Showing papers on "Hypovolemia published in 2015"

Management of Children with Trauma in the PICU: Hemorrhagic Shock

Abstract: Hemorrhagic shock has been studied extensively in the adult population, but evidence is lacking in the pediatric population. Unlike adults, pediatric patients tolerate hypovolemia with less hypotension until they have reached significant blood volume loss. It is imperative they receive prompt intravenous access, crystalloid resuscitation, followed by blood product transfusion. A hemoglobin goal of 7 g/dL has been translated to the pediatric population without evidence of poor outcomes. Massive transfusion protocols involving a 1:1:1 ratio of red blood cells:fresh frozen plasma:platelets has been recommended although further evidence is needed. With the transfusion of multiple blood products, consideration must be taken into account for the side effects, including electrolyte imbalance and lung injury.

Hypohydration and Human Performance: Impact of Environment and Physiological Mechanisms

Abstract: Body water losses of >2 % of body mass are defined as hypohydration and can occur from sweat loss and/or diuresis from both cold and altitude exposure. Hypohydration elicits intracellular and extracellular water loss proportionate to water and solute deficits. Iso-osmotic hypovolemia (from cold and high-altitude exposure) results in greater plasma loss for a given water deficit than hypertonic hypovolemia from sweat loss. Hypohydration does not impair submaximal intensity aerobic performance in cold-cool environments, sometimes impairs aerobic performance in temperate environments, and usually impairs aerobic performance in warm-hot environments. Hypohydration begins to impair aerobic performance when skin temperatures exceed 27 °C, and with each additional 1 °C elevation in skin temperature there is a further 1.5 % impairment. Hypohydration has an additive effect on impairing aerobic performance in warm-hot high-altitude environments. A commonality of absolute hypovolemia (from plasma volume loss) combined with relative hypovolemia (from tissue vasodilation) is present when aerobic performance is impaired. The decrement in aerobic exercise performance due to hypohydration is likely due to multiple physiological mechanisms, including cardiovascular strain acting as the 'lynchpin', elevated tissue temperatures, and metabolic changes which are all integrated through the CNS to reduce motor drive to skeletal muscles.

Septic Shock: Advances in Diagnosis and Treatment

Abstract: Importance Septic shock is a clinical emergency that occurs in more than 230 000 US patients each year. Observations and Advances In the setting of suspected or documented infection, septic shock is typically defined in a clinical setting by low systolic (≤90 mm Hg) or mean arterial blood pressure (≤65 mm Hg) accompanied by signs of hypoperfusion (eg, oliguria, hyperlactemia, poor peripheral perfusion, or altered mental status). Focused ultrasonography is recommended for the prompt recognition of complicating physiology (eg, hypovolemia or cardiogenic shock), while invasive hemodynamic monitoring is recommended only for select patients. In septic shock, 3 randomized clinical trials demonstrate that protocolized care offers little advantage compared with management without a protocol. Hydroxyethyl starch is no longer recommended, and debate continues about the role of various crystalloid solutions and albumin. Conclusions and Relevance The prompt diagnosis of septic shock begins with obtainment of medical history and performance of a physical examination for signs and symptoms of infection and may require focused ultrasonography to recognize more complex physiologic manifestations of shock. Clinicians should understand the importance of prompt administration of intravenous fluids and vasoactive medications aimed at restoring adequate circulation, and the limitations of protocol-based therapy, as guided by recent evidence.

Diagnosis and management of sodium disorders: hyponatremia and hypernatremia.

