Aspiration

Aspiration is defined as inhaling a foreign body or fluid into the lower respiratory tract. This is most often gastric contents or a foreign body. In obstetrics, the aspiration of amniotic fluid or meconium by the newborn.

Swallowing - Topography of the upper respiratory and swallowing tracts

Predisposition

• Disorders of consciousness (coma,intoxication);
• general anesthesia (especially introduction and withdrawal from anesthesia ) and sedation;
• alcoholism;
• tracheostomy;
• endotracheal intubation
• hiatal hernias, esophageal diseases, decreased lower esophageal sphincter tonus (Benzodiazepines, Opiates, Hypnotics, Vagolytics);
• upper airway stenosis.

Patophysiology

• The consequences of aspiration and the resulting clinical pictures can be divided into three groups:
  • aspiration of acidic gastric contents;
  • solid body aspiration;
  • aspiration of bacterial contaminated material.

Aspiration pneumonia in a patient with neurological degenerative disease, parenchymal necrosis and aspirate particles are seen. Stained with hematoxylin-eosin.

Aspiration of an inert body or particle

• Solids, blood clots, food residues;
• occurs immediate airway obstruction (partial or complete), atelectasis and reflective bronchospasm.

Symptoms

• Dyspnoea, tachypnoea, respiratory stridor;
• laryngospasm, bronchospasm, cough;
• chest pain, hemoptoe.

Auscultation

• Lateral differences (weakened breathing), in- or expiratory wheezing (if spasm persists even after airway lavage → suspicion of more foreign bodies).

X-ray image

• Finding a foreign body if it is large enough with X-ray contrast;
• emphysematous changes (valve mechanism) or atelectasis.

Blood gas analysis

• Decrease in p_aO₂ and increase in p_aCO₂

Therapy

• O_2;
• upside-down positioning, foreign body digital removal attempt, direct laryngoscopy, rigid bronchoscopy, Heimlich maneuver;
• endotracheal suction and endobronchial lavage, in the case of small particles we can aspirate using fibrobronchoscopy, larger bodies bronchoscopy with a rigid bronchoscope;
• thoracotomy.

Acidic stomach contents

Synonyms

• Mendelson's syndrome

Symptoms

• dyspnoea, tachypnoea, cough;
• anxiety, fear;
• laryngospasm, bronchospasm, cyanosis, foamy sputum;
• tachycardia, pressure drop, shock.

Complications

• ARDS (approximately 22% of patients);
• secondary infections;
• SIRS, MOF.

Pathophysiology, process

• Chemical-toxic phase
  • in 5 seconds the aspirate enters the central airways;
  • in 15 seconds it is neutralized in the lungs;
  • airway epithelial necrosis - desquamation of the superficial epithelial layer, complete loss of epithelialization in 6 hours, regeneration in 3 days, complete regeneration in 7 days;
  • second type pneumocytes degenerate within 4 hours after aspiration → increased pulmonary permeability and pulmonary edema.

• Inflationary phase
  • acidity-induced proinflammatory changes - cytokines , TNFα, IL-8 → inflammatory reaction → increased permeability → pulmonary edema.

Auscultation

• rhonchi, whistles, squeaks.

X-ray image

• diffuse infiltration of affected areas, atelectasis;
• we scan immediately after aspiration and then 4 hours later (even in an asymptomatic patient) - the first changes recognizable on an X-ray may occur 4-8 hours after aspiration.

Pulmonary function, blood gas analysis

• decrease in p_aO₂ and increase or also decrease in p_aCO₂, decrease in lung compliance , increase in lung resistance, initially respiratory alkalosis later turns into metabolic acidosis, increase in respiratory work;
• decrease in blood pressure, increase in pulmonary arterial pressure.

Therapy

• oropharyngeal suction, endotracheal suction (aspirate analysis - volume, pH, chemical analysis, microbiological examination), upside down position, we do not attempt edobronchial lavage or neutralization;
• O₂ supply (mask, CPAP), endotracheal intubation and artificial lung ventilation with PEEP, humidified air and inhalation therapy, patient positioning;
• fibrobronchoscopy (within one hour of aspiration) - confirmation of the diagnosis, estimation of damage, suction of solids, atelectasis;
• circulatory stabilization - volume therapy, careful catecholamine therapy;
• lungs - use of bronchodilators (β₂ sympathomimetics, theophylline);
• physiotherapy (breathing training);
• ATB - Cephalosporins of the 2nd generation + Metronidazole , alternative: aminopenicillins + lactamase β inhibitor
• Ambroxol in high doses (surfactant and mucus production), surfactant application (locally bronchoscopically, systemically).

