Spinal anesthesia in infants and children: A one year prospective audit

Abstract

Context and Aims:

Spinal anesthesia though gaining popularity in children, the misconceptions regarding its safety and feasibility can be better known with greater use and experience. The objective of this study was to evaluate the success rate, complications and hemodynamic stability related to pediatric spinal anesthesia.

Materials and Methods:

In this 1-year prospective study, 102 pediatric patients aged 6 months to 14 years undergoing infraumbilical and lower extremity surgery were included. Spinal anesthesia was administered using hyperbaric bupivacaine 0.5% in a dose of 0.5 mg/kg (for child < 5 kg), 0.4 mg/kg (for 5-15 kg), 0.3 mg/kg (for >15 kg) in L4-L5 space under all aseptic precautions after sedation. Demographic data, vital parameters, supplemental sedation, number of attempts for lumbar puncture, sensory-motor block characteristics, and complications were noted.

Results:

Spinal anesthesia was successful in 98 (97.1%) patients. Remaining 4 (3.9%) were failures and were given general anesthesia. Lumbar puncture was successful in first attempt (60 [58.82%]) or 2^nd attempt (42 [41.18%]). There was no significant change in vital parameters. Mean peak sensory level was T 6.35 ± 1.20 (T4-T8). Mean sensory level at the end of surgery was T 8.11 ± 1.42 (T6-T10). Modified Bromage score was 3 in 98 (96.08%) patients. Sensory and motor block recovery was complete in all patients. Mean time to two segment regression was 43.97 ± 10.72 (30-70) min. Mean time to return Bromage score to 0 was 111.95 ± 20.54 (70-160). Mean duration of surgery was 52.5 ± 16.056 (25-95) min. Incidence of complications was minimal with hypotension occurring in 2 (2%) and shivering in 3 (2.9%) patients.

Conclusion:

Pediatric spinal anesthesia is a safe and effective anesthetic technique for lower abdominal and lower limb surgeries of shorter duration (<90 min) with high success rate. Owing to, its early motor recovery, it can be a preferred technique for day case surgeries in the pediatric population.

INTRODUCTION

Regional anesthesia in children was first studied by August Bier in 1899. Since then, spinal anesthesia was practiced for years, and a number of cases were published in 1909-1910.[1,2,3] After some years, it fell into disuse owing to the introduction of various muscle relaxants and inhalational agents. In early 1980s, it was reintroduced as an alternative to general anesthesia (GA), especially in high-risk and preterm infants.

Spinal anesthesia is a useful technique in infraumbilical and lower limb orthopedic surgeries.[4] Infants and children are at an increased risk for GA-related complications.[5,6,7,8] Thus, spinal anesthesia could also be indicated as an alternative to GA, especially in situations such as chronic respiratory disease, potentially difficult airway, and malignant hyperthermia.[9,10,11,12,13,14] Spinal anesthesia in infants has been associated with decreased incidence of hypotension, hypoxia, bradycardia, and postoperative apnea as compared to GA;[15,16,17,18,19] therefore, providing a high-degree of cardiovascular and respiratory stability. An important limiting factor for pediatric spinal anesthesia is duration, which can be prolonged by the addition of opioids and clonidine.[20]

Spinal anesthesia though gaining popularity in infants and children, the misconceptions regarding its overall safety, feasibility, and reliability can only be better known with greater use and research. There is no published study from India that highlights the experience of spinal anesthesia in children regarding its safety, success rate, and complications. This made us design this study in which we had prospectively analyzed the success rate, complications, and hemodynamic stability-related to spinal anesthesia in pediatric patients aged 6 months to 14 years over a period of 1-year.

MATERIALS AND METHODS

After approval of Institutional Ethical Committee this study was conducted in the Department of Anesthesia, MB Hospital attached to RNT Medical College, Udaipur, India. Informed consent was obtained from parents of each patient for participation in the study. All pediatric patients 6 months to 14 years of age group who were given spinal anesthesia for infraumbilical or lower extremity surgery during the 1-year period (1^st May, 2012 to 30^th April, 2013) were included in the study. This resulted in sample size of 102 patients. All patients under study were subjected to detailed preanesthetic evaluation. Patients with a known contraindication to lumbar puncture were excluded.

All patients were not allowed to take solid food for 6 h and clear fluid for 2 h before anesthesia. No overnight premedication was given.

