Role of the Internet as an information resource for surgical patients: a survey of 877 patients.

BACKGROUND: This study was conducted to provide preliminary data regarding current Internet use practices for information about anaesthesia in patients undergoing elective surgical procedures at a major academic institution. METHODS: With IRB approval, 2936 patients coming for preanaesthetic evaluation at a tertiary academic hospital's preadmission testing (PAT) centre were invited to voluntarily participate in a 20-item questionnaire designed to obtain participants' characteristics and Internet use for information pertaining to their upcoming surgery. Data were analysed using statistical software SAS (Cary, NC, USA). Descriptive statistics were calculated for continuous variables using mean (sd), and for categorical data using n (%). Association analysis was performed using the Fisher's exact test. RESULTS: Eight hundred and seventy-seven patients (30%) responded. Of these, 356 (41%) looked for information about their medical condition, 321 (37%) for their surgery, 279 (32%) for surgeon, 163 (19%) for the hospital, and only 36 (4%) for information regarding anaesthesia. Of these 36 patients, 14 (39%) said the sites they used helped answer their questions regarding anaesthesia. Of the 831 patients who did not use the Internet for anaesthesia, 503 (57%) indicated that they would be receptive to being directed to specific websites for anaesthesia. CONCLUSIONS: Of the patients coming for elective surgery who responded (30%), the majority did not use the Internet to seek information regarding anaesthesia. Respondents indicated a high degree of interest in being directed to appropriate websites for further information. These results suggest that it may be beneficial to include information regarding reliable web-based resources to interested patients at preoperative visits.

The effect of desflurane on rocuronium onset, clinical duration and maintenance requirements.

Volatile anesthetics potentiate the effects of non-depolarizing agents. This study investigated the interaction between the inhalational anesthetic desflurane and rocuronium. Forty ASA I and II patients randomly received desflurane/N2O/fentanyl, or propofol/ N2O/fentanyl anesthesia, and rocuronium 0.6 mg/kg. Neuromuscular block was assessed at the adductor pollicis muscle. Block onset and clinical duration times were measured; a rocuronium infusion was started when the first twitch on train-of-four returned to 10% of control (T10%). Maintenance infusion requirements and recovery profiles (spontaneous and after reversal) were recorded until recovery of twitch to 90% of control (T90%). Rocuronium onset was prolonged by 67% (p = 0.034), clinical duration by 30% (p = NS), and infusion requirements were lower in the desflurane group (4.5 vs. 7.1 mg/kg/min, p = 0.003). Recovery times were not statistically different. Desflurane significantly delays the onset of neuromuscular block, potentiates rocuronium during maintenance infusion, but does not affect clinical duration or recovery.

How does the plethysmogram derived from the pulse oximeter relate to arterial blood pressure in coronary artery bypass graft patients?

UNLABELLED: Twenty patients scheduled for coronary artery bypass grafting had their ear and finger oximeter and radial artery blood pressure (Bp(meas)) waveforms collected. The ear and finger pulse oximeter waveforms were analyzed to extract beat-to-beat amplitude and area and width measurements. The Bp(meas) waveforms were analyzed to measured systolic blood pressure (BP), mean BP, and pulse pressure. The correlation coefficient was determined between the derived waveforms from the pulse oximeter and Bp(meas) for the first 10 patients. The ear pulse oximeter width (Width(Ear)) had the best correlation (r = 0.8). Linear regression was done between Width(Ear) and Bp(meas) based on slope (b) and intercept (a) values, BP was calculated (Bp(calc)) in the next 10 patients as: [equation: see text] where i = systolic BP, mean BP, and pulse pressure. The initial bias was too large to be clinically useful. To improve clinical applicability a period of calibration was introduced in which the first 50 readings of Width(Ear) and Bp(meas) for each patient were used to calculate the intercept. After calibration the systolic BP, mean BP and pulse pressure bias values were -2.6, -1.88 and -1.28 mm Hg, and the precision values were 15.9 10.09, and 9.94 mm Hg, respectively. The present attempt to develop a clinically useful method of noninvasive BP measuring was partly successful with the requirement of a calibration period. IMPLICATIONS: Statistical comparison was made between measured blood pressure (BP) from arterial line and calculated BP derived from ear pulse oximeter waveform in 10 patients undergoing coronary artery bypass graft surgery. Using 62,077 paired readings, the mean difference for systolic BP, mean BP, and pulse pressure between the 2 methods was -2.6, -1.88, and -1.28 mm Hg, respectively.

