Hemodynamic and metabolic effects of low-dose vasopressin infusions in vasodilatory septic shock

Chemokine receptor hetero-oligomers regulate monocyte chemotaxis

It is known that stress influences immune cell function. The underlying molecular mechanisms are unclear. We recently reported that many chemokine receptors (CRs) heteromerize with α1-adrenoceptors (α1-ARs) through which CRs are regulated. Here, we show that arginine vasopressin receptor 1A (AVPR1A) heteromerizes with all human CRs, except chemokine (C-X-C motif) receptor (CXCR)1, in recombinant systems and that such heteromers are detectable in THP-1 cells and human monocytes. We demonstrate that ligand-free AVPR1A differentially regulates the efficacy of CR partners to mediate chemotaxis and that AVPR1A ligands disrupt AVPR1A:CR heteromers, which enhances chemokine (C-C motif) receptor (CCR)1-mediated chemotaxis and inhibits CCR2-, CCR8-, and CXCR4-mediated chemotaxis. Using bioluminescence resonance energy transfer to monitor G protein activation and CRISPR/Cas9 gene-edited THP-1 cells lacking AVPR1A or α1B-AR, we show that CRs that share the propensity to heteromerize with α1B/D-ARs and AVPR1A exist and function within interdependent hetero-oligomeric complexes through which the efficacy of CRs to mediate chemotaxis is controlled. Our findings suggest that hetero-oligomers composed of CRs, α1B/D-ARs, and AVPR1A may enable stress hormones to regulate immune cell trafficking.

Treatment of Acute Kidney Injury: A Review of Current Approaches and Emerging Innovations

Acute kidney injury (AKI) is a complex and life-threatening condition with multifactorial etiologies, ranging from ischemic injury to nephrotoxic exposures. Management is founded on treating the underlying cause of AKI, but supportive care-via fluid management, vasopressor therapy, kidney replacement therapy (KRT), and more-is also crucial. Blood pressure targets are often higher in AKI, and these can be achieved with fluids and vasopressors, some of which may be more kidney-protective than others. Initiation of KRT is controversial, and studies have not consistently demonstrated any benefit to early start dialysis. There are no targeted pharmacotherapies for AKI itself, but some do exist for complications of AKI; additionally, medications become a key aspect of AKI management because changes in renal function and dialysis support can lead to issues with both toxicities and underdosing. This review will cover existing literature on these and other aspects of AKI treatment. Additionally, this review aims to identify gaps and challenges and to offer recommendations for future research and clinical practice.

Acute Hemodynamics in the Fontan Circulation: Open-Label Study of Vasopressin

OBJECTIVE

To describe the acute hemodynamic effect of vasopressin on the Fontan circulation, including systemic and pulmonary pressures and resistances, left atrial pressure, and cardiac index.

DESIGN

Prospective, open-label, nonrandomized study (NCT04463394).

SETTING

Cardiac catheterization laboratory at Lucile Packard Children's Hospital, Stanford.

PATIENTS

Patients 3-50 years old with a Fontan circulation who were referred to the cardiac catheterization laboratory for hemodynamic assessment and/or intervention.

INTERVENTIONS

A 0.03 U/kg IV (maximum dose 1 unit) bolus of vasopressin was administered over 5 minutes, followed by a maintenance infusion of 0.3 mU/kg/min (maximum dose 0.03 U/min).

MEASUREMENTS AND MAIN RESULTS

Comprehensive cardiac catheterization measurements before and after vasopressin administration. Measurements included pulmonary artery, atrial, and systemic arterial pressures, oxygen saturations, and systemic and pulmonary flows and resistances. There were 28 patients studied. Median age was 13.5 (9.1, 17) years, and 16 (57%) patients had a single or dominant right ventricle. Following vasopressin administration, systolic blood pressure and systemic vascular resistance (SVR) increased by 17.5 (13.0, 22.8) mm Hg ( Z value -4.6, p < 0.001) and 3.8 (1.8, 7.5) Wood Units ( Z value -4.6, p < 0.001), respectively. The pulmonary vascular resistance (PVR) decreased by 0.4 ± 0.4 WU ( t statistic 6.2, p < 0.001), and the left atrial pressure increased by 1.0 (0.0, 2.0) mm Hg ( Z value -3.5, p < 0.001). The PVR:SVR decreased by 0.04 ± 0.03 ( t statistic 8.1, p < 0.001). Neither the pulmonary artery pressure (median difference 0.0 [-1.0, 1.0], Z value -0.4, p = 0.69) nor cardiac index (0.1 ± 0.3, t statistic -1.4, p = 0.18) changed significantly. There were no adverse events.

CONCLUSIONS

In Fontan patients undergoing cardiac catheterization, vasopressin administration resulted in a significant increase in systolic blood pressure, SVR, and left atrial pressure, decrease in PVR, and no change in cardiac index or pulmonary artery pressure. These findings suggest that in Fontan patients vasopressin may be an option for treating systemic hypotension during sedation or general anesthesia.

Running from a Bear: How We Teach Vasopressors, Adrenoreceptors, and Shock

Vasopressors are widely used in the management of shock among critically ill patients. The physiology of vasopressors and adrenoreceptors and their effects on end organs therefore represent important, high-yield topics for learners in the critical care environment. In this report, we describe our approach to teaching this core concept using the stereotypical human physiologic response when running from a bear, in the context of the relevant supporting literature. We use escaping from a threatening predator as a lens to describe the end-organ effects of activating adrenoreceptors together with the effects of endogenous and exogenous catecholamines and vasopressors. After reviewing this foundational physiology, we transition to the clinical environment, reviewing the pathophysiology of various shock states. We then consolidate our teaching by integrating the physiology of adrenoreceptors with the pathophysiology of shock to understand the appropriateness of each therapy to various shock phenotypes. We emphasize to learners the importance of generating a hypothesis about a patient's physiology, testing that hypothesis with an intervention, and then revising the hypothesis as needed, a critical component in the management of critically ill patients.

Refractory septic shock and alternative wordings: A systematic review of literature

BACKGROUND

We reviewed the different studies using the terms "refractory septic shock" and/or "catecholamine resistance" and/or "high dose norepinephrine" so as to highlight the heterogeneity of the definitions used by authors addressing such concepts.

METHOD

A systematic review was conducted assessing the papers reporting data on refractory septic shock. We used keywords as exact phrases and subject headings according to database syntax.

