1. Central Venous Pressure Monitoring
9/18/2018
Central Venous Pressure Monitoring
DR ABDOLLAHI

2. 9/18/2018
Indirect assessment of CVP through physical examination of the neck veins is a fundamental aspect of cardiovascular assessment, but one that has many shortcomings. The jugular veins may be impossible to identify in up to 20% of patients, and the bedside diagnosis of low, normal, or high CVP is often inaccurate, particularly in critically ill patients.

3. 9/18/2018
This problem is compounded in the perioperative period, when visualization of the neck veins is further obscured and abrupt changes, sometimes of great magnitude, are not uncommon. As a result, direct measurement of CVP is frequently necessary in hemodynamically unstable patients and those undergoing major operations.

4. Central Venous Cannulation
9/18/2018
Cannulation of a large central vein is the standard clinical method for monitoring CVP and is also performed for a number of additional therapeutic interventions, such as providing secure vascular access for the administration of vasoactive drugs or to initiate rapid fluid resuscitation. Frequently, the central venous location is the only site available for intravenous access of any kind.

5. 9/18/2018
Patients at risk for venous air emboli may have central venous catheters placed for aspiration of entrained air. In addition, central venous access is required to initiate transvenous cardiac pacing, temporary hemodialysis, or pulmonary artery catheterization for more comprehensive cardiac monitoring.

6. Indications for Central Venous Cannulation
9/18/2018

7. 9/18/2018
The decision to perform central venous cannulation before or after induction of anesthesia is guided most often by individual patient and physician preferences or institutional practice.

8. Choosing the Catheter, Site, and Method of Central Venous Cannulation
9/18/2018
Central venous catheters come in a variety of lengths, gauges, composition, and lumen number. These characteristics vary according to the purpose of the catheterization, whether for CVP monitoring or other therapeutic indications and whether intended for short- or long-term use. This makes it critical for the physician to choose the best catheter for any given application. Seven- French, 20-cm multiport catheters that allow monitoring of CVP and infusion of drugs and fluids simultaneously are the most common.

9. 9/18/2018
It should be noted that rapid fluid resuscitation is more efficient with short, large-bore intravenous catheters inserted peripherally because the smaller diameter of each individual lumen and the overall catheter length increase resistance to flow significantly. For example, according to the manufacturer's product specifications, the maximal flow rate of the 16-gauge lumen of a standard 7-Fr, 20-cm central venous catheter is a quarter that of a 16-gauge, 3-cm intravenous catheter in a large peripheral vein.

10. 9/18/2018
A popular alternative method for multilumen central venous access uses a large introducer sheath with an integrated T- connector sidearm for multiple drug infusions combined with a single-lumen catheter inserted through the hemostasis valve for continuous CVP monitoring. Although use of these larger introducer sheaths is not free of complications, they do allow rapid placement of a pacing wire or pulmonary artery catheter (PAC) for more intensive monitoring should the need arise.

11. 9/18/2018
Selecting the best site for safe and effective central venous cannulation ultimately requires consideration of the indication for catheterization (pressure monitoring versus drug or fluid administration), the patient's underlying medical condition, the clinical setting, and the skill and experience of the physician performing the procedure.

12. 9/18/2018
In patients with severe bleeding diatheses, it is best to choose a puncture site at which bleeding from the vein or adjacent artery is easily detected and controlled with local compression. In such a patient, an internal or external jugular approach would be preferable to a subclavian site

13. 9/18/2018
Likewise, patients with severe emphysema or others who would be severely compromised by pneumothorax would be better candidates for internal jugular than subclavian cannulation because of the higher risk with the latter approach.

14. 9/18/2018
If transvenous cardiac pacing is required in an emergency situation, catheterization of the right internal jugular vein is recommended because it provides the most direct route to the right ventricle.

15. 9/18/2018
Trauma patients with their necks immobilized in a hard cervical collar are best resuscitated via a femoral or subclavian approach; the latter may be used even more safely if the risk of pneumothorax is obviated by prior placement of a thoracostomy tube.

