Pain facts 7

Dr. S. Parthasarathy

MD., DA., DNB, MD (Acu), Dip. Diab. DCA, Dip. Software statistics

PhD (physio)Mahatma Gandhi medical college

and research institute , puducherry – India

Patient controlled analgesia

• The patient controls his own analgesia

• the use of a sophisticated microprocessor-controlled infusion pump that delivers

a preprogrammed dose of opioid when the patient pushes a demand button

Patient controlled analgesia

• Any analgesic given by any route of delivery (i.e., oral, subcutaneous, epidural, peripheral nerve catheter) can be considered PCA if administered on immediate patient demand in sufficient quantities.

• But routine is IV opioids

Background

• The traditional approach of IM opioids

given pro re nata (prn) results in at least 50% of patients experiencing inadequate pain relief after surgery.

• Sechzer - the true pioneer of PCA evaluated the analgesic response to small IV doses of opioid given on patient demand by a nurse in 1968 and then by machine in 1971

We don’t want action after distress

• Pain nurse dilutes prepares drug

Analgesia Blood absor IM

conc.

PCA

MEAC

Indications

• Acute post op pain • Trauma • Cancer • Labour • Burns • Sickle cell crisis • Sedation

Advantages

• Better analgesia with same sedation • Better pulmonary results and less

complications • Length of hospital stay• POCD is less• Patient satisfaction

Relative contraindications

• Sepsis • Fluid electrolyte disturbance • Hepatic or renal disease ( severe disease ) • Sleep apnoea • Severe COPD

PCA system

• Programmable electronic devices • Flexibility ,• Display and memory, cost • Disposable fixed programme devices • Nonweight , hydrostatic pressure based • No alarms, rudimentary but cheap

How to use

• Methods

• Demand dose ,• DD + basal infusion ,• DD + tail • Adjustable infusions

Variables

• Loading dose • Demand dose • Lock out interval • Basal infusion • 1 or 4 hourly maximum

• Variables + drug = prescription

Loading dose

• We should understand that PCA is a maintenance therapy

• It needs loading dose.

Loading dose

• HIGH LOADING DOSE • OPIOID BASED ANAESTHESIA • Correlated with less analgesic requirements

• Morphine – 3 -5 fentanyl 50 mic• Pethidine – 25 tramadol 100

Basal infusion

• Less fluctuation ,increased pt. satisfaction • Sleep more medication

• Per hour doses

• Morphine – 1 fentanyl 10 mic• Pethidine – 25 tramadol 12

Demand dose

• The amount of drug injected as soon as the patient presses the button

• Burp or tweek sound • dose is too small, they stop making demands

• become frustrated with PCA, resulting in

poor pain relief• Upto 5-6 doses / hour

Demand dose

• Demand dose is too large, plasma drug concentration may eventually reach toxic levels- side effects ensue

• Optimal dose • Morphine - 1 mg• Pethidine – 10 mg• Fentanyl – 10 mic

Lock out interval

• Patient cant go on to press 10 times in half hour – get toxic doses

• The time delay before the patient cannot go to the next dose

• Onset of action of the drug • Fentanyl and morphine • Relative onset and duration ??

Classical times

• Morphine – 8 min• Pethidine – 8 min• Fentanyl - 6 minutes

• Short dose and lock out • Large dose and lock out • Fentanyl -- ?

Lock out ??

• Brain to blood

• Blood to brain

• Redistribution

Demand dose or lock out

• Attempts • Sound

• May deliver or not

• Adjusted infusion

Nothing like this

• One size fits all

• Set and forget

• The doses are only approximate

Patient weight prevents toxicity but efficacy ?

Total dose

• 1 hour

• 4 hours

Assumptions

• Side effects are produced at higher brain concentrations than the analgesic effect

• Pain intensities are rarely constant • Pain relief is ideal in MEAC only

Ideal opioid

• Rapid onset • Medium duration • Less side effects• No ceiling to analgesia

• Morphine -- pethidine – fentanyl

Morphine - ?

• Renal insuffiency • Bilirubin • Preeclampsia • Smooth muscle spasm

Pethidine

• Seizures

• Sickle cell crisis nor meperidine increased

• Papillary necrosis in renal dysfunction

Fentanyl

• Ideal for renal and hepatic dysfunction cases

• But short duration should be in mind

• Other drugs – hydromorphone, pentazocine and buprenorphine are used

Monitoring

• Staff • ABG • Respiration• Sedation score

• But pulse oximetry is accepted as the monitor for PCA

Side effects

• Operator error

• Patient error

• Equipment malfunction

Side effects of opioids

• Nausea and vomiting

• No difference

• 30 % Vs 25% - PCA Vs IM• Use of anti emetics – similar

•

Respiratory depression

• PCA is more – wrong

• Lot of studies – 0.5 – 0.9 % Vs

• Old age , COPD, equipment failure, concomitant opioid admin by other routes, wrong doses

Colonic pseudoobstruction

• Abd, distension • Nausea • Vomiting, • Flatus

• Yes but 6/154 in a study of PCA -- not threatening

Others

• Sedation - 20 %• Dizziness - 13 % • Pruritus - 20 %

• In a study with PCA with hydromorphone

PCA adjuncts

• Promethazine – • Droperidol• Metoclopramide • TDS scopolomine • Naloxone

• NSAIDs• Clonidine • Paracetomol• Nerve blocks

Other methods - PCEA

loading – basal – demand- lock out • Morph. 2 0.5 0.2 30

• Peth. 30 10 10 20

• Fentanyl 50 30 10 15

Subcutaneous (clysis)

• 0.2 mg Loading with 0.2 mg demand SC 15 min. lock out of hydromorphone

• Obesity • Edema • Vasculitis • But if no proper IV access – OK

Rare routes

• Intramuscular PCA • Paediatric PCA • Intraspinal PCA • Ventricular implantable PCA • Oral PCA • PCA with ketoroloc, midazolam has been

done

Mr. X

• Mr X bought a scooter • He did not know driving • He was struggling • One friend came near to say don’t worry, it

will normalize in three months • Mr. X put the scooter into the shed to try

it after three months

To understand PCA

• USE it • Make it available in your institutes

Thank you all