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.

Brief hypoxia-ischemia initially damages cerebral neurons.

Rats were studied during cerebral hypoxic ischemia to determine whether neurons or blood vessels suffered the first damage. Ten or more minutes of unilateral carotid artery occlusion combined with systemic hypoxemia (PaO-2, 21 mm Hg) produced neuronal but not vascular damage in the ipsilateral cerebral hemispheres of 18 of 29 rats (62%); two and five minute stresses caused no visible neuronal abnormalities. The longer exposures produced more widespread damage, and neuronal loss and gliomesodermal reaction were evident after prolonged survival. Early neuronal changes correlated with abnormalities of motor behavior (P less than .005). Despite neuronal damage that was sometimes extensive, vascular no-reflow developed in only one of 24 animals after 20 and 30 minutes of hypoxia-ischemia. Production of neuronal and neurological abnormalities in the absence of hypotension or vascular no-reflow indicates that hypoxia-ischemia initially damaged cerebral neurons.

Intravenous cocaine challenges during desipramine maintenance.

Intravenous challenges with placebo and cocaine doses ranging from 0.125 to 0.5 mg/kg were administered to five subjects using a within subjects design during placebo and active desipramine (DMI) maintenance at a fixed dose of 150 mg daily for at least 10 days. The "high" reported after cocaine infusion was not altered by DMI, but "desire for cocaine" after a single dose was attenuated. Together with the results of clinical trials of DMI for cocaine abuse, these laboratory results suggest that DMI may reduce cocaine craving both during and between cocaine binges. Physiologically, baseline heart rate was higher on DMI, but the incremental heart rate response to cocaine was attenuated.

Altered skin flap survival and fluorescein kinetics with hemodilution.

Isovolemic hemodilution is known to reduce blood viscosity. Reduction of either the blood cell concentration or the serum total protein has been found to improve blood flow and ultimate survival of skin flaps. Nutritive blood flow and tissue survival were examined in dorsal pedicle skin flaps in three groups of rats at three hematocrit levels--44% (controls), 31%, and 19%. After hemodilution by phlebotomy and crystalloid replacement, the dye kinetics of intravenously administered fluorescein were measured with the fiberoptic perfusion fluorometer. Skin flap survival at the different hematocrits were also examined. Hematocrits and serum total protein were measured before and after hemodilution and the elevation of the flap. The rate of fluorescein elimination and ultimate flap survival were significantly augmented in the two hemodiluted groups. The maximum benefit was seen in the group of animals hemodiluted to 19%. However, significant improvement in blood flow and skin flap survival was noted in the group of animals that were hemodiluted to a more clinically acceptable level (31%). The decreases in serum total protein following flap elevation did differ among the groups. This study supports the hypothesis that isovolemic hemodilution may be a valuable technique for salvaging marginally ischemic tissues.

Serial fluorometric documentation of fluorescein dye delivery.

Since its introduction in 1980, fiberoptic fluorometry has improved the precision and objectivity of the fluorescein test as a means to delineate nutritive blood flow and predict tissue viability. This study was undertaken primarily to determine if fiberoptic fluorometry could be repeated reliably at close time intervals. Four injections of fluorescein dye were administered at varying dose and time schedules to determine what factors influenced the repeatability of this technique. The results confirm the high accuracy of fluorometric indices as a means to predict the ultimate fate of a skin flap. A method of scanning the flap within 2 minutes after injection of 1.5 mg/kg of fluorescein dye correctly predicted the fate of almost 100% of flap sections. Repeated injections of 1.5, 3.0, and 6.0 mg/kg of dye at 15-minute intervals provided virtually identical predictions of flap viability. Thus fluorometry is readily repeatable and should be of value in assessing the state of tissue perfusion as well as changes in perfusion caused by pharmacologic manipulation or surgical intervention.

Monitoring tissue elimination of fluorescein with the perfusion fluorometer: a new method to assess capillary blood flow.

Visual assessment of tissue staining after intravenous fluorescein is a common technique for predicting viability of questionably perfused tissue. The development of the perfusion fluorometer has permitted quantification of tissue fluorescein, providing increased precision. This study employed this instrument to calculate fluorescein elimination from rats with and without raised dorsal pedicle flaps. Control animals exhibited homogeneous patterns of fluorescein elimination consistent with first-order kinetics. Elimination in experimental animals was assessed after the animals received full back skin flaps with the cephalad pedicle remaining intact. Three distinct patterns of elimination were noted in each flap. In the cephalad portion, elimination was similar to control. At the caudad end, no elimination was noted. Midflap, fluorescein was eliminated slowly. These elimination patterns predicted ultimate viability 14 days postoperatively, as they correspond to viable, dystrophic, and transitional sections, respectively (P less than 0.001). We conclude that perfusion fluorometry can assess capillary flow in healthy and ischemic tissue by documenting elimination as well as delivery of fluorescein.

