Andrea Lübe de S Thiago Pereira, Ruth Guinsburg Maria Fernanda Branco de Almeida, Ana Cristina Monteiro Amélia Miyashiro Nunes dos Santos, Benjamin Israel Kopelman
Original Article
INTRODUCTION
Treating the pain o f pre-verbal patients with different co g nitive levels and with a similar reactio n to several types o f stimulus is a big challeng e. The co rnersto ne to adequate pain treatment in this po pulatio n is the availability o f a de q ua te pa in a sse ssme nt me tho ds.1 ,2 The subjectivity o f pain causes eno rmo us difficulties in e va lua ting ne o na ta l pa in with a sing le , practical and easy-to -apply to o l. Pain evaluatio n in the neo natal perio d sho uld be perfo rmed by valid, safe, useful and feasible metho ds.3 ,4 ,5
Several physio lo g ic parameters can be used to evaluate, measure and qualify the pain stimulus in the neonate. Their specificity, sensitivity and wo rkability are variable, but in general they are easily available in N eo natal Intensive Care Units (N ICU).6 These parameters include: heart rate, respirato ry rate, blo o d pressure, O2 arterial
saturatio n, transcutaneo us o xygen and carbo nic dio xide pressures, vagal to ne, palmar sweating, intracranial pressure and ho rmo nes asso ciated with the endo crine-metabo lic respo nse to stress. Mo st o f them do no t chang e specifically in respo nse to pain.7 These physio lo gic parameters can help to determine the presence o r absence o f pain, but generally they do no t help to qualify
Validity of be havioral and physiologic parame te rs
for acute pain asse ssme nt of te rm ne wborn infants
Neonatal Division of the Department of Pediatrics, Universidade Federal de São Paulo / Escola
Paulista de Medicina, São Paulo, Brazil
ABSTRACT
Contex t: The subjectivity o f pain causes eno rmo us difficulties in evaluating neo natal pain with a single, practical and easy-to -apply to o l. Pain evaluatio n in the neo natal perio d sho uld be perfo rmed by valid, safe, useful and feasible metho ds.
O bjective: To evaluate the validity o f the Neo natal Facial Co ding System (N FCS), N eo natal Infant Pain Scale (N IPS), heart rate (HR) and O2 saturatio n (O2 sat) fo r neo natal pain
assessment.
Design: Pro spective, do uble-blind rando mized trial.
Setting: A seco ndary level maternity ho spital.
Pa rticipa nts: 7 0 healthy neo nates requiring bilirubin do sage were rando mly assigned to receive a veno us puncture (P: n=3 3 , BW 3 .2 kg, SD 0 .6 ; G A 3 9 wk, SD 1 ; 5 9 h o f life, SD 2 5 ) o r an alco ho l swab frictio n (F: n=3 7 ; BW 3 .1 kg, SD 0 .5 ; G A 3 9 wk, SD 1 ; 5 2 h o f life, SD 1 7 ).
Intervention: All measurements were taken prio r to (PRE), during (T0 ), and 1 (T1 ), 3 (T3 ), 5 (T5 ) and 1 0 (T1 0 ) minutes after the pro cedure.
M ea surem ents: A neo nato lo gist evaluated NFCS, NIPS, HR and O2 sat by pulse o xymetry.
Results: Median N FCS and N IPS results at T0 , T1 and T3 were higher in P gro up, co mpared to F. Mo re P neo nates presented N FCS >2 and/ o r N IPS >3 at T0 , T1 and T3 . HR was lo wer in P gro up at T1 . Average O2 sat was abo ve
9 0 % during the who le study perio d in bo th gro ups.
