The influence of thyroid hormone replacement in a porcine brain death model

This study was conducted to determine whether the administration of tri-iodothyronine (T3) to brain-dead donor pigs would improve hemodynamic instability, serum levels of thyroid hormones, or the outcome of transplantation of donor livers. Brain death was caused in young pigs (25-38 kg) by rapid inflation of an intracranially implanted balloon catheter. The animals were maintained on a ventilator and frequent measurements of acid/base balance, electrolytes, and glucose were made. At the end of 16 hr, livers were removed and implanted into prepared recipients. Serum-free tri-iodothyronine fell to zero at the end of 16 hr, and there was a 4-6-fold decline in free thyroxine (T4). The levels of serum reverse T3 (rT3) however, increased up to 6-fold. In animals treated with tri-iodothyronine 2 micrograms/hr, the serum levels of free T3 and T4 were not changed but the levels of serum reverse T3 (rT3) increased further. There were no apparent correlations between any hemodynamic parameter and serum thyroid hormone levels in the donors. After the liver transplants, recipients could be divided into those that survived longer than 6 days and those that did not. Although there were significant differences in the plasma levels of alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase, there was no correlation between survival and whether the donor had received tri-iodothyronine. Although other hormones, including insulin and cortisol, may also be necessary, there is no indication from these studies that the administration of tri-iodothyronine to brain-dead donors of liver grafts benefits the serum hormone levels in the donors or the subsequent survival of the recipients.

Lidocaine decay and hepatic extraction in the pig

Plasma lidocaine decay after injection was studied in five anaesthetized pigs and fitted to a two compartment open model. Derived pharmacokinetic parameters were employed to rapidly achieve plateau concentrations within 60 min of starting a two stage infusion of lidocaine hydrochloride. Hepatic extraction and clearance of lidocaine at steady state were determined in 10 pigs by transhepatic sampling and measurement of hepatic arterial and portal venous blood flow using perivascular ultrasonic flow probes placed at laparotomy. These data were compared with similar studies performed in man as well as the sheep, dog, monkey and cat. The lidocaine extraction ratio of 0.60 in the pig was found to be similar to that determined by others in man.

Liver regeneration after hepatic ischemia and reduced liver autotransplantation in the rat

Current knowledge of liver regeneration after reduced liver transplantation is limited. Warm ischemia is one component of the reduced liver transplantation procedure that could have an impact on the regenerative response. To study this effect, we performed partial hepatectomy on male Long-Evans rats, with animals divided into four groups: group 1 underwent partial hepatectomy only; group 2 underwent partial hepatectomy and 40 min of ischemia; group 3 underwent partial hepatectomy, 40 min of ischemia and portocaval shunt surgery; and group 4 underwent partial hepatectomy and orthotopic autograft surgery. Group 5 consisted of sham-operated animals. Animals were killed 4, 24, 48, 72 and 96 hr after surgery. Thymidine kinase activity, mitotic index, a liver mass index and ornithine decarboxylase levels were used as parameters of liver regeneration. Aspartate transaminase was recorded. Maximal thymidine kinase and mitotic index were observed in group 1 animals at 24 hr. In groups 2, 3 and 4 maximal thymidine kinase activity and mitotic activity were observed 24 hr later at 48 hr. The magnitude of the peak response in these groups appeared to correlate with the duration of portal venous occlusion, with greatest increases occurring in those groups where portal stasis was most prolonged. The increase in liver mass for these groups was also delayed with respect to group 1 animals. The anticipated peak in ornithine decarboxylase levels was seen at 4 hr in group 1. The ornithine decarboxylase response in the other groups was disorganized, with delay of the recorded peaks.(ABSTRACT TRUNCATED AT 250 WORDS)

The cardiovascular and intracranial effects of laryngoscopy and endotracheal intubation in hypercarbic neonatal piglets

Laryngoscopy and endotracheal intubation is a potent sympathetic stimulus in adults. Neonates are frequently intubated, but few data exist on the cerebral effects of this intervention. The cardiovascular and intracranial effects of laryngoscopy and endotracheal intubation were studied in 17 hypercarbic neonatal piglets. The mean arterial pressure in the study group (11 piglets) increased significantly within 2 minutes of the stimulus, and remained elevated for almost 14 minutes. The intubated animals showed significantly more haemorrhage in the basal area of the brain than the 6 control animals. The distribution suggests bleeding in the choroid plexus of the 4th ventricle. The significance of such bleeds is not immediately apparent, since none of the animals was grossly neurologically affected by the intervention. However, subtle long-term neurological deficits cannot be excluded and this aspect requires further study. Laryngoscopy and endotracheal intubation may cause non-lethal haemorrhage in the choroid plexus and central canal of the hindbrain in hypercarbic, neonatal piglets.

