Novel closed-loop control system of dual rotary blood pumps in total artificial heart based on the circulatory equilibrium framework: a proof-of-concept in vivo study.

OBJECTIVE: Total artificial heart (TAH) using dual rotary blood pumps (RBPs) is a potential treatment for end-stage heart failure. A well-noted challenge with RBPs is their low sensitivity to preload, which can lead to venous congestion and ventricular suction. To address this issue, we have developed an innovative closed-loop control system of dual RBPs in TAH. This system emulates the Frank-Starling law of the heart in controlling RBPs while monitoring stressed blood volume (V) based on the circulatory equilibrium framework. We validated the system in in-vivo experiments. METHODS: In 9 anesthetized dogs, we prepared a TAH circuit using 2 centrifugal-type RBPs. We first investigated whether the flow and inlet atrial pressure in each RBP adhered to a logarithmic Frank-Starling curve. We then examined whether the RBP flows and atrial pressures were maintained stably during aortic occlusion (AO) and pulmonary cannula stenosis (PS), whether averaged flow of dual RBPs and bilateral atrial pressures were controlled to their predefined target values for a specific V, and whether this system could maintain the atrial pressures within predefined control ranges under significant changes in V. RESULTS: This system effectively emulated the logarithmic Frank-Starling curve. It robustly stabilized the flow and atrial pressures during AO and PS without venous congestion or ventricular suction, accurately achieved target values in averaged flow and atrial pressures, and efficaciously maintained these pressures within the control ranges. CONCLUSION: This system controls dual RBPs in TAH accurately and stably. SIGNIFICANCE: This system may accelerate clinical application of TAH with dual RBPs.

Computer-controlled closed-loop norepinephrine infusion system for automated control of mean arterial pressure in dogs under isoflurane-induced hypotension: a feasibility study.

Introduction: Intra-operative hypotension is a common complication of surgery under general anesthesia in dogs and humans. Computer-controlled closed-loop infusion systems of norepinephrine (NE) have been developed and clinically applied for automated optimization of arterial pressure (AP) and prevention of intra-operative hypotension in humans. This study aimed to develop a simple computer-controlled closed-loop infusion system of NE for the automated control of the mean arterial pressure (MAP) in dogs with isoflurane-induced hypotension and to validate the control of MAP by the developed system. Methods: NE was administered via the cephalic vein, whereas MAP was measured invasively by placing a catheter in the dorsal pedal artery. The proportional-integral-derivative (PID) controller in the negative feedback loop of the developed system titrated the infusion rate of NE to maintain the MAP at the target value of 60 mmHg. The titration was updated every 2 s. The performance of the developed system was evaluated in six laboratory Beagle dogs under general anesthesia with isoflurane. Results: In the six dogs, when the concentration [median (interquartile range)] of inhaled isoflurane was increased from 1.5 (1.5-1.5)% to 4 (4-4)% without activating the system, the MAP was lowered from 95 (91-99) to 41 (37-42) mmHg. In contrast, when the concentration was increased from 1.5 (1.0-1.5)% to 4 (4-4.8)% for a 30-min period and the system was simultaneously activated, the MAP was temporarily lowered from 92 (89-95) to 47 (43-49) mmHg but recovered to 58 (57-58) mmHg owing to the system-controlled infusion of NE. If the acceptable target range for MAP was defined as target MAP ±5 mmHg (55 ≤ MAP ≤65 mmHg), the percentage of time wherein the MAP was maintained within the acceptable range was 96 (89-100)% in the six dogs during the second half of the 30-min period (from 15 to 30 min after system activation). The median performance error, median absolute performance error, wobble, and divergence were - 2.9 (-4.7 to 1.9)%, 2.9 (2.0-4.7)%, 1.3 (0.8-1.8)%, and - 0.24 (-0.34 to -0.11)%·min-1, respectively. No adverse events were observed during the study period, and all dogs were extubated uneventfully. Conclusion: This system was able to titrate the NE infusion rates in an accurate and stable manner to maintain the MAP within the predetermined target range in dogs with isoflurane-induced hypotension. This system can be a potential tool in daily clinical practice for the care of companion dogs.

