Читать книгу Surgical Critical Care and Emergency Surgery - Группа авторов - Страница 15

Adrian A. Maung, MD1 and Lewis J. Kaplan, MD2,3

1 Yale School of Medicine, New Haven, CT, USA

2 Division of Trauma, Surgical Critical Care and Emergency Surgery, Department of Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA

3 Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA, USA

1 A 73‐year‐old woman is admitted to the intensive care unit after undergoing exploratory laparotomy and subtotal colectomy for C. diff colitis. Her past medical history is significant for smoking and clinically severe obesity with BMI 44.6 (height 160 cm, and weight 114 kg). She is hypotensive on a norepinephrine drip and mechanically ventilated on assist control volume mode of ventilation. The most appropriate initial tidal volume setting is:1100 mL684 mL312 mL520 mL912 mLThe patient is at risk for developing acute respiratory distress syndrome based on her clinical condition as well as risk factors of smoking and morbid obesity. Low tidal volume ventilation, as described by ARDSnet, was the first intervention demonstrated to improve mortality in those with ARDS. Initial tidal volumes should be set at 6–8 mL/kg based on predicted (ideal) body weight. Based on the patient’s height 160 cm, her predicted body weight is 52 kg thus answer C is the correct choice. Choice A is based on 10 mL/kg and actual weight. Choice B is 6 mL/kg but based on actual weight. Choice D is based on 10 mL/kg and ideal body weight and Choice E is 8 mL/kg and actual body weight.Answer: CBrower RG, Matthay MA, Morris A, et al. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med. 2000; 342(18):1301–1308Khan YA and Ferguson ND . What is the Best Mechanical Ventilation Strategy in ARDS in Evidence‐Based Practice of Critical Care , 3rd Edition Elsevier 2020.

2 48‐year‐old man has acute respiratory failure after a motorcycle crash. He is on low tidal volume, high PEEP ventilation with FiO2 100% and his PaO2 is 50 mm Hg. He is started on inhaled nitric oxide (NO). Based on the current evidence, the role of NO in acute respiratory failure is best characterized as:decreased mortality.improved oxygenation but not mortalitydecreased rate of acute kidney injuryNO has no effect on oxygenationroutine ARDS managementCurrent clinical evidence does not support a role for inhaled NO in the routine management of ARDS. Although inhaled NO may improve oxygenation, it has not been shown to improve mortality (Answer B). NO has also been associated with increased rates of acute kidney injury.Answer: BGebistorf F, Karam O, Wetterslev J, et al. Inhaled nitric oxide for acute respiratory distress syndrome (ARDS) in children and adults. Cochrane Database Syst Rev. 2016;(6):CD002787.Ruan SY, Huang TM, Wu HY, et al. Inhaled nitric oxide therapy and risk for renal dysfunction: a systematic review and meta‐analysis of randomized trials. Crit Care. 2015; 19:137.

3 27‐year‐old man with ARDS after debridement for necrotizing soft tissue infection of the perineum has worsening hypoxemia with PaO2 90 mm Hg on 90% FiO2 despite optimal low tidal volume ventilator settings and neuromuscular blockade. The next most appropriate step in his management would be: Inhaled nitric oxideHigh dose steroidsECMO rescueProne positioningContinue current management and start prone positioning if there is no improvement after 72 hours.Clinical evidence supports the use of early prone positioning in patients with severe ARDS (answer D). The PROSEVA trial published in 2013 demonstrated an improved 28‐day mortality with 16 hours of prone positioning per day (16% in the prone group vs 32.8% in control group). Most of the research has focused on early rather than a rescue role for severe ARDS and therefore waiting for 72 hours (choice E) would not be appropriate. Inhaled nitric oxide (choice A) has not been associated with improved outcomes. ECMO (choice C) has a role in the management of refractory hypoxemia but would not be the next step in the management of this patient. The role of early steroids remains controversial but there is no benefit to late (after 14 days) (choice B) steroid administrationAnswer: DGuérin C and Reignier J . PROSEVA study group. “Prone positioning in severe acute respiratory distress syndrome”. N Engl J Med. 2013; 368(23):2159–68. PMID: 23688302.Guérin C, Albert RK, Beitler J, et al. Prone position in ARDS patients: why, when, how and for whom. Intensive Care Med. 2020; 46(12):2385–2396. Epub 2020 Nov 10. PMID: 33169218; PMCID: PMC7652705.