RESULTS

Of 276 papers initially reviewed, we included 8 studies - 3 randomized controlled trials, 3 prospective studies and 2 retrospective studies, representing a total of 562 patients with septic shock. Catecholamine resistance was generally defined as "a decreased vascular responsiveness to catecholamine independently of the administered norepinephrine dose". Refractory septic shock was broadly defined as "a clinical condition characterized by persistent hyperdynamic shock even though adequate fluid resuscitation (individualized doses) and high doses of norepinephrine (≥ 1 μg/kg/min)". Reported "high doses" of norepinephrine were often ≥1 μg/kg/min. However, wide variability was found throughout the literature on the use of these terms.

DISCUSSION

Marked inconsistencies were identified in the usage of the terms for refractory septic shock. There is a pressing need to determine consensus definitions so as to establish a common language in the medical literature and to harmonize future studies.

Norepinephrine vs Vasopressin: Which Vasopressor Should Be Discontinued First in Septic Shock? A Meta-Analysis

BACKGROUND

Patients with septic shock in whom norepinephrine (NE) infusion alone is insufficient to raise blood pressure require the concomitant administration of vasopressin (VP). However, current guidelines do not advise clinicians as to which vasoactive agent to discontinue first once the patient's septic shock begins to resolve. Moreover, there is controversial data guiding clinicians on how to discontinue vasopressors for septic shock patients who are receiving a combination therapy of NE and VP.

METHODS

The PubMed, EMBASE, and Cochrane Central Register databases were searched from the database inception until October 18, 2018. Studies were limited to adult patients with septic shock who received concomitant NE and VP treatment, that included different orders of vasopressor discontinuation. The primary outcome was the incidence of hypotension. Overall mortality, ICU mortality, and length of stay (LOS) in the ICU were secondary outcomes. Sensitivity and subgroup analyses as well as trial sequential analysis were performed.

RESULTS

One prospective randomized controlled trial and seven retrospective cohort studies were included in present meta-analysis. Compared with discontinuing VP first, the incidence of hypotension was significantly lower when NE was discontinued first (odds ratio, OR 0.3, 95% confidence interval, CI 0.10 to 0.86, P = 0.02; I = 91%). No significant difference was detected in either overall mortality (OR 1.28, 95% CI 0.77 to 2.10, P = 0.34) or ICU mortality (OR 0.99, 95% CI 0.74 to 1.34, P = 0.96) between these two groups. Furthermore, ICU LOS was also evaluated in five studies, and no statistical significance was observed between the two groups with different orders in weaning vasopressors (mean difference 1.35, 95% CI -2.05 to 4.74, P = 0.44). The subgroup analyses suggested a significant association between hypotension and the practice of discontinuing VP first specifically in patients with a low usage rate of corticosteroids (odds ratio, OR 0.18, 95% confidence interval, CI 0.04 to 0.78, P = 0.02). The trial sequential analysis indicated a lack of sufficient evidence to draw conclusions from the current results (required information size  = 11 821).

CONCLUSIONS

In adults with septic shock treated with concomitant VP and NE therapy, discontinuing VP first may lead to a higher incidence of hypotension but is not associated with mortality or ICU LOS. Further prospective studies with larger sample sizes are warranted.

Efficacy and safety of vasopressin and terlipressin in preterm neonates: a protocol for a systematic review

BACKGROUND

The use of vasoactive agents like arginine vasopressin (AVP) and terlipressin to treat hypotension or persistent pulmonary hypertension in critically ill preterm neonates is increasing. Therefore, a systematic review of the available data on dosing, efficacy and safety of AVP and terlipressin in this patient population appears beneficial.

METHODS

We will conduct a systematic review of the available evidence on the use of AVP and terlipressin for the treatment of hypotension or persistent pulmonary hypertension in preterm neonates. We will search Ovid MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, Web of Science and Google Scholar from inception to March 2021. Two reviewers will independently screen titles and abstracts, review the full text of eligible studies, extract data, assess the risk of bias and judge the certainty of the evidence. Our primary outcome will be an (1) improvement of end-organ perfusion after initiation of AVP or terlipressin and (2) mortality prior to discharge. Our secondary outcomes will include (1) major neurosensory abnormality and (2) the occurrence of adverse events.

DISCUSSION

The currently available evidence on the efficacy and safety of AVP and terlipressin in preterm neonates is limited. Yet, evidence on the pharmacology of these drugs and the pathophysiology of vasoplegic shock support the biological plausibility for their clinical effectiveness in this population. Therefore, we aim to address this gap concerning the use of vasopressin and terlipressin among critically ill preterm neonates.

TRIAL REGISTRATION

This protocol has been submitted for registration to the international database of prospectively registered systematic reviews (PROSPERO, awaiting registration number).

Vasopressin for Septic Shock in a Medical-Surgical Intensive Care Unit

BACKGROUND

Critically ill patients often need vasopressors to treat hypotension related to septic shock and to maintain adequate systemic perfusion. Although the 2017 guidelines of the Surviving Sepsis Campaign recommend norepinephrine as first-line therapy, they also state that vasopressin may be considered as an adjunctive agent for patients with refractory shock. Limited evidence is available for directing optimal administration of vasopressin. As such, prescribing practices are not standardized and may vary according to the particular clinician, the clinical scenario, and various patient-specific factors.

OBJECTIVES

To review the current practice of administering concomitant norepinephrine and vasopressin therapy to patients with septic shock, to describe variability in vasopressin administration, and to evaluate effects on patient safety in a medical-surgical intensive care unit (ICU).

METHODS

This single-centre retrospective chart review involved 100 adult patients admitted to the ICU who received vasopressin and norepinephrine for septic shock between April and December 2017. The data were analyzed with descriptive statistics.

RESULTS

The mean time to initiation of vasopressin was 12.0 (standard deviation [SD] 21.6) h after initiation of norepinephrine. The mean dose of norepinephrine at the time of vasopressin initiation was 29.5 (SD 19.7) μg/min. The mean vasopressin dose prescribed was 0.04 (SD 0.03) units/min, with a range of tapering and discontinuation regimens. The mean duration of vasopressin therapy was 49.1 (SD 65.2) h, and vasopressin was discontinued before norepinephrine in 49 of the patients. A total of 60 hypotensive events occurred after vasopressor discontinuation and were more common when vasopressin was discontinued before norepinephrine.

CONCLUSIONS

Vasopressin dosing was comparable to that reported elsewhere; however, discontinuation practices were inconsistent. These results show that variability in the literature supporting vasopressin use has led to variability in vasopressin administration and discontinuation practices; however, correlation with improvement in clinical outcomes, such as mortality or ICU length of stay, is unclear, and further research is required to determine the ideal approach to vasopressin use.

