acute perioperative pain

2. Acute Perioperative Pain

3. Fundamental Considerations Millions of patients worldwide undergo surgery. Although developing more effective techniques for postoperative analgesia, many patients experience pain. The concept of perioperative pain management by anesthesiologists is now established in North America and in many other parts of the world.

4. PERIOPERATIVE PHYSICIAN: A physician anesthetist as a consultant and therapist throughout an institution as well as a highly expert in the operating room.

5. Pain : An unpleasant sensory and emotional experience associated with actual or potential tissue damage.

6. Pain Pathways: Tissue damage>>>Algesic substanses release>>>Noxious stimuli>>>A delta and C fibers>>>to theNeuraxis>>>Many toAnt.andAnterolat.Horns>>>Segmenal reflex responses , and others via the Spinothalamic and Spinoreticular tracts>>>Suprasegmental and cortical responses.

7. Segmental reflex responses: Increased skeletal muscle tone , Increased oxygen consumption , Lactic acid production Suprasegmental reflex responses: Increased Sympathetic tone , Hypothalamic stimulation.

8. Adverse effects of perioperative pain:

9. Respiratory effects: Surgery of upper abdomen or thorax: Reduced V.C. ,Vt ,R.V. ,F.R.C. ,F.E.V.1 . Increased abdominal muscle tone +Decreased diafragmatic function , Reduced pulmonary function , Inability to breath deeply or cough , And in some cases Hypoxemia Hypercarbia , Retention of secretions , Atelectasis and Pneumonia . Distended bowel because of ileus and tight binders or dressings may further impair ventilation

10. Cardiovascular effects:

11. Gastrointestinal and Urinary effects: Ileus , Nausea and Vomiting following Surgery. Pain >>> Hypomotility of the Urethra and Bladder. In the case of Ileus , may prolong hospital stay. Postoperative Epidural anesthesia >>> Speed the return of bowel function.

12. Psychologic responses: Pain >>>Fear and Anxiety. When prolonged >>>Anger and adversial relationship with Doctors and Nurses . In some cases , Increased pain reporting .

13. Factors that modify perioperative pain : 1- Site ,nature and duration of surgery. 2- Type and extent of incision. 3- Physiologic and psychologic makeup of the patient. 4- Pre operative preparation of the patient. 5- Presence of complications of surgery. 6- Anesthetic management. 7- Quality of perioperative care. 8- Preoperative treatment of painful stimuli .

14. Preemptive Analgesia : Antinociceptive treatment of that prevents the establishment of altered central prossesing, which amplifies postop. Pain. Windup:functional changes in the dorsal horn because of pain . This type of therapy ,in addition to reducing acute pain ,attenuates chronic postop. Pain.

15. Treatment methods : 1-Systemic opiods. 2-Patient-controlled analgesia. 3-Regional anesthetic techniques . . a : Intraspinal analgesia. b :Patient-controlled epidural analgesia. c :Combined spinal-epidural technique. 4-intraarticular analgesia. 5-Nonopioid analgesics. 6-Cryoanalgesia. 7-T.E.N.S. 8-Psychologic and other methods.

16. Systemic Opioids : Analgesic effects of opioids : via receptors in the CNS. Roots of administeration :I.M. ,I.V. ,Transdermal ,Oral ,Topical ,I.V. regional ,Perineural ,etc. I.M. root is the most treatment choice after surgery. The� As Needed� part of the order is often interpreted to mean �As little as possible� . No relation exists between Gender and opioid requirement.

17. Patient-Controlled Analgesia: PCA was originally developed to minimize the effects of pharmacokinetic and Pharmacodynamic variability among patients. A negative feedback loop exists:experiencing pain>>>Medication demanded>>>Reducing pain >>>No further demand . If Nurses, Relatives,or Parents assume responsibility for drug administration,or if using this device by the patient is for reasons other than pain relief ,this loop fails.

