VASOPRESSIN MEDIATES THE PRESSOR EFFECT OF HYPERTONIC SALINE SOLUTION IN ENDOTOXIC SHOCK

Autonomic Disbalance During Systemic Inflammation is Associated with Oxidative Stress Changes in Sepsis Survivor Rats

Sepsis affects 31.5 million people worldwide. It is characterized by an intense drop in blood pressure driving to cardiovascular morbidity and mortality. Modern supportive care has increased survival in patients; however, after experiencing sepsis, several complications are observed, which may be potentiated by new inflammatory events. Nevertheless, the interplay between sepsis survivors and a new immune challenge in cardiovascular regulation has not been previously defined. We hypothesized that cecal ligation and puncture (CLP) cause persistent cardiovascular dysfunctions in rats as well as changes in autonomic-induced cardiovascular responses to lipopolysaccharide (LPS). Male Wistar rats had mean arterial pressure (MAP) and heart rate (HR) recorded before and after LPS or saline administration to control or CLP survivor rats. CLP survivor rats had similar baseline MAP and HR when compared to control. LPS caused a drop in MAP accompanied by tachycardia in control, while CLP survivor rats had a noteworthy enhanced MAP and a blunted tachycardia. LPS-induced hemodynamic changes were related to an autonomic disbalance to the heart and resistance vessels that were expressed as an increased low- and high-frequency power of pulse interval in CLP survivors after saline and enhancement in the low-frequency power of systolic arterial pressure in control rats after LPS. LPS-induced plasma interferon γ, but not interleukin-10 surges, was blunted in CLP survivor rats. To further access whether or not LPS-induced autonomic disbalance in CLP survivor rats was associated with oxidative stress dysregulation, superoxide dismutase (SOD) activity and thiobarbituric acid reactive substances (TBARS) plasma levels changes were measured. LPS-induced oxidative stress was higher in CLP survivor rats. These findings indicate that key changes in hemodynamic regulation of CLP survivors rats take place in response to LPS that are associated with oxidative stress changes, i.e., reduced SOD activity and increased TBARS levels.

Hypertonic Saline in Human Sepsis: A Systematic Review of Randomized Controlled Trials

The role of hypertonic saline in sepsis remains unclear because clinical data are limited and the balance between beneficial and adverse effects is not well defined. In this systematic literature review, we searched PubMed and Embase to identify all randomized controlled trials up until January 31, 2018 in which hypertonic saline solutions of any concentration were used in patients of all ages with sepsis and compared to a cohort of patients receiving an isotonic fluid. We identified 8 randomized controlled trials with 381 patients who had received hypertonic saline. Lower volumes of hypertonic saline than of isotonic solutions were needed to achieve the desired hemodynamic goals (standardized mean difference, -0.702; 95% CI, -1.066 to -0.337; P < .001; moderate-quality evidence). Hypertonic saline administration was associated with a transient increase in sodium and chloride concentrations without adverse effects on renal function (moderate-quality evidence). Some data suggested a beneficial effect of hypertonic saline solutions on some hemodynamic parameters and the immunomodulatory profile (very low-quality evidence). Mortality rates were not significantly different with hypertonic saline than with other fluids (odds ratio, 0.946; 95% CI, 0.688-1.301; P = .733; low-quality evidence). In conclusion, in our meta-analysis of studies in patients with sepsis, hypertonic saline reduced the volume of fluid needed to achieve the same hemodynamic targets but did not affect survival.

Hypertonic saline resuscitation enhances blood pressure recovery and decreases organ injury following hemorrhage in acute alcohol intoxicated rodents

BACKGROUND

Acute alcohol intoxication (AAI) impairs the hemodynamic and arginine vasopressin (AVP) counter-regulation to hemorrhagic shock (HS) and lactated Ringer's solution (LR) fluid resuscitation (FR). The mechanism of AAI-induced suppression of AVP release in response to HS involves accentuated nitric oxide (NO) inhibitory tone. In contrast, AAI does not prevent AVP response to increased osmolarity produced by hypertonic saline (HTS) infusion. We hypothesized that FR with HTS during AAI would enhance AVP release by decreasing periventricular nucleus NO inhibitory tone, subsequently improving mean arterial blood pressure (MABP) and organ perfusion.

