Resident Readiness General Surgery (65 page)

COMPREHENSION QUESTIONS

1.
A 75-year-old female with factor V Leiden deficiency and atrial fibrillation presents to your clinic after she was referred for a cholecystectomy by her PCP. Further questioning reveals that she also has poorly controlled hypertension and
diabetes. She has been on warfarin for many years. With regard to her hypercoagulability, she states that she developed a left ileofemoral DVT two months ago. Which of the following facts in the patient’s history suggests that her elective cholecystectomy should be delayed?

A. Her poorly controlled hypertension

B. Her CHADS2 score of 2

C. Her recent DVT

D. Her factor V Leiden deficiency

2.
A 42-year-old female with a past medical history of endocarditis requiring placement of a mechanical bileaflet aortic valve, currently anticoagulated with warfarin, is scheduled to undergo a small bowel resection for a gastrointestinal stromal tumor. This will require holding her anticoagulation for approximately 24 hours. She is otherwise healthy and has no other comorbidities. Should she receive bridging therapy?

A. Yes, because her valve is in the aortic position and she is at high risk for a stroke.

B. No, because her valve is in the aortic position and therefore there is a decreased risk of thrombus formation.

C. Yes, because any mechanical heart valve requires bridging.

D. No, because mechanical valves do not require bridging.

Answers

1.
C
. The risk of recurrent DVT is highest within the first three months. This patient’s operation is elective and should therefore be postponed. The other risk factors will not improve with time, and therefore these are not indications for delay.

2.
B
. Any mechanical valve in the mitral position requires bridging because of slower flow rates and stasis around the valve. Aortic valves only require bridging if the valve is an older model (ie, ball and cage type), or if the patient has other comorbidities such as hypertension, CHF, or diabetes.

A 33-year-old Woman Who Needs Postoperative Orders for DVT Prophylaxis

Brian C. George, MD and
Alden H. Harken, MD

Ms. Wang is a 33-year-old female who just underwent a left mastectomy. As the attending is leaving the room she stops to ask if you know how to write “the normal postoperative orders for DVT prophylaxis.”

1.
Why is DVT prophylaxis indicated in this patient?

2.
What kind of DVT prophylaxis would you write for?

3.
When using pharmacologic DVT prophylaxis, should you use heparin or low-molecular-weight heparin and why?

DVT PROPHYLAXIS

Deep venous thrombosis is frighteningly prevalent, especially in some pelvic and oncological surgical subgroups—approaching 50% of patients in some studies. While the data are less robust, an NIH consensus development panel has established the logical link between DVT and pulmonary embolism.

Answers

1.
When deciding whether to write a patient for standing postoperative DVT prophylaxis, you should think about the patient’s risk profile. The most commonly encountered high-risk populations include those with cancer, patients who are not ambulatory, trauma patients, pregnant women, those with a history of a hypercoaguable disorder, and those who are older (increasing risk after age 40). The risk of DVT, however, must be balanced against the risk of bleeding, and the risk of side effects, as well as patient discomfort with multiple subcutaneous injections per day. Furthermore, patients who are at risk of a major bleeding complication (eg, neurosurgical patients) are usually not started on prophylaxis in the immediate postoperative period.

In summary, if the patient is low risk (and especially if the patient is expected to be ambulatory), then DVT prophylaxis is not necessary. If, on the other hand, the patient is at moderate or high risk for DVT, then the patient should always be written for DVT prophylaxis.

2.
The Cochrane database has examined intermittent pneumatic leg compression and pharmacologic prophylaxis individually and together. Interestingly,
pneumatic compression works by diminishing venous stasis, but also works because it promotes fibrinolysis (so you can even put the leg squeezers on the arms). The Cochrane review concludes that pneumatic compression plus pharmacologic prophylaxis (2500 U heparin 2 hours preoperatively and 12 hours postoperatively) is more effective than either strategy alone. Surprisingly, multiple studies report no increase in bleeding with this regimen.

3.
While heparin is the oldest agent, it has a significant risk of causing heparin-induced thrombocytopenia (HIT) (2.6% in one meta-analysis). This contrasts with low-molecular-weight heparin (eg, enoxaparin or dalteparin) with a 10-fold decreased incidence of HIT in a population that consisted mostly of postoperative orthopedic patients. So, in general, it is better to use enoxaparin when you can—but you need to know, of course, when you cannot. There are only two common reasons that you might choose heparin. First, low-molecular-weight heparin is cleared renally, and so it can accumulate and lead to bleeding if given to a patient with renal insufficiency. Second, the half-life of low-molecular-weight heparin is longer than that of heparin and it cannot be easily reversed—both of which mean that heparin is preferred when the risk of bleeding is greatest. This is most commonly seen with epidurals, which the anesthesiologists are reluctant to remove when low-molecular-weight heparin is being used.

TIPS TO REMEMBER

DVTs are a serious and common postsurgical complication—and you will be responsible for ensuring that every patient is on appropriate prophylaxis.

Low-risk patients don’t need DVT prophylaxis, especially if they are ambulating.

Use low-molecular-weight heparin in most patients, except those who may need rapid reversal, those who are going to undergo another procedure in the near term (including removal of an epidural), or those with renal failure.

COMPREHENSION QUESTIONS

1.
A 23-year-old male is in a motor vehicle crash and has a closed femur fracture. His postoperative DVT prophylaxis regimen should include which of the following?

A. Sequential compression device (SCD) on the contralateral leg only

B. Heparin 2500 U × 1 + SCD

C. Heparin 5000 U TID + SCD

D. Enoxaparin 30 mg SQ q12h + SCD

2.
A 54-year-old female just underwent an abdominoperineal resection (APR) for rectal cancer. Her pain is being controlled with an epidural and she has both an
NG tube and Foley in place. Her postoperative DVT prophylaxis regimen should include which of the following?

A. Nothing

B. SCDs only

C. Heparin 2500 U × 1 + SCDs

D. Heparin 5000 U TID + SCDs

E. Enoxaparin 30 mg SQ q12h + SCDs

3.
A 55-year-old male is being admitted for an SBO that is being managed nonoperatively. Your admission orders should include which of the following?

A. No DVT prophylaxis but instructions to the RN to help the patient walk three times per day

B. Heparin 5000 U TID + SCDs

C. Enoxaparin 30 mg SQ q12h + SCDs

4.
A 65-year-old female who is on the kidney transplant list undergoes a right colectomy for colon cancer. Her pain is being controlled with dilaudid IV. Her postoperative DVT prophylaxis regimen should include which of the following?

A. No DVT prophylaxis but instructions to the RN to help the patient walk 3 times per day

B. Heparin 5000 U TID + SCDs

C. Enoxaparin 30 mg SQ q12h + SCDs

Answers

1.
D
. He is a trauma patient with an orthopedic injury that will prevent him from ambulating. He is therefore at high risk of DVT and should be started on both pharmacologic and mechanical (SCD) prophylaxis. He is at low risk of serious bleeding complications, and so the risk of HIT associated with unfractionated heparin (choices B and C) is not justified.

2.
D
. She is at high risk (cancer, unlikely to ambulate well given the operation and the epidural). Heparin is more appropriate because she has an epidural.

3.
A
. If the patient is able to ambulate and he is otherwise at low risk of DVT, then it is reasonable to avoid the injections and side effects of pharmacologic DVT prophylaxis. SCDs are an option, although not strictly indicated—and if the patient is walking, he probably won’t wear them much anyway.

4.
B
. This patient is at high risk of DVT but has renal failure. Low-molecular-weight heparin is therefore contraindicated.