Cardiac I Flashcards Preview

AP III Test 1 > Cardiac I > Flashcards

Flashcards in Cardiac I Deck (39)
Loading flashcards...
1

Preop eval of cardiac patient

  • Cardiac:
    • Severity of disease/hemodynamic status
    • Degree of impairment of contractility
    • Development of compensatory mechanisms
    • Exercise tolerance
    • Hx of CHF, or MI-ST segment changes
    • Angina
    • Dysrhythmias
    • Compensatory increase in sympathetic nervous outflow, ie ­Hr, anxiety, diaphoresis
    • Hx of previous surgery
  • Pulmonary
    •   COPD
  •   Renal
  •   PVD-especially carotid disease
  •   Diabetes
  •   Obesity

2

Laboratory data for cardiac patients?

  -CBC

  -Electrolytes

  -Cardiac Enzymes

  -Serum Creatinine

  -Coagulation profile

  -Type and Cross

Must have PRBCs available

3

Lab data for MI?

  Peak A, early release of myoglobin or CK-MB isoforms after AMI

  Peak B, cardiac troponin after AMI

  Peak C, CK-MB after AMI

  Peak D, cardiac troponin after unstable angina.

  • The most recently described and preferred biomarker for myocardial damage is cardiac troponin. (gold standard)
  • Absolute myocardial tissue specificity
  • High sensitivity
  • Thereby reflecting even microscopic zones of myocardial necrosis.
    • ​will see peak even after only angina

Apex-

  • CKMB
    • initial elevation 3-12 hours
    • peak 24 hours
    • return to baseline 2-3 days
  • Troponin I
    • Initial 3-12 hours
    • Peak 24 hours
    • return 5-10 days
  • Troponin T
    • initial 3-12 hours
    • peak 12-48 hours
    • returnto baseline 5-14 days

 

4

Other cardiac testing you may want to evaluate before cardiac surgery?

  •   Catheterization data
    • LVEDP
    • EF
    • CI
  •   Echocardiography data
    • EF
    • Wall motion abnormalities
  •   Chest X-Ray
    • Cardiomegaly
    • Pulmonary vascular congestion, edema, effusion
  •   Angiography
  •   EKG
    • Ischemia/infarct

5

What cardiac drugs should be continued DOS?

   The following should be continued until the operative day:

  •   *Antiarrhythmics
    • •Amiodarone-special concern (1/2life 30d)
  •   *Ca+ Channel blockers
  •   *Β blockers
  •   *Nitrates

6

Premedication/anxiolysis prior to cardiac surgery?

  Explain operative course and postop to the patient

  Premedication

  Narcotics

  Anxiolytics

  Antibiotics

   

 

n

7

Monitors used for cardiac surgery?

  •   Pulse Ox
  •   TEE
  •   EKG
    • Leads V5 & II
  •   Temperature
  •   ABP
    • Usually radial, sometimes femoral
  •   CVP
    • Mandatory for infusion of drugs
  •   PA Catheter
    • Pts with severe LV dysfunction
    • Pts with profound pulmonary HTN

8

TEE use in cardiac?

  • Intermittent pulses with a frequency of 2.5-7.5 MHz.
  • Can determine:
    • Preload
    • Hypotension
    • CO
    • LV Filling Pressures
    • LV contractility
    • LV afterload
    • Ischemia, emboli, valvular pathology
    • Assessment of surgical repairs

9

Cardiac OR setup?

  •   Usual airway equipment/machine check
  •   Pacemaker
  •   Drips
    • Vary b/w institutions
    • Most commonly:
      • NTG/NTP
      • Epinephrine/Norepinephrine
      • Phenylephrine/Ephedrine
      • Dopamine/Dobutamine as needed
      • Antiarrhythmics (esmolol, lidocaine, mag, amiodarone)
  •   Heparin-and coag. monitoring capability
  •   Emergency drugs
  •   PRBC available in OR

10

Anesthetic agents for cardiac?

  •   Opiods
    • Fentanyl 50-100mg/Kg
    • Sufentanil 10-20mg/Kg
  •   Inhalation Agents
    • Forane
    •   N2O
  •   Induction Drugs
    • Etomidate
    • Benzodiazepines
    •   NM Blockers
      • Pavulon
      • ED95 dose Vecuronium

11

Preinduction period for cardiac surgery?

  •   Evaluate need/effectiveness of premed
  •   Preoxygenation
  •   Monitor placement
  •   Large-bore Ivs
  •   Invasive monitors
    • •In some institutions preinduction vs post
    • •In severe disease --> preinduction

12

Goals of induction and intubation of cardiac patient?

  •   Smooth induction
    • Avoid cough, larygospasm, truncal rigidity
    • Avoid hypo- or hyper- tension
  •   Deep plane of anesthesia
  •   Short duration laryngoscopy
  •   Tape tube, eyes
  •   Pad pressure points
  •   Check monitors in this busy period

13

Considerations for pre-incision period of cardiac surgery?

