A 74-year-old male patient weighing 80 kg with a history of essential hypertension and known subglottic laryngeal cancer is scheduled for elective surgery. He presents with dyspnea (respiratory rate of 45 breaths/min), hypoxemia (SpO2 80% in ambient air), and a highpitched stridor that can be easily localized to the neck. Respiratory sounds are barely heard bilaterally on lung auscultation. A fiberoptic examination shows no space for nasotracheal or orotracheal intubation, so an emergency percutaneous tracheostomy is performed. Invasive mechanical ventilation initiated with assist control volume control ventilation (tidal volume of 600 mL and a PEEP of 8 cm H2O). However, the patient remains hypoxemic with a PO2 of 69 mm Hg despite an FiO2 of 80%. An x-ray shows bilateral infiltrates.
What would be the MOST appropriate first intervention on this patient?
Correct Answer: A
The respiratory failure developing during severe upper airway obstruction typically originates from a negative-pressure pulmonary edema caused by the repeated negative airway pressure that the patient develops in order to overcome the resistance. This causes trans-vascular fluid extravasation and thereby interstitial and alveolar edema. This condition is purely hydrostatic and is generally relieved in 24 to 48 hours if positive pressure ventilation is ensured, and airway resistance is eliminated. The rate of alveolar fluid clearance in this condition is between 14% and 17% per hour, approaching physiological values, while in the presence of lung injury it may be as low as 0% to 3%/h. For this reason, the main intervention to take in this situation is to limit and prevent lung injury by guaranteeing a protective ventilation strategy (6 mL/kg of tidal volume with plateau pressure below 30 cm H2O). Diuretics can accelerate the rate of fluid uptake, but their efficacy is limited in the presence of lung injury. Fiberoptic bronchoscopy may only reveal the presence of pink frothy transudate which may also present by simply performing a tracheal aspiration. The immediate execution of a CT scan is not indicated until the effects of positive pressure ventilation, PEEP, and alveolar clearance clarify the actual damage accumulated by the lung tissue, if any exists.
Which among the following medications is indicated for treatment of high-altitude pulmonary edema, in absence of oxygen while awaiting for descent?
Correct Answer: C
Sustained release oral nifedipine is the drug of choice in high-altitude pulmonary edema (HAPE) (Grade 1C). Other drugs reduce pulmonary vasoconstriction and thus might be useful in treatment of HAPE. However, their clinical efficacy has not been proven. While phosphodiesterase inhibitors have a strong biological rationale, data from prospective studies are missing. Use of inhaled beta-agonist is reported in literature, but there is not enough data to support these drugs. Dexamethasone has been proved to reduce the incidence of HAPE in a placebo-controlled trial, yet its role in treating the established acute disease has not been validated.
A 28-year-old female patient was brought to the emergency room with a complaint of dyspnea. She is awake, breathing 34 times per minute with a SpO2 of 93% in ambient air. She has a body temperature of 37.5°C and bilateral diffuse crackles on auscultation. The patient is a PhD student working in the same hospital where she is admitted, with symptoms starting just before leaving the lab to go back home. She regularly spends time in the animal facility as part of her PhD program. She denies allergies and admits to smoking 5 cigarettes per day. The chest x-ray is unremarkable.
What would be the next MOST appropriate next test for this patient?
Presence of a mild fever and potential occupational exposure to an antigen (triggering respiratory distress) in the absence of wheezing and a negative chest x-ray should point toward hypersensitivity pneumonitis (HP) as an important differential diagnosis. High-resolution CT (HRCT) scan is increasingly used in the initial evaluation of patients suspected with HP. Independently of the disease stage (acute vs subacute vs chronic HP), classic radiologic findings together with a history of appropriate exposure are adequate for establishing diagnosis, and a biopsy can be avoided. CT scan should not be delayed because the classic findings (ground glass opacification in the upper lobes with decreased attenuation of secondary lobules due to air trapping) are best seen during acute presentation and may disappear quickly while symptoms subside. Spirometry may show either a restrictive or an obstructive pattern or both, while diffusion lung carbon monoxide may be impaired in subacute patients and is always impaired in chronic patients. However, these tests are not diagnostic and should not be preferred over a potentially diagnostic HRCT scan. RAST test is useful in determining an IgE-mediated sensitization, which is less likely in this patient especially in the absence of wheezing. ImmunoCAP assay and other techniques to determine IgG-mediated sensitization are useful but may be inconclusive because they lack sensitivity and specificity. Positive findings are not diagnostic for HP and negative findings cannot exclude it. Furthermore, the patient is a smoker, which could yield false positives.
