Perianesthesia care

Because thiopental can have an antianalgesic effect at low concentrations, some patients who have pain may be irrational, hyperactive, and restless during the initial recovery phase. The patient may exhibit some shivering related to lowered body temperature, which can result from a cold operating suite. Of concern to the perianesthesia nurse is the patient admitted with cold, clammy, and cyanotic skin. This effect occasionally occurs with thiopental and is caused, in part, by the peripheral vasoconstrictive action of the drug.

If the anesthesia time exceeds 1 hour or if the total dose of thiopental exceeds 1 g, patients may have a delayed awakening time because of the redistribution of thiopental. This phenomenon is particularly common in obese patients because the drug is highly fat soluble. At present, no antagonist exists for the barbiturates; therefore airway management and monitoring of cardiovascular status are important.

Perianesthesia care

When a patient has received propofol for induction or even via continuous infusion, the perianesthesia nursing care should be based mainly on the other drugs that were used during surgery, because propofol is so rapid and has no cumulative effects; its effects are normally dissipated within 8 to 10 minutes. Consequently, the patient usually arrives in the PACU awake and in pain; therefore analgesics should be titrated to effect. Titration is recommended in the immediate postoperative period because propofol and opioid analgesics can have a synergistic effect.

Propofol is a major component used in modern clinical anesthesia practice. It offers many advantages and few disadvantages. More specifically, propofol has one major advantage over all the other intravenous induction agents: early awakening. It can be used in the PACU if indicated. The major concern for the perianesthesia care of the patient who has received this drug is the level of postoperative pain. The nursing assessment and appropriate interventions for pain are the most important aspects of care of the patient who has received this drug.⁶

Midazolam

Midazolam has become a popular drug in anesthesia practice and in the perianesthesia care of surgical patients. Midazolam can be used for premedication, cardioversion, endoscopic procedures, and induction of anesthesia and as an intraoperative adjunct for inhalation anesthesia. It also is an excellent agent for sedation during regional anesthetic techniques. The principal action of midazolam is on the benzodiazepine receptors in the CNS, particularly on the limbic system, which results in a reduction in anxiety and profound anterograde amnesia. This drug also has excellent hypnotic, anticonvulsant, and muscle-relaxant properties.

The water-soluble midazolam may offer some advantages over diazepam. It causes depression of the CNS by inducing sedation, drowsiness, and finally sleep with increasing doses. Midazolam is three to four times as potent as diazepam, has a shorter duration of action, and has a lesser incidence rate of injection pain and postinjection phlebitis and thrombosis. More specifically, this drug has a rapid onset of action, a peak in action between 10 and 30 minutes, and a duration of action between 1 and 4 hours. Midazolam administered at a dose of 0.2 mg/kg produces a decrease in blood pressure, an increase in heart rate, and a reduction in systemic vascular resistance. Midazolam should be used with caution in patients with myocardial ischemia and in those with chronic obstructive pulmonary disease.⁹ Postoperative patients who have a substantial amount of hypovolemia should not receive midazolam. In addition, midazolam does not affect intracranial pressure.^4,10 Consequently, this drug can be used safely in neurosurgical patients in addition to patients with intracranial pathophysiology.

This drug can be administered in the PACU¹¹; therefore the postanesthesia nurse must monitor the patient for respiratory depression after injection because midazolam causes a dose-dependent respiratory depression. Given that every patient in the PACU has received a plethora of depressant drugs during surgery, midazolam can be potentiated easily when administered in the PACU. Because of this potentiation factor, any dose of midazolam administered in the PACU should be considered effective enough to cause profound respiratory depression. Therefore, oxygen and resuscitative equipment must be immediately available, and a person skilled in maintaining a patent airway and supporting ventilation should be present. Extra care also should be observed in patients with limited pulmonary reserve and in the elderly and debilitated with reduction of the dosage of midazolam by 25% to 30%.

Midazolam can be given via continuous infusion for patients who need sustained sedation.⁷ However, midazolam has a pH-dependent diazepine ring; at physiologic pH, the ring can close, causing CNS penetration. In addition, its metabolites are partially active, all of which make midazolam not the drug of choice for long-term sedation. Midazolam is sometimes used in the treatment of critically ill patients who are agitated. The guidelines for use can be found in Box 21-1.

