Resuscitation of haemorrhagic shock with normal saline vs. lactated Ringer's: effects on oxygenation, extravascular lung water and haemodynamics

Effects of Different Crystalloid Fluids on Renal Tissue in an Experimental Model of Hemorrhagic Shock

Objective

The type of fluid that should be used in uncontrollable hemorrhages remains an area of research. This study was designed to compare the effects of resuscitation with Ringer's lactate (RL) solution versus a normal saline (NS) solution on hemodynamics, renal tissue histopathology, coagulation, and apoptosis in a rat model of hemorrhagic shock.

Methods

The study employed groups designated as the control, hemorrhage, NS, and RL groups. Heart rate, mean arterial pressure, and respiratory rate were monitored. Annexin A5 values were assayed, rotational thromboelastometry analysis was performed, and excised kidney tissue samples were histopathologically analyzed.

Results

Blood pressure levels were found to be significantly higher in the control group than those measured in the other groups. While the clotting time (CT) and clot formation time (CFT) in the hemorrhage group were significantly longer than those in the control and RL groups, the CT and CFT measured in the control group were significantly shorter compared to the RL group. The mean Annexin A5 level was in the hemorrhage group, which was significantly higher compared to the other groups. In the renal histopathological evaluation, the scores of proximal tubular injury, distal renal tubular injury, and interstitial renal tubular injury were found to be significantly lower in the control group compared to the other groups.

Conclusion

This study demonstrated that NS or RL can be used safely to improve the hemodynamic symptoms resulting from hemorrhagic shock as a means to reduce apoptosis, and to decrease findings in favor of coagulopathy in bedside coagulation tests during the early stages of hemorrhagic shock until the time of starting a blood transfusion.

The critical care literature 2021

An emergency physician (EP) is often the first provider to evaluate, resuscitate, and manage a critically ill patient. Over the past two decades, the annual hours of critical care delivered in emergency departments across the United States has dramatically increased. During the period from 2006 to 2014, the extent of critical care provided in the emergency department (ED) to critically ill patients increased approximately 80%. During the same time period, the number of intubated patients cared for in the ED increased by approximately 16%. In addition to seeing more critically ill patients, EPs are often tasked with providing critical care long beyond the initial resuscitation period. Prolonged ED boarding times for critically ill patients is associated with increased duration of mechanical ventilation, increased intensive care unit (ICU) length of stay, increased hospital length of stay, increased medication-related adverse events, and increased in-hospital, 30-day, and 90-day mortality. As a result, it is imperative for the EP to be knowledgeable about recent developments in resuscitation and critical care medicine, so that the critically ill ED patient care receive current evidence-based care. These articles have been selected based on the authors review of key critical care, resuscitation, emergency medicine, and medicine journals and their opinion of the importance of study findings as it pertains to the care of the critically ill ED patient. Topics covered in this article include cardiac arrest, post-cardiac arrest care, rapid sequence intubation, mechanical ventilation, fluid resuscitation, cardiogenic shock, transfusions, and sepsis.

Terlipressin combined with conservative fluid management attenuates hemorrhagic shock-induced acute kidney injury in rats

Hemorrhagic shock (HS), a major cause of trauma-related mortality, is mainly treated by crystalloid fluid administration, typically with lactated Ringer's (LR). Despite beneficial hemodynamic effects, such as the restoration of mean arterial pressure (MAP), LR administration has major side effects, including organ damage due to edema. One strategy to avoid such effects is pre-hospitalization intravenous administration of the potent vasoconstrictor terlipressin, which can restore hemodynamic stability/homeostasis and has anti-inflammatory effects. Wistar rats were subjected to HS for 60 min, at a target MAP of 30-40 mmHg, thereafter being allocated to receive LR infusion at 3 times the volume of the blood withdrawn (liberal fluid management); at 2 times the volume (conservative fluid management), plus terlipressin (10 µg/100 g body weight); and at an equal volume (conservative fluid management), plus terlipressin (10 µg/100 g body weight). A control group comprised rats not subjected to HS and receiving no fluid resuscitation or treatment. At 15 min after fluid resuscitation/treatment, the blood previously withdrawn was reinfused. At 24 h after HS, MAP was higher among the terlipressin-treated animals. Terlipressin also improved post-HS survival and provided significant improvements in glomerular/tubular function (creatinine clearance), neutrophil gelatinase-associated lipocalin expression, fractional excretion of sodium, aquaporin 2 expression, tubular injury, macrophage infiltration, interleukin 6 levels, interleukin 18 levels, and nuclear factor kappa B expression. In terlipressin-treated animals, there was also significantly higher angiotensin II type 1 receptor expression and normalization of arginine vasopressin 1a receptor expression. Terlipressin associated with conservative fluid management could be a viable therapy for HS-induced acute kidney injury, likely attenuating such injury by modulating the inflammatory response via the arginine vasopressin 1a receptor.

Effect of Intraoperative Goal-directed Balanced Crystalloid versus Colloid Administration on Major Postoperative Morbidity

Editor’s Perspective

What We Already Know about This Topic

What This Article Tells Us That Is New

Background

Crystalloid solutions leave the circulation quickly, whereas colloids remain for hours, thus promoting hemodynamic stability. However, colloids are expensive and promote renal toxicity in critical care patients. This study tested the hypothesis that goal-directed colloid administration during elective abdominal surgery decreases 30-day major complications more than goal-directed crystalloid administration.

Methods

In this parallel-arm double-blinded multicenter randomized trial, adults having moderate- to high-risk open and laparoscopically assisted abdominal surgery with general anesthesia were randomly assigned to Doppler-guided intraoperative volume replacement with 6% hydroxyethyl starch 130/0.4 (n = 523) or lactated Ringer’s solution (n = 534). The primary outcome was a composite of serious postoperative cardiac, pulmonary, infectious, gastrointestinal, renal, and coagulation complications that were assessed with a generalized estimating equation multivariate model. The primary safety outcome was a change in serum creatinine concentration up to 6 months postoperatively, compared to baseline concentrations.

Results

A total of 1,057 patients were included in the analysis. Patients assigned to crystalloid received a median [quartile 1, quartile 3] amount of 3.2 l [2.3, 4.4] of crystalloid, and patients assigned to colloid received 1.0 l [0.5, 1.5] of colloid and 1.8 l [1.2, 2.4] of crystalloid. The estimated intention-to-treat common effect relative risk for the primary composite was 0.90 for colloids versus crystalloids (95% CI: 0.65 to 1.23, P = 0.51), and 18% (91 of 523) of colloid patients and 20% (103 of 534) of crystalloid patients incurred at least one component of the primary outcome composite. There was no evidence of renal toxicity at any time.

Conclusions

Doppler-guided intraoperative hydroxyethyl starch administration did not significantly reduce a composite of serious complications. However, there was also no indication of renal or other toxicity.

Optimal crystalloid volume ratio for blood replacement for maintaining hemodynamic stability and lung function: an experimental randomized controlled study

BACKGROUND

Crystalloids are first line in fluid resuscitation therapy, however there is a lack of evidence-based recommendations on the volume to be administered. Therefore, we aimed at comparing the systemic hemodynamic and respiratory effects of volume replacement therapy with a 1:1 ratio to the historical 1:3 ratio.

