SBA Paper 9 Flashcards
1
Q
- A 61-year-old man has been brought to the emergency department intubated and
ventilated. Examination reveals a large frontal haematoma and a single dilated, but
reactive, pupil. His abnormal observations are a blood pressure of 180/100mmHg,
heart rate of 45bpm and temperature of 35.5°C. An arterial blood gas shows Pao2
13 kPa, Paco2 of 6.9kPa and blood glucose 8mmol/L.
Which of the following parameters should be your priority when attempting to
acutely improve this patient’s cerebral perfusion?
A Temperature
B Paco2
C Blood pressure
D Pao2
E Blood glucose
A
- B Paco2
○ This patient is showing signs of raised intracranial pressure (ICP) from an, as yet, undiagnosed cause.
○ The dilated pupil infers imminent risk of coning.
○ The priority is to reduce ICP and optimise cerebral perfusion to prevent secondary ischaemia.
○ Ordinarily, cerebral blood flow (CBF) is autoregulated across a range of cerebral perfusion pressure (CPP) (Figure 9.1).
°This mechanism is uncoupled in the event of traumatic brain injury (TBI).
°The CBF, therefore, becomes directly proportional to the CPP.
○ As the intracranial contents are held within a rigid skull, any increase in volume of those contents (e.g. with haemorrhage) opposes CBF to the brain. ICP must now be considered when calculating CPP. This relationship is described by the following equation:
CPP= MAP–ICP
In the event of TBI, factors that affect MAP and ICP are evaluated when optimising CPP.
Ventilation (Figure 9.2): The current aim for PaO2 is >13kPa to provide adequate
substrate for cerebral metabolism as hypoxia is known to be associated with a worse
outcome. The reactivity of CBF to PaCO2 remains relatively robust in the event of TBI
and subsequently hyperventilation, leading to reduced CBF, may rapidly reduce ICP.
However, if subnormal levels (<4.0kPa) are achieved it is at the expense of perfusion
leading to further cerebral ischaemia. It is therefore advisable to aim for PaCO2 4.5–
5.0kPa.
Blood pressure: Increasing MAP may further increase ICP but, in an injured brain,
this may be required to perfuse in the presence of a space occupying lesion.
It is therefore suggested that a target MAP of 80–90mmHg is maintained. This
can be achieved using intravenous fluid +/– vasopressors. Analgesia should be
administered to obtund any sympathetic response to pain.Cerebral metabolism: Reducing cerebral metabolism with sedation and induction
agents results in a reduction in cerebral requirements. There is nothing conclusive,
as yet, regarding induced hypothermia, and normothermia remains the aim.
Actively warming someone is deleterious. Hyper- and hypoglycaemia confer a worse
outcome. A blood glucose <10mmol/L is therefore the aim.
Fluid management: A normal circulating blood volume is required to maintain MAP.
Fluid shifts may occur due to an ineffective blood brain barrier and are governed
by plasma osmolality, not oncotic pressure. Coupled with this knowledge is the use
of hypertonic saline and mannitol to manipulate the volume of oedematous brain
tissue and thereby the ICP.
Mechanical increases in ICP via increased venous pressure: Neck ties should be
avoided. Mechanical ventilation should be facilitated by the use of muscle relaxant
to avoid coughing. The patient should be nursed with a head -up tilt.
The priority in this man is to correct the abnormal PaCO2 to 4.5–5.0kPa before
attending to the stabilisation of the other values. As can be seen from Figure 9.1,
this will have the most significant impact on this patient’s CBF
2
Q
- You are anaesthetising a 78-year-old man for a right upper lobectomy and
lymphadenectomy for adenocarcinoma via video assisted thoracoscopic surgical
approach (VATS). He is a long-term smoker, has chronic obstructive pulmonary disease (COPD) and takes aspirin 75mg o.d. His FEV1 is 1.5 L. Despite your best efforts, you fail to site a thoracic epidural.
Which of the following would be the most appropriate technique to optimise this
gentleman’s perioperative analgesia?
A Single shot paravertebral injection at T6
B Ask the surgeon to site a paravertebral catheter
C Run a remifentanil infusion perioperatively and leave the patient intubated overnight
D Ask the surgeon to site an intrapleural catheter
E Perform intercostal blocks at T5–8
A
- B Ask the surgeon to site a paravertebral catheter
The aims of analgesia in this scenario are:
t To use a technique that covers the wide surgical field: The camera is inserted at
approximately T8 in the mid clavicular line, with ports between T9 +/– T5. Further
pain may be felt from any trauma to the parietal pleura adjacent to the right
upper lobe
t To allow thoracotomy and rib resection if required: The rate of conversion to
open thoracotomy is around 10%, and the need for a lymphadenectomy, which
may be technically difficult, may increase this conversion rate further
t To provide effective intra- and postoperative analgesia: The patient has
significant respiratory disease and effective analgesia will allow extubation, spontaneous ventilation and coughing. Prompt extubation reduces the risk of
ventilator associated complications in the critical care unit, therefore option C is
not the best choice here
Although thoracic epidural analgesia is seen as the gold standard for this scenario,
injection of local anaesthetic into the paravertebral space aims to block spinal
nerves as they leave the intervertebral foramina; providing unilateral analgesia with
a degree of sympathetic blockade. A single shot injection may give analgesia for
over 20 hours but use of a catheter allows infusion of local anaesthetic in the post
operative period and is the best option of those listed here (option B).
In light of failed attempts to site a thoracic epidural, it may be kinder to perform
further procedures when the patient is asleep; surgically placed catheters during
VATS have been described and it would be worth asking the surgeon whether they
can perform this procedure in the first instance.
Intrapleural local anaesthetic, that is administration of local anaesthetic into the
space between the parietal and visceral pleura, would diffuse around the intercostal
nerves as they travel between the inner and innermost intercostal muscles.
However, disruption of the pleura leads to erratic absorption, potential leakage
into any intercostal drains sited and so less effective analgesia. Systemic absorption
via this route is high so option D is neither the safest nor the most effective of
those given. Intercostal blocks (option E) in general do not have adequate duration
for this scenario and offer inadequate analgesia compared with paravertebral
techniques.
3
Q
- You are asked to urgently review a 57-year-old man 7 days post left
pneumonectomy. He remained intubated and ventilated for 24hours post
operatively due to intraoperative bleeding and hypothermia. A left sided intercostal
drain was removed 24hours ago. He is now complaining of cough, shortness of
breath and chest pain. His oxygen saturations are 89% on 15L/min oxygen. On examination there is new subcutaneous emphysema of the chest wall. Heart
rate is 60 beats per minute and blood pressure is 80/50mmHg.
