aortic stenosis

Question 1

28 year old with PROM and preeclampsia is undergoing induction of labor secondary to maternal fever, chorioamnionitis, and fetal tachycardia.

PMH: multiple sclerosis, migraines, asthma, aortic stenosis (transvalvular gradient of 50 mmHg), DVT during pregnancy

Meds: albuterol, digoxin, methylprednisolone, antibiotics, therapeutic dose lovenox

BP 146/88, T 38.8, Plt 115

what do you think of her transvalvular gradient?

Answer 1

This is very concerning since it may represent severe or critical aortic stenosis. Hyper dynamic circulation of pregnancy can lead to an increased valve gradient and overestimation of the severity, I would review the echo estimate of her valve area. Additionally, a failing LF can lead to a decreased aortic transvalvular gradient and can underestimate the severity. Valve area is a superior method that eliminates these confounding factors.

Question 2

What are the severities and valve areas?

Answer 2

Normal: VA 2.5-4 cm2
Mild: VA 1.5-2.0 cm2, gradient 50 mmHg

Question 3

does this require bacterial endocarditis prophylaxis?

Answer 3

According to the revised AHA guidelines from 2007, aortic stenosis is no longer an independent indication for endocarditis prophylaxis.

Question 4

what are the new guidelines?

Answer 4

they focus on prophylaxis for those conditions associated with the highest risk for adverse outcomes from infectious endocarditis vs those associated with the highest lifetime risk of acquisition of IE. therefore, prophylaxis is reserved for:

1. prosthetic valve or material
2. previous IE
3. unprepared cyanotic congenital heart disease
4. 6 month postop following repair of congenital heart defect
5. cardiac transplant with valvulopathy

Question 5

would you place an epidural?

Answer 5

weighing the risks and benefits of neuraxial anesthesia in this patient with multiple sclerosis, fever, severe aortic stenosis, and preeclampsia, i would place an epidural if enoxaparin had been held for 24 hours prior to placement.

evidence suggests that neuraxial anesthesia may be safely provided even with her increased risk of bacteremia. additionally, although neuraxial anesthesia has been associated with MS exacerbation, it typically occurs with intrathecal injection or epidural with concentrated local anesthetic solutions. the dilute solution to be used for block of labor is considered safe. while preeclampsia effects both platelet quantity and quality, her platelet count is 115 and there are no other signs of coagulopathy. finally, even with severe aortic stenosis, epidural can be safely administered if advanced slowly without epinephrine (which can lead to tachycardia)

i find epidural desirable because it would reliably prevent tachycardia and provides an option if c-section is necessary that would avoid general anesthesia (risk of difficult airway and aspiration increased in pregnancy)

Question 6

the epidural will drop the SVR. is this desirable because it will improve cardiac output?

Answer 6

a decrease in after load often promotes cardiac output normally. however, in severe aortic stenosis this is not the case. the stenotic valve, rather than the SVR creates most of the after load on the LV. therefore a significant drop in SVR is poorly tolerated in these patients with a fixed SV and inability to adequately increase CO. the subsequent diastolic hypotension and compensatory tachycardia places the patient at increased risk for subendocardial ischemia, especially given the likelihood of ventricular hypertrophy.

Question 7

what are the ASRA guidelines for neuraxial anesthesia and anticoagulation?

Answer 7

SUBQ heparin: can be placed immediately, consider following IV guidelines, monitoring: aPTT

IV heparin: placement 2-4 hours after d/c, can give heparin 1 hour after placement, monitoring: aPTT

intraop heparin: placement 2-4 hours after d/c, can give heparin 1 hour after placement

complete heparinization: traumatic needle, delay surgery 12-24 hours, normal can heparinize 60 min after placement, can remove 2-4 hours after normal coagulation restored

low-dose LMWH: (30-40 mg SQ BID, 40 mg SQ QD) placement 10-12 hours after

high dose LMWH: (1 mg/kg BID, 1.5 mg/kg QD) placement 24 hours after

postop LMWH (once daily dosing): catheter removal 10-12 hours after last dose, can reinstate dose 2 hours after catheter removal

postop LMWH (twice daily dosing): catheter removed 2 hours prior to first dose

warfarin: placement once INR normal, removal INR

Question 8

if not enough time had passed, can you check an anti-Xa level or administer protamine to reverse the effects of enoxaparin?

Answer 8

i would not check anti-Xa level because while it may be used to guide dosing, it is not predictive of bleeding risk. i would not administer protamine because it does not adequately reverse LMWH.

Question 9

would you require special monitoring at this point?