METHODS

Anesthetized, ventilated rats randomly included in 3 groups: blood withdrawal and replacement with crystalloid in 1:1 ratio (Group 1, n = 11), traditional 1:3 ratio (Group 3, n = 12) and a control group with no interventions (Group C, n = 9). Arterial blood of 5% of the total blood volume was withdrawn 7 times, and replaced stepwise with different volume rations of Ringer's acetate, according to group assignments. Airway resistance (Raw), respiratory tissue damping (G) and tissue elastance (H), mean arterial pressure (MAP) and heart rate (HR) were assessed following each step of fluid replacement with a crystalloid (CR1-CR6). Lung edema index was measured from histological samples.

RESULTS

Raw decreased in Groups 1 and 3 following CR3 (p < 0.02) without differences between the groups. H elevated in all groups (p < 0.02), with significantly higher changes in Group 3 compared to Groups C and 1 (both p = 0.03). No differences in MAP or HR were present between Groups 1 and 3. Lung edema was noted in Group 3 (p < 0.05).

CONCLUSIONS

Fluid resuscitation therapy by administering a 1:1 blood replacement ratio revealed adequate compensation capacity and physiological homeostasis similar with no lung stiffening and pulmonary edema. Therefore, considering this ratio promotes the restrictive fluid administration in the presence of continuous and occult bleeding.

Supporting preterm cardiovascular function

Preterm infants are at higher risk of adverse neurodevelopmental outcomes. Inadequate cerebral oxygen delivery resulting from poor cardiovascular function is likely to be a significant contributor to preterm brain injury. In this context, improved support of cardiovascular function is integral to improving preterm outcomes. Many of the treatments used to support preterm cardiovascular function are based on adult physiology and may not be appropriate for the unique physiology of the preterm infant. The preterm heart is structurally immature with reduced contractility and low cardiac output. However, there is limited evidence that inotropic support with dopamine and/or dobutamine is effective in preterm babies. Hypovolemia may also contribute to poor preterm cardiovascular function; there is evidence that capillary leakage results in considerable loss of plasma from the circulation of newborn preterm babies. In addition, the vasoconstrictor response to acute stimuli does not develop until quite late in gestation and is limited in the preterm infant. This may lead to inappropriate vasodilatation adding to functional hypovolemia. The first line treatment for hypotension in preterm infants is volume expansion with crystalloid solutions, but this has limited efficacy in the preterm infant. More effective methods of volume expansion are required. Effective support of preterm cardiovascular function requires better understanding of preterm cardiovascular physiology so that treatments can target mechanisms that are sufficiently mature to respond.

Crystalloid fluid choice in the critically ill : Current knowledge and critical appraisal

Intravenous infusion of crystalloid solutions is one of the most frequently administered medications worldwide. Available crystalloid infusion solutions have a variety of compositions and have a major impact on body systems; however, administration of crystalloid fluids currently follows a "one fluid for all" approach than a patient-centered fluid prescription. Normal saline is associated with hyperchloremic metabolic acidosis, increased rates of acute kidney injury, increased hemodynamic instability and potentially mortality. Regarding balanced infusates, evidence remains less clear since most studies compared normal saline to buffered infusion solutes.; however, buffered solutes are not homogeneous. The term "buffered solutes" only refers to the concept of acid-buffering in infusion fluids but this does not necessarily imply that the solutes have similar physiological impacts. The currently available data indicate that balanced infusates might have some advantages; however, evidence still is inconclusive. Taking the available evidence together, there is no single fluid that is superior for all patients and settings, because all currently available infusates have distinct differences, advantages and disadvantages; therefore, it seems inevitable to abandon the "one fluid for all" strategy towards a more differentiated and patient-centered approach to fluid therapy in the critically ill.

Ringer's Lactate Versus Normal Saline in Urgent Cesarean Delivery in a Resource-Limited Setting: A Pragmatic Clinical Trial

BACKGROUND

Crystalloids are used routinely for perioperative fluid management in cesarean delivery. Few studies have determined the crystalloid of choice in obstetric anesthesia. We compared the effects of Ringer's lactate (RL) versus 0.9% normal saline (NS) on maternal and neonatal blood pH and 24-hour postoperative morbidity in urgent cesarean delivery in a low-resource setting. Our hypothesis was that RL would result in 30% less acidosis than NS.

METHODS

This was a pragmatic prospective double-blind randomized controlled trial in the Mulago National Referral Hospital Labor Ward Theater from September 2011 to May 2012. Five hundred parturients were studied; 252 were randomly assigned to NS and 248 to RL groups. Preoperative and postoperative maternal venous blood gases and placental umbilical arterial cord blood gases were analyzed. The primary outcome was incidence of maternal acidosis, as defined by a postoperative drop in venous pH below 7.32 or reduction in base excess below -3 in a previously normal parturient. Maternal 24-hour postoperative morbidity, neonatal pH, and neonatal base excess were the main secondary outcomes. The study was registered in ClinicalTrials.gov as NCT01585740.

RESULTS

The overall incidence of maternal acidosis was 38% in NS and 29% in RL (relative risk, 1.29; 95% confidence interval, 1.01-1.66; P = .04). Thirty-two percent of parturients in NS experienced a drop in venous pH below 7.32 postoperatively, compared with 19% in RL (relative risk, 1.65; 95% confidence interval, 1.18-2.31; P = .003). The comparative drop in base excess postoperatively below -3 between the 2 groups was not statistically significant. There were no significant differences in the incidence of maternal 24-hour postoperative morbidity events and neonatal outcomes between the 2 groups.

CONCLUSIONS

NS may be a safe choice for intraoperative fluid therapy in urgent cesarean delivery as RL, albeit with an increased incidence of metabolic acidosis.

Cytochrome c limits oxidative stress and decreases acidosis in a rat model of hemorrhagic shock and reperfusion injury

BACKGROUND

Hemorrhagic shock and reperfusion (HSR) injury leads to a cascade of reactive oxygen species (ROS) production and mitochondrial dysfunction, which results in energy failure, cell death, and multiple organ dysfunction. Cytochrome c (cyt c) is the final electron carrier in the mitochondrial electron transport chain providing the electrochemical force for ATP production. We sought to determine whether exogenous cyt c administration would improve parameters of organ dysfunction and/or mitochondrial stability in a rat model of HSR.

METHODS

Male rats were hemorrhaged to a mean arterial pressure (MAP) of 33 ± 2.0 mm Hg for 1 hour before resuscitation. Saline or cyt c (0.8 mg [HSR-LoCC] or 3.75 mg [HSR-HiCC]) was administered (i.v.) 30 minutes before resuscitation. Rats were euthanized by cardiac puncture 2 hours post-surgery and tissue collected and analyzed for lipid peroxidation, endogenous antioxidant activity (glutathione peroxidase (GPx) and catalase), TNF-α expression, mitochondrial function (complex-I activity), and circulating mitochondrial DNA (mtDNA).

