CRQ Paper 9 Flashcards
Antonio, a 35-year-old man, presents for a laparoscopic cholecystectomy. He was diagnosed
with myotonic dystrophy 10 years ago.
a) Define myotonic dystrophy (1 mark), state the underlying pathophysiology (1 mark)and Mendelian inheritance. (1 mark)
• Myotonic dystrophy = multisystem genetic condition
• Myotonia (prolonged contraction delayed relaxation of the skeletal
muscles after voluntary stimulation)
• Dystrophy (progressive weakness and muscular atrophy)
○ There are two main types of myotonic dystrophy:
°DM1 due to mutation of the DMPK gene, and DM2 due to mutation of the CNBP gene.
• Pathophysiology: Locus for myotonic dystrophy is found on chromosome 19. The underlying pathophysiology is related to abnormal sodium or chloride channels, which results in the muscle being in an abnormal hyperexcitable state. This leads to repetitive action potentials and sustained muscle contraction, manifesting in the inability to relax.
• Inheritance: autosomal dominant
On pre-operative assessment, you notice that Antonio has the typical appearance of a patient with myotonic dystrophy – list two of these typical features. (2 marks)
• Frontal balding
• Characteristic weakness/wasting of:
– Facial muscles
– Levator palpebrae → bilateral Ptosis
– Muscles of mastication
– Sternocleidomastoid
**The characteristic facial appearance is described as a ‘myopathic’ or ‘hatchet’
appearance.
List the clinical features of myotonic dystrophy related to the respiratory system(2 marks), cardiovascular system (2 marks), central nervous system (1 mark), gastro-
intestinal system (1 mark) and endocrine system. (1 mark)
Respiratory:
• Respiratory muscle weakness
• Restrictive lung disease
• Poor cough
• Central and obstructive sleep apnoea
Cardiovascular:
• Cardiac conduction defects/heart block
• Cardiomyopathy/congestive heart failure
Central nervous system:
• Behavioural problems/cognitive decline
• Central hypersomnia
• Susceptibility to sedatives/analgesics
Gastrointestinal:
• Bulbar weakness/swallowing difficulty
• Delayed gastric emptying
Endocrine:
• Thyroid/adrenal impairment
• Testicular atrophy
• Type II diabetes mellitus
*Myotonic dystrophy is a multisystem disease with many implications for
anaesthetists.
The pre-operative echocardiogram demonstrated moderate left ventricular impairment and on further questioning, the patient’s exercise tolerance is limited by breathlessness at a distance of 400 m.
d) List four considerations related to the induction of anaesthesia specific to myotonic dystrophy. (4 marks)
• Bulbar palsy mandates intubation
• Risk of aspiration pneumonia is high – consider prokinetics,
antacids and rapid sequence induction
• Awake arterial line (given significant cardiovascular
disease)
• Judicious use of intravenous induction agent due to risk of cardiorespiratory depression
• Intubation and maintenance of anaesthesia can be achieved
without use of muscle relaxants
• Avoid suxamethonium – may trigger a myotonic contracture
• Avoid neuromuscular monitoring – may trigger myotonic contraction
e) List four important aspects of intra-operative management specific to myotonic dystro-
phy. (4 marks)
• Avoid hypothermia/shivering: may precipitate myotonic contracture
• Apply defibrillator/pacer pads: high risk of intra-operative arrhythmias
• Avoid nerve stimulator: may precipitate myotonic contraction
• Reversal of neuromuscular blockade: neostigmine may precipitate myotonic contraction
• Multimodal analgesia/judicious use of systemic opioids
• Blood glucose monitoring, as diabetes is common in myotonic dystrophy
Question 2.
Sukesh is a 73-year-old man who has an implanted pacemaker due to sick sinus syndrome. He is listed for an elective right hemi-colectomy for chronic diverticular disease.
a) The fundamental information about a pacemaker can be determined from its pace-maker code – what does each letter represent? (5 marks)
Letter 1: chamber paced
Letter 2: chamber sensed
Letter 3: mode of response/ response to sensing
Letter 4: programmability/rate modulation
Letter 5: multi-site function
*Implantable cardioverter defibrillators (ICDs) have a four-letter coding system:
• Letter 1 = chamber shocked
• Letter 2 = chamber paced during anti-tachycardia functions
• Letter 3 = method through which tachycardia is detected
• Letter 4 = chambers paced during anti-bradycardia functions
b) What is meant by the sensitivity of a pacemaker? (1 mark)
○ Minimum intrinsic atrial or ventricular electrical activity that issensed by the device (measured in mV)
○ If incorrectly set, the device may fail to detect intrinsic
atrial or ventricular activity.
