An Analysis of the Top-cited Articles in Anesthesiology Education Literature.

BACKGROUND: In the same way that impact factor is calculated for journals, the number of citations an article receives can indicate its influence or value to a particular field. This study was designed to identify the most frequently cited articles in anesthesiology education to yield insight into which articles have been most useful for researchers in ongoing research and publication. METHODS: The Web of Science database was searched to capture the top-cited articles in anesthesiology education both in anesthesiology and nonanesthesiology journals. Results were sorted by the most frequently cited. The top 40 cited articles were identified. Articles were included if they (1) related to anesthesiology or included anesthesiologists as subjects and (2) were related to the education of current or future anesthesiologists. The full text was analyzed, and themes were identified. RESULTS: There was a total of 2923 citations of articles in anesthesiology journals and 924 citations of articles in nonanesthesiology journals. Thirty-two of 40 articles (80%) were research studies. Twenty-four of 40 (60%) were about teaching methods. Twenty-five of 40 (63%) focused on simulation, and 31 of 40 (78%) had residents as the subjects. Twenty-eight of 40 (70%) articles were about either case management (15) or learning procedures (13). CONCLUSIONS: This study identifies the most widely cited articles in anesthesiology education. Common themes included procedural learning, interventional research study designs, simulation, and studies involving residents as subjects. This article may be a resource to anesthesiology education researchers to identify what articles are widely cited by other researchers.

Patient selection for day case-eligible surgery: identifying those at high risk for major complications.

BACKGROUND: Due to economic pressures and improvements in perioperative care, outpatient surgical procedures have become commonplace. However, risk factors for outpatient surgical morbidity and mortality remain unclear. There are no multicenter clinical data guiding patient selection for outpatient surgery. The authors hypothesize that specific risk factors increase the likelihood of day case-eligible surgical morbidity or mortality. METHODS: The authors analyzed adults undergoing common day case-eligible surgical procedures by using the American College of Surgeons' National Surgical Quality Improvement Program database from 2005 to 2010. Common day case-eligible surgical procedures were identified as the most common outpatient surgical Current Procedural Terminology codes provided by Blue Cross Blue Shield of Michigan and Medicare publications. Study variables included anthropometric data and relevant medical comorbidities. The primary outcome was morbidity or mortality within 72 h. Intraoperative complications included adverse cardiovascular events; postoperative complications included surgical, anesthetic, and medical adverse events. RESULTS: Of 244,397 surgeries studied, 232 (0.1%) experienced early perioperative morbidity or mortality. Seven independent risk factors were identified while controlling for surgical complexity: overweight body mass index, obese body mass index, chronic obstructive pulmonary disease, history of transient ischemic attack/stroke, hypertension, previous cardiac surgical intervention, and prolonged operative time. CONCLUSIONS: The demonstrated low rate of perioperative morbidity and mortality confirms the safety of current day case-eligible surgeries. The authors obtained the first prospectively collected data identifying risk factors for morbidity and mortality with day case-eligible surgery. The results of the study provide new data to advance patient-selection processes for outpatient surgery.

Identifying patients at high risk for venous thromboembolism requiring treatment after outpatient surgery.

OBJECTIVE: To identify independent predictors of 30-day venous thromboembolism (VTE) events requiring treatment after outpatient surgery. BACKGROUND: An increasing proportion of surgical procedures are performed in the outpatient setting. The incidence of VTE requiring treatment after outpatient surgery is unknown. METHODS: Prospective observational cohort study using the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database from 2005 to 2009. Adult patients who had outpatient surgery or surgery with subsequent 23-hour observation were included. The main outcome measure was 30-day VTE requiring treatment. Patients were randomly assigned to derivation (N = 173,501) or validation (N = 85,730) cohorts. Logistic regression examined independent risk factors for 30-day VTE. A weighted risk index was created and applied to the validation cohort. Stratified analyses examined 30-day VTE by risk level. RESULTS: Thirty-day incidence of VTE for the overall cohort was 0.15%. Independent risk factors included current pregnancy (adjusted odds ratio [OR] = 7.80, P = 0.044), active cancer (OR = 3.66, P = 0.005), age 41 to 59 years (OR = 1.72, P = 0.008), age 60 years or more (OR = 2.48, P < 0.001), body mass index 40 kg/m or higher (OR = 1.81, P = 0.015), operative time 120 minutes or more (OR = 1.69, P = 0.027), arthroscopic surgery (OR = 5.16, P < 0.001), saphenofemoral junction surgery (OR = 13.20, P < 0.001), and venous surgery not involving the great saphenous vein (OR = 15.61, P < 0.001). The weighted risk index identified a 20-fold variation in 30-day VTE between low (0.06%) and highest risk (1.18%) patients. CONCLUSIONS: Thirty-day VTE risk after outpatient surgery can be quantified using a weighted risk index. The risk index identifies a high-risk subgroup of patients with 30-day VTE rates of 1.18%.