Fentanyl-induced muscle rigidity in a dog during weaning from mechanical ventilation after emergency abdominal surgery: A case report.

A 22.5-kg, 8.4-year-old female mixed breed dog was presented for an emergency ovariohysterectomy for pyometra. No neurological abnormalities were observed on preoperative physical examination. Surgery was completed uneventfully under fentanyl- and sevoflurane-based anaesthesia. Cardiorespiratory indices remained stable under mechanical ventilation throughout the procedure. Approximately 23 min after the discontinuation of fentanyl infusion, the investigator noticed jaw closure and stiffness and thoraco-abdominal muscle rigidity. To rule out fentanyl-induced muscle rigidity, naloxone was administered. Following administration of naloxone, there was a return of spontaneous respiratory effort, indicated by capnogram and visible chest wall excursion. Based on the clinical signs and response to naloxone administration, the dog was diagnosed with suspected fentanyl-induced muscle rigidity. Six minutes after the return of spontaneous respiration, the dog was extubated uneventfully without additional naloxone administration. During 4 days of postoperative hospitalization, no recurrent muscle rigidity was observed, and the patient was discharged safely. The total dose of fentanyl administered was 0.61 mg (27 µg kg-1 ).

Antinociceptive effects of the combined use of butorphanol and buprenorphine in mice.

Butorphanol and buprenorphine are mixed opioid receptor agonist-antagonist drugs widely used as analgesics in people and animals. There are few reports concerning the interaction of multiple opioids, and their antinociceptive effects, when combined with other opioids, remain unclear. Therefore, we report the preliminary findings of the antinociceptive effects of the combined use of butorphanol and buprenorphine in C57BL/6JJcl mice. Both drugs were administered either simultaneously or in different orders. Compared with the baseline values, the tail-flick and hot-plate test latencies increased regardless of the order of administration. Furthermore, enhanced latencies were observed on administration of butorphanol followed by buprenorphine. Combined use of these drugs may not attenuate analgesic efficacy. Besides, enhancement of these effects can be obtained by changing the order of the administration of these drugs. It is necessary to further investigate the molecular basis of the underlying mechanism in future definitive studies.

Noninvasive assessment of fluid responsiveness for emergency abdominal surgery in dogs with pulmonary hypertension: Insights into high-risk companion animal anesthesia.

OBJECTIVE: Optimizing cardiac stroke volume during high-risk surgical anesthesia is of particular interest with regard to a therapeutic target to reduce the incidence of postoperative complications. However, intensive fluid management in critically ill small animals with pulmonary hypertension (PH) has been empirically performed, and thus it can be challenging. Stroke volume variation (SVV) has been used as a dynamic preload predictor of fluid responsiveness. We hypothesized that if SVV exhibited robust reliability in the setting of hemodynamically unstable condition, it would provide more precise information on fluid resuscitation to translate it into veterinary anesthesia. Thus the aim of this study was to investigate the utility of SVV measured by the electrical velocimetry (EV) method for predicting fluid responsiveness in dogs with PH. METHODS: Sixteen dogs undergoing emergency abdominal surgery and diagnosed with PH secondary to myxomatous mitral valve disease (MMVD) on preoperative transthoracic echocardiogram were included. Dogs were randomly assigned to 2 groups with and without inotropic cardiac support with dobutamine. Hemodynamic measurements including stroke volume and SVV derived from the EV device were performed under general anesthesia before (baseline) and after surgery (fluid challenge with a colloid solution defined by a SV increase of ≥ 10%). RESULTS: In both groups, SVV elevated significantly after abdominal surgery compared with baseline. In dobutamine infused group, the SVV values decreased significantly after fluid challenge (P < 0.05) with a greater number of responders than saline infused control group (P < 0.01). Receiver operating curve analysis of SVV confirmed high positive predictive value for dogs during dobutamine infusion (P < 0.05; cut-off value of 15%; specificity 90%, sensitivity 82%). CONCLUSIONS: Noninvasive EV monitoring may be useful for the prediction of fluid responsiveness in critically ill dogs with left-sided heart failure-related PH. This normalization of dynamic preload indices, which could be achieved more precisely under inotropic support, may prevent further detrimental consequence of fluid loading.

