Anesthetic Agents

Hello  and welcome. Today we’re going to discuss the different types of anesthetics and their indication / effects.

Anesthesia is the administration of medication in order to cause a loss of sensation. The goal of anesthetics is to comfort the patient while a procedure or event is taking place. They are for short term use. Local anesthesia is direct to a region of the body, while general anesthesia has varying stages of sedation with – its highest efficiency resulting in complete loss of sensation, with loss of consciousness. When you think of local anesthesia, think of the going to the dentist. And when you think of general anesthesia, thing of operating room procedures. LIke the photo here, support will needed if someone is under general sedation.

When you think about anesthesia you have to focus on the body system affected. With the use of this drug class your central and peripheral nervous system are depressed. Now, the CNS system includes the spinal cord, nerves and brain. What does your brain control? That’s right, it controls your heart rate, breathing, and consciousness among other things. So depression on this system might include a respiratory rate of 4 to 5 bpm, leading to respiratory acidosis which would require your patient to need an advanced airway to support proper oxygenation and ventilation. Or your patient could be bradycardic and have perfusion issues requiring medication – perhaps atropine. Or even a patient lacking sensation or function due to blunted cranial nerves. The point being, overall depression to brain function and that requires prompt interventions.

Now, the PNS works within the CNS in providing support to your limbs and organs. Think ‘central’ – brain and spinal cord. ‘peripheral’ – limbs and organs. Is there is depression of the PNS you might see blunting of certain organ activity causing loss of sensory stimulation and muscle relaxation. The patient under anesthesia shouldn’t feel anything and shouldn’t be able to move his or her limbs. Again, advanced airway and support is needed in people under anesthesia because you basically turned their internal computer off. They are like a wet noodles. Unable to follow commands, unable to move. You have chemically disabled their system. Think about it like you trying to use your cellphone and the batter is dead, nothing will happen. That’s a simplified version of what is happening.
Let’s quickly review how local anesthetics work. Normally, sodium channels are open, allowing sodium to entire the neurons. This is the baseline. When local anesthetics are used, those sodium channel are blocked, resulting in sensory and motor impulse impairment. This results in a temporary diminished sensation of pain or movement. The degree of dependent of dose given and strength. Some anesthetics contain additives to intensify the effects and asst eith blood volume loss (an example is epi, which does both). The goal is the anesthetic to last long enough to complete the procedure.

Let’s begin with local anesthesia. It results in a localized (surface) reaction and response. It is often given during dental procedures or procedures focused on one body part of region. Local anesthetics include, topic, infiltration, nerve block, spinal and epidural. We will discuss each one shortly. Just remember, the drugs are centralized thus the response is focused on the body part involved. For a more in depth review on local anesthesia, please check out our perioperative course.

Local anesthesia is classified by its chemical structure and types. The main categories are esters and amides. Esters being the first category, founded in the 1800s. One long time esters was cocaine, yeah! Wild, right? Another one is procaine aka Novocain – which isn’t used in dentistry anymore but it a short time was widely used. Amides replaced esters due to fewer side effects and longer duration of effects. Lidocaine is common drug used in the healthcare setting.

Now, as with any drug there will be adverse effects. With anesthetics, the major ones are life-threatening. This is why caution must be used with these drugs are administered and proper monitoring in crucial. Major side effects mention include Respiratory arrest, circulatory failure and anaphylactoid reactions. The theme here is airway and cardiovascular failure. When you think of anesthetics, think airway and hemodynamics.

Let’s begin with the general anesthesia breakdown. As mentioned before, there is a loss of sensation throughout the body and a loss of consciousness. General anesthesia can be divided into two classes: IV and inhaled.

IV drugs include benzodiazepines, opioids and sedatives / hypnotics drug categories. Benzodiazepines and opioids have their own lesson with more details, I recommend you check them out. These IV drugs are used during general anesthesia. We will cover sedatives / hypnotics here.

This class of sedatives and hypnotics are unique but well-known of medications. A certain celebrity was found dead after taking propofol for insomnia. These drugs are strong, their adverse effects can be life-threatening. Patients under general anesthesia will need ventilatory support as their bodily functions have been blocked. My husband’s heart surgery was 8 hours in length. Without proper monitoring, he would have died. Drugs of this magnitude MUST be supported with advanced devices such as mechanical ventilation.

Now, the alternative to intravenous is inhaled general anesthesia – which includes gas and volatile liquids.

Nitrous oxide is the lone ranger in the gas category. With a common trend of apnea being present, like all anesthesia drugs. I asked an anesthesiologist which was better, gas vs IV and was told – IV and gas are used together to reduce the doses of one another, thereby lowering the potential for adverse effects. Also when combined, they produce greater analgesia and relaxation. We are trying to find that nice balance.

Lastly, we have –  inhaled drug category titled volatile liquids and boy are they volatile. Did you see the adverse effects on this one? Many, many swift life-threatening complications are seen here. Volatile anesthetics are liquid at room temperature and converted into vapor and inhaled to produce their effects. The excreted entirely by the lungs and exhalation. Which means a delay in exhalation, a delay in excretion.

Key nursing concepts include functional ability – As the patient has an altered level of consciousness / cardiovascular & respiratory insufficiency, mobility problems d/t the intense effects of the drugs. And lastly, pharmacology based on medication administered.

Let’s recap – the focus with anesthesia is to understand the pharmacology and it’s impact of the body itself. With these drugs, there are CNS / PNS depression d/t blocked sodium channels. The strength of effect is then based on it’s route (loca, IV, gas, volatile liquids). If it’s a topical application, it wouldn’t have the same overall effect has nitrous oxide, for example. The heavier hitters (IV, gas) will requires external support to the pulmonary and cardiac systems. Those functions are blunted therefore you have stopped their regular functioning. And lastly, the adverse effects are based on the route (local can cause burning, while gas use can cause apnea). If you know what is being altered and how, you will understand the rest. For a more in depth review on local anesthesia, please check out our perioperative course.

Don’t forget to check out the lecture of sodium channels to further understand the drug actions mentioned in this presentation. Now, go out and be your best self today and as always, Happy Nursing!