Comparison of in vivo and ex vivo porcine liver function using the same liver

In vivo and ex vivo liver function was compared using the same livers to exclude interanimal variation in hepatic function. Six male pigs were anesthetized, and catheters and perivascular flow probes placed for transhepatic sampling and hepatic arterial and portal venous flow measurement. After a 2-h in vivo study period, the livers were resected and studied immediately afterwards for a further 2 h ex vivo as an isolated perfused preparation (Experiment A). Hepatic function in a further 6 pig livers (Experiment B) was studied ex vivo only for comparison with the ex vivo livers from Expt. A to determine whether the prior in vivo study had affected hepatic function. Despite using the same livers with similar total hepatic blood flows, (0.91 +/- 0.16 ml.g-1 x min-1) in vivo and (0.84 +/- 0.03 ml.g-1 x min-1) ex vivo, hepatic oxygen consumption (6.5 +/- 0.9 vs 2.6 +/- 0.2 ml O2 x 100 g-1), adenosine-5-triphosphate content (5.22 +/- 0.62 vs 4.14 +/- 0.71 microM.g liver-1) and bile flow (15.1 +/- 1.2 vs 6.0 +/- 1.0 ml.h-1) were initially less ex vivo and remained so throughout the study, while perfusate potassium (initially) (3.7 +/- 0.1 vs 6.4 +/- 0.3 meq.l-1), and aspartate aminotransferase (50 +/- 9 vs 76 +/- 5UL-1) was consistently higher than in vivo values. Initial hepatic energy charge (0.620 +/- 0.034 vs 0.552 +/- 0.061) and total adenine nucleotides 12.49 +/- 0.60 vs 11.66 +/- 0.62 microM.g liver-1) were not different and remained so subsequently.(ABSTRACT TRUNCATED AT 250 WORDS)

Disturbance of plasma thyroid hormone levels after experimental liver transplantation. Is there an association with primary graft nonfunction?

It has been suggested recently that preoperative plasma thyroid hormone levels may be used to predict the success of liver transplantation in prospective recipients and also perhaps that postoperative levels may be used to identify rejection. In the present study of unimmunosuppressed porcine recipients of liver allografts, two groups of animals were identified--those that died within five days postoperatively and the other group that were longer survivors. On the first postoperative day plasma levels of total and free T4 and total and free T3 declined and of total rT3 increased. In survivors these levels returned towards normal within three days, while they persisted in nonsurvivors. As there was no obvious cause of graft failure in nonsurvivors, the state might be considered to represent primary graft nonfunction in pigs, and the changes in plasma thyroid hormone levels may be predictive of this condition; a study in patients may confirm this.

Presentations to the Surgical Research Society of Southern Africa--the second 10 years (1982-1991)

Over the 10-year period 1982-1991, 594 papers were read at the annual meetings of the Surgical Research Society of Southern Africa. One hundred and thirty-five (23%) reported work performed on experimental animals with a trend to an increase from this base; 152 (26%) were presentations from surgeons-in-training, also with a trend to increase over the decade. The distribution by subspecialty was: upper gastro-intestinal tract 28%; hepatobiliary 12%; vascular 16%; immunology/transplantation 9%; further subspecialties 9%; and miscellaneous 26%. Major observations are that the number of papers has doubled since the first decade, probably due to establishment of the poster session, and that presentations by surgeons-in-training remain in the minority at the Society.

