A prospective study of pulmonary function and gas exchange following liver transplantation

Cost Utilization and the Use of Pulmonary Function Tests in Preoperative Liver Transplant Patients

BACKGROUND

Pulmonary function tests (PFTs) are currently recommended for liver transplant candidates. We hypothesized that PFTs may not provide added clinical value to the evaluation of liver transplant patients.

METHODS

We conducted a retrospective cohort study of adult cadaveric liver transplants from 2012 to 2018. Abnormal PFTs were defined as restrictive disease of diffusing capacity of the lungs for carbon monoxide (DLCO) <80% or obstructive disease of ratio of forced expiratory volume in the first 1 second to the first vital capacity of the lungs (FEV1/FVC) <70%.

RESULTS

We analyzed data on 415 liver transplant patients (358 abnormal PFT results and 57 normal results). The liver transplant patients with abnormal PFTs had no difference in number of intensive care unit (ICU) days (P = .68), length of stay (P = .24), or intubation days (P = .33). There were no differences in pulmonary complications including pleural effusion (P = .30), hemo/pneumothorax (P = .74), pneumonia (P = .66), acute respiratory distress syndrome (P = .57), or pulmonary edema (P = .73). The significant finding between groups was a higher rate of reintubation in liver transplant patients with normal PFTs (P = .02). There was no difference in graft survival (P = .53) or patient survival (P = .42).

DISCUSSION

Abnormal PFTs, found in 86% of liver transplant patients, did not correlate with complications, graft failure, or mortality. PFTs contribute to the high cost of liver transplants but do not help predict which patients are at risk of postoperative complications.

Prevalence and Impact of Restrictive Lung Disease in Liver Transplant Candidates

We investigated the prevalence of spirometric restriction in liver transplantation (LT) candidates and the clinical impacts of restriction. We performed a cross-sectional study within the Pulmonary Vascular Complications of Liver Disease 2 (PVCLD2) study, a multicenter prospective cohort study of patients being evaluated for LT. Patients with obstructive lung disease or missing spirometry or chest imaging were excluded. Patients with and without restriction, defined as a forced vital capacity (FVC) <70% predicted, were compared. Restriction prevalence was 18.4% (63/343). Higher Model for End-Stage Liver Disease-sodium score (odds ratio [OR], 1.06; 95% confidence interval [CI], 1.02-1.11; P = 0.007), the presence of pleural effusions (OR, 3.59; 95% CI, 1.96-6.58; P < 0.001), and a history of ascites (OR, 2.59; 95% CI, 1.26-5.33; P = 0.01) were associated with the presence of restriction, though one-third with restriction had neither pleural effusions nor ascites. In multivariate analysis, restriction was significantly and independently associated with lower 6-minute walk distances (least squares mean, 342.0 [95% CI, 316.6-367.4] m versus 395.7 [95% CI, 381.2-410.2] m; P < 0.001), dyspnea (OR, 2.69; 95% CI, 1.46-4.95; P = 0.002), and lower physical component summary Short Form 36 scores indicating worse quality of life (least squares mean, 34.1 [95% CI, 31.5-36.7] versus 38.2 [95% CI, 36.6-39.7]; P = 0.004). Lower FVC percent predicted was associated with an increased risk of death (hazard ratio, 1.16; 95% CI, 1.04-1.27 per 10-point decrease in FVC percent predicted; P = 0.01). Restriction and abnormal lung function are common in LT candidates; can be present in the absence of an obvious cause, such as pleural effusions or ascites; and is associated with worse exercise capacity, quality of life, and survival.

The Relationship Between Airway Occlusion Pressure and Severity of liver Cirrhosis in Candidates for Liver Transplantation

BACKGROUND End-stage cirrhosis is an irreversible condition, and liver transplantation is the only treatment option in for the affected patients. Respiratory problems and abnormal breathing are common findings among these patients. In this study, for the first time, we examined the relationship between the severity of liver cirrhosis and respiratory drive measured by mouth occlusion pressure (P_0.1). METHODS This was a cross-sectional study conducted on 50 candidates for liver transplantation who were referred to the pulmonary clinic of Imam Khomeini Hospital for pre-operative pulmonary evaluations. Arterial blood gas analysis (ABG), pulmonary function tests, and measurement of P0.1 were performed for all patients. The severity of liver disease was assessed using the Model for End-Stage Liver Disease (MELD) score. RESULTS The median P_0.1 was 5 cm H₂ O. P_0.1 was negatively associated with PaCO₂ (r = -0.466, p = 0.001) and HCO3 - (r = -0.384, p = 0.007), and was positively correlated with forced expiratory volume at 1s (FEV1 )/ forced vital capacity (FVC) (r = 0.282, p = 0.047). There was a strong correlation between P_0.1 and MELD score (r = 0.750, p < 0.001). Backward multivariate linear regression revealed that a higher MELD score and lower PaCO₂ were associated with increased P_0.1. CONCLUSION High levels of P_0.1 and strong direct correlation between P_0.1 and MELD score observed in the present study are suggestive of the presence of abnormal increased respiratory drive in candidates for liver transplantation, which is closely related to their disease severity.

