PROCEDURE Central Venous/Right Atrial 67 Pressure Monitoring Reba McVay PURPOSE: Central venous/right-atrial pressure monitoring provides information about the patient ’ s intravascular volume status and right-ventricular preload. The central venous pressure (CVP) or the right atrial pressure (RAP) allows for evaluation of right-sided heart hemodynamics and evaluation of patient response to therapy. CVP and right-atrial pressure are used interchangeably. PREREQUISITE NURSING EQUIPMENT KNOWLEDGE • Pressure transducer system, including fl ush solution rec- • Knowledge of the normal anatomy and physiology of the ommended according to institutional standards, a pressure cardiovascular system is needed. bag or device, pressure tubing with transducer, and fl ush • Knowledge of the principles of aseptic technique and device (see Procedure 75 ) infection control is necessary. • Pressure module and cable for interface with the monitor • Knowledge is needed of the principles of hemodynamic • Dual-channel recorder monitoring. • Leveling device (low-intensity laser or carpenter level) • The CVP/RAP represents right-sided heart preload or the • Nonsterile gloves volume of blood found in the right ventricle at the end of • Sterile injectable or noninjectable caps diastole. Additional equipment (to have available depending on patient • CVP/RAP infl uences and is infl uenced by venous return need) includes the following: and cardiac function. Although the CVP/RAP is used as a • Indelible marker measure of changes in the right ventricle, the relationship is not linear because the right ventricle has the ability to PATIENT AND FAMILY EDUCATION expand and alter its compliance, changes in volume can occur with little change in pressure. • Discuss the purpose of the central venous catheter and • The CVP/RAP normally ranges from 2 to 6 mm Hg in the monitoring with both the patient and family. Rationale: adult. This discussion reduces anxiety and includes the patient • The central venous catheter is inserted in a central vein and family in the plan of care. with the tip of the catheter placed in the proximal superior • Explain the patient ’ s expected participation during the vena cava. procedure. Rationale: The explanation encourages patient • Knowledge is needed of the setup, leveling, and zeroing assistance. of the hemodynamic monitoring system (see Procedure 75 ). • Interpretation of RA/CVP waveforms including identifi - PATIENT ASSESSMENT AND cation of a, c, and v waves is important. The a wave PREPARATION refl ects right-atrial contraction. The c wave refl ects closure of the tricuspid valve. The v wave refl ects passive fi lling Patient Assessment of the atria during right-ventricular systole. The CVP/RAP • Determine hemodynamic, cardiovascular, and peripheral measurement is the mean of the a wave. vascular status. Rationale: This assessment provides • CVP/RAP values are useful in evaluating volume status, baseline data. effect of medication therapy (especially medication that • Determine the patient ’ s baseline pulmonary status. If decreases preload), and cardiac function ( Box 67-1 ). the patient is mechanically ventilated, note the type of • Monitoring parameters from the femoral catheter is not support, ventilator mode, and presence or absence of recommended. The catheter is too distant from the right positive end-expiratory pressure (PEEP) or continuous atrium to produce reliable data. positive airway pressure (CPAP). Rationale: The pres- 578 67 Central Venous/Right Atrial Pressure Monitoring 579 cardia, and dry mucous membranes. Rationale: Assess- BOX 67-1 Central Venous Pressure (CVP) ment data should correlate with a decreased CVP/RAP CONDITIONS CAUSING INCREASED CVP value. Elevated intravascular volume • Assess for signs and symptoms of fl uid volume excess. Depressed right-sided cardiac function (RV infarct, RV failure) Signs and symptoms may include dyspnea, abnormal Cardiac tamponade breath sounds (i.e., crackles), S3 heart sound, peripheral Constrictive pericarditis edema, tachycardia, and jugular vein distention. Ratio- Pulmonary hypertension nale: Assessment data should correlate with an increased Chronic left-ventricular failure CVP/RAP value. CONDITIONS CAUSING DECREASED CVP Reduced intravascular volume * Patient Preparation Decreased mean arterial pressure • Verify that the patient is the correct patient using two Venodilation identifi ers. Rationale: Before performing a procedure, the nurse should ensure the correct identifi cation of the patient * Although the measured CVP is low, cardiac function may be depressed, normal, for the intended intervention. or hyperdynamic when there is reduced vascular volume. • Ensure that the patient and family understand teaching. RV, Right ventricular. Answer questions as they arise, and reinforce information as needed. Rationale: Understanding of previously taught information is evaluated and reinforced. ence of mechanical ventilation alters hemodynamic wave- • Place the patient in the supine position with the head forms and pressures. of the bed fl at or elevated up to 45 degrees. Rationale: • Assess for signs and symptoms of fl uid volume defi cit. This positioning prepares the patient for hemodynamic Signs and symptoms may include thirst, oliguria, tachy- monitoring. Procedure for Central Venous/Right-Atrial Pressure Monitoring Steps Rationale Special Considerations 1 . HH 2 . PE 3. Position the patient in the supine Studies have determined that the CVP/RAP may be accurate for position with the head of the bed CVP/RAP is accurate in this patients in the supine position with at 0–45 degrees. (Level B * ) position. 