Pre-hospital Analgesia

1. Pre-hospital Analgesia Wollongong CGD August 13th Dr. Kent Robinson

2. Pain • Pain is a common presentation. • 78-86% of all presentations to the ED are for pain related issues. • Oligoanalgesia is common with the vast proportion of our patients not receiving adequate analgesia. • Minimal research done on the topic of pre-hospital analgesia.

3. Summary • Analgesia should be given early to patients in acute severe pain. • Intravenous analgesia should be aggressive and titrated to effect • Results in better analgesia • Results in reduced dosages of medications

4. Summary • Opiates should be the mainstay of analgesia • Consider the use of titrated fentanyl • Rapid onset of action • Quicker time to effective analgesia • Use ketamine as an opioid sparing agent • Consider the use of targeted analgesia such as local anaesthetic nerve blockade

5. Pain History • Site of pain • Location • Radiation • Circumstances associated with pain onset • Character of pain • Intensity of pain • At rest • On movement • Duration of pain • Aggravating or relieving factors

6. Pain History • Associated symptoms (nausea) • Effect of pain on sleep and activities • Treatment • Current and previous medications (dose, frequency, efficacy and side effects) • Other treatments (TENS) • Health professionals consulted • Relevant past medical history

7. Pain History • Factors influencing the patients symptomatic treatment • Belief concerning the cause of pain • Knowledge, expectation and preferences for pain management • Expectations of pain treatment • Reduction in pain required for patient satisfaction • Typical coping response for stress or pain (past history of psychiatric disorders)

8. Measurement of Pain • Complex and difficult to measure • Pain is an individual and subjective experience • There are no objective measures for pain • Hyperalgesia • Stress response (cortisol levels) • Behavioral response (facial expressions) • Functional impairment • Physiological responses (changes in heart rate)

9. Numerical Rating Score

10. Verbal Descriptor Scale • Best choice in elderly patients including patients with mild to moderate cognitive impairment. • This type of scale uses descriptor terms such as none, mild, moderate, severe and excruciating

12. General Principles of Pain Care • Many factors can add to the pain • Situation • Movement of patient • Procedures (cannulation, limb splintage, spinal care) • Patients may be anxious or confused and not think to ask for pain relief. • Good analgesia facilitates patient care.

13. General Principles of Pain Care. • Appropriate analgesia should be given via an appropriate route in the shortest time frame possible. • Reassessment of pain should occur to determine the effect of treatment. If pain is severe this should happen every 5-15 minutes (severe pain is defined as a pain score greater than 7). Less severe pain should be reassessed every 30-60 minutes.

14. General Principles of Pain Care • Pain relief has medical benefits • Reduction in pain related tachycardia • Improved in lung function • Reduction in PTSD • Consider targeted analgesia • Pain relief should be ongoing to avoid “wind-up” and increased analgesia requirements • If aggressive with analgesia, total requirements will be lower.

15. General Principles of Pain Care • Patients with severe injuries may require high doses of analgesics which may depress their level of consciousness. • Cause hypoventilation and hypercarbia • Necessitate intubation for analgesic control.

16. Methoxyflurane • Halogenated ether • Highly potent and lipid soluble • Powerful analgesic • Nephrotoxic and hepatotoxic - dose dependent effect (anaesthetic dosages) • Reduce pain sensitivity by altering tissue excitability

18. Methoxyflurane • Extensively used in Australia and New Zealand in the pre-hospital setting • Inhaler – green whistle • 3 ml dose – lasts approximately 30 minutes • Maximum recommended dose is 6 ml per day due to concerns about dose related nephrotoxicity • Pain relief takes effect after 6-8 breaths and continues for several minutes after discontinuation of the drug.

19. Morphine • Naturally occurring alkaloid derived from opium • Strongly lipophobic • Onset time is 5 minutes • Peak effect is 10 minutes • Duration of action 1-4 hours

21. Morphine • Dosage 0.05-0.1 mg/kg (repeat to effect) • Moderate sedative effect • Potent metabolites – analgesia and respiratory depression • Unlikely to cause apnea at therapeutic doses.

