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Biomedical subjects

D G Silverman

Publications and source records attributed to D G Silverman.

At least 37 records · Page 2Linked to original sources
PubMed1996

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.

Adolescent↗
PubMed1996

Reduction of postburn hyperalgesia after local injection of ketorolac in healthy volunteers.

BACKGROUND: Nonsteroidal antiinflammatory drugs may be particularly effective against prostaglandin-mediated, post-injury hyperalgesia and related inflammatory pain. However, their usefulness may be limited by their systemic side effects. The current study determined if local effectiveness can be achieved by low-dose intradermal nonsteroidal antiinflamatory drug administration. METHODS: Ten healthy volunteers were asked to make magnitude estimations of the pain induced by a contact thermal stimulator at 1 degree C increments between 43 and 51 degrees C at three 1 x 1 cm study sites on each forearm during three study phases:(1) baseline; (2) after pretreatment with 10 microl 0.9% saline (n=1 site on each forearm), 0.3 mg ketorolac (n=1 on each forearm), or nothing (n=1 on each forearm); and (3) after "injury" by a mild burn at the ketorolac- and saline-treated sites on one arm or by injection of 10 nmol bradykinin at all three sites on the other arm. The effects of pretreatment on the pain induced by thermal testing were assessed using repeated-measures analysis of variance. RESULTS: Pretreatment with ketorolac had a selective effect on the postburn injury hyperalgesia, reducing the increase in pain intensity (P<0.05) but not the decline in pain threshold. It had no effect on the responses to thermal stimuli before injury or on the pain of burning, which were similar at ketorolac- and saline-treated sites. The effect of pretreatment with ketorolac on bradykinin-induced hyperalgesia was not achieved after bradykinin injection at sites pretreated with saline as well as ketorolac.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1996

Focused versus operating room-wide recovery of unused supplies for overseas reconstructive surgery.

Proliferation of programs that recover surplus operating room supplies may effectively address the needs of volunteer overseas surgical efforts. However, these programs tend to garner supplies highly heterogeneous in nature. In order to evaluate the nature and quantity of supplies generated by plastic and reconstructive procedures, we extrapolated the inventory of 71 consecutive cases from our 33,000-case database. Additionally, we examined the recovery of 7 specific supplies from all cases performed at Yale-New Haven Hospital over a 3-year period. Though consistency is unlikely when only plastic and reconstructive surgical cases are examined, operating room-wide recovery may be a reliable source of usable materials.

Connecticut↗
PubMed1996

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.

Equipment and Supplies↗
PubMed1995

Recovery of train-of-four after mivacurium.

The present study was designed to determine the time-course of recovery of the train-of-four (TOF) ratio during spontaneous recovery from mivacurium-induced block. Fifteen patients, free of neuromuscular disease, undergoing general endotracheal anaesthesia with isoflurane were studied. After anaesthetic induction, patients received a bolus dose of mivacurium 0.15 mg.kg-1. The TOF was then recorded continuously every 12 sec with a mechanogram (adductor pollicis monitor). When the TOF ratio recovered spontaneously to 0.9, an additional 0.05 mg.kg-1 of mivacurium was given. The durations required for recovery from a TOF ratio of 0.3 to 0.7 (DUR0.3-0.7) and from a TOF ratio of 0.3 to 0.9 (DUR0.3-0.9) were determined. The DUR0.3-0.7 averaged 7.0 +/- 2.5 min (range 3.4-12.2 min). The DUR0.3-0.9 averaged 11.8 +/- 3.9 min (range 6.0-20.2 min). There was no evidence of prolongation of recovery times (cumulation) following repeated dosing. The present data indicate that, in patients with normal cholinesterase activity (clinical duration 7-25 min), waiting 20 min beyond the time when fade is no longer apparent by visual or tactile evaluation is sufficient to attain a TOF ratio greater than 0.7-0.9 during spontaneous recovery from mivacurium, and may enable anaesthetists to avoid antagonism of mivacurium-induced block.

Adolescent↗
PubMed1995

Real time versus slow-motion train-of-four monitoring: a theory to explain the inaccuracy of visual assessment.

