KEY CONCEPTS IN ACUTE PAIN MANAGEMENT. John Penning MD FRCPC Director Acute Pain Service

Transcription

1 KEY CONCEPTS IN ACUTE PAIN MANAGEMENT John Penning MD FRCPC Director Acute Pain Service

2 Objectives Why is acute pain management important? Clinical concepts not readily found in texts COX-inhibitors, the foundation of all acute pain protocols Opioid dose:response variability Limitations of T#3 Role of NMDA antagonists

3 Consequences of poorly managed acute post-operative/trauma pain The Patient suffers CVS: MI, dysrhythmias Resp: atelectasis, pneumonia GI: ileus, anastamosis failure Endocrine: stress hormones Hypercoagulable state: DVT, PE Impaired immunological state Infection, cancer, wound healing Psychological: Anxiety, Depression, Fatigue Chronic Post-surgery/trauma Pain

4 Consequences of poorly managed acute post-operative/trauma pain The Hospital Increased costs $$$ Poor staff morale Reputation/Standing in the Community, Nationally Accreditation Litigation The Healthcare professional Morale Complaints to College Litigation

5 The New Challenges in Managing Acute Pain after Surgery and Trauma Patients/Society more aware of their rights to have good pain control We are being held accountable JCAHCO standards, Pain is the Fifth Vital sign Pressure from hospital to minimize length of stay Control pain, limit S/E and complications

6 The New Challenges in Managing Acute Pain after Surgery and Trauma The Opioid Tolerant Patient The greatest change in pain management 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

7 What is the Best Way to manage acute post-operative/trauma pain? FIRST, DO NO HARM Therefore, the best way is a BALANCE Patient Safety Effective Analgesic Modalities

8 KEY POINTS Emphasis is placed on the utilization of a multimodal analgesic approach to maximize analgesia while minimizing side-effects. Transduction Transmission Modulation Perception There is as of yet no single silver bullet!!

9 Pain Pathways

10 Acute Pain Management Modalities Cyclo-oxygenase inhibitors Non-specific COX inhibitors(classical NSAIDs) Selective COX-2 inhibitors, the coxibs Acetaminophen is probably COX-3 Opioids Local Anesthetics NMDA antagonists Ketamine, dextromethorphan

11 Tissue Trauma Cell Membrane Phospholipids Phospholipase Arachidonic Acid Endoperoxides C O X Cyclo-oxygenase Thromboxane Prostaglandins Toxic Oxygen Radicals Prostacyclin

12 Case Problem: Inadequate Analgesia with IV PCA after Open Cholecystectomy 45 yr. female c/o severe pain at rest and difficulty breathing due to incisional pain- 4 hrs. post-op IV PCA morphine: 1mg bolus, 5 min. lock-out 150 demands : 28 good has stopped using PCA because, it is making me sick(n/v) and it s not working received 25 mg gravol X 2 one hour ago which helped just a little with the N/V, but did make her quite groggy Solution? Between a rock and a hard place! as far as the use of opioids goes.

13 Case Problem: Inadequate Analgesia with IV PCA after Open Cholecystectomy Problem: Patient unable to attain required morphine blood level due to intolerable side-effects (N/V, sedation) Solution: Administer COX-inhibitor Toradol IV/IM or Naproxen 500 mg PR Q12H, this may be changed to 250 mg PO TID with meals once eating Control N/V Stemetil, Ondansetron, Decadron May need to consider changing opioid i.e. Demerol Local Anesthetics: intercostals, paravertebral, epidural

14 Analgesia with Opioids alone The harder we push with single mode analgesia, the greater the degree of side-effects Side-effects Analgesia

15 Multi-modal Analgesia With the multimodal analgesic approach there is additive or even synergistic analgesia, while the sideeffects profiles are different and of small degree. Analgesia Side-effects

16 The rationale for COX-Inhibitors in acute pain management The problem with the Little Pain Little Gun, Big Pain Big Gun Approach With opioids, analgesic efficacy is limited by sideeffects Optimal analgesia is often difficult to titrate >10 fold variability in opioid dose:response for analgesia in opioid naïve patients! factors add to the difficulty Opioid tolerance, anxiety, obstructive sleep apnea, sleep deprivation, concomitantly administered sedative drugs

17 The rationale for COX-Inhibitors in acute pain management The problem with the Little Pain Little Gun, Big Pain Big Gun Approach Patient Safety!! If the Big Gun is failing due to dose limiting sedation/respiratory depression, the addition at that time of the Little Gun may kill the patient.