Incidence of Hypotension after Discontinuation of Norepinephrine or Arginine Vasopressin in Patients with Septic Shock: a Systematic Review and Meta-Analysis

BACKGROUND

There has been no consensus regarding the discontinuation order of vasopressors in patients recovering from septic shock treated with concomitant norepinephrine (NE) and arginine vasopressin (AVP). The aim of this study was to compare the incidence of hypotension within 24 hours based on whether NE or AVP was discontinued first in order to determine the optimal sequence for discontinuation of vasopressors.

METHODS

A systematic literature search was conducted in MEDLINE, Embase, and the Cochrane Central Register. The primary end-point was incidence of hypotension within 24 hours after discontinuation of the first vasopressor.

RESULTS

We identified five studies comprising 930 patients, of whom 631 (67.8%) discontinued NE first and 299 (32.2%) discontinued AVP first. In pooled estimates, a random-effect model showed that discontinuation of NE first was associated with a significant reduction of the incidence of hypotension compared to discontinuing AVP first (31.8% vs. 54.8%; risk ratios, 0.35; 95% confidence interval, 0.16 to 0.76; P = 0.008; I² = 90.7%). Although a substantial degree of heterogeneity existed among the trials, we could not identify the significant source of bias. In addition, there were no significant differences in intensive care unit (ICU) mortality, in-hospital mortality, 28-day mortality, or ICU length of stay between the groups.

CONCLUSION

Discontinuing NE prior to AVP was associated with a lower incidence of hypotension in patients recovering from septic shock. However, our results should be interpreted with caution, due to the considerable between-study heterogeneity.

Effect of Low-Dose Vasopressin Infusion on Vital Organ Blood Flow in the Conscious Normal and Septic Sheep

The effect of low-dose vasopressin (AVP) on vital regional circulations may be clinically relevant but has not been fully described. We sought to determine the effect of low-dose AVP on systemic haemodynamics, coronary, mesenteric and renal circulations in the conscious normal and septic mammal.

We studied seven Merino sheep using a prospective randomized cross-over double-blind placebo-controlled animal design. We inserted flow probes around aorta, coronary, mesenteric and renal arteries and, three weeks later, we infused low-dose AVP (0.02 IU/min) or placebo in the normal and septic state induced by intravenous E.coli. In normal sheep, AVP (0.02 IU/min) induced a 17% decrease in mesenteric blood flow (393.0±134.9 vs 472.1± 163.8 ml/min, P<0.05) and a 14% decrease in mesenteric conductance (P<0.05). In septic sheep, AVP decreased heart rate and cardiac output by 28% and 22%, respectively (P<0.05). It also decreased mesenteric blood flow and mesenteric conductance by 23% (flow: 468.5±159.7 vs 611.3±136.3 ml/min, P<0.05; conductance: 6.3±2.7 vs 8.2±2.7 ml/min/mmHg; P<0.05). Renal blood flow was unchanged but urine output and creatinine clearance increased (P<0.05). We conclude that low-dose AVP infusion has similar effects in the normal and septic mammalian circulation: bradycardia, decreased cardiac output, decreased mesenteric blood flow and conductance and increased urine output and creatinine clearance. This information is important to clinicians considering its administration in humans.

Vasopressin vs noradrenaline: Have we found the perfect recipe to improve outcome in septic shock?

PURPOSE

The metabolic and circulatory disturbances in patients with septic shock results in a high mortality rate. There is a lack of high-level evidence on the optimal approach. We present a meta-analysis elucidating the outcomes of regimes with only noradrenaline versus a combination of noradrenaline and vasopressin in managing septic shock.

METHODS

A literature search of studies comparing the use of noradrenaline and vasopressin in septic shock was conducted, using MEDLINE and EMBASE databases. The primary outcome evaluated was mortality rate. Subgroup analysis of secondary measures was also conducted using Review Manager 5.3 software.

RESULTS

Four RCTs of 1039 patients were included. There is good evidence supporting a comparable mortality rate (RR: 0.92, 95% CI: 0.78, 1.08, p = .32, I² = 0%), and moderate evidence supporting an equivalent length of ICU stay (MD: 0.14, 95% CI: -1.37, 1.65, p = .86, I² = 46%) and occurrence of adverse events (RR: 1.19, 95% CI: 0.83, 1.70, p = .35, I² = 13%) between the two cohorts.

CONCLUSION

The two regimes have equivalent outcomes, but vasopressin has a role in selected patients experiencing less severe septic shock beyond a 36-h period. Further work will make definitive clinical recommendations for optimal strategy of vasopressin or noradrenaline usage.

Vasopressin Administration Is Associated With Rising Serum Lactate Levels in Patients With Sepsis

BACKGROUND

Vasopressin is used in conjunction with norepinephrine during treatment of patients with septic shock. Serum lactate is often used in monitoring of patients with sepsis; however, its importance as a therapeutic target is unclear. The objective of this study is to examine the relationship of vasopressin use on serum lactate levels in patients with sepsis.

METHODS

This study uses electronic heath records available via the Medical Information Mart for Intensive Care III. Patients were required to have a serum lactate monitoring during the intensive care unit (ICU) stay. The treatment was the administration of vasopressin between hours 3 and 18 of the ICU stay. Analysis was performed using a matched design.

RESULTS

Patients receiving vasopressin were more likely to have their serum lactate levels rise when compared to matched patients who did not receive vasopressin (odds ratio: 6.6; 95% confidence interval: 3.0-14.6, P < .001). Patients who received vasopressin had a median increase in serum lactate of 0.3 mmol/L, while patients who did not receive vasopressin had a median decrease in serum lactate of 0.7 mmol/L (P < .001). There was no statistically significant difference between the control and treated groups' lactate trajectories prior to possible administration of vasopressin (P = .15). The results did not change significantly when norepinephrine initiation was used as the index time.

CONCLUSIONS

In patients with sepsis, the administration of vasopressin was associated with a statistically significant difference in lactate change over the course of 24 hours when compared to matched patients who did not receive vasopressin.

Incidence of hypotension according to the discontinuation order of vasopressors in the management of septic shock: a prospective randomized trial (DOVSS)

BACKGROUND

Vasopressin (AVP) is commonly added to norepinephrine (NE) to reverse shock in patients with sepsis. However, there are no data to support the appropriate strategy of vasopressor tapering in patients on concomitant NE and AVP who are recovering from septic shock. Therefore, the objective of this study was to evaluate the incidence of hypotension while tapering vasopressors in patients on concomitant NE and AVP recovering from septic shock.

METHODS

Patients with septic shock receiving concomitant NE and AVP were randomly assigned to taper NE first (NE group) or AVP first (AVP group). The primary end point was the incidence of hypotension within one hour of tapering of the first vasopressor. We also evaluated the association between serum copeptin levels and the occurrence of hypotension.

