The Fate of IntravascuIarIy Infused Regional Anesthesia:

A Radiologic Investigation

RAMA KUMAR, MURLI MANOHAR, and R. P. S. TYAGI'

INTRODUCTION

Since the introduction of intravenous regional anesthesia (IRA) , several publica- tions have appeared to support the adop- tion of the technic, though with some modi- fication for the extremities of poor surgical risk patients (1-13). Similar attempts have been made with a great amount of success for analgesia for both fore- as well as hindlimbs of bovines (6, 8, 9, 11, 12). Various types of major operative maneu- vers have been demonstrated success- fully to be easily accomplished on bovine limbs under this form of analgesia (9, 12). Despite the popularity enjoyed by this technic among anesthetists in medical practice and the current interest among veterinarians, the mode of action of this form of analgesia is still a mystery (7), al- though divergent hypotheses have been put forward. One such belief is that the anesthetic gains entry into the extra- vascular space, thereafter spreading into the tissues to produce its effects (9, 13).

In the present investigation, an attempt has been made to trace radiographically the course of contrast material infused intravenously with the hope that it may offer some clue to the fate of an equal amount of local anesthetic agent infused to achieve IRA. Also, it aimed at evaluating the feasibility of performing venography of bovine limbs.

MATERIALS AND METHODS

Group I

Six buffalo calves (2- to 21/z-years-old) between 70 and 95 kg body weight were

utilized. A rubber tourniquet was applied above an elbow and the animal was cast on the same limb. After clipping over the radial vein on the caudal aspect of the carpus, 12 to 15 ml of 70% meglumine and sodium iothalamate2 was infused as a rapid injection into it in the proximal direction.

Radiographs of the limb below the tourniquet were taken before infusion of the contrast medium, immediately upon completion of infusion, and a t 3, 10, 20 and 60 minute intervals after infusion. The radiologic factors were constant for all the exposures (mAs = 10, kV = 65, FFD =

90 cm, no grid).

Group II

On a second group of six buffalo calves the procedures used on Group I were re. peated with the addition of a saline chase, i.e. infusion of 20 ml of normal saline through the same infusion needle imme- diately after the contrast medium was in- jected. The radiographic factors and the exposure schedule were the same as in Group I.

RESULTS

The experimental findings were encourag- ing. The administration of up to 20 ml of contrast medium did not produce any immediate or delayed local, regional or systemic effects. In no instance did the tourniquetted limb become desensitized after the infusion of contrast medium.

Radiographs obtained immediately upon completion of the infusion revealed that the veins could be traced along the entire

From the Department of Surgery and Radiology, Haryana A. University, Hissar, India, where Rama Kumar is a lecturer, Murli Manohar is a graduate student, and R. P. S. Tyagi is a senior Professor and Head.

Conray 420.

87 May and Baker India Ltd.

88 R. KUMAR, M. MANOHAR AND R. P. S. TYAGI 1973

Fig. 1. following infusion of contrast material.

Radiograph of the distal forelimb taken immediately Fig. 3. infusion.

Radiograph of forearm taken ten minutes following (Note the marked increase in soft tissue radiodensity).

length of the limb from the pastern proxi- mally to the elbow (Figs. 1 and 2). The major concentration of contrast medium, however, occurred in the proximal part of the vessel in the forearm (Fig. 2). After a three minute postinfusion interval, none of the venograms demonstrated veins distal to the site of injection. In the region of the forearm, the soft tissue radiodensity had started increasing by this time and was most marked in the tissues near the tourniquet.

After a lapse of 10 minutes the contrast medium was still found in the veins of the forearm and radiodensity of the soft tissues surrounding these veins had increased con- siderably (Fig. 3) . With the elapse of 10 minutes more, the veins were visualized only as very light shadows in the back- ground of markedly increased soft tissue radiodensity. At one hour postinfusion, the tissues of the forearm were uniformly radiopaque (Fig. 8).

The saline chase caused the above de- tailed sequence of events to occur more

Fig. 2. Radiograph of the forearm taken immediately after completion of infusion.

VOL. XIV THE FATE OF INTRAVASCULARLY INFUSED REGIONAL ANESTHESIA 89

Fig. 4. Radiograph of forefoot taken immediately after Fig. 5. Radiograph of the forearm taken immediately after completion of saline chase. completion of saline chase. (Note the marked perivascular

extravasation of the contrast material).

rapidly. Radiographs taken immediately upon completion of infusion showed trace- able veins in the distal part of the limb (Fig. 4). Extensive extravasation of con- trast medium into the perivascular soft tissues of the forearm had occurred (Fig. 5 ) . Three minutes after the infusion the situation resembled that seen after 20 min- utes in the Group I experiments (Fig. 6). The radiographs taken at 10, 20 and 60 minute intervals demonstrated progressive increases in radiodensity of tissues of the forearm (Fig. 7).

The main venous tree of the forearm could be visualized in this manner. This technic can be used for venography of the forelimb.

DISCUSSION

Serial radiographs of the forelimb reveal progressive extravasation of the radi-

surrounding soft tissues, thereby increasing

Fig. 6. Radiograph of forefoot of a group II animal taken three minutes fallowing infusion of contrast material (Arrow Opaque medium and its distribution in the points to the veins).

