Review article: Organ per fusion/permeabilityrelated effects of norepinephrine and vasopressin in sepsis

Hemodynamic Influences on Mesenteric Blood Flow in Shock Conditions

The gastrointestinal (GI) system, is most vulnerable to hypoperfusion among the splanchnic organs. Disturbed perfusion of the mesenteric area may lead to GI dysfunction, cause further injury to the patients and even vital outcomes. However, due to the limitation of detection methods, the hemodynamic influences on mesenteric blood flow in clinical practice are not fully understood. By elucidating the underlying mechanisms, we may be able to recognize disturbed GI perfusion and eventually GI dysfunction at an early phase. Thus, in this review, we will focus on situations where mesenteric blood flow is disturbed due to hemodynamic causes in shock conditions, and the present research status will be discussed. English language articles published before 2020 were identified through a computerized PubMed search using the terms "mesenteric, gastrointestinal, intestinal, splanchnic, blood flow, perfusion" and the cofactors. Relevant publications were retrieved and scanned for additional sources. There were few clinical trials focusing on mesenteric blood flow in shock patients. Most were animal experiments. Based on the best current evidence from these sources, we described the major influences on mesenteric blood flow in the context of physiologic accommodation, disease-related effects and the consequences of medical interventions related to shock conditions. During circulatory shock, sepsis, and medical interventions related to shock treatment, mesenteric blood flow changes and shows different features. We need to carefully consider these issues when making medical decisions, and more work needs to be done on early detection of GI hypoperfusion and its accurate correlation with GI dysfunction.

Comparison of Vasopressin versus Norepinephrine in a Pig Model of Refractory Cardiogenic Shock Complicated by Cardiac Arrest and Resuscitated with Veno-arterial ECMO

BACKGROUND

The choice of the best vasopressor after ExtraCorporeal Membrane Oxygenation (ECMO) implantation after cardiac arrest is not well defined. Circulatory flow recovery with ECMO is associated with vasoplegia and vasopressor need. The present study aimed to compare the effects of norepinephrine and vasopressin in the first 6 h after ECMO initiation.

METHODS

Cardiac arrest was induced in 20 pigs by coronary surgical ligature and veno-arterial-ECMO was started after a 30-min period of cardio-pulmonary resuscitation. Pigs were randomized into two groups, arginine vasopressin (AVP) or norepinephrine (NE), with the drugs titrated to maintain a mean arterial pressure (MAP) at 65 mm Hg. Macrocirculatory and metabolic parameters were assessed by lactate clearance. Microcirculatory parameters were assessed by sublingual microcirculation with Sidestream Dark Field imaging and peripheral Near InfraRed Spectroscopy. Pulmonary edema was evaluated by measuring lung wet/dry weight ratio.

RESULTS

No difference was found between groups regarding ECMO flow and MAP. Fluid resuscitation volume was higher in the NE group (14,000 [11,250-15,250] mL vs. 3,500 [1,750-4,000] mL in the AVP group, P < 0.05). Lung wet/dry weight ratio was higher in the Norepinephrine group. Lactate clearance between H0 and H6 was higher in the AVP group (47.84 [13.42-82.73]% vs. the NE group 25.66 [-7.31 to 35.34)% vs. P < 0.05). No significant difference was observed for sublingual microcirculation values. Baseline tissue oxygen saturation was comparable and higher at both H3 and H6 in the Vasopressin group comparatively to the Norepinephrine group (P < 0.05). Renal and liver function evolution also remained similar in the two groups throughout the study.

CONCLUSIONS

AVP administration in refractory cardiac arrest resuscitated by veno-arterial-ECMO is associated with a faster lactate clearance, less fluid resuscitation, and less pulmonary edema when compared with NE for similar global and regional hemodynamic effects.

In vitro endothelial hyperpermeability occurs early following traumatic hemorrhagic shock

BACKGROUND

Endothelial hyperpermeability is suggested to play a role in the development of microcirculatory perfusion disturbances and organ failure following hemorrhagic shock, but evidence is limited.

OBJECTIVE

To study the effect of plasma from traumatic hemorrhagic shock patients on in vitro endothelial barrier function.

METHODS

Plasma from traumatic hemorrhagic shock patients was obtained at the emergency department (ED), the intensive care unit (ICU), 24 h after ICU admission and from controls (n = 8). Sublingual microcirculatory perfusion was measured using incident dark field videomicroscopy at matching time points. Using electric cell-substrate impedance sensing, the effects of plasma exposure on in vitro endothelial barrier function of human endothelial cells were assessed.