RESULTS

Cyt c administration improved lactate clearance, decreased hepatic lipid peroxidation, increased hepatic GPx activity, restored pulmonary TNF-α to sham activity levels, and increased hepatic complex-I activity. Furthermore, addition of exogenous cyt c decreased circulating levels of mtDNA.

CONCLUSIONS

These studies demonstrate that cyt c reduces markers of physiologic stress, decreases oxidative stress, and lowers levels of circulating mtDNA. The impact of cytochrome c is organ specific. Further studies remain to determine the sum of the effects of cytochrome c on overall outcome.

Effects of Plasma-lyte A, lactated Ringer's, and normal saline on acid-base status and intestine injury in the initial treatment of hemorrhagic shock

BACKGROUND

Several kinds of crystalloid solutions have been used in the treatment of hemorrhagic shock (HS). Clinicians are faced with how to select the resuscitation fluids. The aim of the present study is to compare the effects of 3 crystalloid solutions, such as normal saline (NS), lactated Ringer's (LR), and Plasma-lyte A (PA), on acid-base status and intestine injury in rats subjected to HS.

METHODS

Thirty Wistar rats were divided into 4 groups. The sham group had no blood withdrawal. The other groups were subjected to severe HS and then injected with NS, LR, or PA. All treatments were followed with an infusion of red blood cell suspension. The mean arterial pressure was monitored throughout the experiment. The arterial blood gas, malonaldehyde, and myeloperoxidase levels in the small intestine were assayed 120 minutes after resuscitation.

RESULTS

Plasma-lyte A treatment could restore the pH, base excess (BE), HCO₃^-, Pao₂, and Paco₂. Comparing with sham group, NS failed to correct the decreased pH, BE, and HCO₃^- (P < .05), whereas LR treatment showed the decreased BE and HCO₃^- (P < .05) and increased Pao₂ (P < .05). There were no significant differences in malonaldehyde among the 4 groups (P > .05). Both PA and LR were more effective than NS in decreasing the myeloperoxidase level in the small intestine (P < .01).

CONCLUSIONS

Although the 3 crystalloid solutions play different roles, PA is better at correcting the acid-base balance and improving intestine injury during HS than NS and LR.

Chloride toxicity in critically ill patients: What's the evidence?

Crystalloids have become the fluid of choice in critically ill patients and in the operating room both for fluid resuscitation and fluid maintenance. Among crystalloids, NaCl 0.9% has been the most widely used fluid. However, emerging evidence suggests that administration of 0.9% saline could be harmful mainly through high chloride content and that the use of fluid with low chloride content may be preferable in major surgery and intensive care patients. Administration of NaCl 0.9% is the leading cause of metabolic hyperchloraemic acidosis in critically ill patients and side effects might target coagulation, renal function, and ultimately increase mortality. More balanced solutions therefore may be used especially when large amount of fluids are administered in high-risk patients. In this review, we discuss physiological background favouring the use of balanced solutions as well as the most recent clinical data regarding the use of crystalloid solutions in critically ill patients and patients undergoing major surgery.

Impact of common crystalloid solutions on resuscitation markers following Class I hemorrhage: A randomized control trial

BACKGROUND

Resuscitation after hemorrhage with crystalloid solutions can lead to marked acidosis and iatrogenically worsen the lethal triad. The effect of differing solutions on base deficit and lactate has been sparsely prospectively studied in humans. We sought to quantify the effect of normal saline (NS) and lactated Ringer's (LR) resuscitation in voluntary blood donors as a model for Class I hemorrhage.

METHODS

A prospective randomized control trial was conducted in conjunction with blood drives. Donors were randomized to receive no intravenous fluid (noIVF), 2-L NS, or 2-L LR after blood donation of 500 mL. Lactate and base deficit were measured before and after fluid administration using an iSTAT. The mean laboratory values were compared between groups first using a global test followed by pairwise testing between groups using the Wilcoxon rank-sum and Kruskal-Wallis tests. The Bonferroni correction was used and a statistical significance of p < 0.0167 was set.

RESULTS

A total of 157 patients completed the study. The mean (SD) age was 39.2 (12.7), and 65.0% were female. Patients in each group lost equivalent amounts of total blood volume, and a similar amount was replaced in the crystalloid group (p > 0.0167). Donors had comparable increases in lactate and base deficit after donation regardless of the group (p > 0.0167). After resuscitation with 2-L crystalloid, the lactate level increased higher in the LR group than in the noIVF or the NS group (1.36 mmol/L vs. 1.00 mmol/L vs. 1.54 mmol/L, p < 0.0001). In addition, the resuscitation base deficit increased in the NS group more than in the noIVF or LR group (-0.65 vs. -3.06 vs. -0.34, p < 0.0001).

CONCLUSION

This study is one of the first human studies to prospectively demonstrate quantifiable differences in base deficit and lactate by type of crystalloid resuscitation. LR resuscitation elevated lactate levels, and NS negatively affected the base deficit. These findings are critical to the interpretation of trauma patient resuscitation with crystalloid solutions.

LEVEL OF EVIDENCE

Therapeutic study, level II.

Effect of volume replacement during combined experimental hemorrhagic shock and traumatic brain injury in prostanoids, brain pathology and pupil status

Traumatic brain injury (TBI) is the main cause of trauma-related deaths. Systemic hypotension and intracranial hypertension causes cerebral ischemia by altering metabolism of prostanoids. We describe prostanoid, pupilar and pathological response during resuscitation with hypertonic saline solution (HSS) in TBI. Method Fifteen dogs were randomized in three groups according to resuscitation after TBI (control group; lactated Ringer's (LR) group and HSS group), with measurement of thromboxane, prostaglandin, macroscopic and microscopic pathological evaluation and pupil evaluation.Result Concentration of prostaglandin is greater in the cerebral venous blood than in plasma and the opposite happens with concentration of thromboxane. Pathology revealed edema in groups with the exception of group treated with HSS.Discussion and conclusion There is a balance between the concentrations of prostaglandin and thromboxane. HSS prevented the formation of cerebral edema macroscopically detectable. Pupillary reversal occurred earlier in HSS group than in LR group.

[Recent Advances in Management of Acute Pancreatitis]

Acute pancreatitis is common but remains a condition with significant morbidity and mortality. Despite a better understanding of the pathophysiology of acute pancreatitis achieved during the past few decades, there is no specific pharmacologic entity available. Therefore, supportive care is still the mainstay of treatment. Recently, novel interventions for increasing survival and minimizing morbidity have been investigated, which are highlighted in this review.

Key Controversies in Colloid and Crystalloid Fluid Utilization

Nearly 2 centuries have passed since the use of intravenous fluid became a foundational component of clinical practice. Despite a steady stream of published investigations on the topic, questions surrounding the choice, dose, timing, targets, and cost-effectiveness of various fluid options remain insufficiently answered. In recent years, 2 of the most debated topics reference the role of albumin in acute care and the safety of normal saline. Although albumin has a place in therapy for specific patient populations, its high cost relative to other fluids makes it a less desirable option for hospitals and health systems with escalating formulary scrutiny. Pharmacists bear responsibility for reconciling this disparity and supporting the rational use of albumin in acute care through a careful evaluation of recently published literature. In parallel, it has become clear that crystalloids should no longer be considered a homogenous class of fluids. The past reliance on normal saline has been questioned due to recent findings of renal dysfunction attributable to the solution's supraphysiologic chloride concentration. These safety concerns with 0.9% sodium chloride may result in a practice shift toward more routine use of "balanced crystalloids," such as lactated Ringer's or Plasma-Lyte, that mimic the composition of extracellular fluid. The purpose of this review is to summarize the evidence regarding these 2 important fluid controversies that are likely to affect hospital pharmacists in the coming decades - the evidence-based use of human albumin and the rising role of balanced salt solutions in clinical practice.