Symptomatic phrenic nerve palsy after supraclavicular block in an obese man.

Regional anesthesia has an expanding role in upper extremity surgery. Brachial plexus blocks offer several advantages including providing effective analgesia, reducing narcotic requirements, and facilitating ambulatory care surgery. Despite the popularity of nerve blocks, the surgeon must not forget the complications associated with regional anesthesia. This article describes a case of symptomatic phrenic nerve palsy after supraclavicular brachial plexus block in an obese man. A 46-year-old obese man underwent a left-sided supraclavicular block in preparation for decompression of Guyon's canal for ulnar mononeuropathy at the wrist. The patient experienced acute-onset dyspnea, chest discomfort, and anxiety, and physical examination demonstrated reduced breath sounds in the left hemithorax. Chest radiographs documented elevation of the left hemidiaphragm consistent with an iatrogenic phrenic nerve palsy. The patient was admitted for 23-hour observation and underwent an uncomplicated ulnar nerve decompression under Bier block anesthesia 1 week later. No long-term sequelae have been identified; however, there was a delay in surgical care, admission to the hospital, and transient pulmonary symptoms. We attribute this complication to significant abdominal obesity causing compromised pulmonary reserve and poor tolerance of transient hemidiaphragmatic paresis. In recent studies, waist circumference and abdominal height were inversely related to pulmonary function. We suspect that the incidence of symptomatic phrenic nerve palsy associated with brachial plexus blocks will increase as the prevalence of obesity increases in this country.

Antinociceptive effects of nociceptin/orphanin FQ administered intrathecally in monkeys.

UNLABELLED: Nociceptin/orphanin FQ (N/OFQ) is the endogenous peptide for the NOP receptors. Depending on the doses, intrathecal administration of N/OFQ has dual actions (ie, hyperalgesia and antinociception) in rodents. However, the pharmacological profile of intrathecal N/OFQ is not fully known in primates. The aim of this study was to investigate behavioral effects of intrathecal N/OFQ over a wide dose range and to compare its effects with ligands known to produce hyperalgesia or antinociception in monkeys. Intrathecal N/OFQ from 1 fmol to 1 nmol did not produce any hyperalgesic or scratching responses. In contrast, intrathecal substance P 100 nmol produced hyperalgesia, and intrathecal DAMGO 10 nmol produced antinociception. At the dose range between 10 nmol and 1 micromol, intrathecal N/OFQ dose-dependently produced thermal antinociception against a noxious stimulus in 2 intensities. More importantly, N/OFQ in combined with intrathecal morphine dose-dependently potentiated morphine-induced antinociception without inhibiting morphine-induced itch/scratching. Taken together, this study is the first to provide a unique functional profile of intrathecal N/OFQ over a wide dose range in primates. Intrathecal N/OFQ produces thermal antinociception without anti-morphine actions or scratching responses, indicating that N/OFQ or NOP receptor agonists represent a promising target as spinal analgesics. PERSPECTIVE: Intrathecal administration of N/OFQ only produced thermal antinociception, not hyperalgesia, in monkeys. In addition, intrathecal N/OFQ does not have anti-morphine actions or itch/scratching responses. This study strongly supports the therapeutic potential of N/OFQ or NOP receptor agonists as spinal analgesics for clinical trials.

Effects of butorphanol on morphine-induced itch and analgesia in primates.

BACKGROUND: Butorphanol is an opioid analgesic with partial agonist actions at micro- and kappa-opioid receptors (MOR and KOR). Previous studies have demonstrated that both MOR antagonists and KOR agonists are effective in alleviating intrathecal morphine-induced itch in primates. The aim of the study was to investigate the effectiveness of butorphanol as an antipruritic and to elucidate the receptor mechanisms underlying butorphanol's antipruritic effect in primates. METHODS: Adult rhesus monkeys were used in the behavioral assays for measuring itch/scratching and analgesia. The dose-response curves of butorphanol were studied using selective MOR and KOR antagonists. In addition, the effect of butorphanol as an antipruritic was studied on subcutaneous and intrathecal morphine-induced itch and analgesia. KOR-selective antagonists were further used to compare the degrees of MOR and KOR activation underlying the antipruritic effect of butorphanol. RESULTS: Butorphanol alone produced analgesia with slight itch responses, and both effects were blocked by a MOR antagonist, clocinnamox (0.1 mg/kg). In contrast, a KOR antagonist, 5'-guanidinylnaltrindole (1 mg/kg), increased butorphanol-elicited itch. Systemic butorphanol (0.0032-0.032 mg/kg) dose-dependently attenuated systemic or intrathecal morphine-induced itch. In addition, butorphanol either potentiated or maintained morphine-induced analgesia without producing sedation. KOR-selective antagonists, 5'-guanidinylnaltrindole (1 mg/kg) and nor-binaltorphimine (3.2 mg/kg), only partially reversed the antipruritic effect of butorphanol with different durations of KOR antagonism. CONCLUSIONS: Butorphanol is effective in attenuating systemic or spinal morphine-induced itch without reducing morphine analgesia. This study provides functional evidence that both partial MOR and KOR agonist actions contribute to the effectiveness of butorphanol as an antipruritic in primates.

