Добавил:

Sekretar kiopkiopkiop18@yandex.ru t.me/Prokururor I Вовсе не секретарь, но почту проверяю Опубликованный материал нарушает ваши авторские права? Сообщите нам.

Вуз:

Ростовский Государственный Медицинский Университет

Предмет:

Медицина общая

Файл:

Книга_3080_Библиотеки_им_академика_М_И_Перельмана

.pdf

Скачиваний:

Добавлен:

12.10.2026

Размер:

6 Мб

Скачать

☆

<<< < Предыдущая 1 2 3 4 56 / 406 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 > Следующая >>>

The Patient with Respiratory Distress I

Pulmonary embolus (PE)

Acute hypoxia of unknown cause should always alert the clinician to the pos-

sibility of PE. A massive PE is often accompanied by chest pain and may cause

cardiovascular collapse when severe. Multiple small PEs may occur over time

in some prothrombotic patients, leading to chronic shortness of breath. The

classic ECG changes of SI, QIII, TIII (deep S wave in lead I, Q wave in lead

III, inverted T wave in lead III) are much less common than sinus tachycardia

or signs of right heart dysfunction, e.g. RBBB, right axis deviation, right atrial

enlargement (see Case 9). Examine for signs of deep vein thrombosis (DVT).

Myocardial infarction (MI) or acute cardiac event

Myocardial infarction is usually heralded by chest pain but silent MI is pos-

sible, particularly in patients with neuropathy or poorly controlled diabetes.

Cardiac chest pain may also be misinterpreted as reux and dismissed by the

patient as insignicant.

An event such as rupture of chordae tendineae would probably lead to

catastrophic regurgitation and cardiogenic shock so is unlikely with a BP of

156/98

mmHg.

Renal impairment or metabolic disturbance

Metabolic acidosis due to renal impairment may lead to Kussmaul breathing

(‘air hunger’). Renal impairment may be present but does not alone

explain the clinical picture of hypoxia unless it has also led to signicant

pulmonary oedema.

Underlying malignancy

Lung is the third most common type of cancer in the UK. Approximately 70%

are caused by smoking. A tumour in the lung may predispose the patient to

developing infection, obstruction, lobar collapse, eusions, etc. A tumour may

easily be masked by consolidation on radiographic imaging. Lung malignancy

can be primary or secondary.



Primary



Small cell (15–20%).



Non- small cell (80–85%)–these include adenocarcinoma, squamous

cell carcinoma, large cell and undifferentiated carcinoma.



Other (e.g. Pancoast).



Secondary



Most cancers can metastasise to the lung but the solid tumours which

commonly do this include renal, breast, colon and prostate.

While Georey is in extremis, the priority is not to search for malignancy. If

a cancer does exist, typing, grading and staging could become key in terms of

assessing prognosis and treatment options later on. History should incorpo-

rate exploration of non- specic symptoms suggestive of malignancy, including

anorexia and weight loss.

https://t.me/medicina_free

Clinical Cases in Critical Care

What is your analysis of the situation?

Georey is extremely unwell and will not physically tolerate this degree of com-

promise for much longer. There is evidence of lower respiratory tract infection.

This has the combined eect of impairing oxygen delivery (through reducing

the available alveolar surface area) and increasing oxygen demand (through

raised metabolic rate secondary to sepsis and increased work of breathing).

The compensatory tachycardia and tachypnoea raise oxygen demand through

increased muscle activity. Georey’s work of breathing is a visual reminder

that oxygen demand is exceeding supply. Without intervention, Georey will

probably suer cardiopulmonary arrest.

From the available information, Georey is independent and so it is fair to

assume he should be a good candidate for invasive organ support in critical

care. He has some co-

morbidities which may aect his prognosis and further

information is needed once the situation is stabilised.

What is the alveolar gas equation and what is its

relevance?

OP P PCO RQ

aiatmHOa22 2

F /

is alveolar oxygen, P

atm

is atmospheric pressure at sea level,

is partial

pressure of water, F

is the fraction of inspired oxygen, P

is partial

pressure of carbon dioxide in the alveoli, and RQ is the respiratory quotient.

The alveolar gas equation can be used to understand how oxygenation is

aected by atmospheric pressure, diet and, importantly in this case, hyper-

capnia. From the equation, it can be seen how, without other changes, hypoven-

tilation can lead to decreasing alveolar oxygenation. It can also be seen that

increasing the inspired fraction of oxygen should improve alveolar oxygenation.

What are the types of hypoxia and how can oxygen

delivery be increased?

There are four types of hypoxia:



Hypoxic



Anaemic



Stagnant or ischaemic,i.e. inadequate blood ow to tissues.



Histotoxic or cytotoxic,i.e. inability to utilise oxygen at cellular level

despite good availability.

