The use of the opium plant itself Papaver somniferum has a long human history and probably predates history. It is widely believed that cultivation of these opium poppies was used for ritual purposes and dates back to at least the Neolithic New Stone Age. Further, the writings of Pedanius Dioscorides 40—90 AD , a Greek botanist, pharmacologist and physician, who authored a five-volume encyclopedia about herbal medicine and related medicinal substances, mentioned opium plant. In the late 18th century, when the East India Company gained a direct interest in the opium trade, another opiate recipe called laudanum became very popular among physicians and their patients.
August Bier, a surgeon, and his assistant Hiselbrandt, made history using intrathecal cocaine on each other, at the Royal Chirurgical Clinic in Kiel in They used 5 mg of intrathecal cocaine and complete loss from legs sensations lasted almost 45 minutes. In the United States the first surgeons to utilize spinal anesthesia were Tait and Cuglieri in San Francisco on , which performed an osteotomy of tibia under regional anesthesia. The Romanian surgeon Racoviceanu-Pitesti, who reported his experience using a mixture of cocaine and morphine in Paris in , made the first publication concerning the use of opioids in spinal anesthesia .
The field was plagued with problems that were overcome in the s when spinal opioid receptors were discovered, and it was proven that direct application of morphine into the spine produced analgesia .
This became a tangible reality when Wang et al. The latter authors reported achieving pain relief for between 6 and 24 hours in 10 patients and suggested that there was a direct spinal effect on the specific receptors in the gelatinous substance of the posterior horn of the spinal cord.
Therefore, more than a century passed until it became routine to use opioids via the spinal cord for intra and postoperative analgesia and in labor, as well as for chronic pain, in particular that associated with cancer. It is striking that in the first 50 years of the history of spinal anesthesia the main role was played by the surgeons themselves, and then over time they became less involved, the field now being exclusively the domain of anesthesiologists [7,8]. The physicochemical properties of neuraxial opioids determine their onset time, duration of action, and potency.
Epidural Opioids for Postoperative Pain — Johns Hopkins University
High lipid solubility and low pKa results in a highly potent opioid with a rapid onset of effect, but limited duration of action, whereas decreasing lipophilicity increases the duration of action. Lipid soluble opioids also resemble local anesthetics in terms of their pKa, molecular weight, and partition coefficients that may explain some of the analgesic effects of CSF opioids.
At physiological pH 7. However, it is the hydroxyl groups on the morphine molecule that are responsible for its greater water solubility compared with other opioids. Increased water solubility is responsible for slow onset of effect and long duration of action.
Epidural Morphine for Postoperative Analgesia After Total Knee Arthroplasty
Potency of spinal opioids increases with increasing hydrophobicity . The pharmacokinetics of intrathecal opioids is complex, follows a multi-compartmental model, and is determined by the opioid physicochemical properties and the CSF dynamics. In the systemic circulation, the calculation of pharmacokinetic data such as volume of distribution assumes adequate mixing and equilibration of drug across all compartments. However, the CSF is a poorly mixed compartment with established cephalic-caudal gradients for opioids after administered into the lumbar CSF.
The clinical characteristics of each opioid will be the consequence of the sum of all these types of distribution as they define its bioavailability and its spinal effect. Cephalic movement of opioids injected into the CSF is the result of Bulk flow of drug in a caudal-cephalic direction, fluctuating pressure changes within the thorax as a result of respiration, facilitating cephalic flow of CSF, expansion on systole and relaxation on diastole of the brain, occurring as a result of the cardiac cycle.
This helps to create a backward and a forward motion of CSF with a net transfer of opioid in a cephalic direction . Treatment groups received an epidural containing local anaesthetic with or without opioids.
Control groups received an opioid-based regimen, given either into the blood or through an epidural. The main outcome of interest was return of gut function as measured by time to first flatus after surgery. Other outcomes included pain scores up to hours post-surgery, vomiting within 24 hours, leakage where bowel sections were joined, length of hospital stay and costs. The included trials were of mixed quality ranging from very low to high quality.
Common sources of bias involved treatment allocation, and patients and assessors being aware of pain-relief given. Only six were conducted in the UK. High quality evidence from 22 trials 1, participants found an epidural containing local anaesthetic decreased the time to return of gut function by approximately There was high variability in the results of the individual studies, but subgroup analyses did not significantly affect the result.
For example, the effect was the same regardless of type of abdominal surgery, or whether or not an opioid was added to the epidural. Moderate quality evidence from 35 trials 2, participants found an epidural containing local anaesthetic reduced pain on movement 24 hours after surgery SMD This was equivalent to a reduction of 2.
Low quality evidence found that an epidural with local anaesthetic did not affect the likelihood of vomiting risk ratio [RR] 0. Very low quality evidence from 30 trials 2, participants found that epidural analgesia reduced the time spent in hospital after open surgery by one day SMD Only two small studies provided any information on comparative costs. There is no specific NICE guidance on the use of epidural anaesthesia or opioid injections following abdominal surgery. An increase in the use of opioids for acute postoperative pain was observed in the US following the release of this statement, as was an increase in their side effects.
This updated review provides high quality evidence that an epidural anaesthetic with or without an opioid accelerates return to normal bowel function following abdominal surgery. It may also have a clinically meaningful effect on pain. However, evidence for other outcomes was less reliable. Decisions to use epidural analgesia over other methods of pain-relief following abdominal surgery must be made on a case-by-case basis taking into account patient factors, type of surgery and postoperative ward facilities.
Implications for practice of an increase in epidural use will include nurse training in administering epidural pain-relief on the postoperative ward. Epidural local anaesthetics versus opioid-based analgesic regimens for postoperative gastrointestinal paralysis, vomiting and pain after abdominal surgery. Cochrane Database Syst Rev. White PF, Kehlet H. Improving pain management: are we jumping from the frying pan into the fire? Anesth Analg. Cochrane Database Syst Rev Volume 7 , An epidural involves inserting a catheter narrow tube into the epidural space in the spine.
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This is the space between the vertebrae and the outer membrane that covers the spinal cord and cerebrospinal fluid. J Anesthesiol Clin Pharmacol ; J Opioid Manag ; J Clin Psychopharmacol ; Admixture of clonidine and fentanyl to ropivacaine in epidural anesthesia for lower abdominal surgery. Anesth Essays Res ; Comparative evaluation of dexmedetomidine and fentanyl for epidural analgesia in lower limb orthopedic surgeries. Bupivacaine: A review of 11, cases.
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