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Biomedical subjects

G Singbartl

Publications and source records attributed to G Singbartl.

At least 19 recordsLinked to original sources
PubMed1999

Hypervolemic hemodilution: an alternative to acute normovolemic hemodilution? A mathematical analysis.

BACKGROUND: Hypervolemic hemodilution has been proposed as an alternative to normovolemic hemodilution to reduce homologous blood transfusions. So far, convincing data supporting this concept are unknown. MATERIALS AND METHODS: We therefore present a mathematical model calculating the efficacy of hypervolemic, normovolemic, and "no" hemodilution. Hypervolemic hemodilution constituted volume expansion (20% of estimated blood volume) maintained throughout surgery. Normovolemic hemodilution contained isovolemic exchange of blood (40% of estimated blood volume) vs colloid as well as retransfusing blood plus colloid to maintain minimal acceptable hematocrit, e.g., transfusion trigger. To determine the efficacy of each technique maximal allowable blood loss and final postoperative hematocrit were calculated. Maximal allowable blood loss referred to the amount of blood lost during surgery after which homologous blood transfusion became necessary. RESULTS: Recalculating published clinical data strongly validated the formulas used for our model. Hypervolemic hemodilution always revealed lowest maximal allowable blood losses. Normovolemic hemodilution constantly ensured highest maximal allowable blood losses. For blood losses <40% of blood volume, hypervolemic and normovolemic hemodilution provided almost identical final postoperative hematocrits. But in contrast to normovolemic hemodilution, hypervolemic hemodilution did not carry the risk of severe transient, retransfusion-induced hypervolemia. "No" hemodilution always gave lowest final postoperative hematocrits. CONCLUSIONS: Thus, hypervolemic hemodilution cannot replace normovolemic hemodilution to reduce homologous transfusions, but for blood losses <40% of blood volume hypervolemic hemodilution appears to be superior.

Blood Loss, Surgical↗
PubMed1999

[Cost analysis of autologous transfusion methods--a study of 5,017 patients].

PURPOSE: Cost analysis of autologous blood conservation measures compared to corresponding homologous blood products. METHODS: This study is based on data from 5,017 patients undergoing major bone and joint surgery in 1993 and participating preoperatively in autologous blood donation (ABD) (with hemoseparation (HS) into autologous packed red blood cells (APRBC) and autologous fresh-frozen-plasma (AFFP)), autologous plasmapheresis (APPH) for harvesting AFFP as well as intra-/postoperative blood salvage with mechanically processed autologous transfusion (MAT). RESULTS: Total costs for 3,110 ABD with HS amount to DM 517,586.00 resulting in about DM 167.00 per U of APRBC plus AFFP. Comparatively, costs per U of HPRBC is about DM 202.00. Break-even-point (BEP) is calculated with 2,258 U of APRBC (without considering AFFP additionally obtained by HS). Taking into account this AFFP due to coagulation in 20% lowers BEP to 1,819 U of APRBC. However, this analysis compares the "mere" cost figures only, but does not consider the extent of ABD-induced increase in rbc mass compared to that of HPRBC. Under these circumstances calculated cost per unit of APRBC is up to 90 per cent higher than for 1 U of HPRBC. Total cost for PPH with 15,570 U of AFFP amounts to about DM 1,824,162.00, resulting in about DM 115.00 per U of AFFP. Comparatively, cost per U of HFFP is about DM 136.00. BEP is calculated with 11,595 U of AFFP. However, when considering AFFP on coagulatory reasons' with 20% only, no BEP can be calculated and AFFP is not proven to be cost-efficient. Under these conditions it is about 2.8-times more expensive than HFFP; and if considering AFFP a volume substitute it is even more than twelve times more expensive than artificial colloids (e.g. HES 6%, 200/0.5). MAT--2,690 sets and patients with a total of 5,326 processing cycles--causes a total cost of about DM 1,356,161.00, resulting in about DM 504.00 per set and patient. Under our conditions MAT is not cost-efficient compared to HPRBC as it is about two times more expensive than HPRBC. For reaching cost efficiency the number of processing cycles is either to be increased from about 2 to about 4 cycles per set and patient or hematocrit of the rbc-product obtained by MAT is clearly to be increased. CONCLUSIONS: The "mere" figures of this cost analysis of APRBC versus HPRBC as well as of AFFP versus HFFP and HES appear in favour of the autologous products. However, such an analysis should consider--besides the costs--both the increase in rbc-mass obtained by ABD or MAT, versus homologous rbc, and the indication for administering AFFP. This study does not prove our autologous blood conservation measures to be cost efficient compared to homologous blood products. Therefore, these data may cause a critically reflection on established concepts of autologous transfusion measures and may initiate promoting new and more cost efficient constellations/alternatives of blood conservation measures.

Blood Transfusion, Autologous↗
PubMed1994

Adverse events of erythropoietin in long-term and in acute/short-term treatment.

