Effects of hypertonic saline and dextran 70 on cardiac contractility after hemorrhagic shock

The role of hypertonic saline dextran in trauma resuscitation

Modern trauma management has recognized the importance of using conservative fluid resuscitation regimes in order to prevent complications from fluid overload arising. Hypertonic/hyperoncotic fluids appear to provide an ideal means of facilitating this, requiring only small volumes to rapidly elevate blood pressure. Hypertonic saline dextran (HSD) was introduced in 1985 but its take up has been slow, a large part of this has been due to the lack of human trials and concerns about complications.

The current evidence has been reviewed and it is clear that HSD is an efficient means of correcting hypotension, doing so mainly by the mobilizing endogenous water. It is becoming apparent that early administration has the potential to modulate the inflammatory cascade in patients at risk of developing adult respiratory distress syndrome (ARDS) and multiorgan failure. This is reflected in the handful of human trials that show a trend towards increased survival (particularly for head injuries) and a possible reduction in ARDS. The side effect profile appears to be good, even in the presence of dehydration or penetrating trauma.

Published human trials have methodological problems and lack of power of study this has led to a reliance on animal studies. Clearly there is great potential, but before large-scale prehospital usage can be justified further well-conducted randomized human trials are needed.

Fluid resuscitation in trauma patients: what should we know?

PURPOSE OF REVIEW

Fluid resuscitation in trauma patients could reduce organ failure, until blood components are available and hemorrhage is controlled. However, the ideal fluid resuscitation strategy in trauma patients remains a debated topic. Different types of trauma can require different types of fluids and different volume of infusion.

RECENT FINDINGS

There are few randomized controlled trials investigating the efficacy of fluids in trauma patients. There is no evidence that any type of fluids can improve short-term and long-term outcome in these patients. The main clinical evidence emphasizes that a restrictive fluid resuscitation before surgery improves outcome in patients with penetrating trauma. Fluid management of blunt trauma patients, in particular with coexisting brain injury, remains unclear.

SUMMARY

In order to focus on the state of the art about this topic, we review the current literature and guidelines. Recent studies have underlined that the correct fluid resuscitation strategy can depend on the type of trauma condition: penetrating, blunt, brain injury or a combination of them. Of course, further studies are needed to investigate the impact of a specific fluid strategy on different type and severity of trauma.

Hemodynamic responses elicited by systemic injections of isotonic and hypertonic saline in hemorrhaged rats

PURPOSE

The objectives of this study were (i) to characterize the hemodynamic responses caused by controlled hemorrhage (HEM) in pentobarbital-anesthetized rats, and (ii) to determine the responses elicited by systemic bolus injections of isotonic saline (0.15M) or hypertonic saline (3M) given 5min after completion of HEM.

RESULTS

Controlled HEM (4.3±0.2ml/rat at 1.5ml/min) resulted in a pronounced and sustained fall in mean arterial blood pressure (MAP) to about 40mmHg. The fall in MAP was associated with a reduction in hindquarter vascular resistance (HQR) but no changes in renal (RR) or mesenteric (MR) vascular resistances. Systemic injections of isotonic saline (96-212μmol/kg i.v., in 250-550μl) did not produce immediate responses but promoted the recovery of MAP to levels below pre-HEM values. Systemic injections of hypertonic saline (750-3000μmol/kg, i.v., in 250-550μl) produced immediate and pronounced falls in MAP, RR, MR and especially HQR of 30-120s in duration. However, hypertonic saline prompted a full recovery of MAP, HQR and RR to pre-HEM levels and an increase in MR to levels above pre-HEM values.

CONCLUSIONS

This study demonstrates that (i) HEM induced a pronounced fall in MAP which likely involved a fall in cardiac output and HQR, (ii) isotonic saline did not fully normalize MAP, and (iii) hypertonic saline produced dramatic initial responses, and promoted normalization of MAP probably by restoring blood volume and cardiac output through sequestration of fluid from intracellular compartments.

