SBA 300 Paper 6 Flashcards
1
Q
- A 44-year-old woman is on the intensive care unit having had a grade 3
subarachnoid haemorrhage secondary to an anterior communicating artery
aneurysm one day ago. She is currently stable neurologically. Her past medical history comprises of hypercholesterolaemia, hypertension and smoking. She has a drug history of simvastatin and lisinopril.
Which of the following would most likely prevent the development of delayed cerebral ischaemia in this patient?
A ‘Triple H therapy’
B Magnesium administration
C Statin administration
D Nimodipine administration
E Antiplatelet therap
A
- D Nimodipine administration
○ Delayed cerebral ischaemia describes neurological deterioration that occurs secondary to ischaemia alone (i.e. not hydrocephalus or seizure activity) and persists for greater than 1 hour.
○ It develops in more than 60% of subarachnoid haemorrhage
(SAH) patients and confers a less favourable outcome.
° Patients are at greatest risk of ischaemia from day 3 to day 10 post-SAH. ° Their risk is also augmented by a poor grade of SAH (Table 6.2), a large volume haemorrhage within the subarachnoid space or extending to the ventricles and a smoking history.
○ Delayed ischaemia is frequently labelled as intracranial vasospasm, but until confirmed by investigation the two terms should be separately defined. They are treated in an identical fashion.
○ The use of triple H therapy (hypertension, hypervolaemia and haemodilution) is now controversial.
°Those who advocate it do so in order to improve cerebral blood flow by increasing cerebral perfusion pressure (CPP), volume status and blood rheology.
° Targets for each are CPP >70mmHg, CVP 12–15mmHg and haematocrit
0.3 respectively.
° More recent studies have failed to show conclusive benefits from any element but it is widely accepted that hypovolaemia and hypotension are deleterious.
° The patient’s premorbid blood pressure must also be acknowledged when calculating a suitable target.
○ Hypermagnesaemia has been promoted as reducing the risk of cerebral ischaemia as magnesium is a vasodilator and thought to have a role in neuroprotection.
° The 2011 IMASH trial (Intravenous Magnesium Sulphate in Aneurysmal Subarachnoid Haemorrhage) failed to show any benefit but it is felt that further studies are needed to ascertain the optimum level required to improve outcome.
° A magnesium level below the normal range should definitely be corrected.
○ In addition to treating hypercholesterolaemia, statins have been found to modulate the cytokine response.
° They also reduce the quantity of reactive oxygen molecules produced in brain injury.
° Overall, the subsequent inflammatory response is minimised and they have therefore been suggested as part of the treatment for SAH to prevent vasospasm and delayed ischaemic injury.
° However, data from the international, multicentre, randomised controlled STASH trial (Simvastatin in Aneurysmal Subarachnoid Haemorrhage) published in 2014 suggests that there is no short-term or long-term benefit to using statins in these patients, despite earlier enthusiasm with the idea.
○ In 2007, a Cochrane review noted that antiplatelet therapy was associated with a non-significant trend indicating a benefit to outcome in patients at risk of delayed cerebral ischaemia.
° Unsurprisingly, this trend was counteracted by a parallel increase
in haemorrhage.
° Therefore antiplatelet agents, in this setting, are restricted to use following endovascular stenting for SAH management.
○ The only proven effective treatment in the prevention of delayed cerebral ischaemia is nimodipine.
° As a calcium antagonist it is thought to protect against vasospasm
and there is level 1 evidence that it improves outcome.
°Every patient with a diagnosis of SAH should be started on nimodipine (60mg every 4 hours) for a course of 21 days.
° A side-effect can be systemic hypotension which can be avoided by the
more frequent administration of half doses. If this does not remedy the situation, the blood pressure should take precedence.
○ All of these treatments have been considered in the prevention of delayed cerebral ischaemia. Nimodipine is the only one to have withstood repeated testing with consistent results
2
Q
- A 29-year-old woman who suffered a blow to the left side of her skull vault with a resulting depressed fracture is awaiting transfer to a tertiary centre. She lost consciousness for approximately 1 minute after the incident. Her GCS is currently 14/15 (E4 V4 M6).
Which of the following, in isolation, indicates that intubation is essential before
transfer?
A Pao2 of 13 kPa an Fio2 of 0.6
B A discrete and short-lived seizure en route to your hospital
C Drop in GCS from E4 V4 M6 to E3 V4 M5 in the emergency department
D An increase in respiratory rate leading to a Paco2 of 4.0kPa
E Blood in the oropharynx
A
- B A discrete and short-lived seizure en-route to your
hospital
○ This patient has suffered a head injury by a mechanism significant enough to cause a depressed skull fracture. This will most probably lead to an evolving brain injury secondary to underlying contusions.
○ It is important that she is managed in an appropriate environment, to expedite swift treatment of any complications, and is likely to involve further transfer to a tertiary hospital with on-site neurosurgical care.
○ Prior to transfer it is imperative to assess her ability to maintain her physiology such that secondary brain injury is avoided as much as possible. °This includes adequate ventilation via a patent airway, preservation of an appropriate blood pressure [cerebral perfusion pressure (CPP) = mean arterial pressure (MAP) - intracranal pressure (ICP)] and optimisation of cerebral metabolism. The aim is to minimise further rises in ICP and secure brain tissue perfusion following the suspected injury.
○ The following are suggested targets during transfer:
• PaO2 >13 kPa
• PaCO2 4.5–5.0 kPat MAP >80mmHg
• Adequate analgesia
• Sufficient sedation (and therefore intubation) if agitated
• Treatment of any seizures
• Normothermia
• Blood glucose 6–10mmol
• Optimal cerebral venous drainage – head-up, avoidance of neck ties
○ In the scenario given you are asked to choose an instance that would obligate you intubate the patient in order to maintain each target en route. The AAGBI has published guidelines for the safe transfer of head injured patients they include indications that should initiate intubation and ventilation before any journey:
• Glasgow coma score <8/15
• Glasgow coma score drop of 2 points in the motor score
• PaO2 <13kPa with oxygen administration
• PaCO2 <4.0 or >6.0 kPa
• Concern regarding laryngeal reflexes
• Seizure(s) since the injury
• Bilaterally fractured mandible
• Significant bleeding threatening the airway
○ A PaO2 of 13kPa whilst receiving an FIO2 of 0.6 implies a significant alveolar to arterial gradient. The value for PaO2, however, is acceptable and there is scope to improve it with optimal positioning and increased oxygen administration.
