Vascular resistance and the efficacy of red cell substitutes in a rat hemorrhage model

We have compared polyethylene glycol-modified bovine hemoglobin (PEG-Hb; high O2 affinity, high viscosity, high oncotic pressure) and human hemoglobin cross-linked between the alpha-chains (alpha alpha-Hb; low O2 affinity, low viscosity, low oncotic pressure) with a non-O2-carrying plasma expander (pentastarch, high viscosity and oncotic pressure) after a 50% (by volume) exchange transfusion followed by a severe (60% of blood volume) hemorrhage. Mean arterial pressure and systemic vascular resistance rose significantly in the alpha alpha-Hb but not in the PEG-Hb animals. Two-hour survival was greater in the PEG-Hb animals (93%) than in control (35%), pentastarch (8%), or alpha alpha-Hb (6%) animals. In the PEG-Hb animals, there was no disturbance of acid-base balance, significantly less accumulation of lactic acid, and higher cardiac output than in the other groups. The data suggest that the rise in vascular resistance that follows alpha alpha-Hb exchange transfusion offsets the additional O2 transport provided by the cell-free hemoglobin. When resistance does not rise, as with PEG-Hb, even relatively small amounts of cell-free hemoglobin appear to be a very effective blood replacement.

Stroke volume decline during prolonged exercise is influenced by the increase in heart rate

This study determined whether the decline in stroke volume (SV) during prolonged exercise is related to an increase in heart rate (HR) and/or an increase in cutaneous blood flow (CBF). Seven active men cycled for 60 min at approximately 57% peak O2 uptake in a neutral environment (i.e., 27 degrees C, <40% relative humidity). They received a placebo control (CON) or a small oral dose (i.e., approximately 7 mg) of the beta1-adrenoceptor blocker atenolol (BB) at the onset of exercise. At 15 min, HR and SV were similar during CON and BB. From 15 to 55 min during CON, a 13% decline in SV was associated with an 11% increase in HR and not with an increase in CBF. CBF increased mainly from 5 to 15 min and remained stable from 20 to 60 min of exercise in both treatments. However, from 15 to 55 min during BB, when the increase in HR was prevented by atenolol, the decline in SV was also prevented, despite a normal CBF response (i.e., similar to CON). Cardiac output was similar in both treatments and stable throughout the exercise bouts. We conclude that during prolonged exercise in a neutral environment the decline in SV is related to the increase in HR and is not affected by CBF.

Caffeine alters the temporal dynamics of the visual BOLD response

The blood oxygenation level-dependent (BOLD) responses to visual stimuli, using both a 1-s long single trial stimulus and a 20-s long block stimulus, were measured in a 4-T magnetic field both before and immediately after a 200-mg caffeine dose. In addition, resting levels of cerebral blood flow (CBF) were measured using arterial spin labeling. For the single trial stimulus, the caffeine dose significantly (p<0.05) reduced the time to peak (TTP), the time after the peak at which the response returned to 50% of the peak amplitude (TA50), and the amplitude of the poststimulus undershoot in all subjects (N=5). Other parameters, such as the full-width half-maximum (FWHM) and the peak amplitude, also showed significant changes in the majority of subjects. For the block stimulus, the TTP, TA50, and the time for the response to reach 50% of the peak amplitude (T50) were significantly reduced. In some subjects, oscillations were observed in the poststimulus portion of the response with median peak periods of 9.1 and 9.5 s for the single trial and block responses, respectively. Resting CBF was reduced by an average of 24%. The reproducibility of the results was verified in one subject who was scanned on 3 different days. The dynamic changes are similar to those previously reported for baseline CBF reductions induced by hypocapnia and hyperoxia.

