UMLS:C0020672 - FACTA Search

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Query: UMLS:C0020672 (hypothermia)
17,327 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous reports suggest that activated clotting times do not correlate with heparin concentration during cardiopulmonary bypass. This study was designed to compare whole blood heparin concentration and activated clotting time measurements with laboratory-based plasma heparin concentration. Sixty-two patients having cardiac operations requiring cardiopulmonary bypass were enrolled in this study. The study was conducted in two phases. In phase I of this trial, blood specimens were obtained from 30 patients before heparin administration and after each of three heparin doses (20, 80, and 150 U/kg). In phase II, blood specimens were obtained from 32 patients before heparin administration and 10 minutes after each of the following: heparin administration (250 or 300 U/kg), initiation of cardiopulmonary bypass, achievement of hypothermia, initiation of rewarming, and immediately before discontinuation of bypass. Blood specimens were used to measure activated clotting time (kaolin and celite), whole blood heparin concentration, and anti-factor Xa plasma heparin concentration. In phase I, activated clotting time (celite: r = 0.91; kaolin: r = 0.93) and whole blood heparin concentration (r = 0.98) measurements correlated well with plasma heparin concentration. After initiation of cardiopulmonary bypass (phase II), weak correlations for activated clotting time measurements (celite: r = 0.34; kaolin: r = 0.59) and a strong correlation for whole blood heparin concentration (r = 0.95) were evident when compared with plasma heparin concentration. During bypass, activated clotting time measurements also inversely correlated with temperature (celite: r = -0.21; kaolin: r = -0.19) and hematocrit (celite: r = -0.26; kaolin: r = -0.21). A weak correlation between activated clotting time measurements and plasma heparin concentration is evident during the cardiopulmonary bypass period, probably because of the influence of both reduced hematocrit and temperature on the activated clotting time assay. In contrast, whole blood heparin measurements correlate well with plasma heparin concentration before and during bypass. Further studies are needed to determine whether maintaining heparin levels during cardiopulmonary bypass by monitoring heparin concentration is more effective in preventing consumptive activation of the hemostatic system, reducing bleeding, and minimizing the use of blood products after cardiopulmonary bypass when compared with a protocol based on activated clotting time.
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PMID:Comparison of activated coagulation time and whole blood heparin measurements with laboratory plasma anti-Xa heparin concentration in patients having cardiac operations. 798 77

Hypothermia prolongs clotting times when the tests are performed at hypothermic temperatures, in contrast to standard clinical tests performed at 37 degrees C. The relative impact of hypothermia on plasma clotting factor activity was investigated by determining the specific clotting factor deficiencies required to produce an equivalent effect. Clotting factor concentration curves were constructed for clotting factors II, V, and VII through XII using assayed reference plasma (ARP) diluted with specific factor-deficient plasmas (FDP). Prothrombin times and partial thromboplastin times were measured as appropriate for each factor at test temperatures ranging from 37 degrees to 25 degrees C using a modified fibrometer. The clotting times for each temperature with undiluted ARP were compared with the clotting times at 37 degrees C obtained with FDP dilution. Hypothermia at temperatures below 33 degrees C produces a coagulopathy that is functionally equivalent to significant (< 50% of normal activity) factor-deficiency states under normothermic conditions, despite the presence of normal clotting factor levels.
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PMID:Functional equivalence of hypothermia to specific clotting factor deficiencies. 808 2