Conclusion: N FCS and N IPS are suitable instruments fo r neo natal pain evaluatio n. Heart rate and O2 saturatio n can
be used o nly as auxiliary metho ds.
the pain. Mo reo ver, mo st o f the studies that relate pain to mo dificatio ns in physio lo gic variables evaluate these changes after an acute and sho rt pain stimulus, which is no t the o nly o r the main pain so urce fo r patients admitted to N ICU.8
Stud y o f ne o na ta l b e ha vio r se e ms a pro mising way o f evaluating pain in pre-verbal patients,9 -1 3 and such behavio r includes crying, mo to r activity, and the facial expressio n o f pain. The cry is co nsidered to be the primary way o f co mmunicatio n fo r newbo rn infants.1 4 ,1 5 The message o f distress sent by the infant thro ugh the cry sensitizes the adult, either the child’s mo ther o r ano ther adult who is taking care o f it.1 6 ,1 7 Several studies have tried to relate pain to different characteristics o f the cry.1 8 ,1 9 But the main pro blem in using the cry as a measure o f pain is that appro ximately 5 0 % o f newbo rn infants do no t cry during o r after a painful pro c e dure .1 ,1 0 ,2 0 Mo re o ve r, c rying is no t a specific pain assessment to o l and can be elicited by o ther no n-painful stimuli, such as disco mfo rt and hung er.2 1 Therefo re, the cry is useful in evaluating pain in the infant’s enviro nmental co ntext asso ciated with o ther pain assessment metho ds.2 1 ,2 2
After a pinprick in o ne fo o t, the neo nate withdraws the opposite leg in 0.3 seconds, the affected leg in 0.4 seconds, and he cries in 1.8 seconds.23 Term and preterm newborn infants have an organized repertoire of movements in response to a painful stimulus.24,25 Motor activity is a sensitive method of pain assessment and its specificity is enhanced by the concurrent use of other physiologic and behavioral pain evaluation tools.21
Several studies have indicated that the o bservatio n o f facial expressio n seems to be a non-invasive, sensitive, specific and useful method o f pain evaluatio n in term and preterm newbo rn infants.9 ,1 0 ,2 4 The facial activity o f pre-verbal infants is expressive and can info rm the o bserver about the emotional status of the neonate, beyond the pain, fulfilling the pain-subjective criteria o f the Internatio nal Asso ciatio n fo r the Study o f Pain’s definitio n.2 8 There are several ways o f evaluating pain fro m facial features, but the mo st studied is the N eo natal Facial Activity Co ding
Syste m (N FC S). N FC S e va lua te s e ig ht parameters: bro w bulge, squeezed eyes, naso -labial furro w, o pen lips, stretched mo uth, lip purse, taut to ngue, and chin quiver. Studies sho w that bro w bulge, squeezed eyes, deepening o f naso -labial furro w and o pen lips are present in mo re than 9 0 % o f the neo nates expo sed to a painful stimulus.1 0 Analysis o f facial expressio n allo ws an effective co mmunicatio n between the neo nates and the pro fessio nals that take care o f them.
M ultid ime nsio na l p a in a sse ssme nt is co nsidered ideal because it gives info rmatio n abo ut individual respo nses to pain and their interactio n with the enviro nment.8 Amo ng several published neo natal pain scales, the mo st studied are the N eo natal Infant Pain Scale – N IPS1 2 and the Premature Infant Pain Profile – PIPP.29 The NIPS assesses five behavio ral pain parameters (facial expressio n, cry, po sitio n o f arms and legs and state o f aro usal) and o ne physio lo gic (breathing pa ttern). It is a neo na ta l a da pta tio n o f the Children’s Ho spital o f Eastern O ntario Pain Scale – CHEO PS.3 0 Evaluatio ns are perfo rmed at o ne-minute intervals prio r to , during and after a painful pro cedure. NIPS seems to be a valid pain assessment metho d because it is based o n kno wn behavio ral respo nses to pain, widely repo rted in the literature.12 The scale is able to differentiate term and preterm newbo rn infants that received a painful stimulus from those that had a distressing no n-painful stimulus.1 1
Altho ugh a great number o f neo natal pain a sse ssme nt to o ls a re a va ila b le , no ne is co nco mitantly specific, sensitive and valid.2 1 Therefo re we designed this pro spective study to verify whether the N eo na ta l Fa c ia l Co ding System, the Neo natal Infant Pain Scale, the heart rate and the arterial o xygen saturatio n are valid to o ls fo r assessing acute pain in term neo nates.
