PRINCIPLES & PRACTICE
D A V I D R. S H O R T E N , R N , B S c N , M N P A U L J. B Y R N E , M B , C H A R O B E R T L. J O N E S , M D , P H D
Znfant Responses to Sdine Znsti&tions and Endotrmbd Suctioning
The study examined the effects of endotracheal suction with and without saline instillation on neonates with respiratory distress. In a completely counterbalanced factorial-wtthinsubjects destgn, 2 7 intubated neonates were randomly assigned to two orders of presentation of treatment conditions. Heart rate and blood pressure were continuously recorded throughout both treatment conditions. The ratio of arterial oxygen tension to alveolar oxygen tension was used to assess oxygenation. Results indicated that cllnically stable newborns tolerated instillations of 0.25-0.5 ml. The suctioning protocol used In this study mtnimized changes in tnfants' heart rates and blood pressures. Accepted: April I991
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ndotracheal suctioning is a standard part of nursing care for the intubated neonate. The primary purpose of the procedure is to facilitate the removal of airway secretions, thus preventing obstruction and optimizing oxygenation and ventilation. Many deleterious effects of endotracheal suctioning have been documented in the neonate, including bacteremia,' a t e l e c t a s i ~ , ~h?y~p ~ x e r n i a , ~pneumotho-~ rax,',' tachycardia and brady~ardia;-~*~-ll mucosal trauma,12systemic h y p e r t e n ~ i o n , ~ "and ~ " ~increases in intracranial p r e s ~ u r e . ~ ~ To' ~minimize ~'~ hypoxemia during suctioning, some researchers have used preoxy g e n a t i ~ n ~ ~ and ~ ~ ' hyper~entilation.~~'~ ~*~~*'~ The neonate's tolerance of endotracheal suction is also influenced by other techniques used during the procedure, including the depth and duration of the applied suction, suction pressure, and handling of the newborn.' ' J ~ - ~ ~ An additional factor that may influence the neonate's response to endotracheal suction is the common practice of saline instillation during the procedure. Most researchers studying endotracheal suction in neonates have incorporated instillations routinely into their p r o t ~ ~ o l s . ~Instillation ~ ~ ~ ~ ~is~ thought ~~'~~~-~ to aid in the thinning and subsequent removal of secretions; however, although the procedure is commonly performed during neonatal endotracheal tube toilet, there is no evidence to support the benefit of instillation when compared to endotracheal tube suction alone. It may be that routine instillations are not necessary to maintain airway patency, and indeed, the practice may exacerbate the infant's adverse responses to suctioning. This study examined the physiologic effects of endotracheal suction with and without saline instillation on infants with respiratory distress.
Hypotheses Three hypotheses were formulated: 1 . Receiving a saline instillation with tracheal
suctioning will cause significant changes in heart rate (HR), blood pressure (BP), and the ratio of arterial oxygen tension to alveolar oxygen tension (a/APO,), compared to receiving tracheal suctioning alone (main effect of condition). 2. There will be significant changes in HR, BP, and a/APO, over the 13 time periods (main effect of time). 3. There will be significant changes in HR and BP during or after the treatment period (interaction effect of condition by time).
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Infant Responses to Saline InstilkzttionS and E?z&trahl SuctiOnng
Materials and Method After informed parental consent was obtained, 27 newborns requiring ventilator care in the neonatal intensive care unit (NICU) were enrolled in the study. Neonates with congenital abnormalities were excluded. Criteria for inclusion were that the newborn 1) be in respiratory distress, 2) have undergone endotracheal intubation, 3) have an indwelling arterial line, 4 ) be clinically stable (have stable BP and an unchanged ventilator setting for the preceding four hours), 5) have had previous endotracheal suctioning on at least three occasions, with the most recent suction procedure having taken place two to four hours earlier, and 6) not be under sedation. Heart rate was measured using a bedside monitor (model 78801A, Hewlett Packard, Waltham, MA) and adhesive pre-gelled neonatal cardiac electrodes. Mean arterial BP was measured using a transducer (model 4-327-L, Hewlett Packard) attached to an indwelling arterial catheter. Data were recorded by a 16-channel computer (ASM Acquisition System, University of Alberta, Edmonton, Alberta) programmed to sample at a rate of 10 times per second. Arterial blood gases were measured using a Corning 178 analyzer (Medfield, MA). The ratio of arterial oxygen tension to alveolar oxygen tension was used to assess oxygenation. Alveolar oxygen tension was calculated by a modification of the alveolar air equation PAO, = PIO, - PC0,/0.8, where PAO, is alveolar oxygen tension, PIO, is inspired oxygen tension, and PCO, is carbon dioxide tension. This equation assumes the respiratory exchange ratio to be 0.8 and is often used in clinical practice. A completely counterbalanced factorial-withinsubjects design was used to compare two treatment conditions: tracheal suctioning without instillation and tracheal suctioning with instillation. The order of treatment was randomized. The treatment conditions were separated by a period of two to four hours, depending on the neonates’ regular suction schedules. In the NICU, two nurses perform endotracheal suctioning. In this study, one nurse performed the suctioning, and a second nurse disconnected and reconnected the newborn to the ventilator between suctioning passes. The protocol included measurement of the suction catheter so that the tip of the catheter protracted 1 cm beyond the distal end of the endotracheal tube. Suction pressure was set at 40 mm Hg for newborns weighing less than 1,500 g and 60 mm Hg for newborns weighing more than 1,500 g. The two treatment conditions had the following sequence of phases in common: baseline, prepara-
