Electric impedance for evaluation of body fluid balance in cardiac surgical patients

Thoracic fluid content as a novel and rapid diagnostic indicator of secondary capillary leak syndrome in pediatric patients post-cardiopulmonary bypass

Objective

Capillary leak syndrome (CLS) is an urgent problem in postoperative patients, is challenging to diagnose early, and has a poor prognosis. We investigated a quick and convenient diagnostic indicator of secondary CLS in children after cardiopulmonary bypass (CPB).

Methods

We conducted this single-center, observational, prospective study in the Department of Critical Care Medicine at the Children's Hospital of Chongqing Medical University. All the data were collected within 24 h after cardiopulmonary bypass (CPB). The secondary CLS risk factors were determined using univariate and multivariate logistic regression analysis, and the cut-off point of secondary CLS was found by receiver operating characteristic (ROC) analysis.

Results

Our study included two hundred four pediatric patients in the PICU after cardiopulmonary bypass (CPB). 42.65% (87/204) of patients were diagnosed with secondary CLS. The incidence of acute kidney injury (AKI) was 36.76% (75/204), and the mortality was 5.39% (11/204). Logistic analysis indicated that a pulmonary exudation on chest radiograph, a high thoracic fluid content (TFC) and a higher vasoactive inotropic score (VIS) were independent risk factors for secondary CLS [odds ratio [OR] 23.62, 95% confidence interval [CI] 7.20-90.41, p < 0.001; OR 1.08, 95% CI 1.02-1.16, p = 0.010; OR 1.06, 95% CI 1.01-1.14, p = 0.049; respectively]. According to the ROC analysis, the cut-off point for the TFC was 52 (Ω-1).

Conclusions

The TFC plays a key role in the early prediction of secondary CLS in children after CPB, and this novel indicator may help clinicians initiate intensive treatment as early as possible.

Use of Bioimpedance Spectroscopy for Postoperative Fluid Management in Patients Undergoing Cardiac Surgery with Cardiopulmonary Bypass

OBJECTIVE

To assess whether bioimpedance spectroscopy analysis (BIA) can be used as a tool to guide postoperative fluid management in patients undergoing cardiac surgery.

DESIGN

An observational study.

SETTING

A single tertiary hospital.

PARTICIPANTS

Patients who underwent cardiac surgery with cardiopulmonary bypass between June and November 2023 who were able to undergo BIA measurements.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Correlations between BIA measurements of extracellular fluid (ECF) and total body water (TBW) volumes and daily changes in weight and 24-hour net intake and output (I/O) of fluids were assessed. Correlations between predischarge ECF volume as a percentage of TBW volume (ECF%TBW) and predischarge pro-B-type natriuretic peptide (Pro-BNP) levels and readmissions were analyzed. Changes in daily ECF volume significantly correlated with daily weight changes (p < 0.01) and 24-hour I/O (p < 0 .01). TBW volume significantly correlated with daily weight changes (p < 0.01) and with 24-hour I/O (p = 0.04). Daily weight changes did not correlate with 24-hour I/O (p = 0.06). The patients with predischarge ECF%TBW(%) greater than or equal to 51 had significantly higher predischarge Pro-BNP than those with ECF%TBW(%) less than 51 (p < 0.01). Patients who had heart failure revisits or admissions after discharge had a higher predischarge ECF%TBW(%) on index admission compared with patients who did not have heart failure readmissions (p = 0.01).

CONCLUSIONS

BIA measurements in postoperative cardiac surgery patients may be a valuable tool to quantitatively determine fluid status to help guide fluid management in this patient population. Further studies validating the use of BIA for postoperative care in this population are warranted.

Postoperative Weight Gain within Enhanced Recovery after Cardiac Surgery

Optimal fluid therapy during perioperative care as part of enhanced recovery after cardiac surgery (ERACS) should improve the outcome. Our objective was finding out the effects of fluid overload on outcome and mortality within a well-established ERACS program. All consecutive patients undergoing cardiac surgery between January 2020 and December 2021 were enrolled. According to ROC curve analysis, a cut-off of ≥7 kg (group M, n = 1198) and <7 kg (group L, n = 1015) was defined. A moderate correlation was shown between weight gain and fluid balance r = 0.4, and a simple linear regression was significant p < 0.0001, R² = 0.16. Propensity score matching showed that increased weight gain was associated with a longer hospital length of stay (LOS) (L 8 [3] d vs. M 9 [6] d, p < 0.0001), an increased number of patients who received pRBCs (L 311 (36%) vs. M 429 (50%), p < 0.0001), and a higher incidence of postoperative acute kidney injury (AKI) (L 84 (9.8%) vs. M 165 (19.2%), p < 0.0001). Weight gain can easily represent fluid overload. Fluid overload after cardiac surgery is common and is associated with prolonged hospital LOS and increases the incidence of AKI.

