Quantification of serial changes in cerebral blood volume and metabolism in patients with recurrent glioblastoma undergoing antiangiogenic therapy

OBJECTIVES

To evaluate the usefulness of quantitative advanced magnetic resonance imaging (MRI) methods for assessment of antiangiogenic therapy (AAT) response in recurrent glioblastoma multiforme (GBM).

METHODS

Eighteen patients with recurrent GBM received bevacizumab and 18 patients served as control group. Baseline MRI and two follow-up examinations were acquired every 3-5 months using dynamic susceptibility-weighted contrast (DSC) perfusion MRI and (1)H-MR spectroscopic imaging ((1)H-MRSI). Maps of absolute cerebral blood volume (aCBV) were coregistered with choline (Cho) and N-acetyl-aspartate (NAA) concentrations and compared to usually used relative parameters as well as controls.

RESULTS

Perfusion significantly decreased in responding and pseudoresponding GBMs but also in normal appearing brain after AAT onset. Cho and NAA concentrations were superior to Cr-ratios in lesion differentiation and showed a clear gap between responding and pseudoresponding lesions. Responders to AAT exceptionally frequently (6 out of 8 patients) showed remote GBM progression.

CONCLUSIONS

Quantification of CBV reveals changes in normal brain perfusion due to AAT, which were not described so far. DSC perfusion MRI seems not to be suitable for differentiation between response and pseudoresponse to AAT. However, absolute quantification of brain metabolites may allow for distinction due to a clear gap at 6-9 months after therapy onset.

The effect of dietary salt restriction on hypertension in peritoneal dialysis patients

BACKGROUND/AIM

To investigate the effect of dietary salt restriction on blood pressure levels, total sodium removal, and hydration status of peritoneal dialysis (PD) patients.

MATERIALS AND METHODS

Thirty-one stable PD patients who consulted a renal dietitian monthly for dietary recommendations, including restricted salt intake <5 g/day, and education about hypertension and hypervolemia were included in this study. Baseline and third month clinical and laboratory findings, bioelectrical impedance analysis results, and urinary and peritoneal sodium removal values were recorded.

RESULTS

The mean age of the patients was 47.6 years and the mean time on PD was 39.6 months. The mean total sodium removal decreased slightly from 139.4 ± 69.1 to 136.2 ± 64.8 mmol/day (P > 0.05) for the whole sample, and from 164.3 ± 70.9 to 154.2 ± 72.3 mmol/day (P > 0.05) for the hypertensive subgroup (n: 17). Systolic blood pressure (from 134.3 ± 20.1 to 127.2 ± 19.5 mmHg, P: 0.01), diastolic blood pressure (from 83.2 ± 12.0 to 77.4 ± 10.5 mmHg, P: 0.01) and total body water (from 39.2 ± 10.9 to 38.3 ± 9.3 L, P: 0.04) decreased significantly.

CONCLUSION

We demonstrated that even a little reduction in daily dietary sodium intake caused significant decreases in blood pressure levels and fluid overload.

[Glycocalyx and fluid therapy]

Glycocalyx consisting of proteins and carbohydrates is lining the complete healthy vascular endothelium. Being in continuous interaction with plasma proteins and other plasma components, the glycocalyx forms an endothelial surface layer playing an important role as protective mechanism of the vascular wall, in blood coagulation and regulation of permeability. Tissue swelling is a common problem in the treatment of surgical, trauma and intensive care patients. The extent of tissue swelling is also connected with morbidity and mortality. The question about the volume effect of infusion solutions and, on the other hand, prevention of permeability disturbance still remains highly actual.

