Role of ET and NO in resuscitative effect of diaspirin cross-linked hemoglobin after hemorrhage in rat

Diaspirin cross-linked hemoglobin (DCLHb) is a hemoglobin-based therapeutic agent that produces significant cardiovascular effects, possibly due to its actions on vasoactive substances, such as endothelin (ET) and nitric oxide (NO). We have studied the modulation of cardiovascular effects of DCLHb by an NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), and an ETA-receptor antagonist, FR-139317, in hemorrhaged rats. Control rats resuscitated with vehicle [Ringer lactate (RL), 4 ml/kg iv] did not show any improvement in O2 consumption, base deficit, systemic hemodynamics, or regional blood flow after hemorrhage, and the rats survived for < 70 min. Administration of DCLHb (400 mg/kg iv) significantly improved O2 consumption, base deficit, systemic hemodynamics, and regional blood circulation after resuscitation, and the rats survived for > 120 min after hemorrhage. Plasma ET-1 and guanosine 3',5'-cyclic monophosphate (cGMP) concentrations increased after hemorrhage. DCLHb produced an increase in ET-1 and decreased cGMP concentrations in plasma. Pretreatment with L-NAME (10 mg/kg iv) or FR-139317 (4 mg/kg iv) attenuated the DCLHb-induced improvement in survival time, base deficit, systemic hemodynamics, and regional blood circulation. L-NAME (10 mg/kg iv) per se did not produce any resuscitative effect; therefore the NO mechanism may not be contributing toward the efficacy of DCLHb in hemorrhaged rats. However, FR-139317 attenuated the efficacy of DCLHb; therefore an increase in plasma ET-1 concentration by DCLHb may be contributing toward the efficacy of DCLHb in hemorrhage. Hemorrhage-induced increase in cGMP levels could be attenuated by L-NAME, but L-NAME was not effective in resuscitation of hemorrhaged rats, indicating a lack of role of NO in resuscitation. It is concluded that the ET mechanism is more important in the beneficial effect of DCLHb than the NO mechanism in hemorrhage.

The effects of cross-linked hemoglobin on regional vascular conductance in dogs

Hemoglobin (Hgb) solutions cause systemic vasoconstriction, which might limit their use as intraoperative blood substitutes. This constriction is thought to be caused by interaction between Hgb and nitric oxide (NO). To determine whether alpha-alpha cross-linked hemoglobin (XL-Hgb) interferes with NO-mediated vasodilation caused by acetylcholine (ACh) and sodium nitroprusside (NTP), we infused these compounds into the femoral, superior mesenteric, and circumflex coronary arteries of anesthetized dogs (n = 6) before and after partial exchange transfusion with XL-Hgb. Additional animals (n = 6) were studied after treatment with 5% albumin. XL-Hgb administration increased mean arterial pressure (MAP) from 81 +/- 5 to 112 +/- 8 (P < 0.05). Albumin reduced MAP from 84 +/- 4 mm Hg to 76 +/- 4 mm Hg (P < 0.05). Vascular conductance after XL-Hgb decreased in the femoral artery, was not changed in the mesenteric bed, and increased modestly in the coronary artery (from 0.19 +/- 0.03 to 0.26 +/- 0.02 mL x mm Hg(-1) x min(-1), P < 0.05). After albumin, conductance was unchanged in the femoral artery and increased in the mesenteric artery. Conductance also increased in the coronary bed (from 0.25 +/- 0.02 to 0.49 +/- 0.03 mL x mm Hg(-1) x min(-1), P < 0.05). The vasodilator response to ACh in the femoral or mesenteric beds was either unaffected or augmented by either XL-Hgb or albumin. In the coronary bed, XL-Hgb blunted the dilator responses to ACh and NTP, while albumin augmented the coronary dilator responses to ACh. In five additional dogs, the NO synthase inhibitor N(G)-monomethyl L-arginine caused MAP to increase from 85 +/- 4 to 90 +/- 8 mm Hg and blunted the coronary dilator responses to ACh by approximately 25%. Subsequent XL-Hgb administration caused a further increase in MAP to 112 +/- 19 mm Hg (P < 0.05) and also further blunted ACh-mediated vasodilator responses in the coronary circulation. XL-Hgb has complex effects on the circulatory system, including a reduction in the vasodilator responses to ACh and NTP in canine coronary arteries in vivo. The potential impact of these events on patients with significant coexisting disease is unclear.

