Critical Care 2010;14:325

The electronic version of this article is the complete one and can be found online at: http://ccforum.com/content/14/5/325
The present review of fluid therapy studies using balanced solutions versus isotonic saline fluids (both crystalloids and colloids) aims to address recent controversy in this topic. The change to the acid-base equilibrium based on fluid selection is described. Key terms such as dilutional-hyperchloraemic acidosis (correctly used instead of dilutional acidosis or hyperchloraemic metabolic acidosis to account for both the Henderson-Hasselbalch and Stewart equations), isotonic saline and balanced solutions are defined. The review concludes that dilutional-hyperchloraemic acidosis is a side effect, mainly observed after the administration of large volumes of isotonic saline as a crystalloid. Its effect is moderate and relatively transient, and is minimised by limiting crystalloid administration through the use of colloids (in any carrier). Convincing evidence for clinically relevant adverse effects of dilutional-hyperchloraemic acidosis on renal function, coagulation, blood loss, the need for transfusion, gastrointestinal function or mortality cannot be found. In view of the long-term use of isotonic saline either as a crystalloid or as a colloid carrier, the paucity of data documenting detrimental effects of dilutional-hyperchloraemic acidosis and the limited published information on the effects of balanced solutions on outcome, we cannot currently recommend changing fluid therapy to the use of a balanced colloid preparation.

Best Practice & Research Clinical Anaesthesiology 2009;23:225-236

Haemostatic alterations associated with the use of fluids are related to non-specific dilutional effects and colloid-specific effects, such as acquired von Willebrand syndrome, inhibition of platelet function and fibrin polymerization. Judging by currently available evidence, dextran, hetastarch and pentastarch have a more pronounced impact than tetrastarch, gelatin and albumin. In patients with hypocoagulability, tetrastarch appears to be a suitable volume expander due to its high safety index and volume efficacy. Gelatins have lower inhibitory effects on clot strength compared with tetrastarch, but their volume efficacy is also lower. Dextrans are potent anticoagulants with a high risk for adverse reactions. Albumin has negligible effects on haemostasis, but low volume efficacy and costs limit the use of a blood product as a routine volume replacement fluid. To avoid potential acidosis-induced changes in haemostasis, plasma-adapted carrier solutions may be used instead of saline-based solutions.Haemostatic alterations associated with the use of fluids are related to non-specific dilutional effects and colloid-specific effects, such as acquired von Willebrand syndrome, inhibition of platelet function and fibrin polymerization. Judging by currently available evidence, dextran, hetastarch and pentastarch have a more pronounced impact than tetrastarch, gelatin and albumin. In patients with hypocoagulability, tetrastarch appears to be a suitable volume expander due to its high safety index and volume efficacy. Gelatins have lower inhibitory effects on clot strength compared with tetrastarch, but their volume efficacy is also lower. Dextrans are potent anticoagulants with a high risk for adverse reactions. Albumin has negligible effects on haemostasis, but low volume efficacy and costs limit the use of a blood product as a routine volume replacement fluid. To avoid potential acidosis-induced changes in haemostasis, plasma-adapted carrier solutions may be used instead of saline-based solutions.

Anesth Analg 2011;113: 751-757

Cardiac output (CO) monitoring based on pulse contour analysis (Vigileo-FloTrac) has the potential to be used for goal-directed fluid therapy in the perioperative setting. However, factors such as vasopressor usage may impact Vigileo-FloTrac’s reliability in tracking CO changes. We tested third-generation Vigileo-FloTrac system’s ability to accurately measure the changes in CO induced by vasopressor administration and increased preload in comparison with esophageal Doppler measurements.

Methods
In 33 anesthetized patients, CO was monitored simultaneously by the third-generation Vigileo-FloTrac and esophageal Doppler. Hemodynamic challenges included phenylephrine (to increase vasomotor tone), ephedrine (to increase myocardial contractility and heart rate), and whole-body tilting (to increase preload). Measurements were performed before and after each intervention.

Results
Overall, 176 pairs of CO measurements were obtained. The difference between paired pulse contour and Doppler measurements of CO was 0.14 ± 2.13 L/min (mean ± SD), and the percentage error (2 SD of the difference divided by the mean CO of the reference method) was 66%. The trending ability of pulse contour versus Doppler was 23% (concordance, the percentage of the total number of data points that are in 1 of the 2 quadrants of agreement) after phenylephrine treatment, 69% (concordance) after ephedrine treatment, and 96% (concordance) after whole-body tilting.