18 Case Problem: Severe Respiratory Depression after Toradol? Healthy 34 yr. patient c/o severe incisional pain in PACU after ovarian cystecomy Received 200 g fentanyl with induction and 10 mg morphine during case PCA morphine started in PACU, plus nurse supplements totaled 26 mg in 90 minutes Still c/o pain, 30 mg Toradol IM given with some relief after 15 minutes, so patient sent to ward 60 minutes later found unresponsive, cyanotic, RR 4/min.

19 Case Problem: Severe Respiratory Depression after Toradol? Pharmacodynamic drug interaction between morphine and COX-inhibitor morphine s respiratory depressant effect opposed by the stimulatory effects of pain, busy PACU environment COX-inh. decreases pain, morphine s effect unappossed Gain control of acute pain with fast onset, short acting opioid(fentanyl) Add COX-inhibitor adjunct early Monitor closely for sedation and respiratory depression after pain is alleviated by any means

20 Analgesia with Opioids alone The harder we push with single mode analgesia, the greater the degree of side-effects Pain Opioid Side-effects Resp Depression Analgesia Opioid

21 The rationale for COX-Inhibitors in acute pain management CONCEPT # 1 The foundation of all acute pain Rx protocols. First on : last off sole agent in mild /moderate pain Analgesic efficacy is limited inherently ceiling effect for analgesia exists, but toxicity may continue to increase with increasing dosage

22 The rationale for COX-Inhibitors in acute pain management Opioid dose sparing of 30 50% Less c/o opioid S/E Dose:response is quite uniform from patient to patient S/E and contra-indications well described

23 The rationale for COX-Inhibitors in acute pain management Improved pain scores, especially with activity Greater patient satisfaction Safer for the patient

24 The rationale for pre-operative administration of COX-inh. The benefits of Pre-emptive Analgesia Goal: prevent the establishment of peripheral and central sensitization ( wind-up ), conditions that lead to an augmented response to pain stimuli i.e. prevention of hyper-algesic state Requirements: the analgesic must be pharmacologically active at the time of surgical incision and it s activity must be maintained perioperatively. ( > 1 hr. pre-op for PO/PR COX-inh)

25 Why a Selective COX-2 inhibitor? Equivalent analgesic efficacy with nonselective COX-inhibitors No effects on platelets! 0, ZIPPO Much reduced incidence of upper GI S/E compared to non-selective Duration of action about 24 hr.

26 Cyclo-oxygenase inhibitors Concept # 2 All patient having surgical procedures associated with post-operative pain should receive a pre-emptive COX inhibitor, provided there are no patient contraindications. COX-2 for everyone probably the safest and easiest to organize.

27 The Opioids We have to stop trying to put every patient in the analgesic dose box Meperidine 75 mg IM Q4H prn Tylenol #3 1 2 PO Q4H prn

28 Opioids What are the factors that determine the dose of opioid we choose?

29 Opioids The dose of opioid administered is dependant upon multiple factors Pharmacological tolerance to opioids? Route of administration Age PO, IM/SC, IV bolus, intrathecal Weight Severity of pain

30 Opioids A dose of opioid that is inadequate for patient A can lead to significant S/E or even death in patient B.

31 Opioids Pharmacokinetic + Pharmacodynamic patient to patient variability results in1000 % variability in opioid dose requirements Concept # 1 opioid dosage must be individualized therefore, if parenteral therapy indicated, IV PCA much better suited to individual patient needs than IM/SC

32 Patient Controlled Analgesia with Intravenous Opioids IV PCA: morphine golden standard, pruritus a common problem meperidine a little faster onset than morphine normeperidine a toxic metabolite is a problem for patients with decreased renal function or using large dosages for more than a few days hydromorphone less confusion in elderly patients?

