Management of Acute Pain in Trauma 2
By Dr. Saman Nanayakkara
Opioids, as a result of their high ceiling effect, are very effective analgesics for moderate to severe pain particularly of visceral origin (as opposed to NSAIDs which are better for somatic pain). Repeated use may cause addiction and tolerance but those should not be issues during management of acute pain. Opioids share many side effects though qualitative and quantitative differences exist. The most common side effects are nausea, vomiting and constipation. Large doses can cause sedation, hypotension, change of the size of pupils and respiratory depression. Those complications are the very reasons for some medical staff for not using opioids in the trauma setting. It should be noted that opioids can be used after a careful initial neurological and cardio-respiratory assessment. The patients can be reassessed after an interval and the drugs may be repeated.
In addition to analgesia, morphine also confers euphoria and a state of mental detachment which is beneficial in the management of acute pain. Morphine remains the most valuable opioid in patients with severe pain due to trauma. It can be administered through IV, IM or SC routes at a dose of 0.1mg/kg. Morphine acts for 4-5hrs hence should be repeated for proper analgesia. In an OPD/ward setup with less monitoring facilities it can safely be given as a subcutaneous injection at 0.1mg/kg or in divided doses as an intravenous injection.
It produces a prompt effect (onset of action is quicker than of morphine), but it is less potent and the effect is of shorter duration (2-4hrs). It can be given intramuscularly or intravenously at a dose of 1mg/kg. This has a slight atropine like effect (can cause dry mouth and blurred vision) and can cause a pupillary dilatation (as opposed to pupillary constriction caused by morphine).
Fentanyl is 100 times more potent than morphine and has a very quick onset of action (2-5minutes). The dose is 1-1.5micrograms/kg. However, the duration of action is short (20-40minutes) and it needs to be repeated regularly or should be given as a continuous intravenous infusion (10-50mcg/hr for an adult). A severely injured patient who is haemodynamically less stable can be given a bolus of IV fentanyl (e.g. 25-50mcg) in a monitored set up and should be followed by a morphine SC injection or a fentanyl infusion. It is also available as a transdermal patch (releasing 12/25/50/75 or 100 mcg/hr depending on the strength of the patch used), which has to be changed every 72hrs. Fentanyl lozenges (which have the advantage of the drug avoiding first pass hepatic metabolism) are not available in Sri Lanka.
Patient controlled analgesia (PCA) with intravenous morphine, fentanyl and ketamine are quite popular in the developed world. However, due to unavailability of PCA pumps, use of this technique is limited to a few teaching hospitals in our country. In a morphine-PCA, a patient can get a bolus of 0.5-1mg of morphine every time he presses the delivery button. There is generally a lockout period of 5 minutes during which time the patient would not get the drug even if he presses the delivery button. So a patient can get a maximum of 6-12mg of morphine depending on what has been set in the PCA pump. Fentanyl may set to be delivered at a rate of 10-20mcg/bolus with a 5-minutes lockout.
Local anesthetic agents may be used for local or regional analgesia. They are the most effective out of all anesthetics but needs extra skills for administration especially with regional anesthesia. They have the advantage of being devoid of systemic side effects especially with local anesthesia. These can be used for topical anesthesia (e.g. for burns, contusions), local infiltration (e.g. for wound cleaning, suturing), central neuraxial blocks like epidural blocks and regional anesthesia.
The place of an epidural is invaluable in certain conditions like chest injuries, especially with multiple rib fractures, flail chests, lung contusions, chest and abdominal wall contusions, patients with abdominal injuries undergoing laparotomies, pelvis/bilateral lower limb injuries etc. An early epidural will take care of pain and therefore, the pain/trauma related stress response would be reduced. This will help patients to breathe normally, and to cough, to be upright and to be mobilized, as opposed to a patient on parental opioids who would be sedated, lying supine (with a splinted diaphragm), impaired cough, hyperventilating with small tidal volumes leading to hypoxia, basal lung atelectasis and lower respiratory tract infections. Most commonly administered drugs via an epidural are 0.1-0.125% bupivacaine with/without fentanyl 2-5mcg/ml as boluses of 4-7ml. However, to maintain an epidural, basic resuscitation facilities and expertise to handle common complications should be available wherever it is used. Partial/inadequate block, hypotension, itching etc. are the common complications.
Patients with limb injuries (upper or lower) would benefit immensely from a regional block. Those again need expertise to perform and deal with complications. A mixture of lignocaine (for quick onset of action) and bupivacaine (for longer duration of action) are commonly used.
This is an inhaled mixture of 50% oxygen and 50% nitrous oxide. Entonox provides safe and effective analgesia and anxiolysis while maintaining consciousness and is a quite useful analgesic for various painful procedures like cleaning and dressing of burns, wound cleaning and suturing etc. It has a very quick onset of action (starts to act within 20 seconds and peaks within 2 minutes) and is available only in operating theatres.