Abstract: Hyponatremia and hypernatremia are common findings in the inpatient and outpatient settings. Sodium disorders are associated with an increased risk of morbidity and mortality. Plasma osmolality plays a critical role in the pathophysiology and treatment of sodium disorders. Hyponatremia and hypernatremia are classified based on volume status (hypovolemia, euvolemia, and hypervolemia). Sodium disorders are diagnosed by findings from the history, physical examination, laboratory studies, and evaluation of volume status. Treatment is based on symptoms and underlying causes. In general, hyponatremia is treated with fluid restriction (in the setting of euvolemia), isotonic saline (in hypovolemia), and diuresis (in hypervolemia). A combination of these therapies may be needed based on the presentation. Hypertonic saline is used to treat severe symptomatic hyponatremia. Medications such as vaptans may have a role in the treatment of euvolemic and hypervolemic hyponatremia. The treatment of hypernatremia involves correcting the underlying cause and correcting the free water deficit.

Early dynamic left intraventricular obstruction is associated with hypovolemia and high mortality in septic shock patients

Abstract: Based on previously published case reports demonstrating dynamic left intraventricular obstruction (IVO) triggered by hypovolemia or catecholamines, this study aimed to establish: (1) IVO occurrence in septic shock patients; (2) correlation between the intraventricular gradient and volume status and fluid responsiveness; and (3) mortality rate. We prospectively analyzed patients with septic shock admitted to a general ICU over a 28-month period who presented Doppler signs of IVO. Clinical characteristics and hemodynamic parameters as well as echocardiographic data regarding left ventricular function, size, and calculated mass, and left ventricular outflow Doppler pattern and velocity before and after fluid infusions were recorded. During the study period, 218 patients with septic shock were admitted to our ICU. IVO was observed in 47 (22 %) patients. Mortality rate at 28 days was found to be higher in patients with than in patients without IVO (55 % versus 33 %, p < 0.01). Small, hypercontractile left ventricles (end-diastolic left ventricular surface 4.7 ± 2.1 cm2/m2 and ejection fraction 82 ± 12 %), and frequent pseudohypertrophy were found in these patients. A rise ≥12 % in stroke index was found in 87 % of patients with IVO, with a drop of 47 % in IVO after fluid infusion. Left IVO is a frequent event in septic shock patients with an important correlation with fluid responsiveness. The mortality rate was found to be higher in these patients in comparison with patients without obstruction.

Tissue oxygen saturation and finger perfusion index in central hypovolemia: influence of pain.

Abstract: Objectives:Tissue oxygen saturation and peripheral perfusion index are proposed as early indirect markers of hypovolemia in trauma patients. Hypovolemia is associated with increased sympathetic nervous activity. However, many other stimuli, such as pain, also increase sympathetic activity. Since pai

Cerebral blood velocity regulation during progressive blood loss compared with lower body negative pressure in humans

Abstract: Lower body negative pressure (LBNP) is often used to simulate blood loss in humans. It is unknown if cerebral blood flow responses to actual blood loss are analogous to simulated blood loss during ...

Correction of hypovolemia with crystalloid fluids: Individualizing infusion therapy.

Abstract: Many situations in clinical practice involving patients with hypovolemia or acutely ill patients usually require the administration of intravenous fluids. Current evidence shows that the use of crystalloids should be considered, since most colloids and human albumin are usually associated with increased adverse effects and high cost, respectively. Among crystalloids, the use of normal saline is implicated with the development of hyperchloremic metabolic acidosis and renal vasoconstriction. These observations have led many authors to propose balanced solutions, mainly Lactated Ringer's, as the infusate of choice. However, although the restoration of volume status is the primary target in hypovolemic state, the correction of any associated acid-base or electrolyte disorders that frequently coexist is also of vital importance. This review presents specific situations that are common in daily clinical practice and require targeted infusate therapy in patients with reduced volume status. Furthermore, the review presents an algorithm aiming to help clinicians to make the best choice between normal or hypotonic saline and lactated Ringer's infusates. Lactated Ringer's infusate should not be given in patients with severe metabolic alkalosis, lactic acidosis with decreased lactate clearance, or severe hyperkalemia, and in patients with traumatic brain injury or at risk of increased intracranial pressure. The optimal choice of infusate should be guided by the cause of hypovolemia, the cardiovascular state of the patient, the renal function, as well as the serum osmolality and the coexisting acid-base and electrolyte disorders. Clinicians should be aware of any coexisting disorders in patients with hypovolemia and guide their choice of infusate treatment based on the overall picture of their patients.

