Hemodilution

Relationship between perioperative cardiopulmonary bypass time, platelet count, fibrinogen level, rotational thromboelastometry data, antithrombin level, and blood loss volume and the effects of deep hypothermic circulatory arrest: An observational study

INTRODUCTION

We hypothesized that perioperative fibrinogen level, platelet count, and rotational thromboelastometry (ROTEM) data values decrease in proportion to cardiopulmonary bypass (CPB) time, particularly in patients who underwent deep hypothermic circulatory arrest (DHCA).

METHODS

A total of 160 patients were enrolled and divided into the following three groups depending on CPB time: <2-h, 2- 3-h, and >3-h groups. Blood samples were obtained during CPB weaning. Platelet count, ROTEM data, fibrinogen level, and antithrombin level were determined. For propensity matching, we selected 15 patients who underwent DHCA and 15 patients who did not undergo DHCA and used propensity scores to match CPB time and other characteristics.

RESULTS

The <2-h, 2-3-h, and >3-h groups included 74, 63, and 23 patients, respectively. No significant differences in platelet count and fibrinogen level were observed between the groups. Antithrombin level and amplitude of clot firmness at 10 min in the EXTEM and FIBTEM tests were lowest in the >3-h group. Similarly, blood loss volume and transfusion volume were highest in the >3-h group. Significant differences in platelet count, ROTEM data, lowest esophageal and bladder temperatures, and transfusion volume were observed between patients who underwent DHCA and patients who did not undergo DHCA.

CONCLUSIONS

The longer the CPB time, the greater the perioperative blood loss volume and transfusion volume, particularly if CPB time is greater than 3 hours. Sub-group analysis revealed that DHCA affects perioperative platelet count and function as well as blood loss volume.

Hidden Blood Loss and Its Possible Risk Factors in Full Endoscopic Lumbar Interbody Fusion

BACKGROUND

Full endoscopic lumbar interbody fusion (Endo-LIF) is a representative recent emerging minimally invasive operation. The hidden blood loss (HBL) in an Endo-LIF procedure and its possible risk factors are still unclear.

METHODS

The blood loss (TBL) was calculated by Gross formula. Sex, age, BMI, hypertension, diabetes, ASA classification, fusion levels, surgical approach type, surgery time, preoperative RBC, HGB, Hct, PT, INR, APTT, Fg, postoperative mean arterial pressure, postoperative heart rate, Intraoperative blood loss (IBL), patient blood volume were included to investigate the possible risk factors by correlation analysis and multiple linear regression between variables and HBL.

RESULTS

Ninety-six patients (23 males, 73 females) who underwent Endo-LIF were retrospective analyzed in this study. The HBL was 240.11 (65.51, 460.31) mL (median [interquartile range]). Fusion levels (p = 0.002), age (p = 0.003), hypertension (p = 0.000), IBL (p = 0.012), PT (p = 0.016), preoperative HBG (p = 0.037) were the possible risk factors.

CONCLUSION

Fusion levels, younger age, hypertension, prolonged PT, preoperative HBG are possible risk factors of HBL in an Endo-LIF procedure. More attention should be paid especially in multi-level minimally invasive surgery. The increase of fusion levels will lead to a considerable HBL.

Effects of different plasma expanders on rats subjected to severe acute normovolemic hemodilution

BACKGROUND

Plasma expanders are widely used for acute normovolemic hemodilution (ANH). However, existing studies have not focused on large-volume infusion with colloidal plasma expanders, and there is a lack of studies that compare the effects of different plasma expanders.

METHODS

The viscosity, hydrodynamic radius (R_h) and colloid osmotic pressure (COP) of plasma expanders were determined by a cone-plate viscometer, Zetasizer and cut-off membrane, respectively. Sixty male rats were randomized into five groups with Gelofusine (Gel), Hydroxyethyl Starch 200/0.5 (HES200), Hydroxyethyl Starch 130/0.4 (HES130), Hydroxyethyl Starch 40 (HES40), and Dextran40 (Dex40), with 12 rats used in each group to build the ANH model. ANH was performed by the withdrawal of blood and simultaneous infusion of plasma expanders. Acid-base, lactate, blood gas and physiological parameters were detected.

RESULTS

Gel had a lower intrinsic viscosity than HES200 and HES130 (P < 0.01), but at a low shear rate in a mixture of colloids, red cells and plasma, Gel had a higher viscosity (P < 0.05 or P < 0.01, respectively). For hydroxyethyl starch plasma expanders, the COP at a certain concentration decreases from 11.1 mmHg to 6.1 mmHg with the increase of R_h from 10.7 nm to 20.2 nm. A severe ANH model, with the hematocrit of 40% of the baseline level, was established and accompanied by disturbances in acid-base, lactate and blood gas parameters. At the end of ANH and 60 min afterward, the Dex40 group showed a worse outcome in maintaining the acid-base balance and systemic oxygenation compared to the other groups. The systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) decreased significantly in all groups at the end of ANH. The DBP and MAP in the Dex40 group further decreased 60 min after the end of ANH. During the process of ANH, the Dex40 group showed a drop and recovery in SBP, DBP and MAP. The DBP and MAP in the HES200 group were significantly higher than those in the other groups at some time points (P < 0.05 or P < 0.01).

CONCLUSION

Gel had a low intrinsic viscosity but may increase the whole blood viscosity at low shear rates. R_h and COP showed a strong correlation among hydroxyethyl starch plasma expanders. Dex40 showed a worse outcome in maintaining the acid-base balance and systemic oxygenation compared to the other plasma expanders. During the process of ANH, Dex40 displayed a V-shaped recovery pattern for blood pressure, and HES200 had the advantage in sustaining the DBP and MAP at some time points.

Neutrophil Gelatinase-associated Lipocalin as a Marker of Postoperative Acute Kidney Injury Following Cardiac Surgery in Patients with Preoperative Kidney Impairment

INTRODUCTION

Acute kidney injury (AKI) is a serious complication of cardiac surgery. The current 'gold standard' for determining AKI is change in serum creatinine and urine output, however, this change occurs relatively late after the actual injury occurs. Identification of new biomarkers that detect early AKI is required. Recently, new biomarkers, such as the NephroCheck® Test and AKIRisk have also been tested and found to be good indicators of AKI. Neutrophil gelatinase-associated lipocalin (NGAL) has shown promise in paediatric patients but has displayed varied results in adult populations, particularly post cardiac surgery. The aim of this study was to assess the value of urinary NGAL as a biomarker of AKI in patients with pre-existing renal impairment (eGFR >15ml/min to eGFR<60ml/min).