Protective effect of inhaled lysine acetylsalicylate on allergen-induced early and late asthmatic reactions

Conflicting results have been reported on the effect of non-steroidal antiinflammatory drugs on allergen-induced asthmatic responses. The aim of this study was to investigate the effect of inhaled lysine acetylsalicylate (LASA) on the early and late allergen-induced responses. We studied 16 patients with mild, stable asthma who had an early asthmatic response and 10 patients with a dual (early and late) response. Each patient underwent two challenges with a single dose of allergen assessed in a preliminary test, after inhalation of either 720 mg of LASA in 4 ml of saline solution or placebo, according to a randomized, double-blind protocol. Allergen-induced hyperreactivity to methacholine was measured in six patients from each of the early and the dual response groups 2 hours and 24 hours after the challenge, respectively. In the patients with early response, the maximum fall in FEV1 after challenge was 24% +/- 1% after inhalation of placebo and 14% +/- 2% after inhalation of LASA (p < 0.005). No protection was observed in four patients who received the drug orally instead of by inhalation. In the patients with a dual response, the maximum FEV1 decrease during the early response was 27% +/- 2% after placebo and 21% +/- 2% after LASA (p < 0.025). During the late response (between 3 and 8 hours), the maximum decrease in FEV1 was 28% +/- 4% after placebo and 16% +/- 4% after LASA (p < 0.005). In both groups allergen challenge caused a significant reduction in methacholine PD20 after treatment with placebo but not with LASA. Without allergen challenge, LASA had no effect on methacoline reactivity. We conclude that inhaled LASA significantly reduces both the early and the late asthmatic response to allergen challenge and that it prevents the allergen-induced airway hyperresponsiveness that follows these responses.

Salicylate levels in rat stomach tissues after administration of aspalatone and acetylsalicylic acid in relation to their ulcerogenicity

To study the mechanism for the low ulcerogenicity of the antithrombotic agent aspalatone ([3-[2-methyl-4-pyronyl)]-2-acetyloxybenzoate, CAS 147249-33-0), the metabolism and disposition of aspalatone were compared with those of acetylsalicylic acid (ASA) in the gut wall in relation to the salicylate level in the stomach tissues following oral administration in pyrolus-ligated rats. Both aspalatone and ASA were essentially stable in gastric juice and were absorbed in stomach unchanged. In glandular portion of the stomach, salicylate level found at 10 min post-dose in aspalatone (80 mg/kg)-and in ASA (50 mg/kg)-treated group was 67 +/- 43 nmol/g tissue and 2000 +/- 250 nmol/g tissue, respectively. In non-glandular (rumen) tissue, salicylate was not detected in the aspalatone group, whereas it reached a concentration of up to 1100 +/- 130 nmol/g tissue in the ASA group. As a result of the relative stability of the ester bond connecting the salicylic acid and maltol groups towards hydrolysis in the stomach and entrapment of ASA due to ion trapping, a lower salicylate level was observed in the stomach after oral aspalatone administration, and this may, at least in part, be the underlying mechanism for the low ulcerogenicity of aspalatone.

Inhibitory effects of copper-aspirin complex on platelet aggregation

AIM

To study the inhibitory effects of copper-aspirin complex (CuAsp) on platelet aggregation.

METHODS

With adenosine diphosphate the effects of CuAsp on platelet aggregation in vitro or in vivo were investigated. Radioimmunoassay and fluorophotometry were used to measure thromboxane B2 (TXB2) generation from platelets, the levels of TXB2 and of 6-keto-PGF1 alpha in plasma and the platelet serotonin release reaction.

RESULTS

In vitro, CuAsp inhibited arachidonic acid (AA)-induced aggregation (IC50 = 17 mumol.L-1, 95% confidence limits: 9-33 mumol.L-1), the release of 5-HT (IC50 = 19 mumol.L-1, 95% confidence limits: 10-30 mumol.L-1), and TXB2 generation from platelets (P < 0.05). CuAsp 10 mg.kg-1 i.g. selectively inhibited AA-induced aggregation, and increased the 6-keto-PGF1 alpha concentration in plasma while decreased that of TXB2.

CONCLUSION

CuAsp, in vitro or in vivo, shows more potent inhibitory effects on AA-induced aggregation than aspirin (Asp), related to the inhibition of platelet cyclooxygenase and the release of active substances from platelets.

Repeated doses of combined oral lysine acetylsalicylate and metoclopramide in the acute treatment of migraine

The combination of lysine acetylsalicylate and metoclopramide is effective in the treatment of migraine attacks. It was unknown whether repeated doses could improve efficacy. The aim of this open trial was to evaluate the effects of a second, and eventually a third dose of lysine acetylsalicylate and metoclopramide when a first dose of the treatment was ineffective. Patients were asked to take a second dose 2 hours after a first dose when they thought that the first dose was ineffective. They were allowed to take a third dose or their rescue medication 2 hours after the second dose when they judged that the treatment remained ineffective. Two hundred ninety-two patients were included in the study; 262 of the 292 patients treated 517 attacks. Headache relief (reduction in headache severity from grade 3 or 2 to grade 1 or 0) was observed in 54.8% of attacks after one dose, in 48.1% of attacks after a second dose, and in 40.3% of attacks after a third dose. Complete headache relief without recurrence and without use of a rescue medication was reported in 37% of the total attacks. The patients judged their treatment as good or excellent in 78% of attacks treated with one dose, in 41% of those treated with two doses, and in 19% of those treated with three doses. Tolerance, as judged by the patients, was considered good in 92% of treated attacks. Minor side effects occurred in 6% of attacks after a first dose, in 4.5% of attacks after a second dose, in 1.5% of attacks after a third dose, in 2% after unspecified delay, and in 14% overall. In conclusion, the efficacy of lysine acetylsalicylate and metoclopramide in the treatment of migraine attacks can be improved by repeated doses. It is well tolerated.

