CRQ Paper 7 Flashcards
Question 1.
You are asked to review Catriona, a 28-year-old woman with myasthenia gravis who is listed
for cardiothoracic surgery.
a) List four symptoms and two signs of myasthenia gravis. (6 marks)
Symptoms:
Symptoms:
• Diplopia
* Due to weakness of extraocular muscles.
• Dysphagia
**Due to weakness of palatal/
• Dysarthria/nasal speech pharyngeal muscles.
• Inability to smile/close mouth/impaired facial expression
• Difficulty chewing *Weakness of muscles of mastication.
• Limb weakness
• Dyspnoea
Signs:
• Fatigable weakness
• Ptosis Weakness of levator palpebrae superioris.
• External ophthalmoplegia/
strabismus (squint)
*Weakness of extraocular muscles.
Question 1.
You are asked to review Catriona, a 28-year-old woman with myasthenia gravis who is listed
for cardiothoracic surgery.
:b) What is the surgical procedure most likely to be? (1 mark)
Thymectomy (excision of thymoma)
c) What are the two common proteins targeted by autoantibodies in myasthenia gravis?
(2 marks)
○ Nicotinic acetylcholine receptor
○ Muscle-specific kinase (MuSK)
d) Which subtype of immunoglobulin is produced? (1 mark)
Immunoglobin-G (IgG) **NB it must be IgG because autoantibodies can cross the placenta, resulting in congenital myasthenia gravis
e) List three health conditions associated with myasthenia gravis. (3 marks)
• Autoimmune thyroiditis
• Grave’s disease
• Rheumatoid arthritis
• Type 1 diabetes mellitus
• Scleroderma
• Vitiligo
• Polymyositis/dermatomyositis
• Systemic lupus erythematosus
• Pernicious anaemia
**NB all these diseases are
autoimmune in nature.
f) List three classes of drug that the patient might be prescribed pre-operatively to manage the symptoms of myasthenia gravis. (3 marks)
○ Anticholinesterases E.g. pyridostigmine.
○ Immunosuppression E.g. prednisolone, azathioprine, cyclosporine.
○ Intravenous immunoglobulin or plasma exchange
Catriona is concerned about her risk of requiring post-operative ventilation.
g) Describe two methods you would consider to achieve intubation following induction of
general anaesthesia that could reduce this risk. (2 marks)
• Deep inhalational anaesthesia alone
• Reduced dose of non-
depolarising muscle relaxant
**~30% of normal dose of atracurium, vecuronium or rocuronium
• Increased dose of
suxamethonium
• Remifentanil infusion/total intravenous anaesthesia
Due to a miscommunication, the patient stops taking her medication pre-operatively and presents to the Emergency Department with features of a myasthenic crisis.
h) List two such features. (2 marks)
• Inability to support head
** Chin falls onto chest
• Absent gag reflex: risk of aspiration of oral secretions
• Poor or absent cough
**Accumulation of secretions
• Respiratory distress/use of accessory muscles/paradoxical abdominal breathing/ventilatory failure
Question 2.
Mani is a 64-year-old man with a new diagnosis of lung adenocarcinoma. He is listed for
a lobectomy of the right lung. He has a background history of chronic obstructive pulmon-
ary disease.
a) Complete the following table regarding types of double-lumen tubes. (3 marks)
White:
Right
Yes
Robertshaw:
Both
No
Carlens:
Left
Yes
**The choice of double-lumen endotracheal tube (DLETT) size is based on patient height, gender and size of
main stem bronchi. There is considerable variation in bronchial dimensions in general, smaller tube sizes are best for females since the diameter of their cricoid cartilage is smaller than that of males.
b) State two absolute indications for one-lung ventilation with a relevant example for each.
