Vasopressor Agents After Experimental Brain Death: Effects of Dopamine and Vasopressin on Vitality of the Small Gut

Vasopressin Use in the Support of Organ Donors: Physiological Rationale and Review of the Literature

The objective of this review was to depict the physiological and clinical rationale for the use of vasopressin in hemodynamic support of organ donors. After summarizing the physiological, pharmacological concepts and preclinical findings, regarding vasopressin's pathophysiological impacts, we will present the available clinical data.

DATA SOURCES

Detailed search strategies in PubMed, OVID Medline, and EMBASE were undertaken using Medical Subject Headings and Key Words.

STUDY SELECTION

Physiological articles regarding brain death, and preclinical animal and human studies about the use of vasopressin or analogs, as an intervention in organ support for donation, were considered.

DATA EXTRACTION

Two authors independently screened titles, abstracts, and full text of articles to determine eligibility. Data encompassing models, population, methodology, outcomes, and relevant concepts were extracted.

DATA SYNTHESIS

Following brain death, profound reduction in sympathetic outflow is associated with reduced cardiac output, vascular tone, and hemodynamic instability in donors. In addition to reducing catecholamine needs and reversing diabetes insipidus, vasopressin has been shown to limit pulmonary injury and decrease systemic inflammatory response in animals. Several observational studies show the benefit of vasopressin on hemodynamic parameters and catecholamine sparing in donors. Small trials suggest that vasopressin increase organ procurement and have some survival benefit for recipients. However, the risk of bias is overall concerning, and therefore the quality of the evidence is deemed low.

CONCLUSIONS

Despite potential impact on graft outcome and a protective effect through catecholamine support sparing, the benefit of vasopressin use in organ donors is based on low evidence. Well-designed observational and randomized controlled trials are warranted.

Experimental study to assess the impact of vasopressors administered during maintenance of the brain-dead donation in the quality of the intestinal graft

BACKGROUND

The hemodynamic maintenance of brain-dead donors will influence the quality of the organs procured for transplantation, including the intestine. Although norepinephrine (NE) and dopamine (DA) are commonly used to sustain mean arterial pressure in humans, there are no standardized protocols for their use during maintenance of brain-dead donors. Our aim was to compare the effects of each drug, in the intestinal graft quality using a rat brain-dead donation model.

METHODS

Wistar rats (N = 17) underwent brain death (BD) for 2 hours with NE (NE group) or with DA (DA group) administration; the control group was mechanically ventilated for 2 hours without BD. Jejunum biopsies were obtained at the end of the maintenance period. Histological damage was evaluated using Park-Chiu scale. Villi/crypt ratio, mucosal thickness, Goblet cell count, and villi density were evaluated using ImageJ software (US National Institutes of Health, Bethesda, MD). Barrier damage was assessed by bacterial translocation culture counting on liver samples. The inflammatory status of the intestine was evaluated by CD3+ counting by immunohistochemistry and gene expression analysis of interleukin (IL)-6, IL-22, and CXCL10.

RESULTS

Norepinephrine-treated donors had higher focal ischemic injury in the intestinal mucosa without a substantial modification of morphometrical parameters compared with DA-treated donors. CD3+ mucosal infiltration was greater in intestines procured from brain-dead donors, being highest in NE (p ˂ 0.001). Local inflammatory mediators were affected in BD: DA and NE groups showed a trend to lower expression of IL-22, whereas CXCL10 expression was higher in NE versus control group. Brain death promoted intestinal bacterial translocation, but the use of NE resulted in the highest bacterial counting in the liver (p ˂ 0.01).

CONCLUSION

Our results favor the use of DA instead of NE as main vasoactive drug to manage BD-associated hemodynamic instability. Dopamine may contribute to improve the quality of the intestinal graft, by better preserving barrier function and lowering immune cell infiltration.

