SBA 300 Paper 10 Flashcards
1
Q
- A 36-year-old man requires trans-sphenoidal surgery for a large anterior pituitary tumour with suprasellar extension.Prior to induction, which of the following are you most likely to need to prepare?
A Fibreoptic scope
B Lumbar drain
C Invasive arterial blood pressure monitoring
D Intravenous insulin administration
E Postoperative ventilation
A
- C Invasive arterial blood pressure monitoring
○ The majority of pituitary tumours are approached surgically by the trans-sphenoidal route. This involves passage through the sphenoid sinus and removal of the floor of the pituitary fossa (sella turcica).
○ The fossa is defined laterally by the cavernous sinus and superiorly by the sella diaphragma.
○ It is important to remain aware that the cavernous sinus contains portions of the carotid arteries – a cause of significant and rapid blood loss in the event of surgical trauma. For this reason, in addition to the potential requirement of careful blood pressure manipulation, invasive arterial pressure monitoring is essential for all trans-sphenoidal pituitary surgery.
○ The most common pituitary tumours arise from the anterior lobe and are usually adenomas, 75% of which are hormone secreting.
○ Hyper-or hyposecretion of growth hormone (GH), adrenocorticotrophic hormone (ACTH), prolactin (PRL) and thyroid-stimulating hormone (TSH) can occur depending on the cell-origin or mass effect of the tumour.
○ If an adenoma is present that leads to GH or ACTH secretion, the patient may develop acromegaly or Cushing’s disease respectively. In either case, this may lead to glucose intolerance or frank diabetes requiring insulin.
○ Acromegalic patients often present with soft tissue changes particularly of the
larynx and oropharynx. This leads to thickened mucosa, affecting visualisation of the airway, and glottic stenosis. They may also have an enlarged mandible and
maxilla resulting in poor occlusion of the dental aperture.
○This renders them at risk of a difficult airway which can be graded from 1–4.
°Grade 1 is classified as minimal mucosal involvement,
° grade 2 as mucosal hypertrophy in the region of the naso pharynx and oropharynx,
° grade 3 as isolated glottic changes and
° grade 4 as comprising of elements from both 2 and 3.
○ It is recommended that a fibreoptic intubation is considered for grades 1–2 and a surgical tracheostomy for grades 3–4.
○ Many patients who suffer Cushingoid or acromegalic effects from their tumour
acquire obstructive sleep apnoea. This obligates consideration of safe postoperative airway management and possible ventilation strategies as any positive pressure ventilation applied nasally is prohibited in the immediate period following trans-sphenoidal surgery.
○ Large pituitary tumours may still be resected trans-sphenoidally, provided they remain midline. If suprasellar extension has occurred a lumbar drain may be
required preoperatively. This enables aliquots of normal saline to be introduced
during surgery thereby causing increased intracranial pressure and subsequent
protrusion of the tumour for improved surgical access. It is also used for drainage postoperatively in the event of cerebrospinal fluid leak from the surgical site.
Trans-sphenoidal surgery may require preparation for all of the options but invasive arterial pressure monitoring is always indicated.
2
Q
- A 20-year-old male trauma patient has arrived in the emergency department
was had flaccid paralysis of both lower limbs before being intubated at scene for
transfer. A full body CT scan revealed a complex vertebral fracture of T5 with a
retropulsed fragment and an undisplaced sacral fracture. Despite 2 litres of fluid
resuscitation his blood pressure remains 80/40mmHg with a heart rate of 69 beats
per minute.
Which of the following is the most likely reason for his fluid resistant hypotension?
A Spinal shock
B Tension pneumothorax
C Haemorrhage
D Pulmonary embolus
E Neurogenic shock
A
- E Neurogenic shock
○ A tension pneumothorax should always be considered in a patient who is
undergoing positive pressure ventilation after intubation. As a result of increasing
pressure within the pleural cavity, the lung collapses and ultimately the
mediastinum shifts. This leads to obstructed venous return and therefore persistent
hypotension until the pressure is released by needle decompression or chest drain
insertion. Hypotension is therefore a relatively late sign and considering the recent
CT scan did not show an existing pneumothorax this is not the most likely reason.
○ All trauma patients with hypotension should be treated with ongoing suspicion
of haemorrhage. Most sources of significant blood loss, without obvious external
injury, should be identified by a CT scan using contrast media. Even though this
patient has had negative imaging, a sacral fracture can lead to the development of a
retroperitoneal haematoma. The fracture is, however, undisplaced and although this
is not currently the most likely reason it is still one to bear in mind.
○ Pulmonary embolism is defined as the obstruction of a pulmonary artery or arteriole
by intravascular matter such as air, thrombus or fat. If large, it may lead to prevention
of flow to the left heart, failure of the right heart and subsequent circulatory
collapse. Pulmonary emboli in trauma patients mainly occur as fat (classically
secondary to long bone fractures) or thrombus (more often after significant periods
of lower limb immobilisation). Although this should be considered it is less likely
within the time frame, or associated with the injuries described.
○ Neurogenic shock occurs when the autonomic pathways are interrupted as in a
spinal cord injury. It leads to hypotension and bradycardia. High thoracic injuries are
particularly associated with these signs as the cardiac sympathetic fibres originate
from T2-T5 thereby resulting in reduced inotropy, unchallenged vagal tone and
decreased systemic vascular resistance. This is the most likely reason in this example.
Spinal shock is described as the absence of reflexes below the level of injury. This
would produce the flaccid areflexia noted in this case and although normally seen
with hypotension from neurogenic shock, does not best define the reason for the
patients fluid resistant hypotension.
3
Q
- You are asked to anaesthetise a 68-year-old man for rigid bronchoscopy for biopsy
of a posterior tracheal mass. He has normal mouth opening and neck extension.
Which of the following is the most appropriate anaesthetic technique?
A Spontaneous ventilation with lidocaine topicalisation of the airway and
sedation with intravenous midazolam
B Inhalational induction and maintenance of deep anaesthesia with sevoflurane
and oxygen via a facemask removed when the bronchoscope is inserted
C Intravenous induction with propofol and atracurium. Oxygen and sevoflurane
maintenance with intermittent positive pressure ventilation (IPPV) via a
microlaryngeal tube
D Intravenous induction with propofol and atracurium followed by low
frequency jet ventilation via the bronchoscope. Maintenance of anaesthesia
with propofol and remifentanil target controlled infusion (TCI)
E Placement of cricothyroid cannula followed by anaesthesia with propofol and
remifentanil TCI. Jet ventilation via the cricothyroid cannula
A
3 D Intravenous induction with propofol and atracurium followed by low frequency jet ventilation via the bronchoscope. Maintenance of anaesthesia with propofol
and remifentanil TCI
Anaesthesia for airway surgery raises a number of issues including:
• Shared airway with conflicting needs of the surgeon (clear, unobstructed views
of the operative field) and anaesthetist (airway protection and maintenance of
oxygenation, ventilation and anaesthesia)
• Co-morbidities of the patient group who may have malignant, respiratory and
cardiovascular disease
○ Procedures such as the one outlined above are often relatively short (30 minutes)
but intensely stimulating; smooth balanced anaesthesia is essential to reduce the
risk of perioperative myocardial ischaemia.
○ The rigid bronchoscope is a large instrument and it is highly unlikely that a patient
would be able to tolerate the procedure without general anaesthesia. Although
inhalational induction may be a valid technique, deep anaesthesia alone may
not be sufficient (without paralysis) and the use of intermittently removing the
facemask will increase the risk of awareness as well as hypoxaemia. Use of a
microlaryngeal tube may be acceptable for certain procedures (e.g. supraglottic)
but a microlaryngeal tube may occlude the posterior trachea and when inflated the
cuff will mean any lesions in all but the most proximal part of the trachea would be
inaccessible. These are therefore unfeasible options in this case.
