Intra-operative acute isovolemic hemodilution is safe and effective in eliminating allogeneic blood transfusions during right hepatic lobectomy: comparison of living donor versus non-donors.

BACKGROUND: Multiple studies have shown acute isovolemic hemodilution (AIH) to be safe and effective during liver resection to limit the use of banked blood. However, no studies to date have studied AIH in living donor right hepatectomy. Conventional right hepatectomies for living donors is not identical to non-donor right hepatectomies. Since division of the parenchyma is often performed without devascularization of the right lobe, blood loss may be significantly higher. METHODS: Ten consecutive patients undergoing living donor right hepatectomies (LDRH) and ten consecutive patients undergoing non-donor right hepatectomies (NDRH) were compared using AIH. RESULTS: There was no mortality or morbidity related to the use of AIH. No allogeneic blood transfusions were required in either group, intra-operatively or post-operatively. There was no significant difference in post-operative hematocrit, average estimated blood loss, and average fluid replacement. Average hospital length of stay and operating room time were longer for the LDRH. CONCLUSION: AIH can be performed safely and effectively in both LDRH and NDRH without subjecting patients to unnecessary risks of allogeneic blood transfusions.

Pharmacokinetics and biochemical effects of hepapoietin in patients with chronic liver disease.

BACKGROUND: Hepapoietin is a naturally occurring cytokine that promotes hepatocyte growth. Animal studies have suggested that hepapoietin and hepatocyte growth factor have a potential role in the prevention and management of liver diseases. However, human studies have been lacking. AIM: To evaluate the safety and pharmacokinetics of single escalating doses of hepapoietin in patients with chronic liver disease. METHODS: An open-label, single escalating dose trial with five different doses of hepapoietin (1, 3, 10, 30 and 100 mg) was performed. Adults with chronic, compensated, non-viral liver disease were included. Liver function tests were obtained before dosing, 24 h after hepapoietin administration and on days 4, 7, 30 and 45. All patients were followed for 45 days. RESULTS: Twenty-five subjects received hepapoietin, with five subjects each at 1, 3, 10, 30 and 100 mg of hepapoietin. Significant decreases occurred in total bilirubin, ammonia, partial thromboplastin time and cholesterol levels overall, and both high-density and low-density lipoprotein cholesterol showed a downward trend. An increase in albumin was observed at the 30 mg dose level. Slight decreases in haemoglobin and red blood cell levels were observed at day 4, but returned to normal levels immediately thereafter. Child-Pugh scores from day 0 to day 7 were improved in 24%, stable in 64% and worse in 12% of patients. Hepatic encephalopathy displayed changes from day 0 to day 45 with improvement in 16%, no change in 80% and worsening in 4%. CONCLUSIONS: Hepapoietin in doses up to 100 mg is safe for use in humans. Potential benefits are suggested by significant decreases in bilirubin, ammonia, partial thromboplastin time and cholesterol levels and an increase in albumin. Further studies with multiple dosing regimens are needed to identify the clinical utility of hepapoietin in the management of chronic liver disease.

Transplantation of hepatitis C-positive livers in hepatitis C-positive patients is equivalent to transplanting hepatitis C-negative livers.

A significant number of patients with end-stage liver disease secondary to hepatitis C die of disease-related complications. Liver transplantation offers the only effective alternative. Unfortunately, organ demand exceeds supply. Consequently, some transplant centers have used hepatitis C virus-positive (HCV(+)) donor livers for HCV(+) recipients. This study reviews the clinical outcome of a large series of HCV(+) recipients of HCV(+) liver allografts and compares their course with that of HCV(+) recipients of HCV-negative (HCV(-)) allografts. The United Network for Organ Sharing Scientific Registry was reviewed for the period from April 1, 1994, to June 30, 1997. All HCV(+) transplant recipients were analyzed. Two groups were identified: a group of HCV(+) recipients of HCV(+) donor livers (n = 96), and a group of HCV(+) recipients of HCV(-) donor livers (n = 2,827). A multivariate logistic regression model was used to determine the odds of graft failure and patient mortality, and unadjusted graft and patient survival were determined using the Kaplan-Meier method. There were no differences in demographic criteria between the groups. A greater percentage of patients with hepatocellular carcinoma received an HCV(+) allograft (8.3% v 3.1%; P =.01). Patient survival showed a significant difference for the HCV(+) group compared with the HCV(-) group (90% v 77%; P =.01). Blood type group A, group B, group O incompatibility was significant, with 4.2% incompatibility in the HCV(+) group and only 1.3% in the HCV(-) group (P =.04). Donor hepatitis C status does not impact on graft or patient survival after liver transplantation for HCV(+) recipients. Their survival was equivalent, if not better, compared with the control group. Using HCV(+) donor livers for transplantation in HCV(+) recipients safely and effectively expands the organ donor pool.

Species-area curves, spatial aggregation, and habitat specialization in tropical forests.