Tools for assessing lung fluid in neonates with respiratory distress

Background

Transient tachypnea of the newborn (TTN), as a common cause of neonatal respiratory distress, needs to be distinguished from respiratory distress syndrome (RDS). Various modalities such as lung ultrasonography, cytokine analysis, and electrical cardiometry for the evaluation of lung fluid can be helpful for the exact diagnosis, however, clinical diagnosis has been applied mainly. This study aimed to evaluate the usefulness of the various tools for the diagnosis of TTN and RDS in neonates.

Methods

This study evaluated 22 late-preterm and term infants admitted to the neonatal intensive care unit of Gangnam Severance Hospital because of respiratory distress. Total 9 neonates were diagnosed with TTN and 13 had RDS. In addition to chest radiography, the LUS score was calculated by a neonatologist using the portable ultrasound device. Cytokines in the bronchoalveolar lavage fluid supernatant were measured. Thoracic fluid content was measured using an electrical cardiometry device.

Results

We enrolled 22 patients with median gestational age, 37.1 weeks, and birth weight 3100 g. There is no difference in patient characteristics between RDS and TTN group. Lung ultrasound score was significantly higher in RDS than TTN (11 vs 6, p = 0.001). Score 0 is shown in all infants with TTN. Score 1 is shown as significantly more in RDS than TTN. Between the TTN and RDS groups, there were significant differences in the changes of thoracic fluid content (2 vs − 1.5, p < 0.001), IL-1β levels (2.5 vs 11.3, p = 0.02), and TNF-α levels (20.1 vs 11.2, p = 0.04).

Conclusion

We found lung ultrasound and electrical cardiometry to be reliable diagnostic tools for assessing infants with respiratory distress among late-preterm and term infants. Further studies with a large number of patients are needed to confirm their clinical usefulness.

Hemodilution is associated with underestimation of serum creatinine in cardiac surgery patients: a retrospective analysis

Background

Fluid overload is related to the development and prognosis of cardiac surgery-associated acute kidney injury (CSA-AKI). The study is to investigate the influence of serum creatinine (SCr) corrected by fluid balance on the prognosis of patients with cardiac surgery.

Methods

A retrospective study was conducted in 1334 patients who underwent elective cardiac surgery from January 1 to December 31, 2015. Kidney Disease: Improving Global Outcomes (KDIGO) criteria for AKI were applied to identify CSA-AKI. SCr was measured every 24 h during ICU period and was accordingly adjusted for cumulative fluid balance. Changes in SCr, defined as ∆Crea, were determined by difference between before and after adjustment for cumulative fluid balance. All patients were then divided into three groups: underestimation group (∆Crea ≥ P₇₅), normal group (P₂₅ < ∆Crea < P₇₅) and overestimation group (∆Crea ≤ P₂₅).

Results

The incidence of AKI increased from 29.5% to 31.8% after adjustment for fluid balance. Patients in underestimation group showed prolonged length of ICU stay compared with normal group and overestimation group (3.2 [1.0–4.0] vs 2.1 [1.0–3.0] d, P < 0.001; 3.2  [1.0–4.0] vs 2.3 [1.0–3.0] d, P < 0.001). Length of hospital stay and mechanical ventilation dependent days in underestimation group were significantly longer than normal group (P < 0.001). Multivariate analysis showed age, baseline SCr and left ventricular ejection fraction were independently associated with underestimation of creatinine.

Conclusions

Cumulative fluid balance after cardiac surgery disturbs accurate measurement of serum creatinine. Patients with underestimation of SCr were associated with poor prognosis.

Does Intraoperative Diuretic Therapy Affect the Thoracic Fluid Content and Clinical Outcome in Patients Undergoing Mitral Valve Surgery?

Pulmonary congestion is inevitable in valvular heart disease. The condition worsens when a patient undergoes cardiopulmonary bypass (CPB). Thoracic fluid content (TFC) is an indicator of total volume status of lung in health and disease. We hypothesize that intraoperative diuretic therapy can improve the hemodynamic and clinical outcome in patients undergoing mitral valve surgery by decreasing TFC as measured by impedance cardiography (ICG).