Heparinized Saline Solution vs. Saline Solution (0.9% Sodium Chloride) for the Maintenance of Dorsal Pedal Arterial Catheter Patency in Dogs Undergoing General Anesthesia: A Pilot Study.

Heparin is widely used as an anticoagulant solution for maintaining arterial catheter patency. In humans, increasing evidence suggests that heparinized saline solution (HS) has no advantages over a saline (0.9% sodium chloride) solution (SS) in maintaining arterial catheter patency. To date, no studies have been conducted on the effectiveness of these solutions at maintaining arterial catheter patency in veterinary medicine. The objective of this pilot study was to determine the feasibility of a study and to report the treatment efficacy comparing HS and SS for the maintenance of the dorsal pedal arterial catheter patency during direct arterial blood pressure measurements in anesthetized dogs. Client-owned dogs undergoing abdominal surgery were allocated to two groups to receive either a continuous infusion of HS or SS through the dorsal pedal artery, and the arterial pressure waveform was monitored during general anesthesia. Our feasibility outcomes included the proportion of the screened veterinary patients that completed the study and the success rate of arterial catheter placement. The clinical outcomes were assessed by the number of catheter-flushing procedures, occlusion rate, the duration of the initial catheter-flushing procedures, and the duration of catheter occlusion. Of the 51 dogs screened, 41 (80.4%) completed the study. The success rate of arterial catheter placement in the HS and SS groups were 87.5 and 80.0%, respectively. There were no differences in the number of catheter-flushing procedures and occlusion rate between groups (28.6 vs. 20.0%, relative risk [RR]: 1.429, 95% confidence interval [CI]: 0.472-4.323, P = 0.719 and 14.3 vs. 15.0%, RR: 0.952, 95% CI: 0.217-4.179, P = 1.000, respectively). No differences were found in the probability of time to the initial catheter-flushing procedure and occlusion between groups assessed by the Kaplan-Meier method (P = 0.546 and P = 0.867, respectively). This study revealed the feasibility of a study comparing HS and SS for dorsal pedal arterial catheter patency during direct arterial blood pressure measurements in anesthetized dogs. Clinical outcome analyses were underpowered and thus, could not determine the meaningful differences in treatment efficacy between the groups. However, the information gained from this study provides insight for future study designs.

Advantages of a Novel Device for Arterial Catheter Securement in Anesthetized Dogs: A Pilot Randomized Clinical Trial.

Arterial catheters are used for intraoperative continuous direct blood pressure monitoring in dogs. Factors such as bending and occlusion of the cannula are believed to be involved in direct blood pressure measurement failure. However, no method has been proposed to improve the maintenance of arterial catheter patency in veterinary medicine. The aim of this pilot study was to evaluate the patency of arterial catheters when using an arterial catheter securement device in the dorsal pedal artery of dogs under general anesthesia. Client-owned dogs (n = 120) were anesthetized for surgical procedures, during which direct arterial blood pressure was monitored using an arterial catheter secured with conventional film dressing and medical tape. A securement device, allowing an angle of 12.5° to the skin surface of the dorsal pedal area, was used in 50% of the dogs (n = 60). Significant reductions were observed in the frequency of catheter flushing and rate of occlusion in the experimental group compared to the control group (13.3 vs. 35.0%, relative risk [RR]: 0.381, 95% confidence interval [CI]: 0.183-0.792, P = 0.001 and 8.3 vs. 23.3%, RR: 0.376, 95% CI: 0.145-0.977, P = 0.044, respectively). The Kaplan-Meier curves for assessing the probability of occlusion were significantly different between the groups (P = 0.042). In conclusion, this pilot study suggests that the novel arterial catheter securement device is effective for achieving stable securement of the catheter hub in the dorsal pedal artery and for maintaining a longer duration of arterial catheter patency in dogs under general anesthesia. Therefore, the use of an arterial catheter securement device in the dorsal pedal artery of dogs would be useful for continuous hemodynamic monitoring and improve patient safety when direct arterial blood pressure monitoring is required in dogs undergoing general anesthesia.