18. PCA devices : Consists of a microprocessor-controlled pump triggered by depressing a button . When pump is triggered ,a preset amount of drug is delivered into the patients I.V. line. Lockout interval :A specific period setted in the pump to prevent administration of an additional bolus.

19. Cases of respiratory depression during PCA use have been reported. Causes :advanced age, hypovolemia, large doses, use of background continuous-infusion mode. No difference in respiratory mechanics between PCA and IM opioids (FEV1,FRC,PFR)is seen.

23. Continuous background infusion: Advantages: 1-more constant serum levels. 2-imrpoved analgesia especially during sleep. 3-modulation of the final opioid dose by patients.

24. Disadvantages: 1-difficulty predicting the optimal infusion rate and thus the possibility of overdose . 2-loss of safety in sleeping patient. 3-more human errors.

25. Recommendations for use background continuous-infusion mode: 1-avoid routine use. 2-add this mode for specific indications e.g; pain during sleeping hours. 3-base the rate of infusion on 30-50% of demand mode. 4-decide if this mode is needed only at night or around the clock. 5-provide in-service education to ward nurses.

26. PCA via subcutaneous route: for conditions like: difficult I.V. access, no option for enteric analgesia,� Choice of opioids is the same. The concentration of the opioid solutions should be increased 5-fold to reduce their volume. The incremental doses and lockout intervals are the same.

27. Side effects of PCA: Nausea ,Vomiting ,Itching. Treated by changing opioid or using drugs that provide symptomatic relief. A pre printed set of standard orders can facilitate a uniform standard of care.

29. Regional Anesthetic Techniques: Advantages: Positive respiratory,cardiovascular and neuroendocrine effects; reduced thromboembolic complications and blood loss; and reduced convalescence

30. Interscalene brachial plexus blocks :analgesia for 12-24 hrs. Sciatic and Femoral n. blocks :similar results. Intercostal n. blocks : 6-12 hrs. analgesia. Administration of long acting L.A.s from a catheter into pleural cavity :unilat. Analgesia with little or no sensory block. L.A. infusion into Axillary sheath, Femoral sheath, and the vicinity of the Sciatic n.:analgesia and particularly useful to facilitate perfusion after extensive revascularization or reimplantation surgery, maintain a normal ROM after joint surgery, etc.

31. L.A. boluses or infusions : Advantages over parenteral opioids: Early ambulation, improve bowel function, higher arterial O2 tension, fewer pulmonary complications. For optimal results, the catheter tip should be near the segments innervating the insicision.

32. Intraspinal analgesia: With: Opioids Opioid-L.A. mixture Ketamine Clonidine Neostigmine

33. Opioids: Initial reports in 1979. Single injection of intrathecal Morphin provides about 24 hrs. analgesia. Epidural root uses more, because: Popularity of technique during surgery, ability to leave catheter in place, familiarity with technique, no risk of PDPH.

34. In one study patients receiving epidural morphine reported superior analgesia, ambulated sooner, had fewer pulmonary complications, had earlier return to bowel function, and discharged from hospital earlier than patients receiving I.M. morphine.

37. Elderly patients require remarkably small doses of epidural morphine. Effective 24-hr. morphine dose= 18 � age(0.15) . Fentanyl is useful when rapid onset of epidural analgesia is important. Epidural meperidine is widely used in some parts of the world and as with other opioids, respiratory depression can occure.

38. Agonist-antagonist opioids (e.g. buprenorphine) are popular in some places. This family of drugs offers no significant benefits over pure opioid agonists.

39. To prevent serious injury or death there is no substitute for a high level of vigilance>>> checking the rate and depth of respiration and general status and level of consciousness at frequent intervals by a nurse and respiratory monitors with alarms. A preprinted set of orders can facilitate a high standard of care .

41. Delegation of all responsibility for pain control to one group of physicians minimizes errors.

42. Respiratory depression early: In the first two hrs. Is the result of vascular uptake and redistribution. Delayed: Between 6 and 12 hrs. Consequent of rostral spread of opioid in CSF to respiratory center in the floor of 4th. Ventricle.

