Vasoactive substances in renal transplantation

Risk factors and outcomes associated with a higher use of inotropes in kidney transplant recipients

Preservation of adequate perfusion pressures to the graft is a main focus of intraoperative management during kidney transplantation. We undertook this study to investigate the incidence of the higher use of inotropes in kidney transplant recipients and identify the patient outcomes and preoperative and intraoperative variables related to this.We retrospectively analyzed 1053 patients who underwent kidney transplantation at Asan Medical Center between January 2006 and February 2012, stratified by their inotropic score ([dopamine] + [dobutamine] + [epinephrine × 100] + [norepinephrine × 100]) <7 versus ≥7, wherein all doses are expressed as μg/kg/min. We evaluated preoperative characteristics, hemodynamic parameters, and intraoperative variables as well as postoperative outcomes, such as length of hospital stay and 1-year rejection and mortality rate.Receiver-operating characteristic analysis was performed to determine inotropic score to predict 1-year mortality. An inotropic score of 7 had the best combined sensitivity and specificity. An inotropic score ≥7 (137 patients, 13.0%) was significantly more prevalent in older patients, those with polycystic kidney disease, and at a 2nd transplant. Anesthesia time, the amounts of crystalloid and 5% albumin infused, and the need for red blood cell transfusion were significantly higher in the inotropic score ≥7 group. The patients with a higher use of inotropes required longer postoperative hospital stay and experienced a >2-fold higher rejection within the 1st year and a 4-fold higher 1-year mortality rate.A higher use of inotropes in kidney transplant recipients is more prevalent in older patients, those with a 2nd transplant and in patients with polycystic kidney disease as their primary renal disease. The postoperative hospital stay, rejection within the 1st year, and 1-year mortality rate are increased in patients with an inotropic score ≥7.

The impact of timing of maximal crystalloid hydration on early graft function during kidney transplantation

BACKGROUND

Early graft function is crucial for successful kidney transplantation. Maintaining adequate hydration is complicated by rapid movement of water to the extravascular space. We designed this study to test the effect of maximal hydration during graft ischemia time on early renal function.

METHODS

Forty adult patients with chronic renal failure underwent renal transplantation from related living donors. Study subjects were randomly assigned 1 of 2 regimens for intraoperative hydration. The constant infusion rate group received normal saline 0.9% at an infusion rate 10 to 12 mL . kg(-1) . h(-1) from the start of surgery until the renal vessels were unclamped after vascular anastomosis. The central venous pressure target (CVPT) group received normal saline 0.9% titrated to maintain a specific central venous pressure (CVP). The target CVP from the start of surgery until clamping of the donor renal vessels was 5 mm Hg except for the interval from clamping of the renal vessels until the end of renal vascular anastomosis, when the target CVP was 15 mm Hg. Perioperative hemodynamics, infused saline volumes, rate of infusion, onset of diuresis, graft turgidity, urine volume, and renal function during the first 5 postoperative days were recorded.

RESULTS

At the end of renal ischemia time, both groups had received approximately 3 L crystalloid solution. The CVPT group achieved the highest peak of intravascular volume expansion with an average infusion rate of 48.3 mL . min(-1) during 48 +/- 12 minutes of renal ischemia. The CVPT group had better graft function, required fewer vasopressors and diuretics, and had less postoperative tissue edema than the constant infusion rate group.

CONCLUSIONS

Hydration directed toward maintaining a given CVP during kidney transplantation produced a more stable hemodynamic profile and promoted diuresis. The calculated infusion rate of approximately 45 to 50 mL . min(-1), within an hour ischemia time, seems feasible to enhance early graft function. A larger trial with long-term follow-up of renal function is warranted to confirm the clinical benefit of titrating IV crystalloid administration to maintain a given CVP in this population.