Hyperosmolar therapy for intracranial hypertension

The use of hyperosmolar agents for intracranial hypertension was introduced in the early 20th century and remains a mainstay of therapy for patients with cerebral edema. Both animal and human studies have demonstrated the efficacy of two hyperosmolar agents, mannitol and hypertonic saline, in reducing intracranial pressure via volume redistribution, plasma expansion, rheologic modifications, and anti-inflammatory effects. However, because of physician and institutional variation in therapeutic practices, lack of standardized protocols for initiation and administration of therapy, patient heterogeneity, and a paucity of randomized controlled trials have yielded little class I evidence on which clinical decisions can be based, most current evidence regarding the use of hyperosmolar therapy is derived from retrospective analyses (class III) and case series (class IV). In this review, we summarize the available evidence regarding the use of hyperosmolar therapy with mannitol or hypertonic saline for the medical management of intracranial hypertension and present a comprehensive discussion of the evidence associated with various theoretical and practical concerns related to initiation, dosage, and monitoring of therapy.

Hemodynamic support of the trauma patient

PURPOSE OF REVIEW

The aim of this review is to address and summarize some key issues and recent insights into the hemodynamic support of the trauma patient related to fluid administration.

RECENT FINDINGS

Colloids are not superior to crystalloids in treating hypovolemia in the trauma patient and show no survival benefit. Furthermore, several adverse effects (renal failure, bleeding complications and anaphylaxis) have been reported with the use of artificial colloids. Hypertonic saline is effective and well tolerated in the treatment of hypovolemic shock and traumatic brain injury. Potential benefits are reduced fluid requirements and immune modulation. Resuscitation strategies should depend on the type of injury (penetrating vs. blunt; concomitant brain injury). Excessive fluid resuscitation, which can cause acute respiratory distress syndrome, abdominal compartment syndrome and brain edema, should be avoided. Dynamic parameters to guide volume therapy are probably more reliable than static parameters and minimally invasive techniques to monitor the microcirculation are becoming more important to determine the endpoints of resuscitation.

SUMMARY

Hemodynamic support is an early goal in the treatment of the trauma patient. The use of crystalloids is currently recommended in trauma resuscitation. The amount of fluid we give should be tailored to the individual trauma patient in which clear endpoints of resuscitation are of vital importance to maximize the chances of survival.

Review article: hypertonic saline use in the emergency department

Hypertonic saline (HS) is being increasingly used for the management of a variety of conditions, most notably raised intracranial pressure. This article reviews the available evidence on HS solutions as they relate to emergency medicine, and develops a set of recommendations for its use. To conclude, HS is recommended as an alternative to mannitol for treating raised intracranial pressure in traumatic brain injury. HS is also recommended for treating severe and symptomatic hyponatremia, and is worth considering for both recalcitrant tricyclic antidepressant toxicity and for cerebral oedema complicating paediatric diabetic ketoacidosis. HS is not recommended for hypovolaemic resuscitation.

Comparison of lung injury after normal or small volume optimized resuscitation in a model of hemorrhagic shock

OBJECTIVE

To compare lung injury induced by a hemorrhagic shock resuscitated with normal saline or with small volumes of a hypertonic/hyperoncotic solution.

DESIGN AND SETTING

Randomized, controlled, laboratory study in an animal research laboratory.

SUBJECTS

Nineteen pigs (43 +/- 4 kg).

INTERVENTIONS

After anesthesia and mechanical ventilation animals were bled to induce a 2-h deep shock and resuscitated for 2 h using normal saline (NS, 2 ml/kg per minute, n = 7) or the association of 7.2% NaCl with 6% hydroxyethylstarch 200/0.5 (HSHES, 4 ml/kg in 10 min followed by 0.2 ml/kg per minute, n = 7) to reach cardiac index and mixed venous oxygen saturation goals. Lungs were removed 6[Symbol: see text]h after the initiation of hemorrhage. Five animals were used as controls without hemorrhage.