RESULTS

The study was stopped early due to a significant difference in the incidence of hypotension after 38 and 40 patients were enrolled in the NE group and the AVP group, respectively. There were 26 patients (68.4%) in the NE group versus 9 patients (22.5%) in the AVP group who developed hypotension after tapering the first vasopressor (p < 0.001). There was a similar finding during the subsequent tapering of the second vasopressor (64.5% in the NE vs 25.0% in the AVP group, p = 0.020). Finally, NE tapering was significantly associated with hypotension during the study period (hazard ratio, 2.221; 95% confidence interval, 1.106-4.460; p = 0.025). The serum copeptin level was lower in patients in whom hypotension developed during tapering of AVP than it was in those without hypotension.

CONCLUSIONS

Tapering NE rather than AVP may be associated with a higher incidence of hypotension in patients recovering from septic shock who are on concomitant NE and AVP. However, further studies with larger sample sizes are required to better determine the appropriate strategy for vasopressor tapering.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01493102 . Registered on 15 December 2011.

Neuroendocrine Derangements in Early Septic Shock: Pharmacotherapy for Relative Adrenal and Vasopressin Insufficiency

Septic shock is a leading cause of mortality in intensive care units throughout the world. While this disease state represents a highly complex pathophysiology involving numerous organ systems, the early approach to care includes adequate hemodynamic support traditionally achieved via infusions of vasoactive medications after adequate fluid resuscitation. Relative adrenal and vasopressin deficiencies are a common feature of septic shock that contribute to impaired hemodynamics. Hydrocortisone and vasopressin are endocrine system hormone analogues that target the acute neuroendocrine imbalance associated with septic shock. This clinically focused annotated review describes the pathophysiological mechanisms behind their use and explores the potential clinical roles of early administration and synergy when combined.

Evaluating Vasopressor Discontinuation Strategies in Patients With Septic Shock on Concomitant Norepinephrine and Vasopressin Infusions

BACKGROUND

There is little data guiding clinicians on how to discontinue vasopressors among septic shock patients on concomitant norepinephrine (NE) and vasopressin (VP).

OBJECTIVE

To determine the incidence of hypotension within 24 hours of discontinuing NE (NE DC first) versus VP (VP DC first) first in septic shock patients.

METHODS

This retrospective study evaluated septic shock patients admitted to the medical intensive care unit (MICU) and surgical ICU (SICU) receiving concomitant NE and VP. Receipt of additional vasopressors, mixed shock states, expired or care withdrawn, and NE and VP discontinued simultaneously were exclusion criteria. The primary outcome was incidence of hypotension within 24 hours of first vasopressor discontinuation. Secondary outcomes included time to hypotension, hospital length of stay (LOS), ICU LOS, and ICU mortality.

RESULTS

A total of 80 patients were included (NE DC first [n = 35]; VP DC first [n = 45]), with a median age of 73 years and median modified Acute Physiology and Chronic Health Evaluation II and Sequential Organ Failure Assessment scores of 21 and 7, respectively. More patients in the NE DC first group were in the SICU (42.9% vs 20.0%; P = 0.048) with more intra-abdominal infections (40.0% vs 15.6%; P = 0.021) and fewer appropriate empirical antibiotics (62.9% vs 86.7%; P = 0.018). Hypotension within 24 hours of first agent discontinuation was higher in the VP DC first group (28.6% vs 62.2%; P = 0.004), with similar hospital LOS and ICU mortality. Multivariate analysis identified VP DC first as an independent predictor of hypotension (odds ratio = 7.2; CI = 2.3-22.7).

CONCLUSION

Among septic shock patients on concomitant NE and VP, discontinuation of VP first was associated with an increased incidence of hypotension; future prospective control trials are warranted.

Microcirculation improvement after short-term infusion of vasopressin in septic shock is dependent on noradrenaline

OBJECTIVES

To assess the impact of vasopressin on the microcirculation and to develop a predictive model to estimate the probability of microcirculatory recruitment in patients with septic shock.

METHODS

This prospective interventional study included patients with septic shock receiving noradrenaline for less than 48 hours. We infused vasopressin at 0.04 U/min for one hour. Hemodynamic measurements, including sidestream dark-field imaging, were obtained immediately before vasopressin infusion, 1 hour after vasopressin infusion and 1 hour after vasopressin withdrawal. We defined patients with more than a 10% increase in total vascular density and perfused vascular density as responders. ClinicalTrials.gov: NCT02053675.

RESULTS

Eighteen patients were included, and nine (50%) showed improved microcirculation after infusion of vasopressin. The noradrenaline dose was significantly reduced after vasopressin (p=0.001) and was higher both at baseline and during vasopressin infusion in the responders than in the non-responders. The strongest predictor for a favorable microcirculatory response was the dose of noradrenaline at baseline (OR=4.5; 95% CI: 1.2-17.0; p=0.027). For patients using a noradrenaline dose higher than 0.38 mcg/kg/min, the probability that microcirculatory perfusion would be improved with vasopressin was 53% (sensitivity 78%, specificity 77%).

CONCLUSIONS

In patients with septic shock for no longer than 48 h, administration of vasopressin is likely to result in an improvement in microcirculation when the baseline noradrenaline dose is higher than 0.38 mcg/kg/min.

Predictors of Vasopressin Responsiveness in Critically Ill Adults

BACKGROUND

Vasopressin is commonly used as an adjunct vasopressor in shock. However, response to vasopressin varies among critically ill patients.

OBJECTIVE

To identify patient-specific factors that are associated with vasopressin responsiveness in critically ill adults.

METHODS

This retrospective, multicenter study included adult patients who were admitted to an intensive care unit (ICU) and received vasopressin for shock. Patients were excluded if they received vasopressin for less than 30 minutes, if vasopressin was initiated prior to ICU arrival, or if an additional vasopressor was initiated within 30 minutes of starting vasopressin. Responsiveness was defined as an increase in mean arterial pressure of ≥10 mm Hg or the ability to taper a concurrent catecholamine vasopressor. Patient-specific factors evaluated in a multivariate analysis included age, gender, ethnicity, body mass index, type of shock, serum pH, Sequential Organ Failure Assessment (SOFA) score, and use of stress-dose steroids. These variables were also evaluated in a subgroup analysis of patients with septic shock.

RESULTS

Of 1619 patients screened, 400 patients were included, with 231 identified as vasopressin responsive and 169 as nonresponsive. Vasopressin used as an adjunct vasopressor, as opposed to first line, during shock was the only variable associated with vasopressin responsiveness (odds ratio [OR] = 1.71; 95% CI = 1.10 to 2.65). Among the subgroup of patients with septic shock, female patients had a higher odds of responding than male patients (OR = 2.10; 95% CI = 1.12 to 3.95).

