Hyperdynamic therapy: the nurse's role in the treatment of cerebral vasospasm

The onset of subtle diffuse ischemic neurological deficits often associated with cerebral vasospasm is a major cause of morbidity and mortality following aneurysmal subarachnoid hemorrhage. The exact etiology of cerebral vasospasm is unclear. Increasing intravascular volume, decreasing blood viscosity and inducing hypertension may help prevent or diminish neurological deficits from cerebral vasospasm by improving cerebral blood flow. An intensive multidisciplinary approach is necessary with the role of the neuroscience nurse being pivotal. An understanding of the subtle neurological changes suggestive of cerebral vasospasm and its effects leads to early recognition, and allows for rapid institution of therapy.

[Methods of preoperative hemodilution to reduce homologous blood transfusion]

Many problems arise from homologous blood transfusion in operative patients. The virtues include reduced likelihood of reactions to transfused blood and reduction or elimination of the risk of alloimmunization and transfusion transmitted diseases such as hepatitis C and the human immunodeficiency virus. Provided that skillful surgical technique is applied and the use of blood products is restricted, autologous transfusion techniques (predonation of autologous blood, preoperative plasmapheresis, acute normovolemic hemodilution, and intra- and postoperative blood salvage) can be performed with an acceptable risk for patients. Preoperative collection of blood with hemodilution is a simple method to allow autologous blood transfusion. To have recourse to apheresis techniques allows to increase the number of autologous transfused patients.

Haemodynamic changes and skeletal muscle oxygen tension during complete blood exchange with ultrapurified polymerized bovine haemoglobin

OBJECTIVE

The study investigates the effect of continuous blood exchange with ultrapurified, polymerized bovine haemoglobin (UPBH) in comparison to hetastarch on haemodynamics, oxygen transport and skeletal muscle oxygen tension in a canine model.

DESIGN

Sixteen anaesthetized beagle dogs underwent haemodilution with lactated Ringer's to a starting haematocrit of 20% followed by progressive blood exchange with 6% hetastarch 200,000/0.5 (HES, group 1) or UPBH (haemoglobin 13 +/- 1 g.dl-1, molecular weight (MW) 32-500,000, group 2) to haematocrit target levels of 15%, 10% and 5% or less.

MEASUREMENTS AND RESULTS

Besides haemodynamics, skeletal muscle tissue oxygen tension (tPO2) was measured using a polarographic needle probe. In HES-treated animals, heart rate, cardiac output and blood flow were higher while systemic vascular resistance, systemic and regional arterio-venous oxygen difference (avDO2) and oxygen extraction ratios were lower when compared to the UPBH group. In spite of a higher final haematocrit of 5% in group 1, in comparison to group 2 with 2%, final muscular oxygen uptake (4.7 +/- 4 vs 10.1 +/- 2 ml.min-1) and mean tPO2 (11.8 +/- 2.3 vs 51.1 +/- 2.9 mm Hg) were lower in group 1 than in group 2. While tPO2 histograms were continuously shifted to lower oxygen tensions during progressive haemodilution with HES, UPBH-exchanged animals showed tPO2 histograms shifted to higher values than baseline.

CONCLUSION

In spite of vasoconstriction, UPBH provided more haemodynamic stability and enhanced skeletal muscle tPO2 during progressive blood exchange when compared to HES.

[Experimental isovolemic hemodilution. Study of tissue perfusion with Hb 3% in swine]

BACKGROUND

The aim of the study is to evaluate the limits of the compensatory mechanisms and the tissue damages caused by the low oxygen content during severe normovolemic hemodilution in pigs.

METHODS

The experimental procedure was performed in 10 animals after general anaesthesia was induced and iso-hypervolemic hemodilution to Hct 10% was maintained for five hours without any intensive care. Hemodynamic, biochemical and ultrastructural parameters were detected before and at the end of hemodilution in addition to analysis of oxygen delivery/uptake and mitochondrial enzymes function.

RESULTS

The collected data show: the initial good compensatory mechanism was subsequently exhausted; five animals demonstrated cardiac ischemia and low CO and two of them died before the end of the experiment; no hemodynamic and hemoxymetric data predicted the cardiac ischemia; the dilution caused alterations of some detected biochemical parameters such as hemocoagulation; no evidence of morphologic and ultrastructural tissue damage or interstitial edema; decreasing in mitochondrial enzymes activity significant only for NADH-related.