Central action of rapamycin on early ischemic injury and related cardiac depression following experimental subarachnoid hemorrhage.

Early brain injury and related cardiac consequences play a key role in the devastating outcomes after subarachnoid hemorrhage (SAH). We reported that rapamycin exerts neuroprotection against cortical hypoxia early after SAH, but its mechanism is poorly understood. This in vivo study aimed to determine the potential role of the transcription factor STAT3 in the rapamycin-mediated neuroprotection in a mouse model of SAH. Forty C57BL/6 N mice were treated with an intracerebroventricular injection of rapamycin or vehicle (control) given after SAH induction by a filament perforation method, with or without STAT3 (Stattic) or ERK (PD98059) inhibitor pretreatment. Cerebral blood flow signals (%vascularity), brain tissue oxygen saturation (SbtO2), and cardiac output (CO) were analyzed using an ultrasound/photoacoustic imaging system. Clinically relevant neurocardiac depression was notable in severe SAH mice. Rapamycin improved %vascularity, SbtO2, and CO on day 1 after SAH onset. The beneficial effects of rapamycin on cerebral blood flow and oxygenation persisted until day 3, resulting in a significant reduction in post-SAH new cerebral infarctions and survival, as well as improved neurological functions, compared to the control group. All of the effects were attenuated by pretreatment with Stattic or PD98059. These data suggest that ERK and JAK/STAT3 pathways play an important role in the neurocardiac protection by rapamycin after SAH. We propose that rapamycin is a novel pharmacological strategy to target STAT3 activation, with a possible crosstalk through the ERK pathway, for the treatment of post-SAH early brain injury.

Non-invasive three-dimensional power Doppler imaging for the assessment of acute cerebral blood flow alteration in a mouse model of subarachnoid haemorrhage.

We aimed to evaluate the feasibility of a non-invasive method of cerebral blood flow (CBF) measurement using high-frequency power Doppler ultrasound imaging in a mouse model of subarachnoid haemorrhage (SAH). The 3-dimensionally (3D) reconstructed blood flow signals (%vascularity) within the brain volume of the middle cerebral artery territory correlated well with reference parameters, baseline carotid artery blood flow (r2  = 0.52, P < 0.0001) and normalized CBF changes (r2  = 0.74 P < 0.0001). These data suggest that the 3D power Doppler analysis may have the potential for reflecting real-time CBF changes during the acute phase of experimental SAH, which may be applicable to preclinical studies on early brain injury.

Performance of Electrical Velocimetry for Noninvasive Cardiac Output Measurements in Perioperative Patients After Subarachnoid Hemorrhage.

BACKGROUND: Fluid therapy guided by cardiac output measurements is of particular importance for adequate cerebral perfusion and oxygenation in neurosurgical patients. We examined the usefulness of a noninvasive electrical velocimetry (EV) device based on the thoracic bioimpedance method for perioperative hemodynamic monitoring in patients after aneurysmal subarachnoid hemorrhage. PATIENTS AND METHODS: In total, 18 patients who underwent surgical clipping or endovascular coiling for ruptured aneurysms were examined prospectively. Simultaneous cardiac index (CI) measurements obtained with EV (CIEV) and reference transpulmonary thermodilution (CITPTD) were compared. A total of 223 pairs of data were collected. RESULTS: A significant correlation was found between CIEV and CITPTD (r=0.86; P<0.001). Bland and Altman analysis revealed a bias between CIEV and CITPTD of -0.06 L/min/m, with limits of agreement of ±1.14 L/min/m and a percentage error of 33%. Although the percentage error for overall data was higher than the acceptable limit of 30%, subgroup analysis during the postoperative phase showed better agreement (23% vs. 42% during the intraprocedure phase). Four-quadrant plot and polar plot analyses showed fair-to-poor trending abilities (concordance rate of 90% to 91%, angular bias of +17 degrees, radial limits of agreement between ±37 and ±40 degrees, and polar concordance rate of 72% to 75%), including the subgroup analysis. CONCLUSIONS: Absolute CI values obtained from EV and TPTD are not interchangeable with TPTD for perioperative use in subarachnoid hemorrhage patients. However, considering the moderate levels of agreement with marginal trending ability during the early postoperative phase, this user-friendly device can provide an attractive monitoring option during neurocritical care.

