El-Boghdadly - 7 Flashcards
- You are anaesthetising a previously well 43-year-old woman for a craniotomy to remove a frontoparietal meningioma. The patient is supine, with a 30° head-up tilt.
1 hour into the operation her oxygen saturations suddenly drop from 98% to 65%, her end-tidal CO₂ from 4.5 kPa to 2 kPa and her blood pressure, which initially rises, begins to fall rapidly.
Which of the following best describes your initial step in the management of the situation?
A Administer 100% oxygen
B Insert a right internal jugular central venous pressure catheter and aspirate any air
C Raise the patient’s venous pressure at the operative site by levelling the table +/– inotropic agent +/– performing a Valsalva manoeuvre
D Alert the surgeons and ask them to flood the operative site
E Turn the patient into the left lateral, head down position
D
1. D Alert the surgeons and ask them to flood the operative
site Venous air embolism is a potentially fatal clinical situation. Aspiration of
approximately 1mL/kg can generate an ‘air locked’ pulmonary circulation. It can occur in any surgical position providing the operative site is above the level of the
heart. If the hydrostatic gradient between the site and the right atrium is negative,
air can potentially move into the venous circulation and directly into the right
atrium. From here it passes into the right ventricle and on to the pulmonary artery. If
large enough it will entirely obstruct flow of blood through the ventricular outflow
tract. Subsequently, an air embolism initially increases right heart pressures and
critically impairs gas exchange. Cardiac output, end-tidal CO₂ and O₂ saturations
decrease. Ultimately, such deterioration can lead to cardiac arrest. Neurosurgical
procedures are especially high risk as veins may be held open by boney structures.
Management priorities are to stop further air inflow, reduce the volume or remove
any air that has accumulated and to treat any development of cardiovascular (CVS)
collapse. The initial action should therefore be to immediately alert the surgeons
who should obstruct any further air entry by flooding or applying a wet swab to the
site. 100% oxygen should then be administered, followed by methods to increase
venous pressure at the site. This can be achieved by levelling the table, applying
pressure to the neck, administering a fluid challenge +/- an inotrope or conducting
a Valsalva manoeuvre. If a central venous line is in situ, it should be aspirated. If CVS
collapse occurs the patient should then be turned into the left lateral, head down
position if possible, and cardiopulmonary resuscitation initiated.
- You are caring for a 70 kg man undergoing coronary artery bypass grafting. Long
term 75 mg aspirin (once daily) was discontinued 5 days preoperatively. His
separation from cardiopulmonary bypass (CPB) was uneventful but during sternal
wiring the surgeon states that the patient is ‘oozy’ and you note there is already
500 mL in the mediastinal drain. The activated clotting time (ACT) is 115 seconds.
You send a sample for thromboelastography (TEG).
Based on the results shown below in Table 7.1, what is the most appropriate treatment?
Table 7.1
Parameter Value Reference range
r time 32 mm 15–30 mm
k time 12 mm 6–12 mm
α° 40° 40–50°
Maximum amplitude (MA) 40 mm 50–60 mm
Ly30 5.0% < 7.5%
ACT 115 seconds 90–130 seconds
A Further 50 mg protamine and 2 units of fresh frozen plasma
B 2 g tranexamic acid
C 10 units cryoprecipitate and 50 mg protamine
D 2 units of fresh frozen plasma and 2 pools of platelets
E Re-open the patient and explore for bleeding immediately
D
- D 2 units of fresh frozen plasma and 2 pools of platelets
It has been reported that up to 20% of cardiac surgery patients bleed significantly
postoperatively. The need for resternotomy increases the chance of further
complications including prolonged mechanical ventilation, adult respiratory distress syndrome (ARDS) and wound infection. In addition to obvious surgical causes of bleeding, dysfunction of the coagulation cascade can occur for a variety of reasons
Causes of perioperative coagulopathy can have the mnemonic ‘ACHE’:
• Antiplatelet agents
• Contact with cardiopulmonary bypass circuit
• Haemodilution
• Heparin
• Hypothermia
• Excessive fibrinolysis
Coagulation defects may not be fully appreciated with more simple tests such as the activated clotting time (ACT), prothrombin time (PT) or activated partial thromboplastin time (APTT). The thromboelastograph (TEG) tests the entire process of coagulation and gives five parameters which may be used to identify a coagulation defect (Table 7.3).
r time
Time from test initiation to fibrin formation
Clotting factor activity
15–30 mm
7.5–15 minutes
Prolonged by:
Clotting factor deficiencies
Anticoagulants
Severe hypofibrinogenaemia
k time
Time taken to achieve a certain level of clot strength,
usually 20 mm amplitude
Clotting factors, fibrin and platelets
6–12 mm
3–6 minutes
Prolonged by:
Clotting factor deficiencies
Anticoagulants
Hypofibrinogenaemia
α° Speed at which
clot forms
Fibrin polymerisation
40–50° Decreased by:
Clotting factor deficiencies
Anticoagulants
Hypofibrinogenaemia
Maximum
amplitude
(MA)
Maximum
strength (amplitude)
of clot
Platelet
function
Fibrin bonding
50–60 mm Decreased by:
Thrombocytopenia
Platelet dysfunction
Hypofibrinogenaemia
- You are asked to assess a 78-year-old man scheduled for a tansurethral resection of his prostate (TURP) for prostate cancer. He appears fit and well but complains of being intermittently ‘light headed’. A portion of his ECG is shown in Figure 7.1.