Sixty adult patients with critical mitral stenosis scheduled for mitral valve surgery divided into diuretic (Gr D, n = 30) and control (Gr C, n = 30) group. One mg/kg of furosemide was administered before CPB to Gr D and similar volume of normal saline to Gr C. Hemodynamic and TFC measurements were done by index of contractility (ICON), NICOM monitor at baseline, before anesthesia induction (T1), post skin closure (T2), postoperatively at 6th hour (T3), 24th hour (T4), and 48th hour (T5). The duration of mechanical ventilation (hour), intensive care unit stay (day) and inotropic score was significantly higher in Gr C (5.29 ± 1.4 vs. 2.15 ± 1.1; p = 0.001; 2.11 ± 0.64 vs. 1.67 ± 0.57, p = 0.002; 9 ± 5.4 vs. 5.8 ± 3.2, p = 0.05), respectively. Three patients in Gr C developed respiratory complication during their course of hospital stay. The baseline TFC value was comparable (p = 0.08). In Gr C. it gradually increased over time and never reached the baseline value, whereas in Gr D, there was slight increase in TFC till 6th postoperative hour and it came below the baseline value at 48th hour. A significantly higher TFC value in Gr C in comparison with Gr D from 6th to 48th postoperative hour (p = 0.005, 0.000, and 0.005, respectively) was observed.

The ICON had a gradual improvement from 12th over 48th postoperative hour in Gr D in comparison to Gr C. The systemic vascular resistance index was decreased over time in Gr C, whereas in Gr D there was a mild fall at the end of surgery and it came back to near the baseline value at 48th postoperative hour. A continuous decrease in DO2 I except at 6th postoperative hour was seen in Gr C, whereas it remained near the baseline value in Gr D.

Linear regression analysis showed significant direct correlation of TFC with intraoperative fluid balance (r = 0.524, p = 0.001), cumulative fluid balance (r = 0.680, p = 0.000) and both peak and mean airway pressure (r = 0.436, p = 0.001 and r = 0.548, p = 0.001, respectively).

We concluded that TFC is clearly influenced by intraoperative diuretic therapy. A decrease in TFC has an association with better hemodynamic parameters that could find interesting clinical applications in the decision, whether or not to include a diuretic as a routine therapy during intraoperative management in valve surgery patients.

Fluid Status After Cardiac Surgery Assessed by Bioelectrical Impedance Vector Analysis and the Effects of Extracorporeal Circulation

OBJECTIVE

Hydration status after cardiac surgery can be difficult to assess, often requiring invasive measurements. Bioelectrical impedance vector analysis (BIVA) is based on patterns of resistance (R) and reactance (Xc), corrected by height, and has been used in various clinical scenarios to determine body composition and monitor its changes over time. The purpose of the present study was to apply this method in cardiac surgery patients to assess the variation in hydration status and to compare its changes according to the use of extracorporeal circulation.

DESIGN

Single-center, observational, prospective study including patients older than 18 years undergoing elective or urgent cardiac surgery.

SETTING

Intensive cardiac care unit of a tertiary center in a metropolitan area.

PARTICIPANTS

The study comprised 76 patients with a median age of 60 years and mostly undergoing coronary artery bypass grafting (CABG) (n = 47 [61.8%]) with extracorporeal circulation (n = 54 [73%]).

INTERVENTIONS

Bioimpedance was measured with a standard tetrapolar single-frequency bioimpedance meter using a standardized procedure and plotted in an R-Xc graph.

MEASUREMENTS AND MAIN RESULTS

The study demonstrated an increase in total body water immediately after surgery that was sustained until producing hyperhydration 24 hours later. Off-pump CABG was associated with a normal hydration status after surgery, whereas on-pump CABG produced a significant increase in total body water.

CONCLUSIONS

Fluid status assessment with BIVA in cardiac surgery showed an increase in total body water up to 24 hours after surgery. Off-pump surgery prevented overhydration, which partially could explain the reduction in some of the postoperative complications. BIVA could serve as a useful method for monitoring fluid status in the setting of goal-directed therapy to assist in maintaining euvolemia in cardiac surgical patients.

Thoracic fluid content: a novel parameter for predicting failed weaning from mechanical ventilation

Background

Weaning of patients from the mechanical ventilation remains one of the critical decisions in intensive care unit. This study aimed to evaluate the accuracy of thoracic fluid content (TFC) as a predictor of weaning outcome.