Comparison of Noninvasive Dynamic Indices of Fluid Responsiveness Among Different Ventilation Modes in Dogs Recovering from Experimental Cardiac Surgery.

BACKGROUND Fluid resuscitation is a cornerstone of minimizing morbidity and mortality in critically ill patients, but the techniques for predicting fluid responsiveness is still a matter of debate. In this study, we aimed to evaluate the utility of noninvasive stroke volume variation (SVV), pulse pressure variation (PPV), and systolic pressure variation (SPV) as a dynamic predictor for assessing fluid responsiveness during different ventilation modes in anaesthetized, intubated dogs recovering from cardiac surgery. MATERIAL AND METHODS Thirty-six adult Beagle dogs undergoing experimental surgery for isolated right ventricular failure were monitored for SVV, PPV, and SPV simultaneously using electrical velocimetry device. The relationships between each indicator and SVI before and after volume loading were compared in 3 ventilatory modes: assist control (A/C), synchronized intermittent mandatory ventilation (SIMV), and continuous positive airway pressure (CPAP). Responders were defined as those whose stroke volume index increased by ≥10%. RESULTS In all of the indices, the baseline values were greater in responders than in nonresponders (P<0.01) under A/C and SIMV. Receiver operating curve analysis confirmed the best predictive value during A/C [area under the curve (AUC): SVV, 0.90; PPV, 0.88; SPV, 0.85; P<0.05] followed by SIMV (AUC: SVV, 0.86; PPV, 0.83; CPAP, 0.80; P<0.05), with their sensitivities and specificities of ≥7 5%. By contrast, no statistically significance detected in any parameter during CPAP (AUC: SVV, 0.71; PPV, 0.66; CPAP, 0.65; P>0.05). CONCLUSIONS SVV, PPV, and SVV are all useful to predict cardiac response to fluid loading in dogs during A/C and SIMV, while their reliabilities during CPAP are poor.

Larger Numbers of Glial and Neuronal Cells in the Periaqueductal Gray Matter of µ-Opioid Receptor Knockout Mice.

Background: µ-opioid receptor knockout (MOP-KO) mice display baseline hyperalgesia. We have recently identified changes in tissue volume in the periaqueductal gray matter (PAG) using magnetic resonance imaging voxel-based morphometry. Changes in the structure and connectivity of this region might account for some behavior phenotypes in MOP-KO mice, including hyperalgesia. Methods: Adult male MOP-KO and wild-type (WT) mice were studied. Immunohistochemistry was performed to detect microglia, astrocytes, and neurons in the PAG using specific markers: ionized calcium-binding adaptor molecule 1 (Iba-1) for microglia, glial fibrillary acidic protein (GFAP) for astrocytes, and the neuronal nuclei antigen (NeuN; product of the Rbfox3 gene) for neurons, respectively. Cell counting was performed in the four parallel longitudinal columns of the PAG (dorsomedial, dorsolateral, lateral, and ventrolateral) at three different locations from bregma (-3.5, -4.0, and -4.5 mm). Results: The quantitative analysis showed larger numbers of well-distributed Iba1-IR cells (microglia), NeuN-IR cells (neurons), and GFAP-IR areas (astrocytes) at all the anatomically distinct regions examined, namely, the dorsomedial (DM) PAG, dorsolateral (DL) PAG, lateral (L) PAG, and ventrolateral (VL) PAG, in MOP-KO mice than in control mice. Conclusions: The cellular changes in the PAG identified in this paper may underlie aspects of the behavioral alterations produced by MOP receptor deletion, and suggest that alterations in the cellular structure of the PAG may contribute to hyperalgesic states.