43. It is not known that severe resp. depression is greater after intraspinal opioid . The risk of delayed resp. depression appears to be greatest early in the course of therapy and there is no reported cases occurring later than 24 hrs. Respiratory rate is not an adequate indicator of ventilatory status.

44. Healthy volunteers breathing CO2 mixtures will lose consciousness at press. levels of about 80mmHg. Any deterioration in level of consciousness should be assumed to resp. depression until disproved by ABG analysis. Immediate treatment: support of ventilation and/or Naloxone in titrated doses(0.1 mg.)

45. Pruritus is a common side effect and is seen more in obstetrics patients. Face is a common site of itching. Although it is not due to histamine release, antihistamines provide symptom relief. Nalbuphine is also of value. Naloxone is consistently effective (repeated doses or infusion).

46. Urinary retention is higher in volunteers than in patients and in men than in women. Naloxone prevents or reverses it but may require doses that antagonizes analgesia. Most patients are able to void spontaneously when the catheters are removed.

47. Nausea and vomiting: due to rostral spread of opioid in CSF to the vomiting center and the CTZ . Treatment: first line:antiemetics (may produce unwanted sedation and resp. depression ) , Scopolamine patches. Second line: I.V.droperidol, Ondansetrone.

48. Sedation produced by intraspinal opioids may be the result of spread of the drug in CSF to receptors in the thalamus, limbic system or cortex and hypercarbia can augment it. Epidural buprenorphine 0.15 mg. produces prolonged depression of the CO2 response that lasts 8-12 hrs.

49. Opioid-L.A. anesthetic mixtures The rational: using lower doses of each drug, preserving effecting analgesia, reducing side effects, and some degree of blunting stress response. Opioid in the mixture: inhibiting the release of substance P in the dorsal horn. L.A. in the mixture: blocking transmission of impulses at the level of the nerve axonal membrane.

50. Bupivacaine is the most widely used L.A. .

52. It is possible that dilute Ropivacaine infusions will provide analgesia equivalent to that provided by Bupivacaine with less impact on motor function. The most common opioid used in combination with, are Fentanyl and Morphine. Epidural opioids do not appear to mask complications (e.g. compartment synd.) but in combination with L.A.s it is not known.

53. Ketamine: Produces analgesia via interaction with cholinergic, adrenergic, and serotonergic systems. Side effects: sedation, blurred vision, tachycardia, hypertension, and hallucinations. In some studies on baboons : neurotoxic changes. The routine use of intrathecal ketamine in humans is not recommended.

54. Clonidine: If administered by the oral route can augment spinally mediated opioid analgesia. Epidural or intrathecal clonidine can provide effective analgesia alone. Intrathecal clonidine does not provide surgical anesthesia.

55. Neostigmine: Unlike with L.A.s unwanted axonal blockade does not occure, and unlike alpha-2 agonists is not a direct agonist stimulating all receptors of a certain type. Intrathecal neostigmine >>>inhibiting breakdown of actylcholine>>>analgesia.

56. 50 micro gr.>>>no effect. 150 micro gr.>>>mild nausea. 500-750 micro gr.>>>leg weakness, decreased DTR, and sedation. 750 micro gr.>>>anxiety, increased BP and HR, and decreased ETCO2.

57. Intra spinal analgesia in patients receiving anticoagulants.

58. The development of spinal hematomas is rare. Such hematomas have been reported spontaneously in patients exposed neither to anticoagulants nor neuraxial block. And have been reported in patients on low dose anticoagulant or neuraxial block alone. And have been reported in combination of both therapies together.

59. Evidence of safety: Spinal hematomas in patients undergoing major conduction block while receiving low-dose heparin (and LMWH) is very rare. Although epidural or spinal needle and catheter replacement and subsequent heparinization appears relatively safe, the risk of hematoma in patients who receive thrombolytic therapy is less defined.