MEASUREMENTS AND RESULTS

Resuscitation goals were achieved using 90 +/- 17 ml/kg NS or 6.8 +/- 1.9 ml/kg HSHES. Lung injury was noted in both hemorrhage groups but was not influenced by the type of resuscitation. Extravascular lung water was measured at 9.6 +/- 1.8 ml/kg in the NS group, 9.2 +/- 1.6 ml/kg in the HSHES, group and 6.4 +/- 1 m/kg in the control group. The degree of histological alveolar membrane focal thickening and interstitial neutrophil infiltration were significantly more pronounced in the hemorrhage groups with no difference between the two types of fluid loading. Finally, pulmonary levels of IL-8 were higher after hemorrhage regardless of the type of resuscitation.

CONCLUSIONS

When included in an optimized and goal directed resuscitation, the use of normal saline or a small volume of hypertonic/hyperoncotic solution does not result in a different early hemorrhage-induced lung injury.

Hemodynamic responses elicited by gamma2-MSH or blood replacement in hemorrhaged rats

BACKGROUND

Systemic injections of compounds such as gamma(2)-melanocyte-stimulating hormone (gamma(2)-MSH), which increase sympathetic neurogenic vasoconstriction, may be beneficial in treating hemorrhage-induced hypotension.

METHODS

This study characterized (1) the hemodynamic responses elicited by systemic injections of gamma(2)-MSH in pentobarbital-anesthetized hemorrhaged rats, and (2) the hemodynamic responses elicited by the replacement of withdrawn blood in these rats.

RESULTS

Controlled hemorrhage (4.8 +/- 0.3 mL/rat at 1.5 mL/min) resulted in a pronounced and sustained fall in mean arterial blood pressure (MAP). The fall in MAP was associated with a reduction in heart rate (HR) and hindquarter (HQR) vascular resistance but no changes in mesenteric (MR) or renal (RR) vascular resistances. Systemic injections of gamma(2)-MSH (10-40 microg/kg, i.v.) produced dose-dependent increases in HR, MAP, and vascular resistances of 20 to 60 s in duration in the hemorrhaged rats. In contrast, injection of the withdrawn blood produced an immediate and sustained increase in MAP, which was associated with a pronounced vasodilation in the hindquarter bed but no changes in MR or RR.

CONCLUSIONS

These findings suggest that although gamma(2)-MSH elicits pressor and vasoconstrictor responses in hemorrhaged rats, the bolus injection of this peptide may not in itself be an effective strategy for the sustained restoration of MAP in these rats. Moreover, although blood replacement effectively restores MAP via increases in cardiac output rather than total peripheral resistance, it appears that this manipulation produces an active vasodilation in the hindquarter bed. The possibility that this vasodilation involves a sympathetic neurogenic vasodilator system, which innervates the hindlimb vascular bed but not mesenteric or renal vascular beds, will be discussed.

The Effect of 7.2% Hypertonic Saline Solution on M-Mode Echocardiographic Indices in Normovolemic Dogs

This study investigated whether a small volume of 7.2% hypertonic saline solution (HSS) could affect M-mode echocardiographic indices in dogs. HSS induced significant increase in heart rate, stroke volume and cardiac index, when the fluid infusion was completed (P<0.05). In the HSS group, the left ventricular end-diastolic volume index, as an index of preload, significantly increased (P<0.05), whereas left ventricular end-systolic volume index were not altered. HSS induced slight increases in ejection fraction at end of infusion despite significantly differences were not observed. In conclusion, HSS did not induce a demonstrable effect on M-mode echocardiographic indices of systolic function-enhance cardiac contractility, but it caused preload augmentation that may contribute to an abrupt and transient increase in cardiac output just after HSS infusion.

Effects of hypertonic saline and dextran 70 on cardiac diastolic function after hemorrhagic shock

BACKGROUND

A bolus of 7.5% NaCl-6% Dextran 70 (HSD) is effective in resuscitating hypovolemic shock. Common hemodynamic findings with HSD are restoration of cardiac output, increased blood pressure, and improvement of peripheral circulation. However, the effect of HSD upon cardiac function is still controversial. In our previous study, when HSD did not improve cardiac contractility, it was speculated that it might affect cardiac diastolic function without a change in contractility. Therefore, we studied the effects of HSD on cardiac diastolic function.

