Multi-modal pain assessment: are near-infrared spectroscopy, skin conductance, salivary cortisol, physiologic parameters, and Neonatal Facial Coding System interrelated during venepuncture in healthy, term neonates?

Figures & data

Figure 1 Timeline of the experimental procedure.

Notes: *Pre-venepuncture period, **Post-venepuncture period.
Abbreviations: NFCS, Neonatal Facial Coding System; NIRS, near infrared spectroscopy.

Figure 2 Flowchart of patient selection.

Note: In some patients, the measurements were not adequate, and they were not included in the correlation analyses.
Abbreviations: NFCS, Neonatal Facial Coding System; NIRS, near infrared spectroscopy.

Table 1 Demographic characteristics of the study sample, grouped by the type of measurement performed

Measurement group (time of measurement)	n	Age (days) Mean (SD)	Gestational age (weeks) Mean (SD)	Birth weight (g) Mean (SD)	Male n (%)
NIRS measurement (from −20 to +20 s)	102	2.90 (0.62)	39.27 (1.06)	3,342 (470)	53 (52%)
NFCS at the time of venepuncture (0 min)	103	2.89 (0.62)	39.34 (1.06)	3,360 (469)	54 (52%)
Skin conductance (peaks/s) (from −2 to +2 min)	108	2.88 (0.62)	39.32 (1.06)	3,370 (480)	56 (52%)
Salivary cortisol (–4 to +25 min)	69	2.88 (0.58)	39.30 (0.94)	3,355 (467)	37 (54%)
SpO2 (from −10 to +30 s)	108	2.89 (0.62)	39.31 (1.06)	3,365 (484)	57 (53%)
Heart rate (beats/min) (from −10 to +10 s)	107	2.90 (0.61)	39.30 (1.06)	3,360 (480)	55 (51%)
Respiratory rate (breaths/min) (from −10 to +10 s)	108	2.88 (0.62)	39.31 (1.05)	3,358 (478)	56 (52%)
ANOVA or chi^2		P=0.95	P=0.91	P=0.89	P=1.00

Abbreviations: NFCS, neonatal facial coding system; NIRS, near infrared spectroscopy.

Table 2 Parameter values analyzed to assess changes in responses measured before (–), during (0 s), and after (+) venepuncture

Parameter	Mean (SD)	P-value
Time of measurement
[HbT] (µmol/L); n=102
Mean −20 s; mean +20 sa	53.80 (112.70); 55.29 (115.78)	0.80b
Max +20 sa	88.63 (119.42)	0.03b
Mean −10 s; mean +10 sc	54.94 (110.81); 58.37 (117.12)	0.76b
Max +10 sc	82.09 (119.69)	0.08b
[HbO2] (µmol/L); n=102
Mean −20 s; mean +20 sa	71.81 (113.52); 74.04 (122.73)	0.80b
Max +20 sa	102.17 (120.66)	0.04b
Mean −10 s; mean +10 sc	74.98 (112.96); 77.45 (123.16)	0.74b
Max +10 sc	97.49 (121.60)	0.20b
NFCS (0–4)
−2 min (n=92)	0.52 (1.20)
0 min (n=103)	1.08 (1.64)	<0.01b
+2 min (n=104)	0.21 (0.82)	<0.01b
Skin conductance (peaks/s); n=108
Baseline −2 to 0 min; baseline 0 to +2 min	0.10 (0.17); 0.11 (0.16)	0.95b
Salivary cortisol (µg/dL); n=69
−4 min; +25 min	0.70 (0.68); 1.12 (0.91)	<0.01b
Heart rate (beats/min); n=107
−10 s; +10 s	138 (15); 140 (15)	0.11d
0 s; +10 s	137 (15); 140 (15)	<0.01d
Respiratory rate (breaths/min); n=108
−10 s; +10 s	42 (12); 41 (12)	0.55d
0 s; +10 s	43 (13); 41 (12)	0.17d
SpO2; n=108
−10 s; +10 s	98.4 (3.0); 98.7 (2.3)	0.02d
0 s; +10 s	98.7 (2.8); 98.7 (2.3)	0.49d
−10 s; +30 s	98.4 (3.0); 98.4 (3.9)	0.90d

Notes:

a Pre- or post-venepuncture period (–20 or +20 s) with mean (baseline) or maximum value during the period.

b Wilcoxon test.

c Pre- or post-venepuncture period (−10 or +10 s) with mean (baseline) or maximum value during the period.

d Student’s t-test.

