PROCEDURE Arterial Catheter Insertion 59 (Assist), Care, and Removal Hillary Crumlett and Alex Johnson PURPOSE: Arterial catheters are used for continuous monitoring of blood pressure, assessment of cardiovascular effects of vasoactive drugs, and frequent arterial blood gas and laboratory sampling. In addition, arterial catheters provide access to blood samples that support the diagnostics related to oxygen, carbon dioxide, and bicarbonate levels (oxygenation, ventilation, and acid-base status). PREREQUISITE NURSING aortic valve closes, marking the end of ventricular systole. KNOWLEDGE The closure of the aortic valve produces a small rebound wave that creates a notch known as the dicrotic notch. The • Knowledge of the anatomy and physiology of the vascu- descending limb of the curve (diastolic downslope) repre- lature and adjacent structures is needed. sents diastole and is characterized by a long declining • Knowledge of the principles of hemodynamic monitoring pressure wave, during which the aortic wall recoils and is necessary. propels blood into the arterial network. The diastolic pres- • Understanding of the principles of aseptic technique is sure is measured as the lowest point of the diastolic needed. downslope, which should be less than 80 mm Hg in • Conditions that warrant the use of arterial pressure moni- adults. 21 toring include patients with the following: • The difference between the systolic and diastolic pres- ❖ Frequent blood sampling: sures is the pulse pressure, with a normal value of about Respiratory conditions requiring arterial blood gas 40 mm Hg. monitoring (oxygenation, ventilation, acid-base • Arterial pressure is determined by the relationship between status) blood fl ow through the vessels (cardiac output) and the Bleeding, actual or potential resistance of the vessel walls (systemic vascular resis- Electrolyte or glycemic abnormalities, actual or tance). The arterial pressure is therefore affected by any potential factors that change either cardiac output or systemic vas- Metabolic abnormalities (acid-base, tissue perfu- cular resistance. sion), actual or potential • The average arterial pressure during a cardiac cycle is Monitoring serum levels related to therapeutic inter- called the mean arterial pressure (MAP). MAP is not the ventions (renal replacement therapy, chemotherapy, average of the systolic plus the diastolic pressures because, biotherapy, apheresis therapy, etc.) during the cardiac cycle, the pressure remains closer to ❖ Continuous blood pressure monitoring: diastole than to systole for a longer period (at normal heart Hypotension or hypertension rates). The MAP is calculated automatically by most Shock: cardiogenic, septic, hypovolemic, patient monitoring systems; however, it can be calculated neurogenic with the following formula: Mechanical cardiovascular support MAP=+×()() systolic pressure diastolic pressure 2 Vasoactive medication administration • Arterial pressure represents the forcible ejection of blood 3 from the left ventricle into the aorta and out into the arte- • MAP represents the driving force (perfusion pressure) for rial system. During ventricular systole, blood is ejected blood fl ow through the cardiovascular system. MAP is at into the aorta, generating a pressure wave. Because of the its highest point in the aorta. As blood travels through the intermittent pumping action of the heart, this arterial pres- arterial system away from the aorta, systolic pressure sure wave is generated in a pulsatile manner ( Fig. 59-1 ). increases and diastolic pressure decreases, with an overall The ascending limb of the aortic pressure wave (anacrotic decline in the MAP ( Fig. 59-2 ). limb) represents an increase in pressure because of left- • The location of arterial catheter placement depends on the ventricular ejection. The peak of this ejection is the peak condition of the arterial vessels and the presence of other systolic pressure, which should be less than 120 mm Hg catheters (i.e., the presence of a dialysis shunt is a contra- in adults.21 After reaching this peak, the ventricular pres- indication for placement of an arterial catheter in the same sure declines to a level below aortic pressure and the extremity). Once inserted, the arterial catheter causes little 508 59 Arterial Catheter Insertion (Assist), Care, and Removal 509 • The radial artery is the most common site for arterial pres- sure monitoring. When arterial pulse waveforms are recorded from a peripheral site (compared with a central site), the waveform morphology changes. The anacrotic limb becomes more peaked and narrowed, with increased amplitude; therefore, the systolic pressure in peripheral sites is higher than the systolic pressure recorded from a more central site (see Fig. 59-2 ). In addition, the