Alastair O'Brien

Terlipressin for norepinephrine-resistant septic shock.

Norepinephrine-resistant hypotension when associated with septic shock has a high rate of mortality, which might possibly be reduced by infusion of low-dose vasopressin. However, rebound hypotension often arises after treatment is stopped, and the drug usually has to be administered for several days. We report use of terlipressin, a long-acting vasopressin analogue, in eight patients with septic shock who did not respond to corticosteroids and methylene blue. A significant rise in blood pressure that lasted for at least 5 h was seen in all patients after a single bolus, allowing reduction or cessation of norepinephrine administration in seven patients. We were able to discharge four patients from intensive care subsequently. Terlipressin seems to be an effective rescue therapy, which is able to restore blood pressure in patients with catecholamine-resistant septic shock, without obvious complication.

Nutrition in End-Stage Liver Disease: Principles and Practice

In this review, we examine the mechanisms underlying malnutrition in chronic liver disease, the assessment methods available, and the role of nutritional therapy (advice, supplementation, enteral or parenteral) in the various stages of chronic liver disease. Acute liver failure and transplantation and the emerging data on probiotics are considered separately.

Immunosuppression in acutely decompensated cirrhosis is mediated by prostaglandin E2.

Liver disease is one of the leading causes of death worldwide. Patients with cirrhosis display an increased predisposition to and mortality from infection due to multimodal defects in the innate immune system; however, the causative mechanism has remained elusive. We present evidence that the cyclooxygenase (COX)-derived eicosanoid prostaglandin E2 (PGE2) drives cirrhosis-associated immunosuppression. We observed elevated circulating concentrations (more than seven times as high as in healthy volunteers) of PGE2 in patients with acute decompensation of cirrhosis. Plasma from these and patients with end-stage liver disease (ESLD) suppressed macrophage proinflammatory cytokine secretion and bacterial killing in vitro in a PGE2-dependent manner via the prostanoid type E receptor-2 (EP2), effects not seen with plasma from patients with stable cirrhosis (Child-Pugh score grade A). Albumin, which reduces PGE2 bioavailability, was decreased in the serum of patients with acute decompensation or ESLD (<30 mg/dl) and appears to have a role in modulating PGE2-mediated immune dysfunction. In vivo administration of human albumin solution to these patients significantly improved the plasma-induced impairment of macrophage proinflammatory cytokine production in vitro. Two mouse models of liver injury (bile duct ligation and carbon tetrachloride) also exhibited elevated PGE2, reduced circulating albumin concentrations and EP2-mediated immunosuppression. Treatment with COX inhibitors or albumin restored immune competence and survival following infection with group B Streptococcus. Taken together, human albumin solution infusions may be used to reduce circulating PGE2 levels, attenuating immune suppression and reducing the risk of infection in patients with acutely decompensated cirrhosis or ESLD.

Temporal variation in endotoxin-induced vascular hyporeactivity in a rat mesenteric artery organ culture model

Endotoxin‐induced vascular hyporeactivity to phenylephrine (PE) is well described in rodent aorta, but has not been investigated in smaller vessels in vitro. Segments of rat superior mesenteric artery were incubated in culture medium with or without foetal bovine serum (10%) for 6, 20 or 46 h in the presence or absence of bacterial lipopolysaccharide (LPS; 1 – 100 μg ml−1). Contractions to PE were measured with or without nitric oxide synthase (NOS) inhibitors: L‐NAME (300 μM), aminoguanidine (AMG; 400 μM) 1400W (10 μM) and GW273629 (10 μM); the guanylyl cyclase inhibitor, ODQ (3 μM); the COX‐2 inhibitor, NS‐398 (10 μM). Contractile responses to the thromboxane A2 mimetic, U46619 were also assessed. In the presence of serum, LPS induced hyporeactivity at all time points. In its absence, hyporeactivity only occurred at 6 and 20 h. L‐NAME and AMG fully reversed hyporeactivity at 6 h, whereas they were only partially effective at 20 h and not at all at 46 h. In contrast partial reversal of peak contraction was observed with 1400W (62% at 46 h), GW273629 (57% at 46 h) and ODQ (75% at 46 h). COX‐2 inhibition produced no reversal. In contrast to PE, contractions to U46619 were substantially less affected by LPS. We describe a well‐characterized reproducible model of LPS‐induced hyporeactivity, which is largely mediated by the NO‐cyclic GMP‐dependent pathway. Importantly, long‐term (2‐day) production of NO via iNOS is demonstrated. Moreover, conventional doses of L‐NAME and AMG became increasingly ineffective over time. Thus, the choice of inhibitor merits careful consideration in long‐term models.

