Tetrathiomolybdate Treatment Attenuates Bleomycin-Induced Angiogenesis and Lung Pathology in a Sheep Model of Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive chronic lung disease characterized by excessive extracellular matrix (ECM) deposition in the parenchyma of the lung. Accompanying the fibrotic remodeling, dysregulated angiogenesis has been observed and implicated in the development and progression of pulmonary fibrosis. Copper is known to be required for key processes involved in fibrosis and angiogenesis. We therefore hypothesized that lowering bioavailable serum copper with tetrathiomolybdate could be of therapeutic value for treating pulmonary fibrosis. This study aimed to investigate the effect of tetrathiomolybdate on angiogenesis and fibrosis induced in sheep lung segments infused with bleomycin. Twenty sheep received two fortnightly infusions of either bleomycin (3U), or saline (control) into two spatially separate lung segments. A week after the final bleomycin/saline infusions, sheep were randomly assigned into two groups (n = 10 per group) and received twice-weekly intravenous administrations of either 50 mg tetrathiomolybdate, or sterile saline (vehicle control), for 6 weeks. Vascular density, expressed as the percentage of capillary area to the total area of parenchyma, was determined in lung tissue sections immuno-stained with antibodies against CD34 and collagen type IV. The degree of fibrosis was assessed by histopathology scoring of H&E stained sections and collagen content using Masson's trichrome staining. Lung compliance was measured via a wedged bronchoscope procedure prior to and 7 weeks following final bleomycin infusion. In this large animal model, we show that copper lowering by tetrathiomolybdate chelation attenuates both bleomycin-induced angiogenesis and pulmonary fibrosis. Moreover, tetrathiomolybdate treatment downregulates vascular endothelial growth factor (VEGF) expression, and improved lung function in bleomycin-induced pulmonary fibrosis. Tetrathiomolybdate also suppressed the accumulation of inflammatory cells in bronchoalveolar lavage fluid 2 weeks after bleomycin injury. The molecular mechanism(s) underpinning copper modulation of fibrotic pathways is an important area for future investigation, and it represents a potential therapeutic target for pulmonary fibrosis.

Small airway remodeling in a sheep model of bleomycin-induced pulmonary fibrosis

BACKGROUND

Although IPF is described traditionally as a disease affecting lung parenchyma, there is renewed interest in the alterations in the structure and function of the small airways in both IPF patients, and animal models of pulmonary fibrosis. Small airway remodeling may contribute to the pathophysiology of pulmonary fibrosis. Given the dearth of knowledge of small airway changes in pulmonary fibrosis, this study aims to assess the structural remodeling, as well as functional changes associated with bleomycin-injured small airways in a sheep model of pulmonary fibrosis.

MATERIALS AND METHODS

Two separate lung segments in ten sheep received two challenges of either 3 IU bleomycin, or saline (control), two weeks apart. The animals were euthanized seven weeks after the final bleomycin injury. Airflow resistance in the infused segments was measured with a wedged-bronchoscope procedure. This parameter was measured at baseline before bleomycin/saline-infusion, and at 2-, 4-, and 7-weeks after the final bleomycin-infusion. Inflammation and fibrosis in the airways were assessed by semi-quantitative morphological parameters. The density of blood vessels in the small airway walls was assessed in lung tissue sections immuno-stained with antibodies against collagen type IV.

RESULTS

There were a number of changes in the distal airways of bleomycin-infused lung segments. Bleomycin exposure significantly elevated airway resistance in these lung segments when compared to saline-infused control lung segments. In the peribronchial and peribronchiolar regions of the small airways, there were significantly increased levels of inflammation, fibrosis, airway wall area, and collagen deposition in bleomycin-infused airways when compared to saline-infused airways. Bronchial blood vessel density was not significantly different between bleomycin-and saline-infused lung segments.

CONCLUSIONS

In summary, our results indicate that the distal airways are involved in the pathology induced by bleomycin in this sheep model. This suggests that the sheep model may be useful for studying small airway remodeling in pulmonary fibrosis.

