The Anaesthetic Ketamine as Treatment for Patients With Severe Acute Brain Injury

Severe acute brain injury caused by traumatic brain injury (TBI), aneurysmal subarachnoid haemorrhage (aSAH) or intracerebral haemorrhage (ICH) carries a high morbidity and mortality. In all these conditions, clinical neurological deterioration may occur as a consequence of so-called secondary brain injury, which reduces the chance of a good outcome. Thus, neurological deterioration after the initial injury is generally associated with a worse outcome. Cortical spreading depolarisations (SDs) are pathological depolarisation waves that occur frequently after both TBI, SAH, and ICH and have been related to poor outcome. The SDs, which can be detected by electrocorticography (ECoG, using electrodes placed directly on the brain cortex), propagate across the cerebral cortex and are followed by an excessive upregulation of cerebral metabolism and decrease in cerebral blood flow. In vulnerable brain tissue such as in patients after acute primary brain injury, this combination of hypermetabolism and hypoperfusion is thought to increase the risk of ischaemia and infarction. The anaesthetic drug ketamine, which is an NMDA-receptor antagonist, appears to inhibit SDs both in vitro and in patient series.

The present trial is a randomised, blinded, placebo-controlled, parallel-group pilot and feasibility trial, where participants with clustered SD despite physiological optimisation are allocated 1:1 to infusion of S-ketamine versus matching placebo. In the present trial, participants admitted to the neurointensive care unit with TBI, aSAH or ICH and undergoing craniotomy or craniectomy (for clipping of an aneurysm or removal of a space-occupying haematoma). Patients are monitored at the neurointensive care unit, Rigshospitalet and sedated using standard sedatives. Patients will be monitored both with ECoG, intracranial pressure (ICP), brain tissue oxygen tension (PbtO2), and microdialysis. Patients in whom SDs occur will be subjected to a protocol of physiological optimisation targeting ICP, PbtO2, blood glucose and core temperature following clinical guidelines. If clustered SDs occur despite optimisation, patients are randomly allocated to infusion of either S-ketamine or matching placebo (isotonic saline) at a 1:1 allocation ratio with full blinding of the treatment allocation.

The present trial will continue until 160 participants have been randomised. Since only participants with clustered SDs are randomised, the investigators expect to include no more than 400 participants for ECoG monitoring.

The present trial aims to examine the efficacy of S-ketamine on SDs, the safety, and the feasibility of the trial design. Furthermore, surviving patients will be followed up until six months after the injury, and functional outcome will be recorded by the modified Rankin Scale (mRS).

Inclusion criteria

• Age ≥ 18 years.
• Admitted to the NICU with a diagnosis of traumatic brain injury (TBI), aneurysmal subarachnoid haemorrhage (aSAH) or spontaneous intracerebral haemorrhage (ICH).
• Planned for surgery with a supratentorial craniotomy or craniectomy.
• Expected to continue sedation and mechanical ventilation after surgery.

Exclusion criteria

• Neither patient or next of kin understand Danish or English.
• Known allergy to S-ketamine (the active pharmaceutical ingredient or the excipients).
• Wake-up call to occur immediately after surgery.
• Pregnancy (all female participants aged ≤ 50 years will have a urine or blood hCG taken to control for pregnancy).
• Active anti-psychotic treatment before admission.
• Current abuse of ketamine.
• Decision to withdraw active treatment.
• ICH secondary to a known brain tumour at the time of inclusion.

Since this is an emergency trial informed consent will be obtained from a trial guardian before inclusion of the participant, and informed consent will be sought from next of kin as soon as possible.