○ Low frequency jet ventilation is delivered via a handheld trigger device (e.g.
Manujet) attached via a Luer lock connector to the rigid bronchoscope. The operator
can manually deliver oxygen under pressure at a rate of 10–20 breaths per minute.
Volatile anaesthetic agents cannot be delivered via the rigid bronchoscope so total
intravenous anaesthesia (TIVA) is required. Intravenous induction with propofol
and atracurium with low frequency bronchoscopic jet ventilation and TIVA provides
good surgical conditions as well as anaesthesia and is best response given here. It
should be noted that there is a risk of barotrauma and gas trapping when using jet
ventilation and it is not possible to accurately monitor end tidal carbon dioxide or
airway pressures.
High frequency jet ventilation can be delivered via a cricothyroid cannula which may
be left in place for emergency perioperative oxygenation in patients felt to be ‘at
risk’; for example those will difficult laryngoscopy. This would therefore not be the
first choice technique in this case based on the information given.
As these patients are at risk of complete airway obstruction or complications
4
Q
- A 33-year-old man is extracted from a house fire and admitted to the emergency
department. He cannot remember being rescued and on examination has
singed nasal hair, burns across his neck and productive carbonaceous sputum.
He is receiving high flow oxygen through a non-rebreathing mask and is not in
respiratory distress.
Which investigation will be most useful in assessing and managing his upper airway?
A Pulse oximetry
B Chest X-ray
C Computed tomography
D Arterial blood gas
E Flexible bronchoscopy
A
- E Flexible bronchoscopy
○ Smoke inhalation injury is a serious complication of burns and significantly increases
patient morbidity and mortality. Airway injuries in this context can be difficult to
safely manage and requires an appreciation of the risk factors, natural progression
and appropriate investigations available.
During a fire, the upper airway may be injured from chemical irritation and direct
thermal insult resulting in oedema, erythema and ulceration, which can threaten
airway patency. Other factors detrimental to the airway include the systemic 7ñlammatory response, aggressive fluid administration and accompanying neck
burns causing external compression. The airway oedema is variable but generally
peaks at 24hours and clinical symptoms such as stridor or dyspnoea may not beobvious until this is substantial. A timely and controlled intubation to protect the
airway is preferable to an emergency procedure so determining which patients are
at risk of upper airway injury or obstruction is important.
Patients who have lost consciousness and been exposed to heat or flames in an
enclosed space for a prolonged time are at higher risk of airway injury. Physical signs
suggestive of airway injury include facial burns, singed nasal hairs, carbonaceous
sputum, stridor, hoarseness and drooling. Certain investigations can also guide
assessment and management of inhalational airway injuries
Flexible bronchoscopy is considered the gold standard for early evaluation of
the upper airway in patients with smoke inhalational injuries and it is the correct
answer for the above scenario. Bronchoscopy allows direct visualisation of the
laryngeal structures and an appreciation of any oedema, ulceration, necrosis or
soot contaminating and threatening the airway. Furthermore, bronchoscopy
allows removal of any airway debris, and the placement of an endotracheal tube if
indicated. Repeat examinations can also be performed to assess the progression of
airway injury.
Pulse oximetry provides continuous non-invasive monitoring of the haemoglobin
oxygen saturation in the arterial blood. It is an important monitor for patients
with suspected smoke inhalation injury as desaturations may indicate worsening
associated upper or lower airway damage. However, in the presence of carbon
monoxide, the monitor will provide an inaccurately high saturation reading since
it cannot distinguish between carboxyhaemoglobin and oxyhaemoglobin. Unlike
bronchoscopy, it cannot diagnose nor grade the severity of the upper airway injury.
Admission chest X-rays are frequently performed in patients admitted with burns
but are insensitive for an inhalational injury diagnosis. Since burns patients are at
risk of developing chest infections and acute lung injury during their illness, the
admission chest radiograph is however still important for establishing a baseline.
Computed tomography has a role in selected burns patients where inhalation injury
is suspected. For example the bronchial wall thickness measured by this imaging
modality can be useful as a predictor for the number of ventilator days and the
development of pneumonia. Unlike bronchoscopy however, direct visualisation and
interventions to treat upper airway pathology is not possible.
Arterial blood gas analysis provides important information concerning the adequacy
of ventilation and acid base status of burns patients. If there is co-existing carbon
monoxide poisoning, this can also be assessed by carboxyhaemoglobin levels.
However, a normal blood gas result does not rule out an inhalation injury, and
the investigation provides no direct information on whether the upper airway is
threatened.
5
Q
- A previously well 9-year-old boy is having a laparoscopic appendicectomy.
Anaesthesia was induced uneventfully with thiopentone and suxamethonium,
followed by a sevoflurane/oxygen mix. 10minutes after port insertion his airway
pressures increase and his oxygen saturations begin to fall. Despite adjusted
mechanical ventilation, his end-tidal CO2 reaches 9.0kPa. His heart rate rises to
180 beats per minute and his temperature to 40°C.
Which of the following actions will ameliorate the situation most definitively?
A Hyperventilation with 100% oxygen
B Cooling the patient
C Switching maintenance of anaesthesia to propofol
D Treating any hyperkalaemia
E Dantrolene 1–10mg/kg
A
- E Dantrolene 1–10 mg/kg
○ In the event of an unexplained significant rise in end-tidal CO2 and heart rate
with simultaneous increased oxygen requirements, the possibility of malignant
hyperthermia must not be overlooked.
○ Malignant hyperthermia is a genetically determined error of skeletal muscle
metabolism that is triggered by suxamethonium and volatile anaesthetic agents.
○ It is thought to arise from a defective gene for the ryanodine/dihydropyridine
receptor on chromosome 19. This leads to an uncontrolled inward flux of calcium
ions and subsequent rapid development of skeletal muscle rigidity. This generates
a hypermetabolic state producing dramatic rises in CO2, O2 consumption and
temperature.
○ As the condition persists, haemodynamic instability, rhabdomyolysis,
hyperkalaemia, metabolic acidosis and disseminated intravascular coagulation develop.
○ The mainstays of initial treatment are to rapidly acquire dantrolene at the earliest
point of suspicion, whilst simultaneously minimising the deleterious effects of
the process. These include informing the team of your diagnosis, calling for help,
hyperventilating the patient on 100% oxygen, removing volatile anaesthesia from
the circuit, maintaining anaesthesia via intravenous agents, cooling the patient and
treating any biochemical abnormalities.
Dantrolene is the only known antidote to malignant hyperthermia and is therefore
the most definitive treatment. The Association of Anaesthetists of Great Britain
and Ireland (AAGBI) guidelines on the recommended stages of management are
available on the AABGI website
6
Q
- A 53-year-old man presents for a laparoscopic gastric bypass procedure. He has
a BMI of 46kg/m2 and is an ex-smoker. He has a diagnosis of obstructive sleep
apnoea, but doesn’t really use his CPAP machine. He has severe reflux and a neck
circumference of 46 cm, his Mallampati score is 1 and he has good mouth opening.
The most appropriate anaesthetic plan includes:
A Ramped head-up position, preoxygenation, and a rapid sequence induction
(RSI) with suxamethonium and cricoid pressure. ITU postoperatively
B Ramped head-up position, preoxygenation, and a RSI with rocuronium and
cricoid pressure. HDU postoperatively
C Ramped head-up position, preoxygenation, and a RSI with suxamethonium
and cricoid pressure. HDU postoperatively
D An awake fibreoptic intubation. Ward level postoperative care.
E Ramped head-up position, preoxygenation, standard induction.
