EFFECTS OF COLLOID RESUSCITATION ON PERIPHERAL MICROCIRCULATION, HEMODYNAMICS, AND COLLOIDAL OSMOTIC PRESSURE DURING ACUTE SEVERE HEMORRHAGE IN RABBITS

Goal-directed colloid versus crystalloid therapy and microcirculatory blood flow following ischemia/reperfusion

OBJECTIVE

Ischemia/reperfusion can impair microcirculatory blood flow. It remains unknown whether colloids are superior to crystalloids for restoration of microcirculatory blood flow during ischemia/reperfusion injury. We tested the hypothesis that goal-directed colloid - compared to crystalloid - therapy improves small intestinal, renal, and hepatic microcirculatory blood flow in pigs with ischemia/reperfusion injury.

METHODS

This was a randomized trial in 32 pigs. We induced ischemia/reperfusion by supra-celiac aortic-cross-clamping. Pigs were randomized to receive either goal-directed isooncotic hydroxyethyl-starch colloid or balanced isotonic crystalloid therapy. Microcirculatory blood flow was measured using Laser-Speckle-Contrast-Imaging. The primary outcome was small intestinal, renal, and hepatic microcirculatory blood flow 4.5 h after ischemia/reperfusion. Secondary outcomes included small intestinal, renal, and hepatic histopathological damage, macrohemodynamic and metabolic variables, as well as specific biomarkers of tissue injury, renal, and hepatic function and injury, and endothelial barrier function.

RESULTS

Small intestinal microcirculatory blood flow was higher in pigs assigned to isooncotic hydroxyethyl-starch colloid therapy than in pigs assigned to balanced isotonic crystalloid therapy (768.7 (677.2-860.1) vs. 595.6 (496.3-694.8) arbitrary units, p = .007). There were no important differences in renal (509.7 (427.2-592.1) vs. 442.1 (361.2-523.0) arbitrary units, p = .286) and hepatic (604.7 (507.7-701.8) vs. 548.7 (444.0-653.3) arbitrary units, p = .376) microcirculatory blood flow between groups. Pigs assigned to colloid - compared to crystalloid - therapy also had less small intestinal, but not renal and hepatic, histopathological damage.

CONCLUSIONS

Goal-directed isooncotic hydroxyethyl-starch colloid - compared to balanced isotonic crystalloid - therapy improved small intestinal, but not renal and hepatic, microcirculatory blood flow in pigs with ischemia/reperfusion injury. Whether colloid therapy improves small intestinal microcirculatory blood flow in patients with ischemia/reperfusion needs to be investigated in clinical trials.

Diagnosis and surgical treatment of colonic obstructive foreign bodies in chinchillas (Chinchilla lanigera): a case series (2017-2020)

We describe a case series of colonic foreign bodies in seven chinchillas. These animals had all shown complete lack of fecal output. Ultrasonography was performed in each case, revealing a hyperechoic foreign body with strong acoustic shadowing in the bowel in 6 of the 7 cases (86%). Foreign bodies were removed under exploratory laparotomy in all cases, with a perioperative survival rate of 71% (5/7). The foreign bodies were extracted from the distal ansa of the ascending colon (n=3), descending colon (n=3), or intermediate part of the ascending colon (n=1). This case series suggests chinchillas are affected by colonic obstructive foreign bodies and surgical intervention may be necessary to pursue better prognosis in cases where medical therapies prove ineffective.

Clinical Outcomes and Medical Costs of Hydration Therapy with Hydroxyethyl Starch (130/0.4) or Acute Single Infarction

OBJECTIVES

To investigate the effects of hydration with or without Hydroxyethyl Starch (HES) 130/0.4 on neurological outcomes and medical costs during hospitalisation in patients with a single infarction (SI) in the posterior lenticulostriate artery (LSA) territory.

MATERIALS AND METHODS

In this retrospective, single-centre, non-blinded cohort study, SI in the posterior LSA was defined as an ischaemic lesion with a high-signal intensity area ≥20 mm. All patients received basic stroke care within 48 h of symptom onset between April 2015 and January 2019. Patients were divided into the following two groups by clinician's preference: 1) those administered HES 130/0.4 and 2) those receiving other infusion fluid. The relationships between hospital costs and hydration therapy type were examined.

