Flashcards in Post operative CSRU questions Deck (62):
What pulmonary function tests would prohibit cardiac surgery
No absolute number but operative mortality much higher in those with COPD.
P02 < 60 on room air
pCO2 > 60
FEV1 < 65% VC
FEV1 < 1 to 1.5 L
DLCO < 50% predicted
Vo2 max > 10 cc/kg, the best predictor but rarely measured
failure to response to broncho dilators
What is mechanism of action of Heparin induced thrombocytopenia
IgG antibody binds to complex of platelet factor 4 and heparin leading to the formation of an immune complex.
The immune complex binds to platelets via platelet Fc receptors producing intravascular platelet activation, thrombocytopenia, and the potential complications
What are 3 types of HIT
Type 1: mild drop in plt count that stays > 100 000--management is to observe. repeat the count
Type II: moderate drop in < 100 000---without thrombosis. Treatment is to stop heparin, alternative anticoagulation and monitor for thrombus
Type III: HIT with evidence of thrombosis--mortality is about 30% and rate of amputation is 20%
What are alternatives to Heparin in a pt with HIT
* direct thrombin inhibitors
1) Argatroban (cleared by liver) short half-life
2) Liprudin (cleared by renal)
3) Danaparoid (cleared renal)
List predictors of increased low cardiac output syndrome
LVEF < 20%
recent MI < 30 days
age > 70
What is definition of Low Cardiac output syndrome
SBP < 90 mmHg
CI < 2.2 L.min/m2
need for inotropes or IABP > 30 min in ICU
List 5 surgically correctable complications of acute MI
Ischemic ventricular septal defect (anterior or posterior)
Acute mitral regurgitation
ruptured papillary muscle
Left ventricular aneurysm
Ventricular freewall rupture
Cardiogenic shock from acute occlusion of one or more coronary arteries
What are complications of IABP
bleeding from puncture site
Occlusion of branch vessel
What is mechanism of IABP
Augments diastolic coronary perfusion
reduces after load
Effects on LV
decreases LV afterload during systole
decreased myocardial oxygen consumption
increased myocardial blood supply during diastole
Effects on ascending aorta
lower peak systolic pressure
peak aortic pressure is increased
end diastolic pressure is lower
What are some facts about IABP
augments CO by 10 to 25%
should inflate immediately after closure of dicrotic notch (AV closure)
deflation as late as possible (timed to onset of R wave)
Triggers off arterial wave or ECG
Balloon should occlude aorta during diastole (34 or 40 cc Balloons)
How do you diagnose a perioperative MI
The following new finding on ECG
Q wave (2 contiguous leads)
Loss of R wave progression
Presence of new ST-T changes and serum enzyme rise including one of
Trop > 10
Ck-MB ratio of > 5 %
The presence of perioperative MI must include the presence of ECG changes
New definition in the 2011 guidelines
Increased biomarker 5x upper limit with new Q wave or LBBB
Imaging documentation of loss of viability in new territory
3 causes of diaphragm paresis post-op
Phrenic nerve injury secondary to
Damage during LITA harvest (proximal end of ITA
damage during pericardial incision
damage during retraction of chest wall
0.5% if no topical cooling
32% with slush...(wow!!!)
2-6% with topical saline
Possible causes of recurrent laryngeal nerve injury
Dissection and direct injury during arch procedures
Cold solution in left pleural space
Injury during central line placement
May take 8 - 12 months to recover.
If severe respiratory compromise may need reintubation and traceostomy
medialize the vocal chord by teflon injection
What are complications from Swan
Related to presence in situ
Branch PA rupture
What is management of swan rupture
Blood from ETT, opacity of lung near PA catheter tip, bronchoscopy
ABC, secure airway, large IV, fluid, reverse coagulation aggressivlely
protect good lung
patient with bleeding side down
broch blocker or double lumen ETT or selective intubation
angiography with embolization
risk of death is 30%
What are 6 most common general surgery issues post cardiac surgery
Upper GI bleeding
hollow visucus perforation
8 most common post-op pulmonary complications
Prolonged mechanical ventilation
What are two tests ordered for HIT
Serotonin release assay
What is dosing of argatroban for HIT
What are Classification of neurological deficits post op
Type I: major focal neurological deficit, stupor and coma
Type II: deterioration in intellectual function or memory
List predictors of type I
Proximal aortic atherosclerosis (4.5)
History of prior neurological disease (3.2)
Predictors of type II
Tests for HIT
Serotonin release test: measure release of radio-labeled serotonin from normal platelets washed with platelet serum. A test of platelet degradulation
ELISA: measures the levels of IgG-AB directed towards H-PF4 directly. More sensitive in those who otherwise do not have clinical evidence of disease
List indications for NO
Cardiac transplant pts
Lung transplant pts
pulmonary hypertension post valve surgery
Right ventricular failure
Pediatric cardiac surgery
List some of the toxic byproducts of Nitric Oxide
Nitrogen dioxide (No2)
List ways to decrease PVR
*keep the PEEP low, avoid vasoconstrictors, keep warm, no acidosis!