○ This can result in :
• Over-pacing – firing despite intrinsic activity, which risks triggering malignant tachyarrhythmias.
• Under-sensing – which leads to a failure to pace despite there being no
intrinsic electrical activity
c) Aside from performing a pacemaker check, list three routine investigations you would request pre-operatively in a well patient with a cardiac implantable electronic device (CIED). (3 marks)
• ECG
○ ECG may demonstratepacing activity:
• Atrial pacing = spike followed by a P-wave
• Ventricular pacing = spike followed by a broad QRS complex.
• Chest X-ray
○ Chest X-ray shows the number and configuration of leads, and may also
demonstrate lead fracture or migration.
• Electrolytes
○ Electrolyte abnormalities (especially of potassium and magnesium) may precipitate arrhythmias and/or interfere with pacemaker capture.
d) In which three scenarios should re-programming of a CIED prior to anaesthesia/surgery be considered? (3 marks)
• Any patient with significant permanent pacemaker (PPM)
dependency
* If there is the potential for electromagnetic interference during the procedure, temporary re-programming of the PPM to an asynchronous (non-sensing) mode (e.g. A00,V00 or D00) may be required.
• Any PPM with rate-responsive functions
* Otherwise mechanical ventilation may stimulate excessive pacing rates.
• Any defibrillator function
* Electromagnetic interference during the procedure may trigger inappropriate defibrillation.
*If deactivation is not possible (e.g. emergency surgery), the application of a magnet may be considered.
e) Apart from monopolar or bipolar diathermy, state four devices or procedures that may produce electromagnetic interference of relevance to anaesthesia. (4 marks)
• Medical equipment incorporating wireless technology
• Mobile phones
Procedures:
• Radiofrequency ablation
• Insertion of tissue expanders
• Electroconvulsive therapy
• Transcutaneous electric nerve stimulation
• Radiation therapy
• Extracorporeal shock-wavem lithotripsy
*Diathermy should be avoided where possible; bipolar is considered safer
than monopolar. If monopolar diathermy isabsolutely necessary, short
1–2 s bursts with 10 s pauses should be used, and cutting current is safer than coagulation current.
The pathway from the diathermy to the ground electrode should not pass
near the CIED.
f) What is the commonest response of a permanent pacemaker (PPM) and an implantable cardioverter defibrillator (ICD) to the application of a magnet? (2 marks)
○ PPM: asynchronous mode/fixed rate pacing
** Less commonly, application of a magnet to a PPM initiates a diagnostics
function, followed by reversion to its programmed mode of pacing.
○ ICD: deactivation of shock and anti-tachycardia pacing functions
*Magnet application has no effect on bradycardia pacing of ICDs.
g) When applying external defibrillator pads, how far (in cm) from a CIED should the pads be placed? (1 mark)
○ 10–15 cm
°Anterior–posterior pad placement is usually preferred.
h) Aside from the risk of damage to the device itself, state one consequence of external defibrillation when the pads are positioned too closely to a CIED. (1 mark)
○ Damage to the myocardium as a consequence of excess
current flow
Question 3.
Alice, a 39-year-old woman, presents to hospital with severe epigastric pain. Serum lipase is raised, and the general surgeons suspect acute pancreatitis.
a) What are the functions of the pancreas? (2 marks)
• Exocrine function: secretion of pancreatic juice (bicarbonate, electrolytes and proteolytic enzymes)
• Endocrine function: secretion of insulin, glucagon, somatostatin
**Approximately 1500 mL of pancreatic juice is secreted per day
b) Aside from epigastric pain, list three presenting symptoms and signs of acute pancreatitis. (3 marks)
• Vomiting
• Pyrexia
• Abdominal distension
• Peritonism
The classical signs are a result of retroperitoneal haemorrhage tracking along tissue planes.
