Prevention of intradialytic hypotension in patients with acute kidney injury submitted to sustained low-efficiency dialysis

OBJECTIVES

This study evaluated the effects of a protocol aiming to reduce hypotension in acute kidney injury (AKI) patients submitted to sustained low-efficiency dialysis (SLED).

METHODS

Patients were randomly assigned to two SLED prescriptions-control group, dialysate temperature was 37.0°C with a fixed sodium concentration [138 mEq/L] and ultrafiltration (UF) rate; and profiling group, dialysate temperature was 35.5°C with a variable sodium concentration [150-138 mEq/L] and UF rate.

RESULTS

Sixty-two SLED sessions were evaluated (34 in profiling and 28 in control). Patients (n = 31) were similar in terms of gender, age, and Sequential Organ Failure Assessment (SOFA) score. Dialysis time, dialysis dose, and post-dialysis serum sodium were similar in both groups. The profiling group had significantly less hypotension episodes (23% vs. 57% in control, p = 0.009) and achieved higher UF volume (2.23 ± 1.25 L vs. 1.59 ± 1.03 L in control, p = 0.04) when compared with control group.

CONCLUSIONS

SLED protocol with modulation of dialysate temperature, sodium, and UF profiling showed similar efficacy but less intradialytic hypotension when compared with a standard SLED prescription.

Tetanus-induced acute kidney injury in a renal transplant recipient

A 48-year-old renal transplant recipient who developed tetanus 6 years after transplantation is described. His immunosuppressive protocol was mofetil mycophenolate, sirolimus, and prednisone. The patient presented symptoms of severe tetanus with autonomic dysfunction, requiring ICU care and mechanical ventilation. His clinical course was marked by development of tetanus-induced acute kidney injury and sepsis. He was discharged after 37 days of hospitalization with recovered renal function. Tetanus is a preventable disease associated with a high fatality rate. Its treatment is difficult and requires specialized and intensive care. This case highlights the crucial importance of following adequate immunization guidelines in transplant recipients.

Patients with ischaemic, mixed and nephrotoxic acute tubular necrosis in the intensive care unit--a homogeneous population?

Introduction

Acute tubular necrosis (ATN) is usually studied as a single entity, without distinguishing between ischaemic, nephrotoxic and mixed aetiologies. In the present study we evaluated the characteristics and outcomes of patients with ATN by aetiological group.

Method

We conducted a retrospective comparison of clinical features, mortality rates and risk factors for mortality for the three types of ATN in patients admitted to the general intensive care unit of a university hospital between 1997 and 2000.

Results

Of 593 patients with acute renal failure, 524 (88%) were classified as having ATN. Their mean age was 58 years, 68% were male and 52% were surgical patients. The overall mortality rate was 62%. A total of 265 patients (51%) had ischaemic ATN, 201 (38%) had mixed ATN, and 58 (11%) had nephrotoxic ATN. There were no differences among groups in terms of age, sex, APACHE II score and reason for ICU admission. Multiple organ failure was more frequent among patients with ischaemic (46%) and mixed ATN (55%) than in those with nephrotoxic ATN (7%; P < 0.0001). The complications of acute renal failure (such as, gastrointestinal bleeding, acidosis, oliguria and hypervolaemia) were more prevalent in ischaemic and mixed ATN patients. Mortality was higher for ischaemic (66%; P = 0.001) and mixed ATN (63%; P = 0.0001) than for nephrotoxic ATN (38%). When ischaemic ATN patients, mixed ATN patients and all patients combined were analyzed by multivariate logistic regression, the independent factors for mortality identified were different except for oliguria, which was the only variable universally associated with death (odds ratio [OR] 3.0, 95% confidence interval [CI] 1.64–5.49 [P = 0.0003] for ischaemic ATN; OR 1.96, 95% CI 1.04–3.68 [P = 0.036] for mixed ATN; and OR 2.53, 95% CI 1.60–3.76 [P < 0.001] for all patients combined]).

Conclusion

The frequency of isolated nephrotoxic ATN was low, with ischaemic and mixed ATN accounting for almost 90% of cases. The three forms of ATN exhibited different clinical characteristics. Mortality was strikingly higher in ischaemic and mixed ATN than in nephrotoxic ATN. Although the type of ATN was not an independent predictor of death, the independent factors related to mortality were different for ischaemic, mixed and all patients combined. These data indicate that the three types of ATN represent different patient populations, which should be taken into consideration in future studies.

Risk factors for development of acute renal failure after liver transplantation

BACKGROUND

Acute renal failure (ARF) is a common complication after liver transplantation (LTx). Identification of risk factors may prevent the development and attenuate the impact of ARF on patients outcome after LTX.

