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Biomedical subjects

Admir Hadzic

Publications and source records attributed to Admir Hadzic.

8 recordsLinked to original sources
PubMed2004

Electrical nerve localization: effects of cutaneous electrode placement and duration of the stimulus on motor response.

BACKGROUND: Recommendations regarding the technical aspects of nerve stimulator-assisted nerve localization are conflicting. The objectives of this study were to determine whether the placement of the cutaneous electrode affects nerve stimulation and to determine the duration and intensity of an electrical stimulus that allows nerve stimulation with minimal discomfort. METHODS: Ten healthy volunteers underwent an interscalene and a femoral nerve block. After obtaining a clearly visible motor response of the biceps (interscalene) and quadriceps (femoral) muscles at the minimal current (0.1 ms, 2 Hz), the position of the cutaneous electrode was varied. Next, the duration of the stimulating current was set at 0.05, 0.1, 0.3, 0.5, or 1.0 ms, in random order. Intensity of the motor response and discomfort on stimulation were recorded. RESULTS: The minimal current at which a visible motor response was obtained was 0.32 +/- 0.1 mA (0.23-0.38 mA) for the inter-scalene block and 0.29 +/- 0.1 mA (0.15-0.4 mA) for the femoral block. Changing the position of the return electrodes did not result in any change in the grade of the motor response or in the current required to maintain it. Currents of longer duration caused discomfort and more forceful contraction at a lower current intensity as compared with currents of shorter duration (P < 0.01). When the current was adjusted to maintain the same visible motor response, there was no significant discomfort among studied current durations. CONCLUSION: Site of placement of the cutaneous electrode is not important when constant current nerve stimulators are used during nerve localization in regional anesthesia. There is an inverse relation between the current required to obtain a visible motor response and current duration. Selecting a current duration between 0.05 and 1.0 ms to specifically stimulate sensory or motor components of a mixed nerve does not seem to be important in clinical practice.

Adult↗
PubMed2004

A comparison of infraclavicular nerve block versus general anesthesia for hand and wrist day-case surgeries.

BACKGROUND: General anesthesia (GA) and brachial plexus block have been used successfully for surgery on the upper extremities. Controversy exists as to which method is more suitable in outpatients undergoing hand and wrist surgery. The authors hypothesized that infraclavicular brachial plexus block (INB) performed with a short-acting local anesthetic would result in shorter time to discharge home as compared with "fast-track" GA. METHODS: After obtaining written informed consent, 52 patients (aged 18-65 yr, American Society of Anesthesiologists physical status I-III) were randomly assigned to receive either an INB or GA under standardized protocols (INB = 3% 2-chloroprocaine + HCO3 + epinephrine 1:300000, followed by propofol sedation; GA = 12.5 mg dolasetron, propofol induction, followed by laryngeal mask airway insertion and desflurane for maintenance; 0.25% bupivacaine for wound infiltration). At the conclusion of the procedure, nurses blinded to the study goals and the anesthetic technique used a modified Aldrete score to decide whether patients could bypass the postanesthesia care unit. Additional data were collected regarding time to postoperative pain, ambulation, home readiness, and incidence of adverse events. RESULTS: More patients in the INB group (79%) met the criteria to bypass the postanesthesia care unit compared with patients in the GA group (25%; P < 0.001). Compared with patients in the GA group, fewer patients in the INB group had pain (visual analog scale score > 3) on arrival to the postanesthesia care unit (3% vs. 43%; P < 0.001). None of the patients in the INB group requested treatment for pain while in the hospital, compared with 48% of patients in the GA group (P < 0.001). Patients in the INB group were able to ambulate earlier (82 +/- 41 min) compared with those in the GA group (145 +/- 70 min; P < 0.001). Time to home readiness and discharge times were shorter for patients in the INB group (100 +/- 44 and 121 +/- 37 min) compared with those in the GA group (203 +/- 91 and 218 +/- 93 min; P < 0.001). Adverse events (e.g., nausea, vomiting, sore throat) occurred less frequently in patients undergoing INB as compared with those undergoing GA. CONCLUSION: Infraclavicular brachial plexus block with a short-acting local anesthetic was associated with time-efficient anesthesia, faster recovery, fewer adverse events, better analgesia, and greater patient acceptance than GA followed by wound infiltration with a local anesthetic in outpatients undergoing hand and wrist surgery.

