Question 6

College Answer

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

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 question is identical to Question 28 from the second paper of 2015, and nearly identical to Question 1 from the second paper of 2013 except this patient is not on adrenaline infusion 4μg/min. The discussion section from those questions is therefore reproduced below.

• 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 myocardial workload with IABP especially if there is evidence of ischaemia with inotorope use
  • Maintain satisfactory diastolic pressure with noradrenaline

A generic approach to the haemodynamically unstable cardiac surgical patient is discussed elsewhere.

Weirdly, both this question and  Question 28 from the second paper of 2015 had approximately the same pass rate (95% vs. 94%). However, in 2015 examiners felt the need to make disparaging comments about the candidates (eg. " answers for the management plan were very superficial with generic statements "). Clearly, we have learned from our mistakes this time around, and have made a series of profound and specific statements.

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