KCa3.1 channel blockade attenuates microvascular remodelling in a large animal model of bleomycin-induced pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive lung disease with limited therapeutic options and poor prognosis. IPF has been associated with aberrant vascular remodelling, however the role of vascular remodelling in pulmonary fibrosis is poorly understood. Here, we used a novel segmental challenge model of bleomycin-induced pulmonary fibrosis in sheep to evaluate the remodelling of the pulmonary vasculature, and to investigate the changes to this remodelling after the administration of the K_Ca3.1 channel inhibitor, senicapoc, compared to the FDA-approved drug pirfenidone. We demonstrate that in vehicle-treated sheep, bleomycin-infused lung segments had significantly higher blood vessel density when compared to saline-infused control segments in the same sheep. These microvascular density changes were significantly attenuated by senicapoc treatment. The increases in vascular endothelial growth factor (VEGF) expression and endothelial cell proliferation in bleomycin-infused lung segments were significantly reduced in sheep treated with the senicapoc, when compared to vehicle-treated controls. These parameters were not significantly suppressed with pirfenidone treatment. Senicapoc treatment attenuated vascular remodelling through inhibition of capillary endothelial cell proliferation and VEGF expression. These findings suggest a potential new mode of action for the novel drug senicapoc which may contribute to its efficacy in combatting pulmonary fibrosis.

The efficacy of pirfenidone in a sheep model of pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive fibrotic lung disease with unknown cause. While the drugs nintedanib and pirfenidone have been approved for the treatment of IPF, they only slow disease progression and can induce several side-effects, suggesting that there is still an unmet need to develop new efficacious drugs, and interventions strategies, to combat this disease. We have recently developed a sheep model of pulmonary fibrosis for the preclinical testing of novel anti-fibrotic drugs. The aim of this study was to assess the effects of pirfenidone to ascertain its suitability as a benchmark for comparing other novel therapeutics in this sheep model. To initiate localized fibrosis, sheep were given two infusions of bleomycin (0.6 U/ml per infusion), a fortnight apart, to a specific lung segment. The contralateral lung segment in each sheep was infused with saline to act as an internal control. Two weeks after the final bleomycin infusion, either pirfenidone or methylcellulose (vehicle control) were administered orally to sheep twice daily for 5 weeks. Results showed that sheep treated with pirfenidone had improved lung function, ameliorated fibrotic pathology, lower numbers of active myofibroblasts, and reduced extra cellular matrix deposition when compared with the relevant measurements obtained from control sheep treated with vehicle. This study showed that pirfenidone can attenuate bleomycin-induced pulmonary fibrosis in sheep, and can therefore be used as a positive control to assess other novel therapeutics for IPF in this model.

Cerebral blood flow velocities and cerebrovascular resistance in normal-term neonates in the first 72 hours

AIM

To determine the range of cerebral blood flow velocities (CBFVs) and Doppler indices of cerebrovascular resistance in normal-term neonates as a baseline for a study of hypoxic-ischaemic encephalopathy.

METHODS

The CBFVs, resistive index (RI) and pulsatility index (PI) were measured in the anterior and middle cerebral arteries (ACA and MCA) of 38 normal neonates.

RESULTS

The mean peak systolic, end diastolic and time-averaged velocities (PSV, EDV and TAV) were 36.3 ± 6.6, 12.4 ± 3.9 and 22.0 ± 4.0 cm/s (ACA) and 41.4 ± 13.2, 13.0 ± 5.5 and 25.8 ± 7.9 cm/s (MCA), respectively. All CBFVs in the ACA correlated with gestation; only EDV was correlated to post-natal age. The RI in the ACA (0.67 ± 0.06) and MCA (0.68 ± 0.07) were correlated (r = 0.72, P < 0.001); RI correlated to post-natal age. Two infants with RI < 0.55 were both fed within 25 mins of the study; RI correlated with post-prandial time (dichotomous, pivot 25 min). The mean PI was 1.11 ± 0.18 (ACA) and 1.17 ± 0.23 (MCA). Correlations were observed with post-natal age and post-prandial time (dichotomous). The average angle of insonation was greater in the ACA than in the MCA (median of 5° vs. 18°).

CONCLUSIONS

Results corresponded with previous published studies. No correlation was observed between Doppler indices and gestation as component velocities all increase with advancing gestation. Less variation and smaller standard deviation of CBFV's was associated with a smaller angle of insonation. Low RIs (<0.55), without a pathological cause, warrants further study.

