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Critical Care (London, England) Sep 2016Volume infusions are one of the commonest clinical interventions in critically ill patients yet the relationship of volume to cardiac output is not well understood.... (Review)
Review
Volume infusions are one of the commonest clinical interventions in critically ill patients yet the relationship of volume to cardiac output is not well understood. Blood volume has a stressed and unstressed component but only the stressed component determines flow. It is usually about 30 % of total volume. Stressed volume is relatively constant under steady state conditions. It creates an elastic recoil pressure that is an important factor in the generation of blood flow. The heart creates circulatory flow by lowering the right atrial pressure and allowing the recoil pressure in veins and venules to drain blood back to the heart. The heart then puts the volume back into the systemic circulation so that stroke return equals stroke volume. The heart cannot pump out more volume than comes back. Changes in cardiac output without changes in stressed volume occur because of changes in arterial and venous resistances which redistribute blood volume and change pressure gradients throughout the vasculature. Stressed volume also can be increased by decreasing vascular capacitance, which means recruiting unstressed volume into stressed volume. This is the equivalent of an auto-transfusion. It is worth noting that during exercise in normal young males, cardiac output can increase five-fold with only small changes in stressed blood volume. The mechanical characteristics of the cardiac chambers and the circulation thus ultimately determine the relationship between volume and cardiac output and are the subject of this review.
Topics: Blood Circulation; Blood Pressure; Blood Volume; Cardiac Output; Humans; Stroke Volume
PubMed: 27613307
DOI: 10.1186/s13054-016-1438-7 -
Clinical Microbiology and Infection :... Feb 2020Bloodstream infections (BSIs) are a major cause of morbidity and mortality in paediatric patients. For fast and accurate diagnosis, blood culture (BC) is the reference... (Review)
Review
BACKGROUND
Bloodstream infections (BSIs) are a major cause of morbidity and mortality in paediatric patients. For fast and accurate diagnosis, blood culture (BC) is the reference standard. However, the procedure for blood sampling in paediatric patients, particularly the optimal blood volume, is the subject of controversy stemming from a lack of knowledge of the bacterial load and because of several obstacles such as low intravascular volume and the risk of causing anaemia.
AIMS
The aim of this narrative review is to summarize current knowledge on blood sampling in paediatric patients for BC purposes, in particular blood volume and number and type of BC bottles needed for reasonable future guidelines/recommendations.
SOURCES
A comprehensive literature search of PubMed, including all publications in English, was performed in June 2019 using the search terms 'blood culture', 'blood volume', 'bloodstream infection', 'diagnostic', 'paediatric' and/or 'sepsis'.
CONTENT
The amount of inoculated blood determines the sensitivity, specificity and time to positivity of a BC, and low-level bacteraemia (≤10 cfu/mL) in paediatric patients is presumed to be more common than reported. Current approaches for 'adequate' blood volume for paediatric BC are mainly weight- or age-dependent. Of these recommendations, the scheme devised by Gaur and colleagues seems most appropriate and calls for a sample of 1-1.5 mL for children weighing <11 kg and 7.5 mL for a patient weight of 11-17 kg to be drawn into one BC bottle. Inclusion of a more detailed grading in the weight range 4-14 kg, as published by Gonsalves and colleagues, might be useful.
IMPLICATIONS
This review could be important for future guidelines on paediatric BC collection and thus could contribute to improving patient management and lowering the economic and global health burden associated with BSI. Furthermore, upcoming molecular-based approaches with low sample volumes might be an interesting alternative.
Topics: Bacteremia; Bacterial Load; Blood Culture; Blood Volume; Child; Clinical Trials as Topic; Cross-Sectional Studies; Humans; Infant, Newborn; Pediatrics; Sensitivity and Specificity; Time Factors
PubMed: 31654793
DOI: 10.1016/j.cmi.2019.10.006 -
Journal of the American College of... Sep 2018Neurogenic orthostatic hypotension is a highly prevalent and disabling feature of autonomic failure due to both peripheral and central neurodegenerative diseases.... (Review)
Review
Neurogenic orthostatic hypotension is a highly prevalent and disabling feature of autonomic failure due to both peripheral and central neurodegenerative diseases. Community-based epidemiological studies have demonstrated a high morbidity and mortality associated with neurogenic orthostatic hypotension. It is due to impairment of baroreflex-mediated vasoconstriction of the skeletal muscle and splanchnic circulation and is caused by damage or dysfunction at central and/or peripheral sites in the baroreflex efferent pathway. Nonpharmacological and pharmacological interventions may be implemented to ameliorate the symptoms of orthostatic intolerance and improve quality of life. Many patients will be adequately treated by education, counseling, removal of hypotensive medications, and other nonpharmacological interventions, whereas more severely afflicted patients require pharmacological interventions. The first stage of pharmacological treatment involves repletion of central blood volume. If unsuccessful, this should be followed by treatment with sympathomimetic agents.
