Exam 1 Flashcards

Question

Question 11 In patients who require carotid endarterectomy A. Cerebral autoregulation is often shifted to the right B. Cerebral blood flow varies directly with arterial oxygen content C. Cerebral blood flow varies in an exponential manner with PaCO2 D. Cerebral blood flow is affected by blood viscosity and age E. Hypoxia increases cerebral blood flow

Answer 1

A. Cerebral autoregulation is often shifted to the right D. Cerebral blood flow is affected by blood viscosity and age E. Hypoxia increases cerebral blood flow

Answer 2

C. Changes in AEPs are mostly independent of the anaesthetic agent in use

Answer 3

Considering a frequent social user of cocaine for general anaesthesia B. Chronic use of the drug lowers the seizure threshold C. Chronic pulmonary problems are unlikely D. A dose of Brompton cocktail could be an ideal pre-medicant

Answer 4

``` Cocaine may be taken by inhalation or sniffing as well as injection so needle marks may not be present in the chronic abuser of cocaine. ``` Chronic use may result in serious cardiovascular and cerebral disease and lead to congenital anomalies. Hypertension, tachycardia, arrythmias, myocardial ischemia and infarction may result from cocaine use.

Answer 5

Coronary artery disease does not seem to be induced in cocaine users and coronary vessel spasm is more the cause of ischaemia. Endocarditis may result from intravenous use. Pulmonary disease, apart from episodic pulmonary oedema from cardiovascular reasons, is not frequent. Central nervous system changes may lead to personality changes or more seriously to a seizure disorder which can also be induced on withdrawal

Answer 6

The Brompton Cocktail contains cocaine and so may prevent withdrawal problems in a user presenting for anaesthesia. Cardiovascular instability pre-operatively should be actively managed to prevent arrythmias or myocardial ischaemia occuring

Answer 7

Using the 'Tec 6' vapouriser for desflurane B. The vapour circuit gas flow is not determined by the fresh gas flow C. Compensation for changes in atmospheric pressure are by manual adjustment D. The working pressure of the vaporiser increases linearly with increased fresh gas flow E. Is not possible in event of a power failure

Answer 8

``` The 'Tec 6' is a non-variable bypass vapouriser allowing Desflurane to be used despite its high volatility and moderate potency. ``` It's sump is heated to 39C at which its vapour pressure is twice atmospheric at sea level. This pressure provides the vapour circuit gas flow which is independent of the fresh gas flow .

Answer 9

The 'Tec 6' requires manual adjustment ``` for changes in atmospheric pressure to avoid a fall in absolute partial pressure of anaesthetic for a certain % setting at increased altitude. ``` The working pressure of the vapouriser increases linearly with fresh gas flow to maintain an output of desflurane independent of fresh gas flow.

Answer 10

C. Concurrent administration of phenytoin may increase the plasma concentration of phenobarbitone

Answer 11

Phenytoin can be given as long as the rate does not exceed 50 mg/min in an adult and ECG monitoring is being used. Phenytoin may increase plasma concentrations of phenobarbitone, and decrease those of clonazepam, carbamazepine, lamotrigine and valproate. Lamotrigine should be commenced at a low dose and increased every 2 weeks to reduce the incidence of side effects including Stevens-Johnson syndrome. Carbamazepine may cause hyponatraemia and this side effect has been used with beneficial effects in those with nephrogenic diabetes insipidus

Answer 12

Concerning pulmonary embolism (PE) and its management A. IS FALSE BECAUSE About 90 % are thought to arise in the deep veins of the lower extremities and pelvis B. Pulmonary angiography is the diagnostic gold standard

Answer 13

About 90% of PEs arise from the lower limbs and pelvis. Tachypnoea with shallow breaths is seen in 80% of patients and cyanosis is usually restricted to cases of massive PE. Tachycardia may relate to the site of obstruction and the onset of bradycardia is an ominous sign. It is imperative to maintain right heart filling pressures to perfuse the lungs and maintain right ventricular output therefore diuretics are contraindicated.

Answer 14

Question 17 Renal sodium wasting may result from D. Addison's disease

Answer 15

``` Obstructive uropathy, Polycystic kidney disease, Addison's disease, congenital adrenal hyperplasia, unilateral renal artery stenosis resulting in the 'hyponatraemic hypertensive syndrome'. ```

Answer 16

Nephrotic syndrome, glomerular disease e.g. diabetic nephropathy, chronic renal impairment from any cause, bilateral renal vascular disease. Long term use of lithium may result in nephrogenic diabetes insipidus resulting in hypernatraemia if access to water is impaired.

Answer 17

Cushings Disease is associated with A. Obesity B. Hypertension E. Depression

Answer 18

The obesity in Cushings is typically central affecting the trunk. The associated proximal muscle wasting gives the so called ''lemon on sticks " appearance. Muscle weakness can also occur without wasting and is caused by potassium depletion. Oligomenorrhoea is caused by the steroid excess. Depression affects 20% of patients.

Answer 19

Considering the use of peripheral nerve stimulators A. Force of contraction continues to rise above the maximal stimulation threshold D. Double burst stimuli should be separated by 0.75 seconds

Answer 20

Train of four = 4 supramaximal stimuli at 2Hz with a fixed pulse width of 0.2 ms. Force of contraction continues to slightly increase above the supramaximal threshold as a result of direct muscle stimulation. Therefore delivered current should ideally be 10-20% above the threshold. A train of four stimuli is used to detect fade on repetitive stimulation following non-depolarizing blockade.

Answer 21

Fade is due to non-depolarizer blockade of pre-junctional ACh receptors (which maintain ACH output with repetitive nerve stimulation). Post tetanic facilitation enables a response to occur when none was detectable following single twitches or TO4. The post tetanic count consists of a 5 s 50 Hz stimulus followed by a 3 s pause and then single twitches at 1 Hz. The number of detectable twitches is inversely related to intensity of block. Double burst stimulation = 3 × 50 Hz stimuli separated by 0.75s

Answer 22

The following have autosomal dominant inheritance A. Hereditary spherocytosis E. Acute intermittent porphyria

Answer 23

The aetiology of motor neurone disease and myasthenia gravis is unknown. Duchenne muscular dystrophy is an X linked recessive disorder. Acute intermittent porphyria presents in early adult life usually around the age of 30, women are affected more than men.

Answer 24

Concerning the diagnosis of pneumonia B. Q fever is caught from farm animals C. Endotracheal aspirates correlate poorly with LRTI E. Ventilator acquired Pseudomonas aeruginosa infecion has a high mortality

Answer 25

Pneumonia is the commonest ICU infection. If the infection is present within 48 hrs of hospital admission, it is classified as a community acquired pneumonia. Principal pathogens (in decreasing incidence) are Streptococcus pneumoniae, Mycoplasma pneumoniae, Haemophilus influenzae and legionella species. The latter should be suspected if there has been recent travel abroad. Psittacosis is caught from birds and Q fever from farm animals.

Answer 26

Recent influenza infection should raise the possibility of Staphylococcus aureus infection and steroid therapy the possibility of tuberculosis. Ventilator acquired pneumonia has a mortality above 40%, the highest of which are in those due to Pseudomonas aeruginosa. ``` Common pathogens include enterobacteriacae, P. aeruginosa and S. aureus although S. pneumoniae and H. influenzae are still encountered. ```

Answer 27

