Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3080_Библиотеки_им_академика_М_И_Перельмана
.pdf
Intubation of the Critically Unwell Patient
19
may be given by infusion. Metaraminol may cause profound reex
bradycardia in patients with normal sympathetic tone.
Ephedrine–a synthetic, direct- and indirect- acting, non-
catecholamine sympathomimetic that has activity for both
alpha and beta receptors. It is rarely used as an infusion and
is effective at increasing blood pressure following a bolus
dose. Tachyphylaxis occurs following repeated doses, which
limits its use.
Adrenaline–dilute adrenaline can be useful when anaesthetis-
ing very unstable patients. In experienced hands, boluses of, for
example, 10–20mcg can help stabilise blood pressure while the
patient is in extremis.
Equipment–ensure the right equipment is available before commenc-
ing induction.
Preoxygenation adjuncts
High- ow nasal cannulae if needed.
Facemask.
Oropharyngeal airway (Guedel)–to open the airway, assist
ventilation and reduce likelihood of introducing gas into
the stomach.
Laryngoscopy–to allow visualisation of the vocal cords (can be
direct or indirect). There are many different types available; these
are a few examples:
Direct laryngoscopes–these come in dierent sizes. Macintosh
is commonly used in adults (a curved blade is attached at 90° to
a handle with a light source). The McCoy blade has a moveable
distal tip segment. Magill and Miller have straight blades.
Video laryngoscopes–for example, the McGrath™ video laryn-
goscope facilitates indirect visualisation of the cords and is often
used where the patient has reduced neck movement.
Optical laryngoscopes–for example, the AirTraq Optical
Laryngoscope™ uses a set of magnifying mirrors to visualise
the cords.
Fibreoptic scope–the endotracheal tube is mounted onto the ex-
ible breoptic scope. The scope is inserted via mouth or nose and,
when the cords are identied, the endotracheal tube (ETT) can be
advanced into position over the scope. This is useful when ana-
tomical issues cause reduced mouth opening and restricted neck
movement. If there is airway swelling, there is a risk of causing
obstruction with the scope itself.
Endotracheal tube (ETT)–there are many different types and sizes
available. Specialised elements include the following:
Cued or uncued–a polyvinylchloride or polyurethane cu,
cylindrical, round or conical in shape, can be inated with air
to create a seal between the tube and the trachea. This reduces
the risk of large aspiration and improves the ability to administer
positive pressure ventilation.
https://t.me/medicina_free
Clinical Cases in Critical Care
20
Subglottic secretion drainage ports– usually used where
mechanical ventilation is expected to be ongoing for several days.
It allows suction of secretions which gather above the cu, so
reducing the risk of microaspiration and VAP.
Adjuncts and manoeuvres
Bougie–this instrument can be used where the cords are visu-
alised but the ETT cannot be manipulated to pass through. The
bougie is inserted and the ETT passed over it. It is also often used
when an ETT needs to be replaced in critical care because, for
example, the cu has lost integrity.
Stylet–this is a malleable metal rod which is inserted into the
ETT to allow it to be bent into the optimal shape for intubating
the cords.
BURP (backward, upward, rightward, posterior) pressure–dis-
placement of the larynx through pressure on the cricoid cartilage
can improve visualisation of the cords.
Cricoid pressure (Sellick manoeuvre)–this aims to prevent regur-
gitation of stomach contents by occluding the oesophagus through
pressure on the trachea. It is no longer universally practised as
several studies have demonstrated that it is ineective and can
make laryngoscopy more dicult.
Nasogastric tube (NG)–this may be useful to decompress the
stomach after intubation to improve ventilation and reduce risk of
aspiration. If an NG tube is present prior to intubation, suctioning
gastric contents can help prevent aspiration pneumonitis.
Suction–always have suction available as there may be secretions,
blood or gastric contents in the airway.
Supraglottic airway device (SAD)–these devices sit above the glot-
tis and aim to allow ventilation without fully securing the airway.
They may be useful in the case of failed intubation. There are many
dierent types of SAD, e.g. laryngeal mask airway (LMA Classic®
or Supreme®) or iGel®.