What is the most appropriate next step?
A Urgent chest radiograph (CXR)
B Needle thoracocentesis followed by insertion of 22F intercostal drain
C Immediate insertion of a 12F intercostal drain by the Seldinger technique
D Urgent bronchoscopy
E Urgent CT scan and thoracic surgical opinion
A
- B Needle thoracocentesis followed by insertion of 22F intercostal drain
The clinical signs are suggestive of a massive air leak, possibly from breakdown of the bronchial stump. There are signs of cardiovascular impairment (including
paradoxical bradycardia) suggesting impending cardiovascular collapse. The most likely diagnosis is a bronchopleural fistula leading to tension pneumothorax that should be decompressed immediately by needle thoracocentesis. Other diagnoses could include delayed infection and bleeding so it would be prudent to follow needle decompression with a larger bore (22F) intercostal drain. A smaller 12F
drain inserted via the Seldinger technique may not drain blood/purulent matter
adequately and takes more time to site.
• Obtaining a chest radiograph often takes time that may be detrimental in this scenario.
• Risk factors for bronchopleural fistulae include increased age, poor wound healing, pneumonectomy, previous chemo/radiotherapy and prolonged mechanical ventilation postoperatively.
• Although bronchoscopy +/– CT thorax may be needed to make the diagnosis and assess for any other complications (e.g. empyema) when the patient stabilises, the priority is restoration of oxygenation and adequate cardiovascular parameters. Early bronchial stump breakdown often requires surgical treatment with direct closure or coverage with an intercostal flap.
4
Q
- A 3-year-old boy is under general anaesthesia for the removal of a foreign
body partially obstructing his right main bronchus via rigid bronchoscopy.
He is breathing spontaneously and receiving sevoflurane in air. Foreign body
instrumentation is difficult and after prolonged grasping attempts and suctioning,
he becomes bradycardic with a heart rate of 25 beats per minute.
What is the most likely cause of his clinical deterioration?
A Hypoxia
B Depth of anaesthesia
C Hypothermia
D Hypercarbia
E Vasovagal reflex
A
- A Hypoxia
○ Foreign body aspiration is a dangerous condition most frequently seen in infants
where inadvertent aspiration of objects disrupts the normal airway structure and
function.
○ The classic triad of symptoms consists of paroxysmal coughing, wheezing and reduced breath sounds on the affected side occurring after a witnessed choking
episode.
○ It is a leading cause of death in 1–3 year olds and its safe management is challenging to both surgeon and anaesthetist.
○ The gold standard for managing foreign body aspiration in children is removal via
rigid bronchoscopy under general anaesthesia.
○ The instrument most commonly
used in children is the Storz ventilating bronchoscope which consists of a metal
tube and a removable optical scope (Hopkins rod).
○ During instrumentation, the optical scope is within the lumen of the bronchoscope and provides excellent
visualisation of the airway. The scope however significantly reduces the lumen
of the bronchoscope available for ventilation and should only be used for short periods. Hypoventilation is a real possibility especially if the patient is spontaneously ventilating.
○ Bradycardias during bronchoscopy are uncommon and should be assumed to be
secondary to hypoxia until proven otherwise. Hypoxia can occur if the scope is placed in a bronchus or if instrumentation triggers bronchospasm. ○ Furthermore, when excessive suctioning is performed, there may be atelectasis and a reduction in the inspired oxygen concentration.
○ Also, a feared complication which can cause hypoxia acutely is dislodgement of the foreign body into the trachea creating
complete obstruction of the airway.
○ In order to reduce the risk of foreign body dislodgement whilst allowing
spontaneous ventilation, anaesthesia needs to be deep enough to minimise
coughing and moving without paralysis.
○ Excessive anaesthesia to achieve this can trigger bradycardias, but it is not the most likely cause in the above scenario.
○ The arrhythmia occurred after prolonged instrumentation which would have restricted the spontaneous ventilation and elevated the boy to a lighter plane of anaesthesia.
○ Children are commonly affected by inhaled foreign bodies and it is important for the anaesthetist to also be aware of the challenges of paediatric anaesthesia.
○ Children are at more risk of becoming hypothermic during anaesthesia which if severe, can cause arrhythmias. The patient’s core temperature in the above case however is highly unlikely to be sufficiently low to produce this response.
○ There are vagal sensory nerves within the conducting airways and stimulation
by bronchoscopy can cause reflex spasm and bradycardia. Coughing during
bronchoscopy may also illicit a vagal response. The fact that the bradycardia
occurred after prolonged instrumentation (as opposed to during), and no coughing
occurred makes this diagnosis less likely.Hypercarbia occurs frequently during rigid bronchoscopy, particularly in spontaneously
ventilating patients and where there is frequent use of the optical scope or forceps restricting ventilation. Hypercarbia however is more likely to cause an initial tachycardia
as opposed to a bradycardia due to an increased sympathoadrenal tone
5
Q
- A 48-year-old woman has had an arthroscopic rotator cuff repair. She has received
a general anaesthetic, a supraglottic airway was inserted and had an interscalene
block. Her surgery finished at midday.
Which of the following is most likely to prevent her from being discharged on the
day of surgery?
A Lives in a rural location 30minutes by car to the nearest hospital
B Has an adult relative to act as carer at home only until 20.00
C Hasn’t yet passed urine
D Is taking a public taxi home with an adult relative
E Has residual upper arm weakness
A
- B Has an adult relative to act as carer at home only until 20.00
○ In the ‘ten high impact changes’ document published by the NHS Modernisation Agency it is outlined that day surgery, rather than inpatient surgery, should be treated as the norm for all elective surgery. Locally agreed protocols exist in most day case units for selection and exclusion criteria. These fall broadly into medical, surgical and social considerations (Table 9.1).
○ It is important to note that patients can be discharged with residual effects after
nerve blockade so long as the duration of effects are explained and the patient has
received written and verbal instructions of what to expect.
○ Mandatory oral intake and ability to void are no longer considered essential discharge criteria unless
manipulation of the bladder has occurred. ○ Distance from the hospital should be
individually assessed, but some units set 60 minutes as a practical limit. An escort
home and for the first 24hours are still necessary although this may be relaxed in
the future for minor procedures with very short anaesthetics where patient is not
compromised by the time of discharge.
