Critical haemoglobin concentration in anaesthetized dogs: comparison of two plasma substitutes

We have explored systemic and regional tolerance to haemodilution during anaesthesia with two different synthetic colloids. Eighteen dogs undergoing mechanical ventilation during anaesthesia with ketamine were submitted to progressive normovolaemic haemodilution with either gelatin (GEL; n = 9) or hydroxyethylstarch (HES; n = 9) administered on a 1:1 ratio. Systemic oxygen delivery was calculated from measurement of thermodilution cardiac output and arterial oxygen content, while systemic oxygen consumption was determined from expired gas analysis. Mesenteric oxygen delivery and consumption were determined using ultrasonic flow measurements, and arterial and mesenteric venous oxygen contents. The critical haemoglobin concentration (i.e. the haemoglobin value below which oxygen consumption becomes oxygen delivery dependent) was mean 3.6 (SD 0.8) g dl-1 in the GEL and 3.5 (1.5) g dl-1 in the HES group. The mesenteric critical oxygen extraction ratio (O2ER) (GEL 50.1 (12.1)%; HES 48.5 (13.4)%) was significant lower than the systemic critical O2ER (GEL 66.1 (8.4)%; HES 67.7 (7.1)%). There were no significant differences between the GEL and HES groups for any of these variables, or in the amount of colloid administered. During the study, oxygen delivery decreased almost linearly with reduction in haemoglobin, indicating a lack of cardiac output response to anaemia during ketamine anaesthesia.

r-Hirudin inhibits platelet-dependent thrombosis during cardiopulmonary bypass in baboons

BACKGROUND

Systemic anticoagulation is required during cardiopulmonary bypass (CPB) to inhibit the activation of platelets, the coagulation system and ultimately thrombus formation. Unfractionated heparin is most commonly used, but it is neither entirely safe nor completely effective. The use of protamine sulphate to reverse the anticoagulant effect further complicates the use of heparin. The clinical need for a heparin substitute is therefore obvious. We evaluated the efficacy of r-Hirudin, a potent and specific inhibitor of thrombin, as anticoagulant in a baboon model of cardiopulmonary bypass.

METHODS

Ten baboons, divided into two groups of five each, were used. The one group received 0.7 mg/kg r-Hirudin as a bolus before CPB was started, followed by a constant infusion of 1.4 mg/kg/hr for the 90 min of CPB. The other group received a bolus of 2.5 mg/kg heparin before the start of CPB, followed by maintenance dosages to maintain the activated clotting time (ACT) >400 sec.

RESULTS

Adequate anticoagulation was obtained with both anticoagulants. Haemodilution due to priming the extracorporeal system with Ringer's lactate and appropriately anticoagulated donor blood, was equivalent in both groups. During CPB with heparin, but not with hirudin, there was a significant increase in the number of circulating platelet aggregates, thrombin-antithrombin (TAT) complexes and 111In-labelled platelet accumulation in the oxygenator. After the initial decrease in platelet count due to haemodilution, it further decreased significantly during CPB with heparin but remained relatively constant when r-Hirudin was used.

CONCLUSIONS

Our results strongly suggest that r-Hirudin is superior to heparin especially with respect to its inhibitory effect on platelet dependent thrombogenesis caused by the biomembranes of the oxygenator.

[Hemodynamic effects of hypertonic saline solutions]

Haemodynamic effects of hypertonic saline solutions (HSS) have been extensively studied in animals and humans. Hypertonic sodium chloride (7.5%, 2,500 mOsm.L-1) either alone or combined with colloids, remains the standard solution. The haemodynamic response of HSS observed during treatment of hypovolaemic shock is explained by 1) an increase in preload due to the expansion of the plasma volume and a musculocutaneous vasoconstriction and 2) a decrease in systemic vascular resistance and afterload. A myocardial stimulation has been shown in various experimental conditions and in humans. However, the clinical relevance of this inotropic effect is questionable. Haemorrhagic shock is the main indication for small volume resuscitation with HSS. Other potential situations for the use of HSS are volume replacement in perioperative period, septic shock or burn injury and cardiopulmonary resuscitation. Before recommending the clinical use of HSS, additional clinical studies are required to substantiate the benefits of HSS over colloids.

