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Original Article

Spinal anaesthesia in full-term infants of 0-6 months: are there any differences regarding age?

Köroğlu, A.; Durmuş, M.; Toğal, T.; Özpolat, Z.; Ersoy, M. Ö.

Author Information
European Journal of Anaesthesiology: February 2005 - Volume 22 - Issue 2 - p 111-116
doi: 10.1017/S0265021505000219

Abstract

Spinal analgesia has been described for infants particularly premature and high-risk babies undergoing minor operative procedures. In the 1980s, there was a resurgence in its popularity for high-risk ex-premature infants as an alternative to general anaesthesia [1,2]. Giaufre and colleagues [3] reported the percentage of central blocks to be 61.5% among children in whom regional analgesia was performed, 2.1% of which were spinal blocks. Their study showed that nearly 75% of spinal analgesia was performed on ex-premature babies and high-risk infants younger than 6 months. Currently, despite its relatively low usage, spinal analgesia is preferred in full-term infants for outpatient anaesthesia in many centres. Infants <1 month, those between 1 and 3 months, and those >3 months of age have different features related to developmental physiology, anatomy and pharmacology of local anaesthetics [4].

The aim of this preliminary open study was to report our experiences with spinal analgesia using 0.5% hyperbaric bupivacaine solution without epinephrine at doses of 0.4-0.5 mg kg−1 regarding the effectiveness, complications and safety, and also to determine whether spinal analgesia is equally effective in full-term infants of a range of ages undergoing elective inguinal hernia repair.

Methods

After approval by the Institutional Ethics Committee and parental informed consent, 68 full-term infants aged <6 months and undergoing elective unilateral or bilateral inguinal hernia repairs were included in the study in a prospective and consecutive manner. Patients with coagulopathies, systemic infections, meningitis, hypovolaemia, infection at the puncture site, intracranial hypertension, cerebrospinal fluid drain or congenital anomalies of the lower spine were excluded. Infants were distributed into three groups regarding their ages: Group I (<1 month, n = 20), Group II (1 month or more but <3 months, n = 26) and Group III (3 months or more but <6 months, n = 22).

Patients were fasted for 4 h before surgery and no premedication was used. They were brought to the previously warmed operating room (25°C). During spinal block and operation, infants were kept continuously warmed by a radiant heater. Standard monitoring was undertaken using electrocardiography, non-invasive blood pressure (BP) and pulse oximetry. A secure venous cannula was inserted into a vein on the dorsum of either hand following mask induction with gradually increasing sevoflurane concentration in 2 L min−1 of 50% O2/air mixture. End-tidal sevoflurane concentration was adjusted to 3% in all patients. The spinal block was then performed by an experienced anaesthesiologist (AK) with the patient in the lateral decubitus position and the neck extended to prevent airway occlusion. A maximum of four lumbar puncture attempts were made. No intravenous (i.v.) volume loading was administered prior to the onset of anaesthesia. The infant's back was cleansed with iodophor solution, and a skin wheal raised using 1% procaine. All lumbar punctures were performed with disposable 26-G, 2.5-cm disposable stiletted spinal needles (Atraucan; B. Braun, Melsungen AG, Germany) at the most readily palpable interspace below the third lumbar vertebra. After observing free flow of cerebrospinal fluid, 0.5% hyperbaric bupivacaine (Marcaine spinal; Astra, Sodertalje, Sweden) without epinephrine was injected into the subarachnoid space. Bupivacaine 0.5 mg kg−1 was used for infants 5 kg or less and 0.4 mg kg−1 for infants over 5 kg. The spinal needle was removed immediately after administering the anaesthetic solution. No attempt was made to aspirate cerebrospinal fluid. Five percent of dextrose (i.v.) in 0.225% saline was administered at a dose of 5.0 mL kg−1 h−1 using an infusion pump following spinal analgesia. Attention was paid to prevent any change in patient position (including placement of the electrocautery grounding pad) once the infants were positioned supine for surgery.

Sedation was not given routinely. Infants remained awake, alert or asleep [5], spontaneously breathing and receiving low flow 100% oxygen by face mask at 0.5-1 L min−1. Infants were comforted whenever needed with a nipple containing 5% glucose solution to minimize signs of restlessness such as upper extremity movement and/or crying during operation. However, if the surgical procedure was affected by movement of the infant, a 0.5-1 mg kg−1 bolus of propofol was given i.v. End-tidal carbon dioxide concentration was measured (Drager® Cato Edition, Lubeck, Germany) via a face mask.

