1 Neurosurgery Flashcards
a) Describe the production and circulation of cerebrospinal fluid
(CSF).
.
CSF is produced by the choroid plexus in the lateral, third and fourth
ventricles by:
● Plasma filtration through capillary fenestrations.
● Active transport across the blood/CSF barrier
CSF circulates through the following structures:
● Lateral ventricles.
● Foramen of Monro.
● Third ventricle.
● Aqueduct of Sylvius.
● Fourth ventricle.
● Foramina of Magendie and Luschka.
● Cisterna magna.
● Spinal and cerebral subarachnoid space.
CSF is absorbed by arachnoid granulations into cerebral venous sinuses.
b) How does the intracranial pressure affect the production and
absorption of CSF?
Compensatory mechanisms with a rise in ICP include:
**● Spatial compensation —
displacement of CSF from the cranial into the
spinal subarachnoid space.
● Increased absorption of CSF.
● Does not affect the production of CSF.
c) Give five differentiating features of CSF vs. plasma with regards
to its biochemistry.
Glucose 3-5mmol/L 2.4-4.5mmol/L
Sodium 144-152mmol/L
Potassium 3.5-5 v 2-3mmol/L
Cl 95-105 v123-128mmol/L
Protein 45-60g/l v 0.3
pH 7.4 v 7.3
d) List any four indications for lumbar puncture.
Diagnostic indications:
● Diagnosis of meningitis.
● Suspected CNS infections, e.g. encephalitis.
● Suspected subarachnoid haemorrhage with a negative CT.
● Normal pressure hydrocephalus.
● Idiopathic intracranial hypertension.
● Injection of contrast media for myelography and cisternography.
Therapeutic indications:
● Subarachnoid block.
● Intrathecal chemotherapy.
● Intrathecal antibiotics.
e) Name any six factors that predispose to the development of a
postdural puncture headache after lumbar puncture
Patient factors:
● Young age.
● Female.
● Pregnancy.
Equipment factors:
● Large diameter needles.
● Cutting needles that transect the dural fibres.
Operator factors:
● Multiple attempts.
● Perpendicular orientation of the bevel of a spinal or epidural needle
leads to a reduction in the incidence of postdural puncture headache.
● Intermittent technique for epidural insertion.
● Identifying loss of resistance with air rather than saline.
2 Q2 — Brainstem death and organ donation
A 20-year-old patient in a neurointensive care unit satisfies the criteria for
brainstem death and has been accepted as an organ donor.
2 a) List the main adverse cardiovascular changes associated with
brainstem death.
5
1 ● An initial increase in arterial BP to maintain CPP.
2 ● Effect of pontine ischaemia and a hyperadrenergic response:
- hypertension and bradycardia
(as part of Cushing’s triad with
irregular respiration); - an increase in right and left ventricular afterload.
● Effect of foramen magnum herniation and loss of spinal sympathetic
activity:
- vasodilation;
- reduced cardiac output;
- reduced afterload and preload decreasing aortic diastolic pressure.
● Effect of pituitary ischaemia:
- diabetes insipidus — hypovolaemia and electrolyte imbalance.
● Arrhythmias due to
electrolyte imbalance,
acidosis and
catecholamines.
2 b) What are the physiological goals (with values) required to
ensure optimisation of this donor?
CVS targets:
● Heart rate 60-120 beats/min.
● Systolic arterial pressure >100mmHg.
● Mean arterial pressure >70mmHg but <95mmHg.
● Central venous pressure 6-10mmHg.
● Pulmonary artery occlusion pressure 10-15mmHg.
● Stroke volume variation <10%.
● Cardiac index >2.1L/min/m2.
● Mixed venous saturation >60%.
Mechanical ventilation targets:
● Tidal volume: 6-8ml/kg.
● PEEP >5cm H2O.
● Peak inspiratory pressure <25cm H2O.
● pH 7.35-7.45.
● PaO2 >10kPa.
● PaCO2 4.5-6.0kPa.
● SpO2 >95% for the lowest FiO2, ideally <0.4.
Renal management:
● Avoid hypovolaemia and nephrotoxic drugs.
● Adequate renal perfusion pressure.