Diazepam

Diazepam (Valium) is still a popular drug in anesthesia practice. Because of its ability to allay apprehension, diazepam is indicated for use as a premedicant, as an adjunct to intravenous anesthesia, and as an induction agent. Recovery is usually not prolonged when diazepam is used for the induction of anesthesia. Diazepam can be used as the sole anesthetic agent for short diagnostic and surgical procedures and can be used as sedation to make local anesthesia more acceptable to the patient.

The principal action of diazepam is the depression of limbic system function. Important actions of diazepam are the production of anterograde amnesia for as long as 48 hours after surgery, reduction of anxiety, and provision of minimal cardiovascular depressant effects.¹ Clinical doses of diazepam cause a slight degree of respiratory depression; when it is combined with an opiate, the chance of respiratory depression, including apnea, is greatly increased.

Diazepam may possess some muscle-relaxant properties. Diazepam has been reported to be antagonistic to depolarizing neuromuscular blocking agents, such as succinylcholine, and the action of the nondepolarizing neuromuscular blocking agents (e.g., vecuronium) are reported to be potentiated. Diazepam has been used clinically for psychomotor and petit mal seizures because of its anticonvulsant actions.^2,12

Because many patients who undergo cardioversion are debilitated, diazepam can be used as sedation for this procedure. Increments of 2.5 to 5 mg can be given at 30-second intervals until the speech of the patient is slurred or light sleep occurs. At the time of electric discharge, the patient may have brief muscle contraction and slight arousal. When this technique is used, a significant number of the patients have complete amnesia regarding the event. Diazepam can also be used to provide anesthesia in endoscopic and dental procedures and to control behavior on emergence from ketamine.⁷ Finally, this drug also has strong anticonvulsant activity and can stop generalized seizure activity.

Intramuscularly administered diazepam can be painful to the patient, and absorption is often poor. When diazepam is administered intravenously, thrombophlebitis often occurs. With intravenous administration of diazepam, the drug should be injected slowly, directly into a large vein. The drug should not be mixed with other drugs or diluted. The onset of action of diazepam administered intravenously is immediate, and the duration of action varies from 20 minutes to 1 hour. With intramuscular administration, its onset of action is approximately 10 minutes, and the duration of action may be as long as 4 hours. Adverse reactions to diazepam include hiccups, nausea, phlebitis at the site of injection, and occasional acute hyperexcited states.

Lorazepam

Lorazepam (Ativan), a long-acting benzodiazepine, is used as a premedication in current clinical anesthesia practice and as a long-acting slow-onset benzodiazepine for sedation in the PACU and ICU. This drug has actions similar to those of diazepam, but has a slow onset of action from 20 to 40 minutes; the pharmacologic activity can last as long as 24 hours.⁹ Lorazepam produces profound anterograde amnesia, tranquilization, and a reduction of anxiety, and the drug provides good cardiovascular and respiratory stability. Therapeutic plasma concentrations are achieved in approximately 3 hours when the drug is given orally. The drug is well absorbed via the intramuscular route; however, the patient has a significant amount of pain during the injection of the drug. Lorazepam can also be injected intravenously, and the patient may have some burning on injection. Because of its slow onset and long duration, lorazepam is mainly used as a preanesthetic medication. If this drug has been administered in the preoperative period, the effects of lorazepam may last well into the postoperative period because of its prolonged action. If an opioid is administered in the PACU to a patient who received lorazepam before surgery, the nurse should monitor for increased opioid sedation and respiratory depression because of the potentiation of the opioid by lorazepam.

Caution should be taken with use of lorazepam in the PACU for sedation. Lorazepam does not have any active metabolites. This long-acting but slow-onset benzodiazepine is often delivered via intermittent boluses, but also can be administered as a continuous infusion. Peak effects are not observed for 30 minutes. However, the solvent for lorazepam contains polyethylene glycol 400 and propylene glycol, both of which have been implicated in the development of lactic acidosis, acute tubular necrosis, and hyperosmolar coma when lorazepam is used in prolonged high-dose infusions.¹² The toxic threshold for this effect has not been defined; therefore high-dose infusions should be avoided, and monitoring for these side effects should be initiated.

Lorazepam is sometimes used in the treatment of critically ill patients who are agitated. The guidelines for use can be found in Box 21-2.

