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.



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 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 paO2 and increase in paCO2

Therapy

 * O2;
 * 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.

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 paO2 and increase or also decrease in paCO2, 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).

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 paO2 and increase or also decrease in paCO2, 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 , Klebsielly , 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%.

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.