Page 282 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

186 PART 2: General Management of the Patient

• Casey AL, Mermel LA, Nightingale P, et al. Antimicrobial central the measured Ppw exceeds the pulmonary artery diastolic pressure
venous catheters in adults: a systemic review and meta-analysis.
Lancet Infect Dis. 2008;8:763-776. (Ppad). With pulmonary hypertension, partial wedging may be pres-
ent despite a positive Ppad-Ppw gradient and should be suspected
• Chaiyakunapruk N, Veentra DL, Lipsky BA, et al. Chlorhexidine when the latter markedly narrows in comparison with previous values.
versus povidone-iodine solution for vascular catheter site care: a • Positive end-expiratory pressure (PEEP) and active expiration
meta-analysis. Ann Intern Med. 2002;136:792-801. cause the measured Ppw and Pra to overestimate transmural pres-
• Hemmelgarn BR, Moist LM, Lok CE, et al. Prevention of dialysis cath- sure, with active expiration resulting in greater errors. Simultaneous
eter malfunction with recombinant tissue plasminogen activator. recording of bladder pressure and Pra (or Ppw) can be helpful for
N Engl J Med. 2011;364(4):303-312. assessing the impact of active expiration on transmural pressure.
• Khouli H, Jahnes K, Shapiro J, et al. Performance of medical • Hemodynamic waveforms may be helpful in the diagnosis of certain
residents in sterile techniques during central vein catheterization: cardiac disorders: Large v waves in the Ppw tracing are seen in acute
randomized trial of efficacy of simulation-based training. Chest. mitral regurgitation, but can also occur with hypervolemia. Cardiac
2011;139(1): 80-87. tamponade is characterized by equalization of the Ppw and right
• Merrer J, DeJonghe B, Golliot F, et al. Complications of femoral atrial pressure (Pra) with blunting of the y descent. Tricuspid regur-
and subclavian venous catheterization in critically ill patients: a gitation often produces a broad c-v wave and a prominent y descent.
randomized controlled trial. JAMA. 2001;286:700-707. Inspection of the Pra during narrow complex tachycardias may be
• O’Grady NP, Alexander M, Dellinger EP, et al. Guidelines for the helpful if flutter waves or regular cannon a waves (supraventricular
prevention of catheter-related infections. Morb Mortal Wkly Rep. reentrant tachycardia) are seen.
2002;51(RR1-10):1-29. • Neither the Pra nor the Ppw are reliable predictors of fluid responsive-
• Pronovost P, Goeschel C, Colantuoni E, et al. Sustaining reduc- ness. However, failure of the Pra to fall with spontaneous inspiration
tions in catheter related blood stream infections in Michigan indicates that the patient is unlikely to benefit from a fluid challenge.
intensive care units: observational study. BMJ. 2010;340:1-6.
• Pronovost P, Needham D, Berenholtz S, et al. An intervention
to decrease catheter-related blood stream infections in the ICU. For several decades, decisions regarding therapy with fluids and vasoac-
NEJM. 2006;355:2725-2732. tive drugs in the ICU have relied on intravascular pressures obtained
• Schmidt GA, Kory P. Ultrasound-guided central venous catheter with either a central venous catheter (CVC) or pulmonary artery cath-
insertion: teaching and learning. Intensive Care Med. 2014;40:111-113. eter (PAC). Despite this widespread use, the value of invasive hemody-
1-4
• Timsit J-F, Bouadma L, Mimoz O, et al. Jugular versus femoral namic monitoring is controversial. Randomized studies of the PAC in
a variety of clinical settings have found neither a positive nor negative
short-term catheterization and risk of infection in intensive care impact on mortality. 5-11 To some, these results provide compelling evi-
unit patients: causal analysis of two randomized trials. Am J Respir dence against continued use of the PAC. Others have argued that they
1,2
Crit Care Med. 2013;188(10):1232-1239. establish the safety of the PAC, and that an impact on mortality is an
• Timsit JF, Schwebel C, Bouadma L, et al. Chlorhexidine- unreasonable benchmark for any bedside monitoring device. 12,13 Use
impregnated sponges and less frequent dressing changes for pre- of the CVC for hemodynamic monitoring is also controversial. While
vention of catheter-related infections in critically ill adults. JAMA. guidelines for management of patients with septic shock recommend
2009;301(12):1231-1241. measurement of the central venous pressure (CVP) as a component of
early goal-directed therapy, some have argued that use of the CVP to
14
guide fluid therapy should be abandoned. 3
The increased availability of less invasive tools for bedside hemody-
REFERENCES namic assessment, including point-of-care echocardiography and mini-
Complete references available online at www.mhprofessional.com/hall mally invasive measurement of cardiac output, has clearly reduced the
need for invasive monitoring. 15,16 Nonetheless, we believe that invasive
hemodynamic monitoring can still be useful in managing selected critically
ill patients, especially when noninvasive assessment or empirical therapeu-
tic trials have proven unsuccessful. Implicit in this view is that clinicians
17
CHAPTER Interpretation of should have an in-depth understanding of those aspects of cardiorespira-
tory physiology that form the underpinnings of hemodynamic monitor-
28 Hemodynamic Waveforms ing, and must also be knowledgeable about technical aspects of invasive
James W. Leatherman monitoring, including common pitfalls. Errors in data acquisition and inter-
pretation likely pose a greater risk to patients than catheterization per se.
18,19
John Marini This chapter will focus on use of pressure waveforms obtained from
the PAC and CVC in the management of critically ill patients. Areas of
emphasis will include (1) fundamental principles of hemodynamic data
KEY POINTS acquisition, including common mistakes in interpretation of intravascular
• Randomized trials have found that use of a pulmonary artery cath- pressures, (2) analysis of hemodynamic waveforms in normal individuals
eter did not influence the mortality of critically ill patients with and in various cardiovascular disorders, (3) impact of changes in intratho-
shock or acute respiratory distress syndrome. racic pressure on interpretation of cardiac filling pressures, and (4) assess-
• Although measurement of right atrial (central venous) pressure (Pra) ment of the adequacy of preload and prediction of fluid responsiveness.
is a central component of early goal-directed therapy for septic shock,
use of the Pra to guide hemodynamic management is controversial. PRESSURE MONITORING SYSTEM
• Partial wedging can lead to marked overestimation of the pulmo- Essential system components required for pressure monitoring include
nary artery wedge pressure (Ppw) and should be suspected when a fluid-filled catheter and connecting tubing, a transducer that converts
mechanical energy from the fluid-filled tubing into an electrical signal,

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