Vasopressin: mechanisms of action on the vasculature in health and in septic shock

Role of selective V2-receptor-antagonism in septic shock: a randomized, controlled, experimental study

Introduction

V₂-receptor (V₂R) stimulation potentially aggravates sepsis-induced vasodilation, fluid accumulation and microvascular thrombosis. Therefore, the present study was performed to determine the effects of a first-line therapy with the selective V₂R-antagonist (Propionyl₁-D-Tyr(Et)₂-Val₄-Abu₆-Arg_8,9)-Vasopressin on cardiopulmonary hemodynamics and organ function vs. the mixed V_1aR/V₂R-agonist arginine vasopressin (AVP) or placebo in an established ovine model of septic shock.

Methods

After the onset of septic shock, chronically instrumented sheep were randomly assigned to receive first-line treatment with the selective V₂R-antagonist (1 μg/kg per hour), AVP (0.05 μg/kg per hour), or normal saline (placebo, each n = 7). In all groups, open-label norepinephrine was additionally titrated up to 1 μg/kg per minute to maintain mean arterial pressure at 70 ± 5 mmHg, if necessary.

Results

Compared to AVP- and placebo-treated animals, the selective V₂R-antagonist stabilized cardiopulmonary hemodynamics (mean arterial and pulmonary artery pressure, cardiac index) as effectively and increased intravascular volume as suggested by higher cardiac filling pressures. Furthermore, left ventricular stroke work index was higher in the V₂R-antagonist group than in the AVP group. Notably, metabolic (pH, base excess, lactate concentrations), liver (transaminases, bilirubin) and renal (creatinine and blood urea nitrogen plasma levels, urinary output, creatinine clearance) dysfunctions were attenuated by the V₂R-antagonist when compared with AVP and placebo. The onset of septic shock was associated with an increase in AVP plasma levels as compared to baseline in all groups. Whereas AVP plasma levels remained constant in the placebo group, infusion of AVP increased AVP plasma levels up to 149 ± 21 pg/mL. Notably, treatment with the selective V₂R-antagonist led to a significant decrease of AVP plasma levels as compared to shock time (P < 0.001) and to both other groups (P < 0.05 vs. placebo; P < 0.001 vs. AVP). Immunohistochemical analyses of lung tissue revealed higher hemeoxygenase-1 (vs. placebo) and lower 3-nitrotyrosine concentrations (vs. AVP) in the V₂R-antagonist group. In addition, the selective V₂R-antagonist slightly prolonged survival (14 ± 1 hour) when compared to AVP (11 ± 1 hour, P = 0.007) and placebo (11 ± 1 hour, P = 0.025).

Conclusions

Selective V₂R-antagonism may represent an innovative therapeutic approach to attenuate multiple organ dysfunction in early septic shock.

Effects of a single terlipressin administration on cardiac function and perfusion in cirrhosis

BACKGROUND

The vasoconstrictor terlipressin is widely used in the treatment of the hepatorenal syndrome and variceal bleeding. However, terlipressin may compromise cardiac function and induce ischemia.

AIM

Therefore, we aimed to assess the effects of terlipressin on cardiac function and perfusion.

METHODS

Twenty-four patients with cirrhosis and ascites participated, including nine with refractory ascites. Gated myocardial perfusion imaging, mean arterial blood pressure (MAP), cardiac output (CO), ejection fraction (EF), end-diastolic volume (EDV), perfusion, and motion of the myocardium were determined before and after a bolus injection of 2 mg terlipressin.

RESULTS

MAP increased after terlipressin (P value of less than 0.001). EF and CO fell by -16 and -17%, respectively in the terlipressin group versus 1 and -2%, respectively in the placebo group (P value of less than 0.001 and P value of less than 0.01). In the terlipressin group, EDV increased by 18 versus -4% in the placebo group (P value of less than 0.01). Wall motion in the anterior and posterior walls fell by -18 and -22%, respectively after terlipressin treatment versus 0 and 0% in the placebo group (P value of less than 0.01). In contrast, myocardial perfusion and stroke volume were unaltered in both the groups. The change in EF during terlipressin treatment correlated significantly with the change in MAP (r=-0.60, P value <0.002). Patients with refractory ascites had a higher EF and lower EDV and ESV than the patients with nonrefractory ascites, both at baseline and after terlipressin treatment. The decrease in the left ventricular wall thickening and wall motion correlated with the Child--Pugh score, r=-0.59, P=0.005 and r=-0.48, P=0.03.

CONCLUSION

In advanced cirrhosis, the increase in afterload and EDV after terlipressin treatment result in a decrease in left ventricular wall motion, resulting in reduced CO and EF, but myocardial perfusion is preserved. Alteration in cardiac function at baseline and after terlipressin treatment relates to the stage of decompensation.

Discontinuation of vasopressin before norepinephrine increases the incidence of hypotension in patients recovering from septic shock: a retrospective cohort study

PURPOSE

There are little data regarding the discontinuation of vasoactive medications in patients recovering from septic shock. We designed this retrospective cohort study to evaluate the incidence of hypotension based on the order of removal of norepinephrine (NE) and vasopressin (AVP) in patients receiving concomitant NE and AVP infusions for the treatment of septic shock.

MATERIALS AND METHODS

Consecutive patients receiving concomitant NE and AVP infusions for septic shock admitted to the intensive care units of a tertiary care academic medical center were evaluated.