Heart rate (HR), mean arterial pressure, respiratory rate and oxygen saturation (SPO2) were recorded before any intervention (baseline) and thereafter at 5 min intervals following spinal analgesia. The infants were observed for cessation of lower extremity movement. Duration of analgesia was defined as the time from injection of the hyperbaric bupivacaine solution to the resumption of movements of the lower extremities. A finger pinch was used to determine the sensory level at 5 min intervals after the onset of spinal analgesia until the return of leg movements. Increased HR (>20% of baseline values) and purposeful movement of the upper extremity to finger pinch were determined as positive responses. Surgical procedures were started after sensory block had reached T10.

Following surgery, the infants were transported to the recovery room and monitored by electrocardio-graphy, non-invasive BP and pulse oximetry. After resumption of lower extremity movements and after the level of cutaneous analgesia had decreased to T12, the patients were transferred from the recovery room to the ward. Oral feeding was resumed within 2 h. Infants were discharged from the hospital following observation of normal urination, defaecation and absence of restlessness during oral feeding.

Operation and hospitalization times, analgesic requirement and complications, such as vomiting, urinary retention and constipation were recorded. Analgesics were not administered during or shortly after the induction in order to determine duration and frequency of analgesic requirement. Parents were instructed about the use of a modified objective pain scale to assess postoperative pain and analgesia requirement. This was an observational pain scoring system using five criteria: crying, agitation, movement, posture and localization. Each criterion was scored from 0 to 2 giving a total score between 0 and 10 [6]. Infants were assessed in the ward and after discharge only when restlessness was present. When pain score was above four, analgesia was provided with 10-15 mg kg−1 paracetamol rectally. Parents were requested to inform the hospital by phone after discharge if the pain score rose above four.

Data are reported as mean (range) ± SD. Parametric data were analysed using one-way ANOVA to compare the mean values of groups with post hoc analysis for multiple comparisons using the Tukey test. Differences within groups for repeated measurements were analysed with the paired t-test. Non-parametric data were compared using the Χ2-test. P < 0.05 was considered as statistically significant.

Results

The characteristics of the study groups are shown in Table 1. Patients' weight, doses of bupivacaine, durations of anaesthesia and surgery, time to begin the operation and hospitalization time were not statistically different among groups (Table 1). Two infants were considered as high risk. One of them had a ventricular septal defect and another had Down's syndrome. All other infants were ASA I.

Table 1
Table 1:
Patient characteristics data, surgical and anaesthetic details.

Maximum cutaneous analgesia was obtained significantly faster in Group I compared to other two groups (P < 0.05). Mean level of maximum cutaneous analgesia and time concerning the loss of bilateral leg movement were not statistically different among groups (Table 2).

Table 2
Table 2:
Results of spinal anaesthesia.

Five of the 68 patients (7.8%) had difficult lumbar punctures which required more than three attempts (Table 2). There were no ‘dry taps’ or ‘bloody taps’ in any patients. Failure in obtaining adequate spinal analgesia was not different among groups (Table 2). In four of the 68 (5.9%) infants insufficient analgesia or failure of subarachnoid block occurred. In three of these four infants, spinal analgesia was initially successful, but the level of analgesia (T10) was insufficient for pain control in response to traction on the hernial sac. The spread of local anaesthetics to the external spinal canal may be the reason for insufficient block. In these patients, anaesthesia was supplemented with inhalational mask anaesthesia and maintained with 1-1.5% sevoflurane in 2 L min−1 50% N2O/O2. Spinal block failed in the fourth infant and caudal block was performed (Table 2). Spinal analgesia without i.v. supplementation provided significantly better operating conditions in Group I (95%) than the other two groups (P < 0.05) (Table 2).

Mean arterial pressure and HR decreased significantly after spinal analgesia in all groups (P < 0.05) (Table 3). Mean arterial pressure decreased to 10%, 20% and 15% in Groups I, II and III, respectively. Mean arterial pressure before spinal analgesia was significantly different among groups and after spinal analgesia it was significantly higher in Group III when compared to the other two groups. The decreases in HR in Groups I, II and III were respectively, 14%, 16% and 17% (Table 3). No infant developed haemodynamic instability throughout the investigation even with spinal analgesia as high as C6 to T3.

