Post-operative care of Cardiac Surgery patients Flashcards
What are the minimum MVO2, MAP, SVR and CI goals post-operatively?
MVO2 of about 60%, MAP >65mmHg, SVR 1100 dyns/cm2 and a CI > 2L/min/m2
What is the target hematocrit and O2 sat post-operatively?
Hematocrit >21% and O2 sat over 90%
What are the three goals in management of SAM?
Fill them up (fluids), slow them down (beta blockers), increase afterload (vasoconstrictors)
What percentage of 5% albumin is retained intravascularly at 1 hour?
80%
What is a normal PVR?
50 to 250 dyns/cm2
How do you calculate Fick’s Cardiac Output?
Estimated O2 consumption / A-V O2 difference
What is the most common fluid status after cardiac surgery?
Fluid overload
What is the rule for surgical bleeding takeback to the OR?
> 500cc in 1 hr
400cc for 2 hours
300cc for 3 hours
200cc for 4 hours
What is the last line medication for refractory hypotension?
Methylene blue
What common medications are used in hypertension?
Nitroglycerin and sodium nitroprusside, both cause reflex tachycardia, hydralazine, labetalol, esmolol
What factors cause NSVT post-op?
peri-op ischemia/reperfusion injury, electrolyte abnormalities (hypokalemia and hypomagnesemia) or an increase in exogenous or endogenous sympathetic stimulation.
What % of patients with new onset A-fib post-op are in sinus rhythm at 6 weeks?
90%
When to suspect post-operative ischemia and infarction?
ST changes, new bundle branch block, complete heart block, ventricular arrhythmias or enzyme elevation
Which artery do air embolism’s most likely travel down? How long do coronary air embolism’s usually last up until?
RCA. A few hours.
When will pericardial ST segment changes start to appear?
12 hours + post-op
What is the treatment of LVOT obstruction and/or SAM?
Fill the heart (Volume), slow the heart (beta-blockers), increase afterload
What strategies for RV failure and pHTN?
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
What are the post-operative hemodynamic issues with AS?
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.
What are the post-operative hemodynamic issues with AI?
AI can cause a weak dilated LV. This can lead to low cardiac output post-operatively, which requires optimization of afterload, volume and inotropy.
What are the post-operative hemodynamic issues with MR?
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.
What are the post-operative hemodynamic issues with MS?
Patients with MS typically have preserved LV function. Post-op management typically involves optimizing RV function.
What is the incidence of cardiac arrest following cardiac surgery? What are the common causes?
0.7-2.9% Cardiac tamponade, hemorrhage causing hypovolemia, tension pneumothorax, myocardial ischemia, acute hypoxia, pacing failure
What is the management of HIT positive patients needing cardiac surgery?
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.
What is Beck’s triad?
Hypotension, muffled heart sounds, jugular venous distension
What is Kussmaul’s sign?
A paradoxical rise in the JVP with inspiration, can be a sign of constrictive pericarditis, restrictive cardiomyopathy, PE, cardiac tumours, right heart failure
What is pulsus paradoxus?
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.
What percentage of post-op patients require reintubation? How about those with COPD or previous stroke?
5%, this risk increases to 14% in COPD patients and 10% in patients with previous stroke
When should tracheostomy be considered in intubated patients post-operatively?
after 14 days
What are the components of the CHADS score for a-fib?
CHF history, Hypertension, Age >75, Diabetes, Stroke or TIA previously
Score 0-1 = ASA or nothing, 2+ = anticoagulation recommended
What are the effects of CPB on renal function post-operatively? What are the management options for renal dysfunction intra-op and post-op?
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.
What are the normal levels of electrolytes? K, Ca, PO4, Mg
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
What causes hyperkalemia post-operatively?
Cardioplegia, decreased urine output, decreased insulin levels and RBC hemolysis contribute to hyperkalemia
What is the blood sugar target post-operatively to reduce the incidence of SWI?
<180 mg/dL
When do you suspect adrenal insufficiency post-operatively?
When there is unexplained prolonged vasodilatory shock
What is the incidence of stroke post-operatively? What are risk factors?
1-4% and higher in carotid stenosis >50%, redo surgery, valve surgery, prior stroke, age, calcified aorta, duration of CPB
What is the management for ischemic stroke post-op?
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.
What is the prevalence of delirium post-cardiac surgery? What are the risk factors for delirium?
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
What are the potential causes of peripheral nerve injury after cardiac surgery?
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
What are the potential gastointestinal complications of cardiac surgery?
Mesenteric ischemia, GI bleeding, pancreatitis, acute acalculous cholecystitis, dysphagia (from intubation/TEE), ileus, Ogilvie’s syndrome
What are risk factors for mesenteric ischemia and what are the mortality rates by time after occurrence of ischemia?
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.
What is the incidence of post-operative bacteremia in febrile post-CABG patients?
3.2%, fever is a poor predictive of post-operative bacteremia
What is the incidence of mediastinitis after cardiac surgery?
1-2%
What are risk factors for SWI?
Diabetes, obesity, females, large breasts, bilateral IMA harvesting, low serum albumin, CKD, blood transfusions, COPD, hyperglycemia, prolonged CPB, blood transfusions, re-operations
What are the preventative measures for SWI?
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
What are the therapies for SWI?
Minor - intravenous antibiotics, wound care
Deeper infections - 6 weeks of IV antibiotics, surgical exploration and debridement, VAC therapy
Chances of death based on number of inotropes patient is on
3 or more high dose - 75% 2 high dose - 30% 1 high dose - 18% 1 moderate dose - 8% 1 low dose - 5% none - 2%
