Aspiration- risk, prophylaxis and treatment – Flashcards
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Definition of Mendelson's syndrome
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Determined low pH gastric acid caused aspiration pneumonitis
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Dr. Mendelson advocated the following?
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-withholding of food during labor -Great use of regional anesthesia - administration of antacids -emptying the stomach before administration of general anesthesia -competent administration of general anesthesia
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Definition of aspiration
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That inhalation of either oropharyngeal or gastric contents into the lower airways
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What three types of material cause three different pneumonic syndromes?
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-aspiration of gastric acid -aspiration of bacteria from oral and pharyngeal areas -aspiration of oil
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What does aspiration of gastric acid cause?
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Chemical pneumonia, which has also been called aspiration pneumonitis
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What does aspiration of bacteria from oral and pharyngeal areas cause?
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Bacterial pneumonia
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What does aspiration of oil cause?
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Exogenous lipid pneumonia, a rare form of pneumonia
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What can aspiration of a foreign body cause?
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Acute respiratory emergency and, in some cases, may predispose the patients to bacterial pneumonia
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What problem is associated with the most common cause of anesthesia related maternal death?
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Airway problems associated with the use of general anesthesia
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What is the incidence of aspiration in the general population?
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~ 1/2130
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What is the incidence of aspiration in the C/S population?
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~ 1/660
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Aspiration occurs in __ anesthetics for elective surgery
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1/4000
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Aspiration occurs in __ for emergency surgery
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1/900
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If an endotracheal tube is used, then the aspiration is just as likely after __ as during __
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Extubation Induction
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Do not extubate unless you know the patient can
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Protect their airway
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What causes low risk for aspiration?
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Elective surgery, fasted of food for six hours, clears two hours
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What causes high risk for aspiration?
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-not following mentioned guidelines -delayed gastric emptying -bowel obstruction, GI cancer, critical illness, acidosis, pain, opiates, DM/gastroparesis, incompetent LPS -esophagitis, hiatal hernia, gastric abnormality -previous esophageal Sx -pregnancy -obesity
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What are some aspiration precautions?
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-regional anesthesia -Naso -/Oro - gastric tube for gastric decompression -cuffed tube -R.S. I.: Rapid sequence induction -pre-oxygenation
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What are some aspiration precautions?
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-Sellick maneuver -IV-induction -rapid acting NMB -ETT/ tracheal intubation
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The term rapid sequence induction is related to the?
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-technique reducing the time between loss of consciousness -onset of neuro-muscular blockade -placement of the endotracheal tube
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Patients who develop Mendelson's syndrome become critically ill how many minutes after aspiration?
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30-60 minutes
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How does aspiration present itself with patients who develop Mendelson syndrome?
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-signs and symptoms appear during or very shortly after anesthesia -aspiration or regurgitation may have been "silent" -May have been difficulty with intubation -likely that only a small quantity of gastric juice is required to cause the syndrome
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It has been postulated that as little as how many milliliters of acid gastric juices may be required to develop Mendleson syndrome?
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25 ml
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What are some early signs of aspiration?
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- cyanosis -tachycardia -pulmonary edema -bronchospasm -hypotension -hypovolemia
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What are some later signs of aspiration?
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-cardiac failure accompanied by: * increased pulmonary artery pressure * reduced static lung compliance * hypoxemia * metabolic acidosis * infection
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How many milliliters of acidic fluid per day does the stomach produce and what type of enzyme does it contain?
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1500 mL Proteolytic enzyme pepsin
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What two types of glands are associated with gastric secretions?
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-Oxyntic which produce hydrochloric acid -pyloric which produce pepsinogen
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What is the gastric emptying of a meal slowed by?
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High lipid content high caloric load Large particle size
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Mendelson divided aspiration into:
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-Liquid which is more serious one highly acidic -solid
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The three variables identified for risk factors of aspiration pneumonitis are:
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Chemical nature Physical nature volume
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What treatment is used for aspiration pneumonitis?
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Bronchoscopy Steroids
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Why would one use bronchoscopy?
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- remove large particles
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What are pre-operative oral fluid administration guidelines?
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-ASA NPO standards for healthy pregnant women -risk greater with obesity -clear liquids up to two hours prior surgery -Best to NPO 8 hours: parenteral hydration via IV -should undergo a fasting period for solids of 6-8 hours depending on the type of food ingested
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How many times greater chance of maternal morbidity with general anesthesia compared to regional?