Hypothermia has been shown to cause coagulation abnormalities, primarily related to platelet dysfunction. We reviewed coagulation function and the incidence of delayed traumatic intracerebral hemorrhage in a series of 36 patients with severe head injuries (Glasgow Coma Scale 3-7) enrolled in a prospective, randomized, clinical trial of therapeutic moderate hypothermia. Patients were randomized to a normothermic group (n = 16) or to a group cooled to 32 to 33 degrees C within 6 hours of injury (n = 20). Prothrombin times, partial thromboplastin times, and platelet counts were obtained in the emergency room and then again within 24 hours of randomization. Delayed traumatic intracerebral hemorrhage occurred in 6 of 20 (30%) hypothermic patients and 5 of 16 (31%) normothermic patients. In the hypothermic group, 9 of 17 patients had an increased prothrombin time during hypothermic therapy, as opposed to 11 of 16 in the normothermic group during the corresponding time period. The partial thromboplastin time was prolonged in 2 of 17 hypothermic patients and 2 of 16 normothermic patients. Three patients in the hypothermic group and one in the normothermic group developed thrombocytopenia (a platelet count of less than 100,000). There were no significant differences between the two groups in the incidence of delayed traumatic intracerebral hemorrhage, in measured coagulopathy, or in the mean values of measured coagulation parameters. Although the possibility of a hypothermia-induced coagulopathy has not yet been excluded, the short-term use of hypothermia does not appear to increase the risk for intracranial hemorrhagic complications in head injuries.
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PMID:The effect of hypothermia on the incidence of delayed traumatic intracerebral hemorrhage. 817 85

Definitive laparotomy (DL) for penetrating abdominal wounding with combined vascular and visceral injury is a difficult surgical challenge. Physiologic derangements such as dilutional coagulopathy, hypothermia, and acidosis often preclude completion of the procedure. "Damage control" (DC), defined as initial control of hemorrhage and contamination followed by intraperitoneal packing and rapid closure, allows for resuscitation to normal physiology in the intensive care unit and subsequent definitive re-exploration. The purpose of the study was to compare the damage control technique with definitive laparotomy. Over a 3 1/2-year period, 46 patients with penetrating abdominal injuries required laparotomy and urgent transfusion of greater than 10 units packed red blood cells for exsanguination. Medical records were retrospectively reviewed for degree and pattern of injury, probability of survival, actual survival, transfusion requirements for the preoperative and postoperative phases, resuscitation and operative times, lowest perioperative temperature, pH, and HCO3. No significant differences were identified between 22 DL and 24 DC patients and actual survival rates were similar (55% DC vs. 58% DL). However, in a subset of 22 patients with major vascular injury and two or more visceral injuries (maximum injury subset), otherwise similar to the overall group, survival was markedly improved in patients treated with damage control (10 of 13, 77%*) vs. DLM (1 of 9, 11%) (Fisher's exact test, * p < 0.02). In preparation for return to the operating room, DC survivors averaged 8.4 units of packed red blood cells transfused and 10.3 units fresh frozen plasma over a mean ICU stay of 31.7 hours. Resolution of coagulopathy (mean prothrombin time/partial thromboplastin time 19.5/70.4 to 13.3/34.9), normalization of acid-base balance (mean pH/HCO3 7.37/20.6 to 7.42/24.2), and core rewarming (mean 33.2 degrees C to 37.7 degrees C) were achieved. All patients had gastrointestinal procedures at reoperation (mean operative time, 4.3 hours). We conclude that damage control is a promising approach for increased survival in exsanguinating patients with major vascular and multiple visceral penetrating abdominal injuries.
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PMID:'Damage control': an approach for improved survival in exsanguinating penetrating abdominal injury. 837 Dec 95

The occurrence of bleeding in trauma patients is a life-threatening problem which can be explained by different mechanisms. The infusion of cristalloids, colloids, packed red blood cells, or even fresh frozen plasma is very rarely responsible for bleeding but it can contribute to dilute the patient's platelet pool, and especially dilutional thrombocytopenia is the first cause of bleeding after massive transfusion. Blood coagulation factor activity is decreased after a massive fluid infusion is performed but it has to reach a dramatically low plasma level in order to induce troubles. It has to be emphasized that colloids and especially dextrans can impair the patient's haemostasis by interfering the same way with the factor VIII-von Willebrand complex and fibrin formation. Gelatins do not interfere with platelets or with the coagulation system. A third mechanism that can explain the strong link between haemostasis and haemodilution is the haemostatic role of red cells. It has been shown in experimental models that red cells play a definite function in promoting platelet accretion on the damaged vessel surface. Higher values of haematocrit (Ht) are responsible for a better platelet adhesion On the opposite, platelet adhesion decreases when low values of Ht (< 20%) are reached. Hypothermia can also impair platelet function and worsen the bleeding. A simplified monitoring of haemostasis can be proposed with platelet count, whole blood coagulation clotting time, immediately available activated partial thromboplastin time and prothrombin time with bedside portable monitors and thromboelastography. Haematocrit and body temperature have to be monitored as well.
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PMID:[Traumatic emergencies and hemostasis]. 856 76

