Comparing the compensatory reserve metric obtained from invasive arterial measurements and photoplethysmographic volume-clamp during simulated hemorrhage

PURPOSE

The compensatory reserve metric (CRM) is a novel tool to predict cardiovascular decompensation during hemorrhage. The CRM is traditionally computed using waveforms obtained from photoplethysmographic volume-clamp (PPGVC), yet invasive arterial pressures may be uniquely available. We aimed to examine the level of agreement of CRM values computed from invasive arterial-derived waveforms and values computed from PPGVC-derived waveforms.

METHODS

Sixty-nine participants underwent graded lower body negative pressure to simulate hemorrhage. Waveform measurements from a brachial arterial catheter and PPGVC finger-cuff were collected. A PPGVC brachial waveform was reconstructed from the PPGVC finger waveform. Thereafter, CRM values were computed using a deep one-dimensional convolutional neural network for each of the following source waveforms; (1) invasive arterial, (2) PPGVC brachial, and (3) PPGVC finger. Bland-Altman analyses were used to determine the level of agreement between invasive arterial CRM values and PPGVC CRM values, with results presented as the Mean Bias [95% Limits of Agreement].

RESULTS

The mean bias between invasive arterial- and PPGVC brachial CRM values at rest, an applied pressure of -45mmHg, and at tolerance was 6% [-17%, 29%], 1% [-28%, 30%], and 0% [-25%, 25%], respectively. Additionally, the mean bias between invasive arterial- and PPGVC finger CRM values at rest, applied pressure of -45mmHg, and tolerance was 2% [-22%, 26%], 8% [-19%, 35%], and 5% [-15%, 25%], respectively.

CONCLUSION

There is generally good agreement between CRM values obtained from invasive arterial waveforms and values obtained from PPGVC waveforms. Invasive arterial waveforms may serve as an alternative for computation of the CRM.

Dextran-based Drug Delivery Approaches for Lung Diseases: A Review

Respiratory disorders, such as tuberculosis, cystic fibrosis, chronic obstructive pulmonary disease, asthma, lung cancer, and pulmonary inflammation, are among the most prevalent ailments in today's world. Dextran, an exopolysaccharide formed by Leuconostoc mesenteroides (slimeproducing bacteria), and its derivatives are investigated for several therapeutic utilities. Dextranbased drug delivery system can become an innovative strategy in the treatment of several respiratory ailments as it offers numerous advantages, such as mucolytic action, airway hydration, antiinflammatory properties, and radioprotective effect as compared to other polysaccharides. Being biocompatible, flexible hydrophilic nature, biodegradable, tasteless, odourless, non-mutagenic, watersoluble and non-toxic edible polymer, dextran-based drug delivery systems have been explored for a wide range of therapeutic applications, especially in lungs and respiratory diseases. The present article comprehensively discusses various derivatives of dextran with their attributes to be considered for drug delivery and extensive therapeutic benefits, with a special emphasis on the armamentarium of dextran-based formulations for the treatment of respiratory disorders and associated pathological conditions. The information provided will act as a platform for formulation scientists as important considerations in designing therapeutic approaches for lung and respiratory diseases. With an emphasis on lung illnesses, this article will offer an in-depth understanding of dextran-based delivery systems in respiratory illnesses.

Sepsis-associated acute kidney injury: consensus report of the 28th Acute Disease Quality Initiative workgroup

Sepsis-associated acute kidney injury (SA-AKI) is common in critically ill patients and is strongly associated with adverse outcomes, including an increased risk of chronic kidney disease, cardiovascular events and death. The pathophysiology of SA-AKI remains elusive, although microcirculatory dysfunction, cellular metabolic reprogramming and dysregulated inflammatory responses have been implicated in preclinical studies. SA-AKI is best defined as the occurrence of AKI within 7 days of sepsis onset (diagnosed according to Kidney Disease Improving Global Outcome criteria and Sepsis 3 criteria, respectively). Improving outcomes in SA-AKI is challenging, as patients can present with either clinical or subclinical AKI. Early identification of patients at risk of AKI, or at risk of progressing to severe and/or persistent AKI, is crucial to the timely initiation of adequate supportive measures, including limiting further insults to the kidney. Accordingly, the discovery of biomarkers associated with AKI that can aid in early diagnosis is an area of intensive investigation. Additionally, high-quality evidence on best-practice care of patients with AKI, sepsis and SA-AKI has continued to accrue. Although specific therapeutic options are limited, several clinical trials have evaluated the use of care bundles and extracorporeal techniques as potential therapeutic approaches. Here we provide graded recommendations for managing SA-AKI and highlight priorities for future research.