Renin, angiotensin, and norepinephrine in alloxan diabetes

The renin-angiotensin system and catecholamines were evaluated in short term alloxan diabetic rats which were either “severely diabetic” (polyuric with serum glucose &gt; 450 mg. per 100 ml.) or “mildly diabetic” (normouric with serum glucose &lt;450 mg. per 100 ml.). Plasma renin activity (PRA), renal renin activity (RRA), and the amount of angiotensin II producing an acute 10 mm Hg increase in blood pressure were all significantly decreased in the diabetic rats with this decrease correlating inversely with the severity of the diabetes. Insulin treatment of these rats resulted in partial normalization of angiotensin II responsiveness, PRA, and blood urea nitrogen. Injection of alloxan directly into the left renal artery did not decrease RRA. Protection of the left kidney during systemic alloxan injection did not prevent the decrease in renal renin activity. Streptozotocin-treated diabetic rats had increased vascular responsiveness to injected angiotensin II. Norepinephrine sensitivity (amount producing a 10 mm Hg increase in blood pressure) and norepinephrine stores (blood pressure response to tyramine) were normal in both alloxan- and streptozotocin-treated rats.

Blood volume as related to lean body mass was elevated in the severely diabetic rats thus suggesting one possible mechanism for the decrease in the renin-angiotensin system.

These results suggest that (1) norepinephrine responsiveness and norepinephrine stores are normal, and (2) there is suppression of RRA leading to decreased PRA and increased vascular reactivity to angiotensin II in the acutely diabetic alloxan-treated rat. Further, these abnormalities appear to be related to the degree of diabetes as assessed by serum glucose and twenty-four hour urine volume.

Comparison of the effect of terlipressin and albumin on arterial blood volume in patients with cirrhosis and tense ascites treated by paracentesis: a randomised pilot study

BACKGROUND

Patients with cirrhosis and tense ascites treated by paracentesis alone have a decrease in effective arterial blood volume after ascites removal. Although intravenous albumin is effective in preventing paracentesis induced decreased arterial blood volume, its clinical use is controversial. As paracentesis induces arteriolar vasodilation which plays a role in the development of decreased effective arterial blood volume, administration of a vasoconstrictor (terlipressin) could prevent circulatory alterations due to paracentesis.

AIMS

To perform a pilot study comparing the effects of terlipressin and albumin on effective arterial blood volume in patients with cirrhosis treated by paracentesis for tense ascites.

METHODS

Twenty patients with cirrhosis and tense ascites were randomly assigned to be treated by either paracentesis and terlipressin or paracentesis and albumin. Terlipressin (3 mg) or albumin (8 g/l of removed ascites) were administered on the day of paracentesis. Effective arterial blood volume was assessed by measuring plasma renin concentrations at baseline and on the day of hospital discharge (4-6 days after treatment). Decreased effective arterial blood volume was defined as an increase in plasma renin concentrations on the day of hospital discharge of more than 50% of baseline values.

RESULTS

Irrespective of the treatment group, mean values for plasma renin concentrations at hospital discharge did not differ from their respective baseline values (p=0.10). Baseline plasma levels of renin concentrations did not differ between the terlipressin and albumin groups (p=0.61). Changes from baseline in plasma renin concentrations did not differ between groups (p=0.39). Three patients in the terlipressin group and three in the albumin group developed decreased arterial blood volume.

CONCLUSIONS

This randomised pilot study suggests that terlipressin may be as effective as intravenous albumin in preventing a decrease in effective arterial blood volume in patients with cirrhosis treated by paracentesis for tense ascites.

Improved efficiency of hypervolemic therapy with inhibition of natriuresis by fludrocortisone in patients with aneurysmal subarachnoid hemorrhage

OBJECT

To reduce the risk of ischemic complications in patients with subarachnoid hemorrhage (SAH), hypervolemic therapy is generally advocated. However, such conventional treatment cannot always ensure the maintenance of an effective intravascular volume expansion, because excessive natriuresis and osmotic diuresis occur after SAH. In this prospective study the authors examined the effects of inhibition of natriuresis with fludrocortisone acetate on intravascular volume expansion during hypervolemic therapy.