METHODS

A post-hoc analysis of urinary NGAL concentrations from 125 patients with pre-existing kidney impairment, who participated in a randomised trial of haemofiltration during cardiac surgery, was undertaken. Urinary NGAL was measured using ELISA at baseline, post-operatively and 24 and 48 hours after surgery, and serum creatinine was measured pre and postoperatively and then at 24, 48, 72 and 96 hours as routine patient care. NGAL concentrations were compared in patients with and without AKI determined by changes in serum creatinine concentrations. A Kaplan-Meier plot compared survival for patients with or without AKI and a Cox proportional hazards analysis was performed to identify factors with the greatest influence on survival.

RESULTS

Following surgery, 43% of patients developed AKI (based on KDIGO definition). Baseline urinary NGAL was not found to be significantly different between patients that did and did not develop AKI. Urinary NGAL concentration was increased in all patients following surgery, regardless of whether they developed AKI and was also significant between groups at 24 (p=0.003) and 48 hours (p<0.0001). Urinary NGAL concentrations at 48 hours correlated with serum creatinine concentrations at 48 hours (r=0.477, p<0.0001), 72 hours (r=0.488, p<0.0001) and 96 hours (r=0.463, p<0.0001). Urinary NGAL at 48 hours after surgery strongly predicted AKI (AUC=0.76; P=0.0001). A Kaplan- Meier plot showed that patients with postoperative AKI had a significantly lower 7-year survival compared with those without AKI. Postoperative urinary NGAL at 48 hours >156ng/mL also strongly predicted 7-year survival. However, additive EuroSCORE, age, current smoking and post-operative antibiotics usage were distinctly significantly more predictive of 7-year survival as compared with postoperative urinary NGAL at 48 hours >156ng/mL.

CONCLUSIONS

Our study demonstrated that postoperative urinary NGAL levels at 48 hours postsurgery strongly predicts the onset or severity of postoperative AKI based on KDIGO classification in patients with preoperative kidney impairment and were also strongly related to 7-year survival.

Preoperative Haemoglobin Levels

It is a common practice in many anaesthetic centres throughout the world to require a minimum preoperative haemoglobin level of 10g/100 ml of blood or more, but very few references are quoted by writers on this subject. A search of relevant medical literature has been made in an attempt to establish the origin and significance of the preoperative haemoglobin requirements recommended.

Prognostic Significance of Serum NGAL and Troponin I against Acute Kidney Injury in Egyptian ICU Patients after Open Heart Surgery: A Pilot Study

Background

Acute kidney injury (AKI) is a common complication following cardiac surgery and percutaneous coronary interventions, with an estimated incidence rate around 30%, depicted by long-term intensive care unit stay and culminating renal dysfunction over time, triggering either perpetual renal damage evolving to chronic kidney disease/end-stage renal disease transitions or high vulnerability for sudden death after surgery. The classical diagnosis of AKI is based on a sharp rise in serum creatinine that takes at least 48 h to be visible and is associated with multiple nonrenal factors.

Objective

We aimed to evaluate the predictive performance of both neutrophil gelatinase-associated lipocalin (NGAL) and Klotho for AKI in patients who underwent cardiothoracic surgery using cardiopulmonary bypass (CPB).

Results

Out of the 182 patients included in the study, 65 had AKI and 117 had non-AKI according to the Kidney Disease: Improving Global Outcomes criteria relying on serum creatinine levels. Baseline serum NGAL was 103.5 ± 41.69 μg/L in the AKI group compared to 79.12 ± 48.02 μg/L in the non-AKI group (p < 0.01) and then manifested a peak-fall-rise pattern until 48 h of CPB, with a more remarkable change in the AKI than in the non-AKI group. ROC curve analysis for all measured biomarkers after 2 h of CPB showed that serum NGAL (0.819, > 75% cutoff, 83.5% accuracy) came after serum creatinine (0.864, > 140% cutoff, 85% accuracy), and troponin I was poorer than both (0.606, > 5.5% cutoff, 60% accuracy). Furthermore, multivariate analysis showed that preoperative serum NGAL, preoperative eGFR ≤60 mL/min/1.73 m², and arterial hypertension were possible risk factors for AKI with adverse outcomes.

Conclusions

Our study suggests the role of preoperative serum NGAL as a prognostic tool for renal consequences after cardiac surgery. Besides, postoperative serum NGAL is a sensitive marker for AKI, but is less specific than serum creatinine. Troponin I is considered to be a risk confirmatory tool and may help in the prediction of AKI. However, its diagnostic utility is restricted due to age-dependent cutoff values and poor standardization and harmonization because of interassay variations.

From Low Hematocrit Physiology to Isovolemic Hemodilution

The aim of this study, starting from some concepts of physiology, was to deal with the ever growing question of intentional anemia. Physiology suitably expresses the linear relationship between hematocrit and blood fluidity, and at the same time explains how viscosity and aggregability are important co-factors in the circulation, in disease and in thromboembolic complications. The need to understand how a low hematocrit level, compared to the volemia, is a fundamental requirement in surgery, and even more so in surgery with a high risk of embolism, like orthopedic traumatology surgery. Normovolemic hemodilution was analyzed both for the risks it involves and for how much it sticks to the changes induced by a similar situation on the various organs and apparatus. The authors, based on their experience in the field of anesthesiology, propose an operating schedule to safely perform intentional normovolemic hemodilution, describing the preoperative, intraoperative and finally the postoperative period. In conclusion, the authors advocate a wider use of this technique, confirming its safety in relation to volemia.

Evaluation of acute normovolemic hemodilution in patients undergoing intracranial meningioma resection: A quasi-experimental trial

The aim of this study was to evaluate the safety of acute normovolemic hemodilution (ANH) for patients undergoing intracranial meningioma resection.Eighty patients (aged 48-65 years) with American Society of Anesthesiologists physical status I-II undergoing intracranial meningioma resection were included in this prospective observational study. The patients were randomly divided into group A (ANH group), which underwent a combination of ANH and intraoperative cell salvage (ICS), and group B (control group), which underwent ICS alone. The study parameters were recorded as baseline values before blood drainage (T0), after blood drainage (T1), and before (T2) and after (T3) retransfusion in group A. Whereas in group B, the same parameters were measured 10 minutes after anesthesia induction (T0), before surgery (T1), and before (T2) and after (T3) transfusion of autologous blood.When intraoperative blood loss was <2000 mL, the mean volume of homologous blood transfused in group A patients was 100.8 ± 82.3 mL, compared with the 190.0 ± 91.8 mL in group B. Reduction in homologous blood used in group A was statistically significant (P < .05). In group B, 15.1% patients received homologous blood, whereas only 5.9% patients received homologous blood in group A. The difference in heart rate between both groups at different time points was statistically nonsignificant (P > .05). The mean hemoglobin and hematocrit levels at T1 and T2 in group A were lower than in group B (P < .05). The prothrombin time and activated partial thromboplastin time in both groups were prolonged significantly after T2 (all P < .05), but were all within normal range. There were no significant differences in postoperative hospital stay, mortality, and postoperative infection between the 2 groups.For patients undergoing excision of intracranial meningioma, ANH is an effective procedure to reduce the need for allogeneic transfusions.