16. 9/18/2018
The physician must recognize that the length of catheter inserted to position the catheter tip properly in the superior vena cava will vary according to puncture site, being slightly (3 to 5 cm) greater when the left internal or external jugular veins are chosen versus the right internal jugular vein

17. 9/18/2018
Finally, a physician's personal experience undoubtedly plays a significant role in determining the safest site for central venous cannulation, particularly when the procedure is performed under urgent or emergency circumstances.

18. 9/18/2018
Since its introduction into clinical practice in the late 1960s, percutaneous puncture of the right internal jugular vein has been the method preferred by anesthesiologists for central venous cannulation. Reasons for this preference include consistent, predictable anatomic location of the internal jugular vein, readily identifiable and palpable surface landmarks, and a short, straight course to the superior vena cava. An internal jugular vein catheter is highly accessible during most surgical procedures and has a rate of successful placement of approximately 90% to 99%.

19. Right Internal Jugular Vein Cannulation
9/18/2018
Many different techniques for internal jugular vein cannulation have been described, although the “central” approach described by Daily and colleagues is among the most popular and is described with minor modifications here. Careful positioning will make the patient comfortable, improve identification of surface landmarks, and increase the likelihood of success.

20. 9/18/2018
The patient is placed in the supine position with the head turned slightly to the left to expose the right side of the neck and keep the chin from interfering with the procedure. Pillows that cause the neck to be flexed should be removed, but forceful neck extension or extreme leftward rotation of the head should be avoided because this alters cervical vascular anatomy and may cause the internal jugular vein to overlie the carotid artery, thereby increasing the risk for carotid arterial puncture.

21. 9/18/2018
Anatomic landmarks, including the sternal notch, clavicle, and sternocleidomastoid muscle, should be identified before skin preparation and draping for the sterile procedure because these landmarks are more easily appreciated before they are covered by the sterile drape . The patient should be calm, sedated, receiving supplemental oxygen if necessary, and monitored with an ECG, blood pressure monitor, and pulse oximeter

22. 9/18/2018
Because of the frequency and serious morbidity of infectious complications from central venous catheterization, strict aseptic technique is required.

23. 9/18/2018
Good aseptic technique begins with hand washing before the procedure. A mask, cap, sterile gloves, and gown should always be used, regardless of the procedural setting. The skin is cleaned widely from earlobe to clavicle to sternal notch, preferably with 2% chlorhexidine, an agent that has been shown to be superior to the more traditional 10% povidone-iodine. Aseptic preparation is completed with the application of a large sterile drape that provides maximal barrier precautions, preferably a full-body drape.

24. 9/18/2018
An assistant then places the patient in a slight head-down (Trendelenburg) position to increase jugular vein diameter in the neck. This step may be omitted in a hypervolemic, dyspneic patient. The intended skin is anesthetized by subcutaneous infiltration of a local anesthetic solution (typically 1% lidocaine) with a 25-gauge needle if the patient is awake

25. 9/18/2018

26. 9/18/2018
It is vital to confirm the intravenous location of this catheter. The color of the aspirated blood is examined, and it may be compared with a simultaneously obtained arterial sample, although this technique is not completely reliable. A safer method is to manually transduce the pressure by attaching sterile intravenous extension tubing to the catheter and observing the fluid column.

27. 9/18/2018
Antibiotic ointment should not be applied to the insertion site because it may increase the risk of catheter colonization with multidrug-resistant bacteria or Candida.

28. 9/18/2018
In patients at risk for major intraoperative blood loss and hemodynamic instability, two central venous catheters may frequently be required. Some physicians advocate double cannulation of the same central vein (usually the right internal jugular) with two catheters in close proximity. With this technique, a guidewire is introduced into the internal jugular vein by the standard method. Then, before catheter placement, a second jugular venipuncture is performed, approximately 1 to 2 cm cephalad or caudad, and a second guidewire is introduced into the vein.

29. 9/18/2018
Serious complications of the double-cannulation technique include facial vein avulsion, catheter entanglement, and catheter fracture. Double central venous cannulation must be reserved for patients whose needs for venous access and hemodynamic monitoring cannot be met through single cannulation.

