Comparison of four methods for the determination of platelet function in whole blood in cardiac surgery.
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Bleeding Time↗
Biomedical subjects
G V Dietrich
Publications and source records attributed to G V Dietrich.
What the neurosurgeon needs to know about the coagulation system.
Intracranial surgery is often complicated by thromboembolic events including the life-threatening pulmonary embolism. After head trauma and in patients with brain tumors disseminated intravascular coagulation (DIC) can occur, characterized by the triggering of the coagulation cascade and the depletion of coagulation factors which ultimately leads to bleeding. The identification of patients at high risk as well as the early diagnosis of hemostatic problems uses routine laboratory parameters such as partial thromboplastin time and prothrombin time reflecting the intrinsic and the extrinsic pathway of the coagulation respectively. Thrombin antithrombin III complexes (TAT) and prothrombin fragment 1 + 2 (F1 + 2) are further indicators of an activation of the coagulation whereas fibrinogen degradation products (FDP) refer to the fibrinolytic system. The basic principles of coagulation and fibrinolysis are summarized as well as the changes of laboratory parameters accompanying DIC, hypercoagulability and hyperfibrinolysis.
Blood Coagulation↗
Increase of interleukin-6 plasma levels after elective craniotomy: influence of interleukin-10 and catecholamines.
Accidental and operative trauma are able to induce a systemic reaction of the organism characterized by fever, leukocytosis, catabolism, and an activation of the coagulation system. Interleukin-6 (IL-6) has been found to be an important mediator of this acute-phase response. In this study the influence of elective craniotomy on IL-6 plasma levels was evaluated. Blood samples were obtained from 20 patients undergoing elective craniotomy for vascular or tumorous diseases of the brain. IL-6 increased significantly (p < 0.05) from the pre-operative (0(0-5.4) pg/ml) to the intraoperative (180 min after beginning of surgery) time-point (10.6 (0-18.5) pg/ml). The maximum was reached on the first postoperative morning (13.9(4.3-45.0) pg/ml). Interleukin-10 (IL-10) is an anti-inflammatory cytokine which suppresses IL-6 synthesis in vitro in various cell lines. IL-10 plasma concentrations showed no alterations throughout the study period. Epinephrine plasma concentrations increased significantly from pre-operative values (15 (0-74) pg/ml) to the postoperative time-point (57(9-459) pg/ml). A 4.5-fold increase (p < 0.05) of norepinephrine plasma concentrations was found when comparing the data obtained 60 min after beginning of surgery with the data of the first postoperative morning. In monocytes, which are a major source of plasma IL-6, an elevation of intracellular cAMP stimulates the IL-6 synthesis. The postoperative maximum of IL-6 in plasma could be due to a release of catecholamines. In conclusion this study demonstrated an elevation of IL-6 plasma concentrations during and after elective craniotomy. Increased plasma catecholamine concentrations as well as a damage in the blood-brain barrier due to the surgical trauma with a spill-over of IL-6 from brain tissue into plasma could have contributed to this result.
Acute-Phase Reaction↗
[The in vitro effect of alpha-2 agonists on thrombocyte function and density of thrombocyte alpha-2 receptors].
UNLABELLED: alpha 2-Agonists are being used increasingly in anaesthesia and intensive care medicine because of their antihypertensive, analgesic and sedative properties. Platelets bear alpha 2-receptors on the cell surface. Stimulation of these receptors by agonists induces platelet aggregation. The present study examined whether in vitro incubation of blood with the alpha 2-agonists clonidine and dexmedetomidine decreases alpha 2-receptor density and hereby influences platelet aggregation. METHODS: Whole blood of 20 healthy volunteers was incubated over 24 h at 37 degrees C with 1 ng/ml clonidine or 1 or 10 ng/ml dexmedetomidine. Induced platelet aggregation was determined by means of turbidometry. Epinephrine (22 mumol/l) or collagen (20 mg/l) served as inductors. The density of alpha 2-receptors was measured in radioligand assays with 3H-Yohimbine. Phentolamine was used to assess unspecific binding. The data were analyzed with an analysis of variance. RESULTS: Neither 1 ng/ml clonidine nor 1 ng/ml dexmedetomidine altered platelet aggregation or alpha 2-receptor density in comparison with the control sample. As a major result we found that 10 ng/ml dexmedetomidine caused a significant (P < 0.05) reduction in epinephrine-induced platelet aggregation (16.0 +/- 5.4%, n = 20, mean +/- SEM) compared with the control (46.0 +/- 1.3%, n = 20). alpha 2-Receptor density was not any different from the control. CONCLUSIONS: This in vitro study showed that clinically relevant concentrations of 1 ng/ml clonidine or dexmedetomidine did not alter platelet aggregation or alpha 2-receptor density, even after 24 h exposure. However, 10 ng/ml dexmedetomidine was found to diminish significantly epinephrine-induced platelet aggregation, but did not change alpha 2-receptor density. This result showed that desensitization of platelet aggregation can occur without quantitative changes in alpha 2-receptors.