A controlled resuscitation strategy is feasible and safe in hypotensive trauma patients: results of a prospective randomized pilot trial

BACKGROUND

Optimal resuscitation of hypotensive trauma patients has not been defined. This trial was performed to assess the feasibility and safety of controlled resuscitation (CR) versus standard resuscitation (SR) in hypotensive trauma patients.

METHODS

Patients were enrolled and randomized in the out-of-hospital setting. Nineteen emergency medical services (EMS) systems in the Resuscitation Outcome Consortium participated. Eligible patients had an out-of-hospital systolic blood pressure (SBP) of 90 mm Hg or lower. CR patients received 250 mL of fluid if they had no radial pulse or an SBP lower than 70 mm Hg and additional 250-mL boluses to maintain a radial pulse or an SBP of 70 mm Hg or greater. The SR group patients received 2 L initially and additional fluid as needed to maintain an SBP of 110 mm Hg or greater. The crystalloid protocol was maintained until hemorrhage control or 2 hours after hospital arrival.

RESULTS

A total of 192 patients were randomized (97 CR and 95 SR). The CR and SR groups were similar at baseline. The mean (SD) crystalloid volume administered during the study period was 1.0 L (1.5) in the CR group and 2.0 L (1.4) in the SR group, a difference of 1.0 L (95% confidence interval [CI], 0.6-1.4). Intensive care unit-free days, ventilator-free days, renal injury, and renal failure did not differ between the groups. At 24 hours after admission, there were 5 deaths (5%) in the CR group and 14 (15%) in the SR group (adjusted odds ratio, 0.39; 95% CI, 0.12-1.26). Among patients with blunt trauma, 24-hour mortality was 3% (CR) and 18% (SR) with an adjusted odds ratio of 0.17 (0.03-0.92). There was no difference among patients with penetrating trauma (9% vs. 9%; adjusted odds ratio, 1.93; 95% CI, 0.19-19.17).

CONCLUSION

CR is achievable in out-of-hospital and hospital settings and may offer an early survival advantage in blunt trauma. A large-scale, Phase III trial to examine its effects on survival and other clinical outcomes is warranted.

LEVEL OF EVIDENCE

Therapeutic study, level I.

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.

Microcirculatory effects of intravenous fluid administration in anesthetized dogs undergoing elective ovariohysterectomy

OBJECTIVE

To assess the microcirculatory effects of IV fluid administration in healthy anesthetized dogs undergoing elective ovariohysterectomy.

ANIMALS

49 client-owned dogs.

PROCEDURES

Dogs were sedated, and anesthesia was induced with propofol and diazepam and maintained with isoflurane in oxygen. Dogs received lactated Ringer's solution (LRS) IV at rates of 0, 10, or 20 mL/kg/h. Videomicroscopy was used to assess and record effects of LRS administration on microcirculation in the buccal mucosa. Measurements of microcirculatory (total vessel density, proportion of perfused vessels, microcirculatory flow index, and perfused vessel density by vessel size [< 20 μm, ≥ 20 μm, and all diameters]) and other physiologic variables (heart rate, Doppler-measured blood pressure, oxygen saturation as measured by pulse oximetry, capillary refill time, and body temperature) were compared among groups at baseline (immediately after anesthetic induction), 30 and 60 minutes afterward, and overall.

RESULTS

Neither the proportion of perfused vessels nor microcirculatory flow index varied among treatment groups at any time point, regardless of vessel size. For vessels < 20 μm in diameter and for all vessels combined, total and perfused vessel density were similar among groups. For vessels ≥ 20 μm in diameter, total vessel density was significantly greater in the 20 mL/kg/h group than in other groups, and perfused vessel density was significantly greater in the 20 mL/kg/h group than in the 0 mL/kg/h group, when all time points were considered. Other physiologic variables were similar among groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Total and perfused vessel density of vessels ≥ 20 μm in diameter (mostly venules) were greatest in dogs that received 20 mL of LRS/kg/h. Further research is required to evaluate clinical importance of these findings.

Central venous-to-arterial CO2-gap may increase in severe isovolemic anemia

Despite blood transfusions are administered to restore adequate tissue oxygenation, transfusion guidelines consider only hemoglobin as trigger value, which gives little information about the balance between oxygen delivery and consumption. Central venous oxygen saturation is an alternative, however its changes reflect systemic metabolism and fail to detect regional hypoxia. A complementary parameter to ScvO₂ may be central venous-to-arterial carbon dioxide difference (CO₂-gap). Our aim was to investigate the change of alternative transfusion trigger values in experimental isovolemic anemia. After splenectomy, anesthetized Vietnamese mini pigs (n = 13, weight range: 18–30 kg) underwent controlled bleeding in five stages (T₁–T₅). During each stage approximately 10% of the estimated starting total blood volume was removed and immediately replaced with an equal volume of colloid. Hemodynamic measurements and blood gas analysis were then performed. Each stage of bleeding resulted in a significant fall in hemoglobin, the O₂-extraction increased significantly from T₃ and ScvO₂ showed a similar pattern and dropped below the physiological threshold of 70% at T₄. By T₄ CO₂-gap increased significantly and well correlated with VO₂/DO₂ and ScvO₂. To our knowledge, this is the first study to show that anemia caused altered oxygen extraction may have an effect on CO₂-gap.

The case for 0.9% NaCl: is the undefendable, defensible?

Although 0.9% NaCl solution is by far the most-used fluid for fluid therapy in resuscitation, it is difficult to find a paper advocating its use over other types of crystalloid solutions. Literature on the deleterious effects of 0.9% NaCl has accumulated over the last decade, but critical appraisal of alternative crystalloid solutions is lacking. As such, the literature seems to suggest that 0.9% NaCl should be avoided at all costs, whereas alternative crystalloid solutions can be used without scrutiny. The basis of this negative evaluation of 0.9% NaCl is almost exclusively its effect on acid-base homeostasis, whereas the potentially deleterious effects present in other types of crystalloids are neglected. We have the challenging task of defending the use of 0.9% NaCl and reviewing its positive attributes, while an accompanying paper will argue against the use of 0.9% NaCl. It is challenging because of the large amount of literature, including our own, showing adverse effects of 0.9% NaCl. We will discuss why 0.9% NaCl solution is the most frequently used resuscitation fluid. Although it has some deleterious effects, all fluids share common features of concern. As such the emphasis on fluid resuscitation should be on volume rather than on composition and should be accompanied by a physiological assessment of the impact of fluids. In this paper, we hope to discuss the context within which fluids, specifically 0.9% NaCl, can be given in a safe and effective manner.

