Re-examining the practice of normal saline instillation prior to suctioning

Re-examining the practice of normal saline instillation prior to suctioning

Mary C. Druding

Suctioning of an artificial airway is a common procedure in critical care areas. Presently, due to increasing patient acuity, it has become more common in medical-surgical areas as well. The purpose of endotracheal suctioning is to clear secretions from the airway to maintain a patent airway and to optimize ventilation and oxygenation. The use of an artificial airway diminishes a patient’s natural ability to mobilize and clear secretions. Also, since the purpose of the upper airway is to warm and moisten air and this is bypassed by an artificial airway, the patient must rely upon proper humidification from the closed ventilator circuit. If sufficient moisture is not present in the system the gas will absorb water from the airway, most likely from the mucous, which will then become drier and more tenacious (Ecklund & Ackerman, 1995). Nurses routinely instill 3-10 cc of normal saline solution (NSS) into the airway prior to suctioning to loosen the secretions, lubricate the suction catheter, and increase secretion clearance (Ackerman, 1993). Other reasons for saline instillation include enhancing cough stimulation, mobilizing secretions, as well as diluting secretions (Bostick & Wendelgass, 1987).

Suctioning is a common procedure but it is not benign. Suctioning has been associated with potentially serious and life-threatening complications, such as hypoxemia, cardiac dysrhythmia, cardiac arrest, respiratory arrest, bronchospasm, increased bronchial mucous production, hypertension, vagal stimulation, increased intracranial pressure (ICP), atelectasis, damage to tracheo-bronchial mucosa, pulmonary hemorrhage, patient anxiety and fear, nosocomial infection, and death (Bostick & Wendelgass; 1987; Bronson, Chatburn, & Covington, 1993; Noll, Hix, & Scott, 1990). On the other hand, failure to use the suctioning procedure could result in serious patient complications, including death.


To minimize complications and maximize outcomes it is imperative to establish standards for suctioning. The indications for suctioning as well as procedural steps to be followed must be identified and re-evaluated at intervals to ensure that they are supported by current thinking and research findings.

One role of the advanced practice nurse is to establish and maintain standards of practice based on current research. Another is to serve as change agent. The purpose of this article is to analyze and synthesize the research on saline instillation for suctioning in order to determine the best practice for critically ill patients. Recommendation for practice can form the basis of procedures, policy formation, and outcome management strategies.

Research Analysis

In an earlier article, Demers and Saklad (1973) presented guidelines based on review of the literature and current practice to minimize harmful effects of the suctioning procedure. Included in these guidelines was a discussion of the effect of normal saline solution instillation on the quality of secretions.

Demers and Saklad (1973) concluded that instillation of normal saline solution is not effective in thinning or liquifying secretions and maintained that although “water in the form of aerosol is of proven value in thinning secretions, mucous and [H.sub.2]O in bulk forms are immiscible and occupy separate phases in vitro, even after vigorous shaking” (p. 542).

Bostick and Wendelgass (1987) examined the relationship between normal saline solution instillation and oxygenation in 45 adult post open-heart patients. Each patient was randomly assigned to one of three groups (no saline, 5 cc saline, 10 cc saline) Pa[O.sub.2] was measured at 5 minutes prior to suctioning and 20 minutes after suctioning. No statistically significant difference between the saline group and the nonsaline group in mean Pa[O.sub.2] was found. However, the trend was toward lower Pa[O.sub.2] with larger amounts of saline instillation and the researchers concluded the decrease might be the result of instilled normal saline impeding alveolar-capillary oxygen exchange. Aspirated sputum was weighed for each of the three groups. A significant difference between the two saline groups and the nonsaline group was found. The saline weight was higher. However, the clinical significance is unclear because the weight could have been saline and not mucous.

