Hemodynamic monitoring in the era of evidence-based medicine

Hemodynamic instability frequently occurs in critically ill patients. Pathophysiological rationale suggests that hemodynamic monitoring (HM) may identify the presence and causes of hemodynamic instability and therefore may allow targeting therapeutic approaches. However, there is a discrepancy between this pathophysiological rationale to use HM and a paucity of formal evidence (as defined by the strict criteria of evidence-based medicine (EBM)) for its use. In this editorial, we discuss that this paucity of formal evidence that HM can improve patient outcome may be explained by both the shortcomings of the EBM methodology in the field of intensive care medicine and the shortcomings of HM itself.

Hemodynamic monitoring in the critically ill: an overview of current cardiac output monitoring methods

Critically ill patients are often hemodynamically unstable (or at risk of becoming unstable) owing to hypovolemia, cardiac dysfunction, or alterations of vasomotor function, leading to organ dysfunction, deterioration into multi-organ failure, and eventually death. With hemodynamic monitoring, we aim to guide our medical management so as to prevent or treat organ failure and improve the outcomes of our patients. Therapeutic measures may include fluid resuscitation, vasopressors, or inotropic agents. Both resuscitation and de-resuscitation phases can be guided using hemodynamic monitoring. This monitoring itself includes several different techniques, each with its own advantages and disadvantages, and may range from invasive to less- and even non-invasive techniques, calibrated or non-calibrated. This article will discuss the indications and basics of monitoring, further elaborating on the different techniques of monitoring.

Maternal body fluid composition in uncomplicated pregnancies and preeclampsia: a bioelectrical impedance analysis

OBJECTIVES

Body fluid composition changes during the course of pregnancy and there is evidence to suggest that these changes are different in uncomplicated pregnancies compared to hypertensive pregnancies. The aim of this study was to evaluate the changes in maternal body fluid composition during the course of an uncomplicated pregnancy and to assess differences in uncomplicated pregnancies versus hypertensive pregnancies by using a bio-impedance analysis technique.

STUDY DESIGN

Body fluid composition of each patient was assessed using a multiple frequency bioelectrical impedance analyser. Measurements were performed in 276 uncomplicated pregnancies, 34 patients with gestational hypertension, 35 with late onset preeclampsia and 11 with early onset preeclampsia. Statistical analysis was performed at nominal level α=0.05. A longitudinal linear mixed model based analysis was performed for longitudinal evolutions, and ANOVA with a post-hoc Bonferroni was used to identify differences between groups.

RESULTS

Measurements showed that total body water (TBW), intracellular (ICW) and extracellular water (ECW) and ECW/ICW significantly increase during the course of pregnancy. Late onset preeclampsia is associated with a higher TBW and ECW as compared to uncomplicated pregnancies, the ECW/ICW ratio is higher in preeclamptic patients compared to uncomplicated pregnancies and gestational hypertension, and ICW is not different between groups.

CONCLUSION

Body fluid composition changes differently during the course of uncomplicated pregnancies versus hypertensive pregnancies.

The neglected role of abdominal compliance in organ-organ interactions

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency medicine 2016. Other selected articles can be found online at http://www.biomedcentral.com/collections/annualupdate2016. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.

Methodological background and strategy for the 2012-2013 updated consensus definitions and clinical practice guidelines from the abdominal compartment society

