Early hemodynamic effects after extended liver radiofrequency ablation.

BACKGROUND: The purpose of the present study was to assess early intestinal and systemic hemodynamic effects after extended radiofrequency ablation (RFA) of the liver in terms of investigating their potential contribution to gut barrier disruption. MATERIALS AND METHODS: Ten rabbits were assigned to two groups of five animals each and were subjected to either 30% liver RFA (group RFA-1) or sham operation (group sham-1). Blood flow rate at the superior mesenteric artery (SMA) was monitored for 90 min after operation. Ileal tissue was excised at 48 h for histomorphometric and histopathologic analysis. Eight pigs were assigned to two groups of four animals each and were also subjected to either 30% liver RFA (group RFA-2) or sham operation (group sham-2). A panel of systemic hemodynamic parameters was serially measured up to 90 min after operation. RESULTS: In group RFA-1, SMA blood flow rate was lower than that in group sham-1 throughout the study period. Intestinal mucosa atrophy and a deterioration of histopathologic profile were noted in group RFA-1. In group RFA-2, diastolic pulmonary artery pressure was lower (60-90 min), central venous pressure was gradually decreased, arterial pressure was higher (30-90 min), and systemic vascular resistance was higher (30-90 min) than those in group sham-2. No change was noted in the cardiac output. CONCLUSIONS: In conclusion, SMA blood flow was reduced during the early post-RFA period, justifying an ischemic insult at the intestine. In addition, a gradual decrease of the preload was counterbalanced by an increase of systemic vascular resistance leaving the cardiac output unaffected.

Variations in arterial blood pressure are associated with parallel changes in FlowTrac/Vigileo-derived cardiac output measurements: a prospective comparison study.

INTRODUCTION: The reliability of autocalibrated pressure waveform analysis by the FloTrac-Vigileo(R) (FTV) system for the determination of cardiac output in comparison with intermittent pulmonary arterial thermodilution (IPATD) is controversial. The present prospective comparison study was designed to determine the effects of variations in arterial blood pressure on the reliability of the FTV system in patients undergoing coronary artery bypass grafting (CABG). METHODS: Comparative measurements of cardiac output by FTV (derived from a femoral arterial line; software version 1.14) and IPATD were performed in 16 patients undergoing elective CABG in the period before institution of cardiopulmonary bypass. Measurements were performed after induction of anesthesia, after sternotomy, and during five time points during graft preparation. During graft preparation, arterial blood pressure was increased stepwise in intervals of 10 to 15 minutes by infusion of noradrenaline and lowered thereafter to baseline levels. RESULTS: Mean arterial blood pressure was varied between 85 mmHg and 115 mmHg. IPATD cardiac output did not show significant changes during periods with increased arterial pressure either during sternotomy or after pharmacological manipulation. In contrast, FTV cardiac output paralleled changes in arterial blood pressure; i.e. increased significantly if blood pressure was raised and decreased upon return to baseline levels. Mean arterial blood pressure (MAP) and FTV cardiac output were closely correlated (r = 0.63 (95% confidence interval [CI]: 0.49 - 0.74), P < 0.0001) while no correlation between MAP and IPATD cardiac output was observed. Bland-Altman analyses for FTV versus IPATD cardiac output measurements revealed a bias of 0.4 l/min (8.5%) and limits of agreement from 2.1 to -1.3 l/min (42.2 to -25.3%). CONCLUSIONS: Acute variations in arterial blood pressure alter the reliability of the FlowTrac/Vigileo device with the second-generation software. This finding may help to explain the variable results of studies comparing the FTV system with other cardiac output monitoring techniques, questions the usefulness of this device for hemodynamic monitoring of patients undergoing rapid changes in arterial blood pressure, and should be kept in mind when using vasopressors during FTV-guided hemodynamic optimization.

Extravascular perivenous fibrin support leads to aneurysmal degeneration and intimal hyperplasia in arterialized vein grafts in the rat.