Epoxyeicosatrienoic acids mediate insulin-mediated augmentation in skeletal muscle perfusion and blood volume

Skeletal muscle microvascular blood flow (MBF) increases in response to physiological hyperinsulinemia. This vascular action of insulin may facilitate glucose uptake. We hypothesized that epoxyeicosatrienoic acids (EETs), a family of arachadonic, acid-derived, endothelium-derived hyperpolarizing factors, are mediators of insulin's microvascular effects. Contrast-enhanced ultrasound (CEU) was performed to quantify skeletal muscle capillary blood volume (CBV) and MBF in wild-type and obese insulin-resistant (db/db) mice after administration of vehicle or trans-4-[4-(3-adamantan-1-ylureido)cyclohexyloxy]benzoic acid (t-AUCB), an inhibitor of soluble epoxide hydrolase that converts EETs to less active dihydroxyeicosatrienoic acids. Similar studies were performed in rats pretreated with l-NAME. CEU was also performed in rats undergoing a euglycemic hyperinsulinemic clamp, half of which were pretreated with the epoxygenase inhibitor MS-PPOH to inhibit EET synthesis. In both wild-type and db/db mice, intravenous t-AUCB produced an increase in CBV (65-100% increase at 30 min, P < 0.05) and in MBF. In db/db mice, t-AUCB also reduced plasma glucose by ∼15%. In rats pretreated with l-NAME, t-AUCB after produced a significant ≈20% increase in CBV, indicating a component of vascular response independent of nitric oxide (NO) production. Hyperinsulinemic clamp produced a time-dependent increase in MBF (19 ± 36 and 76 ± 49% at 90 min, P = 0.026) that was mediated in part by an increase in CBV. Insulin-mediated changes in both CBV and MBF during the clamp were blocked entirely by MS-PPOH. We conclude that EETs are a mediator of insulin-mediated augmentation in skeletal muscle perfusion and are involved in regulating changes in CBV during hyperinsulinemia.

Fluid distribution kinetics during cardiopulmonary bypass

OBJECTIVE

The purpose of this study was to examine the isovolumetric distribution kinetics of crystalloid fluid during cardiopulmonary bypass.

METHODS

Ten patients undergoing coronary artery bypass grafting participated in this prospective observational study. The blood hemoglobin and the serum albumin and sodium concentrations were measured repeatedly during the distribution of priming solution (Ringer's acetate 1470 ml and mannitol 15% 200 ml) and initial cardioplegia. The rate of crystalloid fluid distribution was calculated based on 3-min Hb changes. The preoperative blood volume was extrapolated from the marked hemodilution occurring during the onset of cardiopulmonary bypass. Clinicaltrials.gov: NCT01115166.

RESULTS

The distribution half-time of Ringer's acetate averaged 8 minutes, corresponding to a transcapillary escape rate of 0.38 ml/kg/min. The intravascular albumin mass increased by 5.4% according to mass balance calculations. The preoperative blood volume, as extrapolated from the drop in hemoglobin concentration by 32% (mean) at the beginning of cardiopulmonary bypass, was 0.6-1.2 L less than that estimated by anthropometric methods (p<0.02). The mass balance of sodium indicated a translocation from the intracellular to the extracellular fluid space in 8 of the 10 patients, with a median volume of 236 ml.

CONCLUSIONS

The distribution half-time of Ringer's solution during isovolumetric cardiopulmonary bypass was 8 minutes, which is the same as for crystalloid fluid infusions in healthy subjects. The intravascular albumin mass increased. Most patients were hypovolemic prior to the start of anesthesia. Intracellular edema did not occur.

Guiding principles of fluid and volume therapy

Fluid therapy is a core concept in the management of perioperative and critically ill patients for maintenance of intravascular volume and organ perfusion. Recent evidence regarding the vascular barrier and its role in terms of vascular leakage has led to a new concept for fluid administration. The choice of fluid used should be based on the fluid composition and the underlying pathophysiology of the patient. Avoidance of both hypo- and hypervolaemia is essential when treating circulatory failure. In daily practice, the assessment of individual thresholds in order to optimize cardiac preload and avoid hypovolaemia or deleterious fluid overload remains a challenge. Liberal versus restrictive fluid management has been challenged by recent evidence, and the ideal approach appears to be goal-directed fluid therapy.