The present study was undertaken to determine why visual assessment of thumb adduction in response to train-of-four (TOF) stimulation of the ulnar nerve commonly overestimates the ratio that is obtained mechanographically. In patients undergoing general endotracheal anesthesia plus vecuronium for relaxation, 73 data sets were collected at different depths of neuromuscular block in response to supramaximal TOF stimulation. Each data set consisted of: (i) visual estimation of the TOF ratio by an experienced observer; (ii) mechanographic measurement of the TOF ratio with an adductor pollicis force transducer; and (iii) determination of the TOF ratio by measuring the slow-motion thumb displacement recorded on videotape. The last 23 data sets also included visual assessment and videotape recording of evoked responses at low stimulating current (30 mA). Visual inspection at 60 mA overestimated the mechanographic ratio by 0.20 units (48%). Videotape review provided a ratio that was 0.23 units (56%) greater than that determined mechanographically. However, after the first three twitches (T1-3), the thumb did not return to the same resting position as the (original) baseline prior to the first twitch. When the change in thumb position as a result of T1-3 was taken into account, the measured height of T4 was 40% less than it was when measured from the original baseline, and the T4/T1 ratio was identical to that obtained mechanographically. For the 23 data sets obtained at low current visual assessment overestimated the mechanographic value to a lesser degree than when obtained at high current. Again, correction for the T1-3 baseline shift improved the accuracy of videotape analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, General↗
PubMed1995

Pulse width, stimulus intensity, electrode placement, and polarity during assessment of neuromuscular block.

BACKGROUND: Although the intensity of neurostimulation (i.e., charge) is a product of current intensity and pulse duration, the effects of the latter on the amplitude of evoked response and subjective discomfort are unknown. Therefore, the authors investigated the effects of current intensity and pulse width, and their interaction with electrode placement and polarity, on force translation (FTR), accelerography (ACG), and electromyography (EMG) at the adductor pollics muscle. METHODS: Ulnar stimulating electrodes were applied in one of two configurations: over the distal forearm and olecranon groove ("A") or 5 cm apart on the distal forearm ("B"). Stimuli for FTR and EMG with current intensities of 20, 40, 60, and 70 mA and pulse widths of 0.05, 0.1, 0.2, and 0.4 msec resulted in 16 different charges. These combinations were delivered in each of four orientations: "A-" ("A" configuration with negative electrode distal); "A+", "B-", and "B+" (n = 64 stimuli). Eight stimulus combinations (n = 32 stimuli) were used for ACG. For each monitoring technique, the effects of current intensity, pulse width, electrode polarity, and placement were analyzed with repeated measures ANOVA. Pain responses were scored on a 0-100-mm verbal analog scale and analyzed with ANOVA and Fisher's exact test. RESULTS: The evoked response amplitude varied directly with current intensity and pulse width. In both electrode placement configurations, the response was greater when the negative electrode was distal. The electrode positioning ("A" vs. "B") had less of an impact on evoked responses than did polarity, regardless of monitoring technique. The evoked pain varied directly with the amplitude of evoked neuromuscular response in all electrode position-polarity combinations. CONCLUSIONS: The total current charge required for evoking a supramaximal neuromuscular response is much higher than previously appreciated, and electrode polarity is important in attaining a supramaximal plateau. Failure to attain (and maintain) a supramaximal stimulus allows changes in the effectiveness of neurostimulation, thus influencing the magnitude of the evoked neuromuscular response and confounding measurements of neuromuscular block.

Electrodes↗
PubMed1994

Spatial heterogeneity in normal skin perfusion recorded with laser Doppler imaging and flowmetry.

Spatial and temporal variations in forearm skin perfusion captured by laser Doppler perfusion imaging (LDI) have been compared with topographic maps recorded by laser Doppler flowmetry. In order to determine the shortest LDI sampling time required at each measurement site, with an adequate signal-to-noise ratio and with the ability to display the heterogeneity in skin perfusion, the noise-limited resolution of the LDI system as well as various sampling times were tested. The noise-limited resolution for medium and high light intensities were less than 0.5% (temporal) and 0.3% (spatial) of full scale. A sampling time of 1 sec was selected and image presentation was made by performing bilinear interpolation between perfusion values. The same area (10 x 10 mm) was mapped with LDI and topographic mapping at seven different sites. In addition, a larger area covering the surrounding skin was recorded with LDI. The small area recordings with LDI and topographic mapping could be identified in the larger LDI image. High-and low-perfusion spots coincided between the two systems. Temporal variations were studied by repeated LDI recordings of the same areas as above. Small spots were selected in the areas and plotted versus time. Without provocation, the total perfusion changes at each spot showed large variations, but the relative perfusion levels between neighboring spots persisted. Provocation with heat increased the perfusion in all spots.