Adrenergic alpha-2 Receptor Agonists↗
Platelet function and adrenoceptors during and after induced hypotension using nitroprusside.
BACKGROUND: Hypotension induced by sodium nitroprusside can minimize intraoperative blood loss. The release of endogenous catecholamines can influence adrenoceptors of platelets and thus might change the ability of platelets to aggregate. METHODS: Forty patients undergoing nasal septum, tympanoplastic, or sphenoid sinus surgery were randomly divided into two groups, those having controlled hypotension (A) and those serving as controls (B). Blood samples were drawn before the operation, after induction of anesthesia, 1 h after the start of the operation, and on the day after surgery. RESULTS: Epinephrine-induced platelet aggregation only increased in the controls on the day after surgery (A: from 49 +/- 25% to 47 +/- 29%; B: from 53 +/- 24% to 72 +/- 14%; mean +/- SD; P < 0.01). Spontaneous platelet aggregation increased in the controls from a median of 1.2 omega/h to 2.4 during the operation and 2.9 on the day after surgery but not after hypotension. On the day after surgery, alpha 2 receptors reached their maximum (A: 238 +/- 164; B: 234 +/- 80 per platelet). During the operation, the norepinephrine concentrations were significantly greater in group A (median, 419 pg/ml) than in group B (median, 217 pg/ml; P < 0.05). Blood loss was greater in the controls (A: 180 +/- 75; B: 379 +/- 120 ml; P < 0.05). CONCLUSIONS: Controlled hypotension using sodium nitroprusside reduces epinephrine-induced and spontaneous platelet aggregation. Even on the day after hypotension, the usual postoperative reactive increase in platelet aggregation did not occur. These results may be explained by the direct effect of nitroprusside on platelets, the augmented stress response, lower shear stress on platelets due to the lower blood pressure, or the decreased blood loss compared with the controls.
Adult↗
[Autologous blood donation versus homologous blood transfusion--an analysis of cost effectiveness].
Cost-efficiency analysis for autologous transfusions begins with the calculation of the pure production costs. They amount to $35-$75 for one unit of red blood cell concentrate (RBC). One homologous RBC is billed with $80 in Germany. Following factors further increase costs of an autologous blood predeposit: Autologous blood frequently is transfused more generously. The expiration-rate of autologous blood is higher. The haemoglobin content of the second and following RBC is lower. The patient himself has lower haemoglobin on the day of surgery after an autologous blood donation. In scientific examinations it is possible to refer additional costs of autologous blood to a gained "quality adjusted life year". They amount to $40,000 to $1,800,000.
Blood Transfusion, Autologous↗
[Increase in interleukin-6 plasma concentrations following hypotensive anesthesia with sodium nitroprusside].
In animal models authors have dealt with the question of whether hypotension alone can cause an acute-phase response even in the absence of marked blood loss and trauma. Sodium nitroprusside (SNP), which was employed in the animal models, is also used to induce hypotension in humans. Since no data are available on human subjects plasma concentrations of interleukin-6 (IL-6), an important mediator of the acute-phase response, were studied in patients during SNP infusion for induction of hypotension. METHODS. After approval by the local ethics committee, 20 patients scheduled for elective oto-rhino-laryngological operations participated in this randomised prospective study. Anaesthesia was induced with fentanyl, etomidate, vecuronium and succinylcholine and was maintained with isoflurane in 66% N2O and 33% O2. Ten patients received SNP to reduce mean arterial blood pressure to 50 mmHg, while another ten patients served as controls. Blood samples were taken before the induction of anaesthesia, during surgery (at the end of the SNP infusion), 60 min after surgery and on the day after surgery. IL-6 concentrations were determined by means of enzyme-linked immunosorbent assay. Epinephrine and norepinephrine in plasma were measured by high-pressure liquid chromatography with electrochemical detection. RESULTS. The IL-6 plasma concentration increased significantly from 3.2 (0-7.5) pg/ml (median and range) to 31.8 (9-42.2) pg/ml in the SNP group and from 3.5 (0-8.3) pg/ml to 15.2 (7.4-19) pg/ml in the control group on the morning after surgery. The IL-6 values at this time were significantly (P < 0.05) higher in the SNP group than in the controls. Norepinephrine increased significantly from 263 (150-920) pg/ml (median and range) preoperatively to 419 (115-897) pg/ml, and the epinephrine concentrations rose significantly from 77 (12-159) pg/ml to 115 (83-330) pg/ml at the end of SNP administration. No significant changes in the catecholamine concentrations were observed in the control group. CONCLUSIONS. The SNP infusion exerted an important additional stimulus for IL-6 release after relatively mild surgical trauma in both groups. This finding is probably due to the liberation of NO from the SNP molecule and an increase in the intracellular concentration of cGMP. The elevation of the plasma catecholamines immediately after SNP administration should also be taken into account, because an augmentation of the cAMP in various cell types has been proven to result in increased release of IL-6.
