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Biomedical subjects

A H Stammers

Publications and source records attributed to A H Stammers.

43 records · Page 3Linked to original sources
PubMed1995

Aprotinin and methylprednisolone equally blunt cardiopulmonary bypass-induced inflammation in humans.

Cardiopulmonary bypass induces an inflammatory state characterized by tumor necrosis factor-alpha release. Integrin CD11b is a neutrophil surface adhesive glycoprotein integrin that is rapidly and permanently unregulated by tumor necrosis factor-alpha exposure. The CD11b integrin is known to be the primary neutrophil integrin responsible for neutrophil lung and myocardial entrapment after cardiopulmonary bypass and subsequent reperfusion injury. Twenty-four adults admitted to the hospital for myocardial revascularization were equally randomized to one of three groups: group A (control), group B (methylprednisolone before cardiopulmonary bypass), and group C (low-dose aprotinin protocol). Blood was collected at three times: (1) baseline, (2) 50 minutes of cardiopulmonary bypass duration, and (3) 30 minutes after cardiopulmonary bypass termination. Neutrophil CD11b integrin expression was measured by fluorescence-activated cell sorter analysis and plasma tumor necrosis factor-alpha levels measured by enzyme-linked immunosorbent assay. Group A demonstrated significant (p < 0.05) increases in CD11b expression at times 2 and 3 when results were compared with those of the same group baseline and with those of groups B and C at similar times. No significant changes were noted between groups B and C at any time. Group A demonstrated a significant (p < 0.05) increase in levels of tumor necrosis factor-alpha at time 3 when results were compared with those of the same group baseline and of groups B and C at the same time. No significant changes were noted between B and C at any time. These results demonstrate low-dose aprotinin has a similar antiinflammatory effect to that of methylprednisolone in blunting cardiopulmonary bypass-induced systemic tumor necrosis factor-alpha release and neutrophil integrin CD11b upregulation.

Aged↗
PubMed1995

Coagulation monitoring during extracorporeal membrane oxygenation: the role of thrombelastography.

Patients undergoing extracorporeal membrane oxygenation (ECMO) are at an increased risk for developing coagulopathies due to the adverse effects of extracorporeal circulation on the hemostatic mechanism. Methods of determining causative factors of bleeding diathesis are often inconsistent and non-specific. ECMO patients require aggressive transfusion therapy with autogenic blood products to stabilize and maintain hemostasis. The present study evaluated the coagulation status of newborn patients undergoing ECMO therapy, using a viscoelastic monitor (Thrombelastograph -TEG) that measures functional aspects of clot development and stabilization. Seventeen neonatal patients undergoing ECMO for severe respiratory dysfunction were entered into this study. Serial blood samples were obtained and routine coagulation assessment including fibrinogen concentration, platelet count and ionized calcium was performed. In addition, fibrin(ogen) degradation products (FDP), d-Dimers, antithrombin III and plasma free hemoglobin were measured. Transfusion indicators were established and total transfusion requirements recorded. TEG profiles were determined with the use of heparinase, an enzyme that degrades heparin but has little effect on other coagulation factors. The most commonly encountered complication was hemorrhaging which was diagnosed by laboratory and clinical assessment in 11 of 17 patients. Transfusion requirements (measured in ml/kg/ECMO hour) were the following: packed red blood cells--1.34 +/- 0.5; platelets--0.71 +/- 0.57; fresh frozen plasma--0.09 +/- 0.12; cryoprecipitate 0.05 +/- 0.05. Thrombelastograph profiles reflected hemostatic conditions that ranged from severe coagulopathies (DIC) to hypercoagulability. Interpretation of TEG profiles identified hemostatic abnormalities in 57 of 101 profiles (46.5%), with the most common etiology related to platelet dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Coagulation Disorders↗
PubMed1993

Extracorporeal support with a cadaver liver as a bridge to transplantation.

Extracorporeal liver perfusion (ECLP) has been used for detoxifying blood in patients in class IV hepatic encephalopathy. Palliation of the moribund patient utilizing extracorporeal devices with cross-circulation of a cadaver liver has been documented for over three decades. Common problems associated with this procedure which appear in the literature include cadaver liver distention, increased resistance to blood flow, and limited time of extracorporeal support due to cadaver liver failure. This report summarizes the experiences of the perfusion team in utilizing an extracorporeal circuit with an otherwise nontransplantable cadaveric liver, to support the decompensating hepatic patient as a bridge to transplantation. Between January and July 1992, three patients were supported for hepatic failure with ECLP. Two patients were placed on ECLP with a modified circuit containing two positive displacement pumps and one centrifugal pump. The third patient was placed on ECLP with a circuit that contained two centrifugal pumps and one positive displacement pump. Patient age ranged from 6 to 38 years and length of support ranged from 24 to 72 hours. In all three patients, a centrifugal pump was placed in the suprahepatic inferior vena cava line to facilitate cadaver liver drainage and decompression. Intensive monitoring of both patient and cadaver liver hemodynamics, hepatic function, and hematological status was performed. All three patients were successfully weaned from ECLP. Two patients received successful orthotopic liver transplantation. The third died of complications unrelated to ECLP after support was discontinued.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Hematological assessment of patients undergoing plasmapheresis during cardiac surgery.

