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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3080_Библиотеки_им_академика_М_И_Перельмана
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The Patient with Respiratory Distress II
49
motor endplate at the skeletal neuromuscular junction. Nerve conduction is
impaired due to occupation of acetylcholine binding sites by the autoantibody.
Once the number of available postsynaptic receptors decreases to 30%, patients
become symptomatic. Prevalence is approximately 10in 100
000, with a female
preponderance. It is often associated with thymus hyperplasia and other auto-
immune diseases.
What else could cause a similar presentation?
One of the less common variants of Guillain–Barré syndrome (GBS):
Acute motor axonal neuropathy (AMAN).
Acute motor sensory axonal neuropathy (AMSAN)–axons, rather than
the myelin sheath, are affected.
Miller Fisher syndrome–the classic triad is of ophthalmoplegia, ataxia
and areflexia. This disease can present as a pure oculomotor palsy.
It is associated with anti-
GQ1b antibodies although 1in 10 cases is
seronegative.
Bickerstaff’s brainstem encephalitis–this shares similarities with the
Miller Fisher variant with regard to ophthalmoplegia, ataxia and
presence of anti- GQ1b antibodies. However, these patients suffer
altered conscious level and may also show long tract signs (e.g. spas-
ticity and hyper-
reflexia).
Pharyngeal- cervical- brachial variant–oropharyngeal and brachiocer-
vical weakness. There is areflexia in the upper limbs. The condition
is rapidly progressive. This is an axonal neuropathy and half of cases
are associated with anti-
GT1a antibodies.
Pan- dysautonomia –this is an extremely rare variant which presents
with autonomic symptoms alone. There is no motor involvement.
Lambert–Eaton myasthenic syndrome (LEMS)–antibodies against pre-
synaptic voltage- gated calcium channels lead to proximal limb muscle
weakness, usually aecting the legs more than the arms. In contrast to
MG where exercise causes worsening of symptoms, exercise can tempo-
rarily alleviate symptoms in LEMS. It is usually associated with under-
lying malignancy (60%) and can be the presenting feature of small cell
lung cancer.
Toxins (especially heavy metal intoxication)–this would usually present
with abdominal symptoms and confusion, but weakness and paraes-
thesia are also features.
Botulism–often contracted from tinned or foil- wrapped foods, Clos-
tridium botulinum produces botulinum toxin which inhibits the
release of acetylcholine from presynaptic nerve terminals at the neu-
romuscular junction. Presentation is with facial weakness, blurred or
double vision, ptosis, dry mouth, postural hypotension and nausea
and vomiting.
Lyme disease–tick- borne Lyme borreliosis, usually Borrelia burgdorferi,
may present in a variety of ways including facial weakness. Other symp-
toms include palpitations, joint pains, fever, headache and tiredness.
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Clinical Cases in Critical Care
50
Erythema migrans (an erythematous bullseye rash) may be seen at the
site of the tick bite.
Spinal cord pathology–transverse myelitis or spinal cord compression
could account for lower limb weakness but would not explain Jim’s
double vision.
Drugs–certain drugs such as cocaine, bumetanide, amiodarone, phe-
nytoin and vincristine can cause peripheral neuropathy.
Intracranial event–this is an unlikely cause of ascending muscular
weakness but is included for completeness. Jim’s CT head was normal,
which is reassuring. However, brainstem pathologies would be better
visualised using magnetic resonance imaging (MRI). MRI imaging of the
brain can require the patient to lie at for around 45
minutes so always
consider whether it is safe to do this without airway protection.
Why is the medical registrar calling you?
It is reasonable for the medical team to raise awareness of this patient who
is at risk of rapid deterioration. Classically, the symptoms of GBS progress
over 10–12
days. The pattern of weakness is ascending and, in some cases, can
progress to involve the phrenic nerve, intercostal muscles and accessory mus-
cles of respiration. Patients can deteriorate rapidly, leading to the requirement
for invasive ventilatory support. Particularly in rapidly progressive cases, close
monitoring of patients is advisable as the onset of respiratory failure can
easily go unnoticed.
