Effects of verapamil in the prevention of warm ischaemia induced acute renal failure in dogs

Functional, histologic, and ultrastructural study of the protective effects of verapamil in experimental ischemic acute renal failure in the rabbit

The present study was performed in vivo in rabbits to evaluate the functional and morphologic effects of verapamil in a model of ischemic acute renal failure (ARF). Particularly impressive was the ultrastructural integrity of renal tubules in the animals exposed to both ischemia and verapamil. Three groups were studied: Group A: no ischemia; Group B: renal ischemia alone; and Group C: renal ischemia with verapamil. Creatinine clearance was higher in Group C (0.77 mL/min/kg) compared to Group B (0.13 mL/min/kg) at 24 h of reperfusion (p < .005) as well as at 48 and 72 h (0.73 mL/min/kg) vs. 0.35 mL/min/kg; p < .05 and 0.90 mL/min/kg vs. 0.46 mL/min/kg; p < 0.05, respectively). Light microscopic evaluation of Group C rabbits revealed significantly better preservation of proximal tubule (PT) brush border (p < .0005) and less desquamation of PT (p < .05) compared to Group B. Ultrastructural examination of in vivo perfused kidneys also demonstrated decreased loss of microvilli of PT (p < .0005) as well as less cellular edema (p < .005), fewer cells with apical PT membrane rupture (p < .01), better preservation of mitochondria (p < .005), less flattening of the PT basolateral labyrinth (p < .05), and fewer hypertrophic actin bands at the basal surface of PT epithelial cells (p < .05). These results suggest that verapamil markedly attenuates PT morphologic injury in a rabbit model of reversible ischemic ARF. The functional protection observed in these studies may be related, in part, to the improved structural integrity of the renal tubules. Renal transplantation and anticipated renal ischemia (i.e., surgical interventions) are two important situations where treatment with verapamil or other calcium channel blockers may prove to be clinically beneficial.

Ischemic acute renal failure

Underperfusion of the kidneys often results in the development of ischemic acute renal failure. This review summarizes the recent developments in the understanding of the pathophysiology, diagnosis, and treatment of this serious and costly disorder that affects almost 5% of hospitalized patients.

Effects of diltiazem on postischaemic renal cortical microcirculation in the pig

Diltiazem--a calcium entry blocker--was tested in a porcine model under continuous chlormethiazole-pancuronium anaesthesia as protection against renal failure following 60 min of renal ischaemia. Fourteen pigs were randomly allocated to one experimental (diltiazem and ischaemia) and one control group (only ischaemia) (n = 7 in each). Diltiazem was administered as a continuous intravenous infusion started before the ischaemic insult. In two additional animals diltiazem was given but ischemia was not induced. The postischaemic renal cortical microcirculation was simultaneously investigated in four different regions in the left kidney during the first 4 h of reperfusion. Laser Doppler flowmetry (LDF) was performed in two different regions and measurement of tissue oxygenation was done in two other regions. In the two animals treated with diltiazem without ischaemia, only minor variations in central haemodynamic and renal microcirculatory parameters were evident. In the control group (ischaemia), superficial renal cortical blood flow (Qsrc) decreased from 49 +/- 11 (s.d.) arbitrary units at baseline to 24 +/- 4 arb. units 4 h after start of reperfusion (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium antagonists and acute renal failure

PURPOSE

To critically review the question of whether calcium antagonists can prevent or attenuate post-ischemic acute renal failure (ARF).

PATIENTS AND METHODS

Using a computer-assisted search, we identified all experimental and clinical studies published in English between 1980 and 1988 in which the main research question addressed the efficacy of verapamil, diltiazem, or nifedipine in the treatment of post-ischemic ARF. Studies were then selected for review based on clearly specified inclusion criteria and evaluated against accepted methodologic guidelines.

RESULTS

In experimental studies of warm renal ischemia, calcium antagonists provided significant protection of glomerular filtration rate (GFR) when given before and after ischemic injury; however, isolated pre- or post-ischemic treatment produced equivocal results. In autotransplantation studies on protracted cold ischemia, verapamil produced a modest, although physiologically significant, increase in GFR during warm reperfusion but failed to alter graft survival. Studies of calcium antagonists in humans with ARF have been confined to patients undergoing renal transplantation. Diltiazem given both to donor grafts and to recipients produced a significant reduction in the rate of delayed graft function but failed to improve one-year graft survival. This result may be due to the study of small numbers of low-risk patients. At present, there is no conclusive evidence that one calcium antagonist is more efficacious than another in the treatment of post-ischemic ARF.

CONCLUSIONS

Calcium antagonists appear to prevent or reduce the severity of post-ischemic ARF only when given prior to and after the ischemic insult. As a result, these agents will have most utility in the setting of renal transplantation. Although the efficacy of these agents in reducing delayed graft function appears to be established, their failure to improve graft survival is poorly understood and requires further investigation.