RESULTS

Of 50 included patients, the first vasoactive medication discontinued was NE in 32 patients and AVP in 18 patients. The groups had similar Acute Physiology and Chronic Health Evaluation II and Sequential Organ Failure Assessment scores at shock onset and at the time of discontinuation of the first agent. Five patients who had NE discontinued first (16%) versus 10 patients who had AVP discontinued first (56%) developed hypotension within 24 hours (unadjusted relative risk, 3.6; 95% confidence interval, 1.5-4.5; P = .008). In a multivariate analysis, only discontinuation of AVP first was independently associated with hypotension (adjusted relative risk, 5.9; 95% confidence interval, 1.7-21.0; P = .006).

CONCLUSIONS

Discontinuation of AVP before NE may lead to a higher incidence of hypotension in patients recovering from septic shock receiving concomitant AVP and NE.

Copeptin, IGFBP-1, and cardiovascular prognosis in patients with type 2 diabetes and acute myocardial infarction: a report from the DIGAMI 2 trial

OBJECTIVE

To determine whether C-terminal provasopressin (copeptin) explains the prognostic importance of insulin growth factor binding protein-1 (IGFBP-1) in patients with myocardial infarction and type 2 diabetes.

RESEARCH DESIGN AND METHODS

Copeptin and IGFBP-1 were analyzed in 393 patients participating in the Diabetes Mellitus Insulin-Glucose Infusion in Acute Myocardial Infarction (DIGAMI) 2 trial.

RESULTS

Copeptin was associated with IGFBP-1 (Spearman rank correlation test, r = 0.53; P < 0.001). During follow-up there were 138 cardiovascular events (cardiovascular death, myocardial infarction, and stroke). In univariate Cox proportional hazard regression analyses both biomarkers were predictors of events: the hazard ratio for log copeptin was 1.59 (95% CI 1.41-1.81; P < 0.001) and for log IGFBP-1 was 1.49 (1.26-1.77; P < 0.001). In the final model, adjusting for age and renal function, copeptin was the only independent predictor (1.35 [1.16-1.57]; P < 0.001).

CONCLUSIONS

Copeptin is an independent predictor of cardiovascular events and appears to at least partly explain the prognostic impact of IGFBP-1 in patients with type 2 diabetes and myocardial infarction. Copeptin may be a pathogenic factor to address to improve outcome in these patients.

Hormones and antioxidant systems: role of pituitary and pituitary-dependent axes

Oxidative stress, a condition defined as unbalancing between production of free radicals and antioxidant defenses, is an important pathogenetic mechanism in different diseases. Despite the abundant literature, many aspects of hormone role in regulating antioxidant synthesis and activity still remain obscure. Therefore, we reviewed experimental data, in vivo and in vitro, about the effects of the different pituitary- dependent axes on antioxidant levels, trying to give a broad view from hormones which also have antioxidant properties to the classic antioxidants, from the lipophilic antioxidant Coenzyme Q10, strictly related to thyroid function, to total antioxidant capacity, a measure of non-protein non-enzymatic antioxidants in serum and other biological fluids. Taken together, these data underline the importance of oxidative stress in various pituitary-dependent disorders, suggesting a possible clinical usefulness of antioxidant molecules.

cAMP/PKA-dependent increases in Ca Sparks, oscillations and SR Ca stores in retinal arteriolar myocytes after exposure to vasopressin

PURPOSE

To investigate the effects of arginine vasopressin (AVP) on Ca(2+) sparks and oscillations and on sarcoplasmic reticulum (SR) Ca(2+) content in retinal arteriolar myocytes.

METHODS

Fluo-4-loaded smooth muscle in intact segments of freshly isolated porcine retinal arteriole was imaged by confocal laser microscopy. SR Ca(2+) store content was assessed by recording caffeine-induced Ca(2+) transients with microfluorimetry and fura-2.

RESULTS

The frequencies of Ca(2+) sparks and oscillations were increased both during exposure to, and 10 minutes after washout of AVP (10 nM). Caffeine transients were increased in amplitude 10 and 90 minutes after a 3-minute application of AVP. Both AVP-induced Ca(2+) transients and the enhancement of caffeine responses after AVP washout were inhibited by SR 49059, a V(1a) receptor blocker. Forskolin, an activator of adenylyl cyclase, also persistently enhanced caffeine transients. Rp-8-HA-cAMPS, a membrane-permeant PKA inhibitor, prevented enhancement of caffeine transients by both AVP and forskolin. Forskolin, but not AVP, produced a reversible, Rp-8-HA-cAMPS insensitive reduction in basal [Ca(2+)](i).

CONCLUSIONS

AVP activates a cAMP/PKA-dependent pathway via V(1a) receptors in retinal arteriolar smooth muscle. This effect persistently increases SR Ca(2+) loading, upregulating Ca(2+) sparks and oscillations, and may favor prolonged agonist activity despite receptor desensitization.

Hypothalamic-pituitary axis deficiency following traumatic brain injury in a dog

OBJECTIVE

To describe endocrine dysfunction associated with traumatic brain injury in a dog.

SUMMARY

A 12-week-old dog presented with traumatic brain injury and did not respond to traditional supportive care. Continued hypothermia, electrolyte derangements, hypotension, and hyposthenuria prompted screening for and detection of several hypothalamic-pituitary disorders including: hypoadrenocorticism, central diabetes insipidus, hypothyroidism, and growth hormone deficiency. Electrolyte abnormalities, urine osmolarity, and blood pressure improved with treatment for the associated disorders.

NEW OR UNIQUE INFORMATION PROVIDED

This is the first report of generalized hypothalamic-pituitary dysfunction or panhypopituitarism following traumatic brain injury in a dog.

Terlipressin: a promising vasoactive agent in hemodynamic support of septic shock

BACKGROUND

At present, terlipressin is predominantly used for the management of bleeding gastric and esophageal varices, as well as hepato-renal syndrome secondary to liver cirrhosis. Owing to its high and relatively selective affinity to vascular V1 receptors, terlipressin is also increasingly used as an adjunct vasopressor agent in the management of vasodilatory hyperdynamic septic shock.

