Effects of titrated arginine vasopressin on hemodynamic variables and oxygen transport in healthy and endotoxemic sheep

Therapeutic regimens of endotoxaemia in sheep

Endotoxaemia is an inflammatory condition which happens due to the presence of outer cell wall layer of Gram-negative bacteria in blood circulation, containing lipopolysaccharide commonly known as endotoxin. This condition causes high mortality in affected animals and sheep are highly susceptible in this regard. Several researchers have emphasised the therapeutic regimens of endotoxaemia and its sequels in sheep. Furthermore, sheep are among the most commonly used animal species in experimental studies on endotoxaemia, and for the past five decades, ovine models have been employed to evaluate different aspects of endotoxaemia. Currently, there are several studies on experimentally induced endotoxaemia in sheep, and information regarding novel therapeutic protocols in this species contributes to better understanding and treating the condition. This review aims to specifically introduce various treatment methods of endotoxaemia in sheep.

Terlipressin Increases Systemic and Lowers Pulmonary Arterial Pressure in Experimental Acute Pulmonary Embolism

OBJECTIVES

We investigated whether the vasopressin-analog, terlipressin induces systemic vasoconstriction and pulmonary vasodilation in a porcine model of acute pulmonary embolism.

DESIGN

Controlled, animal study.

SETTING

Tertiary medical center research laboratory.

SUBJECTS

Female pigs (n = 12, Cross of Land Race, Duroc, and Yorkshire ~ 60 kg).

INTERVENTIONS

Acute pulmonary embolism was induced by administration of three large autologous emboli. Animals then received four increasing doses of either terlipressin (n = 6) or vehicle (n = 6).

MEASUREMENTS AND MAIN RESULTS

Effects were evaluated in vivo at baseline, after pulmonary embolism and after each dose by invasive hemodynamic measures, transesophageal echocardiography, and blood analysis. Isolated pulmonary arteries were evaluated ex vivo in a myograph. Pulmonary embolism caused a four-fold increase in pulmonary vascular resistance (p < 0.0001) and a two-fold increase in mean pulmonary arterial pressure (p < 0.0001) compared with baseline. Terlipressin increased mean systemic blood pressure (28 ± 5 mm Hg; p < 0.0001) and systemic vascular resistance (1,320 ± 143 dynes; p < 0.0001) compared with vehicle. In the pulmonary circulation, terlipressin decreased mean pulmonary arterial pressure (-6.5 ± 1.8 mm Hg; p = 0.005) and tended to decrease pulmonary vascular resistance (-83 ± 33 dynes; p = 0.07). Terlipressin decreased cardiac output (-2.5 ± 0.5 L/min; p < 0.0001) and increased plasma lactate (2.7 ± 0.2 mmol/L; p < 0.0001), possibly indicating systemic hypoperfusion. A biomarker of cerebral ischemia, S100b, remained unchanged, suggesting preserved cerebral perfusion (0.17 ± 0.11 µg/L; p = 0.51). Ex vivo, terlipressin relaxed pulmonary and constricted mesenteric arteries.

CONCLUSIONS

Terlipressin caused systemic vasoconstriction and pulmonary vasodilation in a porcine in vivo model of acute pulmonary embolism and vasorelaxation in isolated pulmonary arteries. Despite positive vascular effects, cardiac output declined and plasma lactate increased probably due to a predominantly systemic vasoconstrictor effect of terlipressin. These findings should warrant careful translation to the clinical setting and does not suggest routine use in acute pulmonary embolism.

A Selective V(1A) Receptor Agonist, Selepressin, Is Superior to Arginine Vasopressin and to Norepinephrine in Ovine Septic Shock

OBJECTIVE

Selective vasopressin V(1A) receptor agonists may have advantages over arginine vasopressin in the treatment of septic shock. We compared the effects of selepressin, a selective V(1A) receptor agonist, arginine vasopressin, and norepinephrine on hemodynamics, organ function, and survival in an ovine septic shock model.

DESIGN

Randomized animal study.

SETTING

University hospital animal research laboratory.

SUBJECTS

Forty-six adult female sheep.

INTERVENTIONS

Fecal peritonitis was induced in the anesthetized, mechanically ventilated, fluid-resuscitated sheep, and they were randomized in two successive phases. Three late-intervention groups (each n = 6) received IV selepressin (1 pmol/kg/min), arginine vasopressin (0.25 pmol [0.1 mU]/kg/min), or norepinephrine (3 nmol [0.5 μg]/kg/min) when mean arterial pressure remained less than 70 mm Hg despite fluid challenge; study drugs were thereafter titrated to keep mean arterial pressure at 70-80 mm Hg. Three early-intervention groups (each n = 7) received selepressin, arginine vasopressin, or norepinephrine at the same initial infusion rates as for the late intervention, but already when mean arterial pressure had decreased by 10% from baseline; doses were then titrated as for the late intervention. A control group (n = 7) received saline. All animals were observed until death or for a maximum of 30 hours.

MEASUREMENTS AND MAIN RESULTS

In addition to hemodynamic and organ function assessment, plasma interleukin-6 and nitrite/nitrate levels were measured. In the late-intervention groups, selepressin delayed the decrease in mean arterial pressure and was associated with lower lung wet/dry weight ratios than in the other two groups. In the early-intervention groups, selepressin maintained mean arterial pressure and cardiac index better than arginine vasopressin or norepinephrine, slowed the increase in blood lactate levels, and was associated with less lung edema, lower cumulative fluid balance, and lower interleukin-6 and nitrite/nitrate levels. Selepressin-treated animals survived longer than the other animals.

CONCLUSIONS

In this clinically relevant model, selepressin, a selective V(1A) receptor agonist, was superior to arginine vasopressin and to norepinephrine in the treatment of septic shock, especially when administered early.

