|Year : 2008 | Volume
| Issue : 3 | Page : 264-272
Paediatric Spinal Anesthesia
Rakhee Goyal1, Kavitha Jirtjil1, BB Baj2, Sunil Singh1, Santosh Kumar3
1 Consultant, Department of Anesthesiology and Critical Care, Base hospital, New Delhi, India
2 Head of Department, Department of Anesthesiology and Critical Care, Base hospital, New Delhi, India
3 P.G.Student, Department of Anesthesiology and Critical Care, Base hospital, New Delhi, India
|Date of Web Publication||19-Mar-2010|
Department of Anesthesiology and Critical Care, Base hospital, New Delhi
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.
Keywords: Paediatric spinal anaesthesia, Bupivacaine, Infraumbilical surgeries in children
|How to cite this article:|
Goyal R, Jirtjil K, Baj B, Singh S, Kumar S. Paediatric Spinal Anesthesia. Indian J Anaesth 2008;52:264-72
| 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. ,, In 1900, Bainbridge reported a case of strangulated hernia repair under spinal anaesthesia in an infant of three months.  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.
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.  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.  However, paediatric spinal anaesthesia never achieved its popularity because of continuous discoveries of newer and better volatile agents and muscle relaxants for general anaesthesia.
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 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.
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 H 2 O in horizontal position is also much less than that in adults. 
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.
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.  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 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 cc 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.  Various anaesthetics have been used for paediatric spinal anaesthesia but bupivacaine and ropivacaine remain the drugs of choice.
| Indications|| |
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.
Preterm and former preterm infants less than 60 weeks post-conceptual age/less than 3 Kg/hematocrit <30% and with other co-morbidities who are prone to post-operative apnoea,  bradycardia and desaturation after general anaesthesia.
Neonates with respiratory diseases like bronchopulmonary dysplasias, hyaline membrane disease.
Children with history of or high risk for malignant hyperthermia .
Children with acute respiratory conditions, chronic disease of the airways like asthma or cystic fibrosis.
Besides these common indications, there are reports of successful spinal anaesthesia in complex surgeries like meningomyelocele, gastroschisis repair, open heart surgery  etc in addition to light general anaesthesia.
| Contraindications|| |
Refusal of the parents, progressive neurological disease, uncontrolled convulsions, infection of the skin or subcutaneous tissue locally at puncture site, coagulation defects, true allergy to local anaesthetics and severe hypovolemia are some of the contraindications to spinal anaesthesia in children.
| Consent and risk-benefit aspect|| |
Consent from the parents is an important issue before planning a central neuraxial blockade for children. The consent should be informed and written, and the various aspects of regional technique alongwith the risks involved must be explained in detail. There is also an obvious need to assess the risk involved in the procedure on an individual case basis versus the benefits expected depending on the nature and duration of surgery, general condition of the patient and the availability of institutional care intra and postoperatively.
| NPO and premedication protocols|| |
The standard preoperative fasting guidelines are required to be followed before elective spinal anaesthesia. 2-3 hrs fasting for clear fluids, 4 hrs for other fluids and 6 hrs for solids is usually followed in most centers.
Adequate premedication is the key to a smooth regional procedure in children. Various drugs via different routes may be used to achieve a well sedated child who allows venous puncture, placement of monitors and even a lumbar puncture. Oral combination of ketamine 4-6mg.kg -1 , midazolam 0.4mg.kg -1 and atropine 0.03mg.kg -1 is quite effective and safe in most cases.  Other routes of premedication like rectal, sublingual, nasal or intramuscular are also practiced. What ever may be the drug and the route of administration, it is important that it is customized for each type of patient and surgery involved and also safe during the entire perioperative period. 
