KEY CONCEPTS IN ACUTE PAIN MANAGEMENT - 2SURGERY RESIDENTS Nov. 15, 2011

John Penning MD FRCPC

Director Acute Pain Service

The Ottawa Hospital

Objectives Review the “new” acute pain ladder When step # 3 on the ladder isn’t working?

– Pronociception, glial activation??– Role of anti-hyperalgesic drugs

Fundamentals of IV PCA What is an epidural anyway? Epidural pitfalls for the surgeon Review principles discussed by case

presentation– Opioid tolerance, conversion from IV to PO– When, how to use naloxone– Assessing the hypotensive epidural patient

Multi-modal Analgesia Orders

Celecoxib 100 – 200 mg PO Q12H or

Naproxen 250 – 375 mg PO Q8HAvailable OTC as “Aleve” 220 mg

Acetaminophen 650 mg PO Q4H Tramadol 25 – 50 – 75 mg PO Q4H prn Hydromorphone 1 – 2 mg PO Q4H prn

To supplement Tramadol if required

Case Problem:32 yr. Male with multiple ribs # Patient previously healthy, MVA with no other

injuries. In Trauma Unit, c/o 9/10 pain. Difficultly

breathing due to severe splinting.Analgesic orders are: Hydromorphone 2 – 4 mg PO Q4H prn or 1 – 2 mg SC Q4H prnNurse just gave 1 mg S/C one hour ago and

now won’t give anything for 3 hours!What do you do?

Case Problem:32 yr. Male with multiple ribs #

Review of PHx reveals no drug use.

Patient has received total of 3 mg hydromorphone sc in the 6 hours since admission.

Case Problem:32 yr. Male with multiple ribs #Acetaminophen 650 mg PO Q4H W/A

Ketorolac 30 mg IV stat followed by 10 mg IV Q4H.

Tramadol 50 – 75 mg PO Q4H

Hydromorphone 1 – 2 mg s.c. Q2H prn

Hydromorphone 0.5 - 1 mg IV Q1H prn

Case Problem:32 yr. Male with multiple ribs #

You are at the top of the analgesic ladder and the patient still has inadequate control of acute pain.

With more pain is more opioid always the answer?

NO! Why?? The problem likely is HYPERALGESIA

Scientific American Nov 2009. Pg. 54. Douglas Fields

E = MC2

Nociceptive Stimulus Pain

Hyperalgesia

Analgesia

Pro-nociceptive modulation

Anti-nociceptive modulation

Analgesic Drugs that act by Nociceptive Modulation

Pro-antinociceptive– Augments inhibitory modulation of

nociception i.e opioids

Anti-pronociceptive– Inhibits the facilitatory modulation of

nociception i.e. ketamine, gabapentin and pregabalin

Grande et al. Anesth and Analg Oct 08

NMDA Receptor Antagonists -To prevent or reverse “pathological” acute pain

Ketamine, Dextromethorphan– Ketamine is widely known as a dissociative

“general anesthetic” - 3 mg/Kg IV bolus– Ketamine 2.5 - 5.0 mg IV bolus for

analgesia in post-op patient - – Ketamine as co-analgesic - combined

0.5:1 with hydromorphone IV PCA. Better analgesia, less S/E

– Dextromethorphan 30 mg PO Q8H available OTC as Benylin DM, 3 mg/ml.

Case Problem:32 yr. Male with multiple ribs #

IV PCA with hydromorphone / ketamine

Ketorolac changed to naproxen when eating. 250 mg PO Q8H

Or Celecoxib 200 mg PO Q12H for 5 days

then 100 mg Q12H until no longer needed.

Case Problem:32 yr. Male with multiple ribs #

On day three patient is doing well and planning for D/C tomorrow.

Convert to PO hydromorphone.Daily IV PCA use is 20 mg per day.Equals about 40 mg per day orally.Order about 50% as long acting.9 mg HM Contin Q12H and 2 – 4 mg PO

Q4H prn.

Case Problem:32 yr. Male with multiple ribs #

Weaning instructions:

As daily “breakthough” hydromorphone requirements decrease, reduce the HM Contin dose by 25% increments.

