Both the industry and the medical professions have long been aware that venous pressure monitoring may not always detect venous needle dislodgement. The actual reason for this has not been as clear and there has been no clear and simple method to identify high risk patients

Low fistula pressure increase the risk

Hans-Dietrich Polaschegg (ref. 11) has showed that fistula pressure is crucial if you want to identify high-risk patients. Whilst low fistula pressure is optimal for many reasons, the venous pressure monitor is unlikely to detect needle dislodgement if the pressure is below 25 mmHg.

Setting the venous pressure monitor limits too low may increase the possibility of detecting needle dislodgement, but will also cause an unacceptable rate of false-positive (nuisance) alarms. Because the actual value may change during dialysis, the fistula pressure should be rechecked at regular intervals.

Polaschegg recommends that venous fistula pressure is measured before treatment, and that if fistula pressure is below 25 mmHg, the patient should be regarded as high risk patient. According to him, low fistula pressure may be present with more than fifty percent of the patients and thus recommends:

"For patients with low fistula pressure, i.e .the majority of patients, use external devices or other measures"

Other risk factors

Patients considered as high-risk patients for needle dislodgement have typically been those with a medical condition or behavior which causes restlessness. Some sources estimate an increased risk during the last two hours of dialysis, when some patients become more restless. No, or poor, visibility of access due to the patient occupying single room or receiving nocturnal dialysis in wards with lights out are other factors that may affect the risk. (ref. 9).

It's not all about the level of monitoring. Methods of secure needle fixing and a general raised awareness among patients and staff are also important. But as renal failure is a growing problem, dialysis clinics get busier. The added difficulty of trying to keep an eye on a number of dialysis treatments to prevent a bleeding incident puts extra pressure on the staff.

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