A drop in GCS from E4 V4 M6 to E3 V4 M5 is a drop of 2 points and significant
enough to warrant consideration of intubation prior to transfer but guidelines allow
for individual clinical decision making. Intubation is regarded as essential if 2 points
are dropped within the motor score.
An increased respiratory rate leading to hypocapnia in this patient could be as a
result of pain. If, despite treatment, this continues and reduces further to jeopardise
cerebral circulation then control of ventilation may be warranted.
Blood in the oropharynx may be small and resolved or ongoing, potentially
interfering with ventilation. Clinical examination and judgement are required to
assess whether this, in isolation, would necessitate intubation.
Seizures in the period following head trauma imply increased severity of the injury
and may recur to further increase intracranial pressure and cerebral metabolic
requirements. All of the options could trigger a decision to secure the airway before
transfer, but seizure activity makes it essential.
3
Q
- A 65-year-old man presents to the emergency department with acute central
chest pain radiating to the back. He has a history of hypertension and smoking.
The ECG shows evidence of left ventricular hypertrophy and his blood pressure is
190/100mmHg, heart rate 105 beats per minute. There is a collapsing pulse and an
early diastolic murmur.
What is the next most appropriate management step?
A Commencement of sodium nitroprusside infusion
B Site an arterial line
C Arrange urgent aortography
D Titrate intravenous morphine
E Arrange transfer to a cardiothoracic centre
A
- D Titrate intravenous morphine
The history and clinical signs are suggestive of aortic dissection with aortic
regurgitation. Other clinical signs relate to the area of the aorta involved and are summarised in Table 6.3.
○ There are a number of risk factors for aortic dissection, including:
• Hypertension (72% of patients)
• Smoking
• Trauma – deceleration and falls from height
• Aortic surgery/cannulation
• Vasculitis : Syphilis, Takayama arteritis
• Collagen disorders : Marfans, Ellerslie Danlos, Turner’s
○ There are two different classification systems of which the Stanford system is most widely used. It denotes that dissections involving the ascending aorta are Type A with all others as Type B.
○ The priorities are to make an accurate diagnosis, limit the stress on the aortic lumen (by lowering systolic blood pressure and left ventricular contractility) and forming a definitive treatment plan, which may include urgent transfer to a cardiothoracic centre.
○ It is particularly important to diagnose Type A dissections (i.e. those involving the ascending aorta) as these are considered surgical emergencies. ○ Non-invasive diagnostic methods have superseded traditional aortography (option C) with CT, transthoracic and transoesophageal echo being the most common modalities employed.
○ Transthoracic echocardiography can be performed at the bedside but is
not able visualise the distal ascending and descending aorta reliably.
○ The management steps outlined by the European Society of Cardiology guidance
• Detailed medical history and physical examination
• Intravenous line, blood samples, cardiac enzymes
• ECG, heart rate and blood pressure monitoring (both sides)
• Pain relief
• Reduction of systolic blood pressure using beta-blockers/calcium channel
blockers + additional vasodilators if needed
• Diagnostic imaging
• Intensive care level monitoring – right radial arterial line as standard
○ Although pharmacological control of systolic hypertension may be required, a large proportion of patients will have pain which may of course exacerbate hypertension.
○ Titrated morphine is therefore the most appropriate first step in this scenario. If further blood pressure control is required, beta-blockers are recommended before pure vasodilators such as sodium nitroprusside.
○ Attainment of clinical stability and institution of invasive blood pressure monitoring would usually be obtained before transfer to a surgical centre, however planning for this possible eventuality early will ensure timely subsequent management.
○ Survival after surgical repair of Type A dissection is 96% and 91% at 1 and 3 years respectively. Complicated Type B aortic dissections may be amenable to treatment with endovascular stents, although some centres are also treating Type A dissections in this manner as well.
○ Poor prognostic factors at presentation include:
• Age >70 years
• Hypotension, shock or tamponade at presentation
• Preoperative renal failure
• Preoperative bleeding/massive transfusion
• Prior myocardial infarction
• Abnormal ECG are shown below:
4
Q
- A 65-year-old woman is recovering from an uneventful total thyroidectomy
as treatment for a large substernal goitre. On the third postoperative day, she
becomes progressively more stridulous and wheezy. She is tachypnoeic, confused
and complaining of circumoral paraesthesia. There is no obvious neck swelling or
pain.
What is the most likely cause of her symptoms?
A Bilateral vocal cord paralysis
B Tracheomalacia
C Haematoma
D Tracheal necrosis
E Hypocalcaemia
A
- E Hypocalcaemia
○ It is important to remain vigilant for any signs of respiratory distress after head and neck surgery since progression can be rapid with catastrophic consequences.
○ After thyroid surgery, there are a number of complications which can cause respiratory difficulties and an appreciation of the associated signs can help identify them.
○ Iatrogenic injury to the recurrent laryngeal nerve resulting in vocal cord damage is a recognised complication following thyroid surgery.
° Post-operative symptoms depend on whether both the left and right recurrent laryngeal nerves are involved.
° Unilateral injury manifests as a hoarse voice, difficulties phonating and aspiration on swallowing whereas bilateral injuries present acutely following extubation with stridor necessitating reintubation and tracheostomy formation.
° Bilateral vocal cord paralysis is not the most likely cause in the above scenario, as the stridor only
presents after four days. Furthermore, bilateral vocal cord paralysis does not directly cause circumoral paraesthesia or confusion.
○ Tracheomalacia is believed to occur as a result of longstanding extrinsic tracheal compression causing a loss of tracheal cartilage rigidity.
° Removal of this compressive source (thyroidectomy) may then precipitate life threatening dynamic airway collapse.
° It is a very rare complication and does not explain the confusion and paraesthesia in the above scenario.
○ Post-operative haemorrhage is a well recognised complication following thyroid surgery and can result in a rapidly expanding haematoma compromising airway patency.
° The haematoma usually presents as a large, tense and immobile swelling
under the wound, which will have to be re-opened at the bedside if there is
impending airway obstruction.
° The majority of bleeds occur within 24 hours and presenting symptoms can include stridor, dyspnoea, neck pain, dysphagia and confusion.
° Although an important differential to consider, it is not the most likely
diagnosis in the above case due to the normal neck examination and lack of pain.