METHODS
After Ho spital Ethical Co mmittee appro val, 7 0 neo nates fro m a seco ndary level maternity ho spital in the Brazilian state o f São Paulo were studied. Inclusio n criteria co nsisted o f:
1 ) W ritten maternal co nsent prio r to enro llment; 2 ) G estatio nal age between 3 7 weeks and 4 1
weeks and 6 days;
3 ) Healthy neo nates admitted to ro o ming-in with their mo thers, with po st-natal age greater than 2 4 ho urs. At this time their stress respo nse to delivery sho uld have beco me attenuated;3 1 4 ) N ewb o rn infa nts with la te no n-hemo lytic
jaundice32 and indicatio n fo r veno us puncture fo r bilirubin do sage by the clinical staff; 5 ) 3 0 to 4 5 minutes interval between last feeding
and study in o rder to have a calm and reactive patient to o bserve.
Pa tients were exc luded fro m the study when:
1 ) Their mo thers had used any o pio id during pregnancy, labo r o r delivery, since this class o f drugs can cro ss the placenta and alter fetus and newbo rn infant no ciceptio n;3 3
2 ) Their mo thers had had general anesthesia during delivery, b ec a use a nesthetic s c a n readily cro ss the placenta and interfere with neo natal no ciceptio n;3 4
3 ) Apgar sco res3 5 at 1 and 5 minutes were less than 7 . The lo w Apgar sco re co uld be related to alteratio ns in pain afference to the central nervo us system o r to central integratio n o f the no xio us stimuli;3 6
4 ) M a jo r ma lfo rma tio n3 7 -3 9 o r ne uro lo g ic abno rmalities were present.
After pa tient enro llment, the fo llo wing neo natal data were registered: birth weight in
g rams, g estatio nal ag e, g ender, relatio nship between birth weig ht and g estatio nal ag e,4 0 Apgar sco res at 1 and 5 minutes, po st-natal age in ho urs, and minutes after the last feeding.
N e o na te s we re ra ndo mly a ssig ne d to receive o ne o f the fo llo wing pro cedures: veno us puncture in the back o f the hand (P), co nsidered as a painful stimulus; o r alco ho l swab frictio n o n the b a c k o f the ha nd (F), c o nside re d a s a distressing but not painful stimulus. A neonatologist b lind to the p ro c e d ure (P o r F) e va lua te d physio lo gic and behavio ral pain parameters.
After allo catio n, the patient was placed unde r a ra dia nt wa rme r a nd a shie ld wa s po sitio ned between the hand to be punctured o r frictio ned and the rest o f the bo dy, in o rder to o bstruct the visio n o f the neo nato lo gist in charge o f pain assessment. At this time, a pulse o xymeter pro be was lo cated in the fo o t and asepsis o f the hand was perfo rmed. Then, the neo nates rested fo r five minutes prio r to puncture o r frictio n. O nly o ne attempt at veno us puncture was made, fo r all patients, and one milliliter of blood was collected, followed by a quick compression of the hand with dry gauze fo r hemo stasis. F neo nates received an alco ho l swab frictio n in the back o f the hand followed by a quick compression with dry gauze, simulating the hemo static phase. After puncture or friction, the newborn infants were observed for 1 0 minutes. During this perio d, no pain relief attempts were perfo rmed.
The fo llo w ing p a in p a ra me te rs w e re evaluated:
1 ) N eo na ta l Fa c ia l Ac tivity Co ding System (N FCS) sco re, defined by the presence o r absence o f the fo llo wing facial features: bro w bulge, eye squeeze, naso -labial furro w, o pen lips, stretched mo uth, lip purse, taut to ngue and chin quiver. O ne po int was given to each feature present (to tal sco re = 8 ). Pain was considered present when at least three features were o bserved.9
state o f aro usal (0 / 1 po int). The po ssible to tal sco re was seven, and pain was co nsidered present when the sco re was g reater than three.1 2
3 ) Heart rate was evaluated by pulse o xymetry, and co nsidered o nly when the quality o f the wave registered was adequate. Bradycardia was defined by heart rate less than 8 0 bpm and tachycardia by heart rate abo ve 1 6 0 bpm;4 1
4 ) O xyg en saturatio n was also evaluated by pulse o ximetry, taking into acco unt the quality o f the wave registered. Hypo xia was defined by o xygen saturatio n belo w 9 0 %.4 2
These physio lo g ic and behavio ral pain parameters were evaluated at six different times: immediately prio r to the pro cedure (PRE), during hand puncture or friction (T0), one (T1), three (T3), five (T5) and ten (T10) minutes after the procedure. Statistical Metho ds. Statistical analysis of data included the Student t test o r Mann-W hitney test to co mpare quantitative variables between the P and F gro ups at each study time; chi-square o r Fisher tests to co mpare qualitative variables between the P and F gro ups at each study time; and the Friedman test to co mpare the results o btained at the different study times fo r the P and F gro ups. The results were co nsidered significant when p < 0 .0 5 .43
RESULTS
The study po pula tio n c o nsiste d o f 7 0 newbo rn infants divided into two gro ups with the fo llo wing characteristics (Table 1 ). The two g ro ups were simila r in rela tio n to a ll these characteristics, except fo r time after last feeding (t test - P > F: p = 0 .0 2 ).