METHODS

Thirty patients with SAH were randomized and divided into two groups: controls (Group 1, 15 patients) and patients treated with 0.3 mg/day of fludrocortisone (Group 2, 15 patients). In all patients sodium and fluid intake levels were in excess of maintenance requirements in an attempt to maintain a positive water balance and a central venous pressure (CVP) of 8 to 12 cm H2O. The mean sodium and water intake levels for 14 days after SAH were significantly reduced by fludrocortisone in Group 2 (487+/-34.52 mEq/day and 5159.2+/-249.29 ml/day, respectively; p<0.01) compared with Group 1 (634.2+/-42.86 mEq/day and 6611.7+/-365.67 ml/day). Fludrocortisone significantly reduced the urinary sodium excretion (p<0.01) and urine volume (p<0.01) in parallel, and effectively prevented a negative shift in the sodium as well as water balance (p<0.01). The serum sodium level tended to decrease in Group 1, reaching 135 mEq/L on average, but not in Group 2 (p<0.01). Hyponatremia in Group 1 was always observed at the optimal range of CVP values. A decrease in serum potassium level within the range of 2.8 to 3.5 mEq/L was transiently noted in 11 patients (73.3%) of Group 2, but was easily corrected. Possible side effects of fludrocortisone, such as pulmonary edema, were not encountered.

CONCLUSIONS

Intravascular volume expansion in the presence of excessive natriuresis requires a large sodium and water intake and is often associated with hyponatremia. Inhibition of natriuresis with fludrocortisone can effectively reduce the sodium and water intake required for hypervolemia and prevent hyponatremia at the same time.

Orthostatic hypotension in patients with Parkinson's disease: pathophysiology and management

Orthostatic hypotension is common in elderly patients, and is now considered to be an important prognostic factor for cognitive decline and mortality. In patients with Parkinson's disease, the prevalence of symptomatic orthostatic hypotension may be as high as 20%. Two factors could explain this high prevalence. First, dopaminergic drugs may induce or worsen orthostatic hypotension. Secondly, Parkinson's disease is a cause of primary autonomic failure with an involvement of the peripheral autonomic system as shown by the ubiquitous distribution of Lewy bodies and reduced iobenguane [metaiodobenzylguanidine (MIBG)] cardiac uptake. These pathological and pharmacological characteristics clearly differentiate autonomic failure of Parkinson's disease from multiple system atrophy. If autonomic abnormalities appear to be present from the first stage of the disease, early onset (within the first year) of symptomatic orthostatic hypotension in the course of parkinsonism can be considered as an exclusion criteria for idiopathic Parkinson's disease. No specific clinical trials have evaluated the effects of antihypotensive drugs in patients with Parkinson's disease and thus no specific therapeutic strategy can be recommended. The management of orthostatic hypotension in patients with Parkinson's disease should always start with patient education and nonpharmacological treatment. Drug therapy should be reserved for symptomatic patients who do not get benefit from nonpharmacological management. Among the available drugs, alpha1-adrenergic agonists (mainly midodrine) or plasma volume expanders (mainly fludrocortisone) are the most frequently used. There are also some drugs that are currently investigational such as yohimbine and droxidopa. Other drugs such as desmopressin or octreotide may be of interest in some situations. Domperidone is widely used in patients with parkinsonism with no proven effect on orthostatic hypotension.

Postischemic vasodilation in human forearm is dependent on endothelium-derived nitric oxide

