BACKGROUND: Despite the improvements in hemodialysis (HD) technology, 20-30% of sessions are still complicated by hypotension or hypotension-related symptoms. Biofeedback systems have proven to reduce the occurrence of such events, but no conclusive findings can lead to wider adoption of these systems. We conducted this systematic review and meta-analysis of randomized clinical trials to establish whether the use of blood volume tracking systems compared to conventional hemodialysis (C-HD) reduces the occurrence of intradialytic hypotension.
METHODS: The PRISMA guidelines were used to carry out this systematic review. Randomized clinical trials that evaluated the incidence of intradialytic hypotension during C-HD and blood volume tracking-HD were searched in the current literature. PROSPERO registration number: CRD42023426328.
RESULTS: Ninety-seven randomized clinical trials were retrieved. Nine studies, including 347 participants and 13,274 HD treatments were considered eligible for this systematic review. The results showed that the use of biofeedback systems reduces the risk of intradialytic hypotension (log odds ratio = 0.63, p = 0.03) in hypotension-prone patients (log odds ratio = 0.54, p = 0.04). When analysis was limited to fluid overloaded or hypertensive patients, it did not show the same effect (log odds ratio = 0.79, p = 0.38). No correlation was found in systolic blood pressure drop during dialysis and in post-dialysis blood pressure.
CONCLUSIONS: The use of blood volume tracking systems may be effective in reducing the incidence of intradialytic hypotension and allowing for easier attainment of the patients\' ideal dry body weight. New studies to examine the long-term effects of the use of blood volume tracking systems on real hard endpoints are needed.

BACKGROUND: Postpartum haemorrhage (PPH) is the leading cause of maternal mortality in low-income countries and severe maternal morbidity in many high-income countries. Poor outcomes following PPH are often attributed to delays in the recognition and treatment of PPH. Experts have suggested that improving the accuracy and reliability of blood loss estimation is the crucial step in preventing death and morbidity from PPH. However, there is little guidance on how this can be achieved. The aim of this integrative review was to evaluate the various methods of assessing maternal blood loss during childbirth.
METHODS: A systematic, integrative review of published research studies was conducted. All types of studies were included if they developed, tested, or aimed to improve methods and skills in quantifying blood loss during childbirth, or explored experiences of those involved in the process.
RESULTS: Thirty-six studies were included that evaluated the accuracy of visual estimation; tested methods to improve skills in measurement; examined their effect on PPH diagnosis and treatment, and / or explored additional factors associated with blood loss evaluation. The review found that health professionals were highly inaccurate at estimating blood loss as a volume. Training resulted in short term improvements in skills but these were not retained and did not improve clinical outcomes. Multi-faceted interventions changed some clinical practices but did not reduce the incidence of severe PPH or the timing of responses to excessive bleeding. Blood collection bags improved the accuracy of estimation but did not prevent delays or progression to severe PPH. Practitioners commonly used the nature and speed of blood flow, and the condition of the woman to indicate that the blood loss was abnormal.
CONCLUSIONS: Early diagnosis of PPH should improve maternal outcomes, but there is little evidence that this can be achieved through improving the accuracy of blood loss volume measurements. The diagnosis may rely on factors other than volume, such as speed of blood flow and nature of loss. A change in direction of future research is required to explore these in more detail.

OBJECTIVE: Several authors have demonstrated that preoperative embolization of meningiomas reduces blood loss during surgery. However, preoperative embolization is still under debate. Aim of this study is the retrospective evaluation of necrosis score, surgical time, and transfused blood volume, on patients affected by intracranial meningiomas treated with preoperative embolization before surgery, compared with a control group treated only with surgery.
METHODS: Twenty-eight patients with meningiomas were subjected to a preoperative embolization with polyvinyl alcohol (PVA). These patients were divided into two groups: group 1, patients with preoperative embolization performed at least 7 days before surgery; and group 2, patients with preoperative embolization performed less than 7 days before surgery. A statistical evaluation was made by comparing necrosis score, surgical time, and transfused blood volume of these groups. Then, we compared these parameters also with group 3, which included patients with surgically treated meningioma who did not undergo preoperative embolization.
RESULTS: Surgery time and transfused blood volume were significantly lower in patients who had been embolized at least 7 days before definitive surgery. Furthermore, large confluent areas of necrosis were significantly more frequent in patients with a larger time span between embolization and surgery.
CONCLUSIONS: Preoperative embolization with PVA in patients with intracranial meningiomas is safe and effective, as it reduces the volume of transfused blood during surgical operation. However, patients should undergo surgery at least 7 days after embolization, as a shorter time interval has been correlated with a longer surgical time and a higher transfused blood volume.