Fluorometric quantification of low-dose fluorescein delivery to predict amputation site healing.

This retrospective study evaluated quantification of skin fluorescein delivery by fiberoptic fluorometry as a means of predicting the healing potential of an amputation site. Fluorometry uses a dual-channel fiberoptic light guide--one channel transmits blue light to excite the fluorescein in the skin under study, and the other transmits emitted fluorescence from the skin to a photomultiplier tube where it is measured. Ten minutes after intravenous administration of sodium fluorescein (4 to 8 mg/kg), fluorometric readings were obtained at more than 100 reading sites. In the 86 cases without preoperative cellulitis at the site of amputation, preoperative fluorometry clearly distinguished between healing and nonhealing sites. Healing sites averaged 79% of the fluorescence of a healthy reference area (dye fluorescence index [DFI] = 79), while failing sites averaged only 27% (p less than 0.01 by ANOVA). In all but one case where the DFI was greater than 42, the amputation healed. In all cases where the DFI was less than 38, the amputation failed. In general, uncertainty was limited to sites with values between these limits. The technique maintained its high accuracy in patients with diabetes and for distal amputations. However, it was not accurate at sites of active cellulitis (12 cases). There were no significant adverse effects from the slow injection of the low dose of fluorescein used for this technique. We conclude that fluorometry is an effective means of predicting healing in patients undergoing amputation.

Fluorescence assessment of skin perfusion after oral fluorescein.

This study evaluated oral ingestion as the route of fluorescein administration for fluorescence assessment of skin perfusion. In 10 anesthetized rats, dorsal pedicle flaps were raised to produce graded perfusion; then fluorescein (7.5 mg/kg) was administered via an oropharyngeal tube. Quantification of skin fluorescence, performed with the fiberoptic fluorometer 45 minutes after dye ingestion, delineated a significant difference between the perfusion of flap regions that remained viable and those that subsequently became dystrophic (p less than 0.05). The precision was equivalent to that previously reported after intravenous dye. In addition, the gradual delivery of dye after oral administration permitted monitoring of slope of uptake and time to peak. Each of these pharmacokinetic parameters delineated a significant difference between viable and nonviable sections. As measures of relative change in fluorescence, they are independent of skin color and thickness. This feature suggests that the oral route actually may improve the accuracy and reliability of the fluorescein test.

Monitoring skin fluorescein delivery independent of skin pigmentation.

This study evaluated two changes in fluorometric assessment of fluorescein dye delivery: (1) monitoring the proportional, rather than the absolute, increase above the preinjection background reading at each site to obviate the effect of skin color and (2) employing gradual means of dye administration to facilitate monitoring uptake kinetics and to lessen the likelihood and severity of histamine-mediated reactions. In 15 beagles, background and postdye readings were obtained with the fiberoptic fluorometer at 27 pairs of matched light- and dark-skin sites of intact perfusion. After dye administration, the absolute increase in fluorescence at light sites averaged more than twice (approximately 225%) that at dark sites. However, the newly introduced proportional increase (PI) was independent of pigmentation. The PI of comparably perfused light and dark sites differed by an average of 3.9% (p greater than 0.05 for difference between PIdark and PIlight). This consistency was maintained after each of three methods of fluorescein administration. After the color independence of the PI was established, its relation to perfusion was assessed in nine 3 X 12 cm pedicle flaps of varied pigmentation. Background fluorometric readings were obtained at eight sites along the longitudinal axis of each flap. Dye was administered as a 20-minute 0.25 mg/kg/min infusion. The PI clearly delineated gradations in perfusion, correlating highly with more time-consuming kinetic indexes and accurately predicting viability. The pedicle row, last viable row (V1), and first nonviable row (N1) had mean PI values of 10.5 +/- 4.5, 4.2 +/- 2.6, and 0.1 +/- 0.1, respectively, at 25 minutes after the start of infusion (p less than 0.05 for pedicle vs V1, pedicle vs N1, and V1 vs N1).

Cocaine use and acute rupture of ectopic pregnancies.

The hemodynamic changes associated with ingestion of cocaine may precipitate rupture of ectopic pregnancy. Two cases are presented in which this association was suspected. We believe this to be the first report of this clinical entity, representing a risk factor that should be identified in patients with suspected ectopic pregnancy.

