Page 16 - CASA Bulletin of Anesthesiology 2022; 9(5)

CASA Bulletin of Anesthesiology

to reach an OAA/S score of 3 was 43 seconds in group 1, 36 seconds in groups 2, versus 51
seconds in group 3 (p<0.001). The analgesia efficacy for needle blocks was 87% for group 1
(without 10 mg additional ketamine after bolus), and 98% for group 2 (with 10 mg additional
ketamine after bolus), which is similar to group 3, the A6-2-2 group. In group 1, 90% had no
head movement during the ocular block, whereas 100% of group 2 and 3 had no head movement.
88% patients in group 3 has no oxygen desaturation during blocks compared to 94 to 97% in all
the KE6-2-2 groups. Less than 2% of patients had apnea that required airway intervention in all
three groups. Approximately 11% of patients in KE6-2-2 groups 2 had no LOC but 100% had no
recall of the block, compared to 95% of patients with no LOC in the A6-2-2 group, with 96%
having no recall of the block (p< 0.001). In KE6-2-2 group 1, 36% of patients had no LOC with
99% having no recall of the block (p <0.001). Figure 2 summarizes the perioperative sedation
outcomes.

Discussion:

Analgesia is the most important element of MAC to prevent pain and head movement during
ocular blocks (which increases the risk of eye injury 10, 11 ), yet MAC without opioids can be
challenging. A logical approach for opioid-sparing anesthesia is multimodal and utilizes the
additive and synergistic effects from drugs activating different receptors and parts of the central
nervous system 12, 13, 14 . This maximizes analgesia from the non-opioid drugs while minimizing
adverse effects, leading to decreased need for supplemental opioids.

Our non-opioid KE6-2-2 sedation method has several features: 1) the standardized bolus dose
is calculated based on the patient’s age and weight (Table 3); 2) the bolus dose can be safety
administered all at once by hand or infusion pump; 3) an additional ketamine 10 mg after the
bolus increases analgesic efficacy from 87% to 98% for ocular blocks; 4) patient readiness for
ocular block was 43 seconds without and 36 seconds with the additional 10 mg of ketamine; 5)
98-99% of patients had no apnea and 3-6% had transient oxygen desaturation <90% due to
hypoventilation, with 2% of patients requiring brief chin lift but no mask ventilation or
intubation; 6) there was no significant change in MAP or HR after bolus; 7) over 80% of patients
did not receive opioids for pain postoperatively; and 8) 98-100% of patients had no recall of
block even without pre-treatment benzodiazepines. In comparison, patient readiness for ocular
blocks with the opioid A6-2-2 mixture was 51 seconds, and analgesic efficacy was 98%. 2% of
patients had apnea requiring chin lift and 12% of patients had transient oxygen desaturation due
to hypoventilation but recovered quickly. With the exception of KE6-2-2 group 1, all other
groups had no head movement during the block. No patient required supplemental sedation
during the ocular block. While the non-opioid KE6-2-2 mixture provided comparable analgesia
to the opioid-based A6-2-2 mixture, it had faster onset, lower incidence of apnea and hypoxia,
and more stable hemodynamics.

Inclusion of etomidate in the KE6-2-2 mixture did not decrease the MAP after the bolus dose
(Table 2), suggesting that adrenal suppression is unlikely. PONV incidence was less than 15%
even without prophylaxis. Since ketamine could potentially increase HR and BP, it is reasonable
to avoid in patients with severe preoperative hypertension (BP 180/90) or tachycardia
(HR >100/min) (the opioid-based 6-2-2 mixtures are reasonable alternatives) as well as patients
with severe psychiatric disease, especially in those taking multiple medications until future
studies prove its safety. Additionally, in this report, no patient received midazolam as pre-

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