``` Diagnosis of nosocomial pneumonia is difficult as pyrexia, pulmonary infiltrates and purulent ET secretions may be due to other causes. ``` However, these signs and a fall in the PaO2 are often used to diagnose the condition. ET aspirates correlate poorly w/ lower respiratory tract infection. Blood cultures are neither sensitive or specific in this condition. Quantitative culture using bronchoalveolar lavage may be useful.

Answer 28

Question 22 In the management of cerebral oedema C. Fluid restriction requires several days to have an effect D. Steroids are of benefit in patients with tumours

Answer 29

Mannitol and frusemide are equally effective and take 15-60 mins to exert their effect. However acute reduction is best produced by hyperventilation. Steroids should not be used in head injured patients

Answer 30

Question 23 Concerning the effects of a 'massive' transfusion E. A fibrinogen level of 100 mg/dl is an indication for FFP in a bleeding patient

Answer 31

``` The arbitrary definition of a massive transfusion is the replacement of a patient's total blood volume by stored allogenic blood in less than 24 hours or the acute administration of more than 1.5 times the estimated blood volume. ```

Answer 32

The most common abnormality is an absolute thrombocytopaenia, but there is also a dilutional, as well as an absolute, fall in procoagulants and other essential components of the coagulation cascade.

Answer 33

The platelet count falls in proportion to the volume of blood transfused; whereas plasma levels of factors V and VIII corrrelate poorly with transfusion volumes, and factor VII and fibrinogen levels are unrelated to transfusion volume.

Answer 34

The normal haemostatic mechanism can function perfectly well with low procoagulant levels but diffuse microvascular bleeding appears to be mostly related to thrombocytopaenia and severe hypofibrinogenaemia. The most sensitive predictors of microvascular bleeding are a platelet count <50,000/dl or a fibrinogen level < 0.5 g/l.

Answer 35

For procoagulant levels to fall below 20% of their normal limits requires over two times blood volume replacement. ``` The following has been suggested as the level of abnormal coagulation tests justifying treatment with FFP in the presence of generalized microvascular bleeding:- ``` ``` Prothrombin time >1.3 times control Partial thromboplastin time >1.3 times control Thrombin time >1.3 times control Fibrinogen 100 mg/dl Activated coag time >150s ```

Answer 36

Considering lactate metabolism A. Increase in plasma lactate will be matched by an equal mmolar decrease in plasma bicarbonate D. After exercise lactate is largely reconverted into glucose E. Lactate filtered in the kidney is actively reabsorbed

Answer 37

Lactic acid reacts with bicarbonate leading to CO2 and lactate production. At a certain level of exercise the plasma lactate level rises sharply. This is at between 50-80% of maximal O2 consumption.

Answer 38

In an untrained person plasma lactate will rise at a lower level of exercise than in the trained. Glucose metabolism to lactate releases ATP at least twice as rapidly as mitochondrial metabolism And can optimally provide energy for 1.5 minutes of maximal muscle activity.

Answer 39

After exercise 80% of lactate present is reconverted to glucose in the liver and restored in muscle and 20% is metabolised in the citric acid cycle. Filtered lactate is actively reabsorbed by the nephron to a transport maximum of 75 mg/min

Answer 40

D. The cause is most commonly gallstones or alcohol

Answer 41

Acute pancreatitis is most commonly due to gallstones or alcohol, although viral infections, drugs and trauma may provoke an episode. Most patients suffer epigastric pain, but all upper abdominal or chest pain should be viewed with suspicion. Pain may (rarely) be absent. Grey Turner's sign is flank bruising. Cullen's sign describes periumbilical bruising.

Answer 42

Many sufferers recover without high dependency care, but in those with a severe attack, multiple organ dysfunction often occurs. Antibiotics are generally only prescribed when an infected necrotic pancreas is suspected, and in these cases the necrotic area should be debrided. Necrotic pancreatitis can be visualised with a contrast enhanced CT scan. Nasogastric suction, H2 antagonists, TPN with 'bowel rest' and octreotide are often prescribed. The APACHE II severity scoring system is not able to predict individual mortality risk.

Answer 43

E. Dextrose 4% saline 0.18% sodium 30 mmol/l

Answer 44

0.9% saline contains 154 mmol of sodium and chloride per litre. Albumin 4.5% has no calcium and gelofusine less than 0.4 mmol/l. Hence they can be infused before / after blood. Dextrose saline 4%/0.18%, contains 30 mmol/l of sodium and chloride

Answer 45

