B. Carlos. New York University. 2019.
In the retrocrural approach buy rulide 150mg, the tip of the needle is advanced approximately 1 cm anterior to the anterior and upper border of L1 order rulide 150 mg. In the anterocrural or transaortic approach buy rulide with visa, the tip of the needle is advanced through the lower portion of L1 and the aorta on the left side until blood can no longer be aspirated through the needle. For splanchnic nerve block, the tip of the needle is placed at the anterior portion of the T12 vertebral body. Better results are usually seen with local anesthetics because of better spread (phenol is viscous and its vascular absorption may relieve pain). The dosages of the neurolytic agents are 30 to 40 mL for the retrocrural and anterocrural approach, and 10 to 15 mL on each side for splanchnic nerve blockade. Complications from the celiac plexus block include orthostatic hypotension, back pain, retroperitoneal hematoma, reactive pleurisy, hiccups, hematuria, transient diarrhea, abdominal aortic dissection, transient motor paralysis, and paraplegia. The paraplegia and transient motor paralysis may be due to spasm of the lumbar segmental arteries that perfuse the spinal cord, direct vascular or neurologic injury, or retrograde spread to the nerve roots or spinal cord. Note that the tip of the needle is in the upper third of L1 and about 1 cm beyond the border of the vertebral body for the retrocrural technique; the spread of the contrast medium is cephalad. In contrast, the tip of the needle is the lower third of L1 and about 3 cm beyond the border of the vertebral body for the anterocrural technique; the spread of the contrast medium is caudad and in front of the aorta. A meta-analysis of 21 retrospective studies in 1,145 patients concluded that adequate-to-excellent pain relief was achieved in 89% of the patients during the first 2 weeks following the block and partial-to-complete pain relief continued in 90% of the patients at the 3-month interval. The plexus is located in the retroperitoneum, bilaterally extending from the lower third of the fifth lumbar vertebra to the upper third of the first sacral vertebra. For blockade of the plexus, the patient is placed in the prone position and two 7-cm needles are inserted, under fluoroscopy, in medial and caudal directions until the tips lie anterior to the L5 to S1 intervertebral disc space. After injection of contrast medium, 6 to 8 mL of local anesthetic is used for a diagnostic block while phenol or alcohol is employed for neurolysis. Anterior ultrasound-guided superior hypogastric plexus blocks appear to be effective for pelvic pain. Case reports support the efficacy of neurolytic superior hypogastric plexus block both in reducing pelvic pain secondary to cancer and in decreasing opioid consumption. Visceral afferents innervating the perineum, distal rectum, anus, distal urethra, vulva, and distal third of vagina converge at the ganglion. Four to 8 mL of local anesthetic is used for diagnostic block and 8% to 10% phenol or 50% alcohol is used for neurolysis. Similar to superior hypogastric plexus blocks, there are no controlled studies on its efficacy, although case reports confirm its effectiveness in relieving perineal pain secondary to cancer. Pharmacologic Management of Pain Opioids Morphine is the standard for opioid therapy for cancer pain (see Chapter 20, Opioids). The metabolites of morphine include morphine-6-glucuronide, which causes additional analgesia, and morphine-3-glucuronide, which can cause adverse effects. Controlled-release preparations are available, reducing the need to take the drug frequently. Hydromorphone, a μ-receptor agonist, is three to five times more potent than morphine when given orally and five to seven times more potent when given parenterally. Pruritus, sedation, nausea, and vomiting occur less frequently compared with morphine. Its metabolite, hydromorphone-3- glucoronide, lacks analgesic property but possesses properties similar to that of morphine-3-glucuronide. Methadone has a 60% to 95% bioavailability, high potency, and a long duration of action. Its potency compared with morphine ranges from 1:1 to 1:2 on acute dosing but can be 1:4 with chronic dosing. It has a long and unpredictable half-life of 8 to 80 hours that makes it difficult to achieve steady-state plasma concentrations, increasing the risk of accumulation and the need for careful and individualized dosing. There has been an “epidemic” of deaths due to 4050 unintentional overdose from methadone111 because many physicians do not appreciate the consequences of the drug’s long and unpredictable half-life. Most reports are based on high-dose maintenance (>120 mg) for the treatment of addiction; however, such occurrences have also been reported with lower dosages. It