Authors: Giorgio Conti Nicholas S Hill Stefano Nava
Publish Date: 2015/07/07
Volume: 41, Issue: 9, Pages: 1692-1695
Abstract
Sedation and analgesia are commonly used in the ICU to improve patient comfort and tolerance to minimize reactions to painful stimuli and the physiologic stress response and to modulate patient respiratory effort drive or timing Although intolerance is commonly perceived as an important reason for NIV failure that should respond to sedation and analgesia recent studies suggest that they are not used very often for that indication Muriel et al 1 found that sedation and analgesia were used in “only” about 20 of patients using NIV confirming the results of an earlier websurvey performed in North America and Europe 2 Therefore the large majority of patients approximately 80 treated with NIV for acute respiratory failure do not receive any form of sedation and yet tolerate NIV and usually succeed with it 1There are other measures that can be applied to improve tolerance of NIV before consideration of sedation or analgesia Improvements in interface technology have enabled us to choose between numerous different mask types and sizes and employ the socalled rotation strategy avoiding intolerance due to excessive use of a single mask type 3 Furthermore advances in software technology offer newer algorithms that enhance interactions and synchrony between the patient and the ventilator 4 They also have led to improved ventilator monitoring capabilities and graphics that permit analysis of flow and pressure tracings on ventilator screens that may be of help in “fine tuning” the ventilator 5 Successful application of these enhancements also depends on the expertise of the NIV team which performs better as it gains more experience in the administration of NIV 6 This expertise not only enables the team to efficiently make appropriate adjustments in equipment and ventilator settings but also imparts a feeling of confidence to the patient both factors that are likely to contribute to success Thus numerous approaches may be employed to avert NIV failure before considering sedation and analgesia Nonetheless we acknowledge that some patients remain intolerant and uncooperative with poor patient–ventilator synchrony despite application of the aforementioned nonpharmacological strategies under these circumstances administration of analgesia and sedation in an attempt to reverse the situation may be worthwhile before resorting to intubationIntensivists and nurses working in ICUs are very experienced with the administration of sedative and analgesic drugs Dosing of these drugs can be very challenging because of the different sensitivities and rates of metabolism between patients For example chronic users of benzodiazepines or opiates may have high tolerance to these drugs and require high doses whereas naïve users especially those with respiratory failure and chronic CO2 retention may exhibit profound respiratory depression even with relatively small doses Intravenous bolus dosing may be particularly hazardous in this regard Considering that we are seeing fewer COPD patients with acute respiratory failure admitted to the ICU 7 and more use of NIV on regular medical/surgical wards 8 we must be particularly cautious about the use of sedation and analgesia in these less intensively monitored environments Such applications may not only be dangerous for patients but may also have legal implications if there are adverse outcomes at least in litigious countriesThus sedation and analgesia should be administered by experienced staff using the minimum doses required to achieve tolerance avoiding oversedation This should be in a setting where at the very least electrocardiogram and oximetry tracings can be monitored continuously Several sedation scales are available that may be helpful in ensuring that level of sedation is minimized but once again application of these requires trained staffThe depressant effects of sedation and analgesia on respiratory function vary between individuals depending on the choice and dose of the drug its sedative or analgesic effects and sensitivity and metabolic capabilities of the recipient 9 10 11 12 In the few studies examining the clinical use of sedatives in patients receiving NIV 13 14 15 16 17 or more correctly in patients failing NIV for interface intolerance two classes of drugs have been used most often GABAergic agonists usually midazolam or propofol or opiates usually morphine or remifentanil Both classes of drugs may blunt the output of the respiratory center The electrical activity of the diaphragm EAdi provides a direct assessment of respiratory drive and timing close to respiratory centers permitting a better understanding of patient–ventilator interactionBy adopting EAdi monitoring Vaschetto et al 18 showed in intubated patients that propofol significantly interferes with patient–ventilator synchrony in pressure support ventilation PSV at doses producing deep sedation Both during PSV and neurally adjusted ventilator assistance NAVA propofol reduced neural drive and effort while not significantly affecting respiratory timing
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