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Use of Normal Saline Instillation with Suctioning: The Debate Continues
Abstract & Commentary
By Ruth Kleinpell, PhD, RN, Director, Center for Clinical Research and Scholarship, Rush University Medical Center; Professor, Rush University College of Nursing, Chicago, is Associate Editor for Critical Care Alert.
Dr. Kleinpell reports no financial relationship to this field of study.
Synopsis: This randomized clinical trial compared 130 mechanically ventilated patients who received 8 mL instillation of isotonic saline before tracheal suctioning to a control group of 132 patients who did not in a medical surgical intensive care unit (ICU) in an oncology hospital and found a decrease in the incidence of ventilator-associated pneumonia (VAP) in the saline instillation group. No differences were found in the incidence of atelectasis on daily chest radiography and endotracheal tube occlusions.
Source: Caruso P, et al. Saline instillation before tracheal suctioning decreases the incidence of ventilator-associated pneumonia. Crit Care Med 2009;37:32-38.
The use of normal saline instillation with suctioning has been debated over the years due to uncertainty about the benefits of use. Caruso and colleagues assessed the use of the instillation of 8 mL of saline before tracheal suctioning and compared VAP rates among control and treatment patients receiving mechanical ventilation for > 72 hours who had an orotracheal or tracheo-tomy tube. VAP rates diagnosed based on clinical suspicion and confirmed by bronchoalveolar lavage quantitative culture were compared between the groups. The rate of clinically suspected VAP was similar in both groups, while the incidence of microbiologically proven VAP was significantly lower in the saline group (P = 0.008).
The instillation of normal saline prior to endotracheal suctioning was acknowledged as a common clinical practice several decades ago. However, research over the past 2 decades has demonstrated adverse physiological effects with the use of normal saline instillation including decreases in oxygen saturation and desaturation,1-9 increased heart rate,3,6,8 risk of infection due to dislodgement of bacterial colonies,10 and subjective patient reports of pain, anxiety, and dyspnea.11,12 As a result of the evidence from a number of research studies, the routine use of normal saline instillation with suctioning has not been a recommended practice for mechanically ventilated patients. A recent clinical evidence review identified that collectively the research studies examining normal saline instillation provided class III evidence of adverse physiological and psychological effects and support against the routine use of normal saline with suctioning.13
The findings by Caruso and colleagues demonstrated lower rates of VAP found in those patients randomized to normal saline instillation before suctioning. These results are contrary to the research evidence that demonstrated a variety of adverse effects of saline instillation with suctioning. However, the results of the study must be interpreted with caution due to a number of limitations, including the use of an oncology population that differs from general ICU patients in terms of incidence of VAP, antibiotic pretreatment, immunosuppression, and mortality rates.14 Additionally, independent variables with clinical relevance, including antibiotic treatment in the groups, immunosuppression, and age, were excluded as confounding factors.14 It is also unclear as to whether the researchers controlled for other standard interventions to avoid VAP such as oral care, aspiration of subglottic secretions, and maintenance of cuff pressure on the endotracheal tube.13 While the results of the study by Caruso and colleagues did demonstrate decreased rates of VAP in those patients randomized to receive normal saline instillation prior to suctioning, it is evident that additional research is needed before this practice is recommended for routine use in ICU patients, especially as the research evidence base had not supported continuation of this practice.