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Pulmonary hypertension: the role of specialist units

VOL: 97, ISSUE: 34, PAGE NO: 54

NATALIE DOUGHTY, BSc, RGN, research nurse Papworth Hospital, Cambridge

ANN MAINWOOD, RGN, Dip N, ward sister, PVDU, Papworth Hospital, Cambridge

The symptoms of pulmonary hypertension (PH) are subtle and non-specific at the beginning. Patients will complain of unexplained breathlessness on exercise, slowly increasing in severity. In addition they may have a dry cough and oedematous ankles and they may have experienced syncopal episodes. The condition, if untreated, is invariably fatal within two to five years.

The symptoms of pulmonary hypertension (PH) are subtle and non-specific at the beginning. Patients will complain of unexplained breathlessness on exercise, slowly increasing in severity. In addition they may have a dry cough and oedematous ankles and they may have experienced syncopal episodes. The condition, if untreated, is invariably fatal within two to five years.

PH is, as the name suggests, raised blood pressure in the blood vessels of the lungs. The normal pulmonary circulation is a low pressure system, and normal values are about one fifth of the systemic blood pressure. The mean pulmonary artery pressure on average is 15-18mmHg, but up to 24mmHg is the normal range at rest. However, patients with PH can demonstrate pressures greater than 24mmHg at rest and 30mmHg or greater during exercise.

PH can affect both the arterial and venous pulmonary circulation. It usually arises as a secondary complication of another disease, for example chronic thromboembolic disease, or as a complication of chronic obstructive airways disease. The incidence of PH for all forms of the disease is unknown, but it is believed to be underdiagnosed.

Primary PH is a subset of arterial pulmonary hypertension. It tends to affect people in the third or fourth decade of life, and women more often than men. The symptoms are nonspecific and the physical findings can be subtle, so the disease is often only diagnosed in its later stages.

The purpose of specialist centres
The diagnostic classification and assessment of the severity of the disease will affect the treatment offered. During the patients' initial admission they undergo a series of tests and radiological investigations. The results are carefully considered and, following discussion with patient and close relatives, a treatment plan is decided.

There are complex and invasive treatments available to patients in the latter stages of the disease which have been shown to increase life expectancy and improve quality of life, (Higgenbottam et al, 1998). In addition, clinical trials of new treatments and new methods of administration of established treatments are best accessed through a specialist centre.

Management plan
The Papworth pulmonary vascular disease unit (PVDU) accepts referrals from all over the country. It has extensive experience of diagnosing and treating pulmonary hypertension. In addition Papworth PVDU is the UK centre designated by the National Specialist Commissioning Advisory Group for the performance of thromboendarterectomy, a surgical treatment for the thromboembolic form of the disease.

Following patients' initial admission to the PVDU, when they undergo a battery of tests, they start either conservative treatment or more radical interventionist therapy.

Patients return to the unit six weeks after the first admission or sooner if their physical condition dictates, so that the effectiveness of the treatment can be assessed and, if necessary, adjusted. Thereafter, if the patient's condition remains stable, they are reviewed at three-monthly intervals. All patients are encouraged to telephone the unit at any time if they have questions about their treatment or if they notice a change in their condition.

Patients who are assessed as requiring prostaglandin therapy sometimes start this during their initial admission. However, it takes at least two weeks to titrate dosage up to a therapeutic level and to teach the patient and relatives how to safely manage the therapy.

Patients with thromboembolic PH who are assessed as suitable candidates for thromboendarterectomy will be readmitted to the PVDU before surgery for insertion of an interior venacaval filter and to undergo coronary angiogram if coronary artery disease is suspected. Patients who despite treatment are in advanced right heart failure are referred to the transplant service for assessment.

Conservative treatment of PH
Early diagnosis and treatment are important goals in managing this disease. Patients who respond positively to a vasodilatory challenge during right heart catheter are also likely to respond to oral calcium channel blockers, such as diltiazem. Dosages are usually higher than would normally be given for treatment of systemic hypertension. For pulmonary hypertension doses up to 900mg as a once daily, modified-release dose can be given, if tolerated.

People with PH are prone to pulmonary thrombosis formation because platelet activity is enhanced. Warfarin is used in the treatment of the majority of patients, as anticoagulation has been shown to improve survival.

Prostaglandin therapy
Patients whose ordinary daily activities are severely compromised by their disease and who do not respond to calcium channel blockers may be offered prostaglandin therapy. Clinical trials with continuous intravenous prostacyclin have demonstrated improvements in exercise capacity, haemodynamics, quality of life and survival (Higgenbottam et al, 1998).

