Resident Readiness General Surgery 1st Ed.

A 55-year-old Man Who May Require Perioperative β-blockade

Alden H. Harken, MD

and Brian C. George, MD

A 55-year-old banker is driving back to work following a three-martini lunch when he is T-boned by a cement truck. On arrival in the emergency department he is hemodynamically stable and alert. He prides himself on never having graced a physician’s office and he is on no medications. FAST exam reveals fluid in the LUQ. During the next hour his blood pressure drifts down and you are forced to take him to the OR for a splenorrhaphy.

You are writing his postoperative orders using a template, and you arrive at the section with numerous possible options for postoperative β-blockade. As you write your postoperative orders, you wonder: “Should I put this guy on a β-blocker?”

1. Should you put this patient on a β-blocker?

2. If he instead took metoprolol 25 mg PO twice a day at home, what dose would you give him of IV metoprolol while he is NPO?

PERIOPERATIVE β-BLOCKADE

Answers

1. In 1999, Poldermans et al screened almost 800 high-risk vascular patients with dobutamine stress echocardiography. These investigations then culled approximately 200 very, very high-risk vascular patients formidably vulnerable to myocardial ischemia from the original high-risk group. Two weeks of β-blockade prior to the vascular surgical procedure cut the mortality from 34% (control) to 3.4% (β-blockers)—a huge difference.

However, is it permissible to extrapolate from this very, very high-risk vascular surgical group to just high-risk or even moderate-risk patients? Mangano previously stoked the confusion by prospectively randomizing 200 surgical patients into β-blocker and placebo groups. The 30-day mortality was the same, but 2-year mortality statistically favored β-blockade. Taken together, it began to look like preoperative β-blockers were certainly good for very high-risk patients, probably benefited moderate-risk patients, and might be good for everyone. Extending the tenets of a great American philosopher (Mae West opined that “Too much of a good thing is wonderful”) the PeriOperative ISchemic Evaluation (POISE) trial gave up to eight times the recommended dose of extended-release β-blockers to any patient with a heart rate over 60. In this huge study of 8351 patients in 23 countries (they could not talk any US investigators into participating), there was a reduction in myocardial infarction (5.7%-4.2%; P <.0017), but β-blocked patients with heart rates of 60 induced more strokes (0.5%-1.0%) and more deaths (2.3%-3.1%; P <.03). The investigators did not report whether they were surprised by the results of their pharmacological experiment.

Finally, Lindenaur et al retrospectively correlated cardiovascular events and in-hospital mortality with in-hospital β-blockers—another huge 663, 969-surgical-patient study in which β-blockers clearly benefited high-risk patients. Most low-risk patients were not on a β-blocker on hospital admission. This low-risk group did not receive a β-blocker until subsequent to their cardiovascular event, at which time they were statistically included in the β-blocker group. In fairness, this jaw-dropping experimental design flaw was emphasized in a companion editorial. From the flurry of studies examining perioperative β-blockade, several conclusions are permissible:

• Perioperative myocardial infarction, and probably death, is reduced by judicious use of low-dose, short-acting β-blockers (target a preoperative heart rate of 70 and a postoperative heart rate of 80).

• If your patient is on β-blockers on admission, do not stop them perioperatively.

• If your patient should have been on β-blockers preoperatively (ie, the patient had an indication such as hypertension, vascular disease, diabetes, etc), then start them as soon as possible.

• Overdosing any drug is bad, and overdosing long-acting β-blockers is associated with bradycardia, hypotension, CVA, and death.

2. You can figure this out by memorizing a single conversion. Note that both of these are the lowest doses normally used for each of these formulations:

Image

TIPS TO REMEMBER

Image β-Blocker–naïve patients should be written for low-dose, short-acting β-blockers (ie, metoprolol 5 mg IV q6h with hold parameters).

Image Continue any preoperative β-blockers (with appropriate conversion to IV as needed).

Image Start low-dose β-blockers in those patients who should have been on them in the first place.

COMPREHENSION QUESTIONS

1. Do low-dose β-blockers reduce mortality?

A. No, because they increase the rate of strokes.

B. Unsure, the evidence is contradictory.

C. Yes, because they reduce the risk of myocardial infarction.

2. What should you write for a patient on metoprolol 25 mg PO BID at home?

A. No β-blockade

B. 5 mg IV q6h

C. 5 mg IV q12h

D. 10 mg IV q6h

E. 10 mg IV q12h

F. 12.5 mg IV q6h

G. 25 mg IV q12h

3. What should you write for a 65-year-old patient who is not on β-blockers at home and just underwent a right hemicolectomy?

A. No β-blockade

B. Metoprolol 5 mg IV q6h

C. Metoprolol 10 mg IV q6h

D. Metoprolol 10 mg IV q12h

Answers

1. C. The evidence suggests that low-dose β-blockers do indeed reduce the rates of MI and consequently of death. While the POISE trial showed an increase in mortality, the investigators in that study used doses of β-blocker that are higher than what is recommended.

2. D. Remember 12.5 mg PO BID equals 5 mg IV q6h, so twice that is 10 mg IV q6h.

3. B. This β-blocker–naïve patient should be given β-blockade only at the lowest dose, that is, at 5 mg IV q6h, and targeting a HR of less than 80. You should also be careful to write appropriate hold parameters (ie, HOLD for HR <60 or SBP <100).

SUGGESTED READINGS

Lindenaur PK, Pekow P, Wang K, Mamidi DK, Gutierrez B, Benjamin EM. Perioperative beta-blocker therapy and mortality after major noncardiac surgery. N Engl J Med. 2005;353:349.

Mangano DT, Layug EL, Wallace A, Tateo I. Effect of atenolol on mortality and cardiovascular morbidity after noncardiac surgery. Multicenter Study of Perioperative Ischemia Research Group. N Engl J Med. 1996;335:1713.

POISE Study Group, Devereaux PJ, Yang H, et al. Effects of extended-release metoprolol succinate in patients undergoing non-cardiac surgery (POISE trial): a randomised controlled trial. Lancet. 2008;371:1839.

Poldermans D, Boersma E, Bax JJ, et al. The effect of bisoprolol on perioperative mortality and myocardial infarction in high-risk patients undergoing vascular surgery. Dutch Echocardio-graphic Cardiac Risk Evaluation Applying Stress Echocardiography Study Group. N Engl J Med. 1999;341:1789.