Supra-plasma expanders: the future of treating blood loss and anemia without red cell transfusions?

Oxygen delivery capacity during profoundly anemic conditions depends on blood's oxygen-carrying capacity and cardiac output. Oxygen-carrying blood substitutes and blood transfusion augment oxygen-carrying capacity, but both have given rise to safety concerns, and their efficacy remains unresolved. Anemia decreases oxygen-carrying capacity and blood viscosity. Present studies show that correcting the decrease of blood viscosity by increasing plasma viscosity with newly developed plasma expanders significantly improves tissue perfusion. These new plasma expanders promote tissue perfusion, increasing oxygen delivery capacity without increasing blood oxygen-carrying capacity, thus treating the effects of anemia while avoiding the transfusion of blood.

Effect of Normovolemic Hemodilution on Fatal Postoperative Pulmonary Embolism in Major Elective Orthopedic Surgery. A Retrospective Analysis on 4653 Patients

It has been suggested that the benefits of transfusion are currently greatly overrated, with physicians reflexively administering blood in the nearly unchallenged view that failure to transfuse would have dire consequences. As a matter of fact, the tolerability and safety of normovolemic anemia have been well documented for many years in several anesthesiologic settings.

Objective: To assess the impact of normovolemic hemodilution on blood bank resources and in-hospital mortality in major elective orthopedic surgery.

Methods: The authors therefore retrospectively analyzed in-hospital mortality of patients submitted to elective surgery for total hip replacement in the Rizzoli Institute since 1979. From 1979 to 1983, 1488 patients underwent a standard treatment (without normovolemic hemodilution), whereas 4653 patients submitted to surgery from 1984 to 1993 underwent normovolemic hemodilution-up to extreme accepted values of hemoglobin > 6 g/dL.

Results: Homologous blood transfusion was required in 1220/1488 patients of Group I and in 977/4653 patients of Group II (82% vs 21%, P < .001). The number of blood units required for each transfused patient was 2.8 in the 1220 transfused patients of Group I, and 2.1 in the 977 transfused patients of Group II (P < .001). There were 6 deaths in Group I and 7 deaths in Group II (0.4% vs 0.15%, P < .05). The overall incidence of fatal pulmonary thromboembolism was 4/1488 in Group I and 1/4653 in Group 11 (0.27% vs 0.02%, P < .001).

Conclusions: Normovolemic hemodilution was extremely well tolerated in patients undergoing major elective orthopedic surgery and allowed substantial sparing of blood bank resources. It had no detectable unfavorable effect on surgical outcome, but rather it was associated with a dramatic decrease in perioperative mortality of patients under-going total hip replacement, owing to a thirteen-fold reduction in fatal pulmonary thromboembolism.

Efficacy of near-infrared spectrometry for monitoring the cerebral effects of severe dilutional anemia

INTRODUCTION

Clear guidelines for red cell transfusion during cardiac surgery have not yet been established. The current focus on blood conservation during cardiac surgery has increased the urgency to determine the minimum safe hematocrit for these patients. The aim of this study was to determine whether monitoring of cerebral regional oxygen saturation (rSO2) via near-infrared spectrometry (NIRS) is effective for assessing the cerebral effects of severe dilutional anemia during elective coronary arterial bypass graft surgery (CABG).

METHODS

The prospective observational study involved patients who underwent cerebral rSO2 monitoring by NIRS during elective isolated first-time CABG: an anemic group (N=15) (minimum Hemoglobin (Hb) <7 g/dL at any period during cardiopulmonary bypass (CPB) and a control group (N=15) (Hb >8 g/dL during CPB). Mean arterial pressure (MAP), pump blood flow, blood lactate level, pCO2, pO2 at five time points and cross-clamp time, extracorporeal circulation time were recorded for each patient. Group results statistically were compared.

RESULTS

The anemic group had significantly lower mean preoperative Hb than the control group (10.3 mg/dL versus 14.2 mg/dL; P = .001). The lowest Hb levels were observed in the hypothermic period of CPB in the anemic group. None of the controls exhibited a >20% decrease in cerebral rSO2. Eleven (73.3%) of the anemic patients required an increase in pump blood flow to raise their cerebral rSO2.

CONCLUSIONS

In this study, the changes in cerebral rSO2 in the patients with low Hb were within acceptable limits, and this was in concordance with the blood lactate levels and blood-gas analysis. It can be suggested that NIRS monitoring of cerebral rSO2 can assist in decision making related to blood transfusion and dilutional anemia during CPB.

Replacing the Transfusion of 1-2 Units of Blood with Plasma Expanders that Increase Oxygen Delivery Capacity: Evidence from Experimental Studies

At least a third of the blood supply in the world is used to transfuse 1–2 units of packed red blood cells for each intervention and most clinical trials of blood substitutes have been carried out at this level of oxygen carrying capacity (OCC) restoration. However, the increase of oxygenation achieved is marginal or none at all for molecular hemoglobin (Hb) products, due to their lingering vasoactivity. This has provided the impetus for the development of “oxygen therapeutics” using Hb-based molecules that have high oxygen affinity and target delivery of oxygen to anoxic areas. However it is still unclear how these oxygen carriers counteract or mitigate the functional effects of anemia due to obstruction, vasoconstriction and under-perfusion. Indeed, they are administered as a low dosage/low volume therapeutic Hb (subsequently further diluted in the circulatory pool) and hence induce extremely small OCC changes. Hyperviscous plasma expanders provide an alternative to oxygen therapeutics by increasing the oxygen delivery capacity (ODC); in anemia they induce supra-perfusion and increase tissue perfusion (flow) by as much as 50%. Polyethylene glycol conjugate albumin (PEG-Alb) accomplishes this by enhancing the shear thinning behavior of diluted blood, which increases microvascular endothelial shear stress, causes vasodilation and lowering peripheral vascular resistance thus facilitating cardiac function. Induction of supra-perfusion takes advantage of the fact that ODC is the product of OCC and blood flow and hence can be maintained by increasing either or both. Animal studies suggest that this approach may save a considerable fraction of the blood supply. It has an additional benefit of enhancing tissue clearance of toxic metabolites.