- Continuous long-term intravenous infusion of prostacyclin via an indwelling central venous catheter, using a battery-operated syringe driver:

Patients who undergo this form of therapy have to be carefully taught how to manage their infusion safely. They must learn to mix, store and infuse the drug and must satisfy the nurses specialising in this field that they are capable of doing so safely, according to established guidelines. They must know how to look after the syringe driver and what to do if it malfunctions. Patients keep a second back-up pump in case of primary pump failure.

Side-effects associated with this form of therapy include syncope resulting from an acute hypotensive reaction arising from accidental administration of a bolus, facial flushing, jaw and musculoskeletal ache, diarrhoea, headaches, rashes and thrombocytopaenia.

Two serious complications of this method of administration are rebound pulmonary hypertension and serious infection associated with the central venous catheter. The patient must learn to clean and redress the catheter daily after showering, or at 48-hour intervals if the dressing is kept dry, using a transparent semi-permeable dressing.

- Continuous long -term subcutaneous infusion of a prostacyclin analogue using a micro-infusion, positive pressure infusion pump designed for subcutaneous drug delivery

The prostacyclin analogue used for this method of administration is only available through designated specialist centres at present. It is chemically stable and has a half-life of three hours when given subcutaneously. Therapy is initiated on the ward at a dose of 1.25ng/kg/min and subsequently increased as tolerated by the patient.

As with the intravenous administration of prostacyclin, nurses play a key role in patient education and support. Patients are taught how to draw up their medication, how to site the subcutaneous infusion and all aspects of pump maintenance and care.

Side-effects of administering prostanoid therapy in this way are the same as intravenous prostacyclin. A frequent complication of this method is a painful erythematous rash at the site of entry. This does not appear to be dose-related and usually improves after a few weeks. Simple analgesia, such as paracetamol, can be given in the meantime.

- Intermittent inhalations of nebulised Iloprost

There are some patients for whom the option of a continuous infusion of prostanoid therapy is not acceptable or practical. For these patients, nebulised Iloprost is usually a realistic alternative. Iloprost is also a synthetic analogue of prostacyclin. It is chemically stable, and its half life is approximately 40 minutes. Papworth PVDU uses Schill multisonic compressors because the droplet size needed to achieve optimum deposition in the small pulmonary arteries is considerably finer than that achieved by the usual type of compressor. The machine should have the facility to filter during expiration to prevent contamination of the patients environment. These machines are not robust, and patients must be taught to clean and carefully maintain them. If the compressor is not properly maintained the delivery of the drug may be affected.

The Schill multisonic compact and pro-compressors in use at Papworth PVDU have many component parts, each of which has to be replaced at set intervals. The task of keeping track of all infusion pumps and compressors in use by patients, as well as replacing parts and trouble-shooting for patients experiencing problems with their machines, currently falls to a health care assistant.

Therapy is initiated on the ward at a starting dose of 3.3mcg per nebulisation and is carefully titrated over several days to an average daily dose of 140mcg, the rate of increase depending on how well the patient tolerates the inhalations. The optimum volume per nebulisation is 3-4 ml/nebulisation, so each increase is achieved by increasing the concentration of the nebuliser solution, not the volume.

Patients nebulise their first medication at 6am, and then three-hourly for the rest of the day until midnight, a total of seven times in 24 hours, with a six-hour break at night. Patients must learn the correct breathing technique and how to assemble, clean and care for their machine. If the compressor is not properly maintained the delivery of the drug may be affected.

Conclusion
Pulmonary hypertension specialist centres have a responsibility to educate the nursing and medical community, not only with a view to earlier diagnosis but also about the treatment options available, including surgery for suitable patients. A possible diagnosis of pulmonary hypertension should be considered in any case of unexplained breathlessness and in any case of conditions that can be complicated by pulmonary hypertension. Incidental changes on ECG or CXR indicating possible right heart strain or failure should also alert clinical staff to the possibility of pulmonary hypertension.

Untreated pulmonary hypertension carries a high mortality rate. Patients who understand the full implications of the diagnosis of pulmonary hypertension, often feel frightened and isolated. Nurses who come into contact with these patients have a crucial role to play in supporting, teaching and caring for patients and their families. Specialist centres have a wealth of therapeutic options, and use of these have dramatically reduced mortality rates and improved quality of life.

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