BACKGROUND AND AIMS: External support of vein grafts by fibrin glue possibly prevents overdistension, vascular remodeling, and neointimal hyperplasia. Previous animal models of neointimal hyperplasia showed conflicting results. Here, long-term effects of external fibrin glue support were studied in a new rat model of jugular vein to abdominal aorta transposition. MATERIALS AND METHODS AND METHODS: In male Wistar rats (250-300 g) right jugular vein (1.0-1.5 cm) was transposed to the infrarenal aorta. Fibrin glue (0.25 ml) covered the vein before releasing the vascular clamps (n = 6). Control vein grafts were exposed directly to blood pressure. After 16 weeks vein grafts were pressure-fixed for histology. Intima thickness, luminal and intimal area were measured by planimetry and elastic fibers demonstrated by Elastica van Giesson staining. RESULTS: Intimal thickness (74.04 +/- 6.7 microm vs 1245 +/- 187 microm, control vs fibrin treatment; p < 0.001), intimal area (2517.16 +/- 355 mm(2) vs 18424 +/- 4927 mm(2), control vs fibrin treatment; p < 0.05) and luminal area (2184.75 +/- 347 mm(2) vs 7231.85 +/- 1782 mm(2), control vs fibrin treatment; p < 0.05) were significantly increased, elastic fibers in the vessel wall were diminished and the vessel wall infiltrated by mononuclear cells in fibrin glue supported veins. CONCLUSION: External support of vein grafts by fibrin glue leads to aneurysmal degeneration and intimal hyperplasia, thereby possibly jeopardizing long-term graft patency.

Organ toxicity and mortality in propofol-sedated rabbits under prolonged mechanical ventilation.

BACKGROUND: Prolonged administration of propofol at large doses has been implicated in propofol infusion syndrome in intensive care unit patients. In this study we investigated organ toxicity and mortality of propofol sedation at large doses in prolonged mechanically ventilated rabbits and determined the role of propofol's lipid vehicle. METHODS: Eighteen healthy male rabbits were endotracheally intubated and sedated with propofol 2% (Group P), sevoflurane (Group S) or sevoflurane while receiving Intralipid 10% (Group SI). Sedation lasted 48 h or until death (Group P) or the maximum surviving period of Group P (Groups S and SI). The initial propofol infusion rate (20 mg x kg(-1) x h(-1)) or sevoflurane concentration (1.5%) was adjusted, if needed, to maintain a standard level of sedation. Blood biochemical analysis was performed in serial blood samples and histologic examination in the heart, lungs, liver, gallbladder, kidneys, urinary bladder, and quadriceps femoris muscle at autopsy. RESULTS: The mortality rate was 100% (surviving period, 26-38 h) for Group P, whereas 0% for Groups S and SI. The initial propofol infusion rate had to be increased up to 65.7 +/- 4.6 mg x kg(-1) x h(-1) and sevoflurane concentration up to 4%. Serum liver function indices, lipids and creatine kinase were significantly increased (P < 0.05) in Groups P and SI and lactate was increased only in Group P, whereas amylase was increased in all groups. In Group P, histologic examination revealed myocarditis, pulmonary edema with interstitial pneumonia, hepatitis, steatosis, and focal liver necrosis, cholangitis, gallbladder necrosis, acute tubular necrosis of the kidneys, focal loss of the urinary bladder epithelium, and rhabdomyolysis of skeletal muscles; in Group S, low-grade bronchitis and incipient inflammation of the liver and the kidneys; and in Group SI, low-grade bronchitis, liver steatosis and hepatitis, and incipient inflammation of the gallbladder, kidneys, and urinary bladder. CONCLUSIONS: Continuous infusion of 2% propofol at large doses for the sedation of rabbits undergoing prolonged mechanical ventilation induced fatal multiorgan dysfunction syndrome similar to the propofol infusion syndrome seen in humans. Our novel findings including lung, liver, gallbladder, and urinary bladder injury were also noted. The role of propofol's lipid vehicle in the manifestation of the syndrome was minor. Sevoflurane proved to be a safe alternative medication for prolonged sedation.

Tolerance to propofol's sedative effect in mechanically ventilated Rabbits.

Propofol is commonly used for the sedation of critically ill patients undergoing mechanical ventilation. These patients may develop tolerance during long-term administration. Here, we describe the development of tolerance to propofol's sedative effect in rabbits during prolonged mechanical ventilation. Six healthy male New Zealand White rabbits were endotracheally intubated and received propofol by continuous IV infusion to maintain sedation for 48 h. The propofol infusion rate (IR) was adjusted to maintain the desired level of sedation. Assessments of the sedation level were made every 30 min or earlier if there were signs of awakening. Propofol concentrations were measured in arterial plasma after every other IR adjustment, provided there was an adequate level of sedation, using high performance liquid chromatography, and calculations of systemic clearance rates were made. The mortality rate was 100% with a survival period of 30.8 +/- 6.0 h (mean +/- sd). The course of IR adjustments followed a 5-phase pattern: 1) steady IR (mean +/- sd duration; 1.2 +/- 0.6 h), 2) increasing IR (9.4 +/- 5.5 h), 3) steady high-IR (2.3 +/- 1.2 h), 4) decreasing IR (13.7 +/- 1.9 h), and 5) steady low-IR (5.0 +/- 2.7 h). The course of propofol concentrations during the experiment in relation to propofol IR followed a 3-phase pattern: 1) steady concentration with increasing IRs (6.0 +/- 2.7 h), 2) increasing concentrations with increasing IR (5.8 +/- 2.5 h), and 3) increasing concentrations with decreasing IR (18.8 +/- 3.3 h). Propofol systemic clearance rates were progressively increased for 6.0 +/- 2.7 h and then gradually decreased for 24.6 +/- 4.7 h. In conclusion, all rabbits developed tolerance to propofol's sedative effect within the first hours of administration related to changes to the drug's metabolic clearance.