CONCLUSIONS

In conclusion, it seems that, in pigs at least, the compensatory mechanisms can keep a sufficient tissue oxygen supply throughout the experimental time with the exception of cardiac muscle.

Isovolemic hemodilution with purified and polymerized bovine hemoglobin in a rabbit model of focal cerebral ischemia

Isovolemic hemodilution with polymerized bovine hemoglobin (PoBH) was tested as a means of preventing infarction in a rabbit model of focal cerebral ischemia. The animals were divided into one control group and one hemodilution group. All animals underwent two hours of ischemia, caused by clipping the left internal carotid artery, the anterior cerebral artery, and the middle cerebral artery, followed by 4 hours of reperfusion. In the control group, the hematocrit was not manipulated (mean +/- SE: 33.8 +/- 1.3%), while in the hemodilution group, the Hct was reduced to 12.5 +/- 1.9% by exchange of blood with PoBH, before clipping the cerebral vessels. Staining with 2,3,5- triphenyltetrazolium chloride (TTC) was used to evaluate the infarct size. The infarct volume was 427 +/- 52 mm3 in the control animal, and 1026 +/- 311 mm3 (p < 0.01 when compared with the control group) in the animal hemodiluted with PoBH. PoBH hemodilution was found to be associated with vasoconstriction. This pathological vasoconstriction probably counteracted any beneficial effects from the lowered viscosity and explains our negative results. Vasoconstriction has to be overcome before hemodilution can have its beneficial effect in reducing the cerebral ischemia.

Hemodilution with other blood reinfusion techniques in total hip arthroplasty

Acute normovolemic hemodilution has been reported to result in blood savings varying from 18% to 90%. Very few of these are randomized prospective studies. This study attempts to determine the blood transfusion savings if acute normovolemic hemodilution is used in combination with autologous predonated blood and cell saver. Thirty-three patients undergoing total hip arthroplasty were assigned randomly to one of two groups (control, n = 16; hemodilution, n = 17). Patients in both groups entered an autologous predonation program if cleared medically and were placed on Cell Saver intraoperatively and in the postanesthesia care unit. In addition, the hemodilution group underwent acute normovolemic hemodilution preoperatively. Only 41% of the patients in the hemodilution group required any autologous blood transfusion as compared with 75% of the control group. In addition, the hemodilution group required a mean lower quantity of autologous blood transfusion (41% of the estimated blood loss) as compared with the control group (71%). The net anesthesia time increased by an average of 11.4 minutes in the hemodilution group. Acute normovolemic hemodilution is a safe procedure even in an older patient population. Hemodilution resulted in fewer patients needing autologous predonated blood transfusions. The major benefit of hemodilution was seen when predonation was not possible.

Reduction of myocardial ischemia-reperfusion injury by isovolumic hemodilution

In order to study the effects of isovolumic hemodilution and its combination with Danshen solution on acute ischemic reperfused canine myocardium, 24 adult hybrid dogs were used and divided into four groups. Group I was the control group, groups II-IV were treated with Dextron 40, Danshen solution and a combination of the two, respectively. The results showed that either Dextron 40 or Danshen solution alone had a significant increase of +/- dp/dt-max when compared with group I (p < 0.05). Although no significant difference existed between group II and III, the former showed more rapid action. The combination of the two therapies improved +/- dp/dt-max and LVSP, and significantly reduced the necrotic sizes and the MDA contents in the ischemic myocardia compared with not only group I, but also group II or group III (all p < 0.05). The results suggest that isovolumic hemodilution or Danshen may protect the ischemic reperfused myocardium and the former may come into action more rapidly, and that the combination of the two may show a better synergism than each one of the two by itself.

Mathematical considerations in the practice of acute normovolemic hemodilution

BACKGROUND

Acute normovolemic hemodilution (ANH) is recommended as a simple and cost-effective method of autologous transfusion. The present mathematical model, based on the current clinical practice of removing 2 to 3 units of fresh whole blood, defines the indications for ANH.

STUDY DESIGN AND METHODS

A mathematical model and subsequent nomograms were developed to define patients for whom removal of 2 to 3 units (450 mL each) would allow a theoretical red cell savings equivalent to 1 unit of packed red cells (volume, 250 mL; hematocrit, 60%), that is, a successful application of the technique. Minimal safe target hematocrits were defined as 30, 26, and 22 percent.