The Abdominal Compartment Society (www.wsacs.org) previously created highly cited Consensus Definitions/Management Guidelines related to intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS). Implicit in this previous work, was a commitment to regularly reassess and update in relation to evolving research. Two years preceding the Fifth World Congress on Abdominal Compartment Syndrome, an International Guidelines committee began preparation. An oversight/steering committee formulated key clinical questions regarding IAH/ /ACS based on polling of the Executive to redundancy, structured according to the Patient, Intervention, Comparator, and Outcome (PICO) format. Scientific consultations were obtained from Methodological GRADE experts and a series of educational teleconferences were conducted to educate scientific review teams from among the wscacs. org membership. Each team conducted systematic or structured reviews to identify relevant studies and prepared evidence summaries and draft Grades of Recommendation Assessment, Development and Evaluation (GRADE) recommendations. The evidence and draft recommendations were presented and debated in person over four days. Updated consensus definitions and management statements were derived using a modified Delphi method. A writingcommittee subsequently compiled the results utilizing frequent Internet discussion and Delphi voting methods to compile a robust online Master Report and a concise peer-reviewed summarizing publication. A dedicated Paediatric Guidelines Subcommittee reviewed all recommendations and either accepted or revised them for appropriateness in children. Of the original 12 IAH/ACS definitions proposed in 2006, three (25%) were accepted unanimously, with four (33%) accepted by > 80%, and four (33%) accepted by > 50%, but required discussion to produce revised definitions. One (8%) was rejected by > 50%. In addition to previous 2006 definitions, the panel also defined the open abdomen, lateralization of the abdominal musculature, polycompartment syndrome, abdominal compliance, and suggested a refined open abdomen classification system. Recommendations were possible regarding intra-abdominal pressure (IAP) measurement, approach to sustained IAH, philosophy of protocolized IAP management and same-hospital-stay fascial closure, use of decompressive laparotomy, and negative pressure wound therapy. Consensus suggestions included use of non-invasive therapies for treating IAH/ACS, considering body position and IAP, damage control resuscitation, prophylactic open abdomen usage, and prudence in early biological mesh usage. No recommendations were made for the use of diuretics, albumin, renal replacement therapies, and utilizing abdominal perfusion pressure as a resuscitation-endpoint. Collaborating Methodological Guideline Development and Clinical Experts produced Consensus Definitions/Clinical Management statements encompassing the most contemporary evidence. Data summaries now exist for clinically relevant IAH/ACS questions, which will facilitate future scientific reanalysis.

Intravenous balanced solutions: from physiology to clinical evidence

"Balanced" solutions are commonly defined as intravenous fluids having an electrolyte composition close to that of plasma. As such, they should minimally affect acid-base equilibrium, as compared to the commonly reported 0.9% NaCl-related hyperchloremic metabolic acidosis. Recently, the term "balanced" solution has been also employed to indicate intravenous fluids with low chloride content, being the concentration of this electrolyte the most altered and supra-physiologic in 0.9% NaCl as compared to plasma, and based upon a suggested detrimental effect on renal function associated with hyperchloremia. Despite efforts for its identification, the ideal balanced solution, with minimal effects on acid-base status, low chloride content, and adequate tonicity, is not yet available. After the accumulation of pre-clinical and clinical physiologic data, in the last three years, several clinical trials, mostly observational and retrospective, have addressed the question of whether the use of balanced solutions has beneficial effects as compared to the standard of care, sometimes even suggesting an improvement in survival. Nonetheless, the first large randomized controlled trial comparing the effects of a balanced vs. unbalanced solution on renal function in critically-ill patients (SPLIT trial, the 0.9% Saline vs Plasma-Lyte 148 for Intensive Cate Unit Fluid Therapy), just recently published, showed identical equipoise between the two treatments. In the present review, we offer a comprehensive and updated summary on this issue, firstly, by providing a full physiological background of balanced solutions, secondly, by summarizing their potential pathophysiologic effects, and lastly, by presenting the clinical evidence available to support, at the moment, their use.

From cardiac output to blood flow auto-regulation in shock

Shock is defined as a state in which the circulation is unable to deliver sufficient oxygen to meet the demands of the tissues, resulting in cellular dysoxia and organ failure. In this process, the factors that govern the circulation at a haemodynamic level and oxygen delivery at a microcirculatory level play a major role. This manuscript aims to review the blood flow regulation from macro- and micro-haemodynamic point of view and to discuss new potential therapeutic approaches for cardiovascular instability in patients in cardiovascular shock. Despite the recent advances in haemodynamics, the mechanisms that control the vascular resistance and the venous return are not fully understood in critically ill patients. The physical properties of the vascular wall, as well as the role of the mean systemic filling pressure are topics that require further research. However, the haemodynamics do not totally explain the physiopathology of cellular dysoxia, and several factors such as inflammatory changes at the microcirculatory level can modify vascular resistance and tissue perfusion. Cellular vasoactive mediators and endothelial and glucocalix damage are also involved in microcirculatory impairment. All the levels of the circulatory system must be taken into account. Evaluation of microcirculation may help one to detect under-diagnosed shock, and together with classic haemodynamics, guide one towards the appropriate therapy. Restoration of classic haemodynamic parameters is essential but not sufficient to detect and treat patients in cardiovascular shock.

