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Science of Pre-emptive Anesthesia

pre-emptive analgesia

Preemptive analgesia refers to the use of analgesic agents during the perioperative period, specifically before the surgical incision (3). By introducing analgesia before the patient is exposed to any noxious stimuli, preemptive analgesia helps protect the patient’s nervous system against sensitization to stimuli during surgery (1). Compared to intraoperative anesthesia and postoperative pain management alone, administering analgesics preemptively reduces postoperative pain and prevents long-term, chronic pain (5).  

Furthermore, preemptive analgesia can reduce the adverse effects of opioids, morphine, and other analgesics by lowering how much analgesia is necessary for adequate pain control (3). However, the beneficial effects of preemptive analgesia can be limited by the short timeframe in which analgesics can be administered. Rather than focusing on preemptive analgesia alone, combining preemptive analgesia with multimodal pain management throughout the perioperative period is a more effective way to combat central sensitization and the adverse effects of postsurgical pain (4). 

The level of postoperative pain that a patient experiences can vary greatly depending on several factors, such as preexisting pain, mental and emotional state, and fear of pain (4). Without proper treatment, acute pain from a surgical procedure can cause extensive emotional and psychological distress and evolve into long-term, chronic pain (4). Consequently, adequate pain management during surgery is crucial, and preemptive analgesia offers a tool to improve the efficacy of pain management (4). 

Preemptive analgesia works by preventing central sensitization through the use of local analgesics at various sites along pain pathways (1). Our perception of pain involves multiple pathways through which our peripheral nervous system alerts our central nervous system of tissue damage (1). Peripheral nociceptors, sensory receptors that detect signals from damaged tissue, send signals to the dorsal root ganglion in the dorsal horn of the spinal cord (4). Neurotransmitters in the dorsal horn then send alerts to the thalamus and cortex, which mediate our perception of pain (1). 

Central sensitization occurs when a patient’s nervous system changes during surgery and becomes more sensitive to stimuli, amplifying their experience of pain (2). Indeed, painful experiences like surgery can alter our nervous system, causing our pain receptors to elicit a more significant response to the same noxious stimuli (1). As a result, a patient can develop pain hypersensitivity after surgery and experience previously painless sensations as being painful (1). Preemptive analgesia aims to prevent the establishment of altered processing of afferent input (2). Even for short periods, both central mechanisms and afferent input are necessary to maintain pain hypersensitivity (2). As a result, pain hypersensitivity can be prevented or reversed by blocking afferent input at various sites along the pain pathways (2). 

Compared to preemptive analgesia, preventive analgesia is a broader concept that describes pain control throughout the preoperative period with the same goal of preventing central sensitization (3). Unlike preemptive analgesia, analgesics can be administered at any point during the preoperative period for preventive analgesia (4). The increased administration window for preventive analgesia allows a sufficient duration of action for the analgesic drugs to take effect (4). Indeed, although surgical incision is a tissue injury, the impact of inflammatory processes and nerve injuries resulting from surgery have a more prolonged effect on patients’ experience of pain (4). As a result, local anesthetics and anti-inflammatory agents must be applied preoperatively and continuously postoperatively to provide an effective blockade against pain. While preemptive analgesia is a valuable concept for reducing postoperative pain and lowering the amount of necessary analgesics, limiting the application of anesthetics to before the surgical incision prevents the drugs from having a sufficient duration of action and establishing an adequate degree of afferent blockade (2). 

References 

  1. Gottschalk, A and D.S. Smith. “New concepts in acute pain therapy: preemptive analgesia.” American family physician, vol. 63, no. 10, 2001, pp. 1979-84. 
  1. Kissin, Igor and Richard B. Weiskopf. “Preemptive Analgesia.” Anesthesiology, 2000, vol. 93, pp. 1138-1143. doi: 10.1097/00000542-200010000-00040 
  1. Rosero, EB and GP Joshi. “Preemptive, preventative, multimodal analgesia: what do they really mean?” Plastic Reconstruction Surgery, Oct 2014, vol. 132, pp. 85S-93S. doi:10.1097/PRS.0000000000000671 
  1. Vadivelu, Nalini et al. “Preventive analgesia for postoperative pain control: a broader concept.” Local and regional anesthesia vol. 7 17-22. 29 May. 2014, doi:10.2147/LRA.S62160 
  1. Xu, Jianda et al. “The efficacy of pre-emptive analgesia on pain management in total knee arthroplasty: a mini-review.” Arthroplasty, vol. 1, no. 10, 2019. doi: 10.1186/s42836-019-0011-7 

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