Resuscitation with lactated Ringer solution limits the expression of molecular events associated with lung injury after hemorrhage.

The aim of this study was to determine whether hemorrhage altered the caspase-3 activity and the ATP levels in rat lung and ileum tissues and determine whether resuscitation with lactated Ringer solution (LR) or whole blood (WB) reversed these changes. Male Sprague-Dawley rats were briefly anesthetized with isoflurane, and their mean arterial blood pressure was reduced from 110 to 40 mmHg by bleeding. The bled rat was then resuscitated with LR or autologous WB to bring mean arterial blood pressure back to 80 mmHg. Lung and ileum tissues were removed at the end of hemorrhage or at the end of the resuscitation period for specified bioassays. Hemorrhage increased cellular caspase-3 activity in the lung and the ileum. After the hemorrhaged rats received LR or WB, caspase-3 activity returned to the basal level in the lung and ileum, respectively. Likewise, hemorrhage decreased cellular ATP levels in lung and ileum. After LR or WB resuscitation, the cellular ATP level returned to the basal level only in the lung resuscitated with LR. The increased caspase-3 activity was associated with the increased expression of caspase-3 mRNA, which also returned to normal levels after either resuscitation. Similarly, hemorrhage increased the expression of inducible nitric oxide synthase and Kruppel-like factor 6 and decreased expression of Kruppel-like factor 4. Subsequent LR resuscitation normalized the expression of these genes in the lung tissue. Our results demonstrate that resuscitation with LR can reverse the expression of genes and their products that are thought to contribute to hemorrhage-induced lung injury.     

The respiratory change in preejection period: a new method to predict fluid responsiveness.

The accuracy and clinical utility of preload indexes as bedside indicators of fluid responsiveness in patients after cardiac surgery is controversial. This study evaluates whether respiratory changes (Delta) in the preejection period (PEP; DeltaPEP) predict fluid responsiveness in mechanically ventilated patients. Sixteen postcoronary artery bypass surgery patients, deeply sedated under mechanical ventilation, were enrolled. PEP was defined as the time interval between the beginning of the Q wave on the electrocardiogram and the upstroke of the radial arterial pressure. DeltaPEP (%) was defined as the difference between expiratory and inspiratory PEP measured over one respiratory cycle. We also measured cardiac output, stroke volume index, right atrial pressure, pulmonary arterial occlusion pressure, respiratory change in pulse pressure, systolic pressure variation, and the Deltadown component of SPV. Data were measured without positive end-expiratory pressure (PEEP) and after application of a PEEP of 10 cmH2O (PEEP10). When PEEP10 induced a decrease of >15% in mean arterial pressure value, then measurements were re-performed before and after volume expansion. Volume loading was done in eight patients. Right atrial pressure and pulmonary arterial occlusion pressure before volume expansion did not correlate with the change in stroke volume index after the fluid challenge. Systolic pressure variation, DeltaPEP, Deltadown, and change in pulse pressure before volume expansion correlated with stroke volume index change after fluid challenge (r2 = 0.52, 0.57, 0.68, and 0.83, respectively). In deeply sedated, mechanically ventilated patients after cardiac surgery, DeltaPEP, a new method, can be used to predict fluid responsiveness and hemodynamic response to PEEP10.     

Sensitivity to endotoxin in rabbits is increased after hemorrhagic shock.

