Prediction and selective prophylaxis of venous thrombosis in elective gastrointestinal surgery

A New Protocol for Venous Thromboembolism Prophylaxis in Bariatric Surgery

BACKGROUND

Morbidly obese patients are at high risk for developing venous thromboembolism (VTE). The aim of this study was to evaluate the effect of a new VTE prophylaxis protocol (low dosage, low-molecular-weight heparin [LMWH]) with a pneumatic compression device (PCD) in patients undergoing bariatric surgery.

MATERIALS AND METHODS

Between November 2015 and December 2017, 368 patients underwent surgery due to obesity. The patients received 0.2 ml of nadroparin (Fraxiparine, GlaxoSmithKline) 12 h before the operation. A PCD (Kendall SCD Compression System) was applied to the patient during the operation and left on the patient during the subsequent 24 h. Nadroparin 0.4 ml was started subcutaneously after the PCD was removed from the patient and the same dosage of nadroparin was given daily for 15 days following the bariatric operation. Ambulation within 2 h of surgery was encouraged and was performed frequently.

RESULTS

A total of 368 patients underwent laparoscopic bariatric surgery. The median age was 34.1 years (range, 18-61), the median weight was 128 kg (range, 90-182), and the median body mass index (BMI) was 47.2 kg/m² (range, 36-72). No thrombotic events were observed postoperatively or at the 1-, 3-, and 6-month follow-up visits. Four bleedings occurred requiring transfusions. None of these patients required a re-laparotomy for hemorrhage control. The mortality rate was 0% at 30 and 90 days and during the hospitalization.

CONCLUSION

Low dosage LMWH with PCD is very effective for VTE prophylaxis in bariatric surgery.

Relationship between Blood Groups (ABO) and Varicose Veins of the Lower Limbs. A Case-Control Study

Numerous studies have already shown the existence of a relationship between blood groups of the ABO system and certain vascular diseases: group A and atheromatous disease1,4,5,7,9,12; group A and deep venous thrombosis of the lower limbs6,11,13. However, no study has reported an association between varicose veins and the ABO blood groups.

The aim of this study was to investigate the possible existence of such an association.

Thromboembolism prevention in surgery of digestive cancer

BACKGROUND

The venous thromboembolism is a common complication after surgical treatment in general and, in particular, on the therapeutic management on cancer. Surgery of the digestive tract has been reported to induce this complication. Patients with digestive cancer have substantial increased risk of initial or recurrent thromboembolism.

AIM

To provide to surgeons working in digestive surgery and general surgery guidance on how to make safe thromboprophylaxis for patients requiring operations in the treatment of their gastrointestinal malignancies.

METHODS

The guideline was based on 15 relevant clinical issues and related to the risk factors, treatment and prognosis of the patient undergoing surgical treatment of cancer on digestive tract. They focused thromboembolic events associated with operations and thromboprophylaxis. The questions were structured using the PICO (Patient, Intervention or Indicator, Comparison and Outcome), allowing strategies to generate evidence on the main primary bases of scientific information (Medline / Pubmed, Embase, Lilacs / Scielo, Cochrane Library, PreMedline via OVID). Evidence manual search was also conducted (BDTD and IBICT). The evidence was recovered from the selected critical evaluation using discriminatory instruments (scores) according to the category of the question: risk, prognosis and therapy (JADAD Randomized Clinical Trials and New Castle Ottawa Scale for studies not randomized). After defining potential studies to support the recommendations, they were selected by the strength of evidence and grade of recommendation according to the classification of Oxford, including the available evidence of greater strength.

RESULTS

A total of 53,555 papers by title and / or abstract related to issue were found. Of this total were selected (1st selection) 478 studies that were evaluated as full-text. From them to support the recommendations were included in the consensus 132 papers. The 15 questions could be answered with evidence grade of articles with 31 A, 130 B, 1 C and 0 D.

CONCLUSION

It was possible to prepare safe recommendations as guidance for thromboembolism prophylaxis in operations on the digestive tract malignancies, addressing the most frequent topics of everyday work of digestive and general surgeons.