Effects of terlipressin on pulmonary artery pressure in a septic cooled infant: an echocardiographic assessment

Experience with terlipressin (TP) in the neonatal field is scarce. We describe the effects of TP on pulmonary circulation, studied with echocardiography, in an asphyxiated septic cooled infant with pulmonary hypertension (PH) who developed catecholamine-resistant hypotension and exacerbation of PH shortly after the beginning of the rewarming. TP was added to norephinephine and adrenaline infusions at the dose of 0.02 mg kg(-1) every 6 h, because of refractory hypotension and oliguria. After 10 min, blood pressure dramatically and definitely increased, and urinary output was re-established after 60 min. Echocardiographic evaluation 30 min after the second bolus of TP showed unchanged velocity of the tricuspidal valve regurgitation and improved biventricular functional indexes respect to the pre-treatment assessment. TP was continued for 12 h (three doses) without significant adverse effect except for a transient increase in troponin levels. Addition of TP boluses to catecholamine infusion in our newborn was effective in increasing systemic vascular resistance without increasing pulmonary vascular resistance, successfully reversing the hemodynamics of severe PH, and suggesting a potential primary vasodilator effect on pulmonary circulation. Transient increase of troponin levels during TP treatment confirms the risk of excessive coronary vasoconstriction when TP boluses are added to high dose catecholamines.

Copeptin in the assessment of acute lung injury and cardiogenic pulmonary edema

BACKGROUNDS

Copeptin has been studied as an excellent predictor of outcome in a variety of diseases, its value is even superior to that of B-type natriuretic peptide (BNP) in heart failure, but little is known about its characteristics in acute respiratory distress syndrome (ARDS)/acute lung injury (ALI). We sought to assess the diagnostic and prognostic value of copeptin together with N-terminal pro-BNP (NT-proBNP) in patients with ARDS/ALI or cardiogenic pulmonary edema (CPE).

METHODS

Measurement of copeptin and NT-proBNP levels in plasma from 121 consecutive patients with either ARDS/ALI or CPE enrolled in a prospective single center study.

RESULTS

In a derivation cohort of 87 patients with ARDS/ALI and 34 patients with CPE, a copeptin threshold of >40.11 pmol/L provided a specificity of 88.2% and a sensitivity of 60.9% for the diagnosis of ARDS/ALI, a NT-proBNP cut point of <2813 pg/ml had a specificity of 79.4% and sensitivity of 65.5% for it. Multivariate Cox regression analysis showed that copeptin was the strongest predictor for mortality in patients with ARDS/ALI [hazard ratio (HR) = 4.72, P < 0.001] and CPE (HR = 3.52, P = 0.019), the association between increasing copeptin and death was statistically significant in patients with ARDS/ALI (HR = 2.64, P = 0.035) and patients with CPE (HR = 1.62, P = 0.029).

CONCLUSION

Copeptin of >40.11 pmol/L had a high specificity for the diagnosis of ARDS/ALI in patients presenting with ARDS/ALI or CPE. Compared to NT-proBNP, copeptin was a stronger prognostic marker for short-term mortality.

Bench-to-bedside review: Vasopressin in the management of septic shock

This review of vasopressin in septic shock differs from previous reviews by providing more information on the physiology and pathophysiology of vasopressin and vasopressin receptors, particularly because of recent interest in more specific AVPR1a agonists and new information from the Vasopressin and Septic Shock Trial (VASST), a randomized trial of vasopressin versus norepinephrine in septic shock. Relevant literature regarding vasopressin and other AVPR1a agonists was reviewed and synthesized. Vasopressin, a key stress hormone in response to hypotension, stimulates a family of receptors: AVPR1a, AVPR1b, AVPR2, oxytocin receptors and purinergic receptors. Rationales for use of vasopressin in septic shock are as follows: first, a deficiency of vasopressin in septic shock; second, low-dose vasopressin infusion improves blood pressure, decreases requirements for norepinephrine and improves renal function; and third, a recent randomized, controlled, concealed trial of vasopressin versus norepinephrine (VASST) suggests low-dose vasopressin may decrease mortality of less severe septic shock. Previous clinical studies of vasopressin in septic shock were small or not controlled. There was no difference in 28-day mortality between vasopressin-treated versus norepinephrine-treated patients (35% versus 39%, respectively) in VASST. There was potential benefit in the prospectively defined stratum of patients with less severe septic shock (5 to 14 μg/minute norepinephrine at randomization): vasopressin may have lowered mortality compared with norepinephrine (26% versus 36%, respectively, P = 0.04 within stratum). The result was robust: vasopressin also decreased mortality (compared with norepinephrine) if less severe septic shock was defined by the lowest quartile of arterial lactate or by use of one (versus more than one) vasopressor at baseline. Other investigators found greater hemodynamic effects of higher dose of vasopressin (0.06 units/minute) but also unique adverse effects (elevated liver enzymes and serum bilirubin). Use of higher dose vasopressin requires further evaluation of efficacy and safety. There are very few studies of interactions of therapies in critical care - or septic shock - and effects on mortality. Therefore, the interaction of vasopressin infusion, corticosteroid treatment and mortality of septic shock was evaluated in VASST. Low-dose vasopressin infusion plus corticosteroids significantly decreased 28-day mortality compared with corticosteroids plus norepinephrine (44% versus 35%, respectively, P = 0.03; P = 0.008 interaction statistic). Prospective randomized controlled trials would be necessary to confirm this interesting interaction. In conclusion, low-dose vasopressin may be effective in patients who have less severe septic shock already receiving norepinephrine (such as patients with modest norepinephrine infusion (5 to 15 μg/minute) or low serum lactate levels). The interaction of vasopressin infusion and corticosteroid treatment in septic shock requires further study.

Effects of two different dosing regimens of terlipressin on organ functions in ovine endotoxemia

OBJECTIVE AND DESIGN

To test the hypothesis that a continuous infusion of the vasopressin analog terlipressin is associated with less organ dysfunction as compared to intermittent bolus infusion in an ovine sepsis model.

SUBJECTS

Twenty-seven adult female sheep.

TREATMENT

All sheep were subjected to a Salmonella typhosa endotoxin infusion (10 ng/kg/min). After 16 h of endotoxemia, the surviving animals (n = 24) were randomized to (1) an untreated control group, (2) a continuous terlipressin group (2 mg/24 h), or (3) a terlipressin bolus group (1 mg/6 h).

METHODS

Hemodynamic variables were measured and blood was withdrawn at specific time points for the assessment of organ functions.

RESULTS

Continuous terlipressin infusion was associated with improved surrogate parameters of myocardial, renal, and hepatic function as compared with terlipressin bolus infusion. Reduced vascular hyperpermeability was evidenced by an attenuated decrease in plasma protein concentrations in sheep treated with continuous terlipressin infusion as compared to bolus injection or no treatment.