Failed intubation
The Difficult Airway Society (DAS) has produced useful guidelines for
managing the challenging situation of failed intubation. If the rst attempt at
laryngoscopy fails, optimise positioning and muscle relaxation before a second
attempt. Consider using airway adjuncts or selecting an alternative laryngo-
scope. Apply oxygen via facemask or SAD if necessary. If it is impossible to
intubate or ventilate, then declare a Can’t Intubate Can’t Ventilate emergency
and prepare for a cricothyroidotomy.
Front of neck access– this is rarely required but the technique should be
known to all airway trained clinicians. Emergency cricothyroidotomy
is performed using a scalpel to make a stab through the cricothyroid
membrane, a bougie is passed into the trachea, and a size 6.0 mm ETT
is inserted over the bougie.
https://t.me/medicina_free
Intubation of the Critically Unwell Patient
21
Following intubation
Sedation– usually a combination of a hypnotic agent with an anal-
gosedative agent. Later, when weaning, this may be reduced to purely
an analgosedative agent.
Hypnotic– propofol infusion is commonly used in adult ICU (monitor
creatine phosphokinase and lactate if propofol infusion syndrome is
a concern). Midazolam infusions are often used with morphine in
paediatric ICU.
Opioids– for example, fentanyl, alfentanil or remifentanil, are often
used in adult ICU. Remifentanil is a popular choice as it is rapidly
metabolised by plasma and tissue esterases, giving it a short context-
sensitive half- life (3 minutes after a 3- hour infusion). Morphine is
more commonly used in children.
Alpha- 2 adrenergic agonist–such as dexmedetomidine or clonidine.
These agents are sedative and analgesic. Both may induce bradycardia
and hypotension.
Consider paralysis– non- depolarising agents can be used in infusion.
Common choices are rocuronium or cisatracurium.
Invasive monitoring– critical care patients are likely to require invasive
arterial and central venous catheterisation (CVC) for pressure monitoring
and blood sampling. CVCs are used for drug administration, particularly
medications such as vasopressors, chemotherapy agents and parenteral
nutrition. Consider whether vascular access for renal replacement will
also be required at this point.
Tubes
Nasogastric tube.
Urinary catheter.
Drains–some patients benefit from expedited drainage of pleural
effusions or ascites if ventilation is impaired.
Imaging–chest radiography is used to assess the position of the ETT,
the CVC via internal jugular or subclavian routes, and NG tube, as well
as bone and lung elds. It may be necessary to transfer for urgent CT,
MRI, angiography, etc. immediately post intubation.
Setting the ventilator
An experienced clinician will program the ventilator specically for an
individual patient using their understanding of lung mechanics, ow curves
and blood gases as well as knowledge of the underlying illness. Most patients
will benet from a lung- protective strategy to minimise volutrauma, baro-
trauma, atelectrauma and biotrauma. Patients with brain injury may require
a neuroprotective strategy.
Ventilation is discussed in more detail in the cases. A reasonable default
strategy is to aim for the following:
Lung protection
Volumes– aim for approximately 6 mL/kg ideal body weight.
https://t.me/medicina_free
Clinical Cases in Critical Care
22
Pressures– plateau pressure should be <30 cmH
2
O. Use PEEP to
maintain open alveoli and assist oxygenation.
Gas exchange–tolerate hypercapnia if pH >7.25. To maintain low
tidal volumes, respiratory rate may need to be increased.
Driving pressure– aim to maintain lower driving pressures, ideally
less than 14
cmH
2
O.
Further reading
Higgs, A., McGrath, B., Goddard, C. etal. (2019). Guidelines for the management
of tracheal intubation in critically ill adults. Br. J. Anaesth. 120: 323–352. A com-
prehensive guideline that includes useful information and intubation strategies.
Cook, T., Woodall, N., Harper, J. etal. (2011). Major complications of airway
management in the UK: results of the fourth national audit project of the Royal
College of Anaesthetists and the Dicult Airway Society. Part 2: intensive care and
emergency departments. Br. J. Anaesth. 106: 632–642. The NAP4 report gives key
insights into the diculties faced when intubating critically ill patients.
De Jong, A., Molinari, N., Terzi, N. etal. (2013). Early identication of patients at
risk for dicult intubation in the intensive care unit. Am. J. Respir. Crit. Care Med
187: 832–839. Original paper that developed and validated the MACOCHA score.
https://t.me/medicina_free
The Cases
II
Part
https://t.me/medicina_free
https://t.me/medicina_free
Clinical Cases in Critical Care, First Edition. Alice Myers and Theophilus Samuels.