The relationship between species diversity and sampled area is fundamental to ecology. Traditionally, theories of the species-area relationship have been dominated by random-placement models. Such models were used to formulate the canonical theory of species-area curves and species abundances. In this paper, however, armed with a detailed data set from a moist tropical forest, we investigate the validity of random placement and suggest improved models based upon spatial aggregation. By accounting for intraspecific, small-scale aggregation, we develop a cluster model which reproduces empirical species-area curves with high fidelity. We find that inter-specific aggregation patterns, on the other hand, do not affect the species-area curves significantly. We demonstrate that the tendency for a tree species to aggregate, as well as its average clump size, is not significantly correlated with the species' abundance. In addition, we investigate hierarchical clumping and the extent to which aggregation is driven by topography. We conclude that small-scale phenomena such as dispersal and gap recruitment determine individual tree placement more than adaptation to larger-scale topography.

Predicting species diversity in tropical forests.

A fundamental question in ecology is how many species occur within a given area. Despite the complexity and diversity of different ecosystems, there exists a surprisingly simple, approximate answer: the number of species is proportional to the size of the area raised to some exponent. The exponent often turns out to be roughly 1/4. This power law can be derived from assumptions about the relative abundances of species or from notions of self-similarity. Here we analyze the largest existing data set of location-mapped species: over one million, individually identified trees from five tropical forests on three continents. Although the power law is a reasonable, zeroth-order approximation of our data, we find consistent deviations from it on all spatial scales. Furthermore, tropical forests are not self-similar at areas

Use of aerosolized inhaled epoprostenol in the treatment of portopulmonary hypertension.

BACKGROUND: Portopulmonary hypertension is a known complication in the liver transplant candidate. Intravenous epoprostenol has been demonstrated to decrease pulmonary artery pressures and possibly remodel right ventricle geometry. METHODS: In this report, we document the efficacy of inhaled aerosolized epoprostenol in a patient with portopulmonary hypertension. The effect was of rapid onset and offset. RESULTS: After 10 min of delivery, mean pulmonary artery pressure decreased 26%; cardiac output increased by 22%; pulmonary vascular resistance decreased by 42%; and the transpulmonary gradient decreased by 29%. There were no untoward side effects. CONCLUSION: The inhaled route of delivery of epoprostenol is potential alternative for the acute therapy of portpulmonary hypertension.

Intraoperative use of inhaled PGI(2) for acute pulmonary hypertension and right ventricular failure.

Inhaled prostacyclin (PGI(2)) can be used as an effective pulmonary vasodilator intraoperatively to treat pulmonary hypertension and impending right ventricular failure.

Language evolution and information theory.

This paper places models of language evolution within the framework of information theory. We study how signals become associated with meaning. If there is a probability of mistaking signals for each other, then evolution leads to an error limit: increasing the number of signals does not increase the fitness of a language beyond a certain limit. This error limit can be overcome by word formation: a linear increase of the word length leads to an exponential increase of the maximum fitness. We develop a general model of word formation and demonstrate the connection between the error limit and Shannon's noisy coding theorem.

The evolution of syntactic communication.

Animal communication is typically non-syntactic, which means that signals refer to whole situations. Human language is syntactic, and signals consist of discrete components that have their own meanings. Syntax is a prerequisite for taking advantage of combinatorics, that is, "making infinite use of finite means. The vast expressive power of human language would be impossible without syntax, and the transition from non-syntactic to syntactic communication was an essential step in the evolution of human language. We aim to understand the evolutionary dynamics of this transition and to analyse how natural selection can guide it. Here we present a model for the population dynamics of language evolution, define the basic reproductive ratio of words and calculate the maximum size of a lexicon. Syntax allows larger repertoires and the possibility to formulate messages that have not been learned beforehand. Nevertheless, according to our model natural selection can only favour the emergence of syntax if the number of required signals exceeds a threshold value. This result might explain why only humans evolved syntactic communication and hence complex language.

Outcomes of laparoscopic donor nephrectomy in obese patients.

The applicability of laparoscopic donor nephrectomy (LDN) has not been assessed in the obese donor. We hypothesized that obesity is not a technical contraindication to LDN. From May 1998 to February 1999, 40 patients underwent LDN at the Georgetown Transplant Institute with the transperitoneal technique. Prophylaxis against deep venous thrombosis consisted of venous compression stockings, low-molecular weight heparin in obese patients, and early ambulation. The following variables were examined: donor sex, age, weight, height, related versus nonrelated donation, body mass index (BMI; wt/ht2), operating room time, estimated blood loss, length of stay, time out of work, and complications. BMI>31 indicates morbid obesity, BMI>27 indicates >20% over ideal body weight, and normal BMI is 25. The patients were divided into nonobese (BMI< or =31) and obese groups (BMI>31). The two groups do not differ in outcome after LDN. Our data indicate that obesity is not associated with increased morbidity or mortality after LDN.

The evolutionary language game.