CONCLUSIONS

Continuous infusion of low-dose terlipressin preserved several surrogate parameters of organ function better than intermittent bolus injections in sheep with systemic inflammation.

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.

Somatostatin infusion increases intestinal ischemia and does not improve vasoconstrictor response to norepinephrine in ovine endotoxemia

Hemodynamic support of patients with septic shock is often complicated by a tachyphylaxis against exogenous catecholamines. Because an increase in somatotropic hormones may play a pivotal role in the regulation of the inflammatory response to endotoxin, intravenous supplementation of the neuroendocrine hormone somatostatin (SOMA) may attenuate hemodynamic dysfunction resulting from endotoxemia. The objective of the present study was to assess the short-term effects of SOMA alone and in combination with norepinephrine (NE) on cardiopulmonary hemodynamics, global oxygen transport, plasma nitrate/nitrite levels, and intestinal integrity compared with single NE therapy in ovine endotoxemia. After a baseline measurement in healthy sheep (n = 16) had been performed, Salmonella typhosa endotoxin was centrally infused (10 ng x kg(-1) x min(-1)) to induce a hypotensive-hyperdynamic circulation using an established protocol. Animals surviving 16 h of endotoxemia were randomly assigned to one of the two groups (each n = 6). Sheep allocated to the SOMA + NE group received SOMA as a loading dose of 10.5 microg x kg(-1) x min(-1) for 1 h, followed by a continuous infusion of 3.5 microg x kg(-1) x min(-1) for the next 2 h. After the SOMA loading dose had been given, NE was concurrently infused (0.3 microg x kg(-1) x min(-1)) for 2 h. In the NE group (control), NE (0.3 microg x kg(-1) x min(-1)) was continuously infused for 3 h. Endotoxemia caused a decrease in MAP and systemic vascular resistance index in both groups, but to a greater extent in the NE group. Arterial hypotension persisted despite administration of the study drugs. Infusion of SOMA alone and in combination with NE did not significantly increase systemic vascular resistance index. Neither SOMA nor NE infusion alone affected pulmonary vasoregulation. Plasma nitrate/nitrite levels did not differ between groups. However, combined infusion of SOMA and NE significantly increased arterial lactate concentrations, oxygen consumption index, and oxygen extraction rate (P < 0.05) and aggravated ileal mucosal injury. In conclusion, short-term treatment with SOMA failed to attenuate cardiocirculatory shock resulting from endotoxemia and did not improve vasopressor response to NE. In addition, combined SOMA and NE therapy resulted in intestinal injury. Therefore, SOMA does not seem to represent a therapeutic option to treat arterial hypotension resulting from sepsis and systemic inflammatory response syndrome.

Employing dobutamine as a useful agent to reverse the terlipressin-linked impairments in cardiopulmonary hemodynamics and global oxygen transport in healthy and endotoxemic sheep

Although arginine vasopressin and terlipressin have been identified as useful nonadrenergic agents to increase systemic blood pressure in catchecholamine-resistant septic shock, the impairments in cardiac index (CI) and global oxygen transport may limit their clinical applicability. The present study was designed as a prospective controlled laboratory experiment to investigate the effects of dobutamine as an adjunct to terlipressin infusion on cardiopulmonary hemodynamics and global oxygen transport in healthy and endotoxemic sheep. Nine adult ewes were instrumented for chronic study using an established protocol. After a baseline measurement in the healthy state had been performed, 1 mg terlipressin was given as bolus infusion. Thirty minutes later, dobutamine was continuously infused at incremental doses (2 and 5 microg x kg(1) x min(1), each for 1 h). After 24 h of recovery, a hypotensive-hyperdynamic circulation was induced and maintained by a continuous infusion of Salmonella typhosa endotoxin (10 ng x kg(1) x min(1)). After 16 h of endotoxemia, the six surviving sheep received terlipressin and dobutamine according to the same protocol that was used in healthy sheep. Compared with baseline, terlipressin infusion was associated with a significant increase in MAP that, however, occurred at the expense of a compromised CI, oxygen delivery index (DO(2)I), and mixed venous oxygen saturation (SvO(2), each P < 0.05). Dobutamine infusion was followed by a dose-dependent increase in CI, DO(2)I, and SvO(2) in both health and endotoxemia (each P < 0.05). Although the higher dosage of dobutamine exerted favorable effects, such as a decrease in pulmonary vascular resistance index (P < 0.05), the associated onset of tachycardia (P < 0.05) and arterial hypotension (P < 0.05) may limit its therapeutic use under septic conditions. This study provides evidence that dobutamine in a dosage of 2 microg x kg(1) x min(1) is useful to reverse the terlipressin-linked depressions in CI, DO(2)I and SvO(2) in ovine endotoxemia without obvious side effects.

Role of adenosine triphosphate-sensitive potassium channel inhibition in shock states: physiology and clinical implications

Shock states are associated with an impaired tissue oxygen supply-demand relationship and perturbations within the microcirculation, leading to global tissue hypoxia, finally resulting in multiple-organ failure or even death. Two of the most frequent causes of shock are acute hemorrhage and sepsis. Although the origin and the pathophysiology of hemorrhagic and septic shock are basically different, the involvement of adenosine triphosphate-sensitive potassium (KATP) channels, as an important regulator of vascular smooth muscles tone, plays a pivotal role under both conditions. Because the excessive activation of vascular KATP channels is a major cause of arterial hypotension and vascular hyporesponsiveness to catecholamines, the pharmacological inhibition of KATP channels may represent a goal-directed therapeutic option to stabilize the hemodynamic situation in shock states. Despite promising results of preclinical studies, the efficacy of this innovative therapeutic approach remains to be confirmed in the clinical setting. The differences in the species, the comorbidity, and the difficulty in determining the exact onset of shock in clinical practice and, thus, any duration-related alterations in vascular responses and KATP channel activation may explain the discrepancy between the results obtained from experimental and clinical studies. Currently, two of the most relevant problems related to effective KATP blockade in shock states are represented by (1) the dose itself (benefit-risk ratio) and (2) the route of administration (oral vs. i.v.). This review article critically elucidates the published in vivo studies on the role of KATP channel inhibition in both described shock forms and discusses the advantages and the potential pitfalls related to the treatment of human shock states.

