Pencil-point Needles Research Articles

Differential Rates of Inadvertent Intravascular Injection during Lumbar Transforaminal Epidural Injections Using Blunt-Tip, Pencil-Point, and Catheter-Extension Needles.

To quantify the incidence of inadvertent vascular penetration during lumbosacral transforaminal epidural injections using blunt-tip, pencil-point, and catheter-extension needles. This is a prospective, observational, consecutive cohort study. Two hundred consecutive patients undergoing lumbosacral transforaminal epidural injections at an academic outpatient spine center. Four hundred seventy-five fluoroscopically guided lumbosacral transforaminal epidural injections were performed on consecutively consenting patients by one interventional spine physician, using three different needle types. The presence or absence of vascular uptake was determined during contrast injection under live fluoroscopy. Vascular uptake of contrast was observed in 58 of the total 475 injections, for an overall incidence of 12.2%. By needle type, the incidence of inadvertent vascular uptake was 16.6% (26/157) in the pencil-point group, 15.6% (24/154) in the blunt-tip group, and 4.9% (8/164) in the catheter-extension group. The difference in rates is statistically significant between the catheter-extension needle group and both the pencil-point group (P = 0.0009) and blunt-tip group (P = 0.0024). A secondary analysis was performed to quantify the incidence of functional pitfalls between needle groups, with a significantly lower incidence in the pencil-point group compared to both the catheter-extension (P = 0.0148) and blunt-tip needle (P = 0.0288) groups. Blunt-tip and pencil-point needles have comparable risk of inadvertent vascular injection during lumbosacral transforaminal injections. Catheter-extension needles demonstrated a reduce incidence of vascular uptake, but also result in a significantly higher rate of functional pitfalls that limits their usefulness in routine practice.

Influence of needle diameter on spinal anaesthesia puncture failures for caesarean section: A prospective, randomised, experimental study

ObjectivesSpinal anaesthesia represents the technique of choice for elective caesarean section. The purpose of this study was to compare the puncture failure rates with 25, 26 or 27gauge (G) pencil-point, Whitacre type (with introducer) needles during spinal anaesthesia for caesarean section. Study designProspective, randomised, experimental study in healthy subjects. Patients and methodsWe recruited 330 adults, consecutively scheduled parturients, randomised into three groups. The subarachnoid puncture procedure was standardised. The flexibility of the three needle types was assessed in vitro, and a force was applied using a dynamometer. The occurrence of postdural puncture headache was also evaluated. ResultsThe number of spinal puncture failures was significantly higher in the 27G group, than in the 25G (P=0.006) group and the 26G (P<0.001) group, but did not differ between the 25G and 26G groups (P=0.606). Ten postdural puncture headaches were observed without significant differences among the groups. ConclusionsThis prospective study showed that puncture failures occur less frequently with the use of 25G or 26G pencil-point needles as compared to 27G needles, probably due to the higher flexibility of the latter. This characteristic was demonstrated in vitro, in a reproducible model. This experiment suggests that a 26G pencil-point needle is the optimal gauge for performing spinal anaesthesia for scheduled caesarean sections.

Pencil-point needle bevel direction influences ED50 of isobaric ropivacaine with fentanyl in spinal anesthesia for cesarean delivery: a prospective, double-blind sequential allocation study