4 56‐year‐old woman who was initially admitted with necrotizing pancreatitis develops acute respiratory distress and hypotension. She is intubated and admitted to the intensive care unit. Over the next 24 hours, she is given 10 L of crystalloid for persistent hypotension and oliguria. She is on assist control volume‐cycled ventilation (tidal volume 6 mL/kg, FIO2 30%, PEEP of 5) with an SpO2 of 98%. The ventilator is alarming for high pressure. Measurement of the pressures reveals a high peak airway pressure and a normal plateau pressure. The next step in management would be to:Decompressive laparotomy for abdominal compartment syndromeNeuromuscular blockade by continuous infusionChange to pressure support ventilation modeAdjust the ventilator alarm settings thresholdsInhaled bronchodilator therapyElevated airway pressure can occur secondary to different pathologies that affect airway resistance and/or pulmonary compliance. The ventilator in many cases automatically reports the peak airway pressure but it is also important to measure the plateau pressure to distinguish between problems with pulmonary compliance (elevated plateau pressure) vs. problems with airway resistance (difference between peak and plateau pressures). The patient in the clinical vignette is certainly at risk for development of abdominal compartment syndrome but a normal plateau pressure would point away from this diagnosis (choice A). A high peak pressure and normal plateau pressure is most suggestive of increased airway resistance that could be secondary to bronchospasm (Answer E), endotracheal tube occlusion, retained secretions and mucous plugging. Neuromuscular blockade (answer B) or a change to pressure support mode (answer C) would not address increased airway resistance. Ignoring the ventilator alarm (choice D) without further investigation is never a good idea.Answer: EMaung A and Kaplan L . Waveform analysis during mechanical ventilation. Curr Probl Surg. 2013; 50(10): 438–446. PMID: 24156841.

5 Non‐invasive ventilation in the critically ill patients is best supported by clinical evidence for this diagnosis:COPD exacerbationAcute Respiratory Distress SyndromePost‐extubation hypercarbic failureHypercarbia due to severe traumatic brain injuryFacilitating secretion clearance for pneumoniaMultiple randomized trials have shown that non‐invasive ventilation (NIV) decreases rates of intubation and improves mortality compared to standard therapy in patients with COPD exacerbation. (Answer A). NIV has also been shown to be helpful in acute cardiogenic pulmonary edema. There is currently conflicting (and even evidence that demonstrates deleterious effects) with using NIV in ARDS (choice b) and post‐extubation failure (choice c). Contraindications to NIV include severe altered mental status (choice d) and copious secretions (choice e).Answer: APlant PK, Owen JL and Elliott MW . Early use of non‐invasive ventilation for acute exacerbations of chronic obstructive pulmonary disease on general respiratory wards: a multicentre randomised controlled trial. Lancet 2000; 355(9219):1931–5. PMID: 10859037Bourke SC, Piraino T, Pisani L, et al. Beyond the guidelines for non‐invasive ventilation in acute respiratory failure: implications for practice. Lancet Respir Med. 2018; 6(12):935–947. PMID: 30629932.

6 The criterion that is most predictive of a successful attempt at liberation from mechanical ventilation is:Glasgow Coma Score of 8TMinute ventilation of 20 L/minRapid Shallow Breathing Index of 40Maximal inspiratory pressure of −10 cm H2OCalculated PaO2/FiO2 ratio of 125 Although there is no single clinical predictor with the sensitivity and specificity to predict 100% successful liberation from mechanical ventilation, certain objective measures have been validated and used in combination as a screening tool. These include the rapid shallow breathing index < 105 breaths/min/L (answer C), minute ventilation < 10 L/min, an alert and appropriately interactive mental status, maximal inspiratory pressure less than −20 to −25 cm H2O and a P/F ratio ≥ 150.Answer: CBaptistella AR, Sarmento FJ, da Silva KR, et al. Predictive factors of weaning from mechanical ventilation and extubation outcome: a systematic review. J Crit Care. 2018; 48:56–62 PMID: 30172034.

