Justification: A lack of adaptation to the ventilator produces many complications that can further worsen the condition of the critical patient, including respiratory acidosis secondary to hypoventilation and increased CO 2 production; hypocapnia due to hyperventilation; hypoxemia as a result of dyssynchrony between the patient and the ventilator; increased intrathoracic pressure with a decrease in venous return, cardiac minute volume and arterial pressure; and increased O 2 consumption due to the rise in muscle activity.
Sedation and analgesia are commonly indicated in critically ill patients who at the same time require other priority medications or treatments. The indication of sedation and analgesia is established empirically, with a choice of drug and dosage that often proves inadequate. Not all ventilated patients require some or all of these medications, as in the case of the patients with neuromuscular problems e. A patient with severe ARDS will probably need maximum levels of analgesia, sedation and, sometimes, muscle relaxation.
Analgesia implies the absence of sensitivity to pain or to aggressive stimuli such as the presence of an endotracheal tube or the aspiration of secretions. If the administration of analgesics results in disappearance of the physiological alterations, then pain can be confirmed as having been the cause of such alterations.
Sedation in the critical patient is indicated as basic treatment for anxiety and agitation. These two sensations, combined with MV, imply that sedation in these patients is unavoidable, at least in the early stages. Such differences refer not only to the drug used, but also to the method of administration involved..
What are the recommendations for the management of sedation and analgesia in patients subjected to MV?
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The use of a scale for the evaluation of pain and depth of sedation is recommended in patients subjected to MV. Justification: It is important to carry out a reproducible evaluation of whether the analgesia we seek has been satisfactorily obtained. Since pain is essentially subjective, we should try to know the opinion of the patient, if possible.
In the case of sedated patients, in whom it is particularly common to underuse analgesia, it is important to evaluate the somatic and physiological equivalents of pain. Among the former, patient facial expression, movements and body posture can be clear indicators of pain, as in the BPS scale.
Another problem is the difficulty of assessing the depth of sedation. The use of scales for evaluating the depth of sedation during MV is recommended by most consensus guides on the subject. Sedation scales are a fundamental part of the protocols referred to the adaptation of patients with MV 60,61,64, Table Implementation of the sedation and analgesia protocols preferably should be carried out by the nursing personnel.
It is not advisable to apply this recommendation when there are not enough nurses available. Justification: With some exceptions, different authors have reported better results with the application of strict sedation and analgesia protocols controlled and applied by the nursing personnel of the ICU.
However, it is clear that when the number of available nurses is insufficient, they cannot be overburdened by this additional task. Justification: The levels of sedation differ from one type of patient to another. In patients with MV due to complex situations e. With these levels of sedation we often observe anterograde amnesia—a situation which some authors associate to an increased incidence of delirium and post-traumatic stress..
Whenever possible, it is advisable to use conscious or cooperative sedation with titrated doses of a continuous infusion of propofol or dexmedetomidine. Justification: A number of studies have shown this approach to shorten the duration of MV, the days of stay in the ICU, and the incidence and duration of delirium. Likewise, it has been reported that this strategy does not increase the incidence of myocardial ischemia.
Opioids are recommended as the analgesics of choice in the ventilated patient—the first line drugs being fentanyl and morphine—especially in patients requiring prolonged ventilation.
Justification: The most important side effects of the opioids, which are regarded as the drugs of choice for analgesia in the critical patient, are respiratory depression, arterial hypotension, gastric retention and ileus. Despite these adverse effects, correct analgesia is a primary objective in the critical patient subjected to MV. Morphine, in sulfate or hydrochloride form, is the analgesic drug of choice for ventilated patients. Its advantages include analgesic potency, low cost, and an euphorizing effect. Morphine is to be administered via the intravenous route, starting with a loading dose followed by continuous venous infusion.
The recommended loading dose is 0. During the continuous infusion of morphine it is common to need one or more bolus doses at the same dosage as the initial loading dose, in order to secure an adequate analgesic effect. If administration in bolus form is decided, it should be scheduled as repeated doses, once every 3 h, attempting to adjust the dosage according to the therapeutic response obtained. Fentanyl is the analgesic drug of choice for ventilated patients with hemodynamic instability, or in patients with symptoms of histaminic release or allergy with the use of morphine.
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Fentanyl does not cause histamine release—a fact which may explain its lesser effect upon arterial pressure and bronchial smooth muscle. It has a relatively short half-life 30—60 min , due to its rapid distribution. However, the prolonged administration of fentanyl gives rise to accumulation of the drug in the peripheral compartments, and extends its half-life contextual half-life to 16 h.
The routine use of fentanyl is not recommendable in all patients, since its analgesic effect is similar to that of morphine; the drug tends to accumulate as a result of prolongation of its half-life; and its cost is usually greater. It is advisable not to use meperidine, nalbuphine or buprenorphine in the critical patient.
Justification: Meperidine has an active metabolite, normeperidine, which can accumulate and produce excitation of the central nervous system and seizures, particularly in patients with acute neurological damage. Nalbuphine and buprenorphine are usually prescribed to calm mild or moderate pain in the immediate postoperative period.