Methods

An observational cohort study included 64 critically ill surgical patients who were eligible for extubation. Before initiating the spontaneous breathing trial, the TFC was measured using the electrical cardiometry technology. Patients were followed up after extubation and divided into successful weaning group and failed weaning group. Both groups were compared according to respiratory and cardiovascular parameters. Receiver operating characteristic (ROC) curves were constructed to evaluate the ability of TFC to predict weaning outcome.

Results

The number of successfully weaned patients was 41/64 (64%). Twenty (31%) patients had impaired cardiac contractility, and of them, 13/20 (64%) patients were successfully extubated. Both groups, successful weaning group and failed weaning group, were comparable in most of baseline characteristics; however, the TFC was significantly higher in the failed weaning group compared to the successful weaning group. The area under the ROC curves (AUCs) showed moderate predictive ability for the TFC in predicting weaning failure (AUC [95% confidence interval] 0.69 [0.57-0.8], cutoff value > 50 kΩ^-1), while the predictive ability of TFC was excellent in the subgroup of patients with ejection fraction < 40% (AUC [95% confidence interval 0.93 [0.72-1], cutoff value > 50 kΩ^-1).

Conclusions

Thoracic fluid content showed moderate ability for predicting weaning outcome in surgical critically ill patients. However, in the subgroup of patients with ejection fraction less than 40%, TFC above 50 kΩ^-1 has an excellent ability to predict weaning failure.

Phase Angle as a Biomarker for Frailty and Postoperative Mortality: The BICS Study

Background Phase angle (PA) is a bioimpedance measurement that is determined lean body mass and hydration status. Patients with low PA values are more likely to be frail, sarcopenic, or malnourished. Previous work has shown that low PA predicts adverse outcomes after cardiac surgery, but the effect of PA on survival has not previously been assessed in this setting. Methods and Results The BICS (Bioimpedance in Cardiac Surgery) study recruited 277 patients undergoing major cardiac surgery at 2 university-affiliated hospitals in Montreal, QC, Canada. Bioimpedance measurements as well as frailty and nutritional assessments were performed preoperatively. The primary outcome was all-cause mortality. Secondary outcomes were 30-day mortality, postoperative morbidity, and hospital length of stay. There were 10 deaths at 1 month of follow-up and 16 deaths at 12 months of follow-up. PA was associated with age, sex, body mass index, comorbidities, and frailty, as measured by the Short Physical Performance Battery and Fried scales. After adjusting for Society of Thoracic Surgeons-predicted mortality, lower PA was associated with higher mortality at 1 month (adjusted odds ratio, 3.57 per 1° decrease in PA ; 95% confidence interval, 1.35-9.47) and at 12 months (adjusted odds ratio, 3.03 per 1° decrease in PA ; 95% confidence interval, 1.30-7.09), a higher risk of overall morbidity (adjusted hazard ratio, 2.51 per 1° decrease in PA ; 95% confidence interval, 1.32-4.75), and a longer hospital length of stay (adjusted β, 4.8 days per 1° decrease in PA ; 95% confidence interval, 1.3-8.2 days). Conclusions Low PA is associated with frailty and is predictive of mortality, morbidity, and length of stay after major cardiac surgery. Further work is needed to determine the responsiveness of PA to interventions aimed at reversing frailty.

Thoracic fluid content: a novel parameter for detection of pulmonary edema in parturients with preeclampsia

Acute pulmonary oedema is a serious complication of preeclampsia. Early detection of pulmonary edema in preeclampsia would improve fluid management and would also allow earlier detection of severe cases. The aim of this work is to evaluate the ability of thoracic fluid content measured by electrical cardiometry for early detection of pulmonary edema in parturients with preeclampsia. A prospective observational study included a cohort of preeclamptic parturients. On admission, lung ultrasound score was calculated, and thoracic fluid content was recorded using electrical cardiometry ICON device. Area under receiver operating characteristic (AUROC) curve was calculated for lung ultrasound score, thoracic fluid content for detection of pulmonary edema. Spearman correlation coefficient was calculated for correlation between lung ultrasound score and thoracic fluid content. Sixty patients were included in the study; of them, 6 patients (10%) required diuretics for pulmonary edema. Patients with pulmonary edema had higher lung ultrasound score and thoracic fluid content compared to other patients. Good correlation was reported between Lung ultrasound score and thoracic fluid content (r = 0.82). Thoracic fluid content and lung ultrasound score showed excellent diagnostic properties for pulmonary edema {AUROC: 0.941 (0.849-0.986), best cut-off value: 40 k ohm^-1}, and {AUROC: 0.961 (0.887-0.994), best cut-off value of 15.7}. In parturients with preeclampsia, both lung ultrasound score and thoracic fluid content showed excellent properties for detection pulmonary edema. The high negative predictive value of both tests makes them useful screening tests to rule out pulmonary edema. The excellent correlation between both measures suggests that electrical cardiometry could be a promising surrogate to ultrasound for assessment of extravascular lung water.