° Symptom occurrence on day four postoperatively and the presence of circumoral paraesthesia is also not typical.
° The blood supply to the upper trachea is primarily from small branches of the inferior thyroid artery and life threatening tracheal necrosis due to excessive cautery near the trachea has been described.
○ Tracheal disruption is unlikely to be causing
the symptoms in the case described since there is no subcutaneous emphysema (formed from the tracheal air leak).
° Furthermore, stridor, confusion and paraesthesia are not usually associated with this very rare complication.
○ Hypocalcaemia is the most common complication following thyroidectomy and the most likely cause of the clinical picture described.
° Since the parathyroid glands are located on the posterior surface of the thyroid gland, these can be damaged or devascularised following surgery to this area.
° The fall in calcium levels generally occurs within 24–48 hours post-operatively and can be sufficient to produce symptoms.
° Hypocalcaemia directly increases neuromuscular excitability and
many of the clinical manifestations stem from this underlying problem.
° The stridor described in the above case is due to laryngospasm which is an exaggeration of the normal glottic closure reflex.
° Circumoral paraesthesia and bronchospasm also arise as a consequence of neuromuscular irritability
5
Q
- A 36-year-old woman with an impacted food bolus needs to go to theatre
imminently. She has been unable to swallow her saliva for 24 hours. On inquiring
about her anaesthetic history she reports collapsing due to a severe allergic
reaction under anaesthesia, but she is unsure which agent was responsible. There
are no notes available, nor relatives to elaborate on the history.
Which of the following should you avoid as the most likely causative agent?
A Rocuronium
B Latex
C Morphine
D Chlorhexidine
E Gelofusine
A
- A Rocuronium
○ This patient’s limited anaesthetic history raises the suspicion of a previous episode of anaphylaxis.
○ Without prior records available it is prudent to avoid agents most likely
to cause such a reaction.
○ Anaphylaxis is an immune reaction that is triggered by hypersensitivity to an antigen, e.g. the β lactam ring found in some antibiotics. It results in IgE antibody production and a subsequent IgE-antigen mediated cascade of events.
° This leads to the widespread release of inflammatory mediators such as histamine, leukotrienes and prostaglandins.
° The reaction results in an increase in vascular permeability, bronchial hyper-reactivity and subsequent circulatory compromise that can be fatal (10% of those reported to the UK Medicines Control Agency).
○ Similar, and often indistinguishable, reactions may occur that do not involve IgE
release in response to an antigen. They manifest secondary to direct histamine release or activation of the complement pathway by other means. ° They are known as anaphylactoid reactions. An example of which could be initiated by morphine which acts directly on mast cells to cause histamine release.
○ The culture of reporting anaphylactic reactions is variable between countries and thus the frequency of its occurrence (based on information from Australia and France) ranges from 1 in 10 000 to 1 in 20 000. The 6th National Audit Project (Perioperative Anaphylaxis) may help determine the incidence of anaphylaxis in the UK, which is currently unknown.
○ The following table (Table 6.4) lists the most commonly known triggers for
anaphylaxis and their proposed incidence when associated with anaesthesia.
° As muscle relaxants are reported to be the agents with the highest risk of triggering anaphylaxis, rocuronium should be avoided in this scenario if at all possible.
° If the use of a muscle relaxant is necessary, using a benzyl-isoquinolinium instead of an aminosteroid may reduce the risk as they are less associated with such a reaction.
° To further avoid histamine release, and therefore the possibility of an anaphylactoid reaction, cisatracurium may be the best option.
○ The remaining agents can also be associated with anaphylaxis. Further modifications to the anaesthetic, such as fentanyl instead of histamine-producing morphine or iodine in place of chlorhexidine and avoidance of all colloids, can be simple enough to make.
The majority of theatres are now run as ‘latex-free’ or can easily be made so these days.
6
Q
- A 34-year-old man presents for laparoscopic excision of his left adrenal gland for phaeochromocytoma. During your preoperative assessment, he tells you that he has been taking medication for blood pressure for about a month. Which of the following is most likely to indicate that he is prepared for surgery?
A Good exercise tolerance, but a history of dizziness on standing
B Lack of a history of palpitations, and a normal ECG
C A normal echocardiogram, and chest X-ray
D History of dizziness on standing, a 5-minute ECG with no premature
ventricular complexes, and nasal congestion
E Several blood pressure recordings of <160/90mmHg
A
- D History of dizziness on standing, a 5-minute ECG with no premature ventricular complexes (PVCs), and nasal congestion
○ Phaechromocytomas, although rare in clinical practice are more common in exams. This secreting tumour is named a chromaffinoma, because of its derivation from chromaffin cells which evolve from the neural crest to make up the normal sympathetic system.
○ The classical clinical syndrome of severe hypertensive crises
accompanied by headache, sweating, palpitations and anxiety, with resolution afterwards, is variable and depends mainly on the secretory properties of the tumour.
○ Most secrete noradrenaline; with some producing both noradrenaline and adrenaline and a few may also secrete active peptides such as adrenocorticotrophic hormone (ACTH), calcitonin, vasoactive intestinal peptide (VIP) and somatostatin also.
○ Tumours are 90% adrenal and 10% extra-adrenal, known as paragangliomas.
○ The full range of imaging techniques is used for their identification, with functional PET scanning in some centres. M-iodobenzylguanidine (MIBG) isotope uptake scans are useful to identify tumour foci and locate extra-adrenal or secondary deposits.
○ Preoperative assessment and preparation is of paramount importance, and focuses on assessment for pathology associated with the tumour, namely end-organ damage caused by hypertension, and pharmacological suppression.
°With pharmacological suppression the classic target criteria are:
• Blood pressure <160/90mmHg
• Postural hypotension, but not severe (<80/45mmHg)
• ECG free from ST/T wave changes for 7 days
• No greater than one premature ventricular contraction on ECG every 5 minutes
• Nasal congestion
○ Agents used include the non-specific α-blocker phenoxybenzamine (which due to α2 blockade also causes tachycardia, and therefore must be given with a β-blocker).
○ Selective α1 blockers, such as doxazosin can now be used alone.
○ If β-blockade is required, a stable a block has to be established first to prevent the loss of β2 vasodilatation, and therefore increased hypertension.
○ Some of the stems in this question look for signs of α blockade.