RESULTS

The minimal initial hematocrits required for given patient weights are displayed on nomograms derived from the mathematical model. The nomograms also indicate the surgical blood loss allowed without ANH: for example, a 75-kg man, (2-unit ANH, minimal safe hematocrit 22%) requires a minimal initial hematocrit of 42 percent (surgical blood loss of 0.64 x estimated blood volume = 3100 mL).

CONCLUSION

ANH involving the removal of 2 to 3 units (450 mL each) may be useful in patients with anticipated blood loss exceeding 50 percent of estimated blood volume, high initial hematocrit, and a capacity to tolerate dilution-induced anemia.

Application of HELP in nonarteritic anterior ischemic optic neuropathy: a prospective, randomized, controlled study

BACKGROUND

Heparin-induced extracorporeal LDL/fibrinogen precipitation (HELP) eliminates selectively fibrinogen, LDL, cholesterol, triglycerides and LP(a) from blood plasma using extracorporeal circulation. The reduction of fibrinogen and LDL by about 50% after only one procedure immediately improves the hemorheological situation.

METHOD

In a prospective, randomized, controlled study over a period of 3 months, 40 patients with nonarteritic ischemic optic neuropathy (NAION) were randomly assigned to either HELP or hemodilution therapy to determine the efficacy of these two treatments on visual acuity and fields.

RESULTS

After transformation of the Snellen acuity into logMAR units the statistical analysis did not show a significant difference between the two groups (P = 0.48). An increase of the visual acuity by two or more lines was obtained in 9 patients (47.4%) of the HELP group, 10 (52.6%) remained stable and none got worse. In the hemodilution group, visual acuity increased in patients (33.4%), 9 (42.8%) remained stable and 5 (23.8%) experienced a decrease. The calculated mean sensitivity of visual fields at baseline improved statistically significantly (P < 0.01) in the HELP group from 6.83 +/- 4.52 dB to 8.27 +/- 4.89 dB, but did not change significantly in the hemodilution group (6.25 +/- 4.12 dB to 6.12 +/- 3.92 dB).

CONCLUSION

The HELP system seems to be safe and more effective than hemodilution in improving the hemorheological and the functional situation in NAION and could be a promising regimen in the treatment of NAION.

Preoperative acute hypervolemic hemodilution with hydroxyethylstarch: an alternative to acute normovolemic hemodilution?

Acute normovolemic hemodilution (ANH) may help to reduce demand for homologous blood but requires extra time and apparatus. A more simple procedure is acute hypervolemic hemodilution (HHD), where hydroxyethylstarch is administered preoperatively without removal of blood. In a prospectively randomized study we compared ANH (preoperatively 15 mL/kg autologous blood removal and replacement with 15 mL/kg of hydroxyethylstarch with HHD (15 mL/kg of hydroxyethylstarch administered preoperatively) in 49 patients undergoing hip arthroplasty. To avoid excessive intravascular volume, we used the vasodilating effect of isoflurane. No significant differences were found between groups (ANH, n = 23; HHD, n = 26) for intraoperative blood loss (ANH versus HHD, median [minimum-maximum]); 545 [295-785] mL versus 520 [315-825] mL) and postoperative blood loss (730 [525-945] mL versus 780 [495-895] mL), postoperative hemoglobin, hemotocrit, platelet count or coagulation variables, and transfusion requirements (ANH 43% versus HHD 35% of patients received homologous blood) (P > 0.05). Heart rate did not change significantly in either group. In the ANH group mean arterial blood pressure (MAP) decreased after hemodilution (P < 0.05) while in the HHD group MAP did not change over time. Mean time required to perform ANH was 58 (46-62) min versus HHD 16 (12-19) min (P < 0.05). Costs for ANH were $63.60 USD and for HHD $32.75 USD (labor costs not included). In orthopedic patients undergoing hip replacement with a predicted blood loss of about 1000 mL, HHD seems to be a simple as well as time- and cost-saving alternative for ANH.