Patients at risk for clinically significant bleeding and who require urgent or emergent surgical procedures are encountered. Usually local causes are responsible, but a generalized hematologic defect may be uncovered. Quickly and effectively distinguishing the cause may be critical to rapid treatment and survival. A careful history, appropriate use of laboratory tests (e.g., partial thromboplastin time, prothrombin time, and platelet count), and knowledge of possible causes are key to prompt diagnosis and treatment. Bleeding from multiple sites, spontaneous bleeding, or unexpectedly severe bleeding suggests a systemic process. Immunocompromised or suppressed patients or systemically ill patients with chronic hepatic renal, lymphatic, and hematologic disorders are seen with urgent surgical problems. The key is rapid diagnosis and effective systemic and local therapy to counter the problem. The syndrome of diffuse "medical bleeding" frequently confronts the surgeon treating a patient who has received transfusions of more than 1.5 times blood volume. The coagulation defect is almost always associated with hypothermia and acidosis. Treatment consists in control of large-vessel bleeding by appropriate surgical techniques, blunt packing, and tamponade of diffuse bleeding, rapid rewarming of the patient, and adequate resuscitation for shock. Transfusion of platelets and fresh frozen plasma is empiric initially and subsequently guided by the clinical and laboratory coagulation profiles of the patient.
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PMID:Emergency surgery in hematologic patients. 886 72

The haemostatic system and the use of heparin during cardiopulmonary bypass (CPB) have been studied extensively in adults but not in children. Results from adult trials cannot be extrapolated to children because of age-dependent physiologic differences in haemostasis. We studied 22 consecutive paediatric patients who underwent CPB at The Hospital for Sick Children, Toronto. Fibrinogen, factors II, V, VII, VIII, IX, XII, prekallikrein, protein C, protein S, antithrombin (AT), heparin cofactor II, alpha 2-macroglobulin, plasminogen, alpha 2-antiplasmin, tissue plasminogen activator (tPA), plasminogen activator inhibitor, thrombin-AT complexes (TAT), D-dimer, heparin (by both anti-factor Xa assay and protamine titration) and activated clotting time (ACT) were assayed perioperatively. The timing of the sampling was: pre heparin, post heparin, after initiation of CPB, during hypothermia, post hypothermia, post protamine reversal and 24 h post CPB. Plasma concentrations of all haemostatic proteins decreased by an average of 56% immediately following the initiation of CPB due to haemodilution. During CPB, the majority of procoagulants, inhibitors and some components of the fibrinolytic system (plasminogen, alpha 2 AP) remained stable. However, plasma concentrations of TAT and D-dimers increased during CPB showing that significant activation of the coagulation and fibrinolytic systems occurred. Mechanisms responsible for the activation of haemostasis are likely complex. However, low plasma concentrations of heparin (< 2.0 units/ml in 45% of patients) during CPB were likely a major contributing etiology. ACT values showed a poor correlation (r = 0.38) with heparin concentrations likely due to concurrent haemodilution of haemostatic factors, activation of haemostatic system, hypothermia and activation of platelets. In conclusion, CPB in paediatric patients causes global decreases of components of the coagulation and fibrinolytic systems, primarily by haemodilution and secondarily by consumption.
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PMID:Coagulation and fibrinolytic profile of paediatric patients undergoing cardiopulmonary bypass. 915 80