The Role for Prophylaxis Inferior Vena Cava Filters in Patients Undergoing Bariatric Surgery: Replacing Anecdote with Evidence

The number of patients choosing surgical alternatives for weight reduction continues to increase. Despite common thromboembolic preventive methods, which include perioperative subcutaneous heparin injections, early mobilization, and sequential compression devices, postoperative deep vein thrombosis/pulmonary embolism remains a devastating complication after bariatric surgery. The role prophylactic inferior vena cava (IVC) filters may play in bariatric surgery remains controversial, and this article aims to address the risks and benefits of prophylactic IVC filters in high-risk bariatric patients and suggest an evidence-based algorithm for their use.

Routine anticoagulation for venous thromboembolism prevention following laparoscopic gastric bypass

OBJECTIVE

To compare the rates of venous thromboembolism (VTE) by using routine postoperative enoxaparin versus early ambulation, SCDs, hydration, and selective prophylactic pharmacologic anticoagulation.

METHODS

1,692 patients undergoing laparoscopic gastric bypass from October 2001 to October 2008 were included and divided into 2 groups based on when they were operated upon. Group A (435 patients) received routine enoxaparin 12 hours after surgery. Group B (1,257 patients) received selective pharmacologic anticoagulation, in high-risk patients only.

RESULTS

Mean operating time was 144±26 minutes (Group A) and 126±15 minutes (Group B). Mean length of stay was 2.3±1.5 days for Group A and 1.4±1.2 for Group B. Intraluminal bleeding occurred in 21 patients (4.8%) in Group A and 5 (0.9%) in Group B; none required intervention. Five pulmonary embolisms occurred in Group A (1.1%) and none in Group B. Seven patients in Group A (1.7%) and 6 (0.47%) in Group B had clinically evident DVT. Two non-VTE related deaths occurred in Group A.

CONCLUSIONS

Adequate VTE prophylaxis is achieved using SCDs, early ambulation, emphasis on hydration, and shorter operating times. Bariatric surgery can be safely performed without pharmacologic VTE prophylaxis in all but the high-risk population. Fewer bleeding complications occur without the use of anticoagulants.

All I want for coagulation

Evidence-based medicine underpins modern practice of medicine. This paper describes a fictional consultation between Santa Claus and a doctor regarding deep vein thrombosis (DVT) prophylaxis, giving a review of the evidence for DVT prophylaxis in travellers while exposing the difficulty in applying evidence to atypical clinical encounters. Medline and the Cochrane Library were searched, and guidelines reviewed. Keywords used were DVT, thromboembolism, deep vein thrombosis and air travel-related venous thromboembolism. All relevant studies found, have been included in this review, with additional studies identified from the references in these articles. In conclusion, compression stockings, with or without a one-off dose of either aspirin or heparin, are the most evidence-based approaches for prophylaxis in someone with established risk factors for DVT prior to a long-haul flight. Simple exercises should also be encouraged.

Low molecular weight heparin prophylaxis in day case surgery

BACKGROUND

The role of Low molecular weight heparins (LMWH) in day case/short-stay surgery is unknown.

AIM

To characterise the current national use of LMWH prophylaxis in specific day and short stay surgeries.

METHODS

A standardised anonymous postal questionnaire was sent to all consultant general surgeons in Ireland. The operations selected were herniorraphy, anorectal, varicose vein and laparoscopic cholecystectomy.

RESULTS

Questionnaires were sent to 82 surgeons in 2003. There was a response rate of 68.3% (56). Fifty-four per cent of respondents said there was a protocol in place for administration of LMWH in day case surgery. Of these 41% were not confident that their protocols were being adhered. Fifty-nine per cent of all respondents said they stratified patients according to individual risk. Thirteen per cent reported occurrence of VTE post day case surgery

CONCLUSION

This study demonstrates a heterogeneous pattern of administration of LMWH. In the absence of published validated protocols, the authors suggest a consensus day case protocol.

Evidence for the prevention of venous thromboembolism

Patients undergoing major orthopaedic surgery are at high risk of developing venous thromboembolism (VTE). VTE is preventable and venous prophylaxis consensus groups recommend that each patient is assessed for risk of VTE and then stratified into one of the three categories of risk. Rick stratification enables the choice of the most appropriate preventative interventions. This article examines a decision making framework for VTE prevention with particular focus on a validated risk assessment model (RAM) to facilitate risk stratification. The relevant literature is also scrutinised in terms of the best venous antithrombotic strategies, for patients undergoing major orthopaedic surgery, according to scientific evidence.

Critical care of the bariatric patient

OBJECTIVE

To synthesize the current literature on care of obese, critically ill, and bariatric surgical patients.