° These may include postural hypotension, and nasal congestion.
° Lack of cardiac irritability feature in B and D, and are also reassuring, but the normal ECG reading in B cannot exclude ectopic beats.
° The normal chest X-ray and echocardiogram in C are reassuring, but cannot exclude acute physiological changes seen with this condition.
° Repeated blood pressure readings <160/90mmHg (E) are also reassuring about good blood pressure control, but the stem with both reassuring symptoms and physiological investigations is option D.
7
Q
- A 45-year-old man is admitted to the surgical ward with a fever, toothache and neck discomfort. Whilst waiting for surgery you are called to his bedside as he is more breathless and complaining of substernal pain. On examination he is hypotensive and there is tender, ’woody‘ induration of his neck. On auscultation you hear a pericardial rub.
Which investigation is most appropriate to guide management in this scenario?
A Cervical and chest ultrasound
B Cervical and chest computed tomography
C Cervical and chest magnetic resonance imaging
D Cervical and chest radiograph
E Echocardiogram
A
- B Cervical and chest computed tomography
○ The above case describes Ludwig’s angina which is an aggressive, rapidly spreading “woody” cellulitis of the submandibular space, commonly arising from an infected molar tooth.
○ There is a lack of lymphadenopathy since the typically polymicrobial
infection spreads along fascial planes as opposed to the lymphatic system.
○ Two life-threatening complications of Ludwig’s angina are upper airway obstruction and descending necrotising mediastinitis.
○ Sufferers are at risk of airway obstruction due to posterior infective extension and tongue distension with posterior displacement.
○ Descending necrotising mediastinitis describes the spread of infection from neck to mediastinum via contiguous fascial planes which is promoted by gravity and the negative intrathoracic pressure.
○ Since the disease is rare and early symptoms often nebulous, diagnosis and treatment can be delayed with fatal consequences.
○ Computed tomography is the imaging modality of choice for acute deep-seated neck infections and the correct answer to the above scenario. Imaging the neck allows a rapid assessment of the depth of involvement as well as the presence of abscesses which may be amenable to surgical drainage.
○ Chest imaging provides confirmation and allows an assessment of the extent of mediastinal involvement which is important for surgical planning.
○ Since a pericardial rub was heard in the above scenario, computed tomography will also be useful in assessing for secondary pericardial involvement and the presence of an effusion.
○ Magnetic resonance imaging does provide excellent soft tissue resolution and diffusion weighted imaging can help delineate complex fluid collections. ° This imaging modality is particularly useful for infections involving the retropharyngeal space where extension into the spinal column is suspected. However, it is more time consuming than computed tomography and patients may feel claustrophobic during scanning. Patient compatibility also needs to be assessed. In the above scenario where the airway patency can deteriorate rapidly and an early diagnosis and treatment plan is needed, computed tomography is more appropriate.
Cervical ultrasound can be useful in characterising soft tissue masses and collections
but is unable to penetrate bone or air filled structures. It is also operator dependent
and not as accurate as computed tomography in assessing the extent of mediastinal
involvement.
Plain radiography is easily accessible but is of little value in planning the
management of descending necrotising fasciitis complicating Ludwig’s angina.
○ A lateral cervical radiograph can highlight pretracheal gas bubbles and a loss of the normal lordosis, whereas a chest radiograph may show a widened mediastinum and an enlarged cardiac silhouette if there is mediastinitis or a pericardial effusion respectively. Computed tomography however provides a much more accurate picture of the severity of the infection.
○An echocardiogram can provide information regarding the extent of the pericardial effusion and whether it is affecting cardiac function. Echocardiography is not the most appropriate investigation to plan management since it provides no information on the degree of cervical involvement or whether there are any collections amenable to drainage
8
Q
- A 35-year-old cyclist suffered a severe traumatic brain injury with a large subdural haematoma and an associated C2–C3 cervical spine fracture. He is comatose and apnoeic, with neurosurgeons confirming that he is not a candidate for surgery due to poor prognosis. Confirmation of brainstem death is underway, with examination of cranial nerves just being completed.
What is the next most appropriate test that will support the neurological diagnosis of death?
A Apnoea testing
B Somatosensory evoked potentials
C No further tests necessary
D A second neurological examination of the cranial nerves
E Electroencephalogram
A
- E Electroencephalogram
○ The patient fulfils the prerequisites for brainstem testing because he has suffered irreversible brain injury and he is in an apnoeic coma.
○ The neurological confirmation of death consists of cranial nerve II – XI examination and apnoea testing performed by two doctors at two different times.
• At the end of each set of cranial nerves examinations an apnoea test occurs.
• In a patient with a high cervical spine injury, apnoea might not be due to a central cause but due to spinal cord injury, therefore ancillary tests are employed to confirm de the diagnosis.
• Electroencephalogram (EEG) is the most widely used and validated assessment in this circumstance.
• The second battery of brainstem tests cannot be performed in isolation without the apnoea testing; therefore an EEG is the next most appropriate step to support the diagnosis of death by neurological criteria. • Somatosensory evoked potentials are used for monitoring of depth of anaesthesia and play no part in the diagnosis of death.
9
Q
- A 35-year old man for elective ankle surgery is to have an ultrasound guided popliteal nerve block.
What is the most frequently used combination of ultrasound view and needle visualisation for this nerve block?
A Short-axis view with in-plane needle approach
B Long-axis view with out-of-plane needle approach
C Short-axis view with out-of-plane needle approach
D Long-axis view with in-plane needle approach
E Any of the above combinations
A
- A Short-axis view with in-plane needle approach
○ The use of ultrasound (US) in regional anaesthesia has significantly increased in the recent years.
○ Choosing the correct US view and needle orientation is essential for successful and safe nerve block.
○ When scanning nerves the structures viewed by US beam will either be in a short-axis view or long-axis view.
○ In the short-axis view, the nerves and the blood vessels are visualised in section (sliced across their diameter), nerves are easier to find, and the US image is relatively stable making this view ideal for introducing a needle.
○ In the long-axis view, however, the nerves and blood vessels are visualised longitudinally along their length (demonstrating a tube like structure) making the US image produced unstable and not ideal for needle insertion.
○ When introducing the needle, it can be passed either along the long-axis of the US beam (in-plane) or across the short-axis of the beam (out-of-plane). ○ With an in-plane approach, the needle is visualised entirely throughout the block and produces good views of needle-nerve proximity. Therefore this is the safest approach.