A Theoretical Mathematical Model to Estimate Blood Volume in Clinical Practice

Perioperative intravenous (IV) fluid management is controversial. Fluid therapy is guided by inaccurate algorithms and changes in the patient's vital signs that are nonspecific for changes to the patient's blood volume (BV). Anesthetic agents, patient comorbidities, and surgical techniques interact and further confound clinical assessment of volume status. Through adaptation of existing acute normovolemic hemodilution algorithms, it may be possible to predict patient's BV by measuring hematocrit (HcT) before and after hemodilution. Our proposed mathematical model requires the following four data points to estimate a patient's total BV: ideal BV, baseline HcT, a known fluid bolus (FB), and a second HcT following the FB. To test our method, we obtained 10 ideal and 10 actual subject BV data measures from 9 unique subjects derived from a commercially used Food and Drug Administration-approved, semi-automated, BV analyzer. With these data, we calculated the theoretical BV change following a FB. Using the four required data points, we predicted BVs (BVp) and compared our predictions with the actual BV (BVa) measures provided by the data set. The BVp calculated using our model highly correlated with the BVa provided by the BV analyzer data set (df = 8, r = .99). Our calculations suggest that, with accurate HcT measurement, this method shows promise for the identification of abnormal BV states such as hyper- and hypovolemia and may prove to be a reliable method for titrating IV fluid.

Animal model of rapid crystalloid infusion in rats

PURPOSE

To describe an animal model of rapid intravenous infusion with different volumes of crystalloid and discuss the clinical findings.

METHODS

Fifty six male Wistar rats were used, divided randomly in seven groups (n = 8). The rats of groups 1 to 6 received lactated Ringer's solution intravenously, in the rate of 25 ml/min, with different volumes proportional to blood volume (BV). The rats of group 0 were submitted to the same procedure, but did not receive the fluid (control group). The data included respiratory rate, heart rate, saturation of peripheral oxygen (SpO(2)) in two times (before and after the infusion), and upshots (respiratory arrest and death). Dunnett's test and ANOVA were used.

RESULTS

The clinical signs significantly changed in the 2, 2.5 and 3 fold BV groups. The respiratory arrest was observed in the 1.5, 2, 2.5 and 3 fold BV groups, but death was present only in 2.5 and 3 fold BV groups.

CONCLUSIONS

The infusion of crystalloid in the same volume of blood volume did not cause significant variation in respiratory and heart rate, saturation of peripheral oxygen and did not induce respiratory arrest. The infusion of a volume of 3 fold blood volume was lethal to all animals.

Effects of hemodilution after traumatic brain injury in juvenile rats

BACKGROUND

Normovolemic hemodilution (HD) in adult animal studies has shown exacerbation of traumatic brain injury (TBI) lesion volumes. Similar studies in juvenile rats have not been reported and outcomes are likely to be different. This study investigated the effects of normovolemic hemodilution (21% hematocrit) in a juvenile TBI (jTBI) model.

METHODS

Twenty 17-day-old rats underwent moderate cortical contusion impact injury (CCI) and were divided into four groups: CCI/hemodilution (HD) (group HD), CCI/no HD (group C), Sham/HD (group SHD), and Sham/no HD (group S). Regional laser Doppler flowmetry (LDF), edema formation (MRI-T2WI), water mobility assessed using diffusion weighted imaging (MRI-DWI), open field activity tests, and histological analyses were evaluated for lesion characteristics.

RESULTS

Hemodilution significantly increased blood flow in the HD compared to the C group after TBI. T2WI revealed a significantly increased extravascular blood volume in HD at 1, 7, and 14 days post-CCI. Edematous tissue and total contusional lesion volume were higher in HD-treated animals at 1 and 14 days. DWI revealed that HD, SHD, and C groups had elevated water mobility compared to S groups in the ipsilateral cortex and striatum. Histology showed a larger cortical lesion in the C than HD group. Open field activity was increased in HD, C, and SHD groups compared to the S group.

CONCLUSIONS

Hemodilution results in significant brain hyperemia with increased edema formation, extravascular blood volume, and water mobility after jTBI. Hemodilution results in less cortical damage but did not alter behavior. Hemodilution is likely not to be clinically beneficial following jTBI.

Acute normovolemic hemodilution

Acute normovolemic hemodilution (AHN) is a well known but poorly used "blood saving" method. The authors, based on their own experience and on the "low hematocrit" physiology, present some concepts on AHN and a clinical experience to demonstrate the usefulness and affordability of this method. Consequently we offer several tools concerning both the realization of AHN and the safe use of such dilution, suggesting simple and exciting methods to determine if, when and how to apply this blood saving system.

Perioperative Management of a Jehovah's Witness Presenting for Skull Base Surgery

A 22-year-old, otherwise healthy, female Jehovah's Witness underwent resection of a midline skull base chondrosarcoma which had been detected after a work-up for headache and diplopia. After bilateral maxillectomies, ethmoidectomies, and a sphenoidectomy, the patient's chondrosarcoma was resected. Despite proper anesthetic management and meticulous hemostasis, significant intraoperative blood loss occurred. The initial postoperative hemoglobin level was 2.3 gm/dL. The clinical concerns pertaining to the perioperative management of the Jehovah's Witness are discussed along with the patient's course and management.

Reducing perioperative blood loss and allogeneic blood transfusion in patients undergoing major spine surgery

At present, individual techniques, including intraoperative acute normovolemic hemodilution, use of tranexamic acid, use of intrathecal morphine, proper positioning, and modification of operative techniques, seem most promising for reducing perioperative blood loss and allogeneic blood transfusion in patients undergoing major spine surgery. Other techniques including preoperative autologous predonation; mandatory discontinuation of use of antiplatelet agents; intraoperative and postoperative red-blood-cell salvage; use of aprotinin, epsilon-aminocaproic acid, recombinant factor VIIa, or desmopressin; induced hypotension; avoidance of hypothermia; and minimally invasive operative techniques require additional studies to either establish their effectiveness or address safety considerations.

Effect of perioperative blood transfusion on clinical outcomes in hepatic surgery for cancer

Allogeneic blood transfusion during liver resection for malignancies has been associated with an increased incidence of different types of complications: infectious complications, tumor recurrence, decreased survival. Even if there is clear evidence of transfusion-induced immunosuppression, it is difficult to demonstrate that transfusion is the only determinant factor that decisively affects the outcome. In any case there are several motivations to reduce the practice of blood transfusion. The advantages and drawbacks of different transfusion alternatives are reviewed here, emphasizing that surgeons and anesthetists who practice in centers with a high volume of liver resections, should be familiar with all the possible alternatives.

