Cardiac anesthesia: thirty years later--the second annual Arthur E. Weyman lecture.

Cardiac anesthesiology has evolved spectacularly over the past 30 yr, changing from a practice focused on the anesthetic management of patients with cardiovascular diseases to a practice of cardiovascular medicine that contributes to the medical and surgical management of cardiovascular patients. The second Weyman lecture reviews this history, the critical role of the Society of Cardiovascular Anesthesiologists in the evolution of the specialty, and the prospects for continued development for the specialty, the society, and the patients they care for.

Ischemic mitral regurgitation.

Ischemic mitral regurgitation is the regurgitation seen with structurally normal valve leaflets that occurs in approximately 20% of patients after myocardial infarction and 56% of patients with congestive heart failure caused by ischemic or nonischemic cardiomyopathy. The initiating event is an ischemic insult that results in remodeling of the left ventricle toward a more spherical shape and new wall motion abnormalities. These changes lead to annular dilation and subvalvular distortion that prevent the mitral leaflets from coapting and closing completely during the contraction phase. Treatment options include coronary revascularization, ring annuloplasty, valve repair and replacement, or left ventricle reconstruction by way of localized reshaping or resection. Pharmacotherapy, aimed at raising left ventricular pressure without increasing tethering or left ventricular volume, is included in the treatment options for improving ischemic mitral regurgitation.

Paravertebral blocks provide superior same-day recovery over general anesthesia for patients undergoing inguinal hernia repair.

Inguinal herniorrhaphy is commonly performed on an outpatient basis under nerve blocks or local or general anesthesia (GA). Our hypothesis is that use of paravertebral blocks (PVB) as the sole anesthetic technique will result in shorter time to achieve home readiness and improved same-day recovery over a 'fast-track' GA. Fifty patients were randomly assigned to receive either PVB or GA under standardized protocols (PVB = 0.75% ropivacaine, followed by propofol sedation; GA = dolasetron 12.5 mg, propofol induction, rocuronium, endotracheal intubation; desflurane; bupivacaine 0.25% for field block). Eligibility for postanesthetic care unit (PACU) bypass and data on time-to-postoperative pain, ambulation, home readiness, and incidence of adverse events were collected. More patients in the PVB group (71%) met the criteria to bypass the postanesthetic care unit compared with patients in the GA group (8%; P < 0.001). Only 3 (13%) of patients in the PVB group requested treatment for pain while in the hospital, compared with 12 (50%) patients in the GA group, despite infiltration with local anesthetic (P = 0.005). Patients in the PVB group were able to ambulate earlier (102 +/- 55 minutes) than those in the GA group (213 +/- 108 minutes; P < 0.001). Time-to-home readiness and discharge times were shorter for patients in the PVB group (156 +/- 60 and 253 +/- 37 minutes) compared with those in the GA group (203 +/- 91 and 218 +/- 93 minutes) (P < 0.001). Adverse events (e.g., nausea, vomiting, sore throat) and pain requiring treatment in the first 24 hours occurred less frequently in patients who had received PVB than in those who had received GA. In outpatients undergoing inguinal herniorrhaphy, PVB resulted in faster time to home readiness and was associated with fewer adverse events and better analgesia before discharge than GA.

For outpatient rotator cuff surgery, nerve block anesthesia provides superior same-day recovery over general anesthesia.

BACKGROUND: Both general and nerve block anesthesia are effective for shoulder surgery. For outpatient surgery, it is important to determine which technique provides more efficient recovery. The authors' goal was to compare nerve block with general anesthesia with respect to recovery profile and patient satisfaction after rotator cuff surgery. METHODS: In this clinical trial, 50 consenting outpatients (aged 18-70 yr) were randomly assigned to receive either fast-track general anesthesia followed by bupivacaine (0.25%) wound infiltration or interscalene brachial plexus block (0.75% ropivacaine), each under standardized protocols. Blinded recovery room nurses assessed the need for pain treatment and rated patient eligibility for bypass of the phase 1 postanesthesia care unit and for discharge home. Patients were followed up for 2 weeks postoperatively. The primary outcome measures were postanesthesia care unit bypass and same-day discharge. Other same-day recovery outcomes included severity of and treatment for pain and time to ambulation. Postoperative outcomes at home included satisfaction with the anesthesia technique and absence of complications (at 2 weeks). RESULTS: Patients who received nerve block (vs. general anesthesia) bypassed the postanesthesia care unit more frequently (76 vs. 16%; P < 0.001), reported less pain, ambulated earlier, were ready for home discharge sooner (123 vs. 286 min; P < 0.001), had no unplanned hospital admissions (vs. 4 of 25 patients who underwent general anesthesia; P = 0.05), and were more satisfied with their care. No complications were reported in either treatment group. CONCLUSIONS: Nerve block anesthesia for outpatient rotator cuff surgery provides several same-day recovery advantages over general anesthesia.