Flumazenil

Flumazenil (Romazicon), a benzodiazepine antagonist, antagonizes or reverses the effects of benzodiazepine-induced sedation at the benzodiazepine receptors. Consequently, it reverses the CNS effects of benzodiazepines, such as the sedation produced by diazepam and midazolam. This drug also reverses the other effects produced by benzodiazepine agonists, including anxiolytic, muscle-relaxant, ataxic, and anticonvulsant actions. However, flumazenil may not be effective in the treatment for benzodiazepine-induced hypoventilation or respiratory failure. This drug is specific for the benzodiazepines and, more specifically, their receptors. Consequently, this drug does not reverse the effects of barbiturates, opiates, and ethanol. Flumazenil should be used with great caution in patients who have a history of epilepsy or chronic benzodiazepine use, because reversal with flumazenil in these patients can result in seizures. The incidence rate of postoperative nausea and vomiting is increased after flumazenil has been administered.

The usual reversal dose for flumazenil is 0.4 mg administered intravenously in 0.1-mg increments. Flumazenil should be administered slowly to avoid the adverse consequences of abrupt wakening. A maximum dose for this drug is 1 mg. The onset of action is usually within 5 minutes, with a duration of action between 1 and 2 hours. Flumazenil has a shorter duration of action than most of the benzodiazepines, and consequently the risk of resedation can occur after the initial reversal dose was administered. This risk is especially true when high doses of benzodiazepines were previously administered. Therefore, after the administration of flumazenil, the patient should be monitored for resedation and other residual effects of benzodiazepines in the PACU and on the receiving unit. If signs of resedation develop, flumazenil should be given at 20-minute intervals as needed to reverse the sedation. In this situation, no more than 1 mg should be given at any one time, and no more than 3 mg should be given within a 1-hour period.⁵ This drug should prove to be a valuable asset in the care of the patient who has received an excessive dose of a benzodiazepine, such as midazolam or diazepam. Consequently, flumazenil is useful during surgery, after surgery, and in the ICU.⁶

Physostigmine

Physostigmine (Antilirium) is an anticholinesterase that crosses the blood-brain barrier. Its action is inhibition of the enzyme acetylcholinesterase, which results in an increase in the availability of acetylcholine at the receptors that are affected by the benzodiazepines in the CNS. The preponderance of acetylcholine counteracts the negative effects of glycine and GABA. Consequently, this drug provides a nonspecific reversal of the CNS side effects of the benzodiazepines, scopolamine, and ketamine. The dosage is 0.5 to 1 mg, and it should be administered slowly to prevent untoward cholinergic side effects.¹ Because this drug is a nonspecific agent, a number of vagally mediated cholinergic side effects can occur after its administration. These effects include nausea, vomiting, salivation, bradycardia, bronchospasm, and seizures. Because of its nonspecific properties, physostigmine is rarely used for the reversal of the untoward effects of the benzodiazepines.

Haloperidol

Haloperidol (Haldol) is a butyrophenone tranquilizer that has limited use in anesthesia practice because of its long duration of action and its high incidence rate of extrapyramidal reactions⁴; however, it has been found to be an excellent antiemetic. The drug is not approved for intravenous use and is usually administered intramuscularly at a dose of 2 to 5 mg. It is used in the treatment of psychoses and as an antiemetic. Haloperidol is sometimes used in the treatment of critically ill patients who are agitated. The guidelines for use can be found in Box 21-3.

Droperidol

Droperidol (Inapsine) can be used alone or in combination with fentanyl (Sublimaze) as part of a neuroleptanalgesic technique. Droperidol is rarely used during surgery for the purposes of being a component of anesthesia, but it is administered in small doses for its antiemetic effect after surgery. It produces a state of calm, disinclination to move, and disconnection from surroundings. The drug has an alpha-adrenergic blocking effect, which offers some protection against the vasoconstrictive components of shock; it leads to good peripheral perfusion; and it unmasks hypovolemia. More specifically, when a patient has compensation for a borderline hypovolemic state with activation of the alpha-vasoconstriction mechanisms, vital signs are normal. When a drug such as droperidol is administered to this patient, by virtue of droperidol’s alpha-blocking properties, the signs of hypovolemia appear; therefore the patient’s hypovolemia is “unmasked.” Droperidol also protects against epinephrine-induced arrhythmias and has an antiemetic effect. In fact, because of its excellent antiemetic properties, droperidol is sometimes administered toward the end of the surgical procedure or in the PACU to reduce the risk of vomiting and aspiration in anxious patients. The antiemetic dose of droperidol is between 1 and 2.5 mg and can be given intravenously. Because of its alpha-blocking properties, this drug can be administered in the PACU on a short-term basis to reduce the afterload.