Hemodynamic effects of combined focal cerebral ischemia and amyloid protein toxicity in a rat model: a functional CT study

Background/Objective

Clinical evidence indicates that cerebral ischemia (CI) and a pathological factor of Alzheimer's disease, the β-amyloid (Aβ) protein, can increase the rate of cognitive impairment in the ageing population. Using the CT Perfusion (CTP) functional imaging, we sought to investigate the interaction between CI and the Aβ protein on cerebral hemodynamics.

Methods

A previously established rat model of CI and Aβ was used for the CTP study. Iodinated contrast was given intravenously, while serial CT images of sixteen axial slices were acquired. Cerebral blood flow (CBF) and blood volume (CBV) parametric maps were co-registered to a rat brain atlas and regions of interest were drawn on the maps. Microvascular alteration was investigated with histopathology.

Results

CTP results revealed that ipsilateral striatum of Aβ+CI and CI groups showed significantly lower CBF and CBV than control at the acute phase. Striatal CBF and CBV increased significantly at week 1 in the CI and Aβ+CI groups, but not in the Aβ alone or control group. Histopathology showed that average density of dilated microvessels in the ipsilateral striatum in CI and Aβ+CI groups was significantly higher than control at week 1, indicating this could be associated with hyperperfusion and hypervolemia observed from CTP results.

Conclusion

These results demonstrate that CTP can quantitatively measure the hemodynamic disturbance on CBF and CBV functional maps in a rat model of CI interacting with Aβ.

Evaluation of non-invasive multispectral imaging as a tool for measuring the effect of systemic therapy in Kaposi sarcoma

Diffuse multi-spectral imaging has been evaluated as a potential non-invasive marker of tumor response. Multi-spectral images of Kaposi sarcoma skin lesions were taken over the course of treatment, and blood volume and oxygenation concentration maps were obtained through principal component analysis (PCA) of the data. These images were compared with clinical and pathological responses determined by conventional means. We demonstrate that cutaneous lesions have increased blood volume concentration and that changes in this parameter are a reliable indicator of treatment efficacy, differentiating responders and non-responders. Blood volume decreased by at least 20% in all lesions that responded by clinical criteria and increased in the two lesions that did not respond clinically. Responses as assessed by multi-spectral imaging also generally correlated with overall patient clinical response assessment, were often detectable earlier in the course of therapy, and are less subject to observer variability than conventional clinical assessment. Tissue oxygenation was more variable, with lesions often showing decreased oxygenation in the center surrounded by a zone of increased oxygenation. This technique could potentially be a clinically useful supplement to existing response assessment in KS, providing an early, quantitative, and non-invasive marker of treatment effect.

[Efficiency of hydroxyethyl starch use for arterial hypotension and shock in early postoperative period]

It is common knowledge that arterial hypotension is a one of most prevalent pathology of early neonatal period and it causes severe neurological complications. Purpose of the prospective randomized open study was to assess the efficacy of HES 130/0.4 (6% Voluven) as a start medicine for arterial hypotension in early neonatal period in comparison with normal saline solution (0.9% NaCl).

MATERIALS AND METHODS

the study was held from January 2010 to September 2011. Newborns of the ICU with arterial hypotension on the first day of life were included into the study. Acute haemorrhage was an exclusion criterion. Routine monitoring of arterial pressure, heart rate and diuresis was carried out in all newborns. pH, pCO2, pO2 blood glucose, lactate and BE levels were measured before and after the treatment. Echocardiography, examination of regional blood flow in anterior cerebral artery, renal artery and mesenteric artery was held HES 130/0.4 (6% Voluven) and saline solution (0.9% NaCl) were used Parameters of haemostasis, biochemical and haematological analysis monitored after the solutions use. Time of arterial pressure normalization and duration of the treatment positive effect were recorded Episodes of hypotension, amount of cardiotonics per day and per 7 days and duration of cardiotonics administration were recorded as well.