For the bedside physician, the easiest of these to address is hypoxic hypoxia.

Provide high- ow oxygen, preferably accompanied by positive end- expiratory

You are told that Georey has a history of hypertension and COPD but is

independent and acts as the main carer for his wife who has early dementia and

severe arthritis. The chest radiograph shows hyperination and

widespread con-

solidation. His temperature is 39.1 °C. His rapid test for COVID-

19 is negative.

https://t.me/medicina_free

The Patient with Respiratory Distress I

pressure to prevent derecruitment of alveoli and therefore maintain the larg-

est possible surface area for diusion of oxygen across the alveolar–capillary

membrane. Anaemic hypoxia may be addressed through transfusion or, in

non-

emergent situations, drug therapy to stimulate increased production of

haemoglobin. However, the oxygen-

carrying capacity of transfused blood is

less than that of the patient’s own blood and transfusion of blood products is

not to be undertaken lightly due to the potential for complications (see Case 7).

Regional hypoxia due to impaired circulation may need to be dealt with directly

(e.g. intravascular stenting, thrombectomy, reperfusion techniques). Histotoxic

hypoxia may or may not be treatable with specic antitoxins.

Global oxygen delivery can be improved through optimising cardiac output,

haemoglobin, oxygen saturations and arterial oxygenation as reected in the

oxygen delivery equation (see Case 8).

How do you proceed?

Prepare Georey for intubation, call for skilled assistance and ask an appropriate

person to call the patient’s next of kin. There is minimal time to optimise Geof-

frey’s condition. He is at high risk of aspiration and is haemodynamicaly unstable.

Intubate using a modied rapid sequence induction (see Introduction Section 2).

What is compliance and why may Geoffrey’s lungs

feel stiff, i.e. poorly compliant?

Compliance measures how volume changes with a change in pressure. Total

lung compliance incorporates the compliance of both the lungs and the

chest wall.

Geoffrey has COPD which normally increases compliance. Emphysema-

tous disease damages alveoli, resulting in a loss of elastic recoil. Decreased

compliance indicates a problem in addition to his underlying COPD.

Anything which decreases the ability of the system to stretch in response

to an increase in pressure will result in reduced compliance. Causes include

pre- existing conditions such as pulmonary fibrosis or musculoskeletal

abnormalities, acute problems such as acute respiratory distress syndrome

(ARDS), bronchoconstriction, pulmonary oedema, or the rigid chest which can

When you rst arrived in the ED, you exchanged the Hudson mask for a

non-

rebreathe mask, applied 15 L/min of oxygen and gave 250 mL intrave-

nous uid. Now, 10 minutes later, Georey is becoming drowsy. His work

of breathing has not improved.

You successfully intubate Georey with a size 8.5 mm endotracheal tube.

His chest feels sti to bag, suggesting poor compliance. He now requires

frequent boluses of vasopressor to maintain a MAP of 70

mmHg.

https://t.me/medicina_free

Clinical Cases in Critical Care

develop in some patients following high- dose opioids. It can also be seen from

Figure24.2 that compliance is reduced at the extremes of ination.

What action do you take?



Airway–ensure the endotracheal tube (ETT) is patent and well secured.

Check chest expansion, auscultate and review a chest radiograph to

assess whether the ETT is in optimal position.



Breathing–set the ventilator to deliver lung protective breaths (tidal

volumes approximately 6

mL/kg) at a rate sucient to maintain PaCO

less than 8.0

kPa. Review the chest radiograph to look for CVC position,

pneumothorax, consolidation, collapse and any other pathology.



Circulation–insert and transduce intra- arterial and central venous

catheters. Administer uid challenges of 250

mL using a 50 mL syringe,

looking for uid responsiveness. Once Georey is no longer uid respon-

sive, start an infusion of noradrenaline aiming to maintain a MAP

sucient to perfuse his organs (consider 70–75 mmHg given his history

of hypertension).



Take bloods for culture, FBC, U&Es, LFTs, CRP, coagulation, group and

screen, and arterial blood gas analysis.



Administer local protocol antibiotics for severe community- acquired

pneumonia and oseltamivir in case of viral inuenza.



Insert a urinary catheter and send samples for M,C&S, urinary antigens

for Legionella and pneumococcus.



Request a viral inuenza swab.



Insert an NG tube.



12- lead ECG.



Request ED sta to:



call critical care to update them regarding admission



obtain Geoffrey’s medical records and history from the general

practitioner



contact Geoffrey’s next of kin.

Does this new information affect your assessment

or management of Geoffrey?

Georey’s premorbid state is extremely poor. Knowing that he could have been

a candidate for home oxygen therapy highlights how poor his gas exchange is

when he is at his best.

