Treating Pain
Ronald Schleifer in Pain and Suffering, 2014
Unlike anesthetics, analgesics are drugs that relieve pain without affecting consciousness or sensory perception. There are two types of analgesic drugs: anti-inflammatory drugs that alleviate pain by reducing local inflammation; and the opioids, which act on the brain and the central nervous system. Anti-inflammatory drugs are used for short-term pain relief for such conditions as headaches, muscle strain, arthritis. Opioid analgesics are used for relief of severe pain (both short term and long term). The most widely known anti-inflammatory is aspirin—a trade name for acetylsalicylic acid—that is a derivative of salicylic acid. Aspirin was marketed by Friedrich Bayer and Company in the 1890s—it was the first “block buster” pharmaceutical that commanded worldwide sales. Although aspirin has been remarkably effective, it was not until recently that the physiological basis of its effects were discovered: aspirin acts by inhibiting the production of prostaglandins, body chemicals that are necessary for blood clotting and are noted for sensitizing nerve endings to pain. Around 1960 the FDA approved a new anti-inflammatory, acetaminophen, marketed under the brand name Tylenol. Unlike aspirin, Tylenol does not create irritation of the stomach and gastrointestinal tract. Still, the most common cause of acute liver failure in the west is toxicity from acetaminophen, and the vast majority of people suffering from this condition in the United States are women (Thernstrom 2010: 147; see also Fishman 2000: 41).
Propagation of the Action Potential
Nassir H. Sabah in Neuromuscular Fundamentals, 2020
Another optimization condition applies to the ratio l/d, or l/a, assuming that the ratio d/a has been optimized, as discussed in the preceding paragraph. An l that is too small sacrifices some of the advantage of myelination and reduces the speed of conduction by reducing the distance over which the AP “jumps”. If l is too large, the axial resistance of the internode increases together with the total internodal capacitance and conductance of the membrane, which reduces the speed of conduction, as discussed in the preceding paragraph. Moreover, if l is too large and the generation of the AP at a given node is blocked for some reason, the strength of the current at the next node further along in the direction of propagation may not be sufficient to generate an AP at this node. This reduces the safety margin for propagation of the AP. In practice, blocking the generation of the AP even at two adjacent nodes does not stop the propagation of the AP. It may be noted that the effect of local anesthetics is to inhibit the activation of the voltage-gated sodium channels, thereby blocking the propagation of APs along fibers that conduct pain signals to the central nervous system.
Neurosurgery: Functional neurosurgery
Hemanshu Prabhakar, Charu Mahajan, Indu Kapoor in Essentials of Geriatric Neuroanesthesia, 2019
The anesthetic considerations for general anesthesia are similar to the previous description for conscious sedation. The key differences are that (i) intubation is usually performed before the placement of the stereotactic headframe and imaging, and (ii) a controlled light general anesthesia is given during the period of MER. This is often achieved with a combination of low-dose inhalation anesthetic (<0.5 MAC), opioid (such as remifentanil infusion at 0.03–0.06 μg/kg/min), and propofol infusion at 50–75 μg/kg/min. A small case series of five patients reported no changes in MER activities between local anesthesia and general anesthesia using remifentanil at 0.25–1 μg/kg/min and ketamine infusion at 0.5–3 mg/kg/h in the same patient (35). Because of the deliberate reduction of anesthetics, we always inform our patient about the possibility of awareness in the preoperative evaluation. However, there are increasing numbers of neurosurgical centers equipped with iMRI guidance capacity. The need for using controlled general anesthesia for neurophysiological guidance may be less likely to be encountered.