(2 marks)
Controlling distribution of ventilation, e.g. tracheobronchial tree injury/bronchopleural fistula
• Avoiding cross-contamination of
contralateral lung, e.g.
endobronchial haemorrhage/
abscess with empyema/
bronchiectasis/lavage
1 Surgical access is
technically only a relative indication for one-lung ventilation!
c) Mani has had a series of investigations prior to his surgery. What is the FEV1 required to
safely proceed with a lobectomy? (1 mark)
> 1.5 L
For pneumonectomy, an
FEV1 > 2 L is usually
required
Unfortunately, Mani’s pulmonary function tests demonstrate that he does not have an adequate FEV1 to be listed for surgery. He therefore undergoes a calculation of his predicted post-operative FEV1 and predicted post-operative diffusion capacity.
d) What predicted percentage value for these tests would be considered acceptable to proceed with surgery? (1 mark)
> 40% (accept 40%–50%)
** V̇ /Q̇ scanning improves the accuracy of predicted post-operative ventilatory parameters as the pre- operative function of each lung may
Mani’s post-operative predicted ventilatory parameters are not adequate, and he is referred for cardiopulmonary exercise testing (CPET).
e) Which CPET parameter is primarily used for determining fitness for thoracic surgery
(1 mark), and what value is required to be deemed suitable for surgery (1 mark), albeit as
a high-risk candidate?
15 mL/kg/min
Maximal oxygen consumption
(accept V̇ O2 max or V̇ O2 peak)
**Recent literature suggests that patients with a pre-operative V̇ O2 max >20 mL/kg/min are not at increased
risk of complications or
death; those with a V̇ O2 max <10 mL/kg/min have a very high risk of post-operative complications.
f) Hypoxaemia commonly occurs during one-lung ventilation. State three factors which impair hypoxic pulmonary vasoconstriction in the non-ventilated lung. (3 marks)
Factors that increase pulmonary artery pressure:
• Atelectasis in the ventilated lung
• Application of positive end-expiratory pressure (PEEP) in ventilated lung
• Presence of intrinsic PEEP in the ventilated lung (e.g. asthma)
• Diversion of blood to the non- ventilated lung (e.g. use of vasopressors)
Others:
• Failure of lung collapse
• Use of vasodilators (e.g. inhalational anaesthesia, nitrates, calcium channel antagonists)
• Turning to supine position
During the surgery, Mani’s oxygen saturation falls below 88%. You have checked the supply of gas and the position of the double-lumen tube, both of which are adequate. No secretions were present on suctioning of the ventilated lung.
g) List six steps that you would now take to manage the hypoxaemia. (6 marks)
• Administer 100% oxygen
• Administer oxygen to the non-ventilated lung
• Administer continuous positive airway pressure (CPAP) to the non-ventilated lung
• Apply PEEP to the dependent lung
• Ensure adequate haemoglobin/cardiac output
• Revert to two lung ventilation
• Nitric oxide
• Consider high frequency jet ventilation
**Clamping the non-dependent pulmonary artery is not an option here, as
Mani is undergoing a lobectomy – not a pneumonectomy.
h) List one potential advantage and one potential disadvantage of applying positive end-expiratory pressure (PEEP) to the ventilated lung. (2 marks)
Advantage:
• May recruit collapsed alveoli 1
Disadvantage:
• May exacerbate shunt by
impeding pulmonary blood flow
to dependent lung
Any 1
• May reduce venous return with
reduction in cardiac output
Question 3.
Ajmal is a 47-year-old man who is referred to you by the medical team for consideration of
critical care. He is known to have pulmonary hypertension (PH) and has presented with
increasing exertional dyspnoea and pre-syncopal episodes precipitated by acute lower limb
cellulitis.
a) What is the definition of PH? (1 mark)
Elevated mean pulmonary arterial
pressure greater than or equal to
25 mmHg at rest
1 PH is the most common
cause of right ventricular
failure.
The World Health Organization (WHO) has classified PH into five categories.
b) List the five categories (one category has been completed for you). (4 marks)
1. Pulmonary arterial hypertension/idiopathic pulmonary hypertension
• Group 2: due to left heart disease
• Group 3: due to lung disease or
chronic hypoxia
• Group 4: caused by pulmonary
thromboemboli/other pulmonary
artery obstructions
• Group 5: due to haematological
disorders, systemic disease and
metabolic disorders
4 Group 1 contains many
subgroups, including
familial, drug induced and
those associated with
medical conditions.
