tissue interfaces.
29 Answer: E Three twitches on TOF response.
Depth of neuromuscular blockade can be measured using several modes of stimulation such as single twitch, train-of-four, double-burst stimulation, tetanic stimulation and post-tetanic count. Train-of-four is more commonly used both during maintenance and recovery of anaesthesia. It involves stimulating the nerve with four supra-maximal twitch stimuli with a frequency of 2Hz. TOF can be repeated every 10 seconds. If non- depolarizing blockade is present, there will be a loss of twitch height and number, which will indicate the degree of blockade. The presence of no twitches in the TOF response indicates deep muscle blockade and is ideal for intubation. At least three twitches should be present prior to administration of reversal agent. To ensure satisfactory recovery from neuromuscular blockade, the TOF ratio should be >0.9 at extubation.
Further reading
1. Ali HH, Savarese JJ, et al. Twitch, tetanus and train-of-four as indices of recovery from nondepolarizing neuromuscular blockade. Anaesthesiology 2003; 98(5): 1278-80.
2. McGrath CD, Hunter JF. Monitoring of neuromuscular block. British Journal of Anaesthesia CEACCP 2006; 6: 7-12.
30
Answer: E. The dilutional effect of rebreathing.
This is a common clinical observation during low-flow anaesthesia. The dilutional effect of rebreathing contributes to the difference between the dial setting and inspired concentration. The dial setting on the vaporiser reflects the concentration delivered to the breathing system. The inspired concentration detected by the agent analyser reflects the concentration of anaesthetic agent at the tracheal tube end of the breathing system. In low-flow anaesthesia, exhaled gases are recirculated after eliminating the CO2 through the CO2 absorber (sodalime or baralime). The minute volume is composed of the fresh gas flow (FGF) and the recirculated and rebreathed exhaled gases. As FGF is decreased, the exhaled patient gases contribute a more significant portion of the minute volume. In this scenario, anaesthesia is maintained with a low FGF of 0.3L/minute; the
most likely reason for the difference is a dilution effect of the rebreathed gases.
Malfunction of the vaporiser can deliver a lower concentration of anesthetic and malfunction of the agent analyser can also account for the inaccuracy in the measured concentration. Increased uptake of volatile agent by the patient accounts for the increased difference between the inspired and expired concentration rather than increased difference between the dial setting and inspired concentration.
Further reading
1. Hendrickx JFA, Coddens J, Callebaut F, et al. Effect of N2O on sevoflurane vaporizer settings during minimal- and low-flow anesthesia. Anesthesiology 2002; 97: 400-4.
2. Philiph JH. The dilution effect of rebreathing. www.gehealthcare.com/ usen/anesthesia/docs/DilutionEffect.
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1
A 36-year-old primigravida, with a history of polyhydramnios delivers a baby at 34 weeks’ gestation. The midwife notices that the baby chokes and persistently coughs on attempted feeding. Which of the following anatomical tracheo-oesophageal fistulae is most likely to be the cause for these symptoms in the neonate?a. The upper segment ends as a blind pouch and the lower segment communicates with the trachea.
b. The upper segment communicates with the trachea and the lower segment ends as a blind pouch.
c. Both upper and lower segments end as blind pouches.
d. The upper segment communicates with the lower part of the trachea and the lower segment arises from the carina.
e. The two segments join together and communicate with the lower part of the trachea.
2
A 60-year-old female patient underwent a laparotomy with extensive small bowel resection. She has now developed an entero-cutaneous fistula. As a result she is on parenteral nutrition via a central venous catheter inserted through the internal jugular vein. Which of the following complications is most likely in this patient?a. Venous thrombosis. b. Symptomatic liver disease. c. Osteoporosis. d. Osteomalacia. e. Catheter infection.
Set 6 questions
Set
6
3
You are performing spinal anaesthesia on a 65-year-old male patient in the right lateral position for an inguinal hernia repair. As you advance the spinal needle, he complains of sharp stabbing pain in his right leg. The next most appropriate step in the management is: a. Abandon the procedure.b. Advance the needle further inwards in the same direction. c. Withdraw the needle and redirect more medially.
d. Withdraw the needle and direct laterally. e. Inject more local anaesthetic.