GBS can have profound autonomic system involvement leading to cardiac
dysrhythmias, uctuations in blood pressure, urinary retention and severe
constipation leading to pseudo- obstruction.
How will you assess Jim’s respiratory function?
Using a combination of clinical assessment and point- of- care testing, the
key is not to miss a deterioration in symptoms which could lead to Jim
suffering a respiratory arrest on the ward. Assess his respiratory function
and his ability to clear secretions effectively. Postural hypotension can be
a manifestation of autonomic neuropathy, and approximately 30% require
ventilatory support.
Clinical examination–assess cough strength. Can he clear secretions?
Can he sustain lifting his head o the pillow for 5 seconds? Can he raise
his elbows above his head and keep them there for 5 seconds?
Serial lung function testing is mandatory–4- hourly bedside spirometry
should be performed to track progress and identify deterioration. The
You decide to review Jim yourself. On examination, you nd him alert and
comfortable but with symmetrically reduced power in his lower limbs, more
marked distally. He also has double vision at the extremes of lateral gaze.
BP127/47 mmHg lying, 93/33 mmHg sitting, HR 89 bpm, RR 14 breaths per
minute with oxygen saturations of 99% on room air.
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The Patient with Respiratory Distress II
51
following parameters should raise concern and prompt admission to
critical care with consideration of intubation:
Forced vital capacity <15 mL/kg
Maximal inspiratory pressure <30 cmH
2
O
Maximal expiratory pressure <40 cmH
2
O
Rising PaCO
2
on serial arterial blood gas sampling
How do you proceed?
Admit Jim to critical care straight away. He has deteriorated rapidly
which is a poor prognostic sign. Accompany him on the transfer to the
ICU with monitoring in place, a skilled assistant, an emergency intuba-
tion kit and an oxygen supply.
Ask the ward to call Jim’s next of kin.
Proceed to intubation on arrival in intensive care.
Lung- protective ventilation.
Insert arterial and central venous catheters, a urinary catheter and a
nasogastric tube.
Blood pressure management with fluid and vasopressors guided
by clinical assessment, echocardiography and/or cardiac output
monitoring.
Prescribe thromboprophylaxis, aperients and ulcer prophylaxis.
What investigations would you like to perform
now and over the next few days in addition to the
standard critical care blood panel?
Chest radiograph –review central venous catheter positioning and assess
for development of lower respiratory tract infection, possibly secondary
to aspiration.
Lumbar puncture –a high protein level would be consistent with GBS.
A raised white cell count could suggest an alternative cause for the pre-
sentation (e.g. Lyme disease) but could also raise the possibility of an
infective or inammatory condition leading to the development of GBS
in this patient (e.g. HIV or malignancy).
Investigations to identify any immune activating pathogen.
Stool culture for Campylobacter jejuni. Ask about prodromal diar-
rhoea, recent travel and vaccination.
Blood for HIV, CMV, EBV, hepatitis viruses, viral PCR (especially for
arboviruses and influenza), mycoplasma antibodies.
Jim has good respiratory function and you elect not to admit him but leave
strict instructions for regular monitoring and review. Five hours later, you
are called by the nurse on the ward who says that he is worried about Jim
because he appears to be struggling to breathe. When you re-
review him,
his RR is 30–35 breaths per minute, HR 125
bpm, his cough is weak. He is
too tired for spirometry.
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Clinical Cases in Critical Care
52
Immunoglobulins and antiganglioside antibodies (anti- GQ1b, GM1,
GD3, GD1a)–high levels of anti-
GM1 are associated with increased
severity of GBS. Anti-
GD1a is associated with acute motor axonal
neuropathy.
MRI brain/spine –this is sensitive but not specic. It can reveal spinal
root enhancement and surface thickening.
Nerve conduction studies –these may be normal in the early stages and
are most useful at around 14
days. In GBS, there are low- amplitude
or absent sensory nerve action potentials, an absent H reex and an
abnormal F wave. F wave abnormalities are associated with poor prog-
nosis. Patterns of change can help identify subtypes.