The hepatopulmonary syndrome

Introduction

The hepatopulmonary syndrome has been acknowledged as an important vascular complication in lungs developing systemic hypoxemia in patients with cirrhosis and portal hypertension. Is formed by arterial oxygenation abnormalities induced from intrapulmonary vascular dilatations with liver disease. It is present in 4-32% of patients with cirrhosis. It increases mortality in the setting of cirrhosis and may influence the frequency and severity. Initially the hypoxemia responds to low-flow supplemental oxygen, but over time, the need for oxygen supplementation is necessary. The liver transplantation is the only effective therapeutic option for its resolution.

Aim

To update clinical manifestation, diagnosis and treatment of this entity.

Method

A literature review was performed on management of hepatopulmonary syndrome. The electronic search was held of the Medline-PubMed, in English crossing the headings "hepatopulmonary syndrome", "liver transplantation" and "surgery". The search was completed in September 2013.

Results

Hepatopulmonary syndrome is classically defined by a widened alveolar-arterial oxygen gradient (AaPO2) on room air (>15 mmHg, or >20 mmHg in patients >64 years of age) with or without hypoxemia resulting from intrapulmonary vasodilatation in the presence of hepatic dysfunction or portal hypertension. Clinical manifestation, diagnosis, classification, treatments and outcomes are varied.

Conclusion

The severity of hepatopulmonary syndrome is an important survival predictor and determine the improvement, the time and risks for liver transplantation. The liver transplantation still remains the only effective therapeutic.

Dyspnea and respiratory muscle strength in end-stage liver disease

AIM

To investigate the prevalence of chronic dyspnea and its relationship to respiratory muscle function in end-stage liver disease.

METHODS

Sixty-eight consecutive, ambulatory, Caucasian patients with end-stage liver disease, candidates for liver transplantation, were referred for preoperative respiratory function assessment. Forty of these (29 men) were included in this preliminary study after applying strict inclusion and exclusion criteria. Seventeen of 40 patients (42%) had ascites, but none of them was cachectic. Fifteen of 40 patients (38%) had a history of hepatic encephalopathy, though none of them was symptomatic at study time. All patients with a known history and/or presence of co-morbidities were excluded. Chronic dyspnea was rated according to the modified medical research council (mMRC) 6-point scale. Liver disease severity was assessed according to the Model for end-stage liver disease (MELD). Routine lung function tests, maximum static expiratory (Pemax) and inspiratory (Pimax) mouth pressures were measured. Respiratory muscle strength (RMS) was calculated from Pimax and Pemax values. In addition, arterial blood gases and pattern of breathing (VE: minute ventilation; VT: tidal volume; VT/TI: mean inspiratory flow; TI: duration of inspiration) were measured.

RESULTS

Thirty-five (88%) of 40 patients aged (mean ± SD) 52 ± 10 years reported various degrees of chronic dyspnea (mMRC), ranging from 0 to 4, with a mean value of 2.0 ± 1.2. MELD score was 14 ± 6. Pemax, percent of predicted (%pred) was 105 ± 35, Pimax, %pred was 90 ± 29, and RMS, %pred was 97 ± 30. These pressures were below the normal limits in 12 (30%), 15 (38%), and 14 (35%) patients, respectively. Furthermore, comparing the subgroups of ascites to non-ascites patients, all respiratory muscle indices measured were found significantly decreased in ascites patients. Patients with ascites also had a significantly worse MELD score compared to non-ascites ones (P = 0.006). Significant correlations were found between chronic dyspnea and respiratory muscle function indices in all patients. Specifically, mMRC score was significantly correlated with Pemax, Pimax, and RMS (r = -0.53, P < 0.001; r = -0.42, P < 0.01; r = -0.51, P < 0.001, respectively). These correlations were substantially closer in the non-ascites subgroup (r = -0.82, P < 0.0001; r = -0.61, P < 0.01; r = -0.79, P < 0.0001, respectively) compared to all patients. Similar results were found for the relationship between mMRC vs MELD score, and MELD score vs respiratory muscle strength indices. In all patients the sole predictor of mMRC score was RMS (r = -0.51, P < 0.001). In the subgroup of patients without ascites this relationship becomes closer (r = -0.79, P < 0.001), whilst this relationship breaks down in the subgroup of patients with ascites. The disappearance of such a correlation may be due to the fact that ascites acts as a "confounding" factor. PaCO2 (4.4 ± 0.5 kPa) was increased, whereas pH (7.49 ± 0.04) was decreased in 26 (65%) and 34 (85%) patients, respectively. PaO2 (12.3 ± 0.04 kPa) was within normal limits. VE (11.5 ± 3.5 L/min), VT (0.735 ± 0.287 L), and VT/TI (0.449±0.129 L/s) were increased signifying hyperventilation in both subgroups of patients. VT/TI was significantly higher in patients with ascites than without ascites. Significant correlations, albeit weak, were found for PaCO2 with VE and VT/TI (r = -0.44, P < 0.01; r = -0.41, P < 0.01, respectively).