6
Q
- A 78-year-old man is listed for a transurethral resection of his prostate (TURP) under spinal anaesthesia. He has moderate to severe chronic obstructive pulmonary disease (COPD) with ongoing steroid use, ischaemic heart disease, and had a coronary stent inserted 15 months ago. He normally takes aspirin and clopidogrel, but has not been taking the latter for “a few weeks”. He has also recently started taking rivaroxaban 10mg at night for an irregular heart rate.
What is the safest way to proceed?
A Ensuring 18hours after the last dose of rivaroxaban, give a spinal, and then start a heparin infusion postoperatively
B Give a spinal now and use treatment dose low molecular weight heparin
(LMWH) from 2hours postoperatively
C Wait until 24hours after the last dose of rivaroxaban, then proceed with a spinal, and give the next dose immediately postoperatively
D Ensure 12hours after the last dose of rivaroxaban, and give prophylactic
LMWH 6 hours postoperatively
E Discuss with the patient the increased risks of central neuraxial blockade and proceed under general anaesthesia
A
- A Ensuring 18 hours after the last dose of rivaroxaban, give a
spinal, and then start a heparin infusion postoperatively
Vast numbers of patients present for surgery on antiplatelet drugs. The perioperative
management of these medications commonly falls to anaesthetists to coordinate,
and there is a significant overlap also in the assessment of cardiac risk for non-
cardiac surgery. A solid understanding of these issues will help in preparation for
both the written and viva elements of the Final FRCA.
Aspirin and clopidogrel
○ Aspirin is an irreversible inhibitor of platelet cyclooxygenase (COX), and thus normal platelet function relies on new platelet manufacture, which takes approximately 7 days.
○ Aspirin is not contraindicated in central neuraxial blockade (CNB), as the risk of
haematoma is not elevated.
○ Conversely, clopidogrel is associated with haematoma formation in case reports.
- It is a thienopyridine adenosine diphosphate (ADP) blocker, and published advice is to avoid for at least 7days prior to CNB.
- Prasugrel, a more potent thienopyridine, should be avoided for 7–10days and not restarted until 6hours after block or catheter removal, where clopidogrel can be given just afterwards.
Tirofiban/abciximab
○ These two are glycoprotein IIb/IIIa blockers, in the case of abciximab this is via binding of a monoclonal antibody. -Tirofiban is the shorter acting of the two, and CNB can be attempted after 8 hours, whereas antibody persistence means a duration of 24–48hours is needed for abciximab.
Warfarin
- An international normalised ratio (INR) of ≤1.5 is known to be associated with
clotting factor levels of >40% and is regarded as safe for CNB.
Dabigatran/rivaroxaban
- Dabigatran is an oral thrombin inhibitor only licensed for venous thromboembolism (VTE) prophylaxis after surgery.
- CNB should not be established in patients already on this drug, as it is contraindicated by the manufacturer.
- It can be started 6 hours after the risk period.
- Rivaroxaban is a direct oral inhibitor of factor Xa.
- It is becoming more common as the list of approved indications increases. Previously only for postoperative VTE prophylaxis, it is now being used in AF and in Europe as an
adjunct to aspirin and clopidogrel in acute coronary syndromes. CNB should be
12–18hours post-dose, and the drug should only be given 6 hours after a block or catheter removal.
Heparins
- With the low molecular weight heparins (LMWH), the duration between
administration and safe block depends on dosage.
- Therapeutic dose requires a 24-hour delay, whereas prophylactic dose, a gap of 12hours. In both cases 2–4 hours is the duration until restarting following block or catheter removal.
Fondaparinux
- Fondaparinux is another factor Xa inhibiting drug, although with a long half-life of 21hours. It has little effect on thrombin and no antiplatelet effect. At treatment doses no CNB is permitted, but in prophylactic doses, CNB can be performed after 36hours, with 6 hours to elapse before the next dose, but 12hours after epidural catheter removal.
- Use of dual antiplatelet therapy (DAPT) is essential for the prevention of stent
thrombosis following coronary stenting, particularly after a drug eluting stent.
- Here the minimum recommended time for DAPT is normally 12months, and for
stopping or withholding DAPT, the cardiac risk of stent thrombosis often exceeds the operative risks of bleeding. This gentleman has been off clopidogrel greater than the
minimum of 7days, such that his clopidogrel is no longer an issue.
- However, the confounding issue is now the rivaroxaban, which is appearing in the
drug history of more and more patients.
- Mainly used for postoperative venous
thromboprophylaxis there are now indications for atrial fibrillation and in the
treatment of acute coronary syndrome patients.
- The recommended omission
time here is 12–18 hours, and restarting should be 6 hours after block or catheter
removal. The other important safety issue with rivaroxaban is the lack of any
mechanism of reversal, which probably makes its use here in the immediate
postoperative phase unwise.
-Therefore the safest approach for this patient is to have the required 18hours off rivaroxaban before preforming a spinal anaesthetic with a heparin infusion postoperatively.
7
Q
- A 64-year-old man undergoes hip surgery under general anaesthesia. He is positive
pressure ventilated through a size 5 laryngeal mask airway and anaesthesia is
maintained with nitrous oxide and sevoflurane. In recovery, he complains of
paraesthesia over the right anterior aspect of his tongue. There is no dysphagia or
dysarthria and tongue appearance and movements are normal.
What is the most likely cause of his neurological signs in recovery?
A Hypoglossal nerve injury
B Lingual nerve injury
C Recurrent laryngeal nerve injury
D Inferior alveolar nerve injury
E Venous drainage obstruction
A
- B Lingual nerve injury
The laryngeal mask airway (LMA) is a versatile supraglottic airway device which
consists of a tube connected to an inflatable cuff which surrounds a mask designed
to seal off the laryngeal inlet from the gastrointestinal tract. However, it is not a
definitive airway and vigilance against aspiration is advised particularly when used
in conjunction with positive pressure ventilation. Another recognised complication
associated with laryngeal mask airway ventilation is pressure neurapraxia to
anatomically vulnerable nerves within the pharynx or oral cavity.
A neurapraxia refers to a localised and transient conduction block along a nerve
without any anatomical interruption, which in the above case is likely to be caused
by pressure from the cuff. Predisposing factors include the use of nitrous oxide, cuff
over-inflation, using an undersized laryngeal mask airway, the lateral position and a
difficult insertion.