7 A 67‐year‐old woman with COPD is mechanically ventilated after undergoing cytoreductive surgery for ovarian cancer. She is on volume control ventilation with a decelerating waveform for gas delivery. Which of the following best describes the characteristics of the decelerating gas delivery waveform compared to a square waveform?Higher peak airway pressureHigher likelihood of CO2 retentionLower likelihood of CO2 retentionShorter inspiratory timeLower mean airway pressureTwo most commonly used gas flow waveforms in adults are square and decelerating. The square waveform is characterized by higher peak airway pressure, shorter inspiratory time (thus longer expiratory time) and lower mean airway pressure compared to the decelerating waveform (Choices: a, d and e). Since the expiratory time is shorter with the decelerating waveform, there is a higher likelihood of CO2 retention (answer b) especially in patients who have preexisting limitation of expiratory flow such as COPD.Answer: BMaung A and Kaplan L Waveform analysis during mechanical ventilation. Curr Probl Surg. 2013; 50(10): 438–446 PMID: 24156841.

8 19‐year‐old woman has worsening respiratory failure over the past 48 hours. She is ten days after a motor vehicle collision resulting in multiple rib fractures, pulmonary contusions, and a grade 1 liver laceration. She is on low tidal volume ventilation, 100% FiO2 with PaO2/FiO2 ratio of 71. She is being proned and was started on neuromuscular blockade. She is not on vasopressors and has a hemoglobin of 9 mg/dL The next most appropriate intervention would be:High frequency oscillation ventilationVeno‐arterial ECMOVeno‐venous ECMORib fracture fixationHelium‐oxygen mixtureExtracorporeal membrane oxygenation (ECMO) should be considered as salvage therapy in patients with refractory hypoxemia despite receiving standard care. In general, veno‐venous ECMO (answer C) is utilized in patients who do not have severe cardiac dysfunction such as this patient and veno‐arterial (choice b) is used in patients with hemodynamic compromise. Besides the inability to anticoagulated a patient, there are no specific absolute contraindications to ECMO. High frequency oscillatory ventilation (choice a) has been shown to have no benefit and possibly cause harm. Rib fracture fixation (choice d) remains an evolving therapy that is of optimal use in specific patient population but would not be appropriate in this patient due to severe ARDS. Helium‐oxygenation mixture is sometimes utilized in cases with airflow resistance but would be contraindicated in this patient due to her high oxygen requirement.Answer: CTillman BW, Klingel ML, Iansavichene AE, et al. Extracorporeal membrane oxygenation (ECMO) as a treatment strategy for severe acute respiratory distress syndrome (ARDS) in the low tidal volume era: a systematic review J Crit Care. 2017; 41:64–71 PMID: 28499130.Goligher EC, Munshi L, Adhikari NK, et al. High‐frequency oscillation for adult patients with acute respiratory distress syndrome. a systematic review and meta‐analysis. Ann Am Thorac Soc. 2017; 14(Suppl. 4):S289–S296 PMID: 29043832.

9 Causes of postoperative respiratory failure in the immediate post‐anesthesia period include which of the following:Inadequate reversal of neuromuscular blockadeOpioid‐induced respiratory depressionIatrogenic or negative pressure pulmonary edemaReduction in functional reserve capacityAll of the above Early postoperative respiratory complications are common and may arise from multiple etiologies (answer e). General anesthesia and mechanical ventilation can lead to atelectasis and reduction in the functional reserve capacity of up to 50%, even in healthy individuals, especially if no PEEP is used during the procedure. Residual neuromuscular blockade can lead to impaired respiratory muscle strength and upper airway obstruction. Hypoxemia can be due to pulmonary edema, whether due to fluid resuscitation or negative pressure (identified more commonly in young, healthy, and muscular patients). Opioids, which are commonly administered both intraoperatively and postoperatively, can cause decreased respiratory drive, decreased level of consciousness, and upper airway obstruction due to a decrease in the supraglottic airway tone.Answer: EKarcz M and Papadakos PJ Respiratory complications in the postanesthesia care unit: a review of pathophysiological mechanisms Can J Respir Ther Winter. 2013; 49(4): 21–9 PMID: 26078599.Gupta K, Prasad A, Nagappa M, et al. Risk factors for opioid‐induced respiratory depression and failure to rescue, a review. Curr Opin Anaesthesiol. 2018; 31 1:110–119 PMID: 29120929.