The pore‐forming subunit of the KATP channel is an important molecular target for LPS‐induced vascular hyporeactivity in vitro

1 ATP‐sensitive K+ (KATP) channel activation is implicated in the vascular hyporeactivity occurring in septic shock. However, channel inhibition with the sulphonylurea receptor (SUR) antagonist, glibenclamide (Glib) fails to reverse lipopolysaccharide (LPS)‐induced vascular hyporeactivity in vitro. We investigated whether inhibitors that act by binding to the KATP channel pore could be effective. 2 Ring segments of endothelium‐intact rat mesenteric artery were incubated with LPS in culture media for either 6 or 20 h before contractile responses to phenylephrine were assessed in the absence or presence of KATP channel inhibitors. 3 The pore‐forming subunit inhibitors barium chloride (BaCl2; 300 μM) and PNU‐37883A (1 μM) significantly reversed hyporeactivity at both time points, although less so at 20 h. In contrast, the SUR inhibitors, Glib (10 μM), tolbutamide (Tolb) (1 mM) and PNU‐99963 (1 μM) were ineffective. In LPS‐incubated tissues, Glib and Tolb antagonised contractions to the thromboxane A2 mimetic, U46619 (9,11‐dideoxy‐9α, 11α‐methanoepoxy prostaglandin F2α) (10−7 M), whereas the pinacidil‐derived inhibitor, PNU‐99963, did not. 4 Contractions to 60 mM KCl were unaffected by LPS at 6 h, but were significantly depressed by LPS at 20 h, suggesting that K+‐channel‐independent pathways contribute to hyporeactivity at the later time point. 5 The inducible nitric oxide synthase (iNOS) inhibitor, 1400 W (10 μM) and Tolb inhibited the production of nitrite induced by LPS, whereas BaCl2 and PNU‐37883A had no effect. 6 In conclusion, KATP channels contribute to LPS‐induced vascular hyporeactivity via the iNOS pathway in rat mesenteric artery. The effectiveness of pore inhibitors over SUR inhibitors of the KATP channel suggests altered SUR function following LPS administration, which cannot be explained by thromboxane receptor inhibition.

Reversal of life-threatening, drug-related potassium-channel syndrome by glibenclamide

We describe three critically ill patients who received drugs with K(ATP) channel-opening properties and subsequently developed severe life-threatening complications, including hyperkalaemia and cardiovascular disturbances. Administration of the sulfonylurea-receptor inhibitor glibenclamide promptly reversed these abnormalities. Over the past 3 years, we have seen this syndrome and response in five patients taking nicorandil, ciclosporin, or isoflurane, which suggests that this disorder arises more frequently than is currently realised.

Stat2 loss leads to cytokine-independent, cell-mediated lethality in LPS-induced sepsis

Deregulated Toll-like receptor (TLR)-triggered inflammatory responses that depend on NF-κB are detrimental to the host via excessive production of proinflammatory cytokines, including TNF-α. Stat2 is a critical component of type I IFN signaling, but it is not thought to participate in TLR signaling. Our study shows that LPS-induced lethality in Stat2−/− mice is accelerated as a result of increased cellular transmigration. Blocking intercellular adhesion molecule-1 prevents cellular egress and confers survival of Stat2−/− mice. The main determinant of cellular egress in Stat2−/− mice is the genotype of the host and not the circulating leukocyte. Surprisingly, lethality and cellular egress observed on Stat2−/− mice are not associated with excessive increases in classical sepsis cytokines or chemokines. Indeed, in the absence of Stat2, cytokine production in response to multiple TLR agonists is reduced. We find that Stat2 loss leads to reduced expression of NF-κB target genes by affecting nuclear translocation of NF-κB. Thus, our data reveal the existence of a different mechanism of LPS-induced lethality that is independent of NF-κB triggered cytokine storm but dependent on cellular egress.

Defective monocyte oxidative burst predicts infection in alcoholic hepatitis and is associated with reduced expression of NADPH oxidase

