Agents for the Relief of Pain and Anxiety in the Cath Lab

Patients come to us with an understandable apprehension about having a cardiac cath or EP study performed on them. They see the X-ray equipment, sterile table, hats and masks, and it reminds them of something out of a Frankenstein movie. Yet the procedure is so routine to us that we may sometimes overlook their perception and go about our business. The fact is, we make the difference between whether a patient has a positive experience or a miserable one. One secret to making sure their experience is pleasant, beyond our reassuring manner, is located under lock and key in the controlled substances cabinet. In the process of making our patients comfortable, we have an obligation to educate ourselves about the drugs we administer and to provide diligent monitoring of patient response. In this article I will discuss the commonly used medications for the relief of pain and anxiety in the cardiac cath lab, as well as specifics about controlled substances, reversal agents and tips for avoiding medication errors. Controlled Substances. Narcotics, anesthetics and analgesics are grouped into categories (Schedules I-V), based on their potential for physical and psychological dependence and their medical effectiveness, by the Drug Enforcement Agency (DEA), a branch of the United States Justice Department. In 1970, the Controlled Substances Act (also called the Comprehensive Drug Abuse Act) was made into law. It limits the number of refills that can be obtained from a prescription. Controlled substances require proper handling in the hospital setting. Only physicians, veterinarians, podiatrists and dentists can prescribe controlled substances. Schedules of controlled substances. Schedule I drugs carry an unacceptably high potential for abuse and physical and psychological dependence, and are therefore illegal in the U.S. These include marijuana, heroin, mescaline, and LSD. Schedule II drugs have a high potential for abuse and an extreme risk of physical and psychological dependence. They include amphetamines, opioid analgesics and certain barbiturates. Amphetamines are nervous system stimulants that produce insomnia and euphoria. Opioid analgesics are narcotics that are derived from opium or are synthetically created to produce activity similar to opium. Barbiturates are medicines derived from barbituric acid and act as a sedative or hypnotic. Prescriptions may be obtained in writing from a physician, but may not be refilled. Some examples of Schedule II drugs are morphine, codeine, fentanyl, meperidine (Demerol), hydromorphone (Dilaudid) and oxycodone. There are many others. Schedule III medications have less potential for abuse than Schedule II drugs and an intermediate risk for physical and psychological dependence. This group includes specific sedatives and CNS stimulants, as well as limited dosages of certain opioid analgesics. Examples of Schedule III drugs are anabolic steroids, codeine and hydrocodone in combination with nonopioid analgesics, and thiopental. Prescriptions for these medications can be refilled up to five times within 6 months from date of prescription, if authorized by the physician. Schedule IV medications have less abuse potential than Schedule III and minimal liability for physical or psychological dependence. There are too many of these to mention; however, agents specifically used in the cath lab are diazepam and midazolam. Schedule V medications have the least abuse potential of the controlled substances and contain a small amount of narcotic combined with an anti-tussive or an anti-diarrheal. These include codeine, buprenorphine, and diphenoxylate/atropine. The physician who prescribes one of these medications determines the number of refills, and some products, such as cough suppressants with small amounts of codeine, may be available over-the-counter for adults. Narcotic analgesics. Narcotic analgesics are either derived from opium or synthetically produced to mimic opiates. They reduce pain impulse transmission by binding with opiate receptors in the central nervous system, altering the perception of pain and producing euphoria and deep sleep. They also depress respirations, inhibit the cough reflex, constrict the pupils, and decrease peristalsis, emesis and nausea. Narcotic analgesics are used for the relief of moderate to severe pain. Those used most often in the cath lab include morphine, meperidine (Demerol), fentanyl, and hydromorphone (Dilaudid). Morphine is especially helpful for heart patients because it increases venous capacitance and reduces systemic vascular resistance. These actions serve to decrease the workload of the heart muscle by reducing myocardial wall tension and myocardial oxygen demand. Morphine benefits patients diagnosed with an acute MI as well as patients in