DATA SOURCE

A MEDLINE/PubMed search from 1966 to August 2005 was conducted using the search terms obesity, bariatric surgery, and critical illness, and a search of the Cochrane Library was also conducted.

DATA EXTRACTION AND SYNTHESIS

An increase in both the prevalence of obesity and the number of bariatric procedures performed has resulted in an increased number of obese and, specifically, bariatric surgical patients who require intensive care unit care. Obesity is a chronic inflammatory state with resultant effects on immune, metabolic, respiratory, cardiovascular, gastrointestinal, hematologic, and renal function. Principles of care of the critically ill obese patient are reviewed and then applied to critically ill bariatric surgical patients. Pharmacotherapy, vascular access, and the presentation and management of both pressure-induced rhabdomyolysis and anastomotic failure after bariatric surgery are also reviewed.

CONCLUSIONS

Obesity causes a range of pathologic effects on all major organ systems. Knowledge of these effects and issues specific to the intensive care unit care of bariatric patients can help to predict and manage complications in this population.

Incidence of clinically evident deep venous thrombosis after laparoscopic Roux-en-Y gastric bypass

BACKGROUND

Advanced age, major orthopedic surgery, neoplastic disease, prolonged operations, varicose veins, immobilization, estrogen-containing medications, and obesity are known risk factors for the development of postoperative thromboembolic complications. Perioperative heparin is useful for reducing the incidence of deep venous thrombosis (DVT), but it is associated with a discrete bleeding rate. The purpose of this study was to determine the incidence of clinically evident DVT in morbidly obese patients after laparoscopic Roux-en-Y gastric bypass when a pneumatic compression hose is used as the only prophylaxis against DVT instead of anticoagulants.

METHODS

From April 2000 to April 2003, 380 patients underwent laparoscopic Roux-en-Y gastric bypass for morbid obesity by one surgeon (R.H.C.). Prospectively, each patient was clinically evaluated for the presence of DVT during the postoperative period. Calf-length pneumatic compression stockings were placed before the procedure began, and remained in place until the patient was ambulatory. Ambulation was encouraged on the evening of the operation. No pharmacologic anticoagulant was used as a prophylaxis against DVT.

RESULTS

Of the 380 patients, 346 were women and 34 were men with a mean age of 39.3 +/- 9.4 years (range, 14-65 years). The mean weight of these patients was 299.5 +/- 53.6 lb (range, 188-483 lb), and their mean body mass index was 48.5 +/- 6.6 (range, 36-70). The mean operative time was 103. 3 +/- 24.3 min (range, 62-227 min), and mean American Society of Anesthesiology (ASA) score was 2.6. Nine patients had clinical evidence of severe, chronic venous disease preoperatively. One patient (0.26%) experienced a clinically evident DVT limited to the popliteal vein on duplex ultrasonography. The clot resolved completely, as evidenced by follow-up duplex ultrasonography after 2 weeks of subcutaneously injected fractionated heparin. No clinically evident pulmonary thromboembolism occurred in this study group.

CONCLUSIONS

The incidence of clinically evident DVT after laparoscopic Roux-en-Y gastric bypass is low when the procedure is accomplished with a relatively short operative time, with the initiation of calf-length pneumatic compression hose before the induction of anesthesia, and with routine early ambulation. No form of heparin anticoagulation is mandatory when these conditions can be met.

Prevention of venous thromboembolism in Wales: results of a survey among general surgeons

OBJECTIVE

To examine the current attitudes towards the prevention of venous thromboembolism among a cohort of surgeons.

DESIGN

A postal survey, comprising a questionnaire covering various aspects of venous thromboembolism prophylaxis was sent to all (n=84) consultant general surgeons in Wales.

RESULTS

Replies were received from 57 surgeons (68%), all of whom routinely used prophylaxis, the most frequent modalities used being heparin (100%) and graded compression stockings (79%). A combination of physical and pharmacological methods was used by over 89% of surgeons, with 60% starting prophylaxis more than two hours before operation. All surgeons continued prophylaxis after surgery, 53% until patients were mobile, 45% until they were discharged, and one surgeon continued prophylaxis for seven days after discharge. The thrombosis risk factors considered most important by surgeons when deciding about prophylaxis were (i) a previous history of venous thromboembolism, (ii) hypercoagulability, and (iii) malignancy.