Plasma fibronectin levels during acute rejection and acute tubular necrosis in renal transplant patients

Fibronectin (Fn), an acute phase glycoprotein synthesized by the liver, has an important immunomodulatory role. We have investigated the changes in plasma Fn in patients after renal transplantation in order to determine whether these changes predict graft injury or rejection episodes. Besides normal healthy controls, healthy pregnant controls, and a trauma control group, we used two groups of chronic renal failure patients as controls: group I, patients with end-stage renal failure (ESRF) on peritoneal dialysis; group II, patients with ESRF on hemodialysis. These were compared with two groups of renal transplant patients: group III, patients 3 months after successful renal transplantation; group IV, patients studied sequentially 10 days immediately posttransplantation. The renal transplant patients were treated with low-dose cyclosporine, azathioprine, and steroids. Citrated plasma samples were collected for Fn assay by a sandwich-type ELISA and for SDS-PAGE analysis and Western blotting. The mean plasma Fn levels were as follows: healthy controls 311.6 SEM, 13.5 micrograms/ml; healthy pregnant controls 357 SEM, 5.9 micrograms/ml; trauma controls 262.3 SEM 31.7, micrograms/ml; group I 169 SEM, 25.1 micrograms/ml; group II 199 SEM, 27.2 micrograms/ml; group III 272 SEM, 21.7 micrograms/ml; group IV 212 SEM, 27.4 micrograms/ml (day 3 postop). There was a significant difference in the plasma Fn levels on day 3 posttransplant between the patients with delayed and immediate renal function (P less than 0.03) (group IV). A significant decrease in plasma Fn levels occurred immediately after steroid therapy was stopped (P less than 0.03) in patients treated for acute rejection. Plasma Fn levels were significantly decreased in the presence of delayed graft function but did not predict rejection.

Orthotopic liver transplantation at Groote Schuur Hospital

We present data on 10 patients (5 men and 5 women, aged 21-56 yrs) with end-stage liver disease or tumour who underwent orthotopic liver transplantation at Groote Schuur Hospital between October 1988 and June 1991. Standard surgical techniques were used for procuring the donor liver, the recipient hepatectomy and the implantation of the liver. The venovenous bypass method was used in all but 2 patients. Postoperative immunosuppression was usually achieved with cyclosporin, azathioprine and low-dose steroids. Six patients were treated with prophylactic OKT3. Rejection episodes were treated with bolus doses of intravenous steroids. The indications for liver transplantation included chronic active hepatitis progressing to cirrhosis (5), biliary cirrhosis in association with inflammatory bowel disease (1), sclerosing cholangitis (2), alpha 1-antitrypsin deficiency (1), and tumour (1). All patients with chronic liver disease had experienced at least one complication, examples of which included encephalopathy, bacterial peritonitis, ascites, variceal bleeding and septicaemia. Serious postoperative complications included acute rejection of the transplanted liver, renal and liver failure that responded to intensive care support and medical management. One patient died on the 11th postoperative day with complications of bleeding oesophageal ulcer, shock and fungaemia. The remaining patients are alive and well 1-31 months after transplantation.

How rapidly do hyperinsulinaemia and hyperglucagonaemia develop after portacaval shunting?

Elevation of serum insulin and plasma glucagon have been reported during and immediately after clinical and experimental liver transplantation and in patients with cirrhosis and surgically created or spontaneous portacaval shunts. There is controversy about the relative roles of portal diversion and impaired liver function in the genesis of these elevated levels of pancreatic hormones. End-to-side portacaval shunt was made in normal pigs which were fitted with catheters which allowed transhepatic sampling during and for 4 hr after the operation. Within 5 min of opening the shunt, there was a sixfold increase in portal venous insulin concentrations but hepatic clearance of insulin and the arterial concentration were unaltered. The increase in insulin was sustained for 2 hr. A twofold increase occurred within 1 hr in portal venous glucagon concentration which appeared to be predominantly of pancreatic origin and which continued for the 4 hr of the study. Hepatic glucose uptake did not occur after portacaval shunting despite levels of glucose elevated two-fold by iv infusion. There were no changes in aspartate aminotransferase, hepatic tissue energy charge, or total adenine nucleotides, suggesting that hepatic function was intact. It is concluded that portal diversion results in an increase in insulin and glucagon secretion and in the absence of hepatic uptake of glucose. This is a novel observation with relevance especially in liver transplantation when portal diversion for at least 1 hr forms part of the procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Ex vivo versus in situ resection of segmental liver grafts in pigs--a comparison in immediate and four-hour-stored grafts

