Patient-Controlled Analgesia (PCA)

Overview: 

Introduction

  • PCA uses an infusion pump to deliver a pre-programmed dose of an opioid medication when a demand button is pushed. PCA modes of delivery include demand dosing and demand dosing plus continuous basal infusion.
  • The minimal effective analgesic concentration (MEAC) is the lowest plasma opioid concentration at which pain relief can be achieved. PCA can effectively maintain the plasma MEAC, avoiding peaks and troughs that can be associated with side effects and periods of uncontrolled pain.1
Clinical Use: 

Indications: post-operative, severe acute, acute on chronic, and cancer-related pain, inability to use oral/transdermal/rectal routes routes of administration

Adjustable PCA parameters: 

  • Demand dose: amount of opioid delivered when demand button is pushed
  • Lockout interval: time period after a successfully-delivered demand dose when pump will not administer additional opioid, even if demand button is pushed
  • Continuous dose or basal infusion: constant rate delivered regardless of whether demand button is pushed 
  • Breakthrough/incident pain bolus dose: amount of opioid administered by clinician for breakthrough pain, usually nurse-administered
  • 1-hour maximum dose limit: includes demand dose, continuous dose, and breakthrough/incident pain bolus doses

Dosing: Common initial dosing regimens for opioid-naïve adult patients:2

Opioid

Demand dose

Lockout (minutes)

Breakthrough/incident pain bolus dose

1-hour maximum dose

Morphine

1 mg

10

2-4 mg q2h prn

10 mg

Hydromorphone

0.2 mg

10

0.4-1 mg q2h prn

2.2 mg

Fentanyl

10 mcg

10 

20-40 mcg q2h prn

100 mcg

Calculation of initial demand dose for morphine or hydromorphone:

  • Calculate total amount used in a 60-minute period to achieve pain relief. Assume patient will require half of that amount over the next 3 hours (for opioids with half-lives of ~3 hours). Divide that amount by 3 for hourly dose. Divide that amount by 3 again for demand dose allowable every 20 minutes. 
  • Example: Patient requires 9 mg of IV morphine over 60-minute period in the Emergency Room for pain relief. 9/2*3*3 = 9/18 = 0.5 mg. Start with demand dose of 0.5 mg with lockout of 20 minutes.
Special Considerations: 
  • Contraindications: patient inability to independently push demand button, contraindication to selected opioid
  • Avoid basal rate with initial programming, in opioid-naïve patients, patients with comorbidities (renal impairment, hypovolemia, morbid obesity, obstructive sleep apnea)3  that increase the risk of over-sedation and respiratory depression 
  • PCA dosing in opioid-tolerant patients should take account for daily oral morphine equivalents (OME).
    • Example: Patient takes 90 OME daily, approximately equivalent to 30 mg IV morphine daily. 30 mg/24 hours = 1.25 mg/hour. This amount should be incorporated into the demand dose.
References: 

Grass J. Patient-controlled analgesia. Anesthesia & Analgesia. 2005;101:S44–S61.

Mariano ER. Management of acute perioperative pain. In: UpToDate, Fishman S & Crowley M (Eds), UpToDate, Waltham, MA. (Accessed on January 3, 2021).

Macintyre PE. Safety and efficacy of patient-controlled analgesia. British Journal of Anaesthesia. 2001;87:36–46.

Dinges H, Otto S, Stay DK et al. Side effect rates of opioids in equianalgesic doses via intravenous patient-controlled analgesia: A systematic review and network meta-analysis. Anesthesia & Analgesia. 2019;129:1153–1162.

Author: 
Alexandra Chang
Mario De Pinto