30. Alternative Central Venous Cannulation Sites
9/18/2018
Left Internal Jugular Vein Cannulation of the left internal jugular vein may be accomplished with a technique similar to the one described earlier, although several anatomic details make the left side less attractive than the right.

31. 9/18/2018
The cupola of the pleura is higher on the left, thereby theoretically increasing the risk for pneumothorax. The thoracic duct may be injured during the procedure as it enters the venous system at the junction of the left internal jugular and subclavian veins. The left internal jugular vein is often smaller than the right and demonstrates a greater degree of overlap of the adjacent carotid artery during head rotation.

32. Subclavian Vein
9/18/2018
The subclavian vein is an important site for central venous cannulation and is particularly popular among surgeons and other physicians who place central venous catheters for emergency volume resuscitation and long-term intravenous therapy or dialysis rather than for shorter-term monitoring purposes.

33. 9/18/2018
Advantages of subclavian venous cannulation include a lower risk of infection than with internal jugular or femoral sites, ease of insertion in trauma patients who may be immobilized in a cervical collar, and increased patient comfort, especially for long- term intravenous therapy such as hyperalimentation and chemotherapy.

34. Method
9/18/2018
For subclavian central access, the patient is placed in a slight head-down position with the arms fully adducted and the head turned slightly away. A small roll is placed between the shoulder blades to expose the infraclavicular area fully. The skin is punctured 2 to 3 cm caudad to the midpoint of the clavicle, far enough from its inferior edge to avoid downward angulation of the needle as it is inserted just beneath the posterior surface of the clavicle. The needle tip is directed toward the suprasternal notch, which may be constantly identified by the fingers of the operator's other hand.

35. 9/18/2018
Bilateral attempts at subclavian venipuncture are highly discouraged because of the serious morbidity of bilateral pneumothorax and the difficulty detecting and treating injury to the subclavian artery. Perhaps to an even greater degree than with internal jugular vein cannulation, the safety of subclavian venous line placement rests in the experience of the operator. In more practiced hands, the incidence of complications should be low, with pneumothorax developing in less than 2% and arterial puncture in less than 5% of cases.

36. External Jugular Vein
9/18/2018
Both the right and left external jugular veins provide a safe, albeit somewhat problematic alternative to internal jugular or subclavian vein cannulation. Because the external jugular veins are superficial, they allow central venous cannulation with essentially no risk of pneumothorax or unintended arterial puncture.

37. Femoral vein
9/18/2018
Femoral vein cannulation provides a useful site for CVP monitoring when the more common jugular and subclavian sites are not accessible, as is commonly the case in patients with burns or trauma, during surgical procedures that involve the head, neck, and upper part of the thorax, or during cardiopulmonary resuscitation.

38. 9/18/2018
Use of the femoral vein obviates many of the common complications of central venous catheterization, specifically pneumothorax, but it does carry the risk of femoral artery and, more rarely, femoral nerve injury. Femoral venipuncture is performed below the inguinal ligament just medial to the palpated femoral arterial pulse in a manner similar to that used for femoral artery cannulation.

39. 9/18/2018
Disadvantages of the femoral venous route include an increased risk of thromboembolic and infectious complications, as well as vascular injury, which may lead to intra-abdominal or retroperitoneal hemorrhage. Moreover, catheters inserted at the femoral site generally preclude ambulation during recovery.

40. Axillary and Other Peripheral Veins
9/18/2018
In patients with extensive, severe burn injuries, the axillary region is often spared and provides a useful site for either arterial or venous pressure monitoring. Standard 20-cm CVP catheters placed in the axillary veins, approximately 1 cm medial to the palpated axillary artery, allow measurement of pressure from the superior vena cava. Even more distal pressures measured from peripheral veins in the hand and forearm may provide a reasonably accurate estimate of CVP in selected surgical patients.

