Cerebral artery responses to pressure and flow in uremic hypertensive and spontaneously hypertensive rats.

Impaired cerebral blood flow autoregulation is seen in uremic hypertension, whereas in nonuremic hypertension autoregulation is shifted toward higher perfusion pressure. The cerebral artery constricts in response to a rise in either lumen pressure or flow; we examined these responses in isolated middle cerebral artery segments from uremic Wistar-Kyoto rats (WKYU), normotensive control rats (WKYC), and spontaneously hypertensive rats (SHR). Pressure-induced (myogenic) constriction developed at 100 mmHg; lumen flow was then increased in steps from 0 to 98 microl/min. Some vessels were studied after endothelium ablation. Myogenic constriction was significantly lower in WKYU (28 +/- 2.9%) compared with both WKYC (39 +/- 2.5%, P = 0.035) and SHR (40 +/- 3.1%, P = 0.018). Flow caused constriction of arteries from all groups in an endothelium-independent manner. The response to flow was similar in WKYU and WKYC, whereas SHR displayed increased constriction compared with WKYU (P < 0.001) and WKYC (P < 0.001). We conclude that cerebral myogenic constriction is decreased in WKYU, whereas flow-induced constriction is enhanced in SHR.

Temporary vascular access for first dialysis is common, undesirable and usually avoidable.

BACKGROUND: When technically feasible, patients with end-stage renal failure should commence regular dialysis treatment with permanent access to the circulation (by arteriovenous fistula) or peritoneum (by soft peritoneal catheter) in situ, thus avoiding the need for initial hemodialysis employing temporary vascular access. We have examined the frequency, consequences and avoidability of temporary access in such patients. METHODS: 178 patients commencing regular dialysis between August 1993 and April 1995 were analysed retrospectively using case notes. Patients were divided into those who had permanent dialysis access in situ when they commenced dialysis and those who required temporary access. If temporary access was required, the patients were further analysed into those who had been first seen by a nephrologist at least 12 weeks before the first dialysis, and those who had been referred "late". It was assumed that 12 weeks was sufficient time for permanent access to be instituted. Mortality within the first 90 days of commencing dialysis was recorded. RESULTS: Seventy-four of 82 patients opting for regular hemodialysis and 53 of 96 opting for peritoneal dialysis required temporary vascular access. Late referral accounted for 47 and delays within the renal service for 35 of such patients. Late presentation to the medical profession or indecisiveness on the part of the patient accounted for the remainder. Twenty-five of 127 patients requiring temporary access but only one or 51 patients not requiring it died within 90 days of commencement of treatment. CONCLUSION: Late presentation to a renal unit prior to first dialysis is associated with increased mortality. Late referral or late presentation are associated with an increased need for temporary vascular access for first dialysis. Many patients who require temporary access for first dialysis could have been better managed.

Haemofiltration: how to do it.

Haemofiltration and its variants are simple procedures which allow the management of patients with renal failure in intensive therapy units without the need for continual support from renal specialists. In order for non-renal specialists to manage the practical aspects of these treatments logically, safely and successfully it is important to understand the basic principles involved.

Technetium-99m methoxy isobutyl isonitrile (MIBI) imaging of the parathyroid glands in patients with renal failure.

BACKGROUND: Technetium-99m methoxy isobutyl isonitrile (Tc-99m MIBI) scintigraphy has been reported to be at least as reliable as thallium-technetium subtraction imaging in the preoperative localization of hyperplastic parathyroid glands in patients with renal failure. Reports have suggested that 50% of glands can be identified correctly by this method. The aim of this study was to improve on previous results and demonstrate that Tc-99m MIBI imaging has an important place in the preoperative work-up of these patients. METHODS: Eighteen patients on renal replacement therapy were studied. All had tertiary hyperparathyroidism and had Tc-99m MIBI imaging prior to parathyroidectomy. A refined reporting method was employed. The imaging results were compared to the subsequent surgical and histological findings. RESULTS: In the 12 patients in whom serum parathyroid hormone levels fell postoperatively to within or below the normal range, 38 of 46 glands (82.6%) were correctly identified and located in the correct quadrant of the thyroid gland. There were two false positive results where the imaging predicted glands not subsequently found by the surgeon. In the patients who had post-operative hyperparathyroidism, repeat Tc-99m MIBI imaging was able to locate accurately the site of the residual parathyroid tissue. CONCLUSIONS: Tc-99m MIBI imaging is able to identify more than 80% of hyperplastic parathyroid glands in renal failure patients if this reporting process is used, and locate them in the correct quadrant of the thyroid gland. Tc-99m MIBI imaging is of particular value when re-exploration of the neck is required for post-parathyroidectomy hyperparathyroidism. These results represent a significant improvement on the sensitivity of this imaging technique when compared to previous published data.

Antineutrophil cytoplasmic antibody-positive crescentic glomerulonephritis associated with anti-thyroid drug treatment.

Two cases of antineutrophil cytoplasmic antibody (ANCA)-positive vasculitis following treatment with propylthiouracil and carbimazole are described. Both patients had crescentic glomerulonephritis proven by renal biopsy and responded to immunosuppressive therapy and withdrawal of the anti-thyroid drugs. Though systemic vasculitis associated with propylthiouracil is reported, this is the first report to our knowledge of renal biopsy-proven vasculitis associated with either of these drugs.

Identification of auto-transplanted parathyroid tissue by Tc-99m methoxy isobutyl isonitrile scintigraphy.

Parathyroid tissue is sometimes auto-transplanted into the forearm after 'total' parathyroidectomy in patients with renal failure. Recurrent hyperparathyroidism demands identification of the source of PTH secretion which cannot be assumed to be the forearm. To this end, Tc-99m methoxy isobutyl isonitrile (MIBI) scintigraphy was used to identify functioning auto-transplanted parathyroid tissue in seven patients undergoing renal replacement therapy (five with functioning renal transplants and two on haemodialysis). Serum PTH was estimated in venous blood taken proximal and distal to the forearm graft and from the contralateral arm, and subsequent Tc-99m MIBI scanning was carried out without knowledge of the PTH results. Five patients had a significant gradient in PTH levels between sites proximal and distal to the graft, and between the proximal site and the contralateral arm, suggesting functioning parathyroid tissue in the graft. Subsequent Tc-99m MIBI scintigraphy confirmed the activity of the auto-transplanted parathyroid tissue in these five patients. In the remaining two patients without a significant PTH gradient between the sampling sites, Tc-99m MIBI scintigraphy did not identify any functioning forearm parathyroid tissue. The scan results therefore correlated well with the gradients in PTH levels, suggesting that MIBI scintigraphy can be used to identify functioning auto-transplanted parathyroid tissue. The results also indicate that any patient who has undergone auto-transplantation of parathyroid tissue must have blood samples taken from veins proximal to the graft and either distal to it, or from the contralateral arm when parathyroid status is re-assessed, particularly when surgery is being considered for recurrent hyperparathyroidism.