Neurology


Neurology


Matthew J Harris


Outline





Initial Assessment





Circulation



‘The HR is 110 bpm, BP 125/60 mmHg, CRT is 1 second peripherally. The pulse is bounding and the peripheries are warm. Mucous membranes are dry but skin turgor is normal. On cardiovascular examination the JVP is not visible. Heart sounds are normal with no added murmurs. There is no evidence of peripheral oedema.’




Disability



‘The patient is rousable to voice and confused with a GCS of 13 (E 3, V 4, M 6). The pupils are equal and reactive to light and the blood sugar is 4.5 mmol/L.’



ent A full neurological examination is required to assess for any focal neurological deficit; however, initial antibiotic treatment should not be delayed while a lengthy examination is performed


ent Examine the cranial nerves (including fundoscopy), upper and lower limbs. If there is any focal neurological deficit this could suggest raised intracranial pressure which would be a contraindication to lumbar puncture. If there is a pressure difference between the supratentorial and infratentorial compartments, lumbar puncture may increase this pressure difference and cause brain herniation. In such cases, lumbar puncture should not be performed and antibiotics given immediately. Other signs that could suggest raised intracranial pressure include a reduced or fluctuating GCS and papilloedema


ent In a case of meningitis with signs of raised intracranial pressure, the nearest neurosurgical centre should be contacted and the patient should be cared for on an intensive care unit


‘Full neurological examination is limited due to patient confusion; however, there do not appear to be any focal neurological signs. Specifically, there is no evidence of papilloedema on fundoscopy; power, reflexes and tone are normal in all four limbs and there is no facial asymmetry or obvious cranial nerve deficit.’





Initial Investigations



ent Bloods: FBC, U&Es, LFTs, glucose, CRP, clotting, meningococcal and viral PCR. Look for evidence of infection and check platelet count and clotting before performing lumbar puncture. In severe meningitis, disseminated intravascular coagulation can occur causing deranged clotting and low platelets, both of which would be a contraindication to lumbar puncture. Send a meningococcal PCR (this is important for public health)


ent Blood cultures: Ensure aseptic technique when taking blood and that at least 10 mL of blood is collected in each blood culture bottle to give the most chance of culturing an organism


ent Venous blood gas: This is useful to assess the patient’s acid–base status and their lactate. A raised lactate may suggest reduced tissue perfusion which is a poor prognostic sign and an indicator of severe sepsis. Note that partial pressure of oxygen is difficult to assess on a venous blood gas, and if there is a significant concern about this, an arterial blood gas should be performed


ent CT head: If CT scanning is readily available and will not lead to significant delays, a CT head should be performed prior to lumbar puncture in all cases. If CT scanning is not readily available, lumbar puncture can be performed if deemed safe by a neurologist (i.e. none of the contraindications described below). If a neurologist is not available then the EFNS guidelines [2] state antibiotics should be given while awaiting imaging. The CT protocol may vary in individual hospitals


ent Lumbar puncture: This is the key investigation in this case which will give the most diagnostic information. However, as already described there are a number of contraindications to performing a lumbar puncture–these are: reduced or fluctuating GCS, raised intracranial pressure, suspected intracranial mass, focal neurology, septicaemia, shock, respiratory failure, trauma and middle ear pathology. If there are no contraindications, proceed as described below:


ent Ensure that the platelets, clotting and CT scan are normal prior to lumbar puncture and consent the patient if they are able to


ent Measure the opening pressure using a manometer (normal<25 cmH2O)


ent Send the 1st and 3rd bottles for microscopy, culture and sensitivity


ent Send the 2nd bottle for biochemistry (protein and glucose) and send a paired serum glucose


ent Send the 4th bottle for meningococcal PCR and viral PCR (if encephalitis suspected)


ent If subarachnoid haemorrhage is suspected, a CT head should be performed prior to lumbar puncture. If this is clear, a 5th bottle can be sent for xanthochromia (taken at least 12 hours following the time of the suspected subarachnoid haemorrhage)


ent Send the samples urgently to the lab and contact the microbiologist on call to alert them of the patient (urgent microscopy will be required) and for advice on antibiotic choice


ent EEG and MRI head: If there is concern of encephalitis then EEG and MRI can be useful, both usually illustrating changes in the fronto-temporal lobes


ent Throat swab: Send throat swabs for bacterial and viral culture


ent Septic screen: In view of the temperature, a chest X-ray and mid-stream urine analysis should be performed to exclude any evidence of pneumonia or urinary tract infection. In view of the vomiting, aspiration pneumonia should also be suspected; however, clinical examination in this case does not suggest any evidence of pneumonia