What is the most appropriate course of action to take?
A Refer for DDD pacemaker preoperatively
B Schedule for surgery after reviewing a transthoracic echocardiograph
C Refer for an AAI pacemaker preoperatively
D Refer for a VVIR pacemaker postoperatively
E Check electrolytes and if normal schedule for surgery
A
- A Refer for DDD pacemaker preoperatively
The ECG shows Mobitz II atrioventricular (AV) block that is symptomatic based on
the history given. This is a class I indication for pacemaker insertion which should be
performed preoperatively, thereby excluding options B and E. The other indications
for permanent pacemaker insertion in the context of acquired AV block are outlined
in Table 7.4.
As the problem is with AV conduction at a level defined during electrophysiology
(EP) studies, atrial pacing alone (option C) will not prevent ventricular
bradyarrhythmias. Ventricular pacing (option D) alone cannot maintain AV
synchrony and may lead to pacemaker syndrome, where loss of synchrony leads
to symptoms of fatigue and functional limitation. A dual chamber mode with
adaptive rate control (option A) preserves AV synchrony, protects against ventricular
bradycardia and enables a normal chronotropic response to activity. Therefore
the most appropriate management step for this patient is to refer for preoperative
pacemaker on DDD mode.
For full understanding of the pacemaker codes, it is useful to refer to the NAPSE/
BPEG coding system (Table 7.5).
A summary of the various pacing modes is given in Table 7.6.
- A 65-year-old man with severe obstructive sleep apnoea/hypopnoea syndrome has
recently started using an auto-titrating nasal continuous positive airway pressure
(CPAP) device to treat his day time somnolence after lifestyle modifications
failed to help. In clinic, he feels no better and admits to not fully complying with
the treatment because of nasal stuffiness and irritation at night with occasional
epistaxis.
What is the most appropriate next step in managing his sleep apnoea?
A Change to fixed level CPAP
B Change to bilevel positive airway pressure
C Apply humidification
D Introduce a mandibular repositioning device
E Offer uvulopalatopharyngoplasty
C
- C Apply humidification
Obstructive sleep apnoea/hypopnoea syndrome (OSAHS) is a common disorder
characterised by intermittent upper airway collapse during sleep. An apnoea is
defined as a ten second breathing pause due to complete airway closure, whereas
a hypopnoea describes an episode where ventilation is reduced by at least 50% for
10 seconds due to partial collapse. OSAHS is graded into mild, moderate and severe
categories by the apnoea-hypopnoea index (number of events per hour of sleep)
and the severity of symptoms.
In order to improve daytime somnolence, the treatment aim is to reduce the
frequency of nocturnal apnoeas/hypopnoeas with options including lifestyle
modification, dental devices, surgery and the application of continuous positive
airway pressure (CPAP). The National Institute for Health and Care Excellence (NICE)
have recently recommended that all moderate to severe symptomatic cases of
OSAHS should be offered CPAP therapy. There is also a role for CPAP therapy in
symptomatic mild cases of OSAHS, but only if lifestyle modification has failed to
make a difference.
In
the above case, surgery is not the most appropriate management step as there is no
obvious obstructing lesion, and symptoms may improve by increasing adherence to
the CPAP machine alone.
- A 39-year-old woman with a body mass index of 46 kg/m2 for umbilical hernia repair is seen in day surgery pre-assessment clinic. She has well controlled hypertension. She has been told she snores loudly but sleeps well with no daytime somnolence.
Her neck circumference is 35 cm, and her oxygen saturation on air is 96%. Her ECG is normal.
Which of the following options is the most appropriate next action?
A She can proceed for day case surgery
B She should be listed for inpatient surgery
C She should be referred for sleep studies
D She should have a glucose tolerance test
E She should be advised to lose weight prior to surgery
B
- A She can proceed for day case surgery
AAGBI guidelines for perioperative management of obese patients recommend that
patients should not be excluded from day surgery on the basis of their BMI alone.
Units with appropriate resources and experienced staff can safely manage these cases
where their management would not be changed by overnight admission and in fact
benefit from early mobilisation. Patients with morbid obesity should be carefully preassessed
for symptoms of cardiac, respiratory and metabolic disease. Stable OSA with
established CPAP also does not preclude day surgery, but measures such as avoiding
long acting opioids and careful postoperative monitoring are required.
A validated questionnaire STOP-BANG has been developed to identify and riskstratify
patients:
• Snoring – do you snore loudly? (loud enough to be heard through a closed door)
• Tired – do you often feel tired or sleepy during the daytime?
• Observed – has anyone observed you stop breathing in your sleep?
