OBJECTIVE. Proper diagnosis of urinary tract infections depends on obtaining an uncontaminated urine sample for culture. Suprapubic aspiration and transurethral catheterization are the 2 recommended procedures for obtaining specimens for urine culture from young infants. The objective of the current study was to compare the pain that is experienced during these 2 procedures when performed in young infants.
METHODS. A prospective, single-blind, randomized, controlled study was conducted at a university-affiliated hospital in Israel. Institutional Research Ethics Board approved the study. Infants who were 0 to 2 months of age and presented to the emergency department with fever and therefore required urine collection for culture were randomly assigned evenly into 2 sample collection groups: suprapubic aspiration or transurethral catheterization. Patients were excluded when they were born prematurely or had had a previous sepsis workup or other painful procedures or an anomaly of the urogenital system or abdominal wall. Eutectic mixture of local anesthetic cream that contained lidocaine and prilocaine was applied 1 hour before the procedure. The urethra was catheterized using a 5-Fr latex-free feeding tube that was lubricated with sterile water-soluble jelly that contained 2% lidocaine hydrochloride. Pediatric residents who were experienced with the procedures performed both suprapubic aspiration and transurethral catheterization. The parents were instructed to use any comfort strategies that they wished, including verbal or physical comforting and pacifiers. Pain during collection was assessed on a 100-mm visual analog scale by a nurse and a parent. In addition, the infant's upper part of the body was videotaped during the procedure. An investigator, who was blinded to the procedure, assigned a point score according to the Douleur Aigue du Nouveaune neonatal acute pain scale. For ensuring a successful blinding process, the following steps were taken. First, camera recording started 30 seconds before the procedure to prevent the possibility of distinguishing between the procedures on the basis of their duration. Second, the physician and the nurse were asked not to speak during the procedure to avoid revealing the nature of the procedure. Third, the person who videotaped the procedure watched the tape before it was analyzed to ensure the impossibility of identifying the procedure from the tape. The Student's t test was used to compare the groups. The primary outcome was the mean Douleur Aigue du Nouveaune score. Secondary outcomes were the mean visual analogue scale for pain as estimated by the parents and by the nurse. We estimated that 25 patients would be needed in each group to detect a difference in the mean Douleur Aigue du Nouveaune score of at least 2 points with a power of 80% and α of .05.
RESULTS. The study was conducted between April 1, 2004, and April 30, 2005. Fifty-eight infants were recruited; 29 were randomly assigned to suprapubic aspiration, and 29 were randomly assigned to transurethral catheterization. Seven infants were excluded because of consent withdrawal (3 patients), because of technical difficulties during videotaping (3 patients), or because the child voided during the procedure (1 patient). Twenty-seven infants in the suprapubic aspiration group and 24 in the transurethral catheterization group completed the study. All male infants were circumcised. An adequate urine sample was obtained in 18 (66%) of 27 patients in the suprapubic aspiration group and in 20 (83.3%) of 24 in the transurethral catheterization group. The mean Douleur Aigue du Nouveaune score was significantly higher in patients who were randomly assigned to suprapubic aspiration compared with patients who were randomly assigned to transurethral catheterization (7 and 4.5, respectively). The differences in Douleur Aigue du Nouveaune score also were significant in a subgroup analysis of boys and girls. Mean visual analogue scale scores by parents was higher in the suprapubic aspiration group compared with transurethral catheterization (63 ± 27 mm vs 46 ± 26, respectively). Similarly, mean visual analogue scale scores by nurses was higher in the suprapubic aspiration group compared with transurethral catheterization (3 ± 18 mm vs 43 ± 25 mm, respectively).
CONCLUSIONS. In infants who are younger 2 months, suprapubic aspiration is more painful than transurethral catheterization. Health professionals should consider these differences when choosing a method for obtaining a urine sample from young infants.
