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Claret Pressure level Monitoring From a Veterinary Nursing Perspective, Part 2: Techniques

Follow these step-by-pace instructions for measuring blood pressure level to proceeds of import data about the patient's cardiovascular status.

February 6, 2015 |

Lila K. Sierra

CVT, VTS (Emergency and Critical Care)

Lila K. Sierra, CVT, VTS (Emergency and Critical Care) is the assistant nursing supervisor of the intensive care unit at Matthew J. Ryan Veterinary Hospital of University of Pennsylvania. She has lectured at state conferences and has published capacity in diverse veterinary manuals. Her passion lies in all aspects of advanced nursing care, including patient advocacy, innovative nursing evolution, and education of prospective veterinarians and nurses.

Read Articles Written by Lila K. Sierra

Emily Savino

BA, CVT, VTS (Emergency and Critical Intendance)

Emily Savino, BA, CVT, VTS (Emergency and Disquisitional Intendance) is the nursing supervisor of the intensive care unit at Matthew J. Ryan Veterinarian Infirmary of Academy of Pennsylvania. She has lectured on veterinary disquisitional care nursing at conferences, and has published chapters in veterinary texts. She enjoys teaching new veterinarian nurses the art of "critical thinking" and working in an environment where she is learning new things every day.

Read Articles Written by Emily Savino

Systemic arterial blood pressure level is created by the pumping action of the heart, circulating arterial blood volume, and the smooth muscle tone of blood vessel walls.

Arterial claret force per unit area is essential for adequate perfusion of tissues, delivering oxygen for energy demands. The ability to measure out and monitor blood pressure trends provides of import information most patient cardiovascular status and may help define arroyo to handling.

Role 1 of this commodity serial—Overview of Blood Pressure level Monitoring (January/February 2015 issue)—discussed terms associated with blood pressure measurement, indications for measurement, and normal and abnormal blood pressure values. This 2d article describes types of blood pressure monitors and provides pace-by-step instructions on performing blood pressure measurement.

Monitoring Techniques

Arterial claret pressure level tin can be measured in two ways:

1. Direct arterial claret pressure level (DABP) monitoring—considered the gold standard—uses an arterial catheter connected to a pressure transducer. This system allows continuous monitoring of patient systolic, diastolic, and hateful arterial pressure (SAP, DAP, and MAP, respectively)^1-3 and also simplifies drove of samples for arterial claret gas assay. Still, DABP monitoring is not used as frequently as other methods considering an arterial catheter must be placed.
2. Indirect arterial blood pressure (IABP) monitoring relies on noninvasive detection of arterial claret flow or vessel wall movement in a peripheral avenue and provides intermittent measurements of arterial blood pressure.IABP monitoring is the most frequently used technique in clinical do; the nearly commonly used indirect methods are Doppler ultrasonography and oscillometric blood pressure monitoring. To obtain an IABP reading, a gage is inflated over an artery until arterial claret period is occluded.¹

Normal arterial blood pressure values for developed dogs and cats are listed in Table 1.

Table 1. Normal Arterial Blood Pressure Values in Adult Dogs & Catsfour
BLOOD PRESSURE VALUES	DOGS	CATS
Systolic arterial pressure	90 to 140 mm Hg	80 to 140 mm Hg
Diastolic arterial pressure	50 to 80 mm Hg	55 to 75 mm Hg
Mean arterial pressure level	60 to 100 mm Hg	60 to 100 mm Hg

Indirect Blood Force per unit area Monitoring

Doppler Ultrasonography

Doppler technology uses 10 MHz ultrasound waves to discover blood flow in a peripheral artery (Effigy one), which is then fabricated aural via the probe/crystal and a speaker.¹

The Doppler technique does not provide a measurement of MAP or DAP in small-scale animals.^1,4,v While some studies have reported that Doppler readings may more closely reflect MAP than SAP in cats,^i,3 the most recent study was performed on salubrious anesthetized cats.¹ Therefore, almost clinicians consider that Doppler readings in awake animals estimate SAP.

Figure 1. Doppler ultrasonographic blood pressure measurement.