Heart rate variability and stroke volume variability to detect central hypovolemia during spontaneous breathing and supported ventilation in young, healthy volunteers

Abstract: Cardiovascular oscillations exist in many different variables and may give important diagnostic and prognostic information in patients Variability in cardiac stroke volume (SVV) is used in clinical practice for diagnosis of hypovolemia, but currently is limited to patients on mechanical ventilation We investigated if SVV and heart rate variability (HRV) could detect central hypovolemia in spontaneously breathing humans: We also compared cardiovascular variability during spontaneous breathing with supported mechanical ventilationTen subjects underwent simulated central hypovolemia by lower body negative pressure (LBNP) with >10% reduction of cardiac stroke volume The subjects breathed spontaneously and with supported mechanical ventilation Heart rate, respiratory frequency and mean arterial blood pressure were measured Stroke volume (SV) was estimated by ModelFlow (Finometer) Respiratory SVV was calculated by: 1) SVV% = (SVmax - SVmin)/SVmean during one respiratory cycle, 2) SVIntegral from the power spectra (Fourier transform) at 015-04 Hz and 3) SVV_norm = (√SVIntegral)/SVmean HRV was calculated by the same methodsDuring spontaneous breathing two measures of SVV and all three measures of HRV were reduced during hypovolemia compared to baseline During spontaneous breathing SVIntegral and HRV% were best to detect hypovolemia (area under receiver operating curve 081) HRV% ≤ 11% and SVIntegral ≤ 12 ml(2) differentiated between hypovolemia and baseline during spontaneous breathingDuring supported mechanical ventilation, none of the three measures of SVV changed and two of the HRV measures were reduced during hypovolemia Neither measures of SVV nor HRV were classified as a good detector of hypovolemiaWe conclude that HRV% and SVIntegral detect hypovolemia during spontaneous breathing and both are candidates for further clinical testing

Can one size fit all? The fine line between fluid overload and hypovolemia

Abstract: In septic shock like in other types of shock, hypovolemia, whether caused by a true loss of circulating blood volume and/or by vasodilation, results in a decrease of the mean systemic filling pressure, the driving force for venous return to the heart, thereby leading to insufficient cardiac preload and output [1]. Rapid volume expansion using repeated intravenous fluid boluses is thus the mainstay intervention during the first hours of care [2]. Meanwhile, recent data in intensive care unit (ICU) patients [3], or in surgical patients [4], suggest that fluid and salt overload have negative impact on morbidity and mortality. Additionally, in patients with acute respiratory distress syndrome (ARDS), a restrictive fluid administration policy driven by an algorithm based on cardiac filling pressures has been shown to shorten the length of mechanical ventilation and of ICU stay. Therefore, it is essential to strike the right balance in order to not neglecting hypovolemia and its devastating consequences and in the meanwhile not worsening interstitial and pulmonary oedema (Fig. 1). The way fluid management is delivered is not standardized, as reflected by the high variability in the way fluid boluses are decided and guided in real life practice [5]. There is a lack of randomised controlled trials testing different strategies of volume expansion based on objectives measurements during the first days of septic shock. Neither the systematic use of the well-known (but rarely used in ICU practice [5]) fluid challenge technique [6–8] nor the systematic use of the few available predictive indices of fluid responsiveness [9, 10], have been tested against usual care with hard endpoints such as mortality. Conducting such trials is very challenging for physiological reasons (haemodynamic instability does not have a single cause and ‘‘one size fits all’’ algorithm are intrinsically deemed to fail) and for logistical reasons (24/24, 7/7 availability of investigators; rigorous protocol and risk of protocol violation/deviation; need of large sample sizes). In a study recently published in Intensive Care Medicine, Zhang et al. [11] courageously took on the challenge of comparing two strategies of fluid management in the

