OPIOIDS AND POST OPERATIVE PAIN MANAGEMENT

DR S NAIDOOANAESTHESIOLOGY

KALAFONG

WHAT IS PAIN?Not only sensoryUnpleasant and emotional experience

Associated with tissue damage

NOCICEPTIONLatin for damage or injuryOnly refers to the neural response to injury

All nociception causes painBUTOther things also cause pain!!!

Nociception causes ACUTE PAIN – nociceptive pain

Nociception and psycho-behaviouristic factors cause CHRONIC PAIN –

neurogenic pain

THE TRANSMISSION OF PAIN

THE BASIC PAIN

PATHWAY

Tissue injury stimulate free nerve endings

NOCICEPTORSAfferent nerve fibres (A∂ and C)

conduct stimuli centrallyPeripheral afferents project into the

DORSAL HORN and other areas in the SPINAL CORD

SYNAPSES extend over to the SPINOTHALAMIC TRACT and up to the THALAMUS and to the CEREBRAL CORTEX

MODULATION OF PAIN

FACTORS RESPONSIBLE

PERIPHERAL MODULATIONLocally secreted substancesSensitises the nociceptorsSite of action for NSAIDs, glucocorticoids, opioids

SPINAL MODULATION Neurotransmitters like glutamate, aspartate and substance P

SUPRASPINAL MODULATIONDescending inhibition in the dorsal horn

These inhibitory tracts are opioid and ἀ-adrenergic

COGNITIVE MODULATONDistraction of attentionTherefore appropriate treatment agents best suited for various types of pain can be determined from causative agents

PAINRequires treatmentAccompanied by unwanted side

effectsAcute pain untreated adequately

becomes chronic in nature and even more difficult to treat

And has a high morbidity

SO…WHY TREAT PAIN?

SIDE EFFECTS OF PAINPULMONARY Hypoventilation, hypoxaemia,

pneumoniaCARDIOVASCULAR Hypertension, dysrhythmias,

myocardiaI ischaemia and cardiac failure

GASTRO-INTESTINAL Decreased motilityGENITO-URINARY Urine retentionBLOOD CLOTTING Decreased mobility prone to DVTIMMUNOLOGICAL ImmunosuppressionENDOCRINOLOGICAL Stress response, decreased

anabolism, increased catabolism. Na and H2O retention

DRUG THERAPY FOR ACUTE PAIN

NON-OPIATES

NSAIDS AND PARACETAMOLUseful when prostaglandins

contribute to the injuryASPIRIN IBOPROFENDICLOFENAKKETOROLACPARACETAMOL-CODEINE

COMBINATIONS

ἀ₂ AGONISTSKETAMINE – 0,25mg/kgREGIONAL ANAESTHESIAThe only way to blunt the afferent sympathetic influence therefore the stress response

Analgesia for hours

OPIOIDSmomor

OPIOID RECEPTORS3 MAIN CLASSESMu main pharmacological effects of

morphine analgesia, dependence & resp depression

Kappa analgesia, resp depression, gastrointestinal effects

Delta

RECEPTOR PROFILEANTAGONISTS

FULL OR PARTIAL AGONISTS

CENTRAL EFFECTS OF OPIOIDSAnalgesiaAnaesthesia Muscle rigidityPupilsThermoregulationEuphoria

OPIOIDSDrugs of choice for the treatment of severe pain

Patients do not get addicted to opioids, they become tolerant

Besides analgesia, opioids are sedating, suppress ventilation, alleviates coughing and can cause bronchospasm

EXAMPLES OF OPIOIDSNATURAL OCCURRINGMORPHINE, CODEINEPAPAVERINE, NOSCARPINE

SYNTHETICPHENYLPIPERIDINES eg fentanyl,

sufentanil, etcPENTAZOCINE, BUPRENORPHINE

SYSTEMIC EFFECTS OF OPIOIDS

CARDIOVASCULARDECREASED SYMPATHETIC OUTFLOW

HISTAMINE RELEASE – CVS COLLAPSE

BLUNTS THE SYMPATHETIC RESPONSE TO INTUBATION

RESPIRATORY SYSTEMDECREASED SENSITIVITY TO AN

INCREASED PaCO₂HYPOXIC DRIVE DECREASESCHEST WALL RIGIDITY BLUNTS THE RESPONSE TO

INTUBATIONBRONCHOSPASM

CENTRAL NERVOUS SYSTEMREDUCED CEREBRAL O₂ CONSUMPTION, BLOOD FLOW AND INTRACRANIAL PRESSURE

LITTLE EEG CHANGESMIOSISSTIMULATES THE CETZ

GASTROINTESTINAL SYSTEMDECREASED GASTRIC EMPTYING

SPASM OF THE SPHINCTER OF ODDI

CONSTIPATION

ENDOCRINE SYSTEMDECREASED RELEASE OF STRESS HORMONES

ATTENUATES THE INTUBATION RESPONSE

OTHER SIDE EFFECTS OF OPIOIDSNAUSEAVOMITINGCONSTIPATIONPRURITISURINE RETENTIONHISTAMINE RELEASECHEST WALL RIGIDITY

MULTIMODAL ANALGESIA

The application of several modalities to alleviate pain

Used in combination with regional anaesthesia

PRE-EMPTIVE ANALGESIA

Administration of analgesia BEFORE surgery

Found to be less effective in man than animal

HIGH TECHNOLOGY METHODS

Including nerve blocks with or without

Infusions of local anaesthesiaNeuraxial blocks (spinal, epidural block and paravertebral blocks)

Patient controlled analgesia

Nerve Blocks

Neuraxial Blocks

Patient controlled analgesia

So... Please remember:PAIN IS NOT AN OPTION WHEN WE AS PHYSICIANS HAVE SUCH A WIDE RANGE OF MODALITIES TO TREAT IT!

THANK YOU