CONCLUSION

The prevalence of chronic dyspnea is 88% in end-stage liver disease. The mMRC score closely correlates with respiratory muscle strength.

Evaluation of liver transplant candidates: A pulmonary perspective

Chronic liver disease is one of the leading causes of mortality and morbidity in the worldwide adult population. Liver transplant is the gold standard therapy for end-stage liver disease and many patients are on the waiting list for a transplant. A variety of pulmonary disorders are encountered in cirrhotic patients. Pleura, lung parenchyma, and pulmonary vasculature may be affected in these patients. Hypoxemia is relatively common and can be asymptomatic. Hepatopulmonary syndrome should be investigated in hypoxic cirrhotic patients. Gas exchange abnormalities are common and are generally correlated with the severity of liver disease. Both obstructive and restrictive types of airway disease can be present. Abnormal diffusion capacity is the most frequently observed pulmonary function disorder in patients with cirrhosis. Hepatic hydrothorax is another finding which is usually seen in conjunction with, but occasionally without ascites. Portopulmonary hypertension is a complication of long standing liver dysfunction and when severe, is accepted as a containdication to liver transplant. Since respiratory disorders are common and have significant impact on postoperative outcome in patients undergoing liver transplant, a careful preoperative pulmonary assessment is important.

Management of pulmonary complications in pretransplant patients

This article addresses the most common pulmonary issues that affect liver transplant candidates. Pretransplant diagnostic criteria of these pulmonary problems in liver transplant patients are reviewed. Successful pulmonary management schemes and caveats are described. Risks for liver transplant are emphasized.

Gas exchanges and pulmonary vascular abnormalities at different stages of chronic liver disease

BACKGROUND

It is unclear whether and to which extent respiratory function abnormalities may complicate the earliest stages of chronic liver disease (CLD). Aim of this study was to compare pulmonary capillary volumes and gas exchange efficiency of CLD patients with and without cirrhosis.

METHODS

Sixty-seven participants (mean age 56.5 years; women 22.4%) were divided into three groups (matched by age, sex, smoking) according to the baseline CLD stage as follows: (a) healthy controls (Group A, n=20); (b) non-cirrhotic CLD patients (Group B; n=23); (c) cirrhotic CLD patients (Group C; n=24). All participants underwent clinical assessment, respiratory function tests, gas exchange estimation by the alveolar diffusion of carbon monoxide (TLCO) measurement and 6-min walking test. Groups were compared by chi-square and one-way anova tests.

RESULTS

Chronic liver disease patients had significantly lower levels of TLCO (Group B=17.7 ml/min mmHg, and Group C=14.2 ml/min mmHg) compared with healthy controls (Group A=24.4 ml/min mmHg). Consistent results were obtained when analyses were performed using TLCO expressed as percentage of the predicted value. TLCO adjusted for the alveolar volume was lower in cirrhotic patients compared with both controls and non-cirrhotic CLD patients (P<0.001 and P=0.035 respectively). Group C participants presented blood gas parameters tending to a compensated chronic respiratory alkalosis status compared with the other groups.

CONCLUSIONS

Pulmonary microvascular and gas exchange modifications are present at early stages of CLD. Future studies should be focused at evaluating the pathophysiological mechanisms underlying this relationship.

Perioperative risk factors for pulmonary complications after liver transplantation

Using monofactorial and multivariate logistic regression analyses, the correlation of perioperative risk factors with postoperative pulmonary complications (PPCs) within 1 month after orthotopic liver transplantation (OLT) was investigated. Data on 107 patients (median age 46.8 years, 72% male) with end-stage liver disease who received OLT were retrospectively analysed. The incidence of PPCs was 60.7%. Overall mortality was 13.1% and pulmonary causes accounted for 85.7% of deaths. Mortality was 18.5% and 4.8% for patients with and without pulmonary complications, respectively. Independent risk factors for PPCs were a preoperative model for end-stage liver disease (MELD) score > or =25, intraoperative fluid transfusion volume > 10 1 and intraoperative blood transfusion volume > 4 l. A fluid balance of < or = -300 ml for > or =2 days of the first 3 days after surgery was protective. Other variables studied did not predict PPCs. It was concluded that improving the patient's preoperative medical condition, restricting intraoperative transfusion volumes and maintaining a negative fluid balance in the first 3 days after operation may decrease PPCs.

