Per Lilleaasen

The nitric oxide donor sodium nitroprusside protects against hepatic microcirculatory dysfunction in early endotoxaemia.

Objective: Endotoxin rapidly inhibits the activity of the constitutive endothelial nitric oxide synthase (ecNOS); this precedes the production of NO from inducible NOS (iNOS). This leaves a period in early endotoxaemia with a supposed scarcity of NO. The present study was conducted to examine the effects of external supplementation of NO on liver microcirculation and function. Material: 13 male Sprague Dawley rats. Interventions: The rats underwent laparotomy, and the left liver lobe was exteriorised. All animals were given a bolus dose of endotoxin (LPS) 5 mg/kg intraportally. One group (n = 6) had a continuous infusion of sodium nitroprusside (SNP) 1.4 μg/kg per min started concurrently, the other group (n = 7) was treated with normal saline. The study was terminated after 3 h LPS. Measurements and results: Intravital microscopy was performed at baseline, at 2 h and 3 h LPS. Hepatic function was assessed by arterial ketone body ratio, acid base values, and bile flow. At baseline 1 % of the sinusoids were without perfusion. After 2 h LPS this figure had risen to 9.8 ± 1.5 % in the SNP group versus 16.9 ± 1.4 % in the controls (p < 0.05 vs controls). The corresponding values after 3 h LPS were 13.5 ± 1.5 versus 19.3 ± 1.5 % (p < 0.05 vs controls). The leukocyte count in sinusoids and venules had a similar development. Functional parameters were all slightly better preserved in the SNP group, but with no individual significance versus controls. Conclusions: Infusion of the NO donor SNP in early endotoxaemia attenuates the detrimental effects of LPS on liver microcirculation, most probably by alleviating a relative deficit of NO at the microcirculatory level.

Aminoethyl-isothiourea, a selective inhibitor of inducible nitric oxide synthase activity, improves liver circulation and oxygen metabolism in a porcine model of endotoxemia

The role of nitric oxide (NO) in hepatic oxygen transport is unclear. We investigated the effects of aminoethyl-isothiourea (AE-ITU), a selective inhibitor of iNOS activity, on liver blood flow and oxygen consumption (Vo2H) in the pig. Endotoxin (lipopolysaccharide, LPS) was given intraportally (1.7 μg/kg/h), followed by AE-ITU (10 mg/kg) after 3 h (n = 7). LPS controls (n = 8) received LPS for 6 h. AE-ITU controls (n = 6) received saline/AE-ITU. LPS (treatment group) caused significant reductions at 3 h in cardiac output (CO) from 4.4 ± .4 to 2.7 ± .3 L/min, in hepatic artery flow (QHA) from 266 ± 53 to 127 ± 19 mL/min, and in portal venous flow (QPV) from 630 ± 50 to 323 ± 33 mL/min. Hepatic oxygen delivery (Do2H) was reduced from 93 ± 11 to 38 ± 5 mL/min (p < .05), while hepatic oxygen extraction ratio (ERo2H) increased, and Vo2H was maintained. Similar changes were observed in LPS controls. AE-ITU caused no changes in saline controls. After injection of AE-ITU during LPS infusion, CO was unchanged, while QHA increased gradually from 127 ± 20 to 268 ± 40 mL/min over 3 h (p < .05) and Do2H from 38 ± 5 to 60 ± 5 mL/in (p < .05). ERo2H increased from .54 ± .04 to .69 ± .03 in 30 min, while Vo2H increased from 23 ± 4 to 35 ± 3 mL/in in 3 h (p < .05). Thus, AE-ITU restored hepatic arterial blood flow and increased hepatic oxygen consumption in pigs with endotoxemia.

Effects of the nitric oxide synthase inhibitors NG-nitrol-L-arginine methyl ester and aminoethyl-isothiourea on the liver microcirculation in rat endotoxemia