A series of anesthesia-related maternal deaths in Michigan, 1985-2003.

BACKGROUND: Maternal Mortality Surveillance has been conducted by the State of Michigan since 1950, and anesthesia-related maternal deaths were most recently reviewed for the years 1972-1984. METHODS: Records for pregnancy-associated deaths between 1985 and 2003 were reviewed to identify 25 cases associated with a perioperative arrest or major anesthetic complication. Four obstetric anesthesiologists independently classified these cases, and disagreements were resolved by discussion. Precise definitions of anesthesia-related and anesthesia-contributing maternal death were constructed. Anesthesia-related deaths were reviewed to identify the chain of medical errors or care management problems that contributed to each patient death. RESULTS: Of 855 pregnancy-associated deaths, 8 were anesthesia-related and 7 were anesthesia-contributing. There were no deaths during induction of general anesthesia. Five resulted from hypoventilation or airway obstruction during emergence, extubation, or recovery. Lapses in either postoperative monitoring or anesthesiology supervision seemed to contribute to 5 of the 8 anesthesia-related deaths. Other characteristics common to these cases included obesity (n=6) and African-American race (n=6). CONCLUSIONS: The 8 anesthesia-related and seven anesthesia-contributing maternal deaths in Michigan between 1985 and 2003 illustrate three key points. First, all anesthesia-related deaths from airway obstruction or hypoventilation took place during emergence and recovery, not during the induction of general anesthesia. Second, system errors played a role in the majority of cases. Of concern, lapses in postoperative monitoring and inadequate supervision by an anesthesiologist seemed to contribute to more than half of the deaths. Finally, this report confirms previous work that obesity and African-American race are important risk factors for anesthesia-related maternal mortality.

Relative analgesic potencies of levobupivacaine and ropivacaine for epidural analgesia in labor.

BACKGROUND: The minimum local analgesic concentration has been defined as the median effective local analgesic concentration (EC50) in a 20-ml volume for epidural analgesia in the first stage of labor. The aim of this study was to assess the relative analgesic potencies of epidural levobupivacaine and ropivacaine by determination of their respective minimum local analgesic concentrations. METHODS: Parturients at 7 cm of cervical dilation or less who requested epidural analgesia were allocated to one of two groups in this double-blind, randomized, prospective study. After lumbar epidural catheter placement, 20 ml of the test solution was given: levobupivacaine (n = 35) or ropivacaine (n = 35). The concentration of local anesthetic was determined by the response of the previous patient in that group to a higher or lower concentration using up-down sequential allocation. Analgesic efficacy was assessed using 100-mm visual analog pain scale scores, with 10 mm or less within 30 min defined as effective. An effective result directed a 0.01% wt/vol decrement for the next patient. An ineffective result directed a 0.01% wt/vol increment. RESULTS: Of 105 women enrolled, 35 were excluded, leaving 70 for analysis. The minimum local analgesic concentration of levobupivacaine was 0.087% wt/vol (95% CI, 0.081-0.094%), and the minimum local analgesic concentration of ropivacaine was 0.089% wt/vol (95% CI, 0.075-0.103%). Levobupivacaine and ropivacaine were of similar potency with a ropivacaine:levobupivacaine potency ratio of 0.98 (95% CI, 0.80-1.20). No difference in motor effects was observed. CONCLUSIONS: This study demonstrated that levobupivacaine and ropivacaine are of similar potency for epidural analgesia in the first stage of labor.

Activation of kappa-opioid receptors inhibits pruritus evoked by subcutaneous or intrathecal administration of morphine in monkeys.