10 A 46‐year‐old woman is invasively mechanically ventilated after developing pneumonia following a motorcycle crash. She is on assist control ventilation with oxygen saturations in the low 80s. Which of the following maneuvers would be most likely to improve her oxygenation.Increase in tidal volumeIncrease in respiratory rateChange from square to decelerating waveformIncrease in expiratory timeDecrease in inspiratory timeOxygenation most closely correlates with mean airway pressure and reflects the area under the curve described by the gas‐flow waveform. Change to a decelerating waveform (choice C) extends the inspiratory time and the area under the curve thus increasing the mean airway pressure. Increases in tidal volume (choice A) and respiratory rate (choice B) both increase the minute ventilation and likely CO2 clearance but not oxygenation. Increase in expiratory time (choice D) increases the CO2 clearance and maybe helpful in patients with significant airway resistance (e.g. asthma and COPD). This may however lead to poorer oxygenation due to decreased mean airway pressure. Decrease in inspiratory time (choice E) would lead to a lower mean airway pressure and possibly worse oxygenation.Answer: CMaung A and Kaplan L . Waveform analysis during mechanical ventilation. Curr Probl Surg. 2013; 50(10): 438–446 PMID: 24156841.

11 A 52‐year‐old man is 6 days status‐post orthotopic liver transplantation and is evaluated by the rapid response team on the general floor for acute hypercarbic and hypoxemic respiratory failure as well as fever (T = 101.8° F) and hyponatremia (Na = 128 mEq/L). Which of the following modalities is the most appropriate for acute, pre‐ICU management?Diuretic administrationOral endotracheal intubationHigh‐flow nasal cannula (HFNC)Full face‐mask BiPAPNasal mask CPAPThis patient demonstrates acute respiratory failure in the setting of presumed volume overload. However, diuretic therapy will require some time to clear excess fluid in order to support oxygenation and CO2 clearance. HFNC therapy and CPAP are much better at supporting oxygenation than CO2 clearance ‐ and the patient requires both. BiPAP may work but is less effective at immediate rescue in a patient who is anticipated to need higher PEEP, and a longer inspiratory time to support an increased mean airway pressure to correct hypoxemia. Also, BiPAP does not allow one to precisely control minute ventilation as does oral endotracheal intubation and mechanical ventilation regardless of patient location. This patient is expected to have an elevated CO2 production based on fever and will therefore have a higher than usual minute ventilation requirement that is able to be met much better with invasive mechanical ventilation than with a non‐invasive modality.Answer: BMoore S, Weiss B, Pascual JL, et al. Management of acute respiratory failure in the patient with sepsis or septic shock. Surg Infect. 2018; 19(2): 191–201; https://doi.org/10.1089/sur.2017.297.

12 A 43‐year‐old woman is involved in a MVC. She sustains a grade 3 splenic laceration and flail chest with multiple rib fractures on the left side (3–9). She requires oral endotracheal intubation for acute respiratory distress. Which of the following management approaches is likely to result in the shortest duration of mechanical ventilation?Paravertebral blocksMulti‐modal analgesics Liberation to helmet CPAPEpidural analgesic infusionAcute rib‐fracture fixationWhile analgesics aid in managing pain, they do not restore thoracic cage stability. Furthermore, fracture stability also reduces pain. Only acute rib‐fracture fixation accomplishes both goals. After fixation, liberation to helmet CPAP may be helpful in maintaining alveolar recruitment after general anesthesia and reducing work of breathing while in the PACU or SICU in the immediate peri‐operative period.Answer: EChoi J, Gomez GI, Kaghazchi A, et al. Surgical stabilization of rib fracture to mitigate pulmonary complication and mortality: a systematic review and bayesian meta‐analysis. J Am Coll Surg. 2020. DOI:https://doi.org/10.1016/j.jamcollsurg.2020.10.022