Assessment of Changes in Hemodynamics and Intrathoracic Fluid Using Electrical Cardiometry During Autologous Blood Harvest

OBJECTIVE

To evaluate the effect of autologous blood harvest (ABH)-induced volume shifts using electrical cardiometry (EC) in patients with pulmonary artery hypertension secondary to left heart disease.

DESIGN

Prospective, randomized, controlled trial.

SETTING

A tertiary care hospital.

PARTICIPANTS

The study comprised 50 patients scheduled to undergo heart valve replacement.

INTERVENTIONS

Patients were divided randomly into 2 experimental groups that were distinguished by whether ABH was performed. Blood volume extracted in the test group was replaced simultaneously with 1:1 colloid (Tetraspan; B Braun Melsungen, Melsungen, Germany). Hemodynamic, respiratory, and EC-derived parameters were recorded at predefined set points (T1 [post-induction/pre-ABH] and T2 [20 minutes post-ABH]).

MEASUREMENTS AND MAIN RESULTS

Withdrawal of 15% of blood volume in the ABH group caused significant reductions in thoracic fluid content (TFC) (-10.1% [-15.0% to -6.1%]); right atrial pressure (-23% [-26.6% to -17.6%]); mean arterial pressure (-12.6% [-22.2% to -3.8%]); airway pressures: (peak -6.2% [-11.7% to -2.8%] and mean -15.4% [-25.0% to -8.3%]); and oxygenation index (-10.34% [-16.4% to -4.8%]). Linear regression analysis showed good correlation between the percentage change in TFC after ABH and the percentage of change in right atrial pressure, stroke volume variation, autologous blood extracted, peak and mean airway pressures, and oxygen index.

CONCLUSIONS

In addition to its proven role in blood conservation, therapeutic benefits derived from ABH include decongestion of volume-loaded patients, decrease in TFC, and improved gas exchange. EC tracks beat-to-beat fluid and hemodynamic fluctuations during ABH and helps in the execution of an early patient-specific, goal-directed therapy, allowing for its safe implementation in patients with pulmonary hypertension secondary to left heart disease.

Vascular Surgery Kidney Injury Predictive Score: A Historical Cohort Study

OBJECTIVES

To develop a risk-prediction model for acute kidney injury (AKI) in patients undergoing vascular surgery.

DESIGN

A retrospective cohort study.

SETTING

A tertiary referral center.

PARTICIPANTS

Participants included 845 adult patients who underwent vascular surgery between January 3, 2003, and May 29, 2008.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The median age of patients was 72 years (interquartile range 65-80 years), and 653 patients (77%) were male. AKI developed in 258 (30.5%) patients. Patients with AKI had lower estimated glomerular filtration rates (60±21 v 72±21, p<0.001), were older (73 [68-78] years v 71 [65-80] years, p = 0.01), had a higher prevalence of hypertension (81% v 73%, p = 0.02), and were more likely to undergo emergency surgery (5% v 2%, p = 0.02). Patients with AKI also received more diuretics (p<0.001) and β-blockers (p = 0.003) prior to surgery. The multivariate AKI risk-prediction model with preoperative variables (estimated glomerular filtration rate, previous vascular interventions, use of preoperative diuretics and β-blockers, and emergency surgery) showed an area under the receiver operating characteristic curve of 0.67 (95% confidence interval, 0.628-0.710); a model with additional intraoperative variables (procedure duration, fluid balance, and plasma and platelet transfusion) had an area under the receiver operating characteristic curve of 0.72 (95% confidence interval, 0.685-0.760).

CONCLUSIONS

As AKI is a very common complication after vascular surgery, a risk-prediction model was derived to assess the likelihood of postoperative AKI. If validated in an independent cohort, this model may be used to facilitate targeted interventions in vascular surgery patients at high risk for AKI.

Fluid accumulation, recognition and staging of acute kidney injury in critically-ill patients

INTRODUCTION

Serum creatinine concentration (sCr) is the marker used for diagnosing and staging acute kidney injury (AKI) in the RIFLE and AKIN classification systems, but is influenced by several factors including its volume of distribution. We evaluated the effect of fluid accumulation on sCr to estimate severity of AKI.