Peripheral nerve blocks result in superior recovery profile compared with general anesthesia in outpatient knee arthroscopy.

It has been suggested that use of peripheral nerve blocks (PNBs) may have some potential benefits in the outpatient setting. There have been no studies specifically comparing PNBs performed with short-acting local anesthetics with general anesthesia (GA) in patients undergoing outpatient knee surgery. We hypothesized that a combination of lumbar plexus and sciatic blocks using a short-acting local anesthetic will result in shorter time-to-discharge-home as compared with GA. Patients scheduled to undergo knee arthroscopy were randomized to receive a GA (midazolam, fentanyl, propofol, N(2)O/O(2)/desflurane via laryngeal mask airway) or lumbar plexus/sciatic block (PNBs; 2-chloroprocaine). Patients given GA also received an intraarticular injection of 20 mL 0.25% bupivacaine for postoperative pain control. Patients in the PNB group were given midazolam (up to 4 mg) and alfentanil (500-750 microg) before block placement and propofol 30-50 microg . kg(-1) . min(-1) for intraoperative sedation. Relevant perioperative times, postanesthesia care unit bypass rate, severity of pain, and incidence of complications were compared between the two groups. Fifty patients were enrolled in the study; 25 patients each received GA or PNBs. Total operating room time did not differ significantly between the 2 groups (97 +/- 37 versus 91 +/- 42 min). Seventy-two percent of patients receiving PNB met criteria enabling them to bypass Phase I postanesthesia care unit compared with only 24% of those receiving GA (P < 0.002). Time to meet criteria for discharge home (home readiness) and time to actual discharge were significantly shorter for patients given PNBs than for patients given GA (131 +/- 62 versus 205 +/- 94 and 162 +/- 71 versus 226 +/- 96, respectively). Under the conditions of our study, the combination of lumbar plexus and sciatic blocks with 2-chloroprocaine 3% was associated with a superior recovery profile compared with GA in patients having outpatient knee arthroscopy.

Guillain-Barré syndrome in a patient with pancreatic cancer after an epidural-general anesthetic.

Guillain-Barre syndrome is a rare occurrence in medicine and is probably rarer still as a postoperative complication. We report an uneventful operative course, during epidural-general anesthesia, in a patient undergoing pancreatectomy who presented with acute paralysis mimicking an acute cervical spinal cord syndrome or brachial plexus neuropathy. The signs and symptoms of right upper extremity paralysis occurred within 2 h postoperatively. Immediate work-up, which included magnetic resonance imaging, electromyography, and nerve conduction velocity studies, provided the diagnosis.

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.

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.

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.

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.

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).

Comparison of povidone iodine and DuraPrep, an iodophor-in-isopropyl alcohol solution, for skin disinfection prior to epidural catheter insertion in parturients.

BACKGROUND: Although rare, infectious sequelae of epidural analgesia can occur. A recently marketed antiseptic solution (DuraPrep) which contains an iodophor in isopropyl alcohol, may provide enhanced and longer-lasting antimicrobial activity and thus be useful in the obstetric setting. The purpose of this study was to evaluate the antisepsis achieved with DuraPrep compared with povidone iodine (PI). METHODS: Sixty women in active labor who requested epidural analgesia were randomly assigned to receive skin preparation with either PI or DuraPrep solution. A total of three cultures were obtained from each subject. The first was obtained just prior to skin disinfection, the second was obtained immediately following antisepsis, and the third was obtained just before removal of the catheter. In addition, the distal tip of the catheter was also submitted for culture. RESULTS: The clinical characteristics and the risk factors for infection were similar in the two groups. The proportion of subjects with positive skin cultures immediately after skin disinfection differed significantly between the PI and DuraPrep groups (30 3%, respectively, P = 0.01). The number of subjects with any positive skin cultures at the time of catheter removal was greater in the PI group as compared to the DuraPrep group (97 50%, respectively, P = 0.0001), as was the number of organisms cultured from skin (log CFU 1.93 +/- 0.40 0.90 +/- 0.23, respectively, P = 0.03). Six catheters, all from the PI group, yielded positive cultures by the roll-plate technique. CONCLUSION: As compared to PI, DuraPrep solution was found to provide a greater decrease in the number of positive skin cultures immediately after disinfection, as well as in bacterial regrowth and colonization of the epidural catheters.