Journal of Emergencies, Trauma, and Shock

ORIGINAL ARTICLE
Year
: 2012  |  Volume : 5  |  Issue : 4  |  Page : 309--315

Effects of volume and composition of the resuscitative fluids in the treatment of hemorrhagic shock


Pushpa Sharma, Brandi Benford, John E Karaian, Ryan Keneally 
 Department of Anesthesiology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA

Correspondence Address:
Pushpa Sharma
Department of Anesthesiology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814
USA

Abstract

Objectives: To evaluate the effectiveness of normal saline, hypertonic saline, and Ringer«SQ»s lactate solution followed by blood infusion in ameliorating the physiological, biochemical, and organ functions following hemorrhagic shock (HS) in rats. Materials and Methods: Anesthetized, male Sprague-Dawley rats underwent computer-controlled HS, and were randomly divided into five groups consisting of (1) sham, (2) HS without resuscitation, (3) resuscitation with normal saline, (4) resuscitation with hypertonic saline, and (5) resuscitation with Ringer«SQ»s lactate solution. All resuscitated animals were infused with subsequent infusion of shed blood. Animals were continuously monitored for physiological, hemodynamic, biochemical parameters, and organ dysfunctions. Results: Non-resuscitated animals were unable to survive due to hypotension, poor oxygen metabolism, and lactic acidosis. Although these HS related parameters were corrected by all the fluids used in this study, additional blood infusion was more effective than fluid resuscitation alone. Also, hypertonic saline was more effective than Ringer«SQ»s lactate solution, and normal saline was the least effective in preserving the liver and kidney functions and muscle damage. Conclusions: All crystalloid fluids were significantly more effective in reversing the HS outcome when used with blood infusion, but hypertonic salinewith blood was more effective in preventing the organ damage than Lactated Ringers solutions or normal saline in the treatment of HS.



How to cite this article:
Sharma P, Benford B, Karaian JE, Keneally R. Effects of volume and composition of the resuscitative fluids in the treatment of hemorrhagic shock.J Emerg Trauma Shock 2012;5:309-315


How to cite this URL:
Sharma P, Benford B, Karaian JE, Keneally R. Effects of volume and composition of the resuscitative fluids in the treatment of hemorrhagic shock. J Emerg Trauma Shock [serial online] 2012 [cited 2020 Apr 6 ];5:309-315
Available from: http://www.onlinejets.org/text.asp?2012/5/4/309/102372


Full Text

 Introduction



Hemorrhagic shock due to acute blood loss and multiple organ failure is responsible for 30-40% deaths worldwide, and approximately 50% of battlefield casualties. [1],[2] The primary treatment of hemorrhagic shock is control of the source of bleeding as soon as possible and resuscitation. The main objectives of resuscitation are volume replacement for the lost blood, restoration of vital signs, improved oxygen delivery, preventing tissue damage, and enhance survival. [3] There is controversy regarding the composition, rate, and volume of the fluid that is most appropriate for the treatment of HS. [4]

Infusions of isotonic and hypertonic crystalloid solutions and blood transfusions are the mainstays for the pre-hospital and in-hospital treatment of severe hemorrhagic shock. [5] Normal saline (NS) and Ringer's lactate (LR) solution are relatively isotonic fluids which are commonly used, while 5-7.5% saline solution is also available (hypertonic saline (HTS). Several studies have shown that blood transfusion combined with crystalloids is more effective in negating the dilution and hypoxic effects of crystalloids alone. [6] However, the physiological and biochemical mechanism behind the use of blood transfusion and the choice of fluid resuscitation in preventing the organ damage following HS is not known. Also, blood is readily not available in the pre- hospital settings, war theaters and remote areas because it requires refrigeration and typing. Isotonic fluid administration requires large volumes, while hypertonic resuscitation fluids administered in a small volume can have an almost instantaneous hemodynamic effect, can be administrated rapidly, and can be easily transported in combat situations and to remote areas. Animal studies have shown that HTS resuscitation rapidly restored mean arterial pressure (MAP) and reduced the inflammatory response; but not mortality. [7] Despite the many favorable results, all these fluids have been linked to negative side effects, making the selection of the optimal fluid even more challenging. [8]

Due to lack of human studies on the effect of various resuscitative strategies, it is important to understand the effects and interactions of these physiological and biochemical parameters in response to HS and fluid resuscitation with varying composition and volume in animal models of HS. Several animal and human studies have demonstrated the significance of MAP, pH, bicarbonate, base excess and lactate levels as biomarkers of the severity of hemodynamic compensation and survival after HS. [9],[10] In this present study, we will present our data on the effects of using NS, LR, and HTS followed by blood transfusion using a rat model of controlled hemorrhage. All these solutions vary in composition and rate of resuscitation. In addition, this study will mimic the pre-hospital resuscitation condition of shock by using the delayed resuscitation followed by in hospital fluid resuscitation and blood re-infusion strategy.