Co mpariso n o f median NFCS sco res (Table 2 ) revealed significant differences between the vario us study times fo r the P and F gro ups. P gro up median N FCS sco res were higher than F during the pro cedure, o ne minute, and three minutes after the pro cedure. W hen presence o f pain was co nsidered as N FCS > 2 (Table 3 ), significantly more P patients showed signs of pain during the pro cedure, o ne minute, and three
minutes afterwards.
Co mpariso n o f median N IPS sco res (Table 2 ) revealed significant differences between the vario us study times fo r the P and F gro ups. P gro up median N IPS sco res were higher than F during the pro cedure, o ne minute, and three minutes after the pro cedure. W hen presence o f pain was co nsidered as N IPS > 3 (Table 3 ), significantly more P patients showed signs of pain during the pro cedure, o ne minute, and three minutes afterwards.
Co mpariso n o f average heart rate values (Table 4 ) revealed significant differences between the vario us study times fo r the P and F gro ups. The heart rate o f P neo nates was lo wer than the heart rate o f F patients o nly at o ne minute after the procedure. Three minutes after the procedure, 2 1 % o f P neo nates presented bradycardia o r tachycardia versus 3 % o f F neo nates (Table 5 ).
Co mpariso n o f averag e o xyg en arterial saturatio n values (Table 4 ) revealed significant differences between the various study times for the P and F groups. O xygen saturation values were lower in the P group prior to the procedure, one minute, three minutes, and 5 minutes after the procedure. More P patients showed hypoxia (Table 5 ) o ne minute, a nd three minutes a fter the procedure.
DISCUSSION
The fo cus o f this pro spective study was to evaluate the use o f physio lo gic and behavio ral
Ta ble 1 – Demogra phic da ta
Data Puncture group Friction group p-value
(n=33) (n=37)
Birth weight (g) 3160 (SD 556) 3052 (SD 479) 0.38a
Gestational age (wk) 39 (SD 1) 39 (SD 1) 0.93a
Apgar 1min 8 (SD 1) 9 (SD 1) 0.09a
Apgar 5min 9 (SD 0) 9 (SD 0) 0.36a
Males 19 (58%) 25 (68%) 0.39b
AGA 25 (76%) 28 (76%) 0.99b
Hours of life (h) 59 (SD 25) 52 (SD 17) 0.18a
Last feeding (min) 33 (SD 5) 31 (SD 2) 0.02a
parameters as valid assessment to o ls fo r acute pain in healthy term newbo rn infants. In o rder to achieve this go al, the two study gro ups were co mparable in terms o f their main demo graphic characteristics. A statistical difference in the interval between feeding and o bservatio n was detected between the gro ups: the fact that the P gro up was last fed o n average 3 3 minutes prio r to the study and the F gro up 3 1 minutes do es not, however, seem large enough to interfere with the clinical status o f the neo nates and the results here o btained.
