CASE PRESENTATIONAXILLOBIFEMORAL BYPASS

Christopher M. Baylis, SRNAOregon Health and Science University

Disclosure

I have no financial relationship with the manufacturer of a

commercial product or provider of a commercial

service that may be discussed in this

presentation.

December 2012 - February 2013

Case Report 80 y/o, ASA 4, FemaleProcedure: Axillobifemoral BypassAug 2011 Acute Inf. Wall MI

– Stented– ECHO: EF- 15%, A.I. w/ mild stenosis, LVH– ECG: SR, old inf. Infarct– Previous CABG (LIMA LAD)– METS 3-4, denies SOB w/ exertion

Carotid stenosis (50% bi-lat.)PVD

– LUE fatigue/ ischemia?– Claudication

Quit Smoking 2009– 1 ½ PPD x 40+ yrs

Case ReportPre-op Physical Exam

Wt: 66kgHt: 62”BP: 88/42HR: 67 (S1 S2)RR: 10 (CTA Bi-lat)SpO2: 100%Temp: 99.3

Airway MP2Upper and lower dentures

Scott Rigdon, CRNA

President of Oregon Association of Nurse Anesthetists

Definition: Axillobifemoral Bypass

Method of surgical revascularization for the treatment symptomatic aortoiliac occlusive disease for patients without an endovascular option or who cannot undergo an aortofemoral reconstruction.

Axillobifemoral Bypass

radiographics.rsna.org, vascularandvein.com 

Medical Tunneler

www.goremedical.com 

“What is your anesthetic plan?”

• This must have been scheduled in error, we are out in the sticks!

• Do we have resources for this?

• Oh please let’s cancel case

• Transfer the patient to the VA where they are comfortable dealing with this type of pt. population

Options

1. General Anesthetic2. MAC 3. Regional/ Neuraxial 4. Combination of above

Plan

Isobaric spinal– Anesthetize groin to mid thorax

Tumescent (administered by surgeon)– Anesthetize cephalic portions of

the surgery

MAC (Dexmedetomidine gtt)– Sedation for comfort during the

procedure

Isobaric Spinal Anesthesia

CSF Review

Adults: ~500ml CSF/ day predominately from choroid plexus– Reabsorbed mostly

by arachnoid granulations along sagital sinus

– Sagital sinus regulates CSF pressure 5-15 mmHg (Naglehout)

academic.kellogg.edu

CSF Review

~140ml CSF present in the subarachnoid spaces, central canal of cord and ventricles of the cord and brain.

• 30-80 ml present in spinal canal – variable amongst patients

CSF Density

Specific Gravity (ratio): – Density of substance: Density of water

S.G. of CSF=1.004 to 1.008– Vary r/t temperature, location of fluid in

subarachnoid space (i.e. S.G. lumbar > ventricles) dependent on proteins present• S.G. 0.001 per ea. degree change in Celsius

– S.G. increases w/ age • r/t glucose, protein present in CSF

Baracity

Resting position of two fluids w/ differing S.G. when the fluids are mixed (i.e. CSF & LA)

Isobaric = (S.G. CSF to LA = ~ 1.004 to 1.008)– Stay in approx same location as injected– Baracity= 1.004 to 1.008

Hyperbaric = (S.G. of L.A. > CSF)– Sink to lowest anatomical position (gravity & positioning)– Baracity > 1.008

Hypobaric = (S.G. of L.A. < CSF)– Float to highest anatomical position – Baracity <1.004

Glass Spine Model

www.anesthesia.utoronto.ca

Baracity

Clinically change baracityHypobaric: dissolving drug in sterile waterHyperbaric: dissolving drug in 5-8%

dextrose• 0.75% Spinal Bupivicaine

Isobaric: dissolving drug in CSF or NS• 0.25%-0.5% Isobaric Bupivicaine• Tetracaine is really the only LA we would

reconstitute

Cardiovascular Effects

• Sympathectomy & venous pooling HoTN

• T1-T4 cardiac accelerators• Preventative Management: – Co-loading not pre-load• Only 28% of LR remains in the intravascular

space at 30min and 20% at 1hr IVC ISFC (Chestnut)

