Conscious Sedation

Combining academic knowledge and practical experience is a challenge that requires critical thinking and teamwork with other healthcare professionals. A theoretical, policy-based approach may not be appropriate for the fluctuating nuances of patient needs, especially with sedated patients. However, more flexible models focusing on skill and experience depend on the practitioner's expertise (Varndell et al., 2015). Healthcare professionals may struggle to adequately perform conscious sedation if they lack experience with sedation. The precise, prescribed amount of sedation for two seemingly similar patients could result in comfort and tranquility for one and pain and trauma or hypotension and organ damage in the other. Rather than prolonged education about genetic variability in P450 enzyme systems, healthcare professionals are better served by concentrating on effective assessment, intervention, and plan of care to achieve various treatment goals for sedated patients.

Patients who require respiratory assistance via an endotracheal tube or temporary devices such as laryngeal mask airways are considered intubated. These advanced airway devices stimulate the gag and other potent reflexes and initially require positive pressure ventilation. Patients receiving positive pressure via a tracheostomy may not require the same level of sedation to achieve adequate ventilation. Patients who require pressure support from specialized masks may not achieve adequate ventilation if heavily sedated, especially without a nasal or oral pharyngeal airway to decrease obstruction. Obstruction risks increase with obese patients, and medication doses should be adjusted, especially when calculating ideal body weight. Older adults also frequently present with comorbidities increasing sedation risks. When administering, sedation onset may be delayed. Remember, it is easier to give more sedation than it is to take back what has been administered.

Without a firm grasp of normal physiologic parameters, healthcare professionals may struggle to swiftly and correctly assess problems in ventilation and perfusion. For example, trauma patients requiring a chest tube often qualify for conscious sedation. Nurses must remember that air between the visceral pleura and the outer parietal pleura can worsen if a patient requires positive pressure ventilation through a bag and mask or endotracheal tube, resulting in a pneumothorax(Galvagno et al., 2020). Perfusion risks are not absent from scheduled, routine procedures, either. Although rare, exsanguination, or significant blood loss, can occur in many procedures, and sedation drugs may decrease blood pressure (Huei et al., 2017). To summarize, the conservative approach of too little sedation can increase blood pressure, bleeding, and patient movement. Too much sedation increases the risk of apnea in patients who may already be compromised.

Patients will use the chest, neck, and abdominal muscles when struggling to force air in and out of the lungs but quickly tire, as breathing is far more effective as a primarily passive exchange based on volume and pressure. Intubation prevents respiratory acidosis and subsequent respiratory failure from inadequate carbon dioxide elimination, sometimes due to excessive sedation. Once intubated, sedation allows the lungs and thoracic muscles to rest and the patient to tolerate mechanical ventilation(Galvagno et al., 2020).

During normal inspiration, the diaphragm and the external intercostal muscles contract slightly to enlarge the thoracic cavity, decreasing pressure so air will flow into the lungs until atmospheric pressure is reached. The chest and abdomen expand outward, and the diaphragm downward; this provides negative pressure ventilation instead of artificially forcing a specific volume and air pressure into the lungs. When the muscles are relaxed at the end of inspiration, the elastic lungs, and thoracic wall recoil, decreasing in volume to send deoxygenated air out of the lungs. The pressure within the pleural cavity remains negative due to the tendency of alveolar fluid surface tension and elastic lung tissue to pull the lung inward (Sieck et al., 2013). Also keeping the lungs inflated is the thoracic wall, which pulls away from the lung to enlarge the pleural cavity. The surface tension of the pleural fluid prevents actual separation. These opposing forces differentiate intrapleural and intrapulmonary pressures, which keep each lung inflated unless lung or thoracic injury obliterates the pressure gradient. Because of this interplay, the chest will rise and fall despite medication-induced relaxation of pharyngeal muscles, causing obstruction and decreased respiratory drive. The classic chin lift and jaw thrust taught in basic life support classes is often a simple remedy for obstruction.

Both propofol and benzodiazepines, such as midazolam, depress the central nervous system and cause sedation and amnesia via the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). These actions do not affect pain receptors, so a completely sedated patient may still require pain medication. Although effects are dose-dependent, propofol is preferred for anesthesia and has a quicker onset and recovery period. Midazolam does not decrease blood pressure, respiratory reflexes, or brain activity as much as propofol. Because of this added safety, nurses can "push" midazolam during conscious sedation procedures rather than just relying on an infusion. Individual variability requiring changes to the infusion rate is more pronounced in midazolam, as is also the case for opioids (NYSORA, 2023).

Opioids increase the anesthetic effect of sedation drugs but do not provide amnesia. Their primary action is analgesia due to mu receptor binding in the central nervous system. Sedation drugs combined with sufentanil or remifentanil infusions for the intubated and sedated patient may be encountered. However, the most common opioid for conscious sedation is fentanyl. Synergy is an important concept in pharmacology that healthcare professionals should be familiar with since multiple drugs acting on different receptors create various effects.