CONCLUSIONS

This study confirms that Welsh surgeons conform to standard methods, but also highlights some uncertainties that are present in current surgical practice. Those who responded all routinely used prophylaxis, the timing of which was variable. The main risk factors identified when considering prophylaxis were previous history of deep vein thrombosis/pulmonary embolism, hypercoagulability, and the presence of malignancy. Suggestions for future practice are made.

Improved hemodynamic effectiveness and associated clinical correlations of a new intermittent pneumatic compression system in patients with chronic venous insufficiency

PURPOSE

A new intermittent pneumatic compression device (SCD Response System) has recently been shown in healthy volunteers to have the ability to detect the postcompression refilling of the calf veins and to respond by initiating the subsequent cycle when these veins are full. This has proven to be more effective in expelling blood proximally than the conventional intermittent pneumatic compression device (SCD Sequel System). The aim of this study was to test the influence of venous disease on the postcompression refill time detected by means of the SCD Response and the effectiveness of the new system in expelling blood in patients who have venous reflux caused by post-thrombotic syndrome or varicose veins.

METHODS

This open, controlled trial was conducted in an academic vascular unit with 10 patients who had post-thrombotic syndrome and 10 patients who had varicose veins. The new SCD Response System was tested against the existing SCD Sequel System in both legs in the supine, semirecumbent, and sitting positions. The refilling time sensed by means of the device was correlated with the venous filling index by using air plethysmography. The total volume of blood expelled per hour during compression was compared with that expelled by the SCD Sequel System in the same volunteers and in the same positions.

RESULTS

An inverse association was found between the mean postcompression refilling time in the sitting position and the venous filling index of the apparently healthy or less severely affected leg (r = -0.52, P =.019), the refill time being significantly shorter in patients with advanced venous disease. The SCD Response System increased the volume expelled per hour in the post-thrombotic leg, when compared with the SCD Sequel System, by 109.9% (P =.005) in the supine position, by 85.1% (P =.009) in the semirecumbent position, and by 40.2% (P =.005) in the sitting position. The corresponding results in the more severely affected leg in patients with varicose veins were 71.9% (P =.005) in the supine position, 77.9% (P =.005) in the semirecumbent position, and 55.7% (P =.013) in the sitting position. Similar improved results were also found in the contralateral leg in both groups.

CONCLUSIONS

The deflation settings of the new SCD Response System are able to be adjusted selectively, correlating with the physiological severity of chronic venous insufficiency. By achieving more frequent compression cycles, the new system is more effective than the current one in expelling blood proximally, confirming our earlier findings in healthy volunteers. Further studies testing a possible improved efficacy in preventing deep venous thrombosis in this high-risk group are justified.

Effective risk stratification of surgical and nonsurgical patients for venous thromboembolic disease

Effective and safe methods of preventing venous thromboembolism (VTE) are now widely available, but a significant proportion of patients develop VTE either because thromboprophylaxis has not been used or because the intensity of thromboprophylaxis is not matched to the level of risk. Thromboembolic risk varies widely according to the clinical setting and presence of underlying risk factors, but VTE may not be suspected even in high-risk patients. Clinical risk factors for VTE include recent surgery, cancer, stroke, previous VTE, immobilization, and advanced age. Recent attention has focused on the role of inherited and acquired molecular factors in determining overall thromboembolic risk. These factors include the classic thrombophilias-deficiencies of antithrombin III, protein C, and protein S-and several newly described molecular risk factors: factor V Leiden, the prothrombin 20210A gene mutation, and hyperhomocysteinemia. Based on emerging knowledge of risk factors, several risk assessment models (RAMs) have been devised that stratify patients according to overall VTE risk, allowing thromboprophylaxis to be tailored appropriately. Compared with older risk assessment formulas, current RAMs are simpler and include specific recommendations for thromboprophylaxis based on the available scientific evidence. Consensus documents on VTE prevention classify patients into low-, moderate-, and high-risk categories. More recently, a new risk group, very high risk, has been described. Very-high-risk patients are especially prone to thromboembolic complications and need intensive and in some cases prolonged thromboprophylaxis.

