Multiple Choice Questions		X-rays
Clinical Scenario		ECG's

Multiple Choice Questions

1. Hypotension:

   a)	T - If used without atropine or glycopyrrolate, neostigmine may cause bradycardia that may in turn lead to hypotension.
   b)	T - The vasodilation resulting from sympathetic blockade reduces venous return, stroke volume and cardiac output.
   c)	T - IPPV also reduces venous return.
   d)	T - Cardiac output drops with hypovolaemia.
   e)	F - Vecuronium has little effect on blood pressure since there is minimal histamine release, ganglion blockade or vagal blockade.




2. The oxygen-haemoglobin dissociation curve is shifted to the right by: a) F - The curve is shifted to the left by alkalosis, hypothermia, hypocapnia and reduced 2,3-DPG levels. Acidosis, hyperthermia, hypercarbia and raised 2,3- DPG levels shift it to the right. b) F c) F - Nitric oxide has no effect on the ODC. d) T - Because of carbon dioxide retention. e) F - Fetal haemoglobin, methaemoglobin & carbon monoxide poisoning shift the curve to the left.




3. Neonate: a) T - A small decrease in diameter (e.g. due to oedema) may cause a large increase in airway resistance. In the adult the glottis is the narrowest part of the upper airway. b) F - The spinal cord ends at L3 in the newborn. The dural sac extends as far as S3-S4, as opposed to S1 in the adult. c) T - Albumin levels in the child are low until about 1 year of age. d) F - The neonate depends on non-shivering thermogenesis, i.e. metabolism of brown fat. The latter is laid down from 22 weeks' gestation in the mediastinum, axillae, base of the neck and between the scapulae. Shivering does not occur until 3 months of age. e) T - Increased chest wall compliance allows it to be pulled inwards by the lung, decreasing the FRC, which may be less than the closing capacity. This, accompanied by an increase in O2 consumption, predisposes the neonate to rapid desaturation.




4. Obesity:

   a)	F- BMI (Body mass index) = body weight (in kg) / height squared (m) BMI (kg/m) <25 normal 25-30 overweight 30-35 obese >35 morbidly obese Mortality & morbidity rise sharply when the BMI exceeds 30kg/m. Ref: Adams JP, Murphy PG. Obesity in anaesthesia and intensive care. British Journal of Anaesthesia 2000; 85: 91-108
   b)	T - O2 consumption & CO2 production are increased due to the metabolic activity of adipose tissue & the increased workload on supportive tissues. FRC decreases because of reduced chest wall & lung compliance while closing capacity increases, adding to V/Q mismatch that is worsened in the supine position. This leads to impaired gas exchange & hypoxia. Possible sequelae include pulmonary vasoconstriction, pulmonary hypertension, right ventricular hypertrophy & failure. All these factors, coupled with the increased incidence of difficult intubation, predispose the obese patient to the risk of hypoxia on induction, during maintenance & after anaesthesia.
   c)	F - Too small a cuff tends to over-estimate the blood pressure. It may occasionally be necessary to opt for invasive arterial pressure monitoring in these patients. Ref: Hutton P, Prys-Roberts C (Ed.). Monitoring in Anaesthesia and Intensive Care. 1994. WB Saunders Company Ltd
   d)	F - Intramuscular injections may be unpredictable & less effective than intravenous injections in these patients. PCA, if available, is a good option. If intravenous opioids are used small, titrated doses may be given but good nursing observation is required. Regional blocks supplemented by oral NSAIDS or paracetamol are very useful, but may be more difficult to perform.
   e)	T -The incidence is high due to prolonged immobility with venous stasis, raised haematocrit, cardiac failure, reduced fibrinolysis following surgery, and pressure of the increased weight of the abdomen on deep veins. DVT prophylaxis is essential.




5. Physiological response to surgery: Surgery is a form of trauma that causes a stress response characterised by neuro-endocrine and inflammatory changes that are aimed at ensuring survival and promoting wound healing. It consists of a catabolic phase that lasts 5 (or more) days during which fuel production and delivery is increased, sodium and water are retained, and potassium is lost. This is followed by an anabolic phase in which a positive nitrogen balance allows for replacement of lost muscle, and fat stores are replenished. Anaesthetic agents and techniques may modify this stress response.

   a)	T - Gluconeogenesis and glycogenolysis are increased by cortisol and catecholamines; insulin resistance also occurs.
   b)	F - Protein catabolism is enhanced by cortisol.
   c)	T - The sympathetic system, activated by the hypothalamus, causes increased adrenal catecholamine secretion and noradrenaline release from adrenergic neurons.
   d)	F - ADH secretion is increased.
   e)	T - Fibrinogen is an acute phase protein.

