Endocrinologic response to vasopressin infusion in advanced vasodilatory shock

Vasopressin in septic shock: an individual patient data meta-analysis of randomised controlled trials

PURPOSE

We performed an individual patient data meta-analysis to investigate the possible benefits and harms of vasopressin therapy in adults with septic shock both overall and in pre-defined subgroups.

METHODS

Our pre-specified study protocol is published on PROSPERO, CRD42017071698. We identified randomised clinical trials up to January 2019 investigating vasopressin therapy versus any other vasoactive comparator in adults with septic shock. Individual patient data from each trial were compiled. Conventional two-stage meta-analyses were performed as well as one-stage regression models with single treatment covariate interactions for subgroup analyses.

RESULTS

Four trials were included with a total of 1453 patients. For the primary outcomes, there was no effect of vasopressin on 28-day mortality [relative risk (RR) 0.98, 95% CI 0.86-1.12] or serious adverse events (RR 1.02, 95% CI 0.82-1.26). Vasopressin led to more digital ischaemia [absolute risk difference (ARD) 1.7%, 95% CI 0.3%-3.2%] but fewer arrhythmias (ARD - 2.8%, 95% CI - 0.2% to - 5.3%). Mesenteric ischaemia and acute coronary syndrome events were similar between groups. Vasopressin reduced the requirement for renal replacement therapy (RRT) (RR 0.86, 95% CI 0.74-0.99), but this finding was not robust to sensitivity analyses. There were no statistically significant interactions in the pre-defined subgroups (baseline kidney injury severity, baseline lactate, baseline norepinephrine requirement and time to study inclusion).

CONCLUSIONS

Vasopressin therapy in septic shock had no effect on 28-day mortality although the confidence intervals are wide. It appears safe but with a different side effect profile from norepinephrine. The finding on reduced RRT should be interpreted cautiously. Future trials should focus on long-term outcomes in select patient groups as well as incorporating cost effectiveness analyses regarding possible reduced RRT use.

High prolactin levels are associated with more delirium in septic patients

PURPOSES

We investigated whether high prolactin levels were associated with delirium in septic patients because neuropsychiatric disorders are frequently associated with hyperprolactinemia.

MATERIALS AND METHODS

Prolactin levels were measured daily for 4 days in 101 patients with sepsis. Delirium was assessed using the Richmond Agitation Sedation Scale and the Confusion Assessment Method in the ICU.

RESULTS

Delirium developed in 79 patients (78%) and was more common in patients older than 65 years. Prolactin levels were higher in patients with delirium than in those without over the 4 days of observation (P = .032). In patients with delirium, higher prolactin levels were associated with a lower incidence of nosocomial infection (P = .006). Multivariable logistic regression showed that the Sequential Organ Failure Assessment score at intensive care unit admission (odds ratio, 1.24; 95% confidence interval, 1.04-1.48; P = .002) and the combined effect of prolactin levels with age (odds ratio, 1.018; 95% confidence interval, 1.01-1.031; P = .006) were associated with the development of delirium.

CONCLUSIONS

High prolactin levels may be a risk factor for delirium in septic patients.

Therapeutic applications of vasopressin in pediatric patients

CONTEXT

Reports of successful use of vasopressin in various shock states and cardiac arrest has lead to the emergence of vasopressin therapy as a potentially major advancement in the management of critically ill children.

OBJECTIVE

To provide an overview of physiology of vasopressin, rationale of its use and dose schedule in different disease states with special focus on recent advances in the therapeutic applications of vasopressin.

DATA SOURCE

MEDLINE search (1966-September 2011) using terms vasopressin, terlipressin, arginine-vasopressin, shock, septic shock, vasodilatory shock, cardiac arrest, and resuscitation for reports on vasopressin/terlipressin use in children and manual review of article bibliographies. Search was restricted to human studies. Randomized controlled trials, cohort studies, evaluation studies, case series, and case reports on vasopressin/terlipressin use in children (preterm neonates to 21 years of age) were included. Outcome measures were analysed using following clinical questions: indication, dose and duration of vasopressin/terlipressin use, main effects especially on systemic blood pressure, catecholamine requirement, urine output, serum lactate, adverse effects, and mortality.