Prevention of Acute Renal Failure - Fluid Repletion and Colloids

Hypovolemia alone or in conjunction with other factors is a main reason for acute renal failure in critically ill patients. Various crystalloid and colloid solutions are available to correct hypovolemia. Some of them have been implicated in impairment of renal function. Infusion of large amounts of sodium chloride is associated with increased incidence of nausea, vomiting and hyperchloremic metabolic acidosis. While gelatins and HES are preferred colloids in patients with normal kidney function, there is some evidence that the latter are associated with impaired renal function in patients with pre-existing kidney disease. Any hyperoncotic colloid given in large amounts may decrease glomerular filtration, and should therefore be combined with crystalloids.

The interface between monitoring and physiology at the bedside

Hemodynamic instability as a clinical state represents either a perfusion failure with clinical manifestations of circulatory shock or heart failure or 1 or more out-of-threshold hemodynamic monitoring values, which may not necessarily be pathologic. Different types of causes of circulatory shock require different types of treatment modalities, making these distinctions important. Diagnostic approaches or therapies based on data derived from hemodynamic monitoring assume that specific patterns of derangements reflect specific disease processes, which respond to appropriate interventions. Hemodynamic monitoring at the bedside improves patient outcomes when used to make treatment decisions at the right time for patients experiencing hemodynamic instability.

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.

Acute kidney injury and the critically ill patient

Acute kidney injury (AKI) is a serious complication for the critically ill patient. The term has been increasingly adopted over recent years as efforts have been made to capture and better define mild to severe renal dysfunction. Persistent AKI can lead to the subsequent development of renal failure recognized as an important determinant of morbidity and mortality in the critically ill patient. This article explores the clinical implications of AKI for the critically ill patient and how this can have a profound influence on the principal presenting disease and expected outcome.

Fluid and electrolyte management for the surgical patient

For surgical patients, appropriate selection and administration of fluids can mitigate against organ failure, whereas improper dosing can exacerbate already injured systems. Fluid and electrolyte goals and deficiencies must be defined for individual patients to provide the appropriate combination of resuscitation and maintenance fluids. Specific electrolyte abnormalities should be anticipated, identified, and corrected to optimize organ functions. Using the strong-ion approach to acid-base assessment, delivered fluids that contain calculated amounts of electrolytes will interact with the patient's plasma charge and influence the patient's pH, allowing the clinician to achieve a more precise end point.

Association of 6% hetastarch resuscitation with adverse outcomes in critically ill trauma patients

BACKGROUND

Six percent hetastarch is used as a volume expander but has been associated with poor outcomes. The aim of this study was to evaluate trauma patients resuscitated with hetastarch.

METHODS

A retrospective review was performed of adult trauma patients. Demographics, injury severity, laboratory values, outcomes, and hetastarch use were recorded.

RESULTS

A total of 2,225 patients were identified, of whom 497 (22%) received hetastarch. There were no differences in age, gender, injury mechanism, lactate, hematocrit, or creatinine. The mean injury severity score was different: 29.7 ± 12.6 with hetastarch versus 27.5 ± 12.6 without hetastarch. Acute kidney injury developed in 65 hetastarch patients (13%) and in 131 (8%) without hetastarch (relative risk, 1.73; 95% confidence interval [CI], 1.30-2.28). Hetastarch mortality was 21%, compared with 11% without hetastarch (relative risk, 1.84; 95% CI, 1.48-2.29). Multivariate logistic regression demonstrated hetastarch use (odds ratio, 1.96; 95% CI, 1.49-2.58) as independently significant for death. Hetastarch use was independently significant for renal dysfunction as well (odds ratio, 1.70; 95% CI, 1.22-2.36).

CONCLUSIONS

Because of the detrimental association with renal function and mortality, hetastarch should be avoided in the resuscitation of trauma patients.

An Official ATS/ERS/ESICM/SCCM/SRLF Statement: Prevention and Management of Acute Renal Failure in the ICU Patient: an international consensus conference in intensive care medicine

OBJECTIVES

To address the issues of Prevention and Management of Acute Renal Failure in the ICU Patient, using the format of an International Consensus Conference.

METHODS AND QUESTIONS

Five main questions formulated by scientific advisors were addressed by experts during a 2-day symposium and a Jury summarized the available evidence: (1) Identification and definition of acute kidney insufficiency (AKI), this terminology being selected by the Jury; (2) Prevention of AKI during routine ICU Care; (3) Prevention in specific diseases, including liver failure, lung Injury, cardiac surgery, tumor lysis syndrome, rhabdomyolysis and elevated intraabdominal pressure; (4) Management of AKI, including nutrition, anticoagulation, and dialysate composition; (5) Impact of renal replacement therapy on mortality and recovery.

