Evolution of ischemic damage and behavioural deficit over 6 months after MCAo in the rat: Selecting the optimal outcomes and statistical power for multi-centre preclinical trials.

Key disparities between the timing and methods of assessment in animal stroke studies and clinical trial may be part of the reason for the failure to translate promising findings. This study investigates the development of ischemic damage after thread occlusion MCAo in the rat, using histological and behavioural outcomes. Using the adhesive removal test we investigate the longevity of behavioural deficit after ischemic stroke in rats, and examine the practicality of using such measures as the primary outcome for future studies. Ischemic stroke was induced in 132 Spontaneously Hypertensive Rats which were assessed for behavioural and histological deficits at 1, 3, 7, 14, 21, 28 days, 12 and 24 weeks (n>11 per timepoint). The basic behavioural score confirmed induction of stroke, with deficits specific to stroke animals. Within 7 days, these deficits resolved in 50% of animals. The adhesive removal test revealed contralateral neglect for up to 6 months following stroke. Sample size calculations to facilitate the use of this test as the primary experimental outcome resulted in cohort sizes much larger than are the norm for experimental studies. Histological damage progressed from a necrotic infarct to a hypercellular area that cleared to leave a fluid filled cavity. Whilst absolute volume of damage changed over time, when corrected for changes in hemispheric volume, an equivalent area of damage was lost at all timepoints. Using behavioural measures at chronic timepoints presents significant challenges to the basic science community in terms of the large number of animals required and the practicalities associated with this. Multicentre preclinical randomised controlled trials as advocated by the MultiPART consortium may be the only practical way to deal with this issue.

Hypothermia revisited: Impact of ischaemic duration and between experiment variability.

To assess the true effect of novel therapies for ischaemic stroke, a positive control that can validate the experimental model and design is vital. Hypothermia may be a good candidate for such a positive control, given the convincing body of evidence from animal models of ischaemic stroke. Taking conditions under which substantial efficacy had been seen in a meta-analysis of hypothermia for focal ischaemia in animal models, we undertook three randomised and blinded studies examining the effect of hypothermia induced immediately following the onset of middle cerebral artery occlusion on infarct volume in rats (n = 15, 23, 264). Hypothermia to a depth of 33℃ and maintained for 130 min significantly reduced infarct volume compared to normothermia treatment (by 27-63%) and depended on ischaemic duration (F(3,244) = 21.242, p < 0.05). However, the protective effect varied across experiments with differences in both the size of the infarct observed in normothermic controls and the time to reach target temperature. Our results highlight the need for sample size and power calculations to take into account variations between individual experiments requiring induction of focal ischaemia.

Early Decompression following Cervical Spinal Cord Injury: Examining the Process of Care from Accident Scene to Surgery.

Early decompression may improve neurological outcome after spinal cord injury (SCI), but is often difficult to achieve because of logistical issues. The aims of this study were to 1) determine the time to decompression in cases of isolated cervical SCI in Australia and New Zealand and 2) determine where substantial delays occur as patients move from the accident scene to surgery. Data were extracted from medical records of patients aged 15-70 years with C3-T1 traumatic SCI between 2010 and 2013. A total of 192 patients were included. The median time from accident scene to decompression was 21 h, with the fastest times associated with closed reduction (6 h). A significant decrease in the time to decompression occurred from 2010 (31 h) to 2013 (19 h, p = 0.008). Patients undergoing direct surgical hospital admission had a significantly lower time to decompression, compared with patients undergoing pre-surgical hospital admission (12 h vs. 26 h, p < 0.0001). Medical stabilization and radiological investigation appeared not to influence the timing of surgery. The time taken to organize the operating theater following surgical hospital admission was a further factor delaying decompression (12.5 h). There was a relationship between the timing of decompression and the proportion of patients demonstrating substantial recovery (2-3 American Spinal Injury Association Impairment Scale grades). In conclusion, the time of cervical spine decompression markedly improved over the study period. Neurological recovery appeared to be promoted by rapid decompression. Direct surgical hospital admission, rapid organization of theater, and where possible, use of closed reduction, are likely to be effective strategies to reduce the time to decompression.

The benefit of hypothermia in experimental ischemic stroke is not affected by pethidine.

BACKGROUND: Hypothermia is a promising experimental treatment for acute ischemic stroke. Human trials are still at an early stage, with the focus now on using hypothermia in awake patients. Pethidine (meperidine) is the principle agent used to control shivering in humans; however, whether it has any modulating effects on the neuroprotective efficacy of hypothermia is unknown. AIM: The aim of this study was to determine if pethidine influences the neuroprotective effect of hypothermia in experimental stroke. METHODS: Seventy-two male spontaneously hypertensive rats were anesthetized with isoflurane and randomly assigned to either normothermia (37. 4 °C rectal temperature); hypothermia (33 °C maintained for 130 mins); normothermia plus pethidine (2.5 mg/kg); or hypothermia plus pethidine. Temporary (90 mins) endovascular occlusion of the middle cerebral artery was induced blinded to treatment allocation and was confirmed with laser Doppler flowmetry. Pethidine and cooling were started immediately after vessel occlusion. Animals in the normothermia group had active temperature management using a heat lamp and fan. Assessments of outcome were carried out 24 after the induction of injury. RESULTS: Thirteen animals met our prespecified criteria for exclusion, and data for 59 rats were presented here. Hypothermia was associated with a 63% reduction in infarct size, and pethidine had no significant impact on the efficacy of hypothermia. No effects were observed in neurobehavioral outcome or edema volume across experimental groups. CONCLUSIONS: The effects of hypothermia in a model of focal ischemia are not affected by administration of pethidine.