The lingual nerve is a branch from the mandibular division of the trigeminal
nerve and supplies sensory innervation to the anterior 2/3 of the tongue. It also
carries sensory taste fibres from the anterior tongue to the facial nerve via the
chorda tympani. Damage to the lingual nerve characteristically produces a loss of
sensation and taste confined to one side of the anterior tongue without any motor
dysfunction. Although rare, lingual nerve neurapraxia is a recognised complication of laryngeal mask use and is the most likely pathology in the above scenario. The
lingual nerve is vulnerable to compression as it enters the mouth below the superior
constrictor and continues against the medial aspect of the mandible.
The hypoglossal nerve carries purely motor fibres and supplies all the intrinsic
muscles of the tongue. Like its name suggests, it can be found below the tongue
and is vulnerable to compression as it travels above the hyoid bone. Case reports
of damage to this nerve following LMA usage have been documented, although
the symptoms and signs are different from the case above. Sufferers may complain
of difficulties in swallowing, articulating speech and the tongue feeling ‘heavy’.
The protruded tongue will also deviate towards the side of the lesion due to the
unopposed action of the contralateral genioglossus muscle.
The recurrent laryngeal nerve is a branch of the vagus nerve which conveys sensory
and motor innervation to the larynx. This nerve can also be damaged following LMA
siting and symptoms include dysphonia, stridor, dysphagia and postoperative lung
aspiration, but not tongue paraesthesia as in the case above. The recurrent laryngeal
nerve is at risk of being compressed against the cricoid cartilage as it enters the
larynx at the apex of the piriform fossa.
The inferior alveolar nerve is the largest branch of the mandibular division of
the trigeminal nerve, and supplies motor fibres to the floor of the mouth and
sensory innervation to the lower teeth and chin via the mental nerve. Commonly
anaesthetised for dental procedures, blockage of this nerve can also occur following
LMA use. The nerve runs a superficial course between the last molar and the ramus
of the mandible, making it vulnerable to compression there. The featured case
lacked dental or facial symptoms, making this answer incorrect.
The LMA can also impede the venous drainage of the tongue and there have been
case reports of postoperative oedema and cyanosis with or without associated
tongue paraesthesia. The venous drainage of the tongue occurs via the dorsal and
deep lingual veins which can potentially be occluded by the LMA. In the case above,
the normal appearance of the tongue counts against this diagnosis.
8
Q
- A patient with an acute subarachnoid haemorrhage is undergoing coil
embolisation of the aneurysm in the interventional neuroradiology suite.
Anaesthesia is induced with alfentanil, propofol and rocuronium. Maintenance of
anaesthesia is with sevoflurane and remifentanil infusion. Shortly after intubation
the observations are as follows:
r Blood pressure: 220/110mmHg
r Heart rate: 90 beats per minute
r Spo2 98%
r ETCO2 4.9 kPa
r End-tidal sevoflurane 1.9%
What is the most appropriate initial management?
A Alert radiologist
B Increase depth of anaesthesia
C Increase minute ventilation
D Give mannitol 1 g/kg
E Start intravenous esmolol infusion
A
- A Alert radiologist
General anaesthesia is often used for aneurysm coiling as it allows control over
parameters to provide optimal cerebral perfusion pressure (CPP), and provides an
immobile patient. These procedures are carried out often in a site remote from the
theatre complex and can be long.
A sudden rise in blood pressure should alert the anaesthetist to the possibility of
aneurysm rupture, which has an intraoperative incidence of 2–19%. Rupture can occur spontaneously, during induction, or as a result of guidewire, microcatheter
or coil placement. The priority during induction of anaesthesia is to avoid a
hyperdynamic response to laryngoscopy, whilst maintaining adequate cerebral
perfusion pressure. The pressor response can be attenuated using co-induction with
short acting opiates and beta-blockers and confirming adequacy of muscle paralysis
prior to intubation.
Signs of rupture and bleeding under anaesthesia may be subtle and the
radiologist should be immediately alerted of any sudden haemodynamic
changes. Depending on the stage of procedure and degree of bleeding, coiling
may continue, but transfer to theatre may be required for ventriculostomy
or rescue craniotomy and clipping, so assistance should be sought early. The
other options in this question are appropriate actions but should follow after
communication of the changes to the radiologist in case of rupture. Interventions
can then be made to control arterial pressure by deepening anaesthesia or using
beta-blockers and if necessary to control intracranial pressure by head elevation,
maintaining PaCO2 to 4.5–5.0 kPa, administering mannitol or reversing any heparin
administered with protamine.
Other complications that can occur during these procedures are thromboembolic or
iatrogenic occlusion of a vessel, vasospasm, contrast reactions, and displacement of
lines and tubes by movement of the image intensifier.
9
Q
- A 10 kg child with no comorbidities is scheduled for an elective umbilical hernia
repair as a day case.
Which of the following would be the best regime of injectate for caudal epidural
analgesia?
A 10mL of 0.25% levobupivacaine with 10μg fentanyl
B 10mL of 0.25% levobupivacaine
C 10mL of 0.25% plain bupivacaine with 300 μg diamorphine
D 10mL of 0.25% levobupivacaine with 25 μg clonidine
E 10mL of 0.25% bupivacaine
A
- B 10 mL of 0.25% levobupivacaine
Caudal epidural analgesia is the commonest regional technique used in children. It
is suitable for all infraumbilical surgery, including hypospadias repair, circumcision
and inguinal or umbilical hernia repair. It provides a reliable block between T10 and
S5 in children less than 20kg. The combination of minimal side effects and excellent
analgesia make it suitable for day case surgery.
Since motor block is poorly tolerated in awake children, local anaesthetic choice
prioritises weakest motor block and the long lasting analgesic effects possible.
Although bupivacaine meets these criteria, levobupivacaine and ropivacaine are the
drug of choice in paediatric practice. They produce a differential block by preserving
the motor function with the same analgesic effect. They also have less cardiac and
central nervous system toxicity.
The volume of caudally injected local anaesthetic determines the spread of the block
and must be adapted to the procedure. Doses described by Armitage are the most
frequently used regimen in current paediatric practice:
Sacro-lumbar block: 0.5mL/kg, 0.25% bupivacaine or levobupivacaine
Upper abdominal block: 1mL/kg, 0.25% bupivacaine or levobupivacaine
Mid-thoracic block: 1.25mL/kg, 0.25% bupivacaine or levobupivacaineThe addition of clonidine (1–2μg/kg) and preservative-free ketamine (0.5mg/kg)
increases the duration of analgesia by 5–10hours. Both drugs at higher dose are
associated with a greater risk of sedation, apnoea or nausea, and therefore should
be avoided in day case surgery. In option D, the dose of clonidine is higher than the
recommended dose.