Utility of electrical velocimetry-based noninvasive stroke volume variation in predicting fluid responsiveness under different ventilation modes in anaesthetized dogs.

We evaluated the utility of noninvasive stroke volume variation (SVV) as a functional haemodynamic predictor for fluid responsiveness under different ventilation modes [assist control (A/C), synchronized intermittent mandatory ventilation (SIMV), and continuous positive airway pressure (CPAP)] in 45 anaesthetized dogs, using an electrical velocimetry device. Receiver operating curve analysis confirmed the best predictive value during SVVA/C (12.5% of cut-off value; 75% sensitivity and 86% specificity) followed by SVVSIMV (13.5% of cut-off value; 75% sensitivity and 75% specificity), while no statistically significance detected during SVVCPAP (P > .05). These data suggest that SVV is useful for the prediction of fluid responsiveness in laboratory dogs during A/C and SIMV, while its reliability during CPAP is poor. This article is protected by copyright. All rights reserved.

Rapamycin protects against early brain injury independent of cerebral blood flow changes in a mouse model of subarachnoid haemorrhage.

We evaluated the neuroprotective role of rapamycin, a mammalian target of rapamycin (mTOR) kinase inhibitor, in cerebral ischaemia and locomotor function in a mouse model of subarachnoid haemorrhage (SAH). Pretreatment with rapamycin, an mTOR kinase inhibitor, resulted in better recovery from cerebral hypoxia early after SAH than control (P < .05), while the values of peak flow velocity in the middle cerebral artery did not change significantly (P > .05). Average distance travelled and the ratio of central-area distance/total travelled distance determined by open-field test after day 14 was significantly higher in mice pretreated with rapamycin than in control mice (P < .05). Inhibition of the mTOR pathway could be protective against post-SAH early brain injury, ameliorating brain tissue hypoxia and locomotor hypoactivity.

Preceding functional tooth loss delays recovery from acute cerebral hypoxia and locomotor hypoactivity after murine subarachnoid haemorrhage.

Tooth loss and related changes in the functionality may lead to worse outcome of stroke patients, but the effect on hemorrhagic stroke remains unclear. This study aimed to determine the impact of impaired masticatory function on acute cerebral oxygenation and locomotor activity after experimental subarachnoid haemorrhage (SAH). Twenty C57BL/6 mice with (MC-treated group) or without (control group) prior treatment of cutting off the upper molars were subjected to SAH by endovascular perforation. Grading of SAH and acute cerebral infarction were assessed by MR images. Brain tissue oxygen saturation (SbtO2 ) by photoacoustic imaging and parameters related to locomotor activity by open-field test were analyzed serially after SAH. In all mice, global SbtO2 depression was notable immediately after SAH induction (P <.001), which recovered close to the baseline levels until day 3. However, MC-treated mice demonstrated a prolonged relative cerebral hypoxia (<40% of the baseline SbtO2) as compared to the control (3 ± 1 vs 1 ± 1 days; P <.05). The average distance travelled on day 7 and the ratio of central-area distance/total travelled distance by open-field test between days 7 and 14 were significantly lower in MC-treated mice than in the control mice (P <.05), although the occurrences of new infarction were not statistically different (P >.05). These data suggest a possible link between preceding masticatory impairment and early brain injury to deteriorate neurobehavioural function in patients after SAH.

Noninvasive stroke volume variation using electrical velocimetry for predicting fluid responsiveness in dogs undergoing cardiac surgery.