4
During exercise, blood flow to muscles increases significantly. Which one of the following is most likely to contribute to the initial rise in skeletal muscle blood flow at the beginning of exercise? a. Vasodilatation of blood vessels due to local metabolites. b. Increased sympathetic discharge to peripheral vessels. c. Increase in cardiac output.d. Increase in arterial blood pressure. e. Increase in heart rate.
5
You have administered 2L of colloid solution to an anaesthetised 43- year-old healthy male. Which one of the following blood vessels will best accommodate the change in circulatory volume?a. Systemic arteries. b. Systemic veins. c. Systemic capillaries. d. Pulmonary capillaries. e. Pulmonary veins.
6
A 20-year-old male patient is scheduled for an emergency appendicectomy. There is a family history of suxamethonium apnoea. When he was investigated for suxamethonium apnoea, blood tests revealed a dibucaine number of 20 and a genotype of Ea: Ea(homozygous atypical). Which of the following muscle relaxants is most suitable for rapid sequence induction in this patient?
a. Suxamethonium 1mg/kg. b. Rocuronium 0.9mg/kg. c. Rocuronium 0.3mg/kg. d. Rocuronium 0.6mg/kg. e. Rocuronium 0.5mg/kg.
7
A 45-year-old female patient is scheduled for extraction of one pre- molar tooth under local anaesthesia and sedation. She has hypertension which is treated with atenolol 50mg. After establishing baseline monitoring, fentanyl 75µg was administered in aliquots every 2-3 minutes. She also received 0.5mg of midazolam. Subsequently, the surgeon infiltrated 3ml of 3% prilocaine with felypressin. At this stage she required another 50µg of fentanyl intravenously. She became very rigid and complained of difficulty in breathing with tightness in her chest. Which of the following drugs is the most likely cause for this?a. Midazolam. b. Felypressin. c. Prilocaine. d. Fentanyl. e. Atenolol.
8
Inhalational anaesthetic agents affect systemic vascular resistance (SVR). Which one of the following agents has the least effect on SVR? a. Isoflurane. b. Sevoflurane. c. Desflurane. d. Enflurane. e. Halothane. 1719
Protein binding of a local anaesthetic determines its duration of action. Which one of the following sequences correctly indicates the level of protein binding of local anaesthetics in a decreasing order? a. Procaine > bupivacaine > lignocaine > prilocaine.b. Bupivacaine > lignocaine > prilocaine > procaine. c. Prilocaine > bupivacaine > lignocaine > prilocaine. d. Lignocaine > bupivacaine > prilocaine > procaine. e. Bupivacaine > lignocaine > procaine > prilocaine.
10
Which one of the following mechanisms best explains the reason for using sodium nitrite in the management of cyanide toxicity?a. It increases methaemoglobinaemia.
b. It produces increased hepatic sulphydryl groups. c. It increases the conversion to cyanocobalamin. d. It displaces cyanide from haemoglobin.
e. It enhances oxidative phosphorylation.
11
The graph below describes the relationship between true blood pressure and measured blood pressure through an invasive arterial cannula connected to a transducer system (Figure 1). Line A represents the ideal response. Lines B and C represent false readings due to a calibration error. The error represented by line C can best be corrected by:a. Zeroing the system.
b. Replacing the transducer cable. c. Performing a three-point calibration. d. Performing a two-point calibration. e. Performing a square wave test.
12
You are planning to perform inhalational induction using sevoflurane on an adult patient weighing 68kg. Which of the following is the most efficient breathing system for this purpose?a. Mapleson D system. b. Mapleson A system. c. Mapleson B system. d. Mapleson C System. e. The Bain system.
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Figure 1.
The relationship between true blood pressure and measured blood pressure through an invasive arterial cannula connected to a transducer system.13
A 45-year-old female presents for a laparoscopic cholecystectomy. General anaesthesia using intravenous induction followed by maintenance with volatile agents is planned. In view of avoiding awareness, which of the following monitors is most useful? a. Isolated forearm technique.b. Bispectral index.
c. Minimum alveolar concentration (MAC) of volatile anaesthetic agent. d. Lower oesophageal contractility.
e. Late cortical evoked responses.