Answer 9

considering the aortic stenosis, increased risk of bleeding due to preeclampsia and acquired von willebrand disease associated with aortic stenosis, potential for HD changes, i would:

1. FHR monitoring (uterine perfusion)
2. 5-lead EKG
3. arterial line
4. possible CVP to facilitate fluid management
5. TTE

Question 10

would you place a PAC?

Answer 10

although it could prove useful for fluid management, identifying cause of hypotension, and providing means for pacing, i would not use it. first, it may not provide accurate results in the setting of aortic stenosis. the monitor may overestimate the LVEDV due to the decreased compliance of a hypertrophied LV. second, there is no evidence that utilizing it improves outcome.

Question 11

you place a CVL for fluid management. during placement, she develops atrial fib with rate in 130’s. is this concerning?

Answer 11

yes, the risk of myocardial ischemia is greatly increased by atrial fib in patients with aortic stenosis. this patient already has increased myocardial oxygen demand secondary to a hypertrophied LV and increased after load. the rapid ventricular rate leads to even further increased myocardial oxygen demand while also reducing the time for ejection of stroke volume through the stenotic valve, coronary perfusion, and LV filling. it also eliminates the atrial contribution to LV filling (normally 30-40% in the setting of decreased LV compliance), leading to further reduction of LV filling and CO.

Question 12

what will you do?

Answer 12

1. pull back central line
2. order 12 lead EKG
3. administer diltiazem (beta-blockers also an option, but would like to avoid with her asthma)

if hypotension, pulm edema, myocardial ischemia
4. cardioversion with biphasic defibrillator (100-200 J), monophasic (200 J)

Question 13

what are some common causes of atrial fib?

Answer 13

heart failure, cardiomyopathy, acute MI, longstanding hypertension, valvular disease, hyper/hypothyroidism, drugs (cocaine), PE, hypoxemia, SSS

Question 14

assume it has been an appropriate amount of time since her last anticoagulant, how would you proceed with neuraxial anesthesia?

Answer 14

given her history of fever, chorioamnionitis, severe aortic stenosis, and MS i would

1. ensure appropriate antibiotics to treat her possible bacteremia and reduce risk of epidural abscess or meningitis
2. ensure adequate hydration/preload
3. utilize epidural, slowly raising blockade to T10 with small doses of LA without epi (to avoid rapid drop in SVR and tachycardia)
4. administer low concentration local anesthetic to mitigate risk of exacerbating MS

Question 15

how does aortic stenosis affect the heart?

Answer 15

concentric ventricular hypertrophy due to increased intraventricular systolic pressure. this results in diastolic dysfunction (stiff ventricle), increased LVEDP, increased myocardial oxygen demands

Question 16

difference in concentric and eccentric VH

Answer 16

concentric: pressure overload, sarcomeres are added in parallel (thickening, not lengthening), volume not increased
eccentric: volume overload, sarcomeres added in series, volume is increased

Question 17

multiple attempts at epidural placement but you unintentionally enter the intrathecal space. would you place an intrathecal catheter?

Answer 17

no, given the risk of exacerbating multiple sclerosis and also rapidly dropping SVR/afterload in this patient with critical aortic stenosis and risk of preexisting hypovolemia with preeclampsia.

Question 18

what would you do instead?

Answer 18

re-attempt epidural placement and make the patient aware of the risks PDPH

Question 19

what are the s/s of PDPH?

Answer 19

positional frontal-occipital headache, nausea, vomiting, neck stiffness, back pain, photophobia, diplopia, tinnitus

rarely a/w seizures (cerebral vasospasm)
cranial nerve stretching- CN 6 most susceptible (impaired eye abduction) results in diplopia

Question 20

epidural is placed. working well for labor. FHTs are non-reassuring and the OB wants to proceed with c-sxn. would you provide any preoperative medications?

Answer 20

1. albuterol to optimize her asthma
2. metoclopramide, H2 blocker, non particulate antacid to reduce risk of aspiration pneumonitis
3. stress-dose steroids
4. consider beta-blocker to prevent tachycardia (but may exacerbate asthma)

Question 21

would you provide preoperative steroid supplementation and why?

Answer 21

yes, since her prior therapy with steroids may have resulted in hypothalamic-pituitary-adrenal suppression and an inability to produce adequate cortisol during the perioperative period..

that can result in addisonian crisis (life-threatening - fever, abdominal pain, dehydration, n/v, hypoglycemia, acidosis, hyperkalemia, hyponatremia, circulatory collapse, depressed mentation)

Question 22

what is the controversy surrounding steroid replacement?