BackgroundThere is little evidence on the influence of bevel direction of a pencil-point needle on the median effective dose (ED50) of isobaric ropivacaine and fentanyl in spinal anesthesia for cesarean delivery. MethodsIn this prospective, double-blind, sequential allocation study, 82 parturients scheduled for elective cesarean delivery under combined spinal-epidural anesthesia were included. We sought to determine the median effective dose of intrathecal 0.75% isobaric ropivacaine plus fentanyl 15μg with two different bevel directions of a 26-gauge Whitacre needle using up-down sequential allocation. Parturients were randomly allocated to either Group Ce (needle aperture oriented in a cephalad direction) or Group Ca (aperture directed caudally). The initial dose was 0.75% ropivacaine 11.25mg plus fentanyl 15μg in both groups. Each dose was classified as effective if, after 15min and during the next 60min, there was inability to appreciate pin-prick as sharp at T4, a visual analogue pain score <2 and no requirement for an epidural rescue bolus. ResultsEighty patients were included in the analysis. The ED50 in group Ca was significantly higher (13.09mg, 95% CI 12.19–14.00) than in group Ce (10.10mg, 95% CI 9.54–10.65, P <0.001). ConclusionThe orientation of the distal aperture of a 26-gauge Whitacre needle during induction of spinal anesthesia for cesarean delivery influences the ED50 of 0.75% ropivacaine.

Low-dose spinal anaesthesia provides effective labour analgesia and does not limit ambulation

Background: While epidural analgesia for labour pain is standard in high-resource countries, minimal to no analgesia is usually provided in low-resource countries. Intrathecal local anaesthetics provide good pain relief, but the potential impact on ambulation is of concern. Our objective was to determine if a low-dose local anaesthetic combined with an opioid would provide reasonable pain relief, while allowing ambulation in a low-resource setting.Method: This prospective, observational study was conducted at the Tamale Teaching Hospital in Tamale, Ghana. Spinal analgesia was administered to healthy women in labour using a pencil-point 25-G spinal needle at the L3–L4 or L4–L5 interspace, with patients in the sitting position. The intrathecal mixture contained 25 μg of fentanyl, 2.5 mg of bupivacaine and 0.2 mg of morphine. The patient’s ability to ambulate following the administration of a low-dose spinal injection was the primary outcome measured. Pain ratings, blood pressure, nausea, vomiting, pruritus, headaches and foetal bradycardia were also recorded.Results: Three hundred and thirty-two parturients consented to participate. Following spinal injection, 328 women (98.8%) experienced mild to no pain, and 4 (1.2%) moderate pain. The administration of spinal analgesia had no effect on ambulation in 291 (87.7%) patients, and a mild effect in 41 (12.3%) patients. Intrathecal analgesia did not severely limit ambulation in any of the patients.Conclusion: Low-dose intrathecal analgesia can provide effective analgesia for labouring patients in low-resource settings without limiting ambulation.

Conus Medullaris/Cauda Equina Syndrome Following a Repeated Bupivacaine 1% Spinal Anesthesia- Analysis of a Case with Review of the Literature

In the morning a healthy 40 years old female had a successful spinal anesthetic with bupivacaine 1% 10 mg for hemorrhoidectomy followed by a second injection at midnight for severe pain. The second traumatic injection caused a conus medullaris/cauda equina lesion discovered by MRI 45 days later. The contribution of hyperbaric bupivacaine dosage and pencil point needle is discussed.

Postdural puncture headache after spinal anesthesia in cesarean section: Experience in six months in 2736 patients in Kasr El aini teaching hospital – Cairo University

BackgroundThis is a prospective, single-blinded observational study examined the frequency and severity of postdural puncture headache in the Egyptian female patients following spinal anesthesia for cesarean section.MethodAll the females scheduled for cesarean section under spinal anesthesia in Cairo university were included and divided into two groups, one with Quinke needle G22 and one with Quinke needle G20, both groups were followed up for 7 days regarding incidence and severity of PDPH.ResultThe overall incidence of postdural puncture headache was 32.58% in group with Quinke needle G22, while it was 32.86% with the group used Quinke needle G20, PDPH almost relived by the fifth day in both groups, patients rated their headache as mild to moderate on a 10-cm visual analog scale.ConclusionsThis study is a documentation of the Cairo University teaching hospital experience with PDPH in female patient undergoes spinal anesthesia, and it focus on the incidence and severity related to the needle size and Egyptian population. We recommend the usage of the pencil point needle or a smaller needle in Cairo university hospital regardless the economic, teaching and manufacturing reasons.

