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Principles II > Perioperative Managment and Complications, pt 2 > Flashcards

Perioperative Managment and Complications, pt 2 Flashcards

1
Q

describe the important factors in myocardial ischemia

A

-management of oxygen supply and demand

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2
Q

describe myocardial oxygen supply and demand imbalance

A
  • increase in myocardial oxygen demand is of greater significance than a decrease in myocardial O2 supply
  • simultaneous tachycardia and hypotension present greatest risk to pts. with a h/o IHD as it causes increased demand and decreased supply
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3
Q

what populations are at risk for MI?

A
  • MI within the past 6 months
  • CHF
  • previous h/o perioperative myocardial ischemia
  • all cardiac pts. (40% ischemia postop; 60% intraop)
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4
Q

what are major perioperative CV risk factors?

A
  • unstable coronary syndromes: acute/recent MI, unstable angina
  • decompensated heart failure
  • significant dysrhythmias: high-grade AV block, symptomatic ventricular dysrhythmias in presence of heart disease; supraventricular dysrhythmias w/ uncontrolled ventricular rate
  • severe valve disease
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5
Q

what are intermediate perioperative CV risk factors?

A
  • mild angina pectoris
  • previous MI by h/o Q waves on ECG
  • compensated or previous heart failure
  • DM (esp. insulin dependent)
  • renal insufficiency
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6
Q

what are minor perioperative CV risk factors?

A
  • advanced aged (> 70)
  • abnormal ECG: LVH, LBBB, ST-T abnormalities
  • rhythm other than sinus
  • low functional capacity
  • h/o stroke
  • uncontrolled systemic HTN
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7
Q

what contributes to myocardial ischemia?

A
  • increased myocardial oxygen demand

- decreased myocardial oxygen supply

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8
Q

what causes an increased myocardial O2 demand?

A
  • increased HR (tachycardia)
  • increased contractility
  • increased LVEDV
  • increased wall tension (afterload)
  • SNS stimulation
  • HTN
  • increased preload
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9
Q

what causes a decrease in myocardial O2 supply?

A
  • decreased coronary blood flow (vasoconstriction, thrombosis, decreased diastolic time, decreased aortic diastolic pressure, increased ventricular end-diastolic pressure)
  • decreased blood oxygen content: decrease Hct, anemia, decreased O2 sat
  • tachycardia
  • diastolic hypotension
  • hypocapnia (coronary artery vasoconstriction)
  • coronary artery spasm
  • arterial hypoxemia
  • shift of oxyhgb curve to the left
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10
Q

describe TEE use in detecting ischemia

A
  • abnormal regional wall motion via TEE is most reliable and most accepted standard for detection of intraoperative myocardial ischemia
  • abnormal regional wall motion occurs prior to ECG changes
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11
Q

describe PA catheters use in detecting ischemia

A
  • unreliable
  • acute increase in PAWP indicative of decreased LV compliance and performance
  • V waves in PAWP tracing may indicate ischemia
  • limited use b/c PAWP are only taken intermittently
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12
Q

describe EKG ischemia detection

A
  • most commonly utilized modality for detection of ischemia
  • most perioperative myocardial ischemia and infarctions are subendocardial
  • ST depression > 1mm or T wave inversion = subendocardial ischemia
  • ST elevation indicates transmural ischemia
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13
Q

what leads are best for ischemia detection?

A
  • V5 is most sensitive lead for ischemia (detects 75%)

- combining V4 and V5 results in 85% detection

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14
Q

what is important with leads for early detection of myocardial ischemia?

A
  • proper 5 lead ECG placement

- three leads important to improve detection (Lead II, V4, V5)

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15
Q

what area of the heart does Lead II detect ischemia?

A

RCA ischemia: inferior wall supplied 90% of time by RCA

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16
Q

what are of the heart does Leads V4 and V5 detect ischemia?

A

LV ischemia: bulk of left ventricle is supplied by LAD

17
Q

in what ways can myocardial ischemia be prevented?

A
  • minimize hypotension and HTN (maintain BP within 20% of baseline)
  • continue beta blockers therapy
  • avoid hyperventilation (hypocarbia may lead to coronary vasoconstriction)
  • minimize SNS stimulation (pain, hypercarbia, hypovolemia)
  • maintain normal blood oxygen content w/ CAD pts. (monitor excessive blood loss causing dec. hgb)
  • early extubation if criteria met
  • avoid intraoperative hypothermia
  • utilize muscle relaxants that don’t effect HR (no Pavulon)
  • reversal of NMB w/ anti-muscarinic w/ less chronotropic effect (use glycopyrrolate over atropine)
  • short duration direct laryngoscopy (less than 15 sec)
18
Q

what should be considered with chronic HTN pts.

A

-usually volume depleted d/t meds and their autoregulation curve is shifted to the right (used to a higher BP)

19
Q

why is early extubation better with pts. at risk for cardiac ischemia?

A

deeper extubation to prevent increase in HR and BP on emergence which can lead to increased ischemia

20
Q

why should intraop hypothermia be avoided?