The immunoinflammatory response following trauma and hemorrhage may predispose to the development of sepsis and multiple-organ failure syndrome. Cardiac output (CO), arterial pressure, arterial PO2, and pulmonary permeability index were measured. We examined the sensitivity of rabbits to infusions of lipopolysaccharide (LPS) after hemorrhagic shock. Shock was produced by reducing CO to 40% of baseline for 90 min, followed by resuscitation with shed blood and then with lactated Ringer solution to maintain CO near baseline. Animals were assigned to three groups: 1) hemorrhagic shock only, 2) LPS only, and 3) hemorrhagic shock + LPS. Groups 1 and 3 were subjected to hemorrhagic shock on day 1. Escherichia coli LPS was infused (1.0 microgram/kg i.v.) into groups 2 and 3 on day 2. Fluid resuscitation with lactated Ringer solution was continued in an effort to maintain CO at baseline. Five hours after LPS infusion, 125I-albumin was injected intravenously, and rabbits were killed 1 h later for measurement of pulmonary permeability index. LPS infusion after shock (group 3) caused significant decreases in CO, arterial pressure, and PO2 and an increase in pulmonary permeability. These changes were not seen in the groups 1 and 2. We conclude that hemorrhagic shock and resuscitation result in a proinflammatory state, leading to increased sensitivity to subsequent exposure to LPS.     

Fibrinogen availability and coagulation function after hemorrhage and resuscitation in pigs

Hemorrhagic coagulopathy (without neurological injuries) constitutes 40% of injury-related death in civilian hospitals and on the battlefield, and the underlying contributing mechanisms remain unclear. The purpose of this study is to investigate the effects of fibrinogen availability on coagulation function after hemorrhage in pigs. Sixteen crossbred commercial Yorkshire swine were randomized into the control group (group C) (n = 8) and hemorrhage group (group H) (n = 8). Hemorrhage was induced in group H by bleeding 35% of the estimated total blood volume, followed by resuscitation with lactated Ringer solution at three times the bled volume. Pigs in group C were not hemorrhaged or resuscitated. Blood samples were withdrawn at baseline, 15 min, 3 h, 6 h, and 24 h after hemorrhage and lactated Ringer (LR) resuscitation (H-LR). Coagulation was assessed by using thrombelastography. All baseline measurements were similar between groups C and H. Hemorrhage caused a decrease in mean arterial pressure and an increase in heart rate in group H, but LR resuscitation corrected these changes within 1 h. Compared to baseline values, fibrinogen concentrations in group H decreased at 15 min, 3 h and 6 h after H-LR, but increased to double that of the baseline value at 24 h; platelet counts decreased throughout the study; clot strength was decreased at 15 min, 3 h and 6 h, but returned to baseline value at 24 h after H-LR. Hemorrhage caused decreases in fibrinogen and platelets, and compromised clot strength. The rebound of fibrinogen at 24 h restored clot strength despite platelet deficit. These data suggest the potential compensatory role of fibrinogen in restoring coagulation function in vivo after hemorrhagic shock.     

Resuscitation affects microcirculatory polymorphonuclear leukocyte behavior after hemorrhagic shock: role of hypertonic saline and pentoxifylline

We have previously shown that lung injury following fluid resuscitation either with hypertonic saline (HS) or lactated Ringer's (LR) plus pentoxifylline (PTX) attenuated acute lung injury when compared with LR resuscitation. The objective of the present study is to determine whether our previous observations are accompanied by changes in polymorphonu-clear leukocyte (PMN) behavior. To study this, PMN-endothelial cell interactions, microcirculatory blood flow, lung histology, lung PMN infiltration (MPO, Myeloperoxidase), and lung intra-cellular adhesion molecule-1 (ICAM-1) expression were assessed in a controlled hemorrhagic shock model followed by LR, HS, and LR+PTX resuscitation in rodents. Rats (240-300 g) were bled to a mean arterial pressure (MAP) of 35 mm Hg for 1 hr and then randomized into three groups: HS (7.5% NaCl, 4 ml/kg); LR (3x shed blood); and LR+PTX (25 mg/kg). Additionally, total shed blood was reinfused. A sham group underwent no shock and no treatment. The internal spermatic fascia was exteriorized and the microcirculation was observed by closed-circuit TV coupled to a microscope, 2 and 6 hrs after treatment. The number of leukocytes sticking to the venular endothelium was determined 2 hrs after fluid resuscitation. Microcirculatory blood flow was measured by an optical Doppler velocimeter. Lung histology and lung MPO immunostaining were assessed at 6 hrs, and lung ICAM-1 expression was determined by immunostaining at 2 hrs following fluid resuscitation. Two hours after treatment, HS (1.4 +/- 0.4), LR+PTX (1.7 +/- 0.3), and sham (0.4 +/- 0.2) groups presented significant reductions in leukocyte adherence (cells/100 microm venule length), compared with the LR group (4.0 +/- 0.9, P < 0.05). No differences were observed 6 hrs after treatment on leukocyte adherence and microcirculatory blood flow. ICAM-1 expression was significantly higher in LR-treated animals compared with the HS, LR+PTX, and sham groups (P < 0.01). PMN infiltration and overall lung injury were significantly attenuated by HS and LR+PTX. These results support earlier studies that indicated the potential application of HS and PTX in shock therapy and the increase in PMN-endothelial cell interaction and lung injury after LR resuscitation.     