41. 9/18/2018
Peripherally inserted central venous catheters (PICCs) have become a popular alternative to centrally inserted catheters in patients requiring long-term intravenous therapy. Advantages of a PICC include bedside placement under local anesthesia, an extremely low risk of major insertion-related complications, and safe placement by nonphysicians (i.e., registered nurses and physician assistants). This technique may be particularly cost- effective .

42. 9/18/2018
Venous access for a PICC is obtained through an antecubital vein, preferably the basilic vein, which is generally more successfully catheterized than the cephalic vein because of its more linear course.

43. 9/18/2018
Most PICCs are placed for long-term therapeutic indications (chemotherapy or parenteral nutrition) and use very flexible, nonthrombogenic silicone catheters. Less commonly, a standard polyurethane 40-cm intravenous catheter is inserted peripherally and advanced to a central location for short-term infusion of vasoactive drugs or monitoring of CVP or pulmonary artery pressure (PAP).

44. 9/18/2018
CVP recorded via PICCs is slightly higher than the pressure measured with centrally inserted catheters, but this difference is clinically insignificant. When these standard long venous catheters are inserted from an antecubital vein, the catheter tip may advance into the heart as the arm is abducted, thereby increasing the risk for cardiac perforation or arrhythmias.

45. Ultrasound-Guided Central Venous Cannulation
9/18/2018
First described in 1984, ultrasound-guided placement of central venous catheters has proved beneficial in most settings, including the intensive care unit and the operating room. Available evidence suggests that fewer needle passes are required for successful venous cannulation when two- dimensional ultrasound guidance is used. In addition, most investigators have shown that ultrasound guidance reduces the time required for catheterization, increases overall success rates, and results in fewer complications.

46. 9/18/2018
The benefit is most evident when the internal jugular vein rather than the subclavian or femoral vein is cannulated, when inexperienced rather than experienced operators perform the procedure, and for adult rather than pediatric patients. Nonetheless, the use of ultrasound for placement of central venous catheters continues to be low.

47. 9/18/2018
Recent surveys show that both house staff physicians at one academic tertiary care center and a group of practicing American anesthesiologists routinely use ultrasound for central venous cannulation less than 15% of the time. Some aspects of the use of ultrasound for placement of all central venous access remain controversial. It is still largely unknown whether the additional equipment and manipulation associated with real-time ultrasound guidance may increase the rate of catheter-related infections or whether the increased dependence on this technology by trainees will prove detrimental in clinical settings in which it may be unavailable.

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49. 9/18/2018
When using ultrasound guidance, either transverse (short axis) or longitudinal (long axis) views are adequate. In general, the transverse view is easier to learn and allows simultaneous identification of the artery and vein, whereas the longitudinal view allows visualization of the needle tip at all times, which may reduce perforation of the posterior wall of the vein.

50. Confirming Catheter Position
9/18/2018
Central venous catheters placed in the operating room are commonly used for the duration of the surgical procedure without radiologic confirmation of the location of the catheter tip. Before monitoring or infusion commences, aspiration of blood should confirm the intravenous location of each lumen of a multilumen catheter and remove any residual air from the catheter-tubing system.

51. 9/18/2018
After surgery, however, the position of the catheter tip must be confirmed radiographically. Catheter tips located within the heart or below the pericardial reflection of the superior vena cava increase the risk for cardiac perforation and fatal cardiac tamponade.

52. 9/18/2018
Ideally, the catheter tip should lie within the superior vena cava, parallel to the vessel walls, and be positioned below the inferior border of the clavicles and above the level of the third rib, the T4 to T5 interspace, the azygos vein, the tracheal carina, or the takeoff of the right mainstem bronchus.

53. Complications of Central Venous Pressure Monitoring
9/18/2018
Complications of central venous cannulation are increasingly being recognized as major sources of morbidity, with more than 15% of patients experiencing some sort of related adverse event. Although serious immediate complications are infrequent when these procedures are performed by well-trained, experienced clinicians, infectious complications are common, and the use of CVP catheters continues to result in significant morbidity and mortality. Complications are often divided into mechanical, thromboembolic, and infectious causes

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56. Mechanical Complications of Central Venous Catheterization
9/18/2018
The incidence of complications depends on a number of factors, including the catheter insertion site and the patient's medical condition. In general, unintended arterial puncture is the most common acute mechanical complication, with an incidence ranging from 1.9% to 15%. Many of these injuries result in localized hematoma formation, but on rare occasion even small- gauge needle punctures may lead to serious complications such as arterial thromboembolism.