○ With an out-of-plane technique, the needle crosses the US beam as a bright dot and the accurate location of the needle tip is uncertain and it could be advanced in unwanted tissue, making this approach less safe for needle insertion. However, anaesthetists the out-of-plane approach is ideal when inserting catheters as it allows parallel advancement of the catheter along the long-axis of the nerve as it exits the tip of the needle (Figure 6.1).
○ In this example, the combination of short-axis view and in-plane needle visualisation is the safest approach for the above reasons.
10
Q
- You are called to the emergency department to assess a young woman that was rescued from a house fire following a gas leak after being trapped confined in a room. She is awake, with normal observations but suffered 10% body surface area (BS) partial thickness burns over her arms and face. You are asked to transfer her to the nearest burns unit that is 2 hours away. On examination she has singed nasal hair, a normal airway and no change in voice. Burns resuscitation is underway with intravenous fluids and analgesia.
What is the next step in ensuring her safe transfer?
A Add the operating department practitioner to your transfer team
B Full monitoring including invasive blood pressure measurement
C Prepare difficult airway equipment for the transfer
D Prepare Intubating equipment and drugs
E Elective intubation of the patient
A
- E Elective intubation of the patient
○ Inhalational injury is the aspiration of heated gases, hot liquids, steam, or noxious substances of incomplete combustion.
○ It can be categorised as:
• Upper airway thermal injury – supraglottic burns causing stridor, a change in voice quality or uvular oedema
• Lower airway thermal injury – infraglottic burns most commonly by noxious by-products of incomplete combustion leading to dyspnoea, wheeze and secretions
• Noxious gases injury – including inhalation of carbon monoxide and cyanide
○ This patient has a high risk of inhalation injury due to an enclosed space fire with significant burns to the face. The onset of airway oedema is often unpredictable, but fluid resuscitation is likely to worsen any impending oedema, while the relatively long duration of transfer indicates the need to have a secure airway during transfer.
○ Therefore it is appropriate to plan elective intubation of the patient in controlled circumstances with senior support, a difficult airway trolley and skilled assistance.
○ Adding a competent team member to the transfer is reassuring and can help should complications arise during transfer, but it is often impractical. All transfers should have full monitoring, including ECG, pulse oximetry and non-invasive blood pressures, but invasive blood pressure monitoring is only indicated if you anticipate cardiovascular instability or it is required to guide ongoing therapy.
○ Availability of difficult airway equipment is necessary once elective intubation has been decided, and devices such as video laryngoscopes are useful to have when a patient is being transferred. However, the most appropriate approach would be to ensure a secure airway prior to transfer.
11
Q
- You are called to the emergency department to assess a young woman that was
rescued from a house fire following a gas leak after being trapped confined in a
room. She is awake, with normal observations but suffered 10% body surface area
(BS) partial thickness burns over her arms and face. You are asked to transfer her
to the nearest burns unit that is 2 hours away. On examination she has singed nasal
hair, a normal airway and no change in voice. Burns resuscitation is underway with
intravenous fluids and analgesia.
What is the next step in ensuring her safe transfer?
A Add the operating department practitioner to your transfer team
B Full monitoring including invasive blood pressure measurement
C Prepare difficult airway equipment for the transfer
D Prepare Intubating equipment and drugs
E Elective intubation of the patient
A
- E Elective intubation of the patient
Inhalational injury is the aspiration of heated gases, hot liquids, steam, or noxious
substances of incomplete combustion. It can be categorised as:
t Upper airway thermal injury – supraglottic burns causing stridor, a change in
voice quality or uvular oedema
t Lower airway thermal injury – infraglottic burns most commonly by noxious by-
products of incomplete combustion leading to dyspnoea, wheeze and secretions
t Noxious gases injury – including inhalation of carbon monoxide and cyanideThis patient has a high risk of inhalation injury due to an enclosed space fire with
significant burns to the face. The onset of airway oedema is often unpredictable, but
fluid resuscitation is likely to worsen any impending oedema, while the relatively
long duration of transfer indicates the need to have a secure airway during transfer.
Therefore it is appropriate to plan elective intubation of the patient in controlled
circumstances with senior support, a difficult airway trolley and skilled assistance.
Adding a competent team member to the transfer is reassuring and can help
should complications arise during transfer, but it is often impractical. All transfers
should have full monitoring, including ECG, pulse oximetry and non-invasive blood
pressures, but invasive blood pressure monitoring is only indicated if you anticipate
cardiovascular instability or it is required to guide ongoing therapy. Availability of
difficult airway equipment is necessary once elective intubation has been decided,
and devices such as video laryngoscopes are useful to have when a patient is being
transferred. However, the most appropriate approach would be to ensure a secure
airway prior to transfer.
12
Q
- A 72-year-old man has been on the intensive care unit after being treated for an
infective exacerbation of his chronic obstructive pulmonary disease. He has been
mechanically ventilated for 5 days and has acceptable gas exchange. He has been
weaned to pressure support ventilation requiring 12cmH2O inspiratory support
and 5 cmH2O of positive end-expiratory pressure (PEEP) with an inspired oxygen
concentration of 0.35. He is currently obeying commends.
How would you best assess his suitability for extubation?
A Change the patient to continuous positive airway pressure (CPAP) and assess
ventilation and cardiovascular parameters for 30 minutes
B Reduce the pressure support gradually over the next 48 hours by 2 cmH2O per
12 hours and assess ventilation and cardiovascular parameters
C Reduce the inspired oxygen fraction to 0.25 and repeat an arterial blood gas 30
minutes later
D Repeat a chest radiograph to ensure resolution of his consolidative process
E Assess the patient’s sputum production and send a repeat sample for
microscopy to ensure clearance of the infective process
A
- A Change the patient to continuous positive airway
pressure (CPAP) and assess ventilation and cardiovascular
parameters for 30 minutes
The majority of patients who receive mechanical ventilation have acute respiratory
failure in the postoperative period, pneumonia, congestive heart failure, sepsis,
trauma or acute respiratory distress syndrome (ARDS). Respiratory muscle
weakness may not be a contributing factor to their respiratory failure and once
the acute pathophysiological problem is resolved, invasive ventilation may be
downgraded and patients extubated. The duration of mechanical ventilation is
often unnecessarily prolonged in the setting of a short period of ventilator support
(less than 7 days) with the weaning process accounting for up to 50% of the total
ventilation time. A delay of 48 hours in extubation results in an increased risk of
extubation failure, ventilator acquired pneumonia, thromboembolic disease, longer
intensive care and hospital stay and increased mortality.