Dietary glycine inhibits activation of nuclear factor kappa B and prevents liver injury in hemorrhagic shock in the rat.

We investigated the effects of a glycine-containing diet (5%) on liver injury caused by hemorrhagic shock and resuscitation in rats. Anesthetized rats were bled to a mean arterial blood pressure of 35-40 mm Hg for 1 h and then resuscitated with 60% of shed blood and lactated Ringer's solution. Feeding the rats glycine significantly reduced mortality, the elevation of plasma transaminase levels and hepatic necrosis. The increase in plasma TNFalpha and nitric oxide (NO) was also blunted by glycine feeding. Hemorrhagic shock resulted in oxidative stress (significant elevations in TBARS and in the oxidized/reduced glutathione ratio) and was accompanied by a reduced activity of the antioxidant enzymes Mn- and Cu,Zn-superoxide dismutase, glutathione peroxidase and catalase, overexpression of inducible NO synthase (iNOS), and activation of nuclear factor kappa B (NF-kappaB). Glycine ameliorated oxidative stress and the impairment in antioxidant enzyme activities, inhibited NF-kappaB activation, and prevented expression of iNOS. Dietary glycine blocks activation of different mediators involved in the pathophysiology of liver injury after shock.     

ATP-MgCl2 restores renal microcirculation following trauma and severe hemorrhage.

Although ATP-MgCl2 enhances the recovery of renal function after ischemia and reperfusion, it is not known whether this agent has any beneficial effects on renal microcirculation and function in a nonheparinized model of trauma and severe hemorrhage. To study this, a midline laparotomy was performed (i.e., trauma induced) and the rats were bled to and maintained at a mean arterial pressure of 40 mmHg (1 mmHg = 133.32 Pa) until 40% of the maximum shed blood volume was returned in the form of Ringer's lactate (RL) solution. Animals were then resuscitated with 4 times the volume of the shed blood in the form of RL. ATP-MgCl2, 50 mumol/kg body weight, or an equivalent volume of saline, was infused intravenously during and following resuscitation. Renal microcirculation was examined by using colloidal carbon infusion and laser Doppler flow-metry. Glomerular filtration rate (GFR) was assessed with [3H]inulin clearance and cardiac output (CO) was determined by dye dilution technique. The results indicate that the depressed renal microcirculation following hemorrhage and resuscitation was restored by ATP-MgCl2 treatment. GFR was significantly higher in ATP-MgCl2-treated than saline-treated rats. ATP-MgCl2 also increased urine output, restored the decreased CO, and prevented the occurrence of renal edema after hemorrhage and resuscitation. Thus, ATP-MgCl2 appears to be a useful adjunct to crystalloid resuscitation following trauma and severe hemorrhagic shock even in the absence of blood resuscitation.     

Fibrin glue eliminates the need for packing after complex liver injuries.