Adolescent↗
PubMed2004

Continuous parasacral sciatic block: a radiographic study.

UNLABELLED: Parasacral sciatic blockade results in anesthesia of the entire sacral plexus. In this study we sought to determine the spread of the local anesthetic injected through a parasacral catheter, the anatomical location of the inserted catheters, and the extent and reliability of the blockade. In this study, 87 consecutive patients undergoing major lower limb surgery were enrolled. After placement of the catheter and injection of 8 mL of radio-opaque contrast dye, radiographic images were evaluated for dispersion of the injectate. Sensory and motor evaluations were also performed. Radiographic analysis of the injectates revealed that nearly all catheters (86 catheters, 99%) were in the correct anatomical position. The mean volume of local anesthetic injection was 21 +/- 3 mL. All patients developed a full sensory block of all three major components of the sciatic plexus (tibial, common peroneal, and posterior cutaneous nerve of the thigh). We conclude that the parasacral sciatic block results in frequent success of blockade of all three major components of the sciatic plexus and it has a small risk of complications. Contrast radiography can be used to document the catheter placement. IMPLICATIONS: The parasacral sciatic block results in a frequent success rate of blockade of all three major components of the sciatic plexus (tibial, common peroneal, and cutaneous nerve of thigh). A contrast radiography can be used to confirm the proper position of the catheter.

Adolescent↗
PubMed2003

Nerve stimulators used for peripheral nerve blocks vary in their electrical characteristics.

BACKGROUND: Nerve stimulation with a low-intensity electrical current has become a vital part of the performance of peripheral nerve blockade. The purpose of this study was to compare the accuracy and characteristics of peripheral nerve stimulators used in clinical practice in the United States. METHODS: Fifteen peripheral nerve stimulators were fitted with fresh batteries and set to deliver currents ranging from 0.1 to 4.0 mA into a series of high-tolerance resistance loads ranging from 1 to 100 komega. The current output, stimulus duration, morphology, frequency, and maximum voltage output were studied using a factory-calibrated oscilloscope. RESULTS: All peripheral nerve stimulators performed uniformly well when set to deliver currents of 1.0 mA or more into a standard resistance load of 1 or 2 komega. However, at lower currents, the median error (%) increased from 2.4 (-5-144%) at 0.5 mA to 10.4 (-24-180%) at 0.1 mA into a 1 komega load. The morphology of the stimulus was characterized by a regular monophasic square pulse at current outputs of up to 1 mA and at a resistance of 1 komega. The stimulus waveform became particularly distorted as the impedance load was increased. The duration of the default stimulus set by the manufacturer varied from 34.8 to 460 micros among the peripheral nerve stimulators tested. The maximum voltage output ranged from 7.4 to 336 Volts. CONCLUSIONS: Nerve stimulators used for regional anesthesia vary greatly in accuracy of current output and in manufacturer-selected electrical characteristics (e.g., current duration, stimulating frequency, maximum voltage output).

Electric Stimulation↗
PubMedDate not supplied

Painful paresthesiae are infrequent during brachial plexus localization using low-current peripheral nerve stimulation.

BACKGROUND: Considerable controversy exists over the relationship of paresthesia to nerve stimulation. The purpose of this study was to determine the frequency with which patients report paresthesia at the point that an acceptable motor response is obtained to low-intensity current electrical stimulation. METHODS: Low-intensity current nerve stimulation (0.6 mA, 200 microseconds, 2 Hz) was used to identify the brachial plexus in 64 consecutive patients having shoulder or arm surgery with an interscalene block. During nerve localization and while maintaining a motor response (0.20 mA-0.40 mA), the patients were queried regarding any radiating sensation or pain (paresthesia) in the shoulder or extremity on the side of the blockade. Sensory distribution of the block, motor strength of the arm muscles, and adequacy of anesthesia were used to assess the extent of blockade. RESULTS: Ninety-five percent of patients had satisfactory surgical anesthesia. None of the patients spontaneously reported having a paresthesia during nerve stimulation. However, on careful questioning, half of the patients (55%) reported electrical paresthesia, defined as dull tingling sensation traveling down to their hands and coinciding with the motor response. In addition, most patients (71%) spontaneously reported having a mild, radiating paresthesia on initial injection of local anesthetic. CONCLUSIONS: Painful paresthesiae should be infrequent when a low-stimulating current is used to identify the neural components of the brachial plexus and when the block needle is advanced slowly. Low-current intensity nerve stimulation can be used to achieve successful interscalene block with minimal discomfort to the patient.

