Aspiration.ppt

Aspiration in perioperative period

1. University of Gondar
College of medicine and health science
department of anesthesia
Aspiration
Misganaw M
1

2. INTRODUCTION
First recognized as a cause of an anesthetic-related death
in1848
In 1946, Mendelson described the relationship between
aspiration of solid and liquid matter
Rare but potentially devastating complication of general
anaesthesia
2

3. DEFINITION
defined by the inhalation of oro-pharyngeal or gastric
contents into the larynx and the respiratory tract.
Mendelson described the potential consequences of
abolished airway reflexes under anaesthesia and the
subsequent aspiration of gastric contents, which became
synonymous with Mendelson’s syndrome
3

4. Aspiration of solid matter can cause hypoxia by physical
obstruction,
whereas aspiration of acidic gastric fluid can cause a
pneumonitis with the syndrome of progressive dyspnea,
hypoxia. bronchial wheeze and patchy collapse,
consolidation on chest X-ray or all.
The risk of mortality and serious morbidity increases with
bronchial exposure to greater volumes and acidity of
aspirated material.
4

5. INCIDENCEOFASPIRATIONANDANAESTHESIA-
ASSOCIATEDFATALASPIRATION
The incidence of anaesthesia-associated fatal aspiration in
NAP42 was
1 in 350 000, which is lower than the historical
estimates of between
1 in 45 000 and 1 in 240 000.
Aspiration, however, remains the most significant cause of
airway-related mortality.
5

6. It was responsible for 8 of the 16 (50%) anaesthetic
deaths and 23 of the 133 (17%) reported primary
anaesthesia events, defined as airway complications
leading to death,
brain damage,
unanticipated ICU admission, or
the need for an emergency surgical airway.
The incidence of aspiration under anaesthesia remains
significantly greater with higher ASA status and
emergency surgery.
6

7. NORMALPHYSIOLOGICALMECHANISMS TO
PREVENTASPIRATIONOFGASTRICCONTENTS
Gastro-oesophageal junction
Lower oesophageal sphincter
Protective airway reflexes
7

8. NORMALPHYSIOLOGICALMECHANISMS TO
PREVENTASPIRATIONOFGASTRICCONTENTS
LOS acts as a valve preventing the reflux of gastric contents.
Barrier pressure is the difference between LOS pressure
(normally20-30mmhg) and intra-gastric pressure (normally 5-
10mmhg)
Both are influenced by different factors.
Can you list conditions associated with changes in LOS
tone?
What is the difference between regurgitation
and vomiting
8

9. LOS pressure is reduced by
Peristalsis, vomiting, during pregnancy (a progesterone
effect)
as well as pathological conditions such as achalasia, and
various
drugs (anticholinergics, propofol, thiopentone, opioids).
Intragastric pressure is
Increased if the gastric volume exceeds 1000ml, and with
raised intra-abdominal pressure such as that occurring
with pneumoperitoneum during laparoscopy
9

10. VOMITINGVSREGURGITATION
Regurgitation is a passive process that may occur at any
time & often silent.
The common cause of regurgitation is a decreasing in
closing pressure of the sphincter.
In contrast, vomiting is an active process which involves
contraction of abdominal muscles that occur in lighter
stages of anesthesia.
Elderly patients are particularly prone to higher risks of
aspiration under anaesthesia because they, in general,
have less active airway reflexes
10

11. Factors determining the extent of gastric regurgitation
include:
Function of the LOS
Gastric volume is influenced by:-
Rate of gastric secretions (0.6ml/kg/hr)
Swallowing of saliva (1ml/kg/hr)
Ingestion of solids/liquids, and
The rate of gastric emptying .
11

12. RISKFACTORSFORTHEASPIRATIONOFGASTRIC
CONTENTS
The vast majority of anaesthetictechniques attenuate the
protective physiological mechanisms that prevent
regurgitation and aspiration.
Inadequate depth of anaesthesia or unexpected responses to
surgical stimulation may evoke gastrointestinal motor
responses, such as gagging or recurrent swallowing,
increasing gastric pressure over
and above LOS pressure facilitating reflux.
12

13. In the setting of aspiration, regurgitation occurs
three times more commonly than active
vomiting.
13

14. An unprotected airway, excessively light depths of
anaesthesia,
and one or more predisposing risk factors for aspiration
combine to significantly increase the risks of aspiration
Poor assessment of patient and operative
risks, and failure to use airway devices or techniques
offering greater protection against aspiration were
common themes
14

15. RISKFACTORSFORASPIRATION
Patient factors
(a) Full stomach
. Emergency surgery
. Inadequate fasting time
. Gastrointestinal obstruction
(b) Delayed gastric emptying
. Systemic diseases, including diabetes mellitus and
chronic kidney disease
Recent trauma
15

16. Opioids
. Raised intra-cranial pressure
. Previous gastrointestinal surgery
. Pregnancy (including active labour
(c)Incompetentloweroesophagealsphincter
.Hiatushernia
.Recurrentregurgitation
.Dyspepsia
.Previousuppergastrointestinalsurgery
.Pregnancy
16

17. 17
(d)Oesophagealdiseases
.Previousgastrointestinalsurgery
.Morbidobesity
Surgicalfactors
.Uppergastrointestinalsurgery
.Lithotomyorheaddownposition
.Laparoscopy
.Choleocystectomy

