Question 1

College Answer

a) The main clinical and haemodynamic issues identified are:
Elderly female patient post double valve surgery.
Pre-existing renal impairment.
Long bypass time.

Systemic hypotension (MAP 65 unlikely to be adequate for this patient).
Low output state (CI, EF post bypass).
Increased afterload / vascular impedance (SVR).
Probable fluid responsiveness (PAWP, CVP).
Moderate pulmonary hypertension.
Low core temperature.

b) This patient is high risk (female, age, long bypass time, pre-existing renal impairment, low EF). Management consists of:

• Re-warming.
• Judicious fluid replacement as she re-warms.
• Improved volume state may augment CI but given poor EF unlikely to be sole intervention needed.
• Titration of adrenaline infusion, aiming for CI > 2.2
• Bedside echo to evaluate effect of fluid and increased adrenaline, exclude tamponade and check valve function (mitral regurgitation can increase PAP and decrease cardiac output).
• Consideration of other vasoactive agents (dobutamine, milrinone, levosimendan) or IABP insertion if persisting low output state.
• Assess adequacy of pacing and consider changing mode to A-V pacing (heart block common after AVR) and /or increasing rate to 90 bpm.
• Correct post-op coagulopathy and replace blood losses to maintain Hb > 80 G/L. Surgical review if significant blood loss via drains.
• Evaluation of any other cause of low output state e.g. tension pneumothorax, dynamic hyperinflation.
• Close monitoring of renal function and early institution of renal replacement therapy if oligo-anuric or rising creatinine.
• Consideration of inhaled nitric oxide to reduce pulmonary hypertension and RV afterload.

Discussion

This patient they have given you is slightly unwell. I have reformulated the answer into a systematic approach to this problem. The answer below is question-specific (as they generally should be) - a generic approach to the haemodynamically unstable cardiac surgical patient is discussed elsewhere.

• Issues
  • Cardiogenic shock
  • Hypovolemia
  • Pulmonary hypertension
  • Hypothermia

• Assessment
  • Examination, including dynamic manoeuvres to assess for fluid responsiveness
  • ECG to exclude STEMI
  • CXR to exclude pneumothorax
  • Arterial blood gas
  • Mixed venous blood gas
  • Formal TTE to examine valve function and sclude tamponade

• Management
  • Re-warm patient
  • Sedate and paralyse patient to decrease whole-body oxygen demand
  • Maintain Hb ~ 80 and SpO2 ~ 100% to maintain satisfactory tissue oxygen delivery
  • Maintain heart rate and rhythm control with pacing and antiarrhymic drugs (eg. amiodarone); consider increasing rate to 90
  • Optimise RV preload: give fluid bolus 20-40ml/kg
  • Increase RV + LV contractility with milrinone or levosimendan
  • Decrease RV and LV afterload with milrinone or levosimendan (pulmonary and systemic vasodilation)
  • Decrease mycoardial workload with IABP especially if there is evidence of ischaemia with inotorope use
  • Maintain satisfactory diastolic pressure with noradrenaline

Frederick A. Hensley, Jr., M.D., Donald E. Martin, M.D.,  Glenn P. Gravlee, M.D. A Practical Approach to Cardiac Anaesthesia, 3rd ed. Sibylle A. Ruesch and Jerrold H. Levy. CHAPTER 9. The Postcardiopulmonary Bypass Period: A Systems Approach. 2003 by LIPPINCOTT WILLIAMS & WILKINS

André, Arthur C. St, and Anthony DelRossi. "Hemodynamic management of patients in the first 24 hours after cardiac surgery." Critical care medicine 33.9 (2005): 2082-2093.

Eagle, Kim A., et al. "ACC/AHA 2004 guideline update for coronary artery bypass graft surgery: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1999 Guidelines for Coronary Artery Bypass Graft Surgery)." Circulation 110.14 (2004): e340.

Goepfert, Matthias SG, et al. "Goal-directed fluid management reduces vasopressor and catecholamine use in cardiac surgery patients." Intensive care medicine 33.1 (2007): 96-103.