Adult↗
PubMed1994

Peripheral assessment of phenylephrine-induced vasoconstriction by laser Doppler flowmetry and its potential relevance to homeostatic mechanisms.

BACKGROUND: Cutaneous laser Doppler flowmetry enables monitoring of changes in skin perfusion by quantifying the phase shift of laser light induced by moving red blood cells under a fiberoptic probe. It thus can identify the presence of and response to a vasoconstrictive stimulus. However, aspects of the technique must be defined before it can be used with maximum effectiveness. We evaluated the responses of two different laser Doppler outputs, the concentration of moving blood cells (CMBC) and red cell flux (CMBC times cell velocity), and the responses at two sites of probe application, the finger and forearm, during systemic infusions of phenylephrine. METHODS AND RESULTS: Eight healthy volunteers were monitored with a brachial blood pressure cuff, ECG, and laser Doppler flowmeter probes applied to the palmar surface of the fourth finger and volar forearm of the arm opposite the pressure cuff. After baseline readings were obtained, the subjects received three 10-minute intravenous infusions of phenylephrine at rates of 0.4, 0.8, and 1.6 micrograms.kg-1.min-1. The two parameters, flux and CMBC, trended similarly. Flux and CMBC at the finger declined significantly in response to each infusion (P < .05 using repeated-measures ANOVA with Duncan's multiple range test). In contrast, flux and CMBC of the forearm had highly variable responses, with an overall increase during each infusion (P < .05 for % delta of forearm versus % delta of finger readings during the 0.4 microgram.kg-1.min-1 infusion). Heart rate declined significantly during each infusion, consistent with a baroreceptor-mediated response, even though systolic and diastolic blood pressures each increased by less than 2 mm Hg during the 0.4 microgram.kg-1.min-1 infusion. CONCLUSIONS: As expected, laser Doppler readings at the finger decreased during infusion of an alpha 1-agonist. Although, like the digital vessels, forearm vessels have the potential to constrict, the increases in forearm readings suggest that these vessels are highly susceptible to homeostatic responses. The increase in CMBC (a parameter that is sensitive primarily to local changes in vascular caliber) suggested vasodilation of the underlying vessels. The forearm vasodilation and the concomitant decline in heart rate most likely represented vagally mediated baroreceptor activity, which was altered even though blood pressure changed minimally during the 0.4 microgram.kg-1.min-1 infusion. Thus, integrated assessment of skin perfusion at the finger and forearm may provide valuable information about the direct and indirect effects of a vasoactive stimulus. The present application of laser Doppler flowmetry suggests activation of vasodilatory reflexes despite minimal changes in blood pressure.

Blood Flow Velocity↗
PubMed1994

Facilitation of fiberoptic orotracheal intubation with a flexible tracheal tube.

Advancement of a tracheal tube (TT) over a flexible fiberoptic bronchoscope (FOB) is often impeded by obstruction at the arytenoid cartilage or epiglottis. We tested the hypothesis that the use of a flexible, spiral-wound TT, rather than the standard, preformed TT would facilitate tube passage into the trachea over the FOB. Forty patients scheduled to undergo general anesthesia with tracheal intubation were randomized to two groups. Then the trachea was intubated with a FOB, followed by passage of either a standard, preformed TT or a flexible, spiral-wound TT over the FOB. Ease of TT advancement over the FOB into the trachea was graded on a 1 (easy) to 3 (difficult) scale, and differences between the two groups were compared with chi 2 analysis. The overall scores were compared with Wilcoxon's ranked sum test. Statistical significance was defined as P < 0.05. In patients randomized to the regular TT, only 35% (7/20) of first attempts to advance the TT over the FOB were successful. In the patients randomized to the spiral-wound TT, 95% (19/20) of first attempts were successful (P < 0.0001). Of the 13 regular TTs that were not successfully advanced on the first attempt, seven could not be passed after the second or third attempt (necessitating the use of the cross-over spiral-wound TT). In the only instance in which a spiral-wound tube was not successfully passed into the trachea on the first attempt, passage also was not achieved after the second or third attempt.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Case-by-case assessment of recoverable materials for overseas donation from 1318 surgical procedures.