Continuous versus bolus infusion of terlipressin in ovine endotoxemia

In patients with sepsis, hemodynamic support is often complicated by a tachyphylaxis against conventional vasopressor agents. Bolus infusion of terlipressin, a vasopressin analog, has been reported to increase mean arterial pressure in patients with catecholamine-resistant septic shock. However, bolus infusion of terlipressin may be associated with severe side effects, including pulmonary vasoconstriction and impairment of oxygen delivery. We hypothesized that continuous low-dose infusion of terlipressin may reverse sepsis-related systemic arterial hypotension with reduced side effects as compared with the traditional concept of bolus administration. Twenty-seven adult sheep were instrumented for chronic study. After a baseline measurement, Salmonella typhosa endotoxin (10 ng.kg-1.min-1) was continuously administered for the next 40 h. After 16 h of endotoxemia, the surviving sheep (n = 24) were randomly assigned to be treated with either a continuous infusion of terlipressin (2 mg for 24 h), bolus injections of terlipressin (1 mg every 6 h), or placebo (normal saline; each n = 8). Continuous infusion of terlipressin permanently reversed endotoxin-induced systemic arterial hypotension (P < 0.001) and improved left ventricular stroke work index in all sheep (P < 0.05). Intermittent bolus injections of terlipressin were linked to decreases in heart rate and cardiac index and increases in pulmonary vascular resistance index (each, P < 0.001). These unwanted side effects were prevented by continuous low-dose infusion of the drug. In conclusion, continuous infusion of terlipressin stabilized hemodynamics and improved myocardial performance in endotoxemic ewes without obvious side effects. Continuous low-dose terlipressin infusion may represent a useful alternative treatment of arterial hypotension related to sepsis and systemic inflammatory response syndrome.

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.

Comparison of two dose regimens of arginine vasopressin in advanced vasodilatory shock

OBJECTIVE

To evaluate the effects of two arginine vasopressin (AVP) dose regimens (0.033 vs. 0.067 IU/min) on treatment efficacy, hemodynamic response, prevalence of adverse events, and changes in laboratory variables.

DESIGN

Retrospective, controlled study.

PATIENTS

A total of 78 patients with vasodilatory shock (mean norepinephrine dosage, 1.07 microg.kg-1.min-1; 95% confidence interval, 0.82-1.56 microg.kg-1.min-1).

INTERVENTIONS

Supplementary infusion of AVP at 0.033 (n = 39) and 0.067 IU/min (n = 39).

MEASUREMENTS AND MAIN RESULTS

Cardiocirculatory, laboratory, and clinical variables were evaluated and compared between groups before and at 0.5, 1, 4, 12, 24, 48, and 72 hrs after initiation of AVP. Treatment efficacy was assessed by the increase in mean arterial blood pressure and the extent of norepinephrine reduction during the first 24 hrs of AVP therapy. Standard tests and a mixed-effects model were used for statistical analysis. Although the relative increase in mean arterial pressure was comparable between groups (0.033 vs. 0.067 IU/min: 16.8 +/- 18.4 vs. 21.4 +/- 14.9 mm Hg, p = .24), norepinephrine could be reduced significantly more often in patients receiving 0.067 IU/min. AVP at 0.067 IU/min resulted in a higher mean arterial pressure (p < .001), lower central venous pressure (p = .001), lower mean pulmonary arterial pressure (p = .04), and lower norepinephrine requirements (p < .001) during the 72-hr observation period. Increases in liver enzymes occurred more often in patients treated with 0.033 IU/min (71.8% vs. 28.2%, p < .001). The prevalence of a decrease in cardiac index (69.2% vs. 53.8%, p = .24), decrease in platelet count (94.8% vs. 84.6%, p = .26), and increase in total bilirubin (48.7% vs. 71.8%, p = .06) was not significantly different between groups. Bilirubin levels (3.1 +/- 3.4 vs. 5.2 +/- 5.5 mg/dL, p = .04) and base deficit (-7.2 +/- 4.3 vs. -3.9 +/- 5.9 mmol/L, p = .005) were lower and arterial lactate concentrations higher (76 +/- 67 vs. 46 +/- 38 mg/dL, p < .001) in patients receiving 0.033 IU/min.

CONCLUSIONS

AVP dosages of 0.067 IU/min seem to be more effective to reverse cardiovascular failure in vasodilatory shock requiring high norepinephrine dosages than 0.033 IU/min.

Evidence-based medicine in equine critical care

One of the fundamental skills required for practicing evidence-based medicine is the development of a well-built clinical question, which specifies the patient group or problem, intervention, and outcome of interest. For this purpose, various "levels of evidence" have been developed in the human literature, which rank the validity of evidence. Our established conclusions and advice are thus supported by specific "grades of recommendations," which are intended to give an indication of the "strength" of a clinical recommendation. This article was compiled with these principles in mind.

Hemodynamic effects of titrated norepinephrine in healthy versus endotoxemic sheep

In patients with sepsis and systemic inflammatory response syndrome, hemodynamic support is often complicated by a vascular hyporesponsiveness to exogenously administered norepinephrine. Although norepinephrine tachyphylaxis represents a significant clinical problem, the relationship between norepinephrine dosages and mean arterial pressure (MAP) in the presence of systemic inflammation is still not fully understood. This study was, therefore, designed as a prospective, controlled laboratory trial to elucidate the hemodynamic response to incremental norepinephrine doses in healthy and endotoxemic sheep. ANOVA demonstrated that a significantly higher mean infusion rate of norepinephrine was needed to increase MAP by 20 mmHg in endotoxemic versus healthy control sheep (P = 0.007). Whereas the goal-MAP was reached in 100% of healthy controls, it was achieved in only 80% during endotoxemia. Cardiac index increased significantly in healthy, but not in endotoxemic, sheep. Our findings confirm the presence of vascular hyporesponsiveness to norepinephrine in endotoxemia. In addition, this study demonstrates that the presence of systemic inflammation leads to an early hyporesponsiveness against norepinephrine which was caused by a drug-independent mechanism rather than a tachyphylaxis due to long-term administration of norepinephrine.

