Harald Willschke

Ultrasonographic Guidance Improves the Success Rate of Interscalene Brachial Plexus Blockade

Background and Objectives: The use of ultrasonography in regional anesthetic blocks has rapidly evolved over the past few years. It has been speculated that ultrasound guidance might increase success rates and reduce complications. The aim of our study is to compare the success rate and quality of interscalene brachial plexus blocks performed either with direct ultrasound visualization or with the aid of nerve stimulation to guide needle placement. Methods: A total of 160 patients (American Society of Anesthesiologists physical status classification I‐III) scheduled for trauma‐related upper arm surgery were included in this randomized study and grouped according to the guidance method used to deliver 20 mL of ropivacaine 0.75% for interscalene brachial plexus blockade. In the ultrasound group (n = 80), the brachial plexus was visualized with a linear 5 to 10 MHz probe and the spread of the local anesthetic was assessed. In the nerve stimulation group (n = 80), the roots of the brachial plexus were located using a nerve stimulator (0.5 mA, 2 Hz, and 0.1 millisecond bandwidth). The postblock neurologic assessment was performed by a blinded investigator. Results: Sensory and motor blockade parameters were recorded at different points of time. Surgical anesthesia was achieved in 99% of patients in the ultrasound vs 91% of patients in the nerve stimulation group (P < .01). Sensory, motor, and extent of blockade was significantly better in the ultrasound group when compared with the nerve stimulation group. Conclusions: The use of ultrasound to guide needle placement and monitor the spread of local anesthetic improves the success rate of interscalene brachial plexus block.

Ultrasonographic-Guided Ilioinguinal/Iliohypogastric Nerve Block in Pediatric Anesthesia: What is the Optimal Volume?

Recently, our study group demonstrated the usefulness of ultrasonographic guidance in ilioinguinal/iliohypogastric nerve blocks in children. As a consequence, we designed a follow-up study to evaluate the optimal volume of local anesthetic for this regional anesthetic technique. Using a modified step-up-step-down approach, with 10 children in each study group, a starting dose of 0.2 mL/kg of 0.25% levobupivacaine was administered to perform an ilioinguinal/iliohypogastric nerve block under ultrasonographic guidance. After each group of 10 patients, the results were analyzed, and if all blocks were successful, the volume of local anesthetic was decreased by 50%, and a further 10 patients were enrolled into the study. Failure to achieve a 100% success rate within a group subjected patients to an automatic increase of half the previous volume reduction to be used in the subsequent group. Using 0.2 and 0.1 mL/kg of 0.25% levobupivacaine, the success rate was 100%. With a volume of 0.05 mL/kg of 0.25% levobupivacaine, 4 of 10 children received additional analgesia because of an inadequate block. Therefore, according to the protocol, the amount was increased to 0.075 mL/kg of 0.25% levobupivacaine, where the success rate was again 100%. We conclude that ultrasonographic guidance for ilioinguinal/iliohypogastric nerve blocks in children allowed a reduction of the volume of local anesthetic to 0.075 mL/kg.

Ilioinguinal/iliohypogastric blocks in children: where do we administer the local anesthetic without direct visualization?

BACKGROUND:Ultrasonographic observation of peripheral nerve blocks enables direct visualization of the spread of local anesthetic around the targeted nerves. Similarly, ultrasonography may be used to determine the site of local anesthetic placement when landmark-based techniques are used. We performed a study to determine the actual location of local anesthetic when ilioinguinal/iliohypogastric nerve blocks are performed using landmark-based techniques in children in an attempt to explain a failed block. METHODS:After induction of general anesthesia (1 minimum alveolar anesthetic concentration halothane and laryngeal mask airway), 62 children scheduled for inguinal surgery received an ilioinguinal/iliohypogastric nerve block based on standard anatomical landmarks. Ultrasonography was then used to determine the actual location of local anesthetic placement. The anesthesiologist performing the block was blinded to the ultrasonographic investigation. Successful blocks were recorded either when the local anesthetic surrounded the nerves or were based on clinical signs after skin incision. RESULTS:In 14% of the blocks, the local anesthetic was administered correctly around the nerves resulting in successful blocks. In the remaining 86%, the local anesthetic was administered in adjacent anatomical structures (iliac muscle 18%, transverse abdominal muscle 26%, internal oblique abdominal muscle 29%, external oblique abdominal muscle 9%, subcutaneous 2%, and peritoneum 2%), and 45% of these blocks failed. CONCLUSION:Accurate placement of local anesthetic around the ilioinguinal/iliohypogastric nerves in children is seldom possible when landmark-based techniques are used. In the majority of patients, the local anesthetic was inaccurately placed in adjacent anatomical structures with unpredictable block results.