Structural and functional correlations in a large animal model of bleomycin-induced pulmonary fibrosis

Background

Idiopathic pulmonary fibrosis (IPF) is a severe and progressive respiratory disease with poor prognosis. Despite the positive outcomes from recent clinical trials, there is still no cure for this disease. Pre-clinical animal models are currently largely limited to small animals which have a number of shortcomings. We have previously shown that fibrosis is induced in isolated sheep lung segments 14 days after bleomycin treatment. This study aimed to determine whether bleomycin-induced fibrosis and associated functional changes persisted over a seven-week period.

Methods

Two separate lung segments in nine sheep received two challenges two weeks apart of either, 3U bleomycin (BLM), or saline (control). Lung function in these segments was assessed by a wedged-bronchoscope procedure after bleomycin treatment. Lung tissue, and an ex vivo CT analysis were used to assess for the persistence of inflammation, fibrosis and collagen content in this model.

Results

Fibrotic changes persisted up to seven weeks in bleomycin-treated isolated lung segments (Pathology scores: bleomycin12.27 ± 0.07 vs. saline 4.90 ± 1.18, n = 9, p = 0.0003). Localization of bleomycin-induced injury and increased tissue density was confirmed by CT analysis (mean densitometric CT value: bleomycin −698 ± 2.95 Hounsfield units vs. saline −898 ± 2.5 Hounsfield units, p = 0.02). Masson’s trichrome staining revealed increased connective tissue in bleomycin segments, compared to controls (% blue staining/total field area: 8.5 ± 0.8 vs. 2.1 ± 0.2 %, n = 9, p < 0.0001). bleomycin-treated segments were significantly less compliant from baseline at 7 weeks post treatment compared to control-treated segments (2.05 ± 0.88 vs. 4.97 ± 0.79 mL/cmH20, n = 9, p = 0.002). There was also a direct negative correlation between pathology scores and segmental compliance.

Conclusions

We show that there is a correlation between fibrosis and correspondingly poor lung function which persist for up to seven weeks after bleomycin treatment in this large animal model of pulmonary fibrosis.

A novel segmental challenge model for bleomycin-induced pulmonary fibrosis in sheep

BACKGROUND

Idiopathic Pulmonary fibrosis (IPF) is a fatal respiratory disease, characterized by a progressive fibrosis and worsening lung function. While the outcomes of recent clinical trials have resulted in therapies to slow the progression of the disease, there is still a need to develop alternative therapies, which are able to prevent fibrosis.

AIM

This study uses a segmental lung infusion of bleomycin (BLM) to investigate pulmonary fibrosis in a physiologically relevant large animal species.

METHODS

Two separate lung segments in eight sheep received two fortnightly challenges of either 3U or 30U BLM per segment, and a third segment received saline (control). Lung function was assessed using a wedged-bronchoscope procedure. Bronchoalveolar lavage fluid and lung tissue were assessed for inflammation, fibrosis and collagen content two weeks after the final dose of BLM.

RESULTS

Instillation of both BLM doses resulted in prominent fibrosis in the treated lobes. More diffuse fibrosis and loss of alveolar airspace was observed in high-dose BLM-treated segments, while multifocal fibrosis was seen in low-dose BLM-treated segments. Extensive and disorganised collagen deposition occurred in the BLM-treated lobes, compared to controls. Significant loss of lung compliance was also observed in the BLM-treated lobes, which did not occur in controls.

CONCLUSIONS

Fibrosis comparable to IPF was induced into isolated lung segments, without compromising the respiratory functioning of the animal. This model may have potential for investigating novel therapies for IPF by allowing direct comparison of multiple treatments with internal controls, and sampling and drug delivery that are clinically relevant.

K(Ca)3.1 channel-blockade attenuates airway pathophysiology in a sheep model of chronic asthma

Background

The Ca²⁺-activated K⁺ channel K_Ca3.1 is expressed in several structural and inflammatory airway cell types and is proposed to play an important role in the pathophysiology of asthma. The aim of the current study was to determine whether inhibition of K_Ca3.1 modifies experimental asthma in sheep.