RESULTS

51 reports on vasopressin (30 reports) and terlipressin (21 reports) use in pediatric population were identified. A total of 602 patients received vasopressin/terlipressin as vasopressors in various catecholamine-resistant states (septic - 176, post-cardiotomy - 136, other vasodilatory/mixed shock - 199, and cardiac arrest - 101). Commonly reported responses include rapid improvement in systemic blood pressure, decline in concurrent catecholamine requirement, and increase in urine output; despite these effects, the mortality rates remained high.

CONCLUSION

In view of the limited clinical experience, and paucity of randomized controlled trials evaluating these drugs in pediatric population, currently no definitive recommendations on vasopressin/terlipressin use can be laid down. Nevertheless, available clinical data supports the use of vasopressin in critically ill children as a rescue therapy in refractory shock and cardiac arrest.

Vasopressin for treatment of vasodilatory shock: an ESICM systematic review and meta-analysis

OBJECTIVE

To examine the benefits and risks of vasopressin or its analog terlipressin for patients with vasodilatory shock.

DATA SOURCE

We searched the CENTRAL, MEDLINE, EMBASE, and LILACS databases (up to March 2011) as well as reference lists of articles and proceedings of major meetings; we also contacted trial authors. We considered randomized and quasirandomized trials of vasopressin or terlipressin versus placebo or supportive treatment in adult and pediatric patients with vasodilatory shock. The primary outcome for this review was short-term all-cause mortality.

STUDY SELECTION

We identified 10 randomized trials (1,134 patients). Six studies were considered for the main analysis on mortality in adults.

DATA EXTRACTION AND SYNTHESIS

The crude short-term mortality was 206 of 512 (40.2%) in vasopressin/terlipressin-treated patients and 198 of 461 (42.9%) in controls [six trials, risk ratio (RR) = 0.91; 95% confidence interval (CI) 0.79-1.05; P = 0.21; I(2) = 0%]. There were 49 of 463 (10.6%) patients with serious adverse events in the vasopressin/terlipressin arm and 51 of 431 (11.8%) in the control arm (four trials, RR = 0.90; 95% CI 0.49-1.67; P = 0.75; I(2) = 26%). Metaregression analysis showed negative correlation between vasopressin dose and norepinephrine dose (P = 0.03).

CONCLUSIONS

Overall, use of vasopressin or terlipressin did not produce any survival benefit in the short term in patients with vasodilatory shock. Physicians may value the sparing effects of vasopressin/terlipressin on norepinephrine requirement given its apparent safe profile.

Vasopressin: Its current role in anesthetic practice

Vasopressin or antidiuretic hormone is a potent endogenous hormone, which is responsible for regulating plasma osmolality and volume. In high concentrations, it also raises blood pressure by inducing moderate vasoconstriction. It acts as a neurotransmitter in the brain to control circadian rhythm, thermoregulation and adrenocorticotropic hormone release. The therapeutic use of vasopressin has become increasingly important in the critical care environment in the management of cranial diabetes insipidus, bleeding abnormalities, esophageal variceal hemorrhage, asystolic cardiac arrest and septic shock. After 10 years of ongoing research, vasopressin has grown to a potential component as a vasopressor agent of the anesthesiologist's armamentarium in the treatment of cardiac arrest and severe shock states.

The cellular mechanisms underlying the inhibitory effects of isoflurane and sevoflurane on arginine vasopressin-induced vasoconstriction

PURPOSE

Arginine vasopressin (AVP) is a potent vasoconstrictor that is sometimes used for the treatment of refractory vasodilatory shock. AVP constricts vascular smooth muscle by increasing both intracellular calcium concentration ([Ca(2+)](i)) and myofilament Ca(2+) sensitivity. However, the modulation of AVP-mediated vasoconstriction by volatile anesthetics remains to be determined. This study investigates the effects of isoflurane and sevoflurane on AVP-induced vasoconstriction and elucidates the underlying mechanisms, with an emphasis on the Ca(2+)-mediated pathways and Ca(2+) sensitization pathways of rat aortic smooth muscle.