OBJECTIVE

This review article aims to summarize the available knowledge related to hemodynamic support with terlipressin in septic shock.

METHODS

For literature search, PubMed and specific keywords from the MeSH Database were used.

RESULTS/CONCLUSIONS

Terlipressin represents an effective pressor agent in patients with catecholamine-unresponsive septic shock. However, caution should be exercised, as terlipressin may contribute dose-dependently to vasoconstriction and a reflectory decrease in cardiac output. Additional studies are needed to clarify: i) the optimal time of therapy institution; ii) the efficacy and the dosages of continuous infusion versus bolus administration; and iii) the safety and efficacy of this compound in comparison with other nonspecific vasopressinergic drugs, such as arginine vasopressin. Whether or not terlipressin may improve the outcome of septic shock patients compared with standard therapy with catecholamines remains to be determined.

The effects of vasopressin on acute kidney injury in septic shock

OBJECTIVE

To compare the effects of vasopressin versus norepinephrine infusion on the outcome of kidney injury in septic shock.

DESIGN AND SETTING

Post-hoc analysis of the multi-center double-blind randomized controlled trial of vasopressin versus norepinephrine in adult patients who had septic shock (VASST).

PATIENTS AND INTERVENTION

Seven hundred seventy-eight patients were randomized to receive a blinded infusion of either low-dose vasopressin (0.01-0.03 U/min) or norepinephrine infusion (5-15 microg/min) in addition to open-label vasopressors and were included in the outcome analysis. All vasopressors were titrated and weaned to maintain a target blood pressure.

MEASUREMENT AND RESULTS

RIFLE criteria for acute kidney injury were used to compare the effects of vasopressin versus norepinephrine. In view of multiple simultaneous comparisons, a p value of 0.01 was considered statistically significant. Kidney injury was present in 464 patients (59.6%) at study entry. In patients in the RIFLE "Risk" category (n = 106), vasopressin as compared with norepinephrine was associated with a trend to a lower rate of progression to renal "Failure" or "Loss" categories (20.8 vs. 39.6%, respectively, p = 0.03), and a lower rate of use of renal replacement therapy (17.0 vs. 37.7%, p = 0.02). Mortality rates in the "Risk" category patients treated with vasopressin compared to norepinephrine were 30.8 versus 54.7%, p = 0.01, but this did not reach significance in a multiple logistic regression analysis (OR = 0.33, 99% CI 0.10-1.09, p = 0.02). The interaction of treatment group and RIFLE category was significant in predicting mortality.

CONCLUSIONS

Vasopressin may reduce progression to renal failure and mortality in patients at risk of kidney injury who have septic shock.

Low-dose vasopressin increases glomerular filtration rate, but impairs renal oxygenation in post-cardiac surgery patients

BACKGROUND

The beneficial effects of vasopressin on diuresis and creatinine clearance have been demonstrated when used as an additional/alternative therapy in catecholamine-dependent vasodilatory shock. A detailed analysis of the effects of vasopressin on renal perfusion, glomerular filtration, excretory function and oxygenation in man is, however, lacking. The objective of this pharmacodynamic study was to evaluate the effects of low to moderate doses of vasopressin on renal blood flow (RBF), glomerular filtration rate (GFR), renal oxygen consumption (RVO2) and renal oxygen extraction (RO2Ex) in post-cardiac surgery patients.

METHODS

Twelve patients were studied during sedation and mechanical ventilation after cardiac surgery. Vasopressin was sequentially infused at 1.2, 2.4 and 4.8 U/h. At each infusion rate, systemic haemodynamics were evaluated by a pulmonary artery catheter, and RBF and GFR were measured by the renal vein thermodilution technique and by renal extraction of 51chromium-ethylenediaminetetraacetic acid, respectively. RVO2 and RO2Ex were calculated by arterial and renal vein blood samples.

RESULTS

The mean arterial pressure was not affected by vasopressin while cardiac output and heart rate decreased. RBF decreased and GFR, filtration fraction, sodium reabsorption, RVO2, RO2Ex and renal vascular resistance increased dose-dependently with vasopressin. Vasopressin exerted direct antidiuretic and antinatriuretic effects.

CONCLUSIONS

Short-term infusion of low to moderate, non-hypertensive doses of vasopressin induced a post-glomerular renal vasoconstriction with a decrease in RBF and an increase in GFR in post-cardiac surgery patients. This was accompanied by an increase in RVO2, as a consequence of the increases in the filtered tubular load of sodium. Finally, vasopressin impaired the renal oxygen demand/supply relationship.