You transfer Georey to the critical care unit. On day 2 of admission, you

discover that Georey is known to have COPD, ischaemic heart disease

and peripheral vascular disease. His functional capacity is poor, and he has

deteriorated signicantly since a prolonged admission to hospital last year

for COPD. He has been increasingly short of breath at rest since then and

converted to downstairs living 6 months ago. He has not left the house for

some time and has been assessed for a package of care. He was deemed

unsuitable for home oxygen as he is still smoking.

https://t.me/medicina_free

The Patient with Respiratory Distress I

Although he is only 66 years old, he has signicant cardiorespiratory disease

which reduces his chances of surviving critical illness. His Acute Physiology

and Chronic Health Evaluation score (APACHE II) is 30 points, giving him an

estimated mortality of 73%. His Rockwood frailty score is 7, meaning severely

frail. His Simplied Acute Physiology Score (SAPS) II is 58 points, giving him

an in- hospital mortality of 64%.

Georey is likely to have a poor outcome from this admission and this must

be discussed with his next of kin since it cannot be discussed with him.

Do you want any further investigations or any other

specialist review?



Echocardiography–TTE to assess for right heart failure secondary to

chronic respiratory disease and left heart function in light of ischaemic

heart disease.



CT PA–PE remains a potential diagnosis. PE may co- exist with other

pathologies. If Georey has not recently had a CT of his chest, this may

also help to assess his underlying lung condition although widespread

infection can limit the ability to assess lung parenchyma.



Respiratory physician review –advise whether there is potential for

optimising Geoffrey’s COPD and perhaps to clarify his baseline

respiratory function.



Cardiology review–to aid in assessing the extent of Georey’s ischaemic

heart disease and whether there is scope for optimisation.

How do you interpret these lung function tests?

FVC is forced vital capacity, the volume which can be exhaled after maximal

inspiration. FEV

is the forced expiratory volume in the rst second of expi-

ration. This measurement, recorded after administration of bronchodilators,

is used to grade the severity of airway obstruction. An FEV

<30% means

Georey’s COPD is stage 4, i.e. very severe, according to the 2018NICE

guideline CG115 (>80%=stage 1, 50–79%=stage 2, 30–49%=stage 3,

<30%=stage 4).

The FEV

/FVC ratio, or Tieneau–Pinelli index, can be used to dierentiate

obstructive disease (decreased ratio <0.7) from restrictive lung disease (ratio

is normal or increased).

Figure2.1 demonstrates lung volumes and Figure2.2 illustrates the changes

in spirometry and peak ow with obstructive and restrictive lung disease.

CTPA shows widespread dense consolidation throughout both lung elds

with several bullae and evidence of emphysema. Malignancy cannot be ruled

out. There is no evidence of PE. TTE shows globally reduced function, right

ventricle dilation and a severely impaired LV (ejection fraction 20%). The

respiratory consultant tells you Georey's spirometry results from last year:

FEV

= 25% predicted, FVC=85% predicted.

https://t.me/medicina_free

Clinical Cases in Critical Care

What is the pathophysiology of right ventricular

dysfunction in COPD?

Hypoxaemia leads to increased pulmonary vascular resistance through hyp-

oxic pulmonary vasoconstriction. In chronic hypoxia, this leads to remodel-

ling of the pulmonary vascular bed, causing persistently raised right ventricle

Vital

Capacity

To tal

Lung

Capacity

Inspiratory

Reserve

Volume

Tidal

Volume

Expiratory

Reserve

Volume

Residual

Volume

Functional

Residual

Capacity

(FRC)

Residual

Volume

Volume (ml/kg)

Figure 2.1: Lung volumes.

Source: Theophilus Samuels.

Flow (L/s)

Volume

Obstructive

Exhalation

Inhalation

(a) (b)

123 4

Time (sec)

Volume (L)

TLC

FEF

25-75

FEV

FVC

Figure 2.2: (a) Flow- volume loop demonstrating normal, obstructive and restrictive

patterns. (b)

A spirogram is obtained through maximal inspiration followed by rapid and

forceful exhalation as maximally as possible. The FEV

is the volume of air exhaled in the

rst second (normally 70–85% depending on age). FVC is the forced vital capacity (total

volume of air exhaled during a maximal forced exhalation from TLC to residual volume

[RV]). The ratio of FEV

/FVC is usually greater than 70% in healthy adults and less than

70% in obstructive pulmonary disease. FEF

25–75

is the forced expiratory ow between

25% and 75% of vital capacity.

Source: Theophilus Samuels.

https://t.me/medicina_free

The Patient with Respiratory Distress I

end- diastolic pressure which in turn raises right atrial pressure. Over a period

of time, the right ventricle begins to decompensate, leading to right ventric-

ular failure.