METHODS

Male Sprague-Dawley rats received a 15-hour alcohol infusion (2.5 g/kg + 0.3 g/kg/h) or dextrose (DEX) before HS (40 mm Hg × 60 minutes) and FR with HTS (7.5%, 4 ml/kg) or LR (2.4 × blood volume removed). Organ blood flow was determined, and brains were collected for NO content at 2 hours after FR.

RESULTS

HTS improved MABP recovery in AAI (109 vs. 80 mm Hg) and DEX (114 vs. 83 mm Hg) animals compared with LR. This was associated with higher (>60%) circulating AVP levels at 2 hours after FR compared with those detected in LR animals in both groups. Neither AAI alone nor HS in DEX animals resuscitated with LR altered organ blood flow. In AAI animals, HS and FR with LR reduced blood flow to the liver (72%), small intestine (65%), and large intestine (67%) compared with shams. FR with HTS improved liver (threefold) and small intestine (twofold) blood flow compared with LR in AAI-HS animals. The enhanced MABP response to HTS was prevented by pretreatment with a systemic AVP V1a receptor antagonist. HTS decreased periventricular nucleus NO content in both groups 2 hours after FR.

CONCLUSION

These results suggest that FR with HTS in AAI results in the removal of central NO inhibition of AVP, restoring AVP levels and improving MABP and organ perfusion in AAI-HS.

[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.

Cardiorespiratory and neuroendocrine changes induced by methadone in conscious and in isoflurane anaesthetised dogs

The aim of this study was to compare the cardiorespiratory and neurohormonal effects of methadone in conscious and in isoflurane anaesthetised dogs. Six mature dogs (28.0 ± 3.8 kg bodyweight) received intravenous (IV) methadone (1mg/kg) three times, once when conscious and twice during isoflurane anaesthesia (with a wash-out period of 1 week). The vasopressin antagonist relcovaptan (0.1mg/kg IV) was administered before the methadone either during the first or second (selected randomly) isoflurane anaesthesia to evaluate the contribution of vasopressin to methadone-associated vasoconstriction. Cardiorespiratory data, plasma catecholamines and serum vasopressin were recorded before (baseline) and for 90 min after methadone. Methadone induced dysphoria in all conscious dogs and significantly (P<0.05) increased mean arterial pressure (MAP), catecholamines, and vasopressin concentrations. During anaesthesia, in addition to significantly greater decreases in heart rate (HR) and cardiac index (CI) than during the conscious state, methadone induced apnoea and mechanical ventilation was necessary in all dogs. In anaesthetised animals, methadone administration significantly increased vasopressin concentrations and systemic vascular resistance index (SVRI), while MAP did not differ from baseline. Relcovaptan administration did not modify the increase in SVRI associated with methadone injection during anaesthesia. Increases in plasma catecholamines may account for the slight decreases in HR and CI seen after methadone administration in conscious dogs. In contrast, isoflurane enhanced the intensity of the cardiorespiratory changes induced by methadone. Vasoconstrictive responses associated with methadone did not appear to be induced by vasopressin.

Neuronostatin acts in brain to biphasically increase mean arterial pressure through sympatho-activation followed by vasopressin secretion: the role of melanocortin receptors

Neuronostatin is a recently described neuropeptide that is derived from the somatostatin preprohormone. We have shown previously that neuronostatin led to a biphasic, dose-related increase in mean arterial pressure when injected into the lateral cerebroventricle of adult, male rats. Because neuronostatin depolarized both magnocellular and parvocellular, paraventricular nucleus neurons in hypothalamic slice preparations, we hypothesized that neuronostatin elevated mean arterial pressure first by stimulating sympathetic nervous system activity followed by the release of a pressor hormone, specifically vasopressin. We found that the first phase of neuronostatin-induced increase in mean arterial pressure was reversed by pretreatment with phentolamine, indicating that phase 1 was, indeed, due to an increase in sympathetic activity. We also found that centrally injected neuronostatin led to a dose-related increase in vasopressin secretion in a time course consistent with the peak of the second phase. Furthermore, the second phase of arterial pressure elevation was reversed by pretreatment with a vasopressin 1 receptor antagonist, indicating that phase 2 was likely due to an increase in vasopressin secretion. We previously have shown that the anorexigenic and antidipsogenic effects of neuronostatin were reversed by pretreatment with the melanocortin 3/4 receptor antagonist, SHU9119, so we evaluated the ability of SHU9119 to reverse the effects of neuronostatin on MAP and vasopressin secretion. We found that SHU9119 abrogated the second phase of neuronostatin-induced increase in MAP and neuronostatin-induced vasopressin secretion, indicating that neuronostatin acts through the central melanocortin system to increase vasopressin release, ultimately leading to an elevation in MAP.

