Dopamine infusion during resuscitation of experimental hemorrhagic shock

Centhaquin improves survival in a swine model of hemorrhagic shock

BACKGROUND

Hemorrhage is a frequent event in hospital and prehospital settings. The aim of the present study was to investigate whether centhaquin improves 24-h survival and reduces the total volume of required fluids in an established model of swine hemorrhagic shock.

MATERIAL AND METHODS

Twenty-five pigs were instrumented and subjected to hemorrhagic shock. The animals were randomly allocated in two experimental groups, the control (vehicle) (n = 10) and the centhaquin groups (0.015 mg/kg, n = 10); all animals received lactated Ringer solution in the resuscitation phase until their mean arterial pressure reached 90% of the baseline. A sham group (n = 5) was added a posteriori to mimic the hemodynamic profile of the centhaquin group.

RESULTS

A statistically significant difference was observed in the time required for the three groups to reach their target mean aortic pressure, 36.88 ± 3.26 min for the control group versus 9.40 ± 1.01 min for the sham group and 7.10 ± 0.97 min for the centhaquin group (P < 0.001). The total amount of fluids in the control and the sham groups was significantly higher when compared with that of the centhaquin-treated animals (P < 0.001). All 10 animals in the centhaquin group survived for 24 h, whereas only three animals survived in the control group and one animal in the sham group (P = 0.002).

CONCLUSIONS

Centhaquin 0.015 mg/kg administered in the fluid resuscitation phase resulted in lower volume of fluids and better survival compared with control and sham-operated animals.

Microcirculation follows macrocirculation in heart and gut in the acute phase of hemorrhagic shock and isovolemic autologous whole blood resuscitation in pigs

BACKGROUND

Disparity between the macro- and microcirculation is thought to occur as a result of (micro)vascular dysfunction in some types of shock. Whether this occurs during hemorrhagic shock, however, is unknown. We therefore investigated both macro- and microcirculatory variables in the heart as a vital organ and the gut as a nonvital organ. We hypothesized that the microcirculation in the gut would follow the macrocirculation in the acute phase of hemorrhagic shock and isovolemic autologous whole blood resuscitation, but that the microcirculation in the heart would be preserved even under conditions of macrocirculatory depression.

STUDY DESIGN AND METHODS

Eleven pigs (23 ± 4 kg) were anesthetized and subjected to a controlled hemorrhagic shock (30 and 45% reduction of total blood volume) and isovolemic resuscitation with autologous blood. Quantitative measurement of microvascular oxygen pressures (µpO(2)) was performed by phosphorimetry on the gut and heart simultaneously. Measurements of systemic hemodynamic and regional oxygen-derived variables as well as µpO(2) were performed at baseline, after the first and second phases of hemorrhage, and after resuscitation.

RESULTS

Five pigs responded to resuscitation, while six pigs died spontaneously within 20 to 30 minutes after reinfusion of the withdrawn blood, without significant differences in macro- or microcirculatory variables at baseline and after hemorrhage. Correlation analysis showed that microvascular pO(2) in the heart and the gut were closely related to macrocirculatory variables (cardiac index, mean arterial pressure, and oxygen delivery) during hemorrhage and resuscitation.

CONCLUSIONS

This study demonstrated that the microcirculation in the gut (being a nonvital organ) and heart (being a vital organ) follow the macrocirculation in the acute phase of hemorrhagic shock and isovolemic autologous whole blood resuscitation.