Risk factors and impact of chronic obstructive pulmonary disease in candidates for liver transplantation

Chronic obstructive pulmonary disease (COPD) may cause significant symptoms and have an impact on survival. Smoking is an important risk factor for COPD and is common in candidates for liver transplantation; however, the risk factors for and outcomes of COPD in this population are unknown. We performed a prospective cohort study of 373 patients being evaluated for liver transplantation at 7 academic centers in the United States. COPD was characterized by expiratory airflow obstruction and defined as follows: prebronchodilator forced expiratory volume in 1 second/forced vital capacity < 0.70. Patients completed the Liver Disease Quality of Life Questionnaire 1.0, which included the Short Form-36. The mean age of the study sample was 53 +/- 9 years, and 234 (63%) were male. Sixty-seven patients (18%, 95% confidence interval 14%-22%) had COPD, and 224 (60%) had a history of smoking. Eighty percent of patients with airflow obstruction did not previously carry a diagnosis of COPD, and 27% were still actively smoking. Older age and any smoking (odds ratio = 3.74, 95% confidence interval 1.94-7.23, P < 0.001) were independent risk factors for COPD. Patients with COPD had worse New York Heart Association functional class and lower physical component summary scores on the 36-Item Short Form but had short-term survival similar to that of patients without COPD. In conclusion, COPD is common and often undiagnosed in candidates for liver transplantation. Older age and smoking are significant risk factors of COPD, which has adverse consequences on functional status and quality of life in these patients.

The relationship between severity of liver cirrhosis and pulmonary function tests

Pulmonary complications, mainly hepatopulmonary syndrome (HPS), are frequently observed in liver cirrhosis. In this study, the aim was to investigate the frequency of hypoxemia and impairment of pulmonary function tests (PFT) in patients with liver cirrhosis and to examine the relationships of these impairments with liver failure. A total of 39 patients with cirrhosis, 24 males and 15 females, were included in our study. The mean age of the patients was 47.5 +/- 17.2 years. Arterial blood gases, PFT, and carbon monoxide diffusion tests (DLCO) were performed in all patients. Out of 39 cirrhotic patients, 21 (53.8%) had ascites, whereas 18 (46.2%) did not. Seven patients were in the Child-Pugh A group, 21 in the Child-Pugh B group, and 11 patients were in the Child-Pugh C group. Hypoxia was found in 33.3% of the patients. Although the PaO2 and SaO2 values of patients with ascites were lower compared to those without ascites (P < 0.05), no statistically significant difference was determined in the comparison of hypoxia between the groups (P > 0.05). Among the PFT parameters, FEV1/FVC and FEF25-75% values were found to be lower in patients with ascites than those without (P < 0.05). No differences were established between these two groups of patients in terms of DLCO (P > 0.05). While no differences were found in comparison of the DLCO values in between the groups (P > 0.05), there was a statistically significant difference in the ratio of DLCO to the alveolar ventilation (DLCO/VA) in between the groups (P < 0.05). On the other hand, a negative correlation was found between the DLCO/VA and Child points when the relationship between the Child-Pugh score and PFT parameters were investigated (r = -0.371, P < 0.05). Consequently, a relationship was established between the severity of liver failure and diffusion tests showing pulmonary complications invasively. We believe diffusions tests should be performed in addition to the PFT in order to determine pulmonary involvements particularly in patients who are candidates for liver transplantation.

Sustained low diffusing capacity in hepatopulmonary syndrome after liver transplantation

AIM: To study the presence of sustained low diffusing capacity (DL_CO) after liver transplantation (LT) in patients with hepatopulmonary syndrome (HPS).

METHODS: Six patients with mild-to-severe HPS and 24 without HPS who underwent LT were prospectively followed before and after LT at mid-term (median, 15 mo). HPS patients were also assessed at long-tem (median, 86 mo).

RESULTS: Before LT, HPS patients showed lower PaO₂ (71 ± 8 mmHg), higher AaPO₂ (43 ± 10 mmHg) and lower DL_CO (54% ± 9% predicted), due to a combination of moderate-to-severe ventilation-perfusion (V_A/Q) imbalance, mild shunt and diffusion limitation, than non-HPS patients (94 ± 4 mmHg and 19 ± 3 mmHg, and 85% ± 3% predicted, respectively) (P < 0.05 each). Seven non-HPS patients had also reduced DL_CO (70% ± 4% predicted).

At mid- and long-term after LT, compared to pre-LT, HPS patients normalized PaO₂ (91 ± 3 mmHg and 87 ± 5 mmHg), AaPO₂ (14 ± 3 mmHg and 23 ± 5 mmHg) and all V_A/Q descriptors (P < 0.05 each) without changes in DL_CO (53% ± 8% and 56% ± 7% predicted, respectively). Post-LT DL_CO in non-HPS patients with pre-LT low DL_CO was unchanged (75% ± 6% predicted).

CONCLUSION: While complete V_A/Q resolution in HPS indicates a reversible functional disturbance, sustained low DL_CO after LT also present in some non-HPS patients, points to persistence of sub-clinical liver-induced pulmonary vascular changes.

Concomitant Administration of Mannitol and N-Acetylcysteine for the Prevention of Lung Reperfusion Injury

BACKGROUND

Mannitol (MN) and N- acetylcysteine (NAC) are partially successful in preventing lung reperfusion injury after liver ischemia reperfusion (IR). Their concomitant administration might enhance the individual effects of each.