METHODS

The effects of isoflurane and sevoflurane on AVP-induced vasoconstriction and on the AVP-induced increase in [Ca(2+)](i) and Rho activity in rat aorta were investigated by isometric force recording, by measuring [Ca(2+)](i) using fluorescence dye, and by Western blotting techniques.

RESULTS

Arginine vasopressin (10⁻⁷M) elicited a transient contractile response that was inhibited by isoflurane and sevoflurane in a concentration-dependent manner. AVP (10⁻⁷ M) induced a transient increase in intracellular Ca(2+) concentration ([Ca(2+)](i)). Isoflurane and sevoflurane also inhibited an AVP-induced increase in [Ca(2+)](i) in a concentration-dependent manner. AVP (10⁻⁷ M) increased the Rho activity that was attenuated by 2 minimum alveolar concentration of sevoflurane (P < 0.01), but not by an equipotent concentration of isoflurane.

CONCLUSION

Arginine vasopressin-induced vasoconstriction is mediated by an increase in [Ca(2+)](i) and by the activation of the Rho-Rho kinase pathway in rat aortic smooth muscle. Although both isoflurane and sevoflurane, at clinically relevant concentrations, attenuate AVP-induced contraction, the cellular mechanisms of their inhibitory effects appear to differ.

Proven infection-related sepsis induces a differential stress response early after ICU admission

INTRODUCTION

Neuropeptides arginine-vasopressin (AVP), apelin (APL), and stromal-derived factor-1α (SDF-1α) are involved in the dysfunction of the corticotropic axis observed in septic ICU patients. Study aims were: (i) to portray a distinctive stress-related neuro-corticotropic systemic profile of early sepsis, (ii) to propose a combination data score, for aiding ICU physicians in diagnosing sepsis on admission.

METHODS

This prospective one-center observational study was carried out in a medical intensive care unit (MICU), tertiary teaching hospital. Seventy-four out of 112 critically ill patients exhibiting systemic inflammatory response syndrome (SIRS) were divided into two groups: proven sepsis and non sepsis, based on post hoc analysis of microbiological criteria and final diagnosis, and compared to healthy volunteers (n = 14). A single blood sampling was performed on admission for measurements of AVP, copeptin, APL, SDF-1α, adrenocorticotropic hormone (ACTH), cortisol baseline and post-stimulation, and procalcitonin (PCT).

RESULTS

Blood baseline ACTH/cortisol ratio was lower and copeptin higher in septic vs. nonseptic patients. SDF-1α was further increased in septic patients vs. normal patients. Cortisol baseline, ACTH, PCT, APACHE II and sepsis scores, and shock on admission, were independent predictors of sepsis diagnosis upon admission. Using the three first aforementioned categorical bio-parameters, a probability score for predicting sepsis yielded an area under the Receiver Operating Curve (ROC) curves better than sepsis score or PCT alone (0.903 vs 0.727 and 0.726: P = 0.005 and P < 0.04, respectively).

CONCLUSIONS

The stress response of early admitted ICU patients is different in septic vs. non-septic conditions. A proposed combination of variable score analyses will tentatively help in refining bedside diagnostic tools to efficiently diagnose sepsis after further validation.

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.

The vasopressin and copeptin response to infection, severe sepsis, and septic shock

OBJECTIVE

To compare the course of arginine vasopressin (AVP) and copeptin plasma concentrations between patients with infection, severe sepsis, and septic shock.

DESIGN

Prospective, closed-cohort study.

SETTING

Twelve-bed general and surgical intensive care unit and 33-bed internal medicine ward in a university hospital.