Morphine 50μg/kg or diamorphine 30μg/kg may increase the duration of analgesia
by 24hours. However, they commonly cause unpleasant side effects such as nausea
and pruritus, and have a risk of delayed respiratory depression. Opioid additive to
the local anaesthetic agents should be avoided in day case surgery settings because
of the side effects, and is therefore inappropriate in this scenario.
Fentanyl, however, does not prolong the duration of analgesia and significantly
increases the incidence of nausea and vomiting thus would be unsuitable in this
scenario.
10
Q
- A 65-year-old man for elective thoracotomy and pulmonary lobectomy is to have a
thoracic epidural for perioperative analgesia.
Which of the following is the best approach for epidural insertion?
A A midline mid-thoracic epidural under general anaesthesia
B A paramedian mid-thoracic epidural under light sedation or awake
C A paramedian lower-thoracic epidural under general anaesthesia
D A midline upper lumbar epidural under light sedation or awake
E A midline mid-thoracic epidural under light sedation or awake
A
- B A paramedian mid-thoracic epidural under light
sedation or awake
Thoracic epidural analgesia is commonly used in cardiothoracic surgery for
providing sympatholysis and pain relief during and after operations. The main
objective is to allow cardiothoracic pain-free patients to breath adequately, cough
and cooperate with chest physiotherapy.
A good anatomical knowledge is essential for successful epidural block. The spinous
processes of cervical, thoracic and lumbar vertebrae have different alignment. They
are posteriorly directed and relatively straight at the cervical, lower thoracic and
lumbar levels. However, they are caudally inclined in the high- and mid-thoracic
regions. The highest degree of angulation is at T3–T7, making the paramedian
approach easier at this level.
A thoracic epidural catheter for thoracic surgery is usually sited at a level
corresponding to the upper dermatomal level of the incision, most commonly in
the mid-thoracic level (T6–T7). In this example, an upper lumbar approach will not
provide adequate analgesia.
Always examine patient’s back and identify the bony landmarks before inserting
thoracic epidural needle. Classical landmarks are spine of scapula at T3 and the
inferior angle of scapula at T7. You can confirm the correct interspace by counting up
from L3/4.
Thoracic epidural anaesthesia is better performed in a lightly sedated or awake
patient. Insertion of an epidural needle in the lightly sedated/awake patient has two
advantages: pain and/or paraesthesia warn of any potential neurological damage;
and the sensory block extension can be examined before commencing general anaesthesia. Thus in the above clinical scenario, a paramedian mid-thoracic epidural
in a lightly sedated or awake patient would be most appropriate.
11
Q
An 84-year-old ASA 3 woman is listed for multilevel facet joint injections and a
caudal epidural by the orthopaedic surgeons. The patient will need to lie in the
prone position. Comorbidities include moderate chronic obstructive pulmonary
disease (COPD), angina, hypertension and chronic lower back pain. Alongside all
her cardiovascular medications she takes regular co-dydramol and amitriptyline
for her pain.
The safest anaesthetic technique for this procedure is:
A 0.25–0.5mg/kg intravenous ketamine
B Local anaesthesia only with no sedation
C Infusion of remifentanil at 0.25Pg/kg/min
D Target controlled infusion of propofol at a 1Pg/mL
E 0.5μg/kg fentanyl followed after several minutes by small doses of intravenous
midazolam titrated to effect
A
- E 0.5μg/kg fentanyl followed after several minutes by
small doses of intravenous midazolam titrated to effect
Sedation is required in a myriad of clinical settings and across many specialties.
Complications arise not uncommonly and not just from the inappropriate use
of agents, but from the inadequate skills and training of operators, poor patient
assessment, and lack of or failure to use appropriate levels of monitoring. Despite
the fact that anaesthetists have the detailed knowledge and skills required to give
sedation safely, few had received any formal training in sedation per se. Thus, since
August 2010, the curriculum for anaesthetic training now includes sections on
sedation.
Pre-assessment
Poor or absent pre-assessment is a theme common to many adverse events in
sedation practice. Thus, the pre-assessment must be thorough, and to the same
standard as that required for formal general anaesthesia. This must include all
relevant drugs, allergies, comorbidities and an airway assessment to predict features
associated with difficult intubation and/or mask ventilation.
Monitoring
Guidance recommends the use of non-invasive blood pressure, pulse oximetry
and ECG which may be modified to suit the needs of the patient, or the degree of
sedation being provided. Verbal communication is essential as a monitor of depth of
sedation, and if verbal communication is lost the patient requires the same standard
of care as for general anaesthesia. Capnography is very useful, and may be essential
where clinical assessment during the case is limited by access to the patient, e.g.
MRI. Some would recommend capnography for all patients.
Levels of sedation
t Minimal: Normal verbal response, airway normal and responds to pain
t Moderate: Responds purposefully to voice or pain, no airway intervention
required
t Deep: Only responds after repeated pain, may need airway and ventilator support
Principles and drugs
t Single agents are easier to titrate and tend to be safer
t Synergistic effects (e.g. benzodiazepines following an opioid), may increase risks
by reducing safety marginst Anaesthetic agents such as propofol and remifentanil have narrow therapeutic
windows and thus reduced safety margins
t Painful procedures need to include an analgesic agent
t In an opioid/benzodiazepine combination technique, the opioid should be given
and allowed to have a full effect. Then small amounts of benzodiazepine may be
titrated to effect
t Loss of verbal contact requires the same standard of care as for a general
anaesthetic
The key here is that the procedure (and also the positioning) itself is uncomfortable,
even with local anaesthesia infiltration. The patient also takes an opioid in the
community, and has established chronic back pain. Thus analgesia is essential.
Ketamine would provide sedation and analgesia, but the sympathomimetic effects
may be best avoided in the setting of her angina, the severity of which is not stated.
Remifentanil, despite being a nearly ideal short-acting opioid, carries the significant
risk of respiratory suppression. Thus the best combination is fentanyl, followed later
by small aliquots of midazolam
12
Q
- A 62-year-old non-diabetic woman presents to the intensive care unit with severe
urosepsis.
Which of the following glucose levels would be the most appropriate to target?