A
- C Ramped head-up position, preoxygenation, and a
RSI with suxamethonium and cricoid pressure. HDU
postoperatively
Obesity is on the rise in the UK. Weight loss surgery is also a growing field. The
procedures fall into two categories:
Restrictive
The commonest example of this type is the adjustable gastric band (AGB). Here a
fluid-filled band is placed around the proximal stomach creating a small pouch that
fills quickly with food creating the sensation of fullness. The band can be adjusted
by saline insufflation via a subcutaneous port. The AGB is now more popular
than the other types of restrictive treatment, such as the sleeve gastrectomy, and
luminal gastric balloon. The laparoscopic AGB is minimally invasive, reversible and
technically easier and safer than malabsorptive surgery. Complications often relate
to relative obstruction or reflux of food or gastric contents, such as oesophagitis.
Malabsorptive
The most common procedure of this type is the Roux-en-Y gastric bypass. This
surgically creates a small pouch of proximal stomach which is then plumbed
directly to the jejunum, ‘bypassing’ the duodenum altogether. Thus the stomach
firstly has an element of volume restriction, with the added benefit of a degree of
malabsorption. This makes the gastric bypass the gold standard weight loss surgery,
with body mass index (BMI) reductions of 10kg/m2 possible in the first year alone.
It is irreversible, more complex, and has added complications including nutritional
deficiency and dumping syndrome.
Preoperative assessment
Airway assessment should include neck measurement. Studies have shown that
obesity alone doesn’t predict difficult laryngoscopy, but alongside a Mallampati
grade III/IV or a high neck circumference, it does. Difficulty rates were 5% with
a 40cm neck, rising to 35% with a 60cm neck. Medical co-morbidities should
be assessed in the usual manner, but particular attention paid to screening for
obstructive sleep apnoea, pulmonary hypertension, right heart dysfunction and
heart failure. Functional testing in the form of cardiopulmonary exercise testing or
stress echocardiography may be indicated. Bariatric patients are regarded as high
risk of aspiration regardless of reflux symptoms and prokinetics, and antacids are the
norm.
Operative factors
Induction often occurs in theatre on table to avoid moving and handling concerns,
but if required a hover mattress may be used for moving patients. The ideal position
is with the patient ‘ramped’ or ‘stacked’, this uses pillows and blankets to raise the
upper torso, shoulders and head to align the tragus of the ear with the angle of
Louis. This has been shown to improve direct laryngoscopy and should facilitate
preoxygenation by increasing functional residual capacity. A proprietary pillow, the
Oxford HELP pillow, is marketed in the UK for this purpose. The surgical position is
usually a modification of the Lloyd–Davis with steep head-up. A shelf is put at the
foot of the table to avoid slippage, and the arms are often out on arm boards. The
physiological strain of pneumoperitoneum is often well-tolerated, and ventilation is
sometimes better than expected due to the degree of positioning the chest above
the abdomen. Pressure point protection must be fastidious, as obese patients are
at high risk. Greatest risks are from venous thromboembolism, with an incidence of
about 5%, and low molecular weight heparin doses must be adjusted to weight as
per local protocol.
The crucial elements of the stem here are the presence of untreated obstructive
sleep apnoea (OSA), in determining postoperative care, and the airway assessment
influencing induction planning. From the outset this gentleman requires higher than
ward level care for his OSA and the gastric bypass procedure. HDU should suffice
unless he encounters any intraoperative obstacles. In terms of the induction, as
discussed the presence of obesity alone doesn’t equal a difficult laryngoscopy, but
increasing neck circumference is shown to correlate. His neck circumference does not put him into the highest risks group. In any event, ramped positioning is crucial
to facilitate preoxygenation, laryngoscopy and mask ventilation (if required).
7
Q
- A 62-year-old woman who presented for a laparoscopic cholecystectomy
experienced an unanticipated difficult intubation. An endotracheal tube was
eventually correctly sited following multiple attempts and the use of an intubating
stylet. The following day she is febrile with cervical surgical emphysema and
complains of neck stiffness and dysphagia.
What is the most likely cause of her symptoms?
A Oesophageal perforation
B Uvular necrosis
C Tracheal rupture
D Arytenoid dislocation
E Aspiration pneumonia
A
- A Oesophageal perforation
Repeated instrumentation during a difficult intubation can lead to significant
damage to the airway and surrounding structures resulting in potentially
fatal complications. An unrecognised oesophageal perforation can lead to
retropharyngeal abscess formation, acute mediastinitis, pneumonia and eventually
multi-organ failure and death. Early symptoms and signs can be non-specific;
therefore a high index of suspicion is crucial to avoid delays in management. The
case above contains strong risk factors for an oesophageal perforation which
includes female gender, age older than sixty years and a difficult intubation. Early
symptoms of perforation include sore throat, cervical pain, and cough, whilst fever
and dysphagia may indicate secondary bacterial invasion and abscess formation. Air
may also dissect along cervical fascial planes resulting in subcutaneous emphysema,
pneumomediastinum and pneumothorax. Management depends on lesion severity
and includes cessation of oral intake, intravenous antibiotics, parenteral nutrition
and if indicated surgical repair.
Tracheal rupture can also occur following a forceful difficult intubation and repeated
trauma from airway adjuncts. Following atraumatic intubations, tracheal injury
can still occur if the endotracheal tube is incorrectly sized or the tube cuff over-
inflated. The most common clinical signs are subcutaneous emphysema, mediastinal
emphysema and pneumothorax, which often develop soon after extubation. Other
signs include dyspnoea, dysphonia, cough, haemoptysis and pneumoperitoneum.
The history of fever and dysphagia in the case above make oesophageal perforation
more likely. The management of a tracheal rupture can be conservative (intubation
with the cuff distal to the rupture, tracheal aspiration, pleural drain if required and
empirical antibiotics) or involve surgical correction.
Uvular necrosis is a rare occurrence and can result from mechanical trauma during
intubation or suctioning. Intraoperative impingement from the endotracheal tube
compromising uvular blood flow has also been described. Symptoms include a
foreign body sensation, sore throat, pain on swallowing, coughing and in severe
cases airway obstruction. Subcutaneous cervical emphysema as described in the
above case is not a usual presentation of uvular necrosis. Treatment is conservative
and management options reported in the literature includes steroids, antibiotics,
topical adrenaline administration and antihistamines.
Arytenoid dislocation can occur as a consequence of direct trauma to the
cricoarytenoid joint during endotracheal intubation. Symptoms include persistent
hoarseness, sore throat dysphagia and stridor. Prompt diagnosis and early operative
correction is important to prevent articular adhesions and ankylosis. A primary
arytenoid dislocation does not cause surgical emphysema as described in the case
above.
Aspiration of gastric contents into the lung can occur following repeated intubation
attempts to a difficult airway. The clinical manifestations are wide ranging and
depend partly on the type and amount of aspirate. Solid matter aspiration can lead
to an acute airway obstruction resulting in rapidly progressive hypoxia, whereas
gastric acid contamination can result in an aspiration pneumonitis and the acute
respiratory distress syndrome. Infection from bacteria that normally reside in the
stomach or upper airway can give rise to pyrexia, wheezes and crackles. Treatment is
mainly supportive and sometimes prolonged mechanical ventilation is necessary.
Antibiotics should only be administered to patients who develop pneumonia.
Surgical emphysema, dysphagia and neck stiffness are not common presentations of
aspiration pneumonia.
8
Q
- A cardiac arrest call brings you to a 78-year-old man admitted to coronary care
following urgent percutaneous coronary intervention for inferior myocardial
infarction. The coronary care nurses administered a total of 3mg of atropine 5
minutes ago for bradycardia. He is now has a blood pressure of 80/40mmHg, a
heart rate of 35 beats per minute (regular), but is alert.
What is the next appropriate step in the management of his condition?