Acute coagulopathy in pediatric trauma

PURPOSE OF REVIEW

To summarize our current understanding of the pathophysiology, diagnosis, and management of acute traumatic coagulopathy in children.

RECENT FINDINGS

Traumatic coagulopathy is a complex process that leads to global dysfunction of the endogenous coagulation system and results in worse outcomes and increased mortality. Although the cause is multifactorial, it is common in severely injured patients and is driven by significant tissue injury and hypoperfusion. Viscoelastic coagulation tests have been established as a rapid and reliable method to assess traumatic coagulopathy. Additionally, massive transfusion protocols have improved outcomes in adults, but limited studies in pediatrics have not shown any difference in mortality.

SUMMARY

Prospective studies are needed to determine how to best diagnose and manage acute traumatic coagulopathy in children.

Should chloride-rich crystalloids remain the mainstay of fluid resuscitation to prevent 'pre-renal' acute kidney injury?: con

The high chloride content of 0.9% saline leads to adverse pathophysiological effects in both animals and healthy human volunteers, changes not seen after balanced crystalloids. Small randomized trials confirm that the hyperchloremic acidosis induced by saline also occurs in patients, but no clinical outcome benefit was demonstrable when compared with balanced crystalloids, perhaps due to a type II error. A strong signal is emerging from recent large propensity-matched and cohort studies for the adverse effects that 0.9% saline has on the clinical outcome in surgical and critically ill patients when compared with balanced crystalloids. Major complications are the increased incidence of acute kidney injury and the need for renal replacement therapy, and that pathological hyperchloremia may increase postoperative mortality. However, there are no large-scale randomized trials comparing 0.9% saline with balanced crystalloids. Some balanced crystalloids are hypo-osmolar and may not be suitable for neurosurgical patients because of their propensity to cause brain edema. Saline may be the solution of choice used for the resuscitation of patients with alkalosis and hypochloremia. Nevertheless, there is evidence to suggest that balanced crystalloids cause less detriment to renal function than 0.9% saline, with perhaps better clinical outcome. Hence, we argue that chloride-rich crystalloids such as 0.9% saline should be replaced with balanced crystalloids as the mainstay of fluid resuscitation to prevent ‘pre-renal' acute kidney injury.

Diaphragmatic function is preserved during severe hemorrhagic shock in the rat

BACKGROUND

Acute diaphragmatic dysfunction has been reported in septic and cardiogenic shock, but few data are available concerning the effect of hemorrhagic shock on diaphragmatic function. The authors examined the impact of a hemorrhagic shock on the diaphragm.

METHODS

Four parallel groups of adult rats were submitted to hemorrhagic shock induced by controlled exsanguination targeting a mean arterial blood pressure of 30 mmHg for 1 h, followed by a 1-h fluid resuscitation with either saline or shed blood targeting a mean arterial blood pressure of 80 mmHg. Diaphragm and soleus strip contractility was measured in vitro. Blood flow in the muscle microcirculation was measured in vivo using a Laser Doppler technique. Muscle proinflammatory cytokine concentrations were also measured.

RESULTS

Hemorrhagic shock was characterized by a decrease in mean arterial blood pressure to 34 ± 5 mmHg (-77 ± 4%; P< 0.05) and high plasma lactate levels (7.6 ± 0.9 mM; P < 0.05). Although tetanic tension of the diaphragm was not altered, hemorrhagic shock induced dramatic impairment of tetanic tension of the soleus (-40 ± 19%; P < 0.01), whereas proinflammatory cytokine levels were low and not different between the two muscles. Resuscitation with either blood or saline did not further modify either diaphragm or soleus performance and proinflammatory cytokine levels. The shock-induced decrease in blood flow was much more pronounced in the soleus than in the diaphragm (-75 ± 13% vs. -17 ± 10%; P = 0.02), and a significant interaction was observed between shock and muscle (P < 0.001).

CONCLUSION

Diaphragm performance is preserved during hemorrhagic shock, whereas soleus performance is impaired, with no further impact of either blood or saline fluid resuscitation.

Time to Resuscitate a Sacred Cow… with Normal Saline

Normal saline (NS) is not used for trauma resuscitation because of its potential for acidosis. Lactated Ringer's (LR) is preferred instead. However, the two crystalloids have never been compared in trauma patients. We hypothesized that NS would be an acceptable fluid for resuscitation in the trauma patient. In 2011, a Level I trauma center switched resuscitation fluid from LR to NS. Admissions before and after the change were retrospectively reviewed. Demographics, vitals, blood work, and fluid intake were recorded over 24 hours. Acidosis level, stratified by Injury Severity Score (ISS), was compared. Four hundred ten patients were included, 207 in the LR cohort and 203 in the NS. Chloride (LR 105.26 ± 4.75 vs NS 106.48 ± 4.19), base excess (-2.53 ± 3.77 vs -3.28 ± 4.15), pH (7.37 ± 0.08 vs 7.36 ± 0.07), and bicarbonate (22.83 ± 3.45 vs 21.65 ± 5.06) were statistically different but not clinically significant. This was also true when results were stratified by ISS. In addition, there was no difference in the number of blood gases drawn between the groups (584 vs 544, P = nonsignificant). NS resuscitation is a safe, viable alternative to LR in the trauma population studied. Its use carries a potentially substantial cost savings on a national level.

The ideal crystalloid - what is 'balanced'?

PURPOSE OF REVIEW

This review explores the contemporary definition of the term 'balanced crystalloid' and outlines optimal design features and their underlying rationale.

RECENT FINDINGS

Crystalloid interstitial expansion is unavoidable, but also occurs with colloids when there is endothelial glycocalyx dysfunction. Reduced chloride exposure may lessen kidney dysfunction and injury with a possible mortality benefit. Exact balance from an acid-base perspective is achieved with a crystalloid strong ion difference of 24 mEq/l. This can be done simply by replacing 24 mEq/l of chloride in 0.9% sodium chloride with bicarbonate or organic anion bicarbonate substitutes. Potassium, calcium and magnesium additives are probably unnecessary. Large volumes of mildly hypotonic crystalloids such as lactated Ringer's solution reduce extracellular tonicity in volunteers and increase intracranial pressure in nonbrain-injured experimental animals. A total cation concentration of 154 mmol/l with accompanying anions provides isotonicity. Of the commercial crystalloids, Ringer's acetate solution is close to balanced from both acid-base and tonicity perspectives, and there is little current evidence of acetate toxicity in the context of volume loading, in contrast to renal replacement.

SUMMARY

The case for balanced crystalloids is growing but unproven. A large randomized controlled trial of balanced crystalloids versus 0.9% sodium chloride is the next step.

Superiority of acetate compared with lactate in a rodent model of severe hemorrhagic shock

BACKGROUND

Recently, we have shown that the use of lactated Ringer's (LR) solution is inferior to pure Ringer's solution (RS) in treatment of severe hemorrhagic shock in rats. The present study was performed to evaluate whether this is a specific effect of lactate or also applies to another metabolizable anion, namely acetate.