Weaning involves progression from a controlled mode of ventilation to a support
mode and then reduction of support delivered until a trial of readiness for
extubation. This trial is termed a spontaneous breathing trial (SBT).
Typical readiness criteria for attempted weaning include:
t Improvement in the underlying condition that caused the respiratory failure
t Pulmonary: fractional inspired oxygen Ratio (PFR) of more than 200 with a
positive end-expiratory pressure (PEEP) of 5cmH2O
t Haemodynamic stability
t No electrolyte, metabolic, haematological or nutritional deficits
t Neurologically appropriate with cough and gag reflexes present
Once deemed suitable, a SBT may be initiated with minimal pressure support such
as 5cmH2O, CPAP or a T-piece or tracheostomy mask (no PEEP). A SBT should be attempted for a minimum of 30 minutes but should be terminated and deemed
unsuccessful if:
t The respiratory rate remains above 35 breathes per minute for 5 minutes
t Oxygen saturations of less than 90%
t Heart rate increases to over 140 beats per minute
t Systolic blood pressure >180mmHg or <90mmHg
t Panic or diaphoresis
The following classification of the results of the spontaneous breathing trial may be
applied:
t Simple: successful first trial followed by extubation
t Difficult: up to three spontaneous trials but discontinuation of ventilation within
7 days
t Prolonged: more than three unsuccessful trials or more than 7 days of mechanical
ventilation
10–20% of ventilated patients may have prolonged weaning and in-hospital
mortality is increased in this group. In patients who fail a SBT, the strategy is to
reduce the support the patient is receiving and try again. A period of rest between
SBTs is advocated of 24–48 hours. Gradual reductions in the pressure support
by 2–4cmH2O per 24 hours or a short SBT period every hour with increasing the
duration are both advocated.
Even assessing in a careful manner such as described above, 10–15% of extubations
fail, necessitating re-intubation. If this occurs the mortality rate in this group is
increased.
In the patient above, the criteria for initiating a SBT is met and if successful, a trial of
extubation is warranted. In this patient with COPD, a greater-than-average sputum
production and poorer gas-exchange may have been present prior to the acute
infection and must be accepted in order to avoid the complications of on-going
mechanical ventilation.
13
Q
- You are asked to review a 72-year-old man who was admitted to your intensive care unit 6 hours ago following elective coronary artery bypass grafts. He is haemodynamically stable with no evidence of end organ hypoperfusion. The concern is that he has been slowly bleeding into his drains (total 570mL since theatre) and has slow oozing through his sternotomy wound and around his lines and drains. His core temperature is 36.2°C and pH 7.32. An urgent full blood count and clotting tests were sent 30 minutes ago and the results have just come back and show: Haemoglobin concentration 78g/L; platelet count 102 ×109/L; INR 1.4; aPTTr 1.6; fibrinogen 1.8g/L; and ionised calcium 0.9mmol/L. The patient is on long-term aspirin 75mg daily (not stopped for surgery). He received heparin in theatre that was reversed with protamine. He also received a single dose of 1g tranexamic acid.
Given this information the most appropriate treatment strategy is:
A 1 unit packed red blood cells (pRBC) + 1 pool of platelets + 15mL/kg fresh
frozen plasma (FFP) + 1 dose of cryoprecipitate
B 20mmol of calcium chloride + protamine + 1 pool of platelets + tranexamic
acid
C 2 units packed red blood cells (pRBC)
D 20mmol of calcium chloride + 1 pool of platelets + 15mL/kg fresh frozen
plasma (FFP)
E Perform a thromboelastogram
A
- D 20mmol of calcium chloride + 1 pool of platelets +
15mL/kg fresh frozen plasma (FFP)
○ In order to form effective blood clots a patient needs an adequate number of functioning platelets, adequate levels of all the clotting factors, an adequate haematocrit, an adequate level of ionised calcium, a relatively normal pH and an absence of significant hypothermia.
○ The critical levels of these variables cannot be defined and are mutually dependent.
○ The clinical scenario described suggests that there is ongoing bleeding due to a coagulopathy rather than a failure of surgical haemostasis.
○ The temperature, pH, haematocrit and platelet count are acceptable.
°However, the patient has been receiving long term antiplatelet therapy and has been on cardiopulmonary bypass, thus, in the absence of a platelet function test it is reasonable to deduce that platelet transfusion is warranted to correct the coagulopathy.
°The clotting tests suggest there is a consumptive and /or dilutional component to this coagulopathy.
○ Given the degree of abnormality, a dose of FFP should elevate the levels of all factors, including fibrinogen, without the need to give additional cryoprecipitate.
○ Administration of FFP and platelets is likely to result in a further drop in ionised calcium, it would be prudent to administer a replacement dose. Given the scenario and timings, a further dose of protamine is likely to result in an anti-coagulant effect. In the absence of evidence for hyperfibrinolysis, a second dose of tranexamic acid is not indicated at this stage.
○ The threshold for pRBC transfusion in this context is <70g/L.
○ A thromboelastogram would refine the diagnosis further and repetition after intervention guide further therapy. This is a common practice in many centres but not universal.
14
Q
- A 60kg, 55-year-old woman has been admitted to the intensive care unit with severe community acquired pneumonia. Two days later she develops worsening hypoxaemia with new bilateral infiltrates on chest radiography. She is currently ventilated with the following settings:
• Fio2 1.0
• Inspiratory pressure (Pinsp) 35 cmH2O
• Positive end expiratory pressure (PEEP) 12cmH2O
• Inspiratory:expiratory (I:E) ratio 1:1
• Tidal volume (Vt) 250mL
An arterial blood gas reveals results shown in Table 6.1.
Based on current evidence, which of the following would be an appropriate next
step to improve her oxygenation and reduce mortality?
A Extracorporeal membrane oxygenation
B Prone positioning
C Inhaled nitric oxide
D High frequency oscillation ventilation
E Increase Pinsp
A
- B Prone positioning
○ The worsening hypoxaemia, new bilateral radiology infiltrates and low PaO2:FIO2 (P:F ratio) within one week of the onset of severe pneumonia suggests acute respiratory distress syndrome (ARDS).