Urinary tract infection (UTI) is a common cause of fever in infants. 1–3 The presence of UTI should be considered in infants and young children with unexplained fever.4 Proper diagnosis of UTI depends on obtaining an uncontaminated urine sample for culture. Urine that is obtained by suprapubic aspiration (SPA) or transurethral catheterization (TUC) is less likely to be contaminated. SPA and TUC are the recommended techniques in young infants.4,5 SPA has been considered the “gold standard”5 for accurately detecting bacteria in the urine. The technique has limited risks. However, variable success rates have been reported.6–8 SPA requires technical expertise and experience, and many parents and physicians perceive the procedure as unacceptably invasive compared with catheterization. TUC is a simple procedure and in many emergency departments (ED) is performed by the nurses. Skills and experience are needed, however, to obtain uncontaminated specimens, particularly in small infants, girls, and uncircumcised boys. Although urine that is obtained by TUC is highly sensitive for the diagnosis of UTI, contamination rates of up to 11% are reported.9
Neonates feel pain,10–12 and repeated painful stimuli may lower their pain threshold and lead to anticipatory pain behaviors13 and hyperalgesia at an older age.14 Pain in young infants should be treated properly, and every effort should be taken to prevent unnecessary pain.10 To our knowledge, no studies have compared the pain that is experienced by young infants during SPA with that of the pain that is felt during TUC. The purpose of the current study was to compare in infants who are younger than 2 months the severity of pain during SPA with the pain during TUC.
This prospective, single-blind, randomized, controlled study was conducted in the ED and pediatric ward of a university-affiliated hospital in Israel. The Research Ethics Board at Assaf Harofeh Medical Center approved the study.
Infants who were 0 to 2 months of age and presented to the ED at Assaf Harofeh Medical Center with fever (rectal temperature >38°C) and needed a urine culture were included. Patients were excluded when they had been born prematurely, had had a previous sepsis workup or other painful procedures (except for hepatitis B virus vaccination and vitamin K injection, which are given to all newborns in Israel shortly after birth, or circumcision for the boys), had an anomaly of the urogenital system or abdominal wall, or had a known allergy to Eutectic Mixture of Local Anesthetic (AstraZeneca, Södertälje, Sweden) or Esracaine gel (Esracaine Rafa, Jerusalem, Israel). Legal guardians of eligible patients were approached for informed consent.
Using a computerized random-number generator, an allocation sequence was created. The allocation sequence was kept in serially numbered, opaque, sealed envelopes. Patients were allocated in a 1:1 ratio into 2 groups. Urine samples were obtained in 1 group by means of SPA and in the second group through TUC. The urine sample was taken before any other painful procedures (eg, lumbar puncture, blood tests).
Eutectic Mixture of Local Anaesthetic cream that contained lidocaine and prilocaine was applied in a sufficient amount to cover the suprapubic area and covered with an occlusive dressing 1 hour before the procedure. A urine bag was attached to the external genitalia, and aspiration was performed when there was no urine in the bag for 30 minutes or more before the procedure. SPA was performed using standard sterile technique. The suprapubic area was cleaned with a 0.02% chlorhexidine solution. The bladder was punctured in the midline 1 to 2 cm above the symphysis pubis using an 21-gauge needle that was attached to a 5-mL syringe. The needle was angled 10 to 15 degrees cranial to avoid puncturing the trigone.
TUC was performed using standard aseptic technique. The external meatus was cleaned with a 0.02% chlorhexidine solution. The urethra was catheterized using a 5-Fr latex-free feeding tube that was lubricated with sterile water-soluble jelly that contained 2% lidocaine hydrochloride (Esracaine).
Both SPA and TUC were performed by pediatric residents who were experienced with the procedures. The parents were instructed to use any comfort strategies that they wished, including verbal or physical comforting and pacifiers.
Three pain measurement methods were used:
The nurse involved in the procedure and 1 of the child's parents were asked to rank the infant's pain on a 100-mm visual analog scale (VAS; where 0 means no pain and 100 means worst pain possible). The nurse and the parent were blinded to each other's score.
