Chronic Refractory Angina

Nursing Guidance: SPINAL CORD STIMULATION

One of a series of guidance notes for nurses. See associated medical chapter.

1. TENS

2. Patient Counselling

3. Stellate Ganglion Block

4. Paravertabral block

5. Spinal Cord Stimulation

6. High Thoracic Epidural Pump

7. Intrathecal Pump

These Guidance lines have been produced in accordance with the NHS Executive publication "Clinical Guidelines" (May 1996) and incorporate those standards produce by the King's Fund for evidence based clinical practice.

Produced for the National Refractory Angina Centre
E-mail Dave.Trenbath@ccl-tr.nwest.nhs.uk

Introduction (go to clinical section)

Neuromodulation is the suppression of pain by the application of an electronic device to modify nervous system function. The underlying principles behind the therapy are based on the gate of pain control theory ¹, that non-destructive stimuli can interfere with the transmission of pain within the central nervous system and thereby preventing the pain messages from reaching the brain. Spinal Cord Stimulators (SCS) were originally implanted specifically for intractable angina in Australia in 1987². Since then there have been over 70 publications on SCS in refractory angina. These studies have confirmed improvement in quality of life of these patients,³ fewer ischaemic episodes ^{4 5} and reduced frequency of hospital admissions.⁶ Moreover these effects are long lasting⁷and obtained at negligible risk.⁸

Psychologist 

Little research has been done on the role of psycholgists in SCS. In our view it can be helpful if patients are seen by a psychologist to ensure suitability prior to entering the programme for SCS implant. Whilst successful SCS can alleviate depression and anxiety there are simpler methods that should be tried first and psychologists can often identify remediable problems that have been missed in the routine outpatient clinic. In addition the psychologist can suggest coping mechanisms that can assist the patient in addition to SCS..

Treatment contract

It is essential that at all stages of treatment a clear treatment contract is developed with attainable goals set by the patient and careers. SCS cannot cure the problem. The actual aim of the treatment, being to ameliorate the effect of angina so that the patient and their family can enjoy a better quality of life. The treatment program and expectations of the patient and their carers are dealt with at all stages of the treatment by the angina management team. This helps to ensure that the patient and carers expectations on pain relief are not unrealistic and thereby unachievable.

Safety

Spinal cord stimulation is a safe and effective treatment in-patient's where conventional revascularisation (Coronary Artery Bypass Graft (CABG) or Percutaneous Transluminal Coronary Angioplasty (PTCA)) is impossible. It may also be an alternative to redo coronary artery surgery or interventions in high-risk patients

Clinicians are naturally concerned about the potential risks of masking myocardial ischaemia by spinal cord stimulation. However studies have demonstrated that spinal cord stimulation decreases lactate production with pacing⁹ and total ischaemic burden,⁴ without an increase in silent ischaemia. It does not mask the pain of a myocardial infarction¹⁰ and mortality rates in-patients with stimulators are similar to those of the general population of patients with coronary artery disease

Treatment of patients who are anticoagulated

Although epidural haematoma is a rare complication following instrumentation of the epidural space, the possible devastating consequences of this requires serious consideration. Full anticoagulation has long been considered a contraindication to epidural catheter placement. However if this rule were to be applied rigidly, many cardiac patients would be denied SCS, which may represent their most promising therapeutic option. Consultation with haematological colleagues is advised. There are different indications for anticoagulation in cardiac patients, which can be stratified into low-risk e.g. atrial fibrillation with no previous embolic history; and high-risk groups e.g. metal valve replacement, when considering the temporary interruption of their warfarin.

In the low risk group, anticoagulants can be stopped and the stimulator implanted when the INR is <1.4. This usually takes three days. In the high-risk group the "therapeutic window" must be tightly controlled to minimise the embolic risks to the patient without exposing them to the risk of epidural haematoma. The patient should be admitted five days prior to the procedure, warfarin stopped and an intravenous infusion of unfractionated heparin is commenced. Regular APTT estimation is mandatory. On the day of implantation, heparin is discontinued three hours prior to the start of the procedure and APTT is checked once more to ensure there is no coagulopathy. Following implantation, the heparin infusion should be recommenced after 3 hours. Warfarin can be restarted that same evening at the usual loading dose and both drugs should run concomitantly until full anticoagulation is achieved

SCS implantation

The implantation of Spinal cord stimulators is a surgical procedure requiring complete aseptic technique and prophylactic antibiotics.

There are two commonly used types of fully systems. The first is a fully implantable system with its own battery, which in time will need replacing due to battery failure, and the second device has no internal battery and is activated by an external 9volt battery pack that activates an antenna held over the skin.

The SCS system has three fully implantable components and is performed in two stages within an operating theatre:

Stage one

During the first stage of the procedure the patient is awake and the exact positioning of the epidural lead is then determined when the are of paraesthesia produced matches the area where pain is usually experienced.

An epidural lead as a number of electrodes (typically four) over a variable length. This lead is fed through a Tuohy needle at the level of T3-4 or T4-5, the tip of the lead being placed at level of C5 and T1.