diastolic pressure decreases, the diastolic downslope may show a secondary wave, and the dicrotic notch becomes less prominent from distal sites. Figure 59-1 The generation of a pulsatile waveform. This is an aortic pressure curve. During systole, the ejected volume distends • Vasodilators and vasoconstrictors may change the appear- the aorta and aortic pressure rises. The peak pressure is known as ance of the waveforms from distal sites. Vasodilators may the aortic systolic pressure. After the peak ejection, the ventricular cause the waveform to take on a more central appearance. pressure falls; when it drops below the aortic pressure, the aortic Vasoconstrictors may cause the systolic pressure to valve closes, which is marked by the dicrotic notch, the end of the become more exaggerated because of enhanced resistance systole. During diastole, the pressure continues to decline and the in the peripheral arteries. aortic wall recoils, pushing blood toward the periphery. The trough of the pressure wave is the diastolic pressure. The difference • Several potential complications are associated with arte- between the systolic and diastolic pressure is the pulse pressure. rial pressure monitoring. Infection at the insertion site can (From Smith JJ, Kampine JP: Circulating physiology . Baltimore, develop and cause sepsis. Clot formation in the catheter 1980, Williams & Wilkins, 55.) can lead to arterial embolization. The catheter can cause a pseudoaneurysm or vessel perforation with extravasa- tion of blood and fl ush solution into the surrounding tissue. Finally, the distal extremity can develop circulatory or neurovascular impairment. • Ultrasound guidance is recommended to place arterial catheters if the technology is available. 8 EQUIPMENT • 2-inch, 20-gauge, nontapered Tefl on cannula-over-needle or prepackaged kit that includes a 6-inch, 18-gauge Tefl on catheter with appropriate introducer and guidewire (or the specifi c catheter for the intended insertion site) • Pressure module and cable for interface with the monitor • Pressure transducer system, including fl ush solution rec- ommended according to institutional standards, a pressure bag or device, pressure tubing with transducer, and fl ush device (see Procedure 75 ) • Dual-channel recorder • Nonsterile gloves, head covering, goggles, and mask • Sterile gloves and large sterile fenestrated drape • Skin antiseptic solution (e.g., 2% chlorhexidine-based preparation) • Sterile 4 × 4 gauze pads • Transparent occlusive dressing Figure 59-2 Arterial pressure from different sites in the arterial • 1% lidocaine without epinephrine, 1 to 2 mL tree. The arterial pressure waveform varies in confi guration, depend- ing on the location of the catheter. With transmission of the pressure • Sterile sodium chloride 0.9% wave into the distal aorta and large arteries, the systolic pressure • 3-mL syringe with 25-gauge needle increases and the diastolic pressure decreases; with a resulting • Sheet protector heightening of the pulse, pressure declines steadily. (From Smith JJ, • Bedside ultrasound machine with vascular probe Kampine JP: Circulating physiology . Baltimore, 1980, Williams & • Sterile ultrasound probe cover Wilkins, 57.) • Sterile ultrasound gel Additional equipment, to have available as needed, includes the following: or no discomfort to the patient and allows continuous • Sterile gown and full drape blood pressure assessment and intermittent blood sam- • Bath towel pling. If intraaortic balloon pump therapy is necessary, • Small wrist board arterial pressure may be directly monitored from the tip • Sutureless securement device of the balloon catheter in the aorta. • Suture material 510 Unit II Cardiovascular System • Chlorhexidine-impregnated sponge • Review the patient ’ s allergy history (e.g., allergy to • Additional transparent adhesive dressing with tapes heparin, lidocaine, antiseptic solutions, or adhesive tape). 1 (if dressing has no tape, consider the use of 2 -inch Rationale: This assessment decreases the risk for allergic Steri-Strips) reactions. Patients with heparin-induced thrombocytope- • Transducer holder, intravenous (IV) pole, and laser lever nia should not receive heparin in the fl ush solution. for pole-mounted arterial catheter transducers • Assess the neurovascular and peripheral vascular status of the extremity to be used for the arterial cannulation, PATIENT AND FAMILY EDUCATION including color, temperature, presence and fullness of pulses, capillary refi ll, presence of bruit (in larger arteries • Explain the procedure and the purpose of the arterial cath- such as the femoral artery), and motor and sensory func- eter. Rationale: This explanation decreases patient and tion (compared with the opposite extremity). Note: A family anxiety. modifi