| Procedure, needles used, drug dose|| |
The basic procedure of performing a subarachnoid block in children is similar to adults and full aseptic precautions are a must. It is important to access the CSF through appropriate space as per the age of the child as already discussed in order to avoid trauma to the spinal cord. Care should be taken as the child may be asleep or inadequately sedated. However, additional analgesia and sedation is generally required during lumbar puncture. It may be supplemented with low dose ketamine or a short acting drug like thiopental/propofol intravenously or inhalational anaesthetics like oxygennitrous oxide, sevoflurane or halothane during the procedure. Anticholinergic drugs may be added to decrease any undesired secretions. Application of 5% EMLA (eutectic mixture of local anaesthetics-lidocaine and prilocaine) with an occlusive dressing on the appropriate and best palpated interspace about an hour before surgery facilitates painless lumbar puncture without any additional parenteral sedation. EMLA should be used with caution in infants less than three months and those receiving any methemoglobin inducing drugs like sulfonamides, phenytoin, phenobarbital, acetaminophen.  Intraoperatively, sedation can be augmented with midazolam upto 0.1mg.kg -1 . Flavoured pacifiers for young and music or books for older children may be used in case the child is awake and cooperative.
The needles available for paediatric use range from 24-29 G, either short bevelled Quincke or Sprotte and Whitacre with or without introducer with a length shorter than that in adults. If specialised needles are unavailable or their cost is prohibitive, even hypodermic needle or the metal stillete of a small gauge intravenous cannula can be used without much difficulty. Correct placement of the needle is ascertained by free flow of CSF. Some of the needles also have a magnifier hub for fast recognition of flashback of CSF. The child may be kept in the dependent side for a few minutes for lateralisation of the block. A successful block usually takes about 25 mins and care should be taken that the leg is not lifted just after the block for placement of diathermy pads which often results in undesired cephalad spread of the block.
The extent of the sensory block can be checked by pin-prick or skin pinch and that of the motor block by Bromage scale.  This may however be difficult to check in a deeply sedated child and can only be done in the postanesthesia care unit (PACU) to check the block regression. However, it can be clinically ascertained by lack of leg movement and diaphragmatic breathing. Children very often fall asleep with the deafferentation following the block.
Intraoperative fluids only include deficit and maintenance amounts and preload need not be given as in adults. The hypotensive cardiovascular response to sympathectomy is minimal or none in children. However, standard monitoring is mandatory and oxygen by face mask is recommended in all cases.
All patients should be monitored in the PACU for vital signs, two-segment block regression, pain and any other side effect. Children should only be discharged when they are awake and able to walk unaided, the vital signs are stable for at least 1 h, there is no pain, nausea/retching or vomiting, and are able to tolerate clear fluids.
| Intrathecal drugs|| |
Among the various drugs approved by FDA for paediatric intrathecal use, 0.5% bupivacaine and ropivacaine are common and popular. The doses used are institutional though the standard protocol that I have been practicing is 0.5% bupivacaine 0.1ml.kg -1 or 0.5mg.kg -1 for infants weighing 0-5 Kg; 0.08ml.Kg -1 or 0.4mg.kg -1 for 5-15Kg body weight and 0.06ml.kg1 or 0.3mg.kg -1 for >15 Kg weight. 
Levobupivacaine has very similar PH) armacokinetic properties to those of racemic bupiva-caine, but the potential for toxicity with levobupivacaine is less. Kokki et al performed a study on 40 children, aged 1- 14 yr, undergoing elective lower abdominal or lower limb surgery levobupivacaine 5 mg.mL -1 at a mean dose of 0.3 mg.kg 1 body weight, and found equivalent clinical efficacy in spinal anaesthesia in children to that of racemic bupivacaine. ,
Ropivacaine 5mg.ml -1 has also been used in some studies and found to be effective and safe in isobaric form. In a study of 93 children 1-17 years of age, Kokki H et al used 0.5mg.kg -1 (upto 20mg) in lateral decubitus position and achieved good block performance. 