Effects of heparin, desmopressin, and isovolemic hemodilution with dextran on thrombus formation in synthetic vessel grafts inserted into the vena cava of the rabbit

The objective of this study was to investigate the effects of isovolemic hemodilution with dextran-70 on thrombus formation and blood flow in synthetic venous vessel grafts. Polytetrafluoroethylene grafts (length, 11 mm; inner diameter, 3 mm) were inserted into the vena cava of rabbits. Six groups were studied: (1) the control group; (2) animals that underwent isovolemic hemodilution with dextran-70 to a hematocrit of about 30%; (3) animals that underwent isovolemic dextran hemodilution combined with a bolus injection of heparin; (4) animals that underwent heparin treatment only; (5) animals that underwent isovolemic dextran hemodilution combined with infusion of desmopressin; and (6) animals that underwent an identical treatment to group 3 but with a 2-week, instead of a 2-day, follow-up. Vena cava blood flow was measured before and after hemodilution and graft insertion and at the termination of the experiments at 2 days (groups 1 to 5) and 2 weeks (group 6) after surgery. Graft patency and thrombus mass weight were evaluated. In the control group, most of the vessels occluded within 2 days. Hemodilution with dextran improved blood flow and reduced thrombus mass weight significantly. Desmopressin, which increases factor VIII, did not influence the effects of hemodilution with dextran, which suggests that the effects of dextran are not mediated by a reduction in the level of this coagulation factor. A single bolus dose of heparin did not reduce thrombus formation in the grafts but did potentiate the effects of isovolemic hemodilution on thrombus mass and graft blood flow. We conclude that isovolemic dextran hemodilution combined with a single bolus of heparin had beneficial long-lasting effects. The grafts in groups 3 and 6 were all patent.

Differential effects of serial hemodilution with hydroxyethyl starch, albumin, and 0.9% saline on whole blood coagulation

STUDY OBJECTIVES

To determine by thrombelastography assessed coagulation, the effects of progressive hemodilution with three intravascular volume expanders.

DESIGN

Prospective, controlled, whole blood, volumetric ex vivo hemodilution study.

SETTING

University of Pennsylvania Medical Center Operating Rooms.

PATIENTS

60 ASA physical status I and II patients; phlebotomy prior to administration of IV fluids or medications.

INTERVENTIONS

Analysis of whole blood clotting determined by six thrombelastographic channels for control and five volumetric hemodilutions (11%, 25%, 33%, 50%, and 75%) with 0.9% saline, 5% albumin, and 6% hydroxyethyl starch (n = 20 for each diluent group).

MEASUREMENTS AND MAIN RESULTS

Thrombelastographic parameters R (minutes), angle alpha (degree), MA (mm), and lysis (%) were measured and compared to the sample control for each dilution of the same specimen. There was no significant difference between control groups in any thrombelastographic variable (R, angle alpha, MA, or lysis). No changes were seen in any variable from any diluent at 11% hemodilution. Seventy-five percent hemodilution caused significantly hypocoagulable changes from control for all thrombelastographic parameters for all three diluents. Thrombelastographic indices differed significantly from controls at intermediate hemodilutions. Both colloids caused decreases in measured angle alpha and MA at lower hemodilution than did 0.9% saline. Albumin 5% caused significant hypocoagulable changes from control values at lower hemodilution than did either 0.9% saline or 6% hydroxyethyl starch for all thrombelastographic parameters. Saline 0.9% increased angle alpha significantly at 50% hemodilution. Abnormal lysis did not occur at any dilution. Differing ex vivo effects of three different intravascular fluids thrombelastography assessed coagulation are found.

CONCLUSION

No differences were found after 11% hemodilution with any volume expanders. Hemodilution with up to 50% saline maintained thrombelastographic indices. Albumin produced early and profound hypocoagulable effects. Significant hypocoagulability occurred for all three diluents at 75% hemodilution. The study supports the use of albumin in patients at risk for thrombosis, and saline in patients with a need for normal hemostasis.

[Effects of nitric oxide synthase inhibitor on skin blood flow responses to acute isovolemic hemodilution during halothane and isoflurane anesthesia]

Eighteen dogs under halothane or isoflurane anesthesia were subjected for a study in skin blood flow of the forearm under acute isovolemic hemodilution. Hematocrit was intentionally reduced to about 50% of baseline in ten minutes and hematocrit changes were induced by exchange of blood with hydroxyethyl starch. The skin blood flow increase response, measured by laser Doppler flowmetry, to hemodilution was abolished after inhibition of endogenous nitric oxide synthesis by N omega-nitro-L-arginine methyl ester. Skin blood flow responses to hemodilution and N omega-nitro-L-arginine methyl ester were different between halothane group and isoflurane group. Nitric oxide may have an important part to play in vasodilation during acute isovolemic hemodilution, and it may be affected differently by halothane and isoflurane.

