Wrong-site nerve blocks: 10 yr experience in a large multihospital health-care system.

INTRODUCTION: Although wrong-site surgery has garnered extensive scrutiny, the incidence of wrong-site blocks remains unknown. Our study thus sought to quantify the incidence of wrong-site blocks and examine some of their associated risk factors in our multihospital health-care system. METHODS: Using quality-improvement and billing data, we quantified the total number of blocks and wrong-site blocks occurring between July 1, 2002 and June 30, 2012 within the University of Pittsburgh Medical Center Health System. The incidence of wrong-site block was determined by block type, hospital, and type of service involved in performing the block. The incidence of wrong-site block was compared with that of wrong-site surgery. Fisher's exact tests were performed to determine associations between the incidence of wrong-site block and any of the aforementioned variables. A root-cause analysis was performed to determine the source of wrong-site blocks after the implementation of a timeout policy. RESULTS: Of the 85 915 patients receiving blocks, 70 441 received only unilateral blocks, yielding an overall incidence of wrong-site block of 1.28 (95% confidence interval 0.43-2.13) per 10 000 patients receiving unilateral blocks. The incidence of wrong-site block was highest with femoral blocks, and differed from the incidence of wrong-site surgery. All occurrences of wrong-site block after the implementation of the timeout policy involved policy violations. CONCLUSIONS: Our study provides the first incidence data on wrong-site block in a large patient population and can help hospitals to develop policies based on these data. It is yet to be determined whether active intervention can eliminate this adverse event.

Continuous peripheral nerve blocks in acute pain management.

The indications for continuous nerve blocks for the perioperative pain management in hospitalized and ambulatory patients have extended well beyond orthopaedics. These techniques are not only used to control pain in patients undergoing major upper and lower extremity surgery, but also to provide perioperative analgesia in patients undergoing abdominal, plastic, urological, gynaecological, thoracic, and trauma surgeries. Infusion regimens of local anaesthetics and supplements must take into consideration the condition of the patient before and after surgery, the nature and intensity of the surgical stress associated with the surgery, and the possible need for immediate functional recovery. Continuous nerve blocks have proved safe and effective in reducing opioid consumption and related side-effects, accelerating recovery, and in many patients reducing the length of hospital stay. Continuous nerve blocks provide a safer alternative to epidural analgesia in patients receiving thromboprophylaxis, especially with low molecular-weight heparin.

International normalized ratio and prothrombin time values before the removal of a lumbar plexus catheter in patients receiving warfarin after total hip replacement.

BACKGROUND: There is a paucity of data regarding the coagulation status when discontinuing perineural catheters in patients receiving anticoagulant after operation. This retrospective study was designed to establish international normalized ratio (INR) and prothrombin time (PT) at the time of removal of lumbar plexus perineural catheters in patients receiving warfarin after total hip replacement. METHODS: Patients who received a continuous lumbar plexus nerve block for postoperative analgesia and received warfarin after total hip surgery between August 2002 and June 2007 were included in this retrospective study. PT and INRs were recorded before surgery and every day after operation along with any post-surgical nerve injury and bleeding related to the removal of the perineural catheter. RESULTS: Six hundred and seventy patients met the inclusion criteria. Almost all lumbar plexus catheters (89%) were removed on postoperative day 2. At the time of the perineural catheter removal, 36.2% of patients had an INR >1.4 (range: 1.5-3.9). One case of local bleeding was recorded at the time of the catheter removal with an INR of 3.0. This was managed with a direct pressure at the site. CONCLUSIONS: Although in this retrospective analysis, we demonstrated that lumbar plexus catheters were removed with an INR > or =1.5, additional data are required to confirm the safety of such an approach.

An accurate, nontraumatic ultrasonic method to monitor myocardial wall thickening in patients undergoing cardiac surgery.