Hepatic management:
● Restore hepatic glycogen stores — continue enteral feeding.
● Serum sodium <155mmol/L.
● Avoid a high PEEP to reduce hepatic congestion.
● Central venous pressure 6-10mmHg.
Miscellaneous:
● Temperature >34°C.
● Serum glucose 4.0-8.0mmol/L.
● Correct coagulopathies.
2 c) Outline the measures that may be used to achieve the needed
goals.
**
Cardiovascular management:
● TTE or continuous cardiac output monitoring.
● Esmolol, GTN, and SNP to manage hypertension.
● Intravenous fluids and vasopressin to manage hypotension.
● Amiodarone for tachyarrhythmias.
● Bradyarrhythmias are treated with adrenaline or isoprenaline.
● Thyroid hormone replacement to improve cardiac function.
Respiratory management:
● Lung protective ventilation strategies.
● 30° head-up tilt, regular tracheal suction, regular rotation.
● Avoid a positive fluid balance.
● Methylprednisolone to minimise extravascular lung water.
● Bronchoscopy for directed suction.
● CXR to detect neurogenic pulmonary oedema.
Renal management:
● Avoid hypovolaemia and nephrotoxic drugs.
Hepatic management:
● Restoring liver glycogen with adequate nutrition.
● Serum sodium <155mmol/L
to avoid osmosis from recipient to donor cells.
● Avoid a high PEEP to reduce hepatic congestion.
● Central venous pressure 6-10mmHg.
2 d) Name any three medications that you might use to optimise
the endocrine system.*
d) Name any three medications that you might use to optimise
the endocrine system.
● Methylprednisolone.
● Thyroid hormone T3.
● Vasopressin.
● Desmopressin to treat DI.
● Insulin infusion.
Q3 — Status epilepticus
You are asked to review a 27-year-old male who is a known epileptic in
convulsive status epilepticus.
a) Name two opioids contraindicated in seizures. 2
● Alfentanil —
enhances EEG activity.
● Pethidine/meperidine —
metabolite nor-meperidine is a proconvulsant.
● Tramadol —
lowers the seizure threshold.
b) What are the implications of neuromuscular blocking drugs in
epileptic patients? 2
***
1 ● Succinylcholine —
in prolonged status epilepticus, it can cause
dangerous hyperkalaemia.
2 ● Non-depolarising NMBAs —
enzyme-inducing effects of antiepileptic
drugs (AEDs) may cause resistance to the
effects of aminosteroid neuromuscular blockers,
such as rocuronium, pancuronium, and
vecuronium.
3 ● Laudanosine,
a metabolite of atracurium, has epileptogenic potential.
c) Define convulsive status epilepticus. 1
Status epilepticus is defined as continuous seizure activity of at least 5
minutes’ duration or intermittent seizure activity of at least 30 minutes’
duration during which consciousness is not regained.
d) What drugs, including doses, are used during the various stages
of status epilepticus? 5
Premonitory stage:
(prehospital or <5 minutes)
Early stage:
(5-10 minutes)
Established stage:
(0-60 minutes)
Premonitory stage (prehospital or <5 minutes):
● Diazepam 10-15mg PR, repeat after 15 minutes. OR
● Midazolam 10mg buccal.
Early stage (5-10 minutes):
● Lorazepam 0.1mg/kg, repeat after 10-20 minutes.
● Give the usual antiepileptic drugs.
● Glucose 50ml 50% IV and thiamine 250mg IV if there is suspected
alcohol abuse or malnutrition.***
Established stage (0-60 minutes):
● Phenytoin IV 15-18mg/kg at 50mg/min.
e) What investigations would you consider in a patient with
status epilepticus?
**
● Blood investigations —
arterial blood gases and venous blood
sampling for glucose, calcium,
and magnesium levels; renal and liver
function; a full blood count; clotting screen;
AED level assay; and
toxicology screen.
● Brain imaging — CT, MRI.
● Microbiology.
● Lumbar puncture.
● EEG.
f) Sixty minutes after your initial management, the patient
continues to be in status epilepticus. What would be your
further management?
