Donald H. Lambert

Boston, Massachusetts

http://www.debunk-it.org

Spinal - Epidural - Spinal - Epidural - [Combined Spinal Epidural][Combined Spinal Epidural]

Spinal AnesthesiaSpinal Anesthesia

Advantages v. Disadvantages Pharmacology of spinal agents Addition of a vasoconstrictor Baricity Dosing Complications

Spinal AnesthesiaSpinal Anesthesia

Advantages v. Disadvantages Pharmacology of spinal agents Addition of a vasoconstrictor Baricity Dosing Complications

Spinal Anesthesia AgentsSpinal Anesthesia Agents

The dosing in this study was 10 mg, 15 mg, and 20 mg of bupivacaine

The lowest dose limited spread

The lowest dose also resulted in more failures than the higher doses.

Spinal AnesthesiaSpinal Anesthesia

Advantages v. Disadvantages Pharmacology of spinal agents Addition of a vasoconstrictor Baricity Dosing Complications

Spinal AnesthesiaSpinal Anesthesia

Advantages v. Disadvantages Pharmacology of spinal agents Addition of a vasoconstrictor Baricity Dosing Complications

The effect of baricity on the distribution of bupivacaine in spinal model

In spite of the crudeness of this model, the levels of anesthesia predicted by the model are remarkably similar to the levels of anesthesia observed in patients

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Spinal AnesthesiaSpinal Anesthesia

Advantages v. Disadvantages Pharmacology of spinal agents Addition of a vasoconstrictor Baricity Dosing Complications

Spinal AnesthesiaSpinal Anesthesia

Dosing will affect Spread Duration Quality of Anesthesia

That is, the need for supplemental IV medication

Spinal AnesthesiaSpinal Anesthesia

I have been doing spinal anesthesia for 25 years I spent the first 10 years trying to control the level

of spinal anesthesia I have failed I have given up trying If you know how to control the level of spinal

anesthesia please tell me how it is done

Dosing GuidelinesDosing Guidelines Based on the spinal canal

model (and many years in the trench) Hyperbaric solutions extend into

the thoracic region Isobaric solution remain in the

lumbar region

I give hyperbaric solutions for operations above the L1 dermatome and isobaric solutions for those below

Hyperbaric

Isobaric

Dosing GuidelinesDosing Guidelines

Hernia operations and those operations whose innervation is by nerves above L1 HYPERBARIC

Those operations whose innervation is by nerves below L1 (pretty much all lower extremity operation including hip operations) ISOBARIC

CHOOSING A LOCAL ANESTHETIC FOR CHOOSING A LOCAL ANESTHETIC FOR SPINAL ANESTHESIASPINAL ANESTHESIA

BASE DECISION ON THE BASE DECISION ON THE DURATIONDURATION OF OF THE OPERATIONTHE OPERATION

CHOOSING A LOCAL ANESTHETIC FOR CHOOSING A LOCAL ANESTHETIC FOR SPINAL ANESTHESIASPINAL ANESTHESIA

GIVE ENOUGH TO PROVIDE GIVE ENOUGH TO PROVIDE ADEQUATEADEQUATE ANESTHESIAANESTHESIA

BARICITY PROC. LIDO. BUPIV. TETRA.ISOBARIC 80 mg 60 mg 15 mg 15 mgHYPERBARIC 80 mg 60 mg 15 mg 15 mg

? CHLOROPRACAINE, ? ROPIVACAINE

Isobaric Spinal AnesthesiaIsobaric Spinal Anesthesia Epidural Bupivacaine

It says right on the bottle: “Not for spinal anesthesia” What is the value or wisdom behind using that agent?

It works great and I have used it since the 1980’s. I know of no reports of complications associated with using it. Litigation for the off-labeled use of a drug has not appeared in the ASA

closed claims database.

Who would know? Unless you wrote on your anesthesia record, “I used the bupivacaine that

is not for spinal anesthesia.”