18. Anaesthetic factors
. Light anaesthesia
. Supra-glottic airways
. Positive pressure ventilation
. Length of surgery . 2 h
. Difficult airway
Device factors
. First-generation supra-glottic airway devices
18

19. RISKREDUCTIONSTRATEGIESFORTHEASPIRATION
GASTRICCONTENTS
A summary of the available strategies for reducing
aspiration risk
Reducing gastric volume Preoperative fasting
Nasogastric aspiration
Prokinetic premedication
Avoidance of general anaesthetic
Regional anaesthesia
Reducing pH of gastric contents Antacids
19

20. H2 histamine antagonists
Proton pump inhibitors
Airway protection Tracheal intubation
Second-generation supra-glottic airway devices
Prevent regurgitation Cricoid pressure
Rapid sequence induction
Extubation Awake after return of airway reflexes
Position (lateral, head down or upright
20

21. Guidelines to reduce the risk of aspiration
1. Experienced anaesthesia assistance available to all
times
2. Intubate all emergency cases
3. Apply appropriate cricoid pressure with all inductions
using neuromuscular blocking agents
4. Intubate/seriously consider intubation in the following:
21

22. Delayed gastric emptying (pregnancy, opioids,
diabetes mellitus, renal failure)
Increased intra-abdominal pressure (obesity,
ascites, masses)
5. Extubate high-risk cases awake and on their
side. Extubate all others on their side
22

23. ASPIRATION
Classification
1. Aspiration pneumonitis
2. Aspiration pneumonia
3. Particulate-associated aspiration
23

24. ASPIRATIONPNEUMONITIS
Known as mendelson’s syndrome
Involves lung tissue damage as a result of aspiration of non-
infective
but very acidic gastric fluid.
Two phases
1. Desquamation of the bronchial epithelium causing
increased alveolar permeability. Results in:-
Interstitial oedema,
Reduced compliance and
24

25. 2. Due to acute inflammatory response
Occur within 2 to 3 hrs
Mediated by proinflammatory cytokines, i.e.
Tumour necrosis factor alpha
Interleukin 8 and
Reactive oxygen products
Clinically may be Asymptomatic, or
Present as tachypnoea, bronchospasm, wheeze,
cyanosis and respiratory insufficiency
25

26. ASPIRATIONPNEUMONIA
Due to inhaling infected material or
Secondary to bacterial infection following chemical
pneumonitis.
Typical symptoms
Tachycardia, tachypnea, cough and fever
CXR-segmental or lobar consolidation
Unlike CAP, cavitation and lung abscess occur more
26

27. PARTICULATE-ASSOCIATED
ASPIRATION
If particulate matter is aspirated
acute obstruction of small airways will lead to
distal atelectasis.
If large airways are obstructed, immediate
arterial hypoxemia may be rapidly fatal.
27

28. MICROASPIRATIONANDVENTILATOR-ASSOCIATED
PNEUMONIA
Ventilator-associated pneumonia (VAP) is predominantly
caused by microaspiration and strategies should be used
to reduce the risk of VAP.
Tracheal tubes, which allow subglottic secretion
drainage, help reduce the incidence of VAP and
subsequently the duration of mechanical ventilation
28

29. THEASPIRATIONOFBLOOD
aspiratedbloodismostcommonlyassociatedwithintra-oral
surgeryortonsillectomy.
Aspiratedbloodmayclot,causingtotalairwayobstructionand
deathifnotrecognizedpromptly
NAP42documentedtwodeathscausedbytheaspirationof
blood
afterextubation,oneafterdentalsurgeryandtheotherina
childafterroutinetonsillectomy.
Ventilationafterre-intubationwasonlypossibleaftersizeable
bloodclotswereaspiratedfromthetrachea
29

30. Ensuring that patients, especially those
expected to require mechanical ventilation for
72 h, are intubated with tracheal tubes with subglottic
secretion drainage will mitigate
the effects to microaspiration and reduce the associated
VAP
30

31. MANAGEMENT
If aspiration occurs, management is directed to supportive
treatment and organ support
Aspiration will more commonly affect the right lung
because the right main bronchus is more vertical than the
left main bronchus
Early chest X-ray will show consolidation in up to 75% of
cases and early bronchoscopy may help prevent distal
atelectasis if particulate matter has been aspirated
31

32. MANAGEMENT
The main controversies surrounding treatment decisions
involve the decision to use antibiotics and steroids .
Antibiotics should only be used if pneumonia develops, as
early antibiotics may lead to the selection of virulent
bacteria including pseudomonas.
There is no evidence that using steroids either reduces
mortality or improves outcome.
32

33. CONT…
. Initial management
Recognition of aspiration visible gastric
contents in the oropharynx, or
More subtle indications such as
hypoxia,increased inspiratory pressure,
cyanosis, tachycardia or abnormal
auscultation
33

34. CONT…
Differential diagnosis
Bronchospasm
Laryngospasm
Endotracheal tube obstruction
Pulmonary oedema
ARDS
Pulmonary embolism
34

35. Management -key points
Head down tilt
Oropharyngeal suction
100% oxygen
Apply cricoid pressure and ventilate
Deepen anaesthesia/perform RSI
Intubate trachea
Release cricoid once airway secured
Tracheal suction
Consider bronchoscopy
Bronchodilators if necessary
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