A pilot study on pharmacokinetic/pharmacodynamic target attainment in critically ill patients receiving piperacillin/tazobactam

BACKGROUND

In critically ill patients, multi-trauma and intensive therapy can influence the pharmacokinetics (PK) and pharmacodynamics (PD) of antibiotics with time-dependent bacterial killing. Consequently, PK/PD targets (%fT>MIC) - crucial for antimicrobial effects -may not be attained.

METHODS

Two patients admitted to the surgical ICU of the University Hospital in Hradec Králove for multiple-trauma were given piperacillin/tazobactam by 1-hour IV infusion 4/0.5 g every 8h. PK variables: total and renal clearance (CLtot, CLR), volume of distribution (Vd), and elimination half-life (T1/2) were calculated, followed by glomerular filtration rate (MDRD) and cumulative fluid balance (CFB-total fluid volume based on 24-h registered fluid intake minus output). The PK/PD target attainment (100%fT>MIC) was defined as free (f) piperacillin plasma concentrations that remain, during the entire dosing interval (T), above the minimum inhibitory concentration (100%fT>MIC) within days 4-8 (when CFB culminates and disappears). Piperacillin concentrations were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and corrected for unbound fraction (22%).

RESULTS

CFB culminated over days 2-5 reaching 15-30 L and was associated with a large Vd (29-42 L). While MDRD in patient 1 was low (0.3-0.4 mL s⁻¹ 1.7 m⁻²), that of patient 2 was increasing (> 3.1 mL s⁻¹ 1.7 m⁻²), which was associated with augmented CLR. In patient 2, the fT reached only 62, 52, and 44% on days 4, 6, and 8, respectively. In patient 1, the %fT was much higher, attaining values four to fivefold greater than that targeted.

CONCLUSIONS

Critically ill patients are at risk of drug under- or overdosing without dose up-titration with regard to covariate effects and individual drug pharmacokinetics.

Critical care ultrasound in cardiac arrest. Technological requirements for performing the SESAME-protocol--a holistic approach

The use of ultrasound has gained its place in critical care as part of our day-to-day monitoring tools. A better understanding of ultrasound techniques and recent publications including protocols for the lungs, the abdomen and the blood vessels has introduced ultrasound to the bedside of our ICU patients. However, we will prove in this paper that early machines, dating back more than 25 years, were perfectly able to do the job as compared to modern laptop machines with more features but few additional advantages. Ultrasound is not only a diagnostic tool, but should also be seen as an extension of the traditional physical examination. This paper will focus on the use of the SESAME-protocol in cardiac arrest. The SESAME-protocol suggests starting with a lung scan to rule out possible causes leading to cardiac arrest. Firstly, pneumothorax needs to be ruled out. Secondly, a partial diagnosis of pulmonary embolism is done following the BLUE-protocol. Thirdly, fluid therapy can be guided, following the FALLS-protocol. The SESAME-protocol continues by scanning the lower femoral veins to check for signs of deep venous thrombosis, followed by (or before, in case of trauma) the abdomen to detect massive bleeding. Next comes the pericardium, to exclude pericardial tamponade. Finally, a transthoracic cardiac ultrasound is performed to check for other (cardiac) causes leading to cardiac arrest. The emphasis is on a holistic approach, where ultrasound can be seen as the modern stethoscope needed by clinicians to complete the full physiological examination of their critically ill unstable patients.