57. Treatment
9/18/2018
If arterial puncture with a small needle occurs during central venous cannulation, the needle should be removed and external pressure applied for several minutes to prevent hematoma formation. When unintentional carotid artery cannulation occurs, it can usually be managed conservatively by removing the catheter, applying local compression to the puncture site, and monitoring the patient's airway and neurologic status. A vascular surgeon should be consulted promptly to help manage the complication. Only under exceptional circumstances should the catheter be allowed to remain in the vessel because of a high risk for arteritis, thrombus formation, and cerebral embolization.

58. 9/18/2018
Vascular injuries from central venous catheterization have a range of clinical consequences. The most common minor complications are localized hematoma or injury to the venous valves. More serious complications include perforation into the pleural space or mediastinum resulting in hydrothorax, hemothorax, hydromediastinum, hemomediastinum, chylothorax, or any combination of these sequelae.

59. venobronchial fistula, carotid artery–internal jugular vein fistula,
9/18/2018
Other catastrophic and thankfully rare vascular injuries have been reported, including aortic perforation and avulsion of the facial vein.
Delayed vascular complications after central venous catheterization are uncommon but should be considered consequences of this procedure. A number of these delayed complications have been described in the literature, including:
aortoatrial fistula,
venobronchial fistula,
carotid artery–internal jugular vein fistula,
pseudoaneurysm formation

60. 9/18/2018
The most important life-threatening vascular complication of central venous catheterization is cardiac tamponade resulting from perforation of the intrapericardial superior vena cava, right atrium, or right ventricle and subsequent hemopericardium or unintentional pericardial instillation of intravenous fluid.

61. 9/18/2018
This injury was the second most common complication related to central venous catheters in an analysis of the American Society of Anesthesiologists Closed Claims Project in Cardiac tamponade resulted in death in 81% of cases in this report and often had a delayed manifestation (1 to 5 days), thus indicating that this complication is related to catheter maintenance and use more often than to the vascular access procedure itself.

62. DIAGNOSIS
9/18/2018
When cardiac tamponade is caused by catheter-induced cardiac perforation, symptoms develop suddenly, so a high index of suspicion is required if severe hypotension occurs in any patient with a central venous catheter in place. Cardiac arrhythmias may provide an early clue to intracardiac location of the catheter tip. Occasionally, both posteroanterior and lateral chest radiographs, as well as injection of radiopaque contrast material, are required to locate the catheter tip precisely

63. 9/18/2018
Pneumothorax is often cited as the most common complication of subclavian vein cannulation, although it appears that unintended arterial puncture is actually more frequent. Mansfield and coauthors reported a 1.5% incidence of pneumothorax and a 3.7% incidence of arterial puncture in 821 patients who underwent attempted subclavian vein cannulation.

64. 9/18/2018
Small pneumothoraxes may be managed conservatively, whereas tube thoracostomy is the best treatment for larger air collections or pneumothorax in patients receiving positive- pressure mechanical ventilation or scheduled for major surgery. The physician must always be prepared for the possibility of tension pneumothorax and its adverse hemodynamic sequelae. In addition to pneumothorax, other respiratory tract injuries have been reported after central venous catheterization, including subcutaneous and mediastinal emphysema, tracheal perforation, and rupture of an endotracheal tube cuff.

65. 9/18/2018
Nerve injury is another potential complication of central venous cannulation. Damage may occur to the brachial plexus, stellate ganglion, phrenic nerve, or vocal cords. In addition, chronic pain syndromes have been attributed to this procedure.

66. Thromboembolic Complications of Central Venous Catheterization
9/18/2018
Catheter-related thrombosis varies according to the site of central venous catheterization and occurs in as many as 21.5% of patients with femoral vein catheters and 1.9% of those with subclavian vein catheters.