90 R. KUMAR, M. MANOHAR AND R. P. S. TYAGI 1973

Fig. 7. hour postinfusion.

Radiograph of forearm of a group II animal taken one Fig. 8. one hour post infusion.

Radiograph of the forelimb of a group I animal taken

their radiopacity. It is seemingly obvious that solutions of local anesthetics admin- istered for achieving IRA are most likely to meet the same fate. If this is true, the dispersion of the drug in the tissues of the limb should lead to blockade of impulse conduction over the nerves transversing those regions which have thus been ex- posed to the extravasated drug. Since the application of a tourniquet considerably retards the flow of blood into the limb, the extravasation of the infused material is delayed unless its bulk is sufficient to create a high intravascular pressure or it is followed by a forceful chaser of saline. This delay in extravasation of a sufficient amount of the contrast medium is a prob- able explanation for the delay recorded in the onset of analgesia following administra- tion of small quantities of local anesthetic solutions in higher concentrations (8). Our radiographic demonstration of the extravasation and subsequent dispersion of the contrast medium extends the findings that only 15 to 30% of the local anesthetic

enters the systemic circulation upon release of the tourniquet (12). Our experimental results are strongly suggestive that the extravasation and subsequent distribution of local anesthetic following its intra- vascular infusion is primarily responsible for induction and maintenance of analgesia by blocking conduction over the nerve trunks of the region. Another significant derivation that can be made from this is that the local anesthetic solution need not reach all the parts of the limb it desensi- tizes to induce the analgesia.

Since saline chase in the present experi- ments hastened the process of extravasa- tion and subsequent tissue dispersion of the contrast medium due to higher intra- vascular pressure, early onset of analgesia after saline chase supplementation of the intravascular infusion of local anesthetic seems to be explained (10). This also explains the early induction of analgesia observed in the limbs where higher volumes of lower concentrations of local anesthetics are administered (4, 5, 10).

VOL. XIV THE FATE OF INTRAVASCULARLY INFUSED REGIONAL ANESTHESIA 91

Ischemia of the tissues distal to the tourniquet level is believed to play an im- portant role in this form of anesthesia (IRA) (1, 2). It has been found that simple application of a tourniquet for pro- longed periods, the administration of saline alone in the tourniquetted limb (7, 9), and simple exsanguination of the limb is not capable of inducing analgesia. Moreover, the observation that in none of the present experiments did analgesia develop after intravenous administration of contrast medium alone or with saline chase also adds support to these facts. Though several in- vestigators have reported on the reduction of induction time after administration of the anesthetic when exsanguination has been attempted, the situation remains con- fused (1, 2, 7, 11). It has been noted that there is no convincing proof that exsan- guination helps achieve early and better analgesia (4, 9).

Preinjection tourniquet ischemia (PITI) of 15 t o 20 minutes duration considerably reduced the induction time and the dose of the local anesthetic required to produce analgesia (5, 11). It was clearly demon- strated, however, that tourniquet ischemia alone failed to provide analgesia. This early induction of analgesia when PITI is used, can probably be ascribed t o the in- creased permeability of the vessels due to hypoxic acidosis and accumulation of acid metabolites in tissues, thus allowing more rapid extravasation and dispersion of the local anesthetic in the surrounding tissues.

It can be stated that extravasation of the local anesthetic and its subsequent contact with the nerves traversing through the region is primarily responsible for the analgesia obtained by this technic (IRA). Though the ischemia seemingly plays a small direct role, i t does facilitate the early induction of anesthesia.

Although these conclusions have been made out of the present experiments em- ploying radiopaque contrast material, these are tentative and their validity is open to question because of the altogether different consitution of the local anesthetics and Conray 420. Keeping this in view, it is

suggested that experiments may run on parallel lines employing labelled local anesthetics to confirm these findings.

SUMMARY

The present investigation includes 12 buffalo calves. In the first group of six animals, Conray 420 was injected into the radial vein and in another group of six animals, 20 ml of normal saline was in- jected following the infusion of the contrast material. Radiographs of the limb below the tourniquet were taken before the in- fusion of the contrast material, immediately upon completion of infusion, and a t 3, 10, 20 and 60 minute intervals. No regional or systemic effects were produced a t any stage with the administration of up to 20 ml of contrast medium. Serial radiographs of the limb revealed progressive extravasa- tion of the radio-opaque material and its distribution in the surrounding soft-tissues. Extravasation of contrast material occurred more rapidly where the saline chase was performed. It is felt that solutions of local anesthetics administered for achiev- ing IRA are most likely to meet the same fate. Infusion of contrast material with saline chase can be used for venography of the forelimb, as the main venous tree of the forearm could be visualized in this manner. Haryana Agricultural University College of Veterinary Sciences Hissar, India

ACKNOWLEDGMENTS: The authors extend their sincerest appreciation to Dr. A. K. Bhargava and Shri J. R. Jindal for their constant interest and technical assistance.

REFERENCES 1. Atkinson, D. I., Modell, J. and Moya, F.:

Intravenous Regional Anesthesia. Anesth. Analg. 44: 313, 1965.

