Continuous resuscitation after hemorrhage and acute fluid replacement improves cardiovascular responses

Comparative Evaluation of Crystalloid Resuscitation Rate in a Human Model of Compensated Haemorrhagic Shock

Introduction:

The most effective rate of fluid resuscitation in haemorrhagic shock is unknown.

Methods:

We performed a randomized crossover pilot study in a healthy volunteer model of compensated haemorrhagic shock. Following venesection of 15 mL/kg of blood, participants were randomized to 20 mL/kg of crystalloid over 10 min (FAST treatment) or 30 min (SLOW treatment). The primary end point was oxygen delivery (DO₂). Secondary end points included pressure and flow-based haemodynamic variables, blood volume expansion, and clinical biochemistry.

Results:

Nine normotensive healthy adult volunteers participated. No significant differences were observed in DO₂ and biochemical variables between the SLOW and FAST groups. Blood volume was reduced by 16% following venesection, with a corresponding 5% reduction in cardiac index (CI) (P < 0.001). Immediately following resuscitation the increase in blood volume corresponded to 54% of the infused volume under FAST treatment and 69% of the infused volume under SLOW treatment (P = 0.03). This blood volume expansion attenuated with time to 24% and 25% of the infused volume 30 min postinfusion. During fluid resuscitation, blood pressure was higher under FAST treatment. However, CI paradoxically decreased in most participants during the resuscitation phase; a finding not observed under SLOW treatment.

Conclusion:

FAST or SLOW fluid resuscitation had no significant impact on DO₂ between treatment groups. In both groups, changes in CI and blood pressure did not reflect the magnitude of intravascular blood volume deficit. Crystalloid resuscitation expanded intravascular blood volume by approximately 25%.

Central acetylcholinesterase inhibition improves hemodynamic counterregulation to severe blood loss in alcohol-intoxicated rats

Acute alcohol intoxication results in impaired hemodynamic counterregulation to blood loss and is associated with an attenuated hemorrhage-induced release of catecholamines and AVP. We speculated that restoration of the neuroendocrine response to hemorrhage would improve mean arterial blood pressure (MABP) recovery during acute alcohol intoxication. Previously, we demonstrated that intracerebroventricular (i.c.v.) choline, a precursor of acetylcholine, transiently increases sympathetic nervous system (SNS) outflow but is not capable of improving neuroendocrine and hemodynamic compensation to hemorrhage in alcohol-treated rats. We hypothesized that prolongation of the observed effect via i.c.v. neostigmine, an acetylcholinesterase inhibitor, would enhance SNS outflow, restore the neuroendocrine response, and in turn improve hemodynamic responses to hemorrhage during acute alcohol intoxication. I.c.v. neostigmine (1 microg) increased MABP, catecholamines, and AVP within 5 min and reversed hypotension due to 40% hemorrhage and intragastric alcohol (30% wt/vol, 2.5 g/kg) administration in chronically catheterized male Sprague-Dawley rats (225-250 g body wt). Acute alcohol intoxication before 50% hemorrhage decreased basal MABP, accentuated hypotension midhemorrhage, suppressed the hemorrhage-induced release of norepinephrine and AVP, and prevented restoration of MABP to basal levels after fluid resuscitation with lactated Ringer solution. I.c.v. neostigmine (0.5 microg) produced a sustained increase in MABP beginning at 30 min of hemorrhage that persisted throughout fluid resuscitation in control and alcohol-treated animals. I.c.v. neostigmine enhanced epinephrine responses and restored the hemorrhage-induced release of norepinephrine and AVP in alcohol-treated rats. These results demonstrate that inhibition of acetylcholinesterase in the central nervous system enhances SNS outflow, restores the neuroendocrine response to severe blood loss, and thereby improves hemodynamic counterregulation during acute alcohol intoxication. This study provides evidence for a central (and not peripheral) role of alcohol in impairing hemodynamic stability during hemorrhagic shock.

Downregulation of hepatic cytochrome P-450 isoforms and PPAR-gamma: their role in hepatic injury and proinflammatory responses in a double-hit model of hemorrhage and sepsis

BACKGROUND

The "double-hit" model of hemorrhage and sepsis mimics the critically ill patient admitted to the surgical intensive care unit. Although the protein expression of a cytochrome (CYP) P-450 isoform CYP1A2 is reduced in the late stage of sepsis, the effect of hemorrhage on CYP isoforms and the anti-inflammatory nuclear receptor peroxisome proliferator-activated receptor-gamma (PPAR-gamma) has not been investigated. We hypothesized that hemorrhage down-regulates CYP isoforms and PPAR-gamma in the liver, which plays an important role in producing tissue injury and proinflammatory responses after the subsequent sepsis (i.e., double-hit).