Fluid therapy in critically ill patients: perspectives from the right heart

As right heart function can affect outcome in the critically ill patient, a thorough understanding of factors determining right heart performance in health and disease is pivotal for the critical care physician. This review focuses on fluid therapy, which remains controversial in the setting of impending or overt right heart failure. In this context, we will attempt to elucidate which patients are likely to benefit from fluid administration and for which patients fluid therapy would likely be harmful. Following a general discussion of right heart function and failure, we specifically focus on important causes of right heart failure in the critically ill, i.e. sepsis induced myocardial dysfunction, the acute respiratory distress syndrome, acute pulmonary embolism and the effects of positive pressure ventilation. It is argued that fluid therapy should always be cautiously administered with the right heart in mind, which calls for close multimodal monitoring.

Initial resuscitation from severe sepsis: one size does not fit all

Over recent decades many recommendations for the management of patients with sepsis and septic shock have been published, mainly as the Surviving Sepsis Campaign (SSC) guidelines. In order to use these recommendations at the bedside one must fully understand their limitations, especially with regard to preload assessment, fluid responsiveness and cardiac output. In this review we will discuss the evidence behind the bundles presented by the Surviving Sepsis Campaign and will try to explain why some recommendations may need to be updated. Barometric preload indicators, such as central venous pressure (CVP) or pulmonary artery occlusion pressure, can be persistently low or erroneously increased, as is the case in situations of increased intrathoracic pressure, as seen with the application of high positive end-expiratory pressure, or in situations with increased intra-abdominal pressure. Chasing a CVP of 8 to 12 mm Hg may lead to under-resuscitation in these situations. On the other hand, a low CVP does not always correspond to fluid responsiveness and may lead to over-resuscitation and all the deleterious effects on end-organ function associated with fluid overload. We will suggest the introduction of new variables and more dynamic measurements. During the initial resuscitation phase, it is equally important to assess fluid responsiveness, either with a passive leg raising manoeuvre or an end-expiratory occlusion test. The use of functional hemodynamics with stroke volume variation or pulse pressure variation may further help to identify patients who will respond to fluid administration or not. Furthermore, ongoing fluid resuscitation beyond the first 24 hours guided by CVP may lead to futile fluid loading. In patients that do not transgress spontaneously from the Ebb to Flow phase of shock, one should consider (active) de-resuscitation guided by extravascular lung water index measurements.

Hemodynamic monitoring: To calibrate or not to calibrate? Part 2--Non-calibrated techniques

There is much evidence that fluid overload leads to adverse outcomes in perioperative and critically ill patients. Cardiac output monitoring can help us guiding initial and ongoing fluid resuscitation and can help us to assess whether a patient will be responsive to fluids when hypotensive. In recent years, many sophisticated devices that measure a variety of hemodynamic parameters have evolved on the market. We wanted to provide an overview of the different techniques available today, including their validation in different patient populations. In this second part of the review, we focus on non-calibrated techniques, both invasive and non-invasive. For each technique a short overview of the working principle, together with the advantages, disadvantages and the available validation literature is listed. Many promising minimal invasive monitoring devices can help us to further optimize our hemodynamic treatment in both the perioperative and critical care setting. However, the validation data are scarce for many of these techniques, especially in complex circumstances with changing hemodynamics (preload, afterload and contractility), as with the use of fluids and vasoactive medication. The measurements made by these devices, therefore, need to be interpreted with caution. Further improvements and more validation data are needed before these techniques can be implemented in common day practice. Moreover, in severely shocked hemodynamic unstable patients, calibrated techniques are to be preferred over those which are uncalibrated. Hence, the new techniques not only need to be accurate, but also need to be precise in order to keep track of changes.