RESULTS

Eighteen (31%) of 58 patients received HES 130/0.4. The HES group had a significantly lower total cost than the control group (3.6 vs. 6.4 million yen, p=0.006). Moreover, the HES group had a significantly shorter hospital stay duration (79.5 vs. 141.0 days) and lower National Institutes of Health Stroke Scale score on day 7. Multivariate analysis found that HES 130/0.4 administration was an independent factor associated with high costs.

CONCLUSIONS

Hydration therapy with HES 130/0.4 significantly decreased the total costs and hospitalisation duration of patients with SI in the posterior LSA territory.

Colloids and the Microcirculation

Colloid solutions have been advocated for use in treating hypovolemia due to their expected effect on improving intravascular retention compared with crystalloid solutions. Because the ultimate desired effect of fluid resuscitation is the improvement of microcirculatory perfusion and tissue oxygenation, it is of interest to study the effects of colloids and crystalloids at the level of microcirculation under conditions of shock and fluid resuscitation, and to explore the potential benefits of using colloids in terms of recruiting the microcirculation under conditions of hypovolemia. This article reviews the physiochemical properties of the various types of colloid solutions (eg, gelatin, dextrans, hydroxyethyl starches, and albumin) and the effects that they have under various conditions of hypovolemia in experimental and clinical scenarios.

Assessment and Care of the Critically Ill Rabbit

Rabbits have the ability to hide their signs and often present in a state of decompensatory shock. Handling can increase susceptibility to stress-induced cardiomyopathy and specific hemodynamic changes. Careful monitoring with a specific reference range is important to detect early decompensation, change the therapeutic plan in a timely manner, and assess prognostic indicators. Fluid requirements are higher in rabbits than in other small domestic mammals and can be corrected both enterally and parenterally. Critical care in rabbits can be extrapolated to many hindgut fermenters, but a specific reference range and dosage regimen need to be determined.

Changing paradigms in surgical resuscitation

Patients undergoing emergency surgery typically require resuscitation, either because they are hemorrhaging or because they are experiencing significant internal fluid shifts. Intravascular hypovolemia is common at the time of anesthesia induction and can lead to hemodynamic collapse if not promptly treated. Central pressure monitoring is associated with technical complications and does not improve outcomes in this population. Newer modalities are in use, but they lack validation. Fluid resuscitation is different in bleeding and septic patients. In the former group, it is advisable to maintain a deliberately low blood pressure to facilitate clot formation and stabilization. If massive transfusion is anticipated, blood products should be administered from the outset to prevent the coagulopathy of trauma. Early use of plasma in a ratio approaching 1:1 with red blood cells (RBCs) has been associated with improved outcomes. In septic patients, early fluid loading is recommended. The concept of "goal-directed resuscitation" is based on continuing resuscitation until venous oxygen saturation is normalized. In either bleeding or septic patients, however, the most important goal remains surgical control of the source of pathology, and nothing should be allowed to delay transfer to the operating room. We review the current literature and recommendations for the resuscitation of patients coming for emergency surgery procedures.

Insight in microcirculation and histomorphology during burn shock treatment using in vivo confocal-laser-scanning microscopy

PURPOSE

Microcirculatory disturbances are well known during shock; however, the accompanied histomorphological alterations are widely unknown. We used high resolution confocal-laser-scanning microscopy for the evaluation of microcirculation and histomorphology during Burn Shock treatment.

METHODS

Confocal-laser-scanning microscopy was performed in 10 burn shock patients (4 women, 6 men; aged 40.6 +/- 11.4 years, burn extent >20% body surface area) initially and 24 hours after shock resuscitation. Ten matched hemodynamic stable burn intensive care unit patients served as controls. The following parameters were evaluated: quantitative blood cell flow, cell size of the granular layer, basal layer thickness, and epidermal thickness.

RESULTS

Quantitative blood cell flow in controls was 62.45 +/- 3.39 cells per minute. Burn shock significantly reduced blood cell flow to 37.27 +/- 3.64 cells per minute; fluid resuscitation effectively restored baseline blood flow (65.18 +/- 3.76 cells per minute) after 24 hours. Granular cell size was 793.61 +/- 41.58 microm(2) in controls vs 644.27 +/- 42.96 microm(2) during burn shock. Post resuscitation granular cell size measured 932.74 +/- 38.83 microm(2). Basal layer thickness was 14.84 +/- 0.59 microm in controls, 13.26 +/- 0.54 microm in burn patients at admission and before resuscitation, and 17.50 +/- 0.46 microm after resuscitation. Epidermal thickness in control patients was 49.60 +/- 2.36 microm, 37.83 +/- 2.47 microm in burn patients at admission and 69.50 +/- 3.18 microm after resuscitation.