Peripheral Perfusion Index Predicts Hypotension during Fluid Withdrawal by Continuous Veno-Venous Hemofiltration in Critically Ill Patients

Abstract: Aim: Peripheral perfusion may predict harmful hypovolemic hypotension during fluid withdrawal by continuous veno-venous hemofiltration (CVVH) in critically ill patients with acute kidney injury. Methods: Twenty-three critically ill AKI patients were subjected to progressive fluid withdrawal. Systemic hemodynamics and peripheral perfusion index (PPI) by pulse oximetry, forearm-to-fingertip skin temperature gradient (Tskin-diff) and tissue oxygen saturation (StO2, near infra-red spectroscopy) were measured. Results: Most hemodynamic values decreased with fluid withdrawal, particularly in the hypotensive group, except for stroke volume (SV) and cardiac output, which decreased to a great extent in the non-hypotensive patients. Increases in systemic vascular resistance (SVR) were less in hypotension. Baseline pulse pressure and PPI were lower in hypotensive (n = 10) than non-hypotensive patients and subsequent PPI values paralleled SV decreases. A baseline PPI ≤0.82 AU predicted hypotension with a sensitivity of 70%, and a specificity of 92% (AUC 0.80 ± 0.11, p = 0.004). Conclusion: Progressive fluid withdrawal during CVVH is poorly tolerated in patients with less increases in SVR. The occurrence of hypotension can be predicted by low baseline PPI.

Reproducibility of a continuous ramp lower body negative pressure protocol for simulating hemorrhage

Abstract: Central hypovolemia elicited by application of lower body negative pressure (LBNP) has been used extensively to simulate hemorrhage in human subjects. Traditional LBNP protocols incorporate progressive steps in pressure held for specific time intervals. The aim of this study was to assess the reproducibility of applying continuous LBNP at a constant rate until presyncope to replicate actual bleeding. During two trials (≥4 weeks intervening), LBNP was applied at a rate of 3 mmHg/min in 18 healthy human subjects (12M; 6F) until the onset of presyncopal symptoms. Heart rate (HR), mean arterial pressure (MAP), stroke volume (SV), total peripheral resistance (TPR), mean middle and posterior cerebral artery velocities (MCAv, PCAv), and cerebral oxygen saturation (ScO 2 ) were measured continuously. Time to presyncope (TTPS) and hemodynamic responses were compared between the two trials. TTPS (1649 ± 98 sec vs. 1690 ± 88 sec; P = 0.47 [ t ‐test]; r = 0.77) and the subsequent magnitude of central hypovolemia (%Δ SV −54 ± 4% vs. −53 ± 4%; P = 0.55) were similar between trials. There were no statistically distinguishable differences at either baseline ( P ≥ 0.17) or presyncope between trials for HR, MAP, TPR, mean MCAv, mean PCAv, or ScO 2 ( P ≥ 0.19). The rate of change from baseline to presyncope for all hemodynamic responses was also similar between trials ( P ≥ 0.12). Continuous LBNP applied at a rate of 3 mmHg/min was reproducible in healthy human subjects, eliciting similar reductions in central blood volume and subsequent reflex hemodynamic responses.

