Thorsten Steinfeldt

Nerve injury by needle nerve perforation in regional anaesthesia: does size matter?

BACKGROUND In regional anaesthesia, there is a risk of direct nerve injury. The purpose of this study was to determine whether the diameter of the applied needle is associated with the magnitude of nerve injury after needle nerve perforation. METHODS In five anaesthetized pigs, the brachial plexus were exposed bilaterally. Up to eight nerves underwent needle nerve perforation using a 24 G pencil-point cannula (small diameter) or a 19 G pencil-point needle (large diameter). After 48 h, the nerves were resected during anaesthesia. The specimens were processed for visual examination and the detection of inflammatory cells, myelin damage and intraneural haematoma. The grade of nerve injury was scored ranging from 0 (no injury) to 4 (severe injury). RESULTS Forty-eight nerves were examined. The applied injury score was significantly lower in the small-diameter group [median (inter-quartile range) 2.0 (2.0-2.0)] compared with the large-diameter group [3.5 (3.0-4.0) P<0.01]. Myelin damage and intraneural haematoma occurred predominantly in the large-diameter group. Signs of post-traumatic regional inflammation were comparable among both groups. CONCLUSIONS The severity of nerve injury after needle nerve perforation was related to the diameter of the applied cannula. However, no such difference exists for regional inflammation. Functional consequences of these findings need to be determined. Currently, small-diameter cannulae may be advisable for peripheral nerve blocks to minimize the risk of nerve injury in the case of nerve perforation.

Transoral thyroid and parathyroid surgery.

BackgroundTranslumenal endoscopic interventions via so-called natural orifices are gaining increasing interest because they allow surgical treatment without any incision of the skin. Moreover, minimally invasive procedures have found their way into thyroid and parathyroid surgery. Our goal was to develop a new access for thyroid and parathyroid resection via an entirely transoral approach.MethodsWe managed to find an entirely transoral sublingual access to the thyroid region in pigs and human cadavers. Using a modified rigid rectoscope (oraloscope) hemithyroidectomies as well as resection of parathyroid glands were performed via this new approach. Preparation and resection was performed using conventional laparoscopic instruments. In living pigs, integrity of the recurrent laryngeal nerve after resection could be documented by neuromonitoring. An absorbable suture was used to seal the mucosal incision.ResultsFirst, hemithyroidectomy was performed via the transoral access in 10 porcine cadavers, then in 10 living and orally intubated pigs, and finally in five human corpses. In humans, resection of parathyroid glands also was performed. We gained access to the thyroid region by blunt dissection of the layer behind the hyoid bone and the strap muscles of the neck. We did not observe any complication during the insertion, resection, and removal part of the new procedure.ConclusionsEntirely transoral thyroid and parathyroid surgery via sublingual access seems to be feasible. However, further investigations are needed to evaluate the safety of the new technique, especially potential and clinically relevant contamination of the access route has to be excluded.

Transoral thyroid and parathyroid surgery—Development of a new transoral technique

BACKGROUND Transluminal interventions via so-called natural orifices are gaining interest because they allow operative treatment without any skin incision. We previously described a transoral access for (para-)thyroid resection in pigs. To proceed with the first clinical trials, we evaluated the safety of the new technique. METHODS Transoral hemithyroidectomies were performed on 10 living pigs using a special cervicoscope and conventional laparoscopic instruments. Follow-up examinations were carried out for 14 days and followed by autopsy, which included macroscopic evaluation, microbiologic investigations, and blood testing. In addition, refinement of the new technique was achieved by developing the techniques in 10 human cadavers. Finally, transoral parathyroidectomies were performed in 2 patients with primary hyperparathyroidism and a preoperatively localized parathyroid adenoma. RESULTS All animal transoral hemithyroidectomies were performed without complications. Postoperatively, oral intake, weight gain, and white blood cell count remained normal. At autopsy, the access route, and operative field showed no signs of infection, and microbiologic swabs remained sterile. Based on these results, a transoral parathyroidectomy was performed successfully in 2 female patients with primary hyperparathyroidism; 1 patient experienced a transient palsy of the right hypoglossal nerve. CONCLUSION Transoral parathyroid and thyroid operation is feasible; however, additional controlled clinical studies are required to evaluate the safety and success rates of this new technique.