CONCLUSIONS

Vasopressin initiated as an adjunct vasopressor, as opposed to first-line therapy, was associated with response.

American College of Critical Care Medicine Clinical Practice Parameters for Hemodynamic Support of Pediatric and Neonatal Septic Shock

OBJECTIVES

The American College of Critical Care Medicine provided 2002 and 2007 guidelines for hemodynamic support of newborn and pediatric septic shock. Provide the 2014 update of the 2007 American College of Critical Care Medicine "Clinical Guidelines for Hemodynamic Support of Neonates and Children with Septic Shock."

DESIGN

Society of Critical Care Medicine members were identified from general solicitation at Society of Critical Care Medicine Educational and Scientific Symposia (2006-2014). The PubMed/Medline/Embase literature (2006-14) was searched by the Society of Critical Care Medicine librarian using the keywords: sepsis, septicemia, septic shock, endotoxemia, persistent pulmonary hypertension, nitric oxide, extracorporeal membrane oxygenation, and American College of Critical Care Medicine guidelines in the newborn and pediatric age groups.

MEASUREMENTS AND MAIN RESULTS

The 2002 and 2007 guidelines were widely disseminated, translated into Spanish and Portuguese, and incorporated into Society of Critical Care Medicine and American Heart Association/Pediatric Advanced Life Support sanctioned recommendations. The review of new literature highlights two tertiary pediatric centers that implemented quality improvement initiatives to improve early septic shock recognition and first-hour compliance to these guidelines. Improved compliance reduced hospital mortality from 4% to 2%. Analysis of Global Sepsis Initiative data in resource rich developed and developing nations further showed improved hospital mortality with compliance to first-hour and stabilization guideline recommendations.

CONCLUSIONS

The major new recommendation in the 2014 update is consideration of institution-specific use of 1) a "recognition bundle" containing a trigger tool for rapid identification of patients with septic shock, 2) a "resuscitation and stabilization bundle" to help adherence to best practice principles, and 3) a "performance bundle" to identify and overcome perceived barriers to the pursuit of best practice principles.

Hemodynamic Instability Secondary to Vasopressin Withdrawal in Septic Shock

RATIONALE

Vasopressors such as norepinephrine are first line for support of mean arterial pressure (MAP) in the management of septic shock. Their use, however, is commonly associated with many adverse events. These detriments frequently trigger the use of alternative, noncatecholamine therapies, including vasopressin. Vasopressin deficiency is a known physiologic consequence of septic shock, and while guidelines recommend vasopressin in addition to norepinephrine, no consensus exists on the duration of deficiency or ideal time of cessation. Studies have suggested that vasopressin discontinuation prior to other vasopressors may lead to hypotension; however, data are limited. This study evaluates the optimal sequence for the discontinuation of vasopressin therapy in septic shock.

METHODS

This was a 1-year retrospective study of 152 patients admitted to the medical intensive care unit (ICU) with septic shock who received concurrent norepinephrine and vasopressin for vasoactive support. Patients were excluded if death occurred on vasopressors, within 24 hours after discontinuation of vasopressors, or within 48 hours of ICU admission. The primary outcome of hemodynamic instability included incidence of hypotension after vasopressor discontinuation (2 consecutive MAPs < 60 mm Hg), fluid bolus administration, greater than 0.05 μg/kg/min increase in norepinephrine requirements, or addition of an alternative vasopressor. Secondary outcomes included time to hypotension, total vasopressor duration, arrhythmias, mortality, and length of stay.

RESULTS

Ninety-one patients met exclusion criteria, resulting in 61 patients for evaluation. Vasopressin was the first vasoactive therapy to be discontinued in 19 patients and last in 42 patients. Baseline characteristics and the use of potentially confounding treatments known to effect MAP were similar between groups. Discontinuation of vasopressin first was associated with a significant increase in hemodynamic instability (74% vs 16.7%, P < .01), with a shorter time to hemodynamic instability (5 vs 15 hours, P < .01). Secondary outcomes were similar.

CONCLUSION

Vasopressin discontinuation prior to cessation of norepinephrine infusion was associated with an increased risk of hemodynamic instability.

Discontinuation of Vasopressin Before Norepinephrine in the Recovery Phase of Septic Shock

BACKGROUND

Guidance for the discontinuation of vasopressors in the recovery phase of septic shock is limited. Norepinephrine is more easily titrated; however, septic shock is a vasopressin deficient state, which exogenous vasopressin endeavors to resolve. Discontinuation of vasopressin before norepinephrine may result in clinically significant hypotension.

METHODS

This retrospective, cohort study compared discontinuation of norepinephrine and vasopressin in medically, critically ill patients in the recovery phase of septic shock from May 2014 to June 2016. Difference in clinically significant hypotension after norepinephrine or vasopressin discontinuation was evaluated with χ² test. Linear regression was performed, examining the effect of agent discontinuation on clinically significant hypotension. Baseline variables were examined for a bivariate relationship with clinically significant hypotension; those with P < .2 were included in the model.

RESULTS

Vasopressin was discontinued first or last in 62 and 92 patients, respectively. Sequential Organ Failure Assessment scores at 72 hours (7.9 vs 7.6, P = .679) were similar. In unadjusted analysis, when vasopressin was discontinued first, more clinically significant hypotension developed (10.9% vs 67.8%, P < .001). There was no difference in intensive care unit (174 vs 216 hours, P = .178) or hospital duration (470 vs 473 hours, P = .977). In adjusted analyses, discontinuing vasopressin first was associated with increased clinically significant hypotension (odds ratio [OR]: 13.837, 95% confidence interval [CI]: 3.403-56.250, P < .001) but not in-hospital (OR: 0.659, 95% CI: 0.204-2.137, P = .488) or 28-day mortality (OR: 0.215, 95% CI: 0.037-1.246, P = .086).

CONCLUSION

Adult patients receiving norepinephrine and vasopressin in the resolving phase of septic shock may be less likely to develop clinically significant hypotension if vasopressin is the final vasopressor discontinued.

Role of vasopressin and terlipressin in refractory shock compared to conventional therapy in the neonatal and pediatric population: a systematic review, meta-analysis, and trial sequential analysis

Background

Vasopressin (AVP) and terlipressin (TP) have been used as last-line therapy in refractory shock in children. However, the efficacy and safety profiles of AVP and TP have not been determined in pediatric refractory shock of different origins. We aimed to assess the efficacy and safety of the addition of AVP/TP therapy in pediatric refractory shock of all causes compared to conventional therapy with fluid resuscitation and vasopressor and inotropic therapy.