Evidence-Based Practice Recommendations to Prevent/Manage Post-Lumbar Puncture Headaches in Pediatric Patients Receiving Intrathecal Chemotherapy.

Post-lumbar puncture headaches (PLPHs) are a known complication of lumbar puncture procedures. Children undergoing treatment for cancer often undergo multiple lumbar punctures, placing them at increased risk for PLPHs. There are currently no guidelines for the prevention or management of PLPHs in children. A team was therefore assembled to conduct a systematic review of the evidence in relationship to PLPHs in the pediatric population. Clinical questions were developed and used to guide the literature review. Twenty-four articles were deemed appropriate for use and were evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) criteria. Based on the review of evidence, strong recommendations are made for the use of smaller needle sizes and for the use of pencil point needles during lumbar puncture procedures. Weak recommendations are made for needle orientation and positioning following the procedure as well as for interventions used to treat PLPHs once they occur. There is a need for additional, pediatric-specific studies to further examine the issue of PLPH prevention and treatment.

Intracranial hematoma as the cause of headache after subarachnoid anesthesia for cesarean section – a case report

Intracranial subdural hematoma is an exceptionally rare but life-threating complication of epidural and spinal anesthesia. The diagnosis is rather difficult because the initial symptoms mimic post-dural puncture headache. A 33-year-old primipara was admitted to the hospital at 38 weeks gestation for a cesarean section due to premature rupture of membranes and meconium stained amniotic fluid. During the procedure a single puncture between L2 and L3 vertebrae was made with the use of a 26-gauge, pencil-point needle. The amount of 2.8 ml of analgesic solution was administered in order to obtain subarachnoid analgesia at the level of Th4 and Th5 vertebrae. Postpartum recovery was uneventful for the first two days. On the third day the patient developed strong headache in the forehead area and tinnitus. An anesthesiologist diagnosed post-dural puncture headache (PDPH). The patient received 1 g of Paracetamol every 6 hours intravenously together with 3000 ml of crystalloid solution for 24 hours. As a result, the patient recovered and was discharged home with her infant. Five days later the patient presented at the neurology clinic because of strong and chronic temporal lobe headache. No other complaints were reported. Upon admission, the patient had a head CT followed by an MRI examination, which revealed cranial hematomas localized bilaterally in the area of the frontal, temporal and parietal lobes, spreading from the cranial vault to the skull base. The width of the hematomas was: 3-4 mm on the left and 5-6 mm on the right side. Hematomas infiltrated the anterior part of the medial longitudinal fissure. Magnetic resonance angiography showed normal images of the arteries, veins, and the dural venous sinuses. No vascular malformations, which may be a source of intracranial hemorrhage, were found. Other tests showed normal results. Patient condition during hospitalization was stable. Conservative treatment was implemented, i.e. fluids administered intravenously anti-edematous drugs, analgesic medications and bed rest. All pain complaints subsided and a control CT scan showed that hematomas evolved as expected i.e. their HU density decreased. About 6 weeks later the patient had a CT head scan, performed in outpatient settings, which showed complete absorption of extravasated blood. The presented case shows headaches in obstetric patients require thorough diagnostic examinations and appropriate management. In addition to the most typical PDPH, it may be the first sign of life-threatening intracranial pathology

A comparison of Vertical Infraclavicular and Coracoid Approaches in Forearm Surgery

Despite several risks, infraclavicular approaches to the brachial plexus gained popularity. The present study compared success rates, block onset times, block performance times, and frequency of adverse effects of vertical infraclavicular (VIB) and coracoid blocks (CB) in patients undergoing forearm surgery. After ethical committee approval and informed consent 40 patients undergoing forearm surgery were included. The brachial plexus was located using a nerve stimulator and an insulated pencil point needle. Thirty ml bupivacaine 0.5% was used for the block. The blocks were assessed every minute for the first 5 min, then every 5 min for 15 min and then every 15 min and at the end of the operation. Block onset times of both groups were similar. Higher rates of sensory block were found in group CB at the 5th, 10th, and 15th minutes of assessment. Also higher rates of motor block were found in group CB at the 5th, 10th, 15th and 30th minutes of assessment. Time to perform block was shorter in group VIB. One patient in CB group required general anaesthesia. Except two vascular punctures in group CB no other side-effects were observed. Coracapid block provided higher rates of sensorial and motor blocks in a similar onset time without serious complications. CB can be accepted as a safe and reliable alternative to VIB for forearm surgery.