• Blood pressure – do you have or are you treated for high blood pressure?
• Body mass Index > 35 kg/m2
• Age > 50 years
• Neck circumference > 40 cm
• Gender – male
A score of greater than 5 requires further investigation and careful perioperative
management as does the presence of any other features such as poor functional
capacity, abnormal ECG, uncontrolled hypertension or ischaemic heart disease,
saturations less than 94% on air, concurrent airways disease and previous venous
thromboembolism.
In this case, the STOP-BANG score is 3 and further cardio-respiratory investigation is
not required. Sleep studies are not indicated unless symptoms of excessive daytime
sleepiness or witnessed apnoeas in the presence of other risk factors are reported.
In-patient surgery or overnight admission is not required if her postoperative Spo2
is maintained at baseline levels on air without stimulation, and routine discharge
criteria can be met. Although diabetes should be screened for with a random blood
glucose check a formal glucose tolerance test is not indicated. Pre-assessment clinics
are an ideal place for advice regarding lifestyle modification, however weight loss
must be carefully controlled and monitored and is unlikely to alter management in
this case if surgery is postponed.
- A 73-year-old man in the recovery room is extremely confused, combative and is tachypnoeic. The recovery staff are struggling to perform any other observations. He has had a radical robotic prostatectomy for locally confined prostatic
carcinoma. The surgery was technically complex and the procedure duration was nearly 7 hours. On examination the only obvious signs are his severe delirium and agitation, and you also notice significant periorbital swelling.
The immediate treatment for the likely condition includes:
A Non-invasive humidified CPAP by mask
B Non-invasive BiPAP by mask
C Heliox with added entrained oxygen and urgent ENT referral
D Ophthalmology opinion
E Reintubation and head-up positioning
E
- E Reintubation and head-up positioning
Robotic surgery is becoming increasingly widespread, and may now be found in
many centres and specialties including general surgery and gynaecology. In the
UK by far the largest body of established work involves urology, and specifically
prostatectomy. The perceived benefits include increased nerve preservation within
the pelvic field and thus higher chances of retaining urinary continence and erectile
function. There may also be some advantages in terms of comfort/analgesia and
reduced blood loss. Indeed, it is now not uncommon for patients to be discharged in
the first 24 hours following surgery.
The robot
The da Vinci system is the most common system in use in the UK at the current time.
This system is made up of a surgical control console with an immersive high-definition
visual display, a computer tower, and the robotic surgical manipulator. The manipulator
is a large, heavy trolley comprising the surgical arms which is then ‘docked’ to the
patients table. One arm supports the camera, and others are then inserted into the
ports. A scrubbed assistant is still required, while the unscrubbed surgeon sits at the
console, which may be distant from the patient. The robot has no autonomy in function;
it merely acts as a ‘telemanipulator’ transmitting the surgeon’s movements from the
console. There are case reports of surgery having been performed with the surgical
console being situated in a different country from the patient.
The advantage over standard laparoscopic surgery comes from several sources.
First, fewer assistants are required, with one scrubbed surgeon and a scrub nurse.
The camera contains dual optical apparatus meaning that a stereoscopic picture is
possible in the display console, allowing for depth perception. The robot arms have
freedom compared to normal laparoscopic instruments. The apparatus filters tremor
and automatically scales movements, all greatly facilitating microsurgery.
Specific physiological considerations
For the most part the considerations are those of laparoscopic surgery, however
access to the patient is severely limited, and the position is very extreme. This
exaggerates all the physiological changes such that complications may ensue if
precautions are not taken. Due to the time taken to uncouple the robot from the
patient, (may be several minutes) a plan for emergency access to the patient must
be rehearsed.
The surgery requires steep head-down in the Trendelenburg position which may
be as steep as 45°. For this reason, the attention to detail during positioning is vital.
Strapping of the shoulders to prevent patient slipping can produce traction on the
brachial plexus, and the lower limbs must be carefully positioned to reduce the
risk of well leg syndrome and thromboembolism. The transition to this position
can cause movement of the tracheal tube, due to migration of the tube in either
direction, but also movement of the trachea and the diaphragm upward. Once
in this position the added cardiovascular insult of pneumoperitoneum can cause
major haemodynamic instability which if not resolved by countermeasures, may
necessitate conversion to an open procedure.
The degree and duration of Trendelenburg present a series of problems less
common in other types of surgery, but still thankfully rare. Reflux of gastric
secretions can cause chemical damage to the mucosa of the mouth and also
unprotected eyes. Antacid premedication can be helpful. The increase in systemic
vascular resistance, mean arterial pressures and intracranial pressures accompanied
by decreased venous return can cause oedema of the dependent head and
neck tissues, and patients are often warned to expect facial and eye swelling
postoperatively. This has been associated with laryngeal oedema and stridor, and
cerebral oedema with marked confusion, requiring reintubation and head up
positioning for some hours before successful extubation. For this reason, and to
reduce ureteric flow a conservative fluid strategy is often adopted once the head
down position is achieved.
