Cerebral blood flow alterations associated with high volume caudal block in infants.

BACKGROUND: High-volume (1.5 ml kg-1) caudal block in infants results in major reductions of cerebral blood flow velocity (CBFV) and cerebral oxygenation, caused by rostral CSF movement which increases intracranial pressure. The primary aim of this study was to determine the relationship between injected volume and CBFV changes. We hypothesised that this volume-blood flow relationship would have a similar albeit inverted shape to the well-known intracranial pressure volume-pressure curve. METHODS: Fifteen subjects, age 0-6 months, mean (range) weight 4.9 (2.1-6.4) kg, were studied. A 1.5 ml kg-1 caudal injection of 0.2% ropivacaine was administered in three phases separated by two pauses. Subjects were randomised into five groups, in whom the pauses were implemented at different pre-set proportions of the total injected volume. Middle cerebral artery Doppler ultrasonography was used for CBFV measurements (Vmax, peak CBF velocity; Vmin, lowest CBF velocity; velocity time index). Mean flow velocity, pulsatility index, and resistivity index were calculated, and haemodynamic parameters were recorded. RESULTS: CBFV parameters decreased in all patients. The most affected parameter, Vmin, was reduced by ∼50% (range 15-68%) compared with baseline. There was a nonlinear relationship between the volume of the first phase injection and the CBFV measurement during the first pause. Across all time points, there was a linear relationship between volume administered and CBFV. Systemic haemodynamic parameters remained stable throughout the study. CONCLUSIONS: Injection pauses appear to attenuate adverse CBFV increases during administration of a high-volume caudal block.

Alpha-2 adrenoceptor agonists as adjuncts to peripheral nerve blocks in children: a meta-analysis.

BACKGROUND: Adult meta-analyses have verified that adjunct use of alpha-2 adrenoceptor agonists (A2AA) together with local anesthetics (LA) will prolong the duration of peripheral nerve blocks. The standard use of A2AAs for peripheral nerve blockade has recently been recommended also in children, but the evidence base in support of this suggestion has to date been equivocal. The purpose of this meta-analysis was to produce evidence-based data regarding the effect in children. METHODS: Following a thorough literature search, five randomized controlled trials were included in a meta-analysis. Raw data from all studies were gathered and aggregated into patients randomized to receive plain LA (Group PLA) or LA mixed with either adjunct clonidine or dexmedetomidine (Group ADJ). The main outcome parameter was block duration (time to first administration of supplemental analgesic based on predetermined pain scores) analyzed by survival statistics. The total number of supplemental analgesic doses during the first 24 postoperative hours and serious side effects were included as secondary outcomes. RESULTS: Pooling of the study data generated 141 patients in Group PLA and 142 patients in Group ADJ (overall n = 283; age: 0.8-13 years; weight 8-47 kg). Block duration was significantly prolonged (9.75 h vs 3.75 h) compared to the use of plain LA. Survival statistics verified a beneficial effect of using adjunct A2AAs [the log rank (Mantel-Cox) test (P = 0.0078), Gehan-Breslow-Wilcoxon test (P = 0.0027), and hazard ratio (1.653; 95% CI: 1.142 to 2.395)]. The number of patients that needed ≥ 2 doses of supplemental analgesics was higher in Group PLA (n = 19) compared to Group ADJ (n = 6) (P = 0.0088). No serious side effects were reported. CONCLUSION: This meta-analysis provides evidence-based support for the use of adjunct alpha-2 adrenoceptor agonists when performing peripheral nerve blocks in children.

Adjunct analgesic drugs to local anaesthetics for neuroaxial blocks in children.

PURPOSE OF REVIEW: This article reviews various adjunct drugs used in the context of neuroaxial blocks in children and to provide a literature and evidence-based suggestion for the rational use of such adjuncts. RECENT FINDINGS: Contrary to plain local anaesthetics, preservative-free morphine and clonidine, ketamine in neonatal rodents has been found to enhance apoptosis in the spinal cord. Dexmedetomidine has been shown to be equally effective as clonidine as an adjunct to caudal blocks. Systemic dexamethasone is as effective as if it is co-administered together with the local anaesthetic in the context of neural blockade. SUMMARY: Alpha-2 adrenoceptor agonists currently represent the most versatile and well-tolerated adjunct for neuroaxial blockade in children. Preservative-free morphine may be indicated in certain situations but the risk for respiratory depression and other disturbing side-effects must be taken into account. Preservative-free ketamine is an effective adjunct to caudal blockade in children but the use should be restricted to children older than 1 year of age. All other drugs must still be regarded as experimental and should not be used outside clinical trials.