``` 131 mmol/l sodium, 5 mmol/l potassium, 2 mmol/l calcium and 111 mmol/l chloride. ```

Answer 46

The following are true concerning humidity and humidification of gases A. Relative humidity is the ratio of absolute humidity to saturated humidity at a specified temperature C. Heat and moisture exchangers can achieve 40% humidity E. The water trap for a simple bottle humidifier must be as larger as the humidifier bottle

Answer 47

Absolute humidity is defined as the mass of water in a volume of air. Relative humidity is defined as ratio of absolute humidity to saturated humidity at a specified temperature usually presented as a %. ``` Humidification devices can be defined as active or passive; vapour or droplet producing; hot or cold and finally functioning in a breathing system or in the atmosphere. ```

Answer 48

Theatre humidity should be around 60% as a compromise between discomfort (if too high) and the increased risk of explosion due to static electricity (if too low). Heat and moisture exchangers can achieve 70% humidification. A nebuliser works on the venturi or Bernoulli effect. For a bottle humidifier the water trap should be at least the same size as the humidifier bottle

Answer 49

D. Water reservoirs are particularly at risk of contamination with Pseudomonas species

Answer 50

Inspired gas is warmed and humidified in the nasopharynx and Usually has a relative humidity of 90% and a temperature of 32-36°C. By the time gases have reached the alveoli they are fully saturated and at 37°C. Ciliary activity ceases above 41°C and slows down if relative humidity falls below 75% at 37°C.

Answer 51

Humidification of inspired gases during mechanical ventilation reduces pulmonary complications and hypothermia. Methods include: i) Saline drip this is inefficient and dangerous and is not recommended. ii) HMEs retain heat and moisture from the expired gases and return them during inspiration. They have become increasingly efficient and are now suitable for short term ventilation in many patients. They are not recommended for paediatrics or those with lung leaks as in these cases, much of the inspired gas does not pass through the HME on expiration. iii) Cold water humidifiers manage only 50% relative humidity and are not recommended in the critically ill. iv) Hot water humidifiers can be adjusted to administer 100% saturated gas at the endotracheal tube. However, tracheal scalding, condensation in circuits, inconsistent efficiency and infection (particularly Pseudomonas that multiplies in water reservoirs over 45°C in temperature) are disadvantages. v) Nebulisers gas driven, mechanical or ultrasonic which deliver micro-droplets. Ultrasonic nebulisers can cause overhydration, infection and an increase in airway resistance

Answer 52

The following agents decrease the heart rate A. Diltiazem B. Neostigmine E. Halothane

Answer 53

Calcium antagonists selectively prevent ion entry through voltage-sensitive slow channels and are usually classified as Class 1 antagonists (phenylalkylamines) verapamil Class 2 antagonists (dihydropyridines) nifedipine Class 3 antagonists (benzothiazepines) diltiazem

Answer 54

Class 1 and 3 antagonists have significant effects on myocardial contractility and AV conduction whilst class 2 drugs predominantly affect peripheral blood vessels resulting in a reflex tachycardia. Anticholinesterase drugs result in bradycardias from their muscarinic effects

Answer 55

Hydralazine produces direct relaxation of smooth muscle by elevating intracellular cGMP. As there are no effects on the baroreceptors a reflex tachycardia results. Halothane increases vagal tone, depresses the SA node and its response to sympathetic stimulation and depresses AV conduction to produce a sinus bradycardia.

Answer 56

In a patient with a traumatic cervical spinal cord transection B. Hypertension ma be present pre-operatively D. There is increased sensitivity to ACE inhibitors E. Positive pressure ventilation is more likely to cause bradycardia

Answer 57

Spinal shock after a spinal cord transection can last for days to weeks but has usually passed by approximately 3 weeks. ``` Reflexes via the spinal cord below the injury lead to apparent sympathetic nervous system overactivity now unmodulated by higher inputs. ``` These reflexes result from cutaneous or visceral stimulation and occur in 85% of patients. The resulting vasoconstriction can produce resting hypertension and hypertension in response to surgical and other stimuli even if the resting blood pressure is normal.

Answer 58

The renin-angiotensin-aldosterone system is enhanced to help maintain blood pressure and patients may be very sensitive to angiotensin converting enzyme inhibitors. Vagal tone will be the only intact efferent in the baroreflex so bradycardia may be seen with changes in position, with a valsalva manoeuvre, or with increased intrathoracic pressure.

Answer 59

To successfully wean from mechanical ventilation, there must be a central drive, adequate respiratory muscle strength and a manageable load placed on these muscles. Lack of central drive may be due to any depressant medications, head or spinal cord injury or nervous system infection.