Comparison of two spinal needle types to achieve a unilateral spinal block

Unilateral spinal anesthesia is beneficial in patients undergoing unilateral leg surgery. The direction and the shape of the spinal needle are thought to influence the unilateral distribution of the local anesthetic in the intrathecal space. Therefore, to study the effects of different spinal needles we compared the effects of the Whitacre and Quincke spinal needles. This was a prospective, randomized, double-blind study of 60 consecutive outpatients scheduled for unilateral lower-limb surgery. The patients were randomized to receive spinal anesthesia with 1.2ml of 0.5% plain bupivacaine using either a 27-G Whitacre or a Quincke needle. One half of the local anesthetic was injected towards the nondependent side and the other half was directed cranially. The spread of spinal anesthesia, both sensory and motor blocks, was defined as the primary endpoint and was recorded at 10, 20, and 30min after the spinal injection, at the end of the operation, 2h after the spinal injection, and every 30min thereafter until there was no motor block. Secondary endpoints included patient satisfaction and adverse effects. There was no difference in the spread of sensory or motor blocks between the Whitacre and the Quincke groups. However, the sensory and motor blocks on the operated and the nonoperated sides were significantly different at all testing times, as expected. There was no difference in the incidence of adverse effects or patient satisfaction scores between the Whitacre and the Quincke groups. Unilateral spinal block for outpatient surgery can be achieved with both pencil-point (Whitacre) and Quincke needles using 6.0mg of plain bupivacaine. Neither the spread of sensory and motor blocks nor the corresponding recovery times appeared to be different between the groups. Nor was there any difference in patient satisfaction.

PDPH BY USING SAME GAUGE OF NEEDLES

There is increase incidence of Lower Segment Caesarian section (LSCS) being performed under sub-arachnoid block (SAB)because it is relatively safe. One of the complications of SAB is Post Dural Puncture Headache (PDPH) which is very distressing to the patient.Objective: To observe the incidence of PDPH by using two different types of spinal needle of 25 gauge in females undergoing LSCS underSAB. Currently, in our setup 25G cutting (quincke) spinal needle is routinely used. Study design: Randomized controlled trial. Setting:Department of Anesthesia, Officers Family Hospital, Rawalpindi Cantt. Duration of study: 6 months from 15 February 2011 to 15 July 2011.Material and Method: 100 pregnant patients undergoing elective CD under spinal anaesthesia were randomized into two groups A &amp; B. GroupA received SAB with 25G Quincke needle; Group B- received SAB with 25G pencil-point needle. Follow up was done upto 72 hours after thesurgery. Data obtained through study was analysed through computer software SPSS version 12. Quantitative variables like age, weight andheight are presented as mean and standard deviation. The frequency of PDPH was qualitatively analysed in percentage. The frequency ofPDPH was compared between two groups with the application of Chi-square as test of significance at P- value&lt;0.05. Results: It was found thatthe incidence of PDPH with Quincke (cutting tip) needle was significantly higher (7.%) as compared to pencil point needle (0%). Conclusion:pencil-point spinal needle is associated with lesser incidence of PDPH and should be preferred to Quincke needle to achieve SAB in patientsundergoing LSCS.