This study compared the function of reduced grafts prepared in situ or ex vivo and transplanted immediately or after 4 hr of cold storage. Measurements of acid/base balance, plasma electrolytes, albumin, and urea showed no differences between groups. There was no difference between the increase and decline of plasma AST in recipients of grafts transplanted immediately after either ex vivo or in situ reduction; the increase in plasma AST of recipients of stored grafts was up to 10-fold and persisted until the end of the study at 7 days, with some decline. Plasma fibrinogen decreased intraoperatively but levels were restored within 24 hr in all groups; plasma prothrombin and partial thromboplastin times were not significantly disturbed. The patterns of decline and return of tissue adenine nucleotides were similar in all groups. While the regenerative response measured by tissue thymidine kinase and mitotic figures was not different between the groups, comparison with results from a group of partially hepatectomized animals showed a 3-4-fold depression in response in reduced liver grafts. The contributions of the effects of ischemia, flushing, and preservation to the depressed regenerative response of reduced liver grafts need to be determined. The present studies suggest however, that with regard to functional assessment, results are not affected either by ex vivo or in situ reduction of the graft, or by cold storage for 4 hr.

Effect of total hepatectomy on coagulation and glucose homeostasis in the pig

It has been suggested recently that patients with fulminant liver failure should be prepared for transplantation by early hepatectomy, yet the acute effects of removal of the liver upon the coagulation profile and certain hormones are not known. This study was conducted on totally hepatectomized pigs that survived up to 27 hr. Measurements were made of serum insulin, plasma glucagon (IRG and GLI), glucose, catecholamines, and the coagulation profile. The increase in serum insulin was directly related to levels of plasma glucose--there was a 100-fold increase in animals with plasma glucose levels greater than 400 mg/100 ml and none when blood glucose was less than 100 mg/100 ml. Plasma glucagon showed a sharp transient increase within 1 hr of hepatectomy and a slow rise thereafter with levels apparently unrelated to serum insulin or plasma glucose. There was a transient increase in plasma adrenaline but a sharp continuous increase in plasma norepinephrine. No changes of note occurred in the coagulation profile--even levels of fibrinogen only declined by 20% in 27 hr. The study has shown that early total hepatectomy is safe as far as changes in coagulation are concerned but changes in serum insulin and especially plasma norepinephrine may be of more significance.

Energy charge as an indication of liver viability. A comparison of changes in livers that remained intact with those subjected to autografting

As efforts to assess the viability of liver grafts continue, the recent description of noninvasive measurement by fluorimetry or magnetic resonance spectrometry of adenine nucleotides has brought energy charge into focus again as an index of viability. Many previous studies have been conducted in human donor livers that have clinical relevance but which cannot be standardized, or in rats in which the hepatic artery is not anastomosed. In the present study, pig livers were definitively rendered ischemic for 1 or 2 hr. In one group the livers were then revascularized (intact) while in the other, the livers were removed during the final 20-30 min of the ischemic period and were subjected to autograft. There was a marked difference in survival between the intact and the autograft groups. One hour of ischemia in the intact group was associated with survival comparable to that of autograft controls (8-100 days); 2 hr of ischemia caused shortened survival, ranging from 2 to 18 days. In the recipients of autografts, survival after 1 hr of ischemia ranged from 3 to 16 days; after 2 hr of ischemia no autograft recipient survived overnight. The energy charge returned to the preoperative level after 2 hr of ischemia in both intact and autograft groups. The concentrations remained depressed after 2 hr of ischemia in autografted animals, thus being associated with survival. However, the patterns of total adenine nucleotide and adenosine triphosphate were not always similar to those of energy charge. The concentrations of aspartate aminotransferase were similarly elevated in all ischemic groups irrespective of duration or subsequent survival. There was, however, a close association between euglobulin lysis times (ELT) and survival. In the autograft recipients of livers subjected to 2 hr of ischemia that did not survive overnight the ELT remained significantly shortened. It is concluded that adenine nucleotide metabolism is important as an index of viability, but that concentrations of total and individual adenine nucleotides and the energy change all need to be computed. There does, however, appear to be an absolute relationship between survival and euglobulin lysis time that would be clinically useful in patients undergoing liver transplantation or hepatic vascular exclusion.