Abbreviations: HbO₂, oxygenated hemoglobin; HbT, total hemoglobin; NFCS, Neonatal Facial Coding System.

Table 3 Correlation analysis: Pearson and Spearman correlation coefficients show associations between the different parameters analyzed

Parameter	NFCS			ΔCortisol	ΔConductance	ΔRespiratory rate		ΔSpO2			ΔHeart rate
Time of measurement	−2 min	0 min	+2 min	+25/−4 min	+2/−2 min	+10/−10 s	+10/0 s	+10/−10 s	+10/0 s	+30/−10 s	+10/−10 s	+10/+0 s
NFCS
−2 min
0 min			0.34***	0.42+++	0.29++						(0.23*)
+2 min		0.34***		0.30++	0.41+++			(0.20*)
[HbO2]a
ΔMax+20/Mean−20 s		0.27**								0.38+++		0.30**
ΔMean+20/−20 s										0.46+++		0.26++
ΔMax+10/Mean−10 s		(0.21*)		−0.33**						0.32++		(0.25+)
ΔMean+10/−10 s										0.44+++		0.31++
[HbT]
ΔMax+20/Mean−20 s		0.41***										(0.21*)
ΔMean+20/−20 s		(0.24*)
ΔMax +10/Mean−10 s		0.29**			(0.20*)							(0.23*)
ΔMean+10/−10 s		(0.21*)

Notes:

a Δ is the change between values measured at two time points, where the two times points are separated with a slash (/).

* <0.05,

** <0.01,

*** <0.001, Spearman correlations.

+ <0.05,

++ <0.01,

+++ <0.001, Pearson correlations. Only the correlation coefficients with P-values <0.01 were considered statistically significant, to avoid inflation of the alpha risk (Table 3). However, we showed the coefficients with P-values <0.05 in Table 3 (values placed within parentheses).

Abbreviations: HbO₂, oxygenated hemoglobin; HbT, total hemoglobin; NFCS, Neonatal Facial Coding System.

Figure 3 Graphic representations (boxplots) of the significant correlations between NFCS, assessed at the time of the venepuncture (0 min), and changes in various parameters. (A) Change in [HbO₂] (Δ: max [HbO₂] at +20 s − mean [HbO₂] at −20 s); (B) change in [HbT] (Δ: max [HbT] at +20 s − mean [HbT] at −20 s); (C) change in salivary cortisol concentrations (Δ: [cortisol] at +25 min − at −4 min); and (D) change in skin conductance (Δ: peaks/s at +2 min − peaks/s at −2 min).

Notes: The coefficients of determination (R²) were derived from simple linear regressions. Δ: the change in values measured at two time points, where the two times points are separated with a slash (/).
Abbreviations: HbO₂, oxygenated hemoglobin; HbT, total hemoglobin; NFCS, Neonatal Facial Coding System.

Figure 4 Variable factor map representing the two main dimensions (Dim 1, Dim 2) from the principal components analysis.

Notes: Change in [HbO₂] (Δ: max [HbO₂] at +20 s − mean [HbO₂] at −20 s); change in [HbT] (Δ: max [HbT] at +20 s − mean [HbT] at −20 s; Δ: max [HbT] at +10 s − mean [HbT] at −10 s); change in salivary cortisol concentrations (Δ: [cortisol] at +25 min − at −4 min; and change in skin conductance (Δ: peaks/s at +2 min − peaks/s at −2 min). Δ: the change in values measured at two time points, which are separated with a slash (/).
Abbreviations: Dim, dimension; HbO₂, oxygenated hemoglobin; HbT, total hemoglobin; NFCS, Neonatal Facial Coding System.