VRQ397 (CRAVKY): a novel noncompetitive V2 receptor antagonist

Vasopressin type 2 receptor (V2R) exhibits mostly important properties for hydroosmotic equilibrium and, to a lesser extent, on vasomotricity. Drugs currently acting on this receptor are analogs of the natural neuropeptide, arginine vasopressin (AVP), and hence are competitive ligands. Peptides that reproduce specific sequences of a given receptor have lately been reported to interfere with its action, and if such molecules arise from regions remote from the binding site they would be anticipated to exhibit noncompetitive antagonism, but this has yet to be shown for V2R. Six peptides reproducing juxtamembranous regions of V2R were designed and screened; the most effective peptide, cravky (labeled VRQ397), was characterized. VRQ397 was potent (IC(50) = 0.69 +/- 0.25 nM) and fully effective in inhibiting V2R-dependent physiological function, specifically desmopressin-L-desamino-8-arginine-vasopressin (DDAVP)-induced cremasteric vasorelaxation; this physiological functional assay was utilized to avoid overlooking interference of specific signaling events. A dose-response profile revealed a noncompetitive property of VRQ397; correspondingly, VRQ397 bound specifically to V2R-expressing cells could not displace its natural ligand, AVP, but modulated AVP binding kinetics (dissociation rate). Specificity of VRQ397 was further confirmed by its inability to bind to homologous V1 and oxytocin receptors and its inefficacy to alter responses to stimulation of these receptors. VRQ397 exhibited pharmacological permissiveness on V2R-induced signals, as it inhibited DDAVP-induced PGI(2) generation but not that of cAMP or recruitment of beta-arrestin2. Consistent with in vitro and ex vivo effects as a V2R antagonist, VRQ397 displayed anticipated in vivo aquaretic efficacy. We hereby describe the discovery of a first potent noncompetitive antagonist of V2R, which exhibits functional selectivity, in line with properties of a negative allosteric modulator.

Pharmacological optimization of tissue perfusion

After fluid resuscitation, vasoactive drug treatment represents the major cornerstone for correcting any major impairment of the circulation. However, debate still rages as to the choice of agent, dose, timing, targets, and monitoring modalities that should optimally be used to benefit the patient yet, at the same time, minimize harm. This review highlights these areas and some new pharmacological agents that broaden our therapeutic options.

Shock settico

Lo shock settico corrisponde all’associazione di un’infezione e di un’insufficienza emodinamica, eventualmente associata ad altri deficit viscerali. Le definizioni assimilano spesso lo shock settico alla sepsi grave, la cui insufficienza emodinamica è considerata reversibile. I fondamenti del trattamento si basano su misure che si devono applicare in tempi brevi: il trattamento specifico, che corrisponde alla lotta contro l’agente infettivo, e il trattamento sintomatico, in particolare mediante il ripristino di un’emodinamica efficace. L’aumento del numero delle infezioni gravi e degli shock settici nei paesi industrializzati è stato all’origine di sforzi considerevoli allo scopo di migliorarne la gestione. In particolare, il frutto delle riflessioni congiunte di diverse società scientifiche è stato formalizzato in raccomandazioni, riassunte in procedure. In effetti, la strategia che mira a un miglioramento delle pratiche sembra ridurre la mortalità legata alle infezioni. Alcuni ostacoli compromettono tuttavia il loro uso, dal riconoscimento del problema all’organizzazione delle cure.

Novel potential therapies for septic shock

Sepsis is the systemic inflammatory response syndrome secondary to a local infection. Septic shock, the severe complication of sepsis associated with refractory hypotension, is frequently a near-fatal condition requiring prompt diagnosis and management. Although the recent years have been associated with considerable improvements in the knowledge of the pathophysiology of the disease and remarkable advances have been achieved in sepsis treatment, the morbidity and mortality of this disease are still unacceptably high. In this review, we will briefly discuss the ongoing standard treatment of septic shock and describe novel potential therapies, aiming to improve hemodynamic support and/or control inflammatory response in sepsis. These therapies were associated with benefits in experimental studies and have been tested or are currently under testing in randomized controlled studies with septic patients.

Efficacy and safety of terlipressin in cirrhotic patients with variceal bleeding or hepatorenal syndrome

Terlipressin is an analog of the natural hormone arginine-vasopressin. It is used in the treatment of patients with cirrhosis and bleeding esophageal varices (BEV) and in patients with hepatorenal syndrome (HRS): two of the most dramatic and feared complications of cirrhosis. Terlipressin exerts its main pharmacological effect through stimulation of vasopressin-1 receptors. These receptors are located in vascular smooth muscle and mediate vasoconstriction. In patients with cirrhosis and portal hypertension, treatment with terlipressin increases mean arterial pressure and decreases portal flow and pressure within minutes of administration. Furthermore, in patients with ascites terlipressin improves glomerular filtration and excretion of sodium. Terlipressin decreases failure of initial hemostasis by 34%, decreases mortality by 34%, and is considered a first-line treatment for BEV, when available. Terlipressin in combination with albumin reverses type 1 HRS in 33%-60% of cases and is the only treatment with proven efficacy in randomized trials. The safety profile is favorable when considering the clinical efficacy and the high mortality of these clinical entities. Adverse events are mostly cardiovascular and related to vasoconstriction. Mortality and withdrawal of terlipressin due to adverse events occurs in less than 1% of cases. Mild adverse events related to terlipressin treatment occur in 10%-20% of patients. The benefit, however, of terlipressin on long-term survival in HRS remains to be determined. At present, treatment with terlipressin and albumin is considered the most efficient therapy and should therefore be recommended for the treatment of type 1 HRS-1.

Effects of vasopressin in septic shock

Septic shock continues to be one of the leading causes of death in the intensive care unit today. The confluence of many factors contributes to the deterioration of patients' condition in septic shock. Increased levels of nitric oxide, in part, mediate the cardiovascular effects of septic shock. Nitric oxide is major mediator of vasodilation and hypotension as well as myocardial depression. It also contributes to decreased production and release of endogenous vasopressin. Vasopressin effects are actualized by stimulation of V1, V2, and V3 receptors located in various parts of the body. The response is dose dependent. Endogenous vasopressin and angiotensin II act synergistically to preserve and restore blood pressure levels. Decreased circulating vasopressin contributes to adrenal insufficiency via hypothalamic-pituitary-adrenal axis suppression and increased catecholamine resistance to vasopressors. Exogenous vasopressin supplementation in physiologic doses has been shown to improve blood pressure levels and decrease vasopressor needs in patients with septic shock.