The contemporary approach to the care of Jehovah's witnesses

BACKGROUND

Jehovah's Witnesses are widely known for their prohibition on the acceptance of blood transfusion. Such refusal serves as a potential obstacle to optimal therapeutic intervention among critically injured Jehovah's Witnesses. As such, care of these patients requires an aggressive and multidisciplinary approach to therapy.

METHODS

A review of the pertinent English language literature.

RESULTS

Jehovah's Witnesses exercise the right of any adult with capacity to refuse medical treatment and often carry advance directive cards indicating their incontrovertible refusal of blood. Despite their belief regarding transfusion, Jehovah's Witnesses do not have a higher mortality rate after traumatic injury or surgery. Transfusion requirements are often overestimated. Increased morbidity and mortality is rarely observed in patients with a hemoglobin concentration >7 g/dL, and the acute hemoglobin threshold for cardiovascular collapse may be as low as 3 g/dL to 5 g/dL. There are many modalities to treat the Jehovah's Witness patient with acute blood loss. Treatment with recombinant human erythropoietin, albumin, and recombinant activated Factor VIIa have all been used with success. Autologous autotransfusion and isovolemic hemodilution can also be used to treat patients who refuse transfusion. Hemoglobin-based oxygen carriers may play a future role as intravascular volume expanders in lieu of transfusion of red blood cell concentrates.

CONCLUSION

There are many treatment modalities available to assist in the care of Jehovah's Witness patients, especially since their beliefs on the intricacies of the Blood Ban appear to be in flux.

Microvascular experimental evidence on the relative significance of restoring oxygen carrying capacity vs. blood viscosity in shock resuscitation

The development of volume replacement fluids for resuscitation in hemorrhagic shock comprises oxygen carrying and non carrying fluids. Non oxygen carrying fluids or plasma expanders are used up to the transfusion trigger, and upon reaching this landmark either blood, and possibly in the near future oxygen carrying blood substitutes, are used. An experimental program in hemorrhagic shock using the hamster chamber window model allowed to compare the relative performance of most fluids proposed for shock resuscitation. This model allows investigating simultaneously the microcirculation and systemic reactions, in the awake condition, in a tissue isolated from the environment. Results from this program show that in general plasma expanders such as Ringer's lactate and dextran 70 kDa do not sufficiently restore blood viscosity upon reaching the transfusion trigger, causing microvascular collapse. This is in part restored by a blood transfusion, independently of the oxygen carrying capacity of red blood cells. These results lead to the proposal that effective blood substitutes must be designed to prevent microvascular collapse, manifested in the decrease of functional capillary density. Achievement of this goal, in combination with the increase of oxygen affinity, significantly postpones the need for a blood transfusion, and lowers the total requirement of restoration of intrinsic oxygen carrying capacity.

Cardiac surgery as a cause of acute kidney injury: pathogenesis and potential therapies

Cardiopulmonary bypass surgery occurs in nearly 1 million patients per year. Acute kidney injury requiring dialysis can occur in up to 1% of these patients. The development of acute kidney injury is associated with substantial morbidity and mortality independent of all other factors, and many patients are left dependent on dialysis therapies. The pathogenesis of acute kidney injury involves multiple pathways. Hemodynamic, inflammatory, and nephrotoxic factors are involved and overlap each other in leading to kidney injury. Clinical studies have identified risk factors for acute kidney injury that can be used to effectively determine the risk of acute kidney injury in patients undergoing bypass surgery. These high-risk patients can then be targeted for renal protective strategies. Thus far, no single strategy has conclusively demonstrated its ability to prevent renal injury post-bypass surgery. Novel anti-inflammatory agents are in development and offer hope as potential therapies.

Acute normovolemic hemodilution for radical retropubic prostatectomy and radical cystectomy

OBJECTIVES

Radical retropubic prostatectomy (RRP) and radical cystectomy (RCx) are well tolerated and widely performed. Because intraoperative blood loss is one of the most common problems, we performed acute normovolemic hemodilution (ANH) to prevent allogenic blood transfusion (ABT). In this study we tried to clarify the safety, effectiveness and problems of ANH at urologic operations.

METHODS

The study included 169 patients who underwent RRP and 97 patients underwent RCx from April 2003 to March 2006. The eligible patients for ANH were required to have preoperative hemoglobin of 12 g/dL or more without history of myocardial ischemia. The amount of blood collected was 800 mL in RRP and 800 mL or 1200 mL in RCx. Neoadjuvant chemotherapy was performed in 11 (11.3%) of 97 patients with RCx.

RESULTS

ANH was available in 164 (97.0%) of 169 patients in RRP and 41 (42.3%) of 97 patients in RCx. All 11 (11.3%) patients who received neoadjuvant chemotherapy before RCx revealed anemia and all were excluded from ANH. No patients had an hypovolemic event develop during the autologous blood being stored. The median volume of intraoperative blood loss was 1400 mL in 164 RRP and 19 patients (11.6%) required ABT. In 41 patients undergoing RCx, the median volume of blood loss was 1720 mL and 13 patients (32.5%) required ABT. In the postoperative period, no patients had cardiovascular or pulmonary complications develop originated from ANH.

CONCLUSIONS

ANH is a safe and useful method of transfusion during RRP and RCx. ANH can be recommended for patients who need these operations.

Lowering of blood pressure by increasing hematocrit with non nitric oxide scavenging red blood cells

Isovolemic exchange transfusion of 40% of the blood volume in awake hamsters was used to replace native red blood cells (RBCs) with RBCs whose hemoglobin (Hb) was oxidized to methemoglobin (MetHb), MetRBCs. The exchange maintained constant blood volume and produced different final hematocrits (Hcts), varying from 48 to 62% Hct. Mean arterial pressure (MAP) did not change after exchange transfusion, in which 40% of the native RBCs were replaced with MetRBCs, without increasing Hct. Increasing Hct with MetRBCs lowered MAP by 12 mm Hg when Hct was increased 12% above baseline. Further increases of Hct with MetRBCs progressively returned MAP to baseline, which occurred at 62% Hct, a 30% increase in Hct from baseline. These observations show a parabolic "U" shaped distribution of MAP against the change in Hct. Cardiac index, cardiac output divided by body weight, increased between 2 and 17% above baseline for the range of Hcts tested. Peripheral vascular resistance (VR) was decreased 18% from baseline when Hct was increased 12% from baseline. VR and MAP were above baseline for increases in Hct higher than 30%. However, vascular hindrance, VR normalized by blood viscosity (which reflects the contribution of vascular geometry), was lower than baseline for all the increases in Hct tested with MetRBC, indicating prevalence of vasodilation. These suggest that acute increases in Hct with MetRBCs increase endothelium shear stress and stimulate the production of vasoactive factors (e.g., nitric oxide [NO]). When MetRBCs were compared with functional RBCs, vasodilation was augmented for MetRBCs probably due to the lower NO scavenging of MetHb. Consequently, MetRBCs increased the viscosity related hypotension range compared with functional RBCs as NO shear stress vasodilation mediated responses are greater.

