude of hypotension during general anesthesia in low risk patients

BACKGROUND

The increased distribution of crystalloid solution into the interstitial space may decrease the effectiveness of intravascular volume loading in patients. We investigated whether preoperative hydration status after overnight fasting affects interstitial fluid redistribution and thus the magnitude of hypotension during general anesthesia.

METHODS

Sixty ASA physical status I/II patients undergoing tympanoplasty fasted from midnight. Anesthesia was induced by fentanyl and propofol and maintained with sevoflurane and remifentanil. Coinciding with the induction of anesthesia, 15 mL/kg acetated Ringer solution was infused IV over 60 minutes followed by 1 mL/kg acetated Ringer solution over the next 30 minutes. Urine osmolalities after induction of anesthesia and during the study period (pre-U(osm), post-U(osm)) and percent decreases of whole-body bioelectrical resistance for extracellular fluid relative to baseline at the end of the study period (ΔR(e)) were measured. Patients with a pre-U(osm) < the 25th percentile or with a pre-U(osm) > the 75th percentile of pre-U(osm) were categorized in the hydrated or the dehydrated group, respectively. A range of variables, including mean arterial blood pressure during the 30- to 90-minute period relative to baseline, and ΔR(e), were compared between the groups.

RESULTS

The dehydrated group (pre-U(osm) >759.5 mOsm/kg, n = 15) had a lower age (44 vs 52 years, P = 0.049) and had a higher post-U(osm) (181 vs 55 mOsm/kg, P = 0.001) compared with the hydrated group (pre-U(osm) <378.5 mOsm/kg, n = 15). Mean arterial blood pressure during the 30- to 90-minute period relative to baseline (0.67 vs 0.67, P = 0.85) with 95% confidence interval for the difference of means (-0.070 to 0.084) and ΔR(e) (5.6% vs 6.0%, P = 0.58) with 95% confidence interval for the difference of means (-1.85% to 1.06%) were similar for the hydrated and dehydrated groups.

CONCLUSIONS

Preoperative dehydration after overnight fasting as measured by urine osmolality did not alter the magnitude of hypotension during general anesthesia. This finding suggests that intravascular volume loading with crystalloid solution to prevent hypotension during general anesthesia is an unfounded practice for low risk patients after overnight fasting.

Comparison of the effect of 6% hydroxyethyl starch and gelatine on cardiac and stroke volume index: a randomized, controlled trial after cardiac surgery

BACKGROUND AND AIMS

The objective of this study was to find out the effect of various doses of hydroxyethyl starch (HES), gelatine or Ringer's acetate on cardiac and stroke volume index after cardiac surgery.

MATERIAL AND METHODS

Three consecutive boluses (each 7 mL·kg(-1)) of either 6% HES 130/0.4, 4% gelatine, or Ringer's acetate solutions were administered to 45 patients postoperatively. The rate of infusions was adjusted according to haemodynamic measurements. Thereafter, infusion of the study solution (7 mL·kg(-1)) was continued for the following 12 hours. The total dose of study solution was 28 mL·kg(-1).

RESULTS AND CONCLUSION

Mean (SD) cardiac and stroke volume indices were greater in the HES group [2.8 L·min(-1)·m(-2) (0.7), 34.1 (6.7) ml·m( -2)] than in the gelatine group [2.2 L·min(-1)·m( -2) (0.6), 25.8 (7.2) ml·m(-2)] after completion of 7 mL·kg(-1) of study solution. At this stage, the effect of gelatine did not differ from Ringer's acetate. After completion of 14 mL·kg(-1) and 21 mL·kg(-1) of colloids, similar cardiac and stroke volume indices were observed and the haemodynamic response was better in both colloid groups than in the Ringer's acetate group. No differences between groups were detected on the first postoperative morning. In the early postoperative phase after cardiac surgery, the effect of a single dose of HES solution on the haemodynamics was superior to the effect of gelatine or Ringer's acetate. However, after repeated administration of the study solutions, the haemodynamics in the two colloid groups appeared to be similar, but superior to the Ringer's acetate group.

A meta-analysis of randomised controlled trials of intravenous fluid therapy in major elective open abdominal surgery: getting the balance right

The terminology used for describing intervention groups in randomised controlled trials (RCT) on the effect of intravenous fluid on outcome in abdominal surgery has been imprecise, and the lack of standardised definitions of the terms 'standard', 'restricted' and 'liberal' has led to some confusion and difficulty in interpreting the literature. The aims of this paper were to clarify these definitions and to use them to perform a meta-analysis of nine RCT on primarily crystalloid-based peri-operative intravenous fluid therapy in 801 patients undergoing elective open abdominal surgery. Patients who received more or less fluids than those who received a 'balanced' amount were considered to be in a state of 'fluid imbalance'. When 'restricted' fluid regimens were compared with 'standard or liberal' fluid regimens, there was no difference in post-operative complication rates (risk ratio 0.83 (95% CI 0.49, 1.39, P = 0.47) [corrected] or length of hospital stay (weighted mean difference (WMD) - 1.77 (95% CI - 4.36, 0.81) d, P = 0.18). However, when the fluid regimens were reclassified and patients were grouped into those who were managed in a state of fluid 'balance' or 'imbalance', the former group had significantly fewer complications (risk ratio 0·59 (95% CI 0·44, 0·81), P=0·0008) and a shorter length of stay (WMD -3·44 (95% CI -6·33, -0·54) d, P=0·02) than the latter. Using imprecise terminology, there was no apparent difference between the effects of fluid-restricted and standard or liberal fluid regimens on outcome in patients undergoing elective open abdominal surgery. However, patients managed in a state of fluid balance fared better than those managed in a state of fluid imbalance.