Chapter 28 Perioperative Nonopioid Infusions for Postoperative Pain Management Flashcards
KEY POINTS 1. Most of the randomized studies on perioperative intravenous (IV) ketamine infusion showed beneficial effects. The surgeries studied included abdominal, gynecologic, or spine surgery. 2. Ketamine IV infusion appears not to be beneficial when total IV anesthesia is the technique of intraoperative anesthesia. 3. The addition of a ketamine infusion in patients who had patient-controlled epidural analgesia resulted in less opioid requirement and probably a lower incidence of chroni
Ketamine
a noncompetitive N-methyl-D-aspartate glutamate
receptor antagonist and a sodium channel blocker
racemic ketamine
S(+) and R(–) stereoisomers. The S(+) ketamine has
four times greater affinity for the NMDA receptor than the
R(–) ketamine
Ketamine half-life
80 to 180 min.
Ketamine metabolite
norketamine has a longer half-life and is one-third as potent as the parent compound
Effects of Ketamine
analgesic properties at low doses, It does not depress the laryngeal protective reflexes, does not suppress cardiovascular function in the
presence of an intact nervous system, causes less depression
of ventilation compared to opioids, and may stimulate
respiration.
The analgesic effects of ketamine occurs at plasma concentrations of
100 to 150 ng.ml–
undesirable characteristics of ketamine
postoperative malaise, accumulation of metabolites, development of tolerance, cardiovascular excitation, and the occurrence of psychotomimetic side effects
beneficial effects of a low-dose ketamine
infusion
appears to improve the efficacy of epidural analgesia. It does not seem to have any effect when the anesthetic technique is total IV anesthesia where moderate amounts of intraoperative opioid are used.
IV ketamine may find its use as an adjunct in opioidtolerant
patients, or in patients with a higher incidence of chronic postsurgical pain such as thoracotomy, inguinal
herniorraphies, limb amputation procedures, or even
mastectomies
Lidocaine peripheral and central effects suitable for the relief of pain.
Centrally, it has been shown to modify the neuronal responses in the dorsal horn and selectively suppress synaptic spinal transmission
by decreasing C-fiber–evoked activity in the spinal cord
The beneficial effects of IV lidocaine infusion were not
duplicated in patients who had
total hip replacement or
coronary artery bypass graft surgery. The lack of beneficial effect of IV lidocaine infusion may not be evident when the surgical trauma is minimal as in ambulatory surgery or in surgeries where there is a moderate component of neuropathic pain such as in total hip surgery or in thoracic surgery.
Benefit of IV lidocaine
The improved rehabilitation was supported by decreased postoperative pain at 24 hr after surgery, lower incidence of nausea and vomiting, and
shorter duration of ileus.
IV lidocaine has been shown to attenuate the increased levels of proinflammatory cytokines which induce
peripheral and central nervous system sensitization leading to hyperalgesia
IV lidocaine beneficial in what type of surgeries
Abdominal surgery
Pelvic: gynecologic, urologic
Naloxone
a pure mu-receptor antagonist,
Naloxone Effects
reversing the analgesia from the opioid. Naloxone
infusion has been utilized to decrease the incidence of
nausea, vomiting, respiratory depression, and urinary
retention after epidural and intrathecal opioids
naloxone intravenous infusion
at 10 mcg.kg–1.hr–1 reduced the duration and quality of
analgesia from epidural morphine or fentany
biphasic or dual modulatory effect of naloxone
small doses of naloxone produced analgesia while large
doses resulted in hyperalgesia.
mechanisms of analgesic effect of naloxone
maybe related to the release of endorphins or displacement
of endorphins from receptor sites not pertinent to analgesia. another possibility although this upregulation phenomenon
has been demonstrated after prolonged naloxone infusion
(7 days). At higher doses, naloxone blocks the action of the released or displaced endorphin at the postsynaptic receptor.
Naloxone half life
Naloxone has
an alpha half-life of 4 min and a beta half-life of 55 to
60 min
indication for IV naloxone infusion
control the side effects of
neuraxial opioids.
Benefit of wound infusions
reduce postoperative pain, diminish opioid intake and opioid-related side effects, and increase patient satisfaction
effect of wound infusion after abdominal surgery
appears to depend on where the wound catheter is placed
Subcutaneous placement restricts the blockade of parietal nociceptive inputs to the superficial layer of the abdominal wall, while subfascial placements
block the fascia and peritoneum, which are richly innervated tissues
Risk of wound infusion
A risk from the technique is
direct tissue toxicity such as myotoxicity,95 but this possibility
from subcutaneous, subfascial, or preperitoneal
local anesthetic infusions is rare.