What is Dexamedtomidine
Highly selectve alpha 2 adrenorecptor agonist and has anxiolytic, sympatholytic, and anlgesic effects without contributing to respiratory depression, oversedation, or delerium
What is rate of noscomial pneomnia
1% per day of VAP
What is risk of renal failure for cabg
2-4% of all patients
What are treatments of post operative seizer
Valproic acid (750mg)
Dilantin 15-20 mg/kg
Lorazepam 4 mg IV
What are sources/causes for elevated lactate post cardiac surgery
response to B2 adrenergic receptors
and CPB increases lactate concentration and decreases lactate clearance
What is mixed venous sat and what is normal value
MVO sat represents the difference between oxygen delivery and oxygen consumption by the tissue and hence can be used as an indirect measure of cardiac outout
Normal is 60 to 80%
What are causes of low mixed venous sat
Decreased oxygen delivery: low cardiac output, anemia, reduced oxygen saturations
Increased oxygen consumption: secondary to hypertermia, pain and shivering
What causes for high venous saturations
decreased oxygen consumption or extraction, secondary to hypothermia, sepsis or shunting
increased oxygen delivery (raised inspired oxygen concentration
a wedged pulmonary artery catheter
List factors in weaning off ventilator
PO2 > 80mmHg w/ FiO2 ≤ 0.5
pH (on CPAP) ≥ 7.35
PCO2 ≤ 45mmHg
vital capacity (VC) ≥ 15mL/kg
negative inspiratory pressure ≥ 20cm H2O
absence of bleeding, HD instability or dangerous arrhythmia
What is order of injured chambers in a cardiac trauma
RV (35%), LV (25%), RA (24%), and LA (3%) form the order of the most common to the least common injured chambers, respectively.
How does a PA cath measure cardiac output
“thermodilution is used to determine CO. A cold saline bolus is injected into the catheter to measure change in blood temperature as a function of time; this indicates the rate of blood flow. The area under the time-temperature difference curve is measured to determine the CO. A low area under the time-temperature difference curve indicates high CO.”
How does vasopressin work
stimulates V1a receptors in vascular smooth muscle, which results in vasoconstriction.
mediates fluid reabsorption by stimulating V2 receptors in the renal collecting duct system. Based on the level of stimulation, the renal collecting ducts can become either more permeable or less permeable to fluid.”
What's acute lung injury .
“the presence of bilateral infiltrates, and pulmonary capillary wedge pressure < 18 mmHg. degree of hypoxemia distinguishes ALI (PaO2/FiO2 < 300) from ARDS (PaO2/FiO2 < 200).
PaO2/FiO2 ratio is a reflection of the shunt fraction through the lung and is a barometer of gas exchange. ratio < 300 as in ALI, there is increased mortality, and in ARDS with ratios < 200, there is a predicted mortality of 40% to 50%.”
What is treatment ARDS
“Mechanical ventilation using the least FiO2 necessary (goal < 60%), low tidal volume settings (6-8 mL/kg) with peak inspiratory pressure (PIP) < 35 cmH2O, the use of PEEP between 8 and 14 cmH2O
Cardiovascular support with a goal oxygen delivery/consumption > 2:1, hemoglobin > 10 mg/dL, and inotropic support
Nutrition support with adequate nitrogen balance and preference for enteral feeding
further maneuvers include permissive hypercapnea, diuresis, prone positioning, late steroids, ECMO”
What pulsus paradox
pulsus paradoxus, an exaggerated decrease of the systolic blood pressure with inspiration.
Ordinarily, bp decreases up to 10mmHg with inspiration in a spontaneously breathing patient.
In pulsus paradoxus, this decrease in systolic blood pressure is >20 mmHg without a corresponding decrease in diastolic blood pressure (see figure).
What is post op pericardiectomy
Syndrome is characterized by malaise, fever, pleuritic chest pain, pericardial effusion and leukocytosis.
friction rub may be present on examination.
Symptoms usually appear 1-2 weeks after cardiac surgery and may last several weeks. The syndrome is usually self-limited.