pulmonary edema and congestive heart failure. Demerol is used for pre-operative sedation and treatment for moderate to severe pain. It is half as potent as morphine for analgesia and its duration is shorter than most opiates. A common side effect of Demerol is nausea and vomiting, because it stimulates the chemo receptor trigger in the central nervous system. Fentanyl is relatively short-acting with analgesic effects lasting from 30 minutes to 2 hours depending on the route of administration, although respiratory depression may last longer. Hydromorphone is used to treat moderate to severe pain with effects lasting 2-3 hours for IV administration. It is important to note that fentanyl and hydromorphone can cause serious and potentially fatal reactions in patients who have taken MAO inhibitors within the previous 14 days. Benzodiazepines. Diazepam (Valium), lorazepam (Ativan) and midazolam (Versed) belong to a class of drugs known as benzodiazepines. They are used to relieve anxiety and produce conscious sedation prior to and during invasive procedures. These agents affect the psychic functioning and behavior (memory, thinking and perception). Benzodiazepines produce these effects by binding to gamma-aminobutyric acid (GABA) receptor sites within the central nervous system. GABA is an inhibitory neurotransmitter, which reduces the formation of action potentials and neuron firing. When benzodiazepine agents bind to GABA receptor sites, they increase the affinity of GABA and produce generalized CNS depression. Diazepam causes skeletal muscle relaxation and has anti-convulsant effects. It is a long-acting sedative, with effects lasting up to 24 hours with oral administration and 15-60 minutes with IV use. It is available in IV, PO and IM forms. The usual dose given for conscious sedation is 2-10 mg. Lorazepam is another long acting sedative/hypnotic, with effects lasting up to 48 hours. In addition to relieving anxiety, it also provides amnesic and antiemetic effects and is an anticonvulsant. Midazolam is a short-acting sedative/hypnotic with effects lasting 2-6 hours. This agent also produces amnesia and because of this patients may not remember or be able to follow post procedure instructions even though they may seem fully awake. When administered in higher doses, diazepam and midazolam are used for anesthesia induction prior to procedures such as cardioversion, permanent pacemaker insertion, intubation, and transesophageal echocardiography. Nubain. Although nalbuphine (Nubain) is not a controlled substance, it is worth mentioning. It is a potent analgesic with pain-relieving properties equal to that of morphine. Nubain is a narcotic agonist and therefore potentiates the effects of narcotics. It interacts with opiate receptors and decreases pain impulse transmission. Nubain will cause respiratory depression and hypotension when used concurrently with antihistamines, sedatives, skeletal muscle relaxants and of course, narcotic analgesics. Adverse effects. Adverse effects common to narcotic analgesics and benzodiazepines are: respiratory depression hypotension bradycardia confusion Appropriate dosing for conscious sedation should be individualized, being sure to reduce the dose for patients who are elderly or debilitated. These patients can be more sensitive and therefore may require a smaller dose. When any of these medications are used in combination (or in combination with other drugs that cause respiratory depression, such as Benadryl) they may produce more pronounced central nervous system depression. It is important to monitor respiratory status, blood pressure, level of consciousness and patient response when administering controlled substances and before giving subsequent doses. Reversal agents. There are two main reversal agents, Narcan and Mazicon, which are used to counteract controlled substances. Naloxone (Narcan) is an opiate antagonist administered to reverse CNS and respiratory depression in the event of narcotic oversedation. Narcan works by binding to and competing with narcotics at central nervous system receptor sites. Narcan is able to reverse meperidine, hydromorphone, fentanyl, Nubain and morphine. In patients with narcotic addictions, Narcan can cause severe withdrawal symptoms. Adverse reactions include ventricular fibrillation, ventricular tachycardia, hypotension, hypertension and pulmonary edema. Romazicon (mazicon) is a benzodiazepine antagonist used to reverse adverse effects of Ativan, Valium and Versed. It competes with and inhibits activity at benzodiazepine receptor sites, resulting in either complete or partial reversal, depending on the dose. Resedation can result with Narcan and Mazicon, if the antagonist agent is shorter-acting than the drug it is reversing. Additional doses may be repeated every 20 minutes if this occurs.

NULL