PROCEDURE FOR VASCULAR ASSESSMENT BY DOPPLER ULTRASOUND (to achieve Ankle Brachial Pressure Index)

Transcription

1 PROCEDURE FOR VASCULAR ASSESSMENT BY DOPPLER ULTRASOUND (to achieve Ankle Brachial Pressure Index) First Issued Issue Version Purpose of Issue/Description of Change Planned Review Date One To enable nurses to safely perform a vascular assessment and Ankle Brachial Pressure Index (ABPI) for patients with leg ulcers in a community setting 2011 Named Responsible Officer:- Ratified by Date Tissue Viability Nurse Specialist Nursing Policy Group August 2008 Policy File:- Nursing Policy File N o 51 Impact Assessment Screening Complete Date: June 2008 Full Impact Assessment Required Y/N UNLESS THIS VERSION HAS BEEN TAKEN DIRECTLY FROM THE PCT WEB SITE THERE IS NO ASSURANCE THIS IS THE CORRECT VERSION

2 INDEX Introduction 3 Target Group and Training 3 Related Policies 4 Preparation 4 Risk Assessment Contraindication 4 Patient Preparation 5 Procedure for obtaining the Brachial Systolic Pressure 5 Procedure for Obtaining the Ankle 7 pressure Calculation of Ankle Brachial Pressure 8 Index (ABPI) Interpretation of Results 8 Table 1 ABPI Values and Clinical Presentation 9 Table 2 Interpreting Doppler Sounds 9 Table 3 Limitations of the ABPI and Factors to Consider Decontamination of Cuff and Equipment Clinical Incidents 11 References 11 2/11

3 INTRODUCTION PROCEDURE FOR VASCULAR ASSESSMENT BY DOPPLER ULTRASOUND The role of Doppler Ultrasound in detecting arterial insufficiencies is considered an essential part of the assessment process for chronic leg ulcer management (Scottish Intercollegiate Guidelines Network (SIGN 1998), Royal College of Nursing Institute (1998), Leg Ulcer Policy (Wirral PCT 2007). The Ankle Brachial Pressure Index (ABPI) is not used to diagnose the type of ulcer. It does not tell a clinician whether the ulcer is venous or arterial in origin. However, when used in conjunction with a patient s medical history, physical assessment and clinical presentation of the ulcer it helps the clinician to decide care. Doppler assessment of the lower limb seeks to determine the resting pressure index i.e. comparing the brachial pressure compared to the resting ankle systolic pressure and this is presented as a ratio i.e. the ABPI. That calculation combined with a competent interpretation enables the clinician to decide upon the safety of applying compression bandaging. It is important to understand that the following correct procedure is necessary in order to gain an accurate interpretation of the ABPI. Procedure complies with NHS Litigation Authority Risk Management Standards (2008) for PCT s for clinical diagnostic tests. TARGET GROUP This procedure must only be undertaken by competent Registered Nurses in the PCT with a current successfully completed competency as part of leg ulcer prevention and management within the context of a comprehensive medical history together with an assessment of clinical features in order to guide management. TRAINING The procedure should only be performed by nurses who have received specific training i.e. 2 days Leg Ulcer Management Course and have successfully been deemed competent. Competence will include supervised sessions with a more experienced colleague to assist with operating difficulties and interpretation of results. Copies of the competency will be kept in personal file and updated every three years. Clinical updates are mandatory every three years. 3/11

4 PROFESSIONAL EXPERT SUPERVISION If the Practitioner has any concerns about the interpretation of findings, they must seek the advice of a more experienced nurse i.e. a senior nurse or Tissue Viability Nurse. RELATED POLICIES Policy for the Contamination of Reusable Medical Devices Policy for Hand Decontamination Policy for Methicillin Resistant Staphylococcus Aureus (MRSA) Policy on Personal Protective Equipment PCT Health Records Policy PCT Record Keeping for Community Nursing Nursing and Midwifery Council ( 2007) Record Keeping Consent policy PCT Incident Reporting Policy Policy and Procedure for Leg Ulcer Management NB Always use most current versions of PCT and NMC policies as may be superseded at any time PREPARATION The equipment in order to perform an ABPI is as follows: A hand held Doppler with accompanying probe. Ensure you have the correct probe size. Use an 8 megahertz for lower limb assessment and a 5 megahertz probe if there is a lot of oedema. Contact tissue viability service to access 5 megahertz probe Aneroid Sphygmomanometer. Electronic Sphygmomanometer must not be used Ultrasound Gel and tissues Cling film for covering any ulceration RISK ASSESSMENT CONTRA INDICATIONS Do not perform a Doppler ultrasound if suspicion of deep vein thrombosis is present as it may be painful and also may dislodge the clot. The clinical signs of deep vein thrombosis (DVT) may include pain, which becomes worse when standing or walking. Calf pain may be experienced if the calf veins are affected. Individual signs and symptoms vary and poor predictors of the presence or absence of DVT need to be confirmed by appropriate investigations (Goodacre 2005 et al). 4/11