What are the indications, contraindications,
and
complications regarding lumbar puncture?
Indications
Diagnostic–sampling CSF and measuring pressure.
Therapeutic –removal of CSF in certain cases of raised intracranial
pressure (ICP) such as idiopathic intracranial hypertension and communi-
cating hydrocephalus, or facilitating administration of intrathecal drugs.
Contraindications
These are mainly relative contraindications:
Raised ICP leading to risk of brainstem herniation such as in non-
communicating hydrocephalus
Localised infection at the site of LP
Generalised sepsis
Coagulopathy (drug or illness induced)
Anatomical concerns, e.g. spina bida, trauma
Patient refusal
Complications
Headache
Brainstem herniation
Bleeding/epidural haematoma
Infection
Neurological injury (spinal cord or conus medullaris)
What is the pathophysiology of GBS?
Production of auto- antibodies occurs, possibly following a trigger such as infec-
tion with C. jejuni. The reason why certain individuals are aected and others
The next day, Jim is reviewed by the neurology consultant who agrees with
a presumptive diagnosis of GBS.
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The Patient with Respiratory Distress II
53
are not is yet to be fully elucidated. Various patterns of nerve damage can occur
but demyelination is the main pathological process. Peripheral nerves (spinal
and cranial) and autonomic nerves can be aected.
What are the options for management?
Immunomodulation
High- dose intravenous immunoglobulin (IVIg) – 0.4 g/kg/day
for 3–5
days.
Plasmapheresis–ve exchanges usually over 5 days.
Supportive measures
Intubation and ventilation.
Haemodynamic support–cardiovascular instability can result due to
autonomic neuropathy.
Pain control–opiates are useful but sedation is an unwelcome side- eect.
Amitriptyline and gabapentin are often required for neuropathic pain.
Nutrition.
Bowel and bladder care.
Physiotherapy.
Venous thromboprophylaxis.
What is the evidence for plasmapheresis as
compared with IVIg?
A randomised controlled trial published in the New England Journal of Med-
icine in 1992 concluded that IVIg was at least as eective as plasma exchange
for GBS and may be associated with fewer complications. A similar review
in the Lancet in 1997 showed similar ecacy. A Cochrane systematic review
(Hughes 2004) also concluded that IVIg and plasmapheresis are similarly
eective.
Cross-
over therapy appears to confer no benet. IVIg is often the more prac-
tical choice as it is easier to administer and usually more readily available.
Would your treatment plan differ if this were
myasthenia gravis?
As with management of GBS, IVIg and plasmapheresis should be considered
along with meticulous supportive care. There are some dierences in terms of
specic disease management.
Pyridostigmine/rivastigmine–these drugs are acetylcholinesterase inhib-
itors. Therapeutic eects are achieved through delaying the breakdown
of acetylcholine and hence increasing its availability to act at the reduced
number of active receptors. Neostigmine and pyridostigmine act periph-
erally whereas rivastigmine acts centrally.
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Clinical Cases in Critical Care
54
Steroids and azathioprine–steroids are not eective in GBS but are an
important treatment option for modulating T cells in MG. The dose of
prednisolone is gradually increased and then, as it is tapered o, it can
be replaced with azathioprine to achieve longer term control through
inhibition of the cell cycle.
Methotrexate, mycophenolate mofetil, tacrolimus or ciclosporin–can be
considered in non-
responders or those who do not tolerate steroids or
azathioprine.
Thymectomy –a randomised controlled trial published by Wolfe in
the New England Journal of Medicine (2016) found that thymectomy
improved clinical outcomes over a 3-
year period in myasthenia gravis.
Is there an argument to support early tracheostomy
in this case?
A study published in Neurocritical Care by Walgaard (2017) found that patients
who were unable to raise their arms from the bed or who had axonal degener-
ation at 1
week had a high risk of prolonged mechanical ventilation.