No release of cardiac troponin I during major orthopedic surgery after acute normovolemic hemodilution

BACKGROUND

Normovolemic hemodilution is a well-accepted method for intraoperative blood salvage. However, some controversy exists concerning the possible risk of myocardial fiber injury as consequence of the reduced oxygen content. Laboratory diagnosis of perioperative myocardial fiber injury is difficult, since biochemical markers are elevated postoperatively due to the surgical trauma. Cardiac troponin I (cTnI) is a new, highly sensitive and specific marker for the detection of myocardial injury. The aim of our study was to investigate whether normovolemic hemodilution in patients with major orthopedic surgery (13 hemodiluted patients, 15 control) induces a release of cTnI.

METHODS

cTnI as a highly specific and sensitive cardiac parameter, as well as total creatine kinase (CK), creatine kinase isoenzyme MB mass (CKMB mass) and myoglobin were measured after induction of anesthesia, after normovolemic hemodilution, prior to retransfusion of blood components, 3 h after surgery, and on the first and third postoperative days.

RESULTS

Prior to retransfusion of blood components the hematocrit was decreased to 25.4 +/- 1.2% (mean +/- SEM; range: 18%-34%) in the control group and to 20.2 +/- 0.8% (mean +/- SEM; range: 17%-24%) in the hemodilution group. Total CK, CKMB mass as well as myoglobin concentration increased significantly in both groups, reaching their maxima within the first day of surgery. In contrast, cTnI was below the detection limit of assay (< 0.5 micrograms/L) at any time.

CONCLUSIONS

We suggest that pre- and intraoperative hemodilution to a hematocrit of approximately 20% by maintaining normovolemia does not induce myocardial fiber injury in patients without preexisting cardiac diseases.

Proposition of a technique to assess the vasoactive effects of hemoglobin-based oxygen carrying solutions in vivo: preliminary results in the rabbit aorta

Most of hemoglobin-based oxygen carriers (HBOCs) increase the blood pressure after injection in the blood stream by a mechanism involving one or more factors that contribute to the regulation of the vascular tone. Many techniques make it possible to study the vascular effects of HBOCs both in vivo and in vitro. The in vivo methods assess the blood pressure and some estimated regional blood flows (use of radioactive or colored microspheres). Measurements of the real vessel diameter and blood flow would be useful to understand hemoglobin-mediated vasoconstriction mechanism. Our purpose was to elaborate an experimental model in anesthetized rabbits to monitor the diameter and the blood flow velocity in the same vessel in order to calculate the absolute blood flow. The blood flow velocity (in cm/s) was assessed by pulsed Doppler velocimetry and the diameter (in mm) was assessed by a technique of Wall Tracking. The first results indicate that the method is well adapted to study the effects of resuscitative fluids (plasma and blood substitutes) on the aorta vascular tone after hemodilution or resuscitation from severe hemorrhage.

The influence of acute normovolemic hemodilution on the dose-response and time course of action of vecuronium

To evaluate the influence of acute isovolemic hemodilution on the dose-response and time course of action of vecuronium, we studied 60 adult patients with and without hemodilution during surgery. The patients with hemodilution underwent major elective plastic surgery with an anticipated surgical loss of more than 600 mL. Anesthesia was induced with thiopental 4-6 mg/kg and fentanyl 2-4 microg/kg i.v. and was maintained with 60% nitrous oxide in oxygen. Further increments of thiopental 2 mg/kg or fentanyl 2 microg/kg were given as required. Acute isovolemic hemodilution in the hemodilution group was induced by drainage of venous blood and an i.v. infusion of lactated Ringer's solution and 6% dextran, during which hematocrit and hemoglobin decreased from 45.7% to 26.2% and from 148.5 g/L to 90.2 g/L, respectively. Neuromuscular function was assessed mechanomyographically with train-of-four stimulation at the wrist every 12 s, and the percent depression of T1 response was used as the study parameter. The dose-response relationships of vecuronium in the two groups were determined by using the cumulative dose-response technique. The results showed that during hemodilution, the dose-response curve of vecuronium was shifted to the left in a parallel fashion, and the potency of vecuronium was increased. There were significant differences in the 50%, 90%, and 95% effective doses between the two groups. After the i.v. administration of vecuronium 80 microg/kg, vecuronium-induced neuromuscular block was significantly longer in the patients with hemodilution than in the control patients. The duration of peak effect, clinical duration, recovery index, and total duration in the hemodilution patients were significantly different from those in the control patients. We conclude that hemodilution induces significant changes in the pharmacodynamics of vecuronium.