 Materials and Methods



Male Sprague Dawley rats weighing 300-350 Grams (Harlan, Frederick, MD) were used in this study. The protocol and experimental procedures were reviewed and approved by the Institutional Animal Care and Use Committee (IACUC) of the Uniformed Services University of the Health Sciences at Bethesda, MD. All animals were maintained in accordance with the recommendations of the National Institutes of Health Guidelines for the Care and Use of Laboratory Animals.

Anesthesia and surgical procedure

Spontaneously ventilating rats were anesthetized with isoflurane (2.5-3% in air) through a fitted nose cone. The femoral artery and femoral vein were cannulated with polyethylene catheters (PE 50- Clay Adams, Piscataway, NJ). The incision was closed with interrupted sutures. Core temperature (rectal) was maintained at 37°± 0.2°C throughout the experiment with a heat lamp. The isoflurane concentration was reduced to 2.0%. The femoral arterial catheter was connected to a pressure transducer and computer through a three-way stopcock to monitor the mean arterial pressure (MAP). MAP data was recorded and analyzed by Labview 5 software (National Instruments, Austin, TX). The femoral vein catheter was used to infuse the resuscitative fluid or shed blood. Animals were allowed to acclimate to sedation and stress of surgery for 10 min prior to the induction of HS (pre-shock phase-T0).

Induction of hemorrhagic shock and resuscitation

The computer controlled HS was induced by the withdrawal of blood at a rate of 0.5 ml/min for 10-15 min via the femoral arterial catheter to reach a MAP of 40mmHg using an Instech P720 peristaltic pump (Instech Laboratories Inc., Plymouth Meeting, PA). During the 30 minute shock period, MAP was maintained at 40 mmHg either by removal or reinfusion of shed blood (shock phase-T30), followed by fluid resuscitation over 60 min (T90), and subsequently reinfusion of shed blood (T150).

Experimental groups

The animals were randomly assigned to the following five groups according to the treatment they received (n = 6-8 animals/group). All resuscitative fluids were used at room temperature.

Group 1. Sham: instrumented time control rats were anesthetized and instrumented in the same manner as rats in the other shock groups, but did not undergo arterial hemorrhage or resuscitation except the withdrawal of blood for laboratory investigation.

Group 2. NR: Non-resuscitated shock group to determine the tolerance limit of the animal to HS at 40 mmHg. These animals had HS but no resuscitation.

Group 3. NS: Shock animals resuscitated with normal saline (0.9% saline). Infusion volume was 5 ml/kg.

Group 4. LR: Resuscitated with Ringer's lactate (LR) solution equal to 3 times the volume of blood shed. LR solution contained (mEq) 109 NaCl, 4 KCl, 2.7 CaCl 2 and 28 sodium L- lactate.

Group 5. HTS: Resuscitated with 7.5% hypertonic saline (HTS). Infusion volume was 5 ml/kg.

Collection of blood samples and analysis

Approximately 100 ml arterial blood samples were obtained before shock for baseline values (T0), after shock (T30), after fluid resuscitation (T90), and 400 ml blood just before the death (T150) for the measurement of blood gases, pH, base excess (BE), and lactate using hand held ISTAT machine. From the final blood sample, 300 ml blood from the end point blood sample was immediately centrifuged at 3000 g for 10 min. The serum was decanted and utilized to determine liver functions (total bilirubin), hepatic cell damage by alanine aminotransferase (ALT) and aspartate aminotransferase (AST), kidney functions by blood urea nitrogen (BUN) and creatinine, and muscle damage by creatine phosphokinase (CPK).

Statistical analysis used

All data are presented as mean ± standard error of the n number of experiment in each group. The Sigma Stat 3.1 statistical program was used to perform a power analysis to determine the number of animals per group as well as one-way analysis of variance with post-hoc Bonferroni test for multiple comparisons between groups. A level of P < 0.05 was considered statistically significant.