Although endothelium-derived nitric oxide contributes to basal vascular tone, little is known about its role in regulating blood flow during changes in metabolic supply and demand. We examined the contribution of endothelium-derived nitric oxide to reactive hyperemia in the forearm of 20 normal subjects (12 women, 8 men) aged 27 +/- 4 yr (means +/- SD), using the nitric oxide synthase inhibitor, NG-monomethyl-L-arginine (L-NMMA). Forearm ischemia was induced by suprasystolic blood pressure cuff inflation for 5 min, and the subsequent hyperemic flow was recorded for 5 min using venous occlusion strain-gauge plethysmography. The efficacy of nitric oxide blockade was tested by comparing the dose-response relationship to the endothelium-dependent agonist, acetylcholine (3, 10, and 30 mg/min), before and after intra-arterial infusion of up to 2,000 mg/min of L-NMMA. L-NMMA produced a significant downward and rightward shift in the dose-response relationship to acetylcholine and a 39% reduction in response to the maximum dose (P < 0.001). In the presence of L-NMMA, peak hyperemic flow was reduced 16% (26.5 +/- 2.1 to 22.3 +/- 1.5 ml.min-1.100 ml of forearm-1, P < 0.03), and the minimum forearm vascular resistance was increased 22.8% (3.5 +/- 0.3 to 4.3 +/- 0.4 mmHg.ml-1.min.100 ml, P < 0.02). Total hyperemia, calculated from the area under the flow vs. time curve, at 1 and 5 min after cuff release was 17 and 23% less, respectively (13.6 +/- 1.2 vs. 11.3 +/- 1.1 and 31.8 +/- 2.7 vs. 24.6 +/- 1.8 ml/100 ml, P < 0.002), following L-NMMA. These data suggest that endothelium-derived nitric oxide plays a role in both reactive hyperemia and in the maintenance of the hyperemic response following ischemia in the forearm.

Cardiovascular effects of insulin-like growth factor-1 and growth hormone in chronic left ventricular failure in the rat

BACKGROUND

Insulin-like growth factor-1 (IGF-1) appears to have favorable cardiac effects associated with left ventricular remodeling early after myocardial infarction in the rat. The present study was designed to determine whether IGF-1 combined with growth hormone would be beneficial later as well, when infarct healing and cardiac remodeling have occurred.

METHODS AND RESULTS

Four weeks after coronary occlusion, 36 rats were randomized to IGF-1 (3 mg.kg-1.d-1) plus growth hormone (0.1 mg BID) or to placebo for 4 weeks. Treated rats had significant increases in body weight (22%), while the ratio of heart weight to body weight was unchanged. Under anesthesia, cardiac output (fluorescent microspheres) increased 46%, and systemic vascular resistance decreased by 21% (P < .001) in the treated group; a significant (22%) increase of the cardiac index was limited to treated rats with large myocardial infarctions. Small increases in the reduced left ventricular ejection fractions and left ventricular dP/dt(max) values with treatment were not significant. Treated rats showed a borderline (16%) increase in left ventricular end-diastolic volume (angiography), whereas the ratio of left ventricular end-diastolic volume to body weight was reduced in the treated group.

CONCLUSIONS

IGF-1 plus growth hormone administered to rats with left ventricular failure starting 1 month after MI was associated with substantial body growth, decreased systemic vascular resistance, and increased cardiac output. The failing heart also underwent treatment-induced increases in left and right ventricular weights in proportion to body growth, but left ventricular remodeling was minor, and a decrease in the ratio of left ventricular end-diastolic volume to body weight reflected relatively less chamber dilation compared with controls. A significant interaction between size of the myocardial infarction and treatment was observed for several variables, and IGF-1 and growth hormone increased the cardia index (P < .035) in rats with a large myocardial infarction.

Relationship of cerebral blood flow to cardiac output, mean arterial pressure, blood volume, and alpha and beta blockade in cats

The relationship among cerebral blood flow (CBF), blood volume, cardiac output (CO), and mean arterial blood pressure (MABP) at varying levels of arterial CO2 tensions (PaCO2) were studied in 70 normal cats. The CBF was measured from the clearance curve of xenon-133 and CO with a thermal dilution catheter placed in the pulmonary artery. The CBF, CO, and MABP values varied appropriately with changes in PaCO2, confirming the reliability of the preparations and the presence of normal autoregulatory responses. Moderate hypovolemia that did not change MABP did, nevertheless, significantly decrease CO and CBF. In an effort to determine if this decrease in CO and CBF were coupled responses, the effects of beta stimulation, hypervolemia, and alpha and beta blockade were investigated. Propranolol, in a dosage insufficient to change MABP, decreased both CO and CBF. This agent abolished the CO response to elevations in PaCO2 but not the CBF response, making it unlikely that this CBF reduction resulted from impaired cerebral autoregulation. Isoproterenol, which, in contrast to propranolol, does not cross the normal blood-brain barrier, alone or in combination with phenoxybenzamine, produced a 38% and 72% increase in CO, respectively, without a change in CBF. Alpha blockade (no major change in CO) and beta blockage (major decrease in CO) did not significantly effect cerebral autoregulation to changes in MABP from angiotensin. The ability of the brain to resist increases in MABP and CO and maintain normal CBF is explained by normal cerebral autoregulation. However, its vulnerability to modest decreases in blood volume, which cannot be attributed to variations in perfusion pressure, is unexplained but obviously has important therapeutic implications. This may be related to reduction in CO, changes in autonomic activity, or a decrease in the size of the perfused capillary bed.