Management of Shock in Neonates

Abstract: Shock is characterized by inadequate oxygen delivery to the tissues, and is more frequent in very low birth weight infants, especially in the first few days of life. Shock is an independent predictor of mortality, and the survivors are at a higher risk of neurologic impairment. Understanding the pathophysiology helps to recognize and classify shock in the early compensated phase and initiate appropriate treatment. Hypovolemia is rarely the primary cause of shock in neonates. Myocardial dysfunction is especially common in extremely preterm infants, and in term infants with perinatal asphyxia. Blood pressure measurements are easy, but correlate poorly with cerebral and systemic blood flows. Point-of-care cardiac ultrasound can help in individualized assessment of problems, selecting appropriate therapy and monitoring response, but may not always be available, and long-term benefits need to be demonstrated. The use of near-infrared spectroscopy to guide treatment of neonatal shock is currently experimental. In the absence of hypovolemia, excessive administration of fluid boluses is inappropriate therapy. Dobutamine and dopamine are the most common initial inotropes used in neonatal shock. Dobutamine has been shown to improve systemic blood flow, especially in very low birth weight infants, but dopamine is better at improving blood pressure in hypotensive infants. Newer inodilators including milrinone and levosimendan may be useful in selected settings. Data on long-term survival and neurologic outcomes following different management strategies are scarce and future research efforts should focus on this.

Stroke Volume Optimization: The New Hemodynamic Algorithm

Abstract: Critical care practices have evolved to rely more on physical assessments for monitoring cardiac output and evaluating fluid volume status because these assessments are less invasive and more convenient to use than is a pulmonary artery catheter. Despite this trend, level of consciousness, central venous pressure, urine output, heart rate, and blood pressure remain assessments that are slow to be changed, potentially misleading, and often manifested as late indications of decreased cardiac output. The hemodynamic optimization strategy called stroke volume optimization might provide a proactive guide for clinicians to optimize a patient’s status before late indications of a worsening condition occur. The evidence supporting use of the stroke volume optimization algorithm to treat hypovolemia is increasing. Many of the cardiac output monitor technologies today measure stroke volume, as well as the parameters that comprise stroke volume: preload, afterload, and contractility. (Critical Care Nurse. 2015;35[1]:11-28)

Robust monitoring of hypovolemia in intensive care patients using photoplethysmogram signals

Abstract: The paper presents a fingertip photoplethysmography based technique to assess patient fluid status that is robust to waveform artifacts and health variability in the underlying patient population. The technique is intended for use in intensive care units, where patients are at risk for hypovolemia, and signal artifacts and inter-patient variations in health are common. Input signals are preprocessed to remove artifact, then a parameter-invariant statistic is calculated to remove effects of patient-specific physiology. Patient data from the Physionet MIMICII database was used to evaluate the performance of this technique. The proposed method was able to detect hypovolemia within 24 hours of onset in all hypovolemic patients tested, while producing minimal false alarms over non-hypovolemic patients.

Subtotal nephrectomy inhibits the gastric emptying of liquid in awake rats

Abstract: Homeostasis of blood volume (BV) is attained through a functional interaction between the cardiovascular and renal systems. The gastrointestinal tract also adjusts its permeability and motor behavior after acute BV imbalances. We evaluated the effect of progressive nephron loss on gut motility. Male Wistar rats were subjected or not (sham) to 5/6 partial nephrectomy (PNX) in two steps (0 and 7th day). After further 3, 7, or 14 days, PNX and sham operation (control) rats were instrumented to monitor mean arterial pressure (MAP), central venous pressure (CVP), heart rate (HR), and blood collection for biochemical analysis. The next day, they were gavage fed with a liquid test meal (phenol red in glucose solution), and fractional dye recovery determined 10, 20, or 30 min later. The effect of nonhypotensive hypovolemia and the role of neuroautonomic pathways on PNX-induced gastric emptying (GE) delay were also evaluated. Compared with the sham-operated group, PNX rats exhibited higher (P < 0.05) MAP and CVP values as well as increased values of gastric dye recovery, phenomenon proportional to the BV values. Gastric retention was prevented by prior hypovolemia, bilateral subdiaphragmatic vagotomy, coelic ganglionectomy + splanchnicectomy, guanethidine, or atropine pretreatment. PNX also inhibited (P < 0.05) the marker's progression through the small intestine. In anesthetized rats, PNX increased (P < 0.05) gastric volume, measured by a balloon catheter in a barostat system. In conclusion, the progressive loss of kidney function delayed the GE rate, which may contribute to gut dysmotility complaints associated with severe renal failure.

