more predictive than in non‐intubated patients, there was not sufficient correlation among studies to show that IVC diameter throughout the respiratory cycle was a reliable method of predicting volume responsiveness.Answer: ELong E, Oakley E, Duke T, Babl FE ; Paediatric Research in Emergency Departments International Collaborative (PREDICT). Does respiratory variation in inferior vena cava diameter predict fluid responsiveness: A systematic review and meta‐analysis. Shock. 2017; 47(5):550–9.Orso D, Paoli I, Piani T, Cilenti FL, Cristiani L, Guglielmo N. Accuracy of ultrasonographic measurements of inferior vena cava to determine fluid responsiveness: A systematic review and meta‐analysis. J Intensive Care Med. 2020; 35(4):354–363. doi: 10.1177/0885066617752308. Epub 2018 Jan 17. PMID: 29343170.9 You are seeking an additional method to determine fluid responsiveness on the above patient, and one of your colleagues recommends attempting a noninvasive ventilator maneuver. Which of the following ventilator maneuvers can simulate a fluid challenge without actually administering volume? End‐expiratory occlusion (EEO) testDeep inspiratory hold15‐second elevated PEEP holdIncreasing pressure support and decreasing PEEPIncreasing tidal volumeAn end‐expiratory occlusion test is done by increasing intrathoracic pressure during inspiration while on mechanical ventilation. The ventilation is stopped at end‐expiration, at the level of positive end‐expiratory pressure (PEEP). If done long enough, this increase in pressure results in decreased preload to the left ventricle and subsequently a reduced cardiac output. By performing end‐expiratory occlusion (pausing mechanical ventilation at end‐expiration for 15 seconds), the artificially reduced preload is eliminated, and so a preload increase is simulated. If there is significant change in stroke volume on bedside monitoring with inspiratory hold, this predicts that fluid administration would also increase stroke volume. A 2009 study by Monnet et al. evaluated EEO, passive leg raise, and a 500cc fluid bolus administration, and found that an increase in arterial pulse pressure > 5% during EEO was predictive of an increase in CO following volume administration. The other maneuvers listed would all decrease the left‐sided preload and have the opposite effect.Answer: AJalil BA, Cavallazzi R. Predicting fluid responsiveness: A review of literature and a guide for the clinician. Am J Emerg Med. 2018; 36(11):2093–2102. doi: 10.1016/j.ajem.2018.08.037. Epub 2018 Aug 14. PMID: 30122506.Monnet X, Osman D, Ridel C, Lamia B, Richard C, Teboul JL. Predicting volume responsiveness by using the end‐expiratory occlusion in mechanically ventilated intensive care unit patients. Crit Care Med. 2009; 37(3):951–6. doi: 10.1097/CCM.0b013e3181968fe1. PMID: 19237902.
10 A 19‐year‐old man was injured in an MVC. He has a HR of 89 bpm, BP 134/78 mm Hg, SpO2 96%, RR 15 breaths/min, and the EMS crew relates that he was withdrawing to pain in all extremities, but was not opening his eyes or able to make any sounds, even with painful stimuli. A laryngeal mask airway was placed because endotracheal intubation was not successful. You exchange his laryngeal mask airway for an endotracheal tube in order to establish a definitive airway. Which of the following would be unreliable in confirming endotracheal intubation?CapnometryBedside ultrasoundEndotracheal tube foggingFlexible bronchoscopyCapnographyAlthough routinely used, traditional methods for confirming the correct positioning of an endotracheal tube have limited reliability. These include stethoscopic audibility and symmetry of breath sounds and chest rise, direct visualization of the cords, ease of insufflation and recovery of tidal volume, tidal fogging and clearing of the endotracheal tube, palpation of the tube in the larynx, loss of voice, coughing and expulsion of airway secretions (Choice C), expansion of upper chest, and failure of the abdomen to progressively distend during gas delivery. To improve reliability and speed of placement, the physical detection of CO2 during expiration by capnography and capnometry can be used (Choices A, E). CO2 detection and measurement by these methods can occasionally and transiently be misleading. Minimal CO2 is evolved or expelled during shock or circulatory arrest and some CO2 may be liberated initially after esophageal intubation from gas trapped in the gastric pouch. However, this concentration falls rapidly as serial tidal volumes are delivered. When compressed, a large‐capacity squeeze bulb affixed to the endotracheal tube will fail to fill easily if the tube is in the collapsible esophagus. Several studies have also established the efficacy of confirming endotracheal tube placement by direct trans‐tracheal visualization with bedside ultrasound (Choice B). Although not always easily available, flexible bronchoscopy with visualization of the trachea would be confirmatory (Choice D).Answer: CGottlieb M, Holladay D, Peksa GD. Ultrasonography for the confirmation of endotracheal tube intubation: A systematic review and meta‐analysis. Ann Emerg Med. 2018; 72(6):627–36. doi: 10.1016/j.annemergmed.2018.06.024. Epub 2018 Aug 14. PMID: 30119943.Littlewood K, Durbin CG Jr. Evidenced‐based airway management. Respir Care. 2001; 46(12):1392–405; discussion 1406‐7. PMID: 11728299.