Dexmedetomidine as adjunct to ilioinguinal/iliohypogastric nerve blocks for pediatric inguinal hernia repair: an exploratory randomized controlled trial.

BACKGROUND: Adult meta-analysis has identified dexmedetomidine as a potentially useful adjunct to prolong the duration of peripheral nerve blocks. However, no data exist regarding the adjuvant use of dexmedetomidine in the setting of pediatric peripheral nerve blocks. METHODS: Using a prospective, randomized, double-blind design, children (1½-8 years, ASA 1-2) scheduled for outpatient inguinal hernia repair were randomized to receive either an ultrasound-guided ilioinguinal/iliohypogastric nerve block (IINB) with plain ropivacaine 0.197% (Group LA; n = 21) or ropivacaine 0.197% with adjunct dexmedetomidine 0.3 µg·kg(-1) (Group LAD; n = 22). The primary endpoint of the study was time to first postoperative administration of supplemental analgesia (FPASA) triggered by a pain score ≥4 (CHIPPS or NRS scale). Intention-to-treat (ITT) analysis was decided as the primary statistical analysis of the data. RESULTS: The median time to FPASA was prolonged by 88% following the use of adjunct dexmedetomidine (4.0 and 7.6 h in group LA and LAD, respectively) (P = 0.0717). Patients in Group LA displayed a significantly higher number of patients with a CHIPPS score ≥4 in the PACU (7 vs 0; P = 0.0029) as well as a higher incidence of PAED (4 vs 0; P = 0.0485) when compared to patients in Group LAD. No adverse events were recorded in any of the study groups. CONCLUSIONS: The use of dexmedetomidine as an adjunct to an IINB resulted in reduced incidences of CHIPPS pain scores ≥4 and PAED scores of ≥11 during early recovery following pediatric inguinal hernia repair. In addition, the use of adjunct dexmedetomidine was associated with a prolongation of the period to first supplemental analgesia demand. The results of the present exploratory study must be viewed as preliminary and need further validation by future larger sized studies and/or meta-analysis.

EEG response to a high volume (1.5 mL/kg) caudal block in infants less than 3 months.

INTRODUCTION: The substantial compression of the dural sac and the subsequent cranial shift of cerebrospinal fluid caused by a high-volume caudal block has been shown to significantly but transiently reduce cerebral blood flow. The aim of the present study was to determine whether this reduction in cerebral perfusion is significant enough to alter brain function, as assessed by electroencephalography (EEG). METHODS: Following ethics approval and parental informed consent, 11 infants (0-3 months) scheduled to undergo inguinal hernia repair were included in the study. EEG electrodes (using nine electrodes according to the 10-20 standard) were applied following anesthesia induction. Following a 5 min baseline period, a caudal block was performed (1.5 mL/kg), whereafter the EEG, hemodynamic, and cerebral near-infrared spectroscopy responses were followed during a 20 min observation period that was divided into four 5 min segments. Special attention was given to alterations in delta power activity since this may indicate cerebral ischemia. RESULTS: All 11 infants displayed transient EEG changes, mainly represented by increased relative delta power, during the initial 5-10 min postinjection. The observed changes had returned close to baseline values 15 min postinjection. Heart rate and blood pressure remained stable throughout the study. CONCLUSION: A high-volume caudal block appears to increase intracranial pressure, thereby reducing cerebral blood flow, to the extent that it transiently will affect cerebral function as assessed by EEG (increased delta power activity) in approximately 90% of small infants. TRIAL REGISTRATION NUMBER: ACTRN12620000420943.

Segmental distribution of high-volume caudal anesthesia in neonates, infants, and toddlers as assessed by ultrasonography.