After establishment of intravenous access, all were preloaded with crystalloid solution (ringer lactate, isolyte P) 10 ml/kg. Heart rate, blood pressure, and oxygen saturation were measured and noted as baseline values. Injection atropine 0.01 mg/kg was given as premedication. All children except those who were cooperative and calm were sedated on the operating table before subarachnoid block using ketamine 1 mg/kg, fentanyl 1-2 mcg/kg, or midazolam 0.03 mg/kg IV to provide an immobile patient for lumbar puncture. All patients received spinal anesthesia via midline approach with patients in lateral position under aseptic precautions. Lumbar puncture was performed in L4-L5 interspace using standard 25G or 27G quincke spinal needles (9 cm). After getting free flow of cerebrospinal fluid (CSF) hyperbaric bupivacaine (0.5%) in a dose of 0.5 mg/kg (for child <5 kg), 0.4 mg/kg (for 5-15 kg), 0.3 mg/kg (for >15 kg) was injected in the subarachnoid space. The end of injection was taken as time zero for further data recording. Above-mentioned technique is the usual spinal anesthetic technique followed in children in our institute. However, we did not standardize it for all cases. It was left on the discretion of anesthesiologist conducting the case and data were recorded for this observational study. Sensory level was assessed by lack of response to firm skin pinch to the dermatomal level.[21] Desired peak sensory level was aimed to be T10 for assessing the success rate of spinal anesthesia. Similarly, modified Bromage score[22] (0: Free movement of leg and feet with the ability to raise extended leg, 1: Inability to raise extended leg and knee flexion decreased, 2: Inability to raise or flex knees; flexion of ankle and feet present, 3: Inability to raise leg, flex knee or ankle, move toes) was assessed by the same stimulus (firm skin pinch) given on lower limb (thigh) and modified Bromage score was noted. After 10 min of SAB if the peak sensory level was at least T10 and Bromage score was 3 (complete motor block), surgery was allowed to start. If there was no response to surgical stimuli it was considered as successful spinal block. If the peak sensory level was below T10 and Bromage score <3, the case was classified as failed spinal block. Case was given GA with intubation and was excluded from the study for further data analysis. In all cases carried out under spinal anesthesia, sedation was maintained with propofol infusion at the rate of 50-75 mcg/kg/min. If intraoperative pain or lack of relaxation was complained, supplemental anesthesia was accordingly given, and the case was considered as partial successful block. At the end of surgery, all patients received paracetamol rectal suppository (20 mg/kg) on 12 h basis.

Demographic data, indication, type and duration of surgery and vital parameters were noted. Requirement of supplemental sedation, size of spinal needle, local anesthetic dose used and number of attempts for lumbar puncture were noted. Sensory block characteristics, motor block characteristics and complication related to anesthesia such as vomiting, shivering, postdural puncture headache, and any manifestation suggestive of neurological injury were also recorded. The patients were monitored until full recovery. The data were recorded on the patient's assessment performa and analyzed using MS Excel and IBM SPSS 16.0 (Statistical Package for the Social Sciences).

RESULTS

Demographic data

Mean age of patient was 6.62 ± 3.72 years (6 months to 13 years). Eighty-five (83.3%) patients were males and only 17 (16.7%) were females. Mean weight of the patients was 18.42 ± 7.57 (5-35) kg [Table 1]. Spinal anesthesia was provided for a variety of surgeries [Table 2]. Mean duration of surgery was 52.5 ± 16.056 (20-95) min.

Table 1.

Demographic data (n=102)

Table 2.

Type of surgery (n=102)

Fasting hours, premedication, and sedation

Mean fasting hours were 5.92 ± 0.89 h. Injection atropine 0.01 mg/kg was given as premedication. At the time of entering the operation theatre, 92 (90.2%) patients were conscious and crying. Only 10 (9.8%) patients were conscious and calm, who were older in age (>10 years). On the operation table, almost all the patients (n = 98, 97.1%) received sedative drug to prevent any untoward movement during SAB. Most of the patients were given ketamine either alone (n = 56, 54.9%) or with midazolam (n = 23, 22.5%). Other drugs used were diazepam (n = 1, 1%) and fentanyl (n = 7, 6.9%).

