Book Text

ANESTHETIC TECHNIQUES USING OPIOIDS

Sedation and Analgesia

Opioids are frequently used to relieve pain during monitored anesthesia care and regional anesthesia. A single bolus administration of opioids can provide significant pain relief. Morphine is slow in onset and does not allow rapid titration to effect. Meperidine (50–100 mg IV) produces variable degrees of pain relief and is not always effective in patients with severe pain. IV boluses of fentanyl (1–3 µg/kg), alfentanil (10–20 µg/kg), or sufentanil (0.1–0.3 µg/kg) can produce potent and short-lasting analgesia. Infusion rates are 0.01 to 0.05 µg/kg/minute for fentanyl, 0.0015 to 0.01 µg/kg/minute for sufentanil, 0.25 to 0.75 µg/kg/minute for alfentanil, and 0.05 to 0.25 µg/kg/minute for remifentanil. Plasma concentrations of opioids necessary for various purposes are listed in Table 11-8 .

Changes in the excitability of central neurons play an important role in the establishment of pain. Whether preemptive analgesia can be effectively achieved clinically by the early administration of opioids remains uncertain.^[359] ^[360] However,

TABLE 11-8 -- Range of approximate plasma (or whole blood for remifentanil) opioid concentration (ng/ml) required for total intravenous anesthesia

Fentanyl Sufentanil Alfentanil Remifentanil

Predominant agent 15–30 5–10 400–800 —

Major surgery 4–10 1–3 200–400 2–4

Minor surgery 3–6 0.25–1 50–200 1–3

Spontaneous ventilation 1–3 <0.4 <200 0.3–0.6

Analgesia 1–2 0.2–0.4 50–150 0.2–0.4

From Bailey PL, Egan TD, Stanley TH: Intravenous opioid anesthetics. In Miller RD (ed): Anesthesia, 5th ed. New York, Churchill Livingstone, 2000, p 330.

reductions in postoperative pain and improved recovery have been attributed to preemptive analgesia with either epidural fentanyl or bupivacaine after radical prostatectomy. ^[361]

**TABLE 11-8** -- Range of approximate plasma (or whole blood for remifentanil) opioid concentration (ng/ml) required for total intravenous anesthesia
	Fentanyl	Sufentanil	Alfentanil	Remifentanil
Predominant agent	15–30	5–10	400–800	—
Major surgery	4–10	1–3	200–400	2–4
Minor surgery	3–6	0.25–1	50–200	1–3
Spontaneous ventilation	1–3	<0.4	<200	0.3–0.6
Analgesia	1–2	0.2–0.4	50–150	0.2–0.4
From Bailey PL, Egan TD, Stanley TH: Intravenous opioid anesthetics. In Miller RD (ed): Anesthesia, 5th ed. New York, Churchill Livingstone, 2000, p 330.

PCA with opioids is now a cornerstone of postoperative analgesia. PCA with opioids may improve outcome.^[362] Nevertheless, pharmacokinetic optimization of opioid treatment in acute pain is a complex matter. ^[363] Without considering effect site drug concentrations over time, the choice of opioid and the amount, method, and frequency of administration cannot be optimized.^[363] Morphine remains a popular and rational choice for PCA therapy.^[364]