5
**
● General anaesthesia, intubation and ventilation with:
- propofol (1-2mg/kg bolus, followed by an infusion); OR
- thiopentone (3-5mg/kg bolus, followed by an infusion); OR
- midazolam (0.1-0.2mg/kg bolus, followed by an infusion).
● Intensive care management.
● EEG monitoring.
● Intracranial pressure monitoring where appropriate.
● CNS imaging and LP where appropriate.
● Initiate long-term, maintenance antiepileptic drugs.
● Anaesthetic continued for 12-24 hours after
the last clinical or EEG
seizures and gradually weaned.
3 g) What are the complications associated with refractory
convulsive status epilepticus?
3
*
● Excitotoxic CNS injury.
● Hyperthermia.
● Pulmonary oedema.
● Arrhythmias.
● Cardiovascular collapse.
● Acute kidney and liver injury.
● Rhabdomyolysis.
● Fractures.
Q4 — Delirium in critical care
a) Define delirium.
**
Delirium is defined as a disturbance of consciousness
and a change in cognition that
develops over a short period of time.
b) List the key clinical features that are used to diagnose delirium
in critical care.
1 ● Inattentiveness —
difficulty following instructions or easily distracted.
2 ● Disorientation —
to time, place or person.
3 ● Hallucinations and delusions.
4 ● Psychosis.
5 ● Psychomotor agitation or retardation —
agitation requiring the use of
drugs or restraints.
6 ● Inappropriate speech or mood.
7 ● Sleep/wake cycle disturbance.
8 ● Symptom fluctuation.
c) List any six risk factors for delirium in an intensive care patient.
**
Patient characteristics:
● Increasing age.
● Visual or hearing impairment
Pre-existing cognition:
● Depression.
● Dementia.
● History of delirium.
Functional impairment:
● Poor oral intake of diet and fluid.
● Immobility.
● A history of falls.
Drugs:
● Alcohol and other substance withdrawal.
● Narcotics, including tramadol and meperidine.
● Drugs with anticholinergic effects.
● Steroids, digoxin and diuretics.
Medical conditions:
● Electrolyte disturbance, including hypomagnesaemia.
● Chronic renal and liver failure.
● Neurological disease, including stroke.
● Trauma.
d) List some methods of diagnosis and assessment of delirium.
● Confusion Assessment Method for the Intensive Care Unit (CAM-ICU).
● Intensive Care Delirium Screening Checklist (ICDSC).
● Diagnosis by a psychiatrist using DSM IV.
e) In a delirious critical care patient, what are the most common
environmental factors that are potentially treatable?
● Correct visual and hearing impairment with glasses and hearing aids.
● Orientate the patient regularly.
● Promote sleep hygiene.
● Mobilise.
● Use physical restraints only to prevent harm.
f) What medical factors would you correct to treat/prevent
delirium?
● Avoid hypoxia.
● Correct metabolic problems
(dehydration, acidosis, electrolyte
disturbances).
● Treat any infection.
● Administer adequate analgesia.
● Remove lines if not needed.
● Sedation hold and trial of breathing if intubated and ventilated.
g) When is pharmacological treatment indicated and which
classes of drugs can be used?
Pharmacological treatment is indicated when:
● The person is distressed.
● Poses a risk to themselves or others.
● Verbal and non-verbal de-escalation techniques are ineffective or
inappropriate.
The classes of drugs used are:
● D2 receptor antagonist — haloperidol.
● Atypical antipsychotics — olanzapine, quetiapine.
● Avoid benzodiazepines except in delirium due to alcohol withdrawal
— lorazepam.
Q5 — Near-drowning
A 20-year-old man is brought to the emergency department having been
pulled from a river following a near-drowning.
a) What are the effects of near-drowning on the respiratory and
cardiovascular systems?
**
Respiratory system:
● Wash out of surfactant causes atelectasis and lung collapse.
● Osmotic gradients cause alveolar and interstitial oedema.
● Bronchospasm.
● Acute emphysema due to alveolar rupture.
● Toxins in water cause alveolar injury.
● ALI and ARDS.
_______________________________________________________________
Cardiovascular system:
● Hypoxia and hypothermia trigger catecholamine release.
● Catecholamines cause vasoconstriction and acidosis.
● Hypothermia causes arrhythmias and cardiac failure.
