Application of mechanical ventilation weaning predictors after elective cardiac surgery

Abstract

OBJECTIVETo test several weaning predictors as determinants of successful extubation after elective cardiac surgery.METHODSThe study was conducted at a tertiary hospital with 100 adult patients undergoing elective cardiac surgery from September to December 2014. We recorded demographic, clinical and surgical data, plus the following predictive indexes: static compliance (Cstat), tidal volume (Vt), respiratory rate (f), f/ Vt ratio, arterial partial oxygen pressure to fraction of inspired oxygen ratio (PaO2/FiO2), and the integrative weaning index (IWI). Extubation was considered successful when there was no need for reintubation within 48 hours. Sensitivity (SE), specificity (SP), positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (LR+), and negative likelihood ratio (LR-) were used to evaluate each index.RESULTSThe majority of the patients were male (60%), with mean age of 55.4±14.9 years and low risk of death (62%), according to InsCor. All of the patients were successfully extubated. Tobin Index presented the highest SE (0.99) and LR+ (0.99), followed by IWI (SE=0.98; LR+ =0.98). Other scores, such as SP, NPV and LR-were nullified due to lack of extubation failure.CONCLUSIONAll of the weaning predictors tested in this sample of patients submitted to elective cardiac surgery showed high sensitivity, highlighting f/Vt and IWI.

Reduction of ventilatory time using the multidisciplinary disconnection protocol. Pilot study

“…The doctor was responsible for checking daily ( 1 - 3 , 5 , 11 - 16 ) if the reason for IMV instauration was solved or if there was any improvement ( 2 , 5 , 7 - 8 , 11 - 12 , 14 , 17 - 21 ) by clinical evaluation, chest x-ray, arterial blood gasometry or any necessary diagnostic test. In addition, a series of criteria for disconnection ( 1 , 5 , 9 , 17 ) of MV were evaluated, which the patient had to accomplish completely in order to progress within the protocol:a) Respiratory stability: Blood pressure of oxygen (PO2) ≥ 60 mmHg5 , 7 , 14 , 18 , 22 with inspired oxygen fraction (FiO2) ≤ 0.4 ( 5 , 10 , 14 , 16 , 19 , 21 - 22 ) ; respiratory rate (RR) < 35 respirations per minute ( 5 , 19 , 22 - 23 ) and positive end-expiratory pressure level (PEEP) ≤ 5-8 cm H2O ( 2 , 5 , 7 , 9 - 11 , 13 - 14 , 19 , 21 , 24 - 26 ) .b) Hemodynamic stability with stable cardiovascular function ( 5 , 14 , 16 , 22 - 23 ) , heart rate (HR) < 120 beats per minute ( 5 , 7 - 8 ) and no need for vasoactive drugs or a minimum amount ( 2 , 5 , 7 - 8 , 11 , 13 , 18 , 20 - 23 ) , accepting doses of less than 5µ/kg/min of dobutamine ( 2 , 5 , 7 , 19 , 22 , 25 ) and <0.1µg/kg/min of noradrenaline.c) Neurological Stability: Glasgow Coma Scale (GCS) ≥ 9 ( 5 , 18 ) and between -2 and 0 ( 5 , …”

“…In addition, a series of criteria for disconnection ( 1 , 5 , 9 , 17 ) of MV were evaluated, which the patient had to accomplish completely in order to progress within the protocol:a) Respiratory stability: Blood pressure of oxygen (PO2) ≥ 60 mmHg5 , 7 , 14 , 18 , 22 with inspired oxygen fraction (FiO2) ≤ 0.4 ( 5 , 10 , 14 , 16 , 19 , 21 - 22 ) ; respiratory rate (RR) < 35 respirations per minute ( 5 , 19 , 22 - 23 ) and positive end-expiratory pressure level (PEEP) ≤ 5-8 cm H2O ( 2 , 5 , 7 , 9 - 11 , 13 - 14 , 19 , 21 , 24 - 26 ) .b) Hemodynamic stability with stable cardiovascular function ( 5 , 14 , 16 , 22 - 23 ) , heart rate (HR) < 120 beats per minute ( 5 , 7 - 8 ) and no need for vasoactive drugs or a minimum amount ( 2 , 5 , 7 - 8 , 11 , 13 , 18 , 20 - 23 ) , accepting doses of less than 5µ/kg/min of dobutamine ( 2 , 5 , 7 , 19 , 22 , 25 ) and <0.1µg/kg/min of noradrenaline.c) Neurological Stability: Glasgow Coma Scale (GCS) ≥ 9 ( 5 , 18 ) and between -2 and 0 ( 5 , 18 ) on the Richmond Scale ( 27 ) to ensure a low level of sedation ( 2 , 5 , 11 , 15 , 19 ) .d) Absence of fever ( 5 , 7 , 16 , 20 , 22 ) or hypothermia ( 5 , 16 ) , presence of cough reflex ( 2 , 5 , …”

