Download Update 11 - Update in Anaesthesia - WFSA

Update in Anaesthesia 77muscle but as soon as the needle emerges into the spacebetween them it becomes easy to inject and a similarvolume should be injected as above.Circumcision is usually performed under light generalanaesthesia with a local anaesthetic block. The reason isthat under halothane alone laryngeal spasm often occurs.An understanding of the anatomy is important. Caudalanaesthesia is commonly used. The key points in locatingthe caudal canal are to feel the sacral cornua and then pullthe skin cephalad (upwards) until it is just above the apexof the sacral hiatus. The needle can then be inserted justdistal to the finger tip so that it passes through skin whichhas not been touched since being prepared with antiseptic.At this point the sacrococcygeal membrane is thickestand so more easily felt as the needle is inserted. It alsoenters the deepest part of the sacral epidural space andso it is not necessary to angle the needle into the canalalthough many people do this to ensure that they are in thecorrect space. 0.5 ml/kg of 0.25% bupivacaine will providean adequate block.The alternative is to perform a dorsal nerve of penis block.The skin is put on a stretch and the needle is inserted inthe midline below the symphysis pubis. It is safer to angleit 10 degrees from the entry point and to advance andmake injections on both sides of plain bupivacaine 0.5%1ml + 0.1ml /kg. The needle has to penetrate the superficialfascia which can be felt with a short beveled needle or byscratching up and down as the needle is advanced until arough sensation is felt. The fascia divides to form thesuspensory ligament of the penis in the midline. This dividesover the body of the penis but the nerves and blood vesselslie in the midline deep to it. It is to avoid puncturing thesevessels that it is recommended to inject at an angle. As theneedle is advanced under the symphysis gentle pressureon the syringe plunger will be met at first by resistance.When it becomes easy to inject the needle tip has entereda potential space which is pear shaped when filled and liesclose to the nerves. Injection should be made here whereit is easy to inject. The local anaesthetic diffuses easilythrough the fascial layer separating it from the nerves andvessels. It is important to fill this space between thesymphysis and the corpora cavernosa so that the dorsalnerve and its ventral branch are both blocked as they comeforward under the symphysis. The volume suggestedusually achieves this.There are some important consequences ofhypovolaemia which may occur after trauma, burns, oras a result of post-operative bleeding such as occasionallyhappens after tonsillectomy. The redistribution of cardiacoutput, as well as its reduction has important consequenceswhen anaesthesia is induced or analgesia is given. Studentsand young doctors must have the principles instilled intothem because the consequences of not knowing that agreater proportion of the cardiac output goes to the brainand heart in hypovolaemia may result in dangerousmyocardial or respiratory depression if depressant drugsare injected in usual doses. In addition, it is important toknow that analgesics injected intramuscularly will not beeffective until muscle perfusion is improved after correctionof hypovolaemia .An understanding of the application of basic sciences isimportant in the provision of high quality anaesthesia andcare of children undergoing surgery.