Continuously infused glipizide reverses the hyperdynamic circulation in ovine endotoxemia

In advanced sepsis, hemodynamic support is often complicated by a tachyphylaxis against exogenous catecholamines. Although activation of adenosine triphosphate (ATP)-sensitive potassium (K(ATP)) channels plays a pivotal role in the pathogenesis of hyperdynamic vasodilatory shock, previous studies demonstrated only a transient increase in mean arterial pressure (MAP) after bolus administration of K(ATP) channel inhibitors. We hypothesized that a continuous infusion of the sulfonylurea glipizide, a K(ATP) channel inhibitor, may reverse cardiovascular dysfunctions in sepsis permanently. Eighteen adult sheep were instrumented for chronic study. After a baseline measurement in healthy ewes, endotoxin (Salmonella typhosa, 10 ng kg(-1) min(-1)) was continuously infused for 19 h. After 16 h of endotoxemia, the surviving sheep (n = 14) were randomly assigned to be treated with either glipizide (5 mg/kg, followed by a continuous infusion of 8 mg kg(-1) h(-1)) or placebo (normal saline; each n = 7). Measurements of cardiopulmonary hemodynamics, global oxygen transport, acid-base status, and urine output were performed in the healthy state, after 16 h of endotoxemia, and during 3 h of glipizide infusion. Continuous infusion of glipizide reversed the endotoxin-induced hyperdynamic circulation, as indicated by significant increases in MAP and systemic vascular resistance index, as well as decreases in cardiac index and heart rate (P < 0.001 each). In addition, glipizide increased urine output as compared with untreated controls (P < 0.001). The anticipated decrease in glucose plasma levels was prevented by infusion of glucose 5%. From these results, we conclude that continuous glipizide infusion may represent a useful therapeutic option in the treatment of arterial hypotension related to sepsis and systemic inflammatory response syndrome.

Methylprednisolone reverses vasopressin hyporesponsiveness in ovine endotoxemia

Tachyphylaxis against catecholamines often complicates hemodynamic support in patients with septic shock. Recent experimental and clinical research suggests that the hemodynamic response to exogenous arginine vasopressin (AVP) infusion may also be blunted. The purpose of the present study was therefore to clarify whether the efficacy of a continuous AVP infusion (0.04 U x min(-1)) decreases over time in ovine endotoxemia. An additional objective was to determine whether the anticipated hyporesponsiveness can be counteracted by corticosteroids. Fourteen adult ewes (37 +/- 1 kg) were instrumented for chronic hemodynamic monitoring. All ewes received a continuous endotoxin infusion that contributed to a hypotensive-hyperdynamic circulation. After 16 h of endotoxemia, the sheep were randomized to receive either AVP (0.04 U x min(-1)) or the vehicle (normal saline; n = 7 each). After 6 h of AVP or placebo infusion, respectively, methylprednisolone (30 mg x kg(-1)) was injected. Arginine vasopressin infusion increased mean arterial pressure and systemic vascular resistance index at the expense of a reduced cardiac index (P < 0.05 each). Supraphysiologic AVP plasma levels in the treatment group (298 +/- 15 pg x mL(-1)) were associated with increased surrogate parameters of liver, mesenterial, and myocardial dysfunction. After 6 h of continuous AVP infusion, the vasopressor effect was significantly reduced. Interestingly, a bolus infusion of methylprednisolone (30 mg x kg(-1)) reestablished mean arterial pressure by increasing both cardiac index and systemic vascular resistance index. The present study demonstrates that in endotoxemia, (a) the vasopressor effect of AVP infusion may be reduced, (b) corticosteroids may potentially be useful to increase the efficacy of AVP infusion, and (c) even moderate AVP doses may potentially impair myocardial and hepatic function.

Copeptin, C-Reactive Protein, and Procalcitonin as Prognostic Biomarkers in Acute Exacerbation of COPD

BACKGROUND

A novel approach to estimate the severity of COPD exacerbation and predict its outcome is the use of biomarkers. We assessed circulating levels of copeptin, the precursor of vasopressin, C-reactive protein (CRP), and procalcitonin as potential prognostic parameters for in-hospital and long-term outcomes in patients with acute exacerbation of COPD (AECOPD) requiring hospitalization.

METHODS

Data of 167 patients (mean age, 70 years; mean FEV(1), 39.9 +/- 16.9 of predicted [+/- SD]) presenting to the emergency department due to AECOPD were analyzed. Patients were evaluated based on clinical, laboratory, and lung function parameters on hospital admission, at 14 days, and at 6 months.

RESULTS

Plasma levels of all three biomarkers were elevated during the acute exacerbation (p < 0.001), but levels at 14 days and 6 months were similar (p = not significant). CRP was significantly higher in patients presenting with Anthonisen type I exacerbation (p = 0.003). In contrast to CRP and procalcitonin, copeptin on hospital admission was associated with a prolonged hospital stay (p = 0.002) and long-term clinical failure (p < 0.0001). Only copeptin was predictive for long-term clinical failure independent of age, comorbidity, hypoxemia, and lung functional impairment in multivariate analysis (p = 0.005). The combination of copeptin and previous hospitalization for COPD increased the risk of poor outcome (p < 0.0001). Long-term clinical failure was observed in 11% of cases with copeptin < 40 pmol/L and no history of hospitalization, as compared to 73% of patients with copeptin >/= 40 pmol/L and a history of hospitalization (p < 0.0001).

CONCLUSIONS

We suggest copeptin as a prognostic marker for short-term and long-term prognoses in patients with AECOPD requiring hospitalization.

Vasopressin in vasodilatory shock: ensure organ blood flow, but take care of the heart!

Supplementary arginine vasopressin infusion in advanced vasodilatory shock may be accompanied by a decrease in cardiac index and systemic oxygen transport capacity in approximately 40% of patients. While a reduction of cardiac output most frequently occurs in patients with hyperdynamic circulation, it is less often observed in patients with low cardiac index. Infusion of inotropes, such as dobutamine, may be an effective strategy to restore systemic blood flow. However, when administering inotropic drugs, systemic blood flow should be increased to adequately meet systemic demands (assessed by central or mixed venous oxygen saturation) without putting an excessive beta-adrenergic stress on the heart. Overcorrection of cardiac index to hyperdynamic values with inotropes places myocardial oxygen supply at significant risk.