Spinal AnesthesiaSpinal Anesthesia

Advantages v. Disadvantages Pharmacology of spinal agents Addition of a vasoconstrictor Baricity Dosing Complications

Spinal AnesthesiaSpinal Anesthesia

Complications Cardiac arrest Hypotension Headache Nerve injury

Unexpected cardiac arrest during spinal anesthesia: a closed claims analysis of predisposing factors

1988 2004

Number of Claims 900 5,047

Number of Arrests 14 (1.5%) 68 (1.3%)

Mean Age 36 42

ASA Physical Status I - II I - II

Caplan, R A; et al. Unexpected cardiac arrest during spinal anesthesia: a closed claims analysis of predisposing factors. Anesthesiology 1988;68:5-11

Caplan, R A; et al. Injuries Associated with Regional Anesthesia in the 1980s and 1990s: A Closed Claims Analysis. Anesthesiology. 2004;101:143-152

Unexpected cardiac arrest during spinal anesthesia: a closed claims analysis of predisposing factors

Local Anesthetic Tetracaine

Dose 6 - 14 mg

Maximum Level T4

Time of Arrest 12 - 78 minutes

Caplan, R A; et al. Unexpected cardiac arrest during spinal anesthesia: a closed claims analysis of predisposing factors. Anesthesiology 1988;68:5-11

Unexpected cardiac arrest during spinal anesthesia: a closed claims analysis of predisposing factors

Caplan, R A; et al. Unexpected cardiac arrest during spinal anesthesia: a closed claims analysis of predisposing factors. Anesthesiology 1988;68:5-11

1st Clue 2nd Clue CombinedClues

Bradycardia 7 2 9

Hypotension 2 6 8

Cyanosis 4 3 7

LOC 1 1 2

Asystole 0 2 2

Initial Clues of Impending ArrestInitial Clues of Impending Arrest

Unexpected cardiac arrest during spinal anesthesia: a closed claims analysis of predisposing factors

Caplan, R A; et al. Anesthesiology 1988;68:5-11 and Mackey, D C, et al. Anesthesiology 1989;70:866-868

Factors Predisposing to Asystole High level Loss of Cardiac Sympathetic Stimulation Unopposed Vagal Tone Decreased Venous Return

Empty Left Ventricle Activation of Intracardiac Reflexes

? So-called Bezold-Jarisch Reflex or the so-called Vaso-vagal Syncope

Cardiac arrest during spinal anesthesia

How can this be prevented and/or treated? Maintain venous return at all cost Use epinephrine at the first sign of cardiac arrest

Keats, A. S. Anesthesia mortality--a new mechanism.Anesthesiology 1988;68:2-4.

Sandra L. Kopp, et al Anesth Analg 2005; 100: 855-65

Cardiac Arrest During Neuraxial Anesthesia: Frequency and

Predisposing Factors Associated with Survival

Acta Anaesthesiol Scand 1997; 41: 445-5Severe complications associated with epidural and spinal anaesthesias in Finland 1987-1993. A study based on patient insurance claims Aromaa U, Lahdensuu M, Cozanitis DA

Spinal Anesthesia ComplicationsSpinal Anesthesia Complications

Hypotension (happens!)

But, if you want to know something… it happens also

when I do general anesthesia!!

Incidence and risk factors for side effects ofspinal anesthesia in 952 patients

Hypotension in 314 (33%)

Bradycardia in 125 (13%)

Nausea in 175 (18%)

Vomiting in 65 (7%)

Dysrhythmia in 20 (2%)

Carpenter, RL, et al. Anesthesiology 1992;76:906

Reduction of side effects during spinalanesthesia

Minimize peak block height

Perform lumbar puncture at or below L3-L4

Avoid vasoconstrictors

Avoid procaine

Carpenter, RL, et al. Anesthesiology 1992;76:906

The Two Components The Two Components of Spinal Headacheof Spinal Headache

There must have been a lumbar puncture

The headache is related to posture Worst when standing or

sitting Gone or improved with

recumbence

Effect of Age on the Incidence of Spinal Headache

Vandam and Dripps, JAMA 1956;161:586-591

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This and AARP discounts are two of the few advantages to aging!

Spinal Anesthesia ComplicationsSpinal Anesthesia Complications

Nerve injury

Most frequent with lidocaine (10-34% incidence) More frequent with lithotomy position and knee

arthroscopy VAS pain score averages 6 out of 10 Many rate the pain worse than their incision Can last up to three days Least frequent with bupivacaine

How Safe are Spinals?How Safe are Spinals?

TNS/TRI

How Safe are Spinals?How Safe are Spinals?

Spinal AnesthesiaSpinal Anesthesia Is there a reasonable alternative to lidocaine? What are the possibilities?