5 PATIENT PREPARATION The procedure should be explained to the patient and informed and understood consent gained. Although it is not invasive it can be uncomfortable and for some painful because the blood pressure cuff may squeeze the leg over existing ulceration and/or oedema. Patients need to know what to expect so they can stop the nurse from continuing should the pain become unbearable. This information and patient s comments on the procedure must be recorded in the patient health record. Before carrying out the procedure the patient should rest for 10 to 20 minutes (Carter 1969 et al). The emphasis is upon obtaining the resting systolic pressure. Time should be allowed within the nursing schedule for the patient to be rested. The patient should also lie flat in order to minimise hydrostatic pressure variables (Vowden and Vowden 2001). However, many patients will not be able to lie flat and for some having their legs elevated is difficult e.g. in the case of patients with breathing problems or arthritis. In these cases lie the patients as flat as comfortably tolerated and/or with legs elevated as much as possible. The patient s position should be documented. This will contribute to consistency for future readings and put the ABPI within a context which relates to patient positioning. PROCEDURE FOR OBTAINING THE BRACHIAL SYSTOLIC PRESSURE PROCEDURE Verbally check the identity of the patient, by asking for name and date of birth, If not possible check details with family or carers Ensure patient is introduced to staff involved in procedure by name Give clear explanation of the procedure to be performed to gain valid consent, including any risks and the care that will follow Record outcome of discussions and document in care plan, including consent to procedure To obtain the brachial systolic pressure place the blood pressure cuff around the patient s upper arm. As for all blood pressure measurements the cuff should be the correct size to the limb. A range of cuff sizes should be available. The arm should be supported at heart level. Position the cuff with the tubing away from the probe as this may interfere with the probe positioning. Locate the brachial artery. Initially palpating for the artery may be helpful (stethoscope is not used) Apply ultrasound gel over the pulse. Ultrasound gel must be used. A general pea-sized amount of gel should be used. RATIONALE To confirm that the patient is correct recipient for procedure Improves communication and help reduces anxiety To gain patient co-operation and enable informed and understood consent to the procedure Health Records policy and consent policy An elevated ABPI will result if the cuff is too small and the artery cannot be compressed. A stethoscope is not used as the Doppler is more accurate at capturing the pulses than a stethoscope. Other types of gel contain too much water and are ineffective as conductors of sound e.g. KY jelly. Too little there 5/11

6 will not be enough to conduct the sound. Too much and it would be difficult to maintain the position of the probe. Switch the Doppler on. Hold the probe at degree angle to the blood vessel and direct it to the blood flow. Arterial sounds would be different from venous sounds. Doppler measurements are not usually reliable at angles of less than 25 degrees or greater than 60 to 70 degrees (Kremkau 1995). If at first the pulse is not heard do not move the probe to a new location straight away. Try adjusting the angle of the probe. It should be at a 45 to 60 degree angle to the blood vessel or rotate the probe around your fingers as this may eventually locate the artery. The rationale for holding the probe at a degree angle allows the signal to go through a greater cross-section of the artery thereby making it easier to identify the position of the artery. The latter being continuous and whooshy reflecting the respiratory pattern of breathing in and out. If no sound is heard move the probe slowly tracing the path of the artery and listen carefully. Do not press the probe down into the patient. This is uncomfortable and can compress the vessel. Once the pulse is found and the best sound is located keep the probe still. Inflate the cuff whilst holding the probe over the pulse until any sound disappears. Slowly deflate the cuff and when the sound reappears this indicates systolic pressure. The value must be documented and it is important that the cuff is deflated slowly. Once the sound has been identified the cuff should be quickly deflated. Repeat the procedure for the other arm. If done too quickly the initial sound could be missed, particularly in instances of irregular heart beat. Prolonged inflation can be extremely uncomfortable. Reinflation of the cuff before it has been fully deflated and successive inflations without resting the limb will cause low readings (2001 Vowden and Vowden) Both arms need to be considered because of measurement variability, although only 1 reading will be used to calculate the ABPI (1997 Stubbing et al) Use the higher of the two brachial arm readings to calculate the ABPI for both lower limbs. Record results in leg Ulcer Assessment documentation 6/11