The NSAID or coxib is D/C after the opioids D/C

Acetaminophen is last to be D/C

Analgesic Drugs that act by Nociceptive Modulation

Anti-pronociceptive– Inhibits the facilitatory modulation of

nociception i.e. ketamine, gabapentin and pregabalin, lidocaine

Pregabalin for acute pain?

Acute pain is “off-label” use Be cautious of Over-sedation

– Sleep deprivation– Elderly– Patient already has significant opioids

Pregabalin: The Good, The Bad and the Ugly The Good

– Chronic pain in region of surgery, when pronociceptive mechanisms play a role such as joint arthroplasty, bowel surgery in IBD patients, chronic limb ischemic pain, opioid tolerant patients

The Bad– Mild pain when simple analgesics like

acetaminophen, NSAIDs or low dose opioid or tramadol suffice.

The Ugly– Too large a dose in sleep deprived patient already

in state of “morphine-failure”

Pregabalin dosage

This is NOT a one size fits all.– Drugs binding to receptors have

considerable patient to patient variability in dose:response

Alpha-2 delta sub-unit of Voltage-Gated Calcium Channel

75 mg PO 2 hours pre-op (50 – 150) 50 mg PO Q8H for 3 to 5 days (25 – 75)

The New Challenges in Managing Acute Pain after Surgery and Trauma

The Opioid Tolerant Patient– The greatest change in practice/attitudes in

the last 10 years is the now wide spread acceptance of the use of opioids for CHRONIC NON-MALIGNANT PAIN

– Renders the “usual” standard “box” orders totally inadequate in these patients

Get a pre-op Anesthesia/APS consult– The Brief Pain Inventory – “BPI”

Eipe and Penning2009

Opioid Conversions – total daily ORAL dose equivalents

Tramadol 500 mg Tapentadol 250 mg Morphine 100 mg Oxycodone 50 mg Hydromorphone 20 mg

Fentanyl patch 25 mcg/hr

The surgeon and IV PCA?

Hydromorphone opioid of choice – (0.5 mg/ml)– Less active metabolites than morphine– Better tolerated in renal

insufficiency/elderly– Safety? In setting of having both available

it is better to be more familiar with HM (substitution errors) i.e. want to avoid giving HM at the morphine dose!

The surgeon and IV PCA?

Loading dose required– HM: 0.03 mg/kg, 2 mg in 70 kg

Bolus dose– HM: 0.2 mg (0.1 – 0.4)

Lock-out interval – 6 minutes Continuous infusion

– Not always required: (0 – 0.2 mg/hr) One hour limit - ( 1.6 mg)

Naloxone, a two-edged sword!

Is there a down side to the administration of naloxone, 0.4 mg IV in the post-op patient where opioid induced respiratory depression is suspected?

Severe acute pain, sympathetic response, pulmonary edema, MI, dysrhythmias

Case Presentation: Somnolence and hypoxemia while on IV PCA hydromorphone

65 yr. Female with large ventral hernia repair on IV PCA hydromorphone

PMHx: Angioplasty 9 yr. ago, MI, CHF in past– Moderate COPD, NIDDM

Doing well day 1, but day 2 found to be somewhat confused, somnolent and SaO2 remains in high 80s despite Oxygen by N/P

Is Narcan Indicated? Urgently?

Case Presentation: Somnolence and hypoxemia while on IV PCA Hydromorphone

Further patient evaluation– Patient arousable, RR 8-16, pupils slightly

constricted, BP 130/70, pulse 90 and reg.– Chest: A/E fair bil. And some mild basilar

creps– ABG: pH 7.46 pCO2 50 pO2 55 BiCarb 36

FiO2 > .50– Chest X-ray: Extensive bilateral, diffuse,

interstitial infiltrate consistent with ARDS Naloxone would probably have had a serious

adverse effect on this patient. Hypoxemia despite supplemental O2 in a breathing patient. Look beyond the Opioids!