The infant's upper part of the body was videotaped during the procedure. One investigator (D.G.) assigned a point score according to the Douleur Aigue du Nouveaune (DAN) neonatal acute pain scale15 at the time of the procedure. This scale scored pain from 0 (no pain) to 10 (maximal pain) on the basis of 3 parameters: facial expression, limb movement, and vocal expression.
The same investigator (D.G.) measured the duration of cry from the beginning of the procedure until cry had stopped for at least 5 seconds.
For ensuring a successful blinding process, the following steps were taken. First, camera recording started 30 seconds before the procedure to prevent the possibility of distinguishing between the procedures on the basis of their duration. Second, the physician and the nurse were asked not to speak during the procedure to avoid revealing the nature of the procedure. Third, the person who videotaped the procedure watched the tape before it was analyzed to ensure the impossibility of identifying the procedure from the tape.
The primary outcome was the mean DAN score. Secondary outcomes were the mean VAS for pain as estimated by the parents and by the nurse, duration of cry, success rate in obtaining at least 0.5 mL of urine, and the rate of contaminated urine samples. Pain measurements relate to the first attempt to obtain urine, regardless of the procedure success or subsequent attempts.
The Student's t test was used for continuous variables. The χ2 or Fisher's exact test, as appropriate, was used for comparisons of categorical variables (eg, success rate of the procedures). Multiple linear regression was used to predict the effect of other variables, such as age and the use of analgesics on the DAN score. We estimated that 25 patients would be needed in each group to detect a difference in the mean DAN score of at least 2 points with a power of 80% and α of .05.
The study was conducted between April 1, 2004, and April 30, 2005. Fifty-eight infants (girls and boys) were recruited; 29 were randomly assigned to SPA, and 29 were randomly assigned to TUC. Seven infants were excluded because of consent withdrawal (3 patients), because of technical difficulties during videotaping (3 patients), or because the child voided during the procedure (1 patient). Twenty-seven infants in the SPA group and 24 in the TUC group completed the study. All male infants were circumcised. The baseline characteristics of the patients are shown in Table 1. Six patients in the SPA group and 12 in the TUC group were treated with acetaminophen within 4 hours of the procedure (P = .09). An adequate urine sample was obtained in 18 (66%) of 27 patients in the SPA group and in 20 (83.3%) of 24 in the TUC group (P = .3). Three urine cultures were positive in the SPA group. There were no positive cultures in the TUC group. One urine culture, obtained by TUC, grew 4 different types of bacteria and was considered to be contaminated. No complications were noted after the TUC or SPA.
All infants were awake before the procedure. The mean DAN score was 7.0 (±1.9) in patients who were randomly assigned to SPA and 4.5 (±2.1) in patients who were randomly assigned to TUC (difference between means: 2.5; 95% confidence interval: 1.4–3.7). Mean VAS scores also were higher in the SPA group (Table 2).
When results were analyzed separately for boys and girls (Table 3), pain assessments by all parameters were higher for SPA in girls. In boys, SPA was associated with higher DAN scores, but there were no significant differences in VAS scores or duration of cry.
We used a multiple regression model to adjust for possible effects of age and the use of analgesic on the differences in DAN scores between groups. Age and the use of analgesic did not have a significant effect on the DAN score (P = .21 and P = .46, respectively). The only variable that was associated with higher DAN score was obtaining urine by SPA (P = .001).
In the present study we showed, for the first time, that in young infants, SPA is more painful than TUC. Hundreds of thousands of infants are seen every year in EDs for neonatal fever or suspected UTI. In these infants it is recommended that urine be obtained via either SPA or urine catheterization. The findings of the current study may reduce the pain that is experienced by these infants by altering the method of urine collection.