A
  • postop shivering can increase oxygen consumption > 600%

- maintaining normothermia has been shown to reduce perioperative ischemia and subsequent cardiac mortality

21
Q

what NMB are good when you do not want an effect on HR?

A
  • vecuronium
  • rocuronium
  • cisatracurium
22
Q

what can be utilized to blunt the SNS response and increased HR associated with intubation?

A
  • LTA: lidocaine topical anesthesia
  • IV lidocaine
  • fentanyl
  • esmolol
23
Q

what are the effects of ketamine that should be avoided?

A
  • increased HR
  • increased BP
  • increased myocardial O2 requirements
24
Q

how can myocardial O2 supply and demand be optimized?

A
  • volatile agents
  • decrease myocardial oxygen requirements
  • precondition myocardium to tolerate ischemic events in presence of decreased SBP and CPP (cardioprotectant)
  • decreased coronary vascular resistance w/ iso
  • coronary steal (no evidence w/ iso): dilates only normal vessels, stealing blood flow from stenotic vessels
  • avoid tachycardia HR > 80 (use esmolol)
25
Q

describe sympathomimetic use for ischemia

A
  • treat hypotension: restores coronary perfusion pressure (CPP)
  • inotropic support when hemodynamically instable (ischemia reduces CO and causes hypotension)
  • beta adrenergic agonist
  • beneficial: decrease LVEDV and increase aortic diastolic pressure
  • harmful: increase HR and contractility, decreased diastolic time
26
Q

describe alpha agonist use for ischemia

A

alpha adrenergic agonists…

  • increased myocardial oxygen supply by increasing aortic diastolic pressure
  • detrimental effects: increased myocardial O2 demand (arterial pressure increase associated with 60% increase in myocardial O2 consumption); coronary artery vasoconstriction
  • alpha 2 agonists can decrease SNS outflow and decrease HR and BP (dexmetatomidine)
27
Q

describe nitrate use for ischemia

A
  • nitroglycerin (NTG): utilized when ischemia by increased BP; coronary vasodilation (increases supply); decreases preload improving subendocardial blood flow
  • nipride: much like NTG but with afterload reduction; controversial use in myocardial ischemia (possible coronary steal)
28
Q

describe beta blocker use for ischemia

A
  • mixed research regarding reduction in post of cardiac mortality
  • decrease myocardial demand and increase supply
  • decrease HR and contractility but may cause cardiac depression
29
Q

describe calcium channel blocker use for ischemia

A
  • decrease myocardial O2 demand and increase supply

- shown to reduce coronary artery vasospasm

30
Q

describe phosphodiesterase inhibitor use for ischemia

A

-systemic and pulmonary vasodilation w/o increase in HR (usually get a rebound increase in HR)

31
Q

define oliguria

A

urine output less than 0.5 ml/kg/hr

32
Q

what are causes of oliguria?

A
  • prerenal: decreased CO, renal perfusion, fld. volume
  • intrarenal: acute tubular necrosis (ATN), glomerulonephritis, toxins (all leads to improper functioning nephrons)
  • postrenal: obstruction, stones, prostate, neurogenic bladder, catheter obstruction
33
Q

describe management for oliguria

A
  • rule out mechanical obstruction such as block F/C
  • restore perfusion: correct hypotension, increase CO, possible low dose DA infusion
  • correct fluid volume deficit: crystalloids and colloids
  • intraop diuretics: Lasix 2-20 mg IV, mannitol
34
Q

describe cause of pulmonary aspiration

A
  • depressed/absent airway reflexes cant protect the trachea
  • acidic aspirate can damage alveoli in 12-18 seconds
  • pH 0.4 ml/kg can cause: alveolar hemorrhage, collapse, edema, increased airway resistance, hypoxia, large particles can cause obstruction, inflammatory response
35
Q

what populations are at risk for pulmonary aspiration?

A
  • extreme age (decreased airway reflexes)
  • emergency or trauma (inadequate NPO time)
  • hiatal hernia, GERD (check if symptomatic)
  • morbid obesity
  • full stomach or decreased NPO time
  • pregnancy
  • DM (slowed gastric emptying)
  • neuromuscular diseases
  • GI tract diseases
  • altered mental status (decreased airway reflexes)
  • small bowel obstruction
  • increased pain
  • h/o N/V
36
Q

how can pulmonary aspiration be recognized?

A
  • 90% have symptoms within 1 hour
  • awake: cough, cyanosis, wheezing, tachypnea, rales
  • anesthetized: laryngospasm, bronchospasm, wheezing, increased PIPs, decreased BP, VR, and O2 sat
  • CXR may detect pulmonary infiltrates (delayed 6-24 hrs)
  • CXR only definitive diagnosis
37
Q

how should pulmonary aspiration be managed?

A
  • IV PPIs, H2 antagonists, prokinetics
  • po antacids, antiemetics
  • turn head to side to prevent aspirate from falling into trachea
  • RSI for pts. at risk for aspiration
  • immediate suction and 100% FiO2
  • take control of airway w/ severe cases: tracheal intubation
  • administer PEEP and adequate Vt
  • antibiotics, steroids, bronchodilators
  • bronchoscopy may be indicated for removal of large particles obstructing airway

Principles II (18 decks)

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