VK, Al‐Moustadi W, Nates W, Kumar B. Cardiac output monitoring: Technology and choice. Ann Card Anaesth. 2019; 22(1):6–17. doi: 10.4103/aca.ACA_41_18. PMID: 30648673; PMCID: PMC6350438.13 A 73‐year‐old woman undergoes a Roux‐en‐Y reconstruction for a perforated duodenal ulcer. She has an extended ICU stay complicated by ARDS and acute renal failure. A right internal jugular triple‐lumen dialysis catheter is placed for CRRT. On hospital day 14, you notice erythema surrounding her right internal jugular triple‐lumen central line. She also has had a rising leukocytosis and is febrile to 38.9 °C. Which of the following measures would have potentially helped to prevent this complication?Placement of the central line in her right femoral vein.Use of ultrasound during placement (assuming you placed the line without ultrasonographic guidance, and achieved access on the first stick).Placement of a single lumen catheter vs a triple lumen catheter.Use of a chlorhexidine‐impregnated dressing.Securement of the catheter with a suture rather than adhesive to prevent mobility of the line.Central line‐associated blood stream infections (CLABSI) are a major risk of an indwelling central venous access, and major progress has been made with systemic guidelines implemented in most hospital systems to reduce their incidence. Placement of central lines in the subclavian vein has shown decreased rates of infection; however, other locations may be necessary for placement based on the patient's anatomy or injury pattern (Choice A). An increased number of passes before successful cannulation of the vein has been associated with increased risk of infection, and for this reason, ultrasound is recommended to achieve first‐attempt vascular access (Choice B). In addition, ultrasound in real time use during the procedure has become the standard of care to decrease complications. While theoretical risk of infection increases with the number of lumens in a central line, this has not been borne out in literature (Choice C). Chlorhexidine‐impregnated dressings significantly decrease the rate of infection, as do daily chlorhexidine baths of the line. While using a suture to secure a central line provides a more stable anchor, administering another wound (albeit small) to the skin from the needle also increases the risk of surrounding infection (Choice E).Answer: DBell T, O'Grady NP. Prevention of central line‐associated bloodstream infections. Infect Dis Clin North Am. 2017; 31(3):551–9. doi: 10.1016/j.idc.2017.05.007. Epub 2017 Jul 5. PMID: 28687213; PMCID: PMC5666696.Parienti JJ, Mongardon N, Mégarbane B, Mira JP, Kalfon P, Gros A, Marqué S, Thuong M, Pottier V, Ramakers M, Savary B, Seguin A, Valette X, Terzi N, Sauneuf B, Cattoir V, Mermel LA, du Cheyron D ; 3SITES Study Group. Intravascular complications of central venous catheterization by insertion site. N Engl J Med. 2015; 373(13):1220–9. doi: 10.1056/NEJMoa1500964. PMID: 26398070.
14 In the above patient, which organism is most likely to be identified on a culture of the central line?E. coliCoagulase‐negative staphylococci (CoNS)E. faecalisPseudomonasClostridiumPathogen distribution and antimicrobial resistance, as reported to the National Healthcare Safety Network from 2011‐2014 showed that among central line‐associated blood stream infection (CLABSI), the most common causative pathogens were (in order): coagulase‐negative staphylococci (20.9%), staphylococcus aureus (18.1%), Klebsiella spp (9.4%), Enterococcus faecalis (9.1%), Escherichia coli (7.4%), Enterobacter spp (5.5%), and Pseudomonas (3.4%). Multiple strategies have been studied and implemented to reduce the incidence of CLABSI, including antiseptic and antibiotic coating of the central lines; antiseptic/antibiotic impregnated catheters have been shown to result in a 2% absolute risk reduction of CLABSI. Another pillar of CLABSI prevention is catheter removal as soon as the catheter is no longer needed, as well as catheter exchange when there is clinical concern of bloodstream infection. Prophylactic or scheduled catheter exchange versus removal when clinically indicated showed no difference in CLABSI rates, although procedure‐related complications of catheter placement were more frequent in patients undergoing scheduled exchange.Answer: BWeiner‐Lastinger LM, Abner S, Edwards JR, Kallen AJ, Karlsson M, Magill SS, Pollock D, See I, Soe MM, Walters MS, Dudeck MA. Antimicrobial‐resistant pathogens associated with adult healthcare‐associated infections: Summary of data reported to the National Healthcare Safety Network, 2015‐2017. Infect Control Hosp Epidemiol. 2020; 41(1):1–18. doi: 10.1017/ice.2019.296. Epub 2019 Nov 26. PMID: 31767041.Bell T, O'Grady NP. Prevention of central line‐associated bloodstream infections. Infect Dis Clin North Am. 2017; 31(3):551–9. doi: 10.1016/j.idc.2017.05.007. Epub 2017 Jul 5. PMID: 28687213; PMCID: PMC5666696.15 and 16:A 78‐year‐old stunt pilot is involved in a training accident while attempting to land his plane. He sustains a large right subdural hematoma, right 1–9th rib fractures, left 2–7th rib fractures, bilateral pulmonary contusions, and a grade III liver laceration. Once in the ICU, a pulmonary artery catheter is placed, revealing the following values: MAP 60 mm Hg, PAP 40/20 mm Hg, PCWP 18 mm Hg, CVP 10 mm Hg, CO 4 L/min.
