Paediatric spinal anaesthesia | Kavitha Jinjil .edu

Indian Journal of Anaesthesia 2008; 52 (3):264-270

Indian Journal of Anaesthesia, June 2008 Special Article

Paediatric Spinal Anesthesia Rakhee Goyal1, Kavitha Jinjil2, BB Baj3, Sunil Singh4 , Santosh Kumar5

Summary Paediatric spinal anesthesia is not only a safe alternative to general anaesthesia but often the anaesthesia technique of choice in many lower abdominal and lower limb surgeries in children. The misconception regarding its safety and feasibility is broken and is now found to be even more cost-effective. It is a much preferred technique especially for the common daycase surgeries generally performed in the paediatric age group. There is no requirement of any additional expensive equipment either and this procedure can be easily performed in peripheral centers. However, greater acceptance and experience is yet desired for this technique to become popular. Key words

Paediatric spinal anaesthesia, Bupivacaine, Infraumbilical surgeries in children

volatile agents and muscle relaxants for general anaesthesia.

Introduction Regional anaesthesia in children was first studied by August Bier in 1899. Since then, spinal anaesthesia was known to be practiced for several years with a series of cases published as early as in 1909-1910.1-3 In 1900, Bainbridge reported a case of strangulated hernia repair under spinal anaesthesia in an infant of three months.4 Thereafter, Tyrell Gray, a British surgeon published a series of 200 cases of lower abdominal surgeries in infants and children under spinal anaesthesia in 1909-1910. After some years it fell into disuse because of the introduction of various muscle relaxants and inhalational agents and was almost unused after World War II.

In the last decade, it started being advocated again by many centers due to increasing knowledge on pharmacology, safety information and availability of specialized equipment for regional anaesthetic techniques and monitoring in children. In the coming times, paediatric spinal anaesthesia will not only be used in cases where general anaesthesia is risky or contraindicated but also be the preferred choice in most lower abdominal and lower extremity surgeries in children.

Anatomical and physiological differences in children There are certain features of paediatric anatomy and physiology which are different from the adult and thus make the central neuraxial blockade a good alternative anaesthetic technique. The spinal cord ends at L3 level at birth and reaches L-1 by 6-12 months. The dural sac is at the S4 level at birth and reaches S2 by the end of the first year. The line joining the two superior iliac crests (inter-cristal line) crosses at L5-S1 interspace at birth, L5 vertebra in young children and L3/4 interspace in adults. It is for this reason that the lumbar puncture be done at a level below which the

Thereafter, in 1983, in the American Society of Anesthesiologists Regional Anesthesia Breakfast Panel, Abajian et al started the “frenzy” of modern paediatric spinal anaesthesia when they reported 78 cases in 81 infants. 5 The textbook of paediatrics by Leigh and Belton also demonstrated that 10% of all anaesthetic procedures practiced in children at the Vancouver General Hospital were spinal techniques, including pulmonary lobectomies and pneumonectomies.5 However, paediatric spinal anaesthesia never achieved its popularity because of continuous discoveries of newer and better

1. Consultant, 2. Consultant, 3. Head of Department, 4. Consultant, 5.P.G.Student, Department of Anesthesiology and Critical Care, Base hospital, New Delhi, Correspondence to: Rakhee Goyal, Department of Anesthesiology and Critical Care, Base hospital, New Delhi, Email: [email protected] Accepted for publication on: 18.4.08 264

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cord ends, safest being at or below the inter cristal line. The bones of the sacrum are not fused posteriorly in children enabling an access to the subarachnoid space even at this level.

critically ill and moribund neonates who present for surgery in grave haemodynamic instability.

Pharmacology The most important concern with the use of intrathecal local anaesthetics in infants and young children is the risk of toxicity. This age group is particularly prone to direct toxicity to the spinal cord when administered in large doses. Neonates with immature hepatic metabolism and decreased plasma proteins like albumin and α 1 acid glycoprotein have higher serum levels of unbound amide local anaesthetics, which are normally highly protein bound (90%). A relatively higher cardiac output and regional blood flow in infants also increases the drug uptake from neuraxial spaces and can predispose them to local anaesthetic toxicity besides decreasing the duration of action. Infants may have decreased levels of plasma pseudocholinesterase which may augment local anaesthetic toxicity especially with the ester group.8 Various anaesthetics have been used for paediatric spinal anaesthesia but bupivacaine and ropivacaine remain the drugs of choice.

Another feature which is unique in infants is that there is only one anterior concave curvature of the vertebral column at birth. The cervical lordosis begins in the first 3 months of life with the child’s ability to hold the head upright. The lumbar lordosis starts as the child begins to walk at the age of 6-9 months. Therefore, the spread of isobaric local anaesthetic is different in infants particularly as compared to adults. The subarachnoid space is incompletely divided by the denticulate ligament laterally, and the subarachnoid septum medially. The volume of cerebrospinal fluid CSF is 4 ml.kg-1 which is double the adult volume. Moreover, in infants half of this volume is in the spinal space whereas adults have only one-fourth. This significantly affects the pharmocokinetics of intrathecal drugs. The spinal fluid hydrostatic pressure of 30-40mm H2O in horizontal position is also much less than that in adults.6

Indications

The neck can be in extension for lateral positioning while performing a lumbar puncture as cervical flexion is of no benefit in children and in fact, may obstruct the airway during the procedure. It can also be performed in sitting position with the head extended.