© 2023 John Wiley & Sons Ltd. Published 2023 by John Wiley & Sons Ltd.
1
The Patient with
Rising Vasopressor
Requirements
D
uring your night shift, you are asked to urgently review a 65- year- old
patient named David. He is day 5 post-elective right-
sided hemicolec-
tomy with primary anastomosis for a non-
metastatic colorectal carcinoma.
No surgical drains in situ. Earlier that day, he was started on noradrenaline
(0.04
mcg/kg/min) to maintain his mean arterial blood pressure (MAP) above
65 mmHg. He is now hypotensive (80/40 mmHg) and tachycardic (120 bpm)
with a noradrenaline dose of 0.35mcg/kg/min. He is oliguric. His respiratory
rate is 32 breaths per minute with SpO
2
94% on 2 L/min nasal oxygen. There
are bibasal crepitations on auscultation. David is restless, sweating profusely,
talking in a confused manner, and grimacing in pain when his abdomen
is palpated.
What is your initial management?
Airway–his speech, though confused, suggests that he is maintaining
his airway and therefore does not require immediate airway manoeu-
vres (e.g. chin lift, jaw thrust) or adjuncts (e.g. oropharyngeal airway).
Breathing–this appears laboured. He needs high- ow supplementary
oxygen, an urgent portable chest radiograph and an arterial blood sample
for analysis.
Circulation–ensure that he has at least one large- bore peripheral IV
cannula (e.g. 18 G or 16 G) in addition to his central venous access. Take
blood samples for microscopy, culture and sensitivity testing, routine
blood tests including amylase, a repeat group and save, and a coagulation
screen. At this point, a 250–500 mL bolus of crystalloid solution should
be given over a brief period (e.g. 15–20 min). Ideally, the clinician would
deliver this uid bolus personally, using a 50 mL syringe attached to the
IV access. This simple technique allows the clinician to directly observe
the physiological response, while also making it possible to stop giving
uid immediately if the eect is deleterious.
https://t.me/medicina_free
Clinical Cases in Critical Care
26
Disability–his confusion is not posing an immediate danger to himself
or the nursing sta. Check his blood glucose level. Treat hypoglycaemia
if present. Assess pupillary reactions to light.
Exposure –assess him for signs of deep vein thrombosis, rash, and
bleeding per rectum.
Following exposure, reassess whether your interventions (i.e. oxygen therapy,
intravenous uid boluses) are having any impact on his physiology. Request
the senior surgical on- call doctor to review him urgently.
With these results and examination ndings, what is
the most likely diagnosis?
These blood test results suggest an acute inammatory response that is prob-
ably due to sepsis. The raised lactate is most likely due to the overall haemo-
dynamic instability leading to reduced delivery of oxygen.
Given that the patient is day 5 post elective right- sided hemicolectomy with
signs of peritonism, it is very probable that he is suering from an anastomotic
leak with resultant intra-
abdominal infection and septic shock.
Which factors may affect the risk
of anastomotic leakage?
Non- modiable risk factors that are associated with an increased risk include:
Male sex
Age over 60 years
Previous history of radiotherapy
ASA grades II–IV
Underlying pulmonary disease
Pre- existing vascular disease
Renal disease
Renal replacement therapy
Immunosuppressive therapy
Modiable risk factors include:
Active smoking
Obesity
Heavy alcohol intake (>21 units per week)
Immunosuppressants and chemotherapy
Following your initial management, BP increases transiently to 96/60 mmHg,
SpO
2
is maintained at >98% and blood results are as follows: Hb 105 g/L,
WBC 22
× 10
9
/L, plat 560 × 10
9
/L, CRP >350, INR 2.1, pH 7.23, PaO
2
55.6 kPa
(15
L/min), PaCO
2
4.1 kPa, lactate 6.4 mmol/L, amylase 183 U/L. The chest
radiograph demonstrates a mild degree of bibasal atelectasis.
https://t.me/medicina_free
The Patient with Rising Vasopressor Requirements
27
Recent weight loss >10%
Hypoalbuminaemia
Anastomotic leakage is associated with severe morbidity, increased length
of hospital stay and mortality.
Describe how focused ultrasonography can
be useful in assessing uid responsiveness
Images must always be integrated with the rest of the clinical assessment and
should not be used in isolation. Bear in mind that David is not intubated and
is breathing spontaneously.