Use and effect of vasopressors after pediatric traumatic brain injury

BACKGROUND

Vasopressors are commonly used to increase mean arterial blood pressure (MAP) and cerebral perfusion pressure (CPP) after traumatic brain injury (TBI), but there are few data comparing vasopressor effectiveness after pediatric TBI.

OBJECTIVE

To determine which vasopressor is most effective at increasing MAP and CPP in children with moderate-to-severe TBI.

METHODS

After institutional review board approval, we performed a retrospective cohort study of children 0-17 years old admitted to a level 1 trauma center (Harborview Medical Center, Seattle, Wash., USA) between 2002 and 2007 with moderate-to-severe TBI who received a vasopressor to increase blood pressure. Baseline demographic and physiologic characteristics and hourly physiologic monitoring for 3 h after having started a vasopressor were abstracted. We evaluated differences in MAP and CPP at 3 h after initiation of therapy between phenylephrine, dopamine and norepinephrine among patients who did not require a second vasopressor during this time. Multivariate linear regression was used to adjust for age, gender, injury severity score and baseline MAP or CPP and to cluster by subject.

RESULTS

Eighty-two patients contributed data to the entire dataset. The most common initial medication was phenylephrine for 47 (57%). Patients receiving phenylephrine and norepinephrine tended to be older than those receiving dopamine and epinephrine. Thirteen (16%) of the patients received a second vasopressor during the first 3 h of treatment and were thus not included in the regression analyses; these patients received more fluid resuscitation and exhibited higher in-hospital mortality (77 vs. 32%; p = 0.004) compared to patients receiving a single vasopressor. The norepinephrine group exhibited a 5 mm Hg higher MAP (95% CI: -4 to 13; p = 0.31) and a 12 mm Hg higher CPP (95% CI: -2 to 26; p = 0.10) than the phenylephrine group, and a 5 mm Hg higher MAP (95% CI: -4 to 15; p = 0.27) and a 10 mm Hg higher CPP (95% CI: -5 to 25; p = 0.18) than the dopamine group. However, in post hoc analysis, after adjusting for time to start of vasopressor, hypertonic saline and pentobarbital, the effect on MAP was lost, but the CPP was 8 mm Hg higher (95% CI: -10 to 25; p = 0.39) than in the phenylephrine group, and 5 mm Hg higher (95% CI: -14 to 24; p = 0.59) than in the dopamine group.

CONCLUSIONS

Vasopressor use varied by age. While there was no statistically significant difference in MAP or CPP between vasopressor groups, norepinephrine was associated with a clinically relevant higher CPP and lower intracranial pressure at 3 h after start of vasopressor therapy compared to the other vasopressors examined.

Osmoregulation of vasopressin secretion is altered in the postacute phase of septic shock

OBJECTIVE

To determine whether septic shock patients have an abnormal reponse to increasing osmolarity.

DESIGN

Prospective interventional study.

SETTING

Intensive care unit at Raymond Poincaré and Etampes Hospitals.

PATIENTS

Normonatremic patients at > 72 hrs from septic shock onset.

INTERVENTION

Osmotic challenge consisting of infusing 500 mL of hypertonic saline solution (with cumulative amount of sodium not exceeding 24 g) over 120 mins.

MEASUREMENTS AND MAIN RESULTS

Plasma arginine vasopressin levels were measured 15 mins before the test and then four times every 30 mins. A slope of the relation between arginine vasopressin and plasma sodium levels of < 0.5 pg/mEq defined nonresponders. Among the 33 included patients, 17 (52%) were nonresponders. During osmotic challenge, variations throughout the test in plasma sodium levels, blood pressure, and central venous pressure were comparable between the two groups. Arginine vasopressin increased from 4.8 pg/mL [3.3-6.4 pg/mL] to 14.4 pg/mL [11.2-23.3 pg/mL] in responders but only from 2.8 pg/mL [2.3-4.0 pg/mL] to 4.0 pg/mL [3.1-5.3 pg/mL] in nonresponders (p < .0001). Responders had a higher plasma arginine vasopressin levels at baseline and a more severe hematosis alteration. Nonresponders had more frequently bacteremia and liver dysfunction, been referred from the ward and undergone surgery. Critical illness severity, hemodynamic alteration, hydroelectrolytic disturbances, treatment, and outcome did not differ between the two groups.