A Administer 500μg atropine
B Start a dopamine infusion
C Urgent transvenous electrical pacing
D Start an adrenaline infusion
E Give a fluid bolus of 250mL of colloid
A
- D Start an adrenaline infusion
The patient most likely has a symptomatic complete heart block that is usually
associated with an inferior myocardial infarction (MI). He demonstrates adverse
features in the form of hypotension; others to be concerned about include syncope,
heart failure or myocardial ischaemia.
The initial management would be administration of 500μg of atropine intravenously
and assess the patient’s response. If the patient fails to respond to 3 mg of Atropine
in total, the next step is to start a second line agent such as an isoprenaline infusion
at 5μg/minute or an adrenaline infusion at 2–10μg/minute. Alternative drugs can be
considered such as aminophylline, dopamine, glucagon or glycopyrronium bromide,
however in a hypotensive patient, adrenaline is a more appropriate option.
Fluids are an appropriate option to treat hypotension without bradyarrhythmia
following an inferior MI but will not correct the cause of hypotension.
Transcutaneous and transvenous cardiac pacing are suitable alternatives to the
pharmacological treatment, the latter requiring significant expertise that might not
be immediately available, but is ultimately the aim.
9
Q
- A 17-year-old girl presents for surgical correction of a spinal scoliosis. She has dysmenorrhoea and menorrhagia for which she takes oral iron supplementation,
and is otherwise fit and well. Her haemoglobin concentration is 101 g/L. The surgeon reminds you that his current practice involves spinal cord monitoring in
these cases.
Along with two large-bore peripheral cannulae, which of the following would be
the most appropriate anaesthetic technique for this case:
A Volatile with target controlled infusion (TCI) remifentanil maintenance. An internal jugular central line and a radial arterial line. Tranexamic acid.
B A radial arterial line. Propofol and remifentanil TCI. Cell salvage and tranexamic acid.
C Volatile with nitrous oxide maintenance. A radial arterial line. Cell salvage and tranexamic acid.
D Propofol and remifentanil TCI. A radial arterial line. A femoral central line and cell salvage.
E TCI propofol with boluses of fentanyl. A radial arterial line with an internal jugular central line. Tranexamic acid.
A
- B A radial arterial line. Propofol and remifentanil TCI. Cell
salvage and tranexamic acid
○ Operations on the spine are liable to cause serious complications, and the understanding of the type of surgery and the general principles is essential to prevent attendant morbidity.
○ Massive haemorrhage requiring transfusion is one of the most common, but respiratory or airway compromise, eye injuries (including blindness), and spinal cord damage may also occur.
○ Spinal cord monitoring
Monitoring is used to try to reduce the risk of cord damage during surgery, and uses electrophysiology to monitor two types of evoked potentials.
°Somatosensory evoked potentials (SSEPs), are measured from the brain and receive small signals from stimuli applied peripherally, usually to the posterior tibial nerves. These are not affected by volatile anaesthetics, and signals may even be improved by muscle relaxation as muscle tremor noise goes down.
° Motor evoked potentials (MEPs), are larger signals applied to the motor cortex and measured by electrodes in the target muscles. This type of monitoring allows for interrogation of the integrity of specific tracts of interest and is increasingly used both in spinal and neurosurgery. Deep neuromuscular blockade will abolish these measurements and volatile anaesthetic concentrations above 0.5 MAC make the readings invalid, therefore if MEPs are to be used total intravenous anaesthesia (TIVA) is the maintenance of choice.
○ Prone position
Essential for most surgery with a posterior approach, this is best accomplished with diligence and an experienced team. The tracheal tube must be well fixed, and a ‘bail out’ emergency plan for airway loss whilst prone must have been considered and discussed amongst the team. The patient’s body must be supported at the level of the mid chest (lower pectoral) and waist levels, leaving the abdomen relatively free
and uncompressed. There are ready made padding systems to deliver this position, such as the Montreal mattress. If well positioned, there is less compression of the inferior vena cava and less impairment of venous return. This avoids reduced cardiac output and increased transmitted pressure into the epidural venous plexus (which is vulnerable to pressure effects due to an absence of valves), and also reduces the risk of lower limb thrombosis.
Once this position is safely achieved, meticulous detail must be paid to ensuring pressure areas are well padded. Particular problems can be encountered with the ulnar nerve at the elbow, as well as the brachial plexus. Avoiding traction on the brachial plexus is achieved by ensuring the arms, if by the head, have the humeri abducted to <90° and the forearms lying slightly below the level of the chest. If the arms are to be by the side, then the hands should be slightly supinated with the thumbs pointing downward.
○ Eyes
Spinal surgery has the highest rate of eye and visual complications. Postoperative visual loss may result from two types of damage: ischaemic optic neuropathy (ION) and central retinal artery occlusion (CRAO). Of the two, ION is by far the most common. ION is thought to be caused by optic nerve hypoperfusion, and is linked to intraoperative anaemia/massive blood loss, long surgery (especially >6 hours), obesity, and male sex. Interestingly diabetes and vascular disease are not clear risks for ION. CRAO is caused by direct extrinsic pressure, and is mostly unilateral, and seen with other sequelae of damage to the local area such as ptosis.
As described above in this case where cord monitoring is to be used, volatile
anaesthesia will detract from the readings ruling out stems A and C. Given the pre-existing history of anaemia and the type of surgery, most would regard the use of cell salvage as mandatory, removing stem E. The final discriminator between the two remaining options, B and D relates to the use of supplementary central venous access. Whilst many would choose to place a central venous catheter, in this relatively well patient with good peripheral access it is not essential. If used, femoral is not the ideal site for a patient in the prone position.
10
Q
- A 75-year-old man with significant co-morbidities is admitted for elective foot
surgery under an ultrasound-guided ankle block.
In order to minimise the amount of time required to wait for the block to be adequate for surgery, which one of the following nerves needs to be blocked first?
A Superficial peroneal nerve
B Deep peroneal nerve
C Sural nerve
D Saphenous nerve
E Tibial nerve
A
- E Tibial nerve
○ Ankle blocks are indicated for foot and toe surgery. They are easy to perform and
provide adequate analgesia for a variety of procedures on the foot.
○ Five nerves innervate the ankle; four are branches of the sciatic nerve (tibial, superficial and deep peroneal, and sural) and one is a branch of the femoral nerve (saphenous nerve).
Good anatomical knowledge is essential for a successful ankle block. Two of the five
nerves are deep (tibial and deep peroneal) and three are superficial (sural, superficial
peroneal and saphenous nerves) (Figure 10.2)
°Tibial nerve: This is one of the deep terminal branches of the sciatic nerve. The
nerve is divided into medial plantar and lateral plantar nerves, and also gives off
the calcaneal nerve. It innervates the plantar surface of the foot and heel. The tibial
nerve is blocked by injecting local anaesthetic (LA) behind the medial malleolus. The
injecting needle is advanced posterior to the pulsation of the posterior tibial artery.
Once contact with the bone is felt, the needle is withdrawn 2mm, and 2–5mL of LA
is injected at this point. The tibial nerve is the largest terminal branch of the sciatic
nerve and takes up to 20minutes for the nerve block to be established. Therefore,
you should always start an ankle block with the tibial nerve. It is also the only nerve
in the ankle that can be identified by a nerve stimulator (plantar flexion of the toes).
°Deep peroneal nerve: this nerve innervates the webbed space between the 1st
and 2nd toes. This nerve can be blocked just lateral to the tendon of extensor
hallucis longus (EHL). The tendon can be made more obvious by asking the patient
to dorsiflex the big toe. After palpating the dorsalis pedis artery lateral to the EHL,
the needle is introduced until a contact is made with the bone. The needle is then
withdrawn slightly and 2–3mL of LA is injected after aspiration.
