Evaluation of angiographic contrast media and platelet function with impedance aggregometry and the PFA-100TM 'platelet function analyser'

BACKGROUND

Angiographic contrast media are used in balloon angioplasty and may influence thrombotic complications of the procedure. We studied the effect of different media on platelet aggregation in whole blood using impedance aggregometry and the PFA-100 'platelet function analyser' (Dade, USA).

METHODS

Venous blood samples from 18 healthy volunteers were split into four aliquots and mixed with 10% normal saline control, non-ionic medium (iohexol), low-molecular weight ionic medium (ioxaglate) and high-molecular weight ionic medium (diatrizoate). Samples were studied with impedance aggregometry and the PFA-100.

RESULTS

All media caused significant inhibition of aggregation compared with control with both methods (P<0.001). Antiplatelet potency was greatest with diatrizoate, intermediate with ioxaglate and least with iohexol with both methods (P<0.01). Electron microscopy of the PFA-100 membrane demonstrated occlusion of the experimental aperture with platelet thrombus in the control. Inhibition of platelet thrombus was seen with all media, greatest with diatrizoate, intermediate with ioxaglate and least with iohexol.

CONCLUSIONS

The media studied significantly inhibited platelet aggregation in vitro and potency was greater with ionic than non-ionic media. These methods use a combination of shear and chemical agonist with whole blood and may reproduce in vivo arterial conditions better than other techniques.

Sequential development of platelet, neutrophil and red cell autoantibodies associated with measles infection

This study describes the development of autoimmune thrombocytopenia followed by autoimmune haemolytic anaemia in a Negro woman with measles. An IgM platelet autoantibody was detected using a fluorescent labelled antiglobulin technique. The thrombocytopenia resolved spontaneously, although the platelet autoantibody persisted and platelet survival remained shortened, suggesting a compensated thrombocytolytic state. An IgG granulocyte autoantibody was present transiently although the patient was never neutropenic. The haemolytic anaemia was due to an IgM cold autoantibody (anti-I), which was active up to 30 degrees C, and an IgG warm autoantibody, which was detectable only when she was severely anaemic. After an initial blood transfusion, the anaemia resolved and the red cell autoantibodies disappeared. The platelet, granulocyte and red cell autoantibodies were cell-specific and not a single cross-reacting antibody.

Endothelial cell damage in heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia type II is a severe complication of heparin treatment that may result in thrombosis. When thrombosis occurs it carries a 50% mortality rate. The exact pathophysiology is not fully understood but in the majority of cases it is associated with the production of heparin/platelet factor 4 antibodies. The endothelium provides a protective anticoagulant surface over which blood flows. Perturbation of the endothelial cells causes a reversal of the anticoagulant properties of the cells to that of a procoagulant surface. This is often due to release or down-regulation of the anticoagulant membrane proteins such as thrombomodulin and up-regulation of procoagulant factors such as tissue factor. We studied 10 patients in our cardiothoracic institute with clinically and laboratory-confirmed heparin-induced thrombocytopenia type II for evidence of endothelial cell damage. There was a statistically significant rise in the concentrations of von Willebrand factor (P < 0.0001) and soluble thrombomodulin (P = 0.004) when patients with heparin-induced thrombocytopenia type II were compared with healthy laboratory controls and patients having had cardiopulmonary bypass surgery (von Willebrand factor 324 versus 103 versus 108 U/dl and soluble thrombomodulin 9.5 versus 2.3 versus 1.2 ng/ml, respectively). Our findings suggest that endothelial cell damage is a major factor in the pathophysiology of heparin-induced thrombocytopenia.

Factor XII auto-antibodies present in a patient with a B-cell lymphoma

A 64-year-old woman was transferred for investigation of a mediastinal mass, biopsy of which showed a diffuse large B-cell lymphoma. She was also found to have an antiphospholipid antibody. The pre-operative coagulation screen showed a prolonged activated partial thromboplastin time, 71.3 s (normal range, 26-36 s), which was not corrected by the addition of normal plasma. The dilute Russell's viper venom time was positive. Anti-cardiolipin assay was strongly positive, immunoglobulin M was 153 AU; immunoglobulin G was normal, 3.1 AU. Assays of factors VIII, IX and XI showed higher concentrations with increasing dilutions in one-stage factor assays from 1: 10 to 1: 80 suggestive of an inhibitor. Factor XII was 9 U/dl and results were unaffected by increasing dilution, suggesting specific antibodies to factor XII. The factor XII antigen was 40 U/dl. The patient had immunoglobulin M auto-antibodies to factor XII.