METHODS

Rat isolated livers were perfused with Krebs-Henseleit solution (controls) or made globally ischemic (IR) for 2 hours. Separately isolated lungs were paired with livers and each pair was reperfused in-series for 15 minutes. During reperfusion, eight groups were treated with Krebs containing two low and two high doses of MN and/or NAC; one group received no treatment.

RESULTS

The tested lung parameters were unchanged in all control groups. Pulmonary perfusion or ventilatory pressures, weight gain and bronchoalveolar lavage volume increased by 30 to 70% of baseline in the nontreated IR-paired lungs and in the only IR-MN 0.44- and the IR-NAC 0.25 mmol (weight/body weight) treated lungs but remained preserved by the two higher monotherapies (MN 0.55 mmol and NAC 0.37 mmol) and by the four bitherapies. The reduced glutathione content in all lung tissue subgroups treated by the bitherapies was higher by 63 to 124% of the corresponding monotherapy values. Xanthine oxidase activity in the bitherapies-treated IR-lungs decreased 1.5 to twofold compared with the corresponding monotherapies.

CONCLUSIONS

Co-administration of MN and NAC augments the amount of lung protection afforded by each drug individually and enhances their antioxidant potentials.

Pulmonary gas exchange abnormalities in liver transplant candidates

Abnormal diffusing capacity is the commonest pulmonary dysfunction in liver transplant candidates, but severe hypoxemia secondary to hepatopulmonary syndrome and significant pulmonary hypertension are pulmonary vascular manifestations of cirrhosis that may affect the perioperative course. We prospectively assessed the extent of pulmonary dysfunction in patients referred for liver transplantation. A total of 57 consecutive patients with chronic liver disease were evaluated. All patients had a chest radiograph, standing arterial blood gas on room air, pulmonary function testing, and Doppler echocardiogram. Those patients with arterial hypoxaemia (PaO(2) < 10 kPa) also underwent (99m)Tc-macroaggregated albumin lung scan, and nine patients had agitated normal saline injection during echocardiography to define further the existence of pulmonary vascular dilatation. Reduced diffusing capacity for carbon monoxide less than 75% of the predicted value was found in 29 of 57 (51%) patients. Although elevated alveolar-arterial oxygen tension difference was detected in 35% (20/57) of the patients, only four (7%) patients had hypoxemia. We were unable to find evidence of intrapulmonary vascular dilatation either on the lung scan or saline-enhanced echocardiography in any of these patients. Reduction in diffusing capacity for carbon monoxide was noted in 75% (18/24) of patients who were transplanted for primary biliary cirrhosis and was accompanied by widened alveolar-arterial oxygen tension in 10 out of 18 (56%) of patients. This study shows that in liver transplant candidates, diffusion impairment and widened alveolar-arterial oxygen tension difference were frequently detected, especially in patients with primary biliary cirrhosis.

Pulmonary dysfunction in non-cirrhotic patients with chronic viral hepatitis

Background: Hepatopulmonary syndrome (HPS), defined as hypoxemia and functional intrapulmonary right-to-left shunts in the presence of chronic liver disease, is a frequent complication of end-stage liver disease. The aim of this study was to determine the extent of pulmonary dysfunction and the prevalence of HPS in non-cirrhotic patients with chronic viral hepatitis. Methods: Lung function tests were carried out in 178 patients with chronic viral hepatitis (mean age 43.2 years, 95 smokers). To demonstrate intrapulmonary shunting, contrast echocardiography was performed in all patients with hypoxemia (paO(2)<70 mmHg) or a reduced diffusion capacity (DLCO<70% predicted). Results: The median results of lung function parameters (FVC, FEV(1), FEV(1)/FVC, TLC, DLCO, and blood gas analysis) were normal. Despite normal lung function, hypoxemia and/or DLCO reduction were observed in 17 of 178 patients (9.6%). A correlation with inflammatory activity, extent of fibrosis, or etiology was not found. Intrapulmonary shunting was observed in three of 17 patients. Two of these patients fulfilled the diagnostic criteria of HPS. Conclusions: Impaired gas exchange is a common finding even in non-cirrhotic patients with chronic viral hepatitis. HPS, however, was present in 1.1% of patients with chronic viral hepatitis and is thus not restricted to patients with liver cirrhosis, portal hypertension, or acute liver failure.

