Page 41 - CASA Bulletin of Anesthesiology 2019 Issue 6

Vol.6, No.6, 2019

DOI: 10.31480/2330-4871/104
ly leads to a plasma concentration of about 2 mcg/ml cular block and delayed emergence from anesthesia.
[37]. So there is an inbuilt margin of safety when ad- Mg potentiates neuromuscular blocking drugs and
ministering this dose. Cardiac arrest is possible with CNS depressants and these effects need to be tak-
extreme toxicity and given its low therapeutic index it en into consideration. The depth of neuromuscular
is wise to administer lidocaine by continuous infusion block should be carefully monitored and adequacy of
rather than by large intravenous bolus doses. If local neuromuscular reversal should be confirmed prior to
anesthetic systemic toxicity is suspected a bolus dose extubation.
of 1.5 ml/kg intralipid followed by an infusion of 0.25
ml/kg/min should be administered [35]. Regional blocks and centroneuraxial blocks
Gabapentin/Pregabalin Many procedures can be performed under region-
al or centroneuraxial anesthesia. The use of catheters
Gabapentinoids are derivatives of the inhibitory for ongoing post-operative infusion can greatly limit
neurotransmitter gamma aminobutyric acid (GABA). or entirely eliminate the use of perioperative opioids.
Both gabapentin 300 mg PO and pregabalin 150 Many perineural regional techniques like paravertebral
mg PO are effective analgesics that are also useful and pectoral nerve blocks have been used successfully
in neuropathic pain. Their use leads to lower pain [41]. Local wound infiltration with local anesthetic has
scores, reduced opioid consumption and opioid relat- become common in lower limb joint replacement sur-
ed side effects [38,39]. They can be continued into gery because of great efficacy and the absence of motor
the post-operative period. Excessive sedation, dizzi- block [42]. Transversus abdominis plane (TAP) blocks
ness and visual disturbances can be a problem with and the erector spinae plane (ESP) block for abdominal
high doses after prolonged periods. and thoracic surgeries lead to better analgesia and re-
Magnesium duced opioid use [43,44].
Magnesium (Mg) has analgesic action by regulating Mixed agonist/antagonist drugs acting on opioid
calcium flux into the cell and acting as an NMDA recep- receptors
tor antagonist. It also suppresses neuropathic pain. It Mixed agonist/antagonist drugs acting on opioid re-
has been shown to reduce the need for post-operative ceptors like dezocine and buprenorphine are generally
opioids and improve post-operative pain scores [40]. regarded as less addictive and respiratory depressant
The loading dose is 30-50 mg/kg and it may be followed than the full agonists but they may also have a lower
up by an intravenous infusion of 10 mg/kg/hr. analgesic ceiling than the full agonists. These drugs do,
Side effects are hypotension and bradycardia that however, offer significant advantages in the treatment
respond readily to standard therapy but are more of opioid addicted patients. Dezocine has been shown
common when higher doses are administered. When to alleviate morphine-induced dependence and im-
using Mg intra-operatively it is important to reduce prove patient experience in both preclinical and clinical
the amount of muscle relaxants and anesthetic drugs studies [45,46].
that are administered to prevent residual neuromus- In summary, the perioperative use of opioids has

Table 2: Risk and benefits of opioid and non-opioid analgesics.
Opioid Analgesia Opioid free/ Opioid Sparing Analgesia
Risks Respiratory depression Bradycardia with dexmedetomidine
Need for post-op ventilation with Hepatic damage with acetaminophen
ventilator associated pneumonia Bleeding, renal impairment and bronchospasm with ketorolac
Addiction Hallucinations, tachycardia and addiction with ketamine
Nausea & Vomiting Tinnitus, seizures and cardiac arrest with lidocaine
Gastrointestinal dysfunction, ileus Sedation with gabapentin
Pruritus Hypotension with magnesium
Urinary retention
Benefits Analgesia No respiratory depression
Ready acceptance of poor patient No addiction except for ketamine
outcomes by peers, due to the Less need for post op ventilation
conventional nature of the analgesic No nausea and vomiting
therapy
No gastrointestinal dysfunction and ileus
No pruritus
No urinary retention

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