Focused ultrasonography can be used to assess the following:
Inferior vena cava (IVC) index
In spontaneously breathing patients, the IVC collapsibility index (i.e. the
dierence between the maximum diameter in expiration and minimum diam-
eter in inspiration expressed as a percentage) is not a reliable method for deter-
mining uid responsiveness. Clinically, being able to recognise extremes of IVC
diameters is more benecial. Therefore, in patients that are haemodynami-
cally unstable:
near- total collapsibility or small IVC size (<1 cm) may suggest the patient
is uid responsive
a large, distended and non- collapsible IVC probably suggests that the
patient is not uid responsive (Figure1.1a).
It is worth considering that in patients receiving positive pressure venti-
lation, standardised loading conditions to the heart must be met before any
changes in IVC diameter can be interpreted. Patients should be passively ven-
tilated (e.g. no spontaneous eorts, completely dependent on the ventilator)
and receiving a tidal volume of 8–10
mL/kg. An IVC distensibility index (i.e.
the dierence between the maximum diameter in inspiration and minimum
diameter in expiration expressed as a percentage) of greater than 12–18% may
suggest that the patient is uid responsive (Figure1.1b).
However, irrespective of whether the patient is breathing spontaneously or
mechanically ventilated, emphasis should not be placed on determining an
IVC index (either collapsibility or distensibility). Rather, recognising extreme
IVC diameters and integrating this into the clinical picture is a more robust
approach to determining uid responsiveness.
Left ventricle appearance
In the parasternal short- axis view, you can assess for the presence of end-
systolic obliteration (i.e. ‘kissing’ ventricle). The left ventricle appears small
and the papillary muscles appear to meet at the centre at end- systole. This
would suggest that the LV is underlled and hyperdynamic, indicating that
the patient may be uid responsive.
https://t.me/medicina_free
Clinical Cases in Critical Care
28
Presence of A- lines and/or B- lines
A- lines are reverberation artefacts originating from the pleural line, and with
adequate depth can be seen as parallel lines at regular (equidistant) intervals
(Figure1.2a). B-
lines (or ‘comet tails’) are horizontal hyperechoic beams ema-
nating from the inferior margin of the pleural line, which then extend through
to the deep edge of the screen (Figure1.2b). They fan out and move with the
motion of the pleural line, removing the ability to visualise A-
lines. Due to the
lung bases possessing a greater mass of lung tissue, they will often display a
B- line pattern, making examination of an upper lung eld more informative
for the presence of pulmonary oedema. Therefore, if lung ultrasonography
demonstrates absent A- lines but abundant B- lines throughout the chest, this
may suggest that pulmonary oedema has developed, and further uid boluses
may cause more harm than benet.
Why might focused ultrasonography be dicult
in this case?
It may be exceedingly dicult or near impossible to image the IVC due to
the patient’s intra- abdominal pathology and postsurgical abdomen, as it
requires an adequate subcostal view to obtain the necessary measurements.
IVC
MAX
IVC
MIN
EXPIRATION
IVC
MAX
IVC
MIN
Spontaenous
breathing
Positive
Pressure
Ventilation
IVC collapsibility index
(IVC
MAX
- IVC
MIN
) / IVC
MAX
EXPIRATION
INSPIRATION
IVC distensibility index
(IVC
MAX
- IVC
MIN
) / IVC
MAX
Small collapsible
IVC
‘
Likely’ fluid responsive
Lar
ge non-collapsible
IVC
‘
Likely not’ fluid responsive
(a)
(b)
Figure
1.1: Schematic diagram representing the changes in IVC diameter. (a) In
spontaneous breathing patients, the IVC collapsibility index can give an indication
of the uid responsiveness of a patient. Interpreting and recognising the extremes
of IVC diameter in their clinical context is much more useful in patients who are
haemodynamically unstable (see text for details). (b) In patients receiving positive
pressure ventilation, the IVC diameter increases during inspiration, giving rise to
an IVC distensibility index (see text for details). IVC
MAX
, maximum diameter of IVC;
IVC
MIN
, minimum diameter of IVC.
Source: Theophilus Samuels.
https://t.me/medicina_free
Соседние файлы в папке Библиотека им академика М.И. Перельмана