  •   Hypotension
    •   Lack of stimulation
    •   Systemic pressure support
    •   Risks involved with vasoconstrictors
    •   Recall rare at this point, unless   severe hypotension occurs in the   face of purely opiod technique

14

Considerations for incision to bypass period

  • Intense surgical stimuli → STERNOTOMY
    • Hypertension
      • Deepen the anesthetic
      • Narcotics (PAINFUL)
      • Vasoactive agents
        • NTG/NTP
    • Sternotomy
      • Drop lungs
        • Disconnect circuit from ETT/vent (lungs will deflate)
  • Heart Handling by surgeon
    • Communication is of the utmost importance
      • Arrythmias/HoTN common
    • Bleeding can be significant
    • Identifying and localizing ischemia
    • Arterial and Saphenous veins are harvested 

15

Considerations around the administration of heparin prior to initiation of bypass?

MOA of heparin? Dose? Peak?

Anti-coagulate the pt with Heparin

  • MOA:
    • Binds to antithrombin 3 (AT3) and potentiates its natural anticoagulant properties
  • Dose: 200-300units/kg
  • Peak: 2 mins
    • 3 min → Check activated clotting time (ACT)
      • Normal ACT = < 130 seconds (70-110 average)
      • Heparinized ACT = 350-500 seconds acceptable (> 400-450)
        • *Safe to go on bypass
    • Administered through CVP or directly into RA

Considerations:

  • SVR & BP can ↓ by 10-20%
    • D/t blood viscosity reduction
      • While blousing → monitor for HoTN and tx
  • ACT checked after 3-5mins
    • (Should be > 300-400 sec)

16

What are some special cirucmstance that would interfere with heparinization?

Special circumstances that interfere with heparinization- Examples: ACT may not increase

  • Antithrombin III deficiency
  • Long term heparin therapy
  • Excessive hemodilution
    • min fluids → interferes w/ heparinization
  • Heparin-induced thrombocytopenia
    • Antibody mediated response
  • NTG long term
    • Heparin resistance?
  • Alternatives to increase ACT:
    • FFP
    • Thrombate III
      • Scenario: Appropriate heparin dose admin and ACT doesn’t increase appropriately → admin thombate III or FFP, then wait, then give additional dose of heparin and check ACT
      • NEVER go on pump unless appropriate ACT

17

What cannulations are performed to initiate CPB

Bypass:

  • Aorta (Arterial side) → brings O2 rich blood to systemic circulation
  • RA (venous side) → brings O2 blood back from systemic circulation

Cannulation

  • 1st→ Aortic cannulation (Arterial side): must DROP BP!! (esp if calcified)
    • Can cause aortic rupture!
    • Ex: SBP 90-100
      • Cannulated 1st bc perfusionist can rapidly admin fluids through arterial line in case BP drops
  • 2ndRA cannula (venous side):
    • BP might drop &/or arrhythmias can occur while placing
  • 3rdCannulation of the coronary sinus for retrograde cardioplegia to arrest heart
    • Anatomy: Coronary sinus is where coronary vessels empty into to get reperfused
    • Retrograde cardioplegia- providing poor RV myocardial perfusion, stopping the heart
      • Cannulation → similar effects as RA (severe ↓ BP)
        • Tx: Fluids by perfusionists, vasoactive agents
  • *Medicate pt w/ extra Midaz and Fentanyl right before going on bypass
    • Priming fluid of bypass machine increases Vd → diluting anesthetic agents
      • INCREASE RECALL RISK

18

What are some considerations when initiating bypass?

  • Pt placed on bypass, adequate perfusion flow and pressure, pt cooling starts (arterial side)
    1. Cease ventilation (dc circuit)
    2. IV fluids shut off
    3. Volatile anesthetic turned off
    4. Make sure perfusionist has instituted anesthetic
    5. Pull back Swan catheter – tends to float in further
    6. Give NMB to prevent shivering, along with fentanyl/versed    

19

What do the clamps create during CPB?

Clamp separates two sections.

  1. Aortic cannulation allows blood to go to systemic circulation
  2.  Cardioplegia solution- contains high K+ & cold
  • Clamp prevents cold/K+ soln going to arterial side since right next to each other

20

Purpose of cardioplegia solution? Contents?

Heart stops

  • Cold- 4°C
    • Reduces metabolism of heart (protection)
    • V-fib occurs at 25-30°C
  • Contains K+ (high dose)
    • Depolarization of heart

21

What happens with the intiation of bypas?

Significant drop in BP

  • Causes:
    • Hemodilution → ↓ viscosity
      • From priming fluids (perfusionist)
    • Rapid dilution of catecholamines
    • Rapid cooling
      • for brain, heart, liver
    • Aortic cross-clamp-to prevent systemic extravasation of antegrade cardioplegic solution

22

What is the pump primed with?

Primed with 2000 cc of crystalloids (rich in…)

  • Heparin
  • Mannitol
  • NaHCO3-
  • Albumin
  • Corticosteroids
  • Antifibrinolytics (aminocaproic acid/Amicar) to protect blood vessels

23

What hemodynamic changes occur with the initiation of bypass?