Hemostasis after traumatic liver injury can be extremely difficult to obtain, particularly in coagulopathic patients who have suffered extensive liver damage. We determined the ability of a fibrin glue preparation (FG) to terminate ongoing bleeding using a new, clinically relevant porcine model of complex hepatic injury. Anesthetized swine (n = 6, 18 to 19 kg) received an external blast to the right upper abdomen and were immediately anticoagulated with intravenous heparin (200 u/kg). Uncontrolled hemorrhage from blast continued from time of injury (t = 0 minutes) to t = 15 minutes. Lactated Ringer's solution was infused to keep mean arterial pressure (MAP) > 80 mm Hg until the end of experiment (t = 90 minutes). Animals underwent routine surgical techniques to control bleeding, and FG was employed in the event these measures failed. Estimated blood loss and fluid resuscitation volume were measured. Serial MAP, arterial base excess, and temperature were recorded. Animals were severely injured with significant blood loss prior to laparotomy (26 +/- 6 cc/kg) and during routine surgical efforts to arrest hemorrhage (11 +/- 2 cc/kg). Bleeding could not be controlled with standard techniques in any animal. FG rapidly controlled hemorrhage and eliminated the need for packing. Re-bleeding was noted in only one animal (portal vein injury). FG can control severe hepatic hemorrhage when surgical techniques fail. Further work in the clinical arena is warranted to determine the potential benefits of FG in arresting hemorrhage in hemodynamically unstable coagulopathic patients with complex hepatic injuries.     

Hemodynamic response and oxygen transport in pigs resuscitated with maleimide-polyethylene glycol-modified hemoglobin (MP4).

Cell-free Hb increases systemic and pulmonary pressure and resistance and reduces cardiac output and heart rate in animals and humans, effects that have limited their clinical development as "blood substitutes." The primary aim of this study was to evaluate the hemodynamic response to infusion of several formulations of a new polyethylene glycol (PEG)-modified human Hb [maleimide PEG Hb (MalPEGHb)] in swine, an animal known to be sensitive to Hb-induced vasoconstriction. Anesthetized animals underwent controlled hemorrhage (50% of blood volume), followed by resuscitation (70% of shed volume) with 10% pentastarch (PS), 4% MalPEG-Hb in lactated Ringer (MP4), 4% MalPEG-Hb in pentastarch (HS4), 2% MalPEG-Hb in pentastarch (HS2), or 4% stroma-free Hb in lactated Ringer solution (SFH). Compared with baseline, restoration of blood volume after resuscitation was similar and not significantly different for the PS (103%), HS2 (99%), HS4 (106%), and MP4 (87%) animals but significantly less for the SFH animals (66%) (P < 0.05). All solutions that contained MalPEG-Hb restored mean arterial and pulmonary pressure and cardiac output. Systemic vascular resistance was unchanged, and pulmonary arterial pressure and resistance were increased slightly. Both systemic and pulmonary vascular resistance increased significantly in animals that received SFH, despite less adequate blood volume restoration. Oxygen consumption was maintained in all animals that received MalPEG-Hb, but not PS. Base excess improved only with MalPEG-Hb and PS, but not SFH. Red blood cell O2 extraction was significantly increased in animals that received Hb, regardless of formulation. These data demonstrate resuscitation with MalPEG-human Hb without increasing systemic vascular resistance and support our previous observations in animals suggesting that the efficacy of low concentrations of PEG-Hb in the plasma results from reduced vasoconstriction.     