Videolaryngoscopy with glidescope reduces cervical spine movement in patients with unsecured cervical spine.

BACKGROUND Unconscious patients with severe trauma often require urgent endotracheal intubation. In trauma victims with possible cervical spine injury, any movement of the head and neck should be avoided. STUDY OBJECTIVES We investigated the effect of GlideScope videolaryngoscopy on cervical spine movement compared with conventional laryngoscopy in anesthetized patients with unsecured cervical spines. METHODS Sixty patients scheduled for elective surgery with general anesthesia and without anticipated airway problems were enrolled in the study after ethics committee approval and written informed consent. Intubation was performed with videolaryngoscopy (GlideScope(®), Verathon Inc., Bothell, WA) or conventional laryngoscopy (MacIntosh). Using video motion analysis with a lateral view, the maximum extension angle α was measured with reference to anatomical points (baseline and line drawn from processus mastoideus to os frontale [glabella]). Values were analyzed using Mann Whitney U-tests. RESULTS The deviation of α was a median 11.8° in the videolaryngoscope group and 14.3° in the conventional group (p = 0.045), with a maximum of 19.2° (videolaryngoscopy) vs. 29.3° (conventional). Intubation by physicians with some experience in videolaryngoscopy was associated with a reduced angle deviation (α = 10.3°) compared to inexperienced physicians (12.8°, p = 0.019). Intubation time was a median 24 s (min/max 12/75 s) in the MacIntosh group and 53 s (min/max 28/210 s) in the GlideScope group. In 3 patients randomized to the conventional group in whom conventional intubation failed, intubation could be successfully performed using videolaryngoscopy. CONCLUSION GlideScope videolaryngoscopy reduces movements of the cervical spine in patients with unsecured cervical spines and therefore might reduce the risk of secondary damage during emergency intubation of patients with cervical spine trauma.

Forced needle advancement during needle-nerve contact in a porcine model: histological outcome.

BACKGROUND: In this study, we determined whether needle advancement during needle-nerve contact (forced needle-nerve contact) is associated with a higher risk of nerve injury compared with needle-nerve contact without needle advancement (nonforced needle-nerve contact). METHODS: In 8 anesthetized pigs, the brachial plexus nerves underwent forced (0.15 Newton) or nonforced (0.0 Newton) needle-nerve contact without nerve penetration. The grade of nerve injury was histologically assessed using an objective score ranging from 0 (no injury) to 4 (severe injury). RESULTS: Sixty-nine nerves, including controls, were examined. Histology revealed a significant difference between forced and nonforced needle-nerve contact (median [interquartile range] 3 [2–4] vs 2 [1–2]; P = 0.004). Myelin damage and intraneural hematoma occurred only after forced needle-nerve contact. CONCLUSIONS: The severity of structural nerve injury after needle-nerve contact was directly related to force exposure via needle advancement.

Histological analysis after peripheral nerve puncture with pencil-point or Tuohy needletip

BACKGROUND:Continuous peripheral nerve blocks typically are performed with a “through-the-needle technique” and require needles with an inner diameter allowing catheter placement. In case of direct needle–nerve contact, the pencil-point needletip is currently considered less traumatic than are other needle configurations. In this study we determined whether nerve puncture with pencil-point needles is associated with fewer nerve injuries in comparison with Tuohy needles. METHODS:In 6 anesthetized pigs the brachial plexus were exposed bilaterally. Up to 8 nerves underwent nerve puncture with a pencil-point or a Tuohy needle. After 48 hours, the nerves were resected during anesthesia. The specimens were processed for visual examination and the detection of inflammatory cells, myelin damage, and intraneural hematoma. The grade of nerve injury was assessed using an objective score ranging from 0 (no injury) to 4 (severe injury). RESULTS:Fifty-eight nerves, including controls, were examined. According to the applied injury score, there was no significant difference between the pencil-point needle group [median (interquartile range) 3 (3–4)] and the Tuohy needle group [3 (3–4) P = 0.97]. The occurrence of posttraumatic regional inflammation, myelin damage, and intraneural hematoma was similarly high in both groups. CONCLUSIONS:Regardless of the needletip configuration applied for nerve puncture, pencil-point and Tuohy needletips may both lead to comparable magnitude of posttraumatic inflammation and considerable structural changes within the nerve. No significant differences were found comparing pencil-point with Tuohy tip–configured needles.