Measurement of systolic wall thickening by sonomicrometry provides an accurate index of regional left ventricular function, but the trauma of crystal insertion limits its widespread clinical use. The first clinical application of a 10 MHz ultrasonic Doppler probe that can be either sutured or applied by suction to the epicardium and can measure wall thickening at any depth of the left ventricular wall is described. In 18 dogs, measurements obtained with the suction probe correlated well (r = 0.97) with those of a previously validated sutured probe. To assess clinical feasibility, the probe was applied to the epicardium of patients undergoing coronary bypass surgery. Good quality wall thickening signals were obtained with no complications. Transmural left ventricular thickening fraction before bypass surgery was 34 +/- 3% (mean value +/- SE) at the mid-ventricular lateral wall, 33 +/- 4% at the anterior basal wall and 26 +/- 4% at the mid-ventricular posterior wall. Right ventricular thickening fraction averaged 25 +/- 3%. Endocardial thickening fraction tended to exceed epicardial thickening fraction, although the difference attained statistical significance (p less than 0.05) only at the anterior basal wall. On average, thickening fraction during the immediate postoperative period remained unchanged compared with the preoperative values, but a marked individual variability was observed, with 7 of 15 patients exhibiting a decrease and 8 an increase. Exteriorization of the wires attached to the sutured probe allowed continuous in situ monitoring of wall thickening in the postoperative period and subsequent removal of the probe. In six patients the crystal was left in place for 48 to 72 h after surgery and then removed without complications; good wall thickening signals were obtained for the entire period during which the probe was implanted. Thus, the Doppler probe is an accurate, atraumatic method for measuring right and left ventricular regional function. Transmural, endocardial and epicardial function can be mapped at various sites during surgery, and post-operatively one can monitor serial changes of regional function and assess the effects of cardioplegia and other therapeutic interventions. This technique should be useful for both investigative and clinical purposes.

Effect of gender in centrally induced angiotensin II hypertension in dogs.

This study was designed to investigate the relation between gender, an endogenous inhibitor of the Na+-K+ pump, and volume-dependent hypertension induced by stimulation of the brain renin-angiotensin system and increased salt intake. Angiotensin II (20 ng/min i.c.v.) was infused for 4 weeks in five dogs of each sex with saline as the drinking fluid. In male dogs, angiotensin II induced parallel pressor (30%) and dipsogenic responses (70%), whereas no hypertension and no increase in fluid intake were observed in females. In contrast, the activity of the Na+-K+ pump as assessed by 86Rb uptake was independent of gender. Our data provide novel evidence that gender plays a determining role in the physiological properties of centrally administered angiotensin II.

Continuous monitoring of mixed venous oxygen saturation during aortic surgery.

The correlation between mixed venous oxygen saturation (SvO2) and hemodynamic measurements was studied in 13 patients undergoing descending thoracic aortic aneurysm resection (DTAAR). A significant correlation (p less than 0.05) was found between cardiac index (CI) and SvO2 after the induction of anesthesia and at the end of surgery. However, no significant correlation could be found between SvO2 and CI during the most critical periods of the surgery that included the collapse of the left lung, the aortic clamping, and the aortic declamping. During DTAAR, continuous SvO2 monitoring is useful, but it cannot substitute for intermittent cardiac output and oxygen consumption (VO2) determinations.

Cardiovascular effects of NG-methyl-L-arginine in chronically instrumented conscious dogs.

The cardiovascular effects of nitric oxide blockade were examined in five conscious chronically instrumented dogs. The hypothesis tested was that nitric oxide release plays a role in vascular tone and regional organ blood flow under physiological conditions. Aortic pressures; the first derivative of the left ventricular pressure; cardiac output (CO); heart rate; and carotid, coronary, renal, hepatic, and portal blood flows were recorded before and after bolus injection of 5, 10, and 20 mg/kg of NG-methyl-L-arginine (L-NMA). In response to L-NMA, mean arterial pressure increased by 7, 20, and 35%, respectively, in a dose-dependent manner, whereas CO decreased. CO reduction was sustained at the highest dose, whereas peripheral blood flows were not altered. These data suggest that blocking basal nitric oxide synthesis by administering L-NMA leads to a modest dose-dependent pressor response despite a marked and sustained reduction in CO recorded at the highest dose of L-NMA. Moreover, within our dose range, although the nitric oxide synthase inhibition provides a significant pressor response, it does not alter the resting carotid, coronary, renal, hepatic, and portal blood flows.

