The Task Force developed a single strong recommendation: we recommend scheduled eye care that includes lubricating drops or gel and eyelid closure for patients receiving continuous infusions of neuromuscular-blocking agents. The Task Force developed 10 weak recommendations. 1) We suggest that a neuromuscular-blocking agent be administered by continuous intravenous infusion early in the course of acute respiratory distress syndrome for patients with a PaO2/FIO2 less than 150. 2) We suggest against the routine administration of an neuromuscular-blocking agents to mechanically ventilated patients with status asthmaticus. 3) We suggest a trial of a neuromuscular-blocking agents in life-threatening situations associated with profound hypoxemia, respiratory acidosis, or hemodynamic compromise. 4) We suggest that neuromuscular-blocking agents may be used to manage overt shivering in therapeutic hypothermia. 5) We suggest that peripheral nerve stimulation with train-of-four monitoring may be a useful tool for monitoring the depth of neuromuscular blockade but only if it is incorporated into a more inclusive assessment of the patient that includes clinical assessment. 6) We suggest against the use of peripheral nerve stimulation with train of four alone for monitoring the depth of neuromuscular blockade in patients receiving continuous infusion of neuromuscular-blocking agents. 7) We suggest that patients receiving a continuous infusion of neuromuscular-blocking agent receive a structured physiotherapy regimen. 8) We suggest that clinicians target a blood glucose level of less than 180 mg/dL in patients receiving neuromuscular-blocking agents. 9) We suggest that clinicians not use actual body weight and instead use a consistent weight (ideal body weight or adjusted body weight) when calculating neuromuscular-blocking agents doses for obese patients. 10) We suggest that neuromuscular-blocking agents be discontinued at the end of life or when life support is withdrawn. In situations in which evidence was lacking or insufficient and the study results were equivocal or optimal clinical practice varies, the Task Force made no recommendations for nine of the topics. 1) We make no recommendation as to whether neuromuscular blockade is beneficial or harmful when used in patients with acute brain injury and raised intracranial pressure. 2) We make no recommendation on the routine use of neuromuscular-blocking agents for patients undergoing therapeutic hypothermia following cardiac arrest. 3) We make no recommendation on the use of peripheral nerve stimulation to monitor degree of block in patients undergoing therapeutic hypothermia. 4) We make no recommendation on the use of neuromuscular blockade to improve the accuracy of intravascular-volume assessment in mechanically ventilated patients. 5) We make no recommendation concerning the use of electroencephalogram-derived parameters as a measure of sedation during continuous administration of neuromuscular-blocking agents. 6) We make no recommendation regarding nutritional requireme...
Although all astronauts experience symptoms of orthostatic intolerance after short-duration spaceflight, only approximately 20% actually experience presyncope during upright posture on landing day. The presyncopal group is characterized by low vascular resistance before and after flight and low norepinephrine release during orthostatic stress on landing day. Our purpose was to determine the mechanisms of the differences between presyncopal and nonpresyncopal groups. We studied 23 astronauts 10 days before launch, on landing day, and 3 days after landing. We measured pressor responses to phenylephrine injections; norepinephrine release with tyramine injections; plasma volumes; resting plasma levels of chromogranin A (a marker of sympathetic nerve terminal release), endothelin, dihydroxyphenylglycol (DHPG, an intracellular metabolite of norepinephrine); and lymphocyte beta(2)-adrenergic receptors. We then measured hemodynamic and neurohumoral responses to upright tilt. Astronauts were separated into two groups according to their ability to complete 10 min of upright tilt on landing day. Compared with astronauts who were not presyncopal on landing day, presyncopal astronauts had 1). significantly smaller pressor responses to phenylephrine both before and after flight; 2). significantly smaller baseline norepinephrine, but significantly greater DHPG levels, on landing day; 3). significantly greater norepinephrine release with tyramine on landing day; and 4). significantly smaller norepinephrine release, but significantly greater epinephrine and arginine vasopressin release, with upright tilt on landing day. These data suggest that the etiology of orthostatic hypotension and presyncope after spaceflight includes low alpha(1)-adrenergic receptor responsiveness before flight and a remodeling of the central nervous system during spaceflight such that sympathetic responses to baroreceptor input become impaired.
T he human cardiovascular system undergoes profound changes when exposed to spaceflight, including cardiac rhythm disturbances during long-term missions. 1-5 Underlying spaceflight-induced alterations in cardiovascular autonomic regulation may adversely influence cardiac repolarization and thus precipitate these rhythm disturbances. 6 -8 Therefore, we analyzed electrocardiograms or Holter monitor tracings obtained from astronauts who experienced short-and long-duration space missions. Our findings reveal striking differences in cardiac conduction and repolarization between short-and long-duration spaceflight.• • • Informed consent was obtained in accordance with the guidelines of the Committee for the Protection of Human Subjects at the Johnson Space Center. A retrospective analysis of electrocardiograms from 7 astronauts (6 men and 1 woman, average age 44 Ϯ 5 years for short-duration flights and 47 Ϯ 6 years for long-duration flights), who experienced both short-duration spaceflight onboard the space shuttle and long-duration spaceflight onboard Mir or the International Space Station, were used to measure PR, RR, and QT intervals. Threelead electrocardiograms were recorded during 1 minute of supine rest on digital tape 10 days before flight, on landing day (within 2 hours of touchdown), and 3 days after landing for short-and long-duration missions. One minute of data at rest was analyzed from lead II and the results averaged.Twenty-four-hour Holter monitoring recordings from 3 crew members (3 men, average age 45 Ϯ 6 years) were obtained 60 days before launch, at 3 separate times during the mission (4-month flight), and 2 times after transfer to the space shuttle before re-entry on landing day (1 subject's Holter was recorded 2 days after landing) and at 11 or 39 days after landing. PR, RR, and QT intervals from lead V 2 were measured for 10 cardiac cycles at 1, 6, 11, and 16 hours. The results for each interval were averaged at each time period. Activity logs are not available.The PR, RR, and QT intervals were measured manually, in random order, by 2 examiners blinded to flight duration or testing day. The beginning of the P wave and the beginning of the QRS complex defined the PR interval. The beginning of the Q (or R) wave and the end of the T wave at the isolectric point defined the QT interval. The QT interval was corrected for heart rate using Bazett's formula: QTc ϭ QT/(RR) 0.5 . Electrocardiographic data from 1 long-duration astronaut were not collected 3 days after landing. Five of the 7 astronauts from long-duration spaceflights had complete electrocardiographic data sets available from previous short-duration spaceflights for comparison. Serum concentrations of potassium, calcium, and
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