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Pain management (Proceedings)

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Aug 01, 2010

Pain Management Techniques

There are a wide variety of pain management techniques. I hope to cover a few here. Some of the different areas we will cover are injectable analgesia, epidurals, wound soaker catheters, local blocks, NSAIDs, and alternative methods. Each group will be expanded upon, with specific examples.

Injectable analgesia

This section covers many different drugs administered through a variety of routes (IV, IM, SQ). Typically, injectable analgesia is referring to opioids. NSAIDs, alpha-2 agonists, and dissociatives, however, can also be included in this section. The procedure and the patient's analgesic requirements will affect the drug given, the dose given, the frequency at which the drug is given, and also the route of administration.When drugs are not given at a continuous rate, there may be periods of low to no analgesia as the drug is cleared off and then periods with higher analgesia soon after administration. This is known as peaks and valleys. When giving intermittent injections it is important to assess patients often for pain. Examples of procedures where intermittent injections would be appropriate pain management are post-operatively for an ovariohysterectomy, or a simple mass removal.

Some injectable analgesic drugs can also be administered at a continuous rate to achieve optimum analgesia. Most commonly we are referring to opioid agonists such as fentanyl, hydromorphone, or morphine. Other drugs common given as constant rate infusions (CRIs) to help treat pain are lidocaine, ketamine, and alpha-2 agonists. A CRI will provide a consistent level of analgesia. Lower doses of drugs are needed because of the consistent rate. Titration of drugs administered as a CRI is usually possible. Critical patients often benefit from CRIs both under anesthesia and post-operatively. Intra-operative CRIs, of certain drugs, decrease the minimum alveolar concentration, allowing for a decrease in inhalant anesthetic. This is important with critical patients that often do not have good blood pressure.

CRIs can be maintained through a syringe pump or using a fluid bag and drip set. The combination of morphine, lidocaine, and ketamine is often added to a bag of fluids and set to a certain rate for that patient. This bag of fluids can be administered through a fluid pump, or in situations without one, the dial on the drip set can be used to control the rate of the fluid. The later is a bit riskier, if the patient's catheter was a little positional and he was to stretch his leg out, the fluids might speed up and the patient may receive more drug than initially intended. The opposite could be true as well, the line could stop flowing and the patient would not be receiving any medication. A pump will typically alert someone when an occlusion is present. Fentanyl can be administered as a CRI directly through a syringe pump attached to the patient's IV catheter, or diluted within a bag of fluids and administered at a faster rate.



The cost of administering a CRI is typically more than with intermittent injections (depending on the drug). This is because of the additional equipment necessary. The following is an example of a fentanyl CRI dosing chart. When saved as an excel spreadsheet, the patient weight could be added to one box and the program can calculate the rest for you. Using straight fentanyl, a syringe pump would be set for mL/hr.