Gray, McIntyre, and Kronenberger (1990) examined the physiologic responses of heart rate, blood pressure and respiratory rate, Ph, [PCO.sub.2], [PO.sub.2], [O.sub.2] saturation, FVC, peak inspiratory pressure, minute ventilation ([V.sub.E]), amount of material suctioned, and degree of discomfort, with and without saline. Gray et al. (1990) used a repeated measures design involving 15 critically ill patients who were randomly suctioned once with normal saline solution and once without in a 90-minute period. The researchers assessed hemodynamics, gas exchange, and respiratory mechanics before and 15 minutes after each method. There was no statistically significant difference in heart rate, BP, respiratory rate or arterial blood gases between the two treatment methods immediately or 15 minutes after suctioning. They found that suctioning with normal saline caused a significantly greater amount to be aspirated than without normal saline solution. However, secretion content was not analyzed. It was concluded that normal saline does not increase patient discomfort and may enhance secretion clearance through cough stimulation since a cough was elicited more frequently when using saline than not. There was no difference in FVC, [V.sub.E], or peak airway pressure between each suctioning method.

Ackerman and Gugerty (1990) used a single-case experimental design to determine if the use of saline instilled down a patient’s tracheostomy or endotracheal tube had an effect on the amount of aspirated sputum and/or Sa[O.sub.2] values. They selected 26 patients based on the established criterion that they had an endotracheal or tracheostomy tube. The difference in weight between control and experimental sputum samples was statistically significant. However, the clinical significance was questionable in that it could not be concluded whether the experimental group (with saline) had more weight after suctioning because of more mucous produced by the saline bolus or the patient simply had more secretions prior to suctioning. Sa[O.sub.2] was monitored at baseline, after hyperoxygenation, at 15, 30, 45, and 60 seconds, and every minute to 5 minutes. Statistically significant differences in [O.sub.2] saturations were found at 45 seconds through 5 minutes. The [O.sub.2] saturations were lower in the group receiving saline.

Ackerman (1993) used a quasi experimental, single, counter-balanced design to study 40 men requiring suctioning. The nurses used 5 cc saline with every other suctioning procedure and measured the [O.sub.2] saturation immediately before, right after the procedure, and at 1-minute intervals up to 5 minutes. Results indicated that the use of saline had a significant effect on [O.sub.2] saturation that worsened over time. Ackerman found a significant change at 2, 3, 4, and 5 minutes after instillation and suctioning.

Table 1 presents a comparison of the six major studies reviewed here.



The review of the past research demonstrates that empirical evidence to support the use of saline instillation is lacking and, in fact, its use may be harmful to the patient. The use of normal saline solution as a stimulant to cough or decrease the adherence of secretions to the endotracheal tube has not been disproved (Raymond, 1995). The fact that saline instillation elicits a cough, which in turn may loosen secretions, is well established in the literature (Ackerman, 1993). The research does not support the rationale that saline ravage liquifies secretions or dispenses saline into the tracheo-bronchial tree. Studies show that mucous and water are like oil and water and do not mix, even with vigorous shaking. In a study by Hanley, Rudd, and Butler (1978) tagged normal saline was instilled via the endotracheal tube and, with serial x-rays, the distribution of saline was studied. All saline remained in the trachea and main stem bronchi and none reached the periphery of the lungs even after 30 minutes.

Of all studies reviewed, only Ackerman’s (1993) demonstrated possible adverse effects of saline solution instillation on oxygen saturation. The fact that this study seems to demonstrate decreased oxygen saturation at 2 through 5 minutes after the use of saline is clinically important and warrants future investigation. In the meantime, indiscriminant use of saline for all patients prior to suctioning can no longer be recommended.

Recommendation for Practice (see Table 2)

Table 2.

Recommend” Practice Changes for Suctioning

1. Suction based on assessment of need.

a. Audible secretions

b. Rhonchi on auscultation

c. Increased proximal airway pressure on the ventilator

d. Patient request

e. Decreasing pulse ox, [SVO.sub.2], or Pa[O.sub.2]

2. Instill normal saline based on patient need as determined by

response to suctioning.

a. Secretions sticking to tube or catheter

b. Mucous is plugging the airway

c. Suction catheter is not eliciting an acceptable cough

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