• Grey–Turner’s sign: discolouration of the flanks
• Cullen’s sign: peri-umbilical discolouration
• Fox’s sign: discolouration of the inguinal ligament
List five common causes of acute pancreatitis. (5 marks)
Obstructive:
• Gallstones
• Neoplasm/metastasis
• Chronic alcohol abuse
• Cystic fibrosis
Parenchymal:
• Trauma (blunt or penetrating)
• Following endoscopic retrograde cholangiopancreatography
Global:
• Hypoxia/systemic inflammatory response syndrome/sepsis
Toxic:
• Acute alcohol intake
• Drugs (azathioprine, non-steroidal anti-inflammatory drugs, diuretics)
• Hypothermia
• Hypercalcaemia
Other:
• Idiopathic
Not acceptable: scorpion bites, a rare cause of pancreatitis.
List four strong indicators for a critical care admission in a patient with severe acute pancreatitis (SAP). (4 marks)
General factors:
• Age 70 years or older
• Body mass index over 30 kg/m2
Ranson’s criteria is a scoring system to predict acute pancreatitis and
associated mortality. It is scored on admission and at 48 hours. The factors taken into account are
• White cell count
• Lactate dehydrogenase
• Aspartate transaminase
• Age > 55 years
• Glucose
• Serum calcium
• Haematocrit
• Arterial partial pressure of oxygen
• Urea
• Base deficit
• Fluid deficit
In which two situations may surgical intervention be helpful in managing SAP? (2 marks)
• Relieving biliary obstruction (e.g. ERCP)
• Removing infected intra- and extra-pancreatic necrosis
** Necrosectomy carries a high mortality.
When should enteral nutrition be commenced? (1 mark)
○ Within 72 hours
** According to NICE guideline 104.
○ If oral intake is not possible, early EN (within 48 h) shall be performed/initiated in critically ill adult patients rather than early PN Grade of recommendation: A e strong consensus (100% agreement)
** Espen 2019 guidelines
List three benefits of enteral nutrition over parenteral nutrition in SAP. (3 marks)
• Cheaper
• Safer
• Avoids need for central line
• Associated with fewer complications
• Better outcome overall
Question 4.
Miles is a 1-day-old neonate born at 38 weeks’ gestation with a birth weight of 2.0 kg. He was antenatally diagnosed with an isolated tracheoesophageal fistula (TOF) and is listed for urgent repair.
a) What is the incidence of tracheoesophageal fistula? (1 mark)
1 in 3000 live births (accept 1:3000 to 1:5000)
Tracheoesophageal fistulas are often associated with other congenital anomalies.
b) List three congenital anomalies associated with TOF. (3 marks)
• Cardiac
• Vertebral
• Anorectal
• Urogenital
• Laryngo-tracheal/palatal
• Skeletal/limb
• Gastrointestinal
• Renal
** V A C T R E L & C H A R G E
** TOF is associated with the following syndromes/chromosomal abnormalities:
• Holt–Oram syndrome : skeletal and cardiac
• DiGeorge syndrome : cardiac, cleft lip, small jaw, Intel disability, short
• Polysplenia : multi spleen, cardiac git
• Pierre–Robin syndrome : micrognathia, glosoptosis cleft palate
• Trisomy 18
• Trisomy 21
Single association
• Cardiac
• genitourinary
• Vertebral
•Arm
•GIT
•Palte/ lip cleft
c) State three important aspects of the induction and intubation specific to Miles’ condition. (3 marks) TOF
• Avoiding bag–mask ventilation
** Bag–mask ventilation is avoided to prevent problematic gastric inflation.
• Gaseous induction
• Suction/aspiration of upper oesophageal pouch
*Before induction of anaesthesia, the upper pouch tube is aspirated and
then removed.
• Topicalisation of airway
• Intubation under inhalational anaesthesia
**The tracheal tube is then positioned such that it occludes the TOF. Only once the tracheal tube has been correctly positioned is a muscle relaxant given.
• Maintenance of spontaneous ventilation
• Use of flexible bronchoscope to ensure positioning of tracheal tube beyond fistula site
*A rigid bronchoscopic examination of the trachea and main bronchi is
performed to confirm the position of the TOF.