Utilization of Extracorporeal Membrane Oxygenation Alleviates Intestinal Ischemia–Reperfusion Injury in Prolonged Hemorrhagic Shock Animal Model

Intestinal ischemia–reperfusion injury is one of the main factors leading to multiple organ failure after resuscitation of prolonged hemorrhagic shock; however, the current conventional fluid resuscitation still cannot effectively reduce intestinal injury caused by prolonged hemorrhagic shock. To investigate the effect of ECMO resuscitation on alleviating intestinal ischemia–reperfusion injury in a prolonged hemorrhagic shock rabbit model. Thirty New Zealand white rabbits were randomly divided into three groups: control group, conventional fluid resuscitation group, and ECMO resuscitation group. The prolonged hemorrhagic shock model was established by keeping the arterial blood pressure from 31 to 40 mmHg for 3 h through the femoral artery bleeding, and performing the resuscitation for 2 h by conventional fluid resuscitation and ECMO resuscitation, respectively. Chiu’s score of intestinal injury, serum lactate and TNF-α levels, intestinal mucosamyeloperoxidase (MPO) activity, intercellular adhesion molecule (ICAM-1), and Claudin-1expression were detected. The mean arterial blood pressure in Group 2 was significantly higher after resuscitation than in Group 1, but serum lactate and inflammatory cytokines TNF-α level were significantly lower. And Chiu’s score of intestinal injury and myeloperoxidase (MPO) activity level and ICAM-1 expression were significantly lower in the ECMO resuscitation group, in which the Claudin-1 levels were significantly increased. ECMO resuscitation for the prolonged hemorrhagic shock improves tissue perfusion and reduces the systemic inflammation, and thus alleviates intestinal damage caused by prolonged hemorrhagic shock.     

Hypertonic Saline Dextran Ameliorates Organ Damage in Beagle Hemorrhagic Shock

Objective

The goal of this study was to investigate the effect of hypertonic saline with 6% Dextran-70 (HSD) resuscitation on organ damage and the resuscitation efficiency of the combination of HSD and lactated ringers (LR) in a model of hemorrhage shock in dogs.

Methods

Beagles were bled to hold their mean arterial pressure (MAP) at 50±5 mmHg for 1 h. After hemorrhage, beagles were divided into three groups (n = 7) to receive pre-hospital resuscitation for 1 h (R1): HSD (4 ml/kg), LR (40 ml/kg), and HSD+LR (a combination of 4 ml/kg HSD and 40 ml/kg LR). Next, LR was transfused into all groups as in-hospital resuscitation (R2). After two hours of observation (R3), autologous blood was transfused. Hemodynamic responses and systemic oxygenation were measured at predetermined phases. Three days after resuscitation, the animals were sacrificed and tissues including kidney, lung, liver and intestinal were obtained for pathological analysis.

Results

Although the initial resuscitation with HSD was shown to be faster than LR with regard to an ascending MAP, the HSD group showed a similar hemodynamic performance compared to the LR group throughout the experiment. Compared with the LR group, the systemic oxygenation performance in the HSD group was similar but showed a lower venous-to-arterial CO₂ gradient (Pv-aCO₂) at R3 (p < 0.05). Additionally, the histology score of the kidneys, lungs and liver were significantly lower in the HSD group than in the LR group (p < 0.05). The HSD+LR group showed a superior hemodynamic response but higher extravascular lung water (EVLW) and lower arterial oxygen tension (PaO₂) than the other groups (p < 0.05). The HSD+LR group showed a marginally improved systemic oxygenation performance and lower histology score than other groups.

Conclusions

Resuscitation after hemorrhagic shock with a bolus of HSD showed a similar hemodynamic response compared with LR at ten times the volume of HSD, but HSD showed superior efficacy in organ protection. Our findings suggest that resuscitation with the combination of HSD and LR in the pre-hospital setting is an effective treatment.     