Varicose vein surgery and deep vein thrombosis

A questionnaire was sent to 363 members of the Vascular Surgical Society of Great Britain and Ireland about their use of deep vein thrombosis (DVT) prophylaxis at the time of varicose vein surgery. Replies were received from 289 surgeons (80 percent), of whom only 29 percent regarded varicose veins as an important risk factor for DVT. Only 12 percent used subcutaneous heparin prophylaxis routinely, while 71 percent did so selectively, being influenced by a history of thromboembolism (95 percent), obesity (47 percent), age (35 percent), recurrent varicose veins (22 percent) and inpatient status (16 percent). At the end of the operation 52 percent applied crepe bandages, 25 percent other bandages, 13 percent stockings and 10 percent Tubigrip. Subsequently, antiembolism stockings were prescribed by 55 percent. There is a wide variation in opinion regarding DVT prophylaxis for patients having varicose vein surgery, which has both clinical and medicolegal implications.

Prevention of venous thromboembolism in North America: results of a survey among general surgeons

PURPOSE

The purpose of this study was to analyze current attitudes toward the prevention of postoperative venous thromboembolism among North American general surgeons.

METHODS

A survey regarding awareness of the problem of venous thromboembolism and preferred modalities of prophylaxis was sent to 3500 randomly selected Fellows of the American College of Surgeons.

RESULTS

A total of 1018 (29.1%) surveys was returned. Most of the responding surgeons consider venous thromboembolism a serious health problem. Ninety percent of the surgeons use prophylaxis against venous thromboembolism routinely. The most frequently used modalities are intermittent pneumatic compression, low-dose heparin, and elastic stocking. A combination of physical and pharmacologic methods is used by one fourth of respondents, and only 50% start pharmacologic prophylaxis before the surgical procedure. The thrombosis risk factors that are most frequently considered by surgeons when deciding about using prophylaxis are history of venous thromboembolism, immobility, and length of operation.

CONCLUSIONS

North American surgeons who responded to this survey are well aware of the problem of venous thromboembolism and their approach to prevention has been significantly modified in the last 10 years. Compared with similar European surveys this survey reveals a higher implementations of physical methods such as intermittent pneumatic compression and elastic stockings. Because of the limited response rate and possibility of sampling bias, these findings should be interpreted with caution.

Red blood cell aggregability in patients with a history of leg vein thrombosis: influence of post-thrombotic treatment

Reversible aggregation of red blood cells (RBC) plays an important role in determining blood flow properties, and it is this aggregation which increases blood viscosity at low shear rates. The structure and sites of venous thrombi, as well as the fact that stasis is a major predisposing factor in venous thrombosis, suggest a strong association between vein thrombosis, slow blood flow and increased blood viscosity. RBC aggregation and disaggregation were measured (SEFAM erythroaggregameter, France) in 54 patients with a history of unexplained leg vein thrombosis. Results were compared to those of controls classified according to age. Increased RBC aggregability was observed in 41% of the patients, and the mean values indicated a significant elevation of RBC aggregability in patients when compared with controls (P < 0.05). Subgroups were compared to study the influence of thrombus recurrence and thrombosis type (deep versus superficial vein thrombosis) on the aggregation parameters. No significant difference was found between these subgroups. The use of compression stockings and veinotropic drugs tended to reduce the abnormalities in RBC aggregability (P < 0.05). An increase in RBC aggregability and in the shear resistance of RBC aggregates, by predisposing to circulatory stasis, is likely to contribute to the evolution and complications of leg vein thrombosis.

Preliminary study to identify cancer patients at high risk of venous thrombosis following major surgery

This study investigated whether the pre-surgical plasma levels of TAT and F1 + 2 of patients undergoing major surgery for localized tumours could identify patients at higher risk of thrombosis, and how heparin prophylaxis affected in vivo coagulation after cancer surgery. We measured the pre- and post-operative levels of TAT, F1 + 2, total factor VII (FVIIt) and zymogen FVII (FVIIz) in 117 cancer patients, with and without heparin prophylaxis. The end points of this study were DVT, initially detected by 125I-fibrinogen uptake test and confirmed by ascending venography. Pre-operative [TAT] and [F1 + 2] of the cancer patients were significantly higher than those of age-matched control subjects (n = 50) (P < 0.005 and P < 0.05, respectively); pre-operative [FVII] was not significantly different. One of the 83 patients receiving prophylaxis, and 8/34 not receiving prophylaxis developed post-operative DVT. Of the parameters evaluated, only the pre-operative [TAT] > 3.5 ng/ml identified patients at higher risk for post-operative DVT. Heparin reduced plasma TAT levels and FVII consumption following surgery, suggesting that heparin modulates coagulation associated with cancer surgery. The results of this study also suggest that the pre-operative [TAT] may identify patients with higher risk for post-operative DVT.

