Cerebral blood flow alterations associated with high volume caudal block in infants
Paul Castillo1, Marit Lundblad1, Jakob Forestier1
1Paediatric Perioperative Medicine and Intensive Care, Karolinska University Hospital Stockholm, Sweden; Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
Insights
High-volume caudal blocks in infants can reduce cerebral blood flow. Pausing injections during caudal blocks appears to lessen these adverse effects on cerebral blood flow velocity.
Area of Science:
- Anesthesiology
- Pediatric Anesthesia
- Neuroanesthesia
Background:
- High-volume caudal blocks (1.5 ml/kg) in infants significantly reduce cerebral blood flow velocity (CBFV) and oxygenation.
- This reduction is attributed to rostral cerebrospinal fluid (CSF) movement, leading to increased intracranial pressure.
- The study aimed to investigate the relationship between injected volume and CBFV changes, hypothesizing an inverted volume-pressure curve relationship.
Purpose of the Study:
- To determine the relationship between injected volume and changes in cerebral blood flow velocity (CBFV) during high-volume caudal blocks in infants.
- To test the hypothesis that the volume-CBFV relationship mirrors an inverted intracranial pressure-volume curve.
- To evaluate the impact of injection pauses on CBFV during caudal anesthesia.
Main Methods:
- Fifteen infants (0-6 months) received a 1.5 ml/kg caudal injection of 0.2% ropivacaine in three phases with two pauses.
- Subjects were randomized into five groups based on the timing of pauses.
- Cerebral blood flow velocity (CBFV) was measured using middle cerebral artery Doppler ultrasonography; Vmax, Vmin, and velocity time index were recorded.
Main Results:
- Cerebral blood flow velocity (CBFV) parameters decreased in all infants, with Vmin showing the largest reduction (approximately 50%).
- A nonlinear relationship was observed between the volume of the initial injection phase and CBFV during the first pause.
- A linear relationship existed between the total administered volume and CBFV across all time points; systemic hemodynamics remained stable.
Conclusions:
- Implementing pauses during high-volume caudal block administration appears to mitigate adverse effects on cerebral blood flow velocity.
- This strategy may help attenuate the reduction in CBFV observed with rapid, high-volume injections.
- Further research could explore optimal pause durations and volumes for pediatric caudal anesthesia.
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.