Hydroxyethyl starch 130/0.4 versus modified fluid gelatin for volume expansion in cardiac surgery patients: the effects on perioperative bleeding and transfusion needs

In this prospective, randomized, open controlled study we compared the effects on net red blood cell loss of 6% hydroxyethyl starch 130/0.4 (HES: n = 64) and 3% modified fluid gelatin (GEL: n = 68) administered for intravascular volume management in patients undergoing coronary surgery. Blood losses were calculated from determination of circulating blood volume and measurement of preoperative and postoperative hematocrit. Amount of colloids that could be administered was limited to 50 mL/kg. If additional fluids were required, balanced crystalloid solution was used. Anesthetic and surgical techniques were standardized. Both groups were similar with regard to demographic and intraoperative variables. Total study drug was 48.9 +/- 17.2 mL/kg in the HES group and 48.9 +/- 14.6 mL/kg in the GEL group. Total red blood cell loss was 544 +/- 305 mL in the HES group and 504 +/- 327 mL the GEL group. Measured blood losses were also similar in both groups (HES, 19.4 +/- 12.3 mL/kg; GEL, 19.2 +/- 14.5 mL/kg). Exposure to allogeneic blood product was comparable in both groups. In the conditions of the present study, HES 130/0.4 up to 50 mL/kg is a valuable alternative to modified fluid gelatin for plasma volume expansion during and after cardiac surgery.

A randomized, blinded trial comparing the hemostatic effects of pentastarch versus hetastarch

BACKGROUND

HES solutions provide a sterile, alternative colloidal fluid to albumin solutions and/or plasma in the management of patients who need plasma volume expansion. Solutions of HES are widely accepted internationally but are used only modestly in the United States, largely because of concerns over hemostasis.

STUDY DESIGN AND METHODS

A randomized, blinded, two-arm trial comparing the hemostatic effects of pentastarch versus hetastarch when infused in the clinically relevant dose of 90 g of HES dissolved in 1.5 L of saline was conducted. Multiple studies of fibrin clot formation, fibrinogen/fibrinolysis, and platelet (PLT) functions were performed before and on multiple occasions for 70 days following HES infusion.

RESULTS

Several significant abnormalities of hemostasis assay results occurred following HES infusions, with hetastarch causing significantly greater abnormalities than pentastarch. Individual clotting proteins and blood PLTs fell modestly because of plasma volume expansion and hemodilution. A fall in excess of that caused by hemodilution was demonstrated for von Willebrand factor antigen plus its associated FVIII and ristocetin cofactor activities. The partial thromboplastin time was prolonged, whereas the thrombin time was shortened. Plt function abnormalities were seen in most subjects to a modest degree. Studies of fibrinolysis were normal.

CONCLUSIONS

Solutions of hetastarch produce significant abnormalities of some hemostasis laboratory results when infused at clinically relevant doses, but it is unlikely that the modest hemostatic abnormalities produced at these doses per se would lead to clinical bleeding. Hetastarch causes greater hemostatic abnormalities than pentastarch, and because both HES solutions have comparable plasma volume-expanding effects, it is reasonable to prefer pentastarch as a plasma volume expander.