Confusion in recovery is a popular exam topic with a vast array of differentials. The
clue here is the type and duration of surgery, and knowing something about the
position involved during the robotic technique obviously helps. The patient could be
hypoxic, but in this condition is unlikely to tolerate non-invasive ventilation anyway.
Airway oedema can occur in these patients, but no mention is made of stridor in the
stem. Facial swelling and cerebral oedema should subside in hours with supportive
measures and head up position. CT scanning should also be considered.
- A 50-year-old man awaiting surgery for a mediastinal tumour becomes
progressively more tachypnoeic and stridulous on room air. Heliox is administered as a holding measure until more definitive treatment is instituted and his symptoms slowly improve.
Which physical property of helium is most important in improving his respiratory
distress?
A A reduced density compared to air
B A higher viscosity compared to air
C A higher thermal conductivity compared to air
D A lower blood: gas solubility coefficient compared to air
E Its non-reactivity within the airway
A
- A A reduced density compared to air
Helium is an odourless, colourless and biologically inert noble gas whose unique
physical properties can be exploited when managing an upper airway obstruction.
It is presented as Heliox 21, which is the generic name for the mixture of 21% oxygen
and 79% helium. In order to appreciate its role in the management of an upper
airway obstruction, the types of flow within the airway needs to be revisited.
Gas flow within the respiratory tract can be either laminar or turbulent. Laminar flow
is unidirectional and smooth with molecules moving in parallel creating a parabolic
flow profile. This is an efficient type of flow. Turbulent flow on the other hand has an
essentially flat flow profile with molecules swirling in eddies and vortices rather than
an orderly way. This is an inefficient form of flow and conversion from laminar to
turbulent flow approximately halves the flow rate for a given pressure drop.
Whether or not flow is turbulent or laminar depends on a dimensionless number
called the Reynolds number (Re) (turbulent flow being more likely if Re > 2000):
In constricted upper airways, the airflow is turbulent and inefficient. Since heliox
is approximately three times less dense than air, its administration will cause a
reduction in the Reynolds number thus increasing the likelihood of more efficient
laminar flow. Even in situations where turbulent flow persists, heliox still flows much
easier when compared to air since the flow rate is inversely related to the density of
the carrying gas.
The viscosity of helium is in fact very similar to air, and does not explain why heliox
is beneficial in upper airway obstruction scenarios. Flow rate is inversely related to
the gas viscosity in established laminar flow, which is different to the turbulent flows
seen in the above case.
Helium does have a high thermal conductivity and prolonged administration may be
associated with a lowering of body temperature. This however does not significantly
affect the airflow patterns within the respiratory tree.
Another useful physical property of helium is its very low blood: gas solubility. The
helium dilution technique works on the principle that helium remains within the
lung due to its low solubility in blood allowing the functional residual capacity to be
estimated.
Helium is chemically inert because its filled valence orbitals are less able to interact
with other compounds. Helium has no direct pharmacological effects and is not a
treatment in its own right. It should be viewed as a bridging therapy whilst waiting
for the effects of other treatments to have effect (Table 7.7).
- A 55-year-old man is undergoing emergency coronary angioplasty for myocardial infarction in the cardiac catheterisation suite after return of spontaneous circulation from a ventricular fibrillation (VF) cardiac arrest. You have been urgently called to provide a general anaesthetic as he is becoming increasingly drowsy and confused with a Glasgow coma score of 10/15. There is an anaesthetic machine present in the room.
What should you prioritise as your first action?
A Check the anaesthetic machine
B Ensure suction and a tipping trolley is present
C Take a history and perform a brief neurological examination
D Draw up the emergency drugs
E Call for anaesthetic assistance
A
- E Call for anaesthetic assistance
Anaesthesia in remote locations is associated with risk. It represents an unfamiliar
environment, using anaesthetic equipment and monitoring, which may be only used
on occasion, and personnel that do not routinely work together and are unfamiliar
with anaesthetic practices. In the cardiac catheter lab the radiology equipment
often makes it difficult to access and visualise the patient and the table may be fixed
and unable to tilt head down. The focus of the staff is often on the revascularisation
and in these challenging situations especially when dealing with patients that are
critically unstable, communication and effective team working are paramount.
The 2013 Royal College of Anaesthetists (RCoA) guidelines on anaesthesia in nontheatre
settings outline the staffing, drug, equipment and safety requirements that
should be met when anaesthesia is provided in these remote locations. Equipment for
induction, maintenance and emergence from anaesthesia should be available as is in
theatre, and monitoring should be ideally separate from that used by the cardiologist.
Space and equipment should be set up to deal with the possibility of cardiac arrest.
In this scenario, there are many essential checks and tasks that need to be swiftly
performed before anaesthesia can be administered. The RCoA guidelines state
that anaesthesia in remote locations cannot be performed by a single individual,
and that a dedicated, qualified and skilled anaesthetic assistant should always be
available, and provide exclusive help to anaesthetist. Clearly the machine, drug and
equipment checks are all important, however, calling early for anaesthetic assistance
is essential and the other tasks can be conducted once this has been requested.