BACKGROUND/METHODSnThe question whether nitric oxide protects or impairs organ perfusion during early endotoxemia has not been completely answered. To evaluate the regulative function of nitric oxide on organ microvascular perfusion and leukocyte accumulation during endotoxemia, we studied the influence of a non-selective nitric oxide inhibitor and a preferential inducible nitric oxide synthase inhibitor (respectively, N(G)-nitro-L-arginine methyl ester and aminoethyl-isothiourea) on liver microcirculation (intravital fluorescence microscopy) in a rat model.nnnRESULTSnTwo hours after intraportal injection of lipopolysaccharide (5 mg/kg in 10 min) the rats were randomly treated and received a bolus dose of N(G)-nitro-L-arginine methyl ester (10 mg/kg, n = 7), aminoethyl-isothiourea (10 mg/kg, n = 6) or normal saline, (n = 7). After 1 h, N(G)-nitro-L-arginine methyl ester blockade yielded a higher rate of non-perfused sinusoids than normal saline (27 +/- 2% vs 19 +/- 5%, p < 0.05). LPS-induced leukocyte stagnation in sinusoids was further increased (p < 0.05) in all groups after 1 h treatment, but N(G)-nitro-L-arginine methyl ester clearly accentuated leukocyte accumulation in sinusoids as compared to normal saline (69 +/- 19% vs 16 +/- 4%, p < 0.05). Both modalities of nitric oxide blockade elicited a significant enhancement in the number of leukocytes adherent to the postsinusoidal venules in contrast to normal saline (N(G)-nitro-L-arginine methyl ester 48 +/- 17%, aminoethyl-isothiourea 33 +/- 9% vs normal saline 1 +/- 5%, p < 0.05).nnnCONCLUSIONSnWe conclude that complete nitric oxide blockade aggravates lipopolysaccharide-induced hepatic microvascular perfusion failure and enhances leukocyte accumulation, in both sinusoids and post-sinusoidal venules. The preferential inducible nitric oxide synthase inhibitor aminoethyl-isothiourea has a moderate negative effect, favoring leukocyte adhesion in postsinusoidal venules, and its usefulness demands further research, especially concerning its late effects.

Moderate and Extreme Hemodilution in Open-Heart Surgery: Fluid Balance and Acid-Base Studies

Two groups of patients underwent aortic valve replacement. Fifteen patients received moderate hemodilution (mean hematocrit, 27%) with 40% donor blood in the priming solution. Extreme hemodilution was used in 14 patients (mean hematocrit, 18%) with a nonhemic prime and withdrawal of blood at the start of operation. Both groups were given more than 7 liters of fluid during operation; donor blood was primarily used in the moderately diluted patients, and Ringers acetate was primarily given to the other group. The diuretic response to this fluid load was much more pronounced in the extreme than in the moderate hemodilution group. Eighteen hours postoperatively, patients in the moderate and extreme hemodilution groups had an excess of about 2 and 1.5 liters of water, respectively. In the patients who had moderate dilution an average of 1,000 ml of erythrocytes disappeared from circulation; no such disappearance could be found in the other group. The moderate group showed significantly lower arterial PO2 postoperatively than the extreme group. There were, however, no differences between the two groups in mixed venous PO2 during perfusion or in acid-base and osmolality values.

Organ injury and cytokine release caused by peptidoglycan are dependent on the structural integrity of the glycan chain

ABSTRACT Several studies have implicated a role of peptidoglycan (PepG) as a pathogenicity factor in sepsis and organ injury, in part by initiating the release of inflammatory mediators. We wanted to elucidate the structural requirements of PepG to trigger inflammatory responses and organ injury. Injection of native PepG into anesthetized rats caused moderate but significant increases in the levels of alanine aminotransferase, aspartate aminotransferase, γ-glutamyl transferase, and bilirubin (markers of hepatic injury and/or dysfunction) and creatinine and urea (markers of renal dysfunction) in serum, whereas PepG pretreated with muramidase to digest the glycan backbone failed to do this. In an ex vivo model of human blood, PepG containing different amino acids induced similar levels of the cytokines tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), IL-8, and IL-10, as determined by plasma analyses (enzyme-linked immunosorbent assay). Hydrolysis of the Staphylococcus aureus cross-bridge with lysostaphin resulted in moderately reduced release of TNF-α, IL-6, IL-8, and IL-10, whereas muramidase digestion nearly abolished the ability to induce cytokine release and IL-6 mRNA accumulation in CD14+ monocytes compared to intact PepG. However, additional experiments showed that muramidase-treated PepG synergized with lipopolysaccharide to induce TNF-α and IL-10 release in whole blood, despite its lack of inflammatory activity when administered alone. Based on these studies, we hypothesize that the structural integrity of the glycan chain of the PepG molecule is very important for the pathogenic effects of PepG. The amino acid composition of PepG, however, does not seem to be essential for the inflammatory properties of the molecule.

USE OF SELECTIVE AND NONSELECTIVE NITRIC OXIDE SYNTHASE INHIBITORS IN RAT ENDOTOXEMIA: EFFECTS ON HEPATIC MORPHOLOGY AND FUNCTION

Endotoxin has profound effects on nitric oxide (NO) production, and considerable controversies exist as to whether these alterations are beneficial or deleterious. Increased mortality has been reported from nonselective inhibition of NO synthase. Results from selective inhibition of the inducible isoform (iNOS) appear largely positive. In a model of rat endotoxemia we have compared the early effects on hepatic morphology and function of selective and nonselective NO inhibition. Two hours after endotoxin injection (5 mg/kg intraportally) the rats were treated with either the selective iNOS inhibitor aminoethyl isothiourea (AE-ITU, 10 mg/kg), the nonselective NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg), or normal saline. The animals were observed for another hour. Using an immunohistochemical method, induction of iNOS was demonstrated in various tissues in all slices examined. No unequivocal benefit from NO inhibition was noted. Electron microscopic examination revealed widespread alterations of liver morphology, without obvious differences between the groups. Liver function, as assessed by ketone body ratio, hepatic venous acid base values, and bile production, was generally more adversely affected after NO inhibition. Even with the iNOS selective inhibitor AE-ITU no benefit was noted. We conclude that during the early phases of endotoxemia therapeutic reduction of NO production has no positive effects on liver function or morphology.