Three years’ experience of using a 29-gauge atraumatic needle for amniocentesis

To quantify the procedure-related complication rate after using modified technique of amniocentesis with a 29-gauge (29-G) pencil-point needle. This is a prospective, descriptive study of 316 amniocenteses that were performed by means of atraumatic 29-G pencil-point needle under ultrasound control. A total of 316 amniocenteses were observed through the postprocedural period. The median time needed to retrieve 15 mL of amniotic fluid was 4 min. A total of 19 pregnancies were terminated after genetic testing. No case was regarded as procedure-related fetal loss. No other complications were observed. Seventeen children were born before 37 completed weeks of gestation and five children had a birth weight <2000 g. Amniocentesis with the 29-G atraumatic pencil-point needle seems to be a safe procedure with extremely low risk of complications and is a good alternative to the traditional 22-G Quincke needle.

Post-dural puncture headache: haunts the anaesthetist.

Dear Editor, We read with great interest study conducted by Mosaffa et al. (1), designed to compare the rate of post-dural puncture headache (PDPH) in median and paramedian approaches in spinal anesthesia in the September issue of Anesthesiology and Pain Medicine. Spinal anaesthesia has been used in patients from preterm neonates to aged over a hundred years. At present it is a gold standard for many different procedures. We are using spinal anaesthesia not only as an alternative to general anaesthesia but also as the first choice for suitable surgery in both children and adults with or without co-morbidity. We believe that main restrictive complication is named post-dural puncture headache which haunts the anaesthetist and the surgeons who face the complaint next morning after spinal anesthesia. Studies reported that small gauge pencil point needles leads to significantly less incidence of PDPH in children (2) and adults (3). Controversy still exists about the use of thin and pencil point spinal needles since they seem to be difficult to handle, resulting in a reduced success rate and increased cost. We believe that future trials must be planed to be alternative to small gauge pencil point needles like Mosaffa et al. (1) study. We would like to ask to author “ why haven’t they chosen parturient as subjects for evaluated PDPH on the contrary many of reported studies which were evaluted PDPH have taken parturient as subjects who are at a particularly high risk of PDPH?”

Caudal Normal Saline Injections for the Treatment of Post-Dural Puncture Headache

Background: Post-dural puncture headache (PDPH) is the most common complication of procedures in which the dura mater is penetrated. Objectives: To evaluate the effectiveness of caudal saline injections as a therapeutic approach for handling post-dural puncture headache. Study Design: Prospective observational study between 1995 and 2010. Setting: Associated teaching hospital. Methods: A 5-cm 20-gauge short-beveled needle, connected by extension tube to a 20- mL syringe filled with normal saline was used for injection. During injection in increments (limited by patient discomfort), the patients were asked continually to quantify their pain experience on a visual analog scale (VAS) and on a 0-3 verbal categorical rating scale (VRS) after 50, 80 and 100 mL of infusion over a 20 minute period. Limitations: This study is limited by its sample size, observational design, and lack of long-term outcomes. Results: PDPH occurred in 60 of 1,716 patients undergoing dural puncture (3.5%). It was significantly more common in women and occurred more often in young adults. The rate was highest in the spinal catheter group (13%) and lowest in the Sprotte needle group (0.98%). Fifty-six patients underwent caudal saline injections which were repeated in sessions of 1-2 times a day for 1-2 days. Most patients (n = 48) needed 3 or 4 (n=18) sessions. Mean volumes during the 4 sessions were 120.0 mL, 114.9 mL, 106.5 mL, and 97.8 mL. Four patients were finally treated with a blood patch. Conclusions: The use of fine gauge pencil-point needles may reduce the incidence of PDPH. The technique of repeated caudal saline injections is easy, rapid, and effective in providing the patient with almost immediate headache relief. In cases where this treatment fails, a blood patch should be considered. Observations from this study suggest that randomized, controlled, double-blind studies may be warranted. Key words: Post-dural puncture headache (PDPH), dural puncture, spinal anesthesia, caudal saline injection