Most patients respond to non-steroidal anti-inflammatory agents and in some cases steroids are required
Why is ITA better then SVG
Anatomic properties include absent or very thin vaso vasorum, a dense internal elastic lamina with no fenestrations, and a thin medial layer with few smooth muscle cells.
secretes endothelial derived relaxing factors (prostacyclin and nitric oxide) that cause vasodilatation and antagonize endogenous endothilin and calcitonin, which are vasoconstrictors.
smooth muscle cells exhibit very little proliferation in response to platelet derived growth factor, as compared to saphenous vein.
exhibits flow adaptation over time
What are post op concerns of OHT coronary disease
incidence of transplant coronary artery disease is approximately 10% per year following transplantation.
angina and chest pain rare in the denervated heart the diagnosis is usually made by surveillance coronary artery angiogram or angiographic assessment following ECG changes, deterioration in functional status or cardiac function anomalies on echocardiogram.
What are risk of nerve damage with arch surgery
Left recurrent nerve injuries occur in approximately 10% of cases and are usually due to nerve contusion or a traction injury rather than actual nerve transection.
patients will be hoarse and will have difficulty generating a forceful cough.
The risk of aspiration is substantial.
common in descending or thoracoabdominal aneurysm repair where control of the aorta is obtained proximal to the left subclavian artery.
What is advantage of percutaneous trach
By an experienced operator is equivalent to conventional open technique.
Ssimilar effectiveness of gas exchange and with similar long-term success at weaning from the ventilator.
PDT adoption is driven by considerations of convenience and cost. One study suggested an overall cost savings of approximately $30,000 per patient if percutaneous tracheostomy was globally adapted on a cardiothoracic surgery service.
Who are not good candidates for a percent trach
obese necks, thyromegaly, irradiation-induced changes, or other pathology that precludes palpation of the cricoid and tracheal rings are not good candidates for PDT.
List signs of constructive pericarditis
findings consistent with constrictive pericarditis include paradoxical rise in venous pressure with inspiration (Kussmaul's sign)
A steep or exaggerated y descentindicates rapid atrial emptying with rather abrupt cut-off of ventricular filling and rapid rise in the venous pulse trace after the initial drop during diastole. The steep y descent is typical of constrictive pericarditis whereas the y descent is attenuated in tamponade.
What are additional signs that distinguish cp from rp
right and left ventricular pressures are equalized and there is a "dip & plateau" configuration in the diastolic phase of the ventricular pressure tracing.
This square-root sign" and is caused by rapid early diastolic filling followed by limited ventricular filling due to maximal ventricular wall distension allowed by the pericardium.
Limitation of ventricular filling is seen in both cardiac tamponade and constrictive pericarditis.
What is vasoplegia and dose of methylene blue
Vasoplegic syndrome was defined by the presence of the following five criteria: (1) hypotension, (2) low filling pressures, (3) high or normal cardiac index, (4) low peripheral resistance, and (5) vasopressor requirements
1.5 mg/Kg of methylene
What are predictors for vasoplegia syndrome and rate
Occurs in 5 to 8 %
Who does ACE cause Vasoplegia
Increase in Bradykinin levels leads to endothelial dilation
mortality of VS can be as high 25%
What is role of Nitric oxide in Vasoplegia
NO is a mediator in the systemic inflammatory response.
NO stimulate guanylate cyclase enzyme activation and cAMP production which causes smooth vascular muscle relaxation.
How does Methylene blue work
MB is a guanylate cyclase inhibitor
Competitively inhibits NO, in binding to the Iron Hem0 of cGAMP.
This counteraction the effects of NO and other nitrovasodilators in endothelium and vascular smooth muscle.
List side effects of MB
1) Urine blue for about 5 days
2) Falsely low readings on pulse oximetry
3) changes in alveolar gas exchange
4) possible N/V/abdominal discomfort
What are rates of Gross Neurologic system dysfunction
0.5% in young patients
5% in pts over 65
8% in pts older 75
mortality rates are 20%
5% chance of recovery if absence of pupillary light reflex, corneal reflex, caloric relfex, or dolls's eyes
What are rates of cognitive impairment post cardiac surgery
60% have normal cognitive function at 8 weeks after surgery
80% are normal at 6 months to 5 years
What are rates of renal injury
associated mortality of 50%
post op renaly dysfunction (doubling or greater of creatinine occurs in 1%) if preop function normal
What are rates of mortality with GI complications
30 to 50%
5 % develop severe pancreatitis
20% elevated bilirubin
What are rates of bleeding
re-exploration 3 to 5%
> 500/hr x 1
> 400/hr x 2
> 300/hr x 3
> 1000 total in 4 hours
What is most common organ of dysfunction post cardiac surgery
absence of pulmonary flow results in low sheer stress and accentuates neutrophil activation