IMPLICATIONS

We found that patients with hemodilution were 20% more sensitive to vecuronium and had a longer duration of action after the administration of the same dose than the controls. This should be taken into account when vecuronium is used as a muscle relaxant during acute hemodilution.

Acute normovolaemic haemodilution does not aggravate gastric mucosal acidosis during cardiac surgery

OBJECTIVE

Acute normovolaemic haemodilution with subsequent autologous blood transfusion after surgery is widely used to reduce homologous blood requirements during cardiac surgery. The hypothesis tested was whether a low intraoperative haematocrit (Hct) resulting from haemodilution decreases gastric mucosal pH (pHi).

DESIGN

Prospective clinical investigation.

SETTING

University Hospital of Vienna, Austria.

PATIENTS

16 consecutive patients scheduled for elective cardiac surgery.

INTERVENTIONS

The patients were randomly assigned to one of two groups: In 10 patients (group 1), 500 ml of blood was withdrawn and stored after anaesthesia induction. An equal amount of 6% hydroxyethyl starch was simultaneously infused. After discontinuation of cardiopulmonary bypass (CPB), the autologous blood unit was transfused. Six patients (group 2), who were not subjected to haemodilution and autologous blood transfusion served as controls. In all patients, a gastric tonometry probe was inserted.

MEASUREMENTS AND RESULTS

Measurements of pHi and Hct were performed before and after acute normovolaemic haemodilution, during pulsatile hypothermic (30-32 degrees C) CPB, after rewarming, and 30 min after autologous blood transfusion in group 1, and at corresponding time intervals in group 2. Repeated measures analysis of variance and the Mann-Whitney U test were used for statistical analysis. Data are presented as means +/- standard error of the mean. Haemodilution in group 1 caused a significant and persistent decrease in Hct (after haemodilution in group 1 34 +/- 1 vs 40 +/- 1% in group 2). In both groups, pHi decreased during rewarming and after termination of CPB. However, in group 1, pHi was better preserved than in group 2 (rewarming: 7.44 +/- 0.02 vs 7.34 +/- 0.04; after CPB: 7.38 +/- 0.03 vs 7.28 +/- 0.02; p < 0.05).

CONCLUSIONS

Acute normovolaemic haemodilution does not aggravate gastric mucosal acidosis during cardiac surgery.

IV perflubron emulsion versus autologous transfusion in severe normovolemic anemia: effects on left ventricular perfusion and function

Intact cardiac compensatory mechanisms are necessary to maintain adequate tissue oxygenation during acute normovolemic hemodilution (ANH). Left ventricular (LV) perfusion, oxygenation and function were analyzed in an experimental whole-body model of profound ANH (Hct 9%) and effectiveness of a perfluorocarbon-based oxygen carrier in maintaining myocardial oxygenation and function was evaluated. A total of 22 anesthetized dogs were hemodiluted to Hct 20% followed by a simulated, controlled blood-loss phase in which dogs were randomized to either: (1) 1:1 exchange of lost blood with autologous red blood cells (RBC-group), (2) 1:1 exchange with a colloid (control-group) and (3) 1:1 exchange with a colloid after a single dose of 1.8 g/kg BW perflubron i.v. (PFC-group). Myocardial oxygen delivery and consumption as well as endocardial perfusion were determined using radioactive microspheres. LV myocardial contractility (LV MC) was assessed from: (1) the relationship between maximum rate of LV pressure increase (LVdp/dtmax) and LV enddiastolic volume (LVEDV) and (2) analysis of the LV endsystolic pressure volume relationship (ESPVR). LV diastolic properties were reflected by (1) minimum rate of LV pressure increase (LVdp/dtmin), (2) slope and intercept of the enddiastolic pressure-volume relationship (EDPVR) and (3) the time-constant of isovolumic LV pressure decline "tau 1/2". Full sets of LV MC data were obtained from 18 dogs (n = 6 per group). LV MC (LVdp/dtmax-LVEDV relation) increased after perflubron administration. At the lowest Hct level, all parameters reflecting LV MC as well as LVdp/dtmin were significantly higher in the PFC-group than in the control-group. After profound normovolemic hemodilution (Hct 9%) superiority of LV MC and LV diastolic properties was found, when myocardial oxygenation was supported by i.v. perflubron emulsion, a temporary O2 carrier.