○ ARDS is an acute, diffuse inflammatory lung syndrome that results in respiratory failure. The 1994 American-European Consensus Conference definition of ARDS has now been superseded by the 2012 Berlin Definition (Table 6.5).The cause of ARDS in this patient is severe pneumonia, which is a direct (or pulmonary) cause. Other direct causes of ARDS include aspiration, lung contusions and inhalational injury. Indirect (non-pulmonary) causes include sepsis, trauma, pancreatitis and burns.
○ The pathophysiology of ARDS is complex and involves the interplay of various body systems. A simplified view of this pathogenesis is presented here but this is an area of ongoing exploration - Exudative phase: Alveolar capillary membrane disruption resulting in leakage of protein rich fluid. Inflammatory cells (e.g. neutrophils) infiltration forming exudate.
- Proliferative phase: Proliferation of abnormal type II alveolar cells and inflammatory cells. There is a resultant dysfunction in surfactant with decreased pulmonary compliance.
- Fibrotic phase: Infiltration with fibroblasts replacing alveolar cells and ducts resulting in marked reduction in pulmonary compliance.
- Restoration phase: Slow and incomplete repair of pulmonary architecture.
The management of ARDS can be subdivided as below:
○ General (‘FLATHUGS’)
• Feeding – early nutrition
• Lines – as per catheter-related blood stream infection bundle
• Analagesia – adequate to maintain patient comfort, avoid under or oversedation
• Thromboprophylaxis – consider non-pharmacological and pharmacological
• Hydration – FACCT trial (2006) did not show a difference in fluid therapy guided by pulmonary artery flotation catheter versus central venous catheter
• Ulcer prophylaxis – according to local protocol and review daily
• Glycaemic control – no definitive evidence for tight glycemic control, aim for glucose <10mmol/L
• Sedation/Spontaneous breathing trial – consider daily sedation holds and breathing trials
○ Mechanical ventilation (based on ARDSnet mechanical ventilation protocol summary)
• Tidal volume 6mL/kg : ARMA study (2000) investigated 12mL/kg versus 6mL/kg in acute lung injury, lower tidal volumes resulted in improved outcomes
• Plateau pressures (Pplateau)<30 cmH20
• Permissive hypercapnia, aim for pH >7.3
• PEEP; ALVEOLI trial (2004) demonstrated an absence of data proving superiority of lower or higher PEEP for survival
○ ‘Rescue’ therapies for refractory hypoxaemia
° Prone position
-Prone positioning is based on the theory of recruiting areas of lung that are non-dependent in the supine position, leading to reduced ventilation-perfusion mismatching.
-There are additional benefits of improved secretion clearance and increased homogeneity of ventilation due to decreased lung deformation by mediastinal structures.
-There are potential adverse effects such as line or endotracheal tube displacement, reduced preload and functional restriction in cardiac contraction, pancreatitis, raised intracranial pressure and pressure related nerve damage.
-The process itself needs to be meticulously performed with adequate numbers of staff.
-PROSEVA (2013) was a landmark prospective, multicenter randomised control trial investigating early prone positioning in moderate to severe ARDS. It suggests benefit in terms of oxygenation and mortality. Previous studies appeared to show improved oxygenation, but no clear mortality benefit.
° Inhaled nitric oxide
-Nitric oxide (NO) is known to cause pulmonary vasodilatation and hence improve pulmonary blood flow.
-The inhaled route delivers NO selectively to ventilated lung units and hence improves oxygenation.
-Although inhaled nitric oxide improves oxygenation, there does not appear to be a mortality benefit.
° Extracorporeal membrane oxygenation
ECMO involves insertion of large cannulae into central vessels. It is similar to a simple cardiopulmonary bypass circuit. Blood leaves a central vessel and is pumped around a circuit through a membrane oxygenator to allow gas exchange, then returned to the patient via a central vessel. As oxygenation is predominantly achieved through the extracorporeal circuit, ultra low tidal volumes can be used to ventilate the patient minimising ventilator associated lung injury. ECMO requires systemic anticoagulation, carrying a risk of bleeding.
The CESAR trial (2009) was a multicentre randomised control trial investigating conventional management or referral to consideration for treatment by ECMO in severe potentially reversible respiratory failure. It concluded that referral to a tertiary respiratory centre for consideration of ECMO resulted in improved survival.
It is unclear what proportion of this benefit is attributed to optimum conventional ventilation in a tertiary referral centre.
○ High frequency oscillation ventilation
°HFOV works on the principle of high frequency (120–600 breaths/min) oscillation around a continuous high distending airway pressure. This results in lower tidal volumes, approximating at 3mL/kg. The OSCAR (2013) and OSCILLATE (2013) trials were two multicentre randomised control trials investigating the role of HFOV in ARDS. The failed to show a benefit and possibly showed harm with HFOV compared to conventional ventilation. At present, HFOV cannot be recommended in refractory hypoxemia secondary to ARDS in adults.
Of the options given in this question, based on current evidence the options for refractory hypoxaemia in ARDS appear to be prone positioning and ECMO. Given that ECMO remains controversial and requires a specialist centre, prone positioning
would be the most appropriate option in this patient. If an option was given for ‘referral to a tertiary respiratory centre’, that would also be appropriate.
○ Pharmacological
No proven mortality benefit but many have been trialed including surfactant replacement therapy, glucocorticoids, and β-adrenoceptor agonists
15
Q
- A 58-year-old man is brought in by ambulance following a house fire in an
enclosed area. He is confused with a GCS14/15.
On examination he has singed facial hair with voice changes. He is noted to have
partial thickness burns to the front of his torso, bilateral palms and palmar aspect
of upper limbs. His body weight is 70kg.
According to the Parkland formula his estimated fluid requirement in the first 8
hours following his burn is:
A 7560mL
B 4850mL
C 4620mL
D 3910mL
E. 780mL
A
- E 3780mL
This patient has sustained a significant thermal injury with evidence of inhalational injury.
○ Significant burns cause a profound systemic inflammatory response
syndrome and early aggressive management is paramount. Mortality from major burns is in the order of 10–20% with multiorgan failure and sepsis being leading causes.