Hemodynamic Characteristics of Vasopressin in Dogs with Severe Hemorrhagic Shock

The effect of vasopressin was compared with that of the established vasopressor epinephrine in experimentally induced hemorrhagic shock. After rapid crystalloid resuscitation in a ratio of three volumes of 0.9% saline to one volume of blood (3:1 crystalloid resuscitation), six dogs were given 0.4 IU/kg vasopressin and another six dogs were given 0.1 mg/kg epinephrine. Five dogs in the control group were given fluid resuscitation in the same manner as above without administration of any drugs. Administration of vasopressin increased diastolic arterial pressure (DAP) from 45.0 +/- 4.9 to 91.2 +/- 9.6 mmHg within 5 min, compared with epinephrine from 46 +/- 4.0 to 51.8 +/- 7.7, and control from 47.3 +/- 7.5 to 46.3 +/- 7.3. Systolic arterial pressure (SAP) did not increase significantly following vasopressin compared with epinephrine and control group. Results of DAP and systemic vascular resistance index (SVRI) suggested that vasopressin administration was vasoconstrictive after fluid resuscitation in decompensatory hemorrhagic shock in dogs, whereas epinephrine did not compared with control. In addition, epinephrine did not affect the cardiac index (CI) and SVRI, while a significant decrease in CI and increase in SVRI were observed in vasopressin group. The pressor effect of epinephrine in the vascular system was abrupt and only lasted a short period of time (within 5 min), while that of vasopressin was steady and lasted for more than 1 hr, especially regard to in DAP. When compared with epinephrine, vasopressin can be a more effective and safer choice in patients with severe hemorrhagic shock.

Supraceliac aortic cross-clamping and declamping. Effects of dopexamine and dopamine on systemic and mesenteric hemodynamics, metabolism and intestinal tonometry in a rat model

BACKGROUND

The effects of dopexamine and dopamine on mesenteric ischemia during reperfusion following aortic cross-clamping are not known. We determined intramucosal tonometric PCO2 and PCO2 gap using a rat model of supraceliac aortic cross-clamping and declamping.

METHODS

Under pentobarbital and fentanyl anesthesia, 24 rats were surgically instrumented with arterial, right atrial, and portal venous catheters, ultrasonic flowprobes for measurements of abdominal aortic, superior mesenteric and carotid artery blood flow, and a pediatric tonometer for intestinal mucosal PCO2 measurements. Rats were randomized to receive a continuous infusion of dopexamine (10 x microg(-1) x kg(-1) x min(-1), n=8), dopamine (10 microg x kg(-1) x min(-1), n=8 ), or physiologic saline (control, n= 8), infused at a rate of 4 ml x kg(-1) x h(-1), administered throughout the experimental protocol. After 30 min of drug infusion, the aorta was cross-clamped at the supraceliac level for 30 min. Reperfusion following declamping was observed for 180 min.

RESULTS

Intestinal tonometric PCO2 remained unchanged during drug treatment before aortic cross-clamping, increased similarly in all groups following declamping during early reperfusion, and recovered to baseline within 30 min of reperfusion. Dopexamine treatment was associated with higher lactate levels and increased heart rate (P<0.05) during aortic cross-clamping.

CONCLUSIONS

1) Mesenteric ischemia, determined by intestinal tonometric PCO2 and PCO2 gap, recovers within 30 min of reperfusion following 30 min of aortic cross-clamping irrespective of drug treatment and, 2) dopexamine induced higher lactate levels and increased heart rate during aortic cross-clamping and should be carefully analyzed for potentially adverse effects on cardiac function.

Hepatosplanchnic and peripheral tissue oxygenation during treatment of hemorrhagic shock: the effects of pentoxifylline administration

OBJECTIVE

To evaluate the effects of pentoxifylline (PF) administration on liver, gut, and peripheral oxygenation during crystalloid resuscitation of hemorrhagic shock.

SUMMARY BACKGROUND DATA

Hypoperfusion of the hepatosplanchnic vascular bed and hypoxia of vital organs may be prolonged despite adequate therapy of hemorrhagic shock. Vasoconstriction, leukostasis, platelet aggregation, and red blood cell plugging could be the underlying causes. PF has been shown to counteract these effects, but its effects in a large animal shock model have been less studied.