Arginine vasopressin to manage hypoxemic infants after stage I palliation of single ventricle lesions

OBJECTIVE

Management of patients with single ventricle physiology following stage I palliation procedures is often challenging, with optimization of the ratio of pulmonary-to-systemic blood flow as an important goal. Persistent hypoxemia may be a manifestation of elevated pulmonary vascular resistance and therefore decreased blood flow to the lungs. In such situations, the use of arginine vasopressin to increase systemic vascular resistance may be an effective strategy to improve pulmonary blood flow and maintain adequate pulmonary-to-systemic blood flow ratio. We describe three infants in whom persistent hypoxemia improved after institution of arginine vasopressin.

DESIGN

Retrospective chart review.

SETTING

Twenty-four bed medical-surgical pediatric intensive care unit at a large tertiary care academic hospital.

PATIENTS

Three neonates with single ventricle physiology who received arginine vasopressin in the setting of hypoxemia following stage I palliation.

RESULTS

Arginine vasopressin was initiated in all three patients for hypoxemia with a goal to increase systemic vascular resistance and generate a higher driving pressure for pulmonary blood flow. Twelve hours after arginine vasopressin initiation, systemic arterial saturation as determined by pulse oximetry and blood pressure increased, whereas heart rate, inotrope score, and Fio2 decreased in all three patients. Urine output was maintained and arterial lactate decreased during this time. Pulmonary-to-systemic flow ratio increased in one patient in whom it could be determined.

CONCLUSION

In patients with single ventricle physiology and persistent hypoxemia following stage I palliation, administration of arginine vasopressin could improve oxygenation possibly by increasing systemic vascular resistance and therefore the pulmonary blood flow.

Plasma vasopressin concentrations in healthy foals from birth to 3 months of age

BACKGROUND

Arginine vasopressin (AVP) has received increased attention in equine critical care but there is minimal information of AVP concentration in foals. The clinical usefulness of measuring AVP in ill foals depends on knowledge of age-related changes in AVP concentrations in healthy foals.

HYPOTHESIS

Plasma AVP concentrations will be significantly different when measured from birth to 3 months of age in healthy foals.

ANIMALS

Thirteen healthy university-owned foals.

METHODS

Prospective, observational study. Blood was collected from healthy foals at birth and 3, 5, 7, 10, 14, 21, 28, 42, 56, and 84 days of age. Plasma was harvested and plasma AVP concentrations were determined by radioimmunoassay.

RESULTS

No statistically significant differences were detected in plasma AVP concentrations over the study period. Plasma AVP concentrations over the entire study period was 6.2+/-2.5 pg/mL.

CONCLUSIONS AND CLINICAL IMPORTANCE

There was no age-related variation in plasma AVP concentrations detected in healthy foals from birth to 3 months of age suggesting that AVP concentrations are similar across foals of these ages.

Catecholamines induce an inflammatory response in human hepatocytes

OBJECTIVE

The liver is an early target organ in sepsis, severe sepsis, and septic shock, contributing to multiple organ failure, and both lipopolysaccharide and gut-derived catecholamines are implicated in the occurrence of hepatocellular dysfunction. Treatment of septic shock involves administration of vasoactive agents such as exogenous catecholamines or vasopressin in order to reestablish blood pressure. As a prelude to clinical application, we tested the hypothesis that catecholamines could modulate the lipopolysaccharide-induced inflammatory response and function in human liver.

DESIGN

An in vitro human cell culture study.

SETTING

Research laboratory of an academic institution.

SUBJECTS

Primary human hepatocytes and human hepatoma HepaRG cells.

INTERVENTIONS

Primary human hepatocytes and human hepatoma HepaRG cells were exposed to lipopolysaccharide to evaluate effects of epinephrine and several other compounds (norepinephrine, dobutamine, dopamine, dopexamine, phenylephrine, clonidine, salbutamol, and vasopressin). Markers of inflammation (interleukin-6, C-reactive protein) and drug metabolism (cytochrome P450 [CYP] 3A4, CYP2B6, CYP1A2, CYP2E1, constitutive androstane receptor, pregnane X receptor) were analyzed.

MEASUREMENTS AND MAIN RESULTS

Transcripts of C-reactive protein and CYP3A4 were strongly increased and depressed respectively after a 24-hr treatment with 10 ng/mL lipopolysaccharide. Co-treatment with either of the catecholamines failed to reverse lipopolysaccharide effects, whereas when added alone, epinephrine, and to a lesser extent norepinephrine, salbutamol, and dobutamine, mimicked lipopolysaccharide effects. Suppression of CYP3A4 implicated beta-adrenergic receptors and was mediated through overproduction of interleukin-6. By contrast, vasopressin did not elicit an inflammatory response or modify CYP3A4 expression.

CONCLUSIONS

Some catecholamines can induce an inflammatory response and exacerbate the hepatic dysfunction observed during sepsis, favoring the idea that catecholamines could alter the biotransformation of drugs metabolized by CYP3A4 and that alternative vasoactive agents, such as vasopressin, merit further investigation in septic shock patients.