Methodology and Principal Findings

Atopic sheep were administered either 30 mg/kg Senicapoc (ICA-17073), a selective inhibitor of the K_Ca3.1-channel, or vehicle alone (0.5% methylcellulose) twice daily (orally). Both groups received fortnightly aerosol challenges with house dust mite allergen for fourteen weeks. A separate sheep group received no allergen challenges or drug treatment. In the vehicle-control group, twelve weeks of allergen challenges resulted in a 60±19% increase in resting airway resistance, and this was completely attenuated by treatment with Senicapoc (0.25±12%; n = 10, P = 0.0147). The vehicle-control group had a peak-early phase increase in lung resistance of 82±21%, and this was reduced by 58% with Senicapoc treatment (24±14%; n = 10, P = 0.0288). Senicapoc-treated sheep also demonstrated reduced airway hyperresponsiveness, requiring a significantly higher dose of carbachol to increase resistance by 100% compared to allergen-challenged vehicle-control sheep (20±5 vs. 52±18 breath-units of carbachol; n = 10, P = 0.0340). Senicapoc also significantly reduced eosinophil numbers in bronchoalveolar lavage taken 48 hours post-allergen challenge, and reduced vascular remodelling.

Conclusions

These findings suggest that K_Ca3.1-activity contributes to allergen-induced airway responses, inflammation and vascular remodelling in a sheep model of asthma, and that inhibition of K_Ca3.1 may be an effective strategy for blocking allergen-induced airway inflammation and hyperresponsiveness in humans.

Increased vascular density is a persistent feature of airway remodeling in a sheep model of chronic asthma

BACKGROUND

Increases in blood vessel density and vascular area are now recognized as important features of remodeled airways in asthma. However, the time sequence for these vascular changes and whether they resolve in the absence of continued antigenic exposure is not well elucidated. The aim of the present study was to correlate progressive changes in airway vascularity with changes in functional airway responses in sheep chronically challenged with house dust mite (HDM) allergen, and to examine the resolution of vascular remodeling following allergen withdrawal.

METHODS

Progressive changes in vascular indices were examined in four spatially separate lung segments that received weekly challenges with HDM allergen for 0, 8, 16, or 24 weeks. Reversibility of these changes was assessed in a separate experiment in which two lung segments received 24 weeks of HDM challenges and either no rest or 12 weeks rest. Lung tissue was collected from each segment 7 days following the final challenge and vascular changes assessed by a morphometric analysis of airways immunohistochemically stained with an antibody against type IV collagen.

RESULTS

Blood vessel density and percent airway vascularity were significantly increased in bronchi following 24 weeks of HDM challenges compared to untreated controls (P < .05), but not at any of the other time-points. There was no significant correlation between vascular indices and airway responses to allergic or nonspecific stimuli. The increase in blood vessel density induced by repeated allergen exposures did not return to baseline levels following a 12-week withdrawal period from allergen.

CONCLUSIONS

Our results show for the first time that the airways of sheep chronically exposed to HDM allergen undergo vascular remodeling. These findings show the potential of this large animal model for investigating airway angiogenesis in asthma.

Increased mast cell density and airway responses to allergic and non-allergic stimuli in a sheep model of chronic asthma

Background

Increased mast cell (MC) density and changes in their distribution in airway tissues is thought to contribute significantly to the pathophysiology of asthma. However, the time sequence for these changes and how they impact small airway function in asthma is not fully understood. The aim of the current study was to characterise temporal changes in airway MC density and correlate these changes with functional airway responses in sheep chronically challenged with house dust mite (HDM) allergen.

Methodology/Principal Findings

MC density was examined on lung tissue from four spatially separate lung segments of allergic sheep which received weekly challenges with HDM allergen for 0, 8, 16 or 24 weeks. Lung tissue was collected from each segment 7 days following the final challenge. The density of tryptase-positive and chymase-positive MCs (MC_T and MC_TC respectively) was assessed by morphometric analysis of airway sections immunohistochemically stained with antibodies against MC tryptase and chymase.

MC_T and MC_TC density was increased in small bronchi following 24 weeks of HDM challenges compared with controls (P<0.05). The MC_TC/MC_T ratio was significantly increased in HDM challenged sheep compared to controls (P<0.05). MC_T and MC_TC density was inversely correlated with allergen-induced increases in peripheral airway resistance after 24 weeks of allergen exposure (P<0.05). MC_T density was also negatively correlated with airway responsiveness after 24 challenges (P<0.01).

