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Self-assessment

Published:December 19, 2019DOI:https://doi.org/10.1016/j.mpaic.2019.12.001

      Single best answer

      A 70-year-old lady who lives on her own suffered an out of hospital cardiac arrest. It took nearly 20 minutes before the return of spontaneous circulation was achieved by the paramedics. On arrival into A&E, she is intubated and ventilated. Her core temperature is 33oC. She is admitted to ICU for further treatment. Which of the following are true regarding her management and outcome?

      • A.
        Hypothermia increases the production of free radicals
      • B.
        Her 3-month survival is around 5%
      • C.
        Her neurological outcome is better if her temperature is allowed to be around 330C
      • D.
        She should be actively rewarmed by 1oC per hour
      • E.
        It is recommended that her temperature be maintained at around 36oC

      An 82-year-old gentleman is brought into A&E with a GCS of 6. He has pin point pupils and is not moving any of his limbs. His blood pressure is 190/100 mmHg. His temperature is 37°C. He is on warfarin for atrial fibrillation (AF). His current INR is 4. He has been a heavy smoker and has a history of excess alcohol consumption. Which of the following are true regarding his management and outcome?

      • A.
        Intense control of the blood pressure worsens outcome
      • B.
        He should be cooled down to 33°C using external cooling devices
      • C.
        His blood glucose should be tightly controlled between 4 and 6 mmol/l
      • D.
        His presenting GCS of 6 is an independent factor for very poor prognosis
      • E.
        Reversal of coagulopathy has no impact on the outcome

      Multiple choice questions

      Clinical approach to comatose patients

      Which of the following are true regarding the diagnosis and management of comatose patients?
      • A.
        Flumazenil for reversal of suspected benzodiazepine overdose can precipitate seizures in those who have a chronic dependence
      • B.
        Intravenous phenytoin or levetiracetam are of no benefit if there is a suspicion of non-convulsive status epilepticus contributing to coma
      • C.
        Absence of papilloedema excludes raised intracranial pressure
      • D.
        In patients with hypoxic—ischaemic injury following cardiac arrest, prognostication should not be performed before 72 hours after return of spontaneous circulation
      • E.
        High serum levels of neuron specific enolase are associated with poor outcome in patients with traumatic brain injury

      Cerebrospinal fluid and its physiology

      Which of the following are true about the production and composition of CSF?
      • A.
        The CSF pressure is independent of the cerebral activity
      • B.
        Micronutrients required for neuronal cell metabolism such as folate and vitamin C are actively secreted into the CSF
      • C.
        CSF has a reduced acid-base buffering capacity when compared with blood
      • D.
        Reabsorption of CSF by the arachnoid granulations is independent of the intracranial pressure
      • E.
        CSF concentrations of potassium ions is higher than that in plasma

      Pharmacological and pathological modulation of cerebral physiology

      Which of the following anaesthetic agents reduce both the cerebral blood flow and cerebral metabolic rate?
      • A.
        Xenon
      • B.
        Sevoflurane
      • C.
        Ketamine
      • D.
        Propofol
      • E.
        Rocuronium

      Prion diseases

      Which of the following are true regarding the diagnosis and features of variant Creutzfeldt-Jakob disease?
      • A.
        Affects mainly the elderly population
      • B.
        Abnormal prion protein may be expressed in the cellular elements of blood
      • C.
        MRI findings may include a characteristic abnormality seen in the posterior thalamic region, the so-called pulvinar sign
      • D.
        Diagnosis is confirmed by tonsillar biopsy, which is both sensitive and specific
      • E.
        The onset of neurological signs is much earlier in the disease process

