‘Permissive’ hypernatraemia in refractory intracranial hypertension
Continuous infusions rather than bolus osmolar therapy may make physiological sense but concerns have been raised about the hypernatraemia. Continuous hypertonic saline has been used effectively in a number of settings but what about generation of osmotic gradients at the risk of ALI/AKI.
Concerns raised in discussion about inappropriately high targets and picking appropriate patients
Is there a better fluid?
Different dogma’s exist about the suitability of Hartmanns or balanced solution in neuroICU. We know chloride worsens renal function but concerns about using hypotonic or isotonic solutions have meant a preponderance of saline.
Increasing evidence suggests that the chloride can be harmful to the brain as well – we give lots of chloride in hypertonic saline as well. Meta-analyses have suggested hypertonic saline better at reducing ICP but doses were not equimolar, it might not be best for survival and mannitol has additional effects beyond ICP.
What about feeding the brain? Some evidence for lactate containing solutions in treatment of intracranial hypertension. Lactate is a vasodilator and may improve CBF.
Combination therapy might be best – saline + ringers lactate +/- sugar depending on cerebral micro dialysis with control of sugar.
Fixed versus auto regulatory driven CPP targets
Where does ICP threshold 20mmHg comes from old data and BTF guidelines are based on poor quality evidence. Ditto CPP.
BEST-TRIP suggested ICP of 20 but it may be the burden of ICP is the main problem – some people won’t tolerate ICP of 15mmHg. Children almost never do
CPP and ICP targets need to be individualised and hence reactivity with respect to auto regulation is important and might change during treatment. THat’s why you measure it! However, we lack prospective trials and need more data. Delta CPP may correlate with outcome.
Refractory Status Epilepticus
Status epilepticus definition has changed! Now anything other than a single self-limiting status (i.e. > 5 minutes) is now in status.
Refractory status is fits after benzodiazepines and second line AED (about two hours)
Super-refractory status fitting despite anaesthesia (about 24 hours)
Quicker you treat, more likely you are to terminate seizure
Once convulsive status exists, if becomes refractory will always progress to non-convulsive status equivalent to EMD. 48% of patients who don’t wake continue to fit in non-convulsive way.
Give Loraz > Phenytoin
Then equipoise – valproate? keppra? propofol?
Midazolam infusion may be better in refractory status – loading dose of 0.2mg/kg. Propofol infusion rates may be limited by PRIS issues. What about ketamine + midazlolam rather than barbiturate?!