MATERIAL AND METHODS

We subjected male Wistar rats to hemorrhagic shock by dropping the mean arterial blood pressure to 25-30 mm Hg for 60 min, resuscitated with acetated Ringer's (AR) solution, LR solution, RS, or normal saline (NS) within 30 min, and further observed the animals for 180 min.

RESULTS

Administration of AR solution prolonged median survival to 115 min compared with 50 min for resuscitation with LR solution or 85 and 90 min for NS and RS, respectively. Resuscitation with AR solution and LR solution clearly improved metabolic acidosis compared with NS and RS but tissue injury, indicated by plasma enzyme activities, was most pronounced in the LR solution group, medium in the NS and RS groups, and least in the AR solution group.

CONCLUSIONS

In severe hemorrhagic shock, resuscitation with both RS and NS is superior to administration of LR solution but initial outcome is even further improved if AR solution is used. Mere amelioration of the acid-base status by AR solution may explain its superior role compared with RS and NS but cannot be responsible for its superiority compared with LR solution. Here, direct injury by lactate has to be discussed.

Central Venous-to-Arterial CO2 Gap Is a Useful Parameter in Monitoring Hypovolemia-Caused Altered Oxygen Balance: Animal Study

Monitoring hypovolemia is an everyday challenge in critical care, with no consensus on the best indicator or what is the clinically relevant level of hypovolemia. The aim of this experiment was to determine how central venous oxygen saturation (ScvO₂) and central venous-to-arterial carbon dioxide difference (CO₂ gap) reflect hypovolemia-caused changes in the balance of oxygen delivery and consumption. Anesthetized, ventilated Vietnamese minipigs (n = 10) were given a bolus followed by a continuous infusion of furosemide. At baseline and then in five stages hemodynamic, microcirculatory measurements and blood gas analysis were performed. Oxygen extraction increased significantly, which was accompanied by a significant drop in ScvO₂ and a significant increase in CO₂ gap. There was a significant negative correlation between oxygen extraction and ScvO₂ and significant positive correlation between oxygen extraction and CO₂ gap. Taking ScvO₂ < 73% and CO₂ gap >6 mmHg values together to predict an oxygen extraction >30%, the positive predictive value is 100%; negative predicted value is 72%. Microcirculatory parameters, capillary perfusion rate and red blood cell velocity, decreased significantly over time. Similar changes were not observed in the sham group. Our data suggest that ScvO₂ < 73% and CO₂ gap >6 mmHg can be complementary tools in detecting hypovolemia-caused imbalance of oxygen extraction.

Inflammatory activation after experimental cardiac tamponade

BACKGROUND/PURPOSE

Cardiac tamponade is a medical emergency situation associated with a high rate of life-threatening complications, even after immediate interventions. Our aim was to characterize the acute inflammatory consequences of this event in a clinically relevant large animal model.

METHODS

Cardiac tamponade was induced for 60 min in anesthetized, ventilated and thoracotomized minipigs by intrapericardial fluid administration, the mean arterial pressure (MAP) being maintained in the interval of 40-45 mm Hg (n = 8). A further group (n = 7) served as sham-operated control. The global macrohemodynamics, including the right- and left-heart end-diastolic volumes (RHEDV and LHEDV), the pulmonary vascular resistance index (PVRI) and the superior mesenteric artery (SMA) flow, were monitored for 240 min, and the intestinal microcirculatory changes (pCO2 gap) were evaluated by indirect tonometry. Blood samples were taken for the determination of cardiac troponin T and vasoactive inflammatory mediators, including histamine, nitrite/nitrate, big-endothelin, superoxide and high-mobility group box protein-1 levels in association with intestinal leukocyte and complement activation.

RESULTS

The cardiac tamponade induced significant decreases in MAP, cardiac output, LHEDV and SMA flow, while the PVRI and the pCO2 gap increased significantly. After the removal of fluid from the pericardial sac, the MAP and the LHEDV were decreased, while the PVRI and the pCO2 gap remained elevated when compared with those in the sham-operated group. In the posttamponade period, the abrupt release of inflammatory mediators was accompanied by a significant splanchnic leukocyte accumulation and complement activation.

CONCLUSIONS

The macrocirculatory and splanchnic microcirculatory disturbances were accompanied by a significant proinflammatory reaction; endothelin and the complement system may be significant components of the inflammatory cascade that is activated in this porcine model of pericardial tamponade.

Clinical management of patients with acute pancreatitis

Acute pancreatitis is the leading cause of hospitalization for gastrointestinal disorders in the United States. As rates of hospitalization for acute pancreatitis continue to increase, so does demand for effective management. We review approaches to best manage patients with acute pancreatitis, covering diagnosis, risk and prognostic factors, treatment, and complications, considering recommendations from current practice guidelines.

Near infrared spectroscopy: clinical and research uses

BACKGROUND

Pulse oximetry is routinely used to measure hemoglobin saturation and is currently the gold standard to assess oxygenation in patients. Due to attenuation of infrared light by skin, bone, and other organs, pulse oximetry cannot assess end-organ tissue oxygenation (StO(2)). Near infrared spectroscopy (NIS) penetrates a broad range of tissues and utilizes reflection rather than direct transmission between an emitter and receiver pair. NIS is able to measure StO(2) and assess end-organ perfusion in a variety of applications.

STUDY DESIGN AND METHODS

A retrospective review of recent animal and human StO(2) studies was undertaken. StO(2) measurements and outcomes were assessed.

RESULTS

StO(2) measurements identified visceral organ ischemia in animal hemorrhage models. These measurements were also able to guide optimization of resuscitation and end-organ oxygenation. Human studies demonstrated StO(2) changes preceded those seen in traditionally measured parameters such as blood pressure, heart rate, base deficit, serum lactate, and mental status. Additionally, StO(2) thresholds identified trauma patients who required massive transfusions, developed multiple organ dysfunction syndrome, or experienced lower extremity compartment syndrome. StO(2) measurements also demonstrated a benefit in selecting resuscitation fluids, assessing end-organ oxygenation during blood transfusion, and quantifying the oxygen-carrying deficit secondary to the blood storage lesion.

CONCLUSION

StO(2) measurements have been used to guide resuscitation efforts in trauma patients. This technology and its applications continue to evolve and represent a novel change in patient care.

Nebulized hypertonic saline attenuates acute lung injury following trauma and hemorrhagic shock via inhibition of matrix metalloproteinase-13

OBJECTIVE

We hypothesized that aerosolized inhaled hypertonic saline given at the onset of resuscitation will decrease acute lung injury following hemorrhagic shock, by inhibiting the release of epithelial derived proinflammatory mediators.

DESIGN

Animal study.

SETTING

Animal-care facility procedure room in a medical center.

SUBJECTS

Adult male Sprague-Dawley rats.

INTERVENTIONS

Rats underwent hemorrhagic shock followed by 2 hrs of resuscitation and 1 hr of observation. In the study group, nebulized hypertonic saline was delivered at the end of the shock period and after 1 hr and 2 hrs of resuscitation.