Nausea prophylaxis using transdermal scopolamine in the setting of patient-controlled analgesia.

We evaluated the effectiveness of transdermal scopolamine in patients receiving morphine via patient-controlled intravenous analgesia following intra-abdominal gynecologic surgery. Soon after arrival in the post-anesthesia recovery unit (time 0), patients were randomized either to receive or not receive a postauricular transdermal scopolamine patch. Nausea and vomiting were scored on a 0-3 scale at this time and at 2, 4, 6, and 24 hours. Patients were treated with droperidol as deemed necessary by the primary care nurse. Within 2-4 hours, transdermal scopolamine patients evidenced less nausea and vomiting and required less droperidol than their counterparts who did not receive transdermal scopolamine. A significant decline in the severity of nausea was noted in the transdermal scopolamine group between 2-24 hours; significant inter-group differences were noted for changes in nausea severity during the 0-6-hour and 0-24-hour intervals. Transdermal scopolamine patients evidenced a significant (P less than .05) decrease in the severity of vomiting during the first 2 hours, significantly different from the increase in the non-transdermal scopolamine patients. After the 4-hour assessment, no transdermal scopolamine patients required droperidol; nine doses were administered to the patients who were not given transdermal scopolamine (P less than .05). Thus, transdermal scopolamine therapy appears to be an effective means of treating the nausea and vomiting that are encountered after gynecologic surgery.

Doppler ultrasound, laser Doppler, and perfusion fluorometry in bowel ischemia.

Improved accuracy and objectivity in the evaluation of intestinal viability has been reported by some investigators using Doppler ultrasound, and more recently laser Doppler velocimetry and perfusion fluorometry. To compare the sensitivity and clinical applicability of these techniques, intestinal viability was evaluated by each method in nine 15- to 50-cm loops of small bowel prepared by division of the mesenteric vasculature in five anesthetized dogs. The sensitivity of Doppler ultrasound was 86%, of laser Doppler flow velocity 85%, of laser Doppler index 94%, and of perfusion fluorometry 95%. Though the sensitivity of Doppler ultrasound is significantly less than that of laser Doppler and perfusion fluorometry, this is not unexpected since the latter two techniques are more quantitative than Doppler ultrasound. Clinically, Doppler ultrasound compares favorably with laser Doppler and perfusion fluorometry, and its low cost and simplicity suggest its adjunctive use in the operative setting.

Qualitative and quantitative fluorescein fluorescence in determining intestinal viability.

Clinical evaluation and qualitative (visual) and quantitative (fluorometric) fluorescence for predicting intestinal viability were compared in an animal model of temporary arterial occlusion with early revascularization. Quantitative fluorescence was determined with a perfusion fluorometer after an intravenous bolus of fluorescein. Qualitative fluorescence was determined by examination under a Wood's lamp in a darkened room. The effectiveness of each diagnostic technique in determining nonviability was expressed in terms of sensitivity, specificity, and accuracy. All three methods had 100 percent specificity; only bowel deemed nonviable proved to be so. Quantitative fluorescence also had a 100 percent sensitivity, but clinical evaluation and qualitative fluorescence had only a 33 and 11 percent sensitivity, respectively (some segments of bowel that were ultimately nonviable were not correctly predicted to be so). The inaccuracy of qualitative fluorescence was due to the fact that ischemic intestine with a hyperfluorescent pattern often progressed to necrosis. Fluorometric quantitation identified those hyperfluorescent segments that were viable. This study suggests that visual fluorescence is not reliable in assessing intestinal viability after early revascularization after arterial occlusion, but quantitative fluorometric fluorescence is reliable in almost all instances.

A compartment model for fluorometric indication of tissue perfusion.

Sodium fluorescein is an in vivo blood perfusion indicator for soft tissue. When fluorescein dye is introduced into the blood, it distributes throughout the vasculature and the extravascular space. Incident light from an external source causes the dye to fluoresce, the level of which is monitored by a photodetector placed over the tissue. In this study, theoretical analysis incorporating a multicompartmental model for dye distribution is applied to describe the relationship among perfusion, dye kinetics, and fluorescence readings. Errors in calculating perfusion from fluorescence are related to dye concentrations and to measurement errors. These error sources are minimized by selecting the measurement time. The alternatives of measurement during wash-in or during wash-out of dye are compared, as well as the alternatives of introducing dye by bolus injection or by constant infusion. Compensation of wash-in measurements for differences in skin pigmentation is accomplished by the matching of skin optical properties between incident and fluorescing wavelengths. A laboratory study at 80 measurement sites (from ten graded perfusion canine flaps) demonstrated a correlation of wash-in and wash-out perfusion data ranging from 0.88 to 0.96 at typical levels of fluorescein in blood. Since wash-in can be completed in a matter of a few minutes, this is likely to be preferable in the clinical setting to wash-out which can take much longer to complete.