New rapid technique for renal transplantation in the rat

Present techniques for renal transplantation in the rat include a period of 20-25 minutes warm ischemia. Our method combines a recently described sleeve anastomotic technique for the renal artery, conventional end-to-end anastomosis of the renal vein, and implantation of the ureter into the bladder. This has resulted in a reproducible ischemic interval of 12-14 minutes. Plasma creatinine and histological features in animals sacrificed from 10 to 30 days after transplantation were within normal limits with no evidence of ischemic damage. A further advantage of the technique is that kidneys can be exchanged between the donor and recipient. It is recommended that this procedure, which reduces the ischemic interval by up to 50%, should be learned and employed in studies of renal transplantation in the rat, especially if such studies include the prior administration of cyclosporine, which may aggravate the effects of ischemia.

DTPA renal scan assessment of renal allograft dysfunction in rats

The precise cause of allograft dysfunction after renal transplantation often cannot be established by non-invasive means. In clinical practice, radionuclide scans form an integral part of the clinician's armamentarium in the assessment of these patients. Unfortunately, in the clinical setting more than one pathological process may be responsible for the impaired function, making it difficult to correlate the scan appearances with the pathology. In this study in rats we compared the renal DTPA scan appearances of the various pathological processes which may cause renal allograft dysfunction in the immediate post-transplant period.

Comparison of the effects of semi-occlusive polyurethane dressings and hydrocolloid dressings on dermal repair: 1. Cellular changes

The effects on dermal repair of two wound dressings, one the semi-occlusive polyurethane sheet Opsite, the other the hydrocolloid Granuflex, were compared in full-thickness excised lesions on porcine skin during the period from 5 d to 6 months after injury. Quantitative studies were made of changes in the populations of polymorphonuclear leucocytes, macrophages, fibroblasts, and endothelial cells. The progress of repair in the wounds covered with the semi-occlusive dressing showed a decrease in the number of inflammatory cells (polymorphonuclear leukocytes and macrophages) from 5 to 60 d, whereas the number of proliferative phase cells (fibroblasts and endothelial cells) increased from 5 to 7 d. The total cellularity per unit area showed an increase between 5 and 7 d, that is, during the proliferative phase of repair, and then progressively decreased as the proliferative phase was succeeded by the remodeling phase. In contrast, the repair process in the hydrocolloid-dressed wounds was more complex. The number of inflammatory cells remained relatively high throughout and there were consistently fewer endothelial cells present throughout. Fibroblast number showed an initial fall from 5 to 14 d but then started to increase in number from 21 to 60 d. This chronic inflammatory reaction appeared to be in response to particulate matter that had been incorporated into the wound bed and hypodermis, and was still apparent 6 months after injury, when hydrocolloid particles were detectable microscopically in the hypodermis.

Administration of sucralfate prolongs survival of animals with experimental peptic ulceration

Ligation of the pig bile duct (BDL) results in 100% incidence of pars esophageal ulceration within 48 hours of the procedure. Usually such ulceration is uniformly fatal unless a highly selective vagotomy is performed simultaneously with the BDL. The administration of sucralfate to pigs with BDL prolonged their survival for up to 7 days, with evidence of healing of the ulcer on macroscopic and histologic observations. An increase in cell proliferation in the squamous epithelium of the ulcerated area was also seen in this sucralfate group. These features were not seen in controls, pigs with BDL only, or pigs with BDL and with magaldrate (Riopone), colloidal bismuth subcitrate (DeNol), or carbenoxolone. Analysis by Sepharose 2B gel filtration showed that there was no significant difference in the amounts of polymeric mucin in any group, with a wide scatter of the data seen especially for pigs in the untreated BDL-only group. This study suggests that sucralfate may enhance healing in this experimental pig ulcer model via a mechanism independent of the stimulation of mucus secretion. We propose that coating the mucosa with sucralfate provides a temporary substitute barrier that creates a microenvironment conducive to wound repair by mucosal proliferation.

Six-hour porcine liver storage without flushing or perfusion

Livers from normal porcine donors were preserved by surface cooling only, without flushing or perfusion, for periods up to 24 hr. All recipients of livers stored for 6 hr survived until sacrifice at 7 days. In a separate, similar group, survival up to 21 days was noted. Only 2 of 6 recipients survived after 9-hr liver storage, but one of these lived for greater than 120 days. No animals survived longer than 2 days after transplantation of livers stored for 12 or 24 hr. The changes in plasma levels of aspartate aminotransferase of recipients of 6-hr surface-cooled livers were not significantly different from AST levels of recipients of livers stored in University of Wisconsin or Euro-Collins solution as observed in previous studies in this laboratory. At sacrifice after 7 days, there was no histologic evidence of damage after surface cooling. In the light of recent reports of evidence of endothelial and reticuloendothelial damage caused by flushing solutions, it is suggested that surface cooling of the liver may provide adequate preservation for 6 hr in appropriate circumstances. Further studies will be needed to confirm that this method of preservation is applicable to livers removed from brain-dead donors and that it does not cause endothelial damage.