A >4mmol/L
B 4–6mmol/L
C 6–8mmol/L
D <10mmol/L
E <15mmol/L
A
- D <10mmol/L
Whilst poor glycaemic control is associated with worse morbidity and mortality, the
optimal glucose level remains controversial. Early trials suggested benefit from tight
glycaemic control (4–6mmol/L), however recent evidence suggest that there is no
additional benefit and in fact, may cause possible harm.
Leuven I was a single centre trial of surgical intensive care unit patients comparing
intensive (tight) to conventional glucose control. The results suggested a 34%
decrease in mortality with tight glucose control, with additional reductions in the
occurrence of sepsis, acute renal failure and critical illness polyneuropathy. However
these results were not concurred in a subsequent trial (Leuven II) by the same
author in medical intensive care patients. The uncertainty lead to a large multicentre
randomised control trial (Normoglycemia in Intensive Care Evaluation-Survival
Using Glucose Algorithm Regulation; NICE SUGAR) in 2009. 6,000 patients were
randomised to tight (4.5–6mmol/L) or conventional glucose control (<10mmol/L).
The results of NICE SUGAR suggested an increase in mortality (27.5% vs 24.9%) and
a significant increase in hypoglycemic events (6.8% vs 0.5%) in the tight versus the
conventional glucose control groups. The trial evidence was incorporated into the
‘2010 International recommendations for glucose control in the adult non-diabetic
critically ill’:
t <10mmol/L strongly suggested
t severe hypoglycemia is defined as <2.2mmol/L
t glucose levels should be sampled from arterial rather than capillary or venous
blood, using laboratory or blood gas analysers rather than point of care anaylsers
This is reiterated in the 2012 Surviving Sepsis guidelines:1. A protocolised approach to blood glucose management in ICU patients with
severe sepsis commencing insulin dosing when two consecutive blood glucose
levels are >180mg/dL (>10mmol/L). This protocolised approach should target
an upper blood glucose ≤180mg/dL rather than an upper target blood glucose
≤110mg/dL (<6.1mmol/L) - Blood glucose values be monitored every 1–2hours until glucose values and
insulin infusion rates are stable and then every 4 hours thereafter - Glucose levels obtained with point-of-care testing of capillary blood be
interpreted with caution, as such measurements may not accurately estimate
arterial blood or plasma glucose values
Based on these recent guidelines, option D is most appropriate. However this
remains a subject for debate and questions remain whether an interim between
current practice and the intensive glucose targets may be optimal or whether tight
glucose control are in fact beneficial in subgroups of patients.
13
Q
- A 19-year-old male motorcyclist is admitted following a high speed road traffic
accident. The retrieval team report he has clinical evidence of bilateral flail
segments and a significant neurological injury. He is intubated and sedated by the
retrieval service with intermittent doses of ketamine, propofol and rocuronium
and arrives to the intensive care unit. He has been haemodynamically stable with
moderate and escalating ventilator requirements.
The most appropriate sedation regime for this patient on the intensive care unit
would be:
A Propofol and fentanyl
B Clonidine and fentanylC Midazolam and fentanyl
D Ketamine and fentanyl
E Fentanyl alone
A
- A Propofol and fentanyl
Sedation protocols are diverse and consideration of the purpose of sedation, patient
characteristics and the pharmacology of the sedative agents should guide the
decision. The purpose of sedation is to allow a reduction in patients’ awareness and
their response to external stimuli. Under-sedation results in hypercatabolism and
increased sympathetic activity, which can have detrimental effects, for example
myocardial ischaemia. However, oversedation is problematic resulting in increased
mechanical ventilation days, respiratory and cardiovascular depression, delayed
neurological recovery and impairs muscular rehabilitation. It is important that
sedation is titrated to the individual patient’s requirement; scoring systems such as
the Richmond Agitation Sedation Scale (RASS) aid this.
In this example, the patient has been involved in a high speed injury and sustained
a neurological injury and a severe thoracic injury. While the extent of his injuries
are ascertained it is sensible to keep him sedated. Clearly in this patient, who has
escalating ventilator requirements, potentially life threatening injuries such as a
pneumothorax need to be excluded. However, the extent of his neurological injury
will need to be assessed at the earliest opportunity, necessitating an early sedation
hold.
Sedation techniques comprise of non-pharmacological and pharmacological.
Non-pharmacological techniques can be used to reduce anxiety and improve
sleep such as frequent communication, day/night orientation and music therapy.
Pharmacological agents can augment this approach, providing analgesia, anxiolysis,
hypnosis and amnesia. The can be classified as inhalational or intravenous
anaesthetic agents (such as propofol), benzodiazepines (e.g. midazolam, diazepam
and lorazepam), opioids (e.g. fentanyl, alfentanil, remifentanil), α2 agonists (such
as clonidine and the newer dexmedetomidine) and neuroleptic agents (such as
haloperidol and chlorpromazine). In the example of a patient who has sustained extensive chest wall injuries, an
opioid to provide analgesia would seem sensible. Whilst clonidine would also
provide an analgesic component, it can result in haemodynamic compromise and is
unadvisable until visceral or vascular injury has been excluded.
While a pure opioid regime can in theory provide an element of hypnosis, in practice
this is difficult to achieve. The ideal characteristic of the choice of hypnotic agent
should include ease of titration, short half-life, minimal pharmacodynamics adverse
effect, cheap and familiar to both nursing and medical teams.
Of the agents listed, propofol is closest to these ideal characteristics. Midazolam
has active metabolites and there are concerns regarding dependence. Ketamine
provides dissociative anaesthesia with associated neuropsychiatric sequelae.
Ketamine is also a sympathomimetic which may be detrimental especially in the
presence of a severe head injury.
Recent trials show promise with dexmedetomidine, when compared to propofol and
midazolam. However it remains expensive and is still associated with significant side
effects, so its role in the intensive care needs to be further investigated.
14
Q
- A 26-year-old woman who is 32/40 pregnant had a witnessed collapse whilst
shopping. She received bystander cardiopulmonary resuscitation (CPR) and
advanced life support (ALS) by the paramedics for one hour prior to transfer to a
teaching hospital. In hospital, a Caesarean section was performed immediately.
ALS continued for a further 45minutes without return of spontaneous circulation
and a profound metabolic acidosis developed.
What now is the most appropriate management option?