Vascular KCNQ potassium channels as novel targets for the control of mesenteric artery constriction by vasopressin, based on studies in single cells, pressurized arteries, and in vivo measurements of mesenteric vascular resistance

Pressor effects of the vasoconstrictor hormone arginine vasopressin (AVP), observed when systemic AVP concentrations are less than 100 pM, are important for the physiological maintenance of blood pressure, and they are also the basis for therapeutic use of vasopressin to restore blood pressure in hypotensive patients. However, the mechanisms by which circulating AVP induces arterial constriction are unclear. We examined the novel hypothesis that KCNQ potassium channels mediate the physiological vasoconstrictor actions of AVP. Reverse transcriptase polymerase chain reaction revealed expression of KCNQ1, KCNQ4, and KCNQ5 in rat mesenteric artery smooth muscle cells (MASMCs). Whole-cell perforated patch recordings of voltage-sensitive K+ (Kv) currents in freshly isolated MASMCs revealed 1,3-dihydro-1-phenyl-3,3-bis(4-pyridinylmethyl)-2H-indol-2-one (linopirdine)- and 10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone (XE-991)-sensitive KCNQ currents that were electrophysiologically and pharmacologically distinct from other Kv currents. Suppression of KCNQ currents by AVP (100 pM) was associated with significant membrane depolarization, and it was abolished by the protein kinase C (PKC) inhibitor calphostin C (250 nM). The KCNQ channel blocker linopirdine (10 microM) inhibited KCNQ currents in MASMCs, and it induced constriction of isolated rat mesenteric arteries. The vasoconstrictor responses were not additive when combined with 30 pM AVP, and they were prevented by the L-type Ca2+ channel blocker verapamil. Ethyl-N-[2-amino-6-(4-fluorophenylmethylamino)pyridin-3-yl] carbamic acid (flupirtine) significantly enhanced KCNQ currents, and it reversed constrictor responses to 30 pM AVP. In vivo, i.v. administration of linopirdine induced a dose-dependent increase in mesenteric artery resistance and blood pressure, whereas flupirtine had the opposite effects. We conclude that physiological concentrations of AVP induce mesenteric artery constriction via PKC-dependent suppression of KCNQ currents and L-type Ca2+ channel activation in MASMCs.

Pituitary-adrenal response to acute and repeated mild restraint, forced swim and change in environment stress in arginine vasopressin receptor 1b knockout mice

Arginine vasopressin and corticotrophin-releasing hormone synthesised and released from the hypothalamic paraventricular nucleus are the prime mediators of the hypothalamic-pituitary-adrenal (HPA) axis response to stress. These neurohormones act synergistically to stimulate adrenocorticotophin (ACTH) secretion from the anterior pituitary, culminating in an increase in circulating glucocorticoids. Arginine vasopressin mediates this action at the arginine vasopressin 1b receptor (Avpr1b) located on pituitary corticotrophs. Arginine vasopressin is regarded as a minor ACTH secretagogue in rodents but evidence suggests that it has a role in mediating the neuroendocrine response to some acute and chronic stressors. To investigate the role of the Avpr1b in the HPA axis response to an acute and chronic (repeated) stress, we measured the plasma ACTH and corticosterone concentrations in three stress paradigms in both Avpr1b knockout and wild-type mice. Single acute exposure to restraint, forced swim and change in environment stressors elevated both plasma ACTH and corticosterone concentrations in wild-type animals. Conversely, the ACTH response to the acute stressors was significantly attenuated in Avpr1b knockout mice compared to their wild-type counterparts. Plasma corticosterone concentrations were reduced in Avpr1b knockout mice in response to change in environment but not to mild restraint or forced swim stress. Irrespective of genotype, there was no difference in the plasma ACTH or corticosterone concentrations in response to acute and repeated stressors. The data show that a functional Avpr1b is required for an intact pituitary ACTH response to the acute and chronic stressors used in this study. Furthermore, the normal corticosterone response to repeated exposure to change in environment stress also requires the Avpr1b to drive HPA axis responsiveness.

Levels of vasopressin in children undergoing cardiopulmonary bypass

OBJECTIVES

It is accepted treatment to give vasopressin to adults in postcardiotomy shock, but such use in children is controversial. Cardiopulmonary bypass is presumed to attenuate the normal endogenous vasopressin response to shock. We hypothesized that levels of vasopressin in children are altered by bypass, and that children having low endogenous levels perioperatively are more likely to develop hypotension, or require vasopressors.

METHODS

Serial levels of vasopressin were assessed prospectively in children undergoing bypass at a single center.

RESULTS

Of 61 eligible patients, we enrolled 39 (63%). Their median age was 5 months. The mean level of vasopressin prior to bypass was 18.6 picograms per millilitre, with an interquartile range from 2.6 to 11.4. Levels of vasopressin peaked during bypass at 87.1, this being highly significant compared to baseline (p < 0.00005), remained high for 12 hours at a mean of 73.5, again significantly different from baseline (p = 0.002), were falling at 24 hours, with a mean of 28.1 (p = 0.04), and had returned to baseline by 48 hours, when the mean was 7.4 (p = 0.3). Age, gender, and the category for surgical risk had no influence on the levels of vasopressin. There was no statistically significant relationship between the measured levels and hypotension or the requirement for vasopressors, although a few persistently hypotensive patients had high levels subsequent to bypass. Higher levels correlated with higher levels of sodium in the serum (r(s) = 0.37, p < 0.00005), higher osmolality (r(s) = 0.37, p < 0.00005), and positive fluid balance (r(s) = 0.23, p < 0.008). Preoperative use of inhibitors of angiotensin converting enzyme, preoperative congestive cardiac failure, and longer periods of bypass predicted higher levels during the first eight postoperative hours.

CONCLUSIONS

Children do not have deficient endogenous levels of vasopressin following bypass, and lower levels are not associated with hypotension. Any therapeutic efficacy of infusion of vasopressin for post-cardiotomy shock in children is likely due to reasons other than physiologic replacement.

Systemic and hepatosplanchnic macro- and microcirculatory dose response to arginine vasopressin in endotoxic rabbits

OBJECTIVE

Arginine vasopressin (AVP) is being used increasingly to treat vasodilatory hypotension, although its effects on hepatosplanchnic perfusion have been debated.

DESIGN

Prospective study in a university-based experimental research laboratory.