The facial respo nse o f neo nates to pain was well-do cumented in the present research. The N eo natal Facial Activity Co ding System was able to differentiate term neo nates who received the painful stimulus fro m tho se who had the no n-painful stimulus. N o t o nly were
the me d ia n N FC S sc o re s hig he r d uring puncture, co mpared to frictio n, but also there were sig nific a ntly mo re P pa tients sho wing sig ns o f pain during the pro cedure, and at o ne a nd thre e minute s a fte rw a rd s. The re fo re , evaluatio n o f facial mo vements seems to be a va lid a nd sp e c ific to o l fo r a c ute p a in assessment in term neo nates and these finding s a re c o nsiste nt w ith the lite ra ture .9 , 1 1 , 2 4 , 2 7 Ho wever, the mo dificatio ns o f facial mimic in respo nse to pain were transient, and after three minutes they co uld no t be seen anymo re in their full expressio n. This finding raises difficulties fo r the clinical applicatio n o f N FCS to pain evaluatio n at the bedside. N ew studies sho uld clarify ho w o ften the facial mo vements sho uld be mo nito red and fo r ho w lo ng they sho uld remain altered befo re analg esic therapeutic interventio n is initiated o r prio r to analg esic d o se a d justme nts. Furthe r stud ie s sho uld analyze the frequency o f each facial mo vement reco rded during N FCS assessment, and verify whether there is any asso ciatio n between a set o f facial mo vements, namely bro w bulg e, eye squeez e, deepening o f naso -labial furro w and o pen lips, with the painful pro cedure, as
Ta ble 3 - N umber (percenta ge) of pa tients w ith N FCS > 2 or N IPS > 3 a t ea ch study time Cut-off point Group X2 or Fisher
Time Puncture(n=33) Friction(n=37) P-value
N FCS >2
Pre 0 0 1 .0 0
T0 2 5 (7 6 %) 1 2 (3 2 %) 0 .0 0 0 3
T1 2 7 (8 2 %) 9 (2 4 %) < 0 .0 0 0 0 1
T3 1 6 (4 8 %) 1 (3 %) < 0 .0 0 0 0 1
T5 3 (9 %) 2 (5 %) 0 .6 0
T1 0 0 0 1 .0 0
N IPS >3
Pre 0 0 1 .0 0
T0 2 5 (7 6 %) 1 2 (3 2 %) 0 .0 0 0 3
T1 2 6 (7 9 %) 9 (2 4 %) < 0 .0 0 0 0 1
T3 1 3 (3 9 %) 1 (3 %) < 0 .0 0 0 1 5
T5 4 (1 2 %) 2 (5 %) 0 .6 6
T1 0 0 0 1 .0 0
Ta ble 2 - M edia n (ra nge) of the N eona ta l Fa cia l Activity Coding System a nd N eona ta l Infa nt Pa in
Sca le scores a t the six study times Score G roup Mann-W hitney
Times Puncture(n=33) Friction(n=37) P-value
N FCS
Pre 0 (0 to 0 ) 0 (0 to 0 ) 1 .0 0
T0 5 (0 to 8 ) 1 (0 to 8 ) < 0 .0 0 0 0 1
T1 8 (0 to 8 ) 0 (0 to 8 ) < 0 .0 0 0 0 1
T3 0 (0 to 8 ) 0 (0 to 8 ) 0 .0 0 6
T5 0 (0 to 8 ) 0 (0 to 8 ) 0 .8 0
T1 0 0 (0 to 0 ) 0 (0 to 0 ) 1 .0 0
N IPS
Pre 0 (0 to 0 ) 0 (0 to 0 ) 1 .0 0
T0 5 (0 to 7 ) 1 (0 to 7 ) < 0 .0 0 0 0 1
T1 7 (0 to 7 ) 0 (0 to 7 ) < 0 .0 0 0 0 1
T3 0 (0 to 7 ) 0 (0 to 7 ) 0 .0 7 4
T5 0 (0 to 7 ) 0 (0 to 7 ) 0 .7 7
T1 0 0 (0 to 0 ) 0 (0 to 0 ) 1 .0 0
NFCS: Friedman test
- P group (Pre vs. T0 vs. T1 vs. T3 vs. T5 vs. T1 0 ): p < 0 .0 0 0 0 1 - F group (Pre vs. T0 vs. T1 vs. T3 vs. T5 vs. T1 0 ): p = 0 .0 0 2 NIPS: Friedman test
especially in premature infants. It wo uld be interesting to co mpare the perfo rmance o f bo th scales, the N IPS and the PIPP, in a neo natal intensive care unit co ntext.
