Thread: Post operative pain-Management

Postoperative Pain




Adverse Effects Caused By Postoperative Pain


I-Respiratory

1-Surgery involving the upper abdomen or
thorax produces a number of pulmonary
changes including :
VC
Vt
Vr,
FRC
& FEV1

2. Incisions involving upper abdomen cause:
Reflex ↑ in tone in the abdominal muscles
during expiration
↓ in diaphragmatic function, the result is
↓ pulmonary compliance,
muscle splinting,
inability to breathe deeply or cough
forcefully, & in some cases,
hypoxemia,
hypercarbia,
retention of secretions,
atelectasis,
&pneumonia.

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
impair ventilation,
5- Fear of producing or aggravating pain can
cause patients to avoid breathing deeply or
coughing


II-Cardiovascular

- Pain causes stimulation of sympathetic
neurons & subsequent:
Tachycardia,
↑ stroke volume,
↑ cardiac work,
↑ myocardial O2 consumption.
Risk of myocardial ischemia or infarction
may be ↑ as is the risk of DVT, when fear of
aggravating pain:
↓physical activity,
venous stasis,
platelet aggregation



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
(insulin, testosterone).


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
storage depots.
A catabolic state and negative, nitrogen
balance result if the process continues.


V-Psychological

-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
Postoperative Pain


1- The site, nature, and duration of surgery
2- The type and extent of the incision and other
surgical trauma
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
surgery
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
postoperative pain

1- The mechanism of analgesic effects
is most likely inhibition of prostaglandin-mediated
amplification of chemical and mechanical irritants
on the sensory pathways.


Adverse effects

short-term therapy include:
gastrointestinal discomfort,
Long term therapy include:
central nervous system disturbances
(dizziness, drowsiness),
prolonged bleeding
(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:
musculoskeletal,
post-traumatic,
inflammatory pain.

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
opioid receptors
Agonist-antagonist opioids may exhibit altered
affinity for opioid receptors, accounting to the
potential of these drugs to reverse the effects of
an agonist.

2-Absorption/
biotransformation/
elimination.
-Oral Absorption may be extensive, but availability of
the drug may be limited by extensive first-pass
metabolism.
-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.

3-Adverse Effects
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
postoperative pain



Methods of Treating Postoperative Pain

I- Opioid
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)
5-Penile
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- Ketamine

V-Other methods

1-Cryoanalgesia
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
interval).
4-Intravenous (Bolus. Infusion, PCA )
intermittent versus continuous; PCA
5-Central neuraxial analgesia
1. Intrathecal (spinal)
2. Epidural

thanks a lot