Stage two

During this second stage the patient is anaesthetised as the remainder of the procedure can be painful. The lead is attached to the extension, which is then tunnelled under the skin to connect to the generator box, which is placed subcutaneously within the abdomen (see below).

The pulse generator contains the electronics of the system, and looks very similar to a pacemaker.

External components include a transmitter alone or transmitter plus antenna, which is placed on the abdomen over the pulse generator.

As with all interventional procedures there is a steep "learning curve" and training is essential, all operators are therefore urged to attend one of the organised spinal cord stimulator courses.

The commonest complication is infection, which can result in the system having to be removed. The implant can be carried out over two stages but this does carry a higher risk of infection it is therefore more desirable to carry out the entire procedure at one sitting if possible (see below).

Lead displacement requiring re-exploration is relatively common, but might be improved with the newer lead designs. Lead fracture is rare.

We at the NRAC in Liverpool tend to use the external system, firstly because it is cheaper, does not require generator replacement when the battery wears, repeated "box change" procedure are undesirable in this group of patients.

Adverse effects with the use of central nervous system stimulation

• Undesirable change in stimulation possibly related to cellular changes around the electrodes, or shifts in electrode position due to changes in posture this usually settles after. Other causes include loose electrical connections or lead/extension fractures. Patients describe their discomfort as being uncomfortable, "jolting" or "shocking".

• Infection this is the commonest complication.

• Placement of the epidural lead is a surgical procedure, which may expose patient to risk of epidural haematoma, haemorrhage and/or paralysis these however carry a very low risk.

• Patients on anticoagulation therapies may be at risk of post-operative complications such as haematoma the guideline of care for anticoagulated patients is included.

• Persistent pain at the receiver site or tunnelled extension lead.

• Lead and/or receiver erosion or migration this will require system removal.

• Loss of pain relief may return patient to his or her underlying pain condition.

• Hypotension.

Nursing Guidelines

Admission assessment procedure

1. Introduction of the patients named nurse.

2. Clinical Assessment e.g. Physiological - psychological - social history.

3. Commence Pain assessment chart.

4. Referral to physiotherapist for explanation of pre and post operative exercises.

5. Baseline observations.

6. Refractory angina patients will usually be on drugs that may cause hypotension and bradycardia. It is important to observe and record the patients blood pressure pulse and respiratory rate prior to the procedure to establish a base line.

Investigations to be requested by the doctor

Electrocardiograph (ECG), Recent Chest X-ray, (CXR), Full blood count (FBC), Urea and electrolytes (U+E's), International Normalised Ratio (INR) if required.

Anticoagulation therapy:-

Spinal Cord Stimulator (SCS).

1. Confirm that they have failed preceding stages of clinical guidelines.

2. Discuss SCS - goals, benefits, and risks.

3. Document patient's ability to cope with the technology.

4. Assess their level of pain using an analogue chart.

5. Discuss what functional changes may be required of the patient during the initially few weeks following operation e.g. Excessive body movement can dislodge the lead and cause partial or total loss of paraesthesia over area of pain.

Information re SCS

1. Develop realistic expectations about pain relief from SCS with patient is essential.

2. Explain procedure

3. Review medical history and ensure completion of prescription sheet and signed consent for surgery obtained.

4. Reinforce explanation of procedures.

5. Commence pain analogue assessment chart.

6. Identify patients or careers anxieties and address them.

7. Commence discharge planning.

Orientate patient to the ward and if possible give approximate time for surgery along with date.

Day of operation

1. It is essential that at all stages of patient care, the aims and objectives of treatment are reiterated so as to allay any misconceptions that the patient and carer may have.

2. Stop heparin three hours prior to surgery and check final APPT to ensure there is no coagulopathy.

3. Nil by mouth for six hours pre surgery.

4. Prepare for theatre - shave and clean skin if required.

5. Give pre-op medication

6. Check patientÌs valuables are safe.

7. Check consent form signed.

8. Check patientÌs observations prior to theatre.

9. Remind the patient they will be awake during test stimulation and participating in its process and that this part of the procedure can take some time to achieve best results.

10. Ensure that the planned position of the pulse generator (usually in the anterior abdomenal wall) is properly marked with the patient upright.

11. Measure the distance between the pulse generator and the spinous process of T4 using a tape measure. This is especially important for very large patients who may require a long extension lead.

Post operative wound care management and assessment

1. In the operating theatre, following wound closure, an occlusive dressing should be applied, such as a vapour permeable film dressing e.g. Tegaderm or IV3000 or a transparant dressing with an integral pad eg. Steripad. If the exudate is high an occlusive absorbent dressing should be used.

2. The dressing should be inspected regularly, if it is not intact or there is excessive leakage it should be changed using an aseptic technique.

3. Post op observation as normally carried out post surgery.

4. Check wound sites for bleeding. Do not remove dressings if clean.

5. Check regularly the patientÌs level of pain to assess function of SCS.

6. Ensure analgesia is given for wound pain post procedure.

7. If the patient was on a Heparin infusion it can be recommence three hours post surgery.

8. Continue observations as required.

9. Encourage early mobility but for the first 24-48 hours avoid sudden movement.

10. Check programming of SCS and ensure the external antenna is placed over the abdominally implanted generator box and monitor effect of stimulation.