Topics: Algorithms; Autonomic Nervous System Diseases; Baroreflex; Blood Volume; Humans; Hypotension, Orthostatic; Lewy Body Disease; Multiple System Atrophy; Parkinson Disease; Patient Education as Topic; Pure Autonomic Failure; Vasoconstriction
PubMed: 30190008
DOI: 10.1016/j.jacc.2018.05.079 -
Blood Purification 2020Intradialytic hypotension (IDH) occurs in approximately 10-12% of treatments. Whereas several definitions for IDH are available, a nadir systolic blood pressure carries... (Review)
Review
Intradialytic hypotension (IDH) occurs in approximately 10-12% of treatments. Whereas several definitions for IDH are available, a nadir systolic blood pressure carries the strongest relation with outcome. Whereas the relation between IDH may partly be based on patient characteristics, it is likely that also impaired organ perfusion leading to permanent damage, plays a role in this relationship. The pathogenesis of IDH is multifactorial and is based on a combination of a decline in blood volume (BV) and impaired vascular resistance at a background of a reduced cardiovascular reserve. Measurements of absolute BV based on an on-line dilution method appear more promising than relative BV measurements in the prediction of IDH. Also, feedback treatments in which ultrafiltration rate is automatically adjusted based on changes in relative BV have not yet resulted in improvement. Frequent assessment of dry weight, attempting to reduce interdialytic weight gain and prescribing more frequent or longer dialysis treatments may aid in preventing IDH. The impaired vascular response can be improved using isothermic or cool dialysis treatment which has also been associated with a reduction in end organ damage, although their effect on mortality has not yet been assessed. For the future, identification of vulnerable patients based on artificial intelligence and on-line assessment of markers of organ perfusion may aid in individualizing treatment prescription, which will always remain dependent on the clinical context of the patient.
Topics: Blood Pressure; Blood Volume; Humans; Hypotension; Renal Dialysis; Vascular Resistance
PubMed: 31851975
DOI: 10.1159/000503776 -
Colombia Medica (Cali, Colombia) Dec 2020Damage control resuscitation should be initiated as soon as possible after a trauma event to avoid metabolic decompensation and high mortality rates. The aim of this... (Review)
Review
Damage control resuscitation should be initiated as soon as possible after a trauma event to avoid metabolic decompensation and high mortality rates. The aim of this article is to assess the position of the Trauma and Emergency Surgery Group (CTE) from Cali, Colombia regarding prehospital care, and to present our experience in the implementation of the "Stop the Bleed" initiative within Latin America. Prehospital care is phase 0 of damage control resuscitation. Prehospital damage control must follow the guidelines proposed by the "Stop the Bleed" initiative. We identified that prehospital personnel have a better perception of hemostatic techniques such as tourniquet use than the hospital providers. The use of tourniquets is recommended as a measure to control bleeding. Fluid management should be initiated using low volume crystalloids, ideally 250 cc boluses, maintaining the principle of permissive hypotension with a systolic blood pressure range between 80- and 90-mm Hg. Hypothermia must be management using warmed blankets or the administration of intravenous fluids warmed prior to infusion. However, these prehospital measures should not delay the transfer time of a patient from the scene to the hospital. To conclude, prehospital damage control measures are the first steps in the control of bleeding and the initiation of hemostatic resuscitation in the traumatically injured patient. Early interventions without increasing the transfer time to a hospital are the keys to increase survival rate of severe trauma patients.
Topics: Algorithms; Blood Volume; Body Temperature; Emergency Medical Services; Hemorrhage; Humans; Injury Severity Score; Resuscitation; Wounds and Injuries
PubMed: 33795898
DOI: 10.25100/cm.v51i4.4486 -
JACC. Heart Failure Jul 2018Despite advances in biomarkers and technology, the clinical examination (i.e., a history and physical examination) remains central in the management of patients with... (Review)
Review
Despite advances in biomarkers and technology, the clinical examination (i.e., a history and physical examination) remains central in the management of patients with heart failure. Specifically, the clinical examination allows noninvasive assessment of the patient's underlying hemodynamic state, based on whether the patient has elevated ventricular filling pressures and/or an inadequate cardiac index. Such assessments provide important prognostic information and help guide therapeutic decision-making. Herein, the authors critically assess the utility of the clinical examination for these purposes and provide practical tips we have gleaned from our practice in the field of advanced heart failure. The authors note that the ability to assess for congestion is superior to that for inadequate perfusion. Furthermore, in current practice, elevated left ventricular filling pressures are inferred by findings related to an elevated right atrial pressure. They discuss an emerging classification system from the clinical examination that categorizes patients based on whether elevation of ventricular filling pressures occurs on the right side, left side, or both sides.