PATIENTS

Ten patients with infection, 22 with severe sepsis, and 28 with septic shock.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Hemodynamic, laboratory and clinical data were recorded daily during the first 7 days after intensive care unit or hospital admission. Parallel thereto, blood was withdrawn to determine plasma AVP (radioimmunoassay) and copeptin (immunoluminometric assay) concentrations. Standard tests, a mixed effects model, and a linear regression analysis were used for statistical analysis. The AVP response was different between the three study groups (p < 0.001) but did not change over time (p = 0.12). Although patients with severe sepsis and septic shock had higher AVP levels than did patients with infection (both p < 0.001), no difference in AVP concentrations was seen between severe sepsis and septic shock patients (p = 0.98). No difference in AVP was observed between survivors and nonsurvivors at day 28 (p = 0.87). In patients with severe sepsis, serum osmolarity (p < 0.001), arterial pH (p = 0.001), lactate (p < 0.001), and Pao2 (p = 0.04) were associated with the course of AVP plasma levels, whereas it was serum osmolarity alone in patients with septic shock (p = 0.03). Plasma AVP concentrations correlated with copeptin (r = .614, p < 0.001), but this correlation was influenced by continuous veno-venous hemofiltration (p = 0.002).

CONCLUSIONS

Severe sepsis induced a stronger AVP response than infection without systemic inflammation. However, the lack of a difference in AVP plasma concentrations between patients with and without shock indicates that the AVP system does not function normally in severe sepsis. Our data support the hypothesis that impaired AVP response is at least partially responsible for the failure to restore vascular tone in septic shock.

Interaction of vasopressin infusion, corticosteroid treatment, and mortality of septic shock

OBJECTIVE

Vasopressin and corticosteroids are often added to support cardiovascular dysfunction in patients who have septic shock that is nonresponsive to fluid resuscitation and norepinephrine infusion. However, it is unknown whether vasopressin treatment interacts with corticosteroid treatment.

DESIGN

Post hoc substudy of a multicenter randomized blinded controlled trial of vasopressin vs. norepinephrine in septic shock.

SETTING

Twenty-seven Intensive Care Units in Canada, Australia, and the United States.

PATIENTS

: Seven hundred and seventy-nine patients who had septic shock and were ongoing hypotension requiring at least 5 microg/min of norepinephrine infusion for 6 hours.

INTERVENTIONS

Patients were randomized to blinded vasopressin (0.01-0.03 units/min) or norepinephrine (5-15 microg/min) infusion added to open-label vasopressors. Corticosteroids were given according to clinical judgment at any time in the 28-day postrandomization period.

MEASUREMENTS

The primary end point was 28-day mortality. We tested for interaction between vasopressin treatment and corticosteroid treatment using logistic regression. Secondary end points were organ dysfunction, use of open-label vasopressors and vasopressin levels.

MAIN RESULTS

There was a statistically significant interaction between vasopressin infusion and corticosteroid treatment (p = 0.008). In patients who had septic shock and were also treated with corticosteroids, vasopressin, compared to norepinephrine, was associated with significantly decreased mortality (35.9% vs. 44.7%, respectively, p = 0.03). In contrast, in patients who did not receive corticosteroids, vasopressin was associated with increased mortality compared with norepinephrine (33.7% vs. 21.3%, respectively, p = 0.06). In patients who received vasopressin infusion, use of corticosteroids significantly increased plasma vasopressin levels by 33% at 6 hours (p = 0.006) to 67% at 24 hours (p = 0.025) compared with patients who did not receive corticosteroids.

CONCLUSIONS

There is a statistically significant interaction between vasopressin and corticosteroids. The combination of low-dose vasopressin and corticosteroids was associated with decreased mortality and organ dysfunction compared with norepinephrine and corticosteroids.

Vasopressin in the pediatric cardiac intensive care unit: Myth or reality

Pediatric cardiac surgery is undergoing a metamorphosis, with more and more critical patients being operated in our country today. Although the principles of physiology have not changed, it is imperative that care providers continue to stay abreast with developments and newer drugs that may help modify the outcome. The team dynamics have also become more complex, which necessitates the need for all care providers (surgeons, cardiologists, anesthesiologists, and intensivists) to better understand the interactions and benefits of newer drugs. Vasopressin has been used in our adult patients for more than a decade and recently has found its rightful place in the pediatric armoury. The objective of this article is to review the physiology of vasopressin and the rationale of its use in critically ill children with shock, in context of the available published data.