Animal models of fulminant hepatic failure

The six requirements for a satisfactory animal model of fulminant hepatic failure are reversibility, reproducibility, death from liver failure, a therapeutic window, a large animal model, and minimal hazard to personnel. Different models may be required to evaluate the various types of liver failure seen in man. The available models include surgical anheptic and devascularization procedures, as well as hepatotoxic drug administration using agents such as carbon tetrachloride, acetaminophen, or galactosamine. Currently combined surgical and drug models appear to provide the best model but the search for the ideal models continues.

Heparin as the cause of coagulopathy which may complicate grafting of the liver

Disposal of heparin is accomplished rapidly by the normal liver, but the effects of ischemia, flushing and hypothermia during hepatic transplantation have not been investigated before. The results of the present study showed that neither laparotomy, hypothermia nor insertion of the portosystemic bypass seemed markedly to affect the coagulation profile, but autograft associated with 30 to 45 minutes of warm ischemia resulted in a twofold prolongation of the t1/2 heparin as calculated from sequential measurements of the activated clotting time. Unexpectedly, the storage of livers for four hours in EuroCollins solutions seemed to result in more rapid disappearance of heparin than in animals after laparotomy. After hepatectomy, the clearance of heparin was delayed for two hours but, thereafter, the slope of the disappearance resembled that in sham operated animals. Autograft and allograft of livers in normal pigs that did not receive transfusion were also associated with changes in fibrinolysis and declining levels of fibrinogen together with severe intraoperative bleeding problems and rapid death on the operating table in 30 per cent of the pigs. While administration of heparin alone did not appear to precipitate these changes, use of the drug after dissection, mobilization and storage of the liver may release other tissue factors that activate fibrinolysis.

Transhepatic sampling during experimental porcine liver autotransplantation--its application to measurements of insulin, glucagon, and glucose

Controversy still exists in the published literature about the need for administration of intravenous glucose during liver transplantation. The ability of the grafted liver to metabolize insulin and glucagon and the appropriateness of secretion of these hormones are addressed in the present study. Two groups of pigs received unstored liver autografts, one with free infusion of 10% glucose and the other with limited infusion of 2.5% glucose solution, while attempting to maintain plasma glucose levels less than 200 mg/100 ml. In these animals, irrespective of moderate or major hyperglycemia, serum insulin levels were appropriate for blood glucose concentrations. However, in both groups, plasma glucagon levels rose three- to fourfold more than preoperative values and were inappropriate. Although facilities for measurement of blood flow were not available, application of the technique of transhepatic sampling has revealed that hepatic handling of insulin seems to be unimpaired after autograft with limited ischemia. Pancreatic secretion of glucagon, however, appeared to increase during the period immediately after revascularization. It is suggested that transhepatic sampling methods may be used in experimental transplantation to elucidate the effects of storage for prolonged periods.

Function of kidney grafts from brain-dead donor pigs. The influence of dopamine and triiodothyronine

There are conflicting reports about the effects of administration of dopamine to brain-dead donors upon posttransplant organ function. This study compared the survival and serum creatinine levels in pigs that received renal grafts from untreated controls, from controls in which either the donor or donor and recipient received dopamine or from animals rendered brain dead for 16 hr by acute elevation of intracranial pressure, and given standard supportive treatment. In two additional groups, brain-dead donors were given dopamine or dopamine with triiodothyronine. Recipients of grafts from control animals or from brain-dead donors survived the 7-day period of study and showed minimal changes in serum creatinine. Recipients of grafts from brain-dead donors given dopamine however showed reduced survival and progressive increase in serum creatinine. This did not occur in the group given triiodothyronine concurrently with dopamine. It is suggested that if administration of dopamine is essential to treat donor hypotension, concurrent use of triiodothyronine may preserve posttransplant renal function.