Utility of pulse oximetry in the detection of arterial hypoxemia in liver transplant candidates

Hepatopulmonary syndrome, arterial hypoxemia caused by intrapulmonary vasodilatation, occurs in approximately 10% of patients with cirrhosis. The severity of hypoxemia affects liver transplant candidacy and is associated with increased morbidity and mortality posttransplantation. Screening guidelines for detecting the presence of arterial hypoxemia do not exist. The aim of this study is to investigate the accuracy and utility of pulse oximetry in the detection of hypoxemia (PaO(2) < 70 mm Hg) in patients with cirrhosis. Two hundred prospective liver transplant candidates were compared with 94 controls. Arterial oxyhemoglobin saturation was obtained by pulse oximetry (SpO(2)) and compared with simultaneous arterial blood gas (ABG) oxyhemoglobin values (SaO(2); bias = the difference). PaO(2), carboxyhemoglobin, methemoglobin, and routine clinical and biochemical parameters were investigated to account for the bias. SpO(2) overestimated SaO(2) in 98% of patients with cirrhosis (mean bias, 3.37%; range, -1% to 10%). Forty-four percent of patients with cirrhosis and controls had a bias of 4% or greater. No clinical or biochemical parameters of cirrhosis accounted for the overestimation of pulse oximetry. Twenty-five subjects with cirrhosis were hypoxemic, and an SpO(2) of 97% or less showed a sensitivity of 96% and a positive likelihood ratio of 3.9 for detecting hypoxemia. An SpO(2) of 94% or less detected all subjects with an arterial PaO(2) less than 60 mm Hg. Pulse oximetry significantly overestimates arterial oxygenation, and the inaccuracy is not influenced by liver disease. Nevertheless, pulse oximetry can be a useful screening tool to detect arterial hypoxemia in patients with cirrhosis, but a higher threshold for obtaining an ABG must be used.

Hepatopulmonary syndrome in candidates for liver transplantation

BACKGROUND

Hepatopulmonary syndrome (HPS) has been defined as a clinical triad, including chronic liver disease, gas exchange defects (increased alveolar-arterial PO2 difference irrespective of the presence of arterial hypoxemia), and widespread intrapulmonary vascular dilatations. We determined the incidence and the clinical and pulmonary functional characteristics of HPS in candidates for orthotopic liver transplantation (OLT) and tested their predicted accuracy.

METHODS

We studied 80 patients with cirrhosis prospectively, and carried out contrast-enhanced (CE) echocardiography and lung function tests, including ventilation-perfusion (V(A)/Q) distributions.

RESULTS

Fourteen patients had HPS (incidence, 17.5%). Patients with HPS (49 +/- 12 (+/-SD) years) had more cutaneous spiders, finger clubbing and dyspnea (P < 0.05 each) and a lower diffusing capacity (DLCO, 56 +/- 18% predicted; P < 0.001) than non-HPS patients (n = 66). Mild to moderate V(A)/Q inequalities and increased intrapulmonary shunt were predominant in HPS patients, but oxygen diffusion impairment was observed in those with hypoxemia (n = 8) only. The DLCO showed a considerable area under the receiver operating characteristic curve (0.89).

CONCLUSIONS

HPS in cirrhotic patient candidates for OLT shows a high incidence and these patients present with distinctive clinical and functional features compared with non-HPS individuals. The presence of a low DLCO may be of help for the diagnosis of HPS.

Transient hepatopulmonary syndrome in a patient with acute hepatitis A

The hepatopulmonary syndrome is defined as the triad of liver disease, hypoxaemia and intrapulmonary vascular dilatation. This syndrome has been described in patients with liver cirrhosis, noncirrhotic portal hypertension, and fulminant hepatic failure, however, there are no previous descriptions of hepatopulmonary syndrome in patients with acute nonfulminant viral hepatitis. We report a 47-year-old, previously healthy man that presented with acute hepatitis A, and developed progressive dyspnoea, platypnoea and orthodeoxia with no evidence of parenchymal or thromboembolic lung disease. PaO2 on room air was 58 mmHg, O2 saturation was 88% and alveolar-arterial O2 gradient was 62%. During his hospitalization serum albumin level decreased to 3.1 g/dl and prothrombin time was prolonged to 16.8 s, however, he remained alert with no signs of hepatic encephalopathy. Contrast echocardiography revealed left heart chamber opacification 3-4 cardiac cycles after the opacification of the right heart chamber, consistent with hepatopulmonary syndrome. During the following days there was a gradual improvement in the patient's condition, with resolution of his dyspnoea and gradual increase of PaO2. Repeat contrast echocardiography and PaO2 determinations, 3 weeks later, were normal. On long-term follow-up the patient remained asymptomatic with normal liver function tests and normal O2 saturation. This report indicates that hepatopulmonary syndrome may be a transient manifestation of acute hepatitis A in the absence of fulminant liver failure.

Intrathoracic fluid volumes and pulmonary function during orthotopic liver transplantation

BACKGROUND

Impaired pulmonary function is a frequent finding in patients undergoing orthotopic liver transplantation (OLT). Experimental data suggest an essential contribution of splanchnic ischemia and reperfusion as a result of intraoperative volume shifts, i.e., the accumulation of extravascular lung water (EVLW). Increases of intrathoracic blood volume (ITBV) and pulmonary blood volume (PBV) might additionally influence pulmonary capillary fluid filtration. The main objective of this study was to determine the intrathoracic volume changes during OLT and to test whether there were any relationships between intra- and extravascular volume shifts and pulmonary function, as determined by the calculation of venous admixture (QS/QT) and alveolar-arterial oxygen gradient (AaDO2).