Global tissue oxygenation during normovolaemic haemodilution in young children

Sixteen patients (1-8 years) scheduled for major general surgery were chosen for the study. They were divided into two groups according to the replacement solution used for haemodilution (HD); whether 6% middle molecular weight hydroxyethyl starch (HES) or 6% dextran 60 (DEX). After induction of general anaesthesia and pulmonary artery catheterization, a precalculated amount of autologous blood was withdrawn while the patient's autologous blood was simultaneously replaced by either HES or DEX. Autologous blood was retransfused at a minimum haematocrit (Hct.) of 17% or at the end of surgery. The following parameters were measured and/or calculated before and after HD, every 20 min intraoperatively and hourly for 6 h postoperatively: heart rate (HR), mean arterial pressure (MAP), Cardiac index (CI), Hct., arterial and mixed venous oxygen content (CaO2, CvO2) and arterio-venous difference of oxygen content (avDO2), oxygen delivery index (DO2I), oxygen consumption index (VO2I). The cardiovascular system remained stable. There was no significant difference as regards SvO2, despite a significant decrease in CaO2 to 10.8 and 10.0 ml.dl-1 (median values) due to reduction of haemoglobin concentration in the HES and DEX groups respectively. In spite of the low hct. values during surgery DO2I remained in normal range (median value 602 and 710 ml.min-1.m-2) in HEX and DEX group respectively. There was no significant change in VO2I after haemodilution (median value 212 and 243 ml.min-1.m-2) in either group. No statistically significant difference was noticed between either groups regarding: CaO2, CvO2, DO2I, VO2I, and no side effects of the colloids were observed. Isovolaemic haemodilution (Hct. approximately 17%) is well tolerated by young children undergoing major elective surgery; global tissue oxygenation was preserved throughout the procedure and both solutions used for haemodilution were equally effective.

Higher hematocrit improves cerebral outcome after deep hypothermic circulatory arrest

BACKGROUND

Various degrees of hemodilution are currently in clinical use during deep hypothermic circulatory arrest to counteract deleterious rheologic effects linked with brain injury by previous reports.

MATERIAL AND METHODS

Seventeen piglets were randomly assigned to three groups. Group I piglets (n = 7) received colloid and crystalloid prime (hematocrit < 10%), group II piglets (n = 5) received blood and crystalloid prime (hematocrit 20%), group III piglets (n = 5) received blood prime (hematocrit 30%). All groups underwent 60 minutes of deep hypothermic circulatory arrest at 15 degrees C with continuous magnetic resonance spectroscopy and near-infrared spectroscopy Neurologic recovery was evaluated for 4 days (neurologic deficit score 0, normal, to 500, brain death; overall performance category 1, normal, to 5, brain death). Neurohistologic score (0, normal, to 5+, necrosis) was assessed after the animals were euthanized on day 4.

RESULTS

Group I had significant loss of phosphocreatine and intracellular acidosis during early cooling (phosphocreatine in group I, 86.3% +/- 26.8%; group II, 117.3% +/- 8.6%; group III, 110.9% +/- 2.68%; p = 0.0008; intracellular pH in group I, 6.95 +/- 0.18; group II, 7.28 +/- 0.04; group III, 7.49 +/- 0.04; p = 0.0048). Final recovery was the same for all groups. Cytochrome aa3 was more reduced in group I during deep hypothermic circulatory arrest than in either of the other groups (group I, -43.6 +/- 2.6; group II, -16.0 +/- 5.2; group III, 1.3 +/= 3.1; p < 0.0001). Neurologic deficit score was best preserved in group III (p < 0.05 group II vs group III) on the first postoperative day, although this difference diminished with time and all animals were neurologically normal after 4 days. Histologic assessment was worst among group I in neocortex area (group I, 1.33 +/- 0.3; group II, 0.22 +/- 0.1; group III, 0.40 +/- 0.2, p < 0.05, group I vs group II; p = 0.0287, group I vs group III).

CONCLUSION

Extreme hemodilution during cardiopulmonary bypass may cause inadequate oxygen delivery during early cooling. The higher hematocrit with a blood prime is associated with improved cerebral recovery after deep hypothermic circulatory arrest.

Isovolemic hemodilution increases retinal tissue oxygen tension

BACKGROUND

Therapeutic isovolemic hemodilution has been reported to improve blood flow and oxygen delivery. Few reliable measurements have been made, however, showing the effect of hemodilution on tissue oxygen tension.

METHODS

We measured retinal oxygen tension during experimental isovolemic hemodilution in normal cats. Polarographic oxygen microelectrodes were placed in the vitreous humor within 100-200 microns of the retinal surface.