RESULTS AND CONCLUSIONS

The Jury recommended the use of newly described definitions. AKI significantly contributes to the morbidity and mortality of critically ill patients, and adequate volume repletion is of major importance for its prevention, though correction of fluid deficit will not always prevent renal failure. Fluid resuscitation with crystalloids is effective and safe, and hyperoncotic solutions are not recommended because of their renal risk. Renal replacement therapy is a life-sustaining intervention that can provide a bridge to renal recovery; no method has proven to be superior, but careful management is essential for improving outcome.

PRO: hydroxyethylstarch can be safely used in the intensive care patient--the renal debate

INTRODUCTION

Correcting hypovolemia is fundamental when treating the critically ill. Different hydroxyethylstarch (HES) preparations with different physicochemical characteristics (mean molecular weight (Mw), molar substitution (MS), C2/C6 ratio, balanced/unbalanced) are available. The possible detrimental effect of HES on kidney function has become a major objection to using HES.

METHODS

This review focuses on the effect of HES on kidney function.

RESULTS

First and second-generation HES with high Mw (>200 kD) and high MS (>0.5) have been shown to impair kidney function in some studies of septic patients, especially when using hyperoncotic HES. More rapidly degradable HES preparations (Mw 130 kD; MS < 0.5) did not cause deterioration of kidney function in a variety of clinical conditions. Even when kidney function was impaired (serum creatinine >1.5 mg/dL) this HES preparation was without negative effect. Dissolving HES in a balanced solution instead of saline may further improve the safety of HES with regard to kidney function. Dose limitations of the specific HES preparation should be carefully considered.

CONCLUSIONS

Hyperoncotic HES should not be used in patients who are at risk of developing kidney dysfunction. In patients without preexisting kidney dysfunction there seems to be no negative effects of modern HES preparations. In septic patients with reduced kidney function (serum creatinine >2.5 mg/dL) HES should be used cautiously, because studies of these patients are not available. Dissolving HES in a balanced solution further improves the safety of HES with regard to kidney function. At present, there seems to be no good reason to generally ban use of HES in our patients.

Effects of hydroxyethyl starch resuscitation on extravascular lung water and pulmonary permeability in sepsis-related acute respiratory distress syndrome

OBJECTIVE

Hydroxyethyl starch (HES) has greater volume expansion effect and longer intravascular persistence than crystalloids. HES also decreases microvascular permeability and capillary leakage by biophysically plugging endothelial leaks, exerting an anti-inflammatory effect, and decreasing activation of endothelial cells. The aim of our study was to determine whether medium molecular weight HES (pentastarch) resuscitation in the early stage of acute respiratory distress syndrome (ARDS) simultaneously increases cardiac output without worsening pulmonary edema and whether it attenuates pulmonary vascular permeability.

DESIGN

Prospective observational study.

SETTING

Twenty-bed medical intensive care unit of a tertiary medical center.

PATIENTS

Twenty patients with early-stage ARDS.

INTERVENTION

Volume expansion with a 500-mL infusion of 10% pentastarch (HES 200/0.5) at a rate of 10 mL/kg/hr.

MEASUREMENTS AND MAIN RESULTS

Baseline hemodynamics including systemic and pulmonary artery blood pressures, central venous pressure, pulmonary artery occlusion pressure, and cardiac output were obtained from an online HP Component Monitoring System and a pulmonary artery catheter. Intrathoracic blood volume (ITBV), global end-diastolic volume, extravascular lung water (EVLW), and pulmonary vascular permeability (EVLW/ITBV) were measured with a PiCCOplus monitor. Hemodynamic measurements were repeated immediately and 2, 4, and 6 hours after volume expansion. Pentastarch loading significantly increased central venous pressure, pulmonary artery occlusion pressure, pulmonary arterial pressures, and cardiac output. Pulmonary mechanics, venous admixtures, and EVLW values remained unchanged throughout the study. EVLW/ITBV significantly decreased immediately after the pentastarch infusion.

CONCLUSIONS

In patients with early ARDS, pentastarch resuscitation significantly improved their hemodynamics and cardiac output without worsening pulmonary edema and pulmonary mechanics. It even attenuated pulmonary vascular permeability.

Prevention of acute kidney injury

Acute kidney injury is common and carries a high mortality. Many drugs have been evaluated for their role in preventing acute kidney injury, of which some are of no benefit and others may be harmful. This review discusses current interventions to prevent acute kidney injury and reviews the evidence base for each.