Autologous blood transfusion

Autologous blood transfusion is an endorsed blood conservation strategy that has become widely practiced in elective surgical procedures. We review ten years' experience in this arena, along with emerging strategies designed to continue to minimize allogeneic blood exposure but reduce the costs associated with autologous blood procurement. We conclude that point-of-care autologous blood procurement (acute normovolemic hemodilution and intraoperative autologous blood salvage) can replace the predonation of autologous blood in surgical patients when transfusion medicine specialists, anesthesiologists, and surgeons develop a prospective, comprehensive approach to blood conservation.

Intensive predeposit-hemodilution autologous blood donation and IOBS increase in erythropoietic levels in patients undergoing hip arthroplasty

Erythropoietin (EPO) plasma levels were monitored during the perioperative period in 61 consecutive patients (22 males - 39 females), aged 62.5 +/- 9.5 years, scheduled for hip arthroplasty. All patients underwent intraoperative blood salvage (IOBS) and were subdivided into three different groups according to their hemoglobin levels (Hb) 24 hours postoperatively (group A: Hb < 8 g/dl; group B: Hb between 8-9 g/dl; group C: HB > or = 9 g/dl). Seventy-two hours after surgery EPO levels were significantly different in group A (135 +/- 68) compared to group C (54.3 +/- 32), with a positive correlation (p < 0.01) between Hb and EPO levels. On the basis of these results we suggest that a programmed autologous red blood cell collection aimed at obtaining the lowest hemoglobin values during the first 24 hours after surgery, may be of clinical utility in preventing homologous blood needs.

Study of polymerized hemoglobin in experiment

Lyophilized polymerized hemoglobin has no group specificity and does not damage the kidney after 2 days of storage; its T/2 is 14-16 hours. P50 of solution prepared on the hemoglobin basis is 24-28 torr at 37 degrees C and pCO2, 40 torr in 0.05 M Tris-buffer, pH 7.4. As was shown in models of hemorrhagic shock in dogs, the hemodynamic properties of the solutions is such that it is capable of increasing the cardiac output and maintains the arterial pressure at the level close to initial one. Analysis of the oxygen expenditure suggests the expediency of using the solution in doses of 1 gr/kg of body weight. The increase in oxygen capacity of the solutions administered in the said dose is the result of increase in the hemoglobin concentration in blood plasma. Contribution of the solution to blood oxygen capacity is 12-13%. The solution of lyophilized modified hemoglobin can be used for correction of both hemodynamic disorders and decreased oxygen delivery to tissues in hemorrhagic shock.

Evaluation of the oxygen delivery ability of PEG-hemoglobin in Sprague-Dawley rats during hemodilution

Polyethylene glycol (PEG) conjugation allows bovine hemoglobin (Hb) to retain its oxygen delivery capability while increasing its plasma expansion capacity. To determine whether PEG-Hb's ability to sustain life is due to its oxygen delivery capability rather than its plasma expansion capacity, Sprague-Dawley rats were exchange-transfused up to an 85% hematocrit reduction with either PEG-Hb, PEG-50%-methemoglobin (PEG-mHb), PEG-carbon monoxide hemoglobin (PEG-COHb) or PEG-human serum albumin (PEG-HSA). Survival and respiratory rates were monitored during the exchange transfusion, at five minutes, 24 hours and 48 hours post operative. Rats surviving 14 days were evaluated for hematology, blood chemistry and histopathology. Rats infused with PEG-Hb had a survival rate of 100% during the transfusion and 79% at 24 hours, as compared to 24 hour survival rates of 30% for PEG-mHb, and 0% for both PEG-COHb and PEG-HSA. PEG-Hb treated rats that survived the 2 week observation period had normal hematological and blood chemistry levels and no significant morphological effects. Therefore, this study demonstrates that PEG-Hb can sustain life while similar plasma expansion agents with less oxygen delivery capability are not as effective.