Vasopressin in pediatric shock and cardiac arrest

OBJECTIVE

To review the physiology and the published literature on the role of vasopressin in shock in children.

DATA SOURCE

We searched MEDLINE (1966-2007), EMBASE (1980-2007), and the Cochrane Library, using the terms vasopressin, terlipressin, and shock and synonyms or related terms for relevant studies in pediatrics. We searched the online ISRCTN-Current Controlled Trials registry for ongoing trials. We reviewed the reference lists of all identified studies and reviews as well as personal files to identify other published studies.

RESULTS

Beneficial effects have been reported in vasodilatory shock and asystolic cardiac arrest in adults. Solid evidence for vasopressin use in children is scant. Observational studies have reported an improvement in blood pressure and rapid weaning off catecholamines during administration of low-dose vasopressin. Dosing in children is extrapolated from adult studies.

CONCLUSIONS

Vasopressin offers promise in shock and cardiac arrest in children. However, in view of the limited experience with vasopressin, it should be used with caution. Results of a double-blind, randomized controlled trial in children with vasodilatory shock will be available soon.

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.

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.

Selecting a Vasopressor Drug for Vasoplegic Shock After Adult Cardiac Surgery: A Systematic Literature Review

The choice of vasopressors to treat vasodilatory shock after cardiac surgery is a matter of controversy. We have systematically reviewed the literature and found that the data are insufficient to guide choice of agent. However, we found sufficient evidence that when a target blood pressure can not be achieved with a single agent, addition of another is more likely to help achieve the blood pressure target. We also found that there is no evidence that vasopressors induce organ ischemia. Finally, the lack of high quality data indicate that large multicenter trials are needed in this field.

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

BACKGROUND

Vasopressin is essential for cardiovascular homeostasis, acting via the kidney to regulate water resorption, on the vasculature to regulate smooth muscle tone, and as a central neurotransmitter, modulating brainstem autonomic function. Although it is released in response to stress or shock states, a relative deficiency of vasopressin has been found in prolonged vasodilatory shock, such as is seen in severe sepsis. In this circumstance, exogenous vasopressin has marked vasopressor effects, even at doses that would not affect blood pressure in healthy individuals. These two findings provide the rationale for the use of vasopressin in the treatment of septic shock. However, despite considerable research attention, the mechanisms for vasopressin deficiency and hypersensitivity in vasodilatory shock remain unclear.

OBJECTIVE

To summarize vasopressin's synthesis, physiologic roles, and regulation and then review the literature describing its vascular receptors and downstream signaling pathways. A discussion of potential mechanisms underlying vasopressin hypersensitivity in septic shock follows, with reference to relevant clinical, in vivo, and in vitro experimental evidence.

DATA SOURCE

Search of the PubMed database (keywords: vasopressin and receptors and/or sepsis or septic shock) for articles published in English before May 2006 and manual review of article bibliographies.

DATA SYNTHESIS AND CONCLUSIONS

The pathophysiologic mechanism underlying vasopressin hypersensitivity in septic shock is probably multifactorial. It is doubtful that this phenomenon is merely the consequence of replacing a deficiency. Changes in vascular receptors or their signaling and/or interactions between vasopressin, nitric oxide, and adenosine triphosphate-dependent potassium channels are likely to be relevant. Further translational research is required to improve our understanding and direct appropriate educated clinical use of vasopressin.

