Post-operative care of Cardiac Surgery patients

Question 1

What are the minimum MVO2, MAP, SVR and CI goals post-operatively?

Answer 1

MVO2 of about 60%, MAP >65mmHg, SVR 1100 dyns/cm2 and a CI > 2L/min/m2

Question 2

What is the target hematocrit and O2 sat post-operatively?

Answer 2

Hematocrit >21% and O2 sat over 90%

Question 3

What are the three goals in management of SAM?

Answer 3

Fill them up (fluids), slow them down (beta blockers), increase afterload (vasoconstrictors)

Question 4

What percentage of 5% albumin is retained intravascularly at 1 hour?

Answer 4

80%

Question 5

What is a normal PVR?

Answer 5

50 to 250 dyns/cm2

Question 6

How do you calculate Fick’s Cardiac Output?

Answer 6

Estimated O2 consumption / A-V O2 difference

Question 7

What is the most common fluid status after cardiac surgery?

Answer 7

Fluid overload

Question 8

What is the rule for surgical bleeding takeback to the OR?

Answer 8

> 500cc in 1 hr
400cc for 2 hours
300cc for 3 hours
200cc for 4 hours

Question 9

What is the last line medication for refractory hypotension?

Answer 9

Methylene blue

Question 10

What common medications are used in hypertension?

Answer 10

Nitroglycerin and sodium nitroprusside, both cause reflex tachycardia, hydralazine, labetalol, esmolol

Question 11

What factors cause NSVT post-op?

Answer 11

peri-op ischemia/reperfusion injury, electrolyte abnormalities (hypokalemia and hypomagnesemia) or an increase in exogenous or endogenous sympathetic stimulation.

Question 12

What % of patients with new onset A-fib post-op are in sinus rhythm at 6 weeks?

Answer 12

90%

Question 13

When to suspect post-operative ischemia and infarction?

Answer 13

ST changes, new bundle branch block, complete heart block, ventricular arrhythmias or enzyme elevation

Question 14

Which artery do air embolism’s most likely travel down? How long do coronary air embolism’s usually last up until?

Answer 14

RCA. A few hours.

Question 15

When will pericardial ST segment changes start to appear?

Answer 15

12 hours + post-op

Question 16

What is the treatment of LVOT obstruction and/or SAM?

Answer 16

Fill the heart (Volume), slow the heart (beta-blockers), increase afterload

Question 17

What strategies for RV failure and pHTN?

Answer 17

Increase PEEP to recruit atelectatic lung and hyperventilate to decrease the impact of pulmonary vasoconstriction. Inhaled NO and PGI2 can also reduce PVR. Dobutamine and milrinone can improve RV failure

Question 18

What are the post-operative hemodynamic issues with AS?

Answer 18

AS leads to a hypertrophied, non-compliant LV. This can lead to high CO and BP and possibly LVOT in some patients. Patients can also be pre-load dependent due to diastolic dysfunction and hypovolemia and a-fib should be treated.

Question 19

What are the post-operative hemodynamic issues with AI?

Answer 19

AI can cause a weak dilated LV. This can lead to low cardiac output post-operatively, which requires optimization of afterload, volume and inotropy.

Question 20

What are the post-operative hemodynamic issues with MR?

Answer 20

MR can mask LV dysfunction. Post-op, LV function can be poor and patients may need greater inotropic support. Occasionally, LV dysfunction can be result of injury to the LCX.

Question 21

What are the post-operative hemodynamic issues with MS?

Answer 21

Patients with MS typically have preserved LV function. Post-op management typically involves optimizing RV function.

Question 22

What is the incidence of cardiac arrest following cardiac surgery? What are the common causes?

Answer 22

0.7-2.9% Cardiac tamponade, hemorrhage causing hypovolemia, tension pneumothorax, myocardial ischemia, acute hypoxia, pacing failure

Question 23

What is the management of HIT positive patients needing cardiac surgery?

Answer 23

If surgery can be delayed, it should be delayed until the assay is negative (usually 3 months) or if surgery is more urgently required, alternative anticoagulation strategies like bivalirudin or argatroban can be considered.

Question 24

What is Beck’s triad?

Answer 24

Hypotension, muffled heart sounds, jugular venous distension

Question 25

What is Kussmaul’s sign?

Answer 25

A paradoxical rise in the JVP with inspiration, can be a sign of constrictive pericarditis, restrictive cardiomyopathy, PE, cardiac tumours, right heart failure

Question 26

What is pulsus paradoxus?

Answer 26

A drop of systolic BP of more than 10mmHg during inspiration, can be a sign of severe COPD, OSA, croup, constrictive pericarditis. It is due to a number of factors. During inspiration, right heart filling increases but left heart filling decreases, this results in reduced preload to the LA and LV, additionally, the negative intrathoracic pressure, increases the LV to thoracic transmural pressure gradient, which increases the afterload of the LV. In constrictive pericarditis, with equalization of the cardiac chamber pressures, the effect of increased RV filling pushes against the LV causing reduced LV preload and even more reduction in BP.