‘Blood testing reveals WCC 25×109/L, neutrophils 21×109/L, CRP 80 mg/L. Platelets and clotting are normal. Venous gas shows normal acid–base balance and a lactate of 1.5 mmol/L. CXR is clear, blood cultures and MSU are sent. A CT head is arranged prior to lumbar puncture.’





Initial Management [2]



ent Airway support: In this case, no intervention required. Consider intubation in any patient with a GCS<8


ent Supplementary oxygen: Give supplementary oxygen in any patient with saturations<94% or severe sepsis


ent Intravenous fluids: Intravenous fluids should be given to all patients with sepsis. In this case, the patient is given 0.9% saline at 125 mL/h. Reassess fluid status frequently and titrate fluid therapy as necessary. Once the urea and electrolytes are available, further fluids can be prescribed with supplementary potassium added as necessary


ent In a case of suspected meningitis, it is important to maintain neutral fluid balance–patients with sepsis should be given intravenous fluid therapy to maintain good tissue perfusion; however, overhydration can worsen raised intracranial pressure which occurs in meningitis


ent Antibiotics: The choice of antibiotics depends on the local antibiotic policy and early microbiological advice should be sought. Usually, a third generation cephalosporin is given as first line, e.g. cefotaxime 2 g IV 6-hourly. Atypical organisms should be considered in certain cases and advice from the microbiologist will be important in determining the most effective choice of antibiotics. In the elderly, consider Listeria infection which is covered by the addition of amoxicillin. If the patient has recently been abroad, they may have infection with penicillin-resistant pneumococci and you should add high-dose vancomycin


ent Corticosteroids: In cases of community-acquired meningitis (particularly pneumococcal meningitis), there is evidence that high-dose corticosteroids may reduce neurological complications if given before or at the same time as the first dose of antibiotics [3]. Following senior advice, consider starting dexamethasone 10 mg IV QDS. High-dose corticosteroids should not be given in those with meningococcal septicaemia, septic shock, in the immunosuppressed and those who have undergone recent neurosurgery. If corticosteroids are to be given, a proton pump inhibitor (such as omeprazole 40 mg IV OD) should be given in addition to prevent gastric ulceration


ent Antiviral treatment: In cases where encephalitis is suspected (headache, fever, seizures, altered personality, focal neurology), also give aciclovir 10 mg/kg IV TDS. It is reasonable to give it in the above case because of the patient’s confusion. Outcome in encephalitis significantly worsens the longer treatment is delayed; therefore, if you ever suspect encephalitis you should start treatment immediately–this can easily be stopped later when the viral PCR results are available


ent Analgesia: Start regular paracetamol for the patient’s headache. Use opioids with considerable caution in a patient with a reduced GCS


ent DVT prophylaxis treatment: pharmacological prophylaxis with LMWH should initially be avoided. Intracerebral and adrenal haemorrhage can both occur in meningitis as well as clotting abnormalities and consumption of platelets due to sepsis and disseminated intravascular coagulation. In all cases, LMWH treatment should be delayed until at least 6 hours after lumbar puncture. Following initial investigations and treatment, the appropriateness of LMWH prescription for DVT prophylaxis can be determined


ent Notify public health authority: Meningitis is a notifiable disease and close contacts should be treated with antibiotic prophylaxis–the choice of antibiotic depends on the causative organism and microbiology advice should be taken


ent As the GCS is 13, all medications are given intravenously.