Hemodynamic assessment of local anesthetic administration by laser Doppler flowmetry.

OBJECTIVE: The hemodynamic effects of local anesthetic administration with and without a vasoconstrictor were compared by using laser Doppler flowmetry. STUDY DESIGN: Seventeen people participated in a single study session in which they were given 2 intraoral injections. The injections, which were administered in random order, consisted of 1.8 mL lidocaine (2%) with epinephrine (1:100,000) and mepivacaine (3%). Hemodynamic parameters consisting of blood pressure, heart rate, and laser Doppler flowmetry were reordered at regular intervals. RESULTS: The laser Doppler flowmeter detected changes in the peripheral perfusion of the finger that were not detected by changes in blood pressure and heart rate. The greatest change was associated with anxiety and occurred just before the injection. The inclusion of epinephrine in the local anesthetic resulted in a persistence of these changes. CONCLUSION: This investigation has confirmed the sensitivity of laser Doppler flowmetry as an investigational tool for assessing hemodynamic changes associated with anxiety and the administration of local anesthesia.

Different responses of ear and finger pulse oximeter wave form to cold pressor test.

The cold pressor test is often used to assess vasoconstrictive responses because it simulates the vasoconstrictive challenges commonly encountered in the clinical setting. With IRB approval, 12 healthy volunteers, aged 25--50 yr, underwent baseline plethysmographic monitoring on the finger and ear. The contralateral hand was immersed in ice water for 30 s to elicit a systemic vasoconstrictive response while the recordings were continued. The changes in plethysmographic amplitude for the first 30 s of ice water immersion (period of maximum response) of the finger and ear were compared. The data indicate a significant disparity between the finger and the ear signals in response to the cold stimulus. The average finger plethysmographic amplitude measurement decreased by 48% +/- 19%. In contrast, no significant change was seen in the ear plethysmographic amplitude measurement, which decreased by 2% +/- 10%. We conclude that the ear is relatively immune to the vasoconstrictive effects. These findings suggest that the comparison of the ear and finger pulse oximeter wave forms might be used as a real-time monitor of sympathetic tone and that the ear plethysmography may be a suitable monitor of the systemic circulation.

Comparison of ropivacaine 0.2% and lidocaine 0.5% for intravenous regional anesthesia in volunteers.

UNLABELLED: A longer acting local anesthetic such as ropivacaine may offer advantages over lidocaine for IV regional anesthesia (IVRA). The objective of this investigation was to determine whether the use of ropivacaine improves the quality and duration of IVRA. In a randomized, double cross-over design, 10 volunteers received lidocaine 0.5% or ropivacaine 0.2% for IVRA of the upper extremity on two separate days with a standard double-cuff technique. Sensation to pinprick, response to tetanic stimuli, and tourniquet pain were assessed on a 0-10 verbal numeric score scale at 5-min intervals throughout the period of tourniquet inflation. Motor function was evaluated by grip strength. After release of the second (distal) cuff, pinprick sensation, motor strength, and systemic side effects were evaluated at 3, 10, and 30 min. No significant differences were observed for onset times of anesthesia and times to proximal (38 +/- 3 and 36 +/- 3 min) or distal (34 +/- 13 and 36 +/- 13 min) tourniquet release after the administration of ropivacaine and lidocaine, respectively. However, postdeflation hypoalgesia and motor blockade were prolonged with ropivacaine, and postdeflation light-headedness, tinnitus, and drowsiness were more prominent with lidocaine. We conclude that ropivacaine may be an alternative to lidocaine for IVRA. It may result in prolonged analgesia and fewer side effects after tourniquet release. IMPLICATIONS: In this study, volunteers received lidocaine 0.5% or ropivacaine 0.2% for IV regional anesthesia on two study days. Ropivacaine and lidocaine provided similar surgical conditions. However, after release of the distal tourniquet, prolonged sensory blockade and fewer central nervous system side effects were observed with ropivacaine.