Axial heterogeneity of vasopressin-receptor subtypes along the human and mouse collecting duct

Vasopressin and vasopressin antagonists are finding expanded use in mouse models of disease and in clinical medicine. To provide further insight into the physiological role of V1a and V2 vasopressin receptors in the human and mouse kidney, intrarenal localization of the receptors mRNA was determined by in situ hybridization. V2-receptor mRNA was predominantly expressed in the medulla, whereas mRNA for V1a receptors predominated in the cortex. The segmental localization of vasopressin-receptor mRNAs was determined using simultaneous in situ hybridization and immunohistochemistry for segment-specific markers, including aquaporin-2, Dolichos biflorus agglutinin, epithelial Na channels, Tamm Horsfall glycoprotein, and thiazide-sensitive Na+-Cl−cotransporter. Notably, V1a receptor expression was exclusively expressed in V-ATPase/anion exchanger-1-labeled alpha-intercalated cells of the medullary collecting duct in both mouse and human kidney. In cortical collecting ducts, V1a mRNA was more widespread and detected in both principal and intercalated cells. V2-receptor mRNA is diffusely expressed along the collecting ducts in both mouse and human kidney, with higher expression levels in the medulla. These results demonstrate heterogenous axial expression of both V1a and V2 vasopressin receptors along the human and mouse collecting duct. The restricted expression of V1a-receptor mRNA in intercalated cells suggests a role for this receptor in acid-base balance. These findings further suggest distinct regulation of renal transport function by AVP through V1a and V2 receptors in the cortex vs. the medulla.

Vasopressin during cardiopulmonary resuscitation and different shock states: a review of the literature

Vasopressin administration may be a promising therapy in the management of various shock states. In laboratory models of cardiac arrest, vasopressin improved vital organ blood flow, cerebral oxygen delivery, the rate of return of spontaneous circulation, and neurological recovery compared with epinephrine (adrenaline). In a study of 1219 adult patients with cardiac arrest, the effects of vasopressin were similar to those of epinephrine in the management of ventricular fibrillation and pulseless electrical activity; however, vasopressin was superior to epinephrine in patients with asystole. Furthermore, vasopressin followed by epinephrine resulted in significantly higher rates of survival to hospital admission and hospital discharge. The current cardiopulmonary resuscitation guidelines recommend intravenous vasopressin 40 IU or epinephrine 1mg in adult patients refractory to electrical countershock. Several investigations have demonstrated that vasopressin can successfully stabilize hemodynamic variables in advanced vasodilatory shock. Use of vasopressin in vasodilatory shock should be guided by strict hemodynamic indications, such as hypotension despite norepinephrine (noradrenaline) dosages >0.5 mug/kg/min. Vasopressin must never be used as the sole vasopressor agent. In our institutional routine, a fixed vasopressin dosage of 0.067 IU/min (i.e. 100 IU/50 mL at 2 mL/h) is administered and mean arterial pressure is regulated by adjusting norepinephrine infusion. When norepinephrine dosages decrease to 0.2 microg/kg/min, vasopressin is withdrawn in small steps according to the response in mean arterial pressure. Vasopressin also improved short- and long-term survival in various porcine models of uncontrolled hemorrhagic shock. In the clinical setting, we observed positive effects of vasopressin in some patients with life-threatening hemorrhagic shock, which had no longer responded to adrenergic catecholamines and fluid resuscitation. Clinical employment of vasopressin during hemorrhagic shock is experimental at this point in time.

Arginine vasopressin as a rescue vasopressor agent in the operating room

PURPOSE OF REVIEW

This review gives an overview of the current knowledge and research on the use of arginine vasopressin in cardiac arrest and severe shock states.

RECENT FINDINGS

Animal models have revealed the effectiveness of arginine vasopressin in increasing vital organ perfusion during cardiopulmonary resuscitation. A multicentre trial compared arginine vasopressin and epinephrine in out-of-hospital cardiac arrest, and documented a significant improvement in hospital discharge rates in arginine vasopressin-treated (up to 2 x 40 IU) patients with asystole, and a significant benefit of the combined administration of arginine vasopressin and epinephrine on hospital discharge, irrespective of the underlying electrocardiographic rhythm. The stabilization of advanced shock states unresponsive to conventional therapy can be achieved by supplementary arginine vasopressin (1-4 IU/h). A randomized, controlled trial found that the combined infusion of arginine vasopressin and norepinephrine was superior to norepinephrine alone in reversing advanced vasodilatory shock. Furthermore, the successful employment of arginine vasopressin in uncontrolled haemorrhagic shock and other shock states, such as anaphylaxis, hypotension during spinal/epidural anaesthesia, postcardiotomy shock, acute brain injury, brain-dead organ donors, perioperative hypotension in patients chronically treated with angiotensin-converting enzyme inhibitors, shock after pheochromocytoma surgery, and carcinoid crisis have been reported.

