Morphine titration in obese patients
Obese patients with obstructive sleep apnoea have an
increased risk of opioid-induced upper airway obstruction
and require close monitoring.42 There is limited information
available regarding morphine administration in obese
patients in the immediate postoperative period.42 43 Intermittent
i.v. injections of morphine boluses can be used, although
the altered pharmacokinetics of this drug should be
taken into account. Obesity significantly prolongs the elimination
half-life of lipophilic drugs such as fentanyl and sufentanil.
43 Morphine should be used with caution in patients
with obstructive sleep apnoea without non-invasive positive
pressure ventilation42 43.
Limitations of morphine titration
I.V. morphine titration is a simple, efficient, and safe method
for pain relief in the PACU. However, the initial VAS in the
PACU, before morphine titration, is often high (.70)7–9 indicating
severe pain,9 and complete pain relief may take time.
Despite a short time interval between boluses during titration
(5 min), the mean time to achieve complete pain relief is 15
min (range: 5–60 min).7 18 However, few studies have tested
the use of other opioids such as fentanyl but the short duration
of action may be an issue. The technique is timeconsuming.
9 10 Although morphine titration is a useful
method for pain relief, additional studies are required to
analyse titration failure, to improve the timescale of pain
relief, and to assess the implications of a titration regimen
for nursing practice.