Regulatory response to washout of amniotic fluid in sheep

To test the hypothesis that a substance present in the amniotic fluid could serve as a regulator of amniotic fluid volume, we drained and discarded amniotic fluid while replacing it with lactated Ringer solution that was isotonic to amniotic fluid. Seven ewes with singleton fetuses at 119 +/- 1 days of gestation (mean +/- SE) were instrumented with multiple indwelling catheters in the pedal artery, pedal vein, and amniotic cavity. During the exchange periods, an average of 3,019 +/- 171 ml/day of lactated Ringer solution was infused into the amniotic cavity while an equal amount of amniotic fluid was pumped out and discarded. During the control period, amniotic fluid composition and volume were not altered. Exchange and control periods started with the same amniotic fluid volume, lasted 3 or 4 days, and were randomized with regard to order. Amniotic fluid volume measured by vacuum drainage was 556 +/- 98 ml at the end of the control period and 986 +/- 209 ml (P = 0.03) at the end of the exchange period. Fetal arterial blood gases, hemodynamic parameters and the osmolality gradient between fetal plasma and amniotic fluid were not altered by the exchange process. A linear relationship between the control amniotic fluid volume and the volume at the end of the exchange period (P = 0.003) suggests that the animals with larger control volumes responded to isovolumic dilution with a larger volume increase. We conclude that amniotic fluid may contain a substance that regulates amniotic volume.     

Systolic pressure predicts plasma vasopressin responses to hemorrhage and vena caval constriction in dogs

We have proposed that the reflex increase in arginine vasopressin (AVP) secretion in response to hypovolemia is due to arterial baroreceptor unloading. If arterial pressure is the key to the mechanism, the slope relating plasma AVP to arterial pressure should be the same in response to hemorrhage, a model of true hypovolemia, and in response to thoracic inferior vena caval constriction (IVCC), a model of central hypovolemia. We tested this hypothesis in conscious, chronically instrumented dogs (n = 8). The mean coefficient of determination (r(2)) values obtained from the individual regressions of log AVP onto systolic pressure (SP) and mean arterial pressure (MAP) in response to hemorrhage were 0.953 +/- 0.009 and 0.845 +/- 0.047, respectively. Paired comparisons indicated a significant difference between the means (P < 0.05), hence, SP was used in subsequent analyses. The mean slopes relating the log of plasma AVP to SP in response to hemorrhage and IVCC were -0.034 +/- 0.003 and -0.032 +/- 0.002, respectively, and the means were not significantly different (P = 0.7). The slopes were not altered when the experiments were repeated during acute blockade of cardiac receptors by intrapericardial procaine. Finally, sinoaortic denervation (n = 4) markedly reduced the slope in both the hemorrhage and IVCC treatments. We conclude that baroreceptors monitoring arterial pressure provide the principal reflex control of AVP secretion in response to hypovolemia.     

Role of C5a in multiorgan failure during sepsis

In humans with sepsis, the onset of multiorgan failure (MOF), especially involving liver, lungs, and kidneys, is a well known complication that is associated with a high mortality rate. Our previous studies with the cecal ligation/puncture (CLP) model of sepsis in rats have revealed a C5a-induced defect in the respiratory burst of neutrophils. In the current CLP studies, MOF occurred during the first 48 h with development of liver dysfunction and pulmonary dysfunction (falling arterial partial pressure of O(2), rising partial pressure of CO(2)). In this model an early respiratory alkalosis developed, followed by a metabolic acidosis with increased levels of blood lactate. During these events, blood neutrophils lost their chemotactic responsiveness both to C5a and to the bacterial chemotaxin, fMLP. Neutrophil dysfunction was associated with virtually complete loss in binding of C5a, but binding of fMLP remained normal. If CLP animals were treated with anti-C5a, indicators of MOF and lactate acidosis were greatly attenuated. Under the same conditions, C5a binding to blood neutrophils remained intact; in tandem, in vitro chemotactic responses to C5a and fMLP were retained. These data suggest that, in the CLP model of sepsis, treatment with anti-C5a prevents development of MOF and the accompanying onset of blood neutrophil dysfunction. This may explain the protective effects of anti-C5a in the CLP model of sepsis.     