RESULTS

6% Voluven infusion both to 0.9% NaCl infusion normalizes the regional circulation. Furthermore it increases the blood pH and diuresis. Lactate level normalization occurred only after 6% Voluven infusion. There was not change of serum sodium level. Liver enzymes, C-protein, prothrombin index were same in both groups of patients. 6% Voluven use in newborns with extremely low birth weight was accompanied with increasing of creatinine level, prolongation of activated partial thromboplastin time and increasing of intraventricular hemorrhage rate. Newborns with weight over 1000 gram did not have these complications. Voluven advantage in comparison with saline solution is a decreasing of cardiotonics administration in patients with weight over 1000 gram.

CONCLUSIONS

6% Voluven is more effective than 0.9% NaCl for increasing of cardiac output, myocardial contractile ability and diuresis, normalization of liquid balance and lactate level, decreasing of cardiotonics amount. 6% Voluven can be recommended for arterial hypotension treatment in newborns with weight over 1000 gram both to normal saline solution especially in case of shock.

Biphasic change of tau (τ) in mice as arterial load acutely increased with phenylephrine injection

Background

Diastolic dysfunction is the hemodynamic hallmark of hypertensive heart disease. Tau (τ) has been used to describe left ventricle relaxation. The relationship between τ and afterload has been controversial. Our goal was to demonstrate this relationship in mice, because genetically-modified mouse models have been used extensively for studies in cardiovascular diseases.

Methods

Increased arterial load was produced by phenylephrine administration (50 µg/kg iv) (n = 10). A series of pressure-volume loops was recorded with a Millar conductance catheter in vivo as the left ventricle pressure reached the maximum. The arterial load was expressed as Ea (effective arterial elastance). Tau values were computed using three mathematical methods: τ_Weiss, τ_Glantz, and τ_Logistic.

Results

A correlation plot between τ and Ea showed a biphasic relationship a flat phase I and an inclined phase II. The existence of an inflection point was proved mathematically with biphasic linear regression. Pressure-volume area (PVA), a parameter linearly related to myocardial O₂ consumption (MVO₂), was found to be directly proportional to Ea. The plot of τ versus PVA was also biphasic.

Conclusion

We concluded that a small increase of the arterial load by phenylephrine increased PVA (index of MVO₂) but had little effect on τ. However, after an inflection point, further increase of arterial load and PVA resulted in the linear increase of τ.

Near-infrared transillumination back scattering sounding--new method to assess brain microcirculation in patients with chronic carotid artery stenosis

Purpose

The purpose of the study was to assess the responses of pial artery pulsation (cc-TQ) and subarachnoid width (sas-TQ) to acetazolamide challenge in patients with chronic carotid artery stenosis and relate these responses to changes in peak systolic velocity (PSV), cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT) and time to peak response (TTP).

Methods

Fifteen patients with carotid artery stenosis ≥90% on the ipsilateral side and <50% on the contralateral side were enrolled into the study. PSV was assessed using colour-coded duplex sonography, CBF, CBV, MTT and TTP with perfusion computed tomography, cc-TQ and sas-TQ with near-infrared transillumination/backscattering sounding (NIR-T/BSS).

Results

Based on the ipsilateral/contralateral cc-TQ ratio after acetazolamide challenge two groups of patients were distinguished: the first group with a ratio ≥1 and the second with a ratio <1. In the second group increases in CBF and CBV after the acetazolamide test were significantly higher in both hemispheres (ipsilateral: +33.0%±8.1% vs. +15.3%±4.4% and +26.3%±6.6% vs. +14.3%±5.1%; contralateral: +26.8%±7.0% vs. +17.6%±5.6% and +20.0%±7.3% vs. +10.0%±3.7%, respectively), cc-TQ was significantly higher only on the ipsilateral side (+37.3%±9.3% vs. +26.6%±8.6%) and the decrease in sas-TQ was less pronounced on the ipsilateral side (−0.7%±1.5% vs. −10.2%±1.5%), in comparison with the first group. The changes in sas-TQ following the acetazolamide test were consistent with the changes in TTP.

Conclusions

The ipsilateral/contralateral cc-TQ ratio following acetazolamide challenge may be used to distinguish patient groups characterized by different haemodynamic parameters. Further research on a larger group of patients is warranted.