Advantages

Doppler ultrasonography has several advantages when compared with other claret pressure level monitoring techniques; the applied science is:

• Relatively easy to utilize, non requiring a cracking dealof expertise
• Affordable and readily bachelor in most clinical settings
• Appropriate to use in patients with significant hypotension and cardiac arrhythmias¹
• Normally used in small animals (cats, smalldogs, rabbits, ferrets, other exotic species).

Blood Force per unit area Measurement: Step by Step

Table 2 lists the supplies needed for Doppler ultrasonographic blood pressure level measurement.

TABLE ii. Required Supplies for Doppler Measurement

Clippers or alcohol for either clipping or wetting pilus Doppler unit and sphygmomanometer Ultrasound coupling gel Inflatable cuff, the width of which should exist: In dogs, xl% of the limb circumference In cats, thirty% of the limb circumference Rubber tubing, which connects inflatable cuff and sphygmomanometer Earphones, if it is difficult to hear the Doppler point

1. Select a peripheral artery for Doppler probe placement; common locations include the dorsal pedal artery, digital avenue, and coccygeal artery.
2. Clip the hair coat over the called avenue, or wet it with alcohol, and apply ultrasound coupling gel to the Doppler probe.
3. Place the Doppler prober over the avenue, oriented parallel to blood menses (Effigy 2); the probe is considered correctly placed when pulsatile blood flow is audible.

   

   Figure 2. The Doppler crystal, shown in this image, should be placed parallel to the artery'due south blood menstruum.

4. Connect a pressure cuff to a sphygmomanometer and place the cuff proximal to the Doppler probe.
5. Inflate the cuff until the avenue is occluded and Doppler sounds are no longer audible; and then slowly debunk the cuff, while observing the sphygmomanometer.
6. Tape the pressure at which the first aural arterial pulse is heard as the SAP.
7. Obtain several sequent measurements; boilerplate the middle 3 readings, and record the average as the SAP. Make sure to employ the same limb and aforementioned size gage for serial blood pressure level measurements.

Preventing Inaccurate Results

Several factors can result in erroneous readings:

• Cuff size is critically important to obtain accurate Doppler readings.^{1,4,half dozen}
  • A gage that is too large falsely decreases the reading
  • A gage that is too small-scale falsely elevates the reading.
• Patients must exist held/restrained during Doppler measurements; however, this handling may increment the animal'south claret pressure.
• Patient position during Doppler measurement can contribute to inaccurate readings; ideally, patients should prevarication in lateral recumbency, with the cuff positioned on the limb at the level of the right atrium.^one,4
• Obtaining Doppler measurements in patients with severe peripheral vasoconstriction (hypovolemia, shock, significant hypothermia) can be difficult; therefore, accuracy of readings in these patients can be afflicted by degree of vasoconstriction.^three,iv

Indirect Blood Pressure Monitoring

Oscillometric Measurement

Oscillometric measurement (Figure 3) provides values for SAP, MAP, DAP, and pulse rate; therefore, this type of blood pressure monitoring provides more than data than Doppler measurement.^1,three,4 Nigh oscillometric devices measure the MAP; then calculate the SAP and DAP via programmed algorithms; therefore, the MAP is the well-nigh reliable reading.⁴

Figure 3. Oscillometric blood pressure monitor (Cardell 9401 Veterinary Monitor, midmark.com).

Advantages

Oscillometric blood pressure measurement has several advantages over Doppler methodology; the:

• Procedure is more automated, requiring less technical skill; the operator simply chooses the appropriate cuff size, places it on the patient, and hits the start button
• Monitors tin can be programmed to mensurate claret force per unit area at timed intervals (eg, Q 15 min)
• Automated nature of measurement helps ensure that elevated values are less likely a upshot of stressful patient handling.^1,four

Disadvantages

However, oscillometric techniques tend to exist less accurate in patients:^three,iv

• Nether 5 kg
• With cardiac arrhythmias, meaning tachycardia or bradycardia, vasoconstriction, or hypothermia
• That are moving or shivering.

Blood Force per unit area Measurement: Pace by Step

1. Identify the gage—attached to an oscillometric monitor—on a distal avenue; common locations for oscillometric cuff placement are similar to those used for Doppler blood pressure measurement.
2. One time the device is started, the cuff automatically inflates to a pressure that occludes arterial blood flow.
3. Equally the cuff is deflated, the arterial wall oscillations increase at SAP, maximize at MAP, and subtract at DAP.⁴
4. The oscillometric monitor display will show numeric values for SAP, MAP, and DAP as well every bit pulse rate.
5. Compare the oscillometric pulse rate with a manually obtained pulse rate to determine accurateness: if the rates exercise NOT match, it is probable that the blood pressure readings on the monitor are inaccurate.