Pruritus (itch sensation) is the most common side effect associated with spinal administration of morphine given to humans for analgesia. A variety of agents have been proposed as antipruritics with poorly understood mechanisms and they are effective with variable success. kappa-Opioid agonists possess several actions that are opposite to micro -opioid agonists. We proposed to investigate the role of kappa-opioid receptors (KORs) in morphine-induced scratching and antinociception in monkeys. Scratching responses were counted by observers blinded to treatment. Antinociception was measured by a warm water (50 degrees C) tail-withdrawal assay. Pretreatment with low doses of trans-(+/-)-3,4-dichloro-N-methyl-N-(2-[1-pyrrolidinyl]-cyclohexyl)-benzeneacetamide (U-50488H) (0.032-0.18 mg/kg s.c.), a selective KOR agonist, dose dependently suppressed the s.c. morphine dose-effect curve for scratching and potentiated s.c. morphine-induced antinociception. In addition, s.c. U-50488H attenuated i.t. morphine (10 and 32 micro g)-induced scratching while maintaining or enhancing i.t. morphine-induced antinociception. The combination of s.c. or i.t. morphine with low doses of U-50488H did not cause sedation. More importantly, pretreatment with 3.2 mg/kg nor-binaltorphimine, a selective KOR antagonist, blocked the effects of s.c. U-50488H on both s.c. and i.t. morphine-induced scratching. These results indicate that activation of KOR attenuates morphine-induced scratching without interfering with antinociception in monkeys. This mechanism-based finding provides functional evidence in support of the clinical potential of KOR agonists as antipruritics in the presence of MOR agonist-induced pruritus.

An analysis of reintubations from a quality assurance database of 152,000 cases.

STUDY OBJECTIVE: To determine if the majority of reintubations, a potentially preventable adverse event, were predominantly due to residual muscle relaxant effects, we analyzed our quality assurance database to identify the causes of reintubation. DESIGN: Retrospective study. SETTING: University of Michigan Department of Anesthesiology Quality Assurance (QA) database. MEASUREMENTS: We analyzed QA records from 152,939 anesthetic cases performed from 1994 to 1999 at our institution. Of these cases, 107,317 were performed with a general anesthetic. The medical record of each patient requiring reintubation was obtained and reviewed to determine the cause of the reintubation. RESULTS: A total of 191 reintubation events were identified. One hundred twelve of the 191 (59%) reintubations were due to respiratory problems; 11 of the 191 (6%) reintubations were due to complications of neuromuscular blocking drug use. Other causes were unintentional extubation, surgical complication, endotracheal tube problems, and cardiac problems. One hundred five reintubations (105/191, 55%) occurred in the operating room and 86 (86/191, 45%) occurred in the postanesthesia care unit. CONCLUSION: Respiratory complications were the most common cause of reintubation in the perioperative period. Complications related to the neuromuscular blocking drugs were the fourth most common cause of reintubation. More reintubations occurred in the operating room than the postanesthesia care unit. Muscle relaxant effect and opioid effect are rare causes of respiratory failure in the anesthetized patient in the immediate postoperative period.

Effect of epidural epinephrine on the minimum local analgesic concentration of epidural bupivacaine in labor.

BACKGROUND: The minimum local analgesic concentration (MLAC) has been defined as the median effective local analgesic concentration in a 20-ml volume for epidural analgesia in the first stage of labor. The aim of this study was to determine the local anesthetic-sparing efficacy of epidural epinephrine by its effect on the MLAC of bupivacaine. METHODS: In this double-blind, randomized, prospective study, 70 parturients who were at 7 cm or less cervical dilation and who requested epidural analgesia were allocated to one of two groups. After lumbar epidural catheter placement, 20 ml bupivacaine (n = 35) or bupivacaine with epinephrine 1:300,000 (n = 35) was administered. The concentration of bupivacaine was determined by the response of the previous patient in that group to a higher or lower concentration using up-down sequential allocation. Analgesic efficacy was assessed using 100-mm visual analog pain scores, with 10 mm or less within 30 min defined as effective. RESULTS: The MLAC of bupivacaine alone was 0.091% wt/vol (95% confidence interval, 0.081-0.102). The addition of epinephrine 1:300,000 (66.7 microg) resulted in a significant reduction (P < 0.01) in the MLAC of bupivacaine to 0.065% wt/vol (95% confidence interval, 0.047-0.083). The lowest maternal blood pressure was significantly lower in the bupivacaine-epinephrine group (P = 0.03). There were statistically significant reductions in fetal heart rate (P = 0.011) in the bupivacaine-epinephrine group that were not clinically significant. CONCLUSIONS: The addition of epidural epinephrine 1:300,000 (66 microg) resulted in a significant 29% reduction in the MLAC of bupivacaine. Coincident reductions in fetal heart rate and maternal blood pressure were also observed that were not clinically significant.