Conclusions
The pulse contour method of measuring CO, as implemented in the third-generation Vigileo-FloTrac device, accurately tracks changes in CO when preload changes. However, the pulse contour method does not accurately track changes in CO induced with phenylephrine and ephedrine.

Anesth Analg 2001;113:803-810

Minimizing hypotension associated with spinal anesthesia for cesarean delivery by administration of IV fluids and vasopressors reduces fetal and maternal morbidity. Most studies have concentrated on noninvasive systolic blood pressure (SBP) measurements to evaluate the effect of such regimens. We used a suprasternal Doppler flow technique to measure maternal cardiac output (CO) variables in parturients receiving a phenylephrine infusion combined with the rapid administration of crystalloid or colloid solution at the time of initiation of anesthesia (coload). We hypothesized that a colloid coload compared with a crystalloid coload would produce a larger sustained increase in CO and therefore reduce vasopressor requirements.

Methods
We recruited 60 healthy term women scheduled for elective cesarean delivery under spinal anesthesia for this randomized double-blind study. Baseline heart rate, baseline SBP, and CO variables including stroke volume, corrected flow time, and contractility were recorded in the left lateral tilt position. At the time of spinal injection, subjects were allocated to receive a rapid 1-L coload of either 6% w/v hydroxyethyl starch solution (HES) or Hartmann (crystalloid) solution (HS). A phenylephrine infusion was titrated to maintain maternal baseline SBP. CO was measured at 5-minute intervals for 20 minutes after initiation of spinal anesthesia. The primary outcome, CO, was compared between groups, as were secondary outcomes: phenylephrine dose and maternal hemodynamic and fetal outcome data.

Results
Maternal demographics, surgical times, and fetal outcome data were similar between groups. There were no significant differences between groups in any measured CO variable at any time point. CO was transiently higher than baseline at 5 minutes in the HS group and at 5 and 10 minutes in the HES group (range, 0.13–1.74 L/min); the overall mean difference in CO between crystalloid and colloid over the study period was 0.06 L/min (95% confidence interval: −0.46 to 0.58). Stroke volume was higher than baseline in both groups throughout; peak velocity was consistently higher than baseline only in the HES group; and corrected flow time increased in both groups; the effect was transient in the HS but sustained in the HES group. Heart rate was not different at any time point within or between groups but did decrease over time. The total phenylephrine dose from time of spinal anesthesia to delivery was similar between groups.

Conclusion
We found no difference in CO in women randomized to colloid or crystalloid coload. In addition, there were no differences in vasopressor requirements or hemodynamic stability. We conclude that there is no advantage in using colloid over crystalloid when used in combination with a phenylephrine infusion during spinal anesthesia for elective cesarean delivery.

Ann Surg 2011;253:470-483

To provide an updated systematic review on the comparative safety of colloids based on recent clinical studies.
Background: Recent investigations, including large-scale randomized trials and meta-analyses, have sought to determine the effects of colloids on mortality and morbidity. Hypothesized differences in safety profile between hydroxyethyl starch (HES) solutions have also been evaluated in randomized trials.

Methods
Clinical studies reported since 2002 with safety data for acutely ill patients receiving HES, gelatin, dextran, or albumin were sought by computer searches and other methods. Safety endpoints included mortality, morbidity, bleeding and impaired coagulation, and acute kidney injury (AKI). Data extracted from the included study reports were qualitatively summarized.

Results
Sixty-nine clinical studies were included. Of those, 42 were randomized controlled trials (RCTs) with 10,382 total patients. New safety data, since 2002, predominantly concerned albumin or HES. A large RCT of intensive care unit patients showed that albumin does not adversely affect survival. Acute kidney injury and a dose-dependent increase in mortality were observed in a large RCT of patients with severe sepsis or septic shock receiving HES. Impaired coagulation and clinical bleeding were frequently reported after HES infusion, especially in cardiac surgery. In head-to-head randomized comparisons of different HES solutions, observed effects on coagulation and renal function were similar. Gelatin showed less impairment of coagulation than HES. Very few safety data related to dextran were identified.

Conclusions
Albumin displayed a more favorable safety profile than HES. Available evidence does not support the existence of consistent safety differences between HES solutions.