Of the 51 infants who were included in the study, 3 received a diagnosis of UTI. The incidence of UTI in our study was similar to the reported incidence of UTI in infants who were younger than 8 weeks.1,2 Only 1 urine sample in the current study was contaminated. This sample was obtained by TUC. The low incidence of contamination in the current study and in previous reports suggests that both SPA and TUC are reliable methods of urine collection in young infants.
The success rates of obtaining adequate urine samples by TUC (83%) and SPA (66%) indicate that both techniques can be used when urine samples are needed. However, the study was not powered to answer the question of which test has a higher success rate. Previous studies7,8 that compared success rates of obtaining adequate urine samples with SPA versus TUC have yielded conflicting results. Pollack et al7 reported a 100% success rate for TUC, which was significantly higher compared with SPA. Other studies,8,16 however, reported lower success rates for TUC. In a small, randomized, controlled study, Tobianski et al8 did not find significant differences in success rates between SPA and TUC.
Although the accuracy of urine collection seems to be comparable between SPA and TUC, the level of pain that is experienced may not be. Pain is a subjective experience, and young infants obviously cannot report their own pain. Many assessment tools17–22 have been developed to evaluate pain in this age group, but no uniform assessment technique has been accepted.23 Our study assessed pain via 3 methods: the DAN score (which has been validated in newborns), the length of cry, and the VAS score given by a parent and a nurse. There are no established minimum clinically significant differences in DAN and VAS scores in neonates. However, the large difference in DAN scores (7 for SPA vs 4.5 for TUC) and the observed differences in VAS scores (19.6 mm for nurses and 17 mm for parents)m which are higher than the minimum clinically significant difference in VAS pain score for adults24 and older children,25 suggests that the observed differences are clinically important.
Although the duration of cry was shorter in the TUC group, the difference between the groups was not statistically significant. Duration of cry often is used to assess infants' pain,15,26,27 but, as in our study, wide ranges in duration of cry often are present.27 Such variations may explain the lack of difference between the groups.
Developmental changes in pain expression in the first months of life have been described.28 Patients in the TUC group were almost 9 days older than patients in the SPA group, yet it is unlikely that age differences accounted for the observed difference in pain. The difference, although statistically significant, was small, and the differences in pain expression that were noted in a previous study28 between newborns and 2-month-old infants were minor. Moreover, in a multivariate analysis, age was not associated with changes in DAN scores.
Although the number of infants who were treated with acetaminophen before the procedure was higher in the TUC group, the differences between the groups was not statistically significant. It is unlikely, therefore, that treatment with acetaminophen was the cause of the differences between the groups. Similar results were reported in a previous study,29 in which pretreatment with acetaminophen did not reduce pain from heel stick in term neonates. Furthermore, a multivariate analysis in the current study indicated that pretreatment did not affect DAN scores.
We included a separate analysis for girls and boys. In girls, SPA was assessed as more painful by all methods of assessment used, whereas in boys, only the DAN score was higher. One may speculate that these differences are attributable to the different anatomy of external genitalia of boys and girls. It is important to note that all boys who were included in this study were circumcised. We do not know whether pain for TUC would have been similar for uncircumcised boys; this question should be addressed in future studies.
Contrary to our findings, Oswald et al30 reported that SPA was well tolerated and associated with a low pain score independent of age during voiding cystourethrography. TUC, however, was associated with a low pain score only in the younger age group. Several differences between the studies may account for the conflicting results. The patients in the Oswald study were older (mean age: 33 months), the procedure was longer, and the investigators who assessed the pain were not blinded to the procedure.
There are several limitations in the current study. Subjective observations, such as those used in the current study, are inherently biased; however, there are no known objective measures to assess pain in infants. Researchers, therefore, are left to use behavioral scales in this age group.10
The parents and the nurses were not blinded to the procedure, and the observed differences in VAS scores may be reflective of their view of SPA as a more invasive procedure rather than a reflection of the infants' pain. This hypothesis seems unlikely, however, given that in an assessment by a professional nurse who was blinded to the videotaped procedure, SPA was more painful than TUC.
