Acute Perioperative Pain

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Acute Perioperative Pain
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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.

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PERIOPERATIVE PHYSICIAN

• A physician anesthetist as a consultant and
  therapist throughout an institution as well as a
  highly expert in the operating room.

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Pain

• An unpleasant sensory and emotional experience
  associated with actual or potential tissue damage.

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Pain Pathways

• Tissue damagegtgtgtAlgesic substanses
  releasegtgtgtNoxious stimuligtgtgtA delta and C
  fibersgtgtgtto theNeuraxisgtgtgtMany toAnt.andAnterolat.
  HornsgtgtgtSegmenal reflex responses , and others
  via the Spinothalamic and Spinoreticular
  tractsgtgtgtSuprasegmental and cortical responses.

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• Segmental reflex responses
• Increased skeletal muscle tone , Increased oxygen
  consumption , Lactic acid production

• Suprasegmental
• reflex responses
• Increased Sympathetic tone , Hypothalamic
  stimulation.

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Adverse effects of perioperative pain
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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

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Cardiovascular effects

• Paingtgtgt Increased SNS TONE gtgtgt
• Tachycardia , increased SV ,Cardiac work and
  Myocardial O2consumptiongtgtgt Myocardial Ischemia
  and infarct.
• Fear of aggravating Pain gtgtgt Reduced physical
  activity , Venous stasis gtgtgt Risk of DVT .

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Gastrointestinal and Urinary effects

• Ileus , Nausea and Vomiting following Surgery.
• Pain gtgtgt Hypomotility of the Urethra and Bladder.
• In the case of Ileus , may prolong hospital stay.
• Postoperative Epidural anesthesia gtgtgt Speed the
  return of bowel function.

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Psychologic responses

• Pain gtgtgtFear and Anxiety.
• When prolonged gtgtgtAnger and adversial
  relationship with Doctors and Nurses .
• In some cases , Increased pain reporting .

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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 .

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Preemptive Analgesia

• Antinociceptive treatment of that prevents the
  establishment of altered central prossesing,
  which amplifies postop. Pain.
• Windupfunctional changes in the dorsal horn
  because of pain .
• This type of therapy ,in addition to reducing
  acute pain ,attenuates chronic postop. Pain.

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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.

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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.

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Patient-Controlled Analgesia

• PCA was originally developed to minimize the
  effects of pharmacokinetic and
• Pharmacodynamic variability among patients.
• A negative feedback loop existsexperiencing
  paingtgtgtMedication demandedgtgtgtReducing pain gtgtgtNo
  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.

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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.

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• 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.

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Continuous background infusion

• Advantages
• 1-more constant serum levels.
• 2-imrpoved analgesia especially during sleep.
• 3-modulation of the final opioid dose by patients.

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• 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.

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• 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.

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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.

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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.

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Regional Anesthetic Techniques

• Advantages
• Positive respiratory,cardiovascular and
  neuroendocrine effects reduced thromboembolic
  complications and blood loss and reduced
  convalescence

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• 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.

Interscalene
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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.

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Intraspinal analgesia

• With
• Opioids
• Opioid-L.A. mixture
• Ketamine
• Clonidine
• Neostigmine

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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.

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• 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.

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• 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.

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

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• To prevent serious injury or death there is no
  substitute for a high level of vigilancegtgtgt
  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 .

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

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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.

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• 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.

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• 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.)

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• 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).

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• 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.

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

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• 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.

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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.

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

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• 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.

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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.

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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.

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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 gtgtgtinhibiting breakdown
  of actylcholinegtgtgtanalgesia.

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• 50 micro gr.gtgtgtno effect.
• 150 micro gr.gtgtgtmild nausea.
• 500-750 micro gr.gtgtgtleg weakness, decreased DTR,
  and sedation.
• 750 micro gr.gtgtgtanxiety, increased BP and HR, and
  decreased ETCO2.

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• Intra spinal analgesia in patients receiving
  anticoagulants.

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• 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.

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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.

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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.

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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.

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

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Patient-controlled epidural analgesia (PCEA)
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• 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.

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Combined spinal-epidural technique
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• Has become popular in obstetrics and in operating
  room.
• Advantage rapid onset of surgical anesthesia
  with availability to continue analgesia for post
  op. period.

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• 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.

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Role of the anesthesiologist in providing
intraspinal analgesia
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Intra-Articular analgesia

• Following arthroscopic surgery, a combination of
  systemic Ketorolac and intra-articular
  bupivacaine decreased analgesic requirement and
  pain.

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Non-opioid analgesics

• 1-NSAID,s
• 2-N2O.
• 3-Ketamine.

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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).

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• 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.

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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 occurgtgtgtrisk of aspiration.

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• Long term administration causes bone marrow
  suppression and leukopenia (reversible when
  detected early).
• Entonox50mixture of N2O with oxygen.

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Ketamine

• Some concerns have limited its use
• 1-sedation.
• 2-emergence delirium.
• 3-hallucinations.

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• 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.

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Cryoanalgesia

• Temp.s between -5 and -20causes 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.

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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.

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• 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.

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

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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.

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

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Perioperative analgesia in special populations
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Pediatric patients

• Misconceptions about pain in children are common
  (e.g. children dont 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.

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• 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.

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

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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.

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

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• 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 clearancegtgtgtthey doses
  must be decreased.

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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.

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Advantages of regional anesthesia

• Minimizing physiologic trespass.
• Pharmacologic simplicity.
• Reduced blood loss.
• Fewer thromboembolic complications.
• Reduced stress response.
• Less confusion.
• Less postoperative pain.

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Postoperative delirium (POD)

• Incidence7-61.
• 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.

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

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

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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.

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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.

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

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ROLE OF THE ANESTHESIOLOGIST IN PERIOPERATIVE
PAIN MANAGEMENT
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• 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.

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Perioperative pain management services
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• 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.

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