Answer 60

``` infection, malnutrition, acidosis, hypercarbia, hypoxia, hypocalcaemia, hypomagnesaemia and hypophosphatemia ``` ``` Increased respiratory muscle workload may be caused by airways and circuits, hyperinflation, bronchoconstriction, left ventricular failure and auto-PEEP. ``` The latter also makes triggering of assist modes of ventilation more difficult.

Answer 61

Before commencing, the patient should be adequately oxygenated- a PaO2/FiO2 ratio of greater than 250 should normally be present although this can be less in those with chronic lung disease or those with anatomical right to left shunts

Answer 62

When considering weaning from mechanical ventilation C. Hypophosphataemia should be corrected to improve respiratory muscle strength D. The maximum negative pressure generated during inspiration assesses the respiratory muscle strength

Answer 63

The f/Vt ratio during spontaneous ventilation (with CPAP as required) is a useful guide. ``` After 5 minutes, if this is less than 80, success is likely. Above 105 failure is more likely and protracted weaning will probably be necessary. ```

Answer 64

The maximum negative inspiratory pressure generated is useful to assess respiratory muscle strength. If it is less than 20 cmH2O then severe weakness is presen t. If greater than 30 cmH2O then as long as the lungs are compliant, spontaneous breathing should be possible. Most healthy adults acheive 100 cmH2O

Answer 65

Serum Na+ 120 mmol/l and K+ 6.4 mmol/l are consistent with B. Renal failure D. Adrenocortical in sufficiency

Answer 66

Aldosterone causes sodium retention and potassium loss. In chronic renal failure hyponatraemia or hypernatremia can occur. In acute renal failure fluid retention can lead to hyponatraemia. Hyperkalaemia can also occur and is an indication for dialysis.

Answer 67

``` Hypopituitarism leads to a reduced secretion from the anterior pituitary gland and hence ACTH insufficiency and reduced cortisol. ``` ``` Mineralocorticoid production remains largely intact as this is predominantly stimulated by angiotensin II. Destruction of the entire adrenal cortex reduces glucocorticoids, mineralocorticoids and sex steroids. ``` As such hyponatraemia, hyperkalaemia and a raised urea result.

Answer 68

Cushing's results in excess cortisol which has some mineralocorticoid activity. This can lead to loss of potassium

Answer 69

Concerning the management of drowning D. Rapid re-warming may result in circulatory collapse E. If comatose on arrival at hospital, adults have a lower mortality than children

Answer 70

The incidence is 4 times higher in men than women and 2/3rds die in inland waters and 1/3rd in coastal waters. It is the 3rd commones cause of death in chidren following RTAs and burns/smoke inhalation. Outcome is dependent on the patient's state on arrival at hospital: Awake & alert100% survival. Blunted consciousness2/37 died

Answer 71

Initial management revolves around the ABC of resuscitation and remember to record the patient's temperature because they're not dead until warm and dead. Patients with a GCS of 3, fixed dilated pupils and no cardiac output have been successfully resuscitated with no obvious neurological defecit if hypothermic. Patients need to be re-warmed and this should be done slowly with full monitoring on the ITU. Hypothermia results in an elevated SVR, cardiac dysfunction, makes VF difficult to treat if < 28-30°C contributes to the profound acidosis that is often present ( pH <7.1).

Answer 72

Rapid re-warming may result in a rapid drop in the SVR leading to circulatory collapse in an already embarrassed heart. Steroids do not improve outcome and increase the secondary infection rate. There is no evidence that sodium bicarbonate raises arterial pH in drowning patients and it does not reverse intramyocardial acidosis. A rise in ICP is not immediate therefore ICP is not useful as a resuscitation parameter. Later a rise in ICP reflects the severity of brain injury and is therefore too late to affect

Answer 73

Concerning the use of a Sengstaken-Blakemore tube to control variceal bleeding D. Traction on the tube should be equivalent a 300-500 g mass

Answer 74

A Sengstaken -Blakemore tube has 3 lumens; an oesophageal lumen, a gastric balloon lumen and a gastric aspiration lumen. It is passed via the nose or mouth, and once in the stomach the gastric balloon is inflated with about 250 ml of air. This should be done slowly, intermittently checking that the balloon pressure is no more than that when tested prior to insertion (to safeguard against oesophageal rupture). The tube is withdrawn until a resistance is felt, which is the balloon meeting the gasto-oesophageal junction. The tube is now placed on traction and this controls the bleeding as the varices are mainly fed from branches that cross this junction.

Answer 75

``` The oesophageal balloon is less commonly inflated (25-35 mmHg) as the bleeding is often controlled by the gastro- oesophageal tamponade of the gastric balloon, and there is a risk of oesophageal rupture. ``` This should be suggested by chest pain which calls for immediate oesophageal deflation. Pulmonary aspiration is a major risk due to the procedure and the condition of the patient it is being performed on. Endotracheal intubation should be carried out prior to insertion if it is felt there is risk of aspiration, and sedation should not be used to aid insertion

Answer 76

The Kidneys receive 25% of the cardiac output and in health will present the proximal tubule with 180 L of filtrate per day. The oxygen consumption is 6 ml/100g/min, one of the highest in the body. The reabsorption of Na accounts for about half the O2 consumption, which is directly related to the blood flow

Answer 77

In the measurement of gas flow | all false

Answer 78

The rotameter is an example of a constant pressure, variable orifice flowmeter. If the pressure across a variable orifice remains constant the size of the orifice depends on the gas flow. At low flow rates, flow is a function of viscosity because the comparatively longer and narrower annulus between the float and the wall of the meter behaves like a tube i.e., is laminar. With higher flow rates the annulus is shorter and wider and behaves like an orifice so is density dependent.

Answer 79

Readings are taking from the top of the bobbin in the rotameter. The pneumotachograph is a constant orifice, variable pressure flowmeter which senses the pressure difference across a fixed resistance using transducers. It is used to measure laminar flow. The Heidbrink flowmeter is a constant pressure, variable orifice flowmeter. Its bobbin is extended vertically to form a rod which functions in a similar way to the rotameter but does not rotate

Answer 80

Question 37 In positioning patients during anaesthesia A. In the spontaneously breathing patient ventilation to the lower lung will be greater B. Tilted patients with sympathetic dystrophies are at risk of organ hypoperfusion C. In lithotomy pressure on the medial tibial condyle may damage the saphenous nerve D. There should be no more than a 90 degree angle between body and arm

Answer 81

Using doppler ultrasound the incidence of venous air embolism is 50% in the patient sitting for a posterior fossa craniotomy compared to 10% if the patient is lying.

Answer 82

Question 38 Peptic ulceration C. Incidence is increased in smokers E. Duodenal ulcer pain is classically relieved by food

Answer 83

``` Associations for peptic ulceration include smoking, blood group O, hypercalcaemia (and hence hyperparathyroidism), non-steroidal anti-inflammatory drugs as well as steroids. ``` Duodenal ulcers usually occur in the 1st part of the duodenum (unless associated with Zollinger-Ellinson syndrome when they occur anywhere) and cause 'hunger' pain which is relieved by eating (c.f. gastric ulcer pain).