Table 3
Table 3:
Haemodynamic and respiratory changes.

Respiratory rate decreased significantly following spinal analgesia by 15%, 19% and 20% in Groups I, II and III, respectively (P < 0.05). In Group I, the decrease in respiratory rate was lower than the other groups (Table 2). The respiratory rate was significantly different before and after spinal analgesia among the groups. Neither apnoea nor periodic breathing was observed during intra- and postoperative periods. ETCO2 was within normal limits, and oxygen saturation remained 97-100% for all subjects.

Intra- and postoperative complications were not statistically different among groups (Table 4). In one infant, hiccup started intraoperatively, but soon resolved spontaneously. Vomiting was seen in four infants in the postoperative period possibly due to overfeeding. No postoperative analgesia was needed in Group I and there was significant difference between Groups I and III (P < 0.05). The time for first analgesic need was not different among groups (Table 4). All parents reported no irritability and difficulty of feeding in the sitting position for their infants following spinal analgesia.

Table 4
Table 4:
Complications and analgesic requirements.

Discussion

The objective of anaesthesia for inguinal hernia repair in infants is to provide analgesia, relaxation, minimal physiological disturbance, rapid recovery and shorter hospital stay [7]. Spinal analgesia has many advantages: cerebrospinal fluid flow can indicate the exact placement of the needle, the onset is rapid, muscular relaxation is more complete and the risk of local anaesthetic toxicity is minimal. The principal disadvantages of spinal analgesia in infants were reported as technical difficulty, restlessness and less predictability of the spread and duration of analgesia [7,8]. General, lumbar and caudal epidural analgesia may be preferred in these cases. After general anaesthesia laryngeal damage, aspiration pneumonitis and apnoeic spells may occur. Lumbar and caudal epidural analgesia in younger infants and neonates are not as easy as might be expected due to an increased risk of misplacement of the needle outside the epidural space. There may also be inadvertent intrathecal or intravascular injection and insufficient muscle relaxation when compared to spinal analgesia as well as delay in the onset of analgesia [3,9,10].

We obtained adequate (T3 level) analgesia using doses of bupivacaine 0.5% 0.5 mg kg−1 for infants <5 kg or 0.4 mg kg−1 for infants >5 kg. These doses provided enough anaesthesia time but lasted <55 min in our patients. The dose of local anaesthetic agent needed for spinal analgesia in small neonates should be relatively larger and the duration of analgesia should be briefer than that in older subject [11,12]. Different studies have been performed to determine the doses and duration of various local anaesthetics for spinal analgesia in especially high-risk and premature infants. Parkinson and colleagues [13] concluded that spinal analgesia using hyperbaric 0.5% bupivacaine without epinephrine at a dose of 0.3 mg kg−1 provided adequate anaesthesia lasting approximately 75 min or less in infants. Sukhani [11] recommended 0.8-1 mg kg−1 of bupivacaine to obtain a suitable level of spinal analgesia for inguinal hernia repair. However, they reported that bupivacaine doses of 1 mg kg−1 caused high spinal blockade which required intervention in 2.2%. Williams and colleagues [8] used a dose of bupivacaine 0.5% 1 mg kg−1 in inguinal hernia repair for ex-premature infants. Polaner and colleagues [4] recommended bupivacaine at doses of 0.75-1 mg kg−1 to obtain adequate analgesia in inguinal hernia repair operation for infants and neonates. Dalens [14] recommended bupivacaine 0.5% 0.5 mg kg−1 for infants between 2 and 5 kg of weight and 0.4 mg kg−1 for infants weighting >5 kg. The amount of local anaesthetic was reduced in patients >5 kg, as cerebrospinal fluid volume to body weight ratio is less in patients over 5 kg than those under 5 kg [14,15]. We concluded that these doses were suitable for inguinal hernia repair lasting <54 min in full-term infants aged <6 months.

We found the technique to be simple and quick to perform during inhalational mask anaesthesia and provided adequate surgical conditions without additional sedation for full-term infants aged <1 month undergoing inguinal hernia repair. Based on the higher need for i.v. sedation to prevent restlessness during surgery and the higher postoperative analgesic requirement in infants between 1 and 6 months, the advantages of spinal analgesia are reduced in these groups of patients and therefore this technique may not be suitable for older infants.