• Use of muscle relaxant only once tracheal tube is correctly positioned
d) As a neonate, Miles will have a number of physiological differences from adults. For each of the body systems listed below, list three physiological differences of neonates when compared to adults. (9 marks)
Respiratory:
• Ventilation is primarily diaphragmatic
• Diaphragm easily splinted by abdominal organ content
• Lower functional residual capacity (FRC)
Neonatal airway differences
include
• Large head, short neck and a prominent occiput
• Large tongue
• High and anterior larynx, at the level of C3/4
• Rate dependent minute ventilation/unable to increase
tidal volume
• Closing volume > FRC/greater risk of airway collapse
• Respiratory muscles easily fatigued
• Lower number of alveoli
• Long, U-shaped epiglottis that flops posteriorly
• Neonates are obligate nasal breathers
• Airway is funnel shaped and narrowest at the level of the cricoid cartilage
Cardiovascular:
• Cardiac output is rate dependent/fixed cardiac output
• Less compliant myocardium
• Dominant parasympathetic tone/tendency towards bradycardia
• Higher blood volume per kg than adults
The ductus arteriosus
contracts in the first few
days of life and normally
fibroses within 2–4 weeks.
Foramen ovale closure
usually occurs in the
first day of life.
• Transitional circulation In response to hypoxia and
acidosis, reversion to the
transitional circulation may
occur in the first few weeks
after birth.
Haematological:
• Significant proportion of haemoglobin is of foetal HbF type
*At birth, HbF comprises 70%–90% of Hb. At 3 months, HbF comprises only 5%.
• Higher haematocrit/red cell mass
• Oxyhaemoglobin disassociation curve shifted to the left
• Deficient platelet function
• Deficiency of vitamin K dependent clotting factors
Typical newborn Hb is 180–200 g/L (haematocrit ~0.6).
List three reasons why neonates are more vulnerable to hypothermia. (3 marks)
• High surface area to volume 0ratio
• Minimal subcutaneous tissue
• Poorly developed shivering
• Poor vasoconstrictive capabilities
• Brown fat metabolism for thermogenesis requires significant amounts of oxygen
**Hypothermia in neonates causes respiratory depression, acidosis, decreased cardiac output, increases the duration of action of drugs, decreases platelet function and increases the risk of infection.
As a 1-day-old neonate, what is Miles’ 24-hour fluid maintenance requirement (in mL/kg)? (1 mark)
40–60 mL/kg
** 24-hour fluid requirements in the first days of life are dependent on weight and degree of prematurity. For full-term neonates ≥ 2.0 kg, the first 5 days’ fluid requirements are
• Day 1: 40–60 mL/kg/24hours
• Day 2: 60–90 mL/kg/24 hours
• Day 3: 80–100 mL/kg/ 24 hours
• Day 4: 100–120 mL/kg/24 hours
• Day 5: 120–150 mL/kg/24 hours
Question 5.
a) What are the primary functions of the placenta? (3 marks)
• Gas exchange
• Nutrient and waste transfer
• Transfer of immunity
• Hormone secretion
• Barrier function
** The placenta is the sole physical link between mother and foetus, with
a surface area of almost 15 m2
b) List the four main mechanisms of drug transfer across the placenta. (4 marks)
• Simple diffusion 4 E.g. midazolam, paracetamol
• Facilitated diffusion E.g. cephalosporins
• Active transport E.g. noradrenaline
• Pinocytosis
Question 6.
You have been asked to review Simona on the delivery suite. Following a low-risk pregnancy she went into spontaneous labour earlier in the day. She has been struggling with pain and has been transferred to the delivery suite for consideration of additional analgesia.
a) Describe the causes and pathways of visceral (3 marks) and somatic pain (3 marks) in labour.
○ Visceral pain
• Uterine contraction and cervical dilatation
• Unmyelinated C-fibres
• Travel with sympathetic fibres through uterine and cervical plexuses
• T10–L1 nerve roots
*chemical mediators involved include bradykinin, leukotrienes, prostaglandins, serotonin, substance P and lactic acid.