Hemodynamic monitoring: To calibrate or not to calibrate? Part 1--Calibrated techniques

Over recent decades, hemodynamic monitoring has evolved from basic cardiac output monitoring techniques to a broad variety of sophisticated monitoring devices with extra parameters. In order to reduce morbidity and mortality and optimize therapeutic strategies, different monitoring techniques can be used to guide fluid resuscitation and other medical management. Generally, they can be divided in calibrated and non-calibrated techniques. In the first part of this review, the available calibrated techniques, ranging from invasive to non-invasive, will be discussed. We performed a review of the literature in order to give an overview of the current hemodynamic monitoring devices. For each monitoring system, a short overview of the physical principles, the advantages and disadvantages and the available literature with regard to validation is given. Currently, many promising hemodynamic monitoring devices are readily available in order to optimize therapeutic management in both perioperative and ICU settings. Although several of these calibrated techniques have been validated in the literature, not all techniques have been shown to reduce morbidity and mortality. Many new techniques, especially some non-calibrated devices, lack good validation data in different clinical settings (sepsis, trauma, burns, etc.). The cardiac output values obtained with these techniques need therefore to be interpreted with caution as will be discussed in the second part of this concise review. Transthoracic echocardiography forms a good initial choice to assess hemodynamics in critically ill patients after initial stabilisation. However in complex situations or in patients not responding to fluid resuscitation alone, advanced hemodynamic monitoring is recommended with the use of calibrated techniques like transpulmonary thermodilution. Calibrated techniques are preferred in patients with severe shock and changing conditions of preload, afterload and contractility. The use of the pulmonary artery catheter should be reserved for patients with right ventricular failure in order to assess the effect of medical treatment.

Transpulmonary pressure monitoring during mechanical ventilation: a bench-to-bedside review

Different ventilation strategies have been suggested in the past in patients with acute respiratory distress syndrome (ARDS). Airway pressure monitoring alone is inadequate to assure optimal ventilatory support in ARDS patients. The assessment of transpulmonary pressure (PTP) can help clinicians to tailor mechanical ventilation to the individual patient needs. Transpulmonary pressure monitoring, defined as airway pressure (Paw) minus intrathoracic pressure (ITP), provides essential information about chest wall mechanics and its effects on the respiratory system and lung mechanics. The positioning of an esophageal catheter is required to measure the esophageal pressure (Peso), which is clinically used as a surrogate for ITP or pleural pressure (Ppl), and calculates the transpulmonary pressure. The benefits of such a ventilation approach are avoiding excessive lung stress and individualizing the positive end-expiratory pressure (PEEP) setting. The aim is to prevent over-distention of alveoli and the cyclic recruitment/derecruitment or shear stress of lung parenchyma, mechanisms associated with ventilator-induced lung injury (VILI). Knowledge of the real lung distending pressure, i.e. the transpulmonary pressure, has shown to be useful in both controlled and assisted mechanical ventilation. In the latter ventilator modes, Peso measurement allows one to assess a patient's respiratory effort, patient-ventilator asynchrony, intrinsic PEEP and the calculation of work of breathing. Conditions that have an impact on Peso, such as abdominal hypertension, will also be discussed briefly.

An overview on fluid resuscitation and resuscitation endpoints in burns: Past, present and future. Part 1 - historical background, resuscitation fluid and adjunctive treatment

An improved understanding of burn shock pathophysiology and subsequent development of fluid resuscitation strategies has led to dramatic outcome improvements in burn care during the 20th century. While organ hypoperfusion caused by inadequate resuscitation has become rare in clinical practice, there is growing concern that increased morbidity and mortality related to over-resuscitation is occurring more frequently in burn care. In order to reduce complications related to this concept of "fluid creep", such as respiratory failure and compartment syndromes, efforts should be made to resuscitate with the least amount of fluid in order to provide adequate organ perfusion. In this first part of a concise review, historic and current evidence regarding the available fluids is discussed, as well as some adjunctive treatments modulating the inflammatory response. In the second part, special reference will be made to the role of abdominal hypertension in burn care and the endpoints used to guide fluid resuscitation will be discussed. Finally, as urine output has been recognized as a poor resuscitation target, a resuscitation protocol is suggested in part two which includes new targets and endpoints that can be obtained with modern, less invasive hemodynamic monitoring devices.