As sho wn in the litera ture, b o th to o ls, N FCS and N IPS, were valid fo r differentiating the neo nates who received the painful stimulus fro m tho se who had a distressing no n-painful stimulus.9 -1 2 ,2 4 ,2 6 Mo re studies sho uld be do ne to eva lua te these sc a les in the presenc e o f vario us facto rs that co uld mo dulate the pain sensatio n in term and preterm newbo rn infants, fo r instance, the sleep/ alert status, the neo natal c linic a l sta tus a nd the p a tie nts’ p re vio us experience o f pain, amo ng o thers.
In b o th g ro up s the he a rt ra te va lue s decrea sed during a nd o ne minute a fter the puncture o r frictio n and increased afterwards. p re vio usly d e sc rib e d .1 0 Furthe rmo re , the
a d o p tio n o f a hig he r c uto ff to d e fine the presence o f pain by N FCS co uld increase its sensib ility a nd spec ific ity fo r neo na ta l pa in assessment.
Amo ng the several multidimensio nal pain scales described when this study was started, the N eo natal Infant Pain Scale was cho sen because it was a simple and easy-to -apply to o l, with g reat po tential fo r clinical use. N IPS was a b le to d iffe re ntia te te rm ne o na te s w ho received the painful stimulus fro m tho se who had a no n-painful stimulus. Similarly to N FCS, no t o nly w e re me d ia n N IPS sc o re s hig he r during puncture, co mpared to frictio n, but also the re w e re sig nific a ntly mo re P p a tie nts sho wing N IPS g reater than three during the p ro c e d ure , a nd a t o ne a nd thre e minute s a fterwa rds. Therefo re, this multidimensio na l pain scale seems to be a valid and specific to o l fo r acute pain assessment in term neo nates a nd the se re sults a re c o nsiste nt w ith the literature.1 1 ,1 2 It sho uld be no ted ag ain that after three minutes N IPS sco res returned to baseline. Therefo re the relatio nship between the duratio n o f p a in re sp o nse s a nd the ne c e ssity fo r therapeutic interventio ns is no t clear. Mo reo ver, further studies sho uld establish whether this cuto ff (N IPS > 3 = pain) is the ideal o ne, in o rder to achieve the maximum sensitivity and specificity fo r the to o l. In relatio n to its clinical use, the N eo natal Infant Pain Scale is an easier metho d than N FCS, and requires less perso nnel tra ining . A lso , N IPS sc o re s the fa c ia l e xp re ssio n a s a w ho le a nd va lue s o the r behavio ral parameters and o ne physio lo g ic pain parameter, i.e. N IPS takes into acco unt the no tio n that the best to o l fo r evaluating pain is the o ne tha t c o nsid e rs its multip le dimensio ns.8
The Premature Infant Pain Pro file (PIPP) is a no the r struc ture d a nd va lid a te d multid ime nsio na l p a in sc a le re c e ntly described.2 9 Ho wever, PIPP was no t available when this study was co mpleted. Perhaps the use o f the Premature Infant Pain Pro file co uld g ive mo re co nsistent info rmatio n abo ut pain,
Ta ble 4 - M ea n a nd sta nda rd devia tion hea rt ra te (HR) a nd a rteria l ox ygen sa tura tion (O2sa t) va lues
a t the six study times
Da ta Group Mann-W hitney
Time Puncture(n=33) Friction(n=37) P-value
HR (bpm)
Pre 131 (SD 14) 128 (SD 14) 0.31
T0 98 (SD 42) 106 (SD 36) 0.57
T1 88 (SD 39) 113 (SD 30) 0.01
T3 120 (SD 33) 125 (SD 17) 0.95
T5 128 (SD 18) 124 (SD 17) 0.31
T10 131 (SD 13) 127 (SD 12) 0.26
O2 sa t (%)
Pre 95 (SD 2) 97 (SD 2) 0.0066
T0 96 (SD 7) 93 (SD 7) 0.13
T1 90 (SD 8) 95 (SD 4) 0.0002
T3 93 (SD 5) 95 (SD 2) 0.045
T5 95 (SD 3) 96 (SD 2) 0.01
T10 96 (SD 2) 97 (SD 1) 0.107
HR: Friedman test
- P group (Pre vs. T0 vs. T1 vs. T3 vs. T5 vs. T1 0 ): p = 0 .0 0 0 6 - F group (Pre vs. T0 vs. T1 vs. T3 vs. T5 vs. T1 0 ): p = 0 .0 3 O2
sat: Friedman test
O nly at o ne minute after the pro cedure was the average heart rate lower in P neonates compared to F infants. Three minutes after puncture mo re ne o na te s ha d b ra dyc a rdia o r ta c hyc a rdia , co mpared to the frictio n gro up. These findings sho w tha t the va ria tio n o f hea rt ra te is a n inco nsistent and insensitive way to evaluate pain in term newbo rn infants. N o r is the heart rate variatio n specific in relatio n to pain assessment, as o ccurs with o ther physio lo gic variables. It is impo rtant to no te that in mo st infants the increase o r decrease in heart rate during the puncture was no t significant eno ugh to alert the clinician to any need fo r analg esia o r interruptio n o f pro cedure.