The TrachMan study published in JAMA (Young etal. 2013) compared 30-
day mortality in patients receiving a tracheostomy early (day 1–4) or late (day 10
or later) in the course of their ICU admission. Although this large randomised
multicentre trial found no statistical dierence between the groups, it did not
focus specically on cases of neurological weakness.
Jim does not appear to be progressing quickly. He is still extremely weak.
Information gathered at the multidisciplinary team meeting is particularly
useful in the decision-
making process.
What are the indications for tracheostomy?
Some indications will be reversible and others irreversible. In some cases,
reversibility may be unclear at the time of the procedure. Where possible, frank
discussions should be undertaken prior to elective tracheostomy regarding
reversibility and overall prognosis.
Emergency
Upper airway obstruction,e.g. anaphylaxis, tumour, foreign body, etc.
When you return to work after your night shifts, you nd that Jim remains
intubated on day 7 of his admission, having completed 5
days of IVIg.
He is breathing spontaneously on the ventilator with pressure support
of 18
cmH
2
O and PEEP5 cmH
2
O. He has a poor cough and has marked
weakness. The nurse in charge asks you whether you think this patient
will need a tracheostomy.
As a multidisciplinary team, you believe that Jim will benefit from a
tracheostomy at this point due to the likely requirement for prolonged
ventilatory support.
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The Patient with Respiratory Distress II
55
Elective
Where prolonged articial ventilation is required–reduced dead space
allows for reduction in work of breathing. Tracheostomy is better tolerated
than oral endotracheal tube, therefore reducing requirement for sedation.
Airway protection–e.g. in cases of neurodegenerative disease.
Respiratory toilet–where cough or swallow reex is impaired.
Surgical indications–e.g. for certain head and neck procedures.
What are the risks of tracheostomy?
Immediate or procedure related
Haemorrhage
Aspiration
Airway obstruction
Air embolus
Pneumothorax
Haemothorax
Death
Medium term
Infection
Pneumomediastinum
Haemorrhage (particularly from erosion into local vessels)
Tissue necrosis
Tracheo- arterial stula
Dysphagia
Airway obstruction (tube displacement)
Long term
Tracheomalacia
Dysphagia
Stricture/stenosis
Scarring
Fistula
How would you perform a tracheostomy?
There are various techniques for performing tracheostomy based on either
the open surgical technique or percutaneous method. The following princi-
ples can be applied when performing percutaneous tracheostomy within the
critical care setting.
Indications and consent
The critical care team should be satisfied that tracheostomy is indicated.
Patients should be consented directly where possible and if unable to con-
sent, then the relevant proxy consent form (Consent form 4in the UK) should
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Clinical Cases in Critical Care
56
be completed (e.g. signed by two experienced medical professionals) and next
of kin informed as appropriate with potential complications discussed. All
decisions and discussions must be clearly documented.
Preparation
Check coagulation.
Group and save blood sample (two samples required in the UK).
Aspirate NG tube.
Position patient with neck extended.
Ultrasound neck to check there are no blood vessels over the
tracheostomy site.
Full monitoring (including end- tidal CO
2
).
100% oxygen.
Drugs
Sedation.
Muscle relaxation.
Emergency drugs available.
Lignocaine 1% with adrenaline 1in 200 000 for local inltration.
Equipment
Drapes.
Fibreoptic scope.
Appropriately sized tracheostomy tube with surgical set.
Emergency airway trolley for reintubation if needed.
Laryngoscope (direct or video) and usually a breoptic scope will be
required for retraction of endotracheal tube under visualisation.
Personnel
One operator performs tracheostomy.
One airway specialist performs bronchoscopy.
One trained assistant helps with sedation and equipment.
Aseptic technique with surgical scrub and personal protective equipment.
Procedure
Details of technique vary. The following description is consistent with a
Seldinger method.
Using laryngoscopy, the airway clinician deflates the ETT cuff and
withdraws until the cu can be visualised at the cords. The cu may
then be reinated.
Operator then inserts a 14 G cannula into the trachea (usually between
the second and third or third and fourth tracheal rings).