Topics: Blood Volume; Dyspnea; Heart Failure; Hemodynamics; Humans; Jugular Veins; Medical History Taking; Physical Examination; Prognosis; Supine Position; Valsalva Maneuver; Venous Pressure
PubMed: 29885957
DOI: 10.1016/j.jchf.2018.04.005 -
NeuroImage Feb 2019This article aims to provide the reader with an overview of recent developments in Arterial Spin Labeling (ASL) MRI techniques. A great deal of progress has been made in... (Review)
Review
This article aims to provide the reader with an overview of recent developments in Arterial Spin Labeling (ASL) MRI techniques. A great deal of progress has been made in recent years in terms of the SNR and acquisition speed. New strategies have been introduced to improve labeling efficiency, reduce artefacts, and estimate other relevant physiological parameters besides perfusion. As a result, ASL techniques has become a reliable workhorse for researchers as well as clinicians. After a brief overview of the technique's fundamentals, this article will review new trends and variants in ASL including vascular territory mapping and velocity selective ASL, as well as arterial blood volume imaging techniques. This article will also review recent processing techniques to reduce partial volume effects and physiological noise. Next the article will examine how ASL techniques can be leveraged to calculate additional physiological parameters beyond perfusion and finally, it will review a few recent applications of ASL in the literature.
Topics: Arteries; Blood Flow Velocity; Brain; Brain Mapping; Cerebral Blood Volume; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Models, Neurological; Signal-To-Noise Ratio; Spin Labels
PubMed: 29305164
DOI: 10.1016/j.neuroimage.2017.12.095 -
Blood Dec 2017The erythrocyte contains a network of pathways that regulate salt and water content in the face of extracellular and intracellular osmotic perturbations. This allows the... (Review)
Review
The erythrocyte contains a network of pathways that regulate salt and water content in the face of extracellular and intracellular osmotic perturbations. This allows the erythrocyte to maintain a narrow range of cell hemoglobin concentration, a process critical for normal red blood cell function and survival. Primary disorders that perturb volume homeostasis jeopardize the erythrocyte and may lead to its premature destruction. These disorders are marked by clinical, laboratory, and physiologic heterogeneity. Recent studies have revealed that these disorders are also marked by genetic heterogeneity. They have implicated roles for several proteins, PIEZO1, a mammalian mechanosensory protein; GLUT1, the glucose transporter; SLC4A1, the anion transporter; RhAG, the Rh-associated glycoprotein; KCNN4, the Gardos channel; and ABCB6, an adenosine triphosphate-binding cassette family member, in the maintenance of erythrocyte volume homeostasis. Secondary disorders of erythrocyte hydration include sickle cell disease, thalassemia, hemoglobin CC, and hereditary spherocytosis, where cellular dehydration may be a significant contributor to disease pathology and clinical complications. Understanding the pathways regulating erythrocyte water and solute content may reveal innovative strategies to maintain normal volume in disorders associated with primary or secondary cellular dehydration. These mechanisms will serve as a paradigm for other cells and may reveal new therapeutic targets for disease prevention and treatment beyond the erythrocyte.
Topics: Animals; Dehydration; Erythrocyte Volume; Erythrocytes; Homeostasis; Humans
PubMed: 29051181
DOI: 10.1182/blood-2017-04-590810 -
Critical Care (London, England) Apr 2023In patients on mechanical ventilation, positive end-expiratory pressure (PEEP) can decrease cardiac output through a decrease in cardiac preload and/or an increase in... (Clinical Trial)
Clinical Trial
BACKGROUND
In patients on mechanical ventilation, positive end-expiratory pressure (PEEP) can decrease cardiac output through a decrease in cardiac preload and/or an increase in right ventricular afterload. Increase in central blood volume by fluid administration or passive leg raising (PLR) may reverse these phenomena through an increase in cardiac preload and/or a reopening of closed lung microvessels. We hypothesized that a transient decrease in PEEP (PEEP-test) may be used as a test to detect volume responsiveness.