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Figure 5.1



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Figure 5.2



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Figure 5.3






Initial Assessment








Initial Investigations



ent Bloods: FBC, U&Es, LFTs, glucose, CRP, calcium, magnesium, and clotting. Look for evidence of infection or electrolyte abnormality that could have precipitated the seizure. Note that the white blood cell count will often go up secondary to a seizure in and of itself. Consider sending toxicology screen and if the patient is taking antiepileptic medications measure drug levels. If the patient is a woman of child-bearing potential send βHCG levels or perform a urinary pregnancy test after the seizure has terminated. If pregnancy is strongly suspected, perform an emergency ultrasound, or auscultate for a fetal heart: eclampsia usually doesn’t occur until about 20 weeks pregnancy so evidence of a baby should be present!


ent Blood cultures: Infection can precipitate seizures in those with epilepsy or be the primary cause; therefore blood cultures should be taken. If the temperature is elevated this may not always be due to infection as seizures themselves can lead to a rise in body temperature


ent Arterial blood gas: Perform an arterial blood gas if possible, otherwise a venous blood gas can be taken at the same time as cannulation. In particular, check for hypoxia, hyponatraemia and confirm normal glucose levels. Most blood gas machines will also analyse carboxyhaemoglobin levels, although carbon monoxide poisoning is a very rare cause of seizures


ent Respiratory and cardiac monitoring: Arrange for continuous monitoring of the BP, oxygen saturations and ECG tracing (to exclude arrhythmia). It is important to monitor for hypoxia during a seizure as well as changes in the pulse and BP. Some of the medications given to terminate seizures (e.g. phenytoin) can lead to arrhythmias and therefore continuous cardiac monitoring is required if these are given



‘Bloods show a raised white cell count, but are otherwise normal, including the arterial gas.’



Status epilepticus


A seizure lasting for more than 30 minutes or repeated seizures over 30 minutes with little or no recovery of consciousness between seizures. image



Initial Management [4]



ent Seek senior help early in the event of a seizure


ent Airway support: Place in the recovery position, perform airway manoeuvres as needed and insert a nasopharyngeal airway. Consider intubation if needed


ent High-flow oxygen


ent Check blood sugar


ent Obtain IV access and perform ABG (or venous gas if ABG not possible)


ent Terminating the seizure: Many seizures self-terminate without intervention; however, if the seizure is prolonged (i.e. greater than 5 minutes), treatment should be given to prevent hypoxic brain injury. In reality, if the patient hasn’t stopped seizing by the time you have performed all of the above, 5 minutes is likely to have passed and you should give medication to terminate the seizure:


ent The initial choice is a benzodiazepine, e.g. lorazepam 4 mg IV (as a slow injection over 2 minutes). Be aware that benzodiazepines can cause respiratory depression so have resuscitation equipment and flumazenil available in case they are needed. If it is not possible to obtain IV access then diazepam 10 mg can be given rectally or midazolam 10 mg buccally


ent Consider reversible causes:


ent The blood sugar should have already been checked and hypoglycaemia corrected


ent In all alcoholics and those who are malnourished, consider thiamine deficiency and give replacement with intravenous thiamine, e.g. Pabrinex® IV High Potency Injection (ampoules 1 and 2) IV


ent If the patient is pregnant check the BP and consider eclampsia. Call for senior help immediately and contact the obstetric registrar on call. Following senior advice, treatment would consist of magnesium sulphate 4 g in 100 mL 0.9% saline given over 5 minutes with continuous respiratory and cardiac monitoring [2]


ent Prolonged seizures:


ent If after 10 minutes the patient is still seizing then repeat the same dose of benzodiazepine


ent If despite 2 doses of benzodiazepines the patient continues to seize, load with phenytoin 20 mg/kg intravenously. Phenytoin should be given through a large bore intravenous cannula followed by a flush of 0.9% saline as it can cause venous irritation. It is given at a maximum rate of 50 mg/minute. It is diluted in 0.9% saline and the concentration should not exceed 10 mg/mL–therefore usually doses of 1000 mg or less are made up in 100 mL, and doses above 1000 mg in 250 mL of 0.9% saline. Continuous monitoring of observations and ECG is necessary during phenytoin infusion and the infusion should be slowed or stopped if there is a fall in blood pressure or arrhythmias develop. If the patient was already taking phenytoin then phenobarbital may be used as an alternative.

Nov 18, 2017 | Posted by in PHARMACY | Comments Off on Neurology
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