has a high bioavailability (60%) and is associated with a low incidence of itching and hallucinations. The controlled-release preparation (OxyContin, Purdue Pharma) has good analgesic characteristics but became a popular drug for abuse prior to its reformulation to include abuse-deterrent technologies. Oxymorphone has greater affinity to the μ-receptor than morphine and has little or no affinity to the κ-opioid receptor. Due to extensive first-pass hepatic metabolism, the bioavailability of oxymorphone is only 10%. It should not be taken with alcohol because this increases its plasma concentration by as much as 300%. The efficacy of oxymorphone in chronic and cancer pain is similar to other opioids. Buprenorphine is a partial agonist at the μ-receptor, a κ-antagonist, and a weak δ-agonist. It has a rapid onset (30 minutes) when given orally and a long duration of action of 6 to 9 hours. Buprenorphine antagonizes the opioid effects of full agonists such as morphine or hydromorphone due to its partial opioid agonist pharmacodynamics. Approximately 9% of Caucasians do not have the enzyme and do not experience analgesia from codeine. Children under 12 years of age lack maturity of the enzyme and cannot convert the drug to morphine, experiencing the drug’s side effects with minimal analgesia. It has bioavailability of 80% to 90%, low abuse potential, low incidence of constipation, and minimal risk of fatal respiratory depression, which is possibly limited to patients with severe renal failure. Tapentadol is similar to tramadol and also has a dual mode of action as a μ- opioid agonist and a norepinephrine reuptake inhibitor. Tapentadol has side effects and adverse reactions that are similar to those of tramadol, but has a higher risk of addiction and respiratory depression due to its opioid agonism. The oral equianalgesic doses of morphine 10 mg intravenously or 30 mg orally are (1) 200 mg of codeine, (2) 30 mg of hydrocodone, (3) 20 mg of oxycodone, (4) 150 mg of tramadol, and (5) 75 mg of tapentadol. A 2013 study determined, contrary to older studies, that individuals receiving stable doses of 20 mg of morphine or equivalent are at increased risk for motor vehicle collisions and this risk increases substantially at doses above 120 mg. Opioids are commonly used for cancer pain, with long-acting opioids supplemented by short-acting ones for breakthrough pain. Opioid monotherapy in cancer pain is rarely successful and adjuvants and procedural interventions are usually added for increased efficacy. The use of opioids for acute or short-term pain (<3 months) following surgery or traumatic injuries is well accepted and supported by the literature. The use of opioids for treatment of chronic (>3 months) noncancer pain is controversial.
Figure 5-22 Detail of the inside of a circuit breaker box in an isolated power system 150 mg rulide overnight delivery. The bottom arrow points to ground (green) wires meeting at the common ground terminal rulide 150mg online. Arrows 1 and 2 indicate lines 1 and 2 (orange and brown) from the isolated power circuit breaker buy cheap rulide 150mg on line. This is in marked contrast to Figure 5-13, where the neutral and ground wires are attached at the same point. An individual contacting one side of the isolated power system (point A) and standing on the ground (point B) will not receive a shock. In this instance, the individual is not contacting the circuit at two points and thus is not completing the circuit. Point A is part of the isolated power system, and point B is part of the primary or grounded side of the circuit. If a faulty electrical appliance with an intact equipment ground wire is plugged into a standard household outlet, and the home wiring has a properly connected ground wire, then the amount of electrical current that will flow through the individual is considerably less than what will flow through the low-resistance ground wire. However, if that ground wire were broken, the individual might receive a lethal shock. This is an important feature because the faulty piece of equipment may be part of a life-support system for a patient. It is important to note that even though the power is isolated from ground, the case or frame of all electrical equipment is still connected to an equipment ground. The third wire (equipment ground wire) is necessary for a total electrical safety program. As previously discussed, electrical power cords, wires, and electrical motors exhibit capacitive coupling to the ground wire and metal conduits and “leak” 347 small amounts of current to the ground (Fig. Figure 5-24 A faulty piece of equipment plugged into the isolated power system does not present a shock hazard. The figure inset illustrates that the isolated power system is now identical to the grounded power system. Therefore, it