Midazolam and fentanyl are an adequate combination, while propofol and remifentanil may cause a decreased possibility of awareness. Except for remifentanil, opioids accumulate in the body to cause respiratory depression, constipation, and other side effects long after discontinuation. These side effects can complicate subsequent dosing, as can tolerance to initial infusion rates as liver enzymes process opioids more quickly. Traditionally, intravenous and inhaled medications are the gold standard for initially bypassing the liver, avoiding the variability dependent on the metabolizing ability of hepatic enzymes. Intranasal and buccal administration of fentanyl or dexmedetomidine is rising in popularity (NYSORA, 2023). Correct doses of oral non-steroidal anti-inflammatory drugs (NSAIDs) block cyclooxygenase (COX) and play an essential role in pain control. Antidepressants, gabapentin, and pregabalin, typically reserved for nerve disorders, are useful adjuncts. Multimodal and preemptive interventions decrease pain and the risk of respiratory depression, constipation, nausea, pruritus, and other unfavorable side effects associated with opioids that usually require reversal agents to attenuate. By using lesser amounts of multiple drugs, the risk of complications from any particular approach or class of medications will hopefully decrease.

Local anesthetics such as lidocaine prevent or relieve pain by binding to receptors on nerve sodium channels to stop nerve conduction. They pass through lipid-soluble nerve membranes but retain a partially ionic form to be active in the sodium channel. They are manufactured as water-soluble salts but do not work well in acidic environments like infected wounds. The influence of pH also means that adding sodium bicarbonate to a local anesthetic speeds onset while decreasing injection pain. Local anesthetists alter the function of all organs conducting or transmitting nerve impulses, so advanced cardiac life support (ACLS) may be needed if an overdose occurs. Plasma concentration depends on the dose, absorption, vascularization, and other properties of the site injected and metabolism by the body. Sensory disturbances such as tongue numbness and tinnitus typically precede life-threatening reactions. Large doses can be used with peripheral nerve blocks without the seizures, coma, and eventually, respiratory and cardiac failure that could follow the same dose in the bloodstream or spinal cord (Gadsden, 2017).

As opioid tolerance increases in the patient population, options are available to provide simultaneous sedation and analgesia. Ketamine targets the N-methyl-D-aspartate (NMDA) receptor to create a dissociative state, while dexmedetomidine stimulates alpha-2 receptors to provide sedation and suppress the release of pain-stimulating neurotransmitters. As in critically ill patients, parameters such as respiratory rate are no longer valid indicators of pain control. Epidural and regional nerve blocks can provide analgesia for the sedated and intubated patient. Intravenous acetaminophen and the non-steroidal anti-inflammatory ketorolac are useful adjuncts in select patients. The dysphoric effects of ketamine or the sedative and hypotensive side effects of alpha-2 agonists require adequate patient and healthcare professional education (NYSORA, 2023).

Even if these drugs are rarely used outside surgery or the emergency department in some hospitals, nurses in other specialties require a basic knowledge of their duration and effect. Just as volatile anesthesia agents' physiologic and pharmacologic effects extend into the postoperative period, even short-acting drugs can accumulate and cause side effects much later. Potent drugs for intubation may wear off before sedation infusions reach therapeutic levels. The healthcare professional is responsible for understanding and anticipating potential risks and complications.

Nurses continually expand their roles as more and more patients require complex sedation and airway management. The number of critically ill patients seeking medical care has increased by a third over the last few decades. Still, research and education methods preparing nurses to sedate these patients safely are lacking (Varndell et al., 2015). Self-directed learning fails to teach the required skills, and supervision and educational materials insufficiently train nurses to care for these patients.

Nurses need training in the clinical environment and preceptorships with experienced practitioners caring for these patients. It takes time to develop confidence when managing sedated and intubated patients. With experience, nurses realize that clear communication with the physician or nurse anesthetist is integral to best practice. Parameters for vital signs and level of sedation differ considerably depending on the situation (Varndell et al., 2015, Marthur et al., 2022).

Without defined goals and written orders for sedation, healthcare professionals must spend even more time carefully titrating infusions. Titrating can be especially difficult in emergency departments and other parts of the hospital that accept patients with unique situations. Visual cues are an important theme for nurses caring for sedated patients, but those cues need to come from vital signs—and occasionally, brain monitoring for awareness (Mathur et al., 2022). Unlike the other drugs mentioned thus far, ketamine is rarely administered as an infusion, making brain monitoring less accurate. Volatile anesthetics and sedation drugs increase GABA and depress cortical activity in the brain, but ketamine increases theta brain wave activity.