CONCLUSIONS

Confocal-laser-scanning microscopy provides a noninvasive tool for simultaneous evaluation of microcirculation and tissue histomorphology. It may help to assess the adequacy of and response to resuscitation of burn patients early after trauma.

The early effect of Voluven, a novel hydroxyethyl starch (130/0.4), on cerebral oxygen supply and consumption in resuscitation of rabbit with acute hemorrhagic shock

BACKGROUND

Voluven (hydroxyethyl starch [HES] 130/0.4), a new generation of HES product with low molecular weight, has been widely used for the treatment of traumatic and hemorrhagic shock in clinics. However, no data are available whether it affects the balance of cerebral oxygen supply and consumption when applied to resuscitate hemorrhagic shock. The purpose of this study was to address this question in rabbits subjected to a severe hemorrhagic shock.

METHODS

In New Zealand rabbits, an acute hemorrhagic shock was induced by withdrawing 45% to 50% of total blood volume from the femoral vein in 10 minutes when the mean arterial pressure was reduced to 60% of the baseline level. Thirty minutes after the hemorrhage, animals were infused with either an equal amount of Voluven (group V) or a tripled amount of lactated Ringer's solution (group R). The saturation of oxygen was obtained in arterial (Sao2) and venous (SjvO2) blood samples from the femoral artery and jugular bulb, respectively. Arterial oxygen content (Cao2), jugular oxygen content (CjvO2), arteriovenous oxygen difference (AVDO2), and cerebral oxygen extraction rate (CERO2) were calculated accordingly to evaluate the oxygenation state in the brain.

RESULTS

Levels of SjvO2 and CjvO2 were decreased after hemorrhagic shock, and there were increases in AVDO2 and CERO2 values. After resuscitation, the SjvO2, AVDO2, and CERO2 levels in group V were quickly recovered to the basal levels, whereas the values in group R remained in the abnormal levels (p < 0.05). There were significant differences between the groups in their SjvO2 and CERO2 levels at 30 minutes after resuscitation. In addition, the mean arterial pressure was restored to the basal levels in group V but not in group R after resuscitation (p < 0.05).

CONCLUSION

We conclude that early infusion of Voluven is beneficial for maintenance of the hemodynamic stability and for the balance of cerebral oxygen supply and consumption during the resuscitation of acute hemorrhagic shock.

Permissive range of hypercapnia for improved peripheral microcirculation and cardiac output in rabbits*

OBJECTIVES

Permissive hypercapnia improves outcomes in patients with respiratory failure, most likely because of a reduction in ventilator-induced lung injury. Because hypercapnia is a potent vasoactive stimulus, adequate tissue perfusion and oxygen delivery to dilated microvessels may be restored. We examined how Paco2 affects microvascular changes, hemodynamics, and cardiac output in rabbits. We evaluated the permissive range of Paco2 required for maintenance of the peripheral circulation.

DESIGN

Prospective experimental animal study.

SETTING

Animal research laboratory.

SUBJECTS

A total of 31 Japanese domestic white rabbits.

INTERVENTIONS

The animals were anesthetized with pentobarbital. An ear chamber was prepared to examine blood vessels by intravital microscopy. The rabbits were mechanically ventilated with air, oxygen, and CO2. The values of Paco2 were adjusted to about 20 (hypocapnia), 40 (normocapnia), 60, 80, 100, 125, 150, and >250 mm Hg (hypercapnia). After stabilization at each Paco2 level, microvascular changes were recorded with a microscope-closed video camera to permit analysis of arteriolar diameter and blood flow.

MEASUREMENTS AND MAIN RESULTS

The pH and heart rate decreased and mean blood pressure increased progressively as the Paco2 was increased. When Paco2 was increased from 20 to 80 mm Hg, vessel diameter, blood-flow velocity, and blood-flow rate increased markedly. Cardiac output increased slightly. When Paco2 exceeded 100 mm Hg, all of these variables decreased. When Paco2 exceeded 150 mm Hg, all variables were significantly lower than the control values (p < .01).