Case Presentation: Somnolence and hypoxemia while on IV PCA Hydromorphone

Management of suspected opioid induced respiratory depression– Support A/W– Simulate breathing– Supply supplemental oxygen– Assess SaO2, BP, Pulse– Naloxone titration, IF INDICATED

• 0.04 mg Q5 min. X 3 as needed

Hypoxemia is a medical emergency Hypercarbia is NOT

OpioidsIssueWith parenteral opioids the patient may experience intolerable side

effects before adequate analgesia is attained

Opioids

CONCEPT

Targeted regional

administration of opioid

results in enhancement of

the therapeutic index (ratio

of analgesia/side effects)

Neuraxial Opioids – the good

Intrathecal morphine– simple technique– potent analgesia for 12 -16 hrs.– highly effective for pain in lower abdomen

and lower limbs

Neuraxial Opioids – adverse effects

Risk of delayed onset of respiratory depression, peaks at 6 hours

Urinary retention >50% for 16 hours Pruritus, is not an allergy

What is an “EPIDURAL”? Anatomical

– Location of the catheter, C7 – L5• Cervical, thoracic and lumbar epidurals• Segmental Blockade

Drugs– Opioids (hydrophillic vs. lipophillic)

• morphine, hydromorphone, demerol, fentanyl• Hydrophillic drugs migrate rostrally and also

yield greater spinal selectivity

What is an “EPIDURAL”?

Drugs– Local Anesthetics :

• Lidocaine, bupivacaine, ropivacaineVarying concentrations/drug mass produces“Differential Blockade”

sympathetics > somatosensory > motor– Adjuncts: epinephrine

– Mode of Drug Delivery– Intermittent bolus vs. continuous infusions

True or False? Epidural analgesia impairs the

resolution of post-operative ileus i.e. it “slows down the gut” delaying return of normal bowel function.

Epidural analgesia and recovery of bowel motililty??

Thoracic placement of epidural with the administration of local anesthesic and minimal opioid will promote bowel recovery via sympathetic blockade

If the primary mode of epidural analgesia is via potent opioid, recovery of motility may be delayed.

True or False?

Epidural analgesia necessitates a foley catheter until the epidural is removed.

What about epidurals and the foley catheter??

Less Urinary Tract Infection by Earlier Removal of Bladder Catheter in Surgical Patients Receiving Thoracic Epidural Analgesia.

Zaouter C, Kaneva P, Carli F (McGill)

Regional Anesthesia and Pain Medicine Nov-Dec 2009 pp. 542-552.

Epidural Pit-falls for the Surgeon

Epidural hematoma– > 50 reported cases in USA in patients treated

with LMWH– Epidural insertion and removal of the catheter – Risk factors: Elderly, low body weight, twice daily

dosing, anti-coagulation vs. prophylactic dose range

The decision to fully anti-coagulate a patient with an epidural in-situ should be made in consultation with anesthesia and thrombosis medicine

Epidural Pit-falls for the Surgeon More epidural hematoma risks!!

– Heparin 5000 units s.c. Q8H for thromboprophyllaxis??

This is full clinical anti-coagulation for some patients!

Once daily LMWH at thromboprophyllactic dose is safer.

What about anti-platelet agents?

Plavix– ASRA guidelines state no neuraxial anesthesia or

epidural catheters implemented until D/C for 7 days –

– Plavix may be started 12 – 24 hour after neuraxial block or catheter removal

– concensus only, speculative– Obviously risk is much lower than with

heparin/coumadin since reports are extremely rare– New agents on horizon??

Epidural Pit-falls for the Surgeon

“Masked-Mischief”– The potential high efficacy of the modality could

block pain related to complications• Peritonitis; anastomosis dehiscence• Wound infection, wound hematoma• Limb ischemia, compartment syndrome

– Delay in appropriate therapy, diagnosis• Neurological problems inappropriately attributed

to the epidural i.e. anterior spinal artery syndrome

• Hypovolemia

The “Hypotensive” Patient with an Epidural64 yr. female, 48 kg, with no Hx of CVS problems, had

an esophagectomy for cancer with combined GA/epidural anesthesia.

Later that evening you are called because the patient’s BP is 85/50.