Procaine ? Chloroprocaine (non-neurotoxic in isolated nerve)

recent data in rats indicates neural toxicity with i.t. infusion

Prilocaine (low incidence of TRI, but neurotoxic in rat) Mepivacaine (same incidence of TRI as with lidocaine) Low dose bupivacaine ? Ropivacaine

EPIDURAL ANESTHESIAEPIDURAL ANESTHESIA

Advantages Disadvantages Technique Pharmacology of Specific Agents Effect of Dose Mechanism of Action Addition of a Vasoconstrictor Complications Test Dose Comparison with Spinal

EPIDURAL ANESTHESIAEPIDURAL ANESTHESIA

Advantages Disadvantages Technique Pharmacology of Specific Agents Effect of Dose Mechanism of Action Addition of a Vasoconstrictor Complications Test Dose Comparison with Spinal

EPIDURAL ANESTHESIAEPIDURAL ANESTHESIA

Advantages Disadvantages Technique Pharmacology of Specific Agents Effect of Dose Mechanism of Action Addition of a Vasoconstrictor Complications Test Dose Comparison with Spinal

EPIDURAL ANESTHESIA AGENTSEPIDURAL ANESTHESIA AGENTS

DRUG CONC. DOSE VOLUME DURATION(%) (mg) (ml) (min)

CHLOROPROC. 2 - 3 300 - 900 15 - 30 30 - 90LIDOCAINE 1 - 2 150 - 500 15 - 30 60 - 180MEPIVACAINE 1 - 2 150 - 500 15 - 30 60 - 180PRILOCAINE 1 - 3 150 - 600 15 - 30 60 - 180ROPIVACAINE 0.5 - 1.0 75 - 300 15 - 30 180 - 300BUPIVACAINE 0.25 - 0.75 37.5 - 225 15 - 30 180 - 300LEVOBUPIV. 0.25 - 0.75 37.5 - 225 15 - 30 180 - 300ETIDOCAINE 1 - 1.5 150 - 300 15 - 30 180 - 300

EPIDURAL ANESTHESIAEPIDURAL ANESTHESIA

Advantages Disadvantages Technique Pharmacology of Specific Agents Effect of Dose Mechanism of Action Addition of a Vasoconstrictor Complications Test Dose Comparison with Spinal

Truisms on DoseTruisms on Dose

The more you put in The quicker it comes on The better the block The longer it lasts

The more you put in The more likely are you to cause toxicity

EPIDURAL ANESTHESIAEPIDURAL ANESTHESIA

Advantages Disadvantages Technique Pharmacology of Specific Agents Effect of Dose Mechanism of Action Addition of a Vasoconstrictor Complications Test Dose Comparison with Spinal

The are many potential sites where epidural local anesthetics can act.

The highest concentrations of local anesthetic are found in the CSF and nerve roots.

The lowest concentrations are found in the dorsal root ganglia and the substance of the spinal cord.

All sites likely contribute to the mechanism of epidural anesthesia, but the most likely conclusion is that the epidural anesthesia comes about by an intrathecal action.

EPIDURAL ANESTHESIAEPIDURAL ANESTHESIA

Advantages Disadvantages Technique Pharmacology of Specific Agents Effect of Dose Mechanism of Action Addition of a Vasoconstrictor Complications Test Dose Comparison with Spinal

Effect of Epinephrine on Peak VenousEffect of Epinephrine on Peak VenousPlasma Level with Plasma Level with Epidural Epidural AnesthesiaAnesthesia

The more “vasodilating”agents - mepivacaineand lidocaine show thegreatest epinephrineeffect.

The lack of effect withprilocaine may be due toits “ good diffusion.”

The lack of effect withetidocaine andbupivacaine due to theiravid binding to lipids.

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M ipiv500 mg

Lido400 mg

Prilo400 mg

Etido300 mg

Bupiv150 mg

Plain Epi - 5ug/ml

EPIDURAL ANESTHESIAEPIDURAL ANESTHESIA

Advantages Disadvantages Technique Pharmacology of Specific Agents Effect of Dose Mechanism of Action Addition of a Vasoconstrictor Complications Test Dose Comparison with Spinal

Cardiovascular ToxicityCardiovascular ToxicityHYPERTENSION - TACHYCARDIA OWING TO CNS EXCITATION

NEGATIVE INOTROPY

DECREASED CARDIAC OUTPUT

MILD - MODERATE HYPOTENSION

PERIPHERAL VASODILATATION

PROFOUND HYPOTENSION

SINUS BRADYCARDIA

CONDUCTION DEFECTS VENTRICULAR ARRYTHMIAS

CARDIOVASCULAR COLLAPSE

Low doses of epidural localanesthetics have a CNSstimulating affect thatcounteracts vascular depression.