67. Infectious Complications of Central Venous Catheterization
9/18/2018
By far the most common major late complication of central venous cannulation is infection. Bloodstream infections occur in approximately 5% of patients with standard central venous catheters and thus lead to an estimated 150,000 to 250,000 cases of catheter-related bacteremia or fungemia annually.

68. 9/18/2018
As previously noted, the starting point for prevention of infection is meticulous attention to aseptic technique. When more long- term central venous access is anticipated, the subclavian site is preferred because use of the jugular or femoral veins carries a higher risk for infection. Multilumen catheters may carry a higher risk for infection than single-lumen catheters, although the added clinical functionality of such catheters often mandates their use. Catheters are made from materials such as silicone, polyvinyl chloride, Teflon, and polyurethane.

69. 9/18/2018
Heparin-bonded central venous catheters have been shown to reduce the incidence of catheter-related thrombosis and infection in children and adults. Incorporation of antimicrobial treatments onto the catheter surface, such as combinations of chlorhexidine and silver sulfadiazine or monocycline and rifampin, have been shown to reduce rates of catheter colonization and bloodstream infection

70. Other Complications of Central Venous Catheterization
9/18/2018
Miscellaneous other adverse sequelae of central venous cannulation have been reported , and although their incidence is not clearly known, most appear to be uncommon. All physicians performing these procedures should be familiar with them, particularly since many of these complications are related to operator error.

71. 9/18/2018
Use of guidewires, vessel dilators, and large-bore catheters carries certain additional risks that mandate meticulous attention to technique. The proximal tip of the guidewire must remain under the physician's control at all times to avoid inserting the wire too far into the heart and thus causing arrhythmias or potentially losing the guidewire within the circulation

72. 9/18/2018
By design, vessel dilators are stiffer than the catheters and may cause significant trauma if inserted forcefully or farther than necessary to dilate the subcutaneous tissue tract from skin to vein. Large-bore introducer sheaths and multilumen catheters have become popular because of their clinical utility, yet their size may increase the risk for cannulation-associated trauma, hemorrhage from unrecognized line disconnections, and major venous air embolism.

73. Physiologic Considerations for Central Venous Pressure Monitoring: Diastolic Pressure-Volume Relationships and Transmural Pressure
9/18/2018
Cardiac filling pressures are monitored to estimate cardiac filling volumes, which in turn determine the stroke output of the left and right ventricles. According to the Frank-Starling principle, the force of cardiac contraction is directly proportional to end- diastolic muscle fiber length at any given level of intrinsic contractility or inotropy. This muscle fiber length or preload is proportional to end-diastolic chamber volume. Even though it would be ideal to monitor cardiac chamber volumes continuously in critically ill patients, this goal remains elusive in clinical practice.

74. 9/18/2018
When a cardiac filling pressure is measured as a surrogate for estimating cardiac volume, one must not assume that these two variables always change in direct proportion or even in the same direction. In fact, the diastolic pressure-volume relationship in cardiac muscle is not linear, but rather curvilinear, with a progressively steeper slope at higher volumes

75. 9/18/2018
Ventricular diastolic pressure-volume relationship. Along the flat portion of the curve, a 20-mL increase in ventricular volume causes a small increase in ventricular pressure (A to B). In contrast, the same increase in volume along the steep portion of the ventricular filling curve causes a marked increase in filling pressure (C to D). Another problem associated with the use of filling pressure as a surrogate for filling volume arises when shifts in the pressure-volume relationship occur. At point C, ventricular volume is 100 mL and ventricular pressure is 8 mm Hg. An increase in filling pressure to 15 mm Hg may accompany either an increased volume (D) or decreased volume (E). The latter occurs when ventricular compliance changes and shifts the ventricular diastolic pressure-volume relationship up and to the left.