MEASUREMENTS AND MAIN RESULTS

Shock provoked acute lung injury, which was attenuated with inhaled hypertonic saline (1.56 ± 0.2 mg protein/mL vs. 0.95 ± 0.3 mg protein/mL bronchoalveolar lavage fluid, shock vs. shock + hypertonic saline, p < .01). Nebulized hypertonic saline reduced inflammation (cytokine-induced neutrophil chemoattractant-1 accumulation in bronchoalveolar lavage fluid 5999 ± 1267 pg/mL vs. 3342 ± 859 pg/mL, shock vs. shock + hypertonic saline, p = .006). Additionally, nebulized hypertonic saline inhibited matrix -metalloproteinase-13 accumulation in the bronchoalveolar lavage fluid (1513 ± 337 pg/mL bronchoalveolar lavage fluid vs. 230 ± 19 pg/mL, shock vs. shock + hypertonic saline, p = .009) and pretreatment with a matrix metalloproteinase-13 inhibitor was sufficient to attenuate postshock acute lung injury (1.42 ± 0.09 mg/mL vs. 0.77 ± 0.23 mg/mL bronchoalveolar lavage protein, shock vs. shock + matrix metalloproteinase-13 inhibitor CL-82198, p = .002).

CONCLUSION

Inhaled hypertonic saline attenuates postshock acute lung injury by exerting an anti-inflammatory effect on the pulmonary epithelium, suggesting a new clinical strategy to treat acute lung injury/acute respiratory distress syndrome.

Adverse effects of resuscitation with lactated ringer compared with ringer solution after severe hemorrhagic shock in rats

Lactated Ringer (LR) is a widely used resuscitation fluid that is known to mediate beneficial effects on acid-base balance when compared with normal saline. We here compared LR with the more physiological Ringer solution (RS) regarding acid-base status, hemodynamics, survival, and organ injury following fluid resuscitation subsequent to severe hemorrhagic shock. Anesthetized rats were hemorrhaged to a mean arterial blood pressure of 25 to 30 mmHg within 30 min. After 60 min, they were resuscitated with either RS or LR (three times the shed blood volume) or with RS or LR plus blood (shed blood plus twice its volume) within 30 min. Subsequently, the animals were observed for further 150 min. When the rats were resuscitated with pure LR or RS, all animals of the shock/LR group, but only three of eight shock/RS group rats were dead 100 min later (median survival, 50 ± 13.1 vs. 120 ± 14.1 min; P < 0.05). Coadministration of the shed blood with RS or LR increased the survival rates to 100%. In these blood-resuscitated groups, organ injury, especially of the kidney, was diminished by the use of RS compared with LR. Time-matched acid-base parameters were not different in all shock groups until death of the animals or euthanasia at the end of experimental time. We conclude that, in severe hemorrhagic shock, resuscitation with RS leads to an improved outcome compared with resuscitation with LR, regardless whether blood is coadministered or not.

Central venous oxygen saturation is a good indicator of altered oxygen balance in isovolemic anemia

BACKGROUND

Red blood cell transfusion is done primarily as a means to improve oxygen delivery (DO₂). Current transfusion guidelines are based solely on hemoglobin levels, regardless of actual DO₂ need. As central venous oxygen saturation (ScvO₂) may reflect imbalances in DO₂ and consumption (VO₂) the aim of this study was to investigate the value of ScvO₂ as an indicator of oxygen balance in isovolemic anemia.

METHODS

After splenectomy, anesthetized Vietnamese mini pigs (n = 13, weight range: 18-30 kg) underwent controlled bleeding in five stages (T₀-T₅). During each stage approximately 10% of the estimated starting total blood volume was removed and immediately replaced with an equal volume of colloid. Hemodynamic measurements and blood gas analysis were then performed.

RESULTS

Each stage of bleeding resulted in a significant fall in hemoglobin, T₀ : 125 (113-134) to T(5) : 49 (43-55) g/l [T₀ : 7.7 (6.9-8.2) to T₅ : 3.0 (2.6-3.4) mmol/l]. The O₂-extraction (VO₂/DO₂) increased significantly only from T₃ : 35 (21-40) %, P < 0.05. The change of ScvO₂ showed a similar pattern and dropped below the physiological threshold of 70% at T₄ : 68 (61-76) %. At this point, hemoglobin was below the recommended transfusion trigger value, 59 (53-67) g/l [3.6 (3.3-4.1) mmol/l]. There was a strong significant association between ScvO₂< 70%) and VO₂/DO₂ > 30%): r = -0.71, r²  = 0.50, P < 0.001.

CONCLUSION

The results of this study show that ScvO₂ reflects changes of VO₂/DO₂ in isovolemic anemia better than Hb alone, therefore it may be used as an additional indicator of blood transfusion in clinical practice.

Crystalloid resuscitation improves survival in trauma patients receiving low ratios of fresh frozen plasma to packed red blood cells

BACKGROUND

Current trauma resuscitation guidelines recommend giving an initial crystalloid bolus as first line for resuscitation. Recent studies have shown a survival benefit for trauma patients resuscitated with high ratios of fresh frozen plasma (FFP) to packed red blood cells (PRBC). Our aim was to determine whether the volume of crystalloid given during resuscitation correlated with differences in morbidity or mortality based on the ratio of FFP:PRBC given.

METHODS

This was a retrospective review of 2,473 transfused trauma patients at 23 Level I trauma centers from July 2005 to October 2007. Patients were separated based on the ratios of FFP:PRBC they received (<1:4, 1:4-1:1, and >1:1) and then analyzed for morbidity and mortality based on whether or not they received at least 1 L crystalloid for each unit of PRBC. Outcomes analyzed were 6-hour, 24-hour, and 30-day survival as well as intensive care unit (ICU)-free days, ventilator-free days, and hospital-free days.

RESULTS

Massive transfusion patients who received <1:4 ratios of FFP:PRBC had significantly improved 6-hour, 24-hour, and 30-day mortality and significantly more ventilator-free days if they received at least 1 L of crystalloid for each unit of PRBC. Nonmassive transfusion patients who received <1:4 ratios of FFP:PRBC had significantly improved 6-hour, 24-hour, and 30-day mortality and significantly more ICU-free days, ventilator-free days, and hospital-free days if they received at least 1 L crystalloid for each unit of PRBC. In both massive and nonmassive transfusion groups, the survival benefit and morbidity benefit was progressively less for the 1:4 to 1:1 FFP:PRBC groups and >1:1 FFP:PRBC groups.

CONCLUSIONS

If high ratios of FFP:PRBC are unable to be given to trauma patients, resuscitation with at least 1 L of crystalloid per unit of PRBC is associated with improved overall mortality.

Year in review 2009: Critical Care--shock

The research papers on shock that have been published in Critical Care throughout 2009 are related to four major subjects: first, alterations of heart function and, second, the role of the sympathetic central nervous system during sepsis; third, the impact of hemodynamic support using vasopressin or its synthetic analog terlipressin, and different types of fluid resuscitation; as well as, fourth, experimental studies on the treatment of acute respiratory distress syndrome. The present review summarizes the key results of these studies together with a brief discussion in the context of the relevant scientific and clinical background published both in this and other journals.