CONCLUSION

Intravital microscopic visualization of the rabbit ear microcirculation showed that 150 mm Hg is the permissive upper limit of acute hypercapnia with respect to maintenance of the peripheral microcirculation.

Changes in central venous pressure and blood lactate concentration in response to acute blood loss in horses

OBJECTIVE

To evaluate selected hemodynamic, blood gas, and biochemical responses to mild to moderate acute blood loss in standing, awake horses.

DESIGN

Prospective study.

ANIMALS

7 healthy mares.

PROCEDURES

Each horse was restrained in standing stocks, and its head was maintained in a neutral position; sedatives and tranquilizers were not administered. During a 1-hour period, blood was collected into collection bags by use of a suction pump. The rate of blood collection was approximately 16 mL/kg/h (7.3 mL/lb/h). Thirty minutes after blood collection, the blood was readministered at the same rate. Central venous pressure (CVP), central venous blood gas, blood lactate concentration, and heart rate were measured at baseline (after placement of catheters), after removal of blood, and after readministration of blood.

RESULTS

In response to blood loss, CVP decreased and blood lactate concentration increased significantly, compared with baseline values; heart rate and results of central venous blood gas analysis did not change significantly. After readministration of blood, CVP returned to baseline value and blood lactate concentration approached baseline value.

CONCLUSIONS AND CLINICAL RELEVANCE

Changes in CVP and blood lactate concentration appear to be early indicators of hypovolemia in horses, which may represent acute blood loss in trauma patients; these variables should be monitored to assess the potential need for blood transfusions. These variables can be used to monitor responses of horses to blood transfusions when whole blood is administered as the replacement fluid.

Fluid replacement via the rectum for treatment of hypovolaemic shock in an animal model

BACKGROUND

The importance of early and effective fluid resuscitation in hypovolaemic shock treatment is indisputable.

AIM

To examine the effects of fluid replacement via the rectum in an animal model of hypovolaemic shock as a possible life-saving method in situations where veins cannot be accessed quickly.

METHODS

Rabbits were randomly divided into two groups: a control group of 7 animals and a second group of 10, the fluid replacement via the rectum (FRVR) group. The femoral artery of each subject was catheterised and 15 ml blood was withdrawn over 1 min at 5-min intervals. After reaching a mean arterial pressure (MAP) of 30 mm Hg, additional blood was withdrawn until the MAP dropped to <25 mm Hg, at which time blood withdrawal ceased. At this point, control animals were given no treatment and were monitored for 30 min. The FRVR group, however, was given 0.9% sodium chloride solution (amount equal to three times the amount of blood withdrawn) via the rectum over a 15-min period. The MAPs of both groups were then measured, every 5 min after the start of resuscitation, for 30 min.

RESULTS

In the FRVR group, the MAP began to rise significantly after 15 min of receiving fluid per rectum (p = 0.035) and continued to be significantly greater than the control group at 20, 25 and 30 min (p = 0.035, 0.002 and 0.001, respectively).

CONCLUSION

FRVR is a viable alternative for fluid resuscitation in this animal model of hypovolaemic shock. This easy and non-invasive method of fluid replacement may be useful when standard intravenous access is unobtainable, and should be compared with other access routes using varying types and amounts of fluids in future animal studies.

Early hemodynamic and renal effects of hemorrhagic shock resuscitation with lactated Ringer's solution, hydroxyethyl starch, and hypertonic saline with or without 6% dextran-70

BACKGROUND

Considering the renal effects of fluid resuscitation in hemorrhaged patients, the choice of fluid has been a source of controversy. In a model of hemorrhagic shock, we studied the early hemodynamic and renal effects of fluid resuscitation with lactated Ringer's (LR), 6% hydroxyethyl starch (HES), and 7.5% hypertonic saline (HS) with or without 6% dextran-70 (HSD).

MATERIALS AND METHODS

Forty-eight dogs were anesthetized and submitted to splenectomy. An estimated 40% blood volume was removed to maintain mean arterial pressure (MAP) at 40 mm Hg for 30 min. The dogs were divided into four groups: LR, in a 3:1 ratio to removed blood volume; HS, 6 mL kg(-1); HSD, 6 mL kg(-1); and HES in a 1:1 ratio to removed blood volume. Hemodynamics and renal function were studied during shock and 5, 60, and 120 min after fluid replacement.