Inferior vena cava distensibility index predicting fluid responsiveness in ventilated patients

Abstract: Echocardiography is a non-invasive procedure which enables full assesment of cardiac function. The inferior vena cava (IVC) is a compliant blood vessel, easily distended, especially in cases of hypovolemia. Assessment of the physiologic characteristics of the IVC provides a rapid distinction between low and high volume states and offers the clinician a rapid, noninvasive way to guide resuscitation in critically ill patients.

Sex comparisons in muscle sympathetic nerve activity and arterial pressure oscillations during progressive central hypovolemia

Abstract: Increased tolerance to central hypovolemia is generally associated with greater sympathoexcitation, high-frequency oscillatory patterns of mean arterial pressure (MAP), and tachycardia. On average, women are less tolerant to central hypovolemia than men; however, the autonomic mechanisms governing these comparisons are not fully understood. We tested the hypothesis that women with relatively high tolerance (HT) to central hypovolemia would display similar physiological reserve capacity for sympathoexcitation and oscillations in MAP at presyncope compared to HT men. About 10 men and five women were exposed to progressive lower body negative pressure (LBNP) until the presence of presyncopal symptoms. Based on our previous classification system, all subjects were classified as HT because they completed at least −60 mmHg LBNP. Muscle sympathetic serve activity (MSNA) was measured directly from the peroneal nerve via microneurography and arterial pressure (AP) was measured at the finger by photoplethysmography. LBNP time to presyncope was less (P < 0.01) in women (1727 ± 70 sec) than in men (2022 ± 201 sec). At presyncope, average MSNA in men (50 ± 12 bursts/min) and women (51 ± 7 bursts/min) was similar (P = 0.87). Coincident with similar stroke volume (SV) at presyncope, women had similar MAP and heart rates. However, women had less physiological reserve capacity for SV, AP-MSNA coherence, and oscillations in the high-frequency (HF) components of arterial pressure compared to men. Contrary to our hypothesis, lower tolerance to central hypovolemia in women was not associated with sympathoexcitation, but can be explained, in part by lower physiological reserve to elicit oscillatory patterns in AP, maintenance of AP-MSNA coherence and SV when compared to men.

Relative Blood Volume Monitoring during Renal Replacement Therapy in Critically Ill Patients with Septic Shock: A Preliminary Report.

Abstract: Background: Volume management during renal replacement therapy (RRT) in septic shock is always in the conflict between aggravating hypovolemia by undue ultrafiltration (UF) and insufficient reduction of fluid overload which is associated with adverse outcome Relative blood volume (RBV) monitoring could be helpful for timely transition from fluid resuscitation to fluid removal Methods: Data of RBV were continuously monitored and used for guidance of UF and fluid resuscitation in 21 consecutive patients with severe septic multiple organ failure RRT was applied with extended daily hemodiafiltration for median 11 h (range 6-23) Changes in RBV were analyzed during the first 4 treatment sessions Results: During 26 treatments, RBV monitoring revealed an internal volume loss substituted by a median infusion volume of 238 l (maximum 807 l) per treatment to keep the RBV constant In the remaining 40 sessions, a median net-UF of 100 l (range 040-440) was achieved In the first 2 days predominantly substitution was necessary whereas from the third day UF became increasingly possible The 28-day survival rate was 81% Conclusion: Blood volume monitoring proved to be an easy and feasible tool for safe guidance of fluid management maintaining the balance between UF and vascular refilling Video Journal Club ‘Cappuccino with Claudio Ronco' at http://wwwkargercom/?doi=433415

Hypotension in Infants on Chronic Peritoneal Dialysis: Mechanisms, Complications, and Management.