*Transmission to the hypothalamic and limbic systems accounts for the
emotional and autonomic responses associated with pain.
○Somatic pain
• Perineal, pelvic floor and vaginal stretching or injury
• A-δ fibres
• Via pudendal nerves
• S2–S4 nerve roots
• Also via ilioinguinal nerves/ genitofemoral nerves to L1/2
The epidural is continued following delivery to aid the suturing of a first-degree tear.
The midwife asks you to review Simona, as she is concerned about increasing leg weakness.
e) The table below outlines the Bromage scale of motor blockade. Complete the missingcriteria. (2 marks)
Grade 2: free movement of feet, just able to flex knees
Grade 3: free movement of feet, unable to flex knees
On assessment, Simona has a Bromage grade 4 leg weakness. Outline the steps you would take, including when you would request an urgent magnetic resonance imaging(MRI) scan. (2 marks)
Steps:
• Stop the infusion
• Reassess every 30 min
*An epidural haematoma should be suspected if leg strength does not improve.
• Earlier neurosurgical referral should be considered if you do not have access to MRI.
• An epidural haematoma must be evacuated within 8 hours of symptom onset for the best chance of recovery.
Request MRI scan:
• If no improvement in leg strength and 4 hours have elapsed since stopping the epidural
b) List three of Gurd’s minor criteria for a diagnosis of fat embolus. (3 marks)
• Pyrexia > 38.5°C
• Tachycardia > 110 beats/min
• Myocardial ischaemia
• Emboli present on fundoscopy
• A sudden inexplicable drop in haematocrit or platelets
• Increasing ESR
• Lipouria
• Fat globules present in the sputum
* At least one major and four minor of Gurd’s diagnostic criteria must be present for a diagnosis of fat embolism to be made. Alternative diagnostic methods are Lindeque’s criteria and Schonfeld’s criteria.
e) Describe the process through which the oesophageal Doppler probe determines cardiac output. (5 marks)
• Ultrasound waves generated by the transducer are reflected
back to it from moving red blood cells
○Doppler equation:
V ¼ Fdc 2Fo cos θ where F0 is the transmitted Doppler frequency, Fd is the
change in frequency (Doppler shift), V is the velocity of blood in the
descending thoracic aorta, θ is the beam angle and c is the speed of sound in tissue.
• The resultant Doppler shift is used to determine the velocity of blood in the descending thoracic aorta
• The cross-sectional surface area of the aorta is estimated from a nomogram based on the height, weight and age of the patient
• The velocity and the cross-sectional area are multiplied together to determine flow
• A correction factor is made to account for the fact that only ~70% of cardiac output transits the descending thoracic aorta
Complete the following table regarding the common variables produced by the
oesophageal Doppler probe. (4 marks)
Flow time corrected:
○ A low FTc may indicate hypovolaemia or increased afterload.
○ A high FTc may be seen in patients with low afterload.
• Definition: duration of flow during systole, corrected for heart rate
• Normal value: 330–360 ms
Peak velocity: Typical peak velocity values drop with age:
• 70–100 cm/s at 50 years
• 50–80 cm/s at 80 years
Peak velocity is used as a surrogate of left ventricular contractility.
• Definition: highest blood velocity detected during systole
• Normal value: 70–120 cm/s
b) The diagram below shows a normal POC coagulation trace. Explain what each label
represents physiologically. (4 marks)
i) Time taken from the start of the test to initial fibrin formation/concentration of soluble clotting factors in the plasma
ii) Rapidity of fibrin build up and cross linking/rate of clot formation maximum clot strength/total number and function of platelets and fibrinogen concentration
iv) Time to full clot lysis
iii) Strength of fibrin clot/
In the following table, indicate the most appropriate blood product or drug that should
be given to help correct the abnormality. (4 marks)
Increased (i)
Decreased (ii)
Decreased (iii)
Decreased (iv)
Increased (i) → give fresh frozen
plasma (FFP)
1 Normal ranges for the
parameters derived from
point-of-care coagulation
testing vary between
devices.
Decreased (ii) → give
cryoprecipitate/fibrinogen
1
Decreased (iii) → give platelet
transfusion
1
Decreased (iv) → give tranexamic
acid
1