OBJECTIVE: To evaluate the ability of a noninvasive cardiac output monitoring system with electrical velocimetry (EV) for predicting fluid responsiveness in dogs undergoing cardiac surgery. STUDY DESIGN: Prospective experimental trial. ANIMALS: A total of 30 adult Beagle dogs. METHODS: Stroke volume (SV), stroke volume variation (SVV) and cardiac index were measured using the EV device in sevoflurane-anaesthetized, mechanically ventilated dogs undergoing thoracotomies for experimental creation of right ventricular failure. The dogs were considered fluid responsive if stroke volume (SVI; indexed to body weight), measured using pulmonary artery thermodilution, increased by 10% or more after volume loading (10 mL kg-1). Relationships of SVV, central venous pressure (CVP) and pulmonary artery occlusion pressure (PAOP) with SVI were analysed to estimate fluid responsiveness. RESULTS: Better prediction of fluid responsiveness, with a significant area under the receiver operating characteristic curve, was observed for SVV (0.85±0.07; p=0.0016) in comparison with CVP (0.65±0.11; p=0.17) or PAOP (0.60±0.12; p=0.35), with a cut-off value of 13.5% (84% specificity and 73% sensitivity). CONCLUSIONS AND CLINICAL RELEVANCE: SVV derived from EV is useful for identification of dogs that are likely to respond to fluids, providing valuable information on volume status under cardiothoracic anaesthesia.

MRI-based in vivo assessment of early cerebral infarction in a mouse filament perforation model of subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: Experimental subarachnoid hemorrhage (SAH) by endovascular filament perforation method is used widely in mice, but it sometimes present acute cerebral infarctions with varied magnitude and anatomical location. This study aimed to determine the prevalence and location of the acute ischemic injury in this experimental model. METHODS: Male C57BL/6 mice were subjected to SAH by endovascular perforation. Distribution of SAH was defined by T2*-weighted images within 1h after SAH. Prevalence and location of acute infarction were assessed by diffusion-weighted MR images on day 1 after the induction. RESULTS: Among 72 mice successfully acquired post-SAH MR images, 29 (40%) developed acute infarction. Location of the infarcts was classified into either single infarct (ipsilateral cortex, n=12; caudate putamen, n=3; hippocampus, n=1) or multiple lesions (cortex and caudate putamen, n=6; cortex and hippocampus, n=2; cortex, hippocampus and thalamus/hypothalamus, n=3; bilateral cortex, n=2). The mortality rate within 24h was significantly higher in mice with multiple infarcts than those with single lesion (30% versus 0%; P=0.03). Distribution of the ischemic lesion positively correlated with MRI-evidenced SAH grading (r2=0.31, P=0.0002). CONCLUSION: Experimental SAH immediately after the vessel perforation can induce acute cerebral infarction in varying vascular territories, resulting in increased mortality. The present model may in part, help researchers to interpret the mechanism of clinically-evidenced early multiple combined infarction.

Neurocardiac protection with milrinone for restoring acute cerebral hypoperfusion and delayed ischemic injury after experimental subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: Acute cerebral hypoperfusion following subarachnoid hemorrhage (SAH) is highly related to the pathogenesis of delayed cerebral ischemia (DCI), but the therapeutic option is poorly available. This study aimed to clarify the effect of milrinone (MIL) on cerebral blood flow (CBF) and related outcomes after experimental SAH. METHODS: Twenty-seven male C57BL/6 mice were assigned to either sham surgery (SAH-sham; n=6), SAH induced by endovascular perforation (control; n=10), or SAH followed by cardiac support with intravenous MIL (n=11) performed 1.5-h after SAH induction. CBF, neurobehavioral function, occurrence of DCI were assessed by MR-continuous arterial spin labeling, daily neurological score testing, and diffusion- and T2-weighted MR images on days 1 and 3, respectively. RESULTS: Initial global CBF depression was notable in mice of control and MIL groups as compared to the SAH-sham group (P<0.05). MIL raised CBF in a dose-dependent manner (P<0.001), resulted in lower incidence of DCI (P=0.008) and better recovery from neurobehavioral decline than control (P<0.001). The CBF values on day 1 predicted DCI with a cut-off of 42.5ml/100g/min (82% specificity and 83% sensitivity), which was greater in mice treated with MIL than those of control (51.7 versus 37.6ml/100g/min; P<0.001). CONCLUSION: MIL improves post-SAH acute hypoperfusion that can lead to the prevention of DCI and functional worsening, acting as a neurocardiac protective agent against EBI.