Mechanical Ventilation During Cardiopulmonary Resuscitation With Intermittent Positive-pressure Ventilation, Bilevel Ventilation, or Chest Compression Synchronized Ventilation in a Pig Model*

Objective:Mechanical ventilation with an automated ventilator is recommended during cardiopulmonary resuscitation with a secured airway. We investigated the influence of intermittent positive-pressure ventilation, bilevel ventilation, and the novel ventilator mode chest compression synchronized ventilation, a pressure-controlled ventilation triggered by each chest compression, on gas exchange, hemodynamics, and return of spontaneous circulation in a pig model. Design:Animal study. Setting:University laboratory. Subjects:Twenty-four three-month-old female domestic pigs. Interventions:The study was performed on pigs under general anesthesia with endotracheal intubation. Arterial and central venous catheters were inserted and IV rocuronium (1 mg/kg) was injected. After 3 minutes of cardiac arrest (ventricular fibrillation at t = 0 min), animals were randomized into intermittent positive-pressure ventilation (control group), bilevel, or chest compression synchronized ventilation group. Following 10 minute uninterrupted chest compressions and mechanical ventilation, advanced life support was performed (100% O2, up to six defibrillations, vasopressors). Measurements and Main Results:Blood gas samples were drawn at 0, 4 and 13 minutes. At 13 minutes, hemodynamics was analyzed beat-to-beat in the end-inspiratory and end-expiratory cycle comparing the IPPV with the bilevel group and the CCSV group. Data were analyzed with the Mann-Whitney U test. Return of spontaneous circulation was achieved in five of eight (intermittent positive-pressure ventilation), six of eight (bilevel), and four of seven (chest compression synchronized ventilation) pigs. The results of arterial blood gas analyses at t = 4 minutes and t = 13 minutes (torr) were as follows: PaO2 intermittent positive-pressure ventilation, 143 (76/256) and 262 (81/340); bilevel, 261 (109/386) (p = 0.195 vs intermittent positive-pressure ventilation) and 236 (86/364) (p = 0.878 vs intermittent positive-pressure ventilation); and chest compression synchronized ventilation, 598 (471/650) (p < 0.001 vs intermittent positive-pressure ventilation) and 634 (115/693) (p = 0.054 vs intermittent positive-pressure ventilation); PaCO2 intermittent positive-pressure ventilation, 40 (38/43) and 45 (36/52); bilevel, 39 (35/41) (p = 0.574 vs intermittent positive-pressure ventilation) and 46 (42/49) (p = 0.798); and chest compression synchronized ventilation, 28 (27/32) (p = 0.001 vs intermittent positive-pressure ventilation) and 26 (18/29) (p = 0.004); mixed venous pH intermittent positive-pressure ventilation, 7.34 (7.31/7.35) and 7.26 (7.25/7.31); bilevel, 7.35 (7.29/7.37) (p = 0.645 vs intermittent positive-pressure ventilation) and 7.27 (7.17/7.31) (p = 0.645 vs intermittent positive-pressure ventilation); and chest compression synchronized ventilation, 7.34 (7.33/7.39) (p = 0.189 vs intermittent positive-pressure ventilation) and 7.35 (7.34/7.36) (p = 0.006 vs intermittent positive-pressure ventilation). Mean end-inspiratory and end-expiratory arterial pressures at t = 13 minutes (mm Hg) were as follows: intermittent positive-pressure ventilation, 28.0 (25.0/29.6) and 27.9 (24.4/30.0); bilevel, 29.1 (25.6/37.1) (p = 0.574 vs intermittent positive-pressure ventilation) and 28.7 (24.2/36.5) (p = 0.721 vs intermittent positive-pressure ventilation); and chest compression synchronized ventilation, 32.7 (30.4/33.4) (p = 0.021 vs intermittent positive-pressure ventilation) and 27.0 (24.5/27.7) (p = 0.779 vs intermittent positive-pressure ventilation). Conclusions:Both intermittent positive-pressure ventilation and bilevel provided similar oxygenation and ventilation during cardiopulmonary resuscitation. Chest compression synchronized ventilation elicited the highest mean arterial pressure, best oxygenation, and a normal mixed venous pH during cardiopulmonary resuscitation.

