From the Desk of
Joseph A. Caprini, MD, MS, FACS, RVT, DFSVS

The Importance of Updating the Caprini Score

This clinical scenario illustrates the dynamic nature of the Caprini score that goes beyond the initial thrombosis risk assessment. As the clinical course evolves,postoperative problems can occur that elevate the patient’s risk and dictate changes in the thrombosis prophylaxis regime.

Illustrative Hypothetical Patient

Jane Doe was a 43-year -old patient who presented to the emergency room with a 4-day history of abdominal pain, nausea and vomiting. Initial evaluation revealed RUQ tenderness, and normal bilirubin, liver enzymes, and blood counts. Ultrasound examination of the abdomen revealed gallstones with signs of inflammation of the gallbladder. The patient had a BMI of 34.0 but no other risk factors. She underwent a 90-minute laparoscopic cholecystectomy and postoperatively stayed in the hospital overnight.

The initial Caprini score was 4: (age over 40 =1, BMI >25 = 1, Surgery lasting 90 minutes (anesthesia time) =2). Thrombosis prophylaxis using pneumatic compression devices was prescribed during and following the surgical procedure. Low scores do not require anticoagulant prophylaxis, andusing these drugs does not further lower the already low venous thromboembolism (VTE) rate. (Pannucci meta-analysis)

The patient did well initially; however, the following day developed acute abdominal pain and a CT scan revealed a serious bile leak. Emergency ERCP examination demonstrated a cystic duct stump leak with a large intra abdominal fluid collection. A biliary stent was successfully placed to control the leak. A PICC line was inserted due to poor venous access for administration of antibiotics. The patient remained in bed due to severe lingering abdominal pain for the next 24 hours, then her pain improved, and she made short trips to the bathroom.

A chest film was done on the 3rd postoperative day due to a productive cough and a temperature of 102.0 degrees. The x-ray findings included basilar atelectasis and a right lower lobe infiltrate. Infectious Disease was consulted, and antibiotic therapy adjusted based on sputum culture results.

The patient continued to improve with increased ambulation including walking short distances in the hall but required oxygen during this time to maintain her oxygen saturation at normal levels. Repeat chest films the following day showed a stable picture with less basilar atelectasis.

The patient experienced sudden severe chest pain and shortness of breath at 10:00 AM on the 6th postoperative day followed shortly by full cardiac arrest. Resuscitation for >30 minutes was unsuccessful, and the patient expired at 10:42 AM.

Autopsy was performed and showed a saddle pulmonary embolus, as well as resolving pneumonitis involving the right lower lobe of the lung. There were no other positive findings, and the stented common bile duct was intact with minimal residual fluid seen in the peritoneal cavity.

The surgical team was puzzled why this otherwise healthy middle-aged woman with a low Caprini score had suffered a fatal pulmonary embolus. They reviewed the chart and determined that the compression devices were being used appropriately whenever she was in bed, including during the night. The patient’s sister had stayed with the patient and agreed, commenting how efficient the nursing staff was in making sure the devices were on the patient and functioning properly. This protocol should have been more than enough to prevent a fatal PE in someone with a low Caprini score.

Review of this case at morbidity and mortality conference included the discussion that anticoagulant prophylaxis for this patient was not indicated due to the Caprini score of 4 on admission. It is not certain why the surgeons participating in this discussion were unaware of the importance of updating the score as adverse events were known to occur during hospitalization in this patient.The problem was compounded by the ASH 2019 guidelines that recommend against anticoagulant prophylaxis unless the patient has DVT, thrombophilia, or malignancy.

Here is the guideline from ASH 2019 regarding gallbladder surgery

Laparoscopic cholecystectomy

“RECOMMENDATION 18. For patients undergoing laparoscopic cholecystectomy, the ASH guideline panel suggests against using pharmacological prophylaxis (conditional recommendation based on very low certainty in the evidence of effects Å◯◯◯). Remark: Patients with other risk factors for VTE (such as history of VTE,thrombophilia, or malignancy) may benefit from pharmacological prophylaxis.”[1]

COMMENT

The clinical risk of thrombosis specific to Jane Doe is not addressed by this guideline. Combinations of common established risk factors, including central lines, infection, and immobility are known to increase the postoperative VTE risk, and this principle is not addressed. Furthermore, the disclaimer at the end of the guideline could be interpreted that the guideline authors were unsure if prophylaxis should be recommended at all.

This is a good illustration of why guidelines do not necessarily represent the standard of care. In this case the guideline is useless as far as providing thrombosis prophylaxis advice for this patient. The physician needs to look beyond this document in order to decide how to tailor the thrombosis prophylaxis approach for a patient like Jane Doe.