Enhancement of experimental pruritus and mechanically evoked dysesthesiae with local anesthesia.

Pain reduces itch-a commonly known effect of scratching the skin. Experimentally produced itch from histamine is sometimes accompanied by secondary sensations of pain. The present study investigated the effects of eliminating this pain, by means of a local anesthetic, on the itch and the enhanced mechanically evoked itch and pain that occur after an intradermal injection of histamine. In ten human subjects, the volar forearm was injected with either 20 microl of 2% chloroprocaine (experimental arm), or 20 microl of saline (control arm). Histamine 10 microl was injected into each bleb, and the resulting magnitude of itch estimated. The borders of three cutaneous areas were mapped within which mechanical stimulation of the skin surrounding the bleb elicited abnormal sensations (dysesthesiae): alloknesis, defined as itch evoked by innocuous stroking, and hyperalgesia and hyperknesis, characterized, respectively, by enhanced pain and enhanced itch evoked by pricking the skin with a fine tipped filament. The magnitude and duration of itch were significantly greater and the areas of dysesthesia significantly larger for the experimental than for the control arm. It is hypothesized that there exist two classes of histamine-sensitive primary afferent neurons. One class is "pruritic", and mediates itch whereas the other is "antipruritic", and evokes a centrally mediated reduction in histamine-evoked itch and dysesthesiae. It is further suggested that the anesthetic blocked the discharges of the antipruritic afferents, preventing the central inhibition from occurring and thereby unmasking the effects of the pruritic afferents.

Attenuation of experimental pruritus and mechanically evoked dysesthesiae in an area of cutaneous allodynia.

We investigated the effects of tactile allodynia on the itch and mechanically evoked dysesthesiae produced by an intradermal injection of histamine in human volunteers. After an intradermal injection of capsaicin into the volar surface of one forearm, there developed an area of tactile allodynia to stroking and hyperalgesia to pricking the skin. Histamine was then injected simultaneously into the area of allodynia (experimental arm) and into the opposite forearm (control arm). Magnitude estimates of itch were obtained every 15 s for 5 min, and the areas of cutaneous hyperalgesia (pricking-evoked pain), alloknesis (stroking-evoked itch), hyperknesis (pricking-evoked itch) and wheal and flare were measured. The areas of wheal and flare were not significantly different on the two arms. The magnitude of itch and the areas of hyperknesis and alloknesis developed normally on the control arm but were absent or greatly reduced on the experimental arm. Thus, both the itch and the alloknesis and hyperknesis normally induced by histamine were absent or greatly reduced when histamine was injected in an area of capsaicin-induced allodynia. These results are compatible with the hypothesis that activity in capsaicin-sensitive, nociceptive primary afferent neurons evokes a central neuronal inhibitory process that prevents or reduces the itch and mechanically evoked dysesthesiae normally produced by an intradermal injection of histamine.

A method for overcoming the ceiling effect of bounded pain scales.