Fifteen years of ultrasound guidance in regional anaesthesia: Part 2—Recent developments in block techniques

The use of ultrasound guidance for regional anaesthesia has gained enormous popularity in the last 10 yr. The first part of this review article provided information on safety, technical developments, economic aspects, education, advantages, needle guidance techniques, and future developments in ultrasound. The second part focuses on practical and technical details of individual ultrasound-guided nerve blocks in adults. We present a comprehensive review of the relevant literature of the last 5 yr with a commentary based on our own clinical experience in order to provide information relevant to patient management. Upper limb blocks, including interscalene, supra- and infraclavicular, and axillary approaches, are described and discussed. For the lower limb, psoas compartment, femoral, obturator, sciatic, and lateral cutaneous nerve blocks are described, as are some abdominal wall blocks. The potential role of ultrasound guidance for neuraxial block is addressed. The need for further large-scale studies of the role of ultrasound is emphasized.

Does regional anaesthesia really improve outcome

In recent decades, a number of studies have attempted to determine whether regional anaesthesia offers convincing benefits over general anaesthesia. However, today we interpret meta-analyses more carefully, and it remains unclear whether regional anaesthesia reduces mortality. However, regional anaesthesia offers superior analgesia over opioid-based analgesia, and a significant reduction in postoperative pain is still a worthwhile outcome. Recent developments in technical aspects of regional anaesthesia have the potential to provide significant advantages for many patients in all age groups. Moreover, studies focusing on specific outcomes have shown benefits for regional anaesthesia used for surgery and postoperative analgesia.

The effect of hydroxyethyl starch 200 kD on platelet function.

We evaluated the effects of hydroxyethyl starch with a molecular weight of 200 kD (HES 200 kD) on platelets to gain insight into the potential mechanisms involved in the anticoagulant effects of HES 200 kD. Blood was obtained before and after an IV infusion (10 mL/kg) of either saline (n = 15) or HES 200 kD (n = 15) in otherwise healthy patients scheduled for minor elective surgery. Flow cytometry was used to assess the expression of glycoprotein (GP) IIb-IIIa, GP Ib, and P-selectin on agonist-activated platelets. Overall platelet function was evaluated by assessing thromboelastographic maximum amplitude (MA) in celite-activated blood and platelet function analyzer-closure times by using collagen/adenosine diphosphate cartridges. Saline infusion had no effects on platelet variables, whereas HES 200 kD reduced GP IIb-IIIa expression and MA and prolonged platelet function analyzer-closure times, without affecting the expression of P-selectin and GP Ib. In vitro experiments extended these observations by a concentration-related inhibiting effect of HES 200 kD on GP IIb-IIIa expression. This study demonstrates that cellular abnormalities with decreased availability of platelet GP IIb-IIIa are involved in the anticoagulant effects of HES 200 kD. Implications The present data indicate that an antiplatelet effect of hydroxyethyl starch 200 kD should be considered during plasma volume expansion with this synthetic colloid.

Pilot study of neuraxial imaging by ultrasound in infants and children.

Background : Ultrasonography is becoming an important adjunct in regional anesthesia. Epidural anesthesia may pose significant challenges in infants and children because of difficulties in identifying the epidural space. In addition, epidural catheters are sometimes difficult to advance. The present study was performed to evaluate an optimal ultrasound technique for direct visualization of neuraxial structures in children.