Epidural at T5/6 and running hydromorphone 10 µg/ml in 0.1% bupivacaine with epinephrine 2 mcg/ml at 8 ml/hr

The “Hypotensive” Patient with an Epidural

Possibilities? “Normal” for this patient

– all is well and confirmed by Hx and absence of postural changes in BP or HR

– vascular patients may have marked discrepancy between arms – establish baseline pre-op

Surgical complications Medical complications Side-effect of Epidural induced sympathetic block

– decreased venous return and decreased SVR Combination of any 4 above

Is the Epidural causing the hypotension?

What drugs have been administered epidurally? Pure opioids: morphine, hydromorphone,

fentanyl– sympathetics not blocked directly so look for

another cause Demerol

– mild direct sympatholytic effect and some systemic effects in large doses. Rarely cause of significant Hypotension. Be careful to R/O other causes.

Local Anesthetics +/- opioids– In a euvolemic patient with normal CVS function

hypotension is unlikely if < 8 sensory dermatomes blocked

Is the Epidural Local Anesthetic causing the hypotension?

Intrathecal catheter migration

Inadvertent overdose

“Un-masking” of problem with the patient.

“Sensitive” patient

Is the Epidural Local Anesthetic causing the hypotension?

Management ABCs

– supplemental O2, fluid bolus, elevate legs– ephedrine 5 mg or phenylephrine 50 µg IV bolus– Hold the epidural infusion

Quantify the extent of block– motor block? Thoracic epidural?, that’s a problem!– Sensory block (cold, sharp)

• In a euvolemic patient with normal CVS function hypotension is unlikely if < 8 sensory dermatomes blocked

Management of Hypotension Cont’d High thoracic epidural blockade may block the

compensatory tachycardia response to hypovolemia.– Cardio-accelerator sympathetic nerve fibres arise

from T1 - T4– sympathetic block may extend several dermatomes

above the sensory blockade Correct the underlying cause Remove bupicacaine and change to epidural

hydromorphone if patient remains hemodynamically unstable

36 yr. Open Cholecystectomy patient experiencing difficulty weaning from IV PCA

Endometriosis, fibromyalgia and chronic low back pain- has been on Tylenol #3 for several years- functions well and stable usage of 8-10/day

Day 3 post-op Tylenol #3, 2 tabs Q4h started and IV PCA D/C

Patient c/o severe pain, not able to go home

36 yr. Open Cholecystectomy patient experiencing difficulty weaning from IV PCA

Review of APS meds– Acetaminophen 650 mg Q4H– Naproxen 250 mg Q8H– Pregabalin 50 mg Q8H– Tramadol 50 mg Q4H– Plus using 20 mg IV HM in last 24 hr.

Continue above A/N/P/T plus will likely require about 40 mg daily HM PO (4 – 6 mg PO Q4H prn)

Plan for transition back to Fam MD

Conclusion: Key Concepts

The foundation of all acute pain Rx protocols is NSAIDS and acetaminophen.

Codeine is a “pro-drug”. Problems may occur with under or over conversion to morphine

Tramadol to be considered as second step in the acute pain ladder

Naloxone can be a dangerous drug, careful titration is almost always possible

Conclusions

Inadequate analgesia despite cyclo-oxygenase inhibitors and opioids?– Think “Hyperalgesia”– Consider an anti-hyperalgesic like

ketamine, pregabalin All epidurals are not equivalent Epidural pitfalls

Useful texts

Free!! From Canadian Pain Society

Managing Pain: The Canadian Healthcare Professional’s Reference. Edited by Roman Jovey. 2008.

http://www.anzca.edu.au/publications/acutepain.pdf

The above web site has the entire document and is freely Available to download.

ACUTE PAIN MANAGEMENT:SCIENTIFIC EVIDENCE 3nd Edition Feb ‘10Australian and New Zealand College of AnaesthetistsAnd Faculty of Pain Medicine.

Useful websites on Pain

Prospect:Procedure Specific Post-op Pain Management

http://www.postoppain.org/frameset.htm Pain Explained

http://www.painexplained.ca/content.asp?node=4 The Canadian Pain Society

http://www.canadianpainsociety.ca/indexenglish.html

Useful websites on Pain

Pain Institute http://www.medscape.com/infosite/paininstitute/article-5?src=0_0_ad_ldr Internation Association for the Study of Pain

http://www.iasp-pain.org//AM/Template.cfm?Section

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