Preventing Inaccurate Results

Every bit discussed in the Indirect Claret Pressure level Monitoring: Doppler Ultrasonography section:

• Selection of an accordingly sized cuff is crucial to obtaining accurate values; cuff pick is outlined in Table two.
• To ensure accuracy, it is important to take several sequent readings; then compare the readings to ensure that the values are reproducible.
• Ideally, the same size cuff and same limb should be used for all sequent blood pressure measurements.

Directly Blood Pressure Monitoring

In general, DABP monitoring (Figures 4 and v) is indicated for any critical patient, but specific indications in the clinical setting include patients:

• Presenting in hypovolemic or septic shock
• In congestive heart failure, specially whenreceiving powerful vasodilator medication forpurpose of afterload reduction
• Requiring vasopressors or mechanical ventilation
• Receiving medication for severe hypertension
• Demonstrating a high anesthetic risk.

DABP monitoring is Non indicated in good for you, ambulatory patients because these patients are more likely to disconnect an arterial line, or remove the arterial catheter, increasing the risk for arterial hemorrhage.

Figure 4. Simultaneous electrocardiography and direct arterial blood pressure readings (Escort Prism Patient Monitor, invivocorp.com)

FIGURE 5. Simultaneous electrocardiography and direct arterial blood pressure readings demonstrated on a different monitor (PM-9000 Vet Monitor, mindray.com).

Advantages

DABP has many advantages over other methods of blood pressure level monitoring. Two of the most important advantages include:

• "Real-time" monitoring of blood pressureand blood pressure trends, fifty-fifty in extremely hypotensive patients; this upwards-to-the-infinitesimal information nigh a patient's hemodynamic condition enables clinicians to judge whether a specific therapy is working or if additional, immediate intervention is necessary.
• Handling and restraint of the patient is normally limited to the initial arterial catheter placement; therefore, DABP values are less prone to falsely elevated readings related to stress of restraint and treatment.

Disadvantages

Withal, DABP monitoring is not used extensively considering it has several drawbacks:

• The equipment necessary to monitor DABP (eg,pressure transducers, hemodynamic monitors) can be cost prohibitive, especially when not used ofttimes.
• Arterial catheters are invasive, and arterial access can be technically difficult to obtain and maintain.
• Complications that can result from arterial catheterization include bleeding from the catheter insertion site, hematoma formation, meaning hemorrhage if the system becomes disconnected, infection, and arterial thrombosis with possibility of necrosis of the tissues distal to the catheter.

Claret Pressure Measurement: Step by Pace

Tabular array 3 lists the supplies needed for DABP measurement (Figure 6).

TABLE 3. Required Supplies for DABP Measurement

Arterial catheter T-set primed with heparinized saline DABP transducer arrangement primed with heparinized saline Transducer cablevision Physiologic monitor that displays DABP wave form and numeric values for SAP, DAP, and MAP 250-mL bag of heparinized saline (1 U heparin/1 mL 0.nine% sodium chloride) Pressure bag Board for stabilization of the transducer

Effigy half-dozen. DABP supplies: Transpac dispensable pressure transducer (icumed.com), heparinized saline bag within pressurized air handbag, electronic cable to connect Transpac to monitor, transducer board (white), arterial catheter (dorsal metatarsal).

1. Place and secure an arterial catheter; mutual sites for arterial catheterization include the dorsal pedal artery, coccygeal avenue (Figures 7 and 8), and medial auricular artery.^1,two

   

   Figure 7. Patient with coccygeal arterial catheter; notation that arterial catheters should not be maintained in cats for longer than 6 to 12 hours owing to risk for arterial thrombosis.

   

   FIGURE 8. Shut-up image of coccygeal arterial catheter in a cat.