This is a general anesthetic that causes a dissociative state and anterograde amnesia. Ketamine acts very fast (within 1-2 minutes) and provides intense analgesia with much lower doses compared with anesthetic doses. This provides very good somatic analgesia while preserving protective airway reflexes, spontaneous breathing and haemodynamic stability. In fact, it causes a slight tachycardia and a hypertension. Ketamine is a very useful analgesic for extrication of trauma victims and management of initial severe pain during transport to the hospital and within the hospital. A bolus dose of 10-50mg will provide a good pain relief for transferring from the trolley to the bed, transferring and positioning for radiological imaging, wound cleaning-suturing and closed reductions etc. The main adverse effects are hallucinations, agitation on emergence (both can be reduced with a concomitantly administered intravenous benzodiazepine such as midazolam 1-2mg), and increased secretions.
Common Injuries in Trauma and Their Management
Trauma may cause blunt or penetrating chest injuries.
Blunt thoracic trauma
This generally causes chest wall contusion, rib fractures (with or without flail segments), hemo/pneumo thorax and pulmonary contusion.
For wall contusions and 1-2 rib fractures, a combination of regular oral paracetamol, NSAIDs, tramadol (oral/IV) and SC morphine 0.1mg/kg 6-8 hourly works very well. But it is important that a combination of correct doses of these are started and gradually tailed off as the pain subsides.
For flail segments and severe lung contusion a thoracic epidural would be the best option. If it is difficult/the facility unavailable an IV morphine bolus 0.1mg/kg followed by a continuous IV infusion of morphine 1-4mg/hr would be an alternative. A patient controlled analgesia (PCA) with IV morphine would be better than a continuous infusion but it is not freely available in our set up. Patients on continuous morphine infusions should be monitored for respiratory depression and hypotension.
Penetrating chest injuries
These patients will need hemostasis, fluid resuscitation, intercostal tubes and sometimes intubation. As soon as airway, breathing and circulation are controlled they can be given a bolus of IV morphine 0.1mg/kg (or a portion of it, if the blood pressure is low) followed by an infusion of 0.5-4mg/hr. If the patient is intubated starting him on regular nasogastric (NG) paracetamol, tramadol and diclofenac will help both to reduce the IV opioid requirement and to wake him up earlier by stopping IV opioid infusions.
Pain and discomfort, which are commonly associated with head injury, depend on the severity of the injury. This in turn is classified as mild head injury (when GCS is 13-15 or duration of loss of consciousness is less than 1 hour) and moderate-severe head injury (GCS is less than 12 or duration of loss of consciousness is more than 1 hour).
Brachial plexus blocks done at various levels can provide reliable analgesia for upper limb injuries. For shoulder injuries an interscalene block provides a dependable pain relief. A supraclavicular or an infraclavicular block for upper arm injuries and an axillary block for forearm injuries generally work very well.
For lower limb pain lumbar plexus blocks and sciatic nerve blocks provide excellent analgesia. Catheters can be left for continuous regional analgesia infusions or for repeated boluses. After a few days, when the acute severe pain is over, the patients can be started on oral analgesics.
Abdominal and pelvic injuries
Once internal bleeding is excluded they can be offered an epidural block or if it is not possible an IV morphine PCA. If there is no facility for a PCA, the patient can have SC morphine 0.1mg/kg. Later, this can be changed to a combination of oral paracetamol with / without tramadol.
A morphine-PCA is the method of choice for analgesia for burns. In the absence of a PCA subcutaneous (in a non burnt site) or intramuscular morphine should suffice. In addition to the acute intense pain which needs parenteral opioids, there is always a basal unremitting pain which needs some back ground analgesia. In the first few days regular parenteral opioids would be necessary for this and later paracetamol may be sufficient for this. In addition these patients will need frequent wound debridement for which IV or IM ketamine with/without morphine will provide effective pain relief.
Majority of trauma patients would not benefit from a single discipline or a single drug. Therefore, the attending team has to draw an analgesic plan for each individual patient independently considering patient factors and the surgical factors. The analgesic requirements change with time, sometimes quite fast. The analgesic recipe has to be tailored to the existing severity and complexity of pain, disability and other factors like mood, feeds, sleep, bowel motions etc. For example, a patient with multiple rib fractures may be offered a thoracic epidural initially, and after a few days he can be on parenteral opioids and then with a combination of oral analgesics like Paracetamol, tramadol and diclofenac sodium.
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Sri Lanka Association for the Study of Pain
The Sri Lankan Chapter of the International Association for the Study of Pain
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