Effect Of Loose Dose Noradrenaline As The Circulating Screening Standard Of Spontaneous Respiration Trial On Weaning From Mechanical Ventilation

Background:Spontaneous breathing trial(SBT)is the most commonly used and effective method of weaning in patients with mechanical ventilation at present.It includes two parts:safety screening before weaning from mechanical ventilation and SBT.If the patients have passed the SBT safety screening,they could be tested by the SBT to evaluate the final mechanical ventilation weaning feasibility.Therefore,the SBT safety screening also determines the tracheal extubation time.Safety screening involves the assessment of respiratory,circulatory and other systems,and the circulatory evaluation guidelines for weaning from mechanical ventilation give only vague recommendations for"non-vasoactive drugs or low-dose vasoactive drugs".When norepinephrine is used to treat patients with septic shock,some scholars[1-3]used norepinephrine<0.12ug/kg*min as the safety screening standard.However,clinically,we found that many patients could successfully wean from mechanical ventilation above 0.12ug/kg*min of norepinephrine,which suggested that this standard was too strict and caused some patients to delay the weaning.Since norepinephrine is not specifically recommended in the guidelines,clinicians are highly subjective about"small doses of vasoactive agents." For many years,our department's understanding of "small dose" of norepinephrine was ?0.2ug/kg*min.With norepinephrine<0.2ug/kg*min as the safety screening standard,we did not find that the failure rate of weaning increased in clinical work.Our standard was significantly looser than the recommended dose in the literature,so we conducted a retrospective study on the effect of loose norepinephrine dose as a screening standard on SBT weaning.Objective:To evaluate the effect of loose norepinephrine dose as a circulating screening criterion for Spontaneous breathing trial(SBT)on tracheal extubation results.Methods:Case data were collected from patients diagnosed with septic shock and receiving mechanical ventilation support in the intensive care unit(ICU)of our hospital from January 2014 to June 2019.Record patients' gender,age,acute physiology and chronic health evaluation system(APACHE II)score,dose of norepinephrine for the first SBT,oxygenation index before tracheal extubation,lactic acid,mechanical ventilation time,SBT times,the rate of reintubation within 48 hours after tracheal extubation,hospitalization time in ICU and 28-day mortality.Firstly,a multivariate regression analysis was performed on the prognosis of the patients.Secondly,the effects of norepinephrine dose on 28-day mortality,hospitalization time in ICU,the rate of reintubation within 48 hours after tracheal extubation,mechanical ventilation time and number of SBT trials were evaluated.Results:Finally,59 patients with complete data were enrolled,and the total success rate of weaning from mechanical ventilation was 86.4%(the rate of reintubation within 48 hours after tracheal extubation was 13.6%).Logistic regression analysis found that when the dose of norepinephrine in the first SBT was less than 0.2ug/kg*min,it had no significant effect on the rate of reintubation within 48 hours after tracheal extubation or 28-day mortality,and was negatively correlated with the time of mechanical ventilation(Pearson correlation coefficient=-0.555,P<0.05).According to the dose of norepinephrine suggested in the literature(?0.12ug/kg*min),the patients were divided into low dose group(29 cases)(?0.12ug/kg*.min)and loose dose group(30 cases(0.12-0.2ug/kg*min).There's no statistical difference(P>0.05)between the two groups of age,APACHE II,oxygenation index,or the lactic acid level,so it's comparable.There was no statistical difference in the number of SBT times,28-day mortality rate,hospitalization time in ICU or the rate of reintubation within 48 hours after tracheal extubation between the two groups(P>0.05).However,the mechanical ventilation time of the loose group was short(P<0.05),showing a statistical difference.Conclusions:For patients with septic shock and mechanical ventilation,a loose dose of norepinephrine as the circulating screening standard for SBT was not found to increase the rate of reintubation,hospitalization time in ICU or 28-day mortality,but showed a reduction in mechanical assistance time.