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CLINICAL INVESTIGATION
Year : 2012  |  Volume : 56  |  Issue : 4  |  Page : 382-386  

Echo-guided estimation of formula for paravertebral block in neonates, infants and children till 5 years


Department of Anaesthesia, Holy Family Hospital and Research Centre, All India Institute of Physical Medicine and Rehabilitation Centre, Mumbai, Maharashtra, India

Date of Web Publication8-Sep-2012

Correspondence Address:
Vrushali C Ponde
Amber Croft Annexe, 302, Ambedkar Road, Pali Hill, Bandra West, Mumbai, Maharashtra - 400 050
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0019-5049.100825

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Aims: The aim of the study was to derive a clinically useful formula for paravertebral block for thoracic, lumbar (L1) and cervical level (C6) as per the ultrasound-guided measurements in neonates, infants and children up to 5 years of age. Settings and Design: Observational study. Methods: Seventy-five patients from 2 days to 60 months were included. Paravertebral transverse ultrasound scans at cervical (C6), thoracic (T1-12) and lumbar (L1) regions were viewed to determine the optimal insertion point and depth for performing paravertebral blocks. The lateral distance from the spinous process to the insertion point and the depth from the insertion point to the paravertebral space or reference point (point just anterior to the transverse process) were measured. Statistical Analysis: Data was analyzed using the SPSS (V 10.0) package. Preliminary data was collected with the actual values of paravertebral parameters and weight and age. Initially, Pearson Bivariate Correlation Coefficients were calculated between parameters and age and weight so as to predict paravertebral parameters with the help of weight and age. As there were statistically significant associations between parameters and age and weight, an attempt was made to predict parameters with the help of age and weight. Multiple regression method (forward) was applied by taking parameters as dependent variables and age and weight as independent variables. Results: Age and weight correlated very well (statistically significant) with paravertebral parameters; hence, prediction (regression) equations were calculated as: Prediction (regression) equation:
C6A=0.005 × wt + 0.005 × age + 1.31
C6B=0.009 × wt + 0.002 × age + 1.78
T1-12 A=0.02 × wt + 0.003 × age + 0.93
T1 to 12 B=0.03 × wt + 0.03 × age + 1.02
L1A=0.03 × wt + 0.02 × age + 0.91
L1B=0.05 × wt + 0.02 × age + 0.94
Conclusions: We could derive equations to predict the values for paravertebral blocks in centimetres at different levels in the study population.

Keywords: Formula, paravertebral block, patients, paediatric, ultrasound guidance


How to cite this article:
Ponde VC, Desai AP. Echo-guided estimation of formula for paravertebral block in neonates, infants and children till 5 years. Indian J Anaesth 2012;56:382-6

How to cite this URL:
Ponde VC, Desai AP. Echo-guided estimation of formula for paravertebral block in neonates, infants and children till 5 years. Indian J Anaesth [serial online] 2012 [cited 2020 Jul 13];56:382-6. Available from: http://www.ijaweb.org/text.asp?2012/56/4/382/100825


   Introduction Top


An ostensibly renewed interest in paravertebral blocks in paediatric regional anaesthesia [1] is apparent. This is primarily because paravertebral block results in ipsilateral analgesia for unilateral surgeries on the trunk and has been found to be of better quality as compared with other alternatives for post-operative analgesia. [1]

Although there are various studies to guide the distance from spine to insertion point and from the insertion point to the paravertebral space, they are more applicable to adults. [2] The existing formula [2],[3] for children calculates distance from spinous process to paravertebral space in mm=0.12 × body weight (kg) + 10.2, and the formula for depth in mm=0.48 × body weight (kg) + 18.7. This formula takes into account body weight and is restricted to the thoracic level. Such a guideline for lumbar (L1 as beyond this level its more aptly a lumbar plexus block) and cervical (C6) levels for children does not exist.

Secondly, other parameters such as age are likely to change the dimensions of the spine and paravertebral spaces, especially in this age group where the spine is still developing. [4]

The primary objective of our study was to derive a clinically useful formula for paravertebral block for thoracic, lumbar and cervical level as per the ultrasound-guided measurements in neonate, infants and children till 5 years of age. In this cohort study, we included age as well as weight as the parameters to derive this formula, and the distance and depths were calculated in centimetres. The existing formula had these distances measured in millimetres. [2]


   Methods Top


After institutional approval and written informed parental consent, 75 consecutive patients ranging from 2 days to 60 months were included in this study. The demographic data is shown in [Table 1]. Children with spine deformities were excluded.
Table 1: Demographic data

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Paravertebral transverse ultrasound scan at cervical (C6), thoracic (T1-12) and lumbar (L1) regions were performed and reviewed in order to determine the optimal insertion point and depth for performing paravertebral blocks in children.