 Results



Hemodynamic and physiological response to HS, resuscitation and blood transfusion

Data depicted in [Figure 1] show that the MAP was similar in all animals at the start of the hemorrhage and decreased to approximately 40 mmHg in all HS groups during a 10 to 15 min period. Because of similar weights of the animals (350± 5.5 G), the shed blood volume for the induction of shock (55-58% of total blood volume) did not differ significantly among the various hemorrhaged groups (P > 0.05) and was in the range previously reported for the same level (40 mmHg) of HS. [11],[12],[13] As shown in [figure 1]b, animals with hemorrhagic shock and without any fluid resuscitation died within 30 min after hemorrhage. No resuscitative strategy returned the MAP to baseline. However, MAP was increased by all solutions during resuscitation, but always remained significantly below the baseline. The MAP restoration was comparatively better with HTS (90±2.8, [Figure 1]d ) than LR (70±4.1, [Figure 1]e) and NS (55±3.3, [Figure 1]c). However, blood infusion followed by HTS or LR fluid resuscitation was significantly effective in both restoring and sustaining MAP; which was not statistically different between the HTS, LR, or the sham group [Figure 1]a. In contrast, blood infusion in the NS was not able to restore the MAP to baseline levels (baseline - 110 ± 8.1 mmHg, after resuscitation and blood infusion - 65 ± 2.2 mmHg). In sham animals [Figure 1]a MAP remained stable between 100 and 120 mm Hg) throughout the experiment.{Figure 1}

Changes in biochemical parameters and acid base status after HS, resuscitation, and blood transfusion

Severe HS lead to the development of metabolic acidosis and some compensation after HS [Table 1]. A significant drop in HCO 3, development of a lactic acidosis, and a respiratory compensation were noted after HS compared to baseline (P<0.05). All resuscitative fluids significantly corrected these HS-induced parameters, but blood transfusion was more effective than crystalloids alone. Also, blood transfusion following crystalloid resuscitation was effective in improving the lactic acidosis by reducing the serum lactate (50-75% HS values). The pH at all points was never significantly different than the baseline values. Non-resuscitated HS animals did not survive for the complete duration of the experiment and remained alive only for 60-90 minutes. Therefore, final blood samples could not be collected for further analysis.{Table 1}

Changes in serum osmolarity and electrolytes after HS, resuscitation, and blood transfusion

Data presented in [Table 2] shows significant increases in serum osmolarity when compared with the sham (P < 0.05) group. The HTS group had a significant hyperkalemia, hypernatremia, and hyperchlorimia in comparison to the other groups (P < 0.05).{Table 2}

Function of liver, kidney and muscle damage after HS and resuscitation

Data presented in [Table 3] depicts that in comparison to shams, all animals with HS and resuscitation suffered damage to liver, kidneys, and muscle. In comparison to LR, HTS was more effective in preventing the hepatic damage as evidenced by lower elevations in serum total bilirubin, AST, and ALT. HTS was also superior to LR in reducing kidney damage measured by small increases in BUN (blood urea nitrogen or azotemia), creatinine, and muscle damage measured by CPK levels (P < 0.05).{Table 3}

 Discussion



Extensive blood loss due to traumatic injury often results in significant loss of intravascular fluid volume, hemodynamic instability, decreased oxygen delivery, decreased tissue perfusion, cellular hypoxia, HS, multiple organ damage, and death. [14] Although resuscitation is an obligatory intervention during HS, the therapy may exacerbate inflammation. [15],[16] Even blood transfusions contain pro-inflammatory mediators that both prime and activate neutrophils. Animal models of HS have suggested that different fluids or different rates of resuscitation can have a widely divergent impact on the immune response, neutrophil activation, and tissue injury. [17] In an effort to determine an effective resuscitation strategy that can restore normal physiological parameters and ameliorate organ damage after HS, we have compared the effectiveness of isotonic and hypertonic crystalloid solutions followed by shed blood infusion on hemodynamics, biochemical parameters, acid- base status, and multiple organ damage in rats with HS.

Cardiovascular effects of NS, LR, and HTS during HS

Variation in the intensity of the HS was not a likely cause of differences in the treatment groups because of the similarity of the MAP (40 mmHg), amount of shed blood, base excess, pH, pO 2 , pCO 2 , and lactate throughout the shock period (T60). As shown in [Figure 1], animals subjected to the same severity and duration of hemorrhage but resuscitated with fluids varying in composition and volume exhibited higher MAP with HTS and LR, but not with normal saline. Non-resuscitated animals always had blood pressure measurements around 40 mmHg, and died within 70-90 min after the start of hemorrhage indicating that early cardio-respiratory compensation is essential for the survival from HS. [18] Our study indicates that resuscitative fluids could restore the baseline MAP.