Methods of reducing patient exposure to homologous blood transfusions include the technique of intraoperative plasmapheresis for the production of platelet rich plasma (PRP). The present study was designed to determine the patient benefits of PRP by examining hemostatic changes in coagulation screens and viscoelastic whole blood monitoring (Thrombelastography, [TEG]). One hundred fifteen patients undergoing elective cardiac surgery were prospectively randomized into a blinded study. Sixty-three patients had 20 percent of the circulating plasma volume sequestered prior to heparinization and pheresed into PRP, which was reinfused 10 minutes following heparin reversal with protamine. The control (CTR) group of 52 patients were exposed to no sequestration procedure. Patients were followed to discharge and 112 parameters, including anthropometric, operative, and postoperative factors, were measured. There were no significant differences between patient groups in preoperative, cardiopulmonary bypass (CPB), or surgical parameters. Average PRP volume was 600+/-100 ml with a total platelet yield of 1.1 billion platelets per patient. TEG indices were determined at four distinct times during the surgical procedure. The CTR group had significantly higher pre-CPB TEG indices of 2.3+/-1.2 and 2.1+/-1.2 (mean+/-SD), vs. 1.8+/-1.5 and 1.4+/-1.7 in the PRP group (p less than .04). Following heparin reversal, pre-PRP reinfusion TEG values were similar between groups, although both groups had significantly decreased indices when compared to pre-CPB values. Thirty minutes post-PRP infusion the treatment group had significantly improved TEG recovery when compared to the CTR group, 1.0+/-1.2 vs. 0.3+/-1.7 (p less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Protection of the neonatal myocardium during hypothermic ischemia. Effect of cardioplegia on left ventricular function in the rabbit.

The protective effect of cardioplegia upon neonatal myocardium during ischemia has not been clearly established. This study evaluated the effects of cardioplegia on left ventricular function in isolated working neonatal rabbit hearts (aged 1 week) subjected to 120 minutes of global ischemia at 28 degrees C. Four groups were studied: Group 1, hypothermia alone; Group 2, intermittent washout with an oxygenated noncardioplegic solution; Group 3, multidose cardioplegia; Group 4, single-dose cardioplegia. After ischemia, cardiac output was reduced to 72% +/- 5% (mean +/- standard error of the mean) of control (p less than 0.02) in Group 1 and to 56% +/- 4% in Group 2 (p less than 0.001). In contrast, there was no significant reduction from baseline cardiac output in those animals receiving cardioplegic solution (Group 3, 93% +/- 6%, and Group 4, 97% +/- 4%). Group 2 hearts demonstrated significantly worse recovery of cardiac output and stroke volume than all other groups. After ischemia, the first derivative of left ventricular pressure fell to 73% +/- 13% of control in Group 1 (p less than 0.1) and to 89% +/- 5% in Group 2 (p less than 0.05). However, the first derivative of left ventricular pressure was restored to control values in Group 3 (118% +/- 11%) and Group 4 (114% +/- 9%). When compared to baseline, creatine kinase was higher 30 minutes after reperfusion in Group 1 (40 +/- 8 versus 143 +/- 32 IU/L/gm, p less than 0.05) and in Group 2 (39 +/- 7 versus 163 +/- 33 IU/L/gm, p less than 0.05). Creatine kinase remained unchanged from baseline in Groups 3 and 4. This study demonstrates excellent preservation of left ventricular function in the neonatal rabbit heart protected with cardioplegic solution. In contrast, neither hypothermia alone nor intermittent washout with an oxygenated noncardioplegic solution was effective in preventing myocardial dysfunction. As in adults, the administration of cardioplegic solution preserves ventricular function during ischemia in neonatal hearts.

Animals↗
PubMed1986

Recovery of left ventricular function after hypothermic global ischemia. Age-related differences in the isolated working rabbit heart.

The immature myocardium has a greater tolerance for ischemia than does the mature heart. The effect of ischemia when combined with hypothermia on the newborn heart is poorly understood but has important clinical applications. This study examined the metabolic and functional recovery after 90 minutes of global ischemia at 20 degrees C in neonatal (1 week), immature (1 month), and mature (4 month) isolated working rabbit hearts. Following ischemia, aortic flow, cardiac output, heart rate, and stroke work remained at baseline values for neonatal hearts. Only coronary flow was significantly reduced from a control level of 4.5 +/- 1.4 (standard error of the mean) to 3.3 +/- 1.1 ml/min, p less than 0.05. In the immature group, hemodynamic parameters were below baseline, although no statistical differences were noted. Among mature hearts, however, all hemodynamic values were significantly below preischemic control. Water content was significantly higher in immature (73.2% +/- 1.4%) and mature (75.3% +/- 2.5%) hearts when compared with the neonatal group (46.8% +/- 4.6%), p less than 0.001. Coronary sinus creatine kinase was unchanged from baseline at 10 and 30 minutes following ischemia in the neonatal group. Although demonstrating substantial increases from baseline, statistical significance was not seen in the immature group because of the wide variation about the mean. In the mature group, creatine kinase rose significantly from preischemic levels of 15.4 +/- 4.3 IU/L/gm to 184.2 +/- 51.6 IU/L/gm at 10 minutes (p less than 0.01) and 123.7 +/- 31.9 IU/L/gm at 30 minutes (p less than 0.05). This study demonstrated improved tolerance to prolonged hypothermic ischemia in neonatal rabbit hearts when compared with older hearts subjected to the same conditions. The role of cardioplegic solutions in protecting the neonatal heart during cardiac operations when deep hypothermia is used may be of lesser importance than in the older patient.

Aging↗