The risk associated with hyperoncotic colloids in patients with shock

OBJECTIVE

Crystalloids, artificial and natural colloids have been opposed as representing different strategies for shock resuscitation, but it may be relevant to distinguish fluids based on their oncotic characteristics. This study assessed the risk of renal adverse events in patients with shock resuscitated using hypo-oncotic colloids, artificial hyperoncotic colloids, hyperoncotic albumin or crystalloids, according to physician's choice.

PARTICIPANTS AND SETTING

International prospective cohort study including 1,013 ICU patients needing fluid resuscitation for shock. Patients suffering from cirrhosis or receiving plasma were excluded.

MEASUREMENTS AND RESULTS

Influence of different types of colloids and crystalloids on the occurrence of renal events (twofold increase in creatinine or need for dialysis) and mortality was assessed using multivariate analyses and propensity score. Statistical adjustment was based on severity at the time of resuscitation, risks factor for renal failure, and on variables influencing physicians' preferences regarding fluids. A renal event occurred in 17% of patients. After adjustment on potential confounding factors and on propensity score for the use of hyperoncotic colloids, the use of artificial hyperoncotic colloids [OR: 2.48 (1.24-4.97)] and hyperoncotic albumin [OR: 5.99 (2.75-13.08)] was significantly associated with occurrence of renal event. Overall ICU mortality was 27.1%. The use of hyperoncotic albumin was associated with an increased risk of ICU death [OR: 2.79 (1.42-5.47)].

CONCLUSIONS

This study suggests that harmful effects on renal function and outcome of hyperoncotic colloids may exist. Although an improper usage of these compounds and confounding factors cannot be ruled out, their use should be regarded with caution, especially because suitable alternatives exist.

Effect of hydroxyethyl starch solution in normal horses and horses with colic or acute colitis

Hydroxyethyl starch (HES) solution is an effective colloidal infusion solution in humans for treatment of hypovolaemic shock, but it has not been compared with fluids currently available for use in horses. On the basis of plasma-expanding effect of HES in normal horses, a 10% medium-molecular 200/0.5 solution of HES was subsequently tested in hypovolaemic horses. Six normal horses were given five protocols of a single infusion of HES at varying dosage rates (5, 10, 15 ml HES/kg), as well as isotonic saline (15 ml/kg) and hypertonic saline (4 ml/kg b.w.). Dehydrated horses suffering from acute colitis or those which had been treated surgically for ileus of the small or large intestine were given an i.v. infusion of 10 ml HES/kg in combination with 10 ml saline/kg. Clinical data and blood samples for testing were taken before the infusion, and then 10 min, 1 h, 2, 4, 6, 8, 10, 12 and 24 h after infusion (a.i.). A significant decrease in haematocrit was observed in protocol 1-5 for a period of up to 4, 4, 10 h, 10 min and up to 10 min; in group of colitis, during the entire 24-h testing period, and in groups of ileus of small intestine and of large intestine, up to 4 and 10 h a.i. HES decreases better and longer-lasting haematocrit and total protein than either isotonic or hypertonic saline. Half-life of HES increases due to higher dosage (5.83, 7.63 and 11.48 h) and distribution is exclusively intravascular. In normal horses of protocol 1-3 using HES aPTT, sodium and potassium were within the physiological range. Serum amylase activity is increased in horses using HES. On the basis of this clinical study, the decreasing effect of urea and creatinine in colic patients after surgery and fewer instances of postoperative ileus a dosage of 10 ml HES/kg could be recommended.

Influence of volume therapy with a modern hydroxyethylstarch preparation on kidney function in cardiac surgery patients with compromised renal function: a comparison with human albumin

OBJECTIVE

There is continuing concern about the influence of hydroxyethylstarch on renal function in patients with compromised kidney function.

DESIGN

Prospective, randomized, single-center study.

SETTING

University-affiliated hospital.

PATIENTS

Fifty patients undergoing elective, first-time coronary artery bypass grafting using cardiopulmonary bypass with a preoperative serum creatinine between 1.5 and 2.5 mg/dL.

INTERVENTIONS

According to a prospective, randomized sequence, the patients received either hydroxyethylstarch with a low molecular weight (mean molecular weight 130 kD) and a low molar substitution (0.4) (6% hydroxyethylstarch 130/0.4) (n = 25) or 5% human albumin (n = 25). Volume was added to the priming (500 mL) and given perioperatively until the second postoperative day to keep pulmonary artery occlusion pressure or central venous pressure between 12 and 14 mm Hg.