RESULTS

Plasma from traumatic hemorrhagic shock patients collected at ED admission induced a 19% loss of in vitro endothelial resistance compared to plasma from controls (p < 0.001). This loss was due to reduced cell-cell contacts (p < 0.01). Plasma withdrawn at later time points did not affect endothelial barrier function (p > 0.99). Interestingly, in vitro endothelial resistance showed a positive association with in vivo microcirculatory perfusion (r = 0.56, p < 0.01).

CONCLUSIONS

Plasma from traumatic hemorrhagic shock patients obtained following ED admission, but not at later stages, induced in vitro endothelial hyperpermeability. This coincided with in vivo microcirculatory perfusion disturbances.

Vasopressin Continuous Infusion Improves Intracranial Pressure and Patient Outcomes after Surgical Clipping or Endovascular Coiling of Cerebral Aneurysm

Background:

Hypertensive therapy prevents vasospasm-related delayed ischemic neurologic deficit and infarcts. New alternatives would include vasopressin which has vasoconstrictive effects and positive influence on cerebral perfusion pressure (CPP) and intracranial pressure (ICP).

Aims:

The aim of this study is to demonstrate the value of vasopressin intravenous infusion (IVI) in decreasing ICP and preventing vasospasm following surgical clipping or endovascular coiling.

Settings and Design:

A triple-blind prospective randomized controlled study.

Subjects and Methods:

Thirty patients, 25–60 years, both genders, had undergone surgical clipping or endovascular coiling for a cerebral aneurysm, World Federation of Neurosurgical Societies (WFNS) grade 1–3 (15 patients in each); Group I (Vasopressin): 0.1–0.4 unit/min and Group II (Norepinephrine): 5–20 ug/min with target systolic blood pressure 160–180 mmHg.

Statistical Analysis:

SPSS version 25 software was used for analysis.

Results:

Invasive mean arterial pressure (MAP) showed the insignificant difference between the two groups, but ICP showed a significant decrease in Group V from hour 24 to 168 hence calculated CPP showed a significant increase in Group V at most times from hour 36 to 168. Glasgow Coma Scale showed a significant decrease in Group N from hour 138 due to the occurrence of vasospasm. The incidence of vasospasm, mechanical ventilation, and 28-day mortality were significantly lower in Group V with 81% risk reduction of vasospasm and better survival.

Conclusion:

Vasopressin IVI improved ICP, MAP, CPP and patient outcomes safely by reducing the incidence of cerebral vasospasm, and 28-day mortality after clipping or coiling of the cerebral aneurysm.

Evaluation of capillary leakage after vasopressin resuscitation in a hemorrhagic shock model

Background

Hemorrhagic shock (HS) is a major threat to patients with trauma and spontaneous bleeding. The aim of the study was to investigate early effects of vasopressin on metabolic and hemodynamic parameters and endothelium permeability by measuring capillary leakage compared to those of other resuscitation strategies in a HS model.

Methods

Forty-five Sprague-Dawley rats were randomized into five groups: S group (n = 5), sham-operated rats without shock or resuscitation; HS group (n = 10), HS and no resuscitation; RL group (n = 10), HS and resuscitation with Ringer’s lactate (RL); RLB group (n = 10), HS and resuscitation with two-third shed blood plus RL; and vasopressin group (n = 10), HS and resuscitation with RL, followed by continuous infusion of 0.04 U/kg/min vasopressin. The effects of resuscitation on hemodynamic parameters [mean arterial pressure (MAP), superior mesenteric artery blood flow (MBF), and mesenteric vascular resistances (MVR)], arterial blood gases, bicarbonate, base deficit, and lactate levels as well as on capillary leakage in the lung, ileum, and kidney were investigated. Capillary leakage was evaluated with Evans blue dye extravasation.

Results

In the vasopressin group, the MAP was higher than in the RL and RLB groups (p < 0.001), while MBF was decreased (p < 0.001). MVR were increased only in the vasopressin group (p < 0.001). Capillary leakage was increased in the lungs of the animals in the vasopressin group compared to that in the lungs of animals in the RLB group (p < 0.05); this increase was associated with the lowest partial pressure of oxygen (p < 0.05). Conversely, decreased capillary leakage was observed with vasopressin in the ileum (p < 0.05). Increased capillary leakage was observed in the kidney in the RLB and vasopressin groups (p < 0.05). Lastly, vasopressin use was associated with higher base deficit and lactate levels when compared to the RL and RLB groups (p < 0.001).