METHODS

Hemorrhagic shock was created by exsanguination of 31.4 +/- 0.9 ml/kg (NS group) or 29.0 +/- 3.6 ml/kg (HSD group). Then mean BP was maintained at 50 mm Hg for 30 min in both groups. The HSD group (n = 6) received HSD (4 ml/kg) and the NS (control) group (n = 5) received normal saline (40 ml/kg) after the shock. Cardiac diastolic functions were measured in both groups using the peak negative dP/dt and the left ventricular end-diastolic pressure-volume relationship (EDPVR) during the experimental period: before shock, immediately, and 2 h after resuscitation.

RESULTS

Hemodynamic parameters in both groups demonstrated similar changes throughout the experimental period. The peak negative dP/dt, stiffness constant, and elasticity obtained by EDPVR did not differ significantly between the two groups.

CONCLUSION

HSD seems to be an effective resuscitation fluid after hemorrhagic shock because the volume of HSD required to maintain circulation is significantly smaller than that of normal saline. However, our data revealed that HSD does not change cardiac diastolic function after hemorrhagic shock.

Hypertonic preconditioning inhibits macrophage responsiveness to endotoxin

Hypertonic saline has been shown to modulate cell shape and the response of components of the innate immune response. However, the effect of hypertonic saline on the macrophage remains unknown. We hypothesized that hypertonic preconditioning would impair subsequent inflammatory mediator signaling through a reduction in stress fiber polymerization and mitogen-activated protein kinase activity after LPS stimulation. Rabbit alveolar macrophages were stimulated with 100 ng/ml of LPS. Selected cells were preconditioned with 40-100 mM of NaCl, mannitol, or urea for 4 h and returned to isotonic medium before LPS stimulation. Cellular protein was harvested and subjected to Western blot analysis for the dually phosphorylated active forms of p38 and extracellular signal-related kinase (ERK) 1/2. TNF production was determined by an L929 bioassay, and stress fiber polymerization was evaluated by confocal microscopy. Preconditioning of macrophages with NaCl or mannitol resulted in dose-dependent reduction in ERK 1/2 phosphorylation with no effect on p38 phosphorylation. Urea preconditioning had no effect on either mitogen-activated protein kinase. A dose-dependent attenuation of TNF production was seen with NaCl and mannitol preconditioning (p < 0.05), but not with urea. NaCl and mannitol preconditioning resulted in failure of LPS-induced stress fiber polymerization, whereas urea did not. Extracellular hypertonic conditions (i.e., NaCl and mannitol) have an immunomodulatory effect on macrophages, demonstrated through failure of optimal stress fiber polymerization, ERK 1/2 activity, and TNF production. Intracellular hypertonic conditions (i.e., urea) had no significant effect. Hypertonic saline or mannitol resuscitation, therefore, may help protect against multiple-organ dysfunction syndrome as a result of this reduced proinflammatory responsiveness.

Current controversies in shock and resuscitation

Many controversies and uncertainties surround resuscitation of hemorrhagic shock caused by vascular trauma. Whereas the basic pathophysiology is better understood, much remains to be learned about the many immunologic cascades that lead to problems beyond those of initial fluid resuscitation or operative hemostasis. Fluid therapy is on the verge of significant advances with substitute oxygen carriers, yet surgeons are still beset with questions of how much and what type of initial fluid to provide. Finally, the parameters chosen to guide therapy and the methods used to monitor patients present other interesting issues.

Hypertonic immunomodulation is reversible and accompanied by changes in CD11b expression

BACKGROUND

In a two-hit model of hemorrhagic shock and lipopolysaccharide (LPS), we previously showed that hypertonic saline (HTS) resuscitation reduced lung sequestration of neutrophils and the accompanying injury. This effect was partially attributed to suppressed expression of the surface adhesion molecule CD11b. This study investigates the duration of this protective effect after a single HTS dose and the usefulness of repeated infusions.