MEASUREMENTS AND MAIN RESULTS

Serum creatinine and cystatin plasma levels were measured from arterial blood samples. From urine specimens, N-acetyl-beta-D-glucosaminidase, glutathione transferase-alpha, and neutrophil gelatinase-associated lipocalin were measured. Measurements were performed after induction of anesthesia, at the end of surgery, 5 hrs after surgery, and on the first and second postoperative days. A follow-up after discharge from the hospital (60 days) was also done. Similar amounts of hydroxyethylstarch and albumin were infused. Serum creatinine, glomerular filtration rate, and cystatin C plasma levels were without significant differences between the groups. Concentrations of kidney-specific proteins were elevated at baseline and increased significantly after surgery without showing group differences. Urinary levels of neutrophil gelatinase-associated lipocalin increased more in the albumin- than in the hydroxyethylstarch-treated patients. None of the patients developed acute renal failure requiring renal replacement therapy during the hospital stay and thereafter.

CONCLUSIONS

A hydroxyethylstarch preparation with a low molecular weight and a low molar substitution given in cardiac surgery patients with preoperative compromised kidney function did not negatively influence kidney integrity compared with a human albumin-based volume replacement strategy.

[The design of the VISEP trial. Critical appraisal]

The survey transcript of the VISEP interventional trial "Prospective randomized multicenter study on the influence of colloid vs crystalloid volume resuscitation and of intensive vs conventional insulin therapy on outcome in patients with severe sepsis and septic shock" [Clinical trials.gov. identifier: NCT00135473; study start April 2003] comprises, according to the data of the year 2003, methodological shortcomings which challenge a priori the study design and thus the resolution of the purpose of the study, i.e., "determination of the influence of the studied volume and insulin interventions on morbidity and mortality of patients with severe sepsis and septic shock". The most important points of criticism are: 1. A volume therapy with exclusively crystalloids or colloids with the chosen colloid hyperoncotic, hyperchloremic HES solution (10% hydroxyethyl starch: 10% Hemohes) or the crystalloid solution with high lactate content (Sterofundin) is neither acceptable nor practicable, even if only due to exceeding the maximum dosage as recommended by the manufacturer. 2. The fact known since the year 2001 that high molecular weight, poorly biodegradable HES preparations can present an independent risk-factor for acute kidney failure in patients with sepsis or septic shock was ignored: the exclusion criterion of a serum-creatinine value of >320 micromol/l (>3.6 mg/dl) was doubled in relation to the manufacturer's specification. 3. The hyperoncotic colloid solution used (10% Hemohes) may only be employed for a brief period: it is highly hyperchloremic and causes extravascular hypohydration with consecutive reduction of renal excretion, which together with HES is a fatal combination. 4. The crystalloid solution used, i.e., Sterofundin, which contains 45 mmol/l lactate, is contraindicated with septic shock as it increases the patient's O2 consumption, hinders lactate diagnostics as a hypoxia marker by simultaneous lactate infusion, and through increased gluconeogenesis leads to hyperglycemia, at least with diabetics. 5. It is doubtful whether an intensified insulin therapy (Actrapid) can be successful if insulin is administered simultaneously with iatrogenic hyperglycemia as a result of lactate influx. Due to these flaws in the design of the VISEP trial, the only consequence can be that the results of the survey are unusable, especially with regard to the point "HES and kidney function". Thus, any further advance presentations and interpretations should be shelved in expectation of the authors' publication of all the data, in order to begin further discussions including the flaws in study design listed here.

Emergency Department Hypotension is not an Independent Risk Factor for Post-Traumatic Acute Renal Dysfunction

BACKGROUND

Hypotension has been considered to be associated with renal dysfunction. The purpose of this study was to characterize the association of Emergency Department Hypotension (EDHypo) with post-traumatic renal insufficiency (RI) and renal failure (RF).

METHODS

A Level I center Intensive Care Unit database was analyzed. We reviewed all adult trauma patients surviving for more than 24 hours. EDHypo was defined as admission systolic blood pressure of less than 90 mm Hg, RI was defined as a peak serum creatine of > or = 2.0 mg/dL, RF was defined as requiring dialysis.

