El-Boghdadly - 9 Flashcards
- 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 180/100 mmHg, heart rate of 45 bpm and temperature of 35.5°C. An arterial blood gas shows Pao₂ 13 kPa, Paco₂ of 6.9 kPa and blood glucose 8 mmol/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
B
- 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).
- 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 75 mg 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
B
- B Ask the surgeon to site a paravertebral catheter
The aims of analgesia in this scenario are:
• 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
• 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
• 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.
- You are asked to urgently review a 57-year-old man 7 days post left pneumonectomy.
He remained intubated and ventilated for 24 hours post operatively due to intraoperative bleeding and hypothermia. A left sided intercostal drain was removed 24 hours ago. He is now complaining of cough, shortness of breath and chest pain. His oxygen saturations are 89% on 15 L/min oxygen.
On examination there is new subcutaneous emphysema of the chest wall. Heart rate is 60 beats per minute and blood pressure is 80/50 mmHg.
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
B
- 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.
- 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
E
- 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.
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.
- 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 30 minutes 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
B
- 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).
Medical
Preoperative assessment of a
patient’s health status should
be made to determine eligibility
rather than use of arbitrary limits,
e.g. BMI, ASA, age
Chronic stable disease may be
better treated as day case
Surgical
Procedure should not pose any
serious complications, e.g. risk of
haemorrhage and cardiovascular
instability
Oral medications and local
anaesthetic techniques should
be sufficient to manage post
operative symptoms
Procedure should not prevent
resumption of oral intake within
a few hours
Patients should be able to
mobilise but full mobilisation is
not always required
Social
Patients must understand
procedure, postoperative
care and be able to consent
to day surgery
A responsible adult should
escort the patient home and
be present for the first 24
hours postoperatively
Domestic circumstances
should be appropriate for
postoperative care
- 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 10 mg at night for an irregular heart rate.
What is the safest way to proceed?
A Ensuring 18 hours 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 2 hours postoperatively
C Wait until 24 hours after the last dose of rivaroxaban, then proceed with a spinal, and give the next dose immediately postoperatively
D Ensure 12 hours 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
D
- 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 noncardiac
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 7 days prior to CNB. Prasugrel, a more potent thienopyridine, should
be avoided for 7–10 days and not restarted until 6 hours 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 24–48 hours is needed for abciximab.
____________________________________________
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
12–18 hours post-dose, and the drug should only be given 6 hours after a block or
catheter removal.
- 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
- 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:
• Blood pressure: 220/110 mmHg
• Heart rate: 90 beats per minute
• Spo2 98%
• ETCO2 4.9 kPa
• 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
E
- 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.
- 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 10 mL of 0.25% levobupivacaine with 10 μg fentanyl
B 10 mL of 0.25% levobupivacaine
C 10 mL of 0.25% plain bupivacaine with 300 μg diamorphine
D 10 mL of 0.25% levobupivacaine with 25 μg clonidine
E 10 mL 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 20 kg. 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: 0.5 mL/kg, 0.25% bupivacaine or levobupivacaine
Upper abdominal block: 1 mL/kg, 0.25% bupivacaine or levobupivacaine
Mid-thoracic block: 1.25 mL/kg, 0.25% bupivacaine or levobupivacaine
- 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
B
- 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.
- 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 0.25–0.5 mg/kg intravenous ketamine
B Local anaesthesia only with no sedation
C Infusion of remifentanil at 0.25 mg/kg/min
D Target controlled infusion of propofol at a 1 mg/mL
E 0.5 μg/kg fentanyl followed after several minutes by small doses of intravenous midazolam titrated to effect
B
- E 0.5 μg/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.
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.
- 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 > 4 mmol/L
B 4–6 mmol/L
C 6–8 mmol/L
D < 10 mmol/L
E < 15 mmol/L
C
- D < 10 mmol/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 (4–6 mmol/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 (4.5–6 mmol/L) or conventional glucose control (< 10 mmol/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’:
• < 10 mmol/L strongly suggested
• severe hypoglycemia is defined as < 2.2 mmol/L
• 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
- 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 fentanyl
C 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.
- 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 45 minutes 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 10–20 mL 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 6 months) 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:
• Venoarterial ECMO: blood is pumped from the venous to the arterial side
allowing gas exchange and haemodynamic support
• Venovenous: blood is removed from the venous side and then pumped back into
it facilitating gas exchange only
• 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:
• 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
• Thrombosis in the circuit can:
–– Affect the function of the pump or the oxygenator
–– Cause stroke
–– Result in leg ischaemia
• Infective complications can be related to the invasive lines or primary pathology
• Technical complications include:
–– ECMO circuit failure or breakage
–– Cannula displacement
–– Mechanical pump failure
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 14 days. 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.
- 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
D
- 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:
• Fluid balance management
• Hyperkalaemia (potassium over 6.5 mmol/L)
• Metabolic acidosis (pH < 7.1)
• Raised urea (> 30 mmol/L) or symptomatic ureamia
• Severe sepsis to remove inflammatory mediators
• Removal of water-soluble, low protein-bound drugs, e.g. some antibiotics to
increase dose administered.
The different types of renal replacement therapy are:
• 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
• 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
• 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:
• Ensure adequate driving pressure (venous pressure)
• 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
• 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.
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.