Positioning is veried using bronchoscopy.
A guidewire is inserted into the trachea via the cannula.
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The Patient with Respiratory Distress II
57
A series of dilators are then inserted over the guidewire until the trache-
ostomy tube itself can be inserted.
Positioning can be checked via bronchoscopy.
Once the tracheostomy tube is in place and the cu inated, the tube
can be secured as per local protocol.
Postprocedure management
Chest radiograph to exclude pneumothorax.
Once the patient is no longer paralysed, sedation can be reduced
or stopped.
Full documentation in the notes.
Reuseable equipment should be logged and returned for cleaning.
Review ventilator settings and continue full monitoring.
What are the principles behind a respiratory
weaning plan?
It is desirable to wean patients from ventilatory support as soon as possible
since prolonged intubation is associated with longer length of stay, increased
likelihood of ventilator-
associated pneumonia and possibly increased mortality.
Usually, a patient will have failed a spontaneous breathing trial before a wean-
ing plan is created.
There are many ways to approach weaning, with some ICUs preferring to
use a protocol. Some studies have shown that protocols can reduce time on
mechanical ventilation.
Weaning protocols will usually require the patient to be stable from a
cardiorespiratory point of view.
A PEEP of less than 10cmH
2
O is desirable.
NAVA (neurally adjusted ventilatory assist) has been used to great eect
in patients with neuromuscular disorders.
Protocols indicate how and when to decrease pressure support
and PEEP to achieve desired tidal volumes, saturations and end-
tidal CO
2
.
Cuff deflation and use of a one- way speaking valve need to be
considered.
Weaning should challenge the patient without compromising cardiore-
spiratory stability.
The aim is to reduce support as rapidly as is tolerated by the patient to
expedite decannulation.
A multidisciplinary approach involving physiotherapy, psychology and
nursing is vital.
Your consultant agrees that Jim is making slow progress and will probably
benet from tracheostomy at this stage. You perform this successfully
and once the effects of the paralysing agent have worn off, you stop
his sedation.
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Clinical Cases in Critical Care
58
Who should be involved in Jim’s ongoing care?
Critical care physicians and nurses
Neurologist
Physiotherapist
Dietician
Occupational therapist
Pharmacist
Psychologist
Pain specialist, if necessary
And of course, Jim and his family!
What is the likely outcome for Jim?
Approximately 85% of patients are expected to fully recover from GBS with a
usual recovery period of 6–18 months. The remaining 15% have lasting disability
ranging from mild paraesthesia or areexia to severe permanent neurological
damage such as ataxia, muscle wasting, foot drop, etc. Mortality is less than
5% in developed countries. Ongoing pain can be signicant for some survivors.
There is a recurrence rate of 7%.
Scoring systems have been devised to predict which patients will suer
worse outcomes.
mEGOS (modied Erasmus Guillain–Barré Outcome Score) –patients
are scored at admission or day 7 to predict a likelihood of being unable
to walk independently at 6
months. This is a composite score based on
age, presence of prodromal diarrhoea and Medical Research Council
(MRC) muscle weakness score.
EGRIS (Erasmus Guillain–Barré Respiratory Insuciency Score) –this
score predicts the probability of respiratory insuciency within the rst
week of admission. The score is calculated according to days between
onset and hospital admission, presence of facial or bulbar weakness, and
the MRC muscle weakness score.
What post-critical care issues do patients suffer?
Specic problems related to GBS include weakness and pain. Additionally,
post- intensive care syndrome (PICS) is well recognised and occurs in 25–75%
of ICU survivors. The risk of developing PICS is highest in those who suered
delirium, multiorgan failure, hypoxia, severe sepsis and glucose dysregulation,
or who required renal replacement therapy.
PICS comprises psychiatric and physical symptoms. Post- traumatic stress
disorder, depression and anxiety are often described. Residual neuromuscular
Three weeks later, you are able to successfully decannulate Jim and he is
discharged to a medical ward 2days after that.
You invite Jim back to the ICU follow- up clinic in 6months' time.
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