RESULTS

There were 2,574 admissions studied and RI occurred in 8.3% (213) of these patients whereas RF occurred in 1.1% (28). The mortality rate with RI was 41.0% (89) and 50.0% (14) with RF. There was no significant change in the incidence of RI, RF, or RI associated mortality during the study period. EDHypo was present in 7.9% (203) of patients and the incidence of RI was significantly higher than that of non-EDHypo patients (12.2% vs. 7.9%, p = 0.028). The incidence of RF was not different (1.0% vs. 1.1%). EDHypo was not independently associated with RI or RF but Injury Severity Score > 16, renal injury, age > 55, Body Mass Index > 30, male gender, and Intensive Care Unit (ICU) admission creatine kinase > or = 5,000 U/L had an independent association with RI. No risk factor in patients with RI could reliably predict RF.

CONCLUSIONS

EDhypo is not independently associated with post-traumatic RI or RF but severity of injury, renal injury, age, Body Mass Index, male gender, and elevated creatinine kinase are independently associated with RI. In critically ill trauma patients the incidence of RI and RF and the associated mortality rate has not changed significantly during a 6-year period despite, presumably, better understanding of resuscitative strategies.

Management of fluid balance in CRRT: a technical approach

BACKGROUND

The possibility of making fluid balance errors during continuous renal replacement therapy has been identified since the beginning of this modality of treatment. The advent of automated machines has partially overcome this problem. Nevertheless, there are conditions and operation modes in which the potential for fluid balance errors is still present.

OBJECTIVE

To analyse fluid balance management in CRRT therapies across a range of currently marketed machine.

METHODS

The tests were conducted in vitro, utilizing saline solution for the blood circuit and regular dialysate/reinfusate for the dialysate/reinfusion circuit. The methodology used was based on the voluntary creation of a fluid balance error by altering the correct flow in the circuit of the different machines. Subsequently, the time for alarm occurrence and the threshold value for fluid balance error was evaluated. The alarm was overridden and the overall fluid error allowed by the machine was evaluated. Each machine was tested in conditions of different dialysate/filtrate flow rates and in different simulated treatment modalities.

RESULTS

Fluid balance errors can be easily avoided not only by a correct and careful adherence to the protocols of use of the current CRRT machines, but also by the compliance to prescriptions and programmed controls during therapy. Most importantly, if an alarm appears on the machine, one can try to override it without major problems; major problems may occur when multiple override commands are operated without identifying the problem and solving it adequately.

CONCLUSION

Machines seem to be designed with adequate safety features and accurate alarm systems. However, features and alarms can be manipulated by operators creating the opportunity for serious error. Physicians and nurses involved in prescription and delivery of CRRT should have precise protocols and defined procedures in relation to machine alarms to prevent major clinical problems.

MalPEG-hemoglobin (MP4) improves hemodynamics, acid-base status, and survival after uncontrolled hemorrhage in anesthetized swine

OBJECTIVES

MalPEG-hemoglobin, 4 g/dL (MP4), is a hemoglobin-based oxygen carrier with a low hemoglobin concentration, low P50 (oxygen half-saturation pressure of hemoglobin), high colloid osmotic pressure, and high viscosity. This study evaluated resuscitation with MP4 in anesthetized swine hemorrhaged 250 mL by controlled withdrawal, followed by a 5-mm tear in the abdominal aorta.

DESIGN

Randomized, unblinded.

SETTING

Academic animal laboratory.

SUBJECTS

Anesthetized male and female Swedish Landrace pigs.

INTERVENTIONS

Four groups of pigs (n = 7 each) were randomized after hemorrhage by aortic tear to receive 250 mL of MP4, Ringer's acetate, 10% pentastarch, or 4 g/dL of stroma-free hemoglobin, followed by aortic repair and transfusion of 250 mL of autologous blood. End points were 20-hr survival, hemodynamic variables, and acid-base status.

MEASUREMENTS AND MAIN RESULTS

Measurements included continuous aortic, pulmonary arterial, and central venous pressures, cardiac output by thermodilution, arterial and venous blood gases; electrolytes; lactate; base excess; oxygen delivery, consumption, and extraction ratio; hematocrit; hemoglobin; and urine output. Body weight (24-27 kg) and hemorrhage volume (26-33 mL/kg) were similar in the four groups. The nadir of mean arterial pressure (22-28 mm Hg) and the increase in lactic acid (5-8 mEq/L) after hemorrhage were similar in all groups, indicating equivalent shock in the four groups. Survival was greatest in the MP4-treated animals (six of seven) compared with Ringer's acetate (two of seven), 10% pentastarch (one of seven), and stroma-free hemoglobin (two of seven) and was accompanied by an improved recovery of arterial pressure, cardiac output, and lactate. Total hemoglobin concentration was equivalent in all groups. Arterial pressure did not increase above baseline values, and systemic vascular resistance was unchanged following administration of MP4, indicating the lack of peripheral vasoconstriction. Mortality in Ringer's acetate, stroma-free hemoglobin, and 10% pentastarch treated animals was associated with deteriorating acid-base status, low urine output, and hyperkalemia.