Dynamic monitoring of blood-brain barrier integrity using water exchange index (WEI) during mannitol and CO2 challenges in mouse brain

The integrity of the blood-brain barrier (BBB) is critical to normal brain function. Traditional techniques for the assessment of BBB disruption rely heavily on the spatiotemporal analysis of extravasating contrast agents. However, such methods based on the leakage of relatively large molecules are not suitable for the detection of subtle BBB impairment or for the performance of repeated measurements in a short time frame. Quantification of the water exchange rate constant (WER) across the BBB using strictly intravascular contrast agents could provide a much more sensitive method for the quantification of the BBB integrity. To estimate WER, we have recently devised a powerful new method using a water exchange index (WEI) biomarker and demonstrated BBB disruption in an acute stroke model. Here, we confirm that WEI is sensitive to even very subtle changes in the integrity of the BBB caused by: (i) systemic hypercapnia and (ii) low doses of a hyperosmolar solution. In addition, we have examined the sensitivity and accuracy of WEI as a biomarker of WER using computer simulation. In particular, the dependence of the WEI-WER relation on changes in vascular blood volume, T1 relaxation of cellular magnetization and transcytolemmal water exchange was explored. Simulated WEI was found to vary linearly with WER for typically encountered exchange rate constants (1-4 Hz), regardless of the blood volume. However, for very high WER (>5 Hz), WEI became progressively more insensitive to increasing WER. The incorporation of transcytolemmal water exchange, using a three-compartment tissue model, helped to extend the linear WEI regime to slightly higher WER, but had no significant effect for most physiologically important WERs (WER < 4 Hz). Variation in cellular T1 had no effect on WEI. Using both theoretical and experimental approaches, our study validates the utility of the WEI biomarker for the monitoring of BBB integrity.

Rapid insulin-mediated increase in microvascular glycocalyx accessibility in skeletal muscle may contribute to insulin-mediated glucose disposal in rats

It has been demonstrated that insulin-mediated recruitment of microvascular blood volume is associated with insulin sensitivity. We hypothesize that insulin rapidly stimulates penetration of red blood cells (RBC) and plasma into the glycocalyx and thereby promotes insulin-mediated glucose uptake by increasing intracapillary blood volume. Experiments were performed in rats; the role of the glycocalyx was assessed by enzymatic degradation using a bolus of hyaluronidase. First, the effect of insulin on glycocalyx accessibility was assessed by measuring the depth of penetration of RBCs into the glycocalyx in microvessels of the gastrocnemius muscle with Sidestream Dark-field imaging. Secondly, peripheral insulin sensitivity was determined using intravenous insulin tolerance tests (IVITT). In addition, in a smaller set of experiments, intravital microscopy of capillary hemodynamics in cremaster muscle and histological analysis of the distribution of fluorescently labeled 40 kDa dextrans (D40) in hindlimb muscle was used to evaluate insulin-mediated increases in capillary blood volume. Insulin increased glycocalyx penetration of RBCs by 0.34±0.44 µm (P<0.05) within 10 minutes, and this effect of insulin was greatly impaired in hyaluronidase treated rats. Further, hyaluronidase treated rats showed a 35±25% reduction in whole-body insulin-mediated glucose disposal compared to control rats. Insulin-mediated increases in capillary blood volume were reflected by a rapid increase in capillary tube hematocrit from 21.1±10.1% to 29.0±9.8% (P<0.05), and an increase in D40 intensity in individual capillaries of 134±138% compared to baseline at the end of the IVITT. These effects of insulin were virtually abolished in hyaluronidase treated animals. In conclusion, insulin rapidly increases glycocalyx accessibility for circulating blood in muscle, and this is associated with an increased blood volume in individual capillaries. Hyaluronidase treatment of the glycocalyx abolishes the effects of insulin on capillary blood volume and impairs insulin-mediated glucose disposal.