Effectiveness of autologous fibrin tissue adhesive in reducing postoperative blood loss during total hip arthroplasty: a prospective randomised study of 100 cases

PURPOSE

To evaluate the effectiveness of autologous fibrin tissue adhesive (auto-FTA) in reducing blood loss during cementless total hip arthroplasty (THA).

METHODS

From September 2000 to August 2001, 100 patients who predonated 400 ml of autologous blood were randomised to undergo either standard treatment with auto-FTA (auto-FTA group) or standard treatment alone (control group). The volume of postoperative blood loss and the decrease in haemoglobin level were measured. All patients were followed up for 3 years to evaluate the rate of bone ingrowth and heterotopic ossification.

RESULTS

The mean postoperative blood loss was 580 ml (standard deviation [SD], 240 ml) in the auto-FTA group and 810 ml (SD, 341 ml) in the control group; the difference was significant (230 ml, p<0.001). The decrease in haemoglobin concentration was 17 g/l (SD, 11 g/l) in the auto-FTA group and 22 g/l (SD, 12 g/l) in the control group. The difference was significant (5 g/l, p=0.03). The percentage of total blood loss of >1200 ml in any single patient was significantly lower in the auto-FTA group (4%) than in the control group (20%) [p=0.01].

CONCLUSION

Auto-FTA is a safe and effective means of reducing perioperative blood loss in THA.

Acute kidney injury associated with cardiac surgery

Acute renal failure (ARF) occurs in up to 30% of patients who undergo cardiac surgery, with dialysis being required in approximately 1% of all patients. The development of ARF is associated with substantial morbidity and mortality independent of all other factors. The pathogenesis of ARF involves multiple pathways. Hemodynamic, inflammatory, and nephrotoxic factors are involved and overlap each other in leading to kidney injury. Clinical studies have identified risk factors for ARF that can be used to determine effectively the risk for ARF in patients who undergo bypass surgery. These high-risk patients then can be targeted for renal protective strategies. Thus far, no single strategy has demonstrated conclusively its ability to prevent renal injury after bypass surgery. Several compounds such as atrial natriuretic peptide and N-acetylcysteine have shown promise, but large-scale trials are needed.

Subcutaneous Po2 as an index of the physiological limits for hemodilution in the rat

This study was designed to test the hypothesis that changes in subcutaneous Po2 (PscO2) during progressive hemodilution will reliably predict a “critical point” at which tissue O2 consumption (V̇o2) becomes dependent on O2 delivery (Q̇o2). Twelve pentobarbital-anesthetized male Sprague-Dawley rats (315–375 g) underwent stepwise exchange of plasma for blood (1.5 ml of plasma for each 1 ml of blood lost). The initial exchange was equal to 25% of the estimated circulatory blood volume, and each subsequent exchange was equal to 10% of the estimated circulatory blood volume. After nine exchanges, the hematocrit (Hct) fell from 42 ± 1 to 6 ± 1%. Cardiac output and O2 extraction rose significantly. PscO2 became significantly reduced ( P < 0.05) after exchange of 45% of the blood volume (Hct = 16 ± 1%). V̇o2 became delivery dependent when Q̇o2 fell below 21 ml·min−1·kg body wt−1 (mean Hct = 13 ± 1%). Eight control rats undergoing 1:1 blood-blood exchange showed no change in PscO2, pH, HCO3−, or hemodynamics. Measurement of PscO2 may be a useful guide to monitor the adequacy of Q̇o2 during hemodilution.

Alginate plasma expander maintains perfusion and plasma viscosity during extreme hemodilution

Extreme hemodilution was performed in the hamster chamber window model using 6% Dextran 70, lowering systemic hematocrit by 60%. Animals were subsequently divided into three groups and hemodiluted to a hematocrit of 11% using 6% Dextran 70, 6% Dextran 500, and a 4% Dextran 70 + 0.7% alginate solution ( n = 6 each group). Final plasma viscosities were 1.4 ± 0.2, 2.2 ± 0.1, and 2.7 ± 0.2 cp, respectively, ( P < 0.05, high viscosity vs. low viscosity). Blood viscosities were 2.1 ± 0.2, 2.9 ± 0.4, and 3.9 ± 0.3 cp, respectively. The lowest blood and plasma viscosity group had a significantly lower functional capillary density, 37 ± 16%, whereas the two high-viscosity solutions were 71 ± 15% and 76 ± 12% ( P < 0.05, high viscosity vs. low viscosity), respectively. Arteriolar and venular flow in the Dextran 500 and alginate groups was higher than baseline (i.e., normal nontreated animals), whereas the low-viscosity group showed a reduction in flow. These microvascular changes were paralleled by changes in base excess, which was negative for the Dextran 70 group and positive for the other groups. However, tissue Po2 was uniformly low for all groups (average of 1.4 mmHg). Calculation of tissue oxygen consumption in the window chamber based on the microvascular data, flow, and intravascular Po2 showed that only the alginate + Dextran 70 solution-exchanged animals returned to baseline oxygen consumption, whereas the other groups were lower than baseline ( P < 0.05). These results show that hemodilution performed with high-viscosity plasma expanders yields systemic arterial pressures and functional capillary densities that are significantly higher ( P < 0.05) than those obtained with 6% Dextran 70, a fluid whose viscosity is similar to that of plasma. A condition for obtaining these results is that the oncotic pressure of the plasma expander be titrated to near normal, so that autotransfusion of fluid from the tissue into the vascular compartment does not reduce the effects of increasing plasma viscosity and increased shear stress on the microvascular wall.