Conclusions

MC_T and MC_TC density in the small airways correlates with better lung function in this sheep model of chronic asthma. Whether this finding indicates that under some conditions mast cells have protective activities in asthma, or that other explanations are to be considered requires further investigation.

Lung function in developing lambs: is it affected by preterm birth?

Children born before term often have reduced lung function, but the effects of preterm birth alone are difficult to determine owing to iatrogenic factors such as mechanical ventilation. Our objective was to determine the effects of preterm birth alone on airway resistance, airway reactivity, and ventilatory heterogeneity as an index of intrapulmonary gas mixing. Preterm birth was induced in sheep 12 days before term; controls were born at term (∼147 days). Lung function was assessed at 8 wk postterm. To assess medium-large airway function we measured airway resistance and reactivity to carbachol. Multiple breath N2 washout (MBW) was used to assess ventilatory heterogeneity in conducting (Scond) and acinar (Sacin) airways. Baseline airway resistance and responsiveness to carbachol were similar in preterm and term lambs. Airway responsiveness to carbachol was greater in females than males ( P < 0.05), and baseline airway resistance tended to be higher in females than males ( P = 0.06). There were no significant differences in ventilatory heterogeneity between preterm and term lambs; for all animals combined, mean Sacin was 0.29 ± 0.05 liter−1 and Scond was 0.26 ± 0.03 liter−1. Males had significantly higher Scond than females, indicating poorer gas mixing in small conducting airways; there was no sex difference in Sacin. We conclude that preterm birth per se in lambs does not affect baseline airway resistance, airway responsiveness, or ventilatory heterogeneity as measured by MBW. The observed sex-related differences in airway responsiveness and ventilatory heterogeneity in the conducting airways could help explain sex differences in lung function observed in humans.

Oesophageal techniques for deriving the lung dynamics of quietly breathing sheep

An airway monitoring system was developed to record the lung dynamics of sheep using oesophageal pressure techniques. These techniques are minimally invasive and do not impede the animal from breathing spontaneously. This study investigates three methods for deriving lung resistance (R) and compliance (C) by evaluating their ability to select regular breaths amongst artefact effected signals. The Multi Linear Regression method, the Modified Mead-Whittenberger (MMW) method and Isovolumetric method were tested against signals with movement and/or swallowing artifacts. Their coefficient of variation (% CV) revealed that the MMW had the least variation with R at 35% CV and C at 25 % CV. The lung dynamics for 14 quietly breathing sheep were R = 1.5 +/- 0.5 cmH2O/l/s, C = 0.20 +/- 0.08 l/cmH2O, tidal volume = 0.25 +/- 0.05 litres and respiratory rate = 26 +/- 6 bpm.

Chronic airway disease: deteriorating pulmonary function in sheep associated with repeated challenges of house dust mite

The aim of this work was to characterize lung function and cellular responses in a large animal model for chronic asthma. All sheep were sensitized to house dust mite (HDM) by subcutaneous injection of HDM before lung challenges. Groups of sheep were given weekly lung challenges with either HDM (n = 12) or saline (control, n = 5) for 3 months. Post challenge, there were significant increases in lung resistance in 7 out of 12 HDM-challenged sheep, compared to control sheep. In HDM-responding sheep, there was a progressive increase in the magnitude of HDM-induced resistance throughout the trial. All HDM-challenged sheep developed BAL eosinophilia and bronchial hyperresponsiveness. In conclusion, sheep chronically challenged intralung with HDM consistently develop airway hyperresponsiveness and eosinophilia, whereas allergen-specific bronchoconstriction is observed in just over half of these sheep.

Altered airway responsiveness in adult sheep born prematurely: effects of allergen exposure

The aim of this study was to determine the effects of preterm birth per se on airway function in adult sheep. Preterm birth was induced at approximately 0.89 of term. At approximately 1 year of age the authors measured pulmonary resistance (RL) and airway responsiveness before and after house dust mite (HDM) challenge. Mature preterm sheep tended to have greater baseline RL than controls (P = .12): the smaller preterm sheep showed significantly greater RL than controls following bronchoconstrictor challenge. Preterm animals tended to have greater baseline total blood leukocyte count (P = .06). It was concluded that preterm sheep, especially with low postnatal growth, have greater airway responsiveness to bronchoconstrictor and higher baseline RL.