Dobutamine reverses the vasopressin-associated impairment in cardiac index and systemic oxygen supply in ovine endotoxemia

Introduction

Arginine vasopressin (AVP) is increasingly used to treat sepsis-related vasodilation and to decrease catecholamine requirements. However, AVP infusion may be associated with a marked decrease in systemic blood flow and oxygen transport. The purpose of the present study was to evaluate whether dobutamine may be titrated to reverse the AVP-related decrease in cardiac index (CI) and systemic oxygen delivery index (DO₂I) in an established model of ovine endotoxemia.

Methods

Twenty-four adult ewes were chronically instrumented to determine cardiopulmonary hemodynamics and global oxygen transport. All ewes received a continuous endotoxin infusion that contributed to a hypotensive-hyperdynamic circulation and death of five sheep. After 16 hours of endotoxemia, the surviving ewes (n = 19; weight 35.6 ± 1.5 kg (mean ± SEM)) were randomized to receive either AVP (0.04 Umin^-1) and dobutamine (n = 8) or the vehicle (normal saline; n = 6) and compared with a third group treated with AVP infusion alone (n = 5). Dobutamine infusion was started at an initial rate of 2 μg kg^-1min^-1 and was increased to 5 and 10 μg kg^-1 min^-1 after 30 and 60 minutes, respectively.

Results

AVP infusion increased mean arterial pressure (MAP) and systemic vascular resistance index at the expense of a markedly decreased CI (4.1 ± 0.5 versus 8.2 ± 0.3 l min^-1 m^-2), DO₂I (577 ± 68 versus 1,150 ± 50 ml min^-1 m^-2) and mixed-venous oxygen saturation (S_vO₂; 54.5 ± 1.8% versus 69.4 ± 1.0%; all p < 0.001 versus control). Dobutamine dose-dependently reversed the decrease in CI (8.8 ± 0.7 l min^-1 m^-2 versus 4.4 ± 0.5 l min^-1 m^-2), DO₂I (1323 ± 102 versus 633 ± 61 ml min^-1 m^-2) and S_vO₂ (72.2 ± 1.7% versus 56.5 ± 2.0%, all p < 0.001 at dobutamine 10 μg kg^-1 min^-1 versus AVP group) and further increased MAP.

Conclusion

This study provides evidence that dobutamine is a useful agent for reversing the AVP-associated impairment in systemic blood flow and global oxygen transport.

Short-term effects of glipizide (an adenosine triphosphate-sensitive potassium channel inhibitor) on cardiopulmonary hemodynamics and global oxygen transport in healthy and endotoxemic sheep

In severe sepsis and septic shock, hemodynamic support is often complicated by a tachyphylaxis against exogenous catecholamines. Because activation of adenosine triphosphate (ATP)-sensitive potassium (K(ATP)) channels plays a pivotal role in the pathogenesis of hyperdynamic vasodilatory shock, we hypothesized that it may be beneficial to administer a specific K(ATP) channel inhibitor to prevent, or at least attenuate, hemodynamic dysfunction in sepsis. The present study was designed as a prospective and controlled laboratory experiment to elucidate the short-term effects of glipizide, a specific K(ATP) channel inhibitor, on cardiopulmonary hemodynamics and global oxygen transport in healthy sheep and sheep with endotoxemia. Ten adult ewes were anesthetized and operatively instrumented with a pulmonary artery, a femoral artery, and a foley catheter. After 24 h of recovery, healthy sheep received glipizide as a bolus infusion (4 mg/kg over 15 min). After 24 h of recovery, a continuous infusion of endotoxin (Salmonella typhosa, 10 ng.kg.(-1)min) was started in the same sheep and administered for the next 17 h. After 16 h of endotoxemia, glipizide was given as described above. Administration of glipizide was followed by a transient, but significant, increase in mean arterial pressure in both healthy controls (95 +/- 3 mmHg vs. 101 +/- 2 mmHg, P < 0.05) and sheep with endotoxemia (86 +/- 3 mmHg vs. 93 +/- 3 mmHg, P < 0.05). However, the increase in mean arterial pressure was longer lasting in ewes with endotoxemia. Cardiac index, oxygen delivery index, arterial lactate concentrations, and arterial pH were not significantly affected by glipizide. Therefore, administration of glipizide may represent a beneficial therapeutic option to treat arterial hypotension resulting from sepsis and systemic inflammatory response syndrome. Additional studies are required to determine the effects of continuous infusion of glipizide in the presence of systemic inflammation.

The effect of vasopressin and related compounds at V1a and V2 receptors in animal models relevant to human disease

Vasopressin, a neurohypophyseal peptide hormone, is the endogenous agonist at V1a, V1b and V2 receptors. The most important physiological function of vasopressin is the maintenance of water homeostasis through interaction with V2 receptors in the kidney. Vasopressin and related compounds are used in various clinical settings such as acute variceal bleeding associated with portal hypertension, septic shock, diabetes insipidus and coagulation disorders. The effect in the former two indications relates to the V1a receptor, and in the two latter indications the effect relates to the V2 receptor. Vasopressin and related compounds have demonstrated activity in animal models of portal hypertension, sepsis and septic shock, diabetes insipidus and coagulation disorders. The use of the compounds in animal models is reviewed. Generally, the effect of vasopressin and related compounds in animal models reflect the activity in the clinical setting, but in some cases important species differences exist.

Catecholamines and vasopressin during critical illness

In critical care medicine, catecholamines are most widely used to reverse circulatory dysfunction and thus to restore tissue perfusion. However, catecholamines not only influence systemic and regional hemodynamics, but also exert a variety of significant metabolic, endocrine, and immunologic effects. Arginine vasopressin is a vasomodulatory hormone with potency to restore vascular tone in vasodilatory hypotension. Although the evidence supporting the use of low doses of vasopressin or its analogs in vasodilatory shock is increasing, lack of data regarding mortality and morbidity prevent their implementation in critical care protocols.

Effects of arginine vasopressin during resuscitation from hemorrhagic hypotension after traumatic brain injury

OBJECTIVE

Two series of experiments were designed to evaluate whether early arginine vasopressin improves acute outcome following resuscitation from traumatic brain injury and severe hemorrhagic hypotension.

DESIGN

Prospective randomized, blinded animal study.

SETTING

University laboratory.

SUBJECTS

Thirty-three swine.