Thrombophilia in children with cystic fibrosis

In some children with cystic fibrosis (CF), percutaneous long lines occlude sooner than expected (due to thrombophlebitis or thrombosis), and many have a totally implantable venous access device (TIVAD), a recognized complication of which is thrombosis. This complication is more likely if the child has an underlying thrombotic tendency, which may be enhanced in the presence of inflammatory lung disease. There are no reports of an identified association of heritable thrombophilia with CF, although individual cases have been recognized. Our aim was to determine the incidence of thrombophilia in children with CF. In a tertiary pediatric CF center, blood was screened for thrombophilia at annual review, and retested if abnormal. A thrombotic abnormality was found in 41/204 (20%) patients. These included activated protein C resistance (10/204, 5%) with a prevalence similar to that expected, but the following abnormalities had an increased prevalence: antithrombin deficiency (2/204, 1%), protein S deficiency (11/204, 5%), protein C deficiency (8/204, 4%), and lupus anticoagulant (18/204, 9%). There were no differences found in those with thrombophilia for the following parameters: age, gender, genotype, lung function, presence of Pseudomonas aeruginosa, prothrombin time, serum IgE, aspergillus-specific IgE, liver function, and blood inflammatory markers. Fifteen children had TIVADs, 4 of whom had evidence of thrombophilia. In conclusion, a significant proportion of patients had a thrombophilic abnormality. We recommend that thrombophilia screening be performed prior to insertion of a TIVAD, and also in those with a history of venous thrombosis, blocked TIVADs, or recurring problems with long lines.

Teicoplanin-dependent antibodies: detection and characterization

There are only a few reports of thrombocytopenia associated with clinical doses of teicoplanin, a glycopeptide antibiotic used against Gram-positive bacteria. We investigated 39 patients receiving teicoplanin; 31 were thrombocytopenic with platelet counts between 1-105 x 10(9)/l and 8 were not thrombocytopenic. We identified 14 thrombocytopenic cases (45%) and two (25%) non-thrombocytopenic cases with IgG teicoplanin-dependent platelet-reactive antibodies. Use of glycoprotein (GP) capture enzyme-linked immunosorbent assay with platelets and GPIIb/IIIa transfected Chinese Hamster Ovary cells as well as flow cytometry with GP-deficient platelets indicated that the GPIIb/IIIa complex is a major target antigen of these antibodies.

Automated quantitation of peripheral blood neutrophil activation in patients with myocardial ischaemia

BACKGROUND

Coronary ischaemic syndromes are associated with neutrophil activation. The Bayer automated haematology analysers can detect increased light scatter of neutrophil populations, which correlates with neutrophil activation. We aimed to assess the role of an automated analyser in detecting systemic neutrophil activation in peripheral blood samples of patients with coronary ischaemia.

METHODS

A prospective cross-sectional study was undertaken in 18 patients with chronic stable angina, 9 with unstable angina and 26 normal control subjects. Whole blood samples were taken to assess neutrophil count and light scatter, and serum samples were taken from some patients for assessment of Troponin T, C-reactive protein (CRP) and myeloperoxidase (MPO). In addition, whole blood was stimulated in vitro with interleukin (IL)-8 and N-formyl-methionyl-leucyl-phenylalanine (fMLP) to assess changes in neutrophil light scatter detected by the analyser.

RESULTS

Neutrophil light scatter was increased in patients with chronic stable and unstable angina compared to normal control subjects (normal subjects 74.1 (73.3, 75.0) (mean arbitrary units (95% confidence intervals, (CI)) vs. 78.6 (76.9, 80.3) in the chronic stable angina group P<0.001 and 77.1 (75.3, 79.0) in the unstable angina group P<0.007). In vitro stimulation of whole blood produced comparable increases in neutrophil light scatter when morphological changes in neutrophils were demonstrable under electron microscopy.

CONCLUSIONS

Automated measurement of neutrophil activation by light scatter is possible using the Advia 120 analyser and is superior to a neutrophil count in discriminating groups with angina. This technique may be useful in monitoring disease activity and progression in coronary artery disease and in guiding the use of anti-inflammatory therapies.

Prospective double-blind randomized study of the effects of four intravenous fluids on platelet function and hemostasis in elective hip surgery

A prospective randomized double-blind study was performed to determine the effects of three colloids, Haemaccel, Gelofusine and albumin, and also saline on platelet activation, platelet aggregation (induced by adenosine diphosphate (ADP), epinephrine, collagen) platelet agglutination by ristocetin and other hemostatic variables in 55 patients undergoing primary unilateral total hip replacement. The fluids were administered according to normal clinical practice and assessments were made immediately before, at the end, and 2 h after the end of surgery. Surgery was accompanied by thrombin generation (increases in thrombin/antithrombin III complex, prothrombin F1 +2 fragment) platelet activation (betaTG) and compromised coagulation. Generally, the platelet activation appeared to result in platelet desensitization and brought about a persistent reduction in platelet aggregation to ADP and epinephrine, irrespective of the fluid used. Additionally, Haemaccel and Gelofusine inhibited ristocetin-induced platelet agglutination and albumin inhibited collagen-induced platelet aggregation. Gross inhibitory effects of Haemaccel that had been predicted from an earlier in vitro study did not occur. Particular fluids had selective additional effects on the hemostatic system. Albumin infusion served to maintain plasma albumin at normal concentrations postsurgery. The two gelatin preparations, Haemaccel and Gelofusine, maintained plasma viscosity. All three colloids led to a transient increase in activated partial thromboplastin time postsurgery and also a transient fall in the concentration of factor VIII, which were accompanied by a transient increase in bleeding time, but there was no measurable increase in blood loss. Inhibition of platelet aggregation by certain colloids may provide additional protection against the increased thrombotic risk in patients following major surgery.

