Resident Readiness General Surgery (44 page)

Bradyarrhythmias or tachyarrhythmias—resulting in decreased cardiac output

Treatment is based on stabilizing the patient and treating the underlying cause or causes:

Preload—diuresis

Afterload—aggressive management of hypertension

Ischemia—ACS protocol, possibly inotropes, possibly invasive hemodynamic monitors, and emergent cardiology consult

Arrhythmias—pacing or appropriate nodal blocking agents ± cardiology consult

COMPREHENSION QUESTIONS

A 67-year-old man with long-standing hypertension is postoperative day 2 from a right upper lobe wedge resection for lung cancer. You are called by the nurse who tells you that his oxygen saturation has dropped into the mid-eighties and his heart rate is 134. He is hypotensive and his urine output has decreased significantly.

1.
What two studies are likely to be most helpful during immediate initial evaluation in determining the cause of this patient’s symptoms?

A. An echocardiogram and a BNP

B. Cardiac catheterization and a VQ scan

C. An EKG and a CXR

2.
This patient’s heart failure is most likely related to which of the following?

A. Too much preload

B. Too much afterload

C. Decreased contractility

D. Loss of atrial kick

3.
Assuming that the patient is hemodynamically unstable, you should be prepared to do which of the following?

A. Obtain an echocardiogram.

B. Give diuretics.

C. Cardiovert.

D. Give antihypertensives.

4.
Every evaluation of a patient in potential heart failure should include which of the following studies at a minimum?

A. CXR

B. EKG

C. Stress test

Answers

1.
C
. This patient has likely gone into atrial fibrillation, which occurs in 30% to 40% of patients undergoing thoracic surgery. An EKG will make the diagnosis. The hypoxemia is likely related to pulmonary edema as fluid from the left side of the heart backs up into the lungs as a result of a lost atrial kick and decreased diastolic filling time. However, given that the patient underwent a pulmonary wedge resection, a CXR is absolutely critical in ensuring that there is no other cause of hypoxemia such as a pneumothorax. An echocardiogram is a very helpful study, although there is little role for it during the immediate initial workup.

2.
D
. Loss of atrial kick (especially in patients with a stiff left ventricle) can result in a drop in cardiac output by up to 30%.

3.
C
. In a truly hemodynamically unstable patient with a tachyarrhythmia and a shockable rhythm, the first step is to attempt cardioversion.

4.
B
. Every evaluation of postoperative heart failure must include an EKG to rule out ischemia as this is the most serious, and in some cases, irreversible, cause of heart failure.

A 68-year-old Man With Postoperative Hypotension

Allan B. Peetz, MD and
Marie Crandall, MD, MPH

Mr. Patel is a 68-year-old, 90-kg male who underwent an exploratory laparotomy and lysis of adhesions 6 hours ago. You are on call and a nurse informs you that Mr. Patel’s blood pressure is 92/43 and his heart rate is 102. He is completely asymptomatic and says he feels “fine except for the tube in my nose.” You notice that his IVF bag is labeled “D5 0.45 normal saline” and is infusing at a rate of 125 mL/h.

1.
Define hypotension.

2.
What is the diagnosis of exclusion for all patients with postoperative hypotension?

3.
What is the most likely cause of this patient’s hypotension?

HYPOTENSION IN THE IMMEDIATE POSTOPERATIVE PERIOD

Postoperative hypotension is common and potentially serious, with a variety of underlying causes, including hypovolemia, cardiac failure, or sepsis. Because of the possibility of serious underlying pathology, the patient with postoperative hypotension should be rapidly evaluated and a diligent search for potentially life-threatening causes of hypotension should follow.

Answers

1.
In general, a systolic blood pressure (SBP) less than 100 mm Hg or a mean arterial pressure (MAP) less than 65 mm Hg is considered hypotensive. That said, hypotension is best thought of as a
decreased blood pressure
rather than a
low blood pressure
—the difference between the patient’s current and baseline blood pressures is the most critical factor. For example, a blood pressure measurement of 95/43 mm Hg after an uncomplicated laparoscopic appendectomy in an otherwise healthy 25-year-old female whose SBP is normally no greater than 105 mm Hg is probably not hypotension. On the other hand, a blood pressure of 125/64 mm Hg after an uncomplicated laparoscopic appendectomy in a 65-year-old, homeless male who has had many years of untreated kidney disease and whose preoperative blood pressure was 212/103 mm Hg probably
is
hypotension. While the blood pressure reading of 125/64 mm Hg is “normal”
in the conventional sense, the male patient’s tissues and peripheral vasculature have probably compensated for a long history of hypertension and therefore this blood pressure may be too low to provide adequate oxygen delivery to his tissues.

2.
Evaluation of the hypotensive patient starts with urgently ruling out hemorrhage as a cause of the patient’s hypotension. If hemorrhage cannot be ruled out by history and physical exam, a workup including a CBC should be initiated while empiric treatment is begun.

For those patients in whom you suspect hemorrhage, proper management includes infusion of 1 L of 0.9 NS or LR. The patient’s blood pressure should respond soon after receiving the bolus, with an adequate response defined as a return to the patient’s baseline blood pressure and/or improvement in urine output. If the patient’s response is not adequate, a second 1 L bolus should be given, but suspicion for other, more life-threatening causes for the patient’s hypotension should be high and rapid escalation of care should be initiated. This would include notifying the senior resident, possibly an ICU transfer, and a more extensive workup.