7 PROCEDURE FOR OBTAINING THE ANKLE BRACHIAL PRESSURE To obtain the ankle systolic pressure, a similar procedure to that already described is carried out. PROCEDURE The Practitioner needs to be comfortably positioned as this procedure may take time. It is also important to have a clear view of the anatomy of the foot. Cover any ulceration with cling film. Apply the blood pressure cuff just above the malleoli (ankles) to cover the gaiter area. Locate one foot pulse if possible. It is helpful to palpate the foot pulse first as this will also aid in positioning the probe. However, having prior knowledge of the anatomy of the foot and where the foot pulses are located will enable them to be found even in oedematous feet. Two foot pulses will need to be used, there are 4 in each leg. The posterior tibial pulse is located behind the medial malleolus. The peroneal pulse is alongside as well as distal to the lateral malleolus. The anterior tibial and the dorsalis pedis are part of the same artery so choose either of these but not both. Note that when the extremities are cold the pulse may be more difficult to locate. Record in leg ulcer documentation Apply gel to the chosen foot pulse and position the probe in the direction of the blood flow as previously described. Inflate the blood pressure cuff as for the arm until any sound disappears. Slowly deflate the cuff and when the sound reappears this indicates the systolic pressure. The value must be charted. If the sound does not disappear it is because of arterial calcification and thus the artery cannot be compressed. RATIONALE As this can be a prolonged procedure it is important to avoid any manual handing issues with regards to avoiding and muscularskeletal injuries. Covering the ulcer with cling film will reduce contamination by bacteria and reduce contamination of the equipment. Evidence is demonstrated that the cuff placed over the gaiter area i.e. just above the malleolus produces a more accurate signal than placing the cuff over the calf. (Vowden & Vowden 2001) Two pulses are identified but the highest of the 2 readings is utilised for calculating the Ankle Brachial Pressure Index (ABPI). Pre-tibial diagram of the foot with location of the arteries is available. Provided during training, further copies available from Tissue Viability service Please note that a chart giving a visual interpretation of where the pulses are is available from the Tissue Viability Service and is provided as a part of training within the leg ulcer course. Ultrasonic gel allows conduction of sound To ascertain brachial Doppler value. 1. Locate a second foot pulse and repeat the procedure. 2. Take the highest of the two pedal readings to provide the calculation for that leg. 3. Repeat for the other limb. Both limbs need to be assessed regardless of whether only one is ulcerated or appears affected by symptoms such as oedema. Complete Doppler Assessment Form This is to provide a thorough assessment and to offer comparison and also to identify any ischaemia in the other limb. 7/11

8 CALCULATION OF THE ANKLE BRACHIAL PRESSURE INDEX (ABPI) Two calculations will be obtained. Left ABPI: Divide the highest of the two ankle readings for the leg left leg by the highest of the two brachial pressures. Right APBI: Divide the highest of the two ankle readings for the right leg by the highest of the two brachial pressures. ABPI = Ankle systolic pressure (highest ankle pressure for each leg) divided by the brachial systolic pressure (highest of the two arms). Make a record of all Doppler measurements including the blood pressure readings not just the ABPI. The absolute values can be helpful to specialists. Recording the Doppler sounds is helpful as this will assist in determining the status of the artery and will provide complimentary information to the ABPI. INTERPRETATION OF THE RESULTS The ABPI should be interpreted within the context of a full limb assessment. General interpretations are listed in table 1. Interpretation of Doppler Sounds is listed in table 2. The limitations of the ABPI results and the factors to consider when interpreting findings are outlined in table 3. TABLE 1 - ANKLE BRACHIAL PRESSURE INDEX VALUES AND CLINICAL INTERPRETATIONS Greater or the same as 1 is normal High compression can be used Greater or the same as 0.8 exludes significant arterial disease Less than 0.8 indicates arterial disease reduced compression bandaging 0.6 to 0.8 Vascular assessment should be considered as per local protocols Less than 0.5 Contra indicates compression. Urgent vascular referral is required as per local protocols 8/11