76. 9/18/2018
An even more confusing situation arises when the diastolic pressure-volume relationship of the ventricle changes, for example, with the onset of myocardial ischemia. Rather than moving along the same diastolic pressure-volume curve, the ventricle now shifts to a different, steeper curve, where somewhat paradoxically, an increase in filling pressure may accompany a decrease in filling volume. As in this example, not only can one not assume that a given measured change in cardiac filling pressure reflects a proportional change in ventricular preload, it cannot even be assumed that diastolic pressure and volume change in a similar direction.

77. 9/18/2018
Cardiac filling pressures are measured directly from a number of sites in the vascular system. CVP monitoring is the least invasive method, followed by monitoring of PAP and left atrial pressure (LAP). Proper interpretation of all cardiac filling pressures requires knowledge of normal values for these pressures, as well as pressures in the cardiac chambers, the great vessels, and other measured and derived hemodynamic variables

78. 9/18/2018

79. Normal Central Venous Pressure Waveforms
9/18/2018
Strictly speaking, CVP is the pressure measured at the junction of the venae cavae and the right atrium and reflects the driving force for filling the right atrium and ventricle. Because the large veins of the thorax, abdomen, and proximal extremities form a compliant reservoir for a sizable percentage of total blood volume, CVP is highly dependent on intravascular blood volume and the intrinsic vascular tone of these capacitance vessels

80. 9/18/2018
Thus , in clinical practice, CVP monitoring is used for assessment of blood volume and right heart function. Normal CVP in an awake, spontaneously breathing patient ranges between 1 and 7 mm Hg.

81. 9/18/2018
Mechanical events during the cardiac cycle are responsible for the sequence of waves seen in a typical CVP trace. The CVP waveform consists of five phasic events, three peaks (a, c, v) and two descents (x, y) .

82. Central Venous Pressure Waveform Components
9/18/2018

83. 9/18/2018
Normal central venous pressure (CVP) waveform. The diastolic components (y descent, end-diastolic a wave) and the systolic components (c wave, x descent, end-systolic v wave) are all clearly delineated. A mid-diastolic plateau wave, the h wave, is also seen because the heart rate is slow. Identification of the waveform is aided by timing the relationship between individual waveform components and the electrocardiographic R wave. Waveform timing using the arterial (ART) pressure trace is more confusing because of the relative delay in systolic arterial pressure upstroke.

84. 9/18/2018
The most prominent wave is the a wave of atrial contraction, which occurs at end-diastole after the ECG P wave. Atrial contraction increases atrial pressure and provides the “atrial kick” to fill the right ventricle through the open tricuspid valve. Atrial pressure decreases after the a wave as the atrium relaxes. This smooth decline in pressure is interrupted by the c wave.

85. C wave
9/18/2018
This wave is a transient increase in atrial pressure produced by isovolumic ventricular contraction, which closes the tricuspid valve and displaces it toward the atrium. The c wave always follows the ECG R wave because it is generated during the onset of ventricular systole. (Note that the c wave observed in a jugular venous pressure trace might have a slightly more complex origin. This wave has been attributed to early systolic pressure transmission from the adjacent carotid artery and may be termed a carotid impact wave.

86. V wave
9/18/2018
The last atrial pressure peak is the v wave, which is caused by venous filling of the atrium during late systole while the tricuspid valve remains closed.

87. 9/18/2018
The v wave usually peaks just after the ECG T wave. Atrial pressure then decreases, thereby inscribing the y descent, or diastolic collapse, as the tricuspid valve opens and blood flows from atrium to ventricle. (A final component of the CVP waveform, the h wave, occasionally appears as a pressure plateau in mid to late diastole. The h wave is not normally seen unless the heart rate is slow and venous pressure is elevated.

88. 9/18/2018
In summary, the normal venous waveform components may be remembered as follows: the a wave results from atrial contraction; the c wave results from closure of the tricuspid valve and isovolumic right ventricular contraction; the x descent is the systolic decrease in atrial pressure caused by atrial relaxation; the v wave results from ventricular ejection, which drives venous filling of the atrium; and the y descent is the diastolic decrease in atrial pressure caused by flow across the open tricuspid valve.