It must be remembered that they can revert the effect of other opioids through interaction at receptor level. They can be used as an option when the traditional opioids are contraindicated. Whenever possible, it is advisable to minimize or suppress the use of sedatives in prolonged MV, using the sedation scheme based on analgesia. Justification: A number of studies have reported a decrease in the number of days with MV and in the duration of ICU stay when the use of sedatives is suppressed or minimized by the administration of opioid analgesics in continuous infusion in patients with MV.
Remifentanil is a synthetic opioid that exhibits practically no accumulation, since it is quickly metabolized by plasma esterases. It likewise does not accumulate in patients with kidney or liver failure. These properties imply that recovery from the effects of the drug takes place in only a few minutes, even after prolonged administration. The usual analgesic doses are 0. Depending on the dose, remifentanil produces central depressor effects like other opioids.
Some studies recommend its use in analgesia based sedation Schemes. Justification: There are differences in the use of sedating agents in acute or short-lasting situations and in deep sedation accompanying MV in patients with diseases such as those mentioned above Fig. These differences refer not only to the drug employed but also to the method of administration. Algorithm for sedation and analgesia in patients with tracheal intubation..
All parenteral benzodiazepines cause anterograde amnesia, and it should be remembered that they do not have analgesic effects. Although the prototype drug for intravenous sedation is diazepam, it is no longer recommended, because: a it often causes pain and thrombophlebitis when administered through a peripheral vein; b administration in bolus form can lead to excessive sedation; c administration as a continuous intravenous infusion increases its half-life, reaching 7 days in some patients; and d the drug requires dilution in a large volume—which implies a risk of water overload in the context of prolonged administration.
However, it is used in some centers because of its low cost and rapid mechanism of action when performing brief maneuvers electrical cardioversion, TI , being indicated as a single bolus dose.
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The usual midazolam dose for effective sedation during TI maneuvering or other brief procedures is 0. Propofol is an intravenous anesthetic which at sub-anesthetic doses produces sedation and hypnotic effects, as well as a degree of anterograde amnesia. Propofol and midazolam have been shown to have the same sedative effect in comparative studies. Propofol offers fast action after the administration of an intravenous bolus 1—2 min , due to its rapid penetration of the central nervous system, and its effect is short lasting 10—15 min.
When used in prolonged treatments, it should only be administered in continuous infusion with the precaution of using a central vein rather than a peripheral venous access. Propofol also significantly prolongs its half-life when administered for prolonged periods of time, due to accumulation of the drug in the lipid deposits—its half-life reaching — min. If we wish to keep the patient sedated, in the case of continuing with MV, a continuous infusion should be used at a starting dose of 0.
A common maintenance dose is between 0. In recent years, many studies have shown benzodiazepines midazolam and lorazepam to be associated with an increased incidence of coma and delirium in intubated and ventilated patients. This in turn results in longer periods of MV, a longer stay, and greater morbidity—mortality. Lorazepam is one of the drugs suited for prolonged sedation in the ventilated patient.
This intermediate-acting benzodiazepine is less lipophilic than other drugs of the same group, and therefore undergoes less peripheral accumulation. In comparison with midazolam, lorazepam has a longer half-life and a similar capacity to produce anterograde amnesia. In view of its half-life, lorazepam is suitable for administration in intermittent bolus doses, though it can also be used in continuous infusion.
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Since the pharmacological latency period of lorazepam is longer than that of other benzodiazepines, it is advisable to start with a dose of diazepam or midazolam to induce rapid sedation. In prolonged sedation, some authors advise the administration of a continuous infusion of lorazepam at doses of 0. These doses are usually insufficient, however, and can be doubled or tripled in some patients. A number of authors have reported elevated propyleneglycol levels that could prove toxic under these circumstances, though no evident clinical effects have been described.
Dexmedetomidine is recommended as a useful drug for postoperative sedation and analgesia in patients requiring MV for short periods of time, and particularly in septic patients. The drug inhibits the postsynaptic receptors, thereby inducing not only a drop in blood pressure and heart rate but also a clear anxiolytic and sedating effect.
Its action at spinal receptor level also affords an analgesic effect. The maintenance infusion rate is 0. The maintenance dose often must be increased when using dexmedetomidine in prolonged treatments.
The loading bolus can cause bradycardia accompanied by hypotension, which in some cases can be sustained over time, particularly in hypovolemic and elderly patients. Some authors recommend obviating the loading doses in order to avoid these side effects.. This drug does not produce respiratory depression or gas exchange alterations, and can be safely administered in patients with renal failure. Dexmedetomidine likewise does not cause alterations in adrenal cortical or inflammatory function.
In view of these properties, some authors choose dexmedetomidine as the best sedative for weaning from MV, and for conscious sedation. Observational studies also show that dexmedetomidine appears to reduce the incidence of delirium and the mortality rate among septic patients hazard ratio 0. The dosage should be lowered in patients with liver failure.
It is advisable not to use etomidate in sedoanalgesia for patients subjected to MV. Justification: Etomidate should be contraindicated in the critical patient, due to its capacity to produce adrenal gland insufficiency.
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