Correlation between thrombin potential and bleeding after cardiac surgery in adults

We used a sensitive assay to measure thrombin potential in 20 patients who underwent cardiopulmonary bypass surgery for coronary artery bypass grafts. We measured coagulation factors II, V, VII, VIII and X. Blood loss was measured as the total amount in the mediastinal drains in the first 24 h postoperatively. Thrombin potential was median 107 nmol/l.min (range 62-181) preoperatively and median 46 nmol/l.min (range 19-120) postoperatively. Coagulation factors II, V, VII,VIII and X were within normal limits preoperatively. Factor II fell from 77 IU/dl preoperatively to 37 IU/dl at 120 min postoperatively. Factor V fell from 85 IU/dl preoperatively to 61 IU/dl postoperatively. Factor VII fell from 91 IU/dl to 66 IU/dl postoperatively. Factor VIII was 128 IU/dl preoperatively and 127 IU/dl postoperatively. Factor X fell from 90 IU/dl preoperatively to 50 IU/dl postoperatively. Total blood loss in 24 h in the mediastinal drains postoperatively was mean 673 ml, median 650 ml (range 250-2000). Reduction in thrombin potential correlated inversely with postoperative blood loss, r= -0.75 (Spearman correlation). The fall in the thrombin potential correlated with the prothrombin level (r = 0.75) and factor X (r = 0.47).

Abciximab is rapidly effective in preventing and arresting established platelet aggregation

BACKGROUND

Abciximab reduces the thrombotic complications of angioplasty. It is also used, as a 'bail out' treatment when angioplasty is complicated by thrombus but its speed of action is not known. This study sought to establish how quickly abciximab blocks the aggregation of both quiescent and activated platelets to explain this rapid efficacy.

METHODS

Optical aggregometry (OA) and whole blood electrical impedance platelet aggregometry (WBEA) were performed with blood from 10 healthy volunteers. Abciximab 5 microg/ml was added in each case with saline control 5 minutes before agonist, 10 seconds before agonist and during aggregation.

RESULTS

(1) Abciximab administered 5 minutes before agonist, completely inhibited aggregation with OA: (medians and ranges) 0% (all 0), control: 71% (50-95%) p < 0.001. and with WBEA: 0 omega (all 0 omega), control: 7.5 omega (4.8-12.5 omega) p = 0.016. (2) When administered 10 s before agonist with OA a small initial degree of aggregation occurred but this was rapidly reversed (time to reversal: 2 mins (1-4.5 mins) to low levels of aggregation 16.5% (0-22%), control 72.5% (55-95%) p = 0.002. With WBEA aggregation was completely inhibited: 0 omega (all 0 omega), control: 7.5 omega (4.8-12.3 omega) p = 0.016. (3) When administered during aggregation, with OA the rise in the aggregometry tracing was rapidly arrested (time to arrest: 1.5 mins (0.1-3 mins)) with no further aggregation occurring: 42% (30-57%), control: 80% (60-100%) p = 0.002. With WBEA the findings were similar: (time to arrest 1.5 mins (1-2 mins)) 6.3 omega (1.5-11.3 omega), control: 10 omega (3-12 omega) p = 0.031.

CONCLUSIONS

These data suggest that when administered during a procedure in which thrombus has occurred, aggregation may be rapidly arrested. This applies to quiescent platelets but also activated platelets undergoing aggregation.

Study of five cell salvage machines in coronary artery surgery

We evaluated the effectiveness, ease of use and safety of five machines for blood salvage during coronary artery surgery. All were equally effective in concentrating red cells. We measured haemoglobin, packed cell volume, free haemoglobin, white cells, neutrophil elastase, platelets, thrombin-antithrombin complex (TAT), prothrombin activation peptide F1.2, fibrin degradation product (d-dimers), tissue plasminogen activator (tPA) and heparin in wound blood, in washed cell suspensions and in a unit of bank blood prepared for each patient. All machines were equally safe and easy to use and were equally effective in removing heparin and the physiological components measured. There were no adverse effects on patients. Clotting factors are severely depleted both in salvaged blood, even before washing, and in bank blood. Cell savers are a valuable adjunct to coronary artery surgery, but careful monitoring of coagulation is required when the volumes of either bank blood or salvaged blood are large.

Systemic platelet effects of contrast media: implications for cardiologic research and clinical practice

BACKGROUND

Angiographic contrast media cause platelet activation and decrease aggregability in vitro. We have previously shown in vitro a significant antiplatelet effect of contrast media at the concentrations obtained locally in the coronary artery during angioplasty. It is not known, however, whether a systemic effect is present.

METHOD

Thirty patients undergoing diagnostic coronary angiography were prospectively randomized to receive the nonionic medium iohexol, ionic low-molecular-weight medium ioxaglate, or ionic high-molecular-weight medium diatrizoate. Platelet aggregability was measured before and after the investigation with whole blood electrical impedance aggregometry (WBEA) with collagen agonist and the PFA-100 (Dade, Miami, Fla) platelet function analyzer with combined shear, collagen, and adenosine diphosphate as agonists.