OBJECTIVE: To provide a mechanism for addressing the need for consistency and projection in overseas donation of surgical supplies, we conducted a case-by-case inventory of unused materials recovered from all surgical procedures in our facility over a 2.5-month period. DESIGN: Unused surgical supplies were recovered in coded bags from individual cases and inventoried. SETTING: Inpatient operating rooms at Yale-New Haven Hospital. MAIN OUTCOME MEASURE: The weight and dollar value of recovered materials were tallied for each case type; these were then extrapolated according to the frequency with which each procedure is performed in the United States to provide an estimate of the impact of a nationwide recovery program. RESULTS: The value of supplies recovered ranged from $1 (bone marrow transplant) to greater than $40 (liver and vulva/perineum procedures). By extrapolation to case-specific data from the National Hospital Discharge Survey (1990), we estimate that a nationwide recovery program could yield more than $193 million in charitable material and reduce operating room waste by more than 1.7 million kilograms (1948 tons). CONCLUSIONS: Consistency and organization would contribute greatly to efforts to alleviate existing medical supply needs in the developing world. This case-by-case assessment should enable participating centers to project more effectively the outcome of such collections and allow the coordination of efforts. Though unlikely to be adopted by all operating theaters in the United States, the potential charitable contributions from a nationwide recovery program are significant.

Charities↗
PubMed1993

Liquid crystal skin thermometry: an accurate reflection of core temperature?

Oesophageal, rectal, bladder, tympanic and pulmonary artery sites are used intraoperatively to measure body temperature. However, the temperatures measured at each site have different physiological and practical importance. The present two-part study sought to compare liquid crystal (CR) skin temperature with other temperature monitors which are used routinely during surgery. The first part compared CR with oesophageal (OS) temperature during general inhalational anaesthesia. The second part compared CR with OS, pulmonary artery (PA), and bladder (BL) temperatures during the periods of rapid temperature change associated with cardiopulmonary bypass (CPB). During the first part, the mean difference between OS and CR was -0.14 +/- 0.85 degrees C; this difference remained consistent over time (P < 0.05 by repeated measures analysis of variance). During the second part, the difference in temperature readings between CR and each of the other monitors remained consistent except for CR vs PA and CR vs OS during the cooling period of CPB, when the iced cardioplegia slush directly affected the PA and OS temperatures. This study suggests that CR, an inexpensive and noninvasive means of temperature monitoring, reflects trends in temperature changes in the clinical setting.

Anesthesia, Endotracheal↗
PubMed1993

Assessment of double-burst monitoring at 10 mA above threshold current.

We compared fade measurements in response to double-burst stimulation (DBS) at 10 mA above the threshold for the second response (D2) to that for DBS at 60 mA in order to determine the utility of low-current DBS testing. In 20 healthy adults undergoing general endotracheal anesthesia with isoflurane 0.5-1% end-tidal, a vecuronium infusion (0.25-1.5 micrograms.kg-1 x min-1) was delivered until a stable train-of-four (TOF) response to ulnar nerve stimulation was documented with an adductor pollicis force transducer. Then DBS responses were recorded, and the D2/D1 ratios were determined at 60 mA and at 10 mA above the D2 threshold current (TS + 10 mA). The mean difference (bias) between D2/D1 /TS+10 mA and D2/D1 / 60 mA was -0.02 (P < 0.05); the 95% limits of agreement were from -0.12 to +0.08. The bias and limits of agreement were similar to those for T4/T1 of train-of-four. A strong correlation was noted between the degrees of fade determined at the low and high currents (r = 0.95). We conclude that, although stimulation at 10 mA above the D2 threshold is associated with a slight negative bias, it is virtually interchangeable with testing at higher current in the clinical setting. This technique thus may be used effectively to monitor neuromuscular fade in settings where neurostimulation with low current is deemed desirable.