Effects of polymerization on the hypertensive action of diaspirin cross-linked hemoglobin in rats

It is believed that the hypertensive effect of diaspirin crosslinked hemoglobin, a viable blood substitute, can be resolved by polymerization, which reduces the diffusion of this derivative into the interstitial space between nitric oxide-producing endothelium and the target vascular smooth muscle. We studied the systemic and renal responses to infusion of three cell-free human hemoglobins in anesthetized isovolemic rats: unmodified (HbA0), crosslinked (alpha-DBBF), and polymerized crosslinked (poly alpha-DBBF). HbA0 produced a significant increase in mean arterial blood pressure (MAP) throughout the 60-minute infusion. alpha-DBBF, on the other hand, produced a more marked and prolonged increase in MAP over 120 minutes. Only a moderate increase in MAP was observed in rats after a 30-minute infusion with poly alpha-DBBF. The extent of renal insufficiency produced by these proteins, as determined by the glomerular filtration rate, was in the following order: HbA0 > poly alpha-DBBF > alpha-DBBF. Infusion of poly alpha-DBBF, under hypovolemic but not isovolemic conditions in rats, produced an increase in heart rate, cardiac output, and stroke volume and a decrease in total peripheral resistance after 60 minutes. Chemical polymerization to increase the size of alpha-DBBF does not appear to improve its hemodynamic properties in rats, especially under partial exchange transfusion, a more clinically relevant indication for a hemoglobin-based blood substitute.

[Comparison between effects of morning and evening administration of effervescent calcium carbasalate (equivalent of 160 mg aspirin) on the gastroduodenal mucosa in healthy volunteers]

The aim of this randomised, cross-over trial was to compare the gastroduodenal tolerability and anti-aggregating effect of effervescent calcium carbasalate (ECC equivalent to 160 mg aspirin) given once daily either in the morning or in the evening. Twelve healthy volunteers received calcium carbasalate for 2 periods of 5 days (21 days of wash-out between the 2 periods). The principal criterion was the gastroduodenal tolerability assessed by the total number of lesions at upper gastro-intestinal endoscopy. The same treatment-blinded endoscopist performed all evaluations. Efficacy was evaluated by thromboxane B2 measurement and collagen-induced platelet aggregation tests. No difference was observed between morning and evening administration of ECC on gastroduodenal tolerability and platelet agregation. ECC was very well tolerated as assessed by upper gastrointestinal endoscopy and almost totally inhibited platelet aggregation.

Mechanism of action of aspirin-like drugs

Nonsteroid antiinflammatory drugs (NSAIDs) or aspirin-like drugs act by inhibiting the activity of the cyclooxygenase (COX) enzyme. Two isoforms of COX exist, COX-1, which is constitutively expressed, and COX-2, which is an inducible isoform. Prostaglandins synthesized by the constitutively expressed COX-1 are implicated in the maintenance of normal physiological function and have a 'cytoprotective' action in the stomach. COX-2 expression is normally low but is induced by inflammatory stimuli and cytokines. It is thought that the antiinflammatory actions of NSAIDs are caused by the inhibition of COX-2, whereas the unwanted side effects, such as gastrointestinal and renal toxicity, are caused by the inhibition of the constitutively expressed COX-1. Individual NSAIDs show different selectivities against the COX-1 and COX-2 isoforms. NSAIDs that are selective towards COX-2, such as meloxicam, may have an improved side-effect profile over current NSAIDs. In addition to their use as antiinflammatory agents in the treatment of rheumatoid arthritis and osteoarthritis, selective COX-2 inhibitors may also be beneficial in inhibiting colorectal tumor cell growth and in delaying premature labor.