   Endocrine gland	Hormones	Change in secretion
   Anterior pituitary	ACTH Growth hormone TSH FSH and LH	Increases Increases May increase or decrease May increase or decrease
   Posterior pituitary	ADH	Increases
   Adrenal cortex	Cortisol Aldosterone	Increases Increases
   Pancreas	Insulin Glucagon	Often decreases Usually small increases
   Thyroid	Thyroxine, tri-iodothyronine	Decrease

   Ref: Desborough JP. The stress response to trauma and surgery. British Journal of Anaesthesia 2000; 85: 109-117




6. Thiopentone:

   a)	T - Although the mode of action is unclear, GABA A receptors do have a role in the action of barbiturates, benzodiazepines, propofol and etomidate on the CNS. Barbiturates bind to distinct sites on the GABA A receptor and facilitate their response to GABA. GABA receptor activation increases chloride conductance, hyperpolarizes post-synaptic membranes and thereby reduces neuronal excitability.
   b)	T - It should be used with caution in patients who are likely to be sensitive to its hypotensive effects (e.g. hypovolaemia, myocardial disease, valve stenosis), and patients with reduced protein binding resulting in raised free drug levels (e.g. hepatic or renal disease, burns, the elderly, advanced malignancies)
   c)	T - It also reduces cerebral blood flow and intracranial pressure. It can reduce cerebral O2 consumption by up to 50%. The remaining O2 is consumed during processes that are necessary to maintain the integrity of neuronal cells.
   d)	F - Barbiturates induce ALA synthetase. Other drugs considered to be unsafe include etomidate, halothane, antihistamines, steroids, some NSAIDS, lignocaine, theophylline and pentazosine. Ref: British National Formulary Sept 2000
   e)	F - Thiopentone reduces intraocular pressure, while suxamethonium increases it slightly. The risk of aspiration and coughing should be balanced against the risk of raising intra-ocular pressure by using suxamethonium.




7. Ketamine:

   a)	T - It is metabolised in the liver to several active metabolites. Norketamine has 20- 30% of the activity of ketamine. The relative potencies of other metabolites have not yet been determined.
   b)	T - Mean total clearance depends on hepatic blood flow. Halothane reduces hepatic flow.
   c)	T
   d)	T - It increases heart rate and blood pressure, thus increases myocardial oxygen demand.
   e)	T - In children it has been used in a dose of 0.5mg/kg with a local anaesthetic.

   Ref: Cook et al. Comparison of the effect of adrenaline, clonidine and ketamine on the duration of caudal analgesia produced by bupivacaine in children. British Journal of Anaesthesia 1995;75: 698-701




8. Volatile agents:

   a)	F - Epileptiform EEG changes may occur particularly with hypocapnia, and may persist for several weeks. Seizures have been reported after enflurane anaesthesia therefore it is best avoided in epileptic patients.
   b)	F- The extent of metabolism of volatile agents is as follows: halothane 20%, enflurane 2%, isoflurane 0.2%, desflurane 0.02%, sevoflurane 3-5%.
   c)	T - There is little myocardial depression and blood pressure is maintained. Dysrhythmias are rare so the use of adrenaline is relatively safe. Ether also causes some bronchodilatation.
   d)	F - Sevoflurane has a low blood-gas partition co-efficient (0.69 vs. 2.4 for halothane) making induction and recovery smooth and extremely rapid. The blood-gas partition co-efficients of the inhalational agents at 37C are: N2O 0.47, enflurane 1.9, isoflurane 1.4, desflurane 0.42, and ether 12.
   e)	T - Since its boiling point is close to room temperature, standard vaporisers are unsuitable. The Desflurane vaporiser is electrically powered, heating it to 39C. Fresh gas does not enter the vaporisation chamber. Instead, vapour (0-18%) is added to the fresh gas flow at the vaporiser outlet.