Adult↗
PubMed1993

Visual and tactile assessment of neuromuscular fade.

The accuracy of visual and tactile assessment of the neuromuscular fade in response to train-of-four (TOF) and double-burst stimulation (DBS) were compared to assess their relative utility in the clinical setting. For each of 74 data sets with a mechanographic TOF ratio less than 0.70, an observer (blinded to the presence or degree of fade) performed visual and tactile assessments of fade in response to TOF, DBS3,3, and DBS3,2 stimuli at low current (20 and 30 mA) and high current (50 and 60 mA). For the range of mechanographic TOF ratios between 0.41 and 0.70, visual assessment failed to identify TOF, DBS3,3, and DBS3,2 fade in 46%, 18%, and 14% of cases at high current and in 23%, 5%, and 0% of cases at low current, respectively. Tactile assessments failed to identify fade in 55%, 23%, and 14% of cases at high current and in 23%, 14%, and 14% of cases at low current. Overall, the ability to detect fade was comparable for visual and tactile assessments regardless of the method of neurostimulation (P = NS with paired t-test). However, the degree of overestimation of the fade ratio (i.e., quantitative assessment) tended to be less when using tactile means; the difference achieved significance for TOF at low current and DBS3,3 at both low and high currents. We conclude that the differences between the visual and tactile means of assessment are relatively small compared to the differences among the TOF and DBS patterns of neurostimulation. Both subjective techniques are often inadequate in settings in which assurance of full recovery of neuromuscular function is critical.

Adolescent↗
PubMed1993

The effect of a tetanic stimulus on the response to subsequent tetanic stimulation.

We evaluated the effect of tetanic stimulation (5 s, 50 Hz, 60 mA) on the response to tetanic stimulation delivered 2 min (TET@2) and 5 min (TET@5) later in 22 anesthetized patients receiving a vecuronium infusion. Once a consistent mechanomyographic train-of-four ratio was obtained at the adductor pollicis muscle, the first (baseline) tetanic stimulus was delivered. Tetanic sequences were repeated randomly after 2- and 5-min intervals. Tetanic fade was consistent among the study periods: the tetanic fade ratio for the first second of tetanus was 0.35 during baseline tetanic stimulation, 0.32 during TET@2 (P = NS by paired t-test), and 0.33 during TET@5 (P = NS). The respective fade ratios for the entire 5-s period were 0.15, 0.15 (P = NS), and 0.14 (P = NS). In contrast, the peak tetanic height increased from 10.8 mm at baseline to 11.3 mm at TET@2 (P < 0.05), and 11.3 mm at TET@5 (P < 0.05). We conclude that, in light of the consistency exhibited by tetanic fade, the small change in twitch height is clinically insignificant.

Anesthesia, Endotracheal↗
PubMed1993

Depth of block after divided doses of mivacurium spaced 60 seconds apart.

We compared the depth of block attained after divided- and single-dose administration of mivacurium to evaluate our clinical impression that the former regimen resulted in a lesser depth of block. In 30 patients anesthetized with midazolam, fentanyl, thiopental, and nitrous oxide, adductor pollicis contraction was measured in response to train-of-four stimulation at 12-s intervals. Patients then received (by random assignment) mivacurium as a single 0.15 mg/kg bolus (Group I) or two 0.075 mg/kg (Group II) boluses separated by 60 s. All 15 Group I patients developed > or = 95% twitch (T1) depression, and 10/15 attained 100% depression; the maximum depression (mean +/- SD) was 99.1% +/- 1.4%. Only 8/15 Group II patients achieved > or = 95% T1 depression (P < 0.05 for the interregimen comparison with chi 2 analysis), and only 4/15 achieved 100% depression (P = 0.07); the maximum depression was 92.2% +/- 12.9% (P < 0.05 by unpaired t-test). Thus, administration of mivacurium in divided doses spaced 60 s apart does not provide the depth of neuromuscular block that is attained when a single bolus of the same total dose is administered.

Drug Administration Schedule↗