Salt and fluid loading: effects on blood volume and exercise performance

During prolonged exercise, fluid and salt losses through sweating reduce plasma volume which leads to heart rate drift in association with hyperthermia and reductions in performance. Oral rehydration with water reduces the loss of plasma volume and lessens heart rate drift and hyperthermia. Moreover, the inclusion of sodium in the rehydration solution to levels that double those in sweat (i.e., around 90 mmol/l Na(+)) restores plasma volume when ingested during exercise, and expands plasma volume if ingested pre-exercise. Pre-exercise salt and fluid ingestion with the intention of expanding plasma volume has received an increasing amount of attention in the literature in recent years. In four studies, pre-exercise salt and fluid ingestion improved performance, measured as time to exhaustion, either during exercise in a thermoneutral or in a hot environment. While in a hot environment, the performance improvements were linked to lowering of core temperatures and heart rate, the reasons for the improved performance in a thermoneutral environment remain unclear. However, when ingesting pre-exercise saline solutions above 0.9% (i.e., > 164 mmol/l Na(+)), osmolality and plasma sodium increase and core temperature remain at dehydration levels. Thus, too much salt counteracts the beneficial effects of plasma volume expansion on heat dissipation and hence in performance. In summary, the available literature suggests that pre-exercise saline ingestion with concentrations not over 164 mmol/l Na(+) is an ergogenic aid for subsequent prolonged exercise in a warm or thermoneutral environment.

Cerebral oxygenation and haemodynamic effects induced by nimodipine in healthy subjects

The cerebrovascular effects of nimodipine are still poorly understood even in the healthy condition; in particular, its effects on tissue oxygenation have never been investigated. The aim of the present study was to investigate changes in cerebral oxygenation and blood volume upon oral administration of nimodipine (90 mg) in the healthy condition. In eight subjects, changes in cerebral tissue oxygenation and blood volume were determined simultaneously with changes in blood velocity of the middle cerebral artery (VMCA) by using, respectively, near infrared spectroscopy (NIRS) and transcranial Doppler ultrasonography (TCD). The subjects also underwent noninvasive assessment of arterial blood pressure (ABP) and end-tidal CO2. TCD and NIRS CO2 reactivity indices were al-so extracted. Nimodipine significantly reduced ABP (11±13%) and increased heart rate, as well as NIRS oxygenation(6.0±4.8%) and blood volume indices (9.4±10.1%), while V(MCA) was not significantly decreased (2.0±3.5%). Nimodipine slightly but significantly reduced the V(MCA) response to changes in pCO2 whereas the CO2 reactivity of NIRS parameters was improved. The observed changes in cerebral tissue oxygenation and blood volume indicate nimodipine-induced cerebrovascular dilation and increased perfusion, while the effect on V(MCA)possibly results from dilation of the insonated artery. The present results cast doubt on the putative nimodipine-induced impairment of CO2 reactivity.

Volume Kinetics of Intravenous Fluid Therapy in the Prehospital Setting

Introduction:

To study the volume effect of isotonic and hypertonic crystalloid fluid during ambulance transports after mild trauma, a prospective case-control study was initiated, using the ambulance and helicopter transport system in Stockholm.

Methods:

The hemodilution resulting from intravenous infusion of 1.0 L of Ringer's acetate solution (n = 7) or 250 ml of 7.5% sodium chloride (n = 3) over 30 minutes (min) was measured every 10 min during 1 hour when fluid therapy was instituted at the scene of an accident, or on arrival at the hospital. The dilution was studied by volume kinetic analysis and compared to that of matched, healthy controls who received the same fluid in hospital.

Result:

The hemodilution at the end of the infusions averaged 7.7% in the trauma patients and 9.1% in the controls, but the dilution was better maintained after trauma. The kinetic analysis showed that the size of the body fluid space expanded by Ringer's solution was 4.6 L and 3.8 L for the trauma and the control patients, respectively, while hypertonic saline expanded a slightly larger space. For both fluids, trauma reduced the elimination rate constant by approximately 30%.

Conclusion:

Mild trauma prolonged the intravascular persistence of isotonic and hypertonic crystalloid fluid as compared to a control group.