Adult↗
[Does controlled hypotension with nitroprusside affect platelet function?].
Induced hypotension is an accepted technique to reduce intraoperative blood loss and thereby ensures satisfactory operating conditions, especially in microscopic interventions. Sodium nitroprusside (NP), which is often used for induced hypotension, was reported to inhibit platelet aggregation in vitro. Impairment of platelet function implies a higher bleeding risk, which would make the use of NP for induced hypotension questionable. METHODS. With the approval of the local ethics committee, 30 patients scheduled for nasal septum operations were included in this randomised study. For induction of anaesthesia 2 mg vecuronium, 0.1 mg fentanyl, 0.2 mg/kg etomidate, and 1 mg/kg succinylcholine were used. After tracheal intubation the patients inhaled 1.0-1.5 vol.% isoflurane in a gas mixture containing 66% nitrous oxide in oxygen. Fifteen patients received an i.v. infusion of NP for 60 min. The concentrations chosen produced a decrease of mean arterial blood pressure to 50 mm Hg. Blood samples were taken before induction of anaesthesia; after induction of anaesthesia but before beginning of the operation; and 60 min after the beginning of the operation. This time-point coincided with the end of NP administration in the study group. The last blood sample was drawn the morning after the operation. Platelet function was determined in platelet-rich plasma by a turbidometric method after adding 22 mumol/l epinephrine to induce aggregation. The spontaneous aggregation was measured in whole blood using impedance aggregometry. Data within one group were analysed using analysis of variance. Student's t-test for unpaired values served to compare data between the two groups. RESULTS. Biometric data in the two groups were comparable. The blood loss in the control group [265 (190-410) ml] significantly exceeded (P < 0.05) that in the hypotensive group [125 (75-210) ml]. No significant changes in platelet function were found throughout the study period in the patients treated with NP. In the control patients the epinephrine-induced aggregation increased significantly from 53.1 +/- 5.3% before anaesthesia to 72.1 +/- 3.3% the morning after the intervention. The spontaneous aggregation showed a significant increase from 0.718 +/- 0.338 Ohm/h before anaesthesia to 2.164 +/- 0.442 Ohm/h 60 min after the beginning of the operation. The value on the 1st postoperative day (2.266 +/- 0.448 Ohm/h) was also significantly higher than the basal value. CONCLUSIONS. In contradiction to in vitro studies using high concentrations of NP, we could not find a decrease in platelet aggregation due to hypotensive anaesthesia with this drug in vivo. In the control group a significant increase in platelet aggregation was observed, which was probably counteracted in the hypotensive patients by the interaction of NP with cyclic guanosine monophosphate (c-GMP). NP augments the intracellular concentration of c-GMP, which is known to decrease platelet aggregation.
Adolescent↗
Variables influencing the Thrombostat 4000: recommended standardization.
The in vitro bleeding test (IVBT) (Thrombostat 4000) was performed on blood samples from healthy blood donors using a "preliminary standard test." Only one factor of the test procedure was changed each time. We found the following parameters to have a significant influence on the test results: time interval between sampling and testing, diameter of the filter's aperture, capillary diameter, aggregating agents and their concentration, temperature of the blood and cartridges, method of drying the capillaries, the aspiration pressure, and the hematocrit of the blood sample. According to our data, we propose a standard IVBT for routine application and modifications for special diagnostic use.
Adenosine Diphosphate↗
Therapeutic use of phospholipids in thrombocytopenic or thrombocytopathic patients.
Eight thrombocytopenic/pathic patients received an intravenous infusion of phospholipids. In vitro bleeding test (Thrombostat 4000), thrombelastography, and resonance thrombography were performed in order to show the hemostatic effect. In none of the cases did phospholipids exert an effect comparable to platelet transfusion. Two patients, brother and sister, had a severe anaphylactoid reaction after the administration of phospholipids.
Adolescent↗
Beta 2-adrenoceptor density of human lymphocytes after nitroprusside-induced hypotension.