Ann Sug 2011:253;431-441

To determine whether out-of-hospital administration of hypertonic fluids would improve survival after severe injury with hemorrhagic shock.

Background
Hypertonic fluids have potential benefit in the resuscitation of severely injured patients because of rapid restoration of tissue perfusion, with a smaller volume, and modulation of the inflammatory response, to reduce subsequent organ injury.

Methods
Multicenter, randomized, blinded clinical trial, May 2006 to August 2008, 114 emergency medical services agencies in North America within the Resuscitation Outcomes Consortium. Inclusion criteria: injured patients, age >= 15 years with hypovolemic shock (systolic blood pressure <= 70 mm Hg or systolic blood pressure 71-90 mm Hg with heart rate >= 108 beats per minute). Initial resuscitation fluid, 250 mL of either 7.5% saline per 6% dextran 70 (hypertonic saline/dextran, HSD), 7.5% saline (hypertonic saline, HS), or 0.9% saline (normal saline, NS) administered by out-of-hospital providers. Primary outcome was 28-day survival. On the recommendation of the data and safety monitoring board, the study was stopped early (23% of proposed sample size) for futility and potential safety concern.

Results
A total of 853 treated patients were enrolled, among whom 62% were with blunt trauma, 38% with penetrating. There was no difference in 28-day survival-HSD: 74.5% (0.1; 95% confidence interval [CI], -7.5 to 7.8); HS: 73.0% (-1.4; 95% CI, -8.7-6.0); and NS: 74.4%, P = 0.91. There was a higher mortality for the postrandomization subgroup of patients who did not receive blood transfusions in the first 24 hours, who received hypertonic fluids compared to NS [28-day mortality-HSD: 10% (5.2; 95% CI, 0.4-10.1); HS: 12.2% (7.4; 95% CI, 2.5-12.2); and NS: 4.8%, P < 0.01].
Conclusion: Among injured patients with hypovolemic shock, initial resuscitation fluid treatment with either HS or HSD compared with NS, did not result in superior 28-day survival. However, interpretation of these findings is limited by the early stopping of the trial.

Critical Care 2009, 13:R208

Hydroxyethyl starch (HES) solutions are widely used for volume replacement therapy but are also known to compromise coagulation, impair renal function and increase long-term mortality. To test the hypotheses that HES 130/0.4 has less adverse effects than HES 200/0.5 and exerts anti-inflammatory properties we compared the effects of HES130/0.4, HES200/0.5 and saline on in vitro haemostasis and pro-inflammatory platelet function.

Methods
Whole blood samples from healthy volunteers were mixed with 6% HES130/0.4, 10% HES200/0.5, or normal saline to achieve a final haemodilution rate of 10 % or 40 %. Haemostatic capacity was characterised by thromboelastography (ROTEM) and measurement for FXIIIa activity. Platelet activation and pro-inflammatory platelet functions were characterised by flow cytometry measuring the platelet activation marker CD62P and binding of fibrinogen to platelets as well as the formation of heterotypic platelet-leukocyte conjugates.

Results
Compared to saline, HES130/0.4 dose-dependently impaired formation and firmness of the fibrin clot but did not affect the fibrin-crosslinking activity of FXIIIa. At 40 % but not at 10 % haemodilution rate HES200/0.5 also increased platelet fibrinogen binding and both HES solutions increased expression of CD62P, the main receptor for platelet-leukocyte adhesion. HES130/0.4 but not HES200/0.5 increased formation of platelet-neutrophil conjugates and, to a lesser degree, platelet-monocyte conjugates.
HES130/0.4 impairs haemostasis and stimulates pro-inflammatory blood platelet function
Conclusions
Our data demonstrate that HES130/0.4 has similar adverse effects as HES200/0.5. In particular, both types of HES impair coagulation capacity and stimulate rather than attenuate pro-inflammatory platelet function.