A standard ultrasound device (Sonosite Inc-US, 21919 30 drive SE Bothell, Washington, USA) HFL probe (linear 7-13 MHz) was used. The examiner was experienced in ultrasound imaging of the paravertebral region. The patients were placed in lateral position with the side to be measured placed upper most.

Measurements

The lateral distance from the spinous process to the insertion point and the depth from the insertion point till the paravertebral space were measured. The distance from the spine to the insertion point was referred to as "A" and the distance from the insertion point to the paravertebral space was referred to as "B".

Measurements were obtained at C6 [Figure 1], T 1 to 12 [Figure 2]a and b and L1 [Figure 3].
Figure 1: (a) Transverse thoraxic (T6) scan of an infant. SP, spinous process; TP, transverse process; VA, vertebral arch; PD, posterior dura; NR, nerve root; SC, spinal cord; AD, anterior dura; VB, vertebral body; RP, reference point for measurement of paravertebral space; ESM, erector spinae muscle. (b) Transverse thoraxic (T6) scan of a grown up child. SP, spinous process; TP, transverse process; PD, posterior dura; SC, spinal cord; RP, reference point for measurement of paravertebral space; ESM, Erector spinae muscle; VB, vertebral body

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Figure 2: Transverse scan at the C6 level of an infant. SP, spinous process; TP, transverse process; PD, posterior dura; SC, spinal cord; RP, reference point for measurement of paravertebral space; DCM, deep cervical muscles; VB, vertebral body

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Figure 3: Transverse scan at the LI level of an 11-month-old baby. SP, spinous process; TP, transverse process; VB, vertebral body; IP, ilio psoas; PD, posterior dura; SC, spinal cord; AD, anterior dura; RP, reference point for measurement of paravertebral space; PSM, paraspinal muscles

Click here to view


Technique of measurement of distance

To begin with, the paravertebral space was identified.

The criteria for identification of the paravertebral space at each level are as described below. The reference point, which was common for the measurements at to all the level, was taken as the point anterior to the transverse process. This point indicated the depth at which the needle tip should be placed in the paravertebral region.

The thoracic paravertebral space [Figure 1]

The paravertebral space was taken as the space adjacent to the vertebral bodies, confined anterio-laterally by the parietal pleura, posteriorly by the transverse process and medially by the vertebral body.

Cervical parvertebral space [Figure 2]

The paravertebral space was taken as the space adjacent to the vertebral bodies, confined anterior-laterally by the anterior scalene, posteriorly by the middle scalene and transverse process and medially by the vertebra body.

Lumbar paravertebral space [Figure 3]

The paravertebral space was taken as the space adjacent to the vertebral bodies, confined anteriorly by the ilio-psoas, posteriorly by the paraspinal muscles and transverse process medially by the vertebral body.

Measurements of the distances in centimetres

The linear distances were measured in centimetres [Figure 1],[Figure 2] and [Figure 3] using the calibre key on the machine. The distance between the paravertebral space (that is the reference point anterior to the transverse process) and the insertion point was termed as "B" and the distance between the spine and the insertion point was referred to as "A".

Hence,

A=Distance from the spinous process to the insertion point in centimetres

B=Distance from the insertion point to the paravertebral space in centimetres.

The collected data from 75 children was analysed.



Statistical analysis


Data were analysed using SPSS (V 10.0) package. Preliminary data were collected with the actual values of paravertebral parameters and weight and age. To predict paravertebral parameters with the help of weight and age, initially, the Person Bivariate Correlation Coefficients were calculated between parameters and age and weight. As there were statistically significant associations between parameters and age and weight, an attempt was made to predict parameters with the help of age and weight. Multiple regression method (forward) was applied by taking parameters as dependent variables and age and weight as independent variables.


   Results Top


All patients completed the study. Paravertebral anatomy was well appreciated in all the children at all the levels. In infants, detailed structures like the spinal cord in transverse section, nerve roots, dentate ligament, posterior and anterior duramater, vertebral arch, vertebral body pleura and ribs were appreciated. However, in the older children, finer structures such as nerve roots emerging from the spinal canal could not be appreciated. The vertebral bodies were also not visualized as clearly as in infants [Figure 2]b. The spines, transverse processes, ribs and pleura were seen uniformly well in the study population.

[Table 1] shows the demographic data of the patients.

Pearson Correlation coefficient (r): Correlation coefficients (r) of age and weight with paravertebral parameters and significance. (*=S, P<0.05, **=S, P<0.01)



Age and weight correlated very well (statistically significant) with paravertebral parameters and, hence, the prediction (regression) equations were calculated.

Prediction (regression) equation

The equations are as follows:

C6A=0.005 × wt + 0.005 × age + 1.31

C6B=0.009 × wt + 0.002 × age + 1.78

T1-12A=0.02 × wt + 0.003 × age + 0.93

T1 to 12B=0.03 × wt + 0.03 × age + 1.02

L1A=0.03 × wt + 0.02 × age + 0.91

L1B=0.05 × wt + 0.02 × age + 0.94


   Discussion Top


In our study, we found that age and weight correlated well with the paravertebral measurements. The distances (in centimetres) proportionately increased with age and weight, and the correlation was statistically significant.