Answer 84

Question 39 The Apgar score C. Includes an assessment of muscle tone D. Has a maximum score of 10

Answer 85

The apgar score was developed by an anaesthetist to ascertain the effects of anaesthetic agents on newly born infants. It measures 5 parameters, scored from 0-2, and should be measured at 1 and 5 minutes

Answer 86

Question 40 Ventilatory failure is commonly associated with A. A decrease in functional residual capacity C. Increased lung water D. Chest wall abnormalities E. An adequate arterial oxygen content

Answer 87

Any process that significantly decreases FRC will lead to ventilatory failure. These should be thought of in sequence from lesions in the central nervous system (respiratory centre and upper motor neurone), spinal cord (anterior horn cells and lower motor neurone) and neuromuscular junction. Failure of respiratory muscles, chest wall or pleural integrity and inflammatory process within the lung.

Answer 88

Lung compliance, the change in volume per unit pressure is decreased by the accumulation of extra lung water (pneumonia or LVF) and will increase the work of breathing. Ventilatory failure is defined as a pathological reduction of alveolar ventilation below the level required for the maintenance of normal arterial blood gas tensions. Mean normal arterial PCO2 is 5.1kPa, the normal arterial oxygen content is dependent upon arterial PO2 and haemoglobin concentration. Arterial PO2 is affected by inspired oxygen concentration and shunting and the adequacy of ventilation is best defined by the arterial PCO2

Answer 89

Question 41 Pre-eclampsia A. Is associated with polyhydramnios and multiple pregnancy C. Is a contraindication to extradural anaesthesia if the platelet count is <100000 E. If complicated by cerebral irritation is treated with magnesium sulphate

Answer 90

2-12% of pregnancies are complicated by pre-eclampsia. ``` It is a multi-system disorder, diagnosed after the 20th week of pregnancy by the triad of hypertension, peripheral oedema and protein-uria. ``` Magnesium sulphate has a therapeutic range of 1.25-2.5 mmol/l

Answer 91

``` Activated coagulation time A. Is normally 2549 seconds B. Requires 2 ml of blood C. Is 'activated' by kaolin D. Is linearly prolonged in proportion to the dose of heparin administered E. Is prolonged by hypothermia ```

Answer 92

An increase in left ventricular myocardial contractility C. Is a reflex response to an increase in heart rate

Answer 93

Myocardial contractility is not easily defined or measured. At a cellular level it is defined by the relationship between force and velocity of shortening. ``` On the level of organ function, within the patient, dp/dt max. is sensitive to changes in preload and afterload so is a poor description of contractility. ```

Answer 94

``` End systolic elastance (the inverse of compliance) is derived from the pressure volume loop of the ventricle and is a relatively load insensitive measure and so defines contractility well during changes in preload and afterload. ```

Answer 95

An increase in contractility is defined by an increase in end-systolic elastance. An increase in contractility will increase myocardial oxygen consumption and so increase the likelihood of myocardial ischaemia.

Answer 96

An increase in contractility in response to increased heart rate is described in the Bowditch effect. In response to an increase in afterload, contractility rises as defined by the Anrep effect

Answer 97

ctivated coagulation time B. Requires 2 ml of blood D. Is linearly prolonged in proportion to the dose of heparin administered E. Is prolonged by hypothermia

Answer 98

ACT can be measured in theatre using an automated system such as the Haemochron. 2ml of blood is mixed with 12mg of diatomaceous earth (a fine powder providing a large surface area for conversion of factor XII to XIIa).