Effect on postoperative analgesia of small-dose lysine acetylsalicylate added to prilocaine during intravenous regional anesthesia

Nonsteroidal antiinflammatory drugs act largely peripherally by blocking the local synthesis of prostaglandins. The aim of this study was to evaluate whether the addition of a small dose of lysine acetylsalicylate (LA) to the prilocaine used for intravenous regional anesthesia (IVRA) would improve the quality of postoperative analgesia. Sixty patients undergoing lower extremity IVRA for foot or ankle surgery were randomly assigned to three double-blind groups: LA-IVRA where 90 mg of LA was mixed with prilocaine 0.5% for IVRA and 1 mL of 0.9% NaCl administered intravenously (IV) through the forearm catheter after tourniquet inflation; LA-IV where 1 mL of 0.9% NaCl was mixed with prilocaine and 90 mg of LA administered IV; and placebo where 1 mL of 0.9% NaCl was administered both with prilocaine for the IVRA and IV. Duration of analgesia (time elapsed between tourniquet release and first injection of morphine, expressed as mean +/- SD) was significantly longer (P < 0.05) in LA-IVRA (387 +/- 216 min) when compared with LA-IV (175 +/- 264 min) and placebo (126 +/- 201 min). Analgesic requirements remained significantly lower in LA-IVRA when compared with placebo only during the first six postoperative hours, LA-IV being in an intermediate position. Pain scores were significantly lower in LA-IVRA during the first postoperative hour when compared with LA-IV and during the first 3 postoperative hours when compared with placebo. We conclude that 90 mg of LA (corresponding to 50 mg of acetylsalicylic acid) added to prilocaine 0.5% during IVRA improves the quality of postoperative analgesia in the early postoperative period.

Pulmonary hypertension and systemic vasoconstriction may offset the benefits of acellular hemoglobin blood substitutes

OBJECTIVE

We tested the hypothesis that the pharmacologic properties of a small volume of alpha alpha-cross-linked hemoglobin (alpha alpha Hb) could effectively resuscitate pigs subjected to hemorrhage.

METHODS

Fourteen pigs hemorrhaged to a mean arterial pressure (MAP) of 40 mm Hg for 60 minutes were treated with a 4-mL/kg 2-minute infusion of 10 g/dL alpha alpha Hb or 7 g/dL human serum albumin, an oncotically matched control solution.

RESULTS

The removal of blood (17 +/- 1.5 mL/kg) caused the typical physiologic responses to hemorrhagic hypovolemia. Infusion of alpha alpha Hb restored mean arterial pressure and coronary perfusion pressure, but cardiac output and mixed venous O2 saturation did not improve significantly. Pulmonary arterial pressure and pulmonary vascular resistance increased markedly and were higher than baseline levels after alpha alpha Hb. Infusion of human serum albumin produced only minor hemodynamic changes. Brain blood flow did improve to baseline values after alpha alpha Hb, but was the only tissue to do so. In the human serum albumin group, superior mesenteric artery blood flow recovered to baseline values, whereas brain blood flow did not. Blood flows to other tissues were similar in both groups.

CONCLUSION

Small-volume infusion of alpha alpha Hb restored mean arterial pressure and brain blood flow, but pulmonary hypertension and low peripheral perfusion may offset benefits for trauma patients.

Effect of diaspirin crosslinked hemoglobin on systemic and regional blood circulation in pregnant rats

Diaspirin crosslinked hemoglobin (DCLHb: Baxter Healthcare Corp., Round Lake, IL, USA) is a biochemically stable hemoglobin based solution with excellent oxygen carrying capacity. Studies have been conducted in male rats to determine the effect of DCLHb on systemic and regional blood circulation. However, the cardiovascular effect of DCLHb has not been studied in female rats. In the present study the effect of DCLHb (400 mg/kg, i.v.) was observed on systemic hemodynamic parameters and regional blood circulation in non-pregnant rats, and in 9-day pregnant and 18-day pregnant rats. DCLHb increased mean arterial pressure (MAP) and total peripheral resistance (TPR) and increased blood flow to the heart, gastrointestinal tract (GIT), mesentery & pancreas, and skin in all groups of rats. The basal blood flow to the ovaries was higher in 18-day pregnant rats when compared to non-pregnant and 9-day pregnant rats. DCLHb further increased blood flow to the ovaries of 18-day pregnant rats. It is concluded that DCLHb increases blood flow to the heart, GIT and skin as a result of redistribution of blood from the musculoskeletal system. Blood flow in female reproductive organs is not altered by DCLHb in non-pregnant rats and during mid-term pregnancy. However, in advanced stages of pregnancy DCLHb increases blood flow to the ovaries.

Effect of small-volume resuscitation on intracranial pressure and related cerebral variables

BACKGROUND

Head injury outcome is adversely affected by the presence of hypotension. Therapies directed at rapidly correcting hypotension may improve outcome.

METHODS

In two separate studies, we investigated small-volume resuscitation (4 mL/kg) using Ringer's lactate, hypertonic saline and dextran, and diaspirin cross-linked hemoglobin in a porcine model of cryogenic brain injury and shock.

RESULTS

Small-volume resuscitation with hypertonic saline and dextran and diaspirin cross-linked hemoglobin significantly improved mean arterial pressure and cerebral perfusion pressure compared with Ringer's lactate. These data suggest that small-volume resuscitation with hypertonic saline and dextran or diaspirin cross-linked hemoglobin may effectively limit or prevent secondary ischemic brain injury after head injury and shock.