- A 75-year old woman with chronic anaemia and angina is to have a Colles’ fracture reduction under Bier’s block.
Which local anaesthetic agent would be the most appropriate to use for this block?
A Levobupivacaine
B Lignocaine
C Ropivacaine
D Prilocaine
E Chloroprocaine
B
- B Lignocaine
Bier’s block anaesthesia is a form of intravenous regional anaesthesia (IVRA) that
was first introduced by the German surgeon August Bier in 1908. It involves the
administration of local anaesthetic (LA) intravenously into a tourniquet-blocked
limb thus localising the anaesthetic in that limb. The technique is based on the
principle that local anaesthetic diffuses from the vascular bed to the capillary plexus
surrounding the nerve, causing conduction block in the nerve involved.
IVRA is primarily indicated for surgical procedures on the elbow, forearm or hand
requiring anaesthesia for up to one 1 hour, such as fracture manipulation. It can also
be successfully performed on quick lower limb procedures of the foot, ankle and
lower leg. However, the block is difficult to perform in the lower limb and requires
larger amount of local anaesthetic.
The steps to perform a Bier’s block involve: - Before commencing the Bier’s block, patient should be informed and consented
adequately and fully starved. IVRA should be performed in a safe environment
where the patient is fully monitored with resuscitation equipment and
emergency drugs available. - Two intravenous cannulae are established, one in the operated arm (as distal as
possible) and another in the contralateral limb to administer sedation or other
drugs if required. - A double cuff tourniquet is applied on the arm involved. The arm is then
exsanguinated either by applying Esmarch bandage or raising it for two minutes
while compressing the axillary artery. - The distal cuff is inflated to at least 100 mmHg above the patient’s systolic blood
pressure followed by inflating the proximal cuff to the same pressure. - Once the tourniquet is secure, the distal cuff can be deflated.
- The LA solution is injected in the operated arm after confirming the absence of a
radial pulse. It is very important to inject the local anaesthetic slowly to prevent
the peak venous pressure from exceeding the tourniquet occlusion pressure and
hence leakage of LA to the systemic circulation. - Once the injection is completed, remove the cannula and apply pressure on the
puncture site. - After 10–15 minutes, when the anaesthesia is established, the distal cuff is
inflated followed by the deflation of the proximal cuff to relieve the tourniquet
pain below the proximal cuff. The tourniquet must not be deflated before 20
minutes because releasing the tourniquet early may result in a large amount
of LA being released immediately into the systemic circulation, increasing the
danger of LA toxicity. - Once the surgical operation has been completed, the tourniquet should
be deflated in two stages. By deflating the tourniquet for 10 seconds then
reinflating it for 1 minute before the final release, the chance of systemic toxicity
is reduced by gradually washing out the LA from the operated limb. - It is mandatory to continue monitoring the patient for at least 10 minutes after
the procedure..
Although IVRA is a simple and safe technique, specific knowledge in local
anaesthetic pharmacology is required in order to avoid rare but serious
complications.
A variety of local anaesthetic agents have been used to perform a Bier’s block,
however prilocaine and lignocaine are currently the most commonly used drugs.
In the UK, 0.5% prilocaine is the drug of choice for IVRA. It is the least toxic LA as
it is the most rapidly metabolised of the amides. Prilocaine is an amide LA, the
recommended dose is 3 mg/kg (maximum dose is 6 mg/kg), and usually 40 mL of a
0.5% solution is injected in the operated arm.
Prilocaine is associated with methaemoglobinaemia, especially when the dose
exceeds 600 mg. Although this is clinically insignificant in most patients, small
amounts of methaemoglobin can cause a significant decrease in oxygen-carrying
capacity in patients with anaemia and heart disease, hence it should be avoided.
Therefore prilocaine is not appropriate for the patient in this clinical scenario.
In North America, lignocaine remains the most frequent used amide LA in a dose of
not more than 3 mg/kg. Many emergency doctors and anaesthetists in the UK are
- A 65-year-old woman is to have a palmar fasciectomy of the middle finger under axillary nerve block. 30 minutes after performing the block, it is apparent that the median nerve is spared. You decide to perform a supplementary median nerve
block. Which of the following approaches to the median nerve would be the most appropriate for this case?
A Wrist
B Mid-forearm
C Axillary
D Antecubital fossa
E Supraclavicular
B
- D Antecubital fossa
Upper limb peripheral nerve blocks are used to provide analgesia and anaesthesia
for elbow, forearm, wrist and hand surgery. They may also be used to augment a
brachial plexus block or provide perioperative analgesia after a general anaesthesia.
The median nerve (C5-T1) arises from both the medial (C5, C6, C7) and the lateral
cords (C8, T1) of the brachial plexus. In the arm, the nerve passes lateral to the
brachial artery, which it then crosses, and descends on its medial side to the
antecubital fossa. In the forearm, the median nerve lies between the bellies of flexor
digitorum profundus and flexor digitorum superficialis. And at the wrist, it lies
medial to flexor carpi radials and lateral to the tendon of palmaris longus.
