A 76-year-old female is admitted to the ICU following elective aortic and mitral valve replacement. Trans-oesophageal echo assessment at the end of surgery showed an ejection fraction of 20%. Her preoperative creatinine was 340 μmol/L. Total bypass time was 240 minutes. On arrival in Intensive Care Unit the patient has the following indices:

  • Temperature    35oC
  • Atrial pacing (AAI)    80/min
  • Systemic blood pressure    85/55 mmHg
  • Pulmonary artery pressure    60/30 mmHg
  • Cardiac index     1.5 L/min/m2
  • Systemic vascular resistance indexed (SVRI)    1700 dyn.sec.cm-5
  • Pulmonary artery wedge pressure    10 mmHg
  • Central venous pressure    8 mmHg

a)    List the specific clinical and haemodynamic issues for this patient on admission to ICU. (30% marks)

b)    Outline your management of these issues.    (70% marks)

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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.

Additional Examiners’ Comments:

Some answers for the management plan were very superficial with generic statements with inadequate detail e.g. “consider changing pacemaker settings”, ”order bedside echo” and lacking a consultant level approach.

Discussion

This question is nearly identical to Question 1 from the second paper of 2013, except this patient is not on adrenaline infusion 4μg/min. Also, for some reason, the college decided to change the systemic vascular resistance variable. In the 2013 version, the patient is said to have an SVR value of 1700 dyn.sec.cm-5, which is well above the reference range (800-1200). This is surely a case of overconstricted raised afterload, and the college comment in 2013 makes sense ("Increased afterload / vascular impedance (SVR)"). For some reason, in 2015 the college decided to make that parameter to SVRI, but without changing the variable. Because SVRI has a reference range of 1970-2390 dynes-sec/cm5/m2 , this parameter now suggests the patient is slightly vasodilated and requires more pressors. This would be fine if the examiners had not cut-and-pasted thir comments to Question 1 from the second paper of 2013 into this model answer. Thus, "Increased afterload / vascular impedance (SVR)" no longer makes any sense.

In the fine tradition of mindlessly cut-and-pasting, the discussion section from Question 1 from the second paper of 2013 is reproduced below wth minimal modification.

  • 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

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

References

References

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.