Activity of inhaled lysine acetylsalicylate (L-ASA) on bradykinin-induced bronchoconstriction in asthmatics: evidence of contribution of prostaglandins

When administered by inhalation, bradykinin provokes dose-related bronchoconstriction in asthmatic subjects by a mechanism believed to involve activation of sensory nerve endings. However, little is known of the change in airway responsiveness to bradykinin after cyclo-oxygenase blockade. The aim of the present study was to investigate the effect of the potent cyclo-oxygenase inhibitor, lysine acetylsalicylate (L-ASA), administered by inhalation, on bradykinin-induced bronchoconstriction in a group of 12 asthmatic subjects. The subjects attended the laboratory on four separate occasions to receive nebulized L-ASA (solution of 90 mg x mL(-1)) or matched placebo (glycine, solution of 30 mg x mL(-1)) 15 min prior to bronchoprovocation tests with bradykinin and methacholine in a randomized, double-blind order with at least a 5 day interval. Changes in airway calibre were followed as forced expiratory volume in one second (FEV1), and responsiveness to agonists was expressed as the provocative concentration causing a 20% fall in FEV1 from baseline (PC20). Administration both of L-ASA and glycine solution caused a small but significant acute fall in FEV1 from baseline, with gradual recovery within 20 min. When compared to placebo, inhaled L-ASA reduced the airway responsiveness to bradykinin in 11 of the 12 subjects studied, the geometric mean (range) values for PC20 bradykinin increasing significantly (p<0.001) by 1.7 doubling dose from 0.55 (0.11-5.05) to 1.72 (0.26-6.05) mg x mL(-1) after placebo and L-ASA, respectively. No significant change in airway responsiveness to methacholine was recorded after L-ASA. It is concluded that administration of lysine acetylsalicylate by inhalation protects the asthmatic airways against bradykinin-induced bronchoconstriction, thus suggesting that endogenous prostaglandins may play a contributory role in the bronchoconstriction to kinins in human asthma.

Attenuation of aspirin-induced bronchoconstriction by sodium cromoglycate and nedocromil sodium

The protective activity of nedocromil sodium and of sodium cromoglycate against aspirin-induced asthma has never been investigated in controlled studies. Because it has been reported that aspirin-induced platelet-mediated cytotoxic activity in vitro is inhibited after treatment in vivo with nedocromil but not with cromoglycate, we investigated whether these compounds also exhibit a different protective activity against aspirin-induced bronchoconstriction. Ten patients with aspirin-induced asthma underwent three bronchial challenges with a single dose of lysine acetylsalicylate (LASA) that caused a decrease in FEV1 of 25% or more in a preliminary dose-response test 30 min after inhalation of 4 mg nedocromil sodium, 10 mg sodium cromoglycate, or placebo. FEV1 and SRaw were recorded at intervals for 195 min. After placebo, LASA caused a maximal decrease in FEV1 of 42 +/- 4% of baseline. After cromoglycate and nedocromil the maximal decrease in FEV1 was reduced to 20 +/- 3% and 18 +/- 4%, respectively (p < 0.01 versus placebo for both treatments), without significant differences between the two treatments. Similar results were observed with SRaw. We conclude that, at the recommended therapeutic doses, sodium cromoglycate and nedocromil sodium are equally effective in attenuating aspirin-induced bronchoconstriction and that it is unlikely that platelet activation participates in the pathogenesis of aspirin-induced asthma.

Resuscitation of pulmonary contusion: effects of a red cell substitute

OBJECTIVE

To determine the impact of a vasoactive red cell substitute, diaspirin cross-linked hemoglobin, on respiratory derangements after traumatic lung injury.

DESIGN

Randomized, controlled animal experiment.

SETTING

Large-animal laboratory.

SUBJECTS

Mechanically ventilated, anesthetized young Yorkshire male swine (15 to 20 kg).

INTERVENTIONS

Pigs (n = 6/group) received two pneumatic blasts to the right thoracic cage at baseline, were hemorrhaged 30 mL/kg from t = 0 to 20 mins, resuscitated with 0.9% saline (group 1, 90 mL/ kg) or diaspirin cross-linked hemoglobin (group 2, 15 mL/kg) from t = 20 to 40 mins, and then observed to t = 240 mins.

MEASUREMENTS AND MAIN RESULTS

Serial pulmonary and systemic hemodynamic measurements, total thoracic compliance assessment, spiral three-dimensional computed tomography scan, and lung weights (n = 3/group) were used to assess lesion size and lung water. Mean arterial pressure was restored in both animal groups. Mean pulmonary arterial pressure was significantly higher after resuscitation in animals receiving the red cell substitute. Oxygenation worsened mildly in both groups. Compliance diminished in both groups but was significantly worse at the end of the experiment in animals infused with diaspirin cross-linked hemoglobin. Right lung weights and right thoracic computed tomography scan volume were higher with diaspirin cross-linked hemoglobin than with saline.