RESULTS

With WBEA, with iohexol no difference in impedance change was seen: (medians and ranges) before, 9.8 Omega (4.8-19.2 Omega) versus after, 9.6 Omega (2-19.2 Omega) (P not significant [NS]). With ioxaglate a significant fall was seen: before, 8.6 Omega (6.4-15.2 Omega) versus after, 6.6 Omega (0-12.4 Omega) (P =.004). With diatrizoate a significant and greater fall was seen: before, 10.8 Omega (6.4-17.6 Omega) versus after, 6.6 Omega (0-10.8 Omega) (P =.002). With PFA, no difference in closure time was seen with any medium: iohexol before, 99 seconds (79-142 seconds) versus after, 142 seconds (63-128 seconds) (P NS); ioxaglate before, 120 seconds (75-258 seconds) versus after, 95 seconds (74-258 seconds) (P NS); and diatrizoate before, 114.5 seconds (65-250 seconds) versus after, 100.5 seconds (72-300 seconds) (P NS).

CONCLUSIONS

Ionic but not nonionic contrast media have a systemic antiplatelet effect at diagnostic angiographic doses when measured with WBEA. Such an effect has not been shown before. This may explain the observed improved clinical outcome with ionic contrast media but also might confound platelet studies in coronary angioplasty.

High molecular weight kininogen deficiency: a patient who underwent cardiac surgery

A 66 year old male, referred for cardiac surgery, was found to have high molecular weight kininogen deficiency (activity <1%). Apart from activated partial thromboplastin time (APTT) >300 s, tests of haemostasis were otherwise normal (factors VIII, IX, XI, XII and prekallikrein). No inhibitor of coagulation was found. The activated coagulation time (ACT) was 800 s pre-operatively and >1000 s after heparin. Heparin levels were measured directly by an anti-Xa chromogenic assay, with values of between 2.9 and 3.2 u/ml during cardiopulmonary bypass. Thrombin-antithrombin levels rose from 2.3*g/l before surgery to a peak of 83.5*g/l at the end of cardiopulmonary bypass. Cross linked fibrin d-dimers (XDP) levels rose from 100 ng/ml before operation to 600 ng/ml after protamine administration. The patient had no excess bleeding and no thrombotic complications from surgery. This patient shows that high molecular weight kininogen is not required for thrombin formation or fibrinolysis during cardiac surgery and illustrates the need to measure heparin directly in patients with such contact factor deficiencies.

Diurnal variation in platelet aggregation iwth the PFA-100 platelet function analyser

BACKGROUND

Myocardial infarction is commoner in the morning, and previous small studies suggesting diurnal variation in platelet aggregation have been limited to optical aggregometry with platelet-rich plasma and low shear. This phenomenon was studied using whole blood at high shear rates.

METHOD

Fifteen healthy volunteers were venesected at 0800 hrs supine in bed immediately before rising, at 0830 hrs 30 min after rising, at 1200 hrs and 1700 hrs. Samples underwent the high shear method of PFA-100 using additional chemical agonists of collagen with ADP or collagen with epinephrine. PFA-100 results are reported as closure time of the experimental aperture in seconds, a longer time indicating less platelet aggregation.

RESULTS

With both epinephrine and ADP, a non-significant shortening of closure time was seen on rising. Subsequently, with both agonists the closure time lengthened through the day. With ADP the difference was small (medians 0830 hrs: 85 s, 1700 hrs: 87.5 s) but statistically significant (p = 0.03). With epinephrine it was much more marked (medians 0830 hrs: 114.3 s, 1700 hrs: 140.5 s) and highly significant (p = 0.002).

CONCLUSIONS

These findings demonstrate a diurnal rhythm in platelet function using whole blood at high shear rates. This is likely to be more applicable to the in vivo situation than previously reported optical aggregometry studies.

Tissue factor is rapidly elevated in plasma collected from the pericardial cavity during cardiopulmonary bypass

There is growing evidence that the tissue factor/factor VIIa pathway of coagulation is enhanced during cardiopulmonary bypass. Hitherto, available evidence has suggested that upregulated monocyte bound tissue factor is made available, either in the blood collected from the site of surgery or on circulating cells. However, cellular upregulation is slow, while generation of factor VIIa in blood collected from the pericardial cavity is rapid. We have therefore investigated the possibility of an alternative source of tissue factor, plasma (as opposed to cellular) tissue factor in blood samples taken from the central vein catheter (systemic circulation) and collected from the pericardial cavity during cardiopulmonary bypass. Six patients undergoing first time cardiopulmonary bypass grafting were studied. Tissue factor antigen was found to be rapidly elevated (by 15 min) in the pericardial plasma, approximately 5-fold above systemic levels (p <0.004). Similar elevations were found in markers of coagulation activation, factor VIIa antigen (p = 0.066), prothrombin fragment F(1+2) (p <0.003) and thrombin-antithrombin complex (p <0.03). To explore whether plasma tissue factor was (or had been) functionally active, factor VIIa was measured also with the soluble tissue factor functional assay after removal of heparin. Functional factor VIIa activity fell significantly in the systemic circulation, probably due to the heparin-induced increase (approximately 15-fold) in tissue factor pathway inhibitor (TFPI), but was elevated in pericardial blood compared with that taken from the central line catheter (p <0.006). These results demonstrate that both components of the activation complex for the extrinsic pathway of coagulation are rapidly generated in pericardial blood during bypass.