The accurate determination of circulating blood volume (CBV) in children has many clinical applications. The purposes of this article were to review currently available CBV measurement techniques and perform a meta-analysis using values from many small-scale studies that calculated CBV values for normal healthy children. A literature review demonstrated numerous methods by which to determine CBV. However, these methods necessitate repetitive blood sampling, require the introduction of foreign substances into the bloodstream, or address the uncertainty of substance distribution and clearance. Many small-scale studies have calculated CBV values for normal healthy children, and we performed a meta-analysis using these values. Age groups were defined, and within each group, means +/- 1 and 2 standard deviations were compared. A pooled estimate of mean blood volume and a 95% confidence interval was calculated after Q-statistics calculations indicated that the groups were homogeneous. Mean values showed agreement with typically accepted normal values. A large-scale study should be repeated when a gold standard for CBV measurements is developed.

Direct measurement of physiologic systems is often impractical. To overcome these obstacles, indirect physiologic measures have been developed. Indirect physiologic measures such as heart rate, blood pressure, and many others are surrogates that are believed to accurately represent the function of a physiologic system. Although a powerful tool, physiologic measurement has several potential limitations and errors. This can result in erroneous instrument data. For that reason, it is the responsibility of the clinician to question and interpret monitor output and to ultimately correctly assess validity of the measurement. This article reviews commonly used intraoperative monitoring techniques and discusses their potential limitations as they relate to hypovolemia and hemorrhagic shock.

OBJECTIVE: In spontaneously breathing patients, indexes predicting hemodynamic response to volume expansion are very much needed. The present review discusses the clinical utility and accuracy of indexes tested as bedside indicators of preload reserve and fluid responsiveness in hypotensive, spontaneously breathing patients.
METHODS: We conducted a literature search of the MEDLINE database and the trial register of the Cochrane Group.
METHODS: Identification of reports investigating, prospectively, indexes of fluid responsiveness in spontaneously breathing critically ill patients. All the studies defined the response to fluid therapy after measuring cardiac output and stroke volume using the thermodilution technique. We did not score the methodological quality of the included studies before the data analysis.
METHODS: A total of eight prospective clinical studies in critically ill patients were included. Only one publication evaluated cardiac output changes induced by fluid replacement in a selected population of spontaneously breathing critically ill patients.
RESULTS: Based on this review, we can only conclude that static indexes are valuable tools to confirm that the fluid volume infused reaches the cardiac chambers, and therefore these indexes inform about changes in cardiac preload. However, respiratory variation in right atrial pressure, which represents a dynamic measurement, seems to identify hypotension related to a decrease in preload and to distinguish between responders and nonresponders to a fluid challenge.
CONCLUSIONS: Further studies should address the question of the role of static indexes in predicting cardiac output improvement following fluid infusion in spontaneously breathing patients.

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Rapid blood and plasma volume measurements gain increasing interest in order to avoid unnecessary blood transfusions. Only the indocyanine green method seems to satisfy the demand for a fast, safe and reproducible bedside method. We summarized older and newer experiences with this method, and also summarized the results for practical application.

We have recently introduced a new technique for the continuous recording of blood density based on the so-called mechanical oscillator principle. The availability of this technique makes a discussion of the diagnostic meaning of the blood density--defined as mass per unit volume--and its variations under certain conditions worthwhile. In this study, the use of the density dilution method for the determination of distribution volumes of different injected solutions will be discussed. The influence of temperature and of certain artifacts like acceleration forces in the density measuring device has to be considered and may be used for certain additional diagnostic purposes, like the determination of erythrocyte sedimentation velocity. Some most interesting observations are related to the marked influence that fluid shift between extravascular compartments and the intravascular compartment has on blood density. Here, particularly, the effect of the intravenous injection of hypertonic solutions will be discussed. These injections lead to an osmotic fluid shift towards the blood which, in a very characteristic way, reduces blood density and plasma density. A simple model for the description of this reaction is presented. Furthermore, reactions of the blood density to hemorrhage, to different vasoactive substances, and to orthostatic load will be discussed.