Effect of volume expansion on hemodynamic variables in nephrectomized dogs

We have previously demonstrated that blood pressure elevation by acute blood volume expansion is volume-dependent during the infusion period and resistance-dependent in the post-infusion period in normal anesthetized dogs, and that such an increase in blood pressure is associated with a potentiation of the pressor response to norepinephrine. To evaluate the possible renal contribution to these hemodynamic changes, blood volume expansion was performed for 1 h with dextran dissolved in lactated Ringer's solution (20 ml/kg) in 15 nephrectomized dogs. The mean blood pressure, cardiac output and total peripheral resistance at the end of infusion were 126%, 225% and 60%, respectively; 3 h after volume expansion they were 126%, 151%, and 92% respectively. However, in 4 dogs, there was an increase in mean blood pressure (138%) 3 h after volume expansion. This was thought to result from an increase in the total peripheral resistance (133%) associated with the recovery of cardiac output (106%). The pressor response to norepinephrine (0.5 microgram/kg) was potentiated after volume expansion. These results indicate that the handling of volume by the kidney contributed to the maintenance of an elevated level of cardiac output. However, nephrectomy did not seem to interfere with the hemodynamic switching of the causative factor for blood pressure elevation from increased cardiac output to increased total peripheral resistance. Neither was the potentiation of pressor response to norepinephrine affected.     

Detrimental effects of complement activation in hemorrhagic shock.

The complement system has been implicated in early inflammatory events and a variety of shock states. In rats, we measured complement activation after hemorrhage and examined the hemodynamic and metabolic effects of complement depletion before injury and worsening of complement activation after hemorrhage and resuscitation [with a carboxypeptidase N inhibitor (CPNI), which blocks the clearance of C5a]. Rats were bled to a mean arterial pressure of 30 mmHg for 50 min and were then resuscitated for 2 h. Shock resulted in significant evidence of complement consumption, with serum hemolytic activity being reduced by 33% (P < 0.05). Complement depletion before injury did not affect hemorrhage volume (complement depleted = 28 +/- 1 ml/kg, complement intact = 29 +/- 1 ml/kg, P = 0.74) but improved postresuscitation mean arterial pressure by 37 mmHg (P < 0.05) and serum bicarbonate levels (complement depleted = 22 +/- 3 meq/ml, complement intact = 13 +/- 8 meq/ml, P < 0.05). Pretreatment with CPNI was lethal in 80% of treated animals vs. the untreated hemorrhaged group in which no deaths occurred (P < 0.05). In this model of hemorrhagic shock, complement activation appeared to contribute to progressive hypotension and metabolic acidosis seen after resuscitation. The lethality of CPNI during acute blood loss suggests that the anaphylatoxins are important in the pathophysiological events involved in hemorrhagic shock.     

Osmotic Regulation of Toad Bladder Responsiveness to Neurohypophyseal Hormones

The effect of dilution of the interstitial fluids on the responsiveness of the toad urinary bladder to antidiuretic hormones has been examined in vivo and in vitro. Toads were given periodic injections with vasopressin while in water so that their plasma osmolality fell below 190 mosmoles/kg H₂O. The hydraulic conductivity of bladders which had been removed from the animal and fixed with 1% glutaraldehyde was 10-fold less in overhydrated toads than in normally hydrated controls. A similar inhibitory phenomenon was observed in in vitro studies, when the tonicity of Ringer's fluid in which the bladders were suspended was lowered from its isotonic value. Mannitol, but not urea, could be effectively substituted for one-half of the NaCl content of Ringer's fluid. In other experiments it has been shown that the responsiveness of the bladder to vasotocin is depressed during bulk water movement across the tissue. This "flux inhibition" was found to depend upon the velocity and the duration of water flow from mucosa to the serosa. It is suggested that the responsiveness of the toad bladder to antidiuretic hormones diminishes as the effective osmotic pressure of the interstitial fluids declines.     