Fluid management

Ringer lactate was the most frequently used fluid. It was given to 99 (97.1%) patients in the operation theater. Mean amount of fluid given before SAB was 163.82 ± 67.61 ml.

Procedure, needle used, local anesthetic drug, and dose

Lumbar puncture was done in lateral position in L4-L5 space using hyperbaric bupivacaine. 27G Quincke spinal needle was used in 83 (81.4%) patients and 25G in remaining 19 (18.6%) patients. Lumbar puncture was successful in first attempt in 60 (58.82%) patients and remaining 42 (41.18%) patient required second attempt.

Vital parameters

There was no significant change in the mean value of systolic blood pressure, diastolic blood pressure, respiratory rate, and oxygen saturation after subarachnoid block at all time periods. Pulse rate showed a significant increase (11.3%) after 5 min of subarachnoid block as compared with baseline. This can be attributed to atropine and ketamine, which were used for premedication and sedation, respectively. However, afterwards mean pulse rate showed no significant change from baseline. Only 2 (2%) patients had a single episode of hypotension after 10 min of SAB, which was successfully managed [Figure 1].

Figure 1.

Vital parameters (n = 102)

Block characteristics

After 10 min of SAB 98 (96.1%) patients achieved desired peak sensory level of T10 and Bromage score of 3. Surgery was completed in all these cases without anesthetic supplementation. The success rate of the study was 96.1%. Remaining 4 (3.9%) cases were classified as a failure and were given GA [Figure 2].

Figure 2.

Outcome of SAB (n = 102)

In successful spinal cases, mean peak sensory level after 10 min of SAB was T 6.35 ± 1.20 (T4-T8) and the median was T6. Mean sensory level at the end of surgery was T 8.11 ± 1.42 (T6-T10) and the median was T8. In all successful SAB the modified Bromage score was 3, which was seen in 98 (96.08%) patients. Mean time to two segment regression was 43.97 ± 10.72 (30-70) min. Mean time to return Bromage to 0 was 111.95 ± 20.54 (70-160) min. Sensory and motor block recovery was complete in all the patients [Table 3].

Table 3.

Block characteristics (n=98)

Complications

Shivering was seen only in 3 (2.9%) patients intraoperatively, which was treated with tramadol 2 mg/kg. Intraoperative hypotension (>20% fall in systolic blood pressure) was seen only in 2 (2%) patients which was treated with fluid and 3 mg mephentermine. No other complication such as bradycardia, nausea/vomiting, or postdural puncture headache was noted.

DISCUSSION

This study was undertaken to evaluate the efficacy and safety of spinal anesthesia in the pediatric population. Spinal anesthesia in children is a safe, cost-effective, single-shot technique and is ideal for day care surgeries. It provides dense and uniformly distributed sensory block with good muscle relaxation. The stress response to surgery is decreased, and recovery is fast following spinal anesthesia.[20]

Adequate premedication is important for smooth regional procedure in children. Various drugs via different routes may be used to achieve a well-sedated child. Analgesia and sedation is important for pediatric spinal anesthesia in order to prevent any untoward movement during lumbar puncture. It may be provided by using low dose intravenous ketamine/propofol or inhalational anesthetics during the procedure. Anticholinergic drugs may be added to decrease any undesired secretions.

In our study, ketamine was used for sedation in the maximum number of patients (n = 56, 54.9%). Other drugs used were midazolam (n = 3, 2.9%), diazepam (n = 1, 1%), fentanyl (n = 7, 6.9%) or a combination of these drugs. Four (3.9%) patients in our study were not given any sedation before SAB because they were comparatively older in age (>10 years) and cooperative. During the intraoperative period sedation was maintained using propofol infusion (50-75 mcg/kg/min) in all patients. Low dose sedation does not mask the failure of the block. It is better to provide supplemental oxygen during sedation.

In a study conducted by Blaise and Roy[23] on pediatric patients aged 7 weeks to 13 years, 4 of 34 patients required GA due to failure of lumbar puncture after two attempts. Sedation prevents movement of the children during lumbar puncture and might have been an important factor for better results of our study.