Erythropoietin has been shown to be effective both in the reversal of anaemia in patients with end-stage renal failure and to increase the volume of autologous red blood cells donated preoperatively as well as to decrease the units of homologous blood transfused. This review analyzes the side effects of erythropoietin reported in the literature for long-term administration (mainly in patients with end-stage renal failure) as well as for acute/short-term administration (in patients participating in an autologous predeposit programme). The most important adverse events reported for long-term administration are as follows: (a) arterial hypertension; (b) cerebral convulsion/hypertensive encephalopathy; (c) thrombo-embolism; (d) iron deficiency; (e) influenza-like syndrome. The numbers given for these side effects are mainly taken from the first and dose-finding studies in patients with renal failure. These figures differ very much from the data given in controlled studies analyzing adverse events as well. Summarizing the results from controlled, multi-center trials in patients with end-stage renal failure or in AIDS patients, no significant differences have been observed between the control group and the patients treated with erythropoietin. The overall-incidence of side effects occurring in either group of these two studies was of approximately 83% and 95%, respectively. In contrast to these results the data published for the dose finding/treatment studies is approximately 30% for development of arterial hypertension, approximately 5% for occurrence of cerebral convulsion/hypertensive encephalopathy, approximately 10% for thrombo-embolic complications/clotting of vascular access, approximately 50% for development of iron deficiency, and approximately 10% for symptoms summarized as influenza-like syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Transfusion, Autologous↗
PubMed1994

[The present possibilities for routine use of blood-saving measures from the anesthesiologic point of view--theoretical basis and clinical practice. II: Perioperative retransfusion of acute blood loss; plasmapheresis].

Intra- and postoperative blood-salvage with consecutive retransfusion represent an established part within the "Concept of Autologous Transfusion (CAT)". According to the processing technique of the blood salvaged there exist two different systems: Autologous Transfusion System II (ATS II) and Autologous Transfusion System III (ATS III). By using ATS II blood (with or without anticoagulation) is collected within a collecting reservoir after having passed a rough-filter-system. Passing a fine-filter-system the blood collected is retransfused into the patient without any preceding processing (autologous direct-retransfusion, ADR). Because of the activation of the coagulation proteins by the tissue and by the collection system as well as due to the destroyed red blood cells, the white blood cells, the platelets and the free plasma hemoglobin the patient is transfused with an autologous "whole-blood-like product" of minor quality. By administration of ATS III blood is collected and anticoagulated and passes a rough-filter as well; by processing the blood by means of centrifugation and separation and by washing the damaged red blood cells, a great part of the white blood cells, of the platelets and of the plasma hemoglobin (and of the anticoagulatory drug) is eliminated resulting in a washed autologous product, which mainly consists of red blood cells, which are retransfused into the patient through a fine-filter system. This means, that the autologous product obtained by the two different systems differs both regarding its quality and the plasmatic and corpuscular contents. However, undoubtedly either system is able to effectively reduce the need for homologous blood.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Loss, Surgical↗
PubMed1994

[The present possibilities for routine use of blood-saving measures from the anesthesiologic point of view--theoretical bases and clinical practice. III. Autologous blood donation, autologous donation criteria and organizational measures].

This third part of a review on "Autologous Transfusion" deals with preoperative autologous blood donation, with supplemental pharmaco-therapy, with election criteria of the patient as well as with the organizational measures to be taken into account if an intensive autologous predeposit programme is routinely applied. Donation of an autologous predeposit aims at supplying the patient with autologous blood and autologous plasma, respectively, according to the expected blood loss and in order to reduce the need for homologous transfusion. Important aspects, which have to be considered if applying a routine autologous donation programme refer both to the election criteria of the patient and to the organizational programme and measures to be considered. Data in the literature reveal, that the risk of side effects for the patient (who is both the donor and the receiver of the (autologous) blood) during and after donation of an autologous predeposit is definitely not greater than the risk reported for otherwise healthy homologous volunteers. In our opinion, this means, that a patient who has been declared eligible for an elective operative intervention which makes homologous transfusion very probable, can be considered eligible for donating an autologous predeposit; additionally, he should also be eligible for acute normovolemic hemodilution, as donating an autologous predeposit with accompanying volume substitution of the predeposit 'is under hemodynamic aspects' nothing else than an acute and preoperatively performed normovolemic hemodilution. Analysing the data so far reported, volume substitution of the autologous predeposit appears to be a very important component for the patient's safety.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Transfusion, Autologous↗
PubMed1994

[The present possibilities for routine use of blood-saving measures from the anesthesiologic point of view--theoretical bases and clinical practice. IV: Supportive administration of erythropoietin and iron].

In clinical studies erythropoietin has been shown to effectively increase the autologous predeposit in patients undergoing elective surgery; however, the results demonstrating a reduction of homologous transfusion are not equally convincing. Besides the administration of erythropoietin in preoperative blood donation the necessity of which is to be questioned as a routine measure due to the efficacy of apparative-technical methods, more distinct and more specific indications probably emerge for this pharmacological support: preoperative administration of erythropoietin in anemic patients incapable of donating an autologous predeposit, anemic patients unable to undergo an elective surgical intervention due to the severity of the pre-existing anemia, patients who refuse autologous predeposit as well as homologous blood transfusions for religious reasons, and finally short term perioperative (pre- and/or postoperative) administration for reducing the period and the extent of postoperative anemia.