9. Drug interactions:

   a)	T - Enhanced sedative effect
   b)	T - Antibiotics that increase the plasma theophylline levels by inhibiting hepatic metabolism are erythromycin, clarithromycin, ciprofloxacin, and norfloxacin. Rifampicin decreases the levels.
   c)	T - The effect of non-depolarising neuromuscular blocking drugs is enhanced by the following antimicrobials: aminoglycosides, clindamycin, colistin and piperacillin.
   d)	T - There is a risk of severe hypotension, cardiac failure or asystole.
   e)	T - Arrhythmias may occur if adrenaline or isoprenaline are used with halothane.




10. Blood transfusions:

    a)	T
    b)	T
    c)	F
    d)	F
    e)	T

    Infections that may be transmitted by blood transfusion are:

    • Viral - Hepatitis B & C, HIV, HTLV-1, CMV, EBV
    • Bacterial - contaminants during collection and storage (e.g. Pseudomonas, coliforms), syphilis, brucellosis, yaws
    • Parasitic - malaria, trypanosomiasis, leishmaniasis.

    The risk of transfusion-related infections can be reduced by screening donors and blood products, by using autologous blood, and by decreasing the amount of blood transfused. This can be achieved using the following strategies: accepting lower haemoglobin levels in healthy patients, pre-operative haemodilution, minimising intra-operative blood loss, and intra- and postoperative blood salvage. In addition, large blood transfusions may cause the following adverse effects:

    • Coagulopathy due to reduced platelets, fibrinogen and factors V and VIII. Platelet and FFP administration should be guided by the platelet count, fibrinogen level and INR.
    • Impaired oxygen delivery to tissues because of the left shift of the ODC in stored blood (up to 24 hours).
    • Hyperkalaemia - rarely a problem except in patients with pre-existing hyperkalaemia, acidosis, hypothermia or in children. Potassium rapidly re-enters red blood cells after infusion and warming.
    • Hypocalcaemia - following rapid transfusion.
    • Acid-base imbalance - transfused blood has a low pH and may initially cause a metabolic acidosis. Alkalosis may follow the metabolism of citrate to bicarbonate. Citrate intoxication may result from rapid transfusion. A warm, well-oxygenated adult can metabolise the citrate content of one unit of CPD blood in 5 minutes. Rapid infusion may exceed the metabolic rate, causing tremors, arrhythmias, acidosis and hypocalcaemia.
    • Hypothermia - therefore blood should be warmed. Rapid transfusion of cold blood may cause cardiac arrest.

    A massive blood transfusion is defined as the replacement of the total blood volume with transfused blood within 24 hours, or the transfusion of more than 5 units of blood within 1 hour.




11. Neuromuscular blockade:

    a)	T - see below
    b)	F - see below
    c)	F - competitive antagonists
    d)	F - volatile agents potentiate neuromuscular blockade
    e)	F - fasciculations are characteristic of depolarising neuromuscular blocking drugs.

    Neuromuscular blockade (NMB) can be monitored by assessment of a muscle's mechanical response to peripheral nerve stimulation. When a supramaximal stimulus (20-60mA) is applied to a peripheral nerve, avoiding direct stimulation of the muscle, the response obtained allows differentiation between depolarising and non-depolarising blockade.

    Train of four (TOF) involves four 0.2msec stimuli at 2 Hz while double burst stimulation (DBS) consists of two 50Hz tetanic stimuli of 40msec separated by a 750msec interval. Non-depolarising block is characterised by fade on testing with TOF or DBS (mechanical twitch in response to first stimulus is greater than that due to subsequent stimuli). Non-depolarising block is also characterised by post-tetanic facilitation (following a tetanic stimulus of 50Hz for 5 seconds a subsequent TOF response is increased).

    Ref: Hutton P and Prys-Roberts (Ed.) Monitoring in Anaesthesia and Intensive Care. 1994. WB Saunders Company Ltd.




12. Pulse oximetry:

    a)	T
    b)	F
    c)	F
    d)	T
    e)	T

    The pulse oximeter is a non-invasive device used to determine arterial oxygen saturation. The probe consists of two light-emitting diodes emitting red (660nm) and infrared (940nm) light on one side, and a photodetector on the other. Oxy- and deoxyhaemoglobin absorb light at different wavelengths. Comparison of the absorbance at the two different wavelengths enables the oximeter to calculate oxygen saturation. The pulsatile nature of arterial blood flow allows the oximeter to differentiate it from venous blood.