Intracanal pressure in compressive spinal cord injury: reduction with hypothermia.

Most cases of human spinal cord injury (SCI) are accompanied by continuing cord compression. Experimentally, compression results in rapid neurological decline over hours, suggesting a rise in intracanal pressure local to the site of injury. The aim of this study was to measure the rise in local intracanal pressure accompanying progressive canal occlusion and to determine the relationship between raised intracanal pressure and neurological outcome. We also aimed to establish whether hypothermia was able to reduce raised intracanal pressure. We demonstrate that, following SCI in F344 rats, local intracanal pressure remains near normal until canal occlusion exceeds 30% of diameter, whereupon a rapid increase in pressure occurs. Intracanal pressure appears to be an important determinant of neurological recovery, with poor long-term behavioural and histological outcomes in animals subject to 8 h of 45% canal occlusion, in which intracanal pressure is significantly elevated. In contrast, good neurological recovery occurs in animals with near normal intracanal pressure (animals undergoing 8 h of 30% canal occlusion or those undergoing immediate decompression). We further demonstrate that hypothermia is an effective therapy to control raised intracanal pressure, rapidly reducing elevated intracanal pressure accompanying critical (45%) canal occlusion to near normal. Overall these data indicate that following SCI only limited canal narrowing is tolerated before local intracanal pressure rapidly rises, inducing a sharp decline in neurological outcome. Raised intracanal pressure can be controlled with hypothermia, which may be a useful therapy to emergently decompress the spinal cord prior to surgical decompression.

Preclinical drug evaluation for combination therapy in acute stroke using systematic review, meta-analysis, and subsequent experimental testing.

There is some evidence that in animal models of acute ischaemic stroke, combinations of neuroprotective agents might be more efficacious than the same agents administered alone. Hence, we developed pragmatic, empirical criteria based on therapeutic target, cost, availability, efficacy, administration, and safety to select drugs for testing in combination in animal models of acute stroke. Magnesium sulphate, melatonin, and minocycline were chosen from a library of neuroprotective agents, and were tested in a more 'realistic' model favoured by the STAIR (Stroke Therapy Academic Industry Roundtable). Outcome was assessed with infarct volume, neurologic score, and two newly developed scales measuring general health and physiologic homeostasis. Owing to the failure to achieve neuroprotection in aged, hypertensive animals with drug delivery at 3 hours, the bar was lowered in successive experiments to determine whether neuroprotection could be achieved under conditions more conducive to recovery. Testing in younger animals showed more favourable homeostasis and general health scores than did testing in older animals, but infarct volume and neurologic scores did not differ with age, and treatment efficacy was again not shown. Testing with shorter occlusions resulted in smaller infarct volumes; nevertheless, treatment efficacy was still not observed. It was concluded that this combination, in these stroke models, was not effective.

Hypothermia prior to decompression: buying time for treatment of acute spinal cord injury.

Human spinal cord injury (SCI) is usually accompanied by persistent cord compression. Experimental data demonstrate that compression of the traumatized cord results in rapid neurological decline over hours. Undertaking decompression in humans within this time frame has proved impractical, with the time to surgery in studies of urgent decompression averaging between 10 and 24 h. There is, therefore, an important need for a therapy to prevent the neurological deterioration of patients prior to decompressive surgery. The aim of this study was to determine if hypothermia prevents compressive SCI, thereby limiting neurological decline. Rats were subjected to a moderate mid-thoracic SCI and spacers were inserted to compress the spinal cord by 45%. Decompression, by removal of the spacer, was performed immediately, and at 2 or 8 h post-injury. Hypothermia (33 degrees C) was commenced in half the animals at 30 mins post-injury and maintained for 7.5 h, with the other half remaining normothermic (37.3 degrees C). Motor recovery was assessed weekly, and the volume and area of tissue damage determined at the end of the 8-week study period. The results demonstrate that hypothermia significantly improves the behavioral and histological outcome of animals undergoing 8 h of compressive injury (the primary outcome measure). The hypothermia-treated group regained weight-supported locomotion (Basso-Beattie-Bresnahan [BBB] locomotor assessment score 9.5 +/- 0.9), while the normothermic group remained severely paraparetic (BBB score 5.3 +/- 0.6; p

Inducing stroke in aged, hypertensive, diabetic rats.

Animal models of ischemic stroke often neglect comorbidities common in patients. This study shows the feasibility of inducing stroke by 2 h of thread occlusion of the middle cerebral artery in aged (56 week old) spontaneously hypertensive rats (SHRs) with both acute (2 weeks) and chronic (36 weeks) diabetes. After modifying the streptozotocin dosing regimen to ensure that old SHRs survived the induction of diabetes, few died after induction of stroke. Induction of stroke is feasible in rats with multiple comorbidities. Inclusion of such comorbid animals may improve translation from the research laboratory to the clinic.