The most common monitor to interpret electroencephalogram readings into numeric values related to alertness is the Bispectral Index (BIS) monitor. Some companies use separate algorithms that do not correlate exactly to the values the BIS uses, such as between 40 and 60 for general anesthesia, especially during propofol infusions (Mathur et al., 2022). The utility of these monitors in the emergency department and intensive care unit may be limited to patients needing constant paralysis, such as in severe respiratory conditions.

The Glasgow Coma Scale and the Richmond Agitation and Sedation Scale are among the instruments that provide a fuller picture for healthcare workers to evaluate the level of consciousness of critically ill patients before, during, and after sedation. Scales provide an objective method to avoid giving too much or subtherapeutic doses of drugs, which can cause unstable vital signs and iatrogenic harm to the patient. Assessing sedation and pain is a practical and immediate measure to titrate sedation.

If sedation is temporarily halted to assess neurological status, some patients can motion with their fingers to indicate pain intensity on a numeric scale; this is the default method until educated about more reliable alternatives for nonverbal patients. Charts that the patient can point to or write on agreed signals for "yes" and "no" if the patient cannot nod or speak and other nonverbal signaling should complement observational pain scales whenever possible to procure the patient's report of pain (UFHealth, n.d.).

Many pain instruments are appropriate for the sedated patient. Most take into account oxygen saturation and other variables continuously monitored in sedated patients. One example is the Non-Verbal Pain Scale (NVPS), derived and validated as a more specific, adult version of the Face, Legs, Activity, Cry, Consolability (FLACC) tool. Researchers compared the NVPS to the Behavioral Pain Scale (BPS), which researchers specifically developed to provide nurses with the ability to differentiate noxious from non-noxious stimuli in sedated and mechanically ventilated patients. Observation of the face and upper limbs and respiratory factors such as compliance with the ventilator is the only parameters measured by the BPS (UFHealth, n.d.). The simplicity is a distinct advantage because one of the purposes of comparing pain scales is to determine whether staff nurses can use the tools as effortlessly and reliably as trained nurse investigators. But can't nurses determine pain needs by observing patient vital signs? Chronic pain rarely causes increased pulse rate and blood pressure, like acute pain, and many patients requiring conscious sedation are in acute pain situations. The problem is that respiratory rate and other physiologic parameters in acute care settings are influenced by the disease process and the multiple medications required to keep these patients stable.

NVPS and BPS pain scores do not show objective data to indicate increased pain for the patient. With this in mind, nurses should be aware of preconceived notions about anesthesia and analgesia. Generally, pain scores are low for patients who receive continuous sedation or analgesia, but nurses rarely find a consensus value at which most patients require pharmacologic intervention.

Nurses' amount of time communicating with sedated patients also lacks consensus. In one study, nurses spoke to patients for a maximum of 2 minutes per 3-minute encounter, and the worse the patient scored on sedation and consciousness scales, the less time they spent trying to ascertain their needs (Parida et al., 2018). Training in the perception of communication is one method to improve care for sedated patients. Nurses test much better after receiving education about how communication is perceived. However, quality indicators such as the need for physical restraints and heavy sedation did not change after nurse education, nor did pain score documentation or the prevalence of hospital-acquired pressure sores. Information about receptor sites with pharmacologic action or better ways to assess patients does not improve care alone. As mentioned earlier, nurses need a combination of education and supervised clinical training to better care for these complex patients. Misplaced caution from lack of knowledge can lead to inadequate sedation. Conversely, misinterpreting movement as justification to administer more anesthesia or analgesia can lead to overdosing the patient (Parida et al., 2018).

An induction agent such as etomidate or ketamine and a paralytic drug to facilitate intubation should be considered when a patient is unstable. Paralytics do not have amnestic or analgesic effects but affect the skeletal muscle receptors for acetylcholine. Cardiac and smooth muscle remain unaffected, but the diaphragm is a skeletal muscle, so breathing will cease. Succinylcholine or rocuronium are common paralytics but have differing onsets and duration. Like rocuronium, atracurium and cisatracurium can be titrated for long-term use but have the added benefit of reliable elimination independent of kidney and liver function. If the patient cannot maintain adequate oxygen saturation, the nurse may need to rely on ACLS skills and ventilate the patient with a bag and mask while waiting for intubation or reintubation (Bittner, 2021). Additional sedation should be administered at the discretion of the physician or nurse anesthetist intubating the patient.

Conscious sedation is often used to perform procedures not tolerated in a fully conscious state. Sedation, combined with an analgesic, also helps when pain is unmanageable. Different agents can be used to induce sedation, each with different dosages and effect times. Because of the potential risk for subtherapeutic doses or overdoses, it is essential to understand variability and synergistic effects within medications.

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