CONCLUSION

These data demonstrate that restoration of oxygen delivery with a small volume of MP4 yields significant recovery from hemorrhage without systemic vasoconstriction.

Albumin and hydroxyethyl starch 130 kDa/0.4 improve filter clearance and haemocompatibility in haemo- and plasmafiltration—an in vitro study

BACKGROUND

Apart from their standard applications, haemofiltration (HF) and plasmafiltration (PF) may provide helpful therapy for sepsis, multiple organ- and acute liver-failure. Some colloids cause either decreases or increases in blood cell agglomeration. We hypothesized that solutions which reduce cell aggregability may lead to both improved filter clearance and better haemocompatibility due to decreasing rates of clogged hollow fibres.

METHODS

Heparinized porcine blood (5 IU/ml) was used in an in vitro circuit. The filter types tested were from GAMBRO: HF66D (effective membrane surface: 0.6 m2) and PF1000N (effective membrane surface: 0.15 m2). Albumin (ALB), hydroxyethyl starch (HES) 200/0.5, HES 130/0.4, gelatin (GEL) or normal saline (0.9%) were added to the blood (n = 6/group). Recirculation systems were run for 2 h. Spontaneous haemolysis and filter resistance >420 mmHg were selected as indications of maximal flow rates. Sieving coefficients were determined for 17 parameters at the lowest and highest blood flows and filtration rate.

RESULTS

Based on the filter types used, supplementation of ALB and HES130/0.4 led to an improved filter clearance without increasing the number of clogged capillary membranes or causing impaired haemocompatibility. Sieving coefficients for most solutes were independent of volume substitute and flow rate. Haemocompatibility and filter clearance deteriorated after addition of HES200 or GEL to the blood.

CONCLUSIONS

Under standardized in vitro conditions, we found that colloids which reduce cell aggregability cause improved HF- and PF-performance. This phenomenon may provide new options for higher clearances and may lead to new concepts in low dose anticoagulation.

Prevention of perioperative acute renal failure: what works?

Perioperative acute renal failure (ARF) is associated with increased morbidity and mortality. Patients undergoing cardiac, vascular and major abdominal surgery and those with pre-operative renal insufficiency are at increased risk for developing post-operative ARF. The aetiologies of perioperative ARF are multi-factorial. However, pre-renal azotaemia and ischaemic acute tubular necrosis (ATN) are the predominant causes. Preventive strategies involve identifying patients at risk, optimizing intravascular volume as well as renal function with perioperative haemodynamic monitoring, and avoiding nephrotoxins. Various pharmacological agents have been used to optimize renal perfusion and tubular function. Unfortunately, none has been shown to be effective in randomized placebo-controlled trials. In this chapter, we discuss the prophylactic use of fluids, vasoactive drugs, diuretics and other agents, as well as modification of surgical techniques to reduce the incidence of perioperative ARF.

Prevention and nondialytic treatment of acute renal failure

Based on the progress made during the last few years in understanding the pathophysiology of acute renal failure, a plethora of therapeutic drug and nondrug interventions have been developed and tested in animal and human forms of this disease. The first part of this article focuses on the role of volume expansion and vasopressors in the prevention and treatment of acute renal failure in the critically ill. From all prophylactic measures that have been proposed, volume expansion, or at least correction of volume depletion, remains the most efficient and most evidence-based intervention in these patients. Norepinephrine is, out of all the vasopressors, probably the most appropriate to use in cases of hypotension, provided circulating volume is adequate. In hypotensive septic patients, vasopressin has been shown to be useful. Direct renal vasodilating substances, the most popular still being low-dose dopamine, have never been proved to be useful in carefully performed prospective trials. Moreover dopamine especially is associated with a number of side effects and complications. From the agents acting on tubular factors, the diuretic mannitol and loop diuretics are the most prescribed. Only in specific situations such as rhabdomyolysis and kidney transplant surgery has it been shown that mannitol was able to prevent acute renal failure. The loop diuretics are able, after establishing adequate circulating volume, to promote diuresis in some forms of oliguric acute renal failure; however, some recent papers have shown that the administration of loop diuretics may actually be associated with increased mortality and delayed recovery of renal function. The last few years have seen a number of trials with acetylcysteine in the prevention of mainly radiocontrast nephropathy. Although the results are still conflicting, the majority indicates that acetylcysteine, when applied together with adequate volume expansion, may be a useful drug to incorporate in the standard treatment procedures in patients at risk for acute renal failure. Interventions to stimulate the recovery process of the damaged kidney with growth factors, although theoretically sound, have thus far not led to successful results.