Crit Care Med 1990;18:728

The incidence and consequences of fluid overload in the surgical ICU (SICU) have not been well defined, but may influence length of stay, days requiring mechanical ventilation, and mortality. Forty-eight consecutive patients admitted to our SICU were prospectively monitored for acute changes in weight and its impact on clinical management and outcome. When defined as a gain >10% from their preoperative or premorbid weight (or an approximately 20% increase in total body water), 40% of patients had fluid overload. Patients were divided into three groups: those who had gained <=10%, those with a weight gain between 11% and 20%, and those with >20% increase in weight. Significant differences were found with respect to vasopressor dependence, colloid administration, and mortality. When indexed by initial Acute Physiology and Chronic Health Evaluation (APACHE H) mortality prediction scores, all groups had similar degrees of illness. On average, presumably due to volume limitations, patients were inadequately nourished during 85% of their SICU stay. Our results suggest that the morbidity of fluid overload can be significant, and warrants a fresh look at the methods of intraoperative fluid resuscitation.

Br. J. Anaesth. 2009 103: 346-351

Fluid management guided by oesophageal Doppler monitor has been reported to improve perioperative outcome. Stroke volume variation (SVV) is considered a reliable clinical predictor of fluid responsiveness. Consequently, the aim of the present trial was to evaluate the accuracy of SVV determined by arterial pulse contour (APCO) analysis, using the FloTracTM/VigileoTM system, to predict fluid responsiveness as measured by the oesophageal Doppler.

Methods
Patients undergoing major abdominal surgery received intraoperative fluid management guided by oesophageal Doppler monitoring. Fluid boluses of 250 ml each were administered in case of a decrease in corrected flow time (FTc) to <350 ms. Patients were connected to a monitoring device, obtaining SVV by APCO. Haemodynamic variables were recorded before and after fluid bolus application. Fluid responsiveness was defined as an increase in stroke volume index >10%. The ability of SVV to predict fluid responsiveness was assessed by calculation of the area under the receiver operating characteristic (ROC) curve.

Results
Twenty patients received 67 fluid boluses. Fifty-two of the 67 fluid boluses administered resulted in fluid responsiveness. SVV achieved an area under the ROC curve of 0.512 [confidence interval (CI) 0.32–0.70]. A cut-off point for fluid responsiveness was found for SVV > 8.5% (sensitivity: 77%; specificity: 43%; positive predictive value: 84%; and negative predictive value: 33%).

Conclusions
This prospective, interventional observer-blinded study demonstrates that SVV obtained by APCO, using the FloTracTM/VigileoTM system, is not a reliable predictor of fluid responsiveness in the setting of major abdominal surgery.

Anesthesiology 2008;109:723-740

Replacement of assumed preoperative deficits, in addition to generous substitution of an unsubstantiated increased insensible perspiration and third space loss, plays an important role in current perioperative fluid regimens. The consequence is a positive fluid balance and weight gain of up to 10 kg, which may be related to severe complications. Because the intravascular blood volume remains unchanged and insensible perspiration is negligible, the fluid must accumulate inside the body. This concept brings into question common liberal infusion regimens. Blood volume after fasting is normal, and a fluid-consuming third space has never been reliably shown. Crystalloids physiologically load the interstitial space, whereas colloidal volume loading deteriorates a vital part of the vascular barrier. The endothelial glycocalyx plays a key role and is destroyed not only by ischemia and surgery, but also by acute hypervolemia. Therefore, undifferentiated fluid handling may increase the shift toward the interstitial space. Using the right kind of fluid in appropriate amounts at the right time might improve patient outcome.

Principles of perioperative fluid management have received increased interest in recent years within type and amount of crystalloid and colloid, the concept of individualized goal-directed cardiovascular optimization (GDT), and finally assessed on a procedure-specific basis. In this issue, Kimberger et al., investigated the underlying tissue mechanisms during GDT management with crystalloids or colloids for abdominal surgery with a colonic anastomosis. This elegant experimental study in pigs included detailed techniques of postsurgical assessments of conventional cardiovascular variables (blood pressure, heart rate, urinary output) and microcirculatory blood flow and tissue oxygen tension in healthy and perianastomotic colonic tissue. Three types of fluid management were instituted at the end of surgery: restricted Ringer lactate (RL) versus GDT RL or GDT colloid to achieve a mixed venous oxygen saturation (Svo₂) greater than 60%.

Anesthesiology 2009;110:496-504

The aim of this study was to compare the effects of goal-directed colloid fluid therapy with goal-directed crystalloid and restricted crystalloid fluid therapy on healthy and perianastomotic colon tissue in a pig model of colon anastomosis surgery.