13 During a disaster or pandemic when crisis standards have been activated, which of the following describes the best approach to allocating scarce resources such as ICU beds and invasive mechanical ventilators?First‐come‐first‐servedYoungest patients firstMaximum lives savedHighest SOFA score firstBedside clinician decisionFirst‐come‐first‐served is the approach when acute healthcare facilities operate using conventional standards and is in large part a libertarian approach. Age‐based schemes use a life‐cycle approach and may engender an element of ageism that does not incorporate the influence of underlying comorbid conditions such as malignancy. The highest SOFA score (higher score denotes greater organ failure) is an egalitarian approach and is characteristically inappropriate during crisis standards as those with the greatest illness will, in general, consume the greatest resources, including elements already in short supply and in a patient population with a reduced likelihood of survival. Maximum lives saved (greatest good for the greatest number) is the preferred approach as it is utilitarian and may be equitably supported by decision‐making by a triage committee that is not directly involved in patient care.Answer: CMaves RC, Downar J, Dichter JR, et al. Triage of scarce critical care resources in COVID‐19: an implementation guide for regional allocation an expert panel report of the Task Force for Mass Critical Care and the American College of Chest Physicians. Chest. 2020. https://doi.org/10.1016/j.chest.2020.03.063

14 A 62‐year‐old clinically severely obese patient (BMI = 42) presents with presumed moderate COVID‐19 pneumonia. CXR has ground glass opacities in mid ‐ and lower lung fields. Room air ABG = pH 7.32, PaC02 38, Pa02 64; lactic acid = 3.2 mmol/L. Which of the following is the next most appropriate step in therapy after obtaining cultures, initiating fluid resuscitation, and administering empiric antibiotics as well as dexamethasone?Initiate self‐driven prone position therapyImmediate oral endotracheal intubationBegin helmet CPAP therapyNon‐contrast enhanced chest CT scanNebulized hypertonic saline and albuterolThis patient has a body habitus that potentially precludes self‐prone position therapy due to the risk of vomiting and aspiration. There is no acute need for airway control as CO2 clearance is well‐maintained and oxygenation may be addressed using other modalities. Non‐invasive approaches also avoid iatrogenic ventilator‐induced lung injury and ventilator‐associated infection. A non‐contrast enhanced CT scan of the chest may be useful from a diagnostic standpoint but will not help address the current clinical condition. Initial management of oxygenation using a continuous pressure but variable flow approach that also allows the patient to be seated upright is an ideal initial approach. There is heightened concern with nebulized medications in COVID‐19 patients for possibly nosocomial transmission. This patient also does not have an indication for nebulized hypertonic saline at this time as hypertonic saline therapy in combination with albuterol is ideal for reducing the viscoelasticity of thick secretions but is not indicated to manage ground glass opacities.Answer: CGaulton TG, Bellani G, Foti G, et al. Early clinical experience in using helmet continuous positive airway pressure and high‐flow nasal cannula in overweight and obese patients with acute hypoxemic respiratory failure from coronavirus disease 2019. Critical Care Explorations. 2020; 2(9). doi: 10.1097/CCE.0000000000000216

15 In patients undergoing invasive mechanical ventilation, which of the following most strongly corelates with the risk of ventilator‐induced lung injury?Peak airway pressure = 35 cm H2O pressureMean airway pressure = 14 cm H2O pressure Positive End Expiratory Pressure = 12 cm H2O pressurePlateau pressure = 28 cm H2O pressureDriving pressure = 20 cm H2O pressureVentilator‐induced lung injury (VILI) is often described as the impact of asymmetric distribution of a volume of gas into compliant alveoli that occurs over a short period of time and induces structural damage. That structural damage incites inflammation and leads to a process known as biotrauma that reflects activation of cytokines, the initiation of neutrophil trafficking, and the degradation of surfactant. As a result, alveolar interdependency is deranged, and regional time constants are lengthened. High tidal volumes are associated with these events as noted in the initial ARDSNet trials that led to the current common low tidal volume ventilation approach for ARDS. While high peak airway pressures may occur with inappropriate ventilator prescriptions, a peak pressure of 35 cm H20 does not strongly correlate with VILI. Mean pressures of 14 cm H2O may occur as the ventilator is adjusted to address hypoxemia, and a plateau pressure < 30 cm H2O is an appropriate target.PEEP of 12 is an acceptable pressure, is not associated with VILI and instead may define a patient population with a lung that is difficult to recruit. Driving pressures (plateau minus PEEP) > 15 appear strongly correlated with VILI and may be related to intra‐tidal shear as well with rapid changes in pressure with breath cycling.Answer: EWilliams EC, Motta‐Ribeiro GC and Vidal Melo MF Driving pressure and transpulmonary pressure: how do we guide safe mechanical ventilation?. Anesthesiol. 2019; 131: 155–163 doi: https://doi.org/10.1097/ALN.0000000000002731.