Effects of N-methyl-L-arginine on cardiac and regional blood flow in a dog endotoxin shock model.

PURPOSE: Indirect evidence suggests a decrease in organ perfusion as a result of nitric oxide (NO) inhibition in endotoxic shock. Cardiac and regional hemodynamic responses to N-methyl-L-arginine (L-NMA), a nonspecific inhibitor of constitutive and inducible nitric oxide synthase (NOS), were assessed in nine conscious dogs subjected to endotoxin. MATERIALS AND METHODS: Lipopolysaccharide (LPS) was titrated to a maximum of 200 microg/kg, IV, over 45 minutes. L-NMA was given in a dose of 20 mg/kg, IV. Hemodynamic parameters were recorded for 6 hours following L-NMA administration. RESULTS: LPS induced significant decreases in mean arterial blood pressure (MAP), cardiac output (CO), first derivative of left ventricular pressure (dP/dt), coronary blood flow, carotid blood flow, mesenteric blood flow, renal blood flow, and a significant hepatic vasodilation. L-NMA fully reversed the effects of LPS on MAP, heart rate, dP/dt, coronary and carotid blood flow, and reversed mesenteric blood flow and hepatic blood flow at 1 and 3 hours, respectively. L-NMA partially overcame the LPS-induced decrease in renal blood flow at 30 minutes and 1 hour. Except for mesenteric and carotid circulation, L-NMA did not change regional vascular resistance. CONCLUSIONS: It is likely that constitutive NOS is implicated in immediate cardiac, carotid, mesenteric, and renal vascular changes, whereas inducible NOS accounted for delayed responses in hepatic and coronary circulation.

Measurement of cardiac function in conscious rats.

The goal of this study was to establish that 1. blood velocity profile in the rat aorta is parabolic, and 2. measure of left ventricular thickening fraction can be used in rats. Spontaneously hypertensive and normotensive Wistar Kyoto rats were instrumented with a 20-MHz pulsed Doppler flow probe around the thoracic aorta and a 20-MHz pulsed Doppler thickening probe on the left ventricle. Doppler frequency shifts were measured throughout the entire aorta diameter, and individual blood velocity profiles were constructed. It was demonstrated that blood velocity in the ascending aorta of rats is laminar; therefore, cardiac output can be measured using the pulsed Doppler method. In Wistar Kyoto rats, left ventricular thickening fraction was 24 +/- 1% and 25 +/- 1%, 2 and 3 weeks following surgery. In spontaneously hypertensive rats, left ventricular thickening fraction was 22 +/- 2%. Halothane depressed left ventricular thickening fraction, whereas isoproterenol increased left ventricular thickening fraction in conscious rats. Thus, pulsed Doppler technique is a valuable tool for evaluating cardiovascular function in conscious rats.

An ultrasonic method for measuring tissue displacement: technical details and validation for measuring myocardial thickening.

We have developed a method for measuring myocardial thickening from a single ultrasonic transducer attached to the epicardium. Displacement of the underlying myocardial tissue is measured by following the phase of the echoes within a sample volume range-gated across the myocardium. The output is in the form of an analog signal. To verify the accuracy, resolution, and limitations of the system, we derived the equations relating the position of a reflector to the phase of its echo and compared the system output in vitro to a known input using a single moving target and a random distribution of scatterers, and in vivo to that of an ultrasonic transit-time dimension gauge. The results demonstrate that the 10 MHz system can accurately follow the motion of single or multiple targets with a resolution of 0.02 mm. In 25 dogs myocardial thickening measured with the displacement system compared favorably in both waveform and magnitude with thickening measured by the two-crystal transit-time method. Applications for the displacement method include: quantification of regional ventricular function in animal models of cardiovascular diseases, measurement of endocardial to epicardial differences in the deformation of regional myocardium during the cardiac cycle, and evaluation of regional cardiac function in patients during and after corrective cardiac surgery.

