Resident Readiness General Surgery (22 page)

With a suspected transfusion reaction, send blood specimens from both the patient and the transfused blood specimens to the lab.

Acute DIC is most easily recognized as oozing at the IV site.

COMPREHENSION QUESTIONS

1.
A 55-year-old male is still on the ventilator 3 days following an open aortobifemoral graft. His Hbg is 7 g/dL. You decide to give him 2 U of packed red blood cells. The most likely benefit will be an increase in which of the following?

A. P
O
₂
95 → 110 mm Hg

B. O
₂
saturation 95% → 98%

C. CaO
₂
by 25%

D. Hbg 7 → 14 g/dL

E. Hct 20% → 35%

2.
DIC can be most easily recognized by which of the following?

A. Low platelet counts

B. Bleeding around a peripheral IV site

C. Low hematocrit

D. Elevated
D
-dimers

3.
You should stop a transfusion if the patient develops which of the following?

A. A rash

B. Pruritus

C. Hoarseness

4.
Pharmacologic treatment of an acute transfusion reaction could include any of the following
except
which of the following?

A. Acetaminophen

B. Epinephrine

C. Phenylephrine

D. Diphenhydramine

Answers

1.
C
. More red blood cells increase the content of oxygen being carried in the blood. The oxygen saturation of that blood remains the same, as does the partial pressure of oxygen. The Hgb should rise by 1 g/dL for each unit, while the Hct will rise just 3% for each unit.

2.
B
. While these other elements can also be present, they are nonspecific and require a lab test. It is worth first checking the peripheral IV site.

3.
C
. A rash and pruritus are CDC level I–type reactions. You should give an antihistamine and then monitor the patient while you continue the transfusion.

4.
A
. Antihistamines such as diphenhydramine are first-line pharmacologic agents for all levels of transfusion reactions. For more severe reactions, α- and β-agonists are also indicated.

A 37-year-old Man With a Painful Bulge Over His Left Forearm

Eric N. Feins, MD

A 37-year-old man presents to the emergency department complaining of a painful bulge over his left forearm. He states that he noticed some redness around the area 1 week ago, and then over the past few days it has become more swollen and painful, but it has not drained anything. He denies fevers, but thinks he’s had some occasional chills. He has no other medical problems and denies injecting drugs.

On physical exam, he is afebrile, HR 95, and BP 115/75. He has overall good hygiene and is well kempt. Over the dorsolateral aspect of his left forearm there is a 3-cm erythematous, fluctuant mass. It is extremely tender to light palpation and is mobile. Nothing can be expressed from the mass on palpation. There is also a 4- to 5-cm margin of erythema surrounding the mass without any evidence of streaking up the arm.

1.
What, if any, additional imaging would you obtain?

2.
Can you drain this abscess in the ED, or should it be done in the OR?

3.
Is antibiotic therapy warranted for this patient?

SUPERFICIAL ABSCESS

Not all superficial abscesses are created equal and host factors often explain their etiology and severity. Superficial abscesses can arise in otherwise healthy individuals who develop skin breakdown (ie, abrasion, cut, surgical incision) that allows the entry of pathogenic bacteria. These are typically simpler to manage because the patient lacks risk factors and is immunocompetent. In contrast, patients with a history of injection drug use are at risk for recurrent superficial infections and abscesses. Immunocompromised patients (ie, diabetics) are also at risk for developing more severe infections due to their impaired host defenses.

Host factors influence the microbiology of superficial abscesses. Simple abscesses in immunocompetent patients are typically due to skin flora:
Staphylococcus
and
Streptococcus
, although gram-negative and anaerobic bacteria, can be involved. Methicillin-resistant
Staphylococcus aureus
(MRSA) is becoming increasingly common in some regions and is particularly prevalent in recently hospitalized patients, injection drug users, and diabetics.
Pseudomonas aeruginosa
is common in diabetics with abscesses (often on the feet), and is quite virulent if not treated. This is important to consider if antibiotics will be prescribed (see below).