The Modulatory Effect of Ischemia and Reperfusion on Arginine Vasopressin-Induced Arterial Reactions

Aim of the Study. The purpose of this study was to investigate the impact of ischemia and reperfusion on the resistance of arteries to AVP (arginine vasopressin), with a particular emphasis on the role of smooth muscle cells in the action of vasopressin receptors and the role of the cGMP-associated signalling pathway. Materials and Methods. Experiment was performed on the perfunded tail arteries from male Wistar rats. The constriction triggered by AVP after 30 minutes of ischemia and 30 and 90 minutes of reperfusion was analysed. Analogous experiments were also carried out in the presence of 8Br-cGMP. Results. Ischemia reduces and reperfusion increases in a time-dependent manner the arterial reaction to AVP. The presence of 8Br-cGMP causes a significant decrease of arterial reactivity under study conditions. Conclusions. Ischemia and reperfusion modulate arterial contraction triggered by AVP. The effect of 8Br-cGMP on reactions, induced by AVP after ischemia and reperfusion, indicates that signalling pathway associated with nitric oxide (NO) and cGMP regulates the tension of the vascular smooth muscle cells.

Endocrine Considerations of the Pediatric Organ Donor

Patients determined to be neurologically deceased exhibit potentially harmful changes in various endocrine pathways due to disruptions of the body's neurohormonal control mechanisms. These deviations from endocrine homeostasis lead to hemodynamic, metabolic, and immunologic aberrations that are associated with reduced graft procurement and function for the purposes of organ donation. Existing literature has attempted to describe the pathophysiology that associates disruptions in endocrine pathways with organ dysfunction, both to increase understanding and to identify strategies to support the donor. For example, diabetes insipidus due to arginine vasopressin deficiency is commonly encountered, and should be anticipated. The significance of abnormalities in other pathways such as those involving cortisol and thyroid hormone is less established; however, there is increasing support for treating potential organ donors with combined hormonal therapies. While there are published documents aimed at guiding management of organ donors in general, many controversies exist and pediatric-specific literature is scarce. This article aims to review several of the important endocrine-specific aspects of managing the neurologically deceased organ donor, with an emphasis on pediatrics where information is available.

Terlipressin in brain-death donors

BACKGROUND

Metabolic management of brain-death organ donors includes correction of the hormonal perturbations that occur after cerebral death and impair circulatory function. Vasopressin is a hormone secreted by the posterior pituitary gland, which contributes to maintain systemic blood pressure by regulating urine secretion and small arteriole tonus. During brain death, the pituitary gland is damaged and hormone secretion rapidly ceases. Low-dose vasopressin increases systemic blood pressure and decreases the need for catecholamines in brain-dead organ donors but it is not available in many countries. Terlipressin is a synthetic analog of vasopressin characterized by greater selectivity for the V1 receptor than vasopressin. To date, the efficacy of terlipressin as a pressor agent in humans has been reported in a few studies.

METHOD

Pharmacology and literature about the use of terlipressin in shock and in particularly in neurogenic shock following brain death is summarized and our personal experience is reported.

RESULTS AND CONCLUSION

Terlipressin is helpful in controlling severe hypotension; its use allowed to reduce the infusion rate of norepinephrine about 50% in two of three brain-death organ donors, but there are not yet enough data to define its therapeutic range and incidence of collateral effects on the grafts.

Brain death induced renal injury

PURPOSE OF REVIEW

The considerable demand in kidney transplantation against a persisting organ donor shortage has forced most centers to nowadays accept of suboptimal donor kidneys.

RECENT FINDINGS

Despite the substantial increase in the past decade in kidney transplantation with grafts retrieved from living donors and after donation from deceased brain dead (DBD) and extended criteria donation (ECD) donors, the supply of donor kidneys still does not meet the actual numbers needed. Moreover, older and more marginal kidney donors following the physiologically abnormal state of brain death do function less well and have a shorter graft survival.

SUMMARY

In this review, we present an overview of the current knowledge of renal injury induced by pathophysiological effects of brain death and its relevance for renal transplant outcome.The better insight in the role of brain death induced renal injury has clearly demonstrated its detrimental effect on outcome but, also, offers new opportunities for donor management and evaluation of new biomarkers to assess kidney graft quality in the brain dead donor. The option to intervene and selectively block or enhance a pathway as well as identify specific parameters for graft quality at time of organ retrieval in the deceased brain dead donor will ultimately benefit early function and long-term survival.