Adverse Effects Caused By Postoperative Pain
1-Surgery involving the upper abdomen or
thorax produces a number of pulmonary
changes including :
2. Incisions involving upper abdomen cause:
Reflex ↑ in tone in the abdominal muscles
↓ in diaphragmatic function, the result is
↓ pulmonary compliance,
inability to breathe deeply or cough
forcefully, & in some cases,
retention of secretions,
3- muscle tone is a contributing cause of ↑ O2
consumption & ↑ lactic acid production.
4- Distended bowel associated with postoperative
ileus or tight binders or dressings may further
5- Fear of producing or aggravating pain can
cause patients to avoid breathing deeply or
- Pain causes stimulation of sympathetic
neurons & subsequent:
↑ stroke volume,
↑ cardiac work,
↑ myocardial O2 consumption.
Risk of myocardial ischemia or infarction
may be ↑ as is the risk of DVT, when fear of
III- Gastrointestinal and Urinary
- Ileus, nausea, & vomiting following surgery
can occur for a number of reasons that
that including nociceptive impulses from
viscera & somatic structures.
Pain can also cause hypomotility of the
urethra & bladder and consequent
difficulty with urination.
IV-Neuroendocrine and Metabolic
Suprasegmental reflex responses to pain :
↑ sympathetic tone,
↑ hypothalamic stimulation,
↑ catecholamine &
↑ catabolic hormone secretion
(cortisol, ACTH, ADH, GH, cAMP, glucagon,
aldosterone, renin, angiotensin II),
↓ secretion of anabolic hormones
The effects of these changes include:
Na & H2O retention,
↑ blood glucose, free fatty acids,
↑ ketone bodies, and lactate.
Metabolism and oxygen consumption are ↑ &
metabolic substrates are mobilized from
A catabolic state and negative, nitrogen
balance result if the process continues.
-Postoperative pain is a major source of fear &
anxiety in hospitalized patients.
-When prolonged, it can lead to anger, resentment,
an adversarial relationship with doctors & nurses
who are perceived to be withholding pain relief.
-Insomnia may accompany the process with further
detriment to recovery.
-In some cases, ↑ pain reporting may represent an
attempt of patients to obtain pharmacologic relief
for these problems.
Factors That Modify
1- The site, nature, and duration of surgery
2- The type and extent of the incision and other
3- The physiologic and psychological makeup
of the patient
4- The preoperative psychological physiologic,
and pharmacologic preparation of the patient
5- The presence of complications related to the
6- The anesthetic management before, during,
and after surgery
7- The quality of postoperative care
8- Preoperative treatment to eliminate painful
stimuli prior to surgery
By considering how each of these factors
applies to individual patients, optimal care
becomes more likely
Pharmacology Of Postoperative Pain
A. Nonopioid analgesics:
like Aspirin, Acetaminophen, and NSAIDs
used to treat minor or moderate acute
1- The mechanism of analgesic effects
is most likely inhibition of prostaglandin-mediated
amplification of chemical and mechanical irritants
on the sensory pathways.
short-term therapy include:
Long term therapy include:
central nervous system disturbances
(usually reversible in 24-48 hours after
discontinuation of NSAIDs; lasts about
1week after discontinuation of aspirin).
4. Clinical uses of Nonopioid analgesics
are limited to treatment of events associated
with sensitizing effects of prostaglandins:
B. Opioid analgesics
Like : Morphine, Pethidine and Fentanyl
Used to treat severe postoperative pain
1- The mechanism of analgesic effects
is due to interaction with stereoselective
Agonist-antagonist opioids may exhibit altered
affinity for opioid receptors, accounting to the
potential of these drugs to reverse the effects of
-Oral Absorption may be extensive, but availability of
the drug may be limited by extensive first-pass
-Distribution of the drug depends on its lipid solubility.
-Biotransformation followed by renal Elimination of conjugated metabolites (morphine-6-glucuronide is an active metabolite) is the primary mode of elimination.
a. Physical dependence and analgesic
tolerance are not generally a problem when
opioids are used short term.
b. Respiratory depression is more likely when
the opioid is administered intravenously in
high doses and in the absence of pain.
4. Clinical uses.
Opioids remain the primary pharmacologic
therapeutic agents for moderat to severe
Methods of Treating Postoperative Pain
1- Systemic Opioids (IM ,SC,IV)
2- I.V. patient-Controlled Analgesia ( PCA )
3- Intraspinal Opioids
II- Local anesthetics
A-Peripheral nerve blocks
1- Local infiltration.
2-Intra-articular : bupivacaine up to 100 mg.
3-Intercostal : bupivacaine with or without epinephrine; perform
in the midaxillary or posterior axillary line; risk is
pneumothorax; cryoanalgesia lasts 1-3 months.
4-Ilioinguinal : pain relief following inguinal or femoral
herniorrhaphy, appendectomy, procedures on the scrotum)
6-Brachial plexus (continuous analgesia using bupivacaine
0.25% at 6-10 ml•h-1)
B-Regional Intravenous Anesthetic Technique.
C- Neuraxial Block (spinal , epidural),
II- Local anesthetics with Opioids
5- Epidural Local Anesthetic-0pioid Mixtures
6- Patient-Controlled Epidural Analgesia
7- Intra - Articular Analgesia
III- Nonopioid Analgesics
1- Nonsteroidal Anti-Inflammatory Drugs
2-Transcutaneous Electrical Nerve Stimulation
3-Psychological and Other Methods
Routes Of Analgesic Delivery OF Opioids
1- Oral : unpredictable onset and duration; requires
a functioning gastrointestinal tract
2- Transdermal ,Transmucosal
3- Intramuscular administration of analgesics by
this route on a 3-4 hour basis results in plasma
concentrations that exceed the analgesic
requirements for only about 35% of the dosing
4-Intravenous (Bolus. Infusion, PCA )
intermittent versus continuous; PCA
5-Central neuraxial analgesia
1. Intrathecal (spinal)