Local Anaesthesia vs Regional Block for Arteriovenous Fistulae

Overview

End stage renal failure (ESRF)describes an irreversible loss in renal function. The majority of these patients will opt for haemodialysis (HD)as their chosen method of renal replacement therapy (RRT). Arteriovenous fistulae (AVF) are the optimal method of achieving vascular access to permit HD. AVF are created with a small surgical procdure to join the artery and vein together. Over the next 6- 8weeks after surgery the AVF should grow ("mature") into a vessel suitable for needles to be inserted for dialysis. Unfortunately however, around 24% - 35% of AVF fail at an early stage. Some anaesthetic techniques can influence intraoperative blood flow and venous diameter, factors which are associated with fistula success. There remains no conclusive evidence that any particular anaesthetic technique can significantly influence long term surgical outcome. This study aims to investigate whether a regional, compared to local, anaesthetic technique can affect fistula patency.

Chronic kidney disease (CKD) describes abnormal kidney structure or function and is a significant public health problem. It is common, increasingly prevalent with age and often co-exists with significant morbidities, such as diabetes mellitus, hypertension, hyperlipidaemia, cerebrovascular disease and coronary artery disease. Patients with a diagnosis of CKD have a decreased life expectancy compared with individuals without this diagnosis. This is primarily due to cardiovascular disease, but other complications of CKD include bone and mineral disorders, anaemia, depression, and malnutrition. Early recognition and treatment of these complications is recommended. In a proportion of patients, CKD will progress to end stage renal disease (ESRD). This is defined as an irreversible decline in kidney function for which renal replacement therapy (RRT) is required if the patient is to survive. In one UK study, 4% of patients with CKD progressed to develop ESRD requiring RRT over a five and a half year follow up period. The decision to commence RRT takes into account symptoms of biochemical disturbance, in conjunction with the risks and inconvenience of starting RRT. European Best Practice Guidelines recommend that RRT should commence when the estimated Glomerular Filtration Rate (eGFR) falls below 15ml/min/1.73m2 or when symptoms of uraemia, fluid overload or malnutrition are resistant to medical therapy. In an asymptomatic patient, an eGFR of below 6ml/min/1.73m2 would also prompt the initiation of dialysis. It is known that the life expectancy of patients receiving RRT is shorter than that of the general population and varies further dependent on underlying diagnosis and age. For example, the median survival for a patient in Scotland aged 45 - 64 years starting RRT for glomerulonephritis is 7.7 years, whereas the median survival of a patient in the same age group with a diagnosis of diabetic nephropathy is 2.9 years. The life expectancy of a male of the same age group within the general Scottish population is 24.2 years. Instituting RRT prolongs life and reduces the incidence of vasculo-occlusive events in patients with ESRD. As such, patients with CKD should be monitored by a nephrologist in order that timely referral for preparation for RRT can be made. Renal replacement therapy may come in the form of haemodialysis, peritoneal dialysis or renal transplantation, and may be managed both in and out of hospital. Haemodialysis (HD) remains the most common modality of first RRT in Scotland; of 2885 patients commencing RRT during the period 2005-2009, 2264 received HD. In order to undergo HD, there must be a connection between the patient's vascular system and the dialysis machine. The most common method is surgical creation of an arteriovenous fistula (AVF), into which a needle can be inserted that in turn is connected to a dialysis machine. In 2009, 75% of Scottish patients undergoing HD underwent formation of an arteriovenous fistula (AVF). Other options for vascular access include arteriovenous grafts using synthetic materials and long-term central venous catheters, though these are associated with higher rates of occlusive and infective complications. AVF are currently regarded as the optimal form of vascular access for HD and are recommended by National guidelines. There is excellent evidence that good quality, stable vascular access is a major factor in determining survival in this group of CKD patients. Unfortunately however, around 24% - 35% of arteriovenous fistulae (AVF) fail at an early stage. Some anaesthetic techniques can influence intraoperative blood flow and venous diameter, factors which are associated with fistula success. There remains no conclusive evidence that any particular anaesthetic technique can significantly influence long term surgical outcome. This study aims to investigate whether a regional, compared to local, anaesthetic technique can affect fistula patency.