°Saphenous nerve: This is a terminal cutaneous branch of the femoral nerve. It
descends on the medial side of the calf. It supplies the medial aspect of the leg
and the medial malleolus, and may also supply the medial margin of the foot. The
saphenous nerve is blocked with a subcutaneous injection of 5mL of LA above the
medial malleolus.
°Superficial peroneal nerve: This is a branch of the common peroneal nerve. It
travels down the leg between peroneus longus and peroneus brevis muscles. It
then runs under the deep facia in a groove between the peroneus brevis and the
extensor digitorum longus. After piercing the deep fascia, it becomes superficial in
the anterolateral compartment of the leg and then divides into superficial branches
that innervate the dorsum of the foot. Injecting 5mL of LA subcutaneously along the
inter-malleolar line can block the nerve successfully.
°Sural nerve: The sural nerve is derived from the tibial nerve in the popliteal fossa. It
is a superficial nerve and it travels down the posterior aspect of the leg and behind
the lateral malleolus. It supplies the lateral malleolus and the lateral margin of the
foot. Injecting 5 mL of LA in the midpoint between the Achilles tendon and the
lateral malleolus can block this nerve
11
Q
- You are asked to transfer a 27-year-old man to the local neurosurgical centre who
was admitted two hours ago with an acute traumatic subdural haematoma. On
admission he was alert but unable to recall the event, and he vomited twice. On
your assessment, he is asleep but rousable to voice, has slurred speech and is
obeying commands. His observations include a blood pressure of 180/90mmHg,
heart rate of 90 beats per minute sinus rhythm and pupils of equal size and
reacting to light. He continues to vomit in spite of antiemetics.
What the most appropriate next step before the transfer?
A Perform an arterial blood gas
B Repeat the CT scan
C Rapid sequence induction
D Administer mannitol 20 % 0.5 g/kg
E Cool the patient
A
- C Rapid sequence induction
This patient needs urgent neurosurgical intervention to evacuate his haematoma.
His clinical picture suggests rapid progress of the haematoma. A new CT scan
would not add more the clinical picture and it may delay the transfer. Although an
isolated arterial blood gas sample is a useful result to have, it is unlikely to change
the outcome, speed or safety of transfer. A rise in intracranial pressure (ICP) may be
the cause of his deterioration but mannitol is only used as an acutely temporising
measure in a patient who is coning whilst waiting for surgery. Hypothermia for
management of acute brain injury is suggested to be beneficial for reducing the
cerebral metabolic rate of oxygen (CMRO2), but its acute use has not yet been
proven and, again, is unlikely to change the outcome of this patient.
However, the rapid neurological progress and ongoing vomiting renders a transfer
without a secure airway unsafe. Therefore rapid sequence induction and securing the
patients airway is the appropriate next step. This would also enable the anaesthetist
to optimise ventilation to control the intracranial pressure by targeting a PaCO2 of
4.0–5.0 kPa.
12
Q
- A 42-year-old man presents to the emergency department after an out-of-hospital
cardiac arrest. He was successfully defibrillated out of ventricular fibrillation after
20 minutes of cardiopulmonary resuscitation (CPR). The airway was secured and
the patient was transferred to hospital. The blood pressure is 120/76mmHg without
the need for inotropes or vasopressors and he is coughing on the endotracheal tube.
There is no ischaemia demonstrated on his electrocardiogram (ECG).
What is the clinical action that is likely to be most beneficial?
A Administrating anti-platelet therapy via a nasogastric tube
B An urgent coronary angiogram
C An urgent transthoracic echocardiogram
D A CT pulmonary angiogram
E Targeted temperature management for 24hours
A
- E Targeted temperature management for 24hours
This is a difficult question. All are appropriate actions to ensure complete
management of your patient. The differential diagnosis of a sudden collapse is
broad, but most significantly could be:
t Arrhythmogenic (sudden acute arrhythmia such as ventricular fibrillation or
complete heart block);
t Cardiogenic (such as an acute myocardial infarction causing myocardial failure);
t Vascular (aortic aneurysm rupture);
t Obstructive (such as a pulmonary embolism);
t Intracranial event (such as a subarachnoid hemorrhage).
Making efforts to diagnose the cause of arrest will no doubt help in management.
For the options above: - There is no evidence of ischaemia on the ECG, suggesting no sudden occlusion of a
coronary vessel. Therefore anti-platelets may not be the key intervention. Similarly a
coronary angiogram may demonstrate unobstructed coronary arteries. - An urgent echocardiogram is vital to look at cardiac function. It is particularly
helpful at diagnosing a sudden ischaemic event (with regional wall abnormality)
or suggesting a pulmonary embolism (with a dilated right ventricle and high
pulmonary pressures). However since blood pressure is maintained without
augmentation it is questionable whether the echocardiogram will provide you
with information that will alter the management in the immediate-term. - A CT pulmonary angiogram is an important test and may provide a diagnosis.
With a normal blood pressure thrombolysis is not indicated. Treatment with
anticoagulation may be presumptively commenced (also indicated for coronary
vessel disease). - There is no option for an urgent CT head but this would also be a vital investigation
as an intra-cranial event may require emergency surgical management.
The question is asking for the most beneficial intervention, not the first. Therapeutic
hypothermia after out-of-hospital cardiac arrest has got a good body of evidence
that suggests improved neurological outcome and mortality outcomes at 6 months.
A recent study has demonstrated that a targeted temperature management
approach of 36°C is non-inferior to targeting a temperature of 33°C, the suggestion
is that a targeted approach and avoidance of pyrexia are more important than
the specific temperature chosen. Many departments would still opt to target a
temperature of 33°, but this practice appears to be decreasing.
Should a temperature of 32–34°C be chosen, cooling should be commenced in the
emergency department with infusion of cool crystalloids and application of cooling
blankets if possible. In the intensive care unit this is continued until a temperature
of 32–34°C is achieved within 4 hours of return of spontaneous circulation. This
may be done with cooling blankets or intravascular extra-corporeal devices,
controlled electronically and titrated to maintain desired temperature. Hypothermia
is maintained for 12–24 hours before re-warming commences at 0.25–0.5°C/
hour and neurological function can then be assessed. Complications should be
managed in a supportive manner including shivering, which should be treated with pharmaceutical paralysis as it is metabolically demanding and increases myocardial
oxygen demand. It remains to be seen if this therapeutic method will remain
accepted practice in the future, but what is accepted is that targeted temperature
management is perhaps more important than the specific temperature chosen.
13
Q
13 A 59-year-old woman is on the high dependency unit following a bowel resection
for adenocarcinoma which finished 8hours ago. She weighs 60kg, has a past
medical history of type 2 diabetes and has a baseline creatinine of 120μmol/L.
Postoperatively she has been passing 40mL/hour of urine, which has decreased to
10mL/hour for the past 2 hours despite her maintaining a normal blood pressure.
A repeat blood sample demonstrates a creatinine of 180μmol/L.Which of this patient’s risk factors is most significant?
A Chronic renal impairment preoperatively
B Major intra-abdominal surgery
C Oliguria
D Serum creatinine rise
E Diabetes
A
- D Serum creatinine rise
Acute kidney injury (AKI), is defined as an abrupt deterioration in renal function occurring over 48 hours. The prevalence in hospitals is 1–7% and even a small rise in creatinine is associated with an increased mortality, ranging from 10% to 80%.
In 2009 the National Confidential Enquiry into Patient Outcome and Death (NCEPOD) published ‘Adding Insult to Injury’ which found that we were deficient in identifying patients at risk of AKI and in 50% of cases our management could have been more timely to prevent renal deterioration. This prompted the National Institute for Health and Care Excellence (NICE) to publish recommendations highlighting the importance of identification of risk factors and of prompt treatment.