A Terminate life support and organise a team debrief
B Administer thrombolysis and continue ALS
C Continue ALS until the intensive care consultant arrives
D Commence extra-corporeal membrane oxygenation (ECMO)
E Administer 10–20mL of 8.4% sodium bicarbonate
A
- D Commence extra-corporeal membrane oxygenation
(ECMO)
This scenario is based on a real case and this patient and her child both survived to
discharge neurologically intact.
ECMO uses technology refined from cardiopulmonary bypass circuits used for cardiac
surgery. As the technology advances and with the opportunity to gain experience in
its use (the H1N1 swine-flu epidemic of 2009) the complication rates have decreased.
The CESAR trial evaluated the benefits of ECMO in adult respiratory distress syndrome
(ARDS) and demonstrated that patients transferred to a centre offering ECMO had a
better outcome (less death or severe disability at 6months) than those treated at the
original hospital with conventional therapy. However, treatment at the ECMO centre
did not always involve ECMO and the improvement in outcome was not shown when
comparing ECMO verses conventional ventilation at the ECMO centre.
An ECMO circuit can be set up in three ways:
t Venoarterial ECMO: blood is pumped from the venous to the arterial side
allowing gas exchange and haemodynamic support
t Venovenous: blood is removed from the venous side and then pumped back into
it facilitating gas exchange only
t Arteriovenous: arterial pressure moves the blood from the arterial side to the
venous side and facilitates gas exchange. No mechanical pump is required.
The large-bore cannulae are placed surgically or with a percutaneous approach
under ultrasound or X-ray guidance. The circuit is more effective at carbon dioxide
removal than oxygenation due to differences in solubility between the two gases.
Anticoagulation is required as the circuit activates the coagulation cascade.Complications include:
t Haemorrhagic complications (50% of patients):
– 50% of these due to the cannulation, especially at the arterial site
– Intracranial bleeding (5%)
– Bleeding may occur in any organ
t Thrombosis in the circuit can:
– Affect the function of the pump or the oxygenator
– Cause stroke
– Result in leg ischaemia
t Infective complications can be related to the invasive lines or primary pathology
t Technical complications include:
– ECMO circuit failure or breakage
– Cannula displacement
– Mechanical pump failure
A meta-analysis of studies using ECMO as rescue therapy during cardiopulmonary
resuscitation (CPR) demonstrated an increased survival in younger patients after
instigating ECMO during or immediately after manual CPR. There is an increasing
drive to consider early initiation of ECMO, and the emergency department ECMO
project strives to initiate pre-hospital and emergency department ECMO CPR.
Returning to the scenario, this young woman who has had continuous CPR and has
not responded to support measures should be considered for ECMO if it is available.
To ensure the best outcome, oxygenated blood flow to the brain should be restored
as early as possible. Pregnancy is an absolute contra indication to thrombolysis as
is having a major operation within 14days. After a rushed emergency department
cesarean section with a low cardiac output state (and therefore difficulty identifying
bleeding points) thrombolysis would have a high complication rate may only be
considered if no alternative was available
15
Q
- A 76-year-old woman has had an upper gastrointestinal bleed and presented with
an acute kidney injury. After resuscitation and an oesophago-duedenoscopy she
is admitted to the intensive care unit for renal replacement therapy. The nurse
requests that you prescribe the particulars of renal haemofiltration including the
anticoagulation.
The most appropriate choice is:
A Unfractionated heparin loading dose followed by a pre-filter infusion
B No anti-coagulation
C Prostacyclin infusion
D Sodium citrate pre-filter infusion
E Increasing the fraction of replacement fluid added before the filter
A
- C Prostacyclin infusion
One third of critically ill adults develop an acute kidney injury and 5% of these will
require renal replacement therapy. This question highlights some of the complexities
of managing a patient on renal replacement therapy.
The indications for renal replacement therapy include:
t Fluid balance management
t Hyperkalaemia (potassium over 6.5mmol/L)
t Metabolic acidosis (pH <7.1)
t Raised urea (>30mmol/L) or symptomatic ureamia
t Severe sepsis to remove inflammatory mediators
t Removal of water-soluble, low protein-bound drugs, e.g. some antibiotics to
increase dose administered.The different types of renal replacement therapy are:
t Haemo-(ultra)filtration: venous blood is pumped into an extra-corporeal
circuit which creates a hydrostatic pressure gradient across a semi-permeable
membrane. Plasma (ultrafiltrate) and molecules of less than 50,000 Daltons are
forced across by convection. The plasma is replaced by fluid either before or after
the filter to maintain volume and haematocrit
t Haemodialysis: venous blood is pumped into a dialyser in which blood is
separated by a semi-permeable membrane from a countercurrent flow of dialysis
solution. Solute moves along its concentration gradient from blood to dialysis
solution (e.g. urea) or from solution to blood (e.g. bicarbonate) by diffusion
t Haemodiafiltration: this is a combination of the two.
The methods can be applied intermittently or continuously, with continuous
methods (filtration or dialysis) being preferred on the intensive care unit due to
cardiovascular stability.
Anticoagulation is required as all extra-corporeal circuits activate the clotting cascade.
Clot that forms within the catheter causes an access pressure alarm, whereas clot
that forms in the filter will cause a trans-membrane alarm. The latter will reduce the
efficiency of the filter and if it clots of completely then blood within the circuit is lost.
Non-pharmacological methods to prevent clot formation include:
t Ensure adequate driving pressure (venous pressure)
t Ensure adequate flow rates through the vascular-catheter (vascath):
– Correct site choice (femoral preferred over right internal jugular which is in turn
preferred over left internal jugular veins)
– Good insertion technique
– Catheter position and care
t Adding replacement fluid before the filter (pre-dilution) lowers the haematocrit and
reduces the chance of filter clot but reduces the efficacy of the filtration process
If the patient has a coagulopathy (INR >2, APTT >60 seconds) no anti-coagulation is
required, however most patients require pharmacological treatment to prolong the
life of the filter.
Pharmacological methods include:
t Unfractionated heparin: increases anti-thrombin III formation. It is the most
commonly used, fully reversible by protamine and the anticoagulation effect can be
easily titrated by measuring the activated partial thromboplastin ratio (APTR). Given
into the circuit before the filter results in less systemic anticoagulation then when
given systemically, but monitoring is required and the APTR should be less than 2.
There is an increased risk of bleeding and heparin-induced thrombocytopenia
t Prostacyclin or prostaglandin E2 inhibit platelet function and has a short half-life
resulting in rapid reversal of the anti-coagulation effect on termination. It causes
vasodilatation and therefore can worsen cardiovascular instability, hypoxia in
patients dependent on hypoxic pulmonary vasoconstriction, and intracranial
hypertensiont Regional citrate: infused pre-filter chelates calcium and prevents clot-formation.