Day case and short stay surgery: 2

Day case and short stay surgery: 2

Responses to Dural Puncture during Institution of Combined Spinal-Epidural Analgesia: A Comparison of 27 Gauge Pencil-Point and 27 Gauge Cutting-Edge Needles

Pencil-point spinal needles are popular for combined spinal-epidural analgesia because they cause less dural puncture headache than cutting-edge spinal needles. However many parturients move, grimace, vocalise or experience paraesthesia or dysaesthesia during dural puncture when performing 'needle through needle' combined spinal-epidural analgesia. We compared dural puncture responses induced by pencil-point and cutting-edge needles (both 27 gauge). With institutional approval, 115 parturients presenting for elective caesarean section or labour analgesia were audited. After lignocaine infiltration, a Tuohy-type needle was inserted to loss of resistance to saline at a mid-lumbar interspace, and either a 27 gauge cutting-edge or 27 gauge pencil-point needle was inserted 'needle through needle' through the dura. During dural penetration, the occurrence of patient movement, grimacing or vocalisation was noted by a blinded observer, as was the patient's response to the question "Did you feel that?" asked by the anaesthetist. The audit comprised two similar groups of patients (caesarean section, n=30; labour analgesia, n=85). In both groups, grimacing and movement during thecal penetration occurred more frequently with pencil-point needles (P < 0.05 and P < 0.025, respectively). Pooled data analysis revealed that pencil-point and cutting-edge needles induced grimacing and movement in 17 (22%) and 2 (5%), spontaneous vocalisation in 4 (5%) and 1 (3%) and was perceived by 13 (17%) and 3 (8%) parturients (P < 0.025, P=NS, P=NS), respectively. Overall, 34 and 6 objective and subjective patient responses (P < 0.005) occurred when inserting these needles, respectively. Dural puncture by a 27 gauge pencil-point needle inserted 'needle through needle' when instituting combined spinal-epidural analgesia induces more iatrogenic responses than a 27 gauge cutting-edge needle.

Inadvertent Injection of a Cervical Radicular Artery Using an Atraumatic Pencil-Point Needle

Case report and review of the literature. To report the first case of inadvertent injection of a cervical radicular artery using an atraumatic pencil-point needle. Rare complications from cervical transforaminal epidural corticosteroid injection have resulted in infarction of the spinal cord and brain. The most often-hypothesized mechanism is inadvertent intra-arterial injection of particulate corticosteroids with a resulting embolus and infarction. Retrospective review of a patient's history and fluoroscopic imaging. A 30-year-old man with a diagnosed cervical radiculopathy underwent a right C6-C7 transforaminal epidural corticosteroid injection, using a 25-gauge 3.5-inch Whitacre spinal needle. Simultaneous epidural and radicular artery spread were observed under live fluoroscopy. The patient suffered no complications from the procedure. This case demonstrates that the use of pencil-point (Whitacre) needles does not eliminate the risk of inadvertent arterial injection during cervical transforaminal epidurals. Further investigation is required to determine whether the incidence of inadvertent vascular injection is reduced with pencil-point needles compared with sharp-beveled needles.

Do pencil-point spinal needles decrease the incidence of postdural puncture headache in reality? A comparative study between pencil-point 25G Whitacre and cutting-beveled 25G Quincke spinal needles in 320 obstetric patients.

Background:Postdural puncture headache (PDPH) is a distressing complication of the subarachnoid block. The previous studies conducted, including the recent ones, do not conclusively prove that pencil-point spinal needles decrease the incidence of PDPH. In this study, we have tried to find out whether a pencil-point Whitacre needle is a better alternative than the classic cutting beveled, commonly used, Quincke spinal needle, in patients at risk of PDPH.Materials and Methods:Three hundred and twenty obstetric patients, 20-36 years of age, ASA I and II, posted for Cesarean section under subarachnoid block, were randomly assigned into two groups W and Q, where 25G Whitacre and 25G Quincke spinal needles were used, respectively. The primary objective of the study was to find out the difference in incidence of PDPH, if any, between the two groups, by using the t test and Chi square test.Results:The incidence of PDPH was 5% in group W and 28.12% in group Q, and the difference in incidence was statistically significant (P<0.001).Conclusion:The pencil-point 25G Whitacre spinal needle causes less incidence of PDPH compared to the classic 25G Quincke needle, and is recommended for use in patients at risk of PDPH.