METHODS

In 253 patients recruited from a prospective observational study of critically-ill patients with AKI, we calculated cumulative fluid balance and computed a fluid-adjusted sCr concentration reflecting the effect of volume of distribution during the development phase of AKI. The time to reach a relative 50% increase from the reference sCr using the crude and adjusted sCr was compared. We defined late recognition to estimate severity of AKI when this time interval to reach 50% relative increase between the crude and adjusted sCr exceeded 24 hours.

RESULTS

The median cumulative fluid balance increased from 2.7 liters on day 2 to 6.5 liters on day 7. The difference between adjusted and crude sCr was significantly higher at each time point and progressively increased from a median difference of 0.09 mg/dL to 0.65 mg/dL after six days. Sixty-four (25%) patients met criteria for a late recognition to estimate severity progression of AKI. This group of patients had a lower urine output and a higher daily and cumulative fluid balance during the development phase of AKI. They were more likely to need dialysis but showed no difference in mortality compared to patients who did not meet the criteria for late recognition of severity progression.

CONCLUSIONS

In critically-ill patients, the dilution of sCr by fluid accumulation may lead to underestimation of the severity of AKI and increases the time required to identify a 50% relative increase in sCr. A simple formula to correct sCr for fluid balance can improve staging of AKI and provide a better parameter for earlier recognition of severity progression.

[Perioperative fluid management: an analysis of the present situation]

Optimal perioperative fluid management is still controversial. Besides well known perioperative hypovolaemia, hypervolaemia has an influence on perioperative morbidity and mortality, particularly with regard to the patient's medical history, a reduced cardiac and pulmonal function and the operation itself. The concepts of preoperative, intraoperative and postoperative fluid administration are neither adequately validated, nor sufficiently integrated into a perioperative concept. At the present, moderate fluid administration to improve preoperative and postoperative outcome is safe in minor or medium surgical procedures. High-risk surgical patients benefit from a time-oriented or/and goal-oriented monitored fluid therapy. In the past only little attention has been concentrated on postoperative fluid management, but may be stimulated by the new concepts of fast track surgery.

Alteration in transthoracic impedance following cardiac surgery

INTRODUCTION

Haemodynamically significant ventricular tachyarrhythmias are a frequent complication in the immediate post-operative period after cardiac surgery. Successful cardioversion depends on delivery of sufficient current, which in turn is dependent on transthoracic impedance (TTI). However, it is uncertain if there is a change in TTI immediately following cardiac surgery using cardiopulmonary bypass (CPB).

METHODS

TTI was measured on 40 patients undergoing first time isolated cardiac surgery using CPB. TTI was recorded at 30 kHz using Bodystat Multiscan 5000 equipment before operation (with and without a positive end-expiratory pressure (PEEP) of 5 cm of H(2)O) and then at 1, 4 and 24 h after the operation. Data was analyzed to determine the relationship between pre- and post-operative variables and TTI values.

RESULTS

Mean pre-operative TTI was 54.5+/-10.55 ohms without PEEP and 61.8+/-15.4 ohms on a PEEP of 5 cm of H(2)O. TTI dropped significantly (p<0.001) after the operation to 47.2+/-10.6 ohms at 1 h, 42.6+/-10.2 ohms at 4 h and 41.8+/-10.4 ohms at 24 h. A positive correlation was noted between duration of operation and TTI change at 1 h (r=0.38; p=0.016). There was no significant correlation between the duration of bypass and change in TTI.

CONCLUSION

TTI decreases by more than 30% in the immediate post-operative period following cardiac surgery. This state may favour defibrillation at lower energy levels.

The influence of volume management on outcome

PURPOSE OF REVIEW

Fluid (volume) therapy is an integral component in the management of critically ill patients and fluid management may influence outcome. There is much controversy, however, about the type, timing and amount of fluid therapy. Here, we discuss the evidence available to guide such choices.

RECENT FINDINGS

Fluid therapy is widely endorsed for resuscitation of critically ill patients across a range of conditions. Yet, the approach to fluid therapy is subject to substantial variation in clinical practice. Emerging data show that the choice, timing and amount of fluid therapy may affect clinical outcomes. Synthetic colloids may increase the risk of acute kidney injury. Albumin may benefit hypoalbuminemic patients with sepsis and acute lung injury but may worsen outcome in traumatic brain injury. Early administration of fluid therapy in sepsis may improve survival but may be unnecessary in patients with penetrating trauma. Later fluid therapy in acute lung injury patients will increase the duration of ventilator dependence without achieving better survival. A positive cumulative balance likely contributes to increased morbidity and mortality after major surgery.

