Respiratory depression under long-term sedation with sufentanil, midazolamand clonidine has no clinical significance

Objective: Assessment of respiratory depression caused by long-term sedatio n with sufentanil, midazolam and clonidine. Design: Retrospective assessmen t using data from a patient data management system. Setting: University hos pital anaesthesiological ICU. Patients: Three hundred ninety-five surgical and trauma patients with an ICU stay of more than 48 h. Intervention: None. Measurements and results: Arterial blood partial pressure of carbon dioxid e (PCO2) was evaluated during mechanically assisted spontaneous ventilation (continuous positive airway pressure, synchronised intermittent mandatory ventilation, mandatory minute ventilation, bilevel positive airway pressure ). Continuous sedation with sufentanil, midazolam or clonidine or a combina tion of those drugs was administered to achieve a Ramsay score between 2 an d 4. Spontaneously breathing patients without continuous sedation and patie nts on controlled mechanical ventilation (and sedation) served as control g roups. Mean arterial PCO2 from spontaneously breathing patients without con tinuous sedation was 39.5 +/- 7.3 torr compared with 42.7 +/- 6.8 torr unde r sufentanil (median 0.44 mug.kg(-1).h(-1), 98 % of observations between 0. 1 and 2.1 mug. kg(-1).h(-1)), 41.5 +/- 6.1 torr under sufentanil (median 0. 90 mug.kg(-1).h(-1) (0.1-2.8)) plus midazolam (median 45 mug.kg(-1).h(-1) ( 7-170)) and 39.8 +/- 5.6 torr under a combination of sufentanil (median 1.1 5 mug.kg(-1).h(-1) (0.2-3.6)), midazolam (median 45 mug.kg(-1).h(-1) (11-21 6)) and clonidine (median 1.3 mug.kg(-1).h(-1) (0.2-2.5)). Mean arterial PC O2 from patients on controlled mechanical ventilation was 39.9 +/- 6.1 torr . Conclusion: Patients under continuous sedation with sufentanil exhibit a statistically significant rise in arterial PCO2, however this respiratory d epression is only slight and has no clinical significance. Mechanically ass isted spontaneous ventilation modes can safely be used under continuous sed ation with sufentanil, midazolam or clonidine.