22. Morphine • Gold standard for analgesia in severe pain • Average dose to control acute severe pain is 0.4 mg/kg

23. Fentanyl • Synthetic opioid • Highly lipophilic • Onset time < 1 minute • Peak onset 2-3 minutes • Duration of action 30-45 minutes • Dosage 0.25-0.5 mcg/kg (repeat to effect), maximum dose of 100 mcg (equivalent to 10 mg Morphine)

24. Fentanyl • Causes minimal sedation • No active metabolites • High risk of apnea at therapeutic dosages • High risk of chest wall rigidity syndrome • Highly emetogenic compared to other opioids

25. Chest Wall Syndrome • Muscle rigidity can occur with doses as low as 25 mcg in an adult. • Often confused with apnea caused by mu-1 receptor agonism. • Unable to resuscitate or ventilate patient unless given naloxone or neuromuscular blocking drug

26. Fentanyl • Very efficacious • Rapid onset of action • Highly potent • Probably the least safe of the opioids available, but still has a very low side effect profile.

27. Ketamine • NMDA antagonist • Rapid acting GA • Profound analgesia • Normal airway reflexes • Increased skeletal muscle tone • Stimulation of cardiovascular and respiratory system

29. Ketamine • Contraindications • Severe hypertension would result in a hazard • Adverse Reactions • Emergence reactions occur in 12% of patients (lowest incidence in the young and elderly) • BP and HR are frequently elevated • Laryngospasm and bronchorrhoea • Tonic / Clonic movements mimicking seizures

30. Ketamine • Sub-dissociative dosage of drug – 0.25 mg/kg, repeat every 30 minutes • Some studies recommend lower dosages of 1-2 mg boluses (Make up the drug into 1 mg/ml) • Paediatric dosage 0-4 mcg/kg/min • Background infusion of 0.25-0.5 mg/kg/hr if required.

31. Ketamine The use of sub-dissociative doses of ketamine reduces the dosages needed of opiates Opiate sparing medication

32. Ketamine • S+ ketamine is now becoming available • Traditional ketamine contains equivalent amounts of S+ and R- ketamine. • S+ Ketamine has 4 times the affinity for the NMDA receptor resulting in greater analgesic efficacy.

33. Targeted Analgesia • Femoral nerve block • Indicated for injuries to thigh and knee • Landmarks include the inguinal crease and the femoral artery • Can improve accuracy of infiltration with the use of ultrasound

36. Targeted Analgesia • Bupivacaine (Marcaine) • 0.25% or 0.5% strengths • Onset of action is 5 minutes • Duration of action is 2-4 hours • Duration of effect for nerve block is approximately 10 hours • Maximum dose is 2 mg/kg up to 175 mg/dose (35 mL 0.5%, 70 mL 0.25%) • For femoral nerve block, the volume of LA is generally 20 mL or less

39. Summary • Analgesia should be given early to patients in acute severe pain. • Intravenous analgesia should be aggressive and titrated to effect • Results in better analgesia • Results in reduced dosages of medications

40. Summary • Opiates should be the mainstay of analgesia • Consider the use of titrated fentanyl • Rapid onset of action • Quicker time to effective analgesia • Use ketamine as an opioid sparing agent • Consider the use of targeted analgesia such as local anaesthetic nerve blockade

41. References • Kanowitz A et al. Safety and effectiveness of fentanyl administration for prehospital pain management. Prehospital Emergency Care. 2006; 10(1);1-7 • Galinski M et al. A randomized double-blind study comparing morphine with fentanyl in prehospital analgesia. Am J Emerg Med. 2005;23(2);114-119 • Borland et al. Options in prehospital analgesia. Emerg Med. 2002;14(1);77-84 • Prehospital analgesia in NSW, Australia. Prehospital & Disaster Med. 2011;26(6);422-426