METHODS

Twenty-five patients undergoing OLT were studied. Using the transpulmonary double indicator dilution method, ITBV, PBV, and EVLW were determined from the mean transit times and exponential decay times of the indocyanine green and the thermal indicator curves recorded simultaneously with a fiberoptic catheter in the descending aorta. Recordings were made after induction of anesthesia, at the end of the anhepatic stage, immediately after reperfusion, and 1 and 4 h postoperatively.

RESULTS

Significant increases in QS/QT related to changes of ITBV were observed after reperfusion. Only a minor impact on AaDO2 was perceived. EVLW remained constant during the study period.

CONCLUSIONS

Postreperfusion increases of ITBV influence pulmonary function, as demonstrated by the increase in QS/QT. However, they need not be associated with greater EVLW levels, and impact on oxygenation is less severe than assumed. Hence, sufficient mechanisms protecting oxygenation and stalling increased EVLW seem to be present during uncomplicated human OLT.

High prevalence of pulmonary diffusion abnormalities without interstitial changes in long-term survivors of liver transplantation

Abnormalities in lung function are frequent findings in patients with terminal stage chronic liver disease. While spirometric parameters improve early after liver transplantation, a reduction in diffusion capacity has been reported up to 15 months after transplantation. It is unknown to what extent this disturbance in gas exchange occurs among long term survivors after liver transplantation. We assessed lung function in terms of spirometry, and gas exchange as well as pulmonary morphology by high resolution computed tomography (HRCT) in 40 patients 38 months (median, range 20-147 months) after liver transplantation. The prevalence of restrictive or obstructive changes was not different from predicted values. For the whole group of long-term survivors the carbon monoxide transfer coefficient (KCO) was reduced to 71.3 + 12.0% predicted (P < 0.05). HRCT revealed interstitial changes in only 2/40 (5.0%), emphysematous bullae in 2/40 (5.0%) and pleural thickening in 9/40 (22.5%). Diffusion abnormalities are prevalent in the majority of patients after liver transplantation, whereas spirometric abnormalities are absent also in the long term. The high prevalence of impaired gas exchange and the absence of interstitial lesions imply that changes in pulmonary blood vessels are the most likely cause.

Hepatopulmonary syndrome: the paradigm of liver-induced hypoxaemia

The current chapter deals with the concept, clinical manifestations and diagnostic tools of the hepatopulmonary syndrome (HPS) and highlights its most salient pathophysiological, mechanistic and therapeutic aspects. Defined as a clinical triad, including a chronic liver disorder, pulmonary gas exchange abnormalities and generalized pulmonary vascular dilatations, in the absence of intrinsic cardiopulmonary disease, this entity is currently growing in interest with both clinicians and surgeons. The combination of arterial hypoxaemia, high cardiac output with normal or low pulmonary artery pressure, and finger clubbing in a patient with advanced liver disease should strongly suggest the diagnosis of HPS. Its potential high prevalence together with failure of numerous therapeutic approaches depicts a life-threatening unique clinical condition that may dramatically benefit with an elective indication of liver transplantation (LT). A better orchestration of the concepts of the pathophysiology of this lung-liver interplay may foster our knowledge and improve the clinical management and indications of LT.

Frequency and clinical implications of increased pulmonary artery pressures in liver transplant patients

OBJECTIVE

To characterize the pulmonary hemodynamics and identify predictors of pulmonary hypertension in a group of patients before liver transplantation and to determine whether pulmonary hypertension in these patients is related to survival.

MATERIAL AND METHODS

In 362 patients before their first liver transplantation (between 1985 and 1993), the clinical history, laboratory data, and results of pulmonary function tests were recorded. Pulmonary artery (PA) catheterization was performed after induction of anesthesia at the time of transplantation. Monthly follow-up was maintained.

RESULTS

A hyperdynamic circulation was often present -- an increased mean cardiac output (7.6 L/min), increased mean PA pressure (20.9 mm Hg), correlation of mean PA pressure with cardiac output (r = 0.25; P<0.001), and decreased mean pulmonary vascular resistance (60 dynes times s/cm5). Mean PA pressures were more than 25 mm Hg in 72 patients (20%). Pulmonary hypertension (defined as mean PA pressure of more than 25 mm Hg and pulmonary vascular resistance in excess of 120 dynes times s/cm5) occurred in 15 patients (4%). Pulmonary function tests revealed obstruction in 7%, restriction in 18%, and low diffusing capacity in 46%. By univariate analysis, lower forced expiratory volume in 1 second, forced vital capacity, and total lung capacity were the only preoperative factors associated with pulmonary hypertension (P<0.05). Survival was significantly lower in patients with acute fulminant hepatitis (P<0.001), the group with the highest mean PA pressure, than in those with other diagnoses. Increased PA pressures or mild to moderate pulmonary hypertension was not found to be associated with a worse survival by univariate or multivariate analysis.

CONCLUSION

Increased PA pressure is common in liver transplant patients (20%). "True" pulmonary hypertension occurred in only 4% of our patients and was not associated with an adverse outcome.