It supplies sensory innervation to the radial side of the palm, and the palmar surface
of the lateral 3 and half fingers, including their dorsal tip to the first interphalangeal
joint. It provides motor innervation to most of flexor muscles in the forearm and
thenar muscles of the thumb.
One of the most important branches of median nerve is the anterior interosseous
nerve. This nerve arises from the median nerve just distal to the antecubital fossa. It
descends between the ulna and the radius along the interosseous membrane. The
anterior interosseous nerve supplies the flexor pollicis longus, the flexor digitorum
profundus (lateral half ) and the pronator quadratus. It is essential to block the
anterior interosseous nerve for successful median nerve block.
The median nerve can be blocked at various places and can be performed using
peripheral nerve stimulator, landmark technique and/or ultrasound (US) guided with
a high frequency probe.
At the brachial plexus: the median nerve lies in close relation to the axillary artery and
vein in the axilla and can be blocked independently or in conjunction with the ulnar,
radial and musculocutaneous nerves here. See question 4.10 for further details.
At the mid-arm level: the nerve lies above the brachial artery. Using a high frequency
US probe or nerve stimulator, a single injection of 5–7 mL of local anaesthetic is
enough to block the nerve.
At the antecubital fossa: using a high frequency US probe, the median nerve is seen
as a single hyperechoic elliptical structure immediately medial to the brachial artery.
5–7 mL of local anaesthetic is injected after visualising the nerve. With a peripheral
nerve stimulator technique, the needle is directed perpendicularly and the nerve
should be found within 1–2 cm depth, medial to the brachial artery pulsation. After
stimulating the median nerve (pronation, finger flexion and thumb opposition),
5–7 mL of local anaesthetic is injected.
This approach successfully blocks the anterior interosseous nerve, and for this
clinical scenario it is the correct answer.
- A 6-year-old boy with global developmental delay is first on your surgical list for an orchidopexy procedure. At your pre-assessment visit his mother tells you he can be a “nightmare” and is not up to date with vaccinations after a bad experience at their local health centre. She doesn’t think he will cooperate with induction, and is clearly anxious herself. The child will not interact with you and runs off to the play area as you approach. In the anaesthetic room, you make a single attempt for intravenous access, which is unsuccessful. The child is inconsolable and the mother is visibly distressed.
The best way to proceed would be:
A Cancel this elective case and explain to the mother counselling/play therapy will be required before rebooking
B Overpower the child and proceed with an inhalational induction with
sevoflurane at 8% in oxygen
C Overpower the child and proceed with an inhalational induction with
sevoflurane at 8% in oxygen and nitrous oxide
D Send the child back to the ward and prescribe an oral midazolam premedication at a dose of 0.5 mg/kg, resending for the child at 15 minutes post dose
E Send the child back to the ward and prescribe an oral ketamine premedication
at a dose of 5 mg/kg, resending for the child at 15 minutes post dose
D
- Send the child back to the ward and prescribe an
oral midazolam premedication at a dose of 0.5 mg/kg,
resending for the child at 15 minutes post-dose
Having an uncooperative child at induction is not uncommon, in studies distress
at induction occurs in a third of children, with a quarter requiring some form
of physical restraint. There are several factors which predict problems during
anaesthetic induction, and eliciting these can help in making an induction strategy
and preparing the parents beforehand.
Risk factors for induction distress
• Withdrawn, shy, introverted demeanour
• Anxious children
• Ages 1–3 (increased separation anxiety)
Midazolam is the most widespread sedative premedicant in the UK. The oral dose is
0.5 mg/kg, giving an onset at 5-10 minutes peaking at 20–30 minutes. It may also be
given intranasally or sublingually at a dose of 0.2 mg/kg. The intranasal route may be
possible if oral medication is rejected, but it can give a burning sensation.
Fentanyl can be given transmucosally in a lollipop, with a bioavailability of 33%
via this route. A dose of 15–20 μg/kg will produce sedation at 20 minutes with a
peak at 30–40 minutes. The whole host of opioid side-effects including respiratory
depression are a drawback.
Holding and restraint
In general, the principle is to use restraint only as a technique of last resort. Minimal
force required for safety (of staff and patient) should be employed, by appropriate
numbers of experienced/trained staff. The plan should be discussed with the
parent(s) beforehand, and opportunity for debrief discussions with parent and child
should exist afterwards.
In this case the induction process has clearly broken down, and the risk of
proceeding with a distressed child and mother has to be balanced against the
urgency of the procedure. In an emergency if the child had already failed with
premedication and the mother had been warned and was happy to proceed/
participate with an inhalational induction, this might be the next step. However the
risk of laryngospasm in a crying, anxious and distressed child is unacceptable here.
Cancellation is an option, but even with further preparation and psychological input
the risk of induction distress still persists, thus sending the child back to the ward
and trying a premed is valid. Midazolam is the first line in this situation.
- A 35-year-old man has presented with a syncopal episode the day after a fall during a rugby match, and CT scan has confirmed an extra-dural haematoma. What features would indicate that intubation should be performed before transfer to a neurosurgical centre?
