Is ischaemic post-conditoning neuroprotective following perinatal asphyxia?

Context of the research
Problems during birth leading to a lack of oxygen (birth asphyxia) and subsequent brain injury (neonatal encephalopathy) occur in 1-2 per 1000 full term births in the UK. Although therapeutic hypothermia has recently been a significant advance in this field in the developed world, it provides brain protection only to ~50% of those infants cooled. There is therefore a significant unmet need to develop novel, non-invasive approaches, which can be used alone or in combination with hypothermia to augment neuroprotection for neonatal encephalopathy. Currently there are no other technologies or other therapeutic approaches to address this unmet need. We propose that remote ischemic post-conditioning (IPostC) would meet this need. Born from the concept of pre-conditioning first described in 1986, IPostC is advantageous in that prior knowledge of the ischemic insult is not required and thus clinical translation is more far reaching.

Ischaemia-reperfusion injury is a widespread phenomenon that occurs in clinical scenarios where blood supply to tissue is interrupted and then restored. Paradoxically, it is reperfusion rather than ischaemia that causes major damage to tissue. There is, however, a powerful innate protective mechanism against ischemia-reperfusion injury that has evolved in all mammalian species. Brief, transient episodes of ischemia protect against a prolonged period of lethal ischaemia and these episodes can be performed during reperfusion or the first few hours after the index ischaemia. The brief transient episodes are also effective if performed on a non-vital organ such as a limb remote to the affected organ, which forms the basis for remote IPostC.

We will use magnetic resonance spectroscopy (brain lactate /N acetyl aspartate levels) as a surrogate marker of the benefit of IPostC with and without hypothermia - the same surrogate measure used in newborn infants to predict outcome. We will use near infrared spectroscopy to examine brain oxygenation during IPostC. Such multi-modal imaging makes the model unique and a significant resource for understanding efficacy as well and mechanistic and physiological effects of IPostC.

Aims and Objectives
The proposal is to test remote IPostC in a large animal model. The main aims are to determine:
1. if remote IPostC at resuscitation protects the brain
2. if remote IPostC with a delay of 3h after resuscitation protects the brain
3. if remote IPostC (both immediate and delayed) augments hypothermic neuroprotection
4. signalling pathways of IPostC, hypothermia and the interaction between IPostC and hypothermia
5. haemodynamic and metabolic effects of IPostC

Its potential applications and benefits
Successful completion of this project will enable us to proceed directly to a human proof of concept study since there are no toxicology studies needed. In the clinical setting, remote IPostC would involve inflating a cuff to supra-systolic pressure briefly around both lower limbs of the infant after birth. This is analogous to taking the blood pressure on several occasions and holding the cuff inflated for minutes. By doing so, this non-fatal ischaemia has been suggested to activate endogenous neuroprotective pathways, such as anti-apoptotic proteins, reduction in free radical production, attenuation of the hyperaemic response and improvement in cerebral blood flow.

The introduction of this technology to NHS will address two of the top four priorities of NHS (heart disease, cancer, children and maternity). IPostC may become a simple treatment at resuscitation that reduces adverse outcome following birth asphyxia. IPostC may also augment hypothermic neuroprotection, which has been introduced as the current standard of care for infants presenting with encephalopathy at birth. Moreover, it would also be possible to use this technology in places or situations where hypothermia is not available or safe.

Perinatal asphyxia occurs in 1-2 per 1000 births in the UK and is associated with death or major neurodevelopmental impairment. The early induction of therapeutic hypothermia after birth is a significant advance, however, it prevents adverse outcome in only ~50% of cooled infants. There is therefore an unmet need to develop novel, non-invasive approaches which can be used alone or in combination with hypothermia to augment neuroprotection.

Remote ischemic post-conditioning (IPostC) is a novel therapeutic approach initially described in myocardial ischemia. Remote IPostC involves repeated episodes of inflation and deflation of a cuff around the limbs to induce short-lived episodes of mild ischemia. The neuroprotective efficacy of remote IPostC in cerebral ischemia is evident in rodent models of stroke reducing cerebral infarction up to 50%.

We aim to address these research questions in a large validated animal model of perinatal asphyxia with outcome biomarkers : 1. brain 1H MRS lactate/N acetyl aspartate; 2. quantitative Tunel+ cells 8 brain regions:

A. Is remote IPostC at resuscitation after transient hypoxia-ischaemia neuroprotective?
B. Does the therapeutic window of IPostC last up to 3 h.
C. Does remote IPostC (immediate and delayed) augment therapeutic hypothermia?

After surgical preparation, randomization will be (n=14 / group):
(i) No intervention
(ii) Immediate remote IPostC
(iii) Delayed remote IPostC at 3h
(iv) Therapeutic hypothermia from 4-22h (cooling)
(v) Immediate remote IPost C and cooling
(vi) Delayed remote IPostC at 3h and cooling

Continuous NIRS, physiological monitoring, interleaved MRI and EEG will be recorded for 48h after resuscitation.

Because of its simplicity, cost-effectiveness and safety, remote IPostC could be applied in an infant with moderate/severe encephalopathy in most neonatal units. This technology may be complementary to hypothermia and used in settings where hypothermia is not available or safe.

Who might benefit from this research?
Birth asphyxia is a relatively common clinical condition, which results in serious consequences for many of the infants including death, cerebral palsy, epilepsy and other significant cognitive, developmental and behavioural problems. The financial and human costs to infants affected, their parents, professional and wider society are enormous. Some, but by no means all, costs are reflected in awards following medical litigation. An investigation in 2000 by the Chief Medical Officer for England reported that preventing 10% of birth related events would save about £20 million per year.

This proposal is the last step before translating this potential therapy to the human baby. Successful completion of this project will enable us to proceed directly to a human proof of concept study since there are no toxicology studies needed. The introduction of this technology to NHS will address two of the top four priorities of the NHS ( heart disease, cancer, children and maternity). Further more, if remote ischaemic postconditioning (IPostC) is neuroprotective this intervention is likely to lead to a widespread reduction in the global burden of disability due to birth asphyxia. This will benefit infants, families, professionals, wider society and the economy.

Low, mid and high resource settings are all likely to benefit from this research given its simplicity and low cost. If positive this study will focus attention on the newborn and the burden of birth asphyxia.


How might they benefit from this research
This intervention could significantly reduce adverse outcome following birth asphyxia - a reduction in mortality, sensorineural problems, an improvement in memory, cognition, global developmental delay and school performance. Such a reduction in adverse outcome will lead to less suffering of the infant and family, less emotional disruption and less lost potential as the child grows up. Litigation costs will be reduced and the general economy will improve. Less special educational needs will be required.

In the developed world context where therapeutic hypothermia is already a safe therapy, there are still around 50% of treated infants with adverse outcomes. If we show an incremental improvement in outcome with IPostC combined with cooling vs cooling alone, this will reduce the number of infants with adverse outcomes further. As remote IPostC is likely to benefit any organ - not just the brain -beneficial effects may be seen systemically eg on the kidneys, liver and heart. As this technology is non-invasive, safe, easy to apply, inexpensive and will not require high tech equipment or instrumentation clinical trials could start relatively quickly.

In settings where therapeutic hypothermia is not available or safe, IPostC may have an even higher impact. For example, in low and mid resource settings 1 million of the annual 4 million neonatal deaths are due to birth asphyxia - another poorly quantified 1 million infants have with disabilities due to birth asphyxia. The focus on IPostC during the early neonatal period may improve resuscitation practices and postnatal care of the newborn.