Venous thromboprophylaxis in oesophageal cancer surgery

In a retrospective study of 127 patients who underwent resection for oesophageal cancer without anticoagulant thromboprophylaxis, the incidence of clinically established postoperative deep vein thrombosis (DVT) was 1.6 per cent. In a prospective study the Sue-Ling DVT risk factor index was calculated for 53 consecutive patients with oesophageal cancer; the mean (s.d.) value was -4.4(3.5). For 29 patients who underwent resection the following policy of thromboprophylaxis was applied. Patients undergoing transthoracic oesophagectomy with risk score > -4 (four patients) and those undergoing transhiatal resection with risk score > -1 (four) received both anticoagulant and mechanical thromboprophylaxis; the remaining 21 patients received only mechanical thromboprophylaxis. No patient developed DVT after operation. There were no haemorrhagic complications in the group undergoing anticoagulant thromboprophylaxis. The selective approach, based on the Sue-Ling risk factor index and type of operation, spared 72 per cent of the patients operated on from undergoing anticoagulant thromboprophylaxis and produced favourable results in this small series.

[Identification of persons with high risk of venous thrombosis]

The aim of identification of patients with high risk of deep venous thrombosis is a selective and more efficiency prophylaxis. Deficiencies of coagulation inhibiting and fibrinolytic proteins are implicated in less than 10% of patients. However there are several clinical situations with an increased risk of thrombosis. Thus the characterization of blood abnormalities as screening tests for the diagnosis of patients at risk is an important goal.

Prostanoid production in varicose veins: evidence for decreased prostacyclin with increased thromboxane A2 and prostaglandin E2 formation

In this study, formation of arachidonic acid-derived prostanoids was investigated in saphenous veins of varicosed and nonvaricosed patients, all undergoing saphenectomy respectively for varicosis or in preparation for coronary bypass operation. Venous production of prostacyclin (PGI2), thromboxane A2 (TXA2) and prostaglandin E2 (PGE2) was assessed by bioassay and/or radioimmunologic assays as appropriate. Fragments of saphenous veins from varicosed patients produced significantly less PGI2 and more TXA2 and PGE2 than those from the control patients. Addition of arachidonic acid to incubation mixtures dose dependently increased release of these prostanoids, but the levels of PGI2 produced were consistently lower in veins from varicosed patients. No differences were found in varicosed patients between various segments of the same vein, no matter whether macroscopically affected or unaffected. These results demonstrate that the cyclooxygenase pathway in the venous wall of subjects with varicosis is shifted toward lesser formation of PGI2 and higher production of proaggregatory and proinflammatory prostanoids such as PGE2 and TXA2. These biochemical changes may be relevant to inflammation and thrombogenesis in varicosis.

Blood rheology in general medicine and surgery

Traditionally, blood rheology tests have been used in diagnosis and monitoring of infection, rheumatic diseases and malignancy, and are still of clinical value in these conditions. In the last twenty years, clinical and epidemiological studies have shown that the haematological determinants of blood flow resistance (haematocrit, fibrinogen, white cell count and altered red and white cell rigidity) are also associated with nutritional, metabolic, endocrine and vascular disorders. Decreased red cell deformability may contribute to reduced red cell survival and anaemia in burns, malaria, liver disease and kidney failure. In trauma and inflammatory disease, overt hyperviscosity is usually prevented by vasodilatation and reduction in the haematocrit. However, low-flow states may arise systemically from haemoconcentration (contracted plasma volume, Chapter 3) in severe burns, inappropriate red cell transfusion, or dehydration due to illness; systemically in circulatory shock; and locally in venous thrombosis or arterial disease. In such circumstances, the intrinsic flow resistance of blood may perpetuate flow disturbance, ischaemia and thrombosis. Conversely, optimal levels of haematocrit, fibrinogen and white cell count may be lower than normal in low-flow states. Haemodilution by colloid infusion is beneficial in burns, shock, major surgery, prevention of postoperative venous thrombosis, chronic stable claudication and possibly in acute stroke and retinal vein thrombosis. Plasma exchange may be beneficial in severe Raynaud's phenomenon. Defibrination with ancrod is effective in prevention and treatment of venous thrombosis but its role in arterial disease is unproven. The benefits of streptokinase therapy in venous thrombo-embolism and acute myocardial infarction may be partly rheological, due to fibrinogen depletion. Drugs with rheological effects may be beneficial in intermittent claudication.