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 (Cmax), time to Cmax (tmax), the absorption rate constant (ka), the speed of rise of the plasma concentration at Time 0 (dC0/dt), and area under the curve value (AUC) were determined. RESULTS: The ultrasound-guided technique resulted in higher Cmax (sd), ka, dC0/dt, and AUC values and shorter tmax compared with the landmark-based technique (Cmax: 1.78 [0.62] vs 1.23 [0.70] &mgr;g/mL, P < 0.01; ka: 14.4 [10.7] vs 11.7 [11.4] h−1, P < 0.05; dC0/dt: 0.26 [0.12] vs 0.15 [0.03] &mgr;g/mL · min, P < 0.01; AUC: 42.4 [15.9] vs 27.2 [18.1] &mgr;g · 30 min/mL, P < 0.001; tmax: 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.

Epidural Catheter Placement in Neonates: Sonoanatomy and Feasibility of Ultrasonographic Guidance in Term and Preterm Neonates

Background: We report the first prospective sonoanatomic study in neonates with the aim to perform ultrasonographic-guided epidural catheter placement in this age group. Method: One hundred forty-five neonates with a body weight ≤4 kg (0.53-4 kg) were included in this prospective study. The study was divided into 3 consecutive parts. In the first part, the neuraxial sonoanatomy of 60 neonates was evaluated. In the second part, 50 neonates scheduled for major abdominal surgery were enrolled. In this part, the depth of the ligamentum flavum measured with ultrasound was matched up to the depth evaluated clinically with the loss-of-resistance technique. In the third part, ultrasonographic epidural catheter placement was performed in 35 neonates weighing between 620 g and 4 kg. Results: The ligamentum flavum, the dura mater, and the termination of the spinal cord could be identified in all patients. The first part showed a good correlation between body weight and depth of the ligamentum flavum. The median termination of the spinal cord corresponded to vertebral level L2. The second part confirmed a good correlation between depth of the ligamentum flavum evaluated clinically and the depth predicted with ultrasound. Finally, real-time ultrasound-guided epidural placement was possible in all 35 neonates. Conclusion: Ultrasound examination of the spinal cord anatomy provides valuable information for epidural catheter placement in neonates. Ultrasonography enables a real-time identification of the tip of the needle within the epidural space and a visualization of the spread of local anesthetic in these patients.

Propofol-based sedation regimen for infants and children undergoing ambulatory magnetic resonance imaging

BACKGROUND Propofol is widely used for infants and children requiring sedation for magnetic resonance imaging. However, increased doses of propofol may quickly lead to an unintended deep sedation and respiratory depression. Thus, an appropriate low dosage, which nevertheless ensures sufficient sleep for successful magnetic resonance imaging (MRI) completion, would probably minimize respiratory adverse events. We investigated the safety and efficacy of a low-dose propofol-based sedation regimen in a broad age range of children. METHODS We investigated 500 infants and children, prospectively. Premedication consisted of i.v. midazolam 0.1 mg kg(-1). Sedation was induced with i.v. nalbuphine 0.1 mg kg(-1) and propofol 1 mg kg(-1), and maintained with propofol 5 mg kg(-1) h(-1). Outcome measures were induction time, sedation time, recovery time, need for additional sedation, respiratory events, cardiovascular events, paradoxical reactions, and sedation failure. RESULTS Data were obtained from 53 infants and 447 children. Median (IQR) age was 5.3 (4.5, 6.1) yr and body weight was 19.3 (16.5, 24.7) kg. The induction time was 2 (1, 2) min, sedation time 55 (45, 65) min, and recovery time 8 (8, 9) min. Additional sedation was necessary in 11 patients (2.2%), mild respiratory events occurred in five patients (1%). All MRI examinations could be completed without paradoxical reaction or sedation failure. CONCLUSION This sedation regimen provides the shortest induction time so far described, a rare demand for additional sedation, a low incidence of respiratory events, and a rapid recovery.