MATERIAL AND METHODS

The previous two-hit rodent model was used. Neutrophil lung sequestration was measured by bronchoalveolar fluid cell count. CD11b expression was followed by flow cytometry. In vitro studies used isolated human neutrophils.

RESULTS

Eighteen hours following resuscitation, the protective effect of HTS was lost. At this time, LPS caused an increase in both neutrophil lung sequestration and CD11b expression, regardless of the resuscitation regimen used. A second infusion of HTS prevented these changes and restored the lung protection observed earlier. In vitro studies showed that the duration of hypertonic pretreatment is an important determinant of cell responsiveness under the isotonic conditions: Four but not 2 h hypertonic exposure was able to prevent upregulation of CD11b induced by LPS added immediately after reestablishing isotonicity.

CONCLUSIONS

This study demonstrates that HTS resuscitation lessens lung neutrophil sequestration and CD11b surface expression induced by LPS. This protective effect is transient but can be restored by a second HTS infusion suggesting that maintenance of beneficial effect necessitates repeated HTS addition. The reversibility ensures rapid modulation of neutrophil functions, thereby preventing acute tissue damage without causing long-lasting immunosuppression.

Immunomodulatory Effects of Hypertonic Resuscitation on the Development of Lung Inflammation Following Hemorrhagic Shock

Hypertonic resuscitation fluids are known to be effective in restoring circulating volume in the hypovolemic trauma patient. Previous studies have suggested that hypertonicity might exert effects on immune cells leading to an altered host response. The present studies evaluated the effect of hypertonic resuscitation on the development of lung injury in a hemorrhagic shock model in which antecedent shock primes for increased lung neutrophil sequestration in response to intratracheal LPS. Resuscitation with hypertonic saline significantly reduced albumin leak, bronchoalveolar lavage fluid neutrophil counts, and the degree of histopathologic injury compared with resuscitation with Ringer’s lactate. Both in vivo and in vitro data suggest that this beneficial effect may be related to altered adhesion molecule expression by the neutrophil. Specifically, hypertonicity induced shedding of L-selectin and prevented LPS-stimulated expression and activation of CD11b, both of which might contribute to reduced sequestration in the lung. Impaired up-regulation of lung ICAM-1 may have also participated, although ex vivo studies suggest that alterations in neutrophils were sufficient to account for the effect. Lung cytokine-induced neutrophil chemoattractant did not differ between animals resuscitated with hypertonic saline vs Ringer’s lactate. Considered together, these studies demonstrate a possible novel approach to inhibiting organ injury in disease processes characterized by neutrophil-mediated damage.

Effect of hypertonic saline solution and dextran on ventricular blood flow and heart-lung interaction after hemorrhagic shock

BACKGROUND

Hypertonic saline solutions may have beneficial hemodynamic effects in the resuscitation of hemorrhagic shock. The effects on cardiac function and potential interaction with lung function are controversial and served as the basis for this study.

METHODS

Domestic swine were resuscitated from hemorrhagic shock with equivalent sodium loads of lactated Ringer's solution (LR) or 7.5% NaCl plus 10% dextran (HSD). Hemodynamic data were obtained at baseline, shock, and after resuscitation. Right ventricular ejection fraction and left ventricular change in pressure with respect to time (dP/dt) were used to index contractility. Regional myocardial blood flow was determined with microspheres. Lung water was determined gravimetrically.

RESULTS

There were no differences in the ability to restore hemodynamic parameters with equivalent sodium loads of LR and HSD resuscitation. Right ventricular ejection fraction and left ventricular change in pressure with respect to time were only transiently affected by shock and resuscitation. Regional myocardial blood flow was increased above baseline values after HSD. The total resuscitation volumes were 1958 +/- 750 mL and 140 +/- 31 mL with LR and HSD, respectively.

CONCLUSIONS

Although LR and HSD were equally effective in the early resuscitation of hemorrhagic shock, this occurred at the expense of significantly greater volume requirements for resuscitation with LR. This may contribute to cardiac dysfunction in this setting. Enhanced regional myocardial blood flow after HSD resuscitation may be beneficial against ongoing myocardial stress.