INTERVENTIONS

In series 1 (n = 19), after traumatic brain injury with hemorrhage and 12 mins of shock (mean arterial pressure approximately 20 mm Hg), survivors (n = 16) were initially resuscitated with 10 mL/kg crystalloid. After 30 mins, crystalloid and blood with either 0.1 unit x kg(-1) x hr(-1) arginine vasopressin or placebo was titrated to a mean arterial pressure target >or=60 mm Hg. After 90 mins, all received mannitol and the target was cerebral perfusion pressure >or=60 mm Hg. To test cerebrovascular function, 7.5% inhaled CO2 was administered periodically. In series 2 (n = 14), the identical protocol was followed except the shock period was 20 mins and survivors (n = 10) received a bolus of either arginine vasopressin (0.2 units/kg) or placebo during the initial fluid resuscitation.

MEASUREMENTS AND MAIN RESULTS

In series 1, by 300 mins after traumatic brain injury with arginine vasopressin (n = 8) vs. placebo (n = 8), the fluid and transfusion requirements were reduced (both p < .01), intracranial pressure was improved (11 +/- 1 vs. 23 +/- 2 mmHg; p < .0001), and the CO2-evoked intracranial pressure elevation was reduced (7 +/- 2 vs. 26 +/- 3 mm Hg, p < .001), suggesting improved compliance. In series 2, with arginine vasopressin vs. placebo, cerebral perfusion pressure was more rapidly corrected (p < .05). With arginine vasopressin, five of five animals survived 300 mins, whereas three of five placebo animals died. The survival time with placebo was 54 +/- 4 mins (p < .05 vs. arginine vasopressin).

CONCLUSIONS

Early supplemental arginine vasopressin rapidly corrected cerebral perfusion pressure, improved cerebrovascular compliance, and prevented circulatory collapse during fluid resuscitation of hemorrhagic shock after traumatic brain injury.

Arginine vasopressin in 316 patients with advanced vasodilatory shock

OBJECTIVE

To assess the effects of arginine vasopressin (AVP) on hemodynamic, clinical, and laboratory variables and to determine its adverse side effects in advanced vasodilatory shock.

DESIGN

Retrospective study.

PATIENTS

A total of 316 patients.

INTERVENTIONS

AVP infusion (4 units/hr).

MEASUREMENTS AND MAIN RESULTS

Cardiocirculatory, laboratory, and clinical variables were evaluated before, 0.5, 1, 4, 12, 24, 48, and 72 hrs after administration of AVP. AVP increased mean arterial pressure, systemic vascular resistance, and stroke volume index. Heart rate, central venous pressure, mean pulmonary arterial pressure, norepinephrine, milrinone, and epinephrine requirements decreased. There was no difference in the hemodynamic response between patients with septic shock, postcardiotomy shock, or systemic inflammatory response syndrome. Cardiac index decreased in 41.1% of patients during AVP treatment. In patients with hyperdynamic circulation before AVP, cardiac index decreased, whereas it remained uncharged or tended to increase in patients with normodynamic or hypodynamic circulation. During the course of AVP treatment, liver enzymes (28.5% of patients) and total bilirubin concentrations (69.3% of patients) increased, whereas platelet count decreased (73.4% of patients). Simultaneous hemofiltration significantly contributed to the decrease in platelet count (p < .001) and increase in bilirubin (p < .001). Whereas patients with an increase in bilirubin were more likely to die, a decrease in cardiac index or platelet count and an increase in liver enzymes did not affect mortality. Systemic inflammatory response syndrome as admission diagnosis, a high degree of multiple organ dysfunction, and norepinephrine requirements of >0.5 microg x kg x min before AVP treatment were independent risk factors for death from advanced vasodilatory shock treated with AVP. If norepinephrine dosages exceeded 0.6 microg x kg x min before AVP treatment, a substantial increase in mortality occurred.

CONCLUSIONS

Supplementary AVP infusion improved cardiocirculatory function in advanced vasodilatory shock, but an increase in liver enzymes and bilirubin, and a decrease in platelet count occurred during AVP therapy, particularly during simultaneous hemofiltration. Initiation of AVP infusion before norepinephrine requirements exceeding 0.6 microg x kg x min may improve outcome.

Vasopressin in the ICU

PURPOSE OF THE REVIEW

Vasopressin is one of the most important endogenously released stress hormones during shock. In this review, studies published in the past year that add to our understanding of the use of vasopressin in the ICU are discussed.

RECENT FINDINGS

Endogenous vasopressin levels are inappropriately low in adults with severe sepsis but not in children with meningococcal septic shock. Vasopressin but not norepinephrine improved renal blood flow and oxygen delivery and prolonged survival in animal models of septic shock. In human vasodilatory shock, the combination of low-dose vasopressin and norepinephrine was found to be safe and effective. In humans, vasopressin can cause gastrointestinal hypoperfusion and ischemic skin lesions. In hypodynamic animal models of sepsis vasopressin compromised oxygen delivery and decreased systemic and gut blood flow.High-dose bolus vasopressin appeared promising in animal studies of hemorrhagic shock and cardiopulmonary arrest and in a large, randomized clinical trial of vasopressin versus epinephrine in human cardiopulmonary arrest with asystole. However, poor neurologic outcomes raised controversy in introducing vasopressin into CPR guidelines.

SUMMARY

There is growing evidence that vasopressin infusion in septic shock is safe and effective. Several studies published this year support the hypothesis that vasopressin should be used as a continuous low-dose infusion (between 0.01 and 0.04 U/min in adults) and not titrated as a single vasopressor agent. However, multiple studies highlight the clinical equipoise that exists regarding the use of vasopressin in vasodilatory shock. Guidelines on management of septic shock recommend "cautious use of vasopressin pending further studies."

Einsatz von Vasopressin und Terlipressin bei Sepsis und systemischen Entzündungsreaktionen

Vasopressin and terlipressin are increasingly used as alternative non-adrenergic vasopressors for hemodynamic support of septic patients with arterial hypotension. Despite excellent vasopressive effects, vasopressin analogues may potentially impair macro-hemodynamics, oxygen transport and microvascular blood flow. Due to those unwanted side-effects, vasopressin and terlipressin may potentially compromise organ function and possibly foster the development of multiple organ failure. This review article discusses the results of clinical and experimental studies to judge the effects of vasopressin and terlipressin on microcirculation, oxygen supply, metabolism and organ function in patients with sepsis or systemic inflammatory response syndrome (SIRS). Although vasopressin analogues are emerging as promising alternatives to treat catecholamine-refractory hypotension, there is no evidence that vasopressin receptor agonists improve outcome. To date, vasopressin and terlipressin can, therefore, not be recommended for routine clinical use.