Regional analgesia in children was performed under light general anaesthesia in 89% of patients, under sedation in 6% and when fully conscious in 5% [2]. According to Williams and colleagues [8] this technique was associated with a clinically significant failure rate and insufficient anaesthesia time for surgery and also required considerable expertise. They reported a 28% failure rate of lumbar puncture in awake ex-premature infants. Webster and colleagues [7] described a 6.4% failure rate in lumbar puncture in awake infants and 32% restlessness during surgery in high-risk infants. Sartorelli and colleagues [16] reported a 4% failure rate and a 6.8% supplementation requirement in high-risk infants. In the study by Harnik and colleagues [17], 4.8% of spinal blocks in awake infants were unsuccessful and 23.8% of premature infants needed i.v. supplemental anaesthesia. Frumiento and colleagues [18] found that the rate of adequate spinal analgesia after administration of the first dose and the i.v. supplementation requirement were 91.4% and 12.9%, respectively in preterm infants. Operating conditions become unsatisfactory when patients cry during the operation. Thus, this technique may need to be abandoned or supplemented with sedatives or anaesthetic agents [7,8]. After difficult lumbar puncture, the quality and duration of spinal analgesia were often unreliable despite initial positive evidence of subarachnoid block [1]. To relieve these obstacles, we performed spinal analgesia under inhalational mask anaesthesia. In our study, unsuccessful spinal block was not seen and i.v. supplementation with propofol was lower in Group I compared with previous studies. Our failure rate and supplementary i.v. sedation requirement in Groups II and III were higher than Group I, therefore this result was different from previous studies in the literature. The restlessness and irritability during surgery in infants of >1 month of age may be related to an exaggerated response to fasting and an unfamiliar environment.

No cardiovascular instability was seen even with high blocks (C6-T3) in any of the groups in our study. Oberlander and colleagues [19] pointed out that infants younger than 6-yr old tolerated high thoracic spinal analgesia with minimal changes in HR and arterial pressure. Parkinson and colleagues [13] reported that HR and systolic BP decreased by <20% of preoperative values in sensory blocks at the T2-T4 level. Harnik and colleagues [17] found no cardiovascular instability in infants who underwent spinal block. Oberlander and colleagues [19] stated that neither HR nor arterial pressure changed in infants in response to C7-T4 spinal analgesia in spite of the absence of volume loading and reported that age-related differences between children and adults in response to sympathectomy might be due to the poorly developed sympathetic nervous system in infants and small children. Having already demonstrated the safety of spinal analgesia, acute volume loading or i.v. atropine were not used in our study [19]. In our study, decreases in HR and mean arterial pressure after spinal analgesia may be related to the higher baseline values that we obtained in our unpremedicated patients. Cardiovascular responses to spinal analgesia in our patients were similar to previous studies but these responses were fewer in Group I than in the other groups.

Oberlander and colleagues [19] and Gingrich [20] reported that there were no significant changes in transcutaneous carbon dioxide or arterial oxygen saturation with sensory block to C7-T4. Also decreases in respiratory rate after spinal analgesia may be related to the higher baseline values. In our study, a decrease in respiratory rate was observed in all groups; however the decrease was lowest in Group I. We also demonstrated that oxygen saturation and ETCO2 levels were maintained within normal limits even with a higher level of sensory block (C6-T3).

Giaufre and colleagues [3] reported significantly more frequent complications and less morbidity in full-term infants aged 1-6 months receiving central blocks other than spinal analgesia. Sartorelli and colleagues [16] reported 3.8% of the postoperative complication rate in high-risk infants. In some studies complications of spinal analgesia have been reported such as high block requiring intervention and meningitis [15,21]. In our study, no important intra- or postoperative complication occurred.

In conclusion, spinal analgesia using 0.5% hyperbaric bupivacaine at doses of 0.4-0.5 mg kg−1 did not cause haemodynamic and respiratory instability in infants aged <6 months. Despite perfect performance of spinal analgesia in full-term infants aged below 1 month undergoing inguinal hernia repair, adequate quality of anaesthesia in infants between 1 and 6 months was not observed. However, this study was not double blind, randomized or controlled and further studies are needed.

References

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Keywords:

ANAESTHESIA; spinal; ANAESTHETICS; LOCAL; bupivacaine; AGE GROUPS; infants; SURGICAL PROCEDURES; OPERATIVE; inguinal hernia repair

© 2005 European Society of Anaesthesiology