OBJECTIVE: The Verbal Numerical Scale (VNS) for rating pain is bounded between 0 (= no pain) and 10 (= worst pain imaginable). We hypothesized that the limitations inherent to this boundary when rating extremely painful stimuli may be identified by integrating the VNS with an unbounded score such as magnitude estimation of relative change. METHODS: Volunteers received stimuli of increasing current via cutaneous electrodes until they rated >5 on the VNS scale. This stimulus, termed S, was arbitrarily assigned a magnitude estimate of 100%. Then, stimuli of varying currents were delivered; two were 10 mA and 20 mA higher than S (S(+10) and S(+20)), two were 1/2 of the current for the S stimulus (S(1/2)), and one was at the original current (Srepeat). The pain elicited by each stimulus was scored in proportion to the S stimulus. The extrapolated VNS score (VNSext) was determined by multiplying this magnitude estimate (%) by the VNS score for S. MAIN RESULTS: Seventy percent of the stimuli with higher intensity than S generated a VNSext score above 10. The mean magnitude estimations for S(+10) and S(+20) were 186% and 242%: they generated mean (median) VNSext values of 12.4 and 16.2, respectively (p = 0.019 for the difference between them by Wilcoxon signed rank test). CONCLUSIONS: The combined use of VNS and magnitude estimation confirmed that the ceiling of the bounded pain scale may significantly limit a patient's ability to describe a new pain stimulus. VNSext may provide a means of overcoming this limitation.

Assessment of the economic impact of an overage reduction program in the operating room.

STUDY OBJECTIVES: To delineate excessive supply preparation in the operating rooms (ORs) of Yale-New Haven Hospital, and to measure the reduction in such overage as a result of nursing and administration cost-containment efforts. DESIGN: Before and after trial. SETTING: Inpatient ORs of Yale-New Haven Hospital. INTERVENTIONS: After the initial documentation of overage, several cost-containment measures were instituted, including nursing education, review of overage data, and updating of surgical request lists. MEASUREMENTS AND MAIN RESULTS: The hospital cost of case-specific overage generated by all surgical procedures performed during two 2.5-month periods in 1992 and 1994 (before and after the interventions) were compared. One-thousand three hundred eighteen cases in 1992 were compared with 1,367 cases in 1994. A 45% reduction in mean per case overage occurred between the two assessment periods. Extrapolation of the data to the incidence of similar cases throughout the United States projected a comparable savings. CONCLUSIONS: Efforts to increase the efficiency of OR supply management can be measured, in part, by overage evaluation, which can serve as a resource for focusing efforts at cost-containment.

The effect of intradermal administration of lidocaine and morphine on the response to thermal stimulation.

Opioids appear to exert a peripheral effect by gaining access to peripheral opioid receptors. It has been proposed that inflammatory processes and highly osmotic substances could alter the perineural barrier, thereby allowing easy access to opioid receptors. Although local anesthetics do not have osmotic activity, they are highly active on neural tissue and appear to work synergistically with opioids when administered for major conduction blockade. We therefore evaluated, in a double-blind fashion, the combination of lidocaine plus morphine in an attempt to provide a scientific basis for the use of a combination of morphine plus local anesthetics in the periphery. Seven thermal stimuli in 2 degrees C increments (range 40-52 degrees C) were delivered in a random sequence by a computer-controlled thermistor to one of three pretreated sites on 10 volunteers' forearms: reference site (no injection), lidocaine site (0.1-mL intradermal injection of lidocaine 0.5%), or lidocaine plus morphine site (0.1 mL of 0.5 mg of morphine plus lidocaine 1%). Pain responses to the thermal stimuli were rated by the volunteers using the method of magnitude estimation. Pain scores indicated that the combination of lidocaine plus morphine was not more effective than lidocaine alone in attenuating the heat-induced pain. Twenty and 120 min after injection, scores at the lidocaine plus morphine site were 37% and 20% greater than those at the lidocaine site. The addition of morphine to lidocaine did not result in an improvement in the analgesic efficacy and actually had an antianalgesic effect.

Postoperative analgesia with parenteral opioids: does continuous delivery utilizing a transdermal opioid preparation affect analgesic efficacy or patient safety?