Answer 99

``` The end point occurs normally after 70-110 seconds when a clot is formed that prevents a magnetic rod in the bottle from maintaining the contacts between a switch in the base of the machine. ``` The unit must be heated to 37°C to maintain reliable results. Hypothermic samples should be warmed or a correction applied. Haemodilution will also prolong the ACT. Although inter-patient response to heparin varies, individual dose responses are linear.

Answer 100

Question 44 Fibreoptic bronchoscopy in a mechanically ventilated patient C. Is not useful for the removal of foreign bodies E. Can result in hypoxia that lasts for several hours

Answer 101

Fibreoptic bronchoscopy is useful for diagnosis, therapeutic lavage and perhaps tracheal intubation. It is usually of little use in the removal of inhaled foreign bodies where a rigid bronchoscope is used.

Answer 102

It should be performed by someone with experience of the technique- usually a respiratory physician or intensivist. Obstruction of an endotracheal tube by the bronchoscope greatly increases the resistance to flow. Inspiration, being active, can often be manipulated using ventilator controls to maintain tidal volume.

Answer 103

However, the use of bronchoscope suction can reduce the alveolar ventilation. Tidal volume can be reduced by 75% at 21 cmH2O. Expiration, being passive, is also affected and expiratory flow hindered. PEEP values of 20 cmH2O are possible. Bronchoalveolar lavage can cause severe hypoxaemia that persists for hours, and transbronchial biopsy may result in pneumothorax

Answer 104

Question 45 Coeliac Plexus Block A. Is a useful method of treating intractable pain accompanying carcinoma of the pancreas B. Denervates the foregut E. Is most commonly complicated by postural hypotension

Answer 105

Coeliac plexus blockade is undertaken to denervate the foregut, interrupting nociceptive afferents from the pancreas, stomach, liver, and other viscera. It is usually performed under X-ray guidance, at T12-L1 via an angled posterolateral approach. Bilateral injections are performed to place anaesthetic / neurolytic agent anterolateral to the vertebral body in the thoracolumbar sympathetic chain.

Answer 106

The abdominal aorta and inferior vena cava lie anterior to the chain. Although intravascular injection and spread to the lumbar somatic nerves is possible, Postural hypotension is the most common complication due to visceral sympathetic blockade

Answer 107

Question 46 Remifentanil A. Has a similar potency to fentanyl D. Has a recovery time more rapid than alfentanil following intravenous infusion E. Is a pure mu receptor agonist

Answer 108

Remifentanil. a pure mu receptor agonist, is a fentanyl derivative with an ester linkage. This leads to its rapid hydrolysis by non-specific tissue and plasma esterases it is a poor substrate for pseudocholinesterase.

Answer 109

Following cessation of an infusion designed to maintain a constant plasma concentration, the recovery from remifentanil is faster than that from alfentanil. It is equipotent with fentanyl, and 15-30 times more potent than alfentanil. As with other potent opioids, muscle rigidity can occur when large doses are infused intravenously

Answer 110

Question 47 The Myasthenic patient B. Is more likely to display symptoms of toxicity following ester local anaesthesia E. Is more likely to develop Phase II block in response to suxamethonium

Answer 111

Myasthenia gravis is characterized by fluctuating weakness and fatiguability. The patient is extremely sensitive to competitive non-depolarizing blockade due to a reduced receptor population. Sensitivity to suxamethonium is normal or reduced, however there have been numerous cases of Phase II block occurring even at doses of 0.5mg/kg. Anticholinesterase therapy potentiates vagal responses and inhibits pseudocholinesterase activity

Answer 112

Question 48 Concerning the use of hydroxyethyl starch as an intravenous fluid A. Glomerular filtration is the major route of elimination D. The incidence of allergic reactions is similar to that of the gelatins E. Serum amylase concentrations may be elevated up to threefold following its use

Answer 113

Hydroxyethyl starch is a synthetic macro molecular polymer manufactured by hydrolysing corn. It has a molecular weight ranging from 10,000 to over 1 million. The commonly used preparations are the hetastarches which are available in preparations with an average molecular weight of 200,000 and 450,000. The pentastarches have an average molecular weight of 250,000.

Answer 114

Glomerular filtration is the major route of elimination and after 24 hours approximately 40% is left in the plasma. About 30% enters the RES, it is not known if this has any clinical significance. Large volumes lower factor VIII :C and may be clinically significant.

Answer 115

The incidence of anaphylaxis is about 0.085% which is similar to the gelatins. Measured serum amylase may be elevated up to threefold following hydroxyethyl starch administration due to the delayed urinary excretion of amylase bound to the starch molecule.

Answer 116

Question 49 The trachea C. Lateral relations in the neck include the recurrent laryngeal nerve

Answer 117

The trachea extends from C6 to opposite T4 or sometimes T5. It is supplied with blood from the inferior thyroid arteries. Lateral relations in the neck include the common carotid arteries, the lateral lobes of the thyroid, the inferior thyroid arteries and recurrent laryngeal nerves.

Answer 118

``` The trachea is composed of cartilaginous rings , fibrous membrane , muscular fibres , mucous membrane and glands. ``` The muscular fibres are longitudinal and transverse. The longitudinal fibres are the most external and the transverse fibres (trachealis ) are internal and form a thin layer between the ends of the cartilages and the posterior part of the trachea. The thyroid ima artery is a branch of the brachiocephalic artery but does not always exist.

Answer 119

Question 50 Acute arterial embolisation is characterised by A. Immobility of the affected limb B. Pain C. Loss of pin-prick sensation in the affected limb D. Pallor E. Loss of light touch sensation in the affected limb all true

Answer 120

Symptoms andsigns which occur in a limb suffering arterial embolisation are pain, paraesthesia, paralysis, loss of distant pulses and pallor. Paraesthesia due to acute ischaemia of nerves will cause a loss of pin-prick and light touch sensation in a 'stocking' distribution

Answer 121

Concerning echocardiography B. Pressure difference across a valve is calculated from blood velocity C. M mode is useful for assessing timing of events

Answer 122

There are 4 basic modalities of ultrasound (M-mode, 2-D, Doppler, and Colourflow Doppler). Ultrasound is reflected back from tissue interfaces. The further away the tissue is the longer it takes for the reflected wave to return. When recorded against time this provides a typical M-mode display. Whilst useful for recording the timing of events this method has been superceded by the 2-D image for assessing structural detail. Resolution is acceptable down to 2.5 mm.

Answer 123

Doppler makes use of the change in frequency of sound reflected by moving objects. The modified Bernoulli equation allows calculation of the pressure difference across a stenotic valve (mmHg=4x[velocity in m/s]squared).

Answer 124

Blood velocity in the normal heart is less than 1m/s. It will be increased by obstruction and stenosis. Colour flow Doppler superimposes a colour coded image of velocity on the two dimensional image allowing identification of high velocity jets, abnormal flow directions and shunts.

