Pain scores of With inadequate analgesia the initial step should be an appropriate loading dose followed by an increase in the size of the PCA dose.The recommended increase in dose size should be approximately 25%.

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Therefore, the speed of agent onset should be accounted for when determining the lockout interval.

Long lockout reduces the patient's ability to obtain an effective analgesic level if they fall behind, i.e. Lockout Intervals Examples: Morphine 8 minutes Fentanyl 6 minutes Hydromorphone 8 minutes Four-hour Limit (Abbot PCA Pumps) This safety feature prevents a patient from receiving more than a pre-determined amount of opioid within a four-hour period.

The volume of distribution of the opioids in the plasma is weight related resulting in an appropriate blood level of the opioid.

Loading Dosing Examples: PCA (Maintenance) Dose The PCA dose of opioid is the amount of drug the PCA pump will deliver when the demand button is pressed.

The lockout interval (LOI) is a necessary safeguard to prevent patients from taking an additional dose before appreciating the effect of the preceding dose.

The refractory period limits the potential of the patient administering an inadvertent overdose due to the "stacking" of opioid doses.

If a patient reaches the four-hour limit, the site, intensity, and nature of the pain must be assessed before the four-hour limit is discontinued.

Failure to realize that the patient has reached the four-hour limit is one of the most common causes of inadequate analgesia.

If the four hour limit has been reached and the patient is in pain the four limit should be increased and appropriate loading dose / doses should be given.