BACKGROUND: The aim of this prospective, age-stratified, observational study was to determine the cranial extent of spread of a large volume (1.5 ml·kg(-1) , ropivacaine 0.2%), single-shot caudal epidural injection using real-time ultrasonography. METHODS: Fifty ASA I-III children were included in the study, stratified in three age groups; neonates, infants (1-12 months), and toddlers (1-4 years). The caudal blocks were performed during ultrasonographic observation of the spread of local anesthetic (LA) in the epidural space. RESULTS: A significant inverse relationship was found between age, weight, and height, and the maximal cranial level reached by 1.5 ml·kg(-1) of LA. In neonates, 93% of the blocks reached a cranial level of ≥Th12 vs 73% and 25% in infants and toddlers, respectively. Based on our data, a predictive equation of segmental spread was generated: Dose (ml/spinal segment) = 0.1539·(BW in kg)-0.0937. CONCLUSIONS: This study found an inverse relationship between age, weight, and height and the number of segments covered by a caudal injection of 1.5 ml·kg(-1) of ropivacaine 0.2% in children 0-4 years of age. However, the cranial spread of local anesthetics within the spinal canal as assessed by immediate ultrasound visualization was found to be in poor agreement with previously published predictive equations that are based on actual cutaneous dermatomal testing.

Ultrasound-guided infrapatellar nerve block for anterior cruciate ligament repair: a prospective, randomised, double-blind, placebo-controlled clinical trial.

BACKGROUND AND OBJECTIVES: We have previously described an ultrasonography-guided technique to block the infrapatellar nerve that is associated with an extended duration of anaesthesia. The aim of the present study was to investigate the clinical usefulness of this new technique in patients undergoing arthroscopy-assisted anterior cruciate ligament repair. METHODS: Using a prospective, double-blind and placebo-controlled study design, 64 patients were randomised to get an active infrapatellar nerve block (IPNB; 10 ml levobupivacaine 0.5%; n = 31) or a sham block with isotonic saline (n = 33) as a complement to a standardised anaesthetic and analgesic regimen. Pain was recorded hourly and the proportion of patients with a pain intensity of more than 3 (numeric rating scale 0-10) during 12-24 postoperative hours was chosen as the primary end-point of the study. Duration of the block, numbers of hours spent sleeping and other secondary parameters were also recorded. RESULTS: The proportion of patients with a pain score of higher than 3 at rest was significantly lower in patients receiving an IPNB during postoperative hours 16-24 (P = 0.0117) as well as on muscular activity during postoperative hours 16-24 (P = 0.0039). Median block duration was 23 h (95% confidence interval 19-24 h). A significantly larger proportion of patients were asleep during the time period 13-24 h after surgery in patients given active treatment as compared to sham block (P < 0.0269). CONCLUSION: Adjunct use of an ultrasound-guided block of the infrapatellar nerve is associated with improved pain relief and an increased number of sleep hours after arthroscopy-assisted anterior cruciate ligament repair.

Ultrasound versus landmark-based technique for ilioinguinal-iliohypogastric nerve blockade in children: the implications on plasma levels of ropivacaine.

BACKGROUND: Ilioinguinal-iliohypogastric nerve blockade (INB) is associated with high plasma concentrations of local anesthetics (LAs) in children. Ultrasonographic guidance enables exact anatomical administration of LA, which may alter plasma levels. Accordingly, we compared plasma levels of ropivacaine after ultrasonographic versus landmark-based INB. METHODS: After induction of general anesthesia, 66 children (8-84 mo) scheduled for inguinal hernia repair received INB with 0.25 mL/kg of ropivacaine 0.5% (1.25 mg/kg) either by a landmark-based (n = 31) or by an ultrasound-guided technique (n = 35). Ropivacaine plasma levels were measured before (0) and 5, 10, 20, and 30 min after the LA injection, using high-performance liquid chromatography. Maximum plasma concentrations (C(max)), time to C(max) (t(max)), the absorption rate constant (k(a)), the speed of rise of the plasma concentration at Time 0 (dC(0)/dt), and area under the curve value (AUC) were determined. RESULTS: The ultrasound-guided technique resulted in higher C(max) (sd), k(a), dC(0)/dt, and AUC values and shorter t(max) compared with the landmark-based technique (C(max): 1.78 [0.62] vs 1.23 [0.70] microg/mL, P < 0.01; k(a): 14.4 [10.7] vs 11.7 [11.4] h(-1), P < 0.05; dC(0)/dt: 0.26 [0.12] vs 0.15 [0.03] microg/mL . min, P < 0.01; AUC: 42.4 [15.9] vs 27.2 [18.1] microg . 30 min/mL, P < 0.001; t(max): 20.4 [8.6] vs 25.3 [7.6] min, P < 0.05). CONCLUSIONS: The pharmacokinetic data indicate faster absorption and higher maximal plasma concentration of LA when ultrasound was used as a guidance technique for INB compared with the landmark-based technique. Thus, a reduction of the volume of LA should be considered when using an ultrasound-guided technique for INB.