Risk factors include:
• Age over 65 years old
t Male gender
• Pre-existing renal disease
• Co-morbidities:
– Congestive cardiac disease
– Hypertension
– Diabetes
– Ascites
• Surgery:
– Emergency
– Prolonged, major surgery
– Intra-peritoneal
• Anaesthesia:
– Hypotension
– Hypovolaemia
– Blood transfusion
– Nephrotoxic drug administration
The diagnosis may be made with either the RIFLE, AKIN or KDIGO classifications (the latter two being very similar). They are based on RIFLE (Risk, Injury, Failure, Loss, End-stage), which is a useful way to remember the steps to disaster, but the recent modification is more sensitive and reflects recent evidence that even a small increase in the serum creatinine concentration results in significantly increased morbidity and
mortality (see Tables 10.1 and 10.2). To qualify for a particular stage the patient must meet either urine output or serum creatinine criteria.
The patient described above has many risk factors that may pre-dispose her to developing AKI. In addition to her co-morbidities, she has had intra-peritoneal surgery in which crystalloid administration is often rationalised to prevent anastomotic oedema and dehiscence.
Having six of the above risk factors infers a greater than 10% risk of AKI. The oliguria described in the question does not meet AKI criteria by itself. The most evidence-based concerning element in her story is her creatinine rise of 1.5 times her baseline which indicates AKI stage 1 and is associated with a 10% mortality or greater depending on how this situation progresses. Early intervention is indicated to prevent further deterioration in the renal function.
14
Q
- A 72-year-old man with hypertension has been referred to you 2 days after having
an emergency laparotomy for an incarcerated hernia. His oxygen saturations are
94% on an inspired oxygen concentration of 60%, his respiratory rate is 28 breaths
per minute and on auscultation there is bi-basal crepitus. On examination the
blood pressure is 100/60mmHg, the pulse is regular, the heart rate is 110 beats
per minute and the jugular venous pressure (JVP) is visible at 6 cm. He has passed
10mL of urine per hour for the last 6 hours and is agitated.
What is the next appropriate course of action?
A Urgent blood tests to assess renal function
B Continuous positive airway pressure (CPAP) support in the high dependency
unit
C Urgent fluid administration of 5–10mL/kg of fluid and assess response
D Admit to the intensive care unit for haemofiltration
E Intravenous administration of 40mg of furosemide and 2.5mg of diamorphine
A
- E Intravenous administration of 40mg of furosemide and
2.5mg of diamorphine
This man has the following clinical issues: - Clinical evidence of pulmonary oedema with a raised jugular venous pressure
(JVP) - Hypotension with evidence of end-organ dysfunction (agitation)
- Acute kidney injury (AKI) Stage 1 on the basis of his urine output being less than
0.5mL/kg/hour for 6 hours, according to the AKIN classification (see Table 10.2,
Question 13).
The pulmonary oedema may be due to different etiologies, either due to
excess intravascular fluid or ineffective cardiac activity. Excess intravenous fluid
administration for the treatment of oliguria post-operatively may be implicated.
Alternative possibilities include acute cardiac decompensation due to an ischaemic
cardiac event, electrolyte disturbance or a cardiac arrhythmia.
Acute heart failure should be managed with an ABC approach. Sitting the patient
upright reduces the central venous pressure and therefore the preload, which
can result in improved cardiac output. Oxygen therapy, intravenous access,
electrocardiogram, a chest radiograph, an arterial blood gas and repeat blood
science analysis including serum troponin concentration are all immediately
indicated. Treatment options include:
t Treat reversible causes:
– Coronary reperfusion therapies
– Anti-arrhythmic agents
– Electrolyte correction
t To reduce the preload via venodilation:
– Loop diuretic administration results in immediate venodilation
– Diamorphine or morphine administration reduces central sympathetic activity
resulting in venodilation
– Glyceryl trinitrate (GTN) infusion
t To reduce the preload by reducing circulating volume:
– Loop diuretic administration results in delayed diuresis
– Haemofiltration for accurate control of fluid balance
t To augment cardiac output:
– Continuous positive airway pressure or non-invasive ventilation reduces
ventricular distention and improves cardiac contractility
– Inotrope administration
– Mechanical augmentation such as a intra-aortic balloon pump
t To provide cardiac or respiratory replacement:
– Extra-corporeal membrane oxygenation
Regarding the options in the question, all interventions may be needed at some
stage. Investigations are important but take time to yield results and more urgent
action is required in this situation. Fluid administration may be used to treat
hypotension and oliguria but in the presence of pulmonary oedema (the more
pressing clinical priority) may be detrimental. That leaves us with management of his heart failure with the most appropriate therapy at this stage being the easiest to
administer, the least invasive and the most rapid to instigate.
15
Q
- The intensive care unit dietician suggests commencement of enteral nutrition on a
67-year-old patient.
Which of the follow represents an absolute contraindication to starting enteral
nutrition?
A Ischaemic bowel
B Small bowel anastomosis
C Short gut syndrome
D Paralytic ileus
E Pancreatitis
A
- A Ischaemic bowel
During critical illness or the perioperative period, it is important to consider every
patient’s nutritional status and requirements. Nutritional requirements should aim
to address any pre-existing malnutrition, support the catabolic response to surgery
or critical illness and aid rehabilitation. Malnutrition is associated with impaired
immunological function and increased morbidity and mortality.
The detection of acute malnutrition can be challenging and at present no
specific markers exist. Surrogate markers for chronic nutritional status include
anthropometric measures and biomarkers such as albumin, pre-albumin,
transferring and haemoglobin.
Following the advent of acute critical illness, the early (within 24–48 hours)
instigation of nutritional support has been demonstrated to improve patient
outcomes, however conflicting evidence exists concerning the merits of hypocaloric
verses normocaloric targets. Furthermore, the optimal method (continuous verses
bolus) and composition remains undefined.
The National Institute for Health and Care Excellence (NICE) recommendations for
assessing a patient’s nutritional requirements are summarised below: - Screening on admission to include:
t assessment of body mass index (BMI)
t percentage unintentional weight loss and time over which nutrient intake has
been unintentionally reduced
t likelihood of future impaired nutrient intake - Recognise
t Malnutrition
– BMI<18.5kg/m2
– unintentional weight loss>10% in past 3–6 months
– BMI<20kg/m2 or >5% unintentional weight loss
– over 3–6 months
t At risk of malnutrition
– eaten little or nothing for more than 5 days and/or likely to eat little or
nothing for the next 5 days or longer
– poor absorptive capacity, and/or high nutrient losses and/or increased
nutritional needs from causes such as catabolism - Treat
t Oral if safe swallow
t Enteral if unsafe swallow or inadequate oral intake and gastrointestinal tract
accessible
t Parenteral if unsafe swallow or inadequate enteral intake and gastrointestinal
tract inaccessible
t Correct prescribing4. Monitor indications, route, risks, benefits and goals of nutrition support at regular
intervals
There are published guidelines by NICE and The American Society for Parenteral and
Enteral Nutrition (ASPEN) in partnership with the Society of Critical Care Medicine
(SCCM), covering all aspects of nutritional support in the acute patient and critical
care settings. Though much debate continues with regard to the appropriate
indications for parenteral nutrition, most agree that it should not be commenced
unless the enteral route is inaccessible and likely to remain so for >7days. The UK
CALORIES Trial published in October 2014 found no mortality difference between
enteral and parenteral routes of feeding critically ill patients. The current balance
of evidence suggests significant advantages of the enteral route that include less
infectious complications, thought to be secondary to reduced villous atrophy and
bacterial translocation within the gastrointestinal tract.