Methods
Pigs (n = 27, 9 per group) were anesthetized and mechanically ventilated. A hand-sewn colon anastomosis was performed. The animals were subsequently randomized to one of the following treatments: R-RL group, 3 ml [middle dot] kg-1 [middle dot] h-1 Ringer lactate (RL); GD-RL group, 3 ml [middle dot] kg-1 [middle dot] h-1 RL + bolus 250 ml of RL; GD-C group, 3 ml [middle dot] kg-1 [middle dot] h-1 RL + bolus 250 ml of hydroxyethyl starch (HES 6%, 130/0.4). A fluid bolus was administered when mixed venous oxygen saturation dropped below 60%. Intestinal tissue oxygen tension and microcirculatory blood flow were measured continuously.

Results
After 4 h of treatment, tissue oxygen tension in healthy colon increased to 150 +/- 31% in group GD-C versus 123 +/- 40% in group GD-RL versus 94 +/- 23% in group R-RL (percent of postoperative baseline values, mean +/- SD; P < 0.01). Similarly perianastomotic tissue oxygen tension increased to 245 +/- 93% in the GD-C group versus 147 +/- 58% in the GD-RL group and 116 +/- 22% in the R-RL group (P < 0.01). Microcirculatory flow was higher in group GD-C in healthy colon.

Conclusions
Goal-directed colloid fluid therapy significantly increased microcirculatory blood flow and tissue oxygen tension in healthy and injured colon compared to goal-directed or restricted crystalloid fluid therapy.

Curr Opin Anaesthesiol 2009;22:100-108

Perioperative fluid management influences patient outcome. Vascular surgery unites various surgical procedures, mainly with a high impact on patients who often have relevant preexisting illnesses. There are only scarce data on this specialty, forcing the clinician to extrapolate existing data when planning perioperative fluid management. This review aims to summarize the underlying facts.

Recent findings
Perioperative insensible perspiration does not exceed 1 ml/kg per hour. A third space shift does not exist; therefore, its primary substitution is erroneous. Rather, a crystalloid fluid excess causes a tremendous shift towards the interstitial space. Colloidal volume effects are context sensitive, that is, only their use as a substitute when blood or plasma loss occurs leads to maintenance within the circulatory space. Colloidal hypervolaemia and surgical trauma both have the potential to deteriorate the vascular barrier, leading to plasma loss into the interstitial space. Current perioperative fluid therapy should aim to maintain normovolaemia of the individual body fluid compartments as far as possible. This might be achieved by combining a protocol-based replacement of extracellular losses (urinary output plus insensible perspiration) with isotonic balanced crystalloids and blood volume optimization using isooncotic colloids.

Summary
The basis of fluid therapy in vascular surgery is a careful differential indication of the respective classes of preparations. A goal-directed approach might help to avoid hypovolaemia.

Current Opinion in Anaesthesiology 2009;22:163-167

Plasma expanders are reviewed to determine their ability to restore microvascular function as a means for extending the transfusion trigger and delaying the use of blood transfusions. This outcome is currently achievable because of the emergence of a new understanding of optimal tissue function that prioritizes maintenance of functional capillary density, which results from the normalization of blood viscosity via the increase in plasma viscosity with new viscogenic colloids.

Recent findings
Use of viscous plasma expanders in experimental models of extreme hemodilution, hemorrhagic shock and endotoxemia shows that the limiting factor in anemia is not oxygen-carrying capacity but the decline of microvascular function due to the lowering of functional capillary density. In support of this hypothesis, we find that viscogenic colloids including high-molecular-weight starches, dextrans, polyvinylpyrrolidone, keratin and polyethylene glycol-conjugated albumin maintain or restore microvascular function in extreme hemodilution, polyethylene glycol-conjugated albumin yielding the best results.

Summary
Preclinical studies show that polyethylene glycol-conjugated albumin at concentrations in the range of 2-4% extends the transfusion trigger, providing the more extended and complete microvascular and systemic recovery from hemorrhagic shock, extreme hemodilution and endotoxemia, postponing the need of reestablish intrinsic blood oxygen-carrying capacity to hemoglobin concentrations lower than those associated with accepted transfusion triggers.

Critical Care 2009, 13:R40

Perioperative hypovolemia arises frequently and contributes to intestinal hypoperfusion and subsequent postoperative complications. Goal-directed fluid therapy (GDT) might reduce these complications. The aim of this study was to compare the effects of goal-directed administration of crystalloids and colloids on distribution of systemic, hepato-splanchnic and microcirculatory (small intestine) blood flow after major abdominal surgery in a clinically relevant pig model.