Indicators of depressed fibrinolytic activity in pre-operative prediction of deep venous thrombosis

Euglobulin lysis time (ELT), tissue plasminogen activator (tPA), and the fast-acting inhibitor of tPA, were measured pre-operatively in 128 patients who underwent elective major abdominal surgery. Deep venous thrombosis (DVT) was detected by 125I-labelled fibrinogen scan in 37 patients (29 per cent) after operation. Pre-operatively, there was diminished euglobulin lysis activity (332 +/- 197 versus 255 +/- 156 min, mean +/- s.d.; P less than 0.025), and tissue plasminogen activator activity (4.2 +/- 9.9 versus 7.7 +/- 14.3 milliunits/ml, mean +/- s.d.; P = 0.094) in patients who subsequently developed postoperative DVT compared with those who did not. There was no significant difference between the two groups in the level of inhibition of tissue plasminogen activator (160.6 +/- 75.4 per cent versus 152.5 +/- 77.5 per cent, mean +/- s.d.; n = 47). Stepwise logistic discriminant analysis of the data obtained preoperatively showed that tissue plasminogen activator, a more specific measure of fibrinolytic activity, was a weaker predictor of DVT than euglobulin lysis time. The results confirm other observations which indicate that lowered fibrinolytic activity is a risk factor for postoperative DVT. In addition, they suggest that this is not due entirely to low levels of activity of tissue plasminogen activator in plasma.

Pre-operative identification of patients at high risk of deep venous thrombosis after elective major abdominal surgery

Eighteen items of clinical and laboratory information were measured on the day before operation in 85 patients who underwent elective major abdominal surgery. Postoperatively, deep venous thrombosis (DVT) was detected by 125I-fibrinogen scan in 23 patients. Stepwise logistic discriminant analysis was used to identify factors which predicted DVT. Seven such factors were identified, which were then used to construct a predictive index. In descending order of predictive power, they were: age, euglobulin lysis time (ELT), previous abdominal surgery, varicose veins, antithrombin III concentration, cigarette smoking, and platelet count. Pre-operatively, the predictive index correctly identified 91% of the patients in whom DVT developed, and wrongly allocated to the high-risk group 19% of those in whom it did not. A shortened version of the predictive index based only on age and ELT (I = -11.5 + 0.133 age + 0.006 ELT) was 91% sensitive and 63% specific in the prediction of DVT. In a prospective study of 43 patients, this shortened predictive index correctly identified pre-operatively 93% of patients in whom DVT developed, and wrongly allocated to the high-risk group only 17% of those in whom it did not.

Tissue plasminogen activator concentrations in major abdominal surgery. Relationship to postoperative deep vein thrombosis

Tissue plasminogen activator (t-PA) antigen concentrations were studied in 47 patients subjected to major abdominal surgery. The 17 patients, which developed postoperative deep vein thrombosis (DVT), diagnosed with the 125I-fibrinogen uptake test, had higher levels preoperatively, and on the sixth postoperative day, when the thrombi had already formed. The reduced fibrinolytic activity in patients with a predisposition to postoperative deep vein thrombosis is thus not related to any t-PA deficiency. The postoperative fibrinolytic shutdown may however partly be due to a drop in t-PA antigen levels, at least in the patients, which developed DVT.

Oral contraceptives and surgery: reduced antithrombin and antifactor Xa levels without postoperative venous thrombosis in low-risk patients

