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Weaning

Overview

Weaning is the gradual withdrawal of ventilatory assistance with modification of spontaneous breathing and resting periods for respiratory muscles. When a patient shows improvement as clinical indicator of disease resolution, the weaning should be started as the patient is able to maintain airways opened with physiologically normal ventilation cycles. The close continuous monitoring of patient's ventilatory status should be accompanying the disease correction process. Weaning competency is assessed by measurement of cardiovascular and respiratory functions to avoid the possibility of weaning complications.

Spontaneous Breathing Trial (SBT)

Spontaneous Breathing Trials (SBT) assess the patient’s ability to breathe without or with the least respiratory support. In order to accomplish this, ventilators' modes are switched from full respiratory support such as volume-assist control or pressure control to ventilatory modes such as pressure support, continuous positive airway pressure (CPAP), or ventilation with a T-piece (in which there is no positive endexpiratory pressure). Typically, the patient is awake and not sedated during a trial of spontaneous breathing.

Patient Who Will Tolerate Weaning

For a spontaneous-breathing trial to be successful, a patient must breathe spontaneously with little or no ventilator support for at least 30 minutes with absence of any of the following

1. RR>35/min for more than 5 minutes
2. O2 Sat <90%
3. HR >140/min
4. A sustained change in the heart rate of 20%
5. Systolic blood pressure >180 mm Hg or <90 mm Hg
6. Increased anxiety or diaphoresis

After successful SBT there are some factors to be considered before removing the endotracheal tube :

1. The ability to maintain the airways opened upon removing the tube
2. Secretions quantity from airway
3. The strength of cough
4. Adequate mental status

Rapid Shallow Breathing Index

As a predictor for successful weaning ,the RSPI is the frequency of respiration to tidal volume ratio (f/VT). It was originally measured using a hand-held spirometer attached to the endotracheal tube while a patient breathed room air for one minute without any ventilator assistance. As an example, a patient who has a respiratory rate of 25 breaths/min and a tidal volume of 250 mL/breath has an RSBI of (25 breaths/min)/(.25 L) = 100 breaths/min/L. Patients who cannot tolerate independent breathing and thus weaning tend to have rapid (high frequency) and shallow (low tidal volume)breathing. Thus, they generally have a high RSBI.

The sensitivity is the probability that a patient who successfully weans will have an RSBI <105 breaths/min/L and the specificity is the probability that a patient who fails weaning will have an RSBI ≥105 breaths/min/L. The positive predictive value is the probability of successfully weaning when the RSBI is <105 breaths/min/L and the negative predictive value is the probability of failing weaning when the RSBI is >105 breaths/min/L.

Risk Factors For Unsuccessful Weaning

1. Failure of two or more consecutive SBTs
2. CHF
3. PaCO2 >45 mm Hg after extubation
4. More than one coexisting condition other than heart failure
5. Weak cough
6. Upper-airway stridor at extubation
7. Age ≥65 yr
8. APACHE II score >12 on day of extubation(Acute Physiology and Chronic Health Evaluation (APACHE II)range from 0 to 71, with higher scores indicating greater impairment.)
9. Patient in medical, pediatric, or multispecialty ICU
10. Pneumonia as cause of respiratory failure

Fecal Transplant For Relapsing Clostridium Difficile

Overview

Unfortunately the rates and severity of Clostridium Difficile infections are increasing in addition to the expansion of the patients population beyond the traditional scope of inpatients receiving antibiotics. Rates of recurrent C.diff infection is 15-26%, and an extended Vancomycin regimen is used with 60% successful treatment rate for the initiative recurrence, but the efficacy rates decline for further recurrences. The principle for fecal transplant(Bacteriotherapy ) is to compensate the colon normal flora that has been eradicated because of the prolonged use of antibiotics with hospitalized patients, restoring the bacterial balance in GI tract. The American Gastroenterological Association(AGA)has set guidelines regarding the indication ,donor selection and methodologies of fecal bacteriotherapy

Indications

1. Recurrent or relapsing CDI.
   1. At least three episodes of mild-to-moderate CDI and failure of a 6-8 week taper with vancomycin with or without an alternative antibiotic (e.g., rifaximin, nitazoxanide).
   2. At least two episodes of severe CDI resulting in hospitalization and associated with significant morbidity.
2. Moderate CDI not responding to standard therapy (vancomycin) for at least a week.
3. Severe (and perhaps even fulminant C. difficile colitis) with no response to standard therapy after 48 hours.

The severity of c.diff infection plays an essential role in determination the early use of fecal bacteriotherapy.