Droperidol is similar to chlorpromazine (Thorazine) in its CNS effects; however, its mechanism of action is different. Droperidol is more selective than chlorpromazine because it provides more tranquility with less sedation and has less effect on the autonomic nervous system. Droperidol has been classified as a neuroleptic and has some adverse effects that should be assessed throughout the PACU phase. Droperidol may cause hypotension because of its alpha-adrenergic blocking effect and peripheral vasodilatation. It may cause extrapyramidal excitation, such as twitchiness, oculogyric seizures, stiff neck muscles, trembling hands, restlessness, and occasionally, psychologic disturbances (e.g., hallucinations). These excitation can be reversed with atropine or antiparkinsonian drugs such as benztropine mesylate (Cogentin) and trihexyphenidyl hydrochloride (Artane).² Clinically, patients who have received droperidol have reported the dichotomy of appearing outwardly calm while feeling terrified inside and unable to express how they feel. As a result, the perianesthesia nurse should provide emotional support to all patients who have received droperidol.

Droperidol is known to potentiate the action of barbiturates and opioids. It has a high therapeutic margin of safety with a rapid onset of 10 minutes, and its activity is lessened in 2 to 4 hours, although some effects last as long as 10 to 12 hours.

Droperidol is the prototype neuroleptic drug. A neuroleptic drug is one that reduces motor activity, lessens anxiety, and produces a state of indifference in which the person can still respond appropriately to commands. Neuroleptanalgesia is a state of profound tranquilization with little or no depressant effect on the cortical centers; therefore neuroleptanalgesia is achieved with the combination of a neuroleptic such as droperidol and a potent opioid analgesic such as fentanyl. A step further is neuroleptanesthesia, the combination of a neuroleptanalgesic (droperidol plus fentanyl), a skeletal muscle relaxant, and nitrous oxide and oxygen. The main objective in the development of neuroleptanesthesia is to provide, for all types of operations, a technique that does not depress the metabolic, circulatory, or central nervous systems as severely as do the inhalation anesthetics when used alone. Droperidol is rarely used as the neuroleptic component; other sedatives are used in its place, such as midazolam and fentanyl.

The U.S. Food and Drug Administration (FDA) strengthened the warnings and precautions in the labeling for droperidol because the drug was associated with fatal cardiac arrhythmias. More specifically, research has shown QT prolongations that indicate delayed recharging of the heart between beats within minutes after injection of droperidol at the upper end of the labeled dose range. Prolonged QT is dangerous because it can cause a potentially fatal heart arrhythmia known as torsades de pointes. The new warning is intended to facilitate the focus on the potential for cardiac arrhythmias during administration and to urge the practitioner to consider the use of alternative medications in patients at high risk for cardiac arrhythmias.

Dexmedetomidine

Dexmedetomidine (Precedex) is a newer alpha-2 agonist, like clonidine, that is a novel sedative with analgesic properties that controls stress, anxiety, and pain and does not cause respiratory depression. Like clonidine, its mechanism of action is as an agonist of alpha-2 receptors in certain parts of the brain. Consequently, this drug facilitates patient comfort, compliance, and comprehension by providing sedation along with the ability to rouse the patient.

Dexmedetomidine is sevenfold more selective for the alpha receptors and has a shorter duration of action and is considered a full agonist for the alpha-2 receptors. Consequently, it is an excellent drug to decrease the amounts of inhalation anesthetics and opioids. It is also an effective drug in attenuating the cardiostimulatory and postanesthetic delirium effects of ketamine. Dexmedetomidine increases the range of temperatures that do not trigger the thermoregulatory defenses; therefore it is likely to produce some perioperative hypothermia and to be an effective treatment for postoperative shivering.