14
You are planning to evaluate three fluid warmers in a laboratory setting. You need to accurately monitor the temperature of the fluid and would like to detect a very small difference of up to 0.001°C. Which of the following temperature measurement devices is most suitable for this research?a. Mercury thermometer. b. Infrared thermometer.
c. Platinum resistance thermometer. d. Thermistor.
e. Bourdon gauge thermometer.
15
You are planning to undertake research to evaluate the intubating conditions of a new non-depolarising muscle relaxant. Which of the following peripheral muscle and nerve combinations is most appropriate for this purpose?a. Ulnar nerve and adductor pollicis. b. Facial nerve and orbicularis occuli. c. Tibial nerve and abductor hallucis.
d. Common peroneal nerve (lateral popliteal) and extensor hallucis longus.
e. Facial nerve and orbicularis oris.
16
Airway resistance varies along different parts of the respiratory tract. In which of the following areas is the airway resistance greatest? a. Trachea.b. Terminal bronchioles. c. Medium-sized bronchi. d. Alveoli.
e. Alveolar ducts.
17
A 28-year-old male is admitted to the ICU after taking a drug overdose. He is comatose and about to be intubated. His PaCO2was 5.3kPa ten minutes ago, but you discover it is now 9kPa. Which one of the following statements is most likely to be true about this patient?
a. The pH of his CSF is likely to fall more slowly than the pH of his blood.
b. The pH of his blood is likely to fall more slowly than the pH of his CSF.
c. The pH of his blood and CSF will not change because he will rapidly eliminate bicarbonate in the urine in response to the rise in PaCO2. d. The pH of his blood will fall immediately without any change in the
pH of his CSF.
e. The pH of his blood will fall and the pH of his CSF will rise over the next 24 hours.
18
A patient ingests antifreeze and needs to eliminate the ingested acid. Renal elimination of the protons of this excess acid is primarily accomplished by which of the following mechanisms?a. Increased urinary ammonium excretion. b. Increased urinary excretion of phosphates. c. Hyperventilation.
d. Increased urinary free hydrogen ion concentration. e. Increased urinary sulfate excretion.
19
A number of conditions affect the structure or concentration of haemoglobin in blood. Which one of the following conditions is most likely to be associated with a reduced level but normal structure of haemoglobin in the blood?a. Thalassaemia.
b. Anaemia due to chronic blood loss. c. Blood transfusion reaction.
d. Haemolytic anaemia. e. Sickle cell anaemia.
20
A 29-year-old female has puffy skin, a hoarse voice and complains of an intolerance to cold. Her plasma thyroid stimulating hormone (TSH) level is low and this increases significantly if she is given thyrotropin releasing hormone (TRH). Which one of the following is the most likely diagnosis in this woman?a. Hypothyroidism due a primary abnormality in the pituitary gland. b. Hyperthyroidism due to a thyroid tumour.
c. Hypothyroidism due to a thyroid tumour.
d. Hyperthyroidism due to a primary abnormality in the hypothalamus. e. Hypothyroidism due to a primary abnormality in the hypothalamus.
21
A 78-year-old male patient with arthritis, hypertension and congestive cardiac failure is scheduled to have an open prostatectomy. He is on bendrofluazide 5mg o.d., and amiloride 20mg o.d. He is seen in the pre-operative assessment clinic and routine blood tests have been ordered. The most likely abnormal biochemical finding in the blood is:a. Hyponatraemia. b. Hyperuricaemia. c. Hyperphosphataemia. d. Hypomagnesaemia. e. Hypercalcaemia. 176
22
A 64-year-old male is listed for excision of a ganglion on the wrist. He suffers from rheumatoid arthritis and asthma. He takes his salbutamol inhaler 200µg t.d.s. and prednisolone 15mg once a day. He has been on these drugs for over 2 years. Which of the following is the most appropriate with regard to his peri-operative management?a. Prednisolone 15mg on the morning of surgery. b. Hydrocortisone 100mg at induction.
c. Hydrocortisone 50mg at induction and 50mg 6 hours postoperatively.
d. Prednisolone 15mg on the morning of surgery and hydrocortisone 50mg at induction.
e. Hydrocortisone 100mg at induction and 50mg 6 hours postoperatively.