Bovine haemoglobin-based oxygen carrier for patients undergoing haemodilution before liver resection

We have studied the use of ultrapurified polymerized bovine haemoglobin (HBOC-201) in patients undergoing preoperative haemodilution before liver resection. After autologous blood donation of 1 litre, 12 patients (six males, six females, mean age 59 (35-69) yr) received Ringer's lactate solution 2 litre and, in a random design, 6% hydroxyethyl starch 70,000/0.5 (HES) 3 ml kg-1 or HBOC-201 0.4 g kg-1 within 30 min. Blood samples were obtained for blood chemistry, co-oximetry, haematology, coagulation profiles and immunology examinations before operation, on the day of surgery, on days 2-4 and 7 after operation, on the discharge day and 3 months after operation. There were no differences in patient characteristics, blood loss, amount of solutions infused, transfused allogeneic blood or duration of hospital stay. There were no local or systemic allergic reactions with infusion of HES or HBOC-201. Patients receiving HBOC-201 developed more pronounced leucocytosis and reticulocytosis during the early postoperative days compared with HES-treated patients. The mean maximum plasma haemoglobin concentration was 1.0 (SD 0.2) g dl-1 at the end of infusion of HBOC-201 was 8.5 h. Patients in both groups experienced temporary changes in liver enzymes and coagulation variables which returned to normal before discharge. Urinalysis revealed no difference between groups and no free haemoglobin was detected in urine. Patients receiving HBOC-201 showed no IgE and only a slight increase in IgG titres to HBOC-201 on the day of discharge; these were not detectable at 3 months. Single-dose administration of HBOC-201 was well tolerated by patients undergoing elective liver resection surgery and appears to be safe as a substitute during preoperative haemodilution.

Vasoconstriction during acute hypervolemic hemodilution in hypertensive patients is not prevented by calcium blockade

The reduction of blood viscosity by moderate acute hypervolemic hemodilution in untreated hypertensives can be associated with a secondary vasoconstriction. The aim of this study was to examine whether a vasodilating therapy prevents this hemodynamic reaction. Twelve hypertensive patients (WHO stage II) were treated with the vasoselective calcium channel blocker isradipine in a placebo-controlled, double-blind, crossover study. Acute hypervolemic hemodilution was performed twice: at the end of the placebo period and after two months of treatment. Hemodilution was achieved by the intravenous infusion of 1000 mL saline over a 10- to 15-minute period. Arterial blood pressure, heart rate, cardiac output (dye dilution), renal blood flow, glomerular filtration, natriuresis, hematocrit, whole blood, and plasma viscosity were assessed before and after infusion. Flow resistance and vascular hindrance in the central and renal circulation were calculated. Acute hemodilution associated with a significant reduction of blood (P<0.01) and plasma (P<0.01) viscosity did not influence the mean arterial pressure and cardiac output. Consequently, the total flow resistance remained unchanged. However, as a result of hemodilution, the calculated vascular hindrance index in the systemic circulation increased, indicating a vasoconstrictive reaction, both with placebo (from 5.22 to 6.07 U x mPa(-1) x s(-1), P < 0.05) and during chronic treatment with calcium blockade (from 3.75 to 4.22 U x mPa(-1) x s(-1), P<0.02). Vasoconstriction was not observed in the renal circulation, either during the placebo or active treatments. The results of this study indicate that the systemic vasoconstriction evoked by the acute moderate hypervolemic hemodilution in hypertensive patients was not prevented by a calcium channel blockade.

The use of acute hemodilution in parturients undergoing cesarean section

OBJECTIVE

Concern over transmissible disease has increased interest in methods of minimizing homologous blood transfusion during elective surgery. One method is acute hemodilution, a technique previously unreported in parturients. This study was designed to determine its feasibility and safety in women at risk of hemorrhage during cesarean section.

STUDY DESIGN

This technique was performed on 38 parturients. Collected blood was retransfused at the end of surgery or earlier, if required. Hemoglobin was measured before hemodilution, after hemodilution, before transfusion, after transfusion, and 24 hours postoperatively. Neonatal assessment included umbilical blood gases and Apgar scores.

RESULTS

All patients were hemodynamically stable and no fetal heart rate abnormalities were observed during the procedure. One patient received homologous blood and 14 received previously donated autologous blood. Umbilical blood gases were normal and 5-minute Apgar scores were > or = 7.

CONCLUSION

This study suggests that acute hemodilution is well tolerated in parturients undergoing cesarean section. This may limit exposure to homologous blood transfusion.