The role of abdominal compliance, the neglected parameter in critically ill patients - a consensus review of 16. Part 1: definitions and pathophysiology

Over the last few decades, increasing attention has been paid to understanding the pathophysiology, aetiology, prognosis, and treatment of elevated intra-abdominal pressure (IAP) in trauma, surgical, and medical patients. However, there is presently a relatively poor understanding of intra-abdominal volume (IAV) and the relationship between IAV and IAP (i.e. abdominal compliance). Consensus definitions on Cab were discussed during the 5th World Congress on Abdominal Compartment Syndrome and a writing committee was formed to develop this article. During the writing process, a systematic and structured Medline and PubMed search was conducted to identify relevant studies relating to the topic. According to the recently updated consensus definitions of the World Society on Abdominal Compartment Syndrome (WSACS), abdominal compliance (Cab) is defined as a measure of the ease of abdominal expansion, which is determined by the elasticity of the abdominal wall and diaphragm. It should be expressed as the change in IAV per change in IAP (mL [mm Hg]⁻¹). Importantly, Cab is measured differently than IAP and the abdominal wall (and its compliance) is only a part of the total abdominal pressure-volume (PV) relationship. During an increase in IAV, different phases are encountered: the reshaping, stretching, and pressurisation phases. The first part of this review article starts with a comprehensive list of the different definitions related to IAP (at baseline, during respiratory variations, at maximal IAV), IAV (at baseline, additional volume, abdominal workspace, maximal and unadapted volume), and abdominal compliance and elastance (i.e. the relationship between IAV and IAP). An historical background on the pathophysiology related to IAP, IAV and Cab follows this. Measurement of Cab is difficult at the bedside and can only be done in a case of change (removal or addition) in IAV. The Cab is one of the most neglected parameters in critically ill patients, although it plays a key role in understanding the deleterious effects of unadapted IAV on IAP and end-organ perfusion. The definitions presented herein will help to understand the key mechanisms in relation to Cab and clinical conditions and should be used for future clinical and basic science research. Specific measurement methods, guidelines and recommendations for clinical management of patients with low Cab are published in a separate review.

The polycompartment syndrome: a concise state-of-the-art review

A compartment syndrome is defined as an increase in the compartmental pressure to such an extent that the viability of the tissues and organs within the compartment are threatened. The term describes a syndrome and not a disease, and as such there are many diseases and underlying pathophysiological processes that may lead to such a scenario. The aim of this review is to give a state-of-the-art overview on the current knowledge on different compartment syndromes and how they may interact. Suggested definitions are included. There are four major compartments in the human body: the head, chest, abdomen, and the extremities. Initially, the term multicompartment syndrome was suggested when more than one compartment was affected. But this led to confusion as the term multi- or multiple compartment syndromes is mostly used in relation to multiple limb trauma leading to compartment syndrome requiring fasciotomy. Only recently was the term 'polycompartment syndrome' coined to describe a condition where two or more anatomical compartments have elevated pressures. When more than one compartment is affected, an exponential detrimental effect on end-organ function to both immediate and distant organs can occur. Within each compartment, the disease leading towards a compartment syndrome can be primary or secondary. The compliance of each compartment is the key to determining the transmission of a given compartmental pressure from one compartment to another. The intra-abdominal pressure helps to explain the severe pathophysiological condition occurring in patients with cardiorenal, hepatopulmonary and hepatorenal syndromes. Initial treatment of a compartment syndrome should be focused on the primary compartment and is based on three principles: lowering of compartmental pressure, supporting organ perfusion, and optimisation and prevention of specific adverse events. Clinicians need to be aware of the existence of the polycompartment syndrome and the interactions of increased compartmental pressures between compartments.