SUMMARY

Emerging evidence shows that choice, timing and amount of fluid therapy affect outcome. Future studies need to focus on these aspects of fluid therapy by means of larger, more rigorous and blinded controlled trials.

Determinanten des insensiblen Flüssigkeitsverlustes

Accurate perioperative fluid balance is the basis of a targeted infusion regimen. However, neither the initial status nor perioperative changes of the fluid compartments can be reliably measured in daily routine. In particular, insensible losses are not consistently assessed, so that substitution therapy is generally empirical. The object of this paper is to communicate the scientific data on this topic. Preoperative fasting (10 h) does not per se cause intravascular hypovolemia. In adults, total basal evaporation by way of the skin and airways and of any wounds during major abdominal interventions is usually less than 1 ml/kg/h. An inconstant fluid and protein shift towards the interstitial space perioperatively seems to be associated with hypervolemia, which suggests it should be preventable. The decisive factor in this context seems to be deterioration of the endothelial glycocalyx, whose further patho-physiological impact is currently only partially known. Clinical studies have revealed a link between fluid restriction and improved outcome after major abdominal surgery.

Fluid therapy for the surgical patient

Perioperative fluid therapy is the subject of much controversy, and the results of the clinical trials investigating the effect of fluid therapy on outcome of surgery seem contradictory. The aim of this chapter is to review the evidence behind current standard fluid therapy, and to critically analyse the trials examining the effect of fluid therapy on outcome of surgery. The following conclusions are reached: current standard fluid therapy is not at all evidence-based; the evaporative loss from the abdominal cavity is highly overestimated; the non-anatomical third space loss is based on flawed methodology and most probably does not exist; the fluid volume accumulated in traumatized tissue is very small; and volume preloading of neuroaxial blockade is not effective and may cause postoperative fluid overload. The trials of 'goal-directed fluid therapy' aiming at maximal stroke volume and the trials of 'restricted intravenous fluid therapy' are also critically evaluated. The difference in results may be caused by a lax attitude towards 'standard fluid therapy' in the trials of goal-directed fluid therapy, resulting in the testing of various 'standard fluid regimens' versus 'even more fluid'. Without evidence of the existence of a non-anatomical third space loss and ineffectiveness of preloading of neuroaxial blockade, 'restricted intravenous fluid therapy' is not 'restricted', but rather avoids fluid overload by replacing only the fluid actually lost during surgery. The trials of different fluid volumes administered during outpatient surgery confirm that replacement of fluid lost improves outcome. Based on current evidence, the principles of 'restricted intravenous fluid therapy' are recommended: fluid lost should be replaced and fluid overload should be avoided.

The Effect of Gain in Total Body Water on Haemoglobin Concentration and Body Weight Following Cardiac Surgery

BACKGROUND

Haemodilution contributes to a low post-operative haemoglobin concentration in cardiac surgery patients. An assessment of the degree of haemodilution could contribute to the avoidance of red cell transfusion when such an act is based simply on a haemoglobin "transfusion trigger". We have recorded post-operative change in total body water along with body weight to assess the impact of haemodilution on haemoglobin concentration.

METHODS

Total body water, measured by bio-electrical impedance analysis, haemoglobin and body weight were measured pre-operatively and on the 1st, 3rd, 5th and 10th post-operative days. The percentage peri-operative change in all three variables was used to examine the paired associations.

RESULTS

Total body water and body weight underwent a fall from day 1, with both variables significantly associated up until day 10. Haemoglobin rose steadily from day 1 to 10. This rise was associated with falling total body water and body weight until day 5, but not from day 5 to 10.

CONCLUSION

Following cardiac surgery, an individual's fluid state should be considered in determining a patient's need for red cell transfusion. Monitoring body weight provides a simple estimate. Such an approach may reduce the incidence of unnecessary, and potentially counterproductive, transfusion in cardiac surgery patients.

Hemorrhage and operation cause a contraction of the extracellular space needing replacement—evidence and implications? A systematic review

BACKGROUND

Hemorrhagic hypotension or operative trauma is believed to cause a contraction of the extracellular fluid volume (ECV) beyond the measured fluid losses. The aim of this review was to explore the evidence and implications of ECV loss.

METHODS

We performed a systematic review of original trials measuring ECV changes during hemorrhage or operation. PubMed, relevant periodicals, and reference lists were searched until no further original articles appeared. The quality of both the scientific and the technical methods of the trials were evaluated.