Pooled analysis of three large clinical trials to determine the optimal dose of dolasetron mesylate needed to prevent postoperative nausea and vomiting. The Dolasetron Prophylaxis Study Group.

STUDY OBJECTIVE: To identify the maximally effective dolasetron dose (i.e., maximum efficacy with minimum adverse events) for prevention of postoperative nausea and vomiting (PONV) using the statistical power generated in a pooled patient sample from three large, nearly identical clinical trials. DESIGN: Three randomized, multicenter, placebo-controlled, double-blinded trials. SETTING: Trials 1, 2, and 3 enrolled patients at 10, 25, and 17 hospitals and/or surgical centers, respectively. PATIENTS: A total of 1,946 ASA physical status, I, II, and III patients. Trials 1 and 2 enrolled only female patients (n = 916) undergoing gynecologic surgery. Trial three enrolled 722 females (approximately 70% gynecologic surgeries) and 308 males (approximately 46% orthopedic surgeries) undergoing a variety of surgical procedures. INTERVENTIONS: All surgical procedures used balanced general anesthesia. Patients received 12.5, 25, 50, or 100 mg of the antiemetic, dolasetron, near the end of anesthesia. MEASUREMENTS AND MAIN RESULTS: Efficacy endpoints were identical and measured for 24 hours: complete response (no vomiting or rescue medication) and maximum nausea, reported using a 100-mm visual analog scale (VAS). Safety was assessed using adverse event reports, laboratory and electrocardiographic data, and vital signs. All four dolasetron doses produced significant increases in complete response and decreases in maximum VAS nausea compared with placebo (p < 0.01). No increased efficacy was observed with dolasetron doses higher than 12.5 mg. Safety was similar between each dolasetron dose and placebo. CONCLUSION: Dolasetron 12.5 mg, given near the end of anesthesia, is the maximally effective dose studied for preventing postoperative nausea and vomiting.

Cardiovascular deconditioning and venous air embolism in simulated microgravity in the rat.

BACKGROUND: Astronauts conducting extravehicular activities undergo decompression to a lower ambient pressure, potentially resulting in gas bubble formation within the tissues and venous circulation. Additionally, exposure to microgravity produces fluid shifts within the body leading to cardiovascular deconditioning. A lower incidence of decompression illness in actual spaceflight compared with that in ground-based altitude chamber flights suggests that there is a possible interaction between microgravity exposure and decompression illness. HYPOTHESIS: The purpose of this study was to evaluate the cardiovascular and pulmonary effects of simulated hypobaric decompression stress using a tail suspension (head-down tilt) model of microgravity to produce the fluid shifts associated with weightlessness in conscious, chronically instrumented rats. METHODS: Venous bubble formation resulting from altitude decompression illness was simulated by a 3-h intravenous air infusion. Cardiovascular deconditioning was simulated by 96 h of head-down tilt. Heart rate, mean arterial blood pressure, central venous pressure, left ventricular wall thickening and cardiac output were continuously recorded. Lung studies were performed to evaluate edema formation and compliance measurement. Blood and pleural fluid were examined for changes in white cell counts and protein concentration. RESULTS: Our data demonstrated that in tail-suspended rats subjected to venous air infusions, there was a reduction in pulmonary edema formation and less of a decrease in cardiac output than occurred following venous air infusion alone. Mean arterial blood pressure and myocardial wall thickening fractions were unchanged with either tail-suspension or venous air infusion. Heart rate decreased in both conditions while systemic vascular resistance increased. CONCLUSIONS: These differences may be due in part to a change or redistribution of pulmonary blood flow or to a diminished cellular response to the microvascular insult of the venous air embolization.

Cardiopulmonary changes with moderate decompression in rats.