Systemic inflammatory response after single-incision laparoscopic surgery versus standard laparoscopic approach.

PURPOSE: The extent of surgical trauma is reflected by systemic inflammatory response (SIR). The aim of this study was to assess SIR after single-incision laparoscopic surgery (SILS) versus the standard laparoscopic approach. MATERIALS AND METHODS: Twenty pigs were assigned into 4 groups: SILS (group SILS), laparoscopy using 4 trocars (group LAPSC), pneumoperitoneum (group PNE), or a sham-operation (group Sham) group. Blood samples were taken at 0, 1, 3, 6, 24, and 48 hours and 1 week postoperation to measure tumor necrosis factor-α, interleukin (IL)-6, IL-18, and C-reactive protein serum levels. RESULTS: No significant changes were noted among groups for each time point studied regarding tumor necrosis factor-α, IL-6, and IL-18. C-reactive protein levels were significantly lower (P<0.05) in group PNE compared with the other groups at 24 hours, 48 hours, and 1 week. CONCLUSIONS: There is no difference in SIR after SILS versus the standard laparoscopic approach.

Acute pressure overload of the right ventricle. Comparison of two models of right-left shunt. Pulmonary artery to left atrium and right atrium to left atrium: experimental study.

BACKGROUND: In right ventricular failure (RVF), an interatrial shunt can relieve symptoms of severe pulmonary hypertension by reducing right ventricular preload and increasing systemic flow. Using a pig model to determine if a pulmonary artery-left atrium shunt (PA-LA) is better than a right atrial-left atrial shunt (RA-LA), we compared the hemodynamic effects and blood gases between the two shunts. METHODS: Thirty, male Large White pigs weighting in average 21.3 kg ± 0.7 (SEM) were divided into two groups (15 pigs per group): In group 1, banding of the pulmonary artery and a pulmonary artery to left atrium shunt with an 8 mm graft (PA-LA) was performed and in group 2 banding of the pulmonary artery and right atrial to left atrial shunt (RA-LA) with a similar graft was performed. Hemodynamic parameters and blood gases were measured from all cardiac chambers in 10 and 20 minutes, half and one hour interval from the baseline (30 min from the banding). Cardiac output and flow of at the left anterior descending artery was also monitored. RESULTS: In both groups, a stable RVF was generated. The PA-LA shunt compared to the RA-LA shunt has better hemodynamic performance concerning the decreased right ventricle afterload, the 4 fold higher mean pressure of the shunt, the better flow in left anterior descending artery and the decreased systemic vascular resistance. Favorable to the PA-LA shunt is also the tendency--although not statistically significant--in relation to central venous pressure, left atrial filling and cardiac output. CONCLUSION: The PA-LA shunt can effectively reverse the catastrophic effects of acute RVF offering better hemodynamic characteristics than an interatrial shunt.

One-lung ventilation and HIF1alpha expression in lung cancer and pneumothorax.

BACKGROUND/AIM: A prospective study was designed to investigate the effects of anesthesia, particularly that of the one-lung ventilation procedure (OLV), on the expression of hypoxia-inducible factor 1alpha (HIF1alpha) in patients with lung carcinomas and pneumothorax. MATERIALS AND METHODS: The immunohistochemical expression of HIF1alpha was studied in formalin-fixed paraffin-embedded tissues from 60 patients who had undergone thoracic surgery for lung cancer (n=48) or pneumothorax (n=12) under OLV general anesthesia. RESULTS: There was a significant, and rather unexpected, association of HIF1alpha expression with high body mass index (BMI) (p=0.01) and high body weight (p=0.01) of patients with lung carcinomas, but other anesthesia-related parameters, including analysis of arterial oxygen partial tension and anthropometric factors remained insignificant. With regard to pneumothorax cases, these were immunohistochemically unreactive and, hence, no relationship was noted between HIF1alpha and anesthesia parameters. CONCLUSION: Anesthesia and OLV procedure performed for lung cancer or pneumothorax does not affect the expression of HIF1alpha. However, the significant link between high BMI and HIF1alpha expression noted in patients with lung carcinomas brings forward a possible connection between obesity and hypoxia-related molecular pathways.