Fiberoptic fluorometer for skin flap assessment.

The fiberoptic fluorometer permits quantitative measurement of fluorescence after intravenous administration of fluorescein. Accurate assessment of tissue fluorescence can be made at any time after the injection, and both uptake and elimination of fluorescein can be followed. The instrument provides instantaneous digital readout of the fluorescence measured in dye fluorescence (DF) units and an index predictive of viability called the dye fluorescence index (DFI). The unit is portable, can be sterilized for operating room use, and can be operated by paramedical personnel with ease. We have used the instrument extensively in clinical and laboratory investigations, where it has been highly reliable in predicting survival and necrosis of a wide variety of flaps. Little or no operating time is added, and serial, low-dose fluorescein injections may be used to monitor a flap in the recovery room or at the bedside in the early postoperative period.

Monitoring free flap perfusion by serial fluorometry.

An efficient method to evaluate the patency of microvascular anastomoses and to predict flap viability is crucial when free flaps are used in reconstructive surgery. We report a study of 60 neurovascular island flaps in rats where the nutrient artery and/or vein were transected and anastomosed. Fluorescein dye was injected immediately after anastomosis, and the uptake and elimination of dye were quantified at 5-minute intervals with the fiberoptic perfusion fluorometer. Analysis of dye delivery clearly identified six hypofluorescent flaps presumed to be ischemic. In five of these flaps, revision was attempted. Three evidenced improved fluorescein uptake and elimination on reinjection of dye. These flaps survived, whereas the other two necrosed. Of the 54 flaps deemed patent after the first injection, two evidenced poor fluorescence on reinjection 3 hours later. These flaps necrosed and evidenced venous thrombosis (which probably occurred during the 3 hours between the first and second injections). Fiberoptic fluorometry can be employed to assess a free flap immediately after vascular anastomosis and throughout the critical hours postoperatively. Assessment of uptake and elimination after single or serial injections reflects flap perfusion and predicts viability with a high degree of accuracy.

Fluorometric assessment of skin flap viability in the rat: effect of radiation therapy.

The fluorescein test is widely used to assess perfusion in skin flaps but tends to underestimate skin viability when visual inspection under ultraviolet light is employed. Fiberoptic dermofluorometry, which has recently been introduced, more accurately assesses fluorescein distribution in skin flaps than does visual inspection. Viability of the back flap in rats receiving ionizing radiation was evaluated by dermofluorometry. This technique was highly accurate in predicting viability and has great applicability for studying blood flow in irradiated tissues.

Fluorescein elimination as a measure of island flap perfusion.

The fluorescein test has been used as a means of assessing flap viability for almost 40 years. This study was performed in an attempt to determine if recording of the elimination of dye--combined with dye uptake measurement--could provide reliable and consistent monitoring of island flap perfusion.

Beneficial effects of ibuprofen on experimental microvascular free flaps: pharmacologic alteration of the no-reflow phenomenon.

Pharmacologic alteration of the no-reflow phenomenon was determined based on increased tolerance to ischemia in ibuprofen-treated free flaps. Sprague-Dawley rats (N = 60) were divided into control (lactated Ringer's) and treated (ibuprofen) groups and subdivided into six groups of ischemia: 1 hour, 6 hours, 8 hours, 10 hours, 12 hours, and 14 hours of ischemia. Fluorescein uptake was measured after 10, 30, and 60 minutes following microrevascularization. Dye elimination studies were done for each ischemia group that demonstrated good fluorescein uptake. All free flaps in the 1-, 6-, and 8-hour groups survived. The ibuprofen-treated 10- and 12-hour flaps all survived, whereas the 10-hour control and 14-hour ibuprofen-treated free flaps failed to survive. Despite high fluorescein uptake, the 14-hour ibuprofen-treated flaps did not eliminate the fluorescein, whereas all surviving free flaps adequately eliminated the fluorescein. Failure to eliminate dye despite adequate uptake suggested a deranged microcirculation with increasing ischemia time. By inhibiting cyclo-oxygenase, nonsteroidal anti-inflammatory agents such as ibuprofen may block the untoward effects mediated by thromboxane A2, such as vasoconstriction, microvasculature thrombus formation, and intravascular sludging. These effects are theorized in part to be responsible for the failure of a free flap to survive despite revascularization.