Cardiac diastolic dysfunction in renal-transplant recipients is associated with increased circulating Adrenomedullin

BACKGROUND

Renal transplantation is an excellent therapeutic alternative for end-stage renal diseases. Nevertheless, the cardiac function is often impaired in renal-transplant patients (RTR) and importantly determines their prognosis. Adrenomedullin (ADM), a peptide involved in cardiovascular homeostasis, is believed to protect both cardiac and renal functions - by increasing local blood flows, attenuating the progression of vascular damage and remodelling and by reducing glomerular injury - and might be involved in renal-transplantation physiopathology. This work was performed to investigate whether an increase in circulating ADM might be related to RTR cardiac function.

METHODS

Twenty-nine subjects, 19 RTR and 10 healthy subjects, participated in the study. After 15 min rest in supine position, heart rate and systemic blood pressure were measured together with cyclosporine through levels, creatinine and ADM. Systolic and diastolic cardiac functions were assessed, using Doppler echocardiography.

RESULTS

Subjects were similar concerning age, weight, heart rate and blood pressure. Creatinine and ADM (53.8 +/- 6.9 vs. 27.2 +/- 4.1 pmol/L, p = 0.02) were significantly increased in RTR (73 +/- 10 months after transplantation). Cardiac systolic function was normal, but a reduced mitral E:A ratio was observed in RTR (0.90 +/- 0.06 vs. 1.38 +/- 0.10, p < 0.001), reflecting their impaired left ventricular relaxation. Such a ratio was negatively correlated with ADM (r = -0.55, p = 0.002).

CONCLUSIONS

RTR present with an increased ADM is likely related to cardiac diastolic dysfunction. In view of its protective effect on the cardiovascular system, these data support further studies to better define the role and the therapeutic potential of ADM after renal transplantation.

Correlation between endothelin expression in early post-transplant biopsy specimens and long-term allograft function in living-related renal transplantation

OBJECTIVE

We investigated whether degree of immunohistochemically evident endothelin (ET) expression in early post-transplant biopsy specimens could predict long-term allograft function in living-related renal transplantation.

METHODS

Allograft biopsy specimens obtained from 40 patients with living-related transplants were studied. Cases with episodes of acute rejection or calcineurin inhibitor toxicity were excluded. We immunostained graft biopsy specimens obtained at pre-transplantation (PRE) and at 3 months (3M) afterward with anti-ET antibody. The number of stained tubular epithelial cells per 1000 tubular cells was defined as the staining index (SI). In the 21 patients whom we could assess at 3 yr (3Y) after transplantation, the correlation between ET expression and long-term graft function was examined.

RESULTS

Anti-ET antibody staining was appreciable in tubular epithelium but not in glomeruli. Tubular SI at PRE and at 3M were 10.6 +/- 15.3 and 32.0 +/- 35.6 (mean +/- SD) respectively (p < 0.01). When patients were classified according to SI (group A, SI < 25; group B, SI > 25), declining ratio in creatinine clearance at 3Y after transplantation for groups A and B with respect was 21.8% +/- 15.4% and 41.9% +/- 21.6% (p < 0.05).

CONCLUSION

High ET expression in early post-transplantation, biopsy specimens was related to poor long-term allograft function following living-related renal transplantation.

Cell and molecular biology of the multifunctional peptide, adrenomedullin

Adrenomedullin (AM) is a recently discovered regulatory peptide involved in many functions including vasodilatation, electrolyte balance, neurotransmission, growth, and hormone secretion regulation, among others. This 52-amino acid peptide is expressed by specific cell types in many organs throughout the body. A complex receptor system has been described for AM; it requires at least the presence of a seven-transmembrane-domain G-protein-coupled receptor, a single-transmembrane-domain receptor activity modifying protein, and a receptor component protein needed to establish the connection with the downstream signal transduction pathway, which usually involves cyclicAMP. In addition, a serum-binding protein regulates the biological actions of AM, frequently by increasing AM functional attributes. Changes in levels of circulating AM correlate with several critical diseases, including cardiovascular and renal disorders, sepsis, cancer, and diabetes. Whether AM is a causal agent, a protective reaction, or just a marker for these diseases is currently under investigation. New technologies seeking to elevate and/or reduce AM levels are being investigated as potential therapeutic avenues.