– α-adrenergic vasoconstrictors– Sympathomimetic drugs

Respiratory Effects• Most studies show minimal effects on Vt,

RR, min vent and art blood gas tension w/ mid-thoracic level

• Phrenic N. rarely paralyzed (C-3,4,5)– Respiratory arrest occurs r/t inadequate

perfusion to the medulla

• Accessory ABD and intercostals muscles for vent are impaired = inability to cough and clear secretions = aspiration risk

• Care to be taken w/ pts that have poor ventilatory ability

My Choice

Isobaric spinal – 0.5% spinal Bupivicaine (15mg) w/ 20mcg fentanyl

@ L3-4 – Achieved a T-8 sensory block

• ~ T-6 sympathetic block & T-10 motor block

– Rational: • minimize sympathectomy • prevent respiratory compromise (COPD)

Other option was Lumbar epidural – Gradual sympathectomy– Post-op pain management– Not desired by surgeon r/t infection risk, minimal

post-op pain, rumored to have had a prior bad outcome

Tumescent Anesthesia

www.celebritylaserspa.com

Tumescent Anesthesia

Infiltration of large volumes dilute LA subcutaneously

Often used in liposuction for its “wetting effect” facilitates fat suctioning, local anesthetic property and decreases blood loss w/ addition of epinephrine

Dosage

• 0.05%-0.1% (0.5-1mg/ml) Lidocaine w/ 0.5 to 1.5 mg/L epinephrine– 500-1000mg Lidocaine/ Liter

• Addition of sodium bicarbonate may increase absorption, speed of onset and decrease the pain of infiltration

• Steroids (Trimcinolone) can be added to decrease scarring and aid healing

Tumescent: Complications

• Even though theses are dilute solutions, large amounts of LA may be absorbed leading to toxicity. – Only used minimal amounts for this

procedure– Epinephrine slows absorption.

Dexmedetomidine (Precedx)

www.precedex.com

Dexmedetomidine- Overview

• Presynaptic alpha 2- adrenergic agonist– Sedation & analgesia w/o resp. depression – Not an amnestic – Not GABA-mimetic like propofol or

benzodiazepines

• Approved by FDA in 1999 for use in ICU setting

• Approved in 2008 for patients requiring sedation prior to and or during surgical procedures

www.precedex.com

Dexmedetomidine in the OR• Current uses:

– Awake fiberoptic intubation – Carotid endarterectomies – Craniotomies – CABGs – Procedural sedation– Bariatric surgery – ICU sedation.– Current studies for its place in OB

• Rx preeclamptic patients w/ contraindication to regional anesthesia• Possible increases uterine contractions = aid labor/ prevent uterine

atony

• Used alone or as co-adjunct to decrease amount of volatile agent and opioids.

• Has been used in epidurals (0.5-1 mcg/kg) to improve duration and analgesia.

Pharmacokinetics

• Distribution ½ life= 6minutes• Elimination ½ life = 2 hours• 94% protein bound• Almost complete biotransformation

in the liver with urinary excretion of 95%– Lower doses required with patients with

hepatic or renal disease

www.dexmedatomidine.com

Review: Presynaptic Alpha 2 Agonists

• Alpha-2 receptors are located presynaptically in sympathetic nerve endings and in noradrenergic neurons in the CNS.

• Stimulation of these receptors creates a negative feedback loop and decreases the release of norepinephrine.

What other drug that has been around for a while,

works on the pre-synaptic α2-adrenergic receptor?

www.dexmedatomidine.com

Alpha 2 Agonist & Sedation

The receptors in the locus coeruleus of the upper brain stem and the substantia gelatinosa mediate the sedative effects.

www.dexmedatomidine.com

Alpha 2 Agonists & Analgesia

Pain is mediated in the spinal cord by alpha 2 receptors inhibiting transmission from nociceptive neurons to relay neurons in the dorsal horn.