CONCLUSION

Osmoregulation is dramatically altered in half of patients with prolonged septic shock.

Cell volume regulation: physiology and pathophysiology

Cell volume perturbation initiates a wide array of intracellular signalling cascades, leading to protective and adaptive events and, in most cases, activation of volume-regulatory osmolyte transport, water loss, and hence restoration of cell volume and cellular function. Cell volume is challenged not only under physiological conditions, e.g. following accumulation of nutrients, during epithelial absorption/secretion processes, following hormonal/autocrine stimulation, and during induction of apoptosis, but also under pathophysiological conditions, e.g. hypoxia, ischaemia and hyponatremia/hypernatremia. On the other hand, it has recently become clear that an increase or reduction in cell volume can also serve as a specific signal in the regulation of physiological processes such as transepithelial transport, cell migration, proliferation and death. Although the mechanisms by which cell volume perturbations are sensed are still far from clear, significant progress has been made with respect to the nature of the sensors, transducers and effectors that convert a change in cell volume into a physiological response. In the present review, we summarize recent major developments in the field, and emphasize the relationship between cell volume regulation and organism physiology/pathophysiology.

A treatment protocol including vasopressin and hydroxyethyl starch solution is associated with increased rate of return of spontaneous circulation in blunt trauma patients with pulseless electrical activity

BACKGROUND

Survival after cardiopulmonary resuscitation (CPR) using standard vasopressor therapy is disappointing. Vasopressin is a potent vasopressor that could become a useful therapeutic alternative in the treatment of cardiac arrest.

AIMS

The aim of this prehospital prospective cohort study was to assess the influence of treatment with vasopressin and hydroxyethyl starch solution (HHS) on outcome in resuscitated blunt trauma patients with pulseless electrical activity (PEA) cardiac arrest.

METHODS

Two treatment groups of resuscitated trauma patients in cardiac arrest were compared: in the epinephrine group patients received epinephrine 1 mg IV every 3 min only; in the vasopressin group patients first received hypertonic HHS and arginine vasopressin 40 units IV only or followed by epinephrine 1 mg every 3 min until cessation of CPR. Medical trauma care was provided according to advanced trauma life support (ATLS) guidelines.

RESULTS

The study included 31 patients and there were no significant demographic or clinical differences between the treatment groups. Significantly more circulatory restorations [11/13 (85%) vs 3/18 (17%); P < 0.01] and better 24-h survival rates [8/13 (62%) vs 2/18 (11%); P = 0.001] were observed in the vasopressin group. Average mean arterial pressure (100.4 +/- 11.4 mmHg vs 80.3 +/- 12.4 mmHg) and final end-tidal partial pressure of carbon dioxide (PETCO(2)) at admission (4.5 +/- 0.9 kPa vs 2.8 +/- 0.4 kPa) were also higher in the vasopressin group.

CONCLUSION

Our results suggest that victims of severe blunt trauma with PEA should be initially treated with vasopressin in combination with HHS volume resuscitation followed by standard resuscitation therapy and other procedures when appropriate. Vasopressin might be potentially lifesaving in blunt trauma cardiac arrest compared to standard treatment with epinephrine.

Hypertonic saline up-regulates A3 adenosine receptor expression of activated neutrophils and increases acute lung injury after sepsis

OBJECTIVE

Hypertonic saline resuscitation reduces tissue damage by inhibiting polymorphonuclear neutrophils. Hypertonic saline triggers polymorphonuclear neutrophils to release adenosine triphosphate that is converted to adenosine, inhibiting polymorphonuclear neutrophils through A2a adenosine receptors. Polymorphonuclear neutrophils also express A3 adenosine receptors that enhance polymorphonuclear neutrophil functions. Here we investigated whether A3 receptors may diminish the efficacy of hypertonic saline in a mouse model of acute lung injury.