2. Once the arterial catheter is placed and secured, connect it to the DABP monitoring organization.
3. At one terminate of the organisation—the cease farthest abroad from the patient—a fluid administration set is connected to a heparinized bag of 0.9% sodium chloride (Table iii).
4. Pressurize the fluid bag to a range betwixt 250 and 300 mm Hg: the goal is to reach a pressure in the fluid bag greater than the patient's systolic pressure, which prevents back flow of arterial claret into the monitoring system.^1,2
5. The fluid bag tubing connects to a pressure transducer, which is connected by a cablevision to the physiologic monitor, mounted on a board placed at the level of the patient's heart. At the other end of the transducer, semi-rigid tubing connects to the arterial catheter'south T-prepare.
6. One time the pressure transducer is continued to the monitor, zero it at the level of the patient's right atrium. Once zeroed, the force per unit area transducer converts the force per unit area changes in the artery to an electrical signal that is displayed on the monitor every bit a pressure level moving ridge form; numeric values for SAP, MAP, and DAP are also displayed.¹
7. Flush the DABP monitoring system with heparinized saline before connecting it to the patient.
8. Supervise patients with arterial catheters at all times and carefully treat the catheter:
   • Clearly label the catheter, allowing easyidentification equally arterial rather than venous and, thereby, alerting personnel Non to administer medications through the catheter.
   • Rewrap the catheter, at a minimum, one time daily; rewrap soiled catheters promptly.
   • While the catheter is unwrapped, evaluate the insertion site for redness, warmth, swelling, pain, or belch; remove catheters that are painful or oozing from the insertion site.
   • Document when the catheter is rewrapped and note the appearance of the insertion site in the medical tape.
   • Consider putting an E-neckband on patients to prevent access to arterial catheters.
   • Exercise NOT maintain arterial catheters in cats for longer than 6 to 12 hours1 owing to increased risk for arterial thrombosis.

Preventing Inaccurate Results

Although DABP is considered the gold standard in blood pressure monitoring, a number of situations can cause erroneous readings, which can be prevented by:

• Using only semi-rigid tubing to connect the force per unit area transducer to the patient—the utilize of compliant tubing results in excessive damping of the pressure wave, causing inaccurate readings
• Ensuring air bubbles are not present in the system
• Checking the semi-rigid tubing for kinks
• Making sure the pressure bag is inflated to at to the lowest degree 250 mm Hg
• Reassessing the transducer level; if the transducer is displaced, supervene upon it to approximately the level of the right atrium and zero to the patient
• Ensuring that the arterial catheter is patent; flush the arterial catheter if needed.

Summary

Veterinary nurses play a cardinal role in patient care. Appropriately monitoring patient blood pressure, documenting results, interpreting them, and communicating changes and concerns to the clinician provides all members of the veterinary squad with an opportunity to proactively manage potential problems.

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Key to Terms

DABP = direct arterial blood pressure level; DAP = diastolic arterial pressure; IABP = indirect arterial claret pressure; MAP = hateful arterial pressure; SAP = systolic arterial pressure

References

1. Waddell LS, Brown AJ. Hemodynamic monitoring. In Silverstein DC, Hopper Thousand (eds): Small Animal Critical Care Medicine, 2nd ed. St. Louis: Elsevier, 2015, pp 957-962.
2. Cooper E, Cooper S. Direct systemic arterial blood force per unit area monitoring. In Burkitt Creedon JM, Davis H (eds): Advanced Monitoring and Procedures for Small Animal Emergency and Critical Intendance. Ames, IA: Wiley-Blackwell, 2012, pp 122-133.
3. Cooper Due east. Hypotension. In Silverstein DC, Hopper K (eds): Modest Fauna Critical Care Medicine, second ed. St. Louis: Elsevier, 2015, pp 46-50.
4. Williamson JA, Leone S. Noninvasive arterial blood pressure monitoring. In Burkitt Creedon JM, Davis H (eds): Avant-garde Monitoring and Procedures for Small Animal Emergency and Disquisitional Care, Ames, IA: Wiley-Blackwell, 2012, pp 134-144.
5. Caulkett NA, Cantwell SL, Houston DM. A comparison of indirect claret pressure monitoring techniques in the anesthetized cat. Vet Surg 1998; 27:370.
6. Monnet E. Cardiovascular monitoring. In Wingfield WE, Raffe MR (eds): The Veterinary ICU Volume. Jackson, WY: Teton NewMedia, 2002, pp 265-280.

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