METHODS

Retrospective analysis of variables in the pre, intra, and postoperative periods of 92 patients submitted to LTx was performed in order to identify risk factors for development of ARF after LTx. ARF was defined as serum creatinine > or = 2.0 mg/dL in the first 30 days after LTx. Univariate and multivariate analysis by logistic regression were performed.

RESULTS

ARF group comprised 56 patients (61%). Preoperative serum creatinine was higher in ARF group. During the intraoperative period, ARF group required more blood transfusions, developed more episodes of hypotension and presented longer anesthesia time. In the postoperative period, ARF group presented higher serum bilirubin and more episodes of hypotension. Dialysis was required in 10 patients (11%). The identifled risk factors for development of ARF were: preoperative serum creatinine > 1.0 mg/dL. more than five blood transfusions in the intraoperative period, hypotension during intra and postoperative periods. The identified mortality risk factors were hypotension in the postoperative period and no recovery of renal function after 30 days.

CONCLUSIONS

Several factors are involved in the pathogenesis of ARF after LTx and may influence patients outcome and mortality. Pretransplant renal function and hemodynamic conditions in the operative and postoperative periods were identified as risk factors for development of ARF after LTx. Nonrenal function recovery and postoperative hypotension were identified as mortality risk factors after LTx.

Mechanisms underlying the genesis of post-extrasystolic potentiation in rat cardiac muscle

Changes of contractility resulting from changes in stimulation pattern (post-extrasystolic potentiation - PESP) were investigated in right ventricular papillary muscles from female albino rats (EPM strain, 160-200 g). The preparations were superfused with bicarbonate buffered solution at 24 +/- 0.5 degrees C, and stimulated at 0.5 Hz. Maintained paired stimulation was performed at several coupling intervals (360, 500, 660, 770 and 920 ms) with normal Krebs for 30 s. After treatment with ryanodine (1 microM), used as an inhibitor of the release of sarcoplasmic reticulum Ca2+ activity, the same protocol was repeated in the presence of normal Krebs, low Na+ (80 mM, LiCl used as substitute) and low K+ concentrations to change the level of activity of the Na+/Ca2+ exchange mechanism. With normal Krebs, paired pulse stimulation produced a maintained potentiation of the post-extrasystolic beat and an extrasystole with a reduced force generation when compared to the control steady-state contraction. As the interval between the extrasystole and the normal beat was increased the potentiation of the post-extrasystolic beat was reduced and the force of the extrasystole was increased. Ryanodine treatment reduced the force of contraction and increased its duration, and the pattern of the PESP phenomenon was altered. Both the post-extrasystolic and the extrasystolic beats were potentiated compared to the steady-state contraction obtained under ryanodine treatment. The extrasystole displayed a greater potentiation than the post-extrasystolic beat. As the interval between them increased the amplitude of the extrasystolic beat was enhanced.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of isoproterenol on the mechanical activity of isolated papillary muscles and perfused rat hearts in various calcium concentrations

The aim of the study was to examine, in papillary muscles and in a whole heart preparation, the effects of isoproterenol on the myocardial mechanical activity at different extracellular Ca2+ concentrations. Papillary muscles from left ventricles, contracting isometrically, and rat hearts perfused by the Langendorff technique developing isovolumetric pressure at a fixed rate (200 bpm) and diastolic pressure of 5 mmHg were studied at different Ca2+ concentrations for analysis of the effects of increasing doses of isoproterenol. Papillary muscles were treated with isoproterenol (0.5 to 8 ng ml-1) at four extracellular Ca2+ concentrations (0.25, 0.5, 1.25 and 2.5 mM) and Langendorff perfused hearts were stimulated by isoproterenol (0.05 ng ml-1 to 0.8 ng ml-1), also at four extracellular Ca2+ concentrations (0.5, 1.25, 2.5 and 3.75 mM). Both papillary muscles and perfused hearts showed that force and isovolumetric systolic pressure increase in response to isoproterenol at low Ca2+ concentrations. As Ca2+ concentration is increased, isoproterenol's positive inotropic effect subsides. However, papillary muscle isometric contractions showed a similar time to peak tension decrease in response to isoproterenol at all external Ca2+ concentrations used. The results suggest that the positive inotropic response to isoproterenol, in isolated preparations, changes as a function of extracellular Ca2+ concentration decreasing as external Ca2+ increases. Time to peak tension reduction reinforces the idea that this small positive inotropic response to isoproterenol of the rat myocardium, at the physiological Ca2+ concentration, is due to the Ca2+ saturation of the mechanical activity.