RESULTS

Tissue oxygen tension increased initially during isovolemic hemodilution to a maximum approximately 50% above baseline at approximately two thirds of the original hematocrit level. Hemodilution beyond this point to lower hematocrits caused a steady decline in tissue oxygen tension. Cardiac output measured in one cat undergoing isovolemic hemodilution increased as hematocrit was lowered, but the cardiac erythrocyte flux actually decreased steadily.

CONCLUSION

The observed increase in tissue oxygen tension with hemodilution appears to be explained by a lesser reduction in capillary than in systemic hematocrit, coupled with an increased capillary blood flow. The increase in tissue oxygen tension we observed could in part explain the clinically beneficial effects of hemodilution.

[Changes in coagulation physiology and rheology after preoperative normovolemic hemodilution]

AIM

In a prospective randomised controlled trial the effect of preoperative normovolaemic haemodilution on coagulation, plasma viscosity and plasma protein levels was examined.

METHOD

50 patients undergoing gastrectomies were investigated (haemodilution group, n = 30; control group, n = 20). In the haemodilution group a haematocrit of 30% was aimed at. Blood was replaced by normovolaemic infusion of 6% hydroxyethyl starch 200/0.5.

MAIN RESULTS

Haematocrit, colloid osmotic pressure, total serum protein, serum albumin and platelet count were significantly decreased intra- and postoperatively in the haemodilution group compared with control group (p < 0.01). All of these showed no differences between the two groups on the 7th postoperative day. Global coagulation parameters showed dilutional influences without significant differences between the two groups. Measurements of rheological parameters showed a statistically significant decrease in plasma viscosity in the haemodilution group compared with control group (p < 0.01). Haemodilution led to a marked reduction in the use of homologous blood (1 unit/haemodilution group; 10 units/ control group). The average volume of 6% hydroxyethyl starch 200/0.5 administered per patient was 15.2 ml/kgKM/d (7.6-22.2 ml/kgKM/d) in the haemodilution group and 12.7 ml/ kgKM/d (8.4-17.7 ml/kgKM/d) in the control group.

CONCLUSION

Haemodilution induced decreases in plasma coagulation, platelet count and plasma proteins did not cause any functional impairement and may just reflect dilution of these parameters. It seems that infusion of 6% hydroxyethyl starch 200/0.5 in an amount of 10-20 ml/kgKM/d does not result in a relevant decrease in coagulation parameters.

[Acute effects of complete blood exchange with ultra-purified hemoglobin solution or hydroxyethyl starch on liver and kidney in the animal model]

OBJECTIVE

The present animal study investigates the influence of an acute and almost complete isovolaemic haemodilution with a new ultrapurified polymerized bovine haemoglobin (UPBH) on hepatic and renal function and histology in comparison to hydroxyethylstarch (HES).

METHODS

Eighteen anaesthetized dogs underwent progressive isovolaemic haemodilution with either HES (group 1) or UPBH (group 2) to haematocrit target levels of 15, 10 and < 5%. Haemodynamics, arterial and mixed-venous blood gases and blood chemistry were determined at each measurepoint. With a haematocrit value < 5%, biopsies were taken from the liver and kidneys and prepared for light and electron microscopic analysis. One dog without haemodilution figured as control animal. Statistical analysis was performed using ANOVA, with p < 0.05 considered significant.

RESULTS

In group 1, the cardiac output was increased in parallel to a decreasing vascular resistance, while in group 2 haemodynamic parameters remained unchanged. In group 1, avDO2 and final DO2 and VO2 were decreased. In contrast, avDO2 and oxygen extraction ratio were increased, while VO2 remained stable under decreasing DO2 in group 2. In both groups, coagulation values and blood chemistry showed dilution dependent changes. Colloid osmotic pressure and plasma viscosity were increased in both groups but COP was higher in group 1 compared to group 2. A lower urine output in comparison to group 1 and a maximal concentration of 0.27 g/dl of free haemoglobin in urine were seen in group 2. Liver biopsies showed no severe histological changes in both groups. Renal histology revealed severe alterations of proximal tubules after haemodilution with HES. In contrast, no histological indications for acute toxic or ischaemic lesions in the kidneys were seen after UPBH treatment.