The effect of preoperative treatment with an estrogen containing oral contraceptive on the incidence of postoperative thrombosis (detected with 125I-fibrinogen leg scanning) was examined in 221 patients aged 18-49 years who had elective or emergency general intra-abdominal or gynecologic surgery, 99 of whom were taking an oral contraceptive before their operation. Eighty-five percent of the contraceptive treated patients had taken their preparation until 1-7 days before surgery and the rest until within a month of surgery; 81% were taking preparations containing 30 or 50 micrograms estrogen. Postoperative thrombosis developed in 1 of the 122 patients who were not taking a contraceptive and in none of the 99 contraceptive treated patients. As the 95% confidence limits for the 0% thrombosis rate observed in the contraceptive treated patients are 0-3.7%, the added risk of postoperative thrombosis attributable to oral contraceptive treatment before surgery is very small in young women who are otherwise at low risk of thrombosis. Plasma antithrombin level (by immunoassay), antithrombin activity (by chromogenic substrate assay), and antifactor Xa activity (by clotting assay), were measured before surgery in 81 patients, 42 of whom had been taking an oral contraceptive. Contraceptive treatment significantly reduced all 3 assay results. Its most marked effect was on antifactor Xa activity, which was reduced by contraceptive treatment from 103 +/- 24% (range 68 - 172%) to 81 +/- 27% (range 24 - 155%; with less than 80% activity in 54%, and less than 50% activity in 15% of patients). These results suggest that reduced preoperative antifactor Xa activity has a low specificity for thrombosis after moderately extensive surgery in young, otherwise fit, oral contraceptive treated women. This test is therefore unlikely to be a clinically useful predictor for postoperative thrombosis in this group of patients.

Protein C, an anticoagulant protein, is increased in healthy volunteers and surgical patients after treatment with stanozolol

On both oral and intramuscular administration, the anabolic steroid stanozolol was found to increase protein C antigen concentrations in circulating blood. In fourteen healthy young volunteers (who received stanozolol orally, dose 10 mg/day) the average increase was 1.5-1.6 times the normal concentrations after 3-6 weeks' treatment and was accompanied by more moderate increases in the other vitamin K-dependent factors II, IX and X to 1.4, 1.4 and 1.2 times their normal concentration respectively. However, there was no change in factor VII. In sixteen elderly surgical patients, intramuscular injection (50 mg) one day prior to surgery induced a moderate increase within 24 hours (to 1.11 times the pretreatment concentration) and seven days after operation (to 1.19 times), and reduced the postoperative fall in protein C. Stanozolol administration seems to be a promising pharmacological method for increasing anticoagulant protein C levels in congenital and acquired deficiencies.

Thromboembolic complications in Cushing's syndrome

Thromboembolic events are thought to occur with increased frequency in Cushing's syndrome due to the predisposing factors, obesity, hypertension, a raised haematocrit and major surgery plus a 'hypercoagulable state'. To examine this postulate further we have studied 43 patients with Cushing's syndrome retrospectively and 10 patients prospectively to determine the incidence of arterial and venous thrombosis, both spontaneous and post-operative. Arterial events were noted in four cases (9%) and deep vein thrombosis or pulmonary thromboembolism (PTE) occurred in six cases (11%). Post-operative PTE occurred in 2.7% of all operations. These vascular complications tended to occur in the older patients with Cushing's syndrome. In our series, clinically significant thromboembolic episodes appear no more common than expected and the indications for prophylactic anticoagulation (the older and more obese patients) may not be different from other patients undergoing major surgery. An incidental finding was of a greater frequency of hypertension in Cushing's patients due to an adrenal adenoma.

Thromboembolic prophylaxis with dihydroergotamine-heparin in abdominal surgery. A controlled, randomized study

The prophylactic affect of dihydroergotamine-heparin (0.5 mg dihydroergotamine plus 5,000 units of heparin administered twice daily) against postoperative thromboembolic complications after gastrointestinal surgery was compared with the affect of 5,000 units of heparin administered three times daily in a controlled, randomized study. Fifty patients received the dihydroergotamine and heparin combination twice daily and 50 patients received 5,000 units of heparin three times daily. The two groups were comparable with respect to age, sex, body weight, and type of operation. The presence or absence of deep venous thrombosis in the legs was determined postoperatively by the radiofibrinogen uptake test. The frequency of deep venous thrombosis in the dihydroergotamine and heparin group was 12 percent compared with 18 percent in the heparin group (0.1 greater than p greater than 0.05). Wound hematoma developed in two patients in the heparin group and in one patient in the dihydroergotamine and heparin group (4 and 2 percent, respectively). No other hemorrhagic complications occurred. By combining heparin with dihydroergotamine it is possible to reduce the daily heparin dose by one third and still obtain the same level of prophylaxis against thromboembolism. The frequency of bleeding complications was very low in both groups, since only one wound hematoma occurred in the dihydroergotamine and heparin group and two in the heparin group.