and compliance to pulmonary artery wedge pressure during submaximal exercise in healthy older adults. J Physiol. 2016; 594(12):3307–15. doi: 10.1113/JP271788. Epub 2016 Mar 24. PMID: 26880530; PMCID: PMC4824842.17 A 43‐year‐old woman was assaulted with a baseball bat. She proceeds to the OR for laparotomy and splenectomy. She remains intubated, and postoperatively in the ICU, the chief resident places a right internal jugular vein central line to transduce CVP to assist in guiding resuscitation. Which of the following is true regarding the usefulness of CVP in predicting a response to fluid administration?CVP < 9 is predictive of an increase in stroke volume following IV fluid administration.CVP may be useful in predicting fluid responsiveness at extremes (e.g., <6 mm Hg or > 15 mm Hg) but is not reliable for prediction of fluid responsiveness in middle ranges.An increase in CVP is indicative of an increase in cardiac output.CVP should be maintained as high as possible.CVP cannot adequately estimate the risk of extra‐thoracic organ congestion with fluid administration.Due to wide patient variability in Frank‐Starling curves, using a single CVP number as a target for achieving increased SV is unrealistic, and has been shown to have limited clinical value in multiple studies (Choice A). However, using extremes of CVP may be useful to guide IVF administration. Eskesen et al. showed that significantly more patients with a CVP < 6 mm Hg responded to IVF than patients with a CVP > 15 mm Hg (Choice B). RA filling is dependent on a pressure gradient between mean systemic pressure and CVP, suggesting that as CVP rises, the cardiac output may actually decline (Choice C). Keeping CVP as low as possible while still allowing for adequate perfusion is associated with improved outcomes. In patients with ARDS, it has been shown that fewer days of mechanical ventilation were achieved when CVP was maintained as low as possible while still allowing adequate tissue perfusion following initial hemodynamic stabilization (Choice D). AKI has been shown to correlate with increased CVP in patients with CHF or sepsis. In patients undergoing hepatic operations, limiting CVP was associated with less risk of bleeding and improved outcomes. Of note, pulmonary edema does not appear to be linked to CVP (Choice E).Answer: BDe Backer D, Vincent JL. Should we measure the central venous pressure to guide fluid management? Ten answers to 10 questions. Crit Care. 2018; 22(1):43. Published 2018 Feb 23. doi:10.1186/s13054‐018‐1959‐3.Monnet X, Marik PE, Teboul JL. Prediction of fluid responsiveness: an update. Ann Intensive Care. 2016; 6(1):111. doi:10.1186/s13613‐016‐0216‐7.
18 In the above patient, at what point during the respiratory cycle should CVP be measured in order to be most accurate?End‐inspirationEnd‐expirationDuring an inspiratory holdOnly when PEEP is set at zeroCVP can reliably be measured at any point during the respiratory cycle.Intravascular pressure is the pressure of the blood inside the SVC measured at bedside, and is the pressure within the vessel lumen relative to the atmospheric pressure. Transmural pressure is the difference between the intravascular and intrathoracic pressures. As the intrathoracic pressure changes during the respiratory cycle, it will exert an effect on the measured intravascular pressure, and therefore the only time a truly accurate intravascular pressure can be measured is when the intrathoracic pressure is equal to atmospheric pressure. This only occurs at end‐expiration.Answer: BMalbrain ML, De Waele JJ, De Keulenaer BL. What every ICU clinician needs to know about the cardiovascular effects caused by abdominal hypertension. Anaesthesiol Intensive Ther. 2015; 47(4):388–99. doi: 10.5603/AIT.a2015.0028. Epub 2015 May 14. PMID: 25973663.