METHODS

Thirteen anesthetized piglets (mean weight 19.6 kg) were bled steadily to a mean arterial pressure (MAP) of 40 to 50 mmHg and a 70% reduction in cardiac output during 1 hour. These levels were maintained for an additional hour. The animals were resuscitated with acetated Ringer's solution according to MAP and cardiac output values and followed for 80 minutes (total 3 hours and 20 minutes). Seven piglets were given PF boluses (12.5 mg/kg) and infusion (0.2 mg/kg x min), and the rest (n = 6) served as controls. Hemodynamic and systemic oxygen transport variables were recorded. Liver parenchymal and peripheral tissue (subcutaneous, transcutaneous, conjunctival) oxygen tensions (PO2) were measured continuously with polarographic electrodes. Jejunal intramucosal pH (pHi) was calculated every hour by the luminal PCO2, obtained with a balloon tonometer, and arterial bicarbonate concentration.

RESULTS

Cardiac output decreased by a mean of 76% during shock and was restored during resuscitation in both groups. MAP decreased from 110 to 40 mmHg but remained at 70 to 80 mmHg during resuscitation in both groups despite remarkable volume load (2.6 ml/min per kg). Liver parenchymal PO2 decreased from 29+/-1 to 15+/-1 mmHg during shock and increased to 36+/-2 mmHg in the PF group, whereas in control group it remained at 26 mmHg. The difference between groups was significant, but at the end of follow-up the liver PO2 decreased to 21 mmHg in both groups. Gut pHi, peripheral tissue oxygen tensions, and the plasma adrenaline and noradrenaline concentrations did not differ between the groups.

CONCLUSIONS

Pentoxifylline improved specifically, although only transiently, liver tissue oxygenation. Perhaps the microvascular abnormalities after resuscitation of hemorrhagic shock are more prominent in the hepatic vascular bed, rendering PF specifically effective in that area. The lack of any effect of PF on gut and peripheral tissue oxygenation may have resulted from the persistent vasoconstriction and inadequate restoration of blood volume with crystalloid solution.

Dopexamine improves liver oxygenation during crystalloid resuscitation from experimental hemorrhagic shock

OBJECTIVE

To evaluate the effects of dopexamine administration on hemodynamic variables and tissue oxygen tensions during crystalloid resuscitation from hemorrhagic shock.

DESIGN

Randomized, control trial.

SETTING

An animal laboratory at a university center.

SUBJECTS

Twelve piglets, mean weight 22 kg.

INTERVENTIONS

The animals were anesthetized and bled to a state of hemorrhagic shock and resuscitated, using a crystalloid solution infused at a rate of approximately 2.6 mL/min/kg (total amount 208 mL/kg). Cardiac output and mean arterial pressure (MAP were measured as indicators of volume filling during the 20- to 30-min resuscitation period and during the follow-up period until 80 mins from the start of resuscitation. Dopexamine was administered by infusion at 6 micrograms/kg-min from the start of volume replacement (dopexamine group, n = 6). The rest of the animals (control group, n = 6) were given volume replacement only.

MEASUREMENTS AND MAIN RESULTS

Systemic oxygen transport variables were calculated. Tissue oxygen tensions were continuously recorded from the liver, conjunctival layer, and via subcutaneous and transcutaneous electrodes in the abdominal region. MAP decreased from 119 +/- 2 (SEM) to 44 +/- 2 mm Hg and cardiac output decreased by 77% during the shock period. During resuscitation, cardiac output was restored in both groups. MAP increased close to the baseline during the early resuscitation period and decreased slowly during follow-up. Oxygen delivery remained at 46% of baseline, whereas systemic oxygen consumption was restored during resuscitation in both groups. Liver tissue oxygen tension increased well above baseline during resuscitation in the dopexamine group, and liver tissue oxygen tension was significantly higher than in the control group. After 60 mins of resuscitation, the liver oxygen tension decreased to control group values. None of the other tissue oxygen tensions showed any differences between groups.

CONCLUSIONS

Dopexamine administration during crystalloid resuscitation from hemorrhagic shock was well tolerated and resulted in significant and specific, although transient, improvement in liver oxygenation.