Answer 22

it is questionable whether supplementation is necessary beyond the patient’s usual steroid dose. additionally, supra physiologic doses of steroids are not without risk such as: infection, poor wound healing, fluid retention, electrolyte imbalances, immunosuppression, hypertension, hyperglycemia. however many of these side effects are unproven or not clinically significant.

Question 23

what dose of steroid are you concerned causes adrenal suppression?

Answer 23

5 mg prednisone/day (longterm suppression is unlikely at smaller doses)

Question 24

what and how much would you administer?

Answer 24

75 mg hydrocortisone preop, with rapid taper over 1-2 days

Question 25

what are some common regimens?

Answer 25

• 100 mg hydrocortisone preop, 100 mg Q8 hrs DOS
• 25 mg hydrocort induction, 100 mg over 24 hours
• minor surgery: 25 mg hydrocortisone DOS, no addtnl
• major surgery: 50-75 mg preop, 50 mg intraop, 20 mg Q8, usual dose day 2
• severe surgery: 100-150 mg preop, 50 mg intraop, 25-50 mg Q8 for 2 days then normal dose day 3

Question 26

the baby’s heart tones go down into the 50’s for 4 minutes and OB wants to proceed with emergent c-sxn. would you use neuraxial catheter?

Answer 26

although there is risk of difficult airway, aspiration, i would likely proceed with general anesthesia after discussion with OB, as this could be induced quicker and is likely safer than quickly dosing the epidural catheter due to the deleterious consequences associated with sympathectomy in this preeclamptic patient with aortic stenosis.

Question 27

is using a higher concentration LA acceptable for a patient with multiple sclerosis?

Answer 27

there is evidence that using higher conc of LA for epidural analgesia may increase MS exacerbations, but the risk may be minimized by short duration of csxn, which limits the progressive increase in CSF concentration of LA. so, while the use of regional anesthesia for patients with MS i controversial, the benefits of avoiding airway instrumentation, reduced risk of aspiration, superior postop analgesia outweigh the potential risks usually.

Question 28

you aspirate blood through the catheter and decide to provide general anesthesia. patient refuses awake intubation, how will you induce

Answer 28

given her potentially difficult airway and comorbidities, i would:

1. verify lines and monitors
2. make sure all premeds were given, including esmolol to prevent tachycardia (esmolol is beta1 selective for this asthmatic patient)
3. ensure difficult airway equipment, external CV pads (loss of atrial kick is not tolerated in AS patients), phenylephrine
4. place patient in sniff position with LUD
5. cricoid pressure
6. etomidate + narcotics to help avoid tachycardia and bronchospasm
7. rapidly secure airway with endotracheal tube
8. inform neonatal team about narcotics

goals: maintain spont ventilation, avoid tachycardia/bradycardia/myocardial depression, avoid bronchospasm with maintaining SVR and reduce risk of aspiration

Question 29

would you use sch?

Answer 29

only if absolutely necessary given difficult airway possibility and risk of up regulation of ACh receptors with MS

Question 30

how will you maintain anesthesia?

Answer 30

prior to delivery, primarily with VA, administering narcotics only if necessary until after delivery of baby. following delivery i would give a small dose of benzodiazepine and IV narcotics as needed. if i were concerned about depressed LV fxn, i would decrease the concentration of VA given

Question 31

you notice ST depression on EKG, would you give NTG?

Answer 31

no, this would not be my first choice. it could improve CBF to more ischemic areas of the subendocardium and relieve any coronary vasospasm. however, it could also lead to significantly reduced preload. although a reduction in after load is desirable in most patients experiences ischemia, the potential drop in preload could be very negative for this patient. additionally, this patients increased after load is mostly due to the very stenotic aortic valve. therefore, i would probably be more likely to administer a vasoconstrictor and improve coronary perfusion.

if i was concerned about afterload, i would consider nicardipine as it causes less venodilation

Question 32

ST depression resolves, baby is delivered. the uterus is “boggy” and the patient has lost 1400 mL of blood. what do you do?

Answer 32

i would verify the patient was received pitocin (keeping in mind it can cause peripheral vasodilation with subsequent hypotension and tachycardia. i would:

1. 100% FiO2
2. check to make sure patient was HD stable
3. encourage bimanual compression/uterine massage
4. type and cross
5. order CBC, coats
6. observe surgical field - atony vs bleeder

if atony is cause, i would reduce VA and administer extra oxytocin.
if ineffective, i would consider:
- rectal misoprostol (prostaglandin E1 analogue, 800-1000 mcg per rectum)
- intrauterine balloon for tamponade
- ligate internal iliac, uterine, ovarian arteries
- emergency hyst

Question 33

would you administer other uterotonic agents?