With stimulation of the alpha-2 receptors, dexmedetomidine decreases the systolic blood pressure; the systemic vascular resistance is little affected, and the cardiac output, which is initially decreased, returns toward predrug levels. The homeostatic cardiovascular reflexes are maintained, and the problems of orthostatic hypotension are avoided.

In the PACU, if dexmedetomidine is administered via intravenous infusion, the nurse should monitor the patient for significant episodes of bradycardia and hypotension. If intervention is necessary, decreasing or stopping the dexmedetomidine infusion and increasing the rate of intravenous fluid administration along with elevation of the lower extremities may be all that is needed; if the hypotension continues, vasopressor agents may be necessary (see Chapter 11). If the bradycardia continues, the PACU nurse may need to intervene by obtaining a physician order for an anticholinergic such as atropine or glycopyrrolate. A dexmedetomidine infusion is not recommended to last more than 24 hours. Because dexmedetomidine resembles the alpha-2 adrenergic agent clonidine, abrupt withdrawal of the drug can result in symptoms associated with abrupt stoppage of clonidine. Consequently, when dexmedetomidine is discontinued, symptoms that include nervousness, agitation, headaches, and a rapid rise in blood pressure should be monitored and reported to the anesthesia provider immediately.

Dexmedetomidine is usually administered with a controlled infusion device. The drug should be titrated to the desired clinical effect, which is usually less than 3 on the Ramsey Sedation Scale (Table 21-1). Generally, a loading infusion of 1 mcg/kg over 10 minutes followed by a maintenance infusion of 0.2 to 0.6 mcg/kg/h, and the rate of the maintenance infusion can be adjusted to achieve the desired level of sedation.

Table 21-1 Ramsay Level of Sedation Scale

Perianesthesia care

When patients emerge from ketamine anesthesia, they may go through a phase of vivid dreaming, with or without psychomotor activity manifested by confusion, irrational behavior, and hallucinations. The perianesthesia nurse should be aware that such psychic aberrations are usually transient and appear to be preventable by avoiding early verbal or tactile stimulation of the patient, which helps to prevent fear and anxiety reactions. Short-acting barbiturates administered intravenously can effectively control the psychic responses sometimes seen after the administration of ketamine. Pediatric patients seem to be less prone to these psychic disturbances. Results of a study revealed that droperidol may be effective in eliminating some of the adverse psychic emergence phenomena of ketamine. Other sedatives such as diazepam have also been found effective in suppression of these phenomena. In addition, the drug dexmedetomidine (Precedex) can help suppress this adverse phenomena. When a patient is admitted to the PACU, the nurse should be aware of any sedatives or whether dexmedetomidine has been administered to the patient.

On arrival in the PACU, the patient should be secluded from auditory, visual, and tactile stimuli and be observed for any signs of respiratory depression. Mechanical airway obstruction, particularly when caused by marked salivation, accounts for most of the instances of respiratory insufficiency after ketamine anesthesia. When the patient does not have adequate respiratory exchange, oxygen should be administered via mask until it is restored. Other important signs to watch for are persistent blood pressure elevation, tachycardia, bradycardia, dreaming, delirium, hallucinations, euphoria, and increased muscle tone. All PACU personnel must know that attempts to rouse patients while they are still unable to see, hear, and orient themselves may set off a chain of anxiety reactions that may ultimately lead to severe psychomotor responses and even more irrational behavior. Should the patient have this augmented psychomotor behavior, dexmedetomidine (Precedex) or one of the benzodiazepine sedation drugs can be administered to facilitate a reduction in the aberrant behavior.

The widespread use of ketamine requires an entirely different approach to perianesthesia nursing care. It should also be noted that ketamine coupled with a small dose of a benzodiazepine may be continued in a low-dose intravenous for sedation and pain relief in the PACU. Certainly, the agent has some deficiencies, but commonly overlooked is the fact that it is one of the safest anesthetics. Its safety justifies its important place in the drugs used by the anesthesiologist. Ketamine appears to be an excellent anesthetic for pediatric patients, as the sole agent for short procedures, for induction of anesthesia in patients at extremely poor risk, and for patients with burns that necessitate surgical treatment. Certain adult orthopedic and diagnostic procedures have also been found suitable for the use of ketamine anesthesia. Ketamine continues to be popular for certain types of anesthetic procedures. Because ketamine is a dissociative agent, its actions should be well understood by the PACU staff to ensure effective informed care of the patient.