An overview of blood-sparing techniques used in spine surgery during the perioperative period

The problems linked to blood loss and blood-sparing techniques in spine surgery have been less studied than in other fields of orthopedics, such as joint-replacement procedures. Decreasing bleeding is not only important for keeping the patient's hemodynamic equilibrium but also for allowing a better view of the surgical field. In spine surgery the latter aspect is especially important because of the vicinity of major and highly fragile neurologic structures. The techniques and agents used for hemostasis and blood sparing in spinal procedures are mostly similar to those used elsewhere in surgery. Their use is modulated by the specific aspects of spinal approach and its relation to the contents of the spinal canal. Blood-sparing techniques can be divided into two categories based on their goals: either they are aimed at decreasing the bleeding itself, or they are aimed at decreasing the need for homologous transfusion. Various hemodynamic techniques, as well as systemic and local drugs and agents, can be used separately or in combination, and their use in the field of spine surgery is reported. The level of evidence for the efficacy of many of those methods in surgery as a whole is limited, and there is a lack of evidence for most of them in spine surgery. However, several blood-saving procedures and drugs, as well as promising new agents, appear to be efficient, although their efficacy has yet to be assessed by proper randomized controlled trials.

Perioperative normovolemic anemia is safe in pediatric living-donor liver transplantation

BACKGROUND

Perioperative normovolemic anemia was applied in pediatric living-donor liver transplant (LDLT) recipients with the aim of reducing the use of blood products and decreasing transfusion-related risk.

METHODS

The anemic state was allowed to occur by replacing intraoperative blood and transudate loss with colloid solutions and a discriminate use of packed red blood cells. When blood transfusion was required, the amount of blood replacement was calculated to target a hemoglobin level not higher than 8 to 9 g/dL.

RESULTS

Forty-eight pediatric patients underwent LDLT. Their mean hemoglobin and hematocrit levels were maintained below 9 g/dL and 27%, respectively, at the end of the operation, at the time of extubation, postoperative days 3, 10, and 20, and at the time of discharge. The mean ventilatory support time was 15.7 hr, and no patient required reintubation. Graft function normalized within the first week posttransplant in all patients, and there was no documented case of acute hepatic artery thrombosis. All the patients were discharged with acceptable liver function, and 98% of them remain alive to date.

CONCLUSION

Routine application of perioperative normovolemic anemia in pediatric LDLT has allowed the sparing use of blood products. Approximately half of our patients (42%) did not require intraoperative blood transfusion; 31% of the patients went home without receiving any blood products except 5% albumin. There were no adverse effects with this maneuver, and graft function was good in all patients.

Efficacy of a criterion-driven transfusion protocol in patients having pediatric cardiac surgery

OBJECTIVES

Low-hematocrit bypass is one technique used to prevent allogeneic transfusion during cardiopulmonary bypass. The purpose of this study is to determine the efficacy of a criterion-driven transfusion protocol and the effect of low-hematocrit bypass with moderate hypothermia in pediatric cardiac surgery.

METHODS

Seventy-five children who underwent cardiopulmonary bypass with low-hematocrit bypass for repair of congenital heart disease were studied. Criteria for red blood cell transfusion included anemia with a hematocrit level of less than 15% during bypass and 20% after bypass. During cardiopulmonary bypass, venous oxygen saturation, hematocrit values, and regional cerebral oxygenation were continuously monitored. Arterial lactate levels were measured postoperatively.

RESULTS

All patients had an uncomplicated perioperative course, and no perioperative death occurred. Twenty-two patients (29.3%) received a transfusion, and 53 (70.7%) patients did not. The hematocrit levels before and after modified ultrafiltration in the transfused group (21.6 +/- 5.5%, 26.6 +/- 6.5%) were significantly higher than those in the nontransfused group (18.9 +/- 3.7%, 23.1 +/- 4.1%) (P <.05). There was no significant difference between the group's arterial lactate levels immediately after admission to the intensive care unit and 1 day after the operation. The arterial lactate levels 6 hours after the admission to the intensive care unit for the nontransfused patients were higher than with the transfused patients (4.3 +/- 3.0 versus 2.5 +/- 1.5 mmol/L, (P <.05). For arterial lactate level, the relation with patients' weight had the highest correlation (R = 0.678, P <.0001).

CONCLUSIONS

A criterion-driven transfusion program can be effective, and low-hematocrit bypass with a hematocrit value below 20% may affect lactate production or clearance from the body.

Perioperative blood and blood product management for spinal deformity surgery

BACKGROUND CONTEXT

Spinal deformity surgery, like many other orthopedic procedures, involves significant operative blood loss. In order to avoid the necessity of bank blood transfusions, many blood management strategies have been devised.

PURPOSE

The goal of this review is to analyze the utility of current blood management strategies.

STUDY DESIGN/SETTING

Review paper.

METHODS

Using Medline reviews, pertinent data on blood management agents and strategies were assembled.

RESULTS

Techniques can be organized into preoperative, intraoperative and postoperative categories. Preoperative techniques include autologous blood donation and red cell augmentation. In addition to some established surgical and anesthesia techniques, recent pharmacologic agents have become available to include thrombotic agents and antifibrinolytics, which surgeons may add to their intraoperative armamentarium. A brief mention of postoperative blood salvage drains is also included.

CONCLUSIONS

The judicious use of the agents and techniques can significantly reduce the need for blood transfusions in the setting of spinal deformity surgery.

The association of lowest hematocrit during cardiopulmonary bypass with acute renal injury after coronary artery bypass surgery

BACKGROUND

Acute renal injury is a common serious complication of cardiac surgery. Moderate hemodilution is thought to reduce the risk of kidney injury but the current practice of extreme hemodilution (target hematocrit 22% to 24%) during cardiopulmonary bypass (CPB) has been linked to adverse outcomes after cardiac surgery. Therefore we tested the hypothesis that lowest hematocrit during CPB is independently associated with acute renal injury after cardiac surgery.

METHODS

Demographic, perioperative, and laboratory data were gathered for 1,404 primary elective coronary bypass surgery patients. Preoperative and daily postoperative creatinine values were measured until hospital discharge per institutional protocol. Stepwise multivariable linear regression analysis was performed to determine whether lowest hematocrit during CPB was independently associated with peak fractional change in creatinine (defined as the difference between the preoperative and peak postoperative creatinine represented as a percentage of the preoperative value). A p value of less than 0.05 was considered significant.

RESULTS

Multivariable analyses including preoperative hematocrit and other perioperative variables revealed that lowest hematocrit during CPB demonstrated a significant interaction with body weight and was highly associated with peak fractional change in serum creatinine (parameter estimate [PE] = 4.5; p = 0.008) and also with highest postoperative creatinine value (PE = 0.06; p = 0.004). Although other renal risk factors were significant covariates in both models, TM50 (an index of hypotension during CPB) was notably absent.