Inhibition of nitric oxide synthase attenuates blood-brain barrier disruption during experimental meningitis

Increased permeability of the blood-brain (B-B) barrier is observed during meningitis. Preventing B-B barrier alterations is important because adverse neurological outcomes are correlated with breeches in barrier integrity. It was hypothesized that pathological production of nitric oxide (NO) contributes to B-B barrier disruption during meningitis in the rat. Experimental meningitis was induced by intracisternal (i.c.) administration of lipopolysaccharides (LPS) or vehicle. Groups of rats were concomitantly infused intravenously (i.v.) with saline or the NO synthase inhibitor, aminoguanidine (AG). Eight h after i.c. dosing, B-B barrier alterations were quantitated pharmacokinetically using [14C]sucrose. Serum and regional brain tissues were obtained 0-30 min after tracer dosing and sucrose influx transfer coefficients (Kin(app)) were calculated from the brain tissue data. Compared to the control groups (i.c. vehicle/i.v. saline), the Kin(app) of the i.c. LPS/i.v. saline group increased 1.6-2.1-fold in various brain regions, thus confirming previous observations of increased [14C]sucrose barrier penetration during meningeal inflammation. Remarkably, i.v. administration of AG to i.c. LPS-treated rats significantly inhibited meningeal NO synthesis and decreased Kin (app) permeability alterations in the B-B barrier, compared to i.c. LPS/i.v. saline-treated rats. Regional brain Kin (app) estimates in the i.c. LPS/i.v. AG group were similar to control groups (i.c. vehicle/i.v. AG and i.c. vehicle/i.v. saline). In conclusion, these data suggest the general concept that excessive NO production during neuroinflammatory diseases contributes to disruption of the blood-brain barrier.

Volume Efficacy and Reduced Influence on Measures of Coagulation Using Hydroxyethyl Starch 130/0.4 (6%) with an Optimised in???Vivo???Molecular Weight in Orthopaedic Surgery

BACKGROUND AND OBJECTIVE

Different types of hydroxyethyl starch (HES) affect blood coagulation differently. We studied the effects of HES 130/0.4 on coagulation in major orthopaedic surgery in relation to the pharmacological parameter in vivo molecular weight.

METHODS

52 patients were randomly allocated to either HES 130/0.4 (6%, mean molecular weight 130 kDa, molar substitution 0.4) or HES 200/0.5 (6%, control) in a double-blind fashion. Colloidal volume requirements for intra- and postoperative haemodynamic stabilisation were compared. Safety analyses of this pharmacological study included a comparison of coagulation factor tests, in vivo molecular weight, and HES plasma concentrations.

RESULTS

The colloidal volumes given were similar at the end of surgery (1602 +/- 569 for HES 130/0.4 vs 1635 +/- 567mL for HES 200/0.5), 5h later (1958 +/- 467 vs 1962 +/- 398mL), and up to the first postoperative day (2035 +/- 446 vs 2000 +/- 424mL). HES in vivo molecular weight at the end of surgery was 88,707 +/- 13,938 versus 158,374 +/- 33,933Da (p < 0.001) and 5h later was 86,663 +/- 16,126 versus 136,299 +/- 26,208Da (p < 0.001). In parallel to the lower in vivo molecular weight, factor VIII and von Willebrand factor returned to almost normal in the HES 130/0.4 group up to 5h postoperatively, but not in the control group (p < 0.05). Residual HES plasma concentrations after 24h were low in the HES 130/0.4 group (1.0 mg/mL), but higher in the control group (2.6 mg/mL).

CONCLUSION

HES 130/0.4 and HES 200/0.5 were found to be similar with regard to volume efficacy. Sensitive coagulation parameters returned more rapidly to normal in the HES 130/0.4 group. Lower in vivo molecular weight and more rapid excretion of HES 130/0.4 are the likely explanations for the smaller influence on coagulation in this group.

