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.

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.

Incidence and prognosis of intra-abdominal hypertension and abdominal compartment syndrome in severely burned patients: Pilot study and review of the literature.

BACKGROUND: Burn patients are at high risk for secondary intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) due to capillary leak and large volume fluid resuscitation. Our objective was to examine the incidence the incidence of IAH and ACS and their relation to outcome in mechanically ventilated (MV) burn patients. METHODS: This observational study included all MV burn patients admitted between April 2007 and December 2009. Various physiological parameters, intra-abdominal pressure (IAP) measurements and severity scoring indices were recorded on admission and/or each day in ICU. Transpulmonary thermodilution parameters were also obtained in 23 patients. The mean and maximum IAP during admission was calculated. The primary endpoint was ICU (burn unit) mortality. RESULTS: Fifty-six patients were included. The average Simplified Acute Physiology Score (SAPS II) and Sequential Organ Failure Assessment (SOFA) scores were 43.4 (± 15.1) and 6.4 (± 3.4), respectively. The average total body surface area (TBSA) affected by burns was 24.9% (± 24.9), with 33 patients suffering inhalational injuries. Forty-four (78.6%) patients developed IAH and 16 (28.6%) suffered ACS. Patients with ACS had higher TBSAs burned (35.8 ± 30 vs. 20.6 ± 21.4%, P = 0.04) and higher cumulative fluid balances after 48 hours (13.6 ± 16L vs. 7.6 ± 4.1 L, P = 0.03). The TBSA burned correlated well with the mean IAP (R = 0.34, P = 0.01). Mortality was notably high (26.8%) and significantly higher in patients with IAH (34.1%, P = 0.014) and ACS (62.5%, P < 0.0001). Most patients received more fluids than calculated by the Parkland Consensus Formula while, interestingly, non-survivors received less. However, when patients with pure inhalation injury were excluded there were no differences. Non-surgical interventions (n = 24) were successful in removing body fluids and were related to a significant decrease in IAP, central venous pressure (CVP) and an improvement in oxygenation and urine output. Non-resolution of IAH was associated with a significantly worse outcome (P < 0.0001). CONCLUSION: Based on our preliminary results we conclude that IAH and ACS have a relatively high incidence in MV burn patients compared to other groups of critically ill patients. The percentage of TBSA burned correlates with the mean IAP. The combination of high CLI, positive (daily and cumulative) fluid balance, high IAP, high EVLWI and low APP suggest a poor outcome. Non-surgical interventions appear to improve end-organ function. Non-resolution of IAH is related to a worse outcome.

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.

An overview on fluid resuscitation and resuscitation endpoints in burns: Past, present and future. Part 2 - avoiding complications by using the right endpoints with a new personalized protocolized approach.

While organ hypoperfusion caused by inadequate resuscitation has become rare in clinical practice due to the better understanding of burn shock pathophysiology, there is growing concern that increased morbidity and mortality related to over-resuscitation induced by late 20th century resuscitation strategies based on urine output, 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 to provide adequate organ perfusion. In this second part of a concise review, the different targets and endpoints used to guide fluid resuscitation are discussed. Special reference is made to the role of intra-abdominal hypertension in burn care and adjunctive treatments modulating the inflammatory response. Finally, as urine output has been recognized as a poor resuscitation target, a new personalized stepwise resuscitation protocol is suggested which includes targets and endpoints that can be obtained with modern, less invasive hemodynamic monitoring devices like transpulmonary thermodilution.

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.