Thus, the equations to predict the distance from the spine to the insertion point and from the insertion point to the paravertebral space (the depth at which the paravertebral space can be located) could be derived, which was the primary aim of our study.

The derived equation include variables such as age as well as weight, considers thoracic, lumbar and cervical levels and has used centimetres as the measuring units which differentiates it from existing estimation guidelines in the literature. Lo͸nnqvist [2] et al. had derived a similar equation assessed by computed tomography. This was confined to thoracic levels, was based on body weight and the distance was measured in millimetres.

The paravertebral anatomy is clearly visualized in the age group (neonates to 5 years) that we have dealt with. This made it possible for us to measure the distance of the insertion point and the depth of the paravertebral space. As the age advanced, the machine settings were adjusted to get an appropriate image. (Penetration mode revealed better scans in relatively grown up children.)

Serial measurements of these distances enabled us to calculate guideline for paravertebral blocks for practitioners to whom ultrasound guidance is not available for these blocks and depend solely on external measurements and loss of resistance. The loss of resistance is elicited by passage of the needle through costotranverse ligament in the thoracic region. This loss of resistance is quiet subtle and not as well felt as the loss of resistance through the ligament flavum in the epidural space, [5] and a proper guideline that takes into account age as well as weight is required especially in this age group.

Accidental pleural punctures are possible during paravertebral blocks. [5] In our study, the pleura was visualized as the antero-lateral boundary of the paravertebral space in the transverse scan; hence, the puncture point estimated from our equations are unlikely to be lateral enough to cause pleural damage. Secondly, as mentioned earlier, because the give way of the costotransverse ligament is very subtle, the pleural give way can be mistaken for the give way of the costotransverse ligament. [5] While measuring the depth of the paravertebral space at the thoracic level, the probe was placed at the level of spine to reveal the spine transverse process and the rib, which made visualization of costotransverse ligament difficult. Transverse placement of the probe in between the two spines made it possible to visualize costotransverse ligament during the dynamic scanning. Luyet et al. [6] identified the costotransverse ligament and the paravertebral space in cadavers using the curved array transducer placed in a slightly oblique axis.

The study conducted by Naja et al. [7] also estimated the distance from the skin to the intercostal nerve within the paravertebral space at different thoracic levels in adults using the nerve stimulator-guided paravertebral technique, unlike our study. The authors also concluded that the body mass index influences this distance. This study offered estimations of distances of paravertebral depths. We had sonographically measured the distances and derived a formula for the estimation of distances for a given age and weight.

The limitation of this study is that we have not derived a separate formula for each thoracic segment, which is in accordance with Lo͸nnqvist et al. [2] Different formulae for each of the 12 thoracic levels may be clinically cumbersome to remember. At the same time, the fact that the distance from the skin to the paravertebral space differs between thoracic segments except T7-9 [7] cannot be dismissed.

A subsequent study confirming the clinical efficacy of the estimated equations is required.


   Acknowledgments Top


The authors acknowledge Dr. Divatia for his guidance in conceptualizing this study.

 
   References Top

1.Berta E, Spanhel J, Gabrhelik T, Lönnqvist P. Paraverteral block in children Techniques in Regional Anesthesia and Pain Management. Vol 11. USA: Elsevier science; 2007. p. 247-54.  Back to cited text no. 1
    
2.Lönnqvist PA, Hesser U. Location of the paravertebral space in children and adolescents in relation to surface anatomy assessed by computed tomography. Paediatr Anaesth 1992;2:285-9.  Back to cited text no. 2
    
3.Lönnqvist PA. Continuous paravertebral block in children. Initial experience. Anaesthesia 1992;47:607-9.  Back to cited text no. 3
    
4.Lönnqvist PA, MacKenzie J, Soni AK, Conacher ID. Paravertebral blockade: Failure rate and complications. Anaesthesia 1995;50:813-5.  Back to cited text no. 4
    
5.Richardson J, Cheema SP, Hawkins J, Sabanathan S. Thoracic paravertebral space location. A new method using pressure measurement. Anaesthesia 1996;51:137-9.  Back to cited text no. 5
    
6.Luyet C, Eichenberger U, Greif R, Vogt A, Szücs Farkas Z, Moriggl B. Ultrasound-guided paravertebral puncture and placement of catheters in human cadavers: An imaging study. Br J Anaesth 2009;102:534-9.  Back to cited text no. 6
    
7.Naja MZ, Gustafsson AC, Ziade MF, El Rajab M, Al-Tannir M, Daher M, et al. Distance between the skin and the thoracic paravertebral. Anaesthesia 2005;60:680-4.  Back to cited text no. 7
    


    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1]


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