The role of DRP1 in ropivacaine-induced mitochondrial dysfunction and neurotoxicity
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2019
Yan Chen, Lili Yan, Yan Zhang, Xianhui Yang
Anaesthetics are used to prevent pain during medical and dental procedures. Anaesthetics are categorized into two classes: general anaesthetics (GA) and local anaesthetics (LA). The former causes a reversible loss of consciousness, and the latter causes a reversible loss of sensation in a limited region of the body and while maintaining consciousness [1]. Local anaesthetics act by interrupting neural conduction by inhibiting the influx of sodium ions. Generally, neuronal sodium channels exist in a resting state. When the neuron is stimulated, the channels assume an activated or open state and the ions diffuse into the cell where they initiate depolarization. Local anaesthetics (LAs) have a greater affinity for receptors of sodium channels during their activated and inactivated states than when they are in their resting state [2]. Based on the linked chemical group, LAs can be divided into two types: amide and ester [3]. Amide LAs are most commonly used clinically, and ester LAs are mostly used in topical and mucous formulations. The effects of amide LAs can last for 2 to 3 h and toxicity is more likely to occur in patients with impaired liver function [4]. Meanwhile, ester LAs last only a few minutes.
Synthesis of nanocapsules blended polymeric hydrogel loaded with bupivacaine drug delivery system for local anesthetics and pain management
Published in Drug Delivery, 2022
Wentao Deng, Yu Yan, Peipei Zhuang, Xiaoxu Liu, Ke Tian, Wenfang Huang, Cai Li
Postoperative pain management is still one of the most common problems that have largely gone unexplored (Peccora & Zhou, 2015). Clinically, local anesthetics (LA) are used to control pain after operations (including gastrointestinal surgery) or to treat other acute and chronic pain (Sandhu et al., 2021). Antipyretic analgesics (e.g. acetaminophen and celecoxib) and opioids can be used to provide relief (e.g. morphine and oxycodone). However, many drugs, particularly opioids, have serious adverse effects such as nausea, respiratory suppression, and vomiting as well as the potential to cause sensitization (Nersesyan & Slavin, 2007). However, because anesthetics have a low molecular weight, the duration of analgesia generated by a single injection is typically only very few hours, which does not meet the criteria for clinical use (Becker & Reed, 2012). The use of LA in the field of postoperative analgesia has recently received considerable attention in both scientific and clinical studies. Plain LA drugs, on the other hand, have a short duration of action. LA drugs such as lidocaine, bupivacaine (BPV), ropivacaine, and others exhibit small-molecule features such as limited action duration (1–2 h for lidocaine; 2–4 h for bupivacaine and ropivacaine) and fast relocation and encapsulation of LA agents with nanosystems (El-Boghdadly et al., 2018). As a result, the design and implementation of continuous release systems to extend the analgesic activity for days while reducing side effects are essential.
Comparison between pericapsular nerve group block and fascia iliaca compartment block for perioperative pain control in hip surgeries: A meta-analysis from randomized controlled trials
Published in Egyptian Journal of Anaesthesia, 2023
According to Table 1, the selected studies revealed both similarities and differences in several clinical aspects as follows: the sample sizes of all available literature were quite small, they ranged from 24 to 80 patients. All papers evaluated the analgesic efficacy of PENG compared to FICB in hip arthroplasty or hip fracture surgeries. PENG was given to the experimental groups, while FICB was given to the control groups. The dose and type of local anesthetics varied between articles. Preoperative nerve block was applied in eight studies (22,23,25,26,27,29,30,31), postoperative nerve block was used in two studies (24,27), and intra-operative nerve block was applied in one study (28). Nine studies (22,23,24,25,26,27,29,30,31)used spinal anesthesia (SA), and only one study (28) employed the general anesthesia. Participates in five studies (24,27,28,29,31) received patient-controlled analgesia (PCA) with opioids for acute pain management, while the remaining participants received IV analgesics at fixed time intervals with additional rescue opioid doses as needed. Pain intensity was expressed as a visual analog score or numeric rating score at different time points.
Related Knowledge Centers
- Anesthesia
- Awareness
- Consciousness
- Sodium Channel
- Pain
- Drug
- Sense
- General Anaesthetic
- Local Anesthetic
- Analgesic