Conclusion

Although vasopressin was proposed as a vasoactive drug for provisional hemodynamic optimization in the early phase of HS resuscitation, the overall findings of this experimental study focus on the possible critical side effects of vasopressin on metabolic parameters and endothelium permeability.

5-HT Drives Mortality in Sepsis Induced by Cecal Ligation and Puncture in Mice

Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection with a high mortality. 5-Hydroxytryptamine (5-HT) is an important regulatory factor in inflammation. The aim of this study is to investigate the role of 5-HT on cecal ligation and puncture- (CLP-) induced sepsis in the mouse model. CLP was performed on C57B/6 wild-type (WT) mice and tryptophan hydroxylase 1 (TPH1) knockout (KO) mice. The results showed that the 5-HT-sufficient group mice had a significantly lower survival rate than the 5-HT-deficient group in CLP-induced sepsis and septic shock. The KO-CLP sepsis group received a lower clinical score than the WT-CLP sepsis group. Meanwhile, the body temperature of mice in the KO-CLP sepsis group was higher than that in the WT-CLP sepsis group and was much closer to the normal body temperature 24 hours after CLP. The tissue histopathology analysis revealed that 5-HT markedly exacerbated histological damages in the peritoneum, lung, liver, kidney, intestinal tissue, and heart in sepsis. Moreover, significant lower levels of TNF-α, IL-6, bacterial loads, MPO, and ROS were discovered in the KO-CLP sepsis group in contrast to the WT-CLP sepsis group. In conclusion, 5-HT drives mortality and exacerbates organ dysfunction by promoting serum cytokines and bacterial loads as well as facilitating oxidative stress in the process of sepsis.

The role of vasopressin and the vasopressin type V1a receptor agonist selepressin in septic shock

Septic shock remains one of the major causes of morbidity and mortality in the critically ill. Despite early goal therapy and administration of cathecholaminergic agents, up to 30% of patients succumb to the disease. In this manuscript, we first summarize the standard of care of patients with septic shock and current guidelines. We review the physiologic role of vasopressin and its role in septic shock management. We then review the most up-to-date evidence on the potential role of V1a receptor agonists such as Selepressin, in septic shock. Exciting new trials are being completed in order to elucidate the role of V1a receptor agonists as potential first-line vasopressor alternatives in the therapy of circulatory shock in septic patients.

Vasopressin in Septic Shock; Assessment of Sepsis Biomarkers: A Randomized, Controlled Trial

Background and Aims:

Vasopressin (VP) in sepsis apart from vasoconstrictive effect may have some immunomodulatory effects. The aim of this study was to evaluate the effect of VP on different aspect of sepsis by measuring of sepsis biomarkers.

Materials and Methods:

In this trial, a total number of 42 septic shock patients were included. The first group received norepinephrine (NE) infusion to reach the target mean arterial pressure (MAP) of ≥ 65 mm Hg and the second group received arginine vasopressin (AVP) infusion in addition to NE. Serum lactate, C-reactive protein (CRP), interleukin-6 (IL-6), IL-10, pentraxin 3 (PTX3), angiopoietin 1 and 2 (Ang 1 and 2) levels were assessed.

Results:

Level of IL-6 and IL-10 decreased, but there was no significant difference between the two groups after 48 h. CRP and PTX3 levels were not also significantly different between groups. Although Angs were not statistically different, there was a trend toward higher Ang-1 in and lower Ang 2 in AVP group after 24 and 48 h. In addition, lactate level did not differ between NE and AVP groups. There was no interaction between VP and hydrocortisone use on IL-6, IL-10, and PTX3, but a significant statistical interaction on Ang 1 and Ang 2 were observed.

Conclusions:

Although analysis of sepsis biomarkers showed no significant difference between two groups, no immunomodulatory effect for VP alone, subgroup analysis of hydrocortisone used in this study showed that the combination of glucocorticoids and AVP had a significant effect on Angs level which eventually causes less endothelial permeability and higher MAP in this group of patients.