Automated quantitation of circulating neutrophil and eosinophil activation in asthmatic patients

BACKGROUND

Asthma has been associated with eosinophil activation, measured in serum, sputum, bronchoalveolar lavage (BAL) fluid, and urine. A whole blood automated method was developed to assess eosinophil and neutrophil activity in terms of peroxidase content and cell morphology using the Bayer haematology analyser. The method was applied to an in vitro stimulation model when fMLP was added to whole blood and the samples were then analysed for changes in granularity and shape. In addition, cells stimulated with interleukin (IL)-8 were examined by electron microscopy.

METHODS

A cross sectional analysis was performed on venous blood from non-atopic, non-asthmatic normal subjects (n = 37), mild (n = 46) and symptomatic (n = 22) asthmatic patients on inhaled beta(2) agonist only, and more severe asthmatic patients (n = 17) on inhaled and oral corticosteroid therapy. Samples were analysed by the haematology analyser and peroxidase leucograms gated using the WinMDI software program.

RESULTS

There were significant differences in the amount of light scatter by the neutrophil populations in the symptomatic (p = 0.007) and severe asthmatic (p = 0.0001) groups compared with the control group. However, abnormalities in eosinophil populations were not observed. In vitro activation of whole blood with fMLP caused similar changes in neutrophil light scatter, suggesting that neutrophil activation is present in peripheral blood of symptomatic asthmatic patients. IL-8 caused a change in shape of the neutrophils seen using transmission electron microscopy.

CONCLUSIONS

Evidence of neutrophil activation can be seen in whole blood from patients with asthma using a novel automated method. This may potentially be applied to other inflammatory diseases.

Two-chain factor VIIa generated in the pericardium during surgery with cardiopulmonary bypass : relationship to increased thrombin generation and heparin concentration

Several recent studies have proposed that coagulation is triggered during cardiopulmonary bypass surgery by extrinsic pathway activation involving factor VIIa generation, but the methodology was indirect. Therefore, 12 patients were studied during routine cardiac and cardiopulmonary bypass surgery. Samples were taken before, during, and after bypass from the perfusate, from the aorta (retrograde cardiac drainage), pericardium, and collected suction fluid originating from the whole operative field. These samples were analyzed by enzyme-linked immunosorbent assay for 2-chain factor VIIa, by prothrombin F1+2 assay, by thrombin-antithrombin (TAT) assay, and for heparin concentration. Factor VIIa, F1+2, and TAT levels in samples from the pericardium were greatly elevated (mean, 0.92 to 1.01, 227 to 334, and 399 to 526 microg/L, respectively; preoperative mean, 0.33, 32.3, and 1.90 microg/L, respectively; P<0. 05 for all), whereas levels in suction fluid were less consistently high. Factor VIIa and both F1+2 and thrombin-antithrombin levels in samples from the aorta, pericardium, and suction fluid were significantly correlated (r=0.57, P<0.001, n=111; and r=0.51, P<0. 001, n=105, respectively), and all were inversely correlated with heparin levels (r>-0.35, P<0.001, n>92). There was no evidence of factor VIIa generation in the circuit during bypass surgery, and both F1+2 and thrombin-antithrombin levels rose only approximately 2-fold, probably because heparin levels were higher than they were in the pericardium (P<0.05). We concluded that appreciable activation of factor VII occurs on the pericardium and that this is associated with increased thrombin generation. Ineffective local heparinization may be partly responsible. These results suggest that pericardium-induced activation of factor VII should be the target of anticoagulant strategies during cardiopulmonary bypass surgery.

Role of factor XII in thrombin generation and fibrinolysis during cardiopulmonary bypass

During cardiopulmonary bypass, thrombin is generated, which is thought to be initiated by activation of factor XII on the surface of the bypass equipment. We present a patient with severe factor XII deficiency who underwent cardiac surgery. As much thrombin was formed during cardiopulmonary bypass (measured by the prothrombin activation fragment F1 + 2 and thrombin-antithrombin complexes) as in normal patients, showing that factor XII was not necessary for thrombin generation. Factor X, but not factor IX, was activated (as measured by their activation peptides), and this activation correlated with F1 + 2 and thrombin-antithrombin complexes, suggesting that the tissue-factor/factor-VIIa pathway is the trigger for thrombin formation.