Methods
Twenty-seven pigs were anesthetized, mechanically ventilated and underwent open laparotomy. They were randomly assigned to one of the three following treatment groups: the restricted Ringer’s lactate group (R-RL, n=9) received 3 ml.kg-1.h-1 RL; the goal-directed RL group (GD-RL, n=9) received 3 ml.kg-1.h-1 RL and intermittent boluses of 250 ml RL and the goal-directed colloid group (GD-C, n=9) received 3 ml.kg-1.h-1 RL and boluses of 250 ml 6% hydroxyethyl starch (130/0.4). The two latter groups received a bolus infusion when mixed venous oxygen saturation (SvO2) was below 60% (lock out time 30 minutes). Regional blood flow was measured in the superior mesenteric artery and the celiac trunk. In the small bowel, microcirculatory blood flow was measured using laser Doppler flowmetry. Intestinal tissue oxygen tension was measured with intramural Clark-type electrodes.

Results
After 4 hours of treatment, arterial blood pressure, cardiac output, mesenteric artery flow and mixed oxygen saturation were significantly higher in groups GD-C and GD-RL than in group R-RL. Microcirculatory flow in the intestinal mucosa increased by 50% in GD-C but remained unchanged in the other two groups. Likewise, tissue oxygen tension in the intestine increased by 30% in GD-C but remained unchanged in GD-RL and decreased by 18% in the R-RL group. Mesenteric venous glucose concentrations were higher and lactate levels lower in group GD-C compared with the two crystalloid groups.

Conclusions
Goal-directed colloid administration markedly increased microcirculatory blood flow in the small intestine and intestinal tissue oxygen tension after abdominal surgery. In contrast, goal-directed crystalloid and restricted crystalloid administrations had no such effects. Additionally, mesenteric venous glucose and lactate concentrations suggest that intestinal cellular substrate levels were higher in the colloid-treated than in the crystalloid-treated animals. These results support the notion that perioperative goal-directed therapy with colloids might be beneficial during major abdominal surgery.

Acta Anaesthesiol Scand 2008; 52: 522–29

Pre-operative fasting is assumed to cause a deficit in intravascular blood volume (BV), as a result of ongoing urine production and insensible perspiration. Standard regimes consist of volume loading prior or simultaneous to any anaesthetic procedure to minimise the risk of hypotension. However, fluid overload in the context of major abdominal surgery has been shown to deteriorate patient outcome. Our study aimed to quantify total intravascular BV after fasting by direct measurements and to compare it with calculated normal values in comparable non-fasted patients.

Methods
After 10 h of fasting, total plasma volume (PV) and red cell volume (RCV) were measured via the double-label technique (indocyanine green dilution and erythrocytes labelled with fluorescein, respectively) following induction of general anaesthesia in 53 gynaecological patients suffering from malignoma of the cervix. The corresponding normal values were calculated individually from age, body height and body weight.

Results
Measured BV, RCV and PV after fasting were 4123±589, 1244±196 and 2879±496 ml, respectively. The differences to the corresponding calculated normal values were not significant (3882±366, 1474±134 and 2413±232 ml, respectively). The measured haematocrit reflected a slight anaemic state (0.35±0.03).

Conclusion
Our data suggest that even after prolonged pre-operative fasting, cardio-pulmonary healthy patients remain intravascularly normovolaemic. Therefore, hypotension associated with induction of general or neuraxial anaesthesia should perhaps be treated with moderate doses of vasopressors rather than with undifferentiated volume loading

Acta Anaesthesiol Scand 2009;108:311-317

It is unknown whether an intra-operative colloid infusion alters the dynamics of a crystalloid load administered post-operatively.

Methods
Ten patients received 12.5 ml/kg of Ringer’s lactate over 30 min 1–3 days before and 4 h after laparoscopic cholecystectomy, during which 10 ml/kg of a colloid solution, hydroxyethylstarch (HES 130/0.4), was infused. The total body clearance of the pre- and post-operative test infusions was taken as the ratio between the urinary excretion and the Hb-derived dilution of venous plasma over 150 min. The plasma clearance of the infused fluid was calculated using volume kinetics based on the plasma dilution alone. The pre-operative plasma clearance was compared with the post-operative plasma clearance and patients served as their own control.