Ketamine induces dissociative anesthesia causing functional dissociation between cortical and limbic system. Protective airway reflexes are maintained during sedation. Ketamine having a high therapeutic index is a suitable drug for sedation in the pediatric population.[24]

Sedative effects of subarachnoid block itself have also been documented in the literature. Hermanns et al., (2006)[25] conducted a study to evaluate sedation during spinal anesthesia in infants. The presumed mechanism for sedation after SAB is a decreased afferent conduction to reticulo-thalamo-cortical projection pathways which reduces the excitability and the arousal level of brain. Lumbar puncture was performed in all the patients in lateral position. During lateral or sitting position the neck should be in extension as cervical flexion does not provide any benefit in children and in fact, may obstruct the airway during the procedure.[20]

The spinal cord ends at L3 level at birth and reaches L1 by 6-12 months. The dural sac is at the S4 level at birth and reaches S2 by the end of the 1^st 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.[20] In our study, lumbar puncture was successful in 1^st attempt in 60 (58.82%) patients and 2^nd attempt was required in 42 (41.18%) patients. None of the patients required more than two attempts for lumbar puncture, which shows the ease and feasibility of lumbar puncture technique in the pediatric population.

The volume of CSF varies with patient's age. The volume of cerebrospinal fluid CSF is 4 ml/kg, which is double the adult volume. Moreover, in infants half of this volume is in the spinal space, whereas adults have only one-fourth.[20] This significantly affects the pharmacokinetics of intrathecal drugs and explains why larger doses of local anesthetics are required for spinal anesthesia in infants and young children. Among the various drugs approved by Food and Drug Administration for pediatric intrathecal use, 0.5% bupivacaine and ropivacaine are common and popular. Baricity is one of the most significant factors to affect the distribution of the local anesthetic and hence success and spread of the blockade.

Cardiovascular changes related to spinal anesthesia are less common in children than in adults. Children younger than 5-8 years of age have immature sympathetic nervous system and relatively small intravascular volume in the lower extremities and splanchnic system, which limits the venous pooling in this group.[26]

In our study, the desired sensory level of T10 was achieved in 98 (96.1%) patients after 10 min of SAB, and they were considered as successful spinal block. Whereas in 4 (3.9%) patients, T10 level was not achieved and GA was given, and these were considered as failed spinal block. The mean peak sensory level was T 6.35 ± 1.20 and the median was T6. Mean time to two segments regression was 43.97 ± 10.72 (30-70) min. Since the level of surgery was below T10 in all the patients, adequate dermatomal level was present until the end of surgery. Thus, none of the patients required supplemental anesthesia during surgery in our study.

Ahmed et al., (2010)[27] conducted a study on 78 children aged between 2 and 6 years undergoing different type of surgery in the lower part of the body and reported that sensory block showed wide variation of height from T1 to T7, and the median was T4.

In a study conducted by Kokki and Hendolin (2000)[28] to compare hyperbaric bupivacaine 0.5% in 0.9% and 8% glucose solutions for spinal anesthesia in 7-18 years old children, motor block was complete in 53 (96%) patients in group bupivacaine -0.9% glucose solution (n = 55), whereas it was complete in 52 (100%) patients in group bupivacaine -8% glucose solution (n = 52).

It is speculated that the drug uptake is faster in the subarachnoid space in infants owing to proportionally greater blood flow to the spinal cord as compared with adults.[29] With faster drug distribution and elimination, an infant's motor level regression is approximately 5 times faster than in adults. This causes a decreased duration of block. Spinal anesthesia alone for this reason is therefore generally restricted to 1 h duration surgeries only. Duration, however, can be prolonged with the addition of opioids and clonidine.[20]

Shivering was the most frequent complication in our study, which was seen in 3(2.9%) patients and was treated with tramadol 2 mg/kg. Hypotension was seen in 2 (2%) patients and was treated with intravenous crystalloids and mephentermine. No other complications such as bradycardia, nausea, vomiting, PDPH, and urinary retention were noted.

Ahmed et al., (2010)[27] conducted a study to evaluate characteristics of spinal anesthesia on 78 children aged between 2 and 6 years and reported that shivering occurred in five patients and vomiting occurred in one patient. Two patients suffered from hypotension, which was treated with ephedrine and bradycardia was seen in one patient, which was treated with atropine.

CONCLUSION

Owing to high success rate (96.1%) and very low complication rates, our study breaks the misconception regarding the feasibility and safety of pediatric spinal anesthesia. Due to its early motor recovery and no risk of respiratory depression and pulmonary aspiration it can be a preferred technique for daycare surgeries.