Review of blood transfusion practices in thoracic surgery

Between September 1, 1989, and August 31, 1990, 516 patients were admitted to the Royal Brompton National Heart and Lung Hospital for thoracic operations. A prospective audit recorded the nature and extent of operation, the histologic diagnosis, and the number of units of blood prepared and transfused during hospitalization. Cross-matched blood was requested in 243 patients but only 16.1% of these received transfusion. In total, 1,295 units of whole blood or red cell concentrate were cross-matched and made immediately available in the operating suite at the time of operation. Only 322 units were administered (cross-match to transfusion ratio of 4.02:1). Almost half of the patients who received transfusions received 2 units or less, a third received 3 or 4 units, 10% between 5 and 10 units, and 8.4% required more than 10 units during their hospital stay. The nature and extent of resection was an indicator of the need for transfusion. Other important predisposing factors included a previous thoracic operation, resection for inflammatory disease, decortication of empyema thoracis, chest wall resection, or thoracoplasty. Other thoracic procedures such as pleurodesis, pleurectomy, open lung biopsy, pectus correction, operation for bullous lung disease, and mediastinoscopy had a negligible transfusion requirement. The data suggest that understanding risk factors for transfusion requirements of patients undergoing thoracic surgical procedures should optimize present resources. This is critical when exploiting the limited availability of donated blood and blood products. Similarly, anticipation of transfusion requirements takes best advantage of manpower within the blood bank and minimizes unnecessary and avoidable blood wastage and expenditure.

Haemostatic changes and thromboembolic risk during tamoxifen therapy in normal women

Tamoxifen has been implicated as a risk factor for venous thrombosis in advanced breast cancer although the evidence for increased arterial or venous thrombosis with tamoxifen in early breast cancer is less clear. The effect of tamoxifen on haemostasis, and thereby possible thromboembolic risk, was investigated in normal women enrolled in a placebo controlled trial of tamoxifen as a chemopreventative agent for breast cancer. There was an initial reduction in fibrinogen levels in all women on tamoxifen over the first year of follow-up and a marginal reduction in antithrombin III and Protein S in postmenopausal women at 6 months. There were no changes in cross linked fibrinogen degradation products or Protein C for pre or post-menopausal women. There was no increase in the incidence of thromboembolic events on tamoxifen. This study demonstrates that tamoxifen has only marginal effects on factors involved in haemostasis reported to affect the incidence of arterial or venous thromboembolic disease. The follow-up time is relatively short (maximum 36 months) and careful long term follow-up is necessary to detect clinically significant morbidity.

Protein C deficiency associated with massive cerebral thrombosis following open heart surgery

We describe a case of massive cerebral venous thrombosis following open heart surgery in a patient with a reduced level of Protein C (40% of mean level). Protein C deficiency is an inherited disorder which in the homozygous form may result in massive fatal venous thrombosis in the newborn. A Protein C level below 55% is highly suggestive of heterozygous deficiency and has been associated with a tendency to venous thrombosis although its clinical penetrance is variable. This is the first reported case of massive venous thrombosis in a patient following open heart surgery associated with Protein C deficiency.

Megaloblastic anaemia due to vitamin B12 deficiency caused by small intestinal bacterial overgrowth: possible role of vitamin B12 analogues

Megaloblastic anaemia due to bacterial overgrowth of the small intestine is due to vitamin B12 malabsorption. This report describes a patient with bacterial overgrowth of the small intestine who had megaloblastic anaemia and malabsorption of vitamin B12, but persistently normal levels of serum vitamin B12 and normal serum and red cell folate levels. However, there was evidence of vitamin B12 deficiency as shown by an abnormal deoxyuridine suppression test and by the response to treatment with physiological doses of vitamin B12. A relative increase in biologically inactive vitamin B12 analogues may be the explanation for the normal vitamin B12 level in this patient.

Immunohistochemical localization of basement membrane type IV collagen in invasive and metastatic squamous carcinomas of the head and neck

The immunohistochemical localization of basement membrane type IV collagen was investigated with a mouse monoclonal antibody in major surgical resections from 25 patients with invasive squamous carcinomas of the head and neck. Irrespective of site, size or stage of the disease, the 16 primary invasive tumours were almost completely surrounded by a layer of type IV collagen. Focal abnormalities were regularly present, consisting of thickening and aggregation of type IV collagen together with attenuation and segmental loss. Similar changes were seen in metastatic squamous carcinomas in 36 cervical lymph nodes. It is suggested that the probable formation of a normal basement membrane protein by these squamous carcinomas indicates the preservation of a normal function of differentiating squamous epithelia. The results indicate that a major basement membrane component, type IV collagen, continues to co-exist with invasive and metastatic squamous carcinomas.