    It is accurate in the 70-100% range. Machine calibration is done on healthy volunteers so that below 70%, saturation readings are, by necessity, extrapolated. Inaccuracies result from carbon monoxide (gives falsely high values), methaemoglobinaemia (reads 85% regardless of true saturation), coloured nail varnish, IV dyes (e.g. methylene blue), vasoconstriction, excessive movement, venous pulsation, and interference from external fluorescent light.

    The Beer-Lambert law forms the basis of spectrophotometric techniques such as oximetry. It is a combination of two laws that describe the absorption of monochromatic light by a transparent substance through which it passes.

    • Beer's law: intensity of transmitted light decreases exponentially as the concentration of the substance increases.
    • Lambert's law: intensity of transmitted light decreases exponentially as distance travelled through the substance increases.



13. Breathing systems:

    a)	F - Lack = co-axial A; Bain = co-axial D.
    b)	F - It requires a FGF equal to minute ventilation. It is inefficient for controlled ventilation when FGF = 2,5-3 times the minute volume.
    c)	F - Mapleson E.
    d)	T - This is a reason for its popularity in paediatric anaesthesia.
    e)	F - The minimum flow rate that can be used is a flow rate of 100% oxygen that matches the total O2 consumption of the patient (as low as 200-300ml O2/min, depending on metabolic demands). This is only achievable after an initial period of high flow that adequately denitrogenates the patient and delivers volatile anaesthetic at a high enough rate during the initial period of high uptake.




14. The rotameter:

    a)	T
    b)	F
    c)	F
    d)	T
    e)	F

    The Rotameter is a constant pressure, variable orifice flowmeter. Inflow occurs via a needle valve into a tapered glass tube, which widens toward the top. When gas flows, a light metal bobbin floats on the gas jet, the height of the bobbin in the calibrated tube indicating the flow rate. At low flow rates, flow is a function of gas viscosity since the relatively longer and narrower annulus behaves like a tube allowing laminar flow. The Hagen-Poiseuille equation can be applied to calculate flow through a tube:

    Q =	pPr4
    	8hl

    where	Q = flow through a tube
    	P = pressure across the tube r = radius l = length h = viscosity of the gas.

    At high flow rates where the short wide annulus acts like an orifice, flow is turbulent. Here gas density is an important determinant of flow.

    Each rotameter is accurately calibrated at specific pressure and temperature for its particular gas. Temperature changes encountered in clinical practice, however, have insignificant effects on accuracy of flow measurement.

    Inaccuracies may result when the bobbin sticks against the tube because of tilting, static or dirt. Ensuring that the tube is vertical, clean & treated with an antistatic (a thin gold coating or an antistatic spray) will prevent errors in measurement.




15. Obstetric anaesthesia:

    a)	F - A sensory block from T4-6 to S5 is required for adequate analgesia during Caesarean Section. Testing the sacral dermatomes is especially important with an epidural, as these nerve roots are not always blocked. This almost never happens with a spinal anaesthetic.
    b)	T - Sodium citrate is non-particulate. Particulate antacids, if aspirated, may cause pneumonitis. In addition, they do not mix effectively with gastric contents.
    c)	T - Factors contributing to the greater risk of hypoxaemia are the reduced FRC and increased oxygen consumption in pregnancy, and the higher incidence of difficult intubation in this group of patients.
    d)	T - The incidence of post-dural puncture headache (PDPH) is increased when large gauge spinal needles are used, especially if the longitudinal dural fibres are cut transversely by the needle bevel (as with a Quincke point). Pencil point needles split the fibres longitudinally, reducing the risk of a CSF leak. The incidence of PDPH is <1% with 25-29G pencil point needles (e.g. Whitacre or Sprotte).
    e)	T