Ascending noradrenergic projections from the brainstem: evidence for a major role in the regulation of blood pressure and vasopressin secretion

The role of projections from the lateral tegmental (A1, A2) and coeruleal (A6) noradrenergic cell groups in the control of arginine vasopressin (AVP) secretion was studied following lesions to the ventral (VNAB) and dorsal (DNAB) noradrenergic bundles by 6-hydroxydopamine. These lesions were associated with the expected, large reductions in cortical (DNAB) and hypothalamic (VNAB) noradrenaline concentrations. Vehicle injected, control animals and VNAB lesioned animals showed a similar AVP secretory response to haemorrhage, whilst the DNAB group showed a markedly diminished release of AVP in response to this challenge. Following Clonidine injection, both controls and VNAB animals showed major reductions in plasma AVP concentrations, but again the DNAB group behaved in a different manner, with a marked attenuation of the inhibitory effect of Clonidine on AVP secretion. In addition, the DNAB group had a significantly lower basal blood pressure, a greater initial agonist response to Clonidine and a loss of the hypotensive response to Clonidine in comparison to sham and VNAB lesioned groups. All three groups showed a similar AVP response to intravenous nicotine. These data suggest that noradrenergic projections originating in the locus coeruleus, or in the lateral tegmental NA groups but which ascend together with coeruleal axons in the DNAB, modulate the vasopressin response to visceral stimuli and to Clonidine, and that they also play an important role in mediating the hypotensive effect of Clonidine.

The clinical, cardiac, renal, arterial and neurohormonal effects of omapatrilat, a vasopeptidase inhibitor, in patients with chronic heart failure

OBJECTIVES

We sought to examine the effects of long-term vasopeptidase inhibition in patients with heart failure.

BACKGROUND

The long-term effects of omapatrilat, an agent that inhibits both neutral endopeptidase and angiotensin-converting enzyme, on clinical status, neurohormonal indexes and left ventricular function in patients with chronic heart failure (CHF) have not been previously documented.

METHODS

Forty-eight patients in New York Heart Association functional class II or III, with left ventricular ejection fraction (LVEF)< or =40% and in sinus rhythm were randomized to a dose-ranging pilot study of omapatrilat for 12 weeks. Measurements were performed at baseline and 12 weeks.

RESULTS

There was an improvement in functional status, as reported by the patient (p<0.001) and physician (p<0.001) at 12 weeks. Dose-dependent improvements in LVEF (p<0.001) and LV end-systolic wall stress (sigma) (p<0.05) were seen, together with a reduction in systolic blood pressure (p<0.05). There was evidence of a natriuretic effect (p<0.001), and total blood volume decreased (p<0.05). Omapatrilat induced an increase in postdose plasma atrial natriuretic peptide levels (p<0.01) in the high dose groups, with a reduction in predose plasma brain natriuretic peptide (p<0.001) and epinephrine (p<0.01) levels after 12 weeks of therapy. Omapatrilat was well tolerated.

CONCLUSIONS

The sustained hemodynamic, neurohumoral and renal effects of omapatrilat, together with improved functional status, suggest that vasopeptidase inhibition has potential as a new therapeutic modality for the treatment of CHF.

The haemodynamic effects of dopamine and volume expansion in sick preterm infants

AIM

To determine the haemodynamic effects of dopamine and volume expansion in preterm neonates. Effect parameters were mean arterial blood pressure (MABP), left ventricular output (LVO) and global cerebral blood flow (CBF).

METHODS

In a randomised, clinical control trial 36 preterm neonates were randomised to receive either dopamine 5 microg/kg per min, volume expansion with albumin 20% 15 ml/kg or no treatment. Parameters were measured before and 2 h after initiation of treatment.

RESULTS

Dopamine was effective in increasing MABP; both treatments increased LVO, whereas no significant difference between the treatment groups and the control group could be demonstrated with regard to CBF.

CONCLUSION

No effect on global cerebral blood flow could be demonstrated in this study, despite significant effects on systemic circulatory parameters. However, the variance on the measurement of cerebral blood flow indicates that a small but clinically significant effect may have been overlooked.