Objective In order to explain the increased susceptibility to serious infection in alcoholic hepatitis, we evaluated monocyte phagocytosis, aberrations of associated signalling pathways and their reversibility, and whether phagocytic defects could predict subsequent infection. Design Monocytes were identified from blood samples of 42 patients with severe alcoholic hepatitis using monoclonal antibody to CD14. Phagocytosis and monocyte oxidative burst (MOB) were measured ex vivo using flow cytometry, luminometry and bacterial killing assays. Defects were related to the subsequent development of infection. Intracellular signalling pathways were investigated using western blotting and PCR. Interferon-γ (IFN-γ) was evaluated for its therapeutic potential in reversing phagocytic defects. Paired longitudinal samples were used to evaluate the effect of in vivo prednisolone therapy. Results MOB, production of superoxide and bacterial killing in response to Escherichia coli were markedly impaired in patients with alcoholic hepatitis. Pretreatment MOB predicted development of infection within two weeks with sensitivity and specificity that were superior to available clinical markers. Accordingly, defective MOB was associated with death at 28 and 90 days. Expression of the gp91phox subunit of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase was reduced in patients with alcoholic hepatitis demonstrating defective MOB. Monocytes were refractory to IFN-γ stimulation and showed high levels of a negative regulator of cytokine signalling, suppressor of cytokine signalling-1. MOB was unaffected by 7 days in vivo prednisolone therapy. Conclusions Monocyte oxidative burst and bacterial killing is impaired in alcoholic hepatitis while bacterial uptake by phagocytosis is preserved. Defective MOB is associated with reduced expression of NADPH oxidase in these patients and predicts the development of infection and death.

Variable effects of inhibiting iNOS and closing the vascular ATP-sensitive potassium channel (via its pore-forming and sulfonylurea receptor subunits) in endotoxic shock.

Excess production of NO and activation of vascular ATP-sensitive potassium (KATP) channels are implicated in the hypotension and vascular hyporeactivity associated with endotoxic shock. Using a fluid-resuscitated endotoxic rat model, we compared the cardiovascular effects of an iNOS inhibitor and two distinct inhibitors of the KATP channel. Endotoxin (LPS) was administered to anesthetized, spontaneously breathing, fluid-resuscitated adult male Wistar rats, in which MAP, aortic and renal blood flow, and hepatic microvascular oxygenation were monitored continuously. At 120 min, the iNOS inhibitor, GW273629, and the KATP-channel inhibitors, PNU-37883A and glyburide, were administered separately, and their effects on hemodynamics and oxygenation were examined. We found that GW273629 increased MAP over and above the pressor effect achieved in sham animals. Inhibiting KATP channels via the pore-forming subunit (PNU-37883A and high-dose glyburide) produced significant pressor effects, whereas inhibiting the sulfonylurea receptor with low-dose glyburide was ineffective. No agent reversed the fall in aortic or renal blood flow, the fall in hepatic microvascular oxygenation, or the metabolic acidosis that occurred in LPS-treated animals. We conclude that inhibition of the KATP channel via the pore-forming, but not the sulfonylurea receptor subunit, increases blood pressure in a short-term endotoxic model. However, this was not accompanied by any improvement in macrocirculatory or microcirculatory organ blood flow nor reversal of metabolic acidosis. It therefore remains uncertain whether the iNOS pathway or the KATP channel represents a potential target for drug development in the treatment of endotoxic shock.

Systemic inflammatory response syndrome after major abdominal surgery predicted by early upregulation of TLR4 and TLR5

Objectives:To study innate immune pathways in patients undergoing hepatopancreaticobiliary surgery to understand mechanisms leading to enhanced inflammatory responses and identifying biomarkers of adverse clinical consequences. Background:Patients undergoing major abdominal surgery are at risk of life-threatening systemic inflammatory response syndrome (SIRS) and sepsis. Early identification of at-risk patients would allow tailored postoperative care and improve survival. Methods:Two separate cohorts of patients undergoing major hepatopancreaticobiliary surgery were studied (combined n = 69). Bloods were taken preoperatively, on day 1 and day 2 postoperatively. Peripheral blood mononuclear cells and serum were separated and immune phenotype and function assessed ex vivo. Results:Early innate immune dysfunction was evident in 12 patients who subsequently developed SIRS (postoperative day 6) compared with 27 who did not, when no clinical evidence of SIRS was apparent (preoperatively or days 1 and 2). Serum interleukin (IL)-6 concentration and monocyte Toll-like receptor (TLR)/NF-&kgr;B/IL-6 functional pathways were significantly upregulated and overactive in patients who developed SIRS (P < 0.0001). Interferon &agr;-mediated STAT1 phosphorylation was higher preoperatively in patients who developed SIRS. Increased TLR4 and TLR5 gene expression in whole blood was demonstrated in a separate validation cohort of 30 patients undergoing similar surgery. Expression of TLR4/5 on monocytes, particularly intermediate CD14++CD16+ monocytes, on day 1 or 2 predicted SIRS with accuracy 0.89 to 1.0 (areas under receiver operator curves). Conclusions:These data demonstrate the mechanism for IL-6 overproduction in patients who develop postoperative SIRS and identify markers that predict patients at risk of SIRS 5 days before the onset of clinical signs.