is essential that a warning system be in place to alert the personnel that the power is no longer ungrounded. As previously discussed, with perfect isolation, impedance would be infinitely high and there would be no current flow in the event of a first fault situation (Z = E/I; if I = 0, then Z = ∞). Once this preset limit is exceeded, visual and audible alarms are triggered to indicate that the isolation from the ground has been degraded beyond a predetermined limit (Fig. This does not necessarily mean that there is a hazardous situation, but rather that the system is no longer totally isolated from ground. This faulty piece of equipment should be removed and serviced as soon as possible. However, this piece of equipment could still be used safely if it were essential for the care of the patient. It should be remembered, 349 however, that continuing to use this faulty piece of equipment would create the potential for a serious electrical shock. However, the system is still safe and represents a state significantly different from that in the first situation. Both of these monitors would trigger an alarm at 2 mA, which led to annoying “false” alarms. Also, in the event of a second fault, the equipment ground wire provides a low- resistance path to ground for most of the fault current (Fig. If the isolation of the power system is degraded such that more than 2 mA (5 mA in newer systems) of current could flow, the hazard light will illuminate and a warning buzzer will sound. The other possibility is that too many pieces of electrical equipment have been plugged in and the 2 mA limit has been exceeded. If the gauge is between 2 and 5 mA, it is probable that too much electrical equipment has been plugged in. The next step is to identify the faulty equipment, which is done by unplugging each piece of equipment until the alarm ceases. Therefore, if possible, no other electrical equipment should be connected during the remainder of the case, or until the faulty piece of equipment can be safely removed. As Figure 5-5 demonstrates, the current flowing in both the hot and neutral wires is usually equal. If it cannot be reset, then the equipment must be removed from service and checked by the biomedical engineering staff. Double Insulation There is one instance in which it is acceptable for a piece of equipment to have only a two-prong and not a three-prong plug. These instruments have two layers of insulation and usually have a plastic exterior. Double insulation is found in many home power tools and is seen in hospital equipment such as infusion pumps. However, if water or saline should get inside the unit, there could be a hazard because the double insulation is bypassed. The equipment ground wire provides a low-impedance path in which the majority of the leakage current (dashed lines) can flow. Microshock As previously discussed, macroshock involves relatively large amounts of current applied to the surface of the body. The current is conducted through all the tissues in proportion to their conductivity and area in a plane perpendicular to the current. Consequently, the “density” of the current (amperes per meter squared) that reaches the heart is considerably less than what is applied to the body surface. Microshock is a particularly difficult problem because of the insidious nature of the hazard. In the electrically susceptible patient, ventricular fibrillation can be produced by a current that is below the threshold of human perception. The exact amount of current necessary to cause ventricular fibrillation in this type of patient is unknown. If an individual simultaneously touches the case of an instrument where this has occurred and the electrically susceptible patient, he or she may unknowingly cause a discharge to the patient that results in ventricular fibrillation. Once again, the equipment ground wire constitutes the major source of protection against microshock for the electrically susceptible patient. In this case, the equipment ground wire provides a low-resistance path by which most of the leakage current is dissipated instead of stored as a charge. Figure 5-30 illustrates a situation involving a patient with a saline-filled catheter in the heart with a resistance of approximately 500 ohms. A leakage current of 100 μA will divide according to the relative resistances of the two paths. However, if the equipment ground wire were broken, the electrically susceptible patient would be at great risk because all 100 μA of leakage current could flow through the catheter and cause ventricular fibrillation (Fig. Figure 5-31 A broken equipment ground wire results in a significant hazard to the electrically susceptible patient. In this case, the entire leakage current can be conducted to the heart and may result in ventricular fibrillation.