Doppler Ultrasound Estimation of Bubble Removal by Various Arterial Line Filters During Extracorporeal Circulation

The bubble extraction capacity of various arterial line filters was tested in vitro and in vivo. The depth adsorption filtration principle was superior in removing bubbles compared with screen filters, both in vitro and under clinical cardiopulmonary bypass situations.

The NO Donor Sodium Nitroprusside Reverses the Negative Effects on Hepatic Arterial Flow Induced by Endotoxin and the NO Synthase Inhibitor L-NAME

In previous studies we have observed that the nitric oxide synthase inhibitor L-NAME induces a profound deterioration of liver circulation in experimental endotoxemia. Using the same porcine model we now have evaluated the possibility of modulating these effects with the nitric oxide donor sodium nitroprusside. Infusion of endotoxin led to a gradual deterioration of hemodynamic parameters, including liver blood flow. The decreases in portal blood flow paralleled and matched the decreases in cardiac output, and no compensatory increase in hepatic arterial flow occurred. L-NAME had detrimental effects on hemodynamics, including the liver circulation. The latter effects could, however, partially be reversed by sodium nitroprusside. Hepatic arterial flow increased from 1.9 to 7.2 ml/kg/min, with a concomitant decrease in hepatic arterial resistance from 5,364 to 1,746 dyn s/cm5 kg. A control group exhibited no significant change in either flow or resistance. The response to sodium nitroprusside was rapid and vigorous, and probably largely due to relaxation of the hepatic arterioles, and not to abatement of intrahepatic edema or plugging of the sinusoids. Furthermore, we conclude that the endotoxin-induced dysfunction of the hepatic arterial buffer response may be due to a selective inhibition of vascular endothelial function.

Aspects of Cerebral Perfusion in Open-Heart Surgery

A selected series of 25 patients undergoing open-heart surgery were subjected to continuous monitoring of arterial blood pressure (BP), central venous pressure (CVP) and intracranial epidural pressure (EDP). This gave continuous information on the cerebral perfusion pressure (CPP = BP-EDP). In all patients the start of the extracorporeal perfusion caused a rapid fall in CPP (30 mmHg or less in 22 patients, less than 10 mmHg in 5 patients). The combination of grave systemic hypotension and increased EDP contributed to these low CPP states, which varied in duration from 2 to 15 min. Spontaneous, as well as vasopressor-induced BP recovery was accompanied by a concomitant increase in EDP in 15 patients. This prolonged the low CPP state, making an evaluation of CPP from BP alone misleading under such conditions. Increasing EDP secondary to a rise in BP was also observed during termination of the extracorporeal circulation, particularly in 6 patients requiring an intra-aortic balloon pump in addition to large doses of vasopressors to obtain an acceptable BP. An increase in CVP to levels above EDP is transmitted intracranially, thus reducing the CPP. The recordings may improve insight into pathogenic mechanisms leading to harmful effects on the brain in connection with open-heart surgery.

Dextran 70 versus donor plasma as colloid in open-heart surgery under extreme haemodilution

Dextran 70 and donor plasma were compared as colloid in the priming solution during heart-lung perfusion in open-heart surgery. The patients underwent surgery for coronary artery or aortic valve disease. One group of nine patients had plasma in the priming solution, while ten patients received dextran 70. Prior to perfusion the patients in the dextran group received monovalent hapten to prevent anaphylactic reactions towards dextran. During the perfusion the same level of haemodilution was established in both groups; the haematocrit values fell from about 39 vol. per cent before perfusion to about 19 vol. per cent after 45 min of perfusion. Eighteen hours postoperatively, the haematocrit had increased to about 35 vol. per cent. The mean concentrations of total serum protein in preoperative samples from the plasma and dextran group were 66.0 g/l and 66.3 g/l, respectively, and fell to 42.6 g/l and 28.3 g/l in samples taken after 45 min of perfusion. The serum-protein concentration in the dextran group remained significantly lower than that of the plasma group throughout the postoperative period. A similar pattern was seen for the albumin concentration. Preoperatively the mean values of the colloid osmotic pressure of plasma were 24.2 mmHg and 25.5 mmHg in the plasma and dextran group, respectively. Corresponding figures 45 min after start of perfusion were 13.9 mmHg and 16.9 mmHg, respectively, significantly higher in the dextran group than in the plasma group. The colloid osmotic pressure exerted by dextran was about 9 mmHg during heart-lung perfusion and about 4 mmHg 18 h later.(ABSTRACT TRUNCATED AT 250 WORDS)