16. Regional anaesthesia:

    a)	F
    b)	F - While intravenous regional anaesthesia is relatively simple, the technique may be extremely hazardous if caution is not exercised. Measures to ensure safety include: siting a second intravenous cannula in a limb other than the operation site; use of an anaesthetic agent considered to be safe for IVRA (e.g. prilocaine, up to 5mg/kg without adrenaline; bupivacaine is contra-indicated for this purpose); use of a double cuffed tourniquet which has been checked for integrity; injecting the drug slowly so as to avoid exceeding the pressure in the tourniquet; not releasing the tourniquet before at least 20 minutes have elapsed since time of injection.
    c)	T - Complications of brachial plexus blocks see table below
    d)	T - Regional anaesthesia for the lower limb: The lumbar plexus originates from the primary ventral rami of L1-4 ± a contribution from T12. It lies between the quadratus lumborum and psoas muscles. It may be blocked by either an approach from the groin (3-in-1 block) or a posterior approach (lumbar plexus block).
    e)	T - Neuraxial opioids: Opioids were first used clinically by the epidural and intrathecal routes in 1979.Their advantage over local anaesthetic given by these routes is that they produce analgesia without affecting sensory, motor and autonomic function. They bind to opioid receptors in the spinal cord and periaqueductal grey matter of the midbrain, and produce analgesia by inhibiting pain pathways in the dorsal horn of the spinal cord and by stimulating descending inhibitory neuronal pathways. (Gate theory of pain, Melzack & Wall). They are used mainly in combination with local anaesthetics for both intraoperative postoperative analgesia. The combination may result in better analgesia of longer duration than local anaesthetics alone, and because a lower dose of local anaesthetic is used, there may be less motor block and hypotension. The required dose, onset and duration of action, and side effects of spinally administered opioids will depend on their lipid-solubility, molecular weight and shape, degree of ionisation, and the epidural blood flow. These factors affect dural and spinal cord permeability and the systemic absorption of the drugs via epidural veins. Unfortunately, complications of spinally administered opioids include respiratory depression, nausea and vomiting, pruritis (itching) and urinary retention. Pruritis is common after epidural (8.5%) and intrathecal (46%) opioids and may be treated with systemic antihistamines or naloxone. Ref: Ballantyne et al. Pain 1988;33:149-160

    Table - Complications of brachial plexus block
    	Interscalene	Supraclavicular	Axillary
    Phrenic nerve block	+	+	-
    Recurrent laryngeal nerve block	+	+	-
    Horner's syndrome	+	+	-
    Extradural/intrathecal injection	+	-	-
    Intravascular injection	Vertebral artery	Subclavian vessels	Axillary vessels
    Pneumothorax	-	++	-
    Nerve damage	+	+	+




17. Hepatitis and HIV:

    a)	F - The risk of transmission of HIV is 0.3-0.5% whereas that for HBV is 30%
    b)	F - Boosters are required every 5 years
    c)	T - HBV and HIV are killed by autoclaving, ionising radiation, hypochlorite, formaldehyde, and gluteraldehyde
    d)	T - Abdominal symptoms occur in 20-30% of HIV patients, and the diagnosis of acute abdomen may be difficult. Conditions that may present include GI perforation or obstruction, cholecystitis, acute appendicitis (twice as common), anorectal disease and haemorrhage
    e)	T - HIV may cause a lymphocytic myocarditis. In advanced AIDS it may be caused by Cryptococcus, toxoplasmosis, Coxackie B, CMV, Nocardia, Aspergillus, and lymphoma.




18. Difficult intubation:

    a)	F
    b)	T
    c)	T
    d)	T
    e)	T

    Failure to intubate is relatively uncommon but an accurate preoperative assessment of the likely difficulty is obviously very important. Tests that may be used preoperatively include: The Mallampati test: Class 1 = easy, class 4 = difficult. It will predict only 50% of difficult intubations. Thyromental distance >6.5cm = easy (Patil) Wilson et al devised a more complex scoring system based on body weight, extent of head, neck & jaw movement, and presence of receding mandible and prominent teeth.




19. Neck anatomy:

    a)	F - The cricoid cartilage is palpable at C6 and the thyroid cartilage at C4-5
    b)	T
    c)	F
    d)	F - It bifurcates at the level of C3
    e)	F - The artery passes posterior to the scalenus anterior muscle.




20. Tension pneumothorax:

    a)	T - but it is less likely than with the subclavian approach
    b)	F - It is a clinical diagnosis. It is a medical emergency, and treatment (i.e. needle decompression in 2nd intercostal space, mid-clavicular line) is required before a chest X-ray is taken
    c)	T - away from the side of the pneumothorax
    d)	F - IPPV will increase tension. The large bore needle (as above) is left in place until an intercostal drain has been inserted
    e)	T - It must be considered as one of the causes of pulseless electrical activity (or EMD = electromechanical dissociation). The causes to be excluded are Hypoxia Hypovolaemia Hypothermia Hyper- or hypokalaemia or metabolic disorders Tension pneumothorax Tamponade Toxic or therapeutic disturbances Thromboembolic/mechanical obstruction.

(Continued ...)

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