“…If the patient complied with all criteria, the nurse connected the patient in a spontaneous mode with support pressure (SP) ( 2 , 5 , 11 - 12 , 16 , 19 , 23 , 29 ) , assuring a tidal volume (TV) of 6-8 ml/kg ( 5 , 14 , 16 , 25 , 29 - 30 ) of ideal body weight, making pressure decreases ( 5 , 7 , 9 , 18 - 19 , 31 ) of 2 in 2 cm of H2O every 20-30 min ( 5 ) until achieving a SP less than or equal to 8 cm H2O ( 1 - 2 , 5 , 7 , 29 , 32 ) . After each decrease, the patient’s tolerance was checked by measuring parameters such as: HR ( 5 , 8 , 13 , 15 , 18 , 21 - 22 ) , systolic blood pressure ( 5 , 9 , 17 , 26 , 30 ) , O2 saturation ( 5 , 8 , 13 , 15 , 18 , 21 - 23 ) , level of consciousness ( 5 , 16 , 20 , 28 ) , presence of discomfort or diaphoresis ( 5 , 8 , 13 , 15 , 18 , 21 - 23 ) or tachypnea ( 5 , 8 , 13 , 15 , 18 , 21 - 23 , 25 ) .3. If the patient tolerated all the changes made, the nurse suspended the IMV with respirator and passed the T-piece oxygen test for 30-120 minutes ( 2 , 5 , 7 , 12 , 14 - 15 , 22 , 32 ) , remeasuring the same intolerance criteria as in the previous phase and, in addition, the predictors respiratory rate <35rpm and rapid superficial respiration rate (Respiratory Rate/Tidal Volume) < 105 resp/min/ ( …”

“…After each decrease, the patient’s tolerance was checked by measuring parameters such as: HR ( 5 , 8 , 13 , 15 , 18 , 21 - 22 ) , systolic blood pressure ( 5 , 9 , 17 , 26 , 30 ) , O2 saturation ( 5 , 8 , 13 , 15 , 18 , 21 - 23 ) , level of consciousness ( 5 , 16 , 20 , 28 ) , presence of discomfort or diaphoresis ( 5 , 8 , 13 , 15 , 18 , 21 - 23 ) or tachypnea ( 5 , 8 , 13 , 15 , 18 , 21 - 23 , 25 ) .3. If the patient tolerated all the changes made, the nurse suspended the IMV with respirator and passed the T-piece oxygen test for 30-120 minutes ( 2 , 5 , 7 , 12 , 14 - 15 , 22 , 32 ) , remeasuring the same intolerance criteria as in the previous phase and, in addition, the predictors respiratory rate <35rpm and rapid superficial respiration rate (Respiratory Rate/Tidal Volume) < 105 resp/min/ ( 1 , 5 , 7 - 8 , 11 - 12 , 14 - 15 , 18 - 19 , 22 - 23 ) .4. If the patient was still stable, the extraction of arterial gasometry was carried out, and doctor and nurse carried out extubation jointly if they did not find any alteration.…”

“…If the patient was still stable, the extraction of arterial gasometry was carried out, and doctor and nurse carried out extubation jointly if they did not find any alteration. Successful weaning was considered when the patient was able to remain breathing without invasive support for a period greater than or equal to 48 hours ( 5 , 7 - 9 , 11 - 12 , 22 - 23 , 25 ) .5. If the patient did not tolerate the changes made at any point of the protocol or was not a candidate for weaning because the established criteria were not met, mechanical ventilation was resumed in Assisted-Controlled (A/C) mode ( 5 , 7 - 9 ) and weaning was not attempted again until the following day ( 5 , 7 , 13 - 14 , 18 , 22 , 25 ) .…”