Group 2 includes LV
systolic or diastolic
dysfunction, valvular heart
disease and congenital
heart defects.
Group 3 includes chronic
obstructive pulmonary
disease, obstructive sleep
apnoea and high-altitude
exposure.
Group 4 includes other
pulmonary artery
obstructions e.g. arteritis,
stenosis, angiosarcoma.
Group 5 includes
haematological disorders
(e.g. haemolysis), systemic
disorders (e.g. sarcoidosis)
and metabolic disorders
(e.g. Gaucher’s disease).
c) List four clinical signs of PH which you may identify when examining Ajmal.
(4 marks)
• Raised jugular venous pressure
• Peripheral oedema
• Loud P2
• Right ventricular heave
• Hepatomegaly
• Irregular heart rate
• Pansystolic murmur (tricuspid area)
**The most common symptoms of PH are exertional shortness of breath, peripheral oedema and pre-syncope.
d) List three ECG findings you may see with right ventricular hypertrophy. (3 marks)
• Right axis deviation
• Dominant R wave in V1
• Dominant S wave in V6
• QRS < 120 ms
• P pulmonale
• Right ventricular strain pattern –
ST depression or T-wave
inversion in right precordial or
inferior leads
• Right bundle branch block
Any 3 Other investigations: chest
X-ray may show
cardiomegaly and enlarged
pulmonary arteries.
Transthoracic
echocardiogram: systolic
pulmonary artery pressure
> 36 mmHg is suggestive
of PH.
After discussion with your supervising consultant, Ajmal is admitted to the critical care unit.
f) Describe the principles of critical care management in the acutely unwell patient with
pulmonary arterial hypertension. (5 marks)
Tadalafil = phosphodiesterase
V inhibitor
1 Another phosphodiesterase
V inhibitor is sildenafil.
Both drugs are contra-
indicated with systemic
nitrates due to the risk of
significant systemic
hypotension.
→ Increases c-GMP levels 1
→ NO is a potent vasodilator which
acts via c-GMP
Question 4.
Sam is a 5-year-old boy weighing 20 kg who had a tonsillectomy earlier today. He is bleeding from the operative site and needs to return to theatre for haemostasis.
a) Define primary and secondary post-tonsillectomy bleeding. (2 marks)
Primary:Occurring within 24 hours of surgery
**The incidence of bleeding following tonsillectomy is 0.5%–2% depending upon the surgical technique
Secondary:Bleeding after 24 hours and up to 28 days post-surgery
The risk of haemorrhage increases with age, and is higher in males.
A ‘hot’ surgical technique for both dissection and haemostasis (diathermy or radiofrequency coblation) has three times the risk of post-operative
haemorrhage compared to traditional cold steel tonsillectomy.
b) List two arteries that supply blood to the tonsils. (2 marks)
• Ascending pharyngeal artery
• Lesser palatine artery
• Facial artery
• Dorsal lingual artery
• Ascending palatine artery
• External carotid artery
• Tonsillar artery
Venous return is to the
plexus around the tonsillar
capsule, the lingual vein
and the pharyngeal plexus.
Post-tonsillectomy bleeding
is usually venous in origin.
Sam’s previous anaesthetic chart reveals that he had a Cormack and Lehane grade 1 laryngoscopy.
d). Give two reasons why you would anticipate a potentially difficult intubation on return to theatre. (2 marks
• Aspiration risk (of regurgitated swallowed blood or post-operative oral intake)
• Blood obscuring the laryngoscopic view
• Oedema from previous airway instrumentation and surgery
Sam has had a capillary blood gas which shows a haemoglobin of 89 g/L. You note that he is
tachycardic and tachypnoeic. You opt to resuscitate him prior to anaesthesia.
e) State the type of fluid and the volume that you would give for initial resuscitation.
(2 marks)
Fluid: (accept any isotonic crystalloid)
Sam has no
contraindications to
receiving a 20 mL/kg bolus, i.e. no history of cardiac disease, renal disease or trauma. His haemoglobin is not sufficiently low to
warrant transfusion at
present.
