Local anaesthetic infiltration has also been used in rare situations such as:
1. Myotonic dystrophy where it has been used in conjunction with spinal anaesthesia for CS with bupivacaine applied directly to the myometrium to relieve incoordinate cycles of uterine spasm / atony (5)
2. Familial dysautonomia (Riley-Day syndrome) (1)
Advantages of local anaesthetic infiltration:
1. Allows for immediate commencement of surgery in emergency situations.
2. Useable when central neural blockade (CNB) is technically difficult,
eg. kyphoscoliosis (2) , unpredictable in result or contraindicated.
3. Retains the patient's protective airway reflexes.
4. Avoids the sudden haemodynamic changes that may occur with CNB.
Technique:
A long (18 cm) spinal needle minimises the number of individual injections required.
Skin:
The skin of the anterior abdominal wall is supplied by the anterior and lateral cutaneous branches of the lower six intercostal nerves and the iliohypogastric and ilioinguinal nerves. For a transverse suprapubic (Pfannensteil) incision simple subcutaneous infiltration is adequate.
Fat:
The fat layer is relatively devoid of innervation and a large amount of local anaesthetic may be wasted by infiltrating this layer, which is relevant to the often large total dose used.
Fascia:
Direct infiltration can be used; other authors have recommended bilateral rectus sheath blocks (6, 7).
Retropubic space:
This can be a difficult area to anaesthetise and may require additional infiltration retropubically and into the pyramidales muscles.
Parietal peritoneum:
Many authors report this to be a difficult area to anaesthetise and several techniques have been described.
1. The injection of several mls of solution through the fascia (before its division) helps to separate the layers and to anaesthetise the parietal peritoneum.
2. Once the peritoneum is opened, the instillation of 10-15ml of local anaesthetic into the peritoneal cavity.
3. Once the peritoneum is opened, radiate intraperitoneal injections.
Visceral peritoneum / uterus:
These do not need infiltration, but doing so separates the visceral layer of the peritoneum from the lower uterine segment.
Some authors (7, 8) have described field block anaesthetic techniques for vertical classical skin incisions which involve multiple injections and increased discomfort for the patient. They may take longer and require greater skill and use a greater volume of local anaesthetic than simple direct infiltration. These papers, which described the authors personal experiences in the 1950s and 60s cite local anaesthesia as giving better neonatal outcomes than general anaesthesia for CS.
Macintosh (9) warns of the risk of rectus sheath block in a patient with abdominal distension (from whatever cause). As the anterior and posterior layers of the sheath are almost in apposition, the needle may pass through both structures giving the false impression that only the anterior layer has been penetrated.
Drugs, vasoconstrictor and volume:
Many different agents have been used depending on the availability of the drug and the familiarity of the operator with the agent.
Bearing in mind the maximum recommended doses of local anaesthetic agents (Table 36.3), the volume required may be as high as 100ml. Not all of this may be required initially, and further infiltration may be necessary after delivery to close the superficial layers.
Obviously, local anaesthetic toxicity (Chapter 89) to mother and fetus is a significant risk. This should influence the choice of agent in terms of :
1. The concentration which is required for effective infiltration anaesthesia.
2. The decision to add a vasoconstrictor in order to increase the amount of drug that can be used with safety.
3. The toxicity and metabolism profile of the local anaesthetic.
4. The fetal / maternal ratio of the local anaesthetic. Substantial uptake of lignocaine in the fetal liver can occur (10). Ester local anaesthetics such as 2-chloroprocaine have a half-life in neonatal blood of 43 secs (11). Fetal acidosis favours drug ionisation, retention of local anaesthetic within the fetus and increased risk of fetal toxicity.
Choice of agent:
Lignocaine 0.5% or chloroprocaine 1% with 1:200,000 adrenaline is adequate for infiltration anaesthesia and both agents are rapid in onset. The addition of adrenaline allows for the use of a greater overall dose.
Longer acting agents such as bupivacaine have a slower onset time and a lower free drug concentration in the fetal blood (12). The addition of hyaluronidase has been described (8) but may increase absorption.
Surgical technique:
Gentle tissue handling is required and retractors are generally not well tolerated. If adequate retropubic anaesthesia has been obtained, a Doyen retractor can be used. Adequate exposure of the uterus can be obtained by using corner stitches to rotate the uterus (4).
Manoeuvres that can cause significant pain are:
1. Disengagement of the fetal head from the pelvis.
2. Peritoneal traction (may also cause vagal effects).
3. Externalisation of the uterus.
Blood loss is not increased using this technique (4).
In their series of 141 caesarean sections, Ranney and Stannage (7) reported 61 patients having a second, 14 a third and 2 a fourth operation. Only three patients wanted to have general anaesthesia for their repeat procedure.
References:
1. Leiberman JR, Cohen A, Wizniter A, Maayan C, Greemberg L. Cesarean section by local anesthesia in patients with familial dysautonomia. American Journal of Obstetrics and Gynecology 1991;165:110-1.
2. Cooper MG, Feeney EM, Joseph M, McGuinness JJ. Local anaesthetic infiltration for caesarean section. Anaesthesia and Intensive Care 1989; 17: 198-201.
3. Barker A, Barker M. Caesarean section under local analgesia. Tropical Doctor 1976; 6:23-25.
4. Larsen JV, Barker A, Barker M, Brown RS. A technique combining neurolept-analgesia with local analgesia for caesarean section. South African Medical Journal 1971; 45: 750-751.
5. Cope DK, Miller JN. Local and spinal anaesthesia for cesarean section in a patient with myotonic dystrophy. Anesthesia & Analgesia 1986; 65:687-90.
6. Mackey R. Local anaesthesia in obstetrics. Medical Journal of Australia. 1947; 2: 593.
7. Ranney B, Stannage WF. Advantages of local anesthesia for cesarean section. Obstetrics & Gynecology 1975; 45: 163-167.
8. Busby T. Local anesthesia for cesarean section. American Journal of Obstetrics & Gynecology 1963; 87:399-404.
9. Macintosh RR, Bryce-Smith R. Local analgesia: Abdominal Surgery. ES Livingstone Ltd, Edinburgh, 1953; 74-5.
10. Finster M, Morishima HO, Boyes RN, Covino BG. The placental transfer of lidocaine and its uptake by fetal tissues. Anesthesiology 1972; 36: 159-163.
11. Finster M, Perel JM, Hinsvark ON, et al. Pharmacodynamics of 2-chloroprocaine. Fourth European Congress of Anesthesiology, 1974;330:189.
12. Tucker GE, Mather LE. Properties, absorption, and disposition of local anesthetic agents. In: Cousins MJ, Bridenbaugh PO (eds). Neural Blockade in Clinical Anesthesia and Management of Pain, 2nd ed, JB Lippincott Co, Philadelphia,1988.