2 Update in Anaesthesia on patient condition, type of operation proposed, spinal anaesthesia. How to attain this requisite level and the quiet self-confidence that comes with of skill and art is neatly described in this update on experience using the champagne of anaesthetics: the subject. Read it and believe it. SPINAL ANAESTHESIA - A Practical Guide Bleeding. Blood loss during operation is less than when the same operation is done under general Dr Chris Ankcorn, Lecturer in Anaesthesia, Kumasi, anaesthesia. This is as a result of a decreased blood Ghana pressure and heart rate, and improved venous Dr William F Casey FRCA, Consultant Anaesthetist, drainage which results in less oozing. Gloucestershire Royal Hospital, Gloucester, UK Splanchnic blood flow. Because of its effect on Spinal anaesthesia is induced by injecting small increasing blood flow to the gut, spinal anaesthesia amounts of local anaesthetic into the cerebro-spinal reduces the incidence of anastomotic dehiscence. fluid (CSF). The injection is usually made in the Visceral tone. The bowel is contracted by spinal lumbar spine below the level at which the spinal anaesthesia and sphincters relaxed although cord ends (L2). Spinal anaesthesia is easy to perform peristalsis continues. Normal gut function rapidly and has the potential to provide excellent operating returns following surgery. conditions for surgery below the umbilicus. Coagulation. Post-operative deep vein thromboses If the anaesthetist has an adequate knowledge of and pulmonary emboli are less common following the relevant anatomy, physiology and spinal anaesthesia. pharmacology, safe and satisfactory anaesthesia can easily be obtained to the mutual satisfaction of Disadvantages of Spinal Anaesthesia the patient, surgeon and anaesthetist. 1. When an anaesthetist is learning a new technique, The Advantages of Spinal Anaesthesia it will take longer to perform than when he is more practised, and it would be wise to let the surgeon Cost. Anaesthetic drugs and gases are costly and know that induction of anaesthesia may be longer the latter often difficult to transport. The costs than usual. Once competent, however, spinal associated with spinal anaesthesia are minimal. anaesthesia can be very swiftly performed. Patient satisfaction. If a spinal anaesthetic and the 2. Occasionally, it is impossible to locate the dural ensuing surgery are performed skillfully, the space and obtain CSF and the technique has to be majority of patients are very happy with the abandoned. Rarely, despite an apparently faultless technique and appreciate the rapid recovery and technique, anaesthesia is not obtained. absence of side-effects. 3. Hypotension may occur with higher blocks and Respiratory disease. Spinal anaesthesia produces the anaesthetist must know how to manage this few adverse effects on the respiratory system as situationsituation with the necessary resuscitative long as unduly high blocks are avoided. drugs and equipment immediately to hand. As with Patent airway. As control of the airway is not general anaesthesia, continuous, close monitoring compromised, there is a reduced risk of airway of the patient is mandatory. obstruction or the aspiration of gastric contents. 4. Some patients are not psychologically suited to This advantage may be lost with too much sedation. be awake, even if sedated, during an operation. Diabetic patients. There is little risk of They should be identified during the preoperative unrecognised hypoglycaemia in an awake patient. assessment. Diabetic patients can usually return to their normal 5. Even if a long-acting local anaesthetic is used, a food and insulin regime soon after surgery as there spinal is not suitable for surgery lasting longer than is less sedation, nausea and vomiting. approximately 2 hours. If an operation unexpectedly Muscle relaxation. Spinal anaesthesia provides lasts longer than this, it may be necessary to convert excellent muscle relaxation for lower abdominal to a general anaesthetic. and lower limb surgery. Update in Anaesthesia 3 6. There is a theoretical risk of introducing infec- Clotting disorders. If bleeding occurs into the tion into the subarachnoid space and causing men- epidural space because an epidural vein has been ingitis. This should never happen if equipment is punctured by the spinal needle, a haematoma could sterilised properly and an aseptic technique is used. form and compress the spinal cord. Patients with a 7. A postural headache may occur postoperatively. low platelet count or receiving anticoagulant drugs This should be rare: see later. such as heparin or warfarin are at risk. Remember that patients with liver disease may have abnormal Indications for Spinal Anaesthesia clotting profiles whilst low platelet counts as well