○ Management should follow ALTS guidelines, especially where the mechanism is unknown. During the primary survey, early intubation is advised where airway compromise or significant inhalational injury is suspected. A rapid sequence induction is advised and intubation performed with an uncut cuffed endotracheal tube; ideally size 8 or larger to aid assessment of the airway via bronchoscopy.
○ Suxamethonium is considered safe in the first 24 hours following injury, an exaggerated hyperkalaemic response may occur after this time frame.
○ As part of the ‘Breathing’ assessment, carbon monoxide poisoning should be excluded.
○ In this case the confusion at presentation may be an early sign and an arterial blood gas should be done urgently.
○ Normal carbon monoxide levels can be up to 10% in smokers and a level greater than 20% raises the suspicion of significant inhalation injury and carbon monoxide poisoning. It is important to note that pulse oximetry overestimates SpO2 in the presence of carbon monoxide.
°Therefore the saturations of 100% in this case should be corroborated with arterial gas analysis via co-oximetry.
°High-flow oxygen decreases the half-life of carbon monoxide from 4 to 1 hours, and should be administered empirically until carboxyhaemoglobin (HbCO) levels are attained.
○ Another point of concern in this patient as part of the ‘Breathing’ assessment is the anterior torso burn.
°The chest wall should be examined for evidence of circumferential burn which may require early escharotomies.
°There is evidence to support that, where possible, these should be done in specialist burns centres.
°The focus of this question is on the assessment of circulation.
°As the burns surface area affects the management of fluid resuscitation, this must be calculated at this stage.
○ The body surface area (BSA) takes into account partial and full thickness burns and can be calculated using the ‘rule of 9s’. In this patient the burn to the anterior torso represents 18% BSA and bilateral palmar surfaces of upper limbs represent a further 9% (i.e. 2 x 4.5%); the total BSA is 27% (Figure 6.2).
○ The Parkland formula is widely used in the UK for calculation of fluid resuscitation with warmed crystalloid. It calculates the fluid requirement for the first 24 hours, from the time of injury, not the time of first presentation.
° Parkland formula for fluid requirement = 4mL/kg/% BSA
Fluid requirement in this patient = 4mL x 70kg x 27% = 7560mL
° According to the Parkland formula, half of this volume should be given in the first 8 hours making 3780mL correct.
°The Parkland formula is an estimation and fluid therapy should be guided by clinical and physiological parameters; there are detrimental consequences of both under and over resuscitation with fluids.
○ Management of the burn itself with early decontamination and ensuring
normothermia are important early considerations.
○ Antibiotic use should be reserved to where there is a strong clinical suspicion of active infection, there appears to be little evidence for prophylactic antibiotics.
° There are burns specific criteria for diagnosing sepsis which can guide clinical decision making.
° This patient represents a BSA greater than 10%, with burns to hands and a possible inhalational injury mandating discussion and transfer to a regional burns centre.
○ The British Burns Association criteria for referral to a burns centre are shown in Table 6.6 below.
28
Q
- An obese 45-year old patient has undergone an inguinal hernia repair under
general anaesthesia and a first generation supraglottic airway device was used. In
recovery, he becomes hypoxic and short of breath. You are suspecting a pulmonary
aspiration of gastric contents.
Which of the following lung segments is most likely to be contaminated following
an episode of aspiration during a general anaesthetic?
A Apical segments of the lower lobes
B Posterior basal segments of the lower lobes
C Lateral segment of the right middle lobe
D Lateral basal segments of the lower lobes
E Apical segments of the upper lobes
A
- A Apical segments of the lower lobes
Pulmonary aspiration of gastric contents is one of the most serious complications
after general anaesthesia. Acid aspiration may cause immediate lung tissue injury
and subsequent severe inflammatory response.
The anatomy of the lung lobes and bronchopulmonary tree affects zonal
contamination if aspiration of gastric contents happens.
The trachea is a 10–12cm long tube that connects the larynx to the lungs. In the first year
of life, the tracheal diameter is 3mm or less. The diameter then increases by about 1mm
per year until it reaches the adult size (around 20–25mm). The trachea comprises fifteen
to twenty C-shaped cartilaginous rings. These rings are incomplete posteriorly allowing
the trachea to collapse slightly during the passage of the food in the esophagus. It commences at the cricoid cartilage, level with the 6th cervical vertebra (C6), and
divides into right and left main bronchi at the level of the 5th thoracic vertebra (T5).
The right main bronchus (RMB) is about 3cm long. It is shorter, wider and aligned
more vertically than the left main bronchus. Therefore, tracheal intubation and
foreign body inhalation are more likely to happen in the right main bronchus instead
of the left. The RMB gives off to 10 bronchopulmonary segments (3 in the upper lobe,
2 in the middle lobe and 5 in the lower lobe). After around 2.5–3cm, the RMB gives off
the right upper lobe bronchus (RULB). The RULB is further divided into apical, anterior
and posterior segments after. Because the RULB arises early from the right main
bronchus, it is most at risk from occlusion by a right-sided double lumen tube.
The RMB then gives off the right middle lobe bronchus (RMLB). The RMLB is oriented
forwards and downwards and further divides into medial and lateral segments. The
RMB then continues on it’s downwards course as the right lower lobe bronchus
which gives off five segments (apical, medial basal, anterior basal, lateral basal and
posterior basal).
The left main bronchus (LMB) is around 5cm in length, and the anatomy is slightly
different from the right lung. After 5cm, the LMB gives off the left upper lobe
bronchus, which bifurcates into a superior division and a lingular division. The
superior division gives off the apical, posterior and anterior segments of the upper
lobe, while the lingular division gives off the superior and the inferior segments. The
left lower lobe bronchus (LLLB) differs from the right lower lobe bronchus in that it
gives four segments instead of five (apical, anterior basal, lateral basal and posterior
basal). The medial basal segment is usually small and arises with the anterior
segments. Technically, this means there are four rather than five bronchopulmonary
segments on the left (see Figure 6.3). Zonal contamination of the lung lobes and the bronchopulmonary segments after
aspirating is dependent on the patient’s position during the aspiration.
In a supine patient the apical segment of the lower lobe is more likely to be
contaminated because of the direct posterior orientation of the segment. If the
patient is prone, then aspiration is more likely to affect the right middle lobe or the
lingula because of their forward and downward projection. If in the upright sitting
position, the lateral or posterior basal segments of the lower lobes will be the site of
the problem, and in the lateral position, the upper lobes would be contaminated.