The power of the subgroup analysis to detect significant differences in the secondary outcomes and to determine the effects of variables other than the procedure on the outcome was limited by the relatively small sample.
SPA and TUC each require different equipment and conversations between the physician and the nurse. We tried to minimize the possibility that the blinded investigator would recognize the procedure on the basis of these signs by screening the tape before analysis. Although such analysis potentially could lead to selection bias, in none of the cases did the films have to be withdrawn. Other limitations related to the DAN scores are that they were derived by only 1 observer, and no baseline scores were obtained.
In recent years, it has become evident that infants of all ages experience pain, and this pain experience early in life may lead to anticipatory pain behaviors and hyperalgesia at an older age. Every effort should be made, therefore, to reduce the pain that is experienced during invasive procedures. The current study found SPA to be more painful than TUC in infants who were younger then 2 months. Physicians and nurses should consider these findings when selecting a procedure for obtaining urine samples from young infants.
This study was supported by a grant from the Canadian Jewish Research Fund at the Dresnick-Gottlieb Institute for Emergency Medicine and by the Research Institute at Assaf Harofeh Medical Center.
- Accepted January 12, 2006.
- Address correspondence to Eran Kozer, MD, Pediatric Emergency Medicine, Assaf Harofeh Medical Center, Zerifin 70300 Israel. E-mail:
The authors have indicated they have no financial relationships relevant to this article to disclose.
- ↵Crain EF, Gershel JC. Urinary tract infections in febrile infants younger than 8 weeks of age. Pediatrics.1990;86 :363– 367
- ↵Lin DS, Huang SH, Lin CC, et al. Urinary tract infection in febrile infants younger than eight weeks of Age. Pediatrics.2000;105 (2). Available at: www.pediatrics.org/cgi/content/full/105/2/e20
- ↵Practice parameter: the diagnosis, treatment, and evaluation of the initial urinary tract infection in febrile infants and young children. American Academy of Pediatrics. Committee on Quality Improvement. Subcommittee on Urinary Tract Infection. Pediatrics. 1999;103 :843– 852
- ↵Downs SM. Technical report: urinary tract infections in febrile infants and young children. The Urinary Tract Subcommittee of the American Academy of Pediatrics Committee on Quality Improvement. Pediatrics.1999;103 (4). Available at: www.pediatrics.org/cgi/content/full/103/4/e54
- ↵Shaw KN, McGowan KL, Gorelick MH, Schwartz JS. Screening for urinary tract infection in infants in the emergency department: which test is best? Pediatrics.1998;101 (6). Available at: www.pediatrics.org/cgi/content/full/101/6/e1
- ↵Prevention and management of pain and stress in the neonate. American Academy of Pediatrics. Committee on Fetus and Newborn. Committee on Drugs. Section on Anesthesiology. Section on Surgery. Canadian Paediatric Society. Fetus and Newborn Committee. Pediatrics. 2000;105 :454– 461
- ↵Carbajal R, Veerapen S, Couderc S, Jugie M, Ville Y. Analgesic effect of breast feeding in term neonates: randomised controlled trial. BMJ.2003;326 :13
- ↵Lewindon PJ, Harkness L, Lewindon N. Randomised controlled trial of sucrose by mouth for the relief of infant crying after immunisation. Arch Dis Child.1998;78 :453– 456
- ↵Gradin M, Eriksson M, Holmqvist G, Holstein A, Schollin J. Pain reduction at venipuncture in newborns: oral glucose compared with local anesthetic cream. Pediatrics.2002;110 :1053– 1057
- ↵Shah V, Taddio A, Ohlsson A. Randomised controlled trial of paracetamol for heel prick pain in neonates. Arch Dis Child Fetal Neonatal Ed.1998;79 :F209– F211
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