In this study mo st neo nates decreased their heart rate after the puncture instead o f sho wing the usual respo nse, i.e. tachycardia after a painful stimulus. No specific asso ciatio n between a distressing o r painful stimulus o n the back o f the hand and bradycardia co uld be fo und. Po ssibly, technical artifacts interfered with the co rrect evaluatio n o f heart rate.
Nevertheless, it appears important to repeat the study with heart rate evaluatio n perfo rmed
simulta ne o usly b y p ulse o xyme try a nd electro cardio g raphy, in o rder to understand better the heart rate respo nse to painful stimulus in he a lthy te rm ne wb o rn infa nts. W ith the methodology here applied, heart rate assessment was no t useful in detecting the neo natal pain. Since heart rate mo nito ring is ro utine in almo st all neo natal intensive care units, care must be ta ke n in a sso c ia ting its va ria tio ns with the presence o f pain. At best, to gether with o ther behavio ral and multidimensio nal pain scales, and interpreted within the enviro nmental co ntext o f the patient, the heart rate can o nly give a se c o nd a ry sup p o rt to the c linic ia n w ho is evaluating the presence o f pain in the neo nate. The o xygen saturatio n presented a mo re persistent decrease after the painful pro cedure, co mpared to the heart rate, and the decay was mo re pro no unced in the neo nates that received the puncture, co mpared to tho se that received the frictio n. Therefo re O2saturatio n values seem
to be a valid to o l fo r evaluating the newbo rn infants’ pain. However, just as for any physiologic pain parameter, it has a lo w specificity, and it can be altered by o ther no n-painful stimuli.
Altho ugh statistical differences were no ted between P and F gro ups at 1 and 3 minutes after the pro cedure, the average O
2 saturatio n values
were abo ve 9 0 % during the who le study perio d, and o nly a third o f P neo nates had hypo xia after the pro cedure. These finding s mean that the c linic a l imp o rta nc e o f P a nd F sta tistic a l differences is questionable, and that O2 saturation
also has lo w sensitivity as a pain assessment to o l. That is, it wo uld be difficult to use O2saturatio n
values as the o nly indicato r o f pain in neo nates. Altho ug h the mo nito ring o f this physio lo g ic parameter is g enerally available in neo natal intensive care units, it sho uld be co nsidered as an accesso ry to o l fo r pain assessment.
In the p re se nt stud y the va rio us p a in parameters were analyzed separately, and their assessment o f pain presence o ften did no t agree in the same patient. This finding indicates that the use o f multiple info rma tio n c a n help to establish the presence o f neo natal pain, and co nfirms the utility o f co mpo site scales fo r pain
Ta ble 5 - N umber (percenta ge) of pa tients w ith HR < 8 0 bpm a nd/ or HR > 1 6 0 bpm or O2
sa t. <
9 0 % a t ea ch study time
Cut-off point G roup X2 or Fisher
Time Puncture(n=33) Friction(n=37) P-value
HR<8 0 a nd/ or >1 6 0 bpm
Pre 0 0 1 .0 0
T0 1 4 (4 2 %) 1 1 (3 0 %) 0 .5 5
T1 1 9 (5 7 %) 8 (2 2 %) 0 .1 2
T3 7 (2 1 %) 1 (3 %) 0 .0 4 5
T5 1 (3 %) 1 (3 %) 1 .0 0
T1 0 0 0 1 .0 0
O2 sa t < 9 0 %
Pre 0 0 1 .0 0
T0 8 (2 4 %) 7 (1 9 %) 0 .5 9
T1 1 2 (3 6 %) 3 (8 %) 0 .0 0 7
T3 6 (1 8 %) 1 (3 %) 0 .0 4 6
T5 1 (3 %) 1 (3 %) 1 .0 0
assessment in newbo rn infants.