CONCLUSIONS

These results add to concerns that current CPB management guidelines accepting extreme hemodilution may contribute to postoperative acute renal and other organ injury after cardiac surgery.

Sealing the intramedullary femoral canal with autologous bone plug in total knee arthroplasty

In a prospective study of 262 consecutive patients with total knee arthroplasty, we compared the postoperative suction drainage and transfusion requirement in cases in which the defect made by the femoral intramedullary rod was either unplugged (n = 134) or plugged (n = 128). All operations were performed with a single surgical approach and technique. Inflammatory arthritis and lateral releases were excluded. Blood loss was recorded at 24, 48, and 72 hours. The difference in postoperative suction drainage was not statistically significant. The hemoglobin decrease in the unplugged group (3.5 g/dL) was different from that in the plugged group (2.3 g/dL) (P<.05). Of patients, 64.4% (n = 85) in the unplugged group and 35.9% (n = 46) in the plugged group required transfusion (P<.05). Sealing the femoral canal is effective in reducing hemoglobin decrease and blood transfusion in total knee arthroplasty.

Safety and efficacy of methods for reducing perioperative allogeneic transfusion: a critical review of the literature

A number of pharmacologic and nonpharmacologic technologies are in current use to minimize perioperative homologous blood use. Clinical trials, many of them randomized controlled trials, have been done evaluating these approaches and have demonstrated their efficacy. However, data on safety has relied mostly on case reports, uncontrolled studies, and, for the pharmacologic agents, extrapolation from the nonsurgical setting. In this review I analyze the data from the randomized trials and the lower-level evidence studies to provide the best estimates in safety with these alternatives. In general, these alternatives are safe with proper dosing and monitoring of effects. With aprotinin, the primary concern is anaphylaxis, and this predominantly with re-exposure. With aprotinin and with the anti-fibrinolytics, increased venous thromboembolic risk has not been a consistent finding. Tranexamic acid use intraoperatively is advantageous, but postoperative use appears to have no advantage and may be associated with renal dysfunction. DDAVP is low-risk, provided it is not overused, which can induce hyponatremia. Autologous predonation probably has similar risks as homologous blood with respect to transfusion errors and bacterial infection. As with most medical interventions, we must be vigilant to prevent human error.

Perioperative hemodilution

Acute normovolemic hemodilution (ANH) entails the removal of blood from a patient either immediately before or shortly after induction of anesthesia and the simultaneous replacement with cell-free fluid, preferably synthetic colloids with a predictable volume effect (6% dextran 60/70, 6% hydroxyethyl starch 200,000 and 130.000, respectively). Hemodilution is part of the concept for avoiding or limiting the use of allogeneic blood and should be considered for patients undergoing elective surgery free of contraindications and presenting with an initial hemoglobin concentration > or = 12 g/dl and an anticipated blood loss of > or = 1500 ml. The efficacy of ANH, judged by the necessity to transfuse homologous blood, depends on the preoperative (initial) hematocrit, the target hematocrit (to which hemodilution is performed), and the preset intra- and postoperative transfusion trigger. In the past data from clinical trials have shown that in healthy subjects a target hematocrit of 20-25% (7.0-8.0 g/dl hemoglobin concentration) is feasible and safe for the patient. The lower the target hemoglobin concentration, the more extensive monitoring is required: intraoperative target hemoglobin concentrations of 5.0 g/dl and less have been tolerated by young surgical patients without adverse effects. The safety as well as efficacy of acute normovolemic hemodilution in terms of reducing homologous blood transfusion requirements have been demonstrated in various clinical studies. ANH therefore is regarded an integral part of programs aimed at reducing the need for homologous blood, and can thus be successfully combined with preoperative autologous blood deposition, intraoperative blood salvage and carefully adjusted surgical techniques.

Desmopressin impairs microcirculation in donor pancreas and early graft function after experimental pancreas transplantation

BACKGROUND

Protective effects of desmopressin in brain dead organ donors oppose reports on a hypercoagulatory potential and an increased leukocyte-endothelial interaction (LEI) after application of the drug. The aim was to evaluate the effect of desmopressin on organ donor's pancreas and early graft function.

METHODS

Donor microcirculation was evaluated via intra-vital microscopy (IVM) in 24 BR (di/di) rats with central diabetes insipidus, randomly assigned to groups I (control without desmopressin application), II (single i.v. application, no pretreatment) or group III (single i.v. desmopressin application, s.c. pretreatment for 3 days). Microcirculation in recipients was evaluated 1 hr and 6 hr after syngenic pancreas transplantation. Groups III and I served as organ donors. After IVM specimens were taken for histology and immunohistochemistry.

RESULTS

Desmopressin in II vs. I led to temporarily (30') increased LEI (Sticker 274.3+/-87.7 vs. 76.5+/-31.1/mm2 endothelial surface; P<0.01) and impaired microcirculation (MCEV 0.43+/-0.07 vs. 0.99+/-0.06 mm/s; P<0.01). Repeated application reduced MCEV and increased LEI for up to 12 hr. Histology in I vs. III showed increased inflammation (n.s.), necrosis (P<0.05) and vacuolization (P<0.01). Immunohistochemistry revealed increased endothelial P-selectin 20' after application. 6 hr after reperfusion organs from III showed reduced MCEV and increased LEI (P<0.01).

CONCLUSION

Repeated application of desmopressin impairs graft microcirculation. Perfusion of the pancreas is significantly reduced at the beginning of organ tissue conservation as well as after reperfusion. These disturbances might partly be due to observed endothelial P-selectin expression. Application of desmopressin up to 12 hr prior to organ explantation may impact graft quality.

Pulsed venous flow pattern with hemodilution

Venous flow pattern changes and venous flow were assessed in relation to the degree of hemodilution. Femoral vein flow was measured with a duplex scanner in two groups of 11 patients 20 days and 5 days preoperatively, and 1 day postoperatively. In group I, hemodilution was used and patients gave three autologous blood predonations between day 20 and day 5. Perioperative blood loss was reintegrated by electrolyte solution. In group II, hemodilution was not used and autologous blood predonations were not carried out. These patients received a perioperative homologous blood transfusion of 800 mL. Hemoglobin was lower on day 5 (11.3 +/-1.4 vs 13.1 +/-1 g/dL, p<0.05) and on postoperative day 1 (8.9 +/-1.6 vs 10.6 +/-1, p<0.05) in group I. The decrease in hemoglobin was associated with an increase in blood flow and a pulsed venous flow pattern in 14 of 22 veins after autologous blood predonation and in 21 of 22 veins on postoperative day 1 (p<0.05). Increased venous flow in hemodilution is associated with a pulsed venous flow pattern.