Pros of Dexmedetomidine

• Sedation and analgesia without respiratory depression

• Easily arousable and responsive to stimulation without becoming uncomfortable and quick return to sleep-like state- COOPERATIVE PATIENT– Patients receiving Precedex have been observed to be

arousable and alert when stimulated. This alone should not be considered as evidence of lack of efficacy in the absence of other clinical signs and symptoms

• Reduced anesthetic/ analgesic requirements • Wide margin of safety

Side Effects

• Hypotension, bradycardia and sinus arrest

• Atropine and glycopyrolate were effective in treating bradycardia in clinical trails

• Should not be administered to those with heart conduction block, hypotension, hypovolemia or shock

• Transient HTN seen with loading dose

www.dexmedatomidine.com

What to expect

http://www.precedex.com/what-to-expect/

Dexmedetomidine Dosing

• Adults:– Loading dose of 1 mcg/kg over 10 min- titrate to effect of

sedation desired– Maintenance infusion 0.2-0.7 mcg/kg/min- titrate to

desired effect of sedation– If HoTN occurs, decrease/ stop infusion, give fluids, treat

w/ vasopressors

• Lower doses required w/ hepatic or renal disease • Not indicated for infusion >24hrs

– Has not been tested for greater than this time period

• Dilute prior to administration:– W/D 2ml of precedex add 48ml of 0.9% NaCl for total of

50ml w/ final concentration of 4mcg/ml

AFOI Protocol

www.precedex.com

MAC Protocol

www.precedex.com

Conclusion

Thank You!!!

References• Jaffe RA, Samuels SI, Schmiesing CA, Golianu B eds. Anesthesiologist’s Manual

of Surgical Procedures. 4th ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2009.

• Barash PG, Cullen BF, Stoelting RK, Cahalan M. Clinical Anesthesia. Lippincott Williams & Wilkins; 2009.

• Barash P. Handbook of clinical anesthesia. 6th ed. Philadelphia: Lippincott Williams & Wilkins; 2009.

• Nagelhout JJ, Plaus KL. Handbook of Nurse Anesthesia. Elsevier Health Sciences; 2009.

• Morgan GE, Mikhail MS, Murray MJ. Clinical anesthesiology. Lange Medical Books/McGraw Hill; 2005.

• Miller, Ronald D, Manuel Pardo, and Robert K. Stoelting. Basics of Anesthesia. Philadelphia, PA: Elsevier/Saunders, 2011.

• Fauci AS, Braunwald E, Kasper DL, et al. Harrison’s Principles of Internal Medicine-Harrison’s Online. McGraw-Hill Medical; 2008

• Mills, Stacey E., ed. Sternberg’s diagnostic surgical pathology, 4th ed., Philadelphia: Lippincott Williams & Wilkins, 2004. 2 vol.

• Stoelting's Anesthesia and Co-existing Disease, 5th ed. R. L. Hines, and K. E. Marschall. Saunders Elsevier, Oxford, 2008.

• Pandharipande PP, Pun BT, Herr DL, et al. Effect of sedation with dexmedetomidine vs lorazepam on acute brain dysfunction in mechanically ventilated patients: the MENDS randomized controlled trial. JAMA. 2007;298(22):2644-2653.

Aside

• Dr. John J. Nagelhout– “>23 factors thought to effect spread of

LA in CSF, therefore affecting level and quality of anesthesia.”

– “Clinically the most important are the ones that can be manipulated by the provider.”

1. Total dose of LA2. Site of injection3. Baracity of drug

Duration

• Based primarily on L.A. used and total dose– Highly protein bound drugs (i.e. bupiv, ropiv,

tetracaine) long durations of action – Less protein bound drugs (i.e. lidocaine,

mepivicaine) shorter duration of action

• Ephedrine: vasoconstriction delays normal uptake = prolong duration of L.A. – Greatest w/ Tetricaine, less w/ Lido, minimal w/ Bupiv

• Opioids: synergistic effect w/ L.A. and opioids• α2-agonist is not clear but result in prolonged

L.A.

Anesthetic Record