      Answers

      1. Correct Answer: E. It was believed that the inadvertent hypothermia provided a significant degree of neurological protection. This is potentially achieved through: reduction in cerebral metabolic requirement oxygen (CMRO2) by approximately 7% per 1°C, below core body temperature. Reduction of intracranial pressure (ICP) and reduction in free radical formation.
      In 2018, a consensus of recommendations was published in the British Journal of Anaesthesia, to help standardise practice. The following recommendations about targeted temperature management (TTM) were made: TTM should be initiated if a patient's temperature exceeds 37.5°C and infection is excluded, and within 1 hour if pharmacological treatment has not succeeded. TTM should continue for as long as there is potential for secondary brain injury with a target temperature of 37°C ± 0.5°C and rewarming should occur at 0.25°C per hour.
      Despite multiple advances in the management of cardiac arrest, outcomes remain poor. In 2018, the United Kingdom-based PARAMEDIC trial, published in the New England Journal of Medicine (NEJM), showed a 3-month survival of less than 3% and those with favourable neurological outcomes (modified Rankin Scale (mRS) scale 0–3) is approximately 2%. After return of spontaneous circulation (ROSC), neurological injury was the single biggest cause of disability.
      However, in 2013 the TTM trial (2013 NEJM) with nearly 1000 patients showed no difference in neurological outcome or survival in patients cooled to 33°C versus 36°C for 36 hours. Following this, most UK intensive care units have elected to use 36°C as the target temperature, for a minimum of 24 hours, provided there are no significant side effects.
      2. Correct Answer: D. Intracerebral haemorrhage (ICH) accounts for around 10–20% of all strokes and results from a variety of disorders. ICH is more likely to result in death or major disability than ischaemic stroke or subarachnoid haemorrhage. Rapid imaging allows early diagnosis and characterisation of the localisation and severity of the haemorrhage. Patients with significant acute ICH should be managed in a critical care unit. Treatment entails general supportive care, control of blood pressure (BP) and intracranial pressure (ICP), prevention of haematoma expansion and, where indicated, neurosurgical intervention. Patients whose bleed extends into the ventricular system or who have infratentorial bleeds are at increased risk of associated hydrocephalus, rapidly increasing intracranial pressure requiring urgent CSF drainage. The 30-day mortality from intracerebral haemorrhage (ICH) ranges from 35 to 52%. Among survivors, the prognosis for functional recovery depends upon the location of haemorrhage, size of the haematoma, level of consciousness, the patient's age, and overall medical condition.
      Pontine haemorrhage causes coma associated with pinpoint pupils, loss of horizontal eye movements and quadriparesis. Hyperpyrexia and irregular respiratory patterns ensue. Although a large haematoma here is often fatal, the outcome may be good in some patients.
      Higher systolic blood pressure is associated with greater haematoma expansion, neurological deterioration and worse outcome: death and neurological dependency. Early intensive lowering of blood pressure was shown to be safe in the second INTERACT trial. Secondary analyses suggested that this might improve outcome but the effects of rapid blood pressure reduction on cerebral autoregulation and peri-haematoma ischaemia remain uncertain. Following on from the randomized clinical trial (ATACH 2) in 2018 many critical care units (including our own) have adjusted their systolic blood pressure target for the first week following ICH to aim for a systolic value less than 140 mmHg which is now thought to be a relatively safe target.
      Plasma glucose should be monitored regularly and both hyperglycaemia and hypoglycaemia should be avoided because they are linked to poor outcome. A randomized trial showed improved outcomes with tight control (4–6 mmol/l) using insulin infusions in mainly surgical critical care patients. However, more recent studies in stroke patients using ‘tight glucose control’ have demonstrated an increased incidence of systemic and cerebral hypoglycaemic events and better outcomes are seen in stroke patients with more ‘relaxed’ targets. At present, the optimal management of hyperglycaemia in ICH and target glucose level remains to be clarified; our critical care unit protocol targets plasma glucose to between 7 and 12 mmol/l.
      Fever worsens outcome in experimental models of brain injury. Fever is a common finding in ICH patients especially in those who have deep, intraventricular or infratentorial haemorrhage. Recent observational studies have linked fever (>37°C) within the first 72 hours post ICH as an independent factor associated with poor functional outcome. It is therefore wise to control body temperature to under 37°C and external cooling devices can be used to achieve this.
      The prognosis following ICH depends primarily on the location and the size of the haematoma. Presenting GCS of less than 8 is strongly linked with poor outcome.
      3. Correct answers: A, D, E
      4. Correct answers: B, C
      5. Correct answers: A, D
      6. Correct answers: B, C, D