We explore how evolutionary game dynamics have to be modified to accomodate a mathematical framework for the evolution of language. In particular, we are interested in the evolution of vocabulary, that is associations between signals and objects. We assume that successful communication contributes to biological fitness: individuals who communicate well leave more offspring. Children inherit from their parents a strategy for language learning (a language acquisition device). We consider three mechanisms whereby language is passed from one generation to the next: (i) parental learning: children learn the language of their parents; (ii) role model learning: children learn the language of individuals with a high payoff; and (iii) random learning: children learn the language of randomly chosen individuals. We show that parental and role model learning outperform random learning. Then we introduce mistakes in language learning and study how this process changes language over time. Mistakes increase the overall efficacy of parental and role model learning: in a world with errors evolutionary adaptation is more efficient. Our model also provides a simple explanation why homonomy is common while synonymy is rare.

Portopulmonary hypertension and the liver transplant candidate.

The management of the liver transplant (OLT) candidate with portopulmonary hypertension (PPHTN) has dramatically changed in the past 3 years. Careful preoperative evaluation with functional characterization of right ventricular function plays a critical role. The pulmonary vascular response to epoprostenol infusion serves as a deciding factor for OLT candidacy. Careful perioperative attention to avoid right ventricular failure from acutely elevated pulmonary artery pressures or sudden increases in right ventricular preload is a key physiologic tenet of management. With increased surgical expertise, anesthetic sophistication, and availability of epoprostenol, PPHTN is no longer considered an absolute contraindication for OLT.

Transesophageal echocardiographic detection of gas embolism and cardiac valvular dysfunction during laparoscopic nephrectomy.

UNLABELLED: We used transesophageal echocardiography (TEE) to monitor venous gas embolism, cardiac performance, and the hemodynamic effects of positioning and pneumoperitoneum in 16 healthy kidney donors undergoing laparoscopic nephrectomy. A four-chamber view was used continuously, except at predetermined intervals, when a complete TEE examination for cardiac function was performed. Other clinical variables recorded include systolic, diastolic, and mean arterial blood pressure; heart rate (HR), pulse oximetric saturations; and end-tidal CO2. Baseline valvular incompetence was seen in 13 of the 16 patients when supine and asleep. After positioning for surgery and induction of pneumoperitoneum, TEE revealed valvular incompetence with regurgitation more pronounced from baseline in 15 of the 16 patients. In one patient, during renal vein dissection, gas entered the right atrium from the inferior vena cava, worsening tricuspid regurgitation. Hemodynamic variables and ejection fraction were tested by using repeated-measures analysis of variance for significance (P < 0.05). Pneumoperitoneum increased (P < 0.05) systolic blood pressure (from 102.8 +/- 3.89 to 120.8 +/- 3.88 mm Hg) and HR (from 68.9 +/- 3.19 to 75.6 +/- 2.62). Ejection fraction was unchanged. The high incidence of valvular incompetence indicates that further studies are needed to assess these effects during laparoscopic nephrectomy with cardiac disease. IMPLICATIONS: Laparoscopic surgery has gained popularity as a procedure for the removal of donated kidneys. Although the insufflation of gas necessary for this relatively simple approach poses a low risk of venous air embolism, it may increase the risk of changes in valvular competency.

Transverse hepatectomy for symptomatic polycystic liver disease.

Polycystic liver disease can result in massive enlargement of the liver with resultant debilitating symptoms of abdominal pain, chronic fatigue, and severely compromised functional status. Fenestration of hepatic cysts has been advocated as a treatment for polycystic disease. However, in patients with predominant small cyst replacement, fenestration alone often results in limited hepatic volume reduction without improvement in patient functional status. Liver transplantation has also been previously advocated for polycystic liver disease with predominant small cyst replacement, but, with the severe shortage of donor organs, alternative treatment should be considered. In this report we present a case of massive enlargement of the liver with severe clinical debilitation due to polycystic liver disease. Transverse hepatectomy provided a safe and effective alternative to fenestration or liver transplantation.

Acute pancreatitis and fulminant hepatic failure.

BACKGROUND: The association of acute pancreatitis with fulminant hepatic failure (FHF) was first recognized in 1973. Since then, few studies have described the clinical profile of the FHF patient with acute pancreatitis. Identification of the distinguishing attributes of pancreatitis in combination with FHF will provide a more sound basis for clinical management. The purposes of this study were to identify distinguishing clinical characteristics of acute pancreatitis in FHF and to compare outcomes with those of patients with acutely decompensated chronic liver disease and acute pancreatitis (DECOMP). STUDY DESIGN: This was a retrospective survey of 30 patients with FHF and 30 with DECOMP admitted during the period July 1995 to July 1997. RESULTS: The prevalence of acute pancreatitis in FHF and DECOMP was 33% and 23%, respectively. Acute pancreatitis was associated with severe hepatocellular synthetic dysfunction, renal insufficiency, requirement for endotracheal intubation, increased acuity of illness at the time of ICU admission, more rapid decompensation during the disease, and significantly greater mortality in both the FHF and DECOMP groups. CONCLUSIONS: In both FHF and DECOMP, acute pancreatitis increases disease acuity and mortality. Acute pancreatitis does not occur with significantly greater frequency in FHF. Implementation of orthotopic liver transplantation may not be warranted in this setting.