60. Evidence of risk: In a study, 25% of patients with spontaneous spinal hematomas had a coagulopathy. In another study, in47% of patients with an epidural catheter, spinal bleeding occurred after removal of catheter.

61. Conclusions: Increasing the risk of hematomas with anticoagulants is not known. �The presence of anticoagulants, must be considered critical in the formation of spinal bleeding�. Whenever possible must correct defects in coagulation status before techniques.

62. If LMWH is using, the risk of thromboemboli because of omitting anticoagulants is greater than formation a spinal hematoma in presence of LMWH.

63. Patient-controlled epidural analgesia (PCEA)

64. The amount of morphine needed in this technique is lesser than in continuous epidural infusion or I.V. PCA. PCEA Fentanyl has been used successfully, but the results has no difference from I.V PCA. Hydromorphone is both used, with a 4- to 5-fold decrease in needed dose compared with I.V.PCA.

66. Combined spinal-epidural technique

67. Has become popular in obstetrics and in operating room. Advantage: rapid onset of surgical anesthesia with availability to continue analgesia for post op. period.

68. When an initial spinal anesthetic is initiated, testing the function of placed epidural cath. is impossible. Spreading epidural solutions from the hole in the meninges, and subsequent respiratory depresion. The combination routs of administering drug may cause respiratory depression.

69. Role of the anesthesiologist in providing intraspinal analgesia

71. Intra-Articular analgesia Following arthroscopic surgery, a combination of systemic Ketorolac and intra-articular bupivacaine decreased analgesic requirement and pain.

72. Non-opioid analgesics 1-NSAID,s 2-N2O. 3-Ketamine.

73. NSAID,s Advantages: no evidence of unwanted sedation, absence of tolerance, reduction in opioid related side effects. Act through inhibition of PG synthesis. NSAID,s can replace opioids in most patients, both immediately after surgery or later (late analgesia with ketorolac is similar with morphine).

74. In patients with PCA and parenteral ketorolac, opioid requirement, time to return of bowel function, and time to hospital discharge were reduced. Side effects of Ketorolac: bronchospasm, GI bleeding, altered platelet function, perioperative bleeding, and impairment of renal function.

75. Nitrous oxide: Useful, especially for painful experiences of short duration (dressing changes, debridements). Rapid onset of analgesia and rapid recovery. In concentrations of 30-50% is as potent as 10 mg. I.M. morphine. �Anesthesia� may occur>>>risk of aspiration.

76. Long term administration: causes bone marrow suppression and leukopenia (reversible when detected early). Entonox:50%mixture of N2O with oxygen.

77. Ketamine: Some concerns have limited its use: 1-sedation. 2-emergence delirium. 3-hallucinations.

78. Side effects may reduce with: Opioid and scopolamine premedication. Concomitant physostigmine. Small doses of barbiturates, benzodiazepines, or deroperidol. Ketamine may use in patients with opioid tolerance.

79. Cryoanalgesia: Temp.s between -5 and -20`causes disintegration of axons and breakdown of myelin sheaths while the perinurium and epinurium remain intact. Is used most common for thoracotomy pain and hernia repair pain. Residual neuropathic pain has been seen following cryoanalgesia.

80. Transcutaneous electrical nerve stimulation(T.E.N.S.) Uses both for chronic pain and acute perioperative pain. Advantages: absence of opioids side effects (resp. depression, sedation, nausea and vomiting, urinary retention) It is simple, noninvasive and free of toxicity.

81. The mechanism of analgesia by TENS is not known and it may be by: Modulation of nociceptive impulses in the spinal cord (gate control theory). Activation of inhibitory area in the brain stem. Stimulation of the release of endorphins, or a combination of these mechanisms. A placebo effect may play a role.

82. Complications are uncommon: Skin irritation from gel or adhesives. Contraindications: 1-pregnancy(first trimester). 2-cardiac pacemakers.