15 In regards to determining his pulmonary vascular resistance (PVR):It is a measurement obtained directly from the pulmonary artery catheter.It can be calculated by (MAP – PCWP/CO) × 80.It can be calculated by (mean PAP – LAP/CO) × 80.It can be calculated by (LAP – PCWP/CO) × 80.It can be calculated by (RAP – PCWP/CO) × 80. 16
16 The systemic vascular resistance (in dyne/sec/cm−5) of the patient in the above question is:840 dynes/seconds/cm−51000 dynes/seconds/cm−51300 dynes/seconds/cm−51900 dynes/seconds/cm−52200 dynes/seconds/cm−5A major component of afterload is the resistance to ventricular outflow in the aorta and large, proximal arteries. The total hydraulic force that opposes pulsation flow is known as impedance. This force is a combination of 2 forces: a force that opposes the rate of change in flow (compliance), and a force that opposes mean or volumetric flow (resistance). Vascular resistance is derived by assuming that hydraulic resistance is analogous to electrical resistance. Ohm's law predicts that resistance to flow of an electric current (R) is directly proportional to the voltage drop across a circuit (V), and inversely proportional to the flow of current (I): R = V/I. This relationship is applied to the systemic and pulmonary circulations, creating the following derivations: Systemic vascular resistance (SVR) reflects changes in the arterioles, which can affect emptying of the left ventricle. For example, if the blood vessels tighten or constrict, SVR increases, resulting in diminished ventricular compliance, reduced stroke volume, and ultimately a drop in cardiac output. The heart must work harder against an elevated SVR to push the blood forward, increasing myocardial oxygen demand. If blood vessels dilate or relax, SVR decreases, reducing the amount of left ventricular force needed to open the aortic valve. This may result in more efficient pumping action of the left ventricle and an increased cardiac output. If the SVR is elevated, a vasodilator such as nitroglycerine or nitroprusside may be used to treat hypertension. Diuretics may be added if preload is high. If the SVR is diminished, a vasoconstrictor such as norepinephrine, dopamine, vasopressin, or neosynephrine may be used to treat hypotension. Fluids may be administered if preload is low. Pulmonary vascular resistance (PVR) is similar to SVR except it refers to the arteries that supply blood to the lungs. If the pressure in the pulmonary vasculature is high, the right ventricle must work harder to move the blood forward past the pulmonic valve. Over time, this may cause dilation of the right ventricle, and require additional volume to meet the preload needs of the left ventricle. PVR can be calculated by subtracting the left atrial pressure (LAP) from the mean pulmonary artery pressure (PAP), divided by the cardiac output (CO) and multiplied by 80. To obtain the LAP pressure, a pulmonary artery catheter (PAC) is needed to perform a pulmonary artery occlusion pressure (PAOP), also known as pulmonary artery wedge pressure (PAWP). Normal PVR is 100–200 dynes/sec/cm−5.So, for question 15, PVR is equal to the difference between the PAP and the LAP divided by the cardiac output.In question 16, the SVR is calculated by dividing the difference between the MAP and the CVP by the cardiac output and multiplying by the constant 80, such that: [(60 − 10)/4] × 80 = 1000 dynes/seconds/cm−5.Answer: 15 – C, 16 – BKwan WC, Shavelle DM, Laughrun DR. Pulmonary vascular resistance index: Getting the units right and why it matters. Clin Cardiol. 2019; 42(3):334–8. doi: 10.1002/clc.23151. Epub 2019 Feb 27. PMID: 30614019; PMCID: PMC6712411.Wright