Reduction of homologous blood requirement in cardiac surgery by intraoperative aprotinin application--clinical experience in 152 cardiac surgical patients

The protease inhibitor aprotinin interacts with plasmin and kallikrein, which are generated in cardiac surgery during cardiopulmonary bypass (CPB). The influence of high-dose aprotinin application (2 million kallikrein inactivator units given i.v. at the beginning of anaesthesia followed by a 500,000 KIU/h infusion throughout the operation and additional 2 millions KIU added to the priming of the oxygenator) on perioperative blood loss and donor blood requirement was studied in 152 adult cardiac surgical patients. This group was compared to 317 patients having cardiac surgery without the application of aprotinin. Aprotinin reduced the homologous blood requirement by 43% (1783 +/- 100 vs 1015 +/- 131 ml, p less than 0.05), while the reduction of postoperative blood loss was 29% (1070 +/- 43 vs 761 +/- 51 ml, p less than 0.05). Fortytwo percent of the aprotinin treated patients completed their hospital stay without having any donor blood transfusion compared to 18% in the group without aprotinin. The blood saving effect was even more pronounced in operations with prolonged perfusion times. Intra- and postoperative complications were equally distributed in both groups. The blood-saving effect of aprotinin may be due to a platelet-preserving effect and/or kallikrein inhibition during CPB. There were no clinically relevant side effects related to aprotinin observed. It is concluded that high dose aprotinin therapy reduces both postoperative blood loss and homologous blood requirement, and therefore the routine application of aprotinin during cardiac surgical procedures is to be recommended.

Depression of fractional sodium reabsorption by the proximal tubule of the dog without sodium diuresis

The effect of infusions of hyperoncotic solutions on fractional sodium reabsorption by the proximal tubule of the dog was studied by the recollection micropuncture method. Tubule fluid to plasma inulin concentration ratios were measured for identified proximal tubule segments before and after infusion of 25% albumin or dextran solutions. Results were compared with changes in fractional reabsorption during saline diuresis. Plasma volume increased 66% +/- SE 5.8 after infusion of albumin solution and 94% +/- SE 8.2 after infusion of dextran solution. Fractional sodium reabosorption by the proximal tubule was depressed after infusion of both of these hyperoncotic solutions. Nevertheless, changes in sodium excretion after infusion of albumin and dextran were small. In contrast, after infusions of isotonic sodium chloride solution, which increased plasma volume 61% +/- SE 5.8, a decrease in fractional reabsorption of 50.7% +/- SE 7.2 was associated with large changes in sodium excretion.

Expansion of extracellular volume and suppression of atrial natriuretic peptide after growth hormone administration in normal man

Sodium retention and symptoms and signs of fluid retention are commonly recorded during GH administration in both GH-deficient patients and normal subjects. Most reports have however, been casuistic or uncontrolled. In a randomized double blind placebo-controlled cross-over study we therefore examined the effect of 14-day GH administration (12 IU sc at 2000 h) on plasma volume, extracellular volume (ECV), atrial natriuretic peptide (ANP), arginine vasopressin, and the renin angiotensin system in eight healthy adult men. A significant GH induced increase in serum insulin growth factor I was observed. GH caused a significant increase in ECV (L): 20.45 +/- 0.45 (GH), 19.53 +/- 0.48 (placebo) (P less than 0.01), whereas plasma volume (L) remained unchanged 3.92 +/- 0.16 (GH), 4.02 +/- 0.13 (placebo). A significant decrease in plasma ANP (pmol/L) after GH administration was observed: 2.28 +/- 0.54 (GH), 3.16 +/- 0.53 (placebo) P less than 0.01. Plasma aldosterone (pmol/L): 129 +/- 14 (GH), 89 +/- 17 (placebo), P = 0.08, and plasma angiotensin II (pmol/L) levels: 18 +/- 12 (GH), 14 +/- 7 (placebo), P = 0.21, were not significantly elevated. No changes in plasma arginine vasopressin occurred (1.86 +/- 0.05 pmol/L vs. 1.90 +/- 0.05, P = 0.33). Serum sodium and blood pressure remained unaffected. Moderate complaints, which could be ascribed to water retention, were recorded in four subjects [periorbital edema (n = 3), acral paraesthesia (n = 2) and light articular pain (n = 1)]. The symptoms were most pronounced after 2-3 days of treatment and diminished at the end of the period. In summary, 14 days of high dose GH administration caused a significant increase in ECV and a significant suppression of ANP.