83. Psychologic and other methods: After surgery patients may suffer �discomfort� due to headache, NG tubes, drains, IV catheters, or anxiety, fear, and insomnia. Therapy of these problems may result in reporting of less �pain�. Preoperative discussion, reassurance and provision information results in less anxiety, less opioid use and shorter hospital stay.

84. Relaxation tapes prior to surgery results in less analgesic use and a smoother recovery.

85. Perioperative analgesia in special populations:

86. Pediatric patients: Misconceptions about pain in children are common (e.g. children don�t feel pain, or if it is felt it is not remembered. Pain causes suffering and psychologic abnormalities in children of all age. Special scales are available for young children (self reporting of pain). In preverbal children, the interpretation of behavior must be used to estimate intensity of pain.

87. Because of fear of IM injections alternatives are: sublingual, rectal and transdermal routs. I.V. PCA is effective in children. Caudal opioid analgesia can be used in children. Regional techniques: dorsal nerve block of the penis, or lidocaine jelly, or EMLA creams for circumcision, ilioinguinal and iliohypogastric nerve blocks for pains after orchiopexy and herniorrhaphy, etc.

88. NSAID,s are considered as adjuncts rather than as primary agents.

89. Elderly patients: The average age of surgical patients will increase in the future. Older patients have more complex cases than younger. PCA & PCEA is ineffective in some elderly patients because of their reluctance.

90. Treatment of perioperative pain in elderly remains inadequate because: Fear of complications associated with treatment of pain. Pain is reported less in elderly.

91. NSAID,s may have benefits in elderly because: Different site of action that may be more effective. Opioid sparing. An additional anti-inflammatory effect. But they have increased risk of side effects because of decreased renal clearance>>>they doses must be decreased.

92. Why elderly patients require less epidural morphine? 1-increased responsiveness of spinal cord opioid receptors. 2-higher CSF morphine levels. 3-Decreased effectiveness of neural barriers. 4-Overall decrease in CNS function.

93. Advantages of regional anesthesia: Minimizing physiologic trespass. Pharmacologic simplicity. Reduced blood loss. Fewer thromboembolic complications. Reduced stress response. Less confusion. Less postoperative pain.

94. Postoperative delirium (POD) Incidence:7-61%. More common after orthopedic surgeries. Most commonly appears on post operative day 3 or 4. Hallucinations in 40% of patients (often visual). Negative outcomes: increased hospital stay, increased demand on treatment resources, poorer postdischarge functional outcome.

95. Postoperative analgesia in elderly minimizes risk of POD. Many causes of POD: Metabolic, toxic, environmental, or infectious insultes.

96. Patients with chronic pain and /or chronic opioid use

97. General principles: 1-expect high self-reported pain scores. 2-base treatment decision on objective pain assessment (deep breathing, coughing, etc.). 3-recognize and treat nonnociceptive sources of suffering. Continue opioids for as long as is appropriate for acute pain.

98. Addiction: A chronic disorder characterized by compulsive use of a substance resulting in physical, psychologic, or social harm to the user and continued use despite that harm.

99. Clinical triad suggestive of addiction: 1-high self-reported pain scores. 2-high opioid use compared with other patients having similar procedures. 3-a relative absence of opioid-induced side effects.

100. PCA is not good for providing basal opioid replacement. PCA is good for extra opioids needed for postoperative pain.

101. ROLE OF THE ANESTHESIOLOGIST IN PERIOPERATIVE PAIN MANAGEMENT

102. Anesthesiologists are a logical choice to provide periop. Pain relief, because they are: 1-familiar with the pharmacology of analgesics and L.A.s. 2-aware of short- and long-term effects of drugs given intraoperatively. 3-knowledgeable about pain pathways and their interruption. 4-are skilled in techniques available to provide superior pain control.

103. Perioperative pain management services:

104. Surgeons may be reluctant to allow other physicians to assume responsibility for pain management. Departmental conferences and individual discussion are used to inform them of the potential benefits to their patients of a perioperative pain service.