Methods

We conducted a systematic review, meta-analysis, and trial sequential analysis (TSA) comparing AVP and TP to conventional therapy. MEDLINE, EMBASE, Cochrane Library, and ClinicalTrials.gov were searched up to February 2016. The systematic review included all reports of AVP/TP use in the pediatric population. Reports of clinical trials were pooled using random-effects models and TSA. Main outcomes were mortality and tissue ischemia.

Results

Three randomized controlled trials and five “before-and-after clinical” trials (without comparator) met the inclusion criteria. Among 224 neonates and children (aged 0 to 18 years) with refractory shock, 152 received therapy with AVP or TP. Pooled analyses showed no association between AVP/TP treatment and mortality (relative risk (RR),1.19; 95% confidence interval (CI), 0.71–2.00), length of stay in the pediatric intensive care unit (PICU) (mean difference (MD), –3.58 days; 95% CI, –9.05 to 1.83), and tissue ischemia (RR, 1.48; 95% CI, 0.47–4.62). In TSA, no significant effect on mortality and risk for developing tissue ischemia was observed with AVP/TP therapy.

Conclusion

Our results emphasize the lack of observed benefit for AVP/TP in terms of mortality and length of stay in the PICU, and suggest an increased risk for ischemic events. Our TSA suggests that further large studies are necessary to demonstrate and establish benefits of AVP/TP in children.

PROSPERO registry: CRD42016035872

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-016-1589-6) contains supplementary material, which is available to authorized users.

Pharmacologic agents for acute hemodynamic instability: recent advances in the management of perioperative shock- a systematic review

Despite the growing body of evidence evaluating the efficacy of vasoactive agents in the management of hemodynamic instability and circulatory shock, it appears no agent is superior. This is becoming increasingly accepted as current guidelines are moving away from detailed algorithms for the management of shock, and instead succinctly state that vasoactive agents should be individualized and guided by invasive hemodynamic monitoring. This extends to the perioperative period, where vasoactive agent selection and use may still be left to the discretion of the treating physician with a goal-directed approach, consisting of close hemodynamic monitoring and administration of the lowest effective dose to achieve the hemodynamic goals. Successful therapy depends on the ability to rapidly diagnose the etiology of circulatory shock and thoroughly understand its pathophysiology as well as the pharmacology of vasoactive agents. This review focuses on the physiology and resuscitation goals in perioperative shock, as well as the pharmacology and recent advances in vasoactive agent use in its management.

Vasopressin: Applications in Clinical Practice

Arginine vasopressin is a peptide produced in the posterior pituitary whose primary physiologic role is fluid homeostasis. Recent investigations have demonstrated a therapeutic role for arginine vasopressin in adult cardiac arrest as well as adult and pediatric vasodilatory shock. We review the physiology of arginine vasopressin and examine the supporting data behind the developing clinical applications of this naturally produced peptide.

Vasoplegia in sepsis depends on the vascular system, vasopressor, and time-point: a comparative evaluation in vessels from rats subjected to the cecal ligation puncture model

We evaluated the effects of phenylephrine, norepinephrine, angiotensin II, and vasopressin in mesenteric, renal, carotid, and tail arteries, and in perfused mesenteric vascular bed from rats subjected to the cecal ligation and puncture (CLP) model of sepsis. Phenylephrine and angiotensin II were less efficacious in mesenteric arteries from the CLP 6 h and CLP 18 h groups than in preparations from non-septic animals, but no differences were found for norepinephrine and vasopressin between the preparations. In renal arteries, none of the vasoconstrictors had impaired activity in the CLP groups. Nonetheless, carotid arteries from the CLP 18 h group presented reduced reactivity to all vasoconstrictors tested, but only phenylephrine and norepinephrine had their effects reduced in carotid arteries from the CLP 6 h group. Despite the reduced responsiveness to phenylephrine, tail arteries from septic rats were hyperreactive to vasopressin and norepinephrine at 6 h and 18 h after the CLP surgery, respectively. The mesenteric vascular bed from CLP groups was hyporeactive to phenylephrine, norepinephrine, and angiotensin II, but not to vasopressin. The vascular contractility in sepsis varies from the well-described refractoriness, to unaltered or even hyperresponsiveness to vasoconstrictors, depending on the vessel, the vasoactive agent, and the time period evaluated.

Management of Acute Kidney Injury and Acid-Base Balance in the Septic Patient

Acute kidney injury (AKI) is an abrupt decrease in kidney function that takes place over hours to days. Sepsis is the leading cause of AKI and portends a particularly high morbidity and mortality, although the severity may vary from a transient rise in serum creatinine to end-stage renal disease. With regard to acid-base management in septic AKI, caution should be used with hyperchloremic crystalloid solutions, and dialysis is often used in the setting of severe acidosis. In the future, biomarkers may help clinicians identify AKI earlier and allow for potential interventions before the development of severe AKI.

Increased activation of the Rho-A/Rho-kinase pathway in the renal vascular system is responsible for the enhanced reactivity to exogenous vasopressin in endotoxemic rats

OBJECTIVE

We evaluated the role of the renal vascular system and the Rho-A/Rho-kinase pathway in the maintenance of the pressor effects of vasopressin in endotoxemic rats.

DESIGN

In vitro and in vivo animal study.

SETTING

University research laboratory.

SUBJECTS

Male Wistar rats (200-300 g).

INTERVENTION

Rats received either saline or lipopolysaccharide (10 mg/kg, intraperitoneal) 6 or 24 hours before the experiments. The effects of vasopressin on isolated aortic rings, cardiac function, mean arterial pressure, and both the renal vascular perfusion pressure of perfused kidneys in vitro and renal blood flow in situ were evaluated. The role of Rho-kinase in the renal and systemic effects of vasopressin was investigated through administration of the selective inhibitor Y-27632 and Western blot analysis.

MEASUREMENTS AND MAIN RESULTS

The effect of vasopressin on mean arterial pressure was unaltered and that on renal vascular perfusion pressure enhanced in endotoxemic rats at both 6 and 24 hours after lipopolysaccharide, despite reduced contractile responses in aortic rings and the lack of effect on cardiac function. Vasopressin (3, 10, and 30 pmol/kg, IV) produced increased reduction in renal blood flow in endotoxemic rats. In perfused kidneys from lipopolysaccharide groups, administration of Y-27632 reverted the hyperreactivity to vasopressin. Treatment with Y-27632 partially inhibited the effects of vasopressin on mean arterial pressure and significantly reduced the effects of vasopressin on renal blood flow in control but not in endotoxemic rats. Although the protein levels of Rho-A and Rho-kinase I and II had not been impaired, the levels of phosphorylated myosin phosphatase-targeting subunit 1, the regulatory subunit of myosin phosphatase that is inhibited by Rho-kinase, were increased in both the renal cortex and the renal medulla of endotoxemic rats.