MATERIALS AND METHODS

Male Sprague Dawley rats were divided into four groups. Animals in the double-hit group underwent hemorrhage (40 +/- 2 mmHg for 90 min) followed by fluid resuscitation. Polymicrobial sepsis was induced by cecal ligation and puncture (CLP) 20 h after hemorrhage, and the animals were sacrificed 4 h after CLP. Rats in the hemorrhage-alone group were sacrificed 20 h after the insult. Rats in the CLP-alone group were sacrificed 4 h after the onset of sepsis. Animals in the sham-operated group underwent neither hemorrhage nor CLP. The gene expression of P-450 isoforms (i.e., CYP1A2 and 2C11) and PPAR-gamma in the liver was determined using RT-PCR. Serum concentrations of alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate, and proinflammatory cytokines (i.e., IL-6, TNF-alpha) were also assessed.

RESULTS

In the hemorrhage-alone group, hepatic mRNA expression of CYP1A2, CYP2C11, and PPAR-gamma was significantly down-regulated 20 h after the initial stress compared with sham-operated rats. Double-hit did not appear to further decrease CYP and PPAR-gamma gene expression. In contrast, serum levels of AST, ALT, lactate, IL-6, and TNF-alpha did not change significantly in either hemorrhaged or septic animals. Those organ injury indicators and cytokines, however, were significantly elevated after the double-hit of hemorrhage and sepsis.

CONCLUSIONS

Hepatic CYP1A2, CYP2C11, and PPAR-gamma were down-regulated after the initial stress (hemorrhage). These down-regulated CYPs and PPAR-gamma seem to work as important factors contributing to the progression of organ injury and proinflammatory responses after the second stress (CLP).

Influence of fluid therapy on gentamicin pharmacokinetics in colic horses

The aminoglycoside antibiotic gentamicin is commonly used in equine medicine for the prevention and treatment of Gram-negative and staphylococcal bacteria in surgically treated colic patients. The pharmacokinetics of gentamicin in these patients might be altered by the disease status, and/or under the influence of fluid therapy. The purpose of this study was to investigate the effect of intravenous fluid treatment on gentamicin kinetics in colic patients. Colic patients subjected to laparotomy were given fluid infusions according to clinical status. Following gentamicin administration, blood samples were taken for gentamicin analysis at different time points, and the main pharmacokinetic parameters including Vc, Vss, t(1/2) and MRT were calculated. Horses undergoing fluid therapy showed a significantly different t(1/2), clearance and MRT as compared to non-infused patients. However, taking into account the clinical status of the patients receiving fluid support, the data suggest that endotoxaemia, rather than fluid therapy, influence gentamicin pharmacokinetics following laparotomy.

Progesterone administration after trauma and hemorrhagic shock improves cardiovascular responses

OBJECTIVE

Studies have shown that female rats during the proestrus stage have significantly improved cell and organ functions after trauma-hemorrhage compared with male and ovariectomized females. This study investigated the hypothesis that progesterone can improve the depressed cardiovascular function in sex steroid-deficient female rats (i.e., ovariectomized females) after trauma-hemorrhage and resuscitation.

DESIGN

Prospective study.

SETTING

University laboratory.

SUBJECTS

Ovariectomized female Sprague-Dawley rats (weight, 250-300 g).

INTERVENTIONS

Rats underwent a 5-cm midline laparotomy (i.e., soft-tissue trauma), were bled to a mean arterial pressure of 35 mm Hg for approximately 90 mins, and were then resuscitated using Ringer's lactate. A single dose of progesterone (25 mg/kg of body weight) or vehicle was administered subcutaneously during resuscitation.

MEASUREMENTS

At 20 hrs after trauma-hemorrhage or sham operation, cardiac output and heart performance and the circulating blood volume were assessed using the indocyanine green dilution technique and a left ventricular catheter. Furthermore, the binding activity of progesterone receptors in nuclear extracts of left ventricular tissue was determined.

RESULTS

Cardiac output, heart performance, and circulating blood volume were significantly decreased in vehicle-treated animals after trauma-hemorrhage. Administration of progesterone significantly improved cardiac output and heart performance and increased the circulating blood volume. This was associated with an increased progesterone receptor activity in the left ventricular nuclear extracts.

CONCLUSION

Because administration of progesterone after trauma-hemorrhage in sex steroid-deficient females improved cardiovascular responses, this hormone seems to be a useful adjunct for the treatment of cardiovascular depression in postmenopausal and ovariectomized female trauma patients.