Baricity is one of the most significant factors to affect the distribution of the local anaesthetic and hence success and spread of the blockade. The effect of differing degrees of hyperbaricity was evaluated by several workers in paediatric age group. It is not known whether hyperbaric local anaesthetic is better than isobaric in children in contrast to adults where it is proven to be more reliable, safe and effective.  Isobaric bupivacaine has also been used for spinal anaesthesia in children and compared with its hyperbaric form. Kokki H  compared bupivacaine 5 mg.ml -1 , isobaric in saline 0.9% and hyperbaric in 8% glucose, for spinal anaesthesia in 100 children, aged 2-115 months for paediatric day case surgery. The success rate of the block was greater with hyperbaric bupivacaine (96%) compared with isobaric bupivacaine (82%). Intense motor block was associated with adequate sensory block. Spread and duration of sensory block showed a similar wide scatter in both groups. Cardiovascular stability was good in both groups. The study gave an impression of a delayed onset time of spinal block, as most of the nine children who required either fentanyl or a sedative for a mild reaction to skin incision had complete block when transferred to the recovery room after operation.
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 children. Similar success rate, spread and duration of the sensory and motor block are achieved with both baricities of bupivacaine. 
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. 
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.
| 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.
| 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.
Post dural puncture headache (PDPH) is rare in 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  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%.
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 al  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. 
A one year study of 24,409 regional blocks in children by the French-Language Society of Pediatric Anesthesiologists,  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.
| 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.  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. 
| Comparison with general anaesthesia|| |
General anaesthesia may be associated with several life-threatening complications especially in preterm, former preterm, those with co-morbidities like sepsis, necrotising enterocolitis, anaemia (hematocrit<30%), severe respiratory disease like respiratory distress syndrome, bronchopulmonary dysplasias, cystic fibrosis etc. All these neonates are at much higher risk of apnoea, bradycardia and desaturation after general anaesthesia.  Spinal anaesthesia is a safe, reliable and simple technique in a high risk infant. In 1984, Abajian et al sparked an interest in this group and since then all the reports have ascertained this fact. 
In the healthy children, most of the procedures are performed as day-case surgeries like herniotomy, circumcision, minor urological and orthopaedic procedures. Spinal anaesthesia is a very good alternative for such cases were the child can be returned to the family and a lot of stress to the parents is avoided. Since less general anaesthetic drugs including parenteral opioids are used, the risk of postoperative respiratory depression is minimal. The stress response to surgery is also limited and recovery is fast.
Kokki et al studied 100 children for paediatric day-case surgery and found the technique safe and effective.  In his 10 years of experience of paediatric orthopaedic surgery, Bang-Vojdanovski B concluded that spinal anaesthesia is a suitable anaesthetic technique for paediatric surgery.  This method of anaesthesia may avoid the increased incidence of postoperative respiratory complications associated with general anaesthesia.
Intraoperative laryngo and bronchospasm are not uncommon even in healthy infants and children besides episodes of coughing, breath-holding, endotracheal tube obstruction and atelectasis. Moreover, with the increasing incidence of upper respiratory infections, commonly 3-8 times in a year in paediatric age group there will always be a risk of a hyper-reactive airway under general anaesthesia. Besides, there are no preoperative tests feasible which would rule out any mild-moderate respiratory infection in children. Most of the times, the clinician has to rely only on the history provided by the parents. More commonly the symptoms appear only 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.
Kokki et al also conducted a study on forty children, age 2-5 years undergoing paediatric surgery and compared spinal with general anaesthesia.  Time spent in the operation room was shorter in the spinal anaesthesia group because the children were awake and could immediately be transferred. The haemodynamic pattern and respiratory function were stable during spinal anaesthesia. Arterial desaturation (< 90%), vomiting, sore throat and micturition difficulties were the adverse events associated with general anaesthesia. Three patients were restless after spinal anaesthesia.
In a study of 30 cases aged 7 months to 13 years at the Children's National Medical Centre, Washington, open heart surgery was performed under high subarachnoid block along with light general anaesthesia by Finkel JC et al and haemodynamic stability was found to be maintained intra operatively in all cases. 
Spinal anaesthesia has been found to be more cost effective as compared to general anaesthesia. The drugs and equipment required are much less and cheaper besides the length of hospital stay which is also usually shorter. 
Paediatric spinal anaesthesia may have been conceptualized a century ago but its golden years are yet to come. Overall patient safety, feasibility and reliability are the key features of this technique which will only become better with greater use, experience and research.
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