Results
The urinary excretion averaged 350 ml for the pre-operative infusion and 612 ml post-operatively, which corresponds to 46% and 68% of the pre- and post-operative infusions, respectively. The total body clearance of the crystalloid fluid was 30 ml/min before surgery and 124 ml/min after surgery (P<0.01). The plasma clearance, as obtained from the plasma dilution alone, was 28 and 412 ml/min, respectively. The maximal increase in plasma volume was 410 ml pre-operatively vs. 220 ml post-operatively.

Conclusions
Infusion of a colloid solution in combination with a crystalloid during laparoscopic cholecystectomy increased the plasma clearance of a post-operative crystalloid infusion.

Anesth Analg 2009 108: 616-622

Recent studies have emphasized the importance of perioperative fluid restriction. However, fluid restriction regimens may increase the likelihood of insufficient perioperative fluid administration or may result in excess intravascular crystalloid replacement. We postulate that the use of transesophageal echocardiography may reduce the amount of crystalloid administered during open and laparoscopic colorectal surgery.

Methods
Fifteen ASA I and II patients scheduled for open colorectal surgery, and 15 patients scheduled for laparoscopic surgery were studied. Lactated Ringer’s solution was infused during the procedures. Left ventricular end diastolic volume index (LVEDVI) and cardiac index were assessed throughout surgery and used to guide the rate of lactated Ringer’s solution administration. Statistical analysis was performed with Student’s t-test for unpaired samples.

Results
The rate of crystalloid administration required to maintain baseline LVEDVI and cardiac index was 5.9 ± 2 mL · kg^–1 · h^–1 for open surgery and 3.4 ± 0.8 mL · kg^–1 · h^–1 for laparoscopic surgery (P < 0.01). This slower rate for laparoscopic surgery was offset by the longer surgical duration.

Conclusion
The rate of crystalloid solution to maintain baseline LVEDVI and cardiac index was greater in open surgery than laparoscopic surgery, and lower than commonly recommended for colorectal surgery.

NHS National Library of Health

From October 2006 the Association of Surgeons of Great Britain and Ireland, SARS, BAPEN Medical, the Intensive Care Society, the Association for Clinical Biochemistry and the Renal Association nominated core members of a steering committee who came together to establish consensus for good perioperative fluid prescribing. Concern arose from a high incidence of postoperative sodium and water overload, and evidence to suggest that preventing or treating this, by more accurate fluid therapy, would improve outcome.

BJA 2008;101:761-768

Stroke volume variation (SVV) is able to predict adequately the individual response to fluid loading. Our objective was to assess whether the SVV measured by a new algorithm (VigileoTM; FlotracTM) can predict fluid responsiveness.

Methods
Forty mechanically ventilated patients undergoing liver transplantation, who needed volume expansion (VE), were included. VE was done with albumin (4%) 20 mlxBMI over 20 min. SVV, pulse pressure variation (PPV), central venous pressure (CVP), and pulmonary artery occlusion pressure (PAOP) were measured immediately before and after VE. Cardiac output (CO) measured by transthoracic echocardiography (CO-TTE) was used to define responder patients if CO increased by 15% or more after VE, or non-responder otherwise. CO obtained with the pulmonary artery catheter (CO-PAC) and with Vigileo (CO-Vigileo) were also recorded.

Results
Five patients were excluded. Seventeen patients were responders (Rs) and 18 were non-responders (NRs). Before VE (i) SVV and PPV were higher in Rs and (ii) CVP and PAOP were lower in Rs. Baseline SVV and PPV correlated with change in CO induced by VE (respectively, r2=0.72, P<0.0001; r2=0.84, P<0.0001). An SVV threshold of >10% discriminated Rs with a sensitivity of 94% and a specificity of 94%. After VE, the decrease in SVV was significantly correlated with the increase in CO (r2=0.51; P<0.0001). There was no difference between the area under the ROC curves of SVV and PPV. After VE, the change in CO-Vigileo was closely correlated with change in CO-TTE (r2=0.74, P<0.0001) and with change in CO-PAC (r2=0.77, P<0.0001).

Conclusions
The SVV obtained by the Vigileo system may be used as a predictor of fluid responsiveness in patients with circulatory failure after liver transplantation. CO-Vigileo is able to track the change in CO induced by VE.