2. Atkinson, D. I.: The Mode of Action of Intravenous Regional Anesthesia. Acta. Anesth. Scandinav. XXXVI: 131, 1969.

3. Bier, A.: Ueber eiben NevenWeg Local Anesthesie an den Gliedmassen zu Erzeugen. Arch. Klin. Chir., 86: 1007, 1908.

4. Dawkins, 0. S., Russell, E. S., Adams, A. K., Hooper, R. L., Odiakosa, 0. A. and Fleming, S. A.: Intravenous Regional Anesthesia; Canad. Anesth. SOC. J. 11: 243, 1964.

92 R. KUMAR, M. MANOHAR AND R. P. S. TYAGI 1973

5. Harris, W. H., Slater, E. M. and Bell, H. M.: Regional Anesthesia by Intravenous Route. J. Am. Med. Ass. 194: 1273, 1965.

Re- gional Anesthesia of the Lower Parts of the Fore and Hind Limbs in Cattle. Tidschr. Diergeneesk. 36: 1440, 1971.

7. Holmes, C. Mek.: Intravenous Regional Analgesia. Lancet. 1: 245, 1963.

8. Kottman, J.: Intravenous Anesthesia of the Bovine Foot. Tidschr. Diergeneesk. 36(21): 1435, 1971.

9. Manohar, M., Kumar, R. V., Tyagi, R. P. S.: Studies on Intravenous Retrograde Regional Anesthesia of the Forelimb in Buffalo Calves. Brit. Vet. Jr. 127(9): 401, 1971.

10. Trias, A.: The Use of Intravenous Re- gional Anesthesia in Orthopaedic Surgery. Acta. Anesth. Scandinav. XXXVI (Suppl.) 35, 1969.

11. Tyagi, R. P. S., Kumar, R. V. and Manohar, M.: Intravenous Regional Anesthesia for the Forelimbs of Ruminants. Aust. Vet. Jour. (Sub- mitted for publication, November, 1971).

12. Weaver, A. D.: Intravenous Local Anes- thesia of the Lower Limb in Cattle. J.A.V.M.A. 160(1): 55, 1972.

6. Hartman, H. and Wensing, C . J. G.:

13. Wier, J. G.: Minn. Med. 51: 771, 1968.

ZUSAMMENFASSUNG In dieser Untersuchung wurden 12 Biiffelkalber

benutzt. In der ersten Gruppe von Tieren wurde Conray 420 in die Radialvene injiziert, und in einer weiteren Gruppe von 6 Tieren wurden 20 ml nor- maler Salzlosung injiziert, nach einer Infusion des Kontrastmittels. Rontgenaufnahmen des Glied- masses unter der Aderpresse wurden vor der In- fusion gemacht, sofort nach Beendigung der Infusion, und nach drei, zehn, zwanzig und sechzig minutigen Perioden. Keine regionalen oder sys- tematischen Effekte wurden zu irgendeinem Zeit- punkt produziert bei der Eingebung von bis zu 20 ml des Kontrastmediums. Eine Rontgen- strahlenserie des Gliedmasses zeigte progressive

Extravasation des Rontgenstrahlen-undurchlas- sigen Materials und seine Verteilung in die um- liegenden Weichgewebe. Extravasation des Kon- trastmediums geschah schneller, wo die Salzlo- sungseinga‘be durchgefiihrt wurde. Man ist der Meinung, dass Losungen ortlicher Betaubungs- mittel, die zur Erreichung intravenoser ortlicher Betaubung fur IRA eingegeben werden, das gleiche Resultat erreichen. Infusion von Kontrastmaterial mit Salzlosungseingabe kann zur Venographie des Vorderbeines benutzt werden, da der Haupt- venenstrang des Unterarmes in dieser Art und Weise angesehen werden kann.

RESUME

Dans l’exp6rience qui suit on a utilis6 12 buffle- tins. Dans le premier group3 de six animaux Conray 420 a ktB inject6 dans la veine radiale et dans I’autre groupe de six animaux 20 ml d’une solution saline normale aprbs avoir introduit une substance contraste. Des radiographies du mem- bre sous le compresseur ont 6tB faites avant l’in- troduction de cette substance, immkdiatement aprks avoir fini d’introduire celle ci, puis B inter- valles de trois, dix, vingt et soixante minutes. Aucun effet partiel ou systhmatiyue n’a 6th produit k aucune phase avec l’introduction de la dose allant jusqu’h 20 ml de la substance contraste. Une skrie de radiographies du membre ont montrk un epanchement progressif de la substance radio- opaque et de sa repartition dans les tissus mous qui l’entourent. L’Bpanchement de la substance contraste s’est produit plus rapidement h l’endroit 06 la solution saline a kt6 injecthe. On estime que trBs certainement la m&me chose se produit avec des solutions d’anesthBsique locale administrees pour faire une anesthBsie intraveineuse locale. L’introduction de substance contraste avec la solution saline peut etre utiliske pour la vkno- graphie du membre antkrieur puisque de cette facon on peut rendre l’arbre veineux principal visible.