3–5,7,12,14,16,27,28 the head of the bed elevated up to 60 degrees, 5,16 but additional studies are needed to support this. Only one study 13 supports the accuracy of hemodynamic values for patients in the lateral positions; other studies do not. 3,9,12,20,26 The majority of studies support the accuracy of hemodynamic monitoring for patients in the prone position. 1,2,8,11,15,21,25 Two studies demonstrated that prone positioning caused an increase in hemodynamic values. 22,24 4. Level the air-fl uid interface of The phlebostatic axis is at Mark the location of the phlebostatic the monitoring system to the approximately the level of the axis if not already identifi ed. phlebostatic axis (see Procedure atria and should be used as the 75 and Figs. 75-7 and 75-9 ). reference point for the air-fl uid interface. 5. Zero the transducer (see Allows the monitor to use Procedure 75 ). atmospheric pressure as a reference for zero. * Level B: Well-designed, controlled studies with results that consistently support a specifi c action, intervention, or treatment. Procedure continues on following page 580 Unit II Cardiovascular System Procedure for Central Venous/Right-Atrial Pressure Monitoring—Continued Steps Rationale Special Considerations 6. Observe the waveform and Determines whether the system is The square wave test can be perform a dynamic response test damped. This will ensure that performed by activating and (square wave test). the pressure waveform quickly releasing the fast fl ush. components are clearly defi ned. A sharp upstroke should terminate in This aids in accurate measurement. a fl at line at the maximal indicator on the monitor. This should be followed by an immediate rapid downstroke extending below baseline with 1–2 oscillations within 0.12 second and a quick return to baseline (see Fig. 59-3 ). 7. Run a dual-channel strip of the Right-atrial pressures should be Some monitors have the capability of electrocardiogram (ECG) and determined from the graphic “freeze framing” waveforms. A CVP/RAP waveform ( Fig. 67-1 ). recording so that end expiration cursor can be used to determine can be properly identifi ed. pressure measurements. 8. Measure the CVP/RAP at end Measurement is most accurate as expiration. the effects of intrathoracic pressure changes are minimized. 9. With the dual-channel recorded Compares electrical activity with At times, the c wave is not present. strip, draw a vertical line from mechanical activity. Usually, the beginning of the P wave of three waves are present on the one of the ECG complexes down CVP/RAP waveform. to the CVP/RAP waveform. Repeat this with the next ECG complex (see Fig. 72-7 ). 10. Align the PR interval with The a wave correlates with this the CVP/RAP waveform (see interval. Fig. 72-7 ). Figure 67-1 Central venous pressure (CVP) waveform with a, c, and v waves present. The a wave is usually seen just after the p wave of the electrocardiogram (ECG). The c wave appears at the time of the RST junction on the ECG. The v wave is seen in the TP interval. 67 Central Venous/Right Atrial Pressure Monitoring 581 Procedure for Central Venous/Right-Atrial Pressure Monitoring—Continued Steps Rationale Special Considerations 11. Identify the a wave (see Fig. The a wave is seen approximately The a wave refl ects atrial contraction. 67-1 ). 80–100 ms after the P wave. The The c wave refl ects closure of the c wave follows the a wave, and tricuspid valve. The v wave refl ects the v wave follows the c wave. passive fi lling of the right atrium. 12. Identify the scale of the CVP/ Aids in determining the pressure The RAP scale commonly is set at RAP tracing (see Figs. 67-1 and measurement. 20 mm Hg. Scale settings may vary 67-2 ). based on monitoring equipment. 13. Measure the mean of the a wave The a wave represents atrial to obtain the RAP (see Fig. 67-2 contraction and refl ects and Fig. 72-8 ). ventricular fi lling at end diastole. 14. Remove PE and discard used Reduces the transmission of supplies in appropriate microorganisms; Standard receptacles. Precautions. 15. HH Expected Outcomes Unexpected Outcomes • Accurate CVP/RAP measurements • Inaccurate readings • Adequate and appropriate waveforms • CVP/RAP readings that do not correlate with • CVP/RAP readings that correlate with physical physical fi ndings fi ndings • Infection • Evaluation of information obtained to guide • Sepsis therapeutic interventions • Occluded catheter Procedure continues on following page Figure 67-2 Reading the right-atrial pressure (RAP) from paper printout at end expiration in a spontaneously breathing patient.