Answers

1.
A bedside ultrasound can be a useful adjunctive test. Ultrasound will give you 3 important pieces of information:

A.
Whether there really is a drainable collection
: It can sometimes be difficult to determine on physical exam if an abscess is actually present, or if you are just feeling inflamed tissue from a cellulitis (ie, induration). Both cellulitis and abscesses will have warmth, redness, and tenderness (general markers of inflammation), and some abscesses will not have obvious fluctuance. In these cases of uncertainty ultrasound can confirm/rule out the presence of an abscess that needs drainage.

B.
Size and depth
: If there is concern about how big and/or deep the abscess is, an ultrasound will help. This is important if you are concerned the abscess is so big or deep that it requires incision and drainage (I&D) in the OR.

C.
Surrounding structures
: Sometimes abscesses are located near important structures (ie, blood vessels). In these cases, ultrasound can help you avoid such structures during a drainage procedure.

For this particular patient with these physical findings ultrasound would not be necessary because it is clear that there is an undrained abscess, and it is not big enough or deep enough to require I&D in the OR.

2.
This patient requires formal I&D of his undrained abscess under local anesthesia in the ER. This represents “source control,” which is an important principle for the treatment of infections.

In some cases it is more appropriate to drain a superficial abscess in the OR. The following are relative contraindications to a bedside I&D of a superficial abscess:

A.
Size/depth
: There is no fixed size cutoff, but generally, abscesses that are too large or too deep to anesthetize with local anesthesia and/or require an extensive debridement should be done in the OR.

B.
Location
: Abscesses in sensitive locations may require I&D in the OR due to the need for sedation or general anesthesia. In particular, this includes perirectal abscesses. While some are superficial enough to drain under local anesthesia, many are deeper and close to critical structures (ie, anal sphincter). These often require general anesthesia for patient comfort, to attain adequate exposure, and to evaluate for fistulae.

C.
Patient anxiety or pain tolerance
: Some patients cannot tolerate bedside drainage, due to either their expected intolerance of pain or their baseline anxiety about the procedure. The operating room is the appropriate place for
these patients as it allows for improved analgesia and optimal conditions to minimize procedure length.

Adequate drainage of an abscess requires several important components:

A.
Incision
: Your incision must be large enough to ensure adequate drainage. The incision need not extend over the entire length/diameter of the abscess, although if in doubt, you should err on the side of larger. There is no hard rule for incision size, but as an example, a 3-cm abscess might be adequately drained with a 2- or 3-cm incision.

B.
Deloculation
: After opening the cavity, gentle exploration with a cotton-tipped probe and curved hemostat (clamp) is necessary to break up any loculations within the cavity. The patient may require additional deep injection of local anesthetic.

C.
Packing
: After initial drainage the cavity must be kept open to allow for further drainage of leftover fluid/debris. This involves loosely packing the cavity with 0.25- or 0.5-in wide packing ribbon. Insert enough to keep the cavity open, and leave the ribbon extending out of the skin to prevent the skin edges from closing. Premature skin closure can lead to abscess recurrence. The abscess will heal by secondary intention.

Sending a wound culture is always a good idea. If the patient has a soft tissue infection (ie, cellulitis) in addition to an abscess, the culture data can help you narrow the initial empiric treatment. While patients without soft tissue infection will usually improve with drainage alone, if the patient later develops worsening soft tissue infection, then antibiotic therapy could be started and directed toward the culture data.

3.
The 2 main determinants of whether antibiotic therapy is warranted are:
(A) presence of surrounding soft tissue infection and (B) host-related factors
.

A.
Presence of soft tissue infection
: Cellulitis, the most common form of soft tissue infections associated with superficial abscesses, requires treatment with antibiotics. In the patient presented here, there is a significant degree of surrounding erythema/tenderness consistent with cellulitis. Therefore, he will require antibiotic therapy. In many cases, abscesses do not have significant surrounding erythema, warmth, or redness, suggesting absence of cellulitis. In these cases, antibiotics are not warranted.

B.
Host-related factors
: In immunocompetent patients there is no need for antibiotics after abscess drainage, assuming there is no surrounding cellulitis. For them, we rely on their immune defenses to completely eradicate the infection after drainage. However, in immunocompromised patients (ie, diabetics) it is reasonable to consider a short course of antibiotics, and this can be discussed with a senior resident.