11 When inserting a pulmonary artery catheter, as the catheter is advanced from the right atrium into the right ventricle, which of the following pressures being recorded from the catheter changes the most?DiastolicSystolicMeanCentral venous pressureAll change equallyWhen the catheter is inserted via the right internal jugular vein, the balloon is inflated 15 cm from the point of neck entry. From the RIJ approach, the RA is entered at approximately 25 cm, the RV at approximately 30 cm, and the PA at approximately 40 cm; the PCWP can be identified at approximately 45 cm. As a rule of thumb, the catheter tip should not require advancement of more than 20 cm beyond its current position before encountering the next vascular compartment. Coiling within the right ventricle and misdirection of the catheter should be suspected after reaching 45–50 cm and the appropriate PA waveform is not encountered. Fluoroscopy can be a helpful adjunct in difficult cases and is especially worthwhile to consider before attempting an insertion from the femoral site. When advancing the catheter from the RA to the RV, the systolic pressure will climb significantly owing to a functional tricuspid valve. During diastole, the valve is open, allowing for the diastolic pressure to remain the same between the RA and RV.Answer: BWhitener S, Konoske R, Mark JB. Pulmonary artery catheter. Best Pract Res Clin Anaesthesiol 2014; 28(4):323–35. doi: 10.1016/j.bpa.2014.08.003. Epub 2014 Sep 8. PMID: 25480764.Scheeren TWL, Ramsay MAE. New developments in hemodynamic monitoring. J Cardiothorac Vasc Anesth. 2019; 33(Suppl 1):S67–72. doi: 10.1053/j.jvca.2019.03.043. PMID: 31279355.
12 After correctly inserting the pulmonary artery catheter above, you attempt to determine the cardiac output, which is accomplished with the thermodilution principle. The patient with which of the following valvular abnormalities will have a falsely depressed reading?Aortic stenosisAortic regurgitationMitral valve prolapseTricuspid stenosisTricuspid regurgitationThermodilution is an indicator‐dilution method of measuring blood flow. This method is based on the premise that, when an indicator substance is added to circulating blood, the rate of blood flow is inversely proportional to the change in concentration of the indicator over time. This can be accomplished by using a temperature change as an indicator. Using a pulmonary artery catheter, cold fluid is mixed in the right heart chambers and the cooled blood is ejected into the pulmonary artery and flows past the thermistor on the distal end of the catheter. The thermistor records the change in blood temperature over time. This information is sent to an electronic device that records and displays a temperature time curve. The area under the curve is inversely proportional to the rate of blood flow in the pulmonary artery, and this flow is equivalent to the cardiac output. Tricuspid regurgitation causes the cold indicator fluid to be recycled back and forth across the tricuspid valve (Choice E). This produced a prolonged, low‐amplitude thermodilution curve, thus tricuspid regurgitation produces a falsely low thermodilution cardiac output. Aortic regurgitation, aortic stenosis, and mitral prolapse are left‐sided heart abnormalities that can affect cardiac output but will not affect the thermodilutional method (Choices A, B, C). Similarly, tricuspid stenosis will still allow a steady rate of flow across the valve and will not affect thermodilution (Choice D).Answer: EScheeren TWL, Ramsay MAE. New developments in hemodynamic monitoring. J Cardiothorac Vasc Anesth. 2019; 33(Suppl 1):S67–72. doi: 10.1053/j.jvca.2019.03.043.
