RADIOLOGICAL STUDY TO EVALUATE THE SPREADING OF TWO VOLUMES (10 VS. 20 ML) OF RADIOLOGICAL CONTRAST IN THE SERRATUS-INTERCOSTAL PLANE BLOCK IN A PORCINE EXPERIMENTAL MODEL
Interfascial blocks of the thoracic wall are being developed as an alternative to central blocks in breast surgery. However, there are limited studies which have evaluated the anatomical extension of the local anesthetic. Our objective was to analyze with fluoroscopy, the spreading of two volumes (10 vs. 20ml) of radiological contrast in the serratus-intercostal plane block in an experimental pig model.
MATERIALS ANS METHODS
Ten Large-White breed pigs were selected to be performed a bilateral ultrasound serratus-intercostal plane block, administering 10 ml and 20 ml of iopamidol in right and left hemithorax respectively. The spreading of contrast was analyzed by fluoroscopy. The co-relation of Spearman test was used to evaluate the relationship between the administered volume and radiological spreading. The value p<0,05 was considered significative.
Twenty blocks were performed, being able to analyze 18. The administration of 10 ml of contrast was associated to an average spreading of 2.28 ± 0.31 (IC 95% 2.01- 2.54) intercostal spaces, while the administration of 20 ml showed a spreading of 3±0.25 (IC 95% 2.81-3.18) intercostal spaces. There was a significant co-relation between the injected volume and the spreading of the contrast (Spearman correlation coefficient of 0.81; p=0,0001).
The main finding of the present study has been the extension of the radiological contrast in the realization of the serratus-intercostal plane block in the developed pig model, has been proportional to the injected volume, but without keeping a 1: 1 ratio, that is, doubling the volume has meant a 31% increase in blocked segments.
To date, the degree of extension of the interfascial blocks of the chest wall in relation to the volume administered is a poorly evaluated aspect. Previous studies have analyzed the extension of the interfascial blockade but with different objectives in models in healthy volunteers as well as in studies in cadavers.
In clinical practice, clinical studies in thoracic interfascial blocks generally use a volume of local anesthetic that varies between 15-30 ml. When we consider a certain anesthetic technique that involves the administration of local anesthetics, what we intend is to achieve an effective analgesia for the procedure that is going to be performed, but also to limit the toxicity related to the administration of an excessive dose of local anesthetic. In this sense, studies such as the one we have carried out, contribute to improving the knowledge of these relatively novel blockages, allowing the expansion of existing gaps related to interfascial thoracic blocks.
Our results show a spreading of volume subject to the serratus-intercostal plane block, although not keeping a 1:1 ratio. Doubling the volume has increased by 31% the blocked segments. These findings, If corroborated in the clinical practice, they would allow a more precise adjustment in the anesthetic volume administered. Care must be taken before extrapolating these results to the clinical setting in humans.