16 The square waveform for gas delivery during volume cycled ventilation is anticipated to be of benefit in which of the following patient populations?Isolated traumatic brain injuryBlast injury pulmonary contusionsAbdominal compartment syndromeDamage control open abdomenClinically severe obesityBlast injury‐related pulmonary contusions lead to alveolar damage and collapse. Such patients benefit from alveolar recruitment to reduce hypoxic pulmonary vasoconstriction. A decelerating waveform – compared to a square waveform at the same peak flow rate for gas delivery – results in a longer inspiratory time and better matching of regional time constants as well as a lower peak airway pressure and a higher mean airway pressure. A higher mean airway pressure supports oxygenation. Since high peak airway pressures are a problem in those with the ACS, a square waveform is not ideal as it too is associated with higher peak pressures. With an open abdomen, using a decelerating waveform helps recruit the maximum number of alveolar units in preparation for abdominal wall closure and an increase in intra‐abdominal pressure. A square waveform is associated with decreased recruitment by comparison. Since there are no valves between the brain and the right atrium, cerebral venous drainage is enhanced with more time at a lower intra‐thoracic pressure – a direct consequence of a shorter inspiratory and a longer expiratory time, both of which are characteristic of the square waveform gas delivery profile. Those with clinically severe obesity demonstrate increased intra‐abdominal pressure at baseline and therefore benefit from the use of a decelerating waveform to help reduce peak airway pressure and support postero‐basal pulmonary recruitment as well.Answer: AHamahata NT, Sato R and Daoud EG Go with the flow‐clinical importance of flow curves during mechanical ventilation: a narrative review. Can J Respir Ther. 2020; 56: 11–20 doi: 10.29390/cjrt‐2020‐002. PMID: 32844110; PMCID: PMC7427988.

17 A surgical ICU’s data indicates that the mean length of time spent on mechanical ventilation is longer than desired. Which of the following is most likely to reduce the duration of mechanical ventilation for their patient population?Emplacing a night‐time intensivistUsing the ICU liberation bundleDaily bedside physical therapyEliminating benzodiazepine useEliminating opioid analgesic useThe goal of reducing the time spent on mechanical ventilation is a worthy goal for every ICU. This benefits from a multi‐professional approach to care that empowers team members to work together across every shift to facilitate liberation from mechanical ventilation. Reduced time to liberation as well as increased ventilator free days are not associated with a night‐time intensivist, physical therapy, nor eliminating a specific class of therapeutics. Both of those parameters are tightly tied to the A through F ICU liberation bundle that reduces ICU length of stay, duration of mechanical ventilation, delirium and coma, while engaging and empowering family members to participate in care and care planning. An important consequence of using the bundle is that patients often report more pain as sedating agents – including analgesics – are reduced to engage them in their own plan of care. This occurrence supports a multi‐modal non‐opioid approach to analgesia that helps address the opioid crisis as well. While it is unrealistic to eliminate opioid analgesic use, especially in the post‐operative or post‐injury patient, the use of opioids as the sole agent for sedation may be entirely abandoned in favor of other agents that target sedation as needed.Answer: BPun BT, Balas MC, Barnes‐Daly MA, et al. Caring for critically ill patients with the ABCDEF bundle: results of the ICU liberation collaborative in over 15,000 adults. Critical Care Medicine. 2019; 47(1): 3. doi: 10.1097/CCM.0000000000003482.

