Biomedical subjects

David Shemesh

Publications and source records attributed to David Shemesh.

4 recordsLinked to original sources

PubMed2006

Sympathectomy-like effects of brachial plexus block in arteriovenous access surgery.

We used color Doppler ultrasonography to prospectively study the effects of supraclavicular brachial plexus block (BPB) on blood flow and vein diameter in patients undergoing arteriovenous access surgery. BPB might produce a sympathectomy-like effect that could have a role in improving patencty. Thirty-one consecutive patients who underwent arteriovenous access surgery with BPB were studied prospectively, in addition to 5 patients with BPB having other operations and 5 patients undergoing general anesthesia for elective surgery. Vessel diameter and pulsatility index (PI) were among the parameters measured. Mean PI decreased from 6.18 +/- 1.67 before the block to 3.92 +/- 1.75 at 10 min after initiation of the block (p = 0.001). Basilic vein diameter increased from 6.28 +/- 0.86 mm (range 4.85 to 7.30) before the block to 7.83 +/- 1.52 mm (range 5.80 to 12.14) 10 min after the block (p = 0.03). In the general anesthesia control group the PI decreased, but returned to preanesthetic levels immediately after the patients reached the recovery room. In the nonaccess BPB group the PI remained low after the block for at least 5 h. Brachial plexus block causes significant venous dilation and a significant decrease in the pulsatility index. This appears to be due to a beneficial sympathectomy-like effect of the block that might prevent early failure and improve patency in vascular access surgery.

Anesthesia, General↗

PubMed2002

The predictive value of the halo sign in color Doppler ultrasonography of the temporal arteries for diagnosing giant cell arteritis.

OBJECTIVE: The diagnosis of giant cell arteritis (GCA) usually requires a temporal artery biopsy. Recently it has been reported that a periluminal dark halo, detected by color Doppler ultrasonography (US) of the temporal arteries, is a characteristic sign of GCA. We evaluated the predictive value of this dark halo sign in diagnosing GCA. METHODS: During a period of 2 years 69 patients suspected of having GCA were examined by US of both temporal arteries. Temporal artery biopsy was performed in 32 of these patients. The diagnosis of GCA was made if a patient had a biopsy showing arteritis, or met all the following criteria: (1) American College of Rheumatology GCA classification criteria were fulfilled; (2) there was a prompt clinical response to treatment with 40-60 mg/day of prednisone; and (3) no other diagnosis related to the patient's symptoms was made during 6 month followup. RESULTS: Periluminal dark halo was observed in 24 of 69 patients. GCA was diagnosed in 12 of them, giving a positive predictive value (PPV) of only 50%. No halo was detected in 45 cases of which only 2 had GCA, resulting in a high negative predictive value (NPV) of 96%. The sensitivity and specificity of the halo sign for diagnosing GCA were 86% and 78%, respectively. CONCLUSION: The PPV of the halo sign in US of the temporal arteries is unsatisfactory for diagnosing GCA. However, the NPV is very high. Thus the lack of a halo can practically serve to rule out a diagnosis of GCA, and precludes the need for a biopsy in most instances.

Biopsy, Needle↗

PubMedDate not supplied

An integrated vascular management programme.

This paper discusses the development of an integrated approach for the creation and maintenance of arteriovenous access (AVA), under the direction of a dedicated vascular access surgeon in close cooperation with the haemodialysis staff, involving pre-operative imaging, anaesthetic and surgical techniques together with a post-operative graft surveillance programme, in order to maximize autogenous arteriovenous access (AAVA) construction (the preferred access for haemodialysis patients with end-stage renal disease), and to improve patency rates for AAVA and prosthetic arteriovenous access (PAVA).

Algorithms↗

PubMedDate not supplied

Integrated approach to construction and maintenance of prosthetic arteriovenous access for hemodialysis.

Autogenous arteriovenous access is the preferred access for hemodialysis patients with end-stage renal disease but is not feasible in a significant number of patients. The creation of a prosthetic arteriovenous access (PAVA) for hemodialysis using expanded polytetrafluoroethylene is technically simple and the short-term results are usually good, but the PAVA's 1-year patency rate is low (less than 60% in many centers). We have developed an integrated approach for the creation and maintenance of PAVAs, under the direction of a dedicated vascular access surgeon, involving preoperative imaging, anesthetic and surgical techniques, and a postoperative graft surveillance program, to improve patency rates. The design used was a prospective nonrandomized study. Between January 1, 1999 and December 31, 2001, 158 PAVAs were created (37.7% of the 419 fistulae created during this period). High-resolution duplex ultrasonography was added to careful clinical assessment in planning and follow-up of the dialysis access. The preferred method of PAVA creation was the forearm loop using tapered 4 to 7 mm stretch expanded polytetrafluoroethylene. After surgery, patients entered a program of close follow-up and regular graft surveillance and maintenance. Prophylactic surgical revisions and endovascular interventions were performed routinely according to ultrasonography findings to prevent thrombosis. Thrombolysis and thrombectomy were performed without delay when the PAVA thrombosed, minimizing the use of central venous access and salvaging the central veins. No patients were excluded from the study. One-, 2-, and 3-year assisted primary patency rates (including patients without occlusion but who were judged to require prophylactic revision) were 65%, 54.1%, and 48.8%, respectively. With surveillance-directed surgical revisions and endovascular treatment before or after occlusion, the 1-, 2-, and 3-year secondary patency rates (functional patency) were 91.4%, 84.3%, and 78.5%. Of the 158 grafts, 110 never occluded during the study period. There were 155 interventions in 74 PAVAs: 30 surgical revisions, 63 prophylactic endovascular procedures, and 52 instances of thrombolytic therapy combined with percutaneous transluminal angioplasty. The use of prosthetic arteriovenous access for hemodialysis, when autogenous arteriovenous access is not feasible, can still be associated with excellent long-term patency, in spite of previously published poor results, as long as good planning, close follow-up, and aggressive intervention (when indicated) are carried out.

Angioplasty, Balloon↗