19 An 86‐year‐old man with a history of CHF (last echocardiogram was performed 8 years ago, EF of 35%), atrial fibrillation, and pulmonary fibrosis is in your ICU following a left nephrectomy for renal cell carcinoma. On postoperative day 3, he has increased difficulty breathing and requires intubation. Post‐intubation chest x‐ray shows diffuse infiltrates and moderate pulmonary edema bilaterally. In order to ascertain whether his pulmonary edema is due to his heart disease, you utilize the portable ultrasound machine. Which of the following findings on bedside ultrasonography can reliably rule out pulmonary edema?Lung pulseLung slidingA‐line pattern and absence of B‐linesA single B‐line in one rib space>3 B‐lines on the same rib spaceBedside ultrasonography is a noninvasive, readily available, and cost‐effective method for real‐time diagnosis in the ICU patient, and all critical care physicians should be comfortable and competent with routine use. Lung ultrasonography has greater diagnostic capability than physical exam, and can outperform plain film radiography in many instances. When evaluating for pneumothorax, the interface between the parietal and visceral pleura is seen between adjacent ribs; during a respiratory cycle, motion is seen if the two pleuras are in contact with each other (known as lung sliding), ruling out a pneumothorax at that location. Similarly, the pleural interface will show motion with cardiac motion, known as lung pulse. When evaluating the lung parenchyma itself, A‐lines are seen in normal tissue, which are transversely oriented repeating reverberation artifacts with equal distances between them and the pleural line. B‐lines, in contrast, are longitudinally oriented comet‐tail‐like lines that typically indicate pathology. In normal tissue, it is common to have occasional B‐lines over the lower lateral chest and occasionally, single B‐lines can be seen elsewhere; however, more than 3 B‐lines in a single view is abnormal, reflecting an interstitial or alveolar irregularity. This can be due to both cardiogenic and non‐cardiogenic causes (such as ARDS or interstitial lung disease). When a cardiogenic cause is present, the B‐lines are typically diffuse due to a regular, smooth pleural surface. When a non‐cardiogenic cause is present, the B‐lines are nonhomogeneous with small subpleural areas of consolidation, owing to an irregular pleural surface. The presence of an A‐line indicates that the pulmonary artery occlusion pressure is < 18 mm Hg, and can thus rule out cardiogenic pulmonary edema.Answer: CKoenig SJ, Narasimhan M, Mayo PH. Thoracic ultrasonography for the pulmonary specialist. Chest. 2011; 140(5):1332–41. doi: https://doi.org/10.1378/chest.11‐0348. PMID: 22045878.
7 Airway and Perioperative Management
Jared Sheppard, MD, Jeffrey P. Coughenour, MD, and Stephen L. Barnes, MD
Division of Acute Care Surgery, Department of Surgery, University of Missouri, Columbia, MO, USA
1 A 57‐year‐old man with a history of hypertension, hyperlipidemia, obstructive sleep apnea, and obesity (BMI 45 kg/m2) is in your step down unit following a motor vehicle crash (MVC) 3 days ago, in which he sustained multiple bilateral rib fractures with associated pulmonary contusions. Initially, he required only nasal cannula to maintain a SpO2 of 92%, but now requires heated high‐flow nasal cannula at 70 L/min and 100% FiO2, with a saturation of 86%. The decision is made to intubate. After giving RSI, you perform bag/mask ventilation to preoxygenate; however, you note significant difficulty with increasing his SpO2. Which one of the following predicts difficulty of bag/mask ventilation?Age > 40 yearsBMI > 35 kg/m2Neck circumference > 30 cmFacial hairDenturesEffective oxygenation and ventilation, while important, may be impossible in certain patient populations. While there is some dispute as to which factors are most predictive of bag‐mask ventilation failure, Cattano et al. found the following to predict difficulty in BVM in the general surgical population: Age greater than 50 years old, BMI greater than 35, neck circumference greater than 40 cm, history of obstructive sleep apnea, history of difficult intubation, facial hair, and perceived short neck.Answer: BSaghaei M, Shetabi H, Golparvar M. Predicting efficiency of post‐induction mask ventilation based on demographic and anatomical factors. Adv Biomed Res. 2012; 1:10. doi: 10.4103/2277‐9175.96056. Epub 2012 May 11. PMID: 23210069; PMCID: PMC3507007.Cattano D, Killoran PV, Cai C, Katsiampoura AD, Corso RM, Hagberg CA. Difficult mask ventilation in general surgical population: observation of risk factors and predictors. F1000Res. 2014; 3:204. Published 2014 Aug 27. doi: 10.12688/f1000research.5131.1.
2 A