The present study was undertaken to assess the influence of nitroprusside-induced hypotension on beta 2-adrenoceptor density. Twenty-four patients undergoing nose-septum corrections under general anesthesia were allocated randomly to a nitroprusside or control group. beta 2-Receptor density on lymphocytes was measured by binding studies using (-)125-iodocyanopindolol. Lymphocyte subpopulations B, T, Thelper, Tsuppressor, and natural killer cells were determined simultaneously by flow cytometry. Five of 12 nitroprusside-treated patients developed significant intraoperative increases of epinephrine levels (+69% versus preoperatively) which were not seen in the remaining seven patients. In these five patients, beta 2-receptor density of unfractionated lymphocytes was 26% lower (P < 0.05) on the first day after surgery compared with preoperative values. Since no changes in proportions of lymphocyte subpopulations were observed, these results are not caused by redistribution phenomena inducing a decrease of subsets with a high number of beta receptors. These findings suggest that beta 2-adrenergic responsiveness might be diminished after nitroprusside treatment in some patients.
Adrenergic beta-Antagonists↗
[Effect of controlled hypotension using sodium nitroprusside on platelet aggregation].
OBJECTIVE: To determine the influence of sodium nitroprusside (SNP) on platelet aggregation when this agent is used to induce hypotension during surgery. PATIENTS AND METHODS: Spontaneous platelet aggregation (SPA) determined by impedance measurement and induced platelet aggregation (IPA) determined by turbidimetry were studied in 30 subjects scheduled for elective ear, nose or throat surgery. Fifteen patients in the SNP group (SNPG) received SNP in doses adjusted to maintain a mean arterial pressure of 50 mmHg. Another 15 patients who did not receive SNP served as controls. RESULTS: SPA increased progressively in both groups. The greatest increase occurred after anesthetic induction (control group +172%, SNPG +48%); the highest level recorded was reached on the morning of the first day after surgery (control group +215%, SNPG +46%). IPA decreased after anesthetic induction (control group -21%, SNPG -40%) and stayed down throughout surgery. IPA was higher on the first morning after surgery than before the operation (control group +35%, SNPG +2%). SPA was significantly higher 60 minutes after start of surgery than before surgery in the control group; IPA and SPA were likewise higher in these patients the morning after surgery. CONCLUSIONS: Platelet aggregation increases during surgery and in the immediate postoperative period. This increase is attenuated when SPA is given to induce hypotension. SPA should be determined by measurement of impedance in whole blood when the nature of platelet aggregation during surgery is being studied, given that early increases in IPA can be masked as a result of the low sensitivity of turbidimetry.
Blood Coagulation Disorders↗
[Lymphocyte subpopulations in controlled hypotension with sodium nitroprusside].
AIM: Induced hypotension is an anaesthesiological method to reduce blood loss in surgical patients. The aim of this study was to investigate whether induced hypotension with sodium nitroprusside (SNP) causes changes in lymphocyte subpopulations. METHODS: In a prospective randomised evaluation 30 patients undergoing elective oto-rhino-laryngological interventions were studied. In 15 patients SNP was administered to reduce the mean arterial pressure to 50 mmHg. There was a control group of another 15 patients. Anaesthesia was induced with etomidate and maintained with isoflurane. At 7 a.m. on the day of operation (T1), 10 minutes after induction of anaesthesia (T2), 60 minutes after T2 (T3, end of SNP-infusion), 120 minutes (T4) after T2; 180 minutes (T5) after T2, and at 7 a.m. on the following morning (T6) blood samples were taken. A new method (whole blood) was used to mark 6 different lymphocyte subpopulations with monoclonal antibodies which were measured by flow cytometry. RESULTS: In both groups a significant decrease in total lymphocyte count (from 32.7 x 10(9) cells/l preoperatively to 13 x 10(9) cells/l the following morning in the SNP-group and from 31 x 10(9) cells/l to 14.2 x 10(9) cells/l the following morning in the control group) was observed. In the SNP-group the HLA-DR positive T-lymphocytes increased from 11.8% at T1 to 19.2% at T5 and 22.3% at T6. No statistically significant changes were found in percentage of T-, T4-, T8-, B-lymphocytes and natural killer cells. CONCLUSION: The increase in the percentage of activated T-lymphocytes is possibly due to an activation of the sympatho-adrenergic system after sodium nitroprusside-infusion and a subsequent redistribution of these cells from other organs (bone marrow, spleen, lymph nodes). The cell-mediated and the humoral immunity are not altered by induced hypotension. In discussing this result, the age of the patients, the extent of the surgical trauma, the anaesthesiological procedure and the methodological aspects in the lymphocyte assay should be taken into consideration.
Adolescent↗
[Epidural regional anesthesia and low molecular weight heparin: Contra].
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Anesthesia, Epidural↗