New horizons (Baltimore, Md.)
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Paralysis via neuromuscular blockade in ICU patients requires mechanical ventilation. This review historically addresses the technological advances and scientific information upon which ventilatory management concepts are based, with special emphasis on the influence such concepts have had on the use of neuromuscular blocking agents. Specific reference is made to the scientific information and technological advances leading to the newer concepts of ventilatory management. ⋯ However, adequate analgesia, amnesia, and sedation are required. For patients with severe lung disease, alveolar overdistention and hyperoxia should be avoided and may be best accomplished by total ventilatory support techniques, such as pressure control. Total ventilatory support requires neuromuscular blockade and may not provide eucapnic ventilation.
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Aggressive methods of decreasing oxygen consumption, such as therapeutic musculoskeletal paralysis, are used in patients with marginal oxygen delivery associated with cardiac and respiratory insufficiency. This is especially true of new mechanical ventilation methods designed to decrease tidal volume and peak airway pressures. ⋯ Escalated doses of sedatives, followed by oppressive hemodynamic and ventilatory side-effects, sometimes indicate the need for therapeutic musculoskeletal paralysis to quickly control life-threatening agitation syndromes. Cerebral-function monitoring with portable, noninvasive, computer-processed monitors allows quick recognition of brain functions under titrated, suspended animation in real time, facilitating modulation of therapy when the visual clues of neuronal function disappear.
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The practice of critical care medicine has progressed dramatically over the past several decades. With the advent of new pharmacological therapies and technological interventions, our ability to manage a multitude of pathophysiologic conditions has grown. ⋯ Associated with new therapeutic and diagnostic interventions are secondary side effects and complications. It is often the undesired sequela of all interventions that forces clinicians to periodically reevaluate to whom, why, how, and when we employ new drugs or procedures.
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Reported survival rates for severe adult respiratory distress syndrome (ARDS) patients vary from 9% to 84%. Animal study results have suggested that application of the high pressures needed to deliver commonly used tidal volumes (10 to 15 mL/kg) may induce an overexpansion of the remaining small fraction of compliant ARDS lung still capable of gas exchange. Conventional ventilatory therapy might thus superimpose an iatrogenic lung injury on the ARDS lung. ⋯ By standardizing therapy, protocols may significantly reduce the random and nonrandom noise (bias) introduced into the clinical environment by clinical care team members. This is especially important fo the many pertinent clinical questions addressed by clinical trials that cannot be double blinded. Conclusions from protocol-controlled clinical trials should be more credible and more likely to lead to action than those of the past.
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While all neuromuscular blocking agents (NMBAs) effectively interrupt neuromuscular transmission, it must be emphasized that these drugs are completely devoid of analgesic, sedative, or amnestic properties. The increasing use of NMBAs in the ICU requires familiarity with their basic pharmacologic properties, as well as an appreciation of potential problems associated with chronic (> 24 hrs) neuromuscular blockade. Although NMBAs possess an impressive safety record, the majority of recommendations for neuromuscular blocker use in the ICU are extrapolated from short-term perioperative studies in healthy patients. ⋯ Prolonged weakness after discontinuation of NMBAs is increasingly recognized after these agents are used for extended periods. This phenomenon may be related to alterations in the pharmacokinetics and pharmacodynamics, along with altered physiology of the neuromuscular junction, nervous system, or muscle, or other undefined toxic effects. A sound knowledge of the basic physiology of the neuromuscular junction, neuromuscular blocker pharmacology, and standard techniques to assess the degree of neuromuscular blockade provides the rationale for drug selection when paralysis is indicated in ICU patients.