METHODS
Mechanically ventilated patients with PEEP ≥ 10 cmHO ("high level") and without spontaneous breathing were prospectively included. Volume responsiveness was assessed by a positive PLR-test, defined as an increase in pulse-contour-derived cardiac index (CI) during PLR ≥ 10%. The PEEP-test consisted in reducing PEEP from the high level to 5 cmHO for one minute. Pulse-contour-derived CI (PiCCO2) was monitored during PLR and the PEEP-test.
RESULTS
We enrolled 64 patients among whom 31 were volume responsive. The median increase in CI during PLR was 14% (11-16%). The median PEEP at baseline was 12 (10-15) cmHO and the PEEP-test resulted in a median decrease in PEEP of 7 (5-10) cmHO, without difference between volume responsive and unresponsive patients. Among volume responsive patients, the PEEP-test induced a significant increase in CI of 16% (12-20%) (from 2.4 ± 0.7 to 2.9 ± 0.9 L/min/m, p < 0.0001) in comparison with volume unresponsive patients. In volume unresponsive patients, PLR and the PEEP-test increased CI by 2% (1-5%) and 6% (3-8%), respectively. Volume responsiveness was predicted by an increase in CI > 8.6% during the PEEP-test with a sensitivity of 96.8% (95% confidence interval (95%CI): 83.3-99.9%) and a specificity of 84.9% (95%CI 68.1-94.9%). The area under the receiver operating characteristic curve of the PEEP-test for detecting volume responsiveness was 0.94 (95%CI 0.85-0.98) (p < 0.0001 vs. 0.5). Spearman's correlation coefficient between the changes in CI induced by PLR and the PEEP-test was 0.76 (95%CI 0.63-0.85, p < 0.0001).
CONCLUSIONS
A CI increase > 8.6% during a PEEP-test, which consists in reducing PEEP to 5 cmHO, reliably detects volume responsiveness in mechanically ventilated patients with a PEEP ≥ 10 cmHO. Trial registration ClinicalTrial.gov (NCT 04,023,786). Registered July 18, 2019. Ethics Committee approval CPP Est III (N° 2018-A01599-46).
Topics: Humans; Blood Volume; Cardiac Output; Diagnostic Techniques, Cardiovascular; Diagnostic Techniques, Respiratory System; Fluid Therapy; Heart; Hemodynamics; Positive-Pressure Respiration; Respiration, Artificial; ROC Curve
PubMed: 37031182
DOI: 10.1186/s13054-023-04424-7 -
Blood Purification 2019Intermittent infusion hemodiafiltration (I-HDF) has been developed to prevent a rapid drop in blood pressure during a dialysis session and to improve peripheral... (Review)
Review
BACKGROUND
Intermittent infusion hemodiafiltration (I-HDF) has been developed to prevent a rapid drop in blood pressure during a dialysis session and to improve peripheral circulation. In Japan, >10,000 dialysis patients underwent treatment with I-HDF in 2017, and the number of dialysis patients is increasing year by year. I-HDF involves the intermittent infusion of ultrapure dialysis fluid or sterile nonpyrogenic substitution fluid, for example, at a volume of 200 mL and a rate of 150 mL/min by backfiltration every 30 min during treatment. The total infusion volume can therefore be estimated at 200 (mL) × 7 (infusions) or 1.4 L/session. I-HDF may be regarded as online HDF with a very small replacement volume.
SUMMARY
Several clinical trials of I-HDF have been conducted in Japan. (1) In a 2007 study, despite there being no differences noted in the volume of water removal between hemodialysis (HD) and I-HDF, a significantly lower rate of reduction in the time-averaged blood volume was seen in I-HDF than in HD, so the plasma refilling rate was greater during I-HDF. (2) In a 2015 study, at 13 weeks after a switch from HD, I-HDF was found to be significantly superior to HD in terms of the incidence of events needing intervention by medical staff. However, significantly lower blood β2-microglobulin (MG) and α1-MG levels were observed in the predilution online HDF (pre-HDF) group than in the I-HDF group, and the amount of albumin leak was lower in the I-HDF group than in the pre-HDF group. (3) In a 2017 study, compared with HD, I-HDF was associated with a reduced number of interventions for intradialytic hypotension and less severe tachycardia, suggesting less sympathetic stimulation during I-HDF. Key messages: I-HDF is a valid treatment option because it is associated with an increased plasma refilling rate and fewer interventions needed by medical staff.
Topics: Blood Pressure; Blood Volume; Dialysis Solutions; Female; Hemodiafiltration; Humans; Hypotension; Male
PubMed: 31752002
DOI: 10.1159/000503891