Effects of fluid resuscitation with hypertonic saline dextrane or Ringer's acetate after nonhemorrhagic shock caused by pulmonary contusion

BACKGROUND

Injured lungs are sensitive to fluid resuscitation after trauma. Such treatment can increase lung water content and lead to desaturation. Hypertonic saline with dextran (HSD) has hyperosmotic properties that promote plasma volume expansion, thus potentially reducing these side effects. The aim of this study was to (1) evaluate whether fluid treatment counteracts hypotension and improves survival after nonhemorrhagic shock caused by lung contusion and (2) analyze whether resuscitation with HSD is more efficient than treatment with Ringer's acetate (RA) in terms of blood oxygenation, the amount of lung water, circulatory effects, and inflammatory response.

METHODS

Twenty-nine pigs, all wearing body armor, were shot with a 7.62-mm assault rifle to produce a standardized pulmonary contusion. These animals were allocated into three groups: HSD, RA, and an untreated shot control group. Exposed animals were compared with animals not treated with fluid and shot with blank ammunition. For 2 hours after the shot, the inflammatory response and physiologic parameters were monitored.

RESULTS

The impact induced pulmonary contusion, desaturation, hypotension, increased heart rate, and led to an inflammatory response. No change in blood pressure was observed after fluid treatment. HSD treatment resulted in significantly less lung water (p < 0.05) and tended to give better Pao2 (p = 0.09) than RA treatment. Tumor necrosis factor-α release and heart rate were significantly lower in animals given fluids.

CONCLUSION

Fluid treatment does not affect blood pressure or mortality in this model of nonhemorrhagic shock caused by lung contusion. However, our data indicate that HSD, when compared with RA, has advantages for the injured lung.

Liver metabolomic changes identify biochemical pathways in hemorrhagic shock

BACKGROUND

Despite ongoing advances in treatment, thousands of patients still die annually from complications due to hemorrhagic shock, a condition causing dramatic physiologic and metabolic changes as cells switch to anaerobic metabolism in response to oxygen deprivation. As the shift from aerobic to anaerobic metabolism occurs in the peripheral tissues during shock, the liver must increase production of endogenous glucose as well as process excess lactate produced in the periphery. This places the liver at the center of metabolic regulation in the body during hemorrhagic shock. Therefore, we hypothesized that liver tissue from pigs during an in vivo model of hemorrhagic shock (n = 6) would reflect resultant metabolic changes.

MATERIALS AND METHODS

The in vivo model of shock consisted of 45 min of shock followed by 8 h of hypotensive resuscitation (80 mmHg) and subsequent normotensive resuscitation (90 mmHg) ending 48 h after the shock period. Control groups of pigs (n = 3) (1) shock with no resuscitation, and (2) only anesthesia and instrumentation, also were included. Metabolic changes within the liver after shock and during resuscitation were investigated using both proton ((1)H) and phosphorous ((31)P) nuclear magnetic resonance (NMR) spectroscopy.

RESULTS

Concentrations of glycerylphosphorylcholine (GPC) and glycerylphosphorylethanolamine (GPE) were significantly lower at 8 h after shock, with recovery to baseline by 23 and 48 h after shock. Uridine diphosphate-glucose (UDP-glucose), and phosphoenolpyruvate (PEP) were elevated 23 h after shock.

CONCLUSIONS

These results indicate that (1)H and (31)P NMR spectroscopy can be used to identify differences in liver metabolites in an in vivo model of hemorrhagic shock, indicating that metabolomic analysis can be used to elucidate biochemical events occurring during this complex disease process.

Effects of hypertonic saline on CD4+CD25+Foxp3+ regulatory T cells after hemorrhagic shock in relation to iNOS and cytokines

BACKGROUND

Hemorrhagic shock and resuscitation induce immunosuppression. CD4(+)CD25(+)Foxp3(+) regulatory T Cells (Foxp3(+) Tregs), iNOS and cytokines may affect these severe conditions such as acute respiratory distress syndrome and multiple organ failure after hemorrhagic shock and resuscitation. Foxp3(+) Tregs have been described to be specific and play a key role in the control of the immune system. Immune condition may be restored by hypertonic saline resuscitation that inhibits pro-inflammatory effects of cytokine. Our aim was to investigate how hypertonic saline resuscitation affected Foxp3(+) Tregs after hemorrhagic shock and resuscitation in relation to iNOS and cytokines.

METHODS

Male C57BL6/J and B6.129P2- NOS2(tm1Lau)/J (iNOS gene knockout) mice were used in creating hemorrhagic shock model. Mice were divided into two groups, each according to the type of resuscitation. (1) Wild HS: resuscitation with hypertonic saline (4 mL/Kg of 7.5% NaCl) and the shed blood (SB); (2) wild 2LR: resuscitation with lactated Ringer's solution and the SB; (3) iNOS knockout HS: similarly resuscitated as wild HS; (4) iNOS knockout 2LR: similarly resuscitated as wild 2LR. Samples of thymus and spleen were harvested at 2, 6, 24, 48, and 72 h after resuscitation. CD4(+) T cells and Foxp3(+) Tregs were analyzed at 24, 48, and 72 h. At 2, 6, 24, and 48 h, plasma cytokines were assayed and expression of iNOS (NOS2) was also measured by immunofluorescence.

RESULTS

NOS2 of HS and 2LR wild groups at 2 and 6 h in spleen increased compared with the control group. At 6h, NOS2 in HS wild group was significantly lower than in 2LR wild group. Plasma levels of interleukin (IL)-6, TNF- α, MCP-1, and IL-10 increased at 2 h. Both in wild type and iNOS knockout mice, hypertonic saline resuscitation decreased plasma IL-6, TNF-α, and MCP-1 levels at 2 h; CD4(+) T cells in spleen and thymus decreased at 24, 48, and 72 h, and Foxp3(+) Tregs in spleen at 48 h increased, however, hypertonic saline resuscitation did not affect the Foxp3(+).

CONCLUSIONS

These results show that in early phase, the inflammatory cytokines in plasma might affect iNOS expression and cytokines. Further, this study showed that hypertonic saline resuscitation and suppression of iNOS might improve immunosuppressive reaction after hemorrhagic shock.

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.

Resuscitation of hemorrhagic shock with normal saline versus lactated Ringer's: effects on oxygenation, extravascular lung water, and hemodynamics

Which type of fluid to use in the resuscitation from hemorrhagic shock, within and between crystalloids or colloids, is still a matter of debate. In this context, with respect to organ dysfunction, early detection of lung injury is widely considered of particular clinical importance. For these purposes, the transpulmonary thermodilution technique that enables one to assess extravascular lung water as a marker of pulmonary edema is applied in the clinical setting. In this issue of Critical Care, Phillips and colleagues describe that early resuscitation of hemorrhagic shock in pigs with two different crystalloid solutions – normal saline or Ringer's lactate – had little impact on oxygenation when the resuscitation volume was <250 ml/kg. Ringer's lactate had more favorable effects than normal saline, however, on extravascular lung water, pH, and blood pressure but not on oxygenation. Although several pathophysiological aspects remain unanswered, these data are interesting in so far as they indicate that clinically applied amounts of crystalloids per se do not negatively influence pulmonary function, while with larger amounts the type of fluid has different effects on the extent of fluid extravasation in the lungs.