Bacteria-contaminated material

Symptoms

• dyspnoea, tachypnoea;
• bronchospasm;
• later symptoms of pneumonia : fever, productive cough.

Auscultation

• rhonchi, whistles.

X-ray image

• infiltrates in the affected areas of the lungs.

Pulmonary function, blood gas analysis

• decrease in p_aO₂ and increase or also decrease in p_aCO₂, decrease in lung compliance, increase in lung resistance, metabolic acidosis;
• purulent, smelly tracheal secretion;
• decrease in blood pressure, increase in pulmonary arterial pressure.

Therapy

• endotracheal aspiration, fibrobronchoscopy;
• ATB prophylaxis of pneumonia - use of ATB according to the expected spectrum in infected material (Ileus, G negative intestinal flora);
  • typical agents: Bacteroides , anaerobic Streptococci > 80%, Staphylococci , Pneumococci , Klebsiella , Fusobacteria
  • ATB: eg Cefoxitin + Clindamycin or Imipenem (+ Gentamicin) or Cefoxitin + Gentamicin.

Incidence of aspiration in anesthesia and intensive care

• On average 1.4-6.5 : 10000.
• The lowest risk of aspiration is in planned procedures in children older than one year and patients of groups ASA I and II (ASA = American Society of Anesthesiology).
• In infants, patients in groups ASA IV and V, patients undergoing caesarean section and emergency procedures, the risk is ten times higher.
• The highest risk of aspiration is in urgent intubations 375 : 10000.
• Only about one third of all cases are aspiration symptomatic - requires artificial lung ventilation > 24 hours.
• The greatest risk of aspiration is at the beginning of anesthesia, about 56% of aspirations are at the beginning of anesthesia, during anesthesia about 20% and when exiting anesthesia the incidence also reaches about 20%.

Prevention

Non-pharmacological

• we perform for all patients undergoing the planned operation;
• includes preoperative fasting:
  • do not eat any solid food for at least 6 hours before the operation;
  • no consumption of pure fluids (water) for at least two hours preoperatively;
  • in infants, the last breast-feeding within four hours before surgery;
    • if the patient is not fasting, we only perform life-saving surgery using the "crush intubation" technique.

Pharmacological

• use if known risk factors - smoking, gastroesophageal reflux, lower esophageal sphincter disorders, caffeine, body mass index over 30, pregnancy, trauma, shock;
  • increasing the pH of the stomach contents;
    • approximately 10–20 minutes before the operation, we give a solution of sodium citrate (in pregnant women undergoing a caesarean section);
    • histamine H₂ blockers 2 in the evening and in the morning 2-3 hours before surgery - ranitidine, cimetidine;
    • proton pump inhibitors omeprazole, pantoprazole;
  • accelerating the emptying of gastric contents;
    • metoclopramide - 30 minutes before surgery.

Links

Related articles

• Aspiration pneumonia

External links

• Aspiration (English wikipedia)

References

• DOEFFINGER, Joachim and Franz JESCH, et al. Intensive medical notebook. 4th edition. Wiesbaden: Abbott GMBH, 2002.  ISBN 3-926035-35-8 .

• KRETZ, Franz-Josef and Frank TEUFEL. Anesthesia and intensive care. 1st edition. Heidelberg: Springer, 2006. 695 pp.  ISBN 3-540-62739-1 .

• HECK, Michael and Michael FRESENIUS. Repetitorium Anästhesiologie. 5th edition. Heidelberg: Springer, 2007. 642 pp.  ISBN 978-3-540-46575-1 .

• ENGELHARDT, T. and NR WEBSTER. Pulmonary aspiration of gastric contents in anasthesia. British Journal of Anesthesia [online] . 1999, vol. 83, vol. 3, pp. 453-460, also available from < https://academic.oup.com/bja/article/83/3/453/311142?maxtoshow=&hits=10&RESULTFORMAT=&fulltext=pulmonary+aspiration&searchid=+1+&+FIRSTINDEX+=+0+&+resourcetype+=+HWCIT+>. ISSN 1471-6771.