Sprague-Dawley rats were compressed to 616 kPa (a) for 120 min then decompressed at 38 kPa/min to assess the cardiovascular and pulmonary responses to moderate decompression stress. In one series of experiments the rats were chronically instrumented with Doppler ultrasonic probes for simultaneous measurement of blood pressure, cardiac output, heart rate, left and right ventricular wall thickening fraction, and venous bubble detection. Data were collected at baseline, throughout the compression/decompression protocol, and for 120 min post decompression. In a second series of experiments the pulmonary responses to the decompression protocol were evaluated in non-instrumented rats. Analyses included blood gases, pleural and bronchoalveolar lavage (BAL) protein and hemoglobin concentration, pulmonary edema, BAL and lung tissue phospholipids, lung compliance, and cell counts. Venous bubbles were directly observed in 90% of the rats where immediate post-decompression autopsy was performed and in 37% using implanted Doppler monitors. Cardiac output, stroke volume, and right ventricular wall thickening fractions were significantly decreased post decompression, whereas systemic vascular resistance was increased suggesting a decrease in venous return. BAL Hb and total protein levels were increased 0 and 60 min post decompression; pleural and plasma levels were unchanged. BAL white blood cells and neutrophil percentages were increased 0 and 60 min post decompression and pulmonary edema was detected. Venous bubbles produced with moderate decompression profiles give detectable cardiovascular and pulmonary responses in the rat.

The nerve stimulation technique versus the loss of resistance technique for the posterior approach to lumbar plexus block: a randomized, prospective, observer-blinded, pilot study.

BACKGROUND: This prospective, randomized, observer-blinded, pilot study compares the effects of the nerve stimulation guidance technique (NS) with the loss of resistance technique (LOR) on readiness for surgery during the posterior approach to lumbar plexus block. METHODS: Thirty ASA status I-III patients who were 18-85 years old and who were undergoing hip fracture repair were enrolled. After parasacral sciatic nerve block, patients were randomly allocated to receive a continuous posterior lumbar plexus block using nerve stimulation (n=15) or a continuous psoas compartment block using the loss of resistance technique (n=15) with 20 ml of 1.5% mepivacaine. A blinded observer monitored for sensory and motor block onsets every 5 minutes. We defined readiness for surgery as complete numbness to the pinprick test and complete motor block on the surgical side. If incomplete, the lumbar plexus block was supplemented with 10 mL of 1.5% mepivacaine through the catheter before surgery. Intraoperative fentanyl or general anesthesia requirements, pain scores, local anesthetic consumption, morphine requirements for breakthrough pain and side effects were monitored. RESULTS: The mean time to readiness for surgery was 12±6 min Group NS and 22±6 min in Group LOR (P=0.03). Three patients in Group NS and 9 patients in Group LOR required additional boluses of local anesthetic through the lumbar plexus catheter before surgery (P=0.113). CONCLUSION: Nerve stimulation allowed faster readiness for surgery than loss of resistance. Nevertheless, the two techniques seem to be comparable in terms of local anesthetic consumption, morphine requirements and pain scores.

Single-dose aprepitant vs ondansetron for the prevention of postoperative nausea and vomiting: a randomized, double-blind phase III trial in patients undergoing open abdominal surgery.

BACKGROUND: The neurokinin(1) antagonist aprepitant is effective for prevention of chemotherapy-induced nausea and vomiting. We compared aprepitant with ondansetron for prevention of postoperative nausea and vomiting. METHODS: Nine hundred and twenty-two patients receiving general anaesthesia for major abdominal surgery were assigned to receive a single preoperative dose of oral aprepitant 40 mg, oral aprepitant 125 mg, or i.v. ondansetron 4 mg in a randomized, double-blind trial. Vomiting episodes, use of rescue therapy, and nausea severity (verbal rating scale) were documented for 48 h after surgery. Primary efficacy endpoints were complete response (no vomiting and no use of rescue therapy) 0-24 h after surgery and no vomiting 0-24 h after surgery. The secondary endpoint was no vomiting 0-48 h after surgery. RESULTS: Aprepitant at both doses was non-inferior to ondansetron for complete response 0-24 h after surgery (64% for aprepitant 40 mg, 63% for aprepitant 125 mg, and 55% for ondansetron, lower bound of 1-sided 95% CI > 0.65), superior to ondansetron for no vomiting 0-24 h after surgery (84% for aprepitant 40 mg, 86% for aprepitant 125 mg, and 71% for ondansetron; P < 0.001), and superior for no vomiting 0-48 h after surgery (82% for aprepitant, 40 mg, 85% for aprepitant, 125 mg, and 66% for ondansetron; P < 0.001). The distribution of peak nausea scores was lower in both aprepitant groups vs ondansetron (P < 0.05). CONCLUSIONS: Aprepitant was non-inferior to ondansetron in achieving complete response for 24 h after surgery. Aprepitant was significantly more effective than ondansetron for preventing vomiting at 24 and 48 h after surgery, and in reducing nausea severity in the first 48 h after surgery. Aprepitant was generally well tolerated.