Adult↗
PubMedDate not supplied

Injection pressures by anesthesiologists during simulated peripheral nerve block.

BACKGROUND AND OBJECTIVES: Anesthesiologists typically rely on a subjective evaluation ("syringe feel") of possible abnormal resistance to injection while performing a peripheral nerve block (PNB). A greater force required to perform the injection is believed to be associated with intraneural injection. The hypothesis of this study is that anesthesiologists vary in their perception of "normal" injection force, that the syringe feel method is inconsistent in estimating resistance, and that needle design may affect the injection force. METHODS: Thirty anesthesiologists were asked to inject a local anesthetic, as they would in their everyday practice, through a commonly used syringe and needle assembly. Injection force was measured using an in-line manometer coupled to a computer via an analog-to-digital conversion board. In addition, injection force at clinically relevant injection speeds was determined using 3 differently sized needles from 4 different manufacturers. RESULTS: During a steady injection rate, all anesthesiologists perceived an increase in the force required to inject, even with minor pressures changes (0.6 +/- 0.3 psi). However, the 30 anesthesiologists, 21 (70%) initiated injection using a force that resulted in pressures greater than 20 psi; 15 (50%) used a force greater than 25 psi, and 3 (10%) exerted pressures greater than 30 psi. Pressures varied as much as 20-fold among needles of the same gauge/length from different manufacturers (P <.01). CONCLUSIONS: Anesthesiologists vary widely in their perception of appropriate force and rate of injection during PNB. The syringe-feel method of assessing injection force is inconsistent and may be further affected by variability in needle design.

Analysis of Variance↗
PubMedDate not supplied

Combination of intraneural injection and high injection pressure leads to fascicular injury and neurologic deficits in dogs.

BACKGROUND: Unintentional intraneural injection of local anesthetics may cause mechanical injury and pressure ischemia of the nerve fascicles. One study in small animals showed that intraneural injection may be associated with higher injection pressures. However, the pressure heralding an intraneural injection and the clinical consequences of such injections remain controversial. Our hypothesis is that an intraneural injection is associated with higher pressures and an increase in the risk of neurologic injury as compared with perineural injection. METHODS: Seven dogs of mixed breed (15-18 kg) were studied. After general endotracheal anesthesia, the sciatic nerves were exposed bilaterally. Under direct microscopic guidance, a 25-gauge needle was placed either perineurally (into the epineurium) or intraneurally (within the perineurium), and 4 mL of lidocaine 2% (1:250,000 epinephrine) was injected by using an automated infusion pump (4 mL/min). Injection pressure data were acquired by using an in-line manometer coupled to a computer via an analog digital conversion board. After injection, the animals were awakened and subjected to serial neurologic examinations. On the 7th day, the dogs were killed, the sciatic nerves were excised, and histologic examination was performed by pathologists blinded to the purpose of the study. RESULTS: Whereas all perineural injections resulted in pressures < or =4 psi, the majority of intraneural injections were associated with high pressures (25-45 psi) at the beginning of the injection. Normal motor function returned 3 hours after all injections associated with low injection pressures (< or =11 psi), whereas persistent motor deficits were observed in all 4 animals having high injection pressures (> or =25 psi). Histologic examination showed destruction of neural architecture and degeneration of axons in all 4 sciatic nerves receiving high-pressure injections. CONCLUSIONS: High injection pressures at the onset of injection may indicate an intraneural needle placement and lead to severe fascicular injury and persistent neurologic deficits. If these results are applicable to clinical practice, avoiding excessive injection pressure during nerve block administration may help to reduce the risk of neurologic injury.

Anesthetics, Local↗