CONCLUSIONS

After pulmonary contusion, resuscitation with diaspirin cross-linked hemoglobin led to pulmonary hypertension, greater pulmonary contusion lesion size, and stiffer lungs in this porcine model.

Resuscitation from hemorrhagic shock with diaspirin cross-linked hemoglobin, blood, or hetastarch

BACKGROUND

An oxygen-transporting hemoglobin solution should be more effective than a nonhemoglobin solution for resuscitation from hemorrhagic shock. A way to evaluate this effectiveness is to determine whether a hemoglobin solution can reverse the base deficit accumulated during hemorrhage at a faster rate than a nonhemoglobin solution. Using this criterion, we compared the resuscitative powers of autologous blood, hetastarch (Het), and diaspirin cross-linked hemoglobin (DCLHb).

METHODS

Fifteen sedated, spontaneously breathing sheep (37.5 +/- 10.2 kg) were bled until base deficits fell to -5 to -10 mEq/L, and plasma lactate concentrations rose to 6 to 9 mg/L. The animals were resuscitated with autologous blood (n = 5), Het (n = 5), or DCLHb (n = 5) (3.5-4.0 mL/kg every 15 minutes) until base deficits returned to prehemorrhage baseline.

RESULTS

Exsanguination to target base deficits required removal of an average of 41.4 +/- 5.5 mL blood/kg (estimated total blood volume, 80 mL/kg). Resuscitation required 18 +/- 3, 38 +/- 2 (different from blood), and 35 +/- 1 (different from blood) mL/kg of autologous blood, Het and DCLHb, respectively, over periods of 78 +/- 8, 163 +/- 10 (different from blood), and 129 +/- 9 minutes (different from blood and different from Het (p < or = 0.05)). Based on regression analysis, autologous blood, Het, and DCLHb corrected the base deficit at rates of, respectively, 0.074 (different from Het (p < or = 0.05)), 0.016, and 0.056 (different from Het (P < or = 0.05)) mEq/L/min.

CONCLUSIONS

Based on the rate of base deficit correction and the volume of solution required, autologous blood was the most effective resuscitation solution. However, DCLHb was more effective than Het. DCLHb may be an attractive alternative to blood for resuscitation from hemorrhagic shock.

Actions of diaspirin cross-linked hemoglobin on isolated rat and dog vessels

The objectives of these studies were to investigate the responses of isolated blood vessels from rats and dogs to the administration of diaspirin cross-linked hemoglobin (DCLHb) and to determine the mechanisms of these responses. Isolated vascular rings (3 to 5 mm) were suspended at optimal passive tension in Krebs-filled (37 degrees C) tissue baths and bubbled with 95% O2-5% CO2, and isometric tension was recorded. With the vessels under basal conditions increasing concentrations of DCLHb (10(-8)-3 x 10(-6) mol/L) were added. DCLHb addition was repeated during a submaximal contraction with norepinephrine and again during acetylcholine relaxation. The effects of the nitric oxide synthase inhibitor L-nitro arginine (10(-5) mol/L) on the responses to DCLHb were also determined. Dog vessels developed very little tension (1% to 5% of norepinephrine maximum), whereas rat arteries contracted between 9% and 15% when exposed to DCLHb under basal conditions. However, both the dog and rat vessels developed significant tension to DCLHb when they were precontracted (5% to 54%) and also when they were relaxed with acetylcholine (21% to 93%). L-nitro arginine eliminated the contractile responses to DCLHb but did not cause contraction of any of the vessels under basal conditions. We conclude that in this model the mechanism of DCLHb-induced contractions of in vitro dog and rat vessels is dependent on interference with nitric oxide. This is similar to the mechanism of DCLHb action in isolated pig vessels reported previously. Differences in responses of dog, rat, and pig vessels under basal conditions in vitro are the result of active generation of nitric oxide by pig but not by dog or rat vessels.

Role of nitric oxide in desmopressin-induced vasodilation of microperfused rabbit afferent arterioles

We have previously reported that desmopressin (dDAVP) increased the lumen diameter of norepinephrine (NE)-constricted isolated microperfused rabbit afferent arterioles. In this study, we examined the role of nitric oxide in dDAVP-induced vasodilation of afferent arterioles. We microdissected a superficial afferent arteriole from the kidney of a New Zealand white rabbit. Each afferent arteriole was cannulated with a pipette system and microperfused in vitro at 60 mmHg. dDAVP increased the lumen diameter of NE-preconstricted rabbit afferent arterioles dose-dependently. dDAVP-induced vasodilation was abolished by pretreatment with NG-nitro-L-arginine (L-NNA, 10(-4)M) (L-NNA + NE, 6.7 +/- 1.1 microns; L-NNA + NE + dDAVP, 7.3 +/- 1.4 microns, n = 8). dDAVP increased the lumen diameter of NE-preconstricted afferent arterioles pretreated with L-NNA and L-arginine (10(-2)M) (L-NNA + L-arginine + NE, 6.1 +/- 1.1 microns; L-NNA + L-arginine + NE + dDAVP, 8.7 +/- 0.9 microns*; *p < 0.05, n = 6). Aspirin-DL-lysine (10(-4)M) did not influence dDAVP-induced afferent arteriolar vasodilation (aspirin + NE, 6.4 +/- 0.8 microns; aspirin + NE + dDAVP, 9.6 +/- 1.3 microns *; *p < 0.05, n = 5). These results suggest that nitric oxide may be responsible for dDAVP-induced afferent arteriolar vasodilation.