Previous theories mandating ‘resting of the gut’ have been disproven. Traditionally
enteral nutrition was avoided in pancreatitis, however the British Society of
Gastroenterology now recommend enteral feed; there appears to be little difference
in outcomes between nasogastric or nasojejunal routes. Similarly paralytic ileus does
not preclude enteral nutrition and starting a low rate with vigilance for intolerance is
advised. Intolerance should be monitored through 4-hourly feeding tube aspirates
and prokinetics such as metoclopramide and erythromycin can be added pending
no contraindications. Bowel anastomosis should not prevent enteral nutrition
unless a concern regarding anastomotic leak exists. Short bowel syndrome results
in problems with malabsorption and high output stoma / fistulae. Enteral nutrition
can be trialed with the use of thickening agents; however it is likely that a combined
enteral and parenteral approach may need to be adopted. Enteral nutrition may
induce or worsen bowel ischaemia especially in the presence of hypotension and is
therefore not recommended in suspected or proven bowel ischaemia.
16
Q
- A 52-year-old hypertenisve woman presents to the emergency department
with a history of a sudden onset, severe headache, photophobia and confusion.
Her Glasgow coma score (GCS) suddenly declines to 7/15 (E2, V2, M3) with no
focal neurology elicited. She is intubated for a CT head, which shows extensive
subarachnoid blood. Her current location does not have neurosurgical facilities.
According to the World Federation of Neurological Surgeons Scale (WFNSS), her
clinical grade is:
A I
B II
C III
D IV
E V
A
- D IV
Subarachnoid haemorrhage (SAH) is a neurological emergency. Anaesthetists may
be involved at presentation, intraoperatively during neurosurgical procedures or to
manage the patient in a critical care environment. Subarachnoid haemorrhage is bleeding into the subarachnoid space; it is important
to differentiate it from intracerebral haemorrhage (ICH), which is bleeding within the
brain parenchyma.
SAH has female preponderance, usually presenting between 40 and 60 years of
age, as in this case. SAH represents approximately 5% of all cause cerebrovascular
accidents, which is equivalent to 6–12/100,000 of the UK population. Though rare,
it has potentially devastating and rapidly irreversible sequela, with an estimated
mortality of 50%.
Spontaneous (as opposed to traumatic) SAH is invariably caused the rupture of a
saccular aneurysm, at bifurcations within the circle of Willis. Associations include
acquired conditions such as hypertension, atherosclerosis, sympathomimetic use
such as cocaine and alcohol, alongside congenital causes such as polycystic kidney
disease and Ehlers-Danlos syndrome.
The presentation of subarachnoid haemorrhage is classically with a ‘thunderclap’
headache, decreased GCS and signs of meningism as in this case. Focal neurology
may also be present. A careful history is required, where possible, to exclude
differential diagnosis such as cluster migraines, meningitis and other causes of
cerebrovascular accidents.
Urgent imaging is required for diagnosis, and excludes serious complications such
as hydrocephalus and cerebral oedema. Although a non-contrast head CT should
suffice, MRI can also be performed to diagnose SAH; however the logistics involved
are usually not merited in the emergency situation. Where available, CT angiography
should be performed to identify the source of the SAH; this investigation has both
high sensitivity and specificity. Due to the sensitivity of neurological imaging, a
lumbar puncture is reserved where clinical uncertainty persists in the face of non-
conclusive imaging.
Grading the SAH can be clinical or radiological. The World Federation of Neurological
Surgeons Scale (WFNSS) provides a clinical grading system (Table 10.4).Mortality increases from 30% with grade 1 to 90% with a grade V SAH. This patient
had a GCS 7/15 prior to intubation and no focal neurology, thus representing a grade
IV haemorrhage on the WFNSS scale. An alternative grading system is the Fischer
scale which is a radiological grading system.This patient did not present to a neurosurgical centre and timely management
will affect prognosis. The decrease in GCS mandated intubation and ventilation in
view of the diagnosis. As with other neurological emergencies, neuroprotection to
prevent secondary injury is vital.
Specific to the management of a subarachnoid haemorrhage are supportive and
surgical strategies. Supportive strategies include:
t Adequate sedation and analgesia
t Blood pressure <200/100mmHg in unsecured aneurysms, balancing the risks of
further bleeding against those of hypoperfusion
t Avoid hypomagnesaemia, however hypermagnesaemia does not provide
additional benefit (IMASH Trial 2010)
t Nimodipine – to reduce the incidence and severity of cerebral arterial vasospasm
(calcium channel antagonist)
t Non-pharmacological venous thromboprophylaxis and stress ulcer prophylaxis
Fundamentally, urgent neurosurgical advice and intervention should be sought.
Interventional options are:
t neuroradiological: coiling of intracranial aneurysm
t neurosurgical: clipping intracranial aneurysm
The ISAT trial (2005) was a multicenter, randomised controlled trial comparing
coiling to clipping. The trial suggested more independent survivors with coiling
at one year; however the coiling group also had a higher risk of re-bleeding.
Neurosurgical centres now follow local protocols, but increasingly clipping is
reserved for aneurysms not amenable to coiling. Coiling is less expensive and avoids
the patient undergoing a craniotomy.
Securing the aneurysm in a timely fashion is core to the management of SAH.
However a number of complications affect the course of the patient with SAH, which
need to be sought on presentation and during the critical care management.
t Re-bleeding: particularly within first 2 weeks
t Vasospasm: challenging to definitely diagnose, transcranial Doppler maybe
useful. Mainstay of management is currently supportive, intra-arterial vasodilators
are controversial
t Hydrocephalus: relatively common (20–30%), diagnosed on CT and requires
urgent external ventricular drainage
t Seizures: no evidence for prophylactic anti-seizure medications, but aggressive
management of seizures is paramount
t Endogenous catecholamine induced severe myocardial depression: diagnosed
clinically using biomarkers such as troponin and brain natriuretic peptide (BNP)
and echocardiography. Management is supportive
t Endocrine abnormalities including cerebral salt wasting syndrome (SWS) and
syndrome of inappropriate antidiuretic hormone (SIADH, see paper 4, question 2)
23
Q
- A 64-year-old asthmatic man presents with severe burns to his upper left arm and abdomen. The wounds on his left arm extend as far as his shoulder, and now have a foul smelling purulent discharge. He complains of a constant aching pain, which can become very severe at times, both in his arm and his abdomen. The surgeons want to take him to theatre for debridement of his arm wounds.
The most appropriate option for his postoperative analgesia is:
A Left interscalene block
B Paracetamol and ibuprofen
C Left axillary block
D Intraoperative opioids and postoperative patient-controlled analgesia (PCA)
E Left supraclavicular block
A
- D Intraoperative opioids and postoperative patient
controlled analgesia (PCA)
○ Burns are extremely painful, not only at initial presentation, but also throughout their hospital stay pain is a significant cause of distress, and may potentially evolve into a chronic problem. Effective provision of good analgesia at an early stage is vital.
○ Typically, patients may experience a constant dull background discomfort, with sporadic episodes of breakthrough pain. This can be unpredictable and regular assessment and re-assessment of analgesic requirement and provision is essential.
Furthermore, a burns patient may undergo several painful procedures such as skin
grafting, wound debridement, dressing changes and physiotherapy. Occasionally, burns patients may have other causes of pain such as fractures associated with the initial injury or compartment syndrome. These should be sought and addressed appropriately.
Patients should be assessed and analgesia prescribed on an individual basis. Options
include simple analgesics (paracetamol, non-steroid anti-inflammatory drugs (NSAIDs) if not contraindicated), opioids, and regional anaesthetic techniques. Analgesia should ideally be administered in anticipation as a preventive measure, for example, 1 hour
prior to a dressing change. For prolonged procedures, general anaesthesia may be the best option. Multimodal analgesia is frequently required, and the significant psychological burden of substantial burns injuries should not be ignored.
Table 10.5 suggests some analgesic options for some of the problems that may be encountered with burns patients.In this scenario, the patient has an infected wound that would make a suitable
regional block inappropriate. A history of asthma and the fact that significant burns may be associated with a coagulopathy would make NSAIDs less preferable. His abdominal pain, together with his postoperative arm pain would best be managed with a suitable opioid regime.