A 55-year-old female patient is intubated for severe respiratory failure. A CT scan is then performed which shows diffuse bilateral ground glass opacities. On arrival in the intensive care unit, the patient desaturates due to abundant hemorrhagic secretions in the endotracheal tube. A fiberoptic bronchoscopy with deep bronchoalveolar lavages is then performed, yielding a very high percentage (>50%) of hemosiderin-laden macrophages in all samples.
Which among the following components in this patient’s medical history supports the diagnosis?
Correct Answer: B
This patient has diffuse alveolar hemorrhage (DAH) based on the bronchoscopic findings. It is fundamental to quickly understand the underlying pathogenetic disorder in order to promptly prescribe the correct treatment regimen, which may include pulse-dose steroids, immune suppression, and plasmapheresis. The patient described in this scenario may have an undiagnosed primary or secondary (due to systemic lupus erythematosus) antiphospholipid syndrome, which, especially if untreated, is a frequent cause of DAH. In this setting a reasonable first line of treatment could be a combination of glucocorticoids and cyclophosphamide. Antiplatelet agents have been associated with the development of DAH, but this is true only when glycoprotein IIb/IIIa inhibitors, such as abciximab, are administered. Anticoagulant therapy is instead more frequently associated with DAH. Various autoimmune diseases may be involved in determining DAH, yet a link between polyarteritis nodosa and DAH is not described. To date, there is only one report in literature describing a patient with active hepatitis B and polyarteritis nodosa developing DAH, although this patient had multiple comorbidities which are strongly associated with DAH, such as cocaine abuse by inhalation. Chronic hepatitis C, especially in patients who develop cryoglobulinemia, is associated with DAH.
A female 50-year-old patient is undergoing induction of general anesthesia for gastric bypass surgery. Which of the following intraoperative measures would have the MOST impact on preventing the development of postoperative pulmonary atelectasis?
Correct Answer: D
Perioperative hypoxemia is a risk factor for perioperative mortality and for several perioperative complications including cardiac ischemia and delirium leading to increased postoperative length of stay. Perioperative atelectasis is one of the main causes of hypoxemia in surgical patients, with their prevention being mandatory and requiring a multistep approach in all phases of the perioperative period. After surgery, optimal pain control without residual anesthesia together with CPAP and postural changes are all fundamental to pursue this target.
A fundamental mechanism leading to postoperative atelectasis is hyperoxic reabsorption of gases from the alveolar space into circulation. Extubation with a FiO2 of 1.0 has been shown to potentially jeopardize all previous intraoperative efforts to prevent and/or reduce atelectasis, even if a recruitment maneuver is performed prior to extubation. Keeping the lowest FiO2 compatible with the patient’s oxygenation requirements, not only before extubation but throughout the surgery, prevents atelectasis. Clinical studies evaluating fixed-ruled PEEP strategies have shown contradictory results, and thus there is no specific recommendation on the amount of PEEP. High PEEP has theoretical advantages in terms of protection from atelectasis. Studies comparing preset values of low versus high PEEP for intraoperative ventilation yield contradictory results. Preoxygenation with PEEP has a demonstrated role in reducing the incidence of postoperative atelectasis, yet it is not the most impactful strategy among those listed. Using an FiO2 of less than 60% during preoxygenation, induction, and intubation has a dramatic effect leading in many cases to the absence of intraoperative atelectasis. However, this strategy cannot be implemented for safety reasons, especially since this will decrease the duration of safe apnea period.
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