Blood Transfusion, Autologous↗
PubMed1994

[The present possibilities for routine use of blood-saving measures from the anesthesiologic point of view--theoretical basis and clinical practice. I. Potential risks of homologous transfusion; normovolemic hemodilution].

This paper, which is the first part of four, deals with the potential risks of homologous blood transfusion as well as with normovolemic hemodilution, an autologous transfusion method, which is easily to be applied and not expensive. Although the various methods of autologous transfusion are well known for many years the public discussion on the "AIDS-topic" has led to a growing interest in blood-saving measures. However, in contrast to the so-called "AIDS-topic" the potential risks of a transfusion-transmitted hepatitis as well as the immunologic effects of homologous blood are of much greater importance. Moreover, high-court-sentences give the legal background for intensifying autologous transfusion and to offer it to the patients. So far there are four autologous transfusion methods to be applied routinely: 1. normovolemic hemodilution (NHD); 2. intra- and/or postoperative blood salvage (I/PBS) with or without autologous direct-retransfusion (ADR); 3. preoperative autologous plasmapheresis (PPH); 4. preoperative autologous blood donation (ABD). Moreover, drug-induced stimulation of the erythropoiesis by means of erythropoietin and the additional (intravenous) administration of iron may become a further component among autologous transfusion methods. Normovolemic hemodilution means exchange of autologous blood versus an artificial colloid. To make sure for normovolemia is to be considered a "conditio sine qua non" for "functioning" of normovolemic hemodilution.(ABSTRACT TRUNCATED AT 250 WORDS)

Contraindications↗
PubMed1994

[Cryopreservation of erythrocytes using hydroxyethyl starch: in vivo results of an autologous retransfusion model in humans].

The cryopreservation of human red blood cells (RBC) can be greatly beneficial in certain situations such as for rare blood groups, problems due to multiple antibodies, and as an interim aid during temporary shortages. Additionally, cryopreserved erythrocytes may be useful in cases of civil or military disasters. Frozen/thawed autologous RBC are of particular interest as a supplement to liquid storage for elective operations (e.g. orthopedics, vascular and transplantation surgery) to extend the preoperative collection period, which is otherwise limited to 7 weeks. In this study using 7 healthy volunteers, 500 ml of whole blood was replaced by a suspension of cryopreserved autologous RBC [2 aliquots of 216 ml each, hematocrit (HCT) 43 +/- 2% (v/v), HES (hydroxyethyl starch) concentration 11.5% (w/w)]. No washing step was performed after thawing. Viability of the red cells after thawing in terms of saline stability reached 91.9 +/- 0.7% (n = 4). In all 7 cases the frozen/ thawed autologous RBC were tolerated very well. No adverse reactions could be detected. A slight posttransfusional leukocytosis as well as a moderate increase in LDH and bilirubin were observed, but these effects disappeared within 20 h. The concentrations of platelets, electrolytes, urea, protein and creatinine within their physiological ranges. The activities of the liver enzymes and the coagulation parameters investigated remained unchanged. Initially the level of free plasma hemoglobin increased by a factor of 2. Then it decreased within 20 h, accompanied by a restoration of haptoglobin. More than 85% of the HES was eliminated from the plasma within the 1st day.

Blood Preservation↗
PubMed1993

[Quality assurance in preoperative autologous blood collection from the viewpoint of the anesthetist].

From the anesthetist's point of view the following safety measures regarding autologous blood donation have to be considered: [1] inclusion/exclusion criteria for the patient's selection; [2] quality control of the autologous product itself and [3] adequate technical standards of the equipment applied. There is no doubt, the criteria used for the patient's selection of an autologous predeposit program have a great impact both on the number and the severity of complications that might occur. Anesthetists consider a patient eligible for an autologous predeposit program if he/she is considered eligible for an elective operative procedure, too; since this means that this patient demonstrates compensated organ functions (e.g. of the cardiovascular system, of the pulmonary function as well as of the metabolic and hematopoietic system). As shown by data in the literature, these criteria even hold true in patients with serious (but compensated) concomitant diseases. In contrast to the routine procedure of homologous donation, monitoring of a patient during the autologous predeposit procedure as well as an adequate replacement of the volume of the autologous predeposit donated appear to be reasonable, especially in patients with serious risk factors. Following this concept, the number of undesired side effects during the autologous donation is in the same order as it is known from healthy volunteers for homologous donation. It appears wise to apply the same safety and quality standards for an autologous predeposit as for the comparable homologous products. Most important and without any restriction, the autologous product has to be safe for the patient: there should be no bacterial contamination of the autologous product, and the corpuscular content of the autologous plasma should not exceed a definite limit.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, General↗