• 0.9% Saline
• Hartmann’s
• Plasmalyte 148 Volume: 1
400 mL (20 mL/kg)
f) There are two commonly described techniques for inducing anaesthesia in patients with post-tonsillectomy bleeding. Give both techniques, along with one advantage and one
disadvantage for each. (6 marks)
Technique: 1
Inhalational induction in the head
down, lateral position (must state
head down or lateral positioning)
Advantages: Any 1
• Drain blood from the airway by
means of gravity
• Allows for pre-oxygenation
during induction
Disadvantages: Any 1
• Inhalational induction in an
anxious child may be difficult
• Deep inhalational anaesthesia
risks cardiovascular instability in
a potentially hypovolaemic child
• Risk of laryngospasm/aspiration
• Intubation in the lateral position
is unfamiliar to most
anaesthetists
Technique: 1
Rapid sequence induction
Advantages: Any 1
• Reduced risk of aspiration
• Use of muscle relaxants helps
produce ideal conditions for
intubation
• Intravenous induction is less
stressful for the child
Disadvantages: Any 1
• Difficult to adequately pre-
oxygenate an anxious child who
is bleeding
• Facemask ventilation following
muscle relaxant administration
may inflate the stomach,
increasing the risk of pulmonary
aspiration
• Potential for hypoxaemia if
intubation is difficult (absence of
spontaneous ventilation)
h) What is the minimum length of time that Sam needs to remain in hospital following his
return to theatre for bleeding tonsils? (1 mark)
24 hours 1 Due to risk of rebleed.
Question 5.
Kiran is a 27-year-old woman who is 32 weeks into her second pregnancy. She presents to
the maternity unit with abdominal pain and an estimated blood loss of 500 mL per vaginum.
a) List five potential maternal complications of antepartum haemorrhage (APH). (5 marks)
• Anaemia
• Infection
• Maternal shock
• Renal tubular necrosis
• Coagulopathy
• Post-partum haemorrhage (PPH)
• Prolonged hospital stay
• Psychological sequelae
• Complications of transfusion
• Sheehan’s syndrome
• Death
**APH is defined as bleeding from or into the genital tract from 24 weeks until delivery of the baby.
*Causes of APH are placental abruption (one-third), placenta praevia
(one-third) and ‘other’ (one-third).
b) List five risk factors for placental abruption. (5 marks)
Smoking
• Cocaine use
• Amphetamine use
• Previous abruption
• Previous uterine surgery/
previous caesarean section
• Pre-eclampsia/hypertension
• Extremes of maternal age:
<25 years or >35 years
• Multiparity
• Thrombophilia
• Trauma
Any 5 Women who present with
placental abruption
alongside significant foetal
Kiran continues to bleed, and her clotting profile shows significant abnormalities.
c) Define disseminated intravascular coagulation (DIC). (2 marks)
• Systemic activation of
coagulation leading to
consumption of clotting factors
1 Widespread activation of
coagulation leads to
consumption of platelets
and coagulation factors,
increasing haemorrhage
risk. Thrombotic
complications result from
intravascular fibrin
formation.
d) Apart from haemorrhage, list five other obstetric causes of DIC. (5 marks)
• Intrauterine death
• Amniotic fluid embolus
• Sepsis (obstetric source)
• Pre-eclampsia
• Retained products of
conception
• Induced abortion
• Acute fatty liver
Non-obstetric causes include sepsis and severe infections, malignancy,
vascular disorders and severe immunological reactions.
e) With reference to the relevant landmarks, describe where you would inject local
anaesthesia during performance of a fascia iliaca block. (4 marks)
• Draw line between anterior
superior iliac spine and pubic
tubercle
• Insertion point 1 cm caudal to
the junction of lateral and
middle thirds of this line
• Palpate femoral artery to ensure it is medial and away from site of insertion
• Insert needle at 60° cranial angle
• ‘Two-pop’ technique using blunt needle
**The two ‘pops’ refer to passing through the fascia lata and the fascia iliaca.
Traversing these fascial layers is more pronounced when using a blunt needle.