Evaluation of antisperm complement-dependent immune mediators in human ovarian follicular fluid

A "sandwich"-type radiolabeled antiglobulin assay using monoclonal anti-C5b-9 neoantigen and polyclonal anti-C5b-9 was used to evaluate the presence of terminal C complexes (SC5b-9 or MC5b-9) in the sera and ovarian follicular fluid (FF) from 45 infertile women. FF SC5b-9 was detectable in all clinical diagnostic categories. The mean SC5b-9 levels in FF and sera were 399 ng/ml (range 75 to 1350 ng/ml) and 798 ng/ml (range 0 to 2700 ng/ml), respectively. Twelve (26.6%) of the 45 FF samples had normal hemolytic C activity, and all FF (n = 44) samples initiated C8/C9-dependent lysis of sensitized sheep E coated with human C1-7. Human plasma IgG antisperm antibodies (ASA) were capable of activating C in 31 (72%) of 43 FF samples as detected by their ability to deposit MC5b-9 on human sperm. Sera from infertile women with ASA in their sera and FF impaired human sperm binding to human zona pellucida and binding and penetration of zona-free hamster oocytes in vitro. The discovery of SC5b-9 and MC5b-9 in ovarian FF implies that the interaction of ASA and C could have a deleterious effect on sperm during in vivo and in vitro sperm-egg interactions in women with antisperm antibodies.     

A retrospective analysis of the haemodynamic and metabolic effects of fluid resuscitation in Vietnamese adults with severe falciparum malaria

Background

Optimising the fluid resuscitation of patients with severe malaria is a simple and potentially cost-effective intervention. Current WHO guidelines recommend central venous pressure (CVP) guided, crystalloid based, resuscitation in adults.

Methods

Prospectively collected haemodynamic data from intervention trials in Vietnamese adults with severe malaria were analysed retrospectively to assess the responses to fluid resuscitation.

Results

43 patients were studied of whom 24 received a fluid load. The fluid load resulted in an increase in cardiac index (mean increase: 0.75 L/min/m² (95% Confidence interval (CI): 0.41 to 1.1)), but no significant change in acid-base status post resuscitation (mean increase base deficit 0.6 mmol/L (95% CI: −0.1 to 1.3). The CVP and PAoP (pulmonary artery occlusion pressure) were highly inter-correlated (r_s = 0.7, p<0.0001), but neither were correlated with acid-base status (arterial pH, serum bicarbonate, base deficit) or respiratory status (PaO₂/FiO₂ ratio). There was no correlation between the oxygen delivery (DO₂) and base deficit at the 63 time-points where they were assessed simultaneously (r_s = −0.09, p = 0.46).

Conclusions

In adults with severe falciparum malaria there was no observed improvement in patient outcomes or acid-base status with fluid loading. Neither CVP nor PAoP correlated with markers of end-organ perfusion or respiratory status, suggesting these measures are poor predictors of their fluid resuscitation needs.     

Cold acclimation increases physiological responsiveness to intraventricular injection of beta-endorphin in pentobarbital anaesthetized rats. 1. Cardiovascular functions

Intraventricular injection of beta-endorphin (3, 7, 10 and 30 nmol/kg) into the third ventricular of pentobarbital-anaesthetized male Sprague-Dawley rats resulted in a dose-dependent increase in mean arterial pressure (MAP) while injection of the same volume of 0.9% NaCl solution did not cause significant changes in MAP. Naloxone, which did not produce any significant change in MAP, antagonized the vasopressor effect of beta-endorphin, indicating that the response is mediated via the naloxone sensitive opiate receptors. Rats acclimated to cold (5 degrees) for 3 weeks showed a potentiated and prolonged increase in MAP following beta-endorphin injection, indicating an increased responsiveness to the peptide. This increased responsiveness in the cardiovascular system is probably of adaptive value in cold acclimation. Naloxone itself did not alter MAP either, but abolished the cardiovascular response to beta-endorphin completely in cold acclimated rats, indicating an increased effectiveness in its antagonistic effect following cold acclimation as well.