RESULTS

Shock treatment increased MAP similarly in all groups. At 5 min, cardiac filling pressures and cardiac performance indexes were higher for LR and HES but, after 120 min, there were no differences among groups. Renal blood flow and glomerular filtration rate (GFR) were higher in LR at 60 min but GFR returned to baseline values in all groups at 120 min. Diuresis was higher for LR at 5 min and for LR and HES at 60 min. There were no differences among groups in renal variables 120 min after treatment.

CONCLUSIONS

Despite the immediate differences in hemodynamic responses, the low-volume resuscitation fluids, HS and HSD, are equally effective to LR and HES in restoring renal performance 120 min after hemorrhagic shock treatment.

Oxygent as a top load to colloid and hyperoxia is more effective in resuscitation from hemorrhagic shock than colloid and hyperoxia alone

Perfluorocarbon (PFC) emulsions are intravascular oxygen therapeutics that temporarily enhance tissue oxygenation in dilutional anemia. However, PFC emulsions are not resuscitation fluids because PFCs only work optimally in the presence of high O2 partial pressure (hyperoxia); moreover, because they have no oncotic potential, dosing limitations prevent their use to permanently replace large hemorrhage volumes. Our objective was to clarify whether in the presence of hyperoxia a conventional colloid therapy supplemented by PFC is more efficacious than colloid alone. To answer this question, 22 anesthetized, ventilated dogs were hemorrhaged to a mean arterial pressure of 45 mmHg and were kept at this level until a metabolic O2 debt of 120 mL kg(-1) body weight had evolved. Hyperoxia was established and dogs were randomly allocated to receive colloid (6% HES, Hydroxy Ethyl Starch shed blood volume) or colloid together with Oxygent (perflubron emulsion, 60%, w/v; Alliance Pharmaceutical Corp., San Diego, CA; single dose, 4.5 mL kg(-1); i.e., 2.7 g PFC kg body weight) in a blinded fashion. Hemodynamic and O2 transport parameters, intestinal mucosal blood flow (microspheres), and O2 partial pressure (MDO-Electrode; Eschweiler, Kiel, Germany) were measured at baseline, in shock, and during 3 h post-therapy. In the presence of hyperoxia, Oxygent improved the amount of physically dissolved O2 in plasma and increased the contribution of physically dissolved O2 to global O2 delivery (P < 0.05) and thus whole body O2 consumption when compared with colloid alone (P < 0.05). As a result, Oxygent reduced intestinal mucosal hypoxia and global O2 debt within the first hour post-therapy (P < 0.05). We conclude that under hyperoxic conditions, fluid resuscitation supplemented by Oxygent was more efficacious than colloid and hyperoxia alone. PFC temporarily enhanced intestinal mucosal tissue oxygenation during resuscitation.

EVIDENCE FOR MYOCARDIAL DEFECTS UNDER EXTREME ACUTE NORMOVOLEMIC HEMODILUTION WITH HYDROXYETHYL STARCH AND LACTATED RINGER'S SOLUTION

Acute normovolemic hemodilution (ANH) has been proposed to avoid the risks of allogenic transfusion. In reference to its cellular effects, ANH reports in the literature are scarce. Using electron microscopy (EM), we evaluated the effects of ANH on cardiac function and myocardial structure. Twenty-five dogs were prospectively randomized to a control group (n = 5) or to undergo ANH with 6% hydroxyethyl starch (HES; n = 10) or lactated Ringer's solution (LR; n = 10) administered, respectively, at a ratio of 1:1 or 1:3 to the volume of blood removed. Animals were gradually hemodiluted to a hematocrit of 10%, which was accomplished in 80 min. Pulmonary artery catheter and echocardiography were used to evaluate cardiac function. Myocardial samples were taken after the last time point for electron microscopy analysis. Data were obtained during five different stages of ANH, with a mean 20-min interval between each time point. Cardiac index increased significantly in both groups during ANH. A significant decrease in oxygen delivery and oxygen consumption, as well as an increase in oxygen extraction was verified in the LR group. Echocardiography demonstrated a decline in systolic function in the LR group at the end of the experiment. Electron microscopy analysis of the myocardium revealed slight lesions in cardiac cells in the HES group, and moderate-to-significant lesions in the LR group. In this animal species, ANH with HES resulted in better preservation of cardiac function, which was demonstrated by maintenance of systolic function and oxygenation parameters. Minor loss of cellular integrity with HES, in the presence of very low levels of hemoglobin, reinforces these findings.