Answer 125

.Question 52 When prescribing total parenteral nutrition (TPN) the daily allowances of nutrients per kg in a normal adult are A. Glucose 3g D. Sodium 12 mmol E. Water 30 ml

Answer 126

Water 30 ml Energy 10 kcal Nitrogen 0.1-0.2g Glucose 3g Lipid 2g mmol Sodium 12 Potassium 0.7-1 Calcium 0.1 Magnesium 0.1 Phosphorus 0.4

Answer 127

``` Question 53 The following are associated A. Hypothyroidism and oligomenorrhoea B. Bronchial carcinoma and hyponatraemia C. Marfans syndrome and a high arched palate D. Aortic stenosis and sudden death ```

Answer 128

Hypothyroidism is associated with oligomenorrhoea or menorrhagia or amenorrhoea. Bronchial carcinoma, especially small cell, may cause inappropriate ADH which leads to hyponatraemia. A high arch palate is a commonly quoted feature of Marfans which may make intubation difficult, it is however rare. Aortic stenosis leads to a low fixed cardiac output which cannot respond to sudden needs to increase. Arrythmias such as VF can cause death. Hyperparathyroidism causes an increase in serum calcium, tetany is caused by hypocalcaemia

Answer 129

A. Digoxin therapy C. Mesenteric venous thrombosis D. Clostridium difficile infection E. Enteral feed

Answer 130

Diarrhoea in critically ill patients prolongs hospital admission and places them at risk from nosocomial infections. It may be experienced by 34-41% of patients admitted to the ICU. The two commonest causes are due to medications or Clostridium difficile infection. ``` Drugs associated with diarrhoea include antibiotics, magnesium containing antacids, digoxin, diuretics, antihypertensives, thyroid hormones and prokinetic agents. ```

Answer 131

Clostridium difficile is responsible for pseudomembranous colitis and 20% of antibiotic associated colitis. Fulminant colitis and sepsis may follow. Clindamycin, penicillins, cephalosporins, neomycin and metronidazole are the antibiotics with the strongest association with C. difficile infection. Other causes include E. Coli, V. cholerae, other enteric pathogens and faecal impaction. Mesenteric ischaemia, whether due to mesenteric venous thrombosis, acute ischaemia or abdominal aortic aneurysm repair can cause diarrhoea, as can enteral nutrition. If the latter occurs, it may be due to a high osmolality feed, high rate of infusion or increased motility. A thorough review of medications, stool culture for pathogens (ova and parasites are extremely rare if diarrhoea develops more than 48 hrs after admission to hospital) and C. difficile toxin and rectal examination, supplemented where appropriate with sigmoidoscopy and radiological investigations will reveal the majority of causes. Diarrhoea due to enteral feed may require watering down or changing the feed, altering the infusion regime, or controversially, changing to parenteral nutrition

Answer 132

Question 55 Concerning bradycardias and their management A. In suspected sinus node disease with a normal ECG the initial investigation of choice is a 24 hour tape

Answer 133

Lyme disease can cause acute but reversible heart block due to its associated myocarditis. Mobitz type 1 (Wenkebach) heart block is characterized by a progressively lengthening P-R interval, in Mobitz type 2 the P-R interval is constant prior to the non-conducted P wave. Following an inferior MI, second and third degree heart block is usually benign. Pacing is indicated only if the AV block is poorly tolerated and is resistant to atropine. The optimal pacemaker for sinus node disease is AAI ± R

Answer 134

When considering anaesthesia in the radiology department C. Myelography in the paediatric patient requires them to be prone D. Angiography quality can be enhanced by hyperventilation E. Contrast media injection can cause wheeze

Answer 135

The radiation exposure during CT of head is similar to that of a conventional skull X-ray. Exposure values for personnel attending the patient are minimal but precautions are still recommended. Laryngoscopes are not magnetic but the batteries are and so plastic or paper coated ones must be used if a laryngoscope is to be used during magnetic resonance imaging. Myelography requires pinal lumbar puncture to inject the contrast material hence the patient must be prone. Anaesthesia may be required in the paediatric or uncooperative patient.

Answer 136

Angiography to delineate the vasculature of the brain or spinal cord maybe improved by hyperventilation. Hypocarbia allows greater concentration of contrast material by slowing cerebral circulation and improves clarity by constricting cerebral vessels. Contrast media are radio-opaque iodine containing salts. Their injection may cause allergic reactions ranging from pruritus, burning on injection, skin rash, wheezing, dyspnoea, syncope or cardiovascular collapse.

Answer 137

For safe cardio-pulmonary bypass the following are required B. An activated clotting time of greater than 400 seconds D. Examination of carotid pulses to ensure their presence and equality after the onset of bypass

Answer 138

Anticoagulation is required prior to cannulation of the aorta or right atrium. This is most frequently achieved using heparin at a dose of 3 mg or 300 units/kg. The degree of anticoagulation is checked using the activated clotting time which should be longer than 400-480 secs. Although systemic and myocardial cooling are commonly used for organ preservation there is some clinical trend towards warm bypass practice.

Answer 139

If the aortic cannula is misplaced into the innominate artery or placed with its tip too far round the aortic arch one or both carotid pulses may be absent with parallel affects on cerebral perfusion. In the event of a significant arterial air embolism the patient should be placed in steep trendelenberg positon with compression of the carotids until hypothermic retrograde perfusion of the cerebral circulation via the superior vena cava cannula can be instituted with the aim of driving impacted air from the cerebral circulation. Nitrous oxide use should be stopped and the patient ventilated with 100% oxygen. Elective ventilation post-operatively would be appropriate.

Answer 140

When using agents to reduce blood pressure B. Sodium nitroprusside should be avoided in renal failure

Answer 141

Trimetaphan blocks sympathetic and parasympathetic ganglia, releases histamine from mast cells and directly vasodilates blood vessels. It does not cross the blood brain barrier. Sodium nitroprusside causes arteriolar and venular dilatation by increasing nitric oxide levels (a mechanism shared with the nitrates but not with hydralazine which acts directly). It must be protected from the light as cyanide ions are otherwise formed. It can cause cyanide toxicity if the infusion rate is too high.