Minimal current intensity to elicit an evoked motor response cannot discern between needle-nerve contact and intraneural needle insertion.

BACKGROUND:The ability of an evoked motor response (EMR) with nerve stimulation to detect intraneural needle placement reliably at low current intensity has recently been challenged. In this study, we hypothesized that current intensity is higher in needle-nerve contact than in intraneural needle placement. METHODS:Brachial plexus nerves were exposed surgically in 6 anesthetized pigs. An insulated needle connected to a nerve stimulator was placed either with 1 mm distance to the nerve (control position), adjacent to nerve epineurium (needle-nerve contact position), or inside the nerve (intraneural position). Three pulse duration settings were applied in random fashion (0.1, 0.3, or 1.0 milliseconds) at each needle position. Starting at 0.0 mA, electrical current was increased until a minimal threshold current resulting in a specific EMR was observed. Fifty threshold current measurements were scheduled for each needle position-pulse duration setting. RESULTS:Four hundred-fifty threshold currents in 50 peripheral nerves were measured. Threshold current intensities (mA) to elicit EMR showed small differences between the needle-nerve contact position [median (25th–75th percentiles); 0.1 milliseconds: 0.12 (0.08–0.18) mA; 0.3 milliseconds: 0.10 (0.06–0.12) mA; 1.0 milliseconds: 0.06 (0.04–0.10) mA] and the intraneural position (0.1 milliseconds: 0.12 [0.10–0.16] mA; 0.3 milliseconds: 0.08 [0.06–0.10] mA; 1.0 milliseconds: 0.06 [0.06–0.08] mA) that are neither statistically significant nor clinically relevant. Regardless of the pulse duration that was applied, the 98.33% confidence interval revealed a difference of at most 0.02 mA. However, threshold current intensities to elicit EMR were lower for the needle-nerve contact position than for the control position (0.1 milliseconds: 0.28 [0.26–0.32] mA; 0.3 milliseconds: 0.20 [0.16–0.22] mA; 1.0 milliseconds: 0.12 [0.10–0.14] mA). CONCLUSIONS:The confidence interval for differences suggests minimal current intensity to elicit a motor response that cannot reliably discern between a needle-nerve contact from intraneural needle placement. In addition, an EMR at threshold currents <0.2 mA (irrespective of the applied pulse duration) indicates intraneural needle placement or needle-nerve contact.

Basic life support with four different compression/ventilation ratios in a pig model: The need for ventilation ☆

BACKGROUND During cardiac arrest the paramount goal of basic life support (BLS) is the oxygenation of vital organs. Current recommendations are to combine chest compressions with ventilation in a fixed ratio of 30:2; however the optimum compression/ventilation ratio is still debatable. In our study we compared four different compression/ventilation ratios and documented their effects on the return of spontaneous circulation (ROSC), gas exchange, cerebral tissue oxygenation and haemodynamics in a pig model. METHODS Study was performed on 32 pigs under general anaesthesia with endotracheal intubation. Arterial and central venous lines were inserted. For continuous cerebral tissue oxygenation a Licox PtiO(2) probe was implanted. After 3 min of cardiac arrest (ventricular fibrillation) animals were randomized to a compression/ventilation-ratio 30:2, 100:5, 100:2 or compressions-only. Subsequently 10 min BLS, Advanced Life Support (ALS) was performed (100%O(2), 3 defibrillations, 1mg adrenaline i.v.). Data were analyzed with 2-factorial ANOVA. RESULTS ROSC was achieved in 4/8 (30:2), 5/8 (100:5), 2/8 (100:2) and 0/8 (compr-only) pigs. During BLS, PaCO(2) increased to 55 mm Hg (30:2), 68 mm Hg (100:5; p=0.0001), 66 mm Hg (100:2; p=0.002) and 72 mm Hg (compr-only; p<0.0001). PaO(2) decreased to 58 mmg (30:2), 40 mm Hg (100:5; p=0.15), 43 mm Hg (100:2; p=0.04) and 26 mm Hg (compr-only; p<0.0001). PtiO(2) baseline values were 12.7, 12.0, 11.1 and 10.0 mm Hg and decreased to 8.1 mm Hg (30:2), 4.1 mm Hg (100:5; p=0.08), 4.3 mm Hg (100:2; p=0.04), and 4.5 mm Hg (compr-only; p=0.69). CONCLUSIONS During BLS, a compression/ventilation-ratio of 100:5 seems to be equivalent to 30:2, while ratios of 100:2 or compressions-only detoriate peripheral arterial oxygenation and reduce the chance for ROSC.