Pre-bypass myocardial ischaemia in patients undergoing coronary artery surgery

One hundred patients undergoing elective coronary artery surgery were studied to determine the incidence of pre-bypass myocardial ischaemia. Leads II, aVF and V5 of the electrocardiogram (ECG) were recorded at five-minute intervals from arrival in the anaesthetic room until onset of cardiopulmonary bypass. Thirteen patients developed sixteen episodes of significant ST depression on the ECG during the study period. Three patients were diagnosed as having postoperative myocardial infarction by ECG criteria and creatine phosphokinase-MB rise above 80 units. None of these patients had pre-bypass ST depression. Comparisons of these results with similar studies are presented.

EEG monitoring using aperiodic analysis during carotid and open heart surgery

The Cerebral Electrical Activity (CEA) was monitored by Lifescan in 38 patients undergoing carotid surgery under general or regional anaesthesia and another 20 patients during cardiopulmonary bypass undergoing open heart surgery. This monitor uses aperiodic analysis to process the electroencephalogram. Abrupt changes in CEA were observed when blood flow was disrupted due to surgical intervention or administration of thiopentone. Gradual changes in CEA were due to anaesthesia or hypothermia. In one patient a long period of depressed CEA did not result in a neurological deficit and in another patient a neurological event was undetected by the monitor.

Comparison of the processed electroencephalogram and awake neurological assessment during carotid endarterectomy

A processed electroencephalogram (EEG) produced by the Lifescan monitor (Neurometrics), was compared to awake neurological assessment for detecting cerebral ischaemia in seventy patients undergoing carotid endarterectomy under cervical plexus block. Of the six patients demonstrating neurological signs on cross-clamping the carotid, five displayed simultaneous EEG changes, four being detected during surgery, and one being detected after reviewing the EEG postoperatively. Another four patients displayed EEG changes indicative of ischaemia but unassociated with neurological signs. A further patient displayed contralateral intraoperative EEG changes. Hypotension resulted in one EEG change and two cases were associated with technical difficulties with the monitor. The presence of false negatives, possible false positives, technical errors and subjective interpretation associated with the processed EEG make it less reliable than awake neurological assessment for the detection of cerebral ischaemia.

The use of aperiodic analysis of the EEG during carotid artery surgery

A new processed EEG machine, the Lifescan, which uses aperiodic analysis, was used to monitor cerebral activity prospectively in twenty-one patients undergoing carotid artery surgery under general anaesthesia. The machine was easy to apply, use and read. Volatile agents caused a bilateral decrease in high frequency activity. Unilateral changes consistent with cerebral ischaemia at the time of carotid cross-clamping were also seen. One such prolonged change was not associated with neurological deficit. A further patient awoke with neurological deficit without displaying Lifescan evidence of ischaemia. The machine requires further assessment.

Reliability of estimation of pulmonary artery wedge pressures during coronary artery bypass surgery

The ability to reliably estimate pulmonary artery wedge pressure measurements using the clinical and basic cardiovascular parameters was assessed in fifty-six patients having elective coronary artery bypass surgery. The patients were divided into three groups: Group 1 had normal left ventricular function (22 patients), Group 2 had moderate left ventricular dysfunction (20 patients) and Group 3 had more severe left ventricular dysfunction (14 patients). The percentages of correct pulmonary artery wedge pressure estimations were 55%, 56% and 52% in Groups 1, 2 and 3 respectively. We conclude that pulmonary artery wedge pressure measurements can only be reliably estimated from the clinical situation and basic cardiovascular parameters on about 50% of occasions and that the reliability of the estimation does not vary between groups with different left ventricular performance.

Radial artery cannulation--the influence of method on blood flow after decannulation

A prospective randomised study of two hundred patients undergoing open-heart surgery was carried out to determine if the method of radial artery cannulation (direct threading or transfixion) had any influence on the incidence of abnormal flow after decannulation. A standard 20-gauge non-tapered teflon-coated cannula was used and the groups were well matched for age, sex, wrist circumference, duration of cannulation and haematoma formation, all of which have been postulated to influence thrombosis rate. We were unable to demonstrate a statistically significant difference between the two methods of cannulation. The overall abnormal flow rate at five days assessed by Doppler ultrasound was low at 5%.