SUBJECTS AND INTERVENTIONS

We compared the effect of AVP on systemic, gut, and liver blood flow in anesthetized and ventilated rabbits given either saline or endotoxin. Incremental i.v. boluses of AVP ranging from 1 to 1,000[Symbol: see text]ng were administered 90[Symbol: see text]min post-endotoxin or saline.

MEASUREMENTS AND RESULTS

Endotoxin induced a shock state with a transient decrease of mesenteric artery blood flow velocity (pulsed Doppler, in centimeters per second, V(mes)) but had no effect on liver surface microcirculation (laser Doppler in TPU, MicroFl(liver)). Gut microcirculatory (MicroFl(gut)) changes became independent of mean arterial pressure (MAP) after endotoxin. In control rabbits (n = 5), increasing doses of AVP elevated MAP but reduced aortic blood flow (pulsed Doppler, VAo), V(mes), and MicroFl(gut) (p < 0.05). In endotoxic animals (n = 6), AVP produced a similar rise in MAP (p < 0.05), while V(mes) and MicroFl(gut) only decreased for AVP doses above 100[Symbol: see text]ng (p < 0.05). Liver microcirculation was only minimally affected by AVP, although significantly, both in control and endotoxin animals.

CONCLUSION

Preservation of mesenteric blood flow as well as gut and liver microcirculation, with therapeutic doses of AVP during endotoxemia, supports its use as a hemodynamic agent during septic shock.

Diagnosis and treatment of severe sepsis

The burden of infection in industrialized countries has prompted considerable effort to improve the outcomes of patients with sepsis. This has been formalized through the Surviving Sepsis Campaign 'bundles', derived from the recommendations of 11 professional societies, which have promoted global improvement in those practices whose primary goal it is to reduce sepsis-related death. However, difficulties remain in implementing all of the procedures recommended by the experts, despite the apparent pragmatism of those procedures. We summarize the main proposals made by the Surviving Sepsis Campaign and focus on the difficulties associated with making a proper diagnosis and supplying adequate treatment promptly to septic patients.

Potential interventions in sepsis-related acute kidney injury

Sepsis is an important cause of morbidity and mortality. Acute kidney injury often complicates sepsis, leading to greater complexity, cost of care, and worsening prognosis. In recent years, a consensus definition of acute kidney injury has been developed, facilitating research into the pathophysiology and epidemiology of this disorder. New and emerging biomarkers to recognize kidney injury before functional abnormalities are manifest may allow early recognition and facilitate prevention or treatment. Furthermore, advances in the clinical management of sepsis may have secondary benefits with respect to renal outcomes. Existing and hybrid extracorporeal therapies are being investigated not only as means to replace lost kidney function but also to modulate the immune response to sepsis. For those who have more advanced forms of kidney injury, strategies to promote renal recovery are being sought to minimize the long-term consequences of impaired kidney function. This review provides an update on the current state of the science and a glimpse toward the future of intervention in sepsis-related acute kidney injury.

Early goal directed therapy for sepsis during pregnancy

Sepsis is a leading cause of death in pregnancy and results in significant perinatal mortality. These deaths occur despite the younger age of pregnant patients, the low rate of comorbid conditions and the potential for effective interventions that should result in rapid resolution of illness. To date, no "evidence-based" recommendations are specific to the pregnant patient who is critically ill or septic. Optimal care for the septic patient requires a multidisciplinary team with expertise in obstetrics, maternal-fetal medicine, critical care, infectious disease, anesthesia, and pharmacy. Coordination of care and good communication amongst team members is essential. Incorporation of early goal directed therapy for suspected sepsis into obstetric practice is needed to optimize maternal and neonatal outcomes.

Vasopressin vs. terlipressin in the treatment of cardiovascular failure in sepsis

BACKGROUND

Arginine vasopressin (AVP) and terlipressin (TP) are increasingly used as adjunct vasopressors in the treatment of septic shock. Despite important pharmacological differences between the two drugs (e.g., receptor selectivity, effective half-life) the use of either substance is determined mainly by local availability and institutional inventory. We briefly describe the pathophysiology and pharmacology of septic shock relevant to the treatment with vasopressin analogues. In addition, differences in pharmacokinetics and pharmacodynamics between AVP and TP are discussed.

DISCUSSION

The current literature suggests that neither AVP nor TP should be administered in high doses in patients with septic shock. Furthermore, increasing evidence indicates that early administration of vasopressin analogues may improve outcome as compared to a last-resort treatment. Low-dose infusion of AVP (0.6-2.4 U/h) has been demonstrated to be a safe adjunct in the management of septic shock. The V2 agonistic effects of AVP may exert favorable effects on hepatosplanchnic, renal, pulmonary, and coronary perfusion. However, the higher V1 receptor selectivity of TP may prove more potent in restoring arterial blood pressure and avoiding rebound hypotension, while carrying the risk of sustained global and regional vasoconstriction after bolus injection.

CONCLUSIONS

Evidence from experimental studies and initial clinical reports suggests that continuous low-dose infusion of TP may stabilize hemodynamics in septic shock with reduced side effects. However, randomized, controlled trials are necessary to determine the role of bolus or continuous infusion of TP in the treatment of septic shock before this approach can be recommended for routine clinical use.

Differential effects of vasopressin and norepinephrine on vascular reactivity in a long-term rodent model of sepsis

OBJECTIVE

There is escalating interest in the therapeutic use of vasopressin in septic shock. However, little attention has focused on mechanisms underlying its pressor hypersensitivity, which contrasts with the vascular hyporesponsiveness to catecholamines. We investigated whether a long-term rodent model of sepsis would produce changes in endogenous levels and pressor reactivity to exogenous norepinephrine and vasopressin comparable with those seen in septic patients.