STUDY OBJECTIVES: To compare, in patients who underwent major orthopedic surgical procedures, the efficacy of intravenous (IV) patient-controlled analgesia (PCA) with morphine combined with continuous administration of two doses of fentanyl or placebo via transdermal therapeutic system with fentanyl (TTSF) patches. DESIGN: Randomized, double-blind, placebo-controlled study. SETTING: University teaching hospital. PATIENTS: 62 patients aged 18 to 65 years, presenting for elective orthopedic surgery and general anesthesia. INTERVENTIONS: Patients were randomized to one of three groups: group 1 received two placebo patches; group 2 received a 20 cm2 active patch delivering 50 micrograms/hr of fentanyl and a 30 cm2 placebo patch; group 3 received a 30 cm2 active patch delivering 75 micrograms/hr of fentanyl and a 20 cm2 placebo patch. All patches were placed approximately two hours prior to induction of general anesthesia. General anesthesia was induced with thiopental, intubation facilitated by the use of vecuronium or pancuronium, and anesthesia was maintained with isoflurane in an oxygen/nitrous oxide mixture (O2/N2O). Following surgery, IV morphine was provided using IV PCA with 1.5 mg of morphine with a 6-minute lockout and a 4-hour maximum dosage of 30 mg. MEASUREMENTS AND MAIN RESULTS: The time and dosage of morphine administered was recorded. Vital signs, pain intensity at rest, level of sedation, and arterial oxygen saturation (SpO2) were measured at intervals throughout the 72-hour study period and at 6 and 12 hours following patch removal. The presence of side effects was noted. Visual analog pain scores throughout the 72 hours of the study were not significantly different among groups. Patients receiving active TTSF required less IV PCA morphine at all time intervals. However, total opioid consumption was comparable among groups. The incidence of side effects was similar in all groups. CONCLUSIONS: There is no significant advantage to the routine use of continuous transdermal opioid delivery in patients receiving IV PCA after major orthopedic surgery.

Comparative recovery of 50-Hz and 100-Hz posttetanic twitch following profound neuromuscular block.

STUDY OBJECTIVE: To determine if posttetanic twitch following 100-Hz tetanic stimulation enables titration of a nondepolarizing relaxant infusion to a greater depth of block than that achieved with posttetanic twitch following 50 Hz. STUDY DESIGN: Prospective, observational study. SETTING: Operating rooms of a university tertiary care center. PATIENTS: 10 ASA physical status II and III patients free of known neuromuscular disease and undergoing general endotracheal anesthesia for routine elective surgery. INTERVENTIONS: Following induction of general anesthesia, neuromuscular block was maintained with a continuous intravenous vecuronium infusion. Depth of neuromuscular block was assessed by tactile evaluation of the evoked responses of the adductor pollicis muscle following supramaximal stimulation of the ulnar nerve via surface electrodes. The vecuronium infusion was titrated to loss of posttetanic twitch following 100-Hz tetanic stimulation, at which point the infusion was discontinued. MEASUREMENTS AND MAIN RESULTS: 100-Hz tetanic stimulation was repeated every two minutes until recovery of the first posttetanic twitch, at which point 50-Hz tetanic stimulation was repeated every two minutes until recovery of the first posttetanic twitch. The median time (interquartile range) from discontinuation of the vecuronium infusion to recovery of the first posttetanic twitch following 100-Hz tetanic stimulation was 27% faster than the corresponding time to recovery of the first posttetanic twitch following 50-Hz tetanic stimulation [19 (10 to 24) min and 26 (20 to 30) min respectively, p < 0.002]. CONCLUSIONS: Posttetanic twitch following 100-Hz tetanic stimulation enables titration of a vecuronium infusion to a greater depth of block than posttetanic twitch following 50-Hz tetanic stimulation. The present findings should enable more effective titration of this relaxant, thereby reducing the likelihood of unwanted patient movement or unduly prolonged recovery due to relaxant overdosing.

Decreased digital flow persists after the abatement of cocaine-induced hemodynamic stimulation.