Answer 33

as a last resort due to her preeclampsia, asthma, chorio, and severe aortic stenosis.

• methergine (ergot-derivative) may worsen HTN of preeclampsia, cause coronary vasospasm
• hemabate (methyl-prostaglandin F2-alpha) can cause bronchospasm and is relatively contraindicated in asthmatics
• dinoprostone (prostaglandin E2) causes decreased SVR and tachycardia

additionally, prostaglandins tend to be less effective with chorioamnionitis

Question 34

five hours after epidural catheter is pulled, patient is febrile and experiencing back pain and bilateral leg weakness. what do you think?

Answer 34

while her symptoms are possibly from bacteremia due to chorioamnionitis, tissue damage from placement (back pain), and residual epidural block (leg weakness), i would be very concerned that these symptoms were something more significant.

• multiple sclerosis relapse (fever increases her risk)
• epidural/spinal hematoma (permpartum anticoagulants)

Question 35

what would you do?

Answer 35

i would evaluate patient for:
epidural hematoma: back pain/pressure severe and unrelenting, pain on palpation of spinous/paraspinous n.tenderness, bowel/bladder dysfunction, progressive weakness, paresthesia, sensory deficit

MS: paresthesia, weakness, sensory deficit, urinary incontinence, bowel retention, visual/gait disturbance, emotional lability, autonomic dysfunction

Question 36

the patient develops urinary incontinence, what will you do?

Answer 36

urinary incontinence with leg weakness is consistent with multiple sclerosis or epidural hematoma.

1. examine for tenderness
2. progressive vs recessive weakness
3. obtain MRI to look for spinal cord compression
4. consult a neurosurgeon (needs decompression within 6-12 hours)

Question 37

you determine it is a relapse of MS. the ob wants to know when enoxaparin can be restarted?

Answer 37

since she is receiving twice daily dosing, i would recommend restarting 24 hours after surgery. moreover, i would ensure the catheter was pulled at least 2 hours before restarting.

Question 38

prior to restarting enoxaparin, the patient becomes dyspneic. what is the cause?

Answer 38

given her history of DVT, severe AS, asthma, MS relapse, risk of aspiration, and recent CVL my ddx would include:

1. PTE
2. CHF
3. asthma
4. myocardial infarction
5. tension ptx
6. pulm edema
7. aspiration
8. MS involvement of brain stem

Question 39

how do you diagnose PTE?

Answer 39

dyspnea, tachypnea, cough, hemoptysis, tachycardia, fever, split S2, pleuritic pain, localized rales, hypoxemia, hypocapnea, thrombophlebitis, JVD, HD instability, palpitations, CV/PAC changes (normal to low PAOP, increased PAP, increased CVP), new RBB, ST-T wave changes, peaked P waves, RAD

1. LE U/S
2. spiral CT
3. VQ scan
4. pulm angiography
5. CXR
6. d-dimer
7. TTE
8. TEE

Question 40

if it was PE, how would you treat?

Answer 40

1. 100% FiO2
2. administer inotropes and fluid
3. analgesics as HD tolerated
4. consider pulmonary vasodilator (PDE inhibitor, amrinone, milrinone - cause pulm vasodilation and cause improved myocardial contractility)
5. intubate/mech vent if needed
6. ICU

Question 41

would you anticoagulate?

Answer 41

while this would be desirable to prevent formation of new clots, it is probably advisable to avoid given her recent surgery. an IVC filter could be considered. additionally, TTE with pulmonary embolectomy is an option. anticoagulants would be a last resort.

Question 42

two days later she is extubated, stable, complaining of headache. what do you think?

Answer 42

the most common type of postpartum headache is a tension headache. however, with her history of migraines and recent dural puncture, i would be concerned about PDPH and lactation headache, pneumocephalus, preeclampsia, recent chorioamnionitis (meningitis), caffeine withdrawal, sinusitis, cerebral ischemia, intracranial tumor, cranial hemorrhage.

Question 43

assuming it is PDPH, how will you treat her?

Answer 43

epidural blood patch is most effective treatment for PDPH and involves injection of 15-20 mL of her blood into the epidural space at the level of dural puncture. however, assuming she was on anticoagulants for her PE, a blood patch would be inappropriate due to risk of hematoma.

therefore i would:

1. IVF bolus
2. abdominal binder
3. caffeine
4. pain control