Abstract: Hypotension represents a very serious clinical problem in patients receiving renal replacement therapy, and it is associated with a significant increase in mortality risk. Infants on chronic peritoneal dialysis (CPD) can be particularly prone to chronic hypotension because of the hyponatremic hypovolemia risk related to their primary renal disease, their nutritional needs, and their peritoneal membrane characteristics. In this setting, if an acute clinical event leads to a further decline in systolic blood pressure, the counteract and perfusion pressure autoregulatory mechanisms can both be impaired, leading to severe complications. Anterior ischemic optic neuropathy (AION) represents an acute ischemic disorder of the optic nerve head and a dramatic cause of sudden blindness, whose incidence is about 1% in children on CPD. In recent studies, very young age, autosomal recessive polycystic kidney disease, and sustained hypotension were found to be substantial risk factors for AON. In infants at risk, strategies of long-term treatment and prevention of peritoneal dialysis-induced hypotension should be applied to prevent progression in the pathophysiologic cascade that leads to chronic hypotension and its complications.

Assessment of circulating blood volume with fluid administration targeting euvolemia or hypervolemia.

Abstract: The occurrence of hypovolemia in the setting of cerebral vasospasm reportedly increases the risk for delayed ischemic neurologic deficits. Few studies have objectively assessed blood volume (BV) in response to fluid administration targeting normovolemia (NV) or hypervolemia (HV) and none have done so with crystalloids alone. The primary purpose was to evaluate the BV of patients with SAH receiving crystalloid fluid administration targeting NV or HV. The University of Washington IRB approved the study. Prospectively collected data was obtained from patients enrolled in a clinical trial and a concurrent group of patients who received IV fluids during the ICU stay. We defined a normovolemia (NV) and hypervolemia (HV) group based on the cumulative amount of IV fluid administered in mL/kg from ICU admission to day 5; ≥30–60 mL/kg/day (NV) and ≥60 mL/kg/day (HV), respectively. In a subgroup of patients, BV was measured on day 5 post ictus using iodinated 131I-labeled albumin injection and the BVA-100 (Daxor Corp, New York, NY). Differences between the NV and HV groups were compared using Student’s t-test with assumption for unequal variance. Twenty patients in the NV and 19 in the HV groups were included. The HV group received more fluid and had a higher fluid balance than the NV group. The subgroup of patients in whom BV was measured on day 5 (n = 19) was not different from the remainder of the cohort with respect to the total amount of administered fluid and net cumulative fluid balance by day 5. BV was not different between the two groups and varied widely. Routinely targeting prophylactic HV using crystalloids does not result in a higher circulating BV compared to targeting NV, but the possibility of clinically unrecognized hypovolemia remains.

Goal-Directed Resuscitation Aiming Cardiac Index Masks Residual Hypovolemia: An Animal Experiment

Abstract: The aim of this study was to compare stroke volume (SVI) to cardiac index (CI) guided resuscitation in a bleeding-resuscitation experiment. Twenty six pigs were randomized and bled in both groups till baseline SVI (T bsl) dropped by 50% (T 0), followed by resuscitation with crystalloid solution until initial SVI or CI was reached (T 4). Similar amount of blood was shed but animals received significantly less fluid in the CI-group as in the SVI-group: median = 900 (interquartile range: 850-1780) versus 1965 (1584-2165) mL, p = 0.02, respectively. In the SVI-group all variables returned to their baseline values, but in the CI-group animals remained underresuscitated as indicated by SVI, heart rate (HR) and stroke volume variation (SVV), and central venous oxygen saturation (ScvO2) at T 4 as compared to T bsl: SVI = 23.8 ± 5.9 versus 31.4 ± 4.7 mL, HR: 117 ± 35 versus 89 ± 11/min SVV: 17.4 ± 7.6 versus 11.5 ± 5.3%, and ScvO2: 64.1 ± 11.6 versus 79.2 ± 8.1%, p < 0.05, respectively. Our results indicate that CI-based goal-directed resuscitation may result in residual hypovolaemia, as bleeding caused stress induced tachycardia "normalizes" CI, without restoring adequate SVI. As the SVI-guided approach normalized most hemodynamic variables, we recommend using SVI instead of CI as the primary goal of resuscitation during acute bleeding.