Prostaglandins and the mechanism of analgesia produced by aspirin-like drugs. 1973

Resting splenic venous outflow from anaesthetized dogs contains prostaglandin-like material: the concentration increases after intra-arterial injections of bradykinin into the spleen, and is abolished by treatment with indomethacin. Intra-arterial injections of bradykinin into the spleen of lightly anaesthetized dogs elicit a dose-dependent reflex increase in the blood pressure, which is reduced but not abolished by treatment with indomethacin. Addition of prostaglandin E1 or E2 either by injections or by infusions restores the reflex increase in the blood pressure due to bradykinin injections after indomethacin treatment. The sensitizing action of endogenously released prostaglandins at or near the afferent nerve endings is discussed. The analgesic activity of aspirin-like drugs is explained in terms of the removal of the sensitizing activity of prostaglandins.

A new antithrombotic agent, aspalatone, attenuated cardiotoxicity induced by doxorubicin in the mouse; possible involvement of antioxidant mechanism

A new antithrombotic agent, aspalatone (APT; acetyl salicylic acid maltol ester), was synthesized by esterification of acetyl salicylic acid (ASP) and maltol (MAL). It was suggested that APT possessed an antioxidant effect in in vitro. To evaluate the putative antioxidant effect of APT in in vivo, we developed doxorubicin (DOX)-related cardiac damage, which might be implicated by oxidative stress. Vitamin E (Vit E) was included in the present study as an example of an antioxidant. Prolonged treatments with APT, MAL and Vit E significantly reduced the mortality in animals receiving multiple dose of DOX (3 mg/kg x 4). The potential role of APT, MAL and Vit E against DOX insult may be explained by the induction of glutathione peroxidase activity accompanied by the inhibition of lipid peroxidation. Prolonged treatments of APT, MAL and Vit E also ablated histopathological evidence of DOX cardiomyopathy. ASP challenge, however, did not affect the mortality, myocardial lesion and antioxidant deficit induced by DOX treatments. In conclusion, the protective effect of APT was equipotent to that of Vit E against DOX cardiotoxicity. The results also suggest that the antiperoxidative effect of APT plays a protective role in DOX-related cardiotoxic side effect.

Alpha-alpha diaspirin crosslinked hemoglobin, nitric oxide, and cerebral ischemic injury in rats

Prior studies indicate that alpha-alpha diaspirin crosslinked hemoglobin (DCLHb) decreases cerebral ischemia. One mechanism whereby DCLHb may ameliorate cerebral ischemia is by binding nitric oxide (NO), which has been implicated as neurotoxic. We assessed the effect of L-NAME (NO synthase inhibitor) and L-arginine (NO substrate) on ischemic brain injury after DCLHb infusion. Rats were randomized to one of the following groups: Control-no hematocrit manipulation; DCLHb-hematocrit decreased to 16% with 10% DCLHb; DCLHb/L-NAME-hematocrit decreased to 16% with DCLHb, and L-NAME given; DCLHb/L-arg-hematocrit decreased to 16% with DCLHb, and L-arginine given. After 90-min of middle cerebral artery occlusion and 4-hr of reperfusion, infarct volume was determined with TTC stain. Infarct volume (mm3, mean +/- SD) was greater in the Control group (142 +/- 16) than the DCLHb (43 +/- 12), DCLHb/L-NAME (45 +/- 14), and DCLHb/L-arg (71 +/- 18) groups (p < 0.05); was greater in the DCLHb/L-arg group than the DCLHb and DCLHb/L-NAME groups (p < 0.05); but was not different between the DCLHb and DCLHb/L-NAME groups. These data indicate that DCLHb decreases ischemic brain injury, and that binding NO may be one mechanism by which DCLHb decreases ischemic brain injury.