Risk assessment tools are available and one popular approach is to use the Caprini score. This tool represents a thorough history and physical involving 40 risk factors. The number of risk factors and their relative weights are combined resulting in a score. This score has been shown to increase in non-linear fashion with the clinical thrombosis rate in more than 150 studies involving nearly 5 million patients.[2]

The first step is calculating an initial score on admission. It is critical to realize that the score is a dynamic tool that needs to be updated during hospitalization. Recalculating Jane Doe’s score during hospitalization would yield the following result. Her score would have risen to 9: ERCP =1, bedrest =1, PICC line =2, pneumonia =1. Adding the base score of 4 would result in a score of 9. Referring to the results of the Pannucci meta-analysis quoted below, her chance of clinically apparent thrombosis would be at least 10.7%. This would dictate the use of anticoagulant administration to prevent a sublethal or fatal pulmonary embolus.

The following excerpt from the Pannucci meta-analysis including 14,776 patients helps guide the prophylaxis approach for Jane Doe. “The majority of patients received mechanical prophylaxis.

A 14-fold variation in VTE risk (from 0.7% to 10.7%) was identifiedamong surgical patients who did not receive chemoprophylaxis, and patients atincreased levels of Caprini risk were significantly more likely to have VTE.[3] Jane Doe started with a score of 4 that was associated with a low VTE rate (0.7%). During the hospitalization her score became 9 and now without anticoagulation the VTE rate rose to 10.7%. (See the following table.)

“PE is the most common preventable cause of hospital death and is the number one strategy to improve patient safety in hospitals.”[4]

We know that literature over the past 30 years demonstrates that a 66% relative risk reduction in fatal pulmonary emboli was seen in patients receiving heparin prophylaxis compared to those not receiving prophylaxis.[5, 6] A large, more recent trial in 23,078 surgical patients revealed that “the primary outcome measure–autopsy-proven fatal pulmonary embolism recorded up to 14 days after the end of prophylaxis, occurred in 0.152% (95% confidence interval (CI) 0.10, 0.20%; 35 of 23,078 patients) of cases, with no significant difference between those receiving LMWH or unfractionated heparin.”[7] 

Pneumonia: A Confounding Factor Disguising Pulmonary Emboli

A landmark autopsy study from 1982 illustrates the difficulty identifying pulmonary emboli antemortem in the presence of pneumonia. “To evaluate factors associated with the correct antemortem diagnosis of pulmonary embolism, we reviewed all 1,455 autopsy reports at the Peter Bent Brigham Hospital from 1973 to 1977. Of 54 patients identified with anatomically major pulmonary embolism at autopsy, 16 (30 percent) had correct antemortem diagnosis. In contrast, among 21 patients with autopsy-proved major pulmonary embolism who also had pneumonia, no pulmonary embolism was diagnosed before death (p = 0.0001).” [8] 

One May Conclude That the Administration of Heparin or LMWH to Jane Doe Would Have Saved Her Life

It is hoped that going forward Jane’s physician will gain valuable insight from this tragic outcome and address assessment of future patients in a more dynamic fashion. It is hoped that the department chairman will organize a grand-rounds to discuss these issues regarding thrombosis prophylaxis in surgical patients, covering the principles discussed here. 

References

1. Anderson, D., G. Morgano, and C. Bennett, American Society of Hematology 2019 guidelines for management of venous thromboembolism- prevention of venous thromboembolism in surgical hospitalized patients. Blood Advances, 2019. 3(23): p. 3898-3944.
2. Golemi, I., et al., Venous thromboembolism prophylaxis using the Caprini score. Disease-a-Month, 2019. 65: p. 249-298.
3. Pannucci, C.J., et al., Individualized Venous Thromboembolism Risk Stratification Using the 2005 Caprini Score to Identify the Benefits and Harms of Chemoprophylaxis in Surgical Patients: A Meta-analysis. Ann Surg, 2017. 265(6): p. 1094-1103.
4. Geerts, W.H., et al., Prevention of venous thromboembolism: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest, 2004. 126(3 Suppl): p. 338S-400S.
5. Kakkar, V.V., et al., Prevention of Fatal Postoperative pulmonary embolism by low doses of heparin. Reappraisal of results of international multicentre trial. Lancet, 1977. 1(8011): p. 567-9.
6. Collins, R., et al., Reduction in fatal pulmonary embolism and venous thrombosis by perioperative administration of subcutaneous heparin. Overview of results of randomized trials in general, orthopedic, and urologic surgery. N Engl J Med, 1988. 318(18): p. 1162-73.
7. Haas, S., et al., Prevention of fatal pulmonary embolism and mortality in surgical patients: a randomized double-blind comparison of LMWH with unfractionated heparin. Thrombosis & Haemostasis, 2005. 94(4): p. 814-9.
8. Goldhaber SZ, et al., Factors Associated with Correct Antemortem Diagnosis of Major Pulmonary Embolism. Am J Med. 1982., 1982. 73(6): p. 822-826.