  • Once the heart has been arrested (heart goes into fibrillation d/t cardioplegia soln)
    • Revascularization/valve replacement is instituted
  • Flow is no longer pulsatile (no BP, just flow from bypass machine)
    • only have MAP
  • Flow rate (BP is one number, reflective of flow)
    • Flow rate usually 50-60 ml/kg (bypass lecture 2.4L/min/m2
    • BP maintained at 50-60 mmHg
      • Considerations;
        • Lower BP (flow)
          • beneficial for hematology
            • (saving blood cells and preventing blood cell breakdown)
          • Possibly issues perfusing brain/kidneys during non-pulsatile flow
        • Higher BP (flow)
          • beneficial for stroke pts/carotid dz (need extra cerebral perfusion) or kidneys
    • CVP is 0mmHg
      • if higher → may have kink

24

What are some hematological effects of CPB?

  • Effects both extrinsic and intrinsic coagulation pathways
    • Factor XII conversion to Factor XIIa on various surfaces of CPB circuit
  • Directly impairs platelet function
    • Rapid adhesion and conformational alteration of plasma proteins
      • i.e., von Willebrand factor (vWF) and fibrinogen (Fib)
    • Platelet aggregation, and detachment due to shear forces
  • Monocyte and endothelial activation with TF and tissue/vessel injury
  • Tissue (vessel) injury → Extrinsic pathway → release of TF → causes both initiation of intrinsic pathway and common pathway
    • Intrinsic pathway (via IX)
    • Common pathway (via X)
  • Understand adhesion and damage to cell from pt being on bypass

25

How do we provide prophylaxis for bleeding?

  • Prophylactic use of antifibrinolytic drugs before CPB
    • reduces bleeding and transfusion
  • Drugs include:
    • Synthetic lysine analogues
      • ε-aminocaproic acid (EACA) – Amicar
      • Transexamic acid (TXA
    • Serine protease inhibitor = Aprotinin
      • Taken off the market dt significant tissue organ damage
      • Being researched again in Canada
        • Amicar bolus and infusion PRE pump to reduce bleeding and need for transfusion

26

What are some CNS risks while on pump? People at risk?

Risks:

  • Embolization
  • Hypoperfusion
    • Bypass machine at low pressures/flow
  • Inflammation from pulsatile to flow BP

Influencing Factors/predisposition: (people at risk)

  • Aortic atheromatous plaque (atherosclerosis in aorta)
  • Cerebrovascular disease
  • Altered cerebral autoregulation (elderly)
  • HoTN
  • Intracardiac debris
    • Plagues
  • Air
  • Cerebral venous obstruction on bypass
  • Cardiopulmonary bypass circuit surface and damaged blood cells
  • Reinfusion of unprocessed shed blood (cell saver)
  • Cerebral hyperthermia (rewarmed too quickly)
  • Hypoxia (serial ABGs)

27

How can we provide cerebral protection while on bypass?

  • Emboli are biggest culprits
  • PROTECTION:
    • Hypothermia → decrease CMRO2
    • Barbiturate therapy?
      • Used to give TPL/Methohexital decrease BF to brain
    • CCBs
      • increase perfusion to brain
    • Blood gas management
      • Draw from aline 
    • Adequate BP (run machine at good flows)
      • blood cell damage vs. CPP? Individualized
        • (look at risk list above and those prob need higher pressures)
    • Cerebral oximetry

28

Fluid managmeent considerations while on bypass?

  • Minimize crystalloids – hemodilutes pt
    • 1-1.5 L acceptable for crystalloids
  • Replace blood w/:
    • Colloids
    • Cell saver
    • PRBCs

29

Rewarming considerations?

  • Begins at different times: (Surgeon can ask for rewarming of pt)
    • 1. Begins prior to aortic cross-clamp removal (or)
    • 2. Begins with the last distal anastomosis in angioplasty procedure (or)
    • 3. Begins when all the valve sutures are in and knots are being tied down
  • Considerations:
    • 1° C per 3-5 mins (slowly)
      • Usually takes ~ 30-40 mins
    • Turn on heating blanket
    • Temp gradient bt arterial and venous blood should remain < 5-10°C
      • if gradient higher →  higher risk of air emboli
    • Amnestic and NMB agents should be given (recall)
    • SVR drops d/t vasodilation
      • Monitor pressure*
      • Phenylephrine can be given to perfusionist since they have more direct access

30

What must occur prior to the discontinuation of bypass?

  • Pt must be warmed
  • Surgical field should be dry (no bleeding)
  • Lab values checked
    • Admin Ca & Mag to decrease effects of cardioplegic soln (high K)
  • Pulmonary compliance evaluated
    • Begin ventilating lungs slowly (attach circuit)
      • Manually bag pt to see compliance → watch lungs
      • Then switch to ventilator
  • Regulate cardiac rhythm by pacing, defibrillating or pharmacologically
    • Ca, Mg
  • Transfuse pt with pump volume (~50-100cc by perfusionist)
    • Look at:
      • PA Diastolic pressure
      • TEE*
      • Actual heart over drapes (floppy?)
      • VS