Effect of subarachnoid administration of alpha-alpha diaspirin crosslinked hemoglobin on cerebral blood flow in rats

As extravasated red blood cells have been implicated in the pathogenesis of perfusion deficits after subarachnoid hemorrhage, alpha-alpha diaspirin crosslinked hemoglobin (DCLHb) might have a detrimental effect on cerebral perfusion after subarachnoid hemorrhage. We evaluated the effect of subarachnoid administration of DCLHb on cerebral blood flow (CBF). Rats were randomized to receive one of the following solutions into the cisterna magna: Control-0.3 ml of mock cerebrospinal fluid; Blood-0.3 ml of autologous blood; DCLHb-0.3 ml of 10% DCLHb. After 20-min, the area of cerebral hypoperfusion was determined (CBF < 40 ml.100g-1.min-1). The area of hypoperfusion (% area of a coronal brain section, mean +/- SD) was greater in the Blood group (58 +/- 16) than the DCLHb (16 +/- 7) and Control (5 +/- 5) groups (p < 0.05), and was greater in the DCLHb group than the Control group (p < 0.05). These data support a hypothesis that extravasation of blood from the intravascular to the subarachnoid space induces cerebral hypoperfusion. Moreover, the data support the hypothesis that although extravasated molecular hemoglobin decreases CBF, the adverse effect is not as severe as a similar volume of blood.

Effect of hemodilution with diaspirin cross-linked hemoglobin on intracranial pressure, cerebral perfusion pressure, and fluid requirements after head injury and shock

Hemodilution has been shown to increase cerebral blood flow (CBF) and reduce lesion volume in models of occlusive cerebral ischemia, but it has not been evaluated in the setting of head trauma and shock in which ischemia is thought to play a role in the evolution of secondary injury. In a porcine model of brain injury and shock the authors compared hemodilution with diaspirin cross-linked hemoglobin (DCLHb) to a standard resuscitation regimen using Ringer's lactate solution and shed blood. After creation of a cryogenic brain injury followed by hemorrhage, the animals received a bolus of either 4 ml/kg of Ringer's lactate solution (Group 1, six animals) or DCLHb (Group 2, six animals), followed by infusion of Ringer's lactate solution to restore mean arterial pressure (MAP) to baseline. Group 1 received shed blood 1 hour after hemorrhage (R1) in the form of packed red blood cells. Group 2 received shed blood only for an Hb count of less than 5 g/dl. The animals were monitored for 24 hours. At R1, Group 2 had a significantly greater cerebral perfusion pressure ([CPP] 88 +/- 5.7 vs. 68 +/- 2.4 mm Hg, p < 0.05). By 3 hours after hemorrhage (R3) Group 2 had a significantly lower Hb concentration (8.5 +/- 0.4 vs. 12.1 +/- 0.3 g/dl, p < 0.05) and a significantly lower intracranial pressure ([ICP] 9 +/- 0.8 vs. 14 +/- 0.6 mm Hg, p < 0.05). The total 24-hour fluid requirement was significantly less in Group 2 (10,654 +/- 505 ml vs. 15,542 +/- 1094 ml, p < 0.05) There was no difference between the groups regarding levels of regional CBF in the injured hemisphere. Cerebral O2 delivery was not significantly different between groups at any time. Lesion volume as determined at postmortem examination was not significantly different between the groups. The increased MAP and CPP and lower ICP observed in the Group 2 animals indicate that hemodilution with DCLHb may be beneficial in the treatment of head injury and shock.

Cellular responses to surgical trauma, hemorrhage, and resuscitation with diaspirin cross-linked hemoglobin in rats

BACKGROUND

Resuscitation with acellular oxygen carrier solutions offers the potential advantage of improved oxygen delivery compared with crystalloid solutions, but the detailed consequences of improved resuscitation have not been fully evaluated. This study evaluated local and systemic cellular effects of trauma, hemorrhage, and resuscitation in a model of hemorrhage and surgical trauma.

METHODS

Rats with a 10 cm full-thickness incisional wound and a 15 mL/kg hemorrhage were either not resuscitated or resuscitated with blood or diaspirin cross-linked hemoglobin (DCLHb). Cellular proliferative responses were evaluated at 1.5, 6, 24, and 48 hours after wounding by labeling in vivo with 5-bromo-2'-deoxyuridine. Plasma levels of interleukin-6, tumor necrosis factor-alpha, and interferon-gamma were measured by bioassay or enzyme-linked immunosorbent assay (ELISA). Bacterial translocation was measured by culturing liver homogenates.

RESULTS

Trauma inhibited keratinocyte and hepatocyte proliferation at 1.5 and 6 hours, and stimulated subsequent proliferation of keratinocytes and liver nonparenchymal cells. DCLHb stimulated wound keratinocyte proliferation, attenuated the inhibition of hepatocyte proliferation, eliminated bacterial translocation to the liver, protected the intestine from ischemic damage, and induced a rapid increase of interleukin-6 during the early phase of injury.

CONCLUSIONS

Surgical trauma alone, or in combination with hemorrhage, modulated cell proliferation both in the wound and in the remote organs of intestine and liver. DCLHb enhanced wound healing and cell proliferation as well as, or better than, freshly drawn blood, which may be beneficial for trauma care.