DESIGN

In vivo and ex vivo animal study.

SETTING

University research laboratory.

SUBJECTS

Male adult Wistar rats.

INTERVENTIONS AND MEASUREMENTS

Fecal peritonitis was induced in conscious, fluid-resuscitated rats. Biochemical and hormonal profiles were measured at time points up to 48 hrs. Pressor responses to intravenous norepinephrine, vasopressin, and F-180, a selective V1 receptor agonist, were measured at 24 hrs. Contractile responses to these drugs were assessed in mesenteric arteries taken from animals at 24 hrs using wire myography. Comparisons were made against sham operation controls.

MAIN RESULTS

Septic rats became unwell and hypotensive, with a mortality of 64% at 48 hrs (0% in controls). Plasma norepinephrine levels were elevated in septic animals at 24 hrs (1968 +/- 490 vs. 492 +/- 90 pg/mL in controls, p = .003), whereas vasopressin levels were similar in the two groups (4.5 +/- 0.8 vs. 3.0 +/- 0.5 pg/mL, p = not significant). In vivo, the pressor response to norepinephrine was markedly reduced in the septic animals, but responses to vasopressin and F-180 were relatively preserved. In arteries from septic animals, norepinephrine contractions were decreased (efficacy as measured by maximum contractile response, Emax: 3.0 +/- 0.3 vs. 4.7 +/- 0.2 mN, p < .001). In contrast, the potency of vasopressin (expressed as the negative log of the concentration required to produce 50% of the maximum tension, pD2: 9.1 +/- 0.04 vs. 8.7 +/- 0.05, p < .001) and F-180 (pD2 8.2 +/- 0.04 vs. 7.6 +/- 0.02, p < .001) was enhanced (n > or = 6 for all groups).

CONCLUSIONS

This long-term animal model demonstrates changes in circulating vasoactive hormones similar to prolonged human sepsis, and decreased pressor sensitivity to norepinephrine. Ex vivo sensitivity to vasopressin agonists was heightened. This model is therefore appropriate for the further investigation of mechanisms underlying vasopressin hypersensitivity, which may include receptor or calcium-handling alterations within the vasculature.

Mechanisms of sepsis-induced organ dysfunction

BACKGROUND

The past several years have seen remarkable advances in understanding the basic cellular and physiologic mechanisms underlying organ dysfunction and recovery relating to sepsis. Although several new therapeutic approaches have improved outcome in septic patients, the far-reaching potential of these new insights into sepsis-associated mechanisms is only beginning to be realized.

AIM

The Brussels Round Table Conference in 2006 convened >30 experts in the field of inflammation and sepsis to review recent advances involving sepsis and to discuss directions that the field is likely to take in the near future.

FINDINGS

Current understanding of the pathophysiology underlying sepsis-induced multiple organ dysfunction highlights the multiple cell populations and cell-signaling pathways involved in this complex condition. There is an increasing appreciation of interactions existing between different cells and organs affected by the septic process. The intricate cross-talk provided by temporal changes in mediators, hormones, metabolites, neural signaling, alterations in oxygen delivery and utilization, and by modifications in cell phenotypes underlines the adaptive and even coordinated processes beyond the dysregulated chaos in which sepsis was once perceived. Many pathologic processes previously considered to be detrimental are now viewed as potentially protective. Applying systems approaches to these complex processes will permit better appreciation of the effectiveness or harm of treatments, both present and future, and also will allow development not only of better directed, but also of more appropriately timed, strategies to improve outcomes from this still highly lethal condition.

Systemic oxytocin and vasopressin excite gastrointestinal motility through oxytocin receptor in rabbits

The aim of the present study was to investigate the effect of systemic oxytocin (OT) and vasopressin (VP) on the motility of stomach and duodenum. Two plastic balloons made of condom were inserted into stomach and duodenum to monitor the change of mean pressure. Intravenous injection of OT (0.1-0.8 microg kg(-1)) or VP (0.02-0.08 IU kg(-1)) dose-dependently increased the stomach and duodenum pressure. Pretreatment of atosiban (1 microg kg(-1)), the specific OT receptor (OTR) antagonist, attenuated the excitatory effect of OT or VP on the pressure of stomach and duodenum. Pretreatment of V1880 (1 microg kg(-1)), the specific V1 receptor blocker, did not influence this effect. So we conclude that both of OT and VP injected systemically increased the gastric and duodenum motility via OTR.

Vasopressin in vasodilatory and septic shock

PURPOSE OF REVIEW

The aim of this article is to review mechanisms of action of vasopressin and clinical studies of vasopressin in septic shock.

RECENT FINDINGS

Arginine vasopressin is an important stress hormone that has both vasoactive and antidiuretic properties. The vasoactive properties of vasopressin have been more applicable clinically because of the discovery by Landry and colleagues that there is a deficiency of vasopressin in septic shock and that infusion of relatively low doses of vasopressin improves responsiveness to infused catecholamines (such as norepinephrine). There are at least 16 clinical studies of infusion of vasopressin in patients who have septic shock. The majority of studies found that vasopressin infusion increased blood pressure and urine output, and decreased the dose requirement of norepinephrine. Several studies showed that vasopressin infusion increased urine output. Both vasopressin and norepinephrine have important adverse effects including decreased cardiac output, decreased heart rate, arrhythmias, myocardial ischemia, mesenteric ischemia, and digital ischemia.

SUMMARY

It is still unclear whether there is net benefit from low dose vasopressin infusion in patients who have septic shock. There may be certain patients who benefit but there are few studies of a prolonged vasopressin infusion to determine which patients benefit.