Ten good reasons to practice ultrasound in critical care

Over the past decade, critical care ultrasound has gained its place in the armamentarium of monitoring tools. A greater understanding of lung, abdominal, and vascular ultrasound plus easier access to portable machines have revolutionised the bedside assessment of our ICU patients. Because ultrasound is not only a diagnostic test, but can also be seen as a component of the physical exam, it has the potential to become the stethoscope of the 21st century. Critical care ultrasound is a combination of simple protocols, with lung ultrasound being a basic application, allowing assessment of urgent diagnoses in combination with therapeutic decisions. The LUCI (Lung Ultrasound in the Critically Ill) consists of the identification of ten signs: the bat sign (pleural line); lung sliding (seashore sign); the A-lines (horizontal artefact); the quad sign and sinusoid sign indicating pleural effusion; the fractal and tissue-like sign indicating lung consolidation; the B-lines and lung rockets indicating interstitial syndromes; abolished lung sliding with the stratosphere sign suggesting pneumothorax; and the lung point indicating pneumothorax. Two more signs, the lung pulse and the dynamic air bronchogram, are used to distinguish atelectasis from pneumonia. The BLUE protocol (Bedside Lung Ultrasound in Emergency) is a fast protocol (< 3 minutes), also including a vascular (venous) analysis allowing differential diagnosis in patients with acute respiratory failure. With this protocol, it becomes possible to differentiate between pulmonary oedema, pulmonary embolism, pneumonia, chronic obstructive pulmonary disease, asthma, and pneumothorax, each showing specific ultrasound patterns and profiles. The FALLS protocol (Fluid Administration Limited by Lung Sonography) adapts the BLUE protocol to be used in patients with acute circulatory failure. It makes a sequential search for obstructive, cardiogenic, hypovolemic, and distributive shock using simple real-time echocardiography in combination with lung ultrasound, with the appearance of B-lines considered to be the endpoint for fluid therapy. An advantage of lung ultrasound is that the patient is not exposed to radiation, and so the LUCI-FLR project (LUCI favouring limitation of radiation) can be unfolded in trauma patients. Although it has been practiced for 25 years, critical care ultrasound is a relatively young but expanding discipline and can be seen as the stethoscope of the modern intensivist. In this review, the usefulness and advantages of ultrasound in the critical care setting are discussed in ten points. The emphasis is on a holistic approach, with a central role for lung ultrasound.

Fluid overload, de-resuscitation, and outcomes in critically ill or injured patients: a systematic review with suggestions for clinical practice

BACKGROUND

Sepsis is associated with generalised endothelial injury and capillary leak and has traditionally been treated with large volume fluid resuscitation. Some patients with sepsis will accumulate bodily fluids. The aim of this study was to systematically review the association between a positive fluid balance/fluid overload and outcomes in critically ill adults, and to determine whether interventions aimed at reducing fluid balance may be linked with improved outcomes.

METHODS

We searched MEDLINE, PubMed, EMBASE, Web of Science, The Cochrane Database, clinical trials registries, and bibliographies of included articles. Two authors independently reviewed citations and selected studies examining the association between fluid balance and outcomes or where the intervention was any strategy or protocol that attempted to obtain a negative or neutral cumulative fluid balance after the third day of intensive care compared to usual care. The primary outcomes of interest were the incidence of IAH and mortality.

RESULTS

Among all identified citations, one individual patient meta-analysis, 11 randomised controlled clinical trials, seven interventional studies, 24 observational studies, and four case series met the inclusion criteria. Altogether, 19,902 critically ill patients were studied. The cumulative fluid balance after one week of ICU stay was 4.4 L more positive in non-survivors compared to survivors. A restrictive fluid management strategy resulted in a less positive cumulative fluid balance of 5.6 L compared to controls after one week of ICU stay. A restrictive fluid management was associated with a lower mortality compared to patients treated with a more liberal fluid management strategy (24.7% vs 33.2%; OR, 0.42; 95% CI 0.32-0.55; P < 0.0001). Patients with intra-abdominal hypertension (IAH) had a more positive cumulative fluid balance of 3.4 L after one week of ICU stay. Interventions to decrease fluid balance resulted in a decrease in intra-abdominal pressure (IAP): an average total body fluid removal of 4.9 L resulted in a drop in IAP from 19.3 ± 9.1 mm Hg to 11.5 ± 3.9 mm Hg.

CONCLUSIONS

A positive cumulative fluid balance is associated with IAH and worse outcomes. Interventions to limit the development of a positive cumulative fluid balance are associated with improved outcomes. In patients not transgressing spontaneously from the Ebb to Flow phases of shock, late conservative fluid management and late goal directed fluid removal (de-resuscitation) should be considered.

