Instillation of normal saline before suctioning reduces the incidence of pneumonia in intubated and ventilated adults.

Summary of: Caruso P, Denari S, Ruiz SAL, Demarzo SE, Deheinzelin D (2009) Saline instillation before tracheal suctioning decreases the incidence of ventilator-associated pneumonia. Critical Care Medicine 37: 32-38. [Prepared by Mark Elkins, CAP Co-ordinator.]

Commentary

Normal saline instillation (NSI) prior to endotracheal suctioning has been practised widely for over two decades in intensive care units. High quality, clinical evidence about the effects of NSI is limited. In vitro evidence that NSI dislodges bacteria from endotracheal tubes suggests that it would increase contamination of the lower respiratory tract (Hagler and Traver 1994). On this basis, some have recommended that its routine use be discontinued (Thompson 2000). The study by Caruso and colleagues (2009), however, demonstrates that NSI reduces the incidence of VAP in intubated patients. The authors suggest possible mechanisms for this reduction: enhancement of sputum clearance by cough stimulation, dilution and loosening of sputum thus aiding secretion clearance, and a reduction in the endotracheal tube biofilm 'VAP reservoir' by frequent rinsing with NSI. As none of these was measured specifically during this study, the mechanism(s) for the reduction in VAP remains undetermined. Additional studies could clarify the relative impact of these proposed mechanisms.

Wide variation in the administration of NSI is known to occur between intensive care units. Published studies of NSI frequently do not specify the patient's position during NSI, the length of time from NSI to suction, or individual and cumulative NSI dosages. These details would help guide those clinicians continuing to implement NSI. Whilst in this study the difference between groups in atelectasis and endotracheal tube occlusion did not reach statistical significance, these were lower in the NSI group. The lack of statistical significance may be due to the small number of events. However, the results may also have been affected by the physiotherapy interventions subjects received beyond endotracheal suctioning and whether this differed between groups. These important details were not specified.

To date, the debate on the use of NSI has been hampered by the limited evidence available. This may explain why NSI continues to be practised widely by health care professionals despite recommendations to the contrary. This study provides the first high quality, clinical evidence of benefit which must certainly reopen the debate.

Julie C Reeve

AUT University, New Zealand

References

Thompson L (2000) Suctioning adults with an artificial airway. Joanna Briggs Institute for Evidence Based Nursing and Midwifery, Systematic Review No. 9.

Hagler D et al (1994) Am J Crit Care 3: 444-447.