Question 27

What percentage of post-op patients require reintubation? How about those with COPD or previous stroke?

Answer 27

5%, this risk increases to 14% in COPD patients and 10% in patients with previous stroke

Question 28

When should tracheostomy be considered in intubated patients post-operatively?

Answer 28

after 14 days

Question 29

What are the components of the CHADS score for a-fib?

Answer 29

CHF history, Hypertension, Age >75, Diabetes, Stroke or TIA previously

Score 0-1 = ASA or nothing, 2+ = anticoagulation recommended

Question 30

What are the effects of CPB on renal function post-operatively? What are the management options for renal dysfunction intra-op and post-op?

Answer 30

CPB causes hypothermia, hemodilution, ischemia re-perfusion injury and the release of inflammatory cytokines and microparticle emboli from trauma to blood constituents. These factors can adversely affect renal function post-operatively. Operative considerations include limiting the duration of CPB and maintaining MAPs greater than 60mmHg. Beyond optimizing hemodynamics and avoiding nephrotoxic medications, there is no evidence that other treatment is renoprotective post-op.

Question 31

What are the normal levels of electrolytes? K, Ca, PO4, Mg

Answer 31

ionized Ca 1.14–1.28 mmol/L
total Ca 2.12–2.52 mmol/L (affected by serum albumin)
K 3.5–5.1 mmol/L
PO4 0.81–1.58 mmol/L
Mg 0.74–1.03 mmol/L

Question 32

What causes hyperkalemia post-operatively?

Answer 32

Cardioplegia, decreased urine output, decreased insulin levels and RBC hemolysis contribute to hyperkalemia

Question 33

What is the blood sugar target post-operatively to reduce the incidence of SWI?

Answer 33

<180 mg/dL

Question 34

When do you suspect adrenal insufficiency post-operatively?

Answer 34

When there is unexplained prolonged vasodilatory shock

Question 35

What is the incidence of stroke post-operatively? What are risk factors?

Answer 35

1-4% and higher in carotid stenosis >50%, redo surgery, valve surgery, prior stroke, age, calcified aorta, duration of CPB

Question 36

What is the management for ischemic stroke post-op?

Answer 36

Urgent CTA. Endovascular therapy is an option if performed within 6-8 hours of the event or up to 24 hours in patients with posterior circulation occlusion.

Question 37

What is the prevalence of delirium post-cardiac surgery? What are the risk factors for delirium?

Answer 37

Up to 50% of cardiac surgery patients experience delirium. Risk factors include pre-existing organic mental health disorders, prior alcohol consumption, age, intracranial cerebral artery disease, benzodiazepines, opiates, anticholinergics, phenothiazines

Question 38

What are the potential causes of peripheral nerve injury after cardiac surgery?

Answer 38

Brachial plexus injury - excessive retraction of sternotomy or injury during IMA harvest
Ulnar nerve injury - malpositioning of upper arms
Saphenous nerve injury - during vein harvest

Question 39

What are the potential gastointestinal complications of cardiac surgery?

Answer 39

Mesenteric ischemia, GI bleeding, pancreatitis, acute acalculous cholecystitis, dysphagia (from intubation/TEE), ileus, Ogilvie’s syndrome

Question 40

What are risk factors for mesenteric ischemia and what are the mortality rates by time after occurrence of ischemia?

Answer 40

Increased length of CPB, vasopressors, IABP, a-fib, PAD, HIT. Mortality is 50% with early surgical intervention (<6 hours) and 99% with delay in surgical intervention.

Question 41

What is the incidence of post-operative bacteremia in febrile post-CABG patients?

Answer 41

3.2%, fever is a poor predictive of post-operative bacteremia

Question 42

What is the incidence of mediastinitis after cardiac surgery?

Answer 42

1-2%

Question 43

What are risk factors for SWI?

Answer 43

Diabetes, obesity, females, large breasts, bilateral IMA harvesting, low serum albumin, CKD, blood transfusions, COPD, hyperglycemia, prolonged CPB, blood transfusions, re-operations

Question 44

What are the preventative measures for SWI?

Answer 44

Hibiclens wash, clipping of hair, antibiotic prophylaxis, good intra-op hemostasis without bone wax, subcuticular sutures and dermabond rather than skin staples, good glucose control

Question 45

What are the therapies for SWI?

Answer 45

Minor - intravenous antibiotics, wound care

Deeper infections - 6 weeks of IV antibiotics, surgical exploration and debridement, VAC therapy

Question 46

Chances of death based on number of inotropes patient is on

Answer 46

3 or more high dose - 75%
2 high dose - 30%
1 high dose - 18%
1 moderate dose - 8%
1 low dose - 5%
none - 2%