Spinal anaesthesia is best reserved for operations as abnormal clotting can occur in pre-eclampsia. below the umbilicus e.g. hernia repairs, gynaeco- Hypovolaemia from whatever cause e.g. bleeding, logical and urological operations and any operation dehydration due to vomiting, diarrhoea or bowel on the perineum or genitalia. All operations on the obstruction. Patients must be adequately rehydrated leg are possible, but an amputation, though pain- or resuscitated before spinal anaesthesia or they less, may be an unpleasant experience for an awake will become very hypotensive. patient. In this situation it may be kinder to supple- ment the spinal with generous sedation or a light Any sepsis on the back near the site of lumbar general anaesthetic. puncture. Spinal anaesthesia is especially indicated for older Patient refusal. Patients may be understandably patients and those with systemic disease such as apprehensive and initially state a preference for chronic respiratory disease, hepatic, renal and en- general anaesthesia, but if the advantages of spinal docrine disorders such as diabetes. Most patients anaesthesia are explained they may then agree to with mild cardiac disease benefit from the the procedure and be pleasantly surprised at the vasodilation that accompanies spinal anaesthesia outcome. If, despite adequate explanation, the except those with stenotic valvular disease or un- patient still refuses spinal anaesthesia, their wishes controlled hypertension. should be respected. It is suitable for managing patients with trauma if Uncooperative patients. Although spinal they have been adequately resuscitated and are not anaesthesia is suitable for children, their cooperation hypovolaemic. In obstetrics, it is ideal for manual is necessary and this must be carefully assessed at removal of a retained placenta (again, provided the pre-operative visit. Likewise, mentally there is no hypovolaemia). There are definite advan- handicapped patients and those with psychiatric tages for both mother and baby in using spinal problems need careful pre-operative assessment. anaesthesia for Caesarean section. However, spe- Septicaemia. Due to the presence of infection in cial considerations apply to managing spinal an- the blood there is a possiblity of such patients aesthesia in pregnant patients (see later) and it is developing meningitis if a haematoma forms at the best to become experienced in its use in the non- site of lumbar puncture and becomes infected. pregnant patient before using it for obstetrics. Anatomical deformities of the patient’s back. Contra-indications to Spinal Anaesthesia This is a relative contraindication, as it will probably Most of the contra-indications to spinal anaesthesia only serve to make the dural puncture more difficult. apply equally to other forms of regional anaesthe- Neurological disease. The advantages and sia. These include: disadvantages of spinal anaesthesia in the presence Inadequate resuscitative drugs and equipment. of neurological disease need careful assessment. No regional anaesthetic technique should be at- Any worsening of the disease postoperatively may tempted if drugs and equipment for resuscitation be blamed erroneously on the spinal anaesthetic. are not immediately to hand. Raised intracranial pressure, however, is an absolute contra-indication as a dural puncture may precipitate coning of the brain stem. 4 Update in Anaesthesia Reluctant surgeon. If a surgeon is unhappy Anatomy operating on an awake patient or if he is relatively The spinal cord usually ends at the level of L2 in unskilled, spinal anaesthesia may be better avoided. adults and L3 in children. Dural puncture above Physiology of Spinal Anaesthesia these levels is associated with a slight risk of Local anaesthetic solution injected into the damaging the spinal cord and is best avoided. An subarachnoid space blocks conduction of impulses important landmark to remember is that a line along all nerves with which it comes in contact, joining the top of the iliac crests is at L4 to L4/ although some nerves are more easily blocked than 5 others. Remember the structures that the needle will pierce There are three classes of nerve: motor, sensory and before reaching the CSF (fig 1.). autonomic. The motor convey messages for muscles The skin. It is wise to inject a small bleb of local to contract and when they are blocked, muscle anaesthetic into the skin before inserting the spinal paralysis results. Sensory nerves transmit sensations needle. such as touch and pain to the spinal cord and from Subcutaneous fat. This, of course, is of variable there to the brain, whilst autonomic nerves control thickness. Identifying the intervertebral spaces is the calibre of blood vessels, heart rate, gut far easier in thin patients.