SUMMARY

Whereas arginine vasopressin in combination with epinephrine can significantly increase hospital discharge in cardiac arrest, arginine vasopressin combined with catecholamines improved haemodynamics in vasodilatory and haemorrhagic shock, but effects on outcome remain unknown. Nonetheless, in the perioperative setting, arginine vasopressin may already be considered as a potent adjunct vasopressor agent in advanced shock states unresponsive to conventional therapy.

Vasopressin in Hypotensive and Shock States

Clinical reports and experimental studies support the beneficial effects of low-dose vasopressin infusions in vasodilatory shock. Before we can recommend vasopressin for routine clinical use in vasodilatory shock, and particularly septic shock, we must await the results of currently ongoing and recently completed randomized clinical trials to ensure that vasopressin does indeed have beneficial effects on organ function and outcome.

Serum vasopressin concentrations in critically ill patients*

OBJECTIVE

To measure arginine vasopressin (AVP) serum concentrations in critically ill patients.

DESIGN

Prospective study.

SETTING

Twelve-bed general and surgical intensive care unit in a tertiary, university teaching hospital.

PATIENTS

Two-hundred-thirty-nine mixed critically ill patients and 70 healthy volunteers.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Demographic data, hemodynamic variables, vasopressor drug requirements, blood gases, AVP serum concentrations within 24 hrs after admission, multiple organ dysfunction score, and outcome were recorded. Twenty-four hours after admission, study patients had significantly higher AVP concentrations (11.9 +/- 20.6 pg/mL) than healthy controls (0.92 +/- 0.38 pg/mL; p < .001). Males had lower AVP concentrations than females (9.7 +/- 19.5 vs. 15.1 +/- 20.6 pg/mL; p = .014). Patients with hemodynamic dysfunction had higher AVP concentrations than patients without hemodynamic dysfunction (14.1 +/- 27.1 vs. 8.7 +/- 10.8 pg/mL; p = .042). Patients after cardiac surgery (n = 96) had significantly higher AVP concentrations when compared to patients admitted for other diagnoses (n = 143; p < .001). AVP concentrations were inversely correlated with length of stay in the intensive care unit (correlation coefficient, -0.222; p = .002). There was no correlation between serum AVP concentrations and the incidence of shock or specific hemodynamic parameters. Four (1.7%) of the 239 study patients met criteria for an absolute AVP deficiency (AVP, <0.83 pg/mL), and 32 (13.4%) met criteria for a relative AVP deficiency (AVP, <10 pg/mL, and mean arterial pressure, <70 mm Hg). In shock patients, relative AVP deficiency occurred in 22.2% (septic shock), 15.4% (postcardiotomy shock), and 10% (shock due to a severe systemic inflammatory response syndrome) (p = .316).

CONCLUSIONS

AVP serum concentrations 24 hrs after intensive care unit admission were significantly increased in this mixed critically ill patient population. The lack of a correlation between AVP serum concentrations and hemodynamic parameters suggests complex dysfunction of the vasopressinergic system in critical illness. Relative and absolute AVP deficiency may be infrequent entities during acute surgical critical illness, mostly remaining without significant effects on cardiovascular function.

Dear vasopressin, where is your place in septic shock?

Cardiovascular failure is one of the central therapeutic problems in patients with severe infection. Although norepinephrine is a potent and, in most cases, highly effective vasopressor agent, very high dosages leading to significant side effects can be necessary to stabilize advanced shock. As a supplementary vasopressor, arginine vasopressin can reverse hemodynamic failure and significantly decrease norepinephrine dosages. Whether the promising possibility of 'bridging' advanced septic shock when the benefit/risk ratio of catecholamine therapy leaves a clinically tolerable range may improve quantitative and qualitative patient outcome can only be determined by a large, prospective, randomized study.