CONCLUSION

The high degree of purification and polymerization of bovine haemoglobin associated with adequate tissue oxygenation by increased oxygen extraction resulted in normal histological and functional findings after acute and almost complete blood exchange with UPBH. In contrast, HES-treated animals showed severe histological changes of renal tubuli caused by isovolaemic anaemia.

A randomised prospective study of outpatient haemodilution for central retinal vein obstruction

PURPOSE

Central retinal vein obstruction (CRVO) has significant visual morbidity. We prospectively evaluated an outpatient haemodilution (HD) regimen for CRVO.

METHODS

We recruited 59 patients with CRVO of less than three months' duration and visual acuity (VA) worse than or equal to 6/9.5. Thirty patients underwent HD (packed cell volume of <0.35, 12 weeks); there were 29 controls and follow-up was for six months.

RESULTS

Incidence rates for VA improvement (P = 0.708) and rubeosis iridis (P = 0.619) between the two groups were not different. The incidence rate of VA deterioration was 5.315 times higher with HD (P = 0.035, Cox Proportional analysis).

CONCLUSION

This data does not support the previous studies on haemodilution.

Consensus conference on autologous transfusion. Acute normovolaemic haemodilution

ANH is a relatively cheap and logistically straightforward method of autologous transfusion which is attractive in that it may be applied to a wide cross-section of patients, many of whom will not be suitable for pre-deposit. There are, however, concerns about the safety of the procedure, and doubts have been expressed about its efficacy in reducing allogeneic transfusion requirements and, therefore, its cost-effectiveness. Assessment of the value of the procedure is hampered by the lack of large scale prospective, controlled trials. In the present state of knowledge it seems that ANH is most likely to be safe, efficacious and cost-effective when undertaken aggressively (target haematocrit < 0.20) in otherwise healthy, young patients undergoing elective surgery with large expected blood losses.

The impact of pre-donated autologous blood and intra-operative isovolaemic haemodilution on the outcome of transfusion in patients undergoing radical retropubic prostatectomy

OBJECTIVE

To assess the impact of pre-donated autologous blood and intra-operative isovolaemic haemodilution on the outcome of transfusions in patients undergoing radical retropubic prostatectomy.

PATIENTS AND METHODS

The charts and transfusion records of 192 consecutive patients undergoing radical retropubic prostatectomy were reviewed retrospectively.

RESULTS

Of 192 patients, 14% required homologous transfusions, the rate of which varied significantly depending upon blood availability (autologous, haemodilution or homologous) (P < 0.001): 66% of patients with only autologous blood available were transfused a mean of 1.96 units (range 1-6) of blood, of which 87% received autologous alone. 12% both autologous and homologous and 1% homologous blood only. Of the pre-donated autologous units, 44% were wasted.

CONCLUSIONS

Both the pre-donation of autologous blood and intra-operative isovolaemic haemodilution lower the risk of homologous blood transfusion. It is recommended that patients pre-donate 2 units of autologous blood and undergo intra-operative isovolaemic haemodilution before radical prostatectomy.

The effects of hemodilution with polyethylene glycol bovine hemoglobin (PEG-Hb) in a conscious porcine model

BACKGROUND

Severe hemodilution in large mammals has been used rigorously for the safety and efficacy testing of hemoglobin-based red blood cell substitutes. The effects of hemodilution with polyethylene glycol-modified bovine hemoglobin (PEG-Hb) were investigated in an unanesthetized porcine model.

METHODS

Immature Yorkshire cross barrow pigs were subjected to exchange transfusion with PEG-Hb (n = 6) or dextran 70 (n = 4) until an 80% reduction in hematocrit was achieved.

RESULTS

All six (100%) PEG-Hb-infused pigs and only one (25%) dextran 70 control pig survived the resultant reduction in erythrocytes. Heart rates and mean arterial pressure were not significantly affected by PEG-Hb infusion. Pigs infused with PEG-Hb maintained normal levels of blood pH, PO2, and PCO2 while dextran 70 controls showed low PvO2, PaCO2, and the development of acidosis. Histological evaluation revealed that the surviving dextran 70 control animal exhibited possible anoxia-induced hepatic centrilobular necrosis. PEG-Hb-treated pigs demonstrated the presence of renal tubular cell cytoplasmic vacuoles and vacuolated macrophages in spleens.

CONCLUSIONS

The results indicate that PEG-Hb effectively supports life close to lethal levels of anemia.