In co nclusio n, this study helps to validate the N eo natal Facial Activity Co ding System and the N eo natal Infant Pain Scale as valid and suita b le instrume nts fo r ne o na ta l p a in evaluatio n. Heart rate and O2 saturatio n have
lo w sensitivity and specificity fo r evaluating ne o na ta l p a in, a nd c a n b e use d o nly a s a uxilia ry me tho ds. N e w studie s sho uld b e perfo rmed in o rder to validate the N FCS and the N IPS in c ritic a lly ill te rm a nd p re te rm pa tients. The a va ila b ility o f a deq ua te pa in a ssessment to o ls is c ritic a l fo r reduc ing the undertreatment o f neo natal pain.
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Andrea Lübe de S Thia go Pereira - Ex-Fello w in Neo nato lo gy, Neo natal Divisio n o f the Department o f Pediatrics, Federal University o f São Paulo – Paulista Scho o l o f Medicine (UN IFESP-EPM)
Ruth Guinsburg - Asso ciate Pro fesso r o f the Neo natal Divisio n, Department o f Pediatrics, UNIFESP-EPM
M a ria Ferna nda Bra nco de Alm eida - Asso ciate Pro fesso r o f the Neo natal Divisio n, Department o f Pediatrics, UN IFESP-EPM
RESUMO
Contex to: A subjetividade da do r gera uma grande dificuldade para a elabo ração de um méto do único de avaliação e de fácil aplicação na clínica diária. O s méto do s para a avaliação da do r no perío do neo natal devem ser válido s, seguro s, co nfiáveis, úteis e exeqüíveis. O bjetivo: verificar a validade do Sistema de Co dificação da Atividade Facial Neo natal (N FCS), Escala de Do r para o RN (N IPS), freqüência cardíaca (FC) e saturação de o xigênio (SatO2) para a avaliação da do r
no recém-nascido (RN). Tipo de estudo: pro spectivo , duplo -cego e rando mizado . Loca l: maternidade de nível secundário .
Pa rticipa ntes: 7 0 RN a termo saudáveis, co m punção veno sa para bilirrubina, dividido s em do is grupo s: P (n=3 3 ) recebeu um estímulo do lo ro so (punção ) e F (n=3 7 ) um desagradável (fricção na mão ). Intervençã o: o bservação do NFCS, da NIPS, da FC e da SatO2, antes (PRÉ), durante (T0 ) e 1 (T1 ), 3 (T3 ), 5 (T5 ) e 1 0 (T1 0 ) minuto s apó s P o u F. M ensura çã o: testes não
paramétrico s (significância: p<0 .0 5 ). Resulta dos: a mediana do NFCS e da NIPS fo i maio r no G rupo P em T0 , T1 e T3 . Mais RN do G rupo P apresentaram NFCS >2 e/ o u NIPS >3 em T0 , T1 e T3 . A FC fo i inferio r no G rupo P em T1 . A SatO2
manteve-se, em média, acima de 9 0 % no s do is grupo s. Conclusões: o N FCS e a N IPS são válido s para a avaliação da do r aguda no RN a termo . A FC e a SatO2 devem ser utilizadas co mo co adjuvantes.
Ana Cristina M onteiro - Ex-Fello w in Neo nato lo gy, Neo natal Divisio n o f the Department o f Pediatrics, UN IFESP-EPM
Am élia M iy a shiro N unes dos Sa ntos - Asso ciate Pro fesso r o f the Neo natal Divisio n, Department o f Pediatrics, UN IFESP-EPM
Benja m in Isra el Kopelm a n - Full Pro fesso r o f the Neo natal Divisio n, Department o f Pediatrics, UNIFESP-EPM
Sources of Funding: N o t declared
Conflict of interest: N o t declared
La st received: 3 0 July 1 9 9 8
Accepted: 9 No vember 1 9 9 8
Address for correspondence:
Andrea Lübe de S. Thiago Pereira Caixa Po stal 2 0 3 5 9