Why extubate straight to NIV?

Given Georey’s underlying severe COPD, his best chance of successful extu-

bation may be with immediate non-

invasive support.

There is some evidence supporting the value of immediate initiation of NIV

following extubation. Ornico etal. in Crit Care 2013 showed that this approach

prevents reintubation and decreases hospital mortality. Ferrer etal. in the

Lancet 2009 found 90- day mortality was reduced.

What is the signicance of failed extubation?

Reintubation rates vary but can be as high as 25%. Reintubation is associ-

ated with increases in mortality, length of stay and risk of hospital- acquired

pneumonia.

What is an SBT?

An SBT (spontaneous breathing trial) is a technique designed to assess a

patient’s suitability for extubation. When a ventilated patient is haemodynami-

cally stable, and their pathology appears to be resolving, an SBT can be under-

taken. There are methods of doing this either connected to the ventilator with

minimal support or while simply on an Ayre’s T- piece.

After 30–120minutes of breathing, the patient’s rapid shallow breathing

index (RSBI) can be assessed:

RSBI Respiratory rate tidal volume /

An RSBI >105 breaths/min/L has been shown to be predictive of failed

extubation.

On day 8 of admission, Geoffrey's infection has resolved. He remains

intubated but is awake and appropriate with minimal sedation. He is

breathing spontaneously and the pressure support has been weaned to

8 cmH

O with 5 cmH

O PEEP. He has a strong cough and his gas exchange

is acceptable. You decide to extubate him directly onto non-

invasive ven-

tilation (NIV).

After 7 hours on NIV, Georey's work of breathing increases and he looks

exhausted. You reintubate him.

Three days later, Geoffrey has made good progress and passes an SBT.

You decide to extubate. However, he fails extubation again in a similar

manner and is reintubated. You discuss the case in your critical care

MDT meeting.

https://t.me/medicina_free

Clinical Cases in Critical Care

What are the main issues you would like to raise in

the MDT discussion?

Georey has underlying respiratory and cardiac disease. Both conditions are

severe and irreversible. He has been treated for the reversible pathology which

led to his admission, i.e. the lower respiratory tract infection. However, despite

this, Georey has failed extubation twice. He is dependent upon the ventilator.

The critical care team now consider whether Georey should receive a tra-

cheostomy or not. While he is incapacitated, the benets and drawbacks of this

should be discussed with his next of kin to nd out what Georey would want.

It should be explained that there is a possibility, if a tracheostomy is inserted,

that he may take an extremely long time to wean from the ventilator and there

is a chance he may never be strong enough to breathe independently.

If it is decided not to site a tracheostomy, escalation planning and resusci-

tation orders need to be discussed.

Establish that safeguarding procedures have been initiated for Georey’s

wife as she may need additional help at home. This will probably already have

been raised in the ED or on admission to ICU.

How will you document your discussions

and communicate your decisions?

Document in the medical notes and in escalation planning notes that Georey

is for ‘one- way’ extubation. He should not be reintubated and his care will not

be escalated should he deteriorate. He is not to be resuscitated in the case of

cardiac arrest. Complete a ReSPECT form (Recommended Summary Plan for

Emergency Care and Treatment) to this eect. Document all conversations in

the medical notes, identifying all persons present.

With his consent, explain the situation to Georey’s wife. These conversa-

tions can be challenging, and it is important to tailor communication for the

individual with whom you are speaking. Try to establish her baseline under-

standing and be aware that she may struggle to understand or retain com-

plex concepts or large amounts of information because of both her dementia

and the extreme emotion of the situation. One approach may be to explain

that, if simple supportive measures fail to save Georey, it is a sign that his

body is too frail to survive without a ventilator. It is important to recognise

when people enter the nal phase of life so that medical sta can refrain from

aggressive treatments designed to try and reverse what is now irreversible. Instead,

Georey's wife, his next of kin, is brought to the hospital by Georey's best

friend of 40 years. Although she has early- onset dementia, she can have a

coherent conversation with you. She asks that his best friend be present as

well. His wife tells you that Georey does not like doctors or hospitals. She

is sure that he would not want a tracheostomy. His best friend agrees.

On sedation hold the next day, Georey is lucid and well enough to com-

municate. You discuss the issue of tracheostomy with him. He is clear that

he does not want tracheostomy or reintubation again, even if it means he

might die. He also does not wish to be resuscitated.

https://t.me/medicina_free

The Patient with Respiratory Distress I

understanding that this is the dying process allows the focus of care to be on

comfort, prioritising dignity and time with family. Discuss Georey’s case with

the palliative care team and oer to call the hospital chaplain.

Communicate this to the rest of the critical care team and mention the new

DNACPR in the routine daily ICU team safety brief.