Nouember/December 1991
tion, suction I, treatment, suction 11, suction 111, oral suction, recovery I, and recovery I1 (Fig. 1). Immediately prior to the four-minute baseline phase, a presuction arterial blood gas was drawn. During the oneminute preparation phase at the end of the baseline phase, the ventilatory rate and oxygen requirements were both increased to the values used during the neonates’ previous routine suctions. The fraction of inspired oxygen (FiO,) was increased from 0.04 to 0.29 (mean, 0.14), and the ventilatory rate was increased from 0 to 40 breaths per minute (mean, 14.3) over the baseline values. For each neonate, these increases were the same for both treatment conditions. Each of the three suctioning phases consisted of the removal of the neonate from the ventilator, insertion of the suction catheter, application of suction, removal of the suction catheter from the endotracheal tube with suction still applied, and reattachment to the ventilator for a 15-second ventilation period at the FiO, and ventilator rates set during the preparation phase. The two treatments differed only at the point after the first suction phase. During instillation, the neonates were disconnected from the ventilator for 5 seconds and administered a saline solution via the endotracheal tube (0.25 ml for newborns weighing less than 1,500 g and 0.5 ml for newborns weighing more than 1,500 g), followed by 15 seconds of increased FiO, and ventilator rates. When instillation was not performed, the neonates simply were disconnected from the ventilator for 5 seconds, and this was followed by 15 seconds of increased FiO, and ventilator rates. The same nurses performed both treatment conditions on each neonate. After the second and third suction phases, oral suctioning was performed for 10 seconds to clear secretions. Data were collected for 10 minutes after this period. A postsuction arterial blood gas was taken at the end of the second recovery phase. To ensure standardization of the sequence, tape-recorded instructions specifying the procedure and time of each phase were played during each condition for all subjects. Also, all suction treatments were supervised by the same investigator. An analysis of variance was performed on the data to evaluate the main effects of the suction treatment condition and time, as well as the interaction between the condition and time. Paired t-tests were used to compare the pre- and postsuction difference in a/APO,.
Sample Suction studies were carried out on all 27 newborns, but the data on 2 of the newborns were incomplete
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C L I N I C A L S T U D I E S
Baseline phase
Preparation phase
Suction I phase
Treatment phase
Suction II DhaSe
Suction 111 DhaS
Oral suctior phase
Recovery I phase
Recovery II phase
Control
ABG
Cantmi dtian 4 minutes
1 minute
suction period I
Ventilation period I
10 seconds
15 seconds
No ventilation period 5 seconds
Ventilation period II
Suction period II
Ventilatin period 111
Suction period Ill
Ventilation period IV
15 seconds
10 seconds
15 seconds
10 seconds
15 seconds
ABG
10 seconds
5 minutes
5 minutes
Instillation
ABG
lnsllNItlen ralwhm 4 minutes
1 minute
10 seconds
15 seconds
Instillation period 5 seconds
Ventilation period II 15 seconds
ABG 10 seconds
15 seconds
10 seconds
15 seconds
10 seconds
5 minutes
5 minutes
Figure 1. Sequence ofphases ofthe stdy. ABG, arterial blood gases drawn.
and thus excluded. The remaining 25 newborns included 1 set of triplets, 1 set of twins, and 20 singletons. Fourteen newborns were male (56%), and 11 newborns were female (44%). Gestational ages ranged from 25 to 40 weeks (mean, 32.5 weeks) and birth weights from 510 to 3,320 g (mean, 1,879 g). Seventeen (68%) of the neonates had respiratory distress syndrome, 4 neonates (16%) had pneumonia, and 4 neonates (16%) had respiratory distress of varying etiologies. The internal validity of the study was not compromised by including newborns with different etiologies, since each newborn acted as its own control. The newborns were studied as soon as they were stable according to the inclusion criteria. The ages at the time of study ranged from 18 to 198 hours (mean, 91.8 hours). Baseline oxygen requirements were as follows: FiO, ranged from 0.21 to 0.55 (mean, 0.32); peak inspiratory pressure ranged from 16 to 26 cm H,O (mean, 19.8); and positive-end expiratory pressure ranged from 2 to 6 cm H,O (mean, 3.8). Ventilatory rates ranged from 4 to 55 breaths per minute (mean, 15.95).
recovery phase 11. Heart rate decreased significantly toward baseline levels between recovery phase I and recovery phase 11. A factorial analysis of variance of BP revealed no significant difference for the main effect of condition or the interaction of condition by time. The main effect of time was significant ( F = 17.1; df = 12, 204; p < 0.001). Post hoc multiple comparisons of time indicated that BP rose significantly after the baseline phase for all other phases except the two recovery phases (Table 2). There were no significant differences in the pre- and postsuction values a/APO, for both conditions.
Discussion
ther the method of suction nor its interaction with time was significant but that the effect of time itself wassignificant ( F = 9.27; df= 12,288;p