33 PCA order parameters Bolus dose Lock-out Interval Continuous infusion One hour max. limit

34 Opioids Issue With parenteral opioids the patient may experience intolerable side effects before adequate analgesia is attained

35 Opioids CONCEPT # 2 Targeted regional administration of opioid results in enhancement of the therapeutic index (ratio of analgesia/side effects)

36 The proper use of oral opioids The limitations of combination drugs Codeine is a pro-drug Potent oral opioids are under-utilized Offer around the clock not prn In stable situations long acting, slow release formulations may be indicated

37 The Limitations of Tylenol # 3 Codeine is a pro-drug codeine is methylated morphine and needs to be de-methylated to active morphine (up to 10% of patients may not be able to convert codeine to morphine), on the other hand, some patients may over convert and be sensitive Net result is unpredictability

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39 The Limitations of Tylenol # 3 The problem with combination drugs The codeine dose is limited by the maximum allowed dose for acetaminophen 4 grams/day = 12 tabs/day 12 X 30 mg = 360 mg codeine = 60 mg morphine 60 mg PO = parenteral morphine Equals about 1 mg/hr IV/s.c. Adequate for moderate pain in average patient? Net result is limited efficacy

40 The Limitations of Tylenol # 3 The problem with combination drugs Acetaminophen therapy may be limited by intolerance to codeine Patient sensitive to codeine may only want to take 1 T#3 or even 1/2. If all they can tolerate is 15 mg of codeine Q4H, the patient is not receiving the benefit of optimum dose of acetaminophen

41 The Limitations of Tylenol # 3 The constipation problem Codeine may be more constipating than other opioids The codeine allergy problem True immunological allergy is extremely rare > 99% of allergy are sensitivities N/V, excessive sedation, confusion Need to perform adequate drug history, otherwise problems may arise when an even more potent opioid, such as Percocet is substituted for T#3.

42 The Limitations of Tylenol # 3 1/ Codeine is a pro-drug 2/ The problem with combination drugs a. The codeine dose is limited by the maximum allowed dose for acetaminophen b. Acetaminophen therapy may be limited by intolerance to codeine 3/ The constipation problem 4/ The codeine allergy problem

43 Solution to the T #3 limitations Provided codeine works in your Patient The oral analgesic ladder T#3 T#3 Oxy 5 mg T#3 T#3 T#3 T T T

44 Solution to the T #3 limitations Every 12 hours COX-2 inhibitor Long Acting Opioid For breakthough pain Regular opioid PO Q4h prn Acetaminophen 650 mg PO Q4h prn

45 Opioids *Cancer Pain Monograph (H&W, 1984) CONCEPT # 3 Under utilization of high efficacy PO opioids PO opioid equivalence of 10 mg morphine IM/SC * morphine 20 mg codeine 120 mg hydromorphone 4 mg meperidine 200 mg oxycodone 10 mg

46 Opioids Dilaudid 1 4 mg PO/IM/IV Q4H prn NOT! This represents up to 30 fold range in peak effect in any given patient 1 mg PO mg IV bolus homeopathic dose ---- potentially lethal

47 Opioids: Rational multi-route orders? Foundation of Acetaminophen/COX-inh. Morphine 5-10 mg PO Q4h prn Morphine mg s.c. Q4h prn Morphine 1-2 mg IV bolus Q1h prn Hydromorphone 1-2 mg PO Q4h prn Hydromorphone mg s.c Q4h prn Hydromorphone mg IV Q1h prn

48 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 mg/kg IV with induction of general anesthesia has pre-emptive analgesic effects - less pain and less opioid use post-op Ketamine mg IV bolus for analgesia in post-surgery/ trauma patient - Ketamine as co-analgesic - combined 1:1 with morphine IV PCA. Better analgesia, less S/E Dextromethorphan 45 mg PO Q12H

49 Concluding Remarks The foundation of all acute pain Rx protocols is a COX-Inhibitor First on : last off Opioid dosage must be individualized A dose of opioid that is inadequate for patient A can lead to significant S/E or even death in patient B. Limitations of Tylenol # 3

50 Texts Managing Pain. The Canadian Healthcare Professional s Reference Edited by Roman Jovey MD Endorsed by the CPS Available free from Purdue Pharma Medical Pharmacology by Katzung (Lange Series)