Arginine vasopressin reduces intestinal oxygen supply and mucosal tissue oxygen tension

We investigated intestinal oxygen supply and mucosal tissue PO2 during administration of increasing dosages of continuously infused arginine vasopressin (AVP) in an autoperfused, innervated jejunal segments in anesthetized pigs. Mucosal tissue PO2 was measured by employing two Clark-type surface oxygen electrodes. Oxygen saturation of jejunal microvascular hemoglobin was determined by tissue reflectance spectrophotometry. Microvascular blood flow was assessed by laser-Doppler velocimetry. Systemic hemodynamic variables, mesenteric venous and systemic acid-base and blood gas variables, and lactate measurements were recorded. Measurements were performed at baseline and at 20-min intervals during incremental AVP infusion (n = 8; 0.007, 0.014, 0.029, 0.057, 0.114, and 0.229 IU.kg(-1).h(-1), respectively) or infusion of saline (n=8). AVP infusion led to a significant (P < .05), dose-dependent decrease in cardiac index (from 121 +/- 31 to 77 +/- 27 ml.kg(-1).min(-1) at 0.229 IU.kg(-1).h(-1)) and systemic oxygen delivery (from 14 +/- 3 to 9 +/- 3 ml.kg(-1).min(-1) at 0.229 IU.kg(-1).h(-1)) concomitant with an increase in systemic oxygen extraction ratio (from 31 +/- 4 to 48 +/- 10%). AVP decreased microvascular blood flow (from 133 +/- 47 to 82 +/- 35 perfusion units at 0.114 IU.kg(-1).h(-1)), mucosal tissue PO2 (from 26 +/- 7 to 7 +/- 2 mmHg at 0.229 IU.kg(-1).h(-1)), and microvascular hemoglobin oxygen saturation (from 51 +/- 9 to 26 +/- 12% at 0.229 IU.kg(-1).h(-1)) without a significant increase in mesenteric venous lactate concentration (2.3 +/- 0.8 vs. 3.4 +/- 0.7 mmol/l). We conclude that continuously infused AVP decreases intestinal oxygen supply and mucosal tissue PO2 due to a reduction in microvascular blood flow and due to the special vascular supply in the jejunal mucosa in a dose-dependent manner in pigs.

Inotropes and vasopressors in adults and foals

Successful treatment with inotropes and vasopressors depends on an understanding of the interplay of flow, pressure, and resistance in the cardiovascular system and an appreciation of the pathophysiologic mechanisms leading to inadequate tissue perfusion. Any treatment strategy is necessarily a compromise between the requirements of different vascular beds.Furthermore. the underlying hemodynamic derangements can change rapidly. Therefore. inotropes and vasopressors should be titrated to measures of improved hemodynamic status, and the treatments should be frequently reviewed.

Dopexamine Reverses the Vasopressin-Associated Impairment in Tissue Oxygen Supply but Decreases Systemic Blood Pressure in Ovine Endotoxemia

Since arginine vasopressin (AVP) may reduce cardiac output and, in proportion, oxygen delivery, we studied the efficacy of dopexamine (DPX) as an adjunct to AVP infusion. After 1 h of continuous AVP infusion (0.04 U/min) in healthy sheep (n = 7), DPX was additionally administered in incremental doses (1, 5, and 10 microg. kg(-1). min(-1); each dose for 30 min). After a 24-h period of recovery, endotoxin was continuously infused in the same sheep to induce and maintain a hypotensive/hyperdynamic circulation. After 16 h of endotoxemia, AVP and DPX were given as described previously. AVP infusion increased systemic vascular resistance index and decreased cardiac index in both healthy and endotoxemic conditions (P < 0.001 each). This was accompanied by an augmented pulmonary vascular resistance index in endotoxemia (159 +/- 13 dynes. cm(-5). m(-2) versus 202 +/- 16 dynes. cm(-5). m(-2)) and a decrease in oxygen delivery index (health: 842 +/- 66 mL. min(-2). m(-2) versus 475 +/- 38 mL. min(-2). m(-2); endotoxemia: 1073 +/- 49 mL. min(-2). m(-2) versus 613 +/- 44 mL. min(-2). m(-2)) and mixed venous oxygen content (health: 63% +/- 2% versus 47% +/- 2%; endotoxemia: 68% +/- 2% versus 51% +/- 3%; P < 0.001 each). Small doses of DPX (1 and 5 microg. kg(-1). min(-1)) improved not only the AVP-associated depressions in cardiac index, oxygen delivery index, and mixed venous oxygen content, but also the pulmonary vasopressive effect in both groups. While large-dose DPX (10 microg. kg(-1). min(-1)) also reduced mean pulmonary arterial pressure in endotoxemia (27 +/- 1 mm Hg versus 23 +/- 1 mm Hg; P < 0.05 versus baseline), mean arterial blood pressure decreased (105 +/- 4 mm Hg versus 80 +/- 3 mm Hg) and heart rate increased (84 +/- 4 bpm versus 136 +/- 9 bpm; P < 0.001 versus AVP alone), thereby limiting its therapeutic use.

Terlipressin bolus induces systemic vasoconstriction in septic shock

OBJECTIVE

To report the use of a synthetic, long-acting, vasopressin analog, terlipressin, as an effective vasoconstrictor in septic shock.

DESIGN

Case report.

SETTING

A 22-bed pediatric intensive care unit in a tertiary referral center.

PATIENT

An 11-yr-old male with multiple-organism Gram-negative septic shock with high normal cardiac output as assessed by pulse contour analysis and low systemic vascular resistance despite norepinephrine infusion.

INTERVENTION

Two peripherally administered doses of terlipressin (0.5 mg).

MEASUREMENTS AND MAIN RESULTS

Each dose of terlipressin was associated with a rapid increase in systemic vascular resistance, despite weaning and discontinuation of norepinephrine infusion from 0.15 microg.kg(-1).min(-1) lasting approximately 6 hrs.

CONCLUSION

Terlipressin may be useful for sepsis-induced vasodilation.