Removal of inflammatory ascites is associated with dynamic modification of local and systemic inflammation along with prevention of acute lung injury: in vivo and in silico studies

BACKGROUND

Sepsis-induced inflammation in the gut/peritoneal compartment occurs early in sepsis and can lead to acute lung injury (ALI). We have suggested that inflammatory ascites drives the pathogenesis of ALI and that removal of ascites with an abdominal wound vacuum prevents ALI. We hypothesized that the time- and compartment-dependent changes in inflammation that determine this process can be discerned using principal component analysis (PCA) and Dynamic Bayesian Network (DBN) inference.

METHODS

To test this hypothesis, data from a previous study were analyzed using PCA and DBN. In that study, two groups of anesthetized, ventilated pigs were subjected to experimental sepsis via intestinal ischemia/reperfusion and placement of a peritoneal fecal clot. The control group (n = 6) had the abdomen opened at 12 h after injury (T12) with attachment of a passive drain. The peritoneal suction treatment (PST) group (n = 6) was treated in an identical fashion except that a vacuum was applied to the peritoneal cavity at T12 to remove ascites and maintained until T48. Multiple inflammatory mediators were measured in ascites and plasma and related to lung function (PaO2/FIO2 ratio and oxygen index) using PCA and DBN.

RESULTS

Peritoneal suction treatment prevented ALI based on lung histopathology, whereas control animals developed ALI. Principal component analysis revealed that local to the insult (i.e., ascites), primary proinflammatory cytokines play a decreased role in the overall response in the treatment group as compared with control. In both groups, multiple, nested positive feedback loops were inferred from DBN, which included interrelated roles for bacterial endotoxin, interleukin 6, transforming growth factor β1, C-reactive protein, PaO2/FIO2 ratio, and oxygen index. von Willebrand factor was an output in control, but not PST, ascites.

CONCLUSIONS

These combined in vivo and in silico studies suggest that in this clinically realistic paradigm of sepsis, endotoxin drives the inflammatory response in the ascites, interplaying with lung dysfunction in a feed-forward loop that exacerbates inflammation and leads to endothelial dysfunction, systemic spillover, and ALI; PST partially modifies this process.

The selective vasopressin type 1a receptor agonist selepressin (FE 202158) blocks vascular leak in ovine severe sepsis*

OBJECTIVE

To determine if the selective vasopressin type 1a receptor agonist selepressin (FE 202158) is as effective as the mixed vasopressin type 1a receptor/vasopressin V2 receptor agonist vasopressor hormone arginine vasopressin when used as a titrated first-line vasopressor therapy in an ovine model of Pseudomonas aeruginosa pneumonia-induced severe sepsis.

DESIGN

Prospective, randomized, controlled laboratory experiment.

SETTING

University animal research facility.

SUBJECTS

Forty-five chronically instrumented sheep.

INTERVENTIONS

Sheep were anesthetized, insufflated with cooled cotton smoke via tracheostomy, and P. aeruginosa were instilled into their airways. They were then placed on assisted ventilation, awakened, and resuscitated with lactated Ringer's solution titrated to maintain hematocrit ± 3% from baseline levels. If, despite fluid management, mean arterial pressure fell by more than 10 mm Hg from baseline level, an additional continuous IV infusion of arginine vasopressin or selepressin was titrated to raise and maintain mean arterial pressure within no less than 10 mm Hg from baseline level. Effects of combination treatment of selepressin with the selective vasopressin V2 receptor agonist desmopressin were similarly investigated.

MEASUREMENTS AND MAIN RESULTS

In septic sheep, MAP fell by ~30 mm Hg, systemic vascular resistance index decreased by ~50%, and ~7 L of fluid were retained over 24 hours; this fluid accumulation was partially reduced by arginine vasopressin and almost completely blocked by selepressin; and combined infusion of selepressin and desmopressin increased fluid accumulation to levels similar to arginine vasopressin treatment.

CONCLUSIONS

Resuscitation with the selective vasopressin type 1a receptor agonist selepressin blocked vascular leak more effectively than the mixed vasopressin type 1a receptor/vasopressin V2 receptor agonist arginine vasopressin because of its lack of agonist activity at the vasopressin V2 receptor.

Intravenous arginine vasopressin infusion in refractory vasodilatory shock: a clinical study

OBJECTIVE

To assess the efficacy of arginine vasopressin (AVP) as a rescue therapy in children with catecholamine refractory vasodilatory shock and its effect on various hemodynamic, clinical, and laboratory variables.