The ultrasound-guided approach has been found to be superior to the landmark-guided approach.
Question 7.
Ashraf is an 18-year-old man who presents to the Emergency Department 4 hours following
a suicide attempt. He intentionally took 30 paracetamol tablets over the course of 2 hours.
a) Explain how an overdose of paracetamol causes hepatic damage. (4 marks)
• Paracetamol is metabolised bythe liver
** Toxicity is dose dependent:
• <150 mg/kg taken over a period of > 1 hour is unlikely to cause toxicity
• >12 g has the potential to be fatal
• A minor metabolite is N-acetyl-p-benzoquinoneimine (NAPQI) which is toxic/reactive
• Glutathione normally conjugates NAPQI
** NAPQI binds to cellular proteins causing hepatocyte
damage.
• In overdose, glutathione stores are depleted
**N-acetyl cysteine (NAC) is
a precursor of glutathione
and replenishes stores.
Ashraf becomes unwell 48 hours later and is being considered for liver transplantation.f) Name the prediction model most commonly used to identify liver transplant candidates
in paracetamol hepatotoxicity (1 mark), and list three of the criteria. (3 marks)
Prediction model: King’s College criteria
**King’s College criteria are the most widely used in
Criteria:
• pH < 7.3 Liver transplantation is considered if the pH is less than 7.3, or all three of the
remaining criteria are present within a 24-hour
period.
• INR > 6 (accept PT > 100 s)
• Creatinine > 300 µmol/L
• Encephalopathy grade 3 or 4
Rhodri takes metformin, gliclazide and dapagliflozin. He is on the morning surgical list.
c) Complete the following table regarding the perioperative management of these drugs
specific to day-case procedures. (6 marks)
○Metformin
Mechanism:
• Delays gut glucose uptake
• Increases peripheral insulin sensitivity
• Inhibits gluconeogenesis
Dose day of surgery: normal,
○ Gliclazide: Sulphonyurea
Mechanism:
• Displaces insulin from β-cells
• Reduces peripheral insulin resistance
Dose day of surgery: omit if morning op and if taken twice give evening doseif eating. For PM surgery do not take
Dose
○ Dapagliflozin SGLT 2 Inhibitors
Mechanism:
• Sodium–glucose co-transporter type 2 (SGLT2) inhibitor
• Increases urinary glucose excretion
Dose day of surgery: halve (accept omit)
2021 guidelines = omit day before and day of surgery regardless of timing of op
**Dose alterations may be needed for the following oral diabetic medication
classes:
• Meglitinides (e.g. repaglinide,nateglinide)
• Sulphonylureas (e.g.glibenclamide, gliclazide, glipizide)
• SGLT-2 inhibitors (e.g.dapagliflozin, canagliflozin)
• Acarbose
• On rare occasions, SGLT2 in hibitors have been associated with ketoacidosis in fasting patients, therefore the 2015 AAGBI guidelines recommend halving the dose on the day of surgery.
Subsequently, omission of SGLT2 has been recommended.
b) What is the most likely cause for his abnormal observations? (1 mark)
Haemorrhage
**A heart rate of 125 beats/min and systolic blood pressure of 92 mmHg
suggest class III shock.
Question 12.
Vivek, a 39-year-old man, is listed for insertion of a vagal nerve stimulator.
a) List the three nuclei of the vagus nerve. (3 marks)
• Dorsal nucleus of the vagus
** Sends parasympathetic output to the viscera,especially the intestine.
• Nucleus ambiguus
** Motor fibres to pharynx, soft palate and larynx, and parasympathetic output to the heart.
• Nucleus tractus solitarius
**Receives sensory information from viscera.
d) List six branches of the vagus nerve. (6 marks)
• Small meningeal nerve
• Auricular nerve
• Pharyngeal nerve
• Carotid body branches
• Superior laryngeal nerve
• Recurrent laryngeal nerve
• Superior and inferior cardiac
branches
• Anterior and posterior
bronchial branches
• Anterior vagal trunk
• Posterior vagal trunk