23
A 62-year-old male patient with end-stage liver disease and cirrhosis is scheduled for an emergency laparotomy. Which of the following non-depolarising neuromuscular blocking agents is most suitable for this patient? a. Vecuronium. b. Pancuronium. c. Mivacurium. d. Rocuronium. e. Atracurium.24
A 46-year-old male is diagnosed with a vascular occlusion in his left leg. He is taken to the emergency theatre for an embolectomy and femoral cross-over graft surgery. He is known to have end-stage renal disease and is on daily peritoneal dialysis. He is in theanaesthetic room for induction. His ECG shows a prolonged PR interval and tall T waves. His blood results are shown in Table 1.
Which of the following is the next immediate step in the management of hyperkalaemia?
a. Intravenous 10ml of 10% calcium chloride over 5 minutes. b. Intravenous salbutamol 250µg.
c. Intravenous insulin 50 units over an hour. d. Intravenous furosemide 20mg.
e. Intravenous sodium bicarbonate 50mmols over an hour.
25
A 30-year-old male is due to undergo an urgent laparotomy. He has a family history of suxamethonium apnoea. Induction with propofol and rocuronium is planned. In the event of an unanticipated failed intubation, which of the following is the most appropriate in reversing the neuromuscular blockade?a. Intravenous neostigmine 0.07mg/kg and glycopyrrolate 0.01mg/kg. b. Intravenous neostigmine 0.1mg/kg and glycopyrrolate 0.05mg/kg. c. Intravenous sugammadex 16mg/kg.
d. Intravenous sugammadex 4mg/kg. e. Intravenous edrophonium 0.1mg/kg.
26
You are anaesthetising a patient at high altitude where atmospheric pressure is 380mm Hg. If the set concentration on the isoflurane178
Na+ K+ Urea Creatinine
139mmol/L 7.2mmol/L 15mmol/L 182µmol/L
vaporiser is 2%, in reality which one of the following indicates the correct concentration of vapour delivered in the inspiratory flow to the patient? a. 1%. b. 2%. c. 3%. d. 4%. e. 0.5%.
27
A defibrillator has a capacitor with a potential of 4000 Volts and a charge of 0.2 coulombs. What will be the maximum stored energy in this defibrillator? a. 100J. b. 150J. c. 360J. d. 400J. e. 460J.28
A 60-year-old female patient is scheduled to undergo a vaginal hysterectomy in the lithotomy position under general anaesthesia. The anticipated surgical duration is 75 minutes. Which one of the following characteristics of a ProSeal® LMA makes it most suitableover a classic LMA?
a. Presence of a flexible wire reinforced airway tube.
b. Better haemodynamic stability as compared to a classic LMA. c. Reduced incidence of cough and sore throat in the postoperative
period.
d. Improved airway seal, enabling positive pressure ventilation. e. Shorter and reinforced tube with an integral bite block.
29
A 72-year-old male patient is scheduled to undergo a total hip replacement under spinal anaesthesia. You have administered spinal anaesthesia using 2.6ml of 0.5% heavy bupivacaine. Which of the following is least useful in assessing the height of block?a. Peripheral oxygen saturation. b. Bispectral index monitoring.
c. Checking the level of touch sensation. d. Monitoring blood pressure.
e. Checking the level of cold sensation.
30
A 68-year-old male patient is undergoing a total knee replacement. The airway is secured with an i-Gel® supraglottic airway.Anaesthesia is maintained with sevoflurane 2.5% in oxygen and nitrous oxide with a total fresh gas flow of 0.8L/minute through a circle breathing system. The patient is breathing spontaneously. About an hour after starting the procedure, the patient showed signs of being in a light plane of anaesthesia, despite the sevoflurane dial set at 3%. The inspired sevoflurane is 2.6% and expired sevoflurane is 1.2%. Which of the following is the most likely cause for the gross difference in the inspired and expired concentration of sevoflurane? a. Malfunction of the vaporiser.
b. Malfunction of the vapour analyser.
c. Increased uptake of sevoflurane by the patient.
d. Suboptimal positioning of the i-Gel® airway resulting in air
entrainment.
e. Use of low fresh gas flow.
181