METHODS

This prospective hospital based study was conducted from January 2008 through July 2008 at a tertiary pediatric cardiac critical care unit. Twelve post cardiac surgery patients with advanced vasodilatory shock requiring intravenous vasopressin infusion longer than 60 min were included and continuous vasopressin infusion was given. The primary outcome measures were restoration of Mean arterial blood pressure (MAP) after starting AVP infusion and decrease in other concurrent catecholamines requirement. The secondary outcome measures were survival to hospital discharge, adverse effects, and laboratory variables.

RESULTS

Vasopressin was infused in the dose range of 0.0005 to 0.003 units/kg/min for a mean duration of 55.6 h. MAP improved from 41.08  ±  6.15 mmHg at baseline to 48.92  ±  10.05 mmHg after 1 h (P < 0.05), to 57.01  ±  8.30 mmHg after 4 h of AVP infusion (P < 0.001), and to 62.33  ±  8.55 mmHg after 12 h (P < 0.001), which further increased to 71.75  ±  9.55 mmHg after 24 h (P < 0.001). Inotrope score and requirement of other concurrent inotropes declined significantly in all patients after starting AVP infusion (P < 0.001). Lactate levels also declined significantly (P < 0.0001). No significant adverse effect due to end organ ischemia was observed. Only one patient expired while on vasopressin infusion due to refractory hypotension.

CONCLUSIONS

Concurrent addition of vasopressin at an appropriate stage help improving MAP significantly with decreased dependence on high dose catecholamines without any significant adverse effects.

Peritoneal negative pressure therapy prevents multiple organ injury in a chronic porcine sepsis and ischemia/reperfusion model

Sepsis and hemorrhage can result in injury to multiple organs and is associated with an extremely high rate of mortality. We hypothesized that peritoneal negative pressure therapy (NPT) would reduce systemic inflammation and organ damage. Pigs (n = 12) were anesthetized and surgically instrumented for hemodynamic monitoring. Through a laparotomy, the superior mesenteric artery was clamped for 30 min. Feces was mixed with blood to form a fecal clot that was placed into the peritoneum, and the abdomen was closed. All subjects were treated with standard isotonic fluid resuscitation, wide spectrum antibiotics, and mechanical ventilation, and were monitored for 48 h. Animals were separated into two groups 12 h (T12) after injury: for NPT (n = 6), an abdominal wound vacuum dressing was placed in the laparotomy, and negative pressure (-125 mmHg) was applied (T12 - T48), whereas passive drainage (n = 6) was identical to the NPT group except the abdomen was allowed to passively drain. Negative pressure therapy removed a significantly greater volume of ascites (860 ± 134 mL) than did passive drainage (88 ± 56 mL). Systemic inflammation (e.g. TNF-α, IL-1β, IL-6) was significantly reduced in the NPT group and was associated with significant improvement in intestine, lung, kidney, and liver histopathology. Our data suggest NPT efficacy is partially due to an attenuation of peritoneal inflammation by the removal of ascites. However, the exact mechanism needs further elucidation. The clinical implication of this study is that sepsis/trauma can result in an inflammatory ascites that may perpetuate organ injury; removal of the ascites can break the cycle and reduce organ damage.

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

OBJECTIVE AND DESIGN

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

SUBJECTS

Twenty-seven adult female sheep.

TREATMENT

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Continuous Terlipressin Infusion as Rescue Treatment in a Case Series of Children with Refractory Septic Shock

Background:

Despite intensive therapy, refractory pediatric septic shock has a high rate of morbidity and mortality. Additional treatments are needed to improve outcomes in such cases.

Objective:

To report the clinical effects of continuous terlipressin infusion as rescue treatment for children with septic shock refractory to high catecholamine doses.

Methods:

Sixteen episodes of catecholamine-resistant septic shock were recorded in 15 children (aged from newborn to 15 years) who received compassionate rescue treatment with terlipressin at 6 pediatric intensive care units. Terlipressin treatment consisted of a loading dose (20 μg/kg) followed by continuous infusion at a rate of 4–20 μg/kg/h. Terlipressin was titrated at increases of 1 μg/kg/h to maintain mean arterial pressure (MAP) in normal range for age and to reduce catecholamine dosage. The main outcome was survival of the episode. Secondary outcomes included hemodynamic effects, ischemia, and terlipressin-related adverse events.