Pulmonary complications of liver transplantation

The preoperative pulmonary evaluation of organ transplant candidates involves the diagnosis of unexplained pulmonary infiltrates or symptoms, interpretation of pulmonary function abnormalities, and an assessment of surgical risk. Pretransplant pulmonary considerations in patients with end-stage hepatic diseases relate primarily to hypoxemia from poorly understood intrapulmonary vascular dilatations, mechanical dysfunction, and states of increased extravascular lung water. Except in severe cases, however, these generally do not prohibit liver transplantation, and even are likely to improve after transplant surgery. Early postoperative complications may be categorized as those expected from extensive intra-abdominal surgery that requires significant volume resuscitation, which typically are managed in the usual manner for those clinical situations. As immunosuppression begins to have an effect, the LTx recipient becomes susceptible to the same opportunistic infectious organisms (with their frequent pulmonary involvement) that cause significant morbidity and mortality in recipients of other solid organ transplants. Because many of the immunosuppressive agents also are the same, noninfectious side effects such as pulmonary edema and malignancy also are similar. As with all immunocompromised patients, prophylaxis, when possible, persistent infection surveillance, and an aggressive diagnostic and therapeutic approach help decrease the impact of pulmonary dysfunction in LTx recipients.

Recent pulmonary observations in alpha 1-antitrypsin deficiency, primary biliary cirrhosis, chronic hepatitis C, and other hepatic problems

Patients with metabolic, immunologic, viral, and other types of hepatic disorders can have a spectrum of complicating pulmonary abnormalities. The natural history of these associations is poorly understood. Significant reversibility in hepatic and pulmonary dysfunction, however, has been well documented in the era of organ transplantation. The continued relationship among pulmonologists, hepatologists, and transplant surgeons hopefully will provide enlightening data on these interesting clinical associations, their natural histories, and their response to evolving therapeutic approaches.

Mechanisms of gas exchange impairment in patients with liver cirrhosis

This article reviews the basic pathophysiologic mechanisms underlying the abnormal pulmonary gas exchange often seen in patients with cirrhosis. To summarize, the following keypoints seem appropriate: (1) Patients with cirrhosis have a low pulmonary vascular tone characterized by a poor or absent hypoxic pressor response. This results in a marked dilation of the pulmonary vasculature. (2) This abnormal pulmonary vascular tone, independently of airway disease, causes VA/Q mismatch and mild to moderate hypoxemia. Yet, as liver disease progresses and hepatocellular function deteriorates, more severe degrees of intrapulmonary shunt emerge and, probably, O2 diffusion limitation ensues, causing severe respiratory failure (see Table 1). (3) At rest, the high cardiac output and minute ventilation of cirrhosis minimize the degree of arterial hypoxemia that otherwise would be expected from the observed degree of both VA/Q inequality and intrapulmonary shunt. During exercise, the relative "normalization' (with respect to metabolic demands) of the hemodynamic and ventilatory status of the patient explains the fall in PaO2. (4) A clear pathogenic mechanism of these pathophysiologic abnormalities is still lacking, although available evidence suggests that both the liver and the endothelial cells may play a pivotal role in the regulation of the pulmonary vascular tone in these patients. (5) To date, no pharmacologic intervention has been effective in treating hypoxemia in these patients. Yet liver transplantation helps in most of them. This observation reinforces the functional nature of the gas exchange abnormalities of cirrhosis.

Pulmonary complications of orthotopic liver transplantation

We retrospectively reviewed the pulmonary complications and associated morbidity and mortality of 44 consecutive patients who underwent 52 orthotopic liver transplantations (OLTs) at the Mayo Clinic during 1987. All survivors participated in follow-up for 1 year after OLT. Of the five deaths in the study group, three were associated with pulmonary infections. On postoperative chest roentgenograms, 24 cases of pulmonary infiltrates were noted; 12 were caused by infections. Ten opportunistic pulmonary infections developed in nine patients: four cytomegalovirus, three Pneumocystis carinii pneumonia, and one each of Cryptococcus, Aspergillus, and Candida. All except one of the opportunistic infections were diagnosed after the sixth postoperative week. Fiberoptic bronchoscopy was helpful for diagnosing opportunistic pulmonary infections in six patients. One Aspergillus pulmonary infection was diagnosed by transthoracic needle aspiration. Bacterial pneumonia occurred in five patients. Preoperative pulmonary function tests, performed in 40 patients, revealed a restrictive ventilatory defect in 28% and impaired gas transfer in 52%. Pleural effusion was present in 18% of patients preoperatively and in 77% during the first week after OLT. Preoperative severity of liver disease and results of arterial blood gas determinations, pulmonary function tests, and chest roentgenography were not associated with postoperative mortality and pulmonary infections. Infectious and noninfectious pulmonary complications are common in liver transplant recipients. Attempts to decrease the frequency and severity of pulmonary complications by early diagnosis and effective treatment may diminish the morbidity and mortality associated with OLT.