Lockout interval

Many postoperative patients require less narcotics when they are able to self-administer a narcotic for pain. Because the self-administration system is under the control of the nurse, who adds the drug to die infusion pump and sets the time interval (or lockout interval) between doses, the patient cannot receive an overdose of the drug. 

Patient-controlled analgesia (PCA) IV Loading dose 50-100 mg. Intermittent bolus 5-30 mg. Lockout interval 10-20 min. Continuous infusion 5 0mg/hr. Maximum (4-hr) 200-300 mg. 

PCA IV Loadingdose 5-lOmg. Intermittent bolus 0.5-3mg. Lockout interval 5-12 min. Continuous infusion 1-10 mg/h. 4-hr limit 20-30 mg. 

The minimum amount of time allowed between each demand dose is called the lockout interval. After the patient self-administers a dose, the PCA delivery system will not deliver the next dose until the lockout interval has expired. Typical lockout intervals for commonly used opioids are listed in Table 17-1. 

Some PCA systems can be set to limit the total amount of drug given in a 1- or 4-hour period. The use of these parameters is somewhat questionable, however, because other parameters such as the demand dose and lockout interval automatically limit the total amount of drug that can be given in a specific period of time. 

Drug (Concentration) Demand Dose Lockout Interval (min)... 

Successful demands occur when the patient activates the PCA delivery system and actually receives a demand dose of the drug. Demands made during the lockout interval are not considered successful, but are added to the number of successful demands to indicate the total demands. A large number of unsuccessful demands may indicate that the PCA parameters are not effective in providing adequate analgesia. Therefore, most PCA systems record the number of total demands so that the demand dose can be adjusted if a large number of unsuccessful demands are being made. 

Lockout interval The minimum amount of time that must expire between each dose of medication that is administered by patient-controlled analgesia (PCA). The PCA pump is inactivated during the lockout interval so that the patient cannot self-administer excessive amounts of drugs. 

PCA syringe concentration is generally 0.2-0.3 mg per mL. This requires that up to 10 ampoules be opened and diluted with saline to make up a standard 30 mL PCA syringe. Earlier clinical trials employed oxymorphone PCA doses of 0.3 mg with a 6-8 minute lockout interval [9,10]. This dose was associated with a high incidence of nausea and vomiting, particularly when a 0.3 mg/hoiu- basal infusion was employed [ 11 ]. To reduce adverse events, we recommend lower doses of 0.1-0.2 mg every 6 min. PCA dosing guidelines for oxymorphone are presented in Table 24.1. 

In a similar study, 64 patients undergoing laminectomy received morphine 0.15 mg/kg and were later randomized to receive morphine alone (0.02 mg/kg intravenous with 15 minutes lockout time) or morphine and dexmedetomidine (0.02 mg/kg intravenous morphine - - 0.1 microgram/kg dexmedetomidine, lock out interval 15 minutes) the combination treatment produced higher sedation scores but a lower incidence of nausea [118. ... 

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