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Chapter: Clinical Cases in Anesthesia : Acute Postoperative Pain

What is preemptive analgesia? Can it reliably be performed in this patient?

Preemptive analgesia is a technique via which an anal-gesic modality is introduced prior to the painful procedure so that the patient will have less pain in the postoperative period.

What is preemptive analgesia? Can it reliably be performed in this patient?

 

Preemptive analgesia is a technique via which an anal-gesic modality is introduced prior to the painful procedure so that the patient will have less pain in the postoperative period. This idea is based on the theory of “central nervous system wind-up”, whereby if the spinal cord receives a con-stant barrage of painful stimuli it becomes hyperexcitable and thus more prone to evoke a pain response, even to less painful stimuli. Different modalities have been investi-gated, such as the use of preoperative NSAIDs to provide peripheral analgesia, the use of local anesthetic peripheral nerve or neuraxial block to prevent transmission of painful impulses into the spinal cord, as well as the use of high doses of systemic narcotics, to blunt cortical perception.

 

Unfortunately, a reliable way to achieve preemptive analgesia in association with major abdominal surgery has not been achieved. A few small studies have shown efficacy with the use of neuraxial opioids, but no large study has been able to confirm this. In a recent study (Aida et al., 1999) epidural catheters were placed preoperatively in their respective areas (cervical placement for upper limb surgery, low thoracic placement for abdominal surgery, lumbar placement for lower limb surgery, etc.) and an appropriate anesthetic level with local anesthetics was achieved pre-incision. A preemptive analgesic effect was noted in the limb and mastectomy patients but not in the laparotomy patients. The authors concluded that to per-form preemptive analgesia properly, one must completely block all afferent input into the spinal cord, and that as some input is provided via the vagus nerve which was not blocked with the epidural, preemptive analgesia could not be reliably achieved.

Many questions remain to be answered with respect to preemptive analgesia. The first and foremost is, does it clin-ically exist, and if so, by what modality can it be achieved? Perhaps a single procedure, such as the administration of a properly placed epidural with local anesthetic prior to the surgical stimulation, can provide pre-emptive analge-sia. Most likely, we will discover that both central and peripheral modalities will need to be utilized. Another question is whether a single procedure prior to the initial stimulus will be sufficient for preemptive analgesia, or whether it will be necessary to continue this technique dur-ing the entire procedure, as well as into the postoperative period.

 

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Clinical Cases in Anesthesia : Acute Postoperative Pain : What is preemptive analgesia? Can it reliably be performed in this patient? |


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