Answer 142

This is exacerbated by renal failure as cyanide in the presence of thiosulphate is converted to thiocyanate which is renally excreted. Cyanide toxicity is treated with dicobalt edetate alone, or sodium nitrite followed by sodium thiosulphate. Dimercaprol is used for the treatment of heavy metal poisoning.

Answer 143

Haemophilia A is associated with A. Haemarthrosis C. Normal bleeding time D. Hepatitis B E. Successful treatment with desmopressin

Answer 144

Hemarthroses are often spontaneous and can lead to arthritic changes. The prothrombin time is sensitive to depletion of factors in the common and extrinsic coagulation pathway. In haemophilia A the intrinsic pathway is slowed so prothrombin time is normal. The bleeding time is a test for vascular disorders and platelet function.

Answer 145

0.4 mcg/kg of desmopressin intravenously may increase levels of factor VIII transiently in mild cases. Tranexamic acid (1g orally for adults) can also be given. Hepatitis B is due to numerous blood transfusions. It may eventually be possible to produce factor VIII by bioengineering methods.

Answer 146

Question 60 Repeated enteral doses of activated charcoal enhance the elimination of the following drugs E. Quinine

Answer 147

Repeated doses of charcoal 50 gm initially then every 4 hours enhances the elimination of: ``` Aspirin Carbamazepine Dapsone Phenobarbitone Quinine Theophylline ```

Answer 148

Question 61 Regarding a variable that has a normal distribution A. The mode, mean a d median will be the same

Answer 149

Standard deviation is the square root of the variance, the coefficient of variance is the mean divided by the standard deviation and will depend on the shape of the distribution. By definition 5% of normal values will be beyond 1.96 SD's and sample means are used to represent population means

Answer 150

62 Neuromuscular monitoring A. A T4:T1 ratio of 0.75 means that the patient is suitably reversed for extubation D. Normal neuromuscular function will display no fade with a supramaximal 50Hz stimulus for 5 seconds

Answer 151

The mainstay of intra-operative neuromuscular monitoring is the train-of-four. On reversal of the blockade the return of a T4:T1 ratio of 0.75 suggests suitability for extubation, and correlates well with clirical signs. As the T4:T1 ratio is difficult to assess without a relaxograph, double burst stimulation was developed to allow more accurate consideration of the ratio. Post-tetanic count is used to monitor deep relaxation, when the train-of-four will not show any twitches.

Answer 152

Normal neuromuscular function allows a sustained contraction when a supramaximal stimulus of 50Hz is supplied for 5 seconds. If the stimulus is of a higher frequency the fade may be seen with normal neuromuscular function. Tetanic stimuli (including post-tetanic count) can only be used once every 5 minutes

Answer 153

In surgical correction for scoliosis B. Harrington rods may be employed C. Pre-operative right ventricular hypertrophy is a feature D. One lung anaesthesia may be necessary

Answer 154

Scoliosis may result in restrictive pulmonary deficit leading to pulmonary hypertension and right ventricular hypertrophy. Corrective surgery may be necessary to prevent further respiratory insufficiency or cardiovascular compromise. Harrington rods are used for surgical fixation, allowing distraction of vertebra using a ratchet.

Answer 155

The 'wake-up' test involves intra-operative wakening to allow assessment of spinal cord function after the spine has been straightened. It is also used to assess cerebral function after basilar artery clipping. Recall is uncommon with careful anaesthetic technique

Answer 156

Gastroduodenal stress ulceration A. Has become less common over the last 20 years B. Is more common in certain groups of patients C. Prevention with antacids is associated with an increased rate of nosocomial pneumonia

Answer 157

The occurrence of gastroduodenal stress ulceration has reduced over the last few decades independently of specific prophylaxis, probably due to better management. The incidence of stress ulceration in the critically ill depends on the diagnostic criteria. Abnormal findings at endoscopy or a positive gastrocult may be present in over 70%. However, a 'significant bleed' i.e. haematemesis, coffee ground nasogastric aspirate, malaena or a haemoglobin drop of 2 g/dl (complicated by cardiovacular instability or transfusion requirement) occurs in 5- 20%.

Answer 158

Risk factors include CNS insults, hepatic, renal, respiratory or coagulation failure, burns, sepsis, shock, major surgery or trauma, organ transplantation and a history of peptic ulcer disease. Antacids are effective in reducing ulceration, but have been linked to an increased risk of nosocomial pneumonia. This may be due to increases in gastric intraluminal pH allowing bacterial colonization, but the volume of antacid and necessary presence of a nasogastric tube also result in increased risk of aspiration. H2 antagonists are effective prophylactic agents. However, some (but not all) studies indicate a higher risk of nosocomial pneumonia. Sucralfate combines mucosal barrier protection, mucosal blood flow enhancement, stimulation of bicarbonate, mucus and prostaglandin secretion. Most studies indicate a lower incidence of bleeding compared with H2 antagonists

Answer 159

Question 65 When managing a confused patient in the intensive care unit A. Vitamin abnormalities are a possible cause B. The cause may be the blockage of a urinary catheter

Answer 160

i) metabolic-urea, electrolyte, glucose and vitamin abnormalities. ii) cerebral hypoxia, hypercarbia, acidosis or hypertension. iii) drugs- administration and withdrawal (alcoholics may develop Wernicke's encephalopathy without rapid treatment) iv) infection or fever. v) pain. vi) psychiatric, endocrine or organic brain disease. vii) intracranial pathology. viii) cardiopulmonary bypass. ix) fat emboli. x) ICU psychosis- which should only be diagnosed when all others have been excluded. Treatment is of the underlying cause, reassurance and communication (relatives and 'friendly faces' are often of great use), helping with sleep and occasionally restraint, sedation and psychiatric consultation

Answer 161

A diagnosis of acute appendicitis in a patient with right iliac fossa pain is unlikely if A. There is a pyrexia of 40 degrees celsius B. Pyuria >1000 WC/mm3 D. The patient is hungry

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