CONCLUSION

Our data suggest that activation of Rho-kinase potentiates the vascular effects of vasopressin in the kidneys, contributing to the maintenance of the hypertensive effects of this agent during septic shock.

The anesthetic effects on vasopressor modulation of cerebral blood flow in an immature swine model

BACKGROUND

The effect of various sedatives and anesthetics on vasopressor modulation of cerebral blood flow (CBF) in children is unclear. In adults, isoflurane has been described to decrease CBF to a lesser extent than fentanyl and midazolam. Most large-animal models of neurocritical care use inhaled anesthetics for anesthesia. Investigations involving modulations of CBF would have improved translatability within a model that more closely approximates the current practice in the pediatric intensive care unit.

METHODS

Fifteen 4-week-old piglets were given 1 of 2 anesthetic protocols: total IV anesthesia (TIVA) (midazolam 1 mg/kg/h and fentanyl 100 μg/kg/h, n = 8) or ISO (isoflurane 1.5%-2% and fentanyl 100 μg/kg/h, n = 7). Mean arterial blood pressure, intracranial pressure (ICP), CBF, and brain tissue oxygen tension were measured continuously as piglets were exposed to escalating doses of arginine vasopressin, norepinephrine (NE), and phenylephrine (PE).

RESULTS

Baseline CBF was similar in the 2 groups (ISO 38 ± 10 vs TIVA 35 ± 26 mL/100 g/min) despite lower baseline cerebral perfusion pressure in the ISO group (45 ± 11 vs 71 ± 11 mm Hg; P < 0.0005). Piglets in the ISO group displayed increases in ICP with PE and NE (11 ± 4 vs 16 ± 4 mm Hg and 11 ± 8 vs 18 ± 5 mm Hg; P < 0.05), but in the TIVA group, only exposure to PE resulted in increases in ICP when comparing maximal dose values with baseline data (11 ± 4 vs 15 ± 5 mm Hg; P < 0.05). Normalized CBF displayed statistically significant increases regarding anesthetic group and vasopressor dose when piglets were exposed to NE and PE (P < 0.05), suggesting an impairment of autoregulation within ISO, but not TIVA.

CONCLUSION

The vasopressor effect on CBF was limited when using a narcotic-benzodiazepine-based anesthetic protocol compared with volatile anesthetics, consistent with a preservation of autoregulation. Selection of anesthetic drugs is critical to investigate mechanisms of cerebrovascular hemodynamics, and in translating critical care investigations between the laboratory and bedside.

Severe sepsis and septic shock in pregnancy

Pregnancies complicated by severe sepsis and septic shock are associated with increased rates of preterm labor, fetal infection, and preterm delivery. Sepsis onset in pregnancy can be insidious, and patients may appear deceptively well before rapidly deteriorating with the development of septic shock, multiple organ dysfunction syndrome, or death. The outcome and survivability in severe sepsis and septic shock in pregnancy are improved with early detection, prompt recognition of the source of infection, and targeted therapy. This improvement can be achieved by formulating a stepwise approach that consists of early provision of time-sensitive interventions such as: aggressive hydration (20 mL/kg of normal saline over the first hour), initiation of appropriate empiric intravenous antibiotics (gentamicin, clindamycin, and penicillin) within 1 hour of diagnosis, central hemodynamic monitoring, and the involvement of infectious disease specialists and critical care specialists familiar with the physiologic changes in pregnancy. Thorough physical examination and imaging techniques or empiric exploratory laparotomy are suggested to identify the septic source. Even with appropriate antibiotic therapy, patients may continue to deteriorate unless septic foci (ie, abscess, necrotic tissue) are surgically excised. The decision for delivery in the setting of antepartum severe sepsis or septic shock can be challenging but must be based on gestational age, maternal status, and fetal status. The natural inclination is to proceed with emergent delivery for a concerning fetal status, but it is imperative to stabilize the mother first, because in doing so the fetal status will likewise improve. Aggressive [corrected] treatment of sepsis can be expected to reduce the progression to severe sepsis and septic shock and prevention strategies can include preoperative skin preparations and prophylactic antibiotic therapy as well as appropriate immunizations.

[Septic shock. Update of treatment using hypertonic saline and antidiuretic hormone-vasopressin]

Safety in the use of small volumes of hypertonic saline solution for hypovolaemic shock and in the treatment of intracranial hypertension has been demonstrated in studies in the field of resuscitation. There is little experience of this for septic shock in humans. Beneficial immunomodulatory effects have been detected in pre-clinical studies. Interactions with the pituitary-adrenal axis and with the secretion of anti-diuretic hormone are varied and suggestive, but are not sufficiently understood. On the other hand, vasopressin has cardiovascular, osmoregulatory, and coagulation effects, and also acts on the hypothalamic-pituitary-adrenal axis. There is a relative deficit of vasopressin in septic shock. Its use in these patients does not seem to have any advantages as regards mortality, but may be beneficial in patients at risk from acute renal failure, or those who receive corticosteroids. Terlipressin is a vasopressin analogue that has also been studied. The synergy between vasopressin and hypertonic saline is a hypothesis that is mainly supported in pre-clinical studies. The use of hypertonic saline solution in septic shock, although promising, is still experimental, and must be restricted to the field of controlled clinical trials.

Experimental sepsis in pigs--effects of vasopressin on renal, hepatic, and intestinal dysfunction

INTRODUCTION

Low-dose arginine vasopressin (AVP) has been proposed as an adjunctive vasopressor for the treatment of advanced vasodilatory shock. However, its effects on renal, hepatic, and intestinal dysfunction during sepsis remain controversial.

METHODS

Fecal peritonitis was induced in 20 anesthetized, invasively monitored, mechanically ventilated female pigs. Following the time point of septic shock (defined as mean artery pressure (MAP) ≤65 mmHg), animals were randomly assigned to the following groups (n = 10): 1) a norepinephrine group with MAP between 65 and 75 mmHg; and 2) an AVP group with a constant infusion rate of 0.5 mU.kg(-1).min(-1).

RESULTS

MAP, pulmonary capillary wedge pressure, hematocrit, TNF-α, IL-6, and IL-10 were similar in the two groups during the 28-h observation period. Infusion of AVP was associated with lower total norepinephrine and fluid requirements. There was a statistically significant improvement in renal function as assessed by increased urine output and renal blood flow, and decreased serum creatinine, in the AVP group when compared with the norepinephrine group (P < 0.05). Histological analyses of the intestine, liver, and kidney showed similar light microscopical appearance of the two groups. Apoptotic cells in the liver were significantly fewer in the AVP group when compared with the norepinephrine group (P < 0.05).