This study determined whether the development of delayed ischemic sequelae due to cocaine use--after the return of arterial blood pressure (BP) and heart rate to near-baseline values--may be attributable to regional vasoconstriction which persists beyond the acute systemic hemodynamic response. Five cocaine-using volunteers received intravenous infusions of saline placebo and cocaine 0.50 mg/kg several days apart in a double-blinded cross-over design. The intensity and duration of the cocaine-induced decrease in peripheral blood flow (as documented by laser Doppler flowmetry of the finger) were compared to the increases in BP (obtained with a Dinamap) and heart rate using paired t-test and repeated-measures analysis of variance. A significant increase in BP and a significant decrease in finger flow were noted by the first time point (5 min). Within 15 min, cocaine induced a 36% +/- 5% increase in BP and a 73% +/- 18% decline in finger flow (P < 0.05 for difference between percent change in BP and percent change in flow). Dinamap(systolic) and Dinamap(diastolic) returned to within 15% of baseline within 30 min, while finger flow remained more than 50% below baseline for the remainder of the 60-min study period (P < 0.05). Changes in heart rate paralleled those in BP. Except for isolated cases of documented coronary vasoconstriction in patients presenting with complications after cocaine use, this study is the first to document the persistence of cocaine-induced vasoconstriction of a sensitive vascular bed beyond the hypertensive response. It thus helps to explain the development of ischemic injury after cocaine use despite a stable rate-pressure product.

Recovery of unused operating room supplies for overseas orthopedic surgery.

Recovery of surplus operating room (OR) materials may contribute needed supplies to volunteer overseas surgical efforts. However, recovery often generates supplies that are highly heterogeneous in nature. In order to evaluate the nature and quantity of supplies useful to orthopedic surgical missions, the present investigation evaluated the material generated from 381 consecutive orthopedic cases performed during three 3-month assessment periods over 3 years. The amount of recovered material varied markedly within and among procedure types as well as surgeons. Nevertheless, the long-term, OR-wide recovery program at Yale-New Haven Hospital has provided a highly reliable source of usable materials over the 4-year life of the program.

Efficacy and safety of divided dose administration of mivacurium for a 90-second tracheal intubation.

STUDY OBJECTIVE: To compare the safety and effectiveness of 0.25 mg divided doses of mivacurium chloride to succinylcholine for a 90-second tracheal intubation. DESIGN: Randomized, double-blind, multicenter study in two groups. SETTING: Operating rooms at four university medical centers. PATIENTS: 200 healthy ASA status I and II adult patients scheduled for elective surgery with general anesthesia and endotracheal intubation. INTERVENTIONS: Patients were premedicated with 1 to 2 mg midazolam and 2 micrograms/kg fentanyl. Anesthesia was induced with 2 mg/kg propofol. Group A received 0.25 mg/kg mivacurium given as a divided dose (0.15 mg/kg followed in 30 seconds with 0.1 mg/kg). Group B (control) received 1.5 mg/kg succinylcholine (SCh) preceded two minutes earlier by 50 micrograms/kg d-tubocurarine (dtc). MEASUREMENTS AND MAIN RESULTS: Tracheal intubation grading, train-of-four response of the adductor pollicis, heart rate (HR), and mean arterial blood pressure (MAP) were measured and evaluated. Chi-square analysis was performed for comparison between Group A and Group B with respect to the frequency distribution of intubation using the scores excellent, good, and poor and not possible (combined). Group B had a significantly higher excellent score of intubation than Group A, 84% versus 56% (p < 0.0001). No significant difference was found between the two groups when the scores excellent and good were combined (Fisher's Exact test, p = 0.28). The changes in MAP and HR were similar for the two groups. CONCLUSIONS: When Sch is not desirable, mivacurium 0.25 mg/kg given as a divided dose provides good to excellent intubation conditions 90 seconds after the initial dose without significant changes in MAP or HR. It can be an appropriate alternative for short surgical procedures. It must be emphasized that this conclusion does not apply to rapid-sequence induction-intubation.