With higher local anestheticdoses, cardiovascular depressionis more apparent.

Epinephrine contributes tovascular depression by its betaeffect, which lower peripheralvascular resistance.

Hypovolemia contributes tocardiovascular collapse (vaso-depressor syncope?).

The deleterious effect ofhypovolemia is counteracted bythe addition of epinephrine tothe local anesthetic.

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MAP PVR CO

LEVEL T5 T1 T2-3 T5 T5

Lido (ug/ml) <4 <4 >4 <4 <4

Epinephrine 0 0 0 + +

Hypovolemia 0 0 0 0 +

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MAP PVR CO

LEVEL T5 T1 T2-3 T5 T5 T5

Lido (ug/ml) <4 <4 >4 <4 <4 <4

Epinephrine 0 0 0 + 0 +

Hypovolemia 0 0 0 0 + +

The Two Components The Two Components of Spinal Headacheof Spinal Headache

There must have been a lumbar puncture

The headache is related to posture Worst when standing or

sitting Gone or improved with

recumbence

Accidental puncture Accidental puncture during labor epiduralduring labor epidural

About a 1% chance of less

About 60% will develop a headache

About 70% will require a blood patch

Guidelines for Regional Anesthesia in Guidelines for Regional Anesthesia in the Anticoagulated Patientthe Anticoagulated Patient

See Consensus Statement at the ASRA Web site:

http://www.asra.com/items_of_interest/consensus_statements/

EPIDURAL ANESTHESIAEPIDURAL ANESTHESIA

Advantages Disadvantages Technique Pharmacology of Specific Agents Effect of Dose Mechanism of Action Addition of a Vasoconstrictor Complications Test Dose Comparison with Spinal

Test DoseTest Dose

Used to prevent intravascular injection of local anesthetic

Epinephrine most frequently advocated and most extensively studied 15 ug of epinephrine produces a tachycardia within 20

seconds Reliability diminished by beta blockade, aging,

general or combined general-epidural anesthesia

Mulroy, MF RAPM 27:556-561;2002

Test DoseTest Dose

When epinephrine is not practical Use moderate doses of local anesthetic while

monitoring for CNS effects 100 mg of lidocaine or chloroprocaine 25 mg of bupivacaine Requires non pre-medicated patient Medication with midazolam will interfere

Mulroy, MF RAPM 27:556-561;2002

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IV injection

Death

No test dose

Mulroy, MF RAPM 27:556-561;2002

Local Anesthetic ToxicityLocal Anesthetic ToxicityRate of InjectionRate of Injection

Slow rates of injection are less likely to result in systemic toxicity

Intermittent injections, at slow rates will lessen further the likelihood of systemic toxicity

These two steps, in my opinion, are better than a test dose of local anesthetic with epinephrine as tracer

Test Dose QuizTest Dose QuizEpidural anesthesia for cesarean delivery is planned for a 30-year-old woman in labor. She has preeclampsia and takes propranolol for mitral valve prolapse. A test dose of 3 ml of 2% lidocaine containing 15 g of epinephrine is administered, and no change in heart rate is noted by palpation of the pulse. Prior to injection of more local anesthetic, blood is freely aspirated from the catheter. Explanations for failure of the intravenous test dose include:

(1) The pain of labor masked the change usually seen with the test dose

(2) Pre-existing beta-adrenergic blockade blunted the tachycardia from the intravenous epinephrine

(3) Changes in pulse rate were too brief to be noted by palpation of the

pulse

(4) Preeclampsia decreased the sensitivity to exogenously administered catecholamines

EPIDURAL ANESTHESIAEPIDURAL ANESTHESIA

Advantages Disadvantages Technique Pharmacology of Specific Agents Effect of Dose Mechanism of Action Addition of a Vasoconstrictor Complications Test Dose Comparison with Spinal

Comparing spinal to epiduralComparing spinal to epidural

Spinal easier to do No chance systemic

toxicity Increased risk of neural

toxicity Duration too short Low incidence of spinal

headache

Epidural more difficult Systemic toxicity possible Less chance neural toxicity

except with certain agents and accidental spinal injection

Unlimited duration Incidence of spinal headache

about the same as spinal

Good luck with your exam!Good luck with your exam!

If you still have unanswered questions

OR

If you have answers you want questioned

You can contact me (no bunk):You can contact me (no bunk):donlam@debunk-it.orgdonlam@debunk-it.org

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Don’t for get the “dash” between “debunk” and “it”