Validation of a novel method for measuring intra-abdominal pressure and gastric residual volume in critically ill patients

BACKGROUND

Gastric residual volume (GRV) can be measured in a variety of ways in critically ill patients, most often, the nasogastric tube is disconnected and the GRV is aspirated via a 60 mL syringe. Bladder pressure (IBP) measurement is the gold standard for intra-abdominal pressure (IAP) estimation. This study will look at the validation of a novel method combining measurement of GRV and estimation of IAP via intra-gastric pressure (IGP).

METHODS

In total 135 paired IAP and 146 paired GRV measurements were performed in 37 mechanically ventilated ICU patients. The IAP was estimated via the bladder (i.e. IBP) using the FoleyManometer and via the stomach (i.e. IGP) with the new device. The GRV was measured with the new device (GRVprototype) and via the classic method (GRVclassic). The devices were provided by Holtech Medical (Charlottenlund, Denmark) and data were retrospectively analysed.

RESULTS

The number of paired measurements in each patient was 4 ± 1. The mean IBP was 10.7 ± 4.1 and mean IGP was 11.6 ± 4.1 mm Hg. Correlation between the IBP and IGP was significant, however moderate (R2 = 0.51). Analysis according to Bland and Altman showed a bias and precision of 0.8 and 2.7 mm Hg respectively, however the limits of agreement (LA) were large and ranged from -4.5 to 6.1 mm Hg. Changes in IGP correlated well with changes in IBP. The median GRVprototype was 80 mL (0-1050) and equal to the median GRVclassic of 80 mL (0-1250). Correlation between the 2 methods was excellent (R2 = 0.89). Analysis according to Bland and Altman showed a bias and precision of -0.8 and 52.3 mL respectively and the LA ranged from -103 to 102 mL. Changes in GRVclassic correlated well with changes in GRVprototype.

CONCLUSIONS

The results of this multicentre pilot study show that GRV can be measured with the new device. Furthermore this allows simultaneous screening for intra-abdominal hypertension with IAP estimation via IGP.

Management of abdominal sepsis--a paradigm shift?

The abdomen is the second most common source of sepsis and secondary peritonitis. The most common causes of abdominal sepsis are perforation, ischemic necrosis or penetrating injury to the abdominal viscera. Management consists of control of the infection source, restoration of gastrointestinal tract (GI) function, systemic antimicrobial therapy and support of organ function. Mortality after secondary peritonitis is still high. Excluding patient-related factors such as age or co-morbidities that can not be influenced at the time of intervention, delay to surgical intervention and inability to obtain source control are the main determinants of outcome. In patients with severe physiological derangement or difficult intraperitoneal conditions, where a prolonged operation and complete anatomical repair may not be possible or appropriate, it is becoming increasingly popular to utilize a damage control strategy with abbreviated laparotomy and planned reoperations. The main components of damage control laparotomy for secondary peritonitis are postponing the reconstruction of intestinal anastomoses to a second operation (deferred anastomosis) and leaving the abdomen open with some form of temporary abdominal closure (TAC). Advances in the management techniques of the open abdomen and new negative pressure-based TAC-devices have significantly reduced the previously observed prohibitive morbidity associated with open abdomens. These advancements have led to current fascial closure rates after TAC approaching 90%. The cornerstones of appropriate antimicrobial therapy are the timing, spectrum and dosing of antibiotics. Enteral nutrition should be started as soon as possible in hemodynamically stable patients but withheld when the patient is on a significant dose of vasopressors or whenever GI hypoperfusion is suspected. Timely source control with appropriate use of antimicrobial agents and early intensive care offers the best chance of survival for patients with abdominal sepsis. The introduction of the concept of damage control to the management of secondary peritonitis represents a paradigm shift in the same way as in management of major trauma. Although limited and repeated surgical interventions have been shown to be safe, the actual benefits need to be demonstrated in controlled studies.