Electrical velocimetry for noninvasive cardiac output and stroke volume variation measurements in dogs undergoing cardiovascular surgery.

OBJECTIVE: To compare electrical velocimetry (EV) noninvasive measures of cardiac output (CO) and stroke volume variation (SVV) in dogs undergoing cardiovascular surgery with those obtained with the conventional thermodilution technique using a pulmonary artery catheter. STUDY DESIGN: Prospective experimental trial. ANIMALS: Seven adult Beagle dogs with a median weight of 13.6 kg. METHODS: Simultaneous, coupled cardiac index (CI; CO indexed to body surface area) measurements by EV (CIEV) and the reference pulmonary artery catheter thermodilution method (CIPAC) were obtained in seven sevoflurane-anaesthetized, mechanically ventilated dogs undergoing experimental open-chest cardiovascular surgery for isolated right ventricular failure. Relationships between SVV or central venous pressure (CVP) and stroke volume (SV) were analysed to estimate fluid responsiveness. Haemodynamic data were recorded intraoperatively and before and after fluid challenge. RESULTS: Bland-Altman analysis of 332 matched sets of CI data revealed an overall bias and precision of - 0.22 ± 0.52 L minute-1 m-2 for CIEV and CIPAC (percentage error: 30.4%). Trend analysis showed a concordance of 88% for CIEV. SVV showed a significant positive correlation (r2 = 0.442, p < 0.0001) with SV changes to a volume loading of 200 mL, but CVP did not (r2 = 0.0002, p = 0.94). Better prediction of SV responsiveness (rise of SV index of ≥ 10%) was observed for SVV (0.74 ± 0.09; p = 0.014) with a significant area under the receiver operating characteristic curve in comparison with CVP (0.53 ± 0.98; p = 0.78), with a cut-off value of 14.5% (60% specificity and 83% sensitivity). CONCLUSIONS AND CLINICAL RELEVANCE: In dogs undergoing cardiovascular surgery, EV provided accurate CO measurements compared with CIPAC, although its trending ability was poor. Further, SVV by EV, but not CVP, reliably predicted fluid responsiveness during mechanical ventilation in dogs.

Inotropic support against early brain injury improves cerebral hypoperfusion and outcomes in a murine model of subarachnoid hemorrhage.

Early brain injury/ischemia is a recent therapeutic target that contributes to triggering delayed cerebral ischemia (DCI) in the setting of subarachnoid hemorrhage (SAH). This study aimed to determine the role of dobutamine for inotropic cardiac support in improving cerebral blood flow (CBF) and outcomes after experimental SAH, mediated by hypoxia-inducible factor (HIF). Thirty-one mice were subjected to SAH by endovascular perforation, and assigned to either 2% isoflurane postconditioning performed between 1 and 2.5h after SAH induction or concomitant intravenous dobutamine infusion (15µg/kg/min) with or without HIF inhibitor 2-methoxyestradiol (2ME2) (10mg/kg) administered intraperitoneally. Neurobehavioral function was assessed daily by neurological scores and open field testing. DCI was defined 3days later by detecting a new infarction on MRI. Global CBF depression was notable early after SAH, but dobutamine showed significant improvement in CBF, lower incidence of DCI, and better recovery of neuroscores and open field test variables compared with isoflurane postconditioning (P<0.05). CBF over the entire brain on day 1 predicted DCI with a cut-off of 36.5ml/100g/min (80% specificity and 67% sensitivity), with a better area under the curve (0.83 versus 0.75) than the hemispheric CBF measured on the perforated side. The dobutamine-mediated outcomes were attenuated (P<0.05) by 2ME2 pretreatment. The data suggest that cardiac support with dobutamine improves global CBF depression induced by early brain injury, leading to reduced prevalence of DCI and better functional outcomes after experimental SAH, in which HIF may be acting as a critical mediator.