Results:

Terlipressin increased median MAP from 48 (range 42–63) to 68 (45–115) mm Hg 30 minutes after terlipressin administration (p < 0.01). MAP was subsequently sustained, which allowed for the reduction of norepinephrine infusion from 2 μg/kg/min (1–4) at baseline to 1.5 μg/kg/min (0.4–4) at 1 hour, 1.3 μg/kg/min (0–8) at 4 hours, 1 μg/kg/min (0–2) at 12 hours, 0.45 μg/kg/min (0–1.4) at 24 hours, and 0 μg/kg/min (0–0.6) at 48 hours (p < 0.05 vs baseline in all cases). In 8 (50%) of the 16 septic shock episodes the patients survived, 7 (44%) without sequelae. One patient survived with sequelae (minor amputation and mild cutaneous ischemia). Eight patients had signs of ischemia at admission; terlipressin induced reversible ischemia in another 4 patients. Meningococcal infection, prior ischemia, and MAP were risk factors for mortality.

Conclusions:

Continuous terlipressin infusion may improve hemodynamics and survival in some children with refractory septic shock. Terlipressin could contribute to tissue ischemia.

Vasopressin in pediatric vasodilatory shock: a multicenter randomized controlled trial

RATIONALE

Vasopressin has been proposed as a potent vasoactive agent in the treatment of vasodilatory shock in adults and children. The objective of this trial was to evaluate the efficacy and safety of vasopressin as an adjunctive agent in pediatric vasodilatory shock.

METHODS

In this multicenter, double-blind trial, children with vasodilatory shock were randomized to receive low-dose vasopressin (0.0005-0.002 U/kg/min) or placebo in addition to open-label vasoactive agents. Vasoactive infusions were titrated to clinical endpoints of adequate perfusion. The primary outcome was time to vasoactive-free hemodynamic stability. Secondary outcomes included mortality, organ-failure-free days, length of critical care unit stay, and adverse events.

MEASUREMENTS AND MAIN RESULTS

Sixty-five of 69 children (94%) who were randomized received the study drug (33 vasopressin, 32 placebo) and were included in the analysis. There was no significant difference in the primary outcome between the vasopressin and placebo groups (49.7 vs. 47.1 hours; P = 0.85). There were 10 deaths (30%) in the vasopressin group and five (15.6%) in the placebo group (relative risk, 1.94; 95% confidence interval, 0.75-5.05; P = 0.24). There were no significant differences with respect to organ failure-free days (22 vs. 25.5 days; P = 0.11), ventilator-free days (16.5 23 days; P = 0.15), length of stay (8 vs. 8.5 days; P = 0.93), or adverse event rate ratios (12.0%; 95% confidence interval, -2.6 to 26.7; P = 0.15).

CONCLUSIONS

Low-dose vasopressin did not demonstrate any beneficial effects in this pediatric trial. Although not statistically significant, there was a concerning trend toward increased mortality. Clinical trial registered with www.controlled-trials.com (ISRCTN11597444).

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.

Modulation of aquaporin-2/vasopressin2 receptor kidney expression and tubular injury after endotoxin (lipopolysaccharide) challenge

OBJECTIVE

Sepsis-induced organ dysfunctions remain prevalent and account for >50% of intensive care unit admissions for acute renal failure with a mortality rate nearing 75%. In addition to the fact that the mechanisms underlying the pathophysiology of sepsis-related acute renal failure are unclear, the impact on septic-induced acute renal failure of either norepinephrine, a gold-standard vasopressor, and arginine vasopressin, a candidate alternative, are not well understood.

DESIGN

Randomized and controlled in vivo study.

SETTING

Research laboratory and animal facilities.

SUBJECTS

Adult rats treated with endotoxin (lipopolysaccharide) and/or vasopressors.

INTERVENTIONS

Rats were intraperitoneally injected with lipopolysaccharide (12 mg/kg) or saline and then infused with either saline, 0.375 microg/microL arginine vasopressin, or 32.5 microg/microL norepinephrine for 18 hrs. These vasopressor rates yielded respective targeted blood levels observed in human septic shock.

