Tight Hemodynamic Control in Patients Who Are Chronically on Metoprolol

This study proposes to assess the effect of the standard of care, which is continuation of the pre op beta blocker dose into the post operative period compared to the administration of esmolol titrated to a pre determined target HR. The primary outcome will compare postoperative plasma levels of metoprolol in 2 cohorts in a group who has been continued on metoprolol (administrated via a nasogastric tube in NPO patients) to a group who has been withdrawn from metoprolol but given an esmolol infusion titrated to HR. Secondary outcomes will compare a) the hemodynamic responses, documenting the incidence of unplanned hypotension and bradycardia and b) to compare the effects of Heart rate to the incidence of myocardial ischemia, arrhythmias, delirium and infarction.

The number of high-risk patients undergoing non-cardiac surgery has increased continuously over the last two decades. There is a paucity of data exist about the bioavailability of postoperative administrated beta-blockers. One study reported adequate plasma levels of Propanolol after administration via nasogastric tube but not after oral administration in patient undergoing thyroid surgery.Thus it is possible that patients maintained on oral beta blockers may in fact be experiencing a withdrawal syndrome. Because of the importance of avoiding withdrawal of beta blockers, intravenous administration may be the only alternative in cases where oral administration fails to achieve adequate plasma levels perioperatively. Furthermore, due to changes in pharmacodynamics, intravenous dosage may be the optimal way to achieve tight hemodynamic control. There is, however, no data on the post-operative hemodynamic effects of orally administered beta blockers in patients on chronic beta blockers.

• Vascular Disease
• Hypertension
• Angina
• Cardiac Disease

• Drug: Esmolol
  Baseline treatment consists of a bolus of 500ug/kg/min followed by an infusion of 50ug/kg/min for 4 minutes and titrating in increment of 50ug/kg/min up to a maximum of 300ug/kg/min to maintain a HR within 10% of the target HR (≤ 70 bpm), which is 70± 7 bpm.
• Drug: Metoprolol
  The night and morning before surgery, the patients in the metoprolol arm will receive their standard dose of beta blocker metoprolol.These patients will receive their daily beta blockers orally or via nasogastric tube postoperatively if they are NPO (Group A).

• Active Comparator: Metoprolol oral dose or Placebo infusion
  Intervention: Drug: Metoprolol
• Experimental: Esmolol infusion or Placebo oral dose
  Intervention: Drug: Esmolol

Patient inclusion criteria:

• Elective vascular surgery

• Any of the following co morbidities

  • Diabetes
  • Angina
  • Congestive heart failure
  • A serum creatinine above 176 mmol/l
• All patients must be on stable dose of oral metoprolol (≥ 30 days)
• Age ≥ 20 years and ≤ 80 years
• Written informed consent to participate to the study

Patient exclusion criteria:

• Inability to understand the study protocol
• Prior gastric surgery or small bowel resection
• Pacemaker ( since it precludes the measurement of ST changes)
• Malabsorption syndromes
• Body Mass Index < 18 and > 35
• Any patient with suspected of diagnosed Cerebral vascular disease. (We chose to exclude CVA patients due to the ongoing controversy about the increased incidence of stroke in patients have surgery and who are taking beta-blockers.)