26
Q
- A 78-year-old woman is admitted with a type 4 (Crawford classification) aortic aneurysm. She is haemodynamically stable but the surgical team is asking for your help in siting an arterial line in preparation for an endovascular repair of her aneurysm using a fenestrated aortic graft.
Which of the following sites would be most appropriate for inserting an arterial line?
A Right radial artery
B Left radial artery
C Right dorsalis pedis artery
D Left dorsalis pedis artery
E Right femoral artery
A
- B Left radial artery
Crawford classification of the aortic thoracoabdominal aneurysms (TAAA) consists of five types:
• Type I involves most of the descending thoracic aorta from the origin of the left subclavian to the suprarenal abdominal aorta
• Type II is the most extensive, extending from the subclavian to th aortoiliac
bifurcation
• Type III involves the distal thoracic aorta to the aortoiliac bifurcation
• Type IV TAAAs are limited to the abdominal aorta below the diaphragm
• Safi’s group have modified this scheme by adding Type V, which extends from the distal thoracic aorta including the celiac and superior mesenteric origins but not the renal arteries
Deploying a fenestrated aortic graft requires multiple guide wires to correctly align the fenestrations with the renal arteries and the mesenteric arteries. Right axillary/subclavian access is usually required for deploying the superior mesenteric artery guide wire due to the angle of take off of the artery from the aorta which makes it impossible to wire from the common femoral or external iliac arteries. The aortic stent is inserted via the common femoral artery which makes this site and pedal arteries site impractical for insertion of arterial lines. This means the left upper limb arteries are the only possible arterial monitoring access points that are possible and practical.
27
Q
- A 72-year-old man requires a unilateral intercostal nerve block for severe pain caused by a fractured rib.
When performing the intercostal nerve block, where would be the most
appropriate place to infiltrate the local anaesthetic to achieve the highest success rate for the block?
A At the angle of the rib
B Any point proximal to the mid-axillary line
C Medial to the angle of the rib
D At the mid-axillary line
E Lateral to the angle of the rib
A
- A At the angle of the rib
The intercostal nerve (ICN) block is used to provide effective analgesia for breast surgery, thoracic and upper abdominal surgery (thoracotomy, cholecystectomy and gastrectomy) and fracture ribs. It also used for acute and chronic pain conditions like herpes zoster, post-thoracotomy pain and cancer related pain. The analgesia provided by the block is usually lasts for up to 12 hours.
The thoracic nerve roots exit from their respective intervertebral foramina,
then divide into ventral and dorsal primary rami. The dorsal ramus supplies the paravertebral skin and muscles. The ventral ramus continues as the intercostal nerve, which enters the subcostal groove of the corresponded rib to lie initially between
the pleura and the posterior intercostal membrane (medial to the rib angle). At the angle of the rib, the ICN passes between the internal intercostal and the innermost
muscles. At the mid-axillary line, it gives off the lateral cutaneous branch that supplies the skin and the muscles of the lateral chest and abdominal walls. The final
branch arises as the anterior cutaneous branch which is the continuation of the ICN, and innervates the skin and the muscles of the anterior thoracic and abdominal walls.
During its course in the subcostal groove of the rib, the ICN runs in a neurovascular bundle containing the intercostal vein superiorly, the intercostal artery in the middle and the intercostal nerve inferiorly.
There are some specific differences at certain levels. T1 intercostal nerve lacks the lateral and the anterior cutaneous branches. T2 and T3 contribute to the intercostobrachial nerve. T12 is really a subcostal nerve and some its fibres join with fibres from the lumbar plexus to form ilioinguinal, iliohypogastric and genitofemoral nerves.
An ICN block can be performed in different positions, including the prone position,, lateral decubitus, supine or sitting position. However, it is best performed in prone position with a pillow under the abdomen and the arms hangings from the sides of the bed. This accentuates the intercostal spaces and rotates the scapula laterally
The injection point for an ICN block must be proximal to the mid-axillary line before the the nerve divides. Performing the block at or lateral to the mid-axillary line might fail to anaesthetise the lateral cutaneous branch. The optimal place to perform the ICN block is at the angle of the rib where the rib is thicker and the intercostal space
is wider, decreasing the chance to contact the pleura (Figure 10.3). The chance of pneumothorax increases if the block performed lateral to the angle of the rib.
If the injection site is medial to the angle of the rib, there is a possibility of
subarachnoid spread because the dural sack can extend up to 8 cm from the midline.After cleaning the area with antiseptic solution, the skin over the blocked area is tensed gently up before a 23–25 G needle is advanced to come in contact with the lower surface of the rib. The tension is then released, allowing the needle to move to its correct position and angulation (about 20° cephalad). Maintaining the 20° cephalad angulation increases the chances that the block needle is in close
proximity to the nerve.
The needle is carefully walked off the inferior edge of the rib. and is then advanced a further 2-3mm in the intercostal groove to pierce the posterior intercostal membrane and enter the neurovascular bundle. About 3–5mL of long acting local anaesthetic is injected after a negative aspiration. The block then can be repeated in the remaining spaces.
Complications of the ICN block include pneumothorax (incidence <1%), local
anaesthetic toxicity due to rich vascular supply and rapid vascular absorption, visceral and peritoneal injury and spinal anaesthesia
30
Q
- You have been asked to re-write the departmental guidelines for the treatment of postoperative nausea and vomiting. As part of the research you are reviewing a recent meta-analysis of pharmacological therapy. With regards to the forest plot in Figure 10.1 which of the following answers is
most appropriate?
A All studies would be expected to be weighted equally
B Gipasone should be part of the treatment algorithm for postoperative nausea and vomiting
C We can have the most confidence that the results of Butler et al., are
representative of the observed effect
D We would expect that all studies comparing Gipasone with Hurlatron would be included in the meta-analysis
E Sample size determines the size of the box assigned to each study
A
- C We can have the most confidence that the results of Butler et al., are representative of the observed effect
○ A meta-analysis is a means to combine the results of a number of studies statistically, thus aiming to increase the power of any subsequent analysis and th accuracy and precision of any conclusion drawn from the data.
The process begins with a systematic review of the relevant literature. Prior to starting the review the reviewers must draw up criteria that each study must fulfill in order to be included. Studies which do not fulfill these criteria are rejected as significant methodological flaws may distort the results and lead to incorrect conclusions. Such methodological considerations include the randomisation process, blinding, placebo-control and number of participants.
Answer D is therefore not the best one given here. Once the appropriate studies have been identified and appraised, data can be
extracted and the studies can then be weighted. There are a number of ways in which this is done but the principle is to assign more weight to those studies that provide more information about the treatment in question, in this case the ability of a drug to treat postoperative nausea and vomiting. It is expected that larger studies exhibit less variance than smaller ones, and therefore large studies are often weighted more; making answer A incorrect. The effect of the weighting process could be that smaller, valid studies have less impact on the final position of the ‘diamond’.
Methods of weighting used, for example, by the Cochrane Collaboration take into account the sample size and the event rate. The statistical concept encompassing these is the variance. The degree of weighting is shown by the size of the box.
Answer E is therefore only partially correct, in addition to sample size; the event rate is needed to calculate variance.
Although the results of this fictitious meta-analysis suggest that Gipatron is a
superior treatment for post operative nausea and vomiting, integration into clinical practice requires further considerations pertaining to side effect profile, cost,
availability, routes of administration etc. More information is therefore needed before choosing option B.
The horizontal line is the confidence interval and a measure of how uncertain we are about the described effect. A longer line therefore implies less confidence in the effect and therefore the true value described in the study. It can be seen that the study by Butler et al. appears to have the narrowest confidence intervals and so statistically speaking we can be more confident in those results not being due to chance.