DESIGN

Randomized animal study and laboratory investigation.

SETTING

University research laboratory.

INTERVENTIONS

The effect of A3 receptors on the efficacy of hypertonic saline resuscitation was assessed in A3 receptor knockout and wild-type mice. Animals were treated with hypertonic saline (7.5% NaCl, 4 mL/kg) before or after cecal ligation and puncture, and acute lung injury and mortality were determined. The effect of timing of hypertonic saline exposure on A3 receptor expression and degranulation was studied in vitro with isolated human polymorphonuclear neutrophils.

MEASUREMENTS AND MAIN RESULTS

Treatment of human polymorphonuclear neutrophils with hypertonic saline before stimulation with formyl methionyl-leucyl-phenylalanine inhibited A3 receptor expression and degranulation, whereas hypertonic saline-treatment after formyl methionyl-leucyl-phenylalanine-stimulation augmented A3 receptor expression and degranulation. Acute lung injury in wild-type mice treated with hypertonic saline after cecal ligation and puncture was significantly greater than in wild-type mice pretreated with hypertonic saline. This aggravating effect of delayed hypertonic saline-treatment was absent in A3 receptor knockout mice. Similarly, mortality in wild-type mice with delayed hypertonic saline-treatment was significantly higher (88%) than in animals treated with hypertonic saline before cecal ligation and puncture (50%). Mortality in A3 receptor knockout mice remained only 50% regardless of timing of hypertonic saline administration.

CONCLUSIONS

Polymorphonuclear neutrophil A3 receptors expression determines whether hypertonic saline resuscitation inhibits or aggravates polymorphonuclear neutrophil-induced acute lung injury. These findings suggest that A3 antagonists could improve the efficacy of hypertonic saline resuscitation by reducing side effects in patients whose polymorphonuclear neutrophils are activated before hypertonic saline treatment.

Intravenous hypertonic NaCl acts via cerebral sodium-sensitive and angiotensinergic mechanisms to improve cardiac function in haemorrhaged conscious sheep

Acute NaCl loading as resuscitation in haemorrhagic hypovolaemia is known to induce rapid cardiovascular recovery. Besides an osmotically induced increase in plasma volume the physiological mechanisms of action are unknown. We hypothesized that a CNS mechanism, elicited by increased periventricular [Na(+)] and mediated by angiotensin II type 1 receptors (AT(1)), is obligatory for the full effect of hypertonic NaCl. To test this we investigated the cardiovascular responses to haemorrhage and subsequent hypertonic NaCl infusion (7.5% NaCl, 4 ml (kg BW)(-1)) in six conscious sheep subjected to intracerebroventricular (i.c.v.) infusion of artificial cerebrospinal fluid (aCSF; control), mannitol solution (Man; 75 mmol l(-1) [Na(+)], total osmolality 295 mosmol kg(-1)) or losartan (Los; 1 mg ml(-1), AT(1) receptor antagonist) at three different occasions. Man normalized (144 +/- 6 mmol l(-1), mean +/- s.d.) the increase in i.c.v. [Na(+)] seen after aCSF (161 +/- 2 mmol l(-1)). Compared with control, both Man and Los significantly (P < 0.05) attenuated the improvement in mean arterial blood pressure (MAP), cardiac index and mesenteric blood flow (SMBF) in response to intravenous hypertonic NaCl: MAP, rapid response +45 mmHg versus +38 mmHg (Man) and +35 mmHg (Los); after 180 min, +32 mmHg versus +21 mmHg (Man) and +19 mmHg (Los); cardiac index after 180 min, +1.9 l min(-1) (m(2))(-1) versus +0.9 l min(-1) (m(2))(-1) (Man) and +0.9 l min(-1) (m(2))(-1) (Los); SMBF rapid response, +981 ml min(-1) versus +719 ml min(-1) (Man) and +744 ml min(-1) (Los); after 180 min, +602 ml min(-1) versus +372 ml min(-1) (Man) and +314 ml min(-1) (Los). The results suggest that increased periventricular [Na(+)] and cerebral AT(1) receptors contribute, together with plasma volume expansion, to improve systemic haemodynamics after treatment with hypertonic NaCl in haemorrhagic hypovolaemia.