A Glasgow coma score (GCS) 11/15
B An episode of vomiting
C A seizure
D Suspected skull fracture
E A drop in GCS by 1 point on the verbal scale
C
- C A seizure
Intubation for transfer is indicated in patients who have:
• GCS 8 or less
Drop in GCS of 2 points or 1 point in the motor scale
• Loss of protective laryngeal reflexes
• Ventilatory insufficiency: Pao2 < 13 kPa on oxygen, Paco2 > 6 kPa
• Spontaneous hyperventilation with Paco2< 4 kPa
• Irregular respiratory pattern
• Seizures
• Unstable facial fractures
• Bleeding into the airway
Principles during transfer should be to reduce and avoid surges in intracranial
pressure, maintain cerebral perfusion pressure and prevent secondary brain injury.
• The patient should receive sedation and analgesia via a syringe driver and
adequate muscle relaxation. Aims should be for a Pao2 > 13 kPa, Paco2 4.5–5 kPa
unless there is clinical or radiological evidence of raised intracranial pressure
where hyperventilation to a Paco2> 4 kPa with a higher Fio2 is justified
• Endotracheal tubes should be secured but tight tube ties avoided. The patient
should be placed in a 15–30 degree head up position
• Avoid hypotension. Hypovolaemia is poorly tolerated during transfer due to the
effects of motion, and circulating volume should be normalised before departure.
Inotropes may be indicated to achieve an adequate mean arterial pressure
(> 80 mmHg) after volume expansion if hypotension persists
• Consider loading with an anticonvulsant, e.g. phenytoin prior to transfer
• Avoid hypoglycaemia
- A 45-year-old man has suffered an isolated, catastrophic, irrecoverable traumatic brain injury. In the last few minutes he has become progressively tachycardic, hypotensive and polyuric despite aggressive filling with intravenous crystalloid.
His observations include: heart rate 100 beats per minute sinus rhythm, blood pressure 75/45 mmHg, stroke volume 82 mL.
The first vasoactive drug of choice in this scenario is:
A Adrenaline
B Dopamine
C Labetalol
D Vasopressin
E Metaraminol
D
- D Vasopressin
As catastrophic brain injury progresses into brainstem death, dramatic changes in
cardiovascular physiology often occur due to one or more of the following:
• hypovolaemia secondary to diabetes insipidus caused by acute posterior pituitary
failure
• myocardial depression due to catecholamine and cytokine toxicity
• the transition from hypertensive catecholamine excess into vasoplegic
hypotension
- A 76-year-old man has undergone an uneventful 3-vessel on-pump coronary artery bypass grafting (CABG) 4 hours ago and is currently sedated and ventilated on the intensive care unit. He has normal ventricular function demonstrated on a pre-operative transthoracic echo (TTE). On review the noradrenaline dose has increased from 0.08 μg/kg/min to 0.2 μg/kg/min to maintain a target blood pressure while the central venous pressure is static at 12 mmHg. There is a total of 300 mL of blood in the chest drains. An arterial blood gas demonstrates a worsening metabolic acidosis.
What is the next appropriate intervention?
A Organise an urgent TTE
B Request the cardiothoracic surgeon to attend immediately
C Give sequential intravenous crystalloid boluses of 100 mL
D Commence dobutamine at 2.5 μg/kg/min
E Insert a pulmonary artery catheter to guide fluid therapy
C
- C Give sequential intravenous crystalloid boluses of
100 mL
The priorities after coronary artery bypass grafting are as follows: warm, wean, and
wake. This simple list (which has obviously been designed by a surgeon) allows the
consideration of problems at each stage:
Warming
• As warming occurs vasodilation may occur which may result in relative
hypovolaemia
• Reperfusion may result in transient metabolic disturbances
Weaning
• Refers to reducing vasoconstrictor, inotrope and ventilator requirements, which
should be routine if there are no complications as a result of surgery or anaesthesia
Waking
There are several causes of prolonged waking which may be respiratory function
related, metabolic, temperature-related, or anaesthetic and analgesic related, but
most concerning are:
• ‘Pump-head’ a multi-factorial syndrome causing global cerebral dysfunction
due to micro-emboli (particulate and gas) and hypo-perfusion
• Embolic stroke (regional deficit)
• Haemorrhagic stroke (regional deficit)
Cardiac pump-failure
• Global myocardial dysfunction due to pre-existing disease, myocardial
stunning, metabolic and electrolyte disturbances or inappropriate
vasoconstrictor and inotrope usage
• Regional myocardial dysfunction due to a thrombosed graft, embolic
obstruction, a kinked graft or poor cardioplegia delivery
• Arrhythmias:
–– Tachycardia (atrial fibrillation is the most common) treated with
pharmacological measures or rarely electrical cardioversion
–– Bradycardia treated with either atrial pacing (if no atrioventricular
conduction delay is present), ventricular pacing (if an atrioventricular block
is present), or with atrioventricular sequential pacing
Mechanical obstruction
• Tension pneumothorax (pleura surgically opened if internal mammary arteries
used for grafting)
• Cardiac tamponade
• Haemothorax if drains are obstructed with blood clot formation
Bleeding which may be assessed by monitoring the chest drain output
• Surgical
–– Graft anastomotic site
–– Venous graft tributary
–– Site of cannulation (aortic or atrial), suture lines, sternal wire holes
• ‘Anaesthetic’
–– Dilutional coagulopathy
–– Inadequately reversed unfractionated heparin
In the case above there is evidence of worsening haemodynamic performance (an
increased vasoconstrictor requirement) and end-organ perfusion (a worsening
metabolic acidosis) without an obvious bleeding source and without an increased
central venous pressure. An ABC approach is needed to identify which of the
differential diagnosis are most likely. The immediate intervention, if no obvious
cause is found, is a trial of intravenous fluid therapy (100 – 250 mL boluses) and
assessment of fluid-responsiveness. As mentioned before, the combination of
warming, reperfusion, fluid re-distribution and a small amount of blood loss may be
all that is wrong.