Speed spinal anesthesia revisited: new drugs and their clinical effects.

Purpose of review Spinal anesthesia (SPA) has not been popular for day-case surgery because of prolonged neurologic blockade with long-acting local anesthetics such as bupivacaine, thereby delaying discharge. Although the intermediate duration of action of lidocaine and mepivacaine appears to be more suitable for day-case surgery, their use is not deemed appropriate by many because of a high incidence of transient neurologic symptoms (TNSs). The present review summarizes recent clinical data on the intrathecal use of alternative local anesthetics and adjuvants that may offer valuable alternatives to general anesthesia in day-case surgery. Recent findings Prilocaine has a similar intrathecal pharmacokinetic profile as lidocaine but with a significantly lower risk of TNSs. Onset of spinal after 2-chloroprocaine is comparable with lidocaine or prilocaine, but with a considerably shorter duration of action. Also, TNS is clearly less frequent compared with lidocaine. Although its intrathecal use has recently been approved in Europe, this is still considered to be off-label in the USA. Articaine provides an extraordinary fast onset and a short duration of spinal block, the latter being approximately intermediate between chloroprocaine and prilocaine. However, articaine is associated with a high risk for intraoperative hypotension and a small risk for TNS, albeit but less frequent than after lidocaine. Concerns regarding possible neurotoxicity of articaine remain to be resolved. Summary SPA for day cases might become a most valuable method for ambulatory surgery when using short acting local anesthetics. This, however, not only depends on drugs being used but also on infrastructure (post anaesthesia care unit) and organizational issues.PURPOSE OF REVIEW Fluid therapy is a complex intervention with insufficient resuscitation, as well as overinfusion and fluid accumulation being associated with adverse outcomes. Early goal-directed therapy with later conservative fluid management (i.e. prevention of positive fluid balance and weight gain) appears to markedly improve the survival of patients with severe sepsis. The impact of colloids in resuscitation of patients with sepsis has been the topic of several recently published studies. The purpose of the present review is to outline the indication of fluid administration in critically ill patients, discuss the recent findings of trials involving hydroxyethyl starch (HES) solutions and highlight the impact of different raw materials for HES synthesis. RECENT FINDINGS Pragmatic trials of modern HES solutions versus crystalloids in critically ill patients show either no difference or adverse outcomes associated with HES infusion. However, fluid therapy was not protocolized in most of these studies and probably associated with overinfusion and hemodilution. Data on the use of waxy maize-derived 6% HES 130/0.4 during early goal-directed therapy show no evidence for harm and an improvement in microvascular blood flow. In addition, experimental data suggest that waxy maize-derived 6% HES 130/0.4 may have different biological effects compared to potato-derived 6% HES 130/0.42 with potentially reduced pulmonary inflammation. SUMMARY Adverse effects of fluid resuscitation in critically ill patients appear to be a consequence of dose and timing rather than the type of fluid itself. Modern waxy maize-derived 6% HES 130/0.4 may have advantages over crystalloids in the very early course of the disease. Clinical trials of early, goal-directed and protocolized therapy with innovative endpoints of resuscitation comparing balanced crystalloids and balanced, waxy maize-derived 6% HES 130/0.4 as the initial resuscitation fluid are warranted.