Interaction of sodium bicarbonate and Na+/H+ exchanger inhibition in the treatment of acute metabolic acidosis in pigs.

Abstract: Objective Administration of NaHCO3 does not improve cellular function or reduce the mortality of acute lactic acidosis. This might be related to aggravation of intracellular acidosis, but it could also be due to activation of Na+/H+ exchanger with a deleterious increment in intracellular calcium ([Ca2+]i). This study examined the impact of coadministration of NaHCO3 and a selective inhibitor of Na+/H+ exchanger, sabiporide on cardiovascular function, changes in proinflammatory cytokines, and organ function in a model of acute lactic acidosis produced by hemorrhagic hypotension followed by infusion of lactic acid. Design Experimental, prospective study. Setting Medical Center research laboratory. Subjects Male Yorkshire pigs. Interventions Anesthetized pigs were subjected to hypovolemia for 30 minutes and followed by DL-lactic acid infusion, and then either saline or sodium bicarbonate was infused. Measurements and main results Hypovolemia followed by a DL-lactic acid infusion resulted in severe acidemia with a blood pH~6.8. Administration of NaHCO3 did not improve cardiovascular performance or decrease the levels of proinflammatory responses, whereas administration of sabiporide prior to acid or NaHCO3 infusion improved cardiopulmonary performance and blood oxygenation, reduced nuclear factor-κB activation, neutrophil accumulation, and proinflammatory cytokine production, and attenuated organ injury. Exposure of rat cardiac myocytes to a pH of 7.2 led to a marked increase of [Ca2+]i, and release of lactate dehydrogenase from cells which were further augmented after increase in external pH by addition of NaHCO3. Both the increase in [Ca2+]i and release of lactate dehydrogenase were attenuated in the presence of sabiporide. Conclusions Coadministration of Na/H exchanger inhibitor with sodium bicarbonate improves cardiovascular performances, reduces proinflammatory responses, and attenuates organ injury. This improvement in these variables appears to be related to prevention of a rise in intracellular calcium occurring after both exposures to acid and bicarbonate.

Cardiac power parameters during hypovolemia, induced by the lower body negative pressure technique, in healthy volunteers.

Abstract: Changes in cardiac power parameters incorporate changes in both aortic flow and blood pressure. We hypothesized that dynamic and non-dynamic cardiac power parameters would track hypovolemia better than equivalent flow- and pressure parameters, both during spontaneous breathing and non-invasive positive pressure ventilation (NPPV). Fourteen healthy volunteers underwent lower body negative pressure (LBNP) of 0, −20, −40, −60 and −80 mmHg to simulate hypovolemia, both during spontaneous breathing and during NPPV. We recorded aortic flow using suprasternal ultrasound Doppler and blood pressure using Finometer, and calculated dynamic and non-dynamic parameters of cardiac power, flow and blood pressure. These were assessed on their association with LBNP-levels. Respiratory variation in peak aortic flow was the dynamic parameter most affected during spontaneous breathing increasing 103 % (p < 0.001) from baseline to LBNP −80 mmHg. Respiratory variation in pulse pressure was the most affected dynamic parameter during NPPV, increasing 119 % (p < 0.001) from baseline to LBNP −80 mmHg. The cardiac power integral was the most affected non-dynamic parameter falling 59 % (p < 0.001) from baseline to LBNP −80 mmHg during spontaneous breathing, and 68 % (p < 0.001) during NPPV. Dynamic cardiac power parameters were not better than dynamic flow- and pressure parameters at tracking hypovolemia, seemingly due to previously unknown variation in peripheral vascular resistance matching respiratory changes in hemodynamics. Of non-dynamic parameters, the power parameters track hypovolemia slightly better than equivalent flow parameters, and far better than equivalent pressure parameters.