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16.7 times greater
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Pregnancy has what effect on gastroesophageal reflux?
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-common complication of pregnancy -increased gastric pressure -Progesterone
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The mean rate of gastric acid secretion is reduced during what trimester?
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Second trimester
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What are three aspects to think about when using steroid treatment of aspiration during pregnancy?
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-Controversial -no benefit in the treatment of adult/acute respiratory distress syndrome -May be beneficial in preventions of fibrosing alveolitis
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In regards to antacids, what type, what dosage amount and within what timeframe should they be used?
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-use non-particulate (sodium citrate) versus particulate antacid -use 0.3 M 30-35 cc "Bicitra" -use within 30 minutes prior to procedure
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Why should one use H2 receptor antagonists?
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-Efficacious in reducing gastric acidity and volume -Block histamine receptors at oxyntic cells -60-90 minutes to peak effect
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Characteristics of Cimetidine ("Tagamet")
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-60-90 minutes - May inhibit drug clearance (Lidocaine) -binds to cytochrome P450, decreases hepatic bloodflow -crosses placental barrier
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Characteristics of ranitidine ("Zantac")
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-60 minutes to pH greater than 2.5 -sustained eight hours -no interaction with P450 system
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Characteristic of Nizatidine ("Axid") and Famotidine ("Pepcid")
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-newer H2- blockers -> 10 hours duration - no interaction with p450 system
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Characteristics of Omeprazole ("Prilosec"), Lansoprazole ("Prevacid")
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-Inhibit hydrogen ion pump on surface of oxyntic cell -Long duration of action -Little toxicity -Similar in efficacy as H2-receptor antagonists -Two dose regimen at night and on morning of surgery
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Characteristics of Esomeprazole ("Nexium"), pantoprazole ("Protonix"), rabeprazole ("Aciphex")
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-newer proton pump inhibitors -efficacy and safety not yet established
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MCP stimulates gut motility by affecting what?
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Different receptors in the GI tract
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MCP acts as an antagonist of?
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Dopamine D2 receptor subtype
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Dopamine has a direct relaxant effect on the gut by activating muscular D2 receptors where?
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Lower esophageal sphincter and stomach (fundus and Antrum)
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What do most of the side effects from MCP result from?
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Its ability to cross the blood - brain barrier and are observed in up to 30% of patients
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What are the most frequent extra-pyramidal side effect from MCP?
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Acute dystonic reactions
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When do acute dystonic reactions occur, what percentage of patients do they affect and how does incidence increase?
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-within 24-48 h of initiating treatment -affect ~0.2-6% of patients taking MCP -incidence increases with higher doses
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Definition of dystonia
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Consists of spasmodic or sustained involuntary muscle contractions resulting in twisting, repetitive movements or abnormal postures
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How does dystonia present itself?
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As facial spasm, torticollis, oculogyric crisis, trismus, tortipelvic spasm (abdominal rigidity) or opisthotonos (spasm of entire body)
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How acute dystonic reactions typically resolved?
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With discontinuation of the drug
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How does Akithisia present itself, what is the incidence range and what does it depends on?
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-With subjective feelings of inner restlessness as well as objective findings of motor restlessness -incidence ranges from 10-25% -depends on mode of MCP administration
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What can prolonged therapy with MCP result in?
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Parkinsonian - like symptoms, including bradykinesia, tremor, rigidity
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When do parkinsonian symptoms generally resolve after discontinuation of MCP?
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Within 2-3 months
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What is the most feared complication of chronic MCP use?
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Tardive Dyskinesia (TD)
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What is tardive dyskinesia characterized by?
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Involuntary movements of the face, tongue or extremities
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True or False? Tardive dyskinesia may not reverse even after discontinuation of drug
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True
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MCP should not be used whenever stimulation of GI motility might be dangerous:
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In the presence of GI hemorrhage, mechanical obstruction, or perforation
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Why is MCP contraindicated in patients with pheochromocytoma?
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The drug may use a hypertensive crisis (due to release of catecholamines from the tumor)
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MCP is contraindicated in patients with?
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Known sensitivity or intolerance
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Why should MCP not be used in epileptics or patients receiving other drugs which are likely to cause extrapyramidal of reactions?
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Frequency and severity of seizures or extrapyramidal reactions may be increased
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Anticipated difficult intubations requiring GETA should receive?
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Awake fiber-optic intubation