Guidelines for the clinical use of albumin: comparison of use in two Italian hospitals and a third hospital without guidelines

BACKGROUND

In the absence of clinical practice guidelines prior to 1999, the consumption of human albumin in the Liguria region of Italy was very high, despite possible adverse effects, limited supply, and significant cost.

OBJECTIVE

The purpose of this study was to assess the impact of comprehensive guidelines on the amount of albumin used in 2 general hospitals and to compare it with that of a third general hospital that did not adopt the guidelines.

METHODS

We analyzed the influence of the guidelines on albumin use in 2 general hospitals (hospitals 1 and 2) in the Liguria region by comparing albumin consumption during the year before the distribution of the guidelines (1999) with consumption in the 2 years after their distribution (2000 and 2001). We compared these data with those of a third general hospital that did not adopt the guidelines (hospital 3). The parameters considered were total consumption of albumin, consumption per bed, consumption per hospital stay, mean time to discharge, expenditure per bed, and mortality rate.

RESULTS

In the years 2000 and 2001, the adoption of guidelines reduced albumin consumption in hospitals 1 and 2. In hospital 1, where the release of albumin was carefully controlled by the transfusion service, albumin use per hospital stay decreased 8.7% in 2000 and 7.6% in 2001 from 1999; in hospital 2, use decreased 73.8% and 77.4%, respectively, from 1999. In hospital 3, rejection of the guidelines was coupled with an increase of 2.9% and 8.4%, respectively, in the amount of albumin used per hospital stay. In the years 2000 and 2001, the savings in the expenditure for albumin was ∼17,000 euro in hospital 1 and ∼200,000 euro in hospital 2.

CONCLUSION

This study confirms that the adoption of guidelines may substantially reduce the inappropriate use of albumin and relative costs.

Techniques for assessing and achieving fluid balance in acute renal failure

Fluid therapy, together with attention to oxygen supply, is the cornerstone of resuscitation in all critically ill patients. Hypovolemia results in inadequate blood flow to meet the metabolic requirements of the tissues and must be treated urgently to avoid the complication of progressive organ failure, including acute renal failure. The kidney plays a critical role in body fluid homeostasis. Renal dysfunction disturbs this homeostasis and requires special attention to issues of fluid balance and fluid overload. In addition, fluid therapy is the only treatment that has been shown to be effective in the prevention of acute renal failure. Special attention to volume status is therefore required in patients at risk for acute renal failure. Hypovolemia is also a major causal factor of morbidity during hemodialysis and may contribute to further renal insults. Although the importance of fluid management is generally recognized, the choice of fluid, the amount, and assessment of fluid status are controversial. As the choice of fluids becomes wider and monitoring devices become more sophisticated, the controversy increases. This article provides an overview of the concept of fluid management in the critically ill patient with acute renal failure.

The Thoracic Surgical Patient: Initial Postoperative Care

Thoracic surgery patients require complex perioperative care. Accurate preoperative screening of pulmonary conditions can only partially predict the requirement of postoperative mechanical ventilation. In general, extensive lung resections are associated with significant gas exchange abnormalities. In this group of patients, a mechanical ventilation strategy protective from barotrauma and volutrauma and a conservative use of intraoperative and postoperative fluid limit the inevitable increase of extravascular lung water and gas exchange impairment. A wise use of pulmonary vasodilatatory and bronchodilating drugs and airway manipulation including suctioning and bronchoscopy can also significantly affect postoperative respiratory dysfunction and hospital stay. A number of acute postoperative complications have been described specifically related to the type of surgery or pleural space suctioning devices. The role of the intensivist is to maintain a low index of suspicion for such complications, when acute hemodynamic or pulmonary deterioration occurs and be prepared to immediately correct them or alert the thoracic surgeon. In general, when these roles are observed, thoracic surgery can be safely performed with a low perioperative mortality.

Current controversies in shock and resuscitation

Many controversies and uncertainties surround resuscitation of hemorrhagic shock caused by vascular trauma. Whereas the basic pathophysiology is better understood, much remains to be learned about the many immunologic cascades that lead to problems beyond those of initial fluid resuscitation or operative hemostasis. Fluid therapy is on the verge of significant advances with substitute oxygen carriers, yet surgeons are still beset with questions of how much and what type of initial fluid to provide. Finally, the parameters chosen to guide therapy and the methods used to monitor patients present other interesting issues.