9 TABLE 2 - INTERPRETING DOPPLER SOUNDS Doppler Sound Status of Vessel Characteristics Comments Tri-phasic Bi-Phasic Healthy Vessel has become less elastic. This may be part of the normal physiological process of aging or due to stenosis Sound has thee parts; is pulsatile (bouncy in nature) and is heard at a higher frequency than that of a diseased vessel Sound has two parts, is more dampened that the tri-phasic and heard at a lower frequency Monophasic Diseased Vessel Sound has a simple component and is of lower frequency. Sound descriptors include whooshy, roaring wind, or soldiers marching. In a very diseased vessel the sound can be similar to a vein which appears as an almost continuous whoosh. Oedema may distort a tri-phasic sound so that it is heard as bi-phasic. If the optimum position for the probe has not been found a pulse may appear to be biphasic because the best possible location for the artery has not been determined. Arterial sounds can be distinguished from venous as the latter modulate with the respiratory cycle by mirroring the breathing pattern. IF ANY CLINICAL CONCERNS DISCUSS WITH TISSUE VIABILITY NURSE TABLE 3 - LIMITATIONS OF THE ABPI AND FACTORS TO CONSIDER ABPI Determinations Limitation Rationale Management Implications The ABPI is a calculation of ankle pressure by determining the pressure within the major arterial vessels in the lower limb. It does not assess micro-vessel status. It therefore cannot assess micro-vessel disease in diabetes, vasculitis and rheumatoid arthritis. Microvascular disease occurs in diabetes, vasculitis and rheumatoid arthritis. Caution with high compression bandaging and hosiery. Refer to medical history and presenting clinical symptoms. Doppler sounds may be helpful. Further investigations may be needed. Elevated ABPI above 1.3 The elevated ABPI may be due to In general proceed with caution as too high a 9/11

10 incompressibility of the artery (arteriosclerosis, atherosclerosis) reading, compression bandaging may not be suitable. Refer to medical history and presenting clinical symptoms and discuss with Tissue Viability Specialist Nurse ABPI is inversely related to the patient s blood pressure status (Hughes et al (1988), Belcaro and Nicolaides (1989), Carser (2001). Practitioner inexperience (Ray et al (1994)). ABPI may be calculated as low where hypotension is found. Results will be affected by: Deviations from the procedure Difficulties associated with carrying out the procedure Difficulties in interpreting the results Refer to medical history and presenting clinical symptoms. Doppler sounds may be helpful. If unsure refer to: A more experienced Practitioner Clinical Nurse Specialist (Leg Ulcer or Tissue Viability) IF ANY CLINICAL CONCERNS DISCUSS WITH TISSUE VIABILITY NURSE DECONTAMINATION OF CUFF AND EQUIPMENT Please follow Infection Control Policy for the Decontamination of Reusable Medical Devices for cleaning the cuff and the Doppler probe. Designated low risk for contamination:- Cleanse with pre-impregnated detergent wipes. Dry equipment using a disposable cloth. Alcohol wipes used if disinfection is required. CLINICAL INCIDENTS Any related incidents arising from Doppler assessment which may involve a clinical error or near miss must be reported following the PCT Incident Reporting Policy 10/11

11 REFERENCES 1. NHS Litigation Authority (2008) Risk Management Standards for PCT s. April. 2. Royal Collage of Nursing Institute (1998) Clinical Practice Guidelines: The Management of Patients with venous Leg Ulcers. RCN Institute, London in association with the centre for evidence based nursing, University of York, and the School of Nursing, Midwifery and Health Visiting, University of Manchester 3. Scottish Intercollegiate Guidelines Network (SIGN) (1998) the Care of Patients with Chronic Venous Ulcers: A national Clinical Guideline. No 26. SIGN Publications, Edinburgh 4. Leg Ulcer Policy Wirral Primary care Trust (PCT) 5. Goodacre S, Sutton AJ, Sampson FC (2005) Meta-Analysis: the value of clinical assessment in the diagnosis of deep venous thrombosis. Annals Internal Med 143(2): Carter SA (1969) Clinical Measurement of systolic pressures in limbs with arterial occlusive disease JAMA 207: Vowden P & Vowden K (2001) Doppler Assessment and ABPI: Interpretation in the Management of Leg Ulceration. World Wide Wounds, March ( 8. Stubbing GNJ, bailey P, Poole M (1997) protocol for accurate measurement of ABPI in patients with leg ulcers. J Wound Care 6(9): Warboys, F. (2006) How to obtain the resting ABPI in leg Ulcer Management. Wound Essentials. Volume 1. 11/11