RESULTS

A total of 61 original articles were found. The pattern appeared that all investigators reporting shock or operation to cause a disparate reduction of the ECV had measured the ECV with the same method. The ECV was calculated from very few blood samples that were withdrawn after 20 to 30 minutes of equilibration of a tracer (the (35)SO(4)-tracer). Trials calculating ECV from multiple blood samples, after longer equilibration times, or using other tracers did not find a contraction of the ECV. On the contrary, trials using a bromide tracer found the ECV to be expanded after operation.

CONCLUSIONS

The evidence supporting the idea that hemorrhage or operation cause a contraction of the ECV is weak, and probably a result of flawed methodology.

Bioelectrical impedance analysis-part II: utilization in clinical practice

BIA is easy, non-invasive, relatively inexpensive and can be performed in almost any subject because it is portable. Part II of these ESPEN guidelines reports results for fat-free mass (FFM), body fat (BF), body cell mass (BCM), total body water (TBW), extracellular water (ECW) and intracellular water (ICW) from various studies in healthy and ill subjects. The data suggests that BIA works well in healthy subjects and in patients with stable water and electrolytes balance with a validated BIA equation that is appropriate with regard to age, sex and race. Clinical use of BIA in subjects at extremes of BMI ranges or with abnormal hydration cannot be recommended for routine assessment of patients until further validation has proven for BIA algorithm to be accurate in such conditions. Multi-frequency- and segmental-BIA may have advantages over single-frequency BIA in these conditions, but further validation is necessary. Longitudinal follow-up of body composition by BIA is possible in subjects with BMI 16-34 kg/m(2) without abnormal hydration, but must be interpreted with caution. Further validation of BIA is necessary to understand the mechanisms for the changes observed in acute illness, altered fat/lean mass ratios, extreme heights and body shape abnormalities.

Effects of intravenous fluid restriction on postoperative complications: comparison of two perioperative fluid regimens: a randomized assessor-blinded multicenter trial

OBJECTIVE

To investigate the effect of a restricted intravenous fluid regimen versus a standard regimen on complications after colorectal resection.

SUMMARY BACKGROUND DATA

Current fluid administration in major surgery causes a weight increase of 3-6 kg. Complications after colorectal surgery are reported in up to 68% of patients. Associations between postoperative weight gain and poor survival as well as fluid overload and complications have been shown.

METHODS

We did a randomized observer-blinded multicenter trial. After informed consent was obtained, 172 patients were allocated to either a restricted or a standard intraoperative and postoperative intravenous fluid regimen. The restricted regimen aimed at maintaining preoperative body weight; the standard regimen resembled everyday practice. The primary outcome measures were complications; the secondary measures were death and adverse effects.

RESULTS

The restricted intravenous fluid regimen significantly reduced postoperative complications both by intention-to-treat (33% versus 51%, P = 0.013) and per-protocol (30% versus 56%, P = 0.003) analyses. The numbers of both cardiopulmonary (7% versus 24%, P = 0.007) and tissue-healing complications (16% versus 31%, P = 0.04) were significantly reduced. No patients died in the restricted group compared with 4 deaths in the standard group (0% versus 4.7%, P = 0.12). No harmful adverse effects were observed.

CONCLUSION

The restricted perioperative intravenous fluid regimen aiming at unchanged body weight reduces complications after elective colorectal resection.

Segmental bioelectrical impedance analysis

PURPOSE OF REVIEW

The bioelectrical impedance analysis method is a non-invasive, rapid accurate and practical method for assessing body composition. During last decade evidence has been gathered that supports the use of this method to monitor hydration status. This review critically examines different approaches and applications of segmental bioelectrical impedance analysis in the healthy and clinical situations.

RECENT FINDINGS

Segmental bioelectrical impedance analysis may be useful to assess appendicular lean body mass, to estimate muscle volume and to investigate possible relationships between muscle size and strength in a limited segment of the limb. The method may become a tool for the bedside detection of fluid accumulation in critical care.

SUMMARY

This is a review of segmental bioelectrical impedance. The preponderance of the published applications of bioelectrical impedance analysis focused on applications in a healthy population and in the field indicate the validity of the methods. A short description of the set-up of the segmental method is also given. This review discusses the application of segmental bioelectrical impedance analysis in children in different ethnic populations, in clinical situations. We also examine the application of the method to assessing body composition, and monitoring rapid changes in internal fluid balance in the field of haemodialysis and during surgery.