89. 9/18/2018
In relation to the cardiac cycle and ventricular mechanical actions, the CVP waveform can be considered to have three systolic components (c wave, x descent, v wave) and two diastolic components (y descent, a wave). By recalling the mechanical actions that generate the pressure peaks and troughs, it is easy to identify these waveform components properly by aligning the CVP waveform and the ECG trace and using the ECG R wave to mark end-diastole and the onset of systole.

90. 9/18/2018
When the radial artery pressure trace is used for timing of the CVP waveform instead of the ECG, confusion may arise because the arterial pressure upstroke occurs nearly 200 msec after the ECG R wave . This normal physiologic delay reflects the times required for spread of electrical depolarization through the ventricle (∼60 msec), isovolumic left ventricular contraction (∼60 msec), transmission of the rise in aortic pressure to the radial artery (∼50 msec), and transmission of the rise in radial artery pressure through fluid-filled tubing to the transducer (∼10 msec).

91. 9/18/2018
The normal CVP peaks are designated systolic (c, v) or diastolic (a) according to the phase of the cardiac cycle in which the wave begins. However, one generally identifies these waves not by their onset or upstroke but rather by the location of their peaks. For instance, the a wave generally begins and peaks in end- diastole, but the peak may appear delayed to coincide with the ECG R wave, especially in a patient with a short PR interval. In this instance the a and c waves merge, and this composite wave is termed an a-c wave.

92. 9/18/2018
Although three distinct CVP peaks (a, c, v) and two troughs (x, y) are discernible in the normal venous pressure trace, heart rate changes and conduction abnormalities alter this pattern. A short ECG PR interval causes fusion of the a and c waves, and tachycardia reduces the length of diastole and the duration of the y descent, which causes the v and a waves to merge. In contrast, bradycardia causes each wave to become more distinct, with separate x and x′ descents visible and a more prominent h wave.

93. Abnormal Central Venous Pressure Waveforms
9/18/2018
Various pathophysiologic conditions may be diagnosed or confirmed by examination of the CVP waveform .

94. Central Venous Pressure Waveform Abnormalities
9/18/2018

95. 9/18/2018
One of the most common applications is rapid diagnosis of cardiac arrhythmias. In atrial fibrillation, the a wave disappears and the c wave becomes more prominent because atrial volume is greater at end-diastole and the onset of systole as a result of the absence of effective atrial contraction .

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97. 9/18/2018
Occasionally, atrial fibrillation or flutter waves may be seen in the CVP trace when the ventricular rate is slow. Isorhythmic atrioventricular dissociation or junctional (nodal) rhythm .

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99. 9/18/2018
alters the normal sequence of atrial contraction before ventricular contraction. Instead, atrial contraction now occurs during ventricular systole when the tricuspid valve is closed, thereby inscribing a tall “cannon” a wave in the CVP waveform. Absence of normal atrioventricular synchrony during ventricular pacing can be identified in a similar fashion by searching for cannon waves in the venous pressure trace. In these instances, the CVP waveform helps diagnose the cause of the arterial hypotension; loss of the normal end-diastolic atrial kick may not be as evident in the ECG trace as it is in the CVP waveform.

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101. 9/18/2018
Right-sided valvular heart diseases alter the CVP waveform in different ways. Tricuspid regurgitation produces abnormal systolic filling of the right atrium through the incompetent valve.

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A broad, tall systolic c-v wave results, beginning in early systole and obliterating the systolic x descent in atrial pressure. The CVP trace is said to be ventricularized and resembles right ventricular pressure.

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Unlike tricuspid regurgitation, tricuspid stenosis produces a diastolic defect in atrial emptying and ventricular filling (see Fig B ).

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Not only can individual CVP waveforms provide unique diagnostic clues about the circulation, but trends in CVP over time may also be useful in estimating fluid or blood loss and guiding replacement therapy. It is important to remember that there is a significant range of normal values and that a small change in CVP may reflect a significant alteration in circulating blood volume and right ventricular preload. Additional useful information may be derived from examining how a fluid bolus simultaneously alters CVP and other variables of clinical interest, such as blood pressure, urine output, and so forth.