[Effect of acute moderate isovolumic hemodilution on the pharmacokinetics of vecuronium]

OBJECTIVE

To determine the effect of acute moderate isovolemic hemodilution on pharmacokinetics of vecuronium.

METHODS

Twenty-six adult patients, ASA grade I, undergoing elective plastic surgery, were randomly divided equally into the control and hemodilution group. The blood samples were taken for 5 hours following intravenous bolus of 100 micrograms/kg of vecuronium in two groups. The plasma concentrations of vecuronium were determined with an improved fluorometry and the pharmacokinetic parameters were obtained by fitting the data with a 3P87 program.

RESULTS

The disposition of vecuronium can be best described by a three compartment open model. As comparison with the control group, the values of Vc and Vdss in hemodilution group were greater than that in the control, while T1/2 beta was markedly prolonged in this group. There were no significant differences in T1/2 phi, T1/2 alpha, K12, K21, K13, K31, K10, MRT, AUC, and Cl between the two groups.

CONCLUSION

Acute moderate isovolemic hemodilution could change the pharmacokinetics of vecurinium, particularly in distribution and elimination phases.

Acute normovolemic hemodilution can replace preoperative autologous blood donation as a standard of care for autologous blood procurement in radical prostatectomy

Predonation of autologous blood (PAD) is a standard of care for patients undergoing radical prostatectomy, but recent studies have shown that PAD is not cost-effective. Acute normovolemic hemodilution (ANH) is an alternative autologous blood procurement technique that is much less costly than PAD. We compared the efficacy and costs of ANH alone to ANH combined with PAD. Two hundred-fifty patients who predonated fewer than 3 units of autologous blood before radical prostatectomy underwent ANH to a target hematocrit of 28%. Perioperative hematocrit levels, transfusion outcomes and costs, and postoperative outcomes were compared for patients who predonated 0, 1, or 2 units of blood before surgery. A computer model was used to estimate the savings in red blood cells (RBC) associated with each autologous intervention. ANH alone resulted in a 21% allogeneic transfusion rate and contributed a mean net savings of 112 mL RBC in blood conservation (equivalent to 0.6 unit of blood). The addition of 1 or 2 units of PAD reduced allogeneic exposure rates to 6% or 0%, respectively. Overall, patients who predonated blood had a mean net loss of 198 mL of RBC (equivalent to 1 blood unit), due to both an absence in compensatory erythropoiesis and to the wastage of 60% of the blood units donated. Patients who underwent ANH alone had a 60% reduction in mean total transfusion costs ($103 +/- $102) compared with patients who predeposited 2 units of autologous blood in addition to ANH ($269 +/- $11, P < 0.05). We conclude that ANH can replace PAD as an autologous blood option because it is less costly and equally effective. A combination of ANH and PAD can further decrease allogeneic blood exposure, but it increases transfusion costs and wastage.

IMPLICATIONS

A patient's own blood can be obtained for use in surgery by predonation or acute normovolemic hemodilution on the day of surgery. Both blood collection techniques decrease the need for blood bank transfusions, but acute normovolemic hemodilution is less expensive and more convenient for patients.

In vitro evaluation of the effect of profound haemodilution with hydroxyethyl starch 6%, modified fluid gelatin 4% and dextran 40 10% on coagulation profile measured by thromboelastography

Synthetic colloids have been implicated as a cause of coagulopathy when administered in large quantities. The effect of profound haemodilution (50%) on coagulation profile was measured in vitro by thromboelastography. Blood samples were taken from 11 ASA grade 1 patients prior to induction of anaesthesia for elective surgery. Each sample was simultaneously tested in four different preparations: undiluted blood (control sample); blood diluted with hydroxyethyl starch 6%; blood diluted with modified fluid gelatin 4%; blood diluted with dextran 40 10%. There was a significant decrease in reaction time in the preparations treated with hydroxyethyl starch 6% and modified fluid gelatin 4%, reflecting activation of initial fibrin formation. A significant increase in clot formation time was noted in the hydroxyethyl starch 6%-treated preparations. There was also a significant decrease in clot formation rate and maximum amplitude in the hydroxyethyl starch 6% group. Clot formation time, clot formation rate and maximum amplitude did not change in the modified fluid gelatin 4% group. Profound haemodilution with dextran 40 10% exerted extreme effects on the measured variables, very often resulting in a straight line on the thromboelastography profile.