Analgesic agents. Pharmacology and application in critical care

Sedation Analgesia and Neuromuscular Blockade in Pediatric Critical Care: Overview and Current Landscape

Sedation is a mainstay of therapy for critically ill children. Although necessary in the care of the critically ill child, sedative drugs are associated with adverse effects, such as disruption of circadian rhythm, altered sleep, delirium, potential neurotoxicity, and immunosuppression. Optimal approaches to the sedation of the critically ill child should include identification of sedation targets and sedation interruptions, allowing for a more individualized approach to sedation. Further research is needed to better understand the relationship between critical illness and sedation pharmacokinetics and pharmacodynamics, the impact of sedation on immune function, and the genetic implications on drug disposition and response.

Regional analgesia in intensive care

JUSTIFICATIONS AND OBJECTIVES: regional analgesia plays an important role in multimodal pain management in critically ill patients, minimizing patient discomfort and reducing the associated physiological and psychological stress. Lower doses of systemic opioids reduce some of its side effects, such as withdrawal syndrome, possible psychological changes, and gastrointestinal dysfunction. Despite these benefits, its use is controversial, as patients in intensive care units often have contraindications, such as coagulopathy, hemodynamic instability, and difficulty in neurological assessment and implementation of regional technique.

CONTENT

The authors present a review of regional analgesia in intensive care, focusing on the main advantages and limitations of its use in critically ill patients, and describe the most commonly used regional techniques and its applicability.

Pain management in the ICU

Pain management in the intensive care unit (ICU) is a complex process. Both the experience of pain as well as its treatment can have consequences relating to the overall outcome of the patient. Further, lack of the ability of many patients in the ICU to communicate their distress makes it even more critical for the ICU practitioner to understand the typical causes of pain in this setting and the applicability of many pain management regimens.

[Daily interruption of sedation: always a quality indicator?]

The Spanish Society of Critical Care Medicine (SEMICYUC) has recently published an updated version of Quality Indicators in Critical Care. Daily sedative interruption is included among them. As this practice is controversial, research studies are revised and guidelines for its implementation are proposed.

Pharmacology of commonly used analgesics and sedatives in the ICU: benzodiazepines, propofol, and opioids

The ideal sedative or analgesic agent should have a rapid onset of activity, a rapid recovery after drug discontinuation, a predictable dose response, a lack of drug accumulation,and no toxicity. Unfortunately, none of the earlier analgesics, the benzodiazepines,or propofol share all of these characteristics. Patients who are critically ill experience numerous physiologic derangements and commonly require high doses and long durations of analgesic and sedative therapy. There is a paucity of well designed clinical trials evaluating the safety and efficacy of earlier sedative and analgesic agents in the ICU. In addition, the ever-changing dynamics of patients who are critically ill makes the use of sedation a continual challenge during the course of each patient’s admission. To optimize care, clinicians should be familiar with the many pharmacokinetic, pharmacodynamic, and pharmacogenetic variables that can affect the safety and efficacy of sedatives and analgesics.

Alterations of drug metabolism in critically ill animals

Critically ill animals are by nature a diverse group with multiple presenting complaints and differing levels of organ function. Pharmacokinetics and pharmacodynamics of administered compounds are affected both by the disease processes and by the interventions of the treating veterinarian. Polypharmacy is not an exception but a rule within this caseload. Basic principles of pharmacology allow for safe and effective administration of pharmaceuticals, especially in the critically ill. Future research evaluating the pharmacokinetics and pharmacodynamics of drugs important in the management of critically ill animals is imperative, and will allow evidence-based dose modification.

Pharmacokinetics and pharmacodynamics in the critically ill child

An understanding of pharmacokinetics and pharmacodynamics can allow for a rational approach to prescribing medications for critically ill children. Absorption, distribution, metabolism, elimination, and the response to medications are affected by age and disease state. Various medications are used in the care of critically ill children. Many medications are prescribed for children based on dosing guidance from adult studies, however. Care providers must be cautious of the high risk for drug interactions and adverse reactions in the intensive care setting.

Drug dosing in chronic kidney disease

Patients with chronic kidney disease (CKD) are at high risk for adverse drug reactions and drug-drug interactions. Drug dosing in these patients often proves to be a difficult task. Renal dysfunction-induced changes in human pathophysiology regularly results may alter medication pharmacodynamics and handling. Several pharmacokinetic parameters are adversely affected by CKD, secondary to a reduced oral absorption and glomerular filtration; altered tubular secretion; and reabsorption and changes in intestinal, hepatic, and renal metabolism. In general, drug dosing can be accomplished by multiple methods; however, the most common recommendations are often to reduce the dose or expand the dosing interval, or use both methods simultaneously. Some medications need to be avoided all together in CKD either because of lack of efficacy or increased risk of toxicity. Nevertheless, specific recommendations are available for dosing of certain medications and are an important resource, because most are based on clinical or pharmacokinetic trials.

Pharmacology and pharmacokinetics of sedatives and analgesics

The agents used for sedation and analgesia during endoscopy have complex pharmacokinetic and pharmacodynamic properties. Knowledge of these characteristics is necessary for determining the proper agent and dose for specific patient needs. Short-acting agents, such as fentanyl, midazolam, and propofol, provide rapid sedation with a short duration of action that allows patients to return to normal functioning rapidly. When designing a dosing regimen with these agents, age and organ (liver, kidney) function of patients and concomitant medications that may interfere with metabolic and elimination pathways must be considered.

Pain in the older adult in the intensive care unit

Effective pain management of the older adult begins with pain assessment using the proper tools. Understanding the complexities of the older adult in the ICU is the first step; this can be done by integrating the evidence-based practice guidelines provided by the American Geriatrics Society, the Joint Commission on Accreditation of Health Care Organizations (JCAHO pain standards: www.jcaho.org/standard/pm_hap.html), and the Society of Critical Care Medicine into physicians' and nurses' practice. Joint Commission on Accreditation of Health Care Organizations now recommends considering pain as the "fifth vital sign" (JCAHO pain standards: www.jcaho.org/standard/pm_hap.html). In summary, Park et al highlight key concepts that must be considered for all effective treatment plans: "anticipation, recognition, quantification, treatment and reassessment of the needs of the patient." Only then can we anticipate the impacts of chronic and critical illnesses and realize reliable and superior comfort for the elderly.

Opioid and non-opioid analgesics

Opioids are the most potent analgesics. Toxicity results either from effects mediated by variation in affinity and intrinsic efficacy at specific opioid receptors or, rarely, from a direct toxic effect of the drugs. For some adverse effects, opioids exhibit a 'dual pharmacology' whereby these effects are usually observed only in pain-free individuals, and are not seen in patients in pain. Paracetamol, although generally very safe in therapeutic doses, displays potentially fatal toxicity in overdose requiring specific treatment. Non-steroidal anti-inflammatory drugs (NSAIDs) are known to act by inhibiting COX-1 and COX-2 isoenzymes to various degrees. Toxicity arises primarily from undesired inhibition at these enzyme sites. Knowledge of the mechanism of action of these drugs is fundamental to the understanding of their potential for toxicity, the details of which are still emerging.