18 The use of flexible bronchoscopy and bronchoalveolar lavage for the invasive diagnosis of pneumonia in the critically ill is associated with which of the following benefits?Reduced FIO2 requirementImproved cardiac outputIncreased anti‐fungal agent useReduced antibiotic durationIncreased multi‐drug resistanceFlexible bronchoscopy and bronchoalveolar lavage (BAL) to invasively identify pneumonia confers the anticipated benefit of having confidence in the diagnosis of “no pneumonia”. The lack of an infecting organism supports termination of empiric antibiotic therapy, reduced driving pressure for resistant organism genesis, and enhances an institutional approach to antibiotic stewardship. This in turn helps drive investigations into alternate explanations for the clinical findings and presentation. Flexible bronchoscopy for relief of lobar collapse from airway obstruction (but not BAL) is associated with reduced FIO2 and improved cardiac output. Anti‐fungal use is not increased by BAL, as those with risk factors for fungal pneumonia – and who have a compatible presentation – are generally empirically treated for fungal pathogens; guidelines to direct anti‐fungal use have been articulated by a variety of organizations including the Infectious Disease Society of America.Answer: DRanzani OT, Senussi T, Idone F, et al. Invasive and non‐invasive diagnostic approaches for microbiological diagnosis of hospital‐acquired pneumonia. Critical Care. 2019; 23(1): 51. https://doi.org/10.1186/s13054‐019‐2348‐2

19 A 38‐year‐old patient with chest and abdominal blunt injury after a MVC has progressive ARDS and is managed using epinephrine and vasopressin infusions as well as glucocorticoid therapy for critical illness‐related cortico‐adrenal insufficiency. He has ongoing hypoxemic acute respiratory failure. Which of the following best supports pursuing cannulation for veno‐venous extracorporeal membrane oxygenation (VV‐ECMO)?PaO2/FIO2 ratio of 135 on a FIO2 of 0.7Stabilized thoracic spine fracturesInability to undergo prone position therapyIncreasing epinephrine dose for MAP supportEjection fraction of 30%VV‐ECMO provides oxygenation support and clears CO2. It does not support cardiac performance. Therefore, an increasing need for vasopressor infusion or depressed ejection fraction does not drive one towards VV‐ECMO but would instead favor veno‐arterial ECMO. A PaO2/FIO2 ratio of 135 on an FIO2 of 0.7 indicates additional opportunity for oxygenation management such that ECMO is not required. Stabilized spine fractures should not generally influence the decision for VV ECMO. However, the inability to pursue standard care such as prone position therapy supports pursuing cannulation as rescue therapy, particularly in those with an escalating O2 requirement or the progressive inability to clear CO2.Answer: CMenk M, Estenssoro E, Sahetya SK, et al. Current and evolving standards of care for patients with ARDS. Intensive Care Med. 2020; 46:2157–2167. https://doi.org/10.1007/s00134‐020‐06299‐6

20 A patient with COPD has undergone an uneventful right hepatectomy for malignancy and arrives to the SICU intubated and mechanically ventilated. Settings are AC RR 12 breaths/minute, tidal volume 650 mL, FIO2 50%, PEEP 5, decelerating waveform, peak flow rate = 60 LPM; Pawpeak = 32; Pawmean = 8; SpO2 = 96%; ETCO2 = 42 torr and he is breathing with the ventilator. VS: T = 100.2°F, HR = 84 beats/minute, and BP = 132/74 mm Hg. One hour later, you are called for HR = 132 beats/minute, BP = 82/46, T = 98.9°F, SpO2 = 84%, ETCO2 = 58; RR = 20 breaths/minute. The most appropriate initial intervention is which of the following?Return to the OR for hemorrhage controlStart a continuous epinephrine infusionTherapeutic cardioversion for atrial fibrillationDisconnect the patient from the ventilatorEmergency pleural decompression Patients with COPD often undergo surgery for unrelated conditions such as the patient in this question. Given that COPD eases gas entry but renders gas exit more difficult, such patients are at increased risk of gas trapping and increased intra‐thoracic pressure. This is a particular risk on volume cycled ventilation when the patient’s respiratory rate increases (anesthesia emergence, anxiety, pain, delirium, etc.) and their coupled expiratory time decreases. The physiology resembles tension pneumothorax in that venous return is compromised leading to decreased cardiac performance, but no pleural space occupying lesion is present. Instead, pulmonary overdistension is the issue in this unique patient population. Tachycardia and hypotension as well as hypoxemia and hypercarbia ensue, the former especially related to decreased pulmonary flow. Therefore, the initial therapy of choice is to disconnect from the ventilator and allow for exhalation.Answer: DMosier JM and Hypes CD Mechanical ventilation strategies for the patient with severe obstructive lung disease. Emerg Med Clin. 2019; 37(3): 445–58. DOI: https://doi.org/10.1016/j.emc.2019.04.003