CONCLUSION

An adjunctive AVP to norepinephrine infusion exhibits a favorable impact on renal function without deleterious effects on the liver and intestine in a porcine model of experimental sepsis when compared with norepinephrine infusion alone.

Concerns of the anesthesiologist: anesthetic induction in severe sepsis or septic shock patients

Septic patients portray instable hemodynamic states because of hypotension or cardiomyopathy, caused by vasodilation, thus, impairing global tissue perfusion and oxygenation threatening functions of critical organs. Therefore, it has become the primary concern of anesthesiologists in conducting anesthesia (induction, maintenance, recovery, and postoperative care), especially in the induction of those who are prone to fall into hemodynamic crisis, due to hemodynamic instability. The anesthesiologist must have a precise anesthetic plan based on a thorough preanesthetic evaluation because many cases are emergent. Primary circulatory status of patients, including mental status, blood pressure, urine output, and skin perfusion, are necessary, as well as more active assessment methods on intravascular volume status and cardiovascular function. Because it is difficult to accurately evaluate the intravascular volume, only by central venous pressure (CVP) measurements, the additional use of transthoracic echocardiography is recommended for the evaluation of myocardial performance and hemodynamic state. In order to hemodynamically stabilize septic patients, adequate fluid resuscitation must be given before induction. Most anesthetic induction agents cause blood pressure decline, however, it may be useful to use drugs, such as ketamine or etomidate, which carry less cardiovascular instability effects than propofol, thiopental and midazolam. However, if blood pressure is unstable, despite these efforts, vasopressors and inotropic agents must be administered to maintain adequate perfusion of organs and cellular oxygen uptake.

Gluco- and mineralocorticoid biological effects of a 7-day treatment with low doses of hydrocortisone and fludrocortisone in septic shock

PURPOSE

The benefits of low-dose steroids in septic shock remain controversial. We investigated if these low doses were able to induce their expected hormonal effects by analyzing the biological modifications observed during the study, which first demonstrated the survival benefit of low-dose steroids.

METHODS

This was a multicenter, placebo-controlled, randomized, double-blind study in which 299 septic shock patients received a 7-day treatment with a combination of hydrocortisone (50 mg intravenously four times daily) and fludrocortisone (50 μg orally once daily) or matching placebos. Gluco- and mineralocorticoid biological effects observed during the 7 days of treatment were compared between groups.

RESULTS

Steroids significantly decreased eosinophil counts from day 2 to day 7. Steroids significantly increased plasma glucose from day 2 (compared with placebos: +0.8 mmol/l) to day 7 (+1.8 mmol/l) and cholesterol from day 3 (+0.54 mmol/l) to day 7 (+0.39 mmol/l). Steroids significantly increased plasma sodium from day 3 (+2 mmol/l) to day 7 (+5 mmol/l) and significantly decreased plasma potassium on day 7 (-0.2 mmol/l). Steroids significantly decreased urinary sodium/potassium ratio from day 2 (-47 %) to day 7 (-57 %) and sodium fractional excretion from day 3 (-25 %) to day 7 (-66 %). Steroids significantly increased urine output on day 4 and 5 and osmolar clearance from day 4 to day 7, and decreased free-water clearance from day 4 to day 7, this effect being significant on day 4 and 6.

CONCLUSIONS

In septic shock, low-dose steroids induced both gluco- and mineralocorticoid biological effects and seemed to improve renal function. Most of these effects appeared after 2-3 days of treatment and lasted at least until the end of treatment.

Vascular reactivity in human arteries: from experimental study to clinical application

The principal function of VSM cells in mature animals is contraction. The endothelium is now recognized to elaborate various vasoactive factors and to play a critical part in regulation of vascular tone. Many circulating mediators and hormones have effects on vascular tone that are mediated via multiple receptors. Vasoactive agents also exert their effects on tissues by acting on one or more processes in the contraction–relaxation cycle in VSM. In humans,systemic, pulmonary, and various organ circulation(s) are maintained by an intricate and complex cardiovascular system. We expect future studies to clarify the sophisticated but complex mechanisms of VSM in humans.

Effects of Low Dose Vasopressin in Catecholamine Resistant Septic Shock

BACKGROUND

Septic shock commonly leads to death in critically ill patients. Severe hypotension resistant to conventional catecholamine leads to multiorgan failure. We studied the effectiveness of low dose vasopressin in resistant septic shock.

METHODS

Thirty critically ill patients with catecholamine resistant hypotension were included in the study. After adequate fluid resuscitation, infusion of norepinephrine and dobutamine was started. If the patient remained hypotensive, vasopressin was infused at a fixed rate of 0.04 unit/minute for 24 hours. Haemodynamic parameters and mortality rates were recorded.

RESULT

There was a significant improvement in systolic and mean arterial pressure within four hours of starting vasopressin. This improvement continued throughout the 24-hour period. In addition, it was possible to withdraw dopamine in all the patients and significantly reduce infusion rates of dobutamine and norepinephrine. No significant complication was noted.

CONCLUSION

Low dose vasopressin at the rate of 0.04 unit/minute is an effective vasopressor in adult patients with catecholamine resistant septic shock.

Inotrope and vasopressor therapy of septic shock

The ultimate goals of hemodynamic therapy in shock are to restore effective tissue perfusion and to normalize cellular metabolism. In sepsis, both global and regional perfusion must be considered. In addition, mediators of sepsis can perturb cellular metabolism, leading to inadequate use of oxygen and other nutrients despite adequate perfusion; one would not expect organ dysfunction mediated by such abnormalities to be corrected by hemodynamic therapy. Despite the complex pathophysiology of sepsis, an underlying approach to its hemodynamic support can be formulated that is particularly pertinent with respect to vasoactive agents. Both arterial pressure and tissue perfusion must be taken into account when choosing therapeutic interventions and the efficacy of hemodynamic therapy should be assessed by monitoring a combination of clinical and hemodynamic parameters. It is relatively easy to raise blood pressure, but somewhat harder to raise cardiac output in septic patients. How to optimize regional blood and microcirculatory blood flow remains uncertain. Specific end points for therapy are debatable and are likely to evolve. Nonetheless, the idea that clinicians should define specific goals and end points, titrate therapies to those end points, and evaluate the results of their interventions on an ongoing basis remains a fundamental principle. The practice parameters were intended to emphasize the importance of such an approach so as to provide a foundation for the rational choice of vasoactive agents in the context of evolving monitoring techniques and therapeutic approaches.

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.

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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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