Bleeding remains a complication of certain complex surgical procedures, particularly those cardiac operations associated with long bypass times and profound hypothermia. Clinical and novel experimental strategies to reduce bleeding and the need for blood and blood-product transfusions are the focus of this review. Preoperative assessment of the patient will identify drug-induced, acquired, or inherited coagulation defects that may contribute to this problem. The main attention is directed to the perioperative period, and broad areas discussed include the preoperative use of erythropoietin to increase red blood cell mass, autologous donation either preoperatively or before bypass, autotransfusion/hemofiltration, and acceptance of relative anemia both during the operation and into the postoperative period. A further, often overlooked, management strategy in treating major coagulopathies is the consideration of the cost and half-lives of the coagulation factors in individual blood components. Prevention of bleeding has become possible both by manipulation of the control of coagulation and inflammatory processes and by the introduction of pharmacologic agents such as aprotinin. Aprotinin is widely used and has proven efficacy in the management of excess bleeding. It is a serine protease inhibitor and has several possible mechanisms of action, including inhibition of the plasma enzyme systems activated by contact with the foreign surface of the bypass circuit and preservation of platelet function. Safety issues include the possibility of hypersensitivity and anaphylactic reaction on a second exposure. Concerns that aprotinin may induce a prothrombotic or coagulant state have no basis in theory or any good evidence in the current literature. A recent study specifically sought to identify the presence of disseminated microvascular platelet-fibrin thrombi present at autopsy in patients who had received aprotinin therapy. The study concluded that diffuse platelet-fibrin thrombi were not a direct complication of aprotinin therapy. Finally, modern molecular biology has led to the recent development of an inhibitor for factor IXa that competitively replaced IXa in the intrinsic complex and blocked the conversion of factor X to factor Xa. This compound is under investigation in animal studies. These have so far shown efficacy in reducing blood loss after bypass in comparison with standard heparin anticoagulation.
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PMID:Management of bleeding complications in redo cardiac operations. 956 96

Automated activated clotting time (ACT) is utilized as the primary means of assessing anticoagulation status for cardiopulmonary bypass (CPB) procedures. Influences on the clotting cascade during CPB such as hypothermia, hemodilution, and platelet dysfunction are known to affect ACT. The recently introduced Thrombolytic Assessment System (TAS) has been reported to be less sensitive to changes in hemodilution and hypothermia during CPB than more conventional ACT devices. This study evaluated the ability of TAS, and two other commercially available automated ACT systems, the HemoTec and Hemochron, to correlate with circulating heparin levels. Reference standards for circulating heparin were determined by inactivation of factor Xa assay. Nineteen patients undergoing moderate hypothermic CPB served as subjects for this investigation. Blood samples were obtained for study at four time periods: 1) baseline (control), 2) post heparin administration (300-400 U/kg) prior to CPB, 3) during CPB, and 4) post protamine. Study results demonstrated a high correlation between the HemoTec and Hemochron (r = 0.99), increased heparin dose response on CPB compared to pre-CPB activity (p < 0.05), and a significant (p < 0.05) negative correlation between devices and patient hematocrit during CPB. Additionally, device correlation with anti-Xa assay during collection periods 2 and 3 showed negative correlations in each of the three devices evaluated. We conclude that all automated devices tested demonstrated an inability to predict circulating heparin at levels necessary for CPB, and that these discrepancies become magnified during CPB procedures.
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PMID:Correlation of ACT as measured with three commercially available devices with circulating heparin level during cardiac surgery. 1017 51

A porcine model of hemorrhagic shock was used to study the effect of hypothermia on hemodynamic, metabolic, and coagulation parameters. The model was designed to simulate the events of severe blunt injury with hemorrhage occurring initially, to a systolic blood pressure of 30 mm Hg, followed by simultaneous hemorrhage and crystalloid volume replacement, followed by cessation of hemorrhage and blood replacement. Half of the animals were rendered hypothermic by external application of ice, and half remained normothermic. There was seven pigs in each group. Two deaths occurred in each during the hemorrhage phase. The hypothermic pigs demonstrated larger reduction in cardiac output than normothermic pigs. Volume replacement in the normothermic group restored cardiac output to baseline values. In the hypothermic group, cardiac output remained depressed despite volume replacement. Prothrombin times and partial thromboplastin times showed significantly more prolongation in the hypothermic group. Furthermore, this was not corrected by replacement of shed blood in the hypothermic group, as was seen in the normothermic group. We conclude that when shock and hypothermia occur together, their deleterious effect on hemodynamic and coagulation parameters are additive. The effects of hypothermia persist despite the arrest of hemorrhage and volume replacement. Thus, it is necessary to aggressively address both shock and hypothermia when they occur simultaneously.
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PMID:Hypothermia-induced coagulopathy during hemorrhagic shock. 1077 71

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