Calcium is added post-filter. It is effective and reduces bleeding rates, but may
cause metabolic abnormalities and is rarely used in the UK
t Danaparoid and lepirudin may be used instead of heparin if heparin-induced
thrombocytopenia develops but is no more effective, bleeding rates are equivocal
and they are not easily reversed.
Therefore, in this patient who has been resuscitated (which in the context of a
gastrointestinal bleed means the coagulation has been normalised), the safest
option in this case would be prostacyclin infused into the filter, which will result in
minimal systemic anti-coagulation and may be reversed by terminating the infusion.
Heparin given into the circuit still causes systemic anticoagulation and increases the
bleeding risk.
16
Q
- A 65-year-old man is recovering on the high dependency unit after an
emergency laparotomy for small bowel perforation for which he received an
effective epidural. His background includes treated hypertension, a smoker of
20 cigarettes per day and mild depression. Overnight he becomes very agitated
and confused and attempts to remove his invasive lines and monitoring.
Examination, review of his blood science investigations and blood gas results are
all unremarkable.
What is the most appropriate course of treatment?
A Reassure the patient regarding his situation
B Call his wife to hospital to help calm him down
C Prescribe vitamin replacement therapy and benzodiazepine sedation
D Prescribe haloperidol
E Commence sedation with clonidine
A
- D Prescribe haloperidol
Delirium in critically ill patients is common, with 60–80% of patients being affected.
It is characterised by an acute change in cognition and disturbance of consciousness
and may follow a fluctuating course. There is an increased length of ventilation,
intensive care stay, hospital stay, risk of infection, risk of long-term cognitive
impairment and mortality. There is a much higher rate of adverse incidents such as
self-extubation and removal of catheters and lines.
The different types of delirium are:
t Hyperactive delirium (5–22%), which is the case described above, and includes
agitation, hallucinations and aggressiont Hypoactive delirium is more common, presenting with inattention and decreased
situational awareness, but may be peaceful and compliant so is often not diagnosed
t Mixed delirium is a fluctuation between the two extremes above
The risk factors for developing delirium are show in Table 9.2.
There are two different delirium assessment methods in the intensive care unit to be
aware of for the exam, both of which are described in detail in the references below:
t Intensive Care Delirium Screening Checklist (ICDSC): Patients are scored for
alertness from waking, and then their attention, orientation, agitation or
retardation, hallucinations, speech and mood and sleep cycle is scored daily. A
score of 4 or more has a sensitivity of 99% but a low specificity of 64%
t Confusion Assessment Method in the intensive care unit (CAM-ICU): This is
designed for ventilated patients and has a high sensitivity and specificity.
Following a level of consciousness assessment (Richmond agitation sedation scale
is commonly used), attention, organised thinking and ability to follow instructions
is assessed
Preventative management includes ensuring a correct and adequate sleep pattern,
constant information and reassurance regarding their situation and as consistent
as possible attendants (family members are the best). The management of delirium
is multi-factorial, and includes exclusion of reversible organic causes as described
above, which requires an examination and review of relevant investigations.
Pharmacological management can be considered in an escalating fashion:
t Haloperidol 2.5mg intravenously, doubling the dose every 30minutes until
settled followed by a regular regime. Side-effects include prolongation of the QT
interval and an extra-pyramidal movement disorders
t Olanzapine 5mg orally or intramuscularly may be considered as an alternative
t Quetiapine, an atypical antipsychotic is being used increasingly as an alternative
to haloperidol, has equal efficacy and safety, without extra-pyramidal side effects
t Dexmedetomidine, an α2 adrenoceptor agonist, similar to clonidine, has also been
used in ventilated patients with delirium and is as effective as haloperidol. A bolus
of 0.1Pg/kg followed by 0.2-0.7Pg/kg/hour may be used.
It is worth noting that other sedation methods including opioids and
benzodiazepines may contribute to delirium, although benzodiazepines do have a
role in alcohol withdrawal.
The question describes a patient in danger of harming himself in the immediate-
term, and therefore the preventative measures are likely to be unhelpful. There is
no firm evidence of alcohol consumption excess and it is too early in the patients
clinical course to blame this on alcohol withdrawal, therefore benzodiazepine
treatment may exacerbate his condition. The first line treatment is haloperidol,
followed by other measures if unsuccessful.
30
Q
- You are reviewing a study that randomised two groups of patients to receive
sedation either at the discretion of the caregivers or by following a strict protocol.
The study hypothesis is that protocolisation reduces the total cumulative dose of
sedative medications.
Which of the following statistical tests would be most appropriate to analyse the
results of this pilot study?
A Unpaired Student’s t-test
B Paired Student’s t-test
C Chi Squared test
D Mann-Whitney U test
E Paired ANOVA
A
- D Mann-Whitney U test
Statistics is an essential part of critical appraisal. To ascertain the most appropriate
statistical test to be applied, a flow chart may help (see Figure 9.3). First the
data needs to be ascertained as either qualitative (categorical) or quantitative
(continuous).
Qualitative data is descriptive data such as gender, eye colour or ethnicity. The Chi
squared test is a good example of a statistical test used for analysis of qualitative
data. For smaller samples where the results can be collated by a ‘2 by 2’ table, the
Fisher’s exact test may be more appropriate.
Quantitative data can be classified as either parametric (normal) or non-parametric.
Further decisions can be guided by whether there are two groups or more than
two groups in the study. Within the groups the data can be paired, that is the
data was collected from the same sample group. An example would be a study
investigating blood pressure measurements in a group of patients before and after
a trial antihypertensive is given. Unpaired data suggests two different groups were
studied. For example, this study, which compares two groups of patients; those who
received discretionary sedation versus those who received protocolised sedation.
From the statistical test employed, a p-value is derived. The p-value reflects the
probability the result happened by chance. A commonly applied threshold p-value
in clinical trials is <0.05. This means there is a less than 5% (or 1 in 20) chance
of the result occurring by chance. As clinicians, the fundamental outcome has
to be considered on the basis of clinical significance, rather than pure statistical
significance. As can be seen from Figure 9.3, the data presented in the study in question is
qualitative and non-parametric, as a normal distribution cannot be assumed. There
are two independant groups of patients, therefore the data is unpaired. In this
instance, a Mann-Whitney U test is best applied.