MEASUREMENTS AND MAIN RESULTS

Renal function, including glomerular filtration rate and fraction, renal blood flow, aquaporin-2, and arginine vasopressin-2 (V2 receptor) networking, water and salt handling, and urinary protein excretion, were evaluated. After lipopolysaccharide challenge arginine vasopressin infusion: 1) impaired creatinine clearance without affecting renal blood flow, glomerular filtration rate, and fraction but reduced free-water clearance, both of which being partially restored by the V2 receptor antagonist SR-121463B; 2) decreased the recognized ability of arginine vasopressin alone to recruit aquaporin-2 to the apical membrane increase its mRNA expression and urinary release; 3) increased urinary protein content but decreased specific kidney injury molecule-1, and Clara cell protein-16 release (p < 0.05 vs. lipopolysaccharide alone). Conversely, norepinephrine infusion did not add to lipopolysaccharide-induced alteration of urine biochemistry, except for improved creatinine clearance and increased microalbuminuria.

CONCLUSION

In this endotoxic model, dose-targeted arginine vasopressin infusion increased lipopolysaccharide-induced renal dysfunction without affecting renal blood flow and glomerular function, but with particular disruption of aquaporin-2/V2 receptor networking, consecutive decreased salt and water handling ability. This is in clear contrast with norepinephrine infusion and suggests specific arginine vasopressin-induced "tubular epithelial dysfunction."

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.

Assessment of vascular permeability in an ovine model of acute lung injury and pneumonia-induced Pseudomonas aeruginosa sepsis

OBJECTIVE

To assess the time changes and mechanism of pulmonary and peripheral vascular permeability in sheep with acute lung injury and sepsis.

DESIGN

Prospective, controlled, randomized trial.

SETTING

University research laboratory.

SUBJECTS

A total of 21 chronically instrumented, adult female sheep.

INTERVENTIONS

Sheep were instrumented with lung and prefemoral lymph fistulas and allocated to either an uninjured control group (n = 5) or sepsis group (n = 5). The sheep in the sepsis group received cotton smoke inhalation injury followed by instillation of Pseudomonas aeruginosa into the lungs. All sheep were mechanically ventilated and fluid resuscitated for the entire duration of the 24-hr experiment. Additional sheep (n = 11) received injury and were killed at different time points for the measurement of vascular endothelial growth factor in lung tissue.

MEASUREMENTS AND MAIN RESULTS

The injury induced a hypotensive-hyperdynamic circulation; increases in pulmonary capillary pressure, net fluid balance, lung and prefemoral lymph flow and protein content, lung water content, abdominal and thoracic fluid and protein content, neutrophil accumulation in the lung, and vascular endothelial growth factor expression in lung tissue; and decreases in PaO2/FiO2 ratio, plasma protein concentration, plasma oncotic pressure, and myocardial contractility.

CONCLUSIONS

Lung edema formation in this model was the result of marked increases in both pulmonary microvascular permeability and pressure. Pulmonary vascular hyperpermeability peaked 12 hrs postinjury and was related to vascular endothelial growth factor overexpression. Early myocardial failure was a potential contributor to the constant increase in pulmonary capillary pressure. The sepsis-induced increase in peripheral microvascular permeability was associated with significant accumulation of fluid and protein in the third space.

Clinical impact of vasopressin infusion on hemodynamics, liver and renal function in pediatric patients

OBJECTIVE

To study effects of vasopressin on hemodynamic, clinical, and laboratory variables in children with advanced vasodilatory shock.

DESIGN AND SETTING

Retrospective study in a multidisciplinary tertiary pediatric critical care unit.

PATIENTS AND PARTICIPANTS

Patients (n = 117; 32 noncardiac, 85 postcardiac surgery) requiring intravenous vasopressin infusion longer than 60 min for advanced shock (January 2004 to December 2005).

INTERVENTIONS

Vasopressin infusion (n =157).

MEASUREMENTS AND RESULTS

Both cardiac and noncardiac patients showed a significant decrease in inotrope requirement without change in central venous saturation or lactate during infusion. Both groups had increased urea and creatinine and decreased urine output with longer duration/higher cumulative dose of vasopressin. There was a significant increase in conjugated bilirubin level in the noncardiac group during vasopressin infusion; noncardiac patients showed higher AST levels with higher cumulative dose or longer duration of infusion. Postcardiac surgical patients showed a trend towards normal INR values which persisted after vasopressin infusion. Platelet counts were significantly lower during infusion in both groups.

CONCLUSIONS

Vasopressin infusion improved the hemodynamic state in advanced shock without compromising cardiac function. Urine output and creatinine levels were adversely affected but were reversible. This effect was more pronounced with higher dose or duration of infusion. There was no major effect on liver function but a significant reduction in platelet counts. These data suggest that vasopressin is useful in states of vasodilatory shock with limitations regarding to its adverse renal effects and on platelet counts.