A transthoracic or oesophageal echo is an extremely useful investigation. A visualised
tamponade or regional wall abnormality that may indicate a graft-malfunction
indicates the need to return to theatre however a collection of blood posterior to
the heart causing tamponade may not be visualised. Global dysfunction seen on the
echo due to myocardial stunning may be treated with correction of metabolic and
electrolyte abnormalities or an inotrope such as dobutamine or milrinone.
A repeat full blood count and clotting analysis including a thrombelastogram (TEG)
is helpful to guide blood product administration if bleeding is suspected.
The surgical team should be informed of the developments early. Cardiothoracic
surgeons are experienced in weaning patients after bypass grafting and often have
useful insights regarding the particulars of the surgery. If the patient continues to
deteriorate, a repeat thoracotomy in theatre (or on the intensive care unit in extreme
situations) may be required
- A 65-year-old man with an established history of moderate COPD was admitted with an acute, infective exacerbation 5 days ago. He has never required invasive ventilation and has a good exercise tolerance.
Following a sedation hold, the patient is awake and co-operative. He appears comfortable on CPAP 5 cmH2O with 18 cmH2O of inspiratory pressure support (iPS). His Pao2 is 8.5 kPa on a Fio2 of 0.28. He coughs spontaneously with moderate strength but has a significant secretion load.
He is cardiovascularly stable. A spontaneous breathing trial is performed, but within 5 minutes he has rapid shallow breaths and looks to be struggling, while a repeat blood gas shows a significant increase in his Paco2, recurrence of a mild acute respiratory acidosis and a modest fall in his Pao2.
On the basis of this spontaneous breathing trial the best strategy is:
A Extubate onto mask ventilation
B Perform a percutaneous tracheotomy later today and wean the iPS as tolerated
C Institute protocolised gradual reduction in pressure support
D Initiate titrated interval sprint weaning (work and rest cycles)
E Re-sedate and recommence synchronised intermittent mandatory ventilation (SIMV)
C
- D Initiate titrated interval sprint weaning (work and rest
cycles)
The scenario suggests a mixed picture of good and bad prognostic factors. In
particular, declining exercise tolerance, low body mass index and/or significant
recent weight loss and more than two hospital admissions per year are poor
prognostic markers in patients with chronic obstructive pulmonary disease (COPD).
This patient fulfils all the criteria for a spontaneous breathing trial, the purpose of
which is to assess the likelihood of successful extubation. He resoundingly fails the
trial by all criteria.
Ventilatory management in this population is challenging and arguably more of an
art than a science. The best answer suggested here is controversial.
Though there is increasing enthusiasm for extubation and immediate application
of mask ventilation in scenarios such as that outlined, the risks and benefits are
complex and the relative merits of this approach are currently the subject of a
number of large, randomised control trials. This patient has a relative contraindication
in having a heavy secretion load with only a moderate strength cough.
Non-invasive ventilation (NIV) will increase his difficulty in secretion clearance and
therefore places him at significant risk of ventilator failure despite NIV and requiring
re-intubation. Should this occur, this sequence of events is associated with a higher
morbidity and mortality that continuing invasive support.
Performing a tracheostomy at day 5, would be considered too early by most
practitioners, unless, the educated guess was that a patient would clearly need
> 10–14 days of invasive support. There is no clear evidence to support either an
‘always early’ or ‘always late’ strategy.
Protocolised weaning is advocated by many practitioners. Its success is probably
more attributable to the organisational and logistic benefits rather than any
physiological rationale. However, given that respiratory muscle fatigue is the
principal cause of weaning failure in COPD patients, there is a growing body of
evidence ranging from exercise physiology to cardiac rehabilitation to support
a titrated work rest cycle approach utilising short bursts of high activity with
prolonged periods of effective rest. Hence D is considered the best answer.
In the scenario given there is no rationale to re-sedate and SIMV is proven to be
detrimental to weaning as opposed to CPAP with iPS, which promotes it.