Lysis of type-I collagen by squamous carcinomas of the head and neck

Lysis of type-I collagen by squamous carcinomas of the head and neck has been studied in freshly excised tissues, xenografts and established cell lines. Investigations with 35 freshly excised tumours showed only low levels of active and total collagenase in both carcinomas and controls. A difference became apparent when the tissues were set up in explant organ culture where a significant (p less than 0.05) increase in total collagenase was found in 13/19 tumours compared with paired control tissues over a 4-week culture period. Two xenografts showed little capacity to lyse collagen in vitro and there was only limited evidence of an increase in total collagenase after explantation and growth in organ culture. Twenty tumour cell lines showed low levels of active collagenase. Total collagenase levels were significantly increased (p less than 0.05) in 4 of the cell lines derived from cancers of the tongue; this activity was sustained in subsequent passages. Six control fibroblastoid cell lines also showed low levels of active collagenase. Levels of total collagenase were consistently high, but this activity was transient and declined in subsequent passages. Co-cultivation experiments with II tumour-cell lines and 5 fibroblastoid cell lines showed some enhanced, synergistic destruction of collagen. Parallel experiments with supernatant media from the carcinoma and fibroblastoid lines showed no enhancement, indicating that intact carcinoma cells and fibroblastoid cells are required for synergistic collagenolysis to take place.

Absent ileal uptake of IF-bound vitamin B12 in vivo in the Imerslund-Grasbeck syndrome (familial vitamin B12 malabsorption with proteinuria)

A Syrian family is described with three children who had inherited selective vitamin B12 malabsorption associated with proteinuria. (Imerslund-Grasbeck syndrome). Although inherited the defect was apparently not present at birth. A third child had less severe vitamin B12 malabsorption, was not vitamin B12 deficient and had no proteinuria. Studies on two of the affected children with subcellular fractionation of the uptake of radioactive vitamin B12 by ileal tissue in vivo indicate a defect in the ileal receptors for IF-bound vitamin B12. These findings are different from the single in vitro experiment on a patient with this condition that has been previously reported.

Further observations on mechanisms of bone destruction by squamous carcinomas of the head and neck: the role of host stroma

Mechanisms of bone invasion by squamous carcinomas of the head and neck have been investigated using fresh tumours and established tumour cell lines in an in vitro bone resorption assay with 45Ca-labelled mouse calvaria. Fresh tumours regularly resorb bone in vitro. Activity is consistently reduced by indomethacin. The tumours release E2 prostaglandins (PGE2) in amounts sufficient to account for approximately 50% of the bone resorption observed. Small amounts of non-prostaglandin (indomethacin-resistant) osteolytic factors are also produced. Control non-neoplastic tissues show a variable capacity to resorb bone in vitro; PGE2 levels in these tissues may be related to their content of inflammatory cells. Tumour cell lines also resorb bone in vitro but, for most lines, activity is not significantly blocked by indomethacin and PGE2 levels are generally insufficient to account for the osteolysis observed. Non-prostaglandin bone resorbing factors thus predominate. It is concluded that most squamous cancers of the head and neck are osteolytic in vitro and release a mixture of prostaglandin and non-prostaglandin factors which stimulate osteoclastic bone resorption. These factors are derived from both neoplastic and stromal elements, and are "tumour-associated" rather than "tumour-specific". In vitro bone resorption and prostaglandin release does not correlate with pathological features of the tumour or with post-operative survival.

Patterns and mechanisms of bone invasion by squamous carcinomas of the head and neck

Patterns and mechanisms of local bone invasion by squamous carcinomas of the head and neck have been investigated. Detailed surgical pathology has shown that these tumors invade contiguous skeletal or metaplastic bone principally through an indirect process; the normal bone resorbing cells of the host (osteoclasts) are activated and erode bone in front of the advancing tumor edge. Tumor cells take over the destructive process when the osteoclast response has waned. These morphologic patterns have been reproduced in an in vitro model where calcium-45-labelled mouse calvaria, cocultured with a tumor for 3 days, are resorbed by osteoclasts. Freshly excised tumors, established tumor cell lines, and tumor xenografts release osteolysins in vitro which act as osteoclastic stimulants. They include both prostaglandins E2 and F2 alpha, and nonprostaglandin factors, and are derived from tumor cells and from the associated host stroma. Virtually all the tumors examined released osteolysins and resorbed bone in vitro independent of their site, size, degree of differentiation, and the presence or absence of clinical bone invasion.

Severe megaloblastic bone marrow change associated with unsuspected mild vitamin B12 deficiency

Two patients are reported who developed peripheral blood abnormalities and marked megaloblastic bone marrow change within eleven days of cardiac bypass surgery. The patients were shown to have unsuspected mild vitamin B12 deficiency due to Addisonian pernicious anaemia. The megaloblastic changes were presumed to be precipitated by the increased demand for erythrocytes and platelets after surgery.

Some mechanisms of local bone destruction by squamous carcinomas of the head and neck

An in vitro osteolysis assay with 45Ca-labelled mouse calvaria has been used to investigate mechanisms of direct bone invasion by squamous carcinomas of the head and neck. Short-term (3-day) organ cultures of 8 fresh squamous carcinomas showed varying degrees of in vitro bone-resorbing activity which was blocked by indomethacin, an inhibitor of prostaglandin synthesis. Supernatant media from 6 established cell lines also induced bone resorption in vitro and evoked an osteoclastic response in the cultured calvaria. Osteolysis by supernatant media was not blocked by indomethacin in all the tumour-cell lines, and the production of non-prostaglandin osteolysins by the indomethacin-resistant lines is postulated. The two principal findings that emerge are: (1) Stimulants for osteoclastic activity are derived from both squamous-carcinoma cells and from host cells in the tumour stroma. (2) These stimulants are diverse. Indomethacin-sensitive agents, presumed to be prostaglandins, are most convincingly demonstrated in the fresh tumours. Indomethacin-resistant agents, presumably not prostaglandins, are more characteristic of the carcinoma cell lines.