In addition, transfusion of shed blood after fluid resuscitation was able to restore the baseline MAP. Takasu et al., also reported the improved survival time in HS rats resuscitated with LR followed by shed blood transfusion. [19] Meta-analysis of clinical studies of hypertonic saline treatment of HS showed an increase in blood pressure and cardiac output but there was no significant improvement in survival. [20] This suggests that in addition to increase MAP, there are other parameters that are important for the shock survival that may depend on the composition and volume of fluid with or without blood transfusion. In this study, we have used 3:1 volume replacement to blood loss regimens for the isotonic fluid treatments and 0.9% normal saline for volume control, and (5 mL/kg) hypertonic saline as osmotic and volume control. Therefore, we cannot discount potential differences in volume status or cardiovascular performance affecting the results because those parameters were not measured.

Electrolyte balance and resuscitation after HS

The shock state is characterized by hypotension caused by the fluid loss and decreased cardiac output, which could be compensated by the recruitment of extracellular volume. Fluid and electrolyte disorders after HS are related to volume and/or composition of the resuscitative fluid. Several studies suggested that normal saline and Ringer's lactate solution were equally effective in maintaining the intravascular volume after hemorrhage, [17],[21] but complications such as hypernatremia were reported with the use of HTS without any adverse sequelae. [22] These authors suggested the safety of using HTS for resuscitation in trauma patients. [22] These observations also support our current findings that in spite of increasing and restoring the MAP, HTS significantly increased Na + in comparison to LR, NS, and sham. All animals in this group survived the complete duration of study. We believe that there is a potential mechanism for this effect because HTS infusion significantly increased plasma Na + relative to Cl− concentration. This difference between positively and negatively charged electrolytes is associated with a natural consumption of hydrogen ions to preserve electrical neutrality and correction of HS-induced acid-base imbalances.

Acid-base status and electrolytes after HS and resuscitation

Reduction in blood volume during HS results in reduced oxygen supply and its incomplete metabolism for cellular ATP production by the mitochondria through anaerobic respiration. [23] The HS group in our study developed a metabolic acidosis as evidenced by a decrease in serum pH, CO 2 , HCO 3 , increased lactate, base excess, hyperkalemia, and death in non-resuscitated animals. This contrasted with sham control animals in which no significant hemodynamic, blood gas, lactate, microcirculatory, and tissue pCO 2 abnormalities were observed. However, all the fluids examined were significantly able to improve these parameters, but subsequent blood transfusion was more effective than the fluid alone. This suggests that resuscitation with fluid alone is not sufficient to enhance the oxygen metabolism.

Organ damage in HS and effect of resuscitation

Among multiple organs damaged by HS, the liver and kidneys are critical due to their role in key important biochemical reactions, inflammatory cascade and elimination of chemical waste. The well-known biomarkers of liver damage are increased alanine aminotransferase (AST), alanine aminotransferase (ALT), and total bilirubin in HS. Our present study indicates that both HTS and NS had beneficial effects on preventing the liver and kidney damage in comparison to LR. The mechanism behind the protective effects of HTS and NS in preventing the liver and kidney damage may be due to the attenuation of immune-mediated cellular injury and reduced apoptosis. [15] Boomer et al., reported an increased inflammatory systemic cytokine levels and elevated lung, liver, intestine, and smooth muscle injury after LR infusion compared with HTS or NS. In addition, these authors did not find any significant apoptosis with HTS or NS. [24] Similarly, in our current study, we found that HS-induced plasma CPK (a muscle specific enzyme) levels were reduced by NS and HTS compared to LR, possibly through the inflammatory mechanisms triggered by LR resuscitation. Our studies indicate that HTS is a better resuscitative fluid than LR in reducing HS-induced liver, kidney, and muscle damage.

Summary

The novel findings of this study significantly contribute to our understanding of the altered physiology and biochemistry of hemorrhagic shock, and the impact of fluid resuscitation on cellular metabolism, cell death, organ damage, and finally death. The future use of HTS resuscitation followed by blood transfusion in HS may potentially reduce tissue-mediated injury, prevent organ damage, and increase survival following HS.

Limitation of the study

We did not evaluate the adequacy of resuscitation in either group, and the question of whether all three groups were equally well resuscitated could be raised. We have reported only the end point results of electrolytes, osmolality, liver, kidneys, and muscle enzymes. Therefore, sequential progression of electrolyte imbalance and organ damage due to HS, resuscitation, and blood infusion could not be reported in this study.

 Conclusion



In hemorrhagic shock, treatment strategy using crystalloids with varying volumes and composition is not enough to normalize the physiological and biochemical parameters. Early resuscitation with HTS followed by blood infusion can be an effective treatment to reverse the harmful effects of HS, prevent organ damage, and death.

 Acknowledgement



This research was supported by a grant to PS from The U.S. Army Medical Research and Materiel Commands (USAMRMC) award number W81XWH-10-1-0507.

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