Use of appropriate pattern and settings of the SCS transmitter for optimal stimulation and pain coverage.

1. Document electrode combinations as tested.

2. Record optimal settings and responses.

3. Monitor patient's skills and progress with SCS.

4. Patient involvement in monitoring and recording of pain assessment chart.

5. Document patient's response to SCS post surgery in terms of level of pain relief, functional ability and overall quality of life.

General care

1. Wound management observe and monitor for signs of infection.

2. General observations.

3. Medication/analgesia

4. Check general condition.

Safety precautions

The SCS system can be safely used in the home around most common household appliances, including:

• Microwave ovens

• Television, AM/FM radios, stereos, remote controls, video games.

• Tabletop appliances such as toasters, blenders, electrical can openers.

• Hand held items such as hair dryers, shavers, and cellular phones.

• Electric heating blankets and heating pads.

• Small power tools and gardening machinery.

• Computers, copy machines electric typewriters.

The following are best avoided if possible

• Theft detectors Airport/security screening systems

• Large stereo speakers with magnets.

• Electric arch welding equipment

• High voltage power lines.

• Electric substations and power generators.

• Magnetic resonance imaging (MRI scanners).

The internally powered system (IPG) can be effected by magnets, which can turn an IPG on, or off, but this will not change the programmed stimulation settings.

Conventional radiological investigations can be performed without special precautions. However the rapid pace of new technological developments means that it is essential that patients with SCS implant must inform/remind the doctor that they have a spinal cord stimulator well in advance of any treatment or investigation.

Physiotherapy

1. Changes in stimulation due to body movements.

2. Dos and Don'ts

3. Instruction to improve muscle strength

Registration of implant

Presently patient's are registered through the manufacturers registry system and it takes approximately six weeks before the patient receives an international registration card. Initially a temporary card will be given. An international registry is being piloted for general use.

The patient must be made aware that the implant can activate security systems at airports and within shopping centres they are therefore advised to carry the registration card at all times.

District nurse

1. To call on the patient 24 to 48 hours post discharge and then ten days post discharge to remove sutures if required.

2. To check on wound healing process on the back, abdomen and side of chest.

3. To check on antibiotic use.

4. Removal of all sutures by the 10^th day.

5. Seromas and discomfort may occur around IPG pocket as scar tissue forms and will disappear in time. Treatment with cold therapy will help (ice packs)

6. Managing pain through effective use of SCS.

7. Level of musculo-skeletal pain and adequate analgesia.

8. Postural changes will alter stimulation due to movement of the lead.

9. Advice from the doctor on medication reduction as appropriate inline with the effectiveness of the SCS.

References

1. Melzack R, Wall PD. Pain mechanisms: a new theory. Science 1965;150:971-9.

2. Murphy DF, Giles KE. Dorsal column stimulation for pain relief from intractable angina pectoris. Pain 1987;28:365-8.

3. DeJongste MJL, Hautvast RWM, Hillege JL, Lie KI on behalf of the working group on neurocardiology. Efficacy of spinal cord stimulation as adjuvant therapy for intractable angina pectoris. J Am Coll Cardiol 1994;23:1592-7.

4. DeJongste MJL, Haaksma J, Hautvast RWM, Hillege JL, Meyler JW, Staal MJ, Sanderson JE, Lie KI. Effects of spinal cord stimulation on myocardial ischaemia during daily life in patients with severe coronary artery disease. A prospective ambulatory electrocardiographic study. Br Heart J 1994;71:413-8.

5. Sanderson JE, Brooksby P, Waterhouse D, Palmer RGB, Neubauer K. Epidural spinal electrical stimulation for severe angina: a study of its effect on symptoms, exercise tolerance and degree of ischaemia. Eur Heart J 1992;13:628-633.

6. Murray S, Carson KGS, Collins PD, James MA. Spinal cord stimulation significantly reduces hospital readmissions in patients with intractable angina pectoris. Heart 1998;79(suppl):48.

7. Greco S, Auriti A, Fiume D, Gazzeri G, Gentilucci G, Antonini L, Santini M. Spinal cord stimulation for the treatment of refractory angina pectoris: a two year follow-up. PACE 1999;22:26-32.

8. Mannheimer C, Eliasson T, Augustinsson L-E, Blomstrand C, Emanuelsson H, Larsson S, Norrsell H, Hjalmarsson â. Electrical stimulation versus coronary artery bypass surgery in severe angina pectoris. The ESBY study. Circulation 1998;97:1157-63.

9. Mannheimer C, Eliasson T, Andersson B, Berg C-H, Augustinsson L-E, Emanuelsson H, Waagstein F. Effects of spinal cord stimulation in angina pectoris induced by pacing and possible mechanisms of action. BMJ 1993;307:477-80

10. Anderson C, Hole P, OxhØj H. Does pain relief with spinal cord stimulation for angina conceal myocardial infarction? Br Heart J 1994;71:419-421.

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