Epidural Tramadol, is it a Good Option for Cesarean Section?

Dear Editor, I read the article entitled “The Maternal and Neonatal Effects of Adding Tramadol to 2% Lidocaine in Epidural Anesthesia for Cesarean Section” (1). The authors demonstrated that tramadol 50 mg or 100 mg associated to lidocaine is appropriate for this surgery and also improve sensory and motor blockade effects without any increase in complications. However some important reflections and some missing data may be consider for full understanding of the article. For instance, one question came to my mind during the analysis-why haven’t the article focused on tramadol applied on spinal anesthesia? Neuraxial anesthesia is undoubtedly the most appropriate technique for elective cesarean delivery since the relative risk of mortality from general versus regional anesthesia is 16. 7 (2). General anesthesia in obstetric patients is a procedure with higher rates of serious and life-threatening complications, mainly related to airway management once the physiologic changes of pregnancy determine higher incidence of pulmonary aspiration of gastric contents and difficult airway (3,4). Until 1980, epidural anesthesia was the primary choice of neuraxial technique for cesarean delivery because spinal anesthesia was associated with a high risk of postdural puncture headache. After this period, the introduction of pencil-point spinal needles and several other advantages, the single-shot spinal anesthesia became the technique of choice for cesarean (5, 6). Besides that, tramadol intrathecal have been used with success for labor and major gynecological surgeries (7, 8). Other important comments when reflecting about the results section, I was wondering the following points could have been provided to allow fully result analysis: The mean dose of lidocaine and sufentanil request intraoperative were presented, but it was not showed the number of patients that demanded complementation analgesia and when; Around 30% of patients present some complications but they did not mention what kind of complications and these numbers is relatively bigger than other found on literature (9) and They also comment that general anesthesia is an option when maternal apnea lasts longer than 20 seconds or enable to speech or if the mother lost consciousness or did not respond to stimuli but they did not comment if some patients need it, considering the risks of general anesthesia, it is an important date. Finally, the article core idea is very interesting, since epidural tramadol has comparable analgesic efficacy with lower side effects than epidural morphine, specifically concerning about respiratory depression (10). Although, this article still demands further improvements.

Testing Haptic Sensations for Spinal Anesthesia

Having identified key determinants of teaching and learning spinal anesthesia, it was necessary to characterize and render the haptic sensations (feeling of touch) associated with needle insertion in the lower back. The approach used is to match recreated sensations (eg, "pop" through skin or dura mater) with experts' perceptions of the equivalent clinical events. The study was performed using a haptic device (Phantom Desktop) that simulated the tactile elements of predefined clinical events. Twenty-four experts (anesthetists) were invited to assess rendered versions of 3 basic sensations, which typically occur during the performance of spinal anesthesia with a 25-gauge pencil point needle: (1) touching different surfaces (skin, bone), (2) the "pop" sensations (skin, dura mater), and (3) the sensations associated with advancement of the spinal needle through particular tissues (subcutaneous tissue, ligaments, intrathecal space). The perceptions of each participant were recorded. The relationships between each rendered sensation and the corresponding participant's perception was modeled using standard random effects techniques. Experts seem to possess a specific haptic perception regarding most sensations. The coefficient of variation was less than 0.50 for all sensations with the exception of intrathecal space. However, there is considerable within-rater variation when experts are presented with the same haptic rendering on more than one occasion for bone surface, skin pop, dura pop, and subcutaneous tissue. The importance of this finding is that it demonstrates the feasibility of an "expert perception"-based approach to the design of medical simulators.