Evaluation of gamma camera-based measurement of individual kidney function using iodine-123 orthoiodohippurate

Effects of isoflurane anaesthesia depth and duration on renal function measured with [99mTc]Tc-mercaptoacetyltriglycine SPECT in mice

BACKGROUND

The influence of anaesthetic depth and the potential influence of different anaesthetic beds and thus different handling procedures were investigated in 86 severe combined immunodeficient (SCID) mice using semi-stationary dynamic single photon emission computed tomography (SPECT) for kidney scintigraphy. Therefore, isoflurane concentrations were adjusted using respiratory rate for low (80-90 breath/min) and deep anaesthesia (40-45 breath/min). At low anaesthesia, we additionally tested the influence of single bed versus 3-mouse bed hotel; the hotel mice were anaesthetized consecutively at ~ 30, 20, and 10 min before tracer injections for positions 1, 2, and 3, respectively. Intravenous [99mTc]Tc-MAG3 injection of ~ 28 MBq was performed after SPECT start. Time-activity curves were used to calculate time-to-peak (Tmax), T50 (50% clearance) and T25 (75% clearance).

RESULTS

Low and deep anaesthesia corresponded to median isoflurane concentrations of 1.3% and 1.5%, respectively, with no significant differences in heart rate (p = 0.74). Low anaesthesia resulted in shorter aortic blood clearance half-life (p = 0.091) and increased relative renal tracer influx rate (p = 0.018). A tendency toward earlier Tmax occurred under low anaesthesia (p = 0.063) with no differences in T50 (p = 0.40) and T25 (p = 0.24). Variance increased with deep anaesthesia. Compared to single mouse scans, hotel mice in position 1 showed a delayed Tmax, T50, and T25 (p < 0.05 each). Furthermore, hotel mice in position 1 showed delayed Tmax versus position 3, and delayed T50 and T25 versus position 2 and 3 (p < 0.05 each). No difference occurred between single bed and positions 2 (p = 1.0) and 3 (p = 1.0).

CONCLUSIONS

Deep anaesthesia and prolonged low anaesthesia should be avoided during renal scintigraphy because they result in prolonged blood clearance half-life, delayed renal influx and/or later Tmax. Vice versa, low anaesthesia with high respiratory rates of 80-90 rpm and short duration (≤ 20 min) should be preferred to obtain representative data with low variance.

Relative kidney hyperfiltration in primary aldosteronism: a meta-analysis

INTRODUCTION

Since the phenomenon of hyperfiltration in primary aldosteronism (PA) was first noted in 1996, subsequent clinical studies have produced conflicting results. To determine the development of relative hyperfiltration in PA, we performed a meta-analysis.

METHODS

MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials (CENTRAL) were searched through to July 2009. Reference sections of original articles, meta-analyses, and reviews on hyperfiltration in PA were reviewed. Hypertensive patients provided the controlled data for hyperfiltration. Two authors independently extracted the data.

RESULTS

A total of seven studies were included. One study was from the data of the TAIPAI group. Overall, there was strong evidence that relative kidney hyperfiltration existed in PA (fixed-effects model: standardised mean difference (SMD), 0.13; 95% confidence interval (CI), 0.03-0.22, p = 0.007; random-effects model: SMD, 0.35; 95% CI, -0.01-0.71, p = 0.05), though with a significant heterogeneity (p < 0.0001). In the secondary meta-analysis with five top-quality studies, the relative kidney hyperfiltration was more significant. Mean age in each enrolled study was the only factor significantly associated with the existence of heterogeneity among the selected studies in the meta-regression analysis.

CONCLUSIONS

Current evidence suggests that relative kidney hyperfiltration is the hallmark in PA and the phenomenon is beyond the effect of hypertension of PA. Clinicians should be aware of the possibility of occult renal damage in patients with PA.