Inherited lack of transcobalamin II in serum and megaloblastic anaemia: a further patient

We have studied a patient, unrelated to the patients previously described, with inherited lack of the vitamin B12 binding protein Transcobalamin II. Severe haematological abnormalities were found within a few weeks of birth and responded to treatment with both vitamin B12 and folic acid. He was maintained in partial remission with such treatment until adolescence, except for a time in early childhood when folic acid alone was given and he suffered severe neurological deterioration. A the age of 18 years he was admitted to hospital because of convulsions; the deoxyuridine suppression test showed intracellular deficiency of B12 despite a normal serum B12 and normal haemoglobin concentration. His serum failed to promote the uptake of radioactive B12 by bone marrow cells, and analysis of serum B12 binding proteins demonstrated the lack of Transcobalamin II. Treatment with injections of 1000 micrograms of B12 three times weekly corrected the abnormality shown in the deoxyuridine suppression test; following this treatment, together with changes in anticonvulsive therapy, he remains healthy without occurrence of further convulsions, and is haematologically normal.

Megaloblastic haemopoiesis in patients receiving nitrous oxide

In a prospective study the incidence of megaloblastic change after ventilation with nitrous oxide for periods of up to 24 h has been determined and the cause of the altered D.N.A. synthesis studied with the deoxyuridine (dU) suppression test in 22 patients undergoing cardiac bypass surgery. 8 patients who received nitrous oxide and oxygen for 24 h had megaloblastic bone-marrow aspirates and abnormal dU suppression tests at the end of ventilation. 5 patients who received no nitrous oxide had normoblastic aspirates and normal dU suppression test. Of the remaining 9 patients, who received nitrous oxide during the operation only, 3 had abnormal dU suppression tests at 24 h. The abnormality revealed by the dU suppression tests was identical with that found in vitamin-B12 deficiency, but the patients' serum-B12 concentrations were normal. These results suggest that nitrous oxide interferes with the function of vitamin B12. Nitrous oxide oxidises vitamin B12 in vitro, and probably also in vivo when premixed 50% nitrous oxide and 50% oxygen mixture ('Entonox') is given.

Reversible C3 hypocomplementaemia in megaloblastic anaemia due to vitamin B12 deficiency

Serum C3 and C4 levels have been determined in patients with Addisonian pernicious anaemia (PA) and megaloblastic anaemia due to vitamin B12 deficiency from other causes, before and after treatment, in order to study the interaction between vitamin B12 deficiency and complement and the role of complement in the pathogenesis of the gastric lesion of PA. C3 levels are significantly reduced in vitamin B12 deficiency and return to normal on treatment; C3 levels correlate with the degree of anaemia but not with serum vitamin B12 levels at diagnosis. C4 levels are normal. These observations suggest that the observed C3 hypocomplementaemia is not a consequence of immune mechanisms, but may be due to altered synthesis of C3 complement component.

The serum vitamin B12 level: its assay and significance

1. Low serum B12 levels can be measured with considerable precision by microbiological assay with the Euglena gracilis assay and B12 deficiency can be recognised with a high level of consistency by either the Euglena or L. leichmannii assays. Either method is ideally suited for the assay of large numbers of specimens. The Lactobacillus leichmanii technique requires preliminary extraction of protein and it has been suggested that this may be a source of inaccuracy. 2. The radioisotope dilution assay should be the ideal method of measuring B12 levels in small or moderate numbers of specimens for it is a simple method that can be carried out in any laboratory with suitable counting equipment. After many false starts the conditions required for accurate assay are now understood. Each of 40 to 50 radioisotopic dilution techniques that have been introduced claims to be capable of differentiating B12 deficiency from control subjects but the reported correlations between the actual levels found in the two different assays are variable and the levels may be much higher with some radioisotopic methods. 3. The subnormal serum levels which are found in pernicious anaemia with all these techniques indicate severe reduction of the liver B12 level. A low serum B12 level in other conditions has, in the absence of associated folate or iron deficiency, the same significance. If the fall in the serum B12 level is associated with folate or iron deficiency, the tissue B12 levels are usually reduced but not to the low levels found in B12 deficiency states. 4. In practice, a subnormal B12 level is a valuable pointer not only to unsuspected pernicious anaemia but also to other gastrointestinal or nutritional disorders. The significance of a fall in the B12 level can only be understood if its cause is defined by a full clinical and gastroenterological investigation. 5. Falsely low serum B12 levels are found under certain iatrogenic conditions and B12 levels may be normal in spite of cellular deficiency of B12 under the rare circumstances of pernicious anaemia being associated with chronic myeloid leukaemia or when there is deficiency of TC 2.