Infraumbilical extraperitoneal surgeries like inguinal hernia, circumcision, hypospadias, orchidopexy, cystoscopy, colostomy for imperforate anus, rectal biopsy and other perineal surgeries; lower extremity orthopaedic and reconstructive surgeries.

The physiological impact of sympathectomy is minimal or none in smaller age groups. The fall in blood pressure and a drop in the heart rate are practically not seen in children less than five years. Therefore there is no role of preloading with fluids before a subarachnoid block. This may be due to the immature sympathetic nervous system in children younger than five–eight years or a result of the relatively small intravascular volume in the lower extremities and splanchnic system limiting venous pooling and relatively vasodilated peripheral blood vessels. 7 Infants respond to high thoracic spinal anaesthesia by reflex withdrawal of vagal parasympathetic tone to the heart. It is one of the reasons why spinal anaesthesia has been the technique of choice in

Preterm and former preterm infants less than 60 weeks post-conceptual age/less than 3 Kg/hematocrit 15 Kg weight.6

However, in an article published two years later the same authors, Kokki H et al demonstrated that bupivacaine in 0.9% glucose and in 8% glucose solutions are equally suitable for spinal anaesthesia in small

Levobupivacaine has very similar PH) armacokinetic properties to those of racemic bupiva-caine, 267

Indian Journal of Anaesthesia, June 2008

children. Similar success rate, spread and duration of the sensory and motor block are achieved with both baricities of bupivacaine. 19

paediatric patients and some authors have even challenged its existence. In his study on 200 children using two different sizes spinal needles of 25 G and 29 G Quinke, Kokki et al 21 found that 10 had PDPH with no difference regarding the type of needle used. The failure rate of attempted spinal anaesthesia was 4% and even when the subarachnoid space was reached and the local anaesthetic injected, the overall success rate of the technique was only 91%.

Various studies have been done with child in lateral or sitting position for a subarachnoid block. In a study on 30 preterm infants for inguinal herniotomy, Vila et al found spinal anaesthesia to be equally effective in both lateral and sitting position. 20 Duration is an important and a limiting factor for paediatric spinal anaesthesia especially in infants and younger children. Spinal anaesthesia alone for this reason is therefore generally restricted to one hour duration surgeries only. The duration is longer with larger doses in infants and varies directly with the age of the child. It has been seen that the duration of long acting local anaesthetics like bupivacaine is only about 45 min in neonates and 75-90 min in children upto five years. There is no difference in duration by adding epinephrine to bupivacaine.

Transient neurological symptom (TNS) has been reported by some authors following spinal anaesthesia due to direct toxicity of large doses of local anaesthetics. In his study on 95 patients using 0.5% isobaric ropivacaine, Kokki et al16 reported mild to moderate TNS in four children which was transient and was not followed by any permanent neurological sequelae. In another study by the same author similar results were found with 0.5% bupivacaine.17 A one year study of 24,409 regional blocks in children by the French-Language Society of Pediatric Anesthesiologists, 22 the largest known study on complications, revealed a complication rate of 1.5 per 1000 in the 60% of children receiving central neuraxial blocks. However, most of these cases were those of caudal and some of epidural technique.

Additives Since the duration of spinal anaesthesia does not cover most of the postoperative period, it is essential to add intravenous or rectal acetaminophen or ketoprofen routinely to all patients. Profound postoperative analgesia can be achieved by adding a low dose local anaesthetic with or without an opioid (fentanyl), clonidine 1-2µg.kg-1 or any other additive in caudal space at the time of performing the subarachnoid block. A caudal catheter can also be placed and local anaesthetic plus opioid added for prolonged analgesia postoperatively.

Advantages Spinal anaesthesia produces a reliable, profound and uniformly distributed sensory block with rapid onset and good muscle relaxation, and it results in more complete control of cardiovascular and stress responses than epidural or opioid anaesthesia.23 It is ideal for daycase surgeries and is safe and cost-effective. There is no additional requirement of any special drug or equipment for the procedure. Because of these benefits, spinal anaesthesia has gained acceptance for children undergoing surgery in the lower part of the body.24

Complications The complications related to spinal anaesthesia are usually either due to the needle used to perform the procedure (backache, headache, nerve or vascular injury and infection) or the drugs injected (high or total spinal, drug toxicity). However, little data is available regarding the incidence as compared to adults.

Comparison with general anaesthesia General anaesthesia may be associated with several life-threatening complications especially in preterm,

Post dural puncture headache (PDPH) is rare in 268

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on the day of surgery and it becomes a difficult decision to cancel the surgery. Spinal anaesthesia is relatively safer in all these instances where spontaneous airway can be maintained by the patient.

former preterm, those with co-morbidities like sepsis, necrotising enterocolitis, anaemia (hematocrit