Stimulating or conventional perineural catheters after hallux valgus repair: a double-blind, pharmaco-economic evaluation.

BACKGROUND: We prospectively evaluated direct analgesia-related costs of continuous sciatic nerve block using either a stimulating or conventional catheter after hallux valgus repair. METHODS: The perineural catheter was inserted through a stimulating introducer either blindly (group Conventional, n= 38) or while stimulating via the catheter (group Stimulating, n= 38). Nerve block was induced with 25 ml of mepivacaine 15 mg/ml, and was followed 3 h later by a patient-controlled infusion of ropivacaine 2 mg/ml (basal infusion: 3 ml/h; incremental dose: 5 ml; lock-out time: 30 min). Rescue tramadol [100 mg intravenous (i.v.)] was given if required. Local anesthetic consumption, need for rescue tramadol and post-operative nausea and vomiting (PONV) treatment, and patient's satisfaction were recorded during first 24-h infusion. Cost calculations were based on the acquisition cost of drugs and devices. RESULTS: Both techniques were similarly effective, but local anesthetic consumption and need for rescue analgesics were lower in the Stimulating group [respectively, 120 vs. 153 ml (P= 0.004) and 21% vs. 60% (P= 0.001)]. The analgesia-related costs for 24 h were similar when 100-ml bags of ropivacaine 2 mg/ml were used (66 euro vs. 67 euro; P= 0.26). When 200-ml bags of ropivacaine were used, the analgesia-related costs were higher in the Stimulating group than the Conventional group (75 euro vs. 55 euro; P= 0.0005). CONCLUSIONS: Direct costs of continuous sciatic nerve block ranged from 55 to 75 euro. Stimulating catheters reduced local anesthetic consumption and need for rescue analgesics. This was only cost effective when 100-ml bags of 2 mg/ml ropivacaine were used, while the cheapest combination was the use of conventional catheters and 200-ml bags of ropivacaine.

Blocks at the wrist provide effective anesthesia for carpal tunnel release.

PURPOSE: Distal blocks are not recommended even for a short procedure when a tourniquet is used. This study was designed to evaluate the tolerance, effectiveness, patient acceptance and safety of distal blocks at the wrist. METHODS: Consecutive patients (n=273, mean age 53 +/-15 yr) undergoing endoscopic carpal tunnel release with a pneumatic tourniquet were included in this study. The median nerve was blocked 6 cm above the wrist crease by injecting 10 mL of 2% lidocaine and 0.5% bupivacaine (v/v). The ulnar nerve was blocked by injecting 8 mL of the same anesthetic mixture below the flexor carpi ulnaris tendon 6 cm above the wrist crease. Finally, 2 mL of local anesthetic were infiltrated sc and laterally below the crease to block the musculocutaneous nerve. The intensity of the block was evaluated after five, ten and 20 min. In addition, pain associated with block performance and tolerance of the tourniquet were evaluated. Finally, neurological complications associated with this technique were investigated. Data are presented as means +/- SD. RESULTS: At ten minutes after the block was performed, 9% and 32% of patients required an additional injection to complete the block in the median and ulnar territories, respectively. In more than 75% of patients, performance of the block was associated with either no or mild pain. The tourniquet was inflated for 12.6 +/- 5.4 min and was well tolerated in 99% of patients. Finally, neither transient nor permanent neurological deficit were recorded postoperatively. CONCLUSION: Blocks at the wrist are effective, well accepted by the patient and safe when a pneumatic tourniquet is used for a short procedure.