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Biomedical subjects

N L Pace

Publications and source records attributed to N L Pace.

At least 19 recordsLinked to original sources
PubMed1992

Technology assessment of anesthesia monitors.

This essay argues that optimal utilization of anesthesia monitors requires careful technology assessment. This careful assessment is important because monitors may produce spurious or uninterpretable values, or they may damage patients. In addition, resources should be spent only for truly beneficial devices. The types of evidence that this essay describes for use in technology assessment include questions concerning data reliability, data interpretability, and data outcome. Considerable evidence bearing on technology assessment has already been amassed. I propose synthesizing this evidence by meta-analysis. Additional primary studies of technology assessment are also needed.

Anesthesiology↗
PubMed1992

Iontophoretic delivery of morphine for postoperative analgesia.

Iontophoresis is a method of transdermal administration of ionized drugs in which electrically charged molecules are propelled through the skin by an external electrical field. This was a prospective, randomized, single-blind study to determine the effectiveness of iontophoretically delivered morphine HCl for the control of postoperative pain. Thirty-eight patients who underwent total knee or hip replacement completed this clinical trial. Informed consent was obtained before surgery and patients were instructed on the use of a patient-controlled analgesia (PCA) device. Postoperatively, pain in the recovery room was initially controlled with IV meperidine, and thereafter with PCA therapy using meperidine, 2 mg/cc, with a dose of 10 mg IV and a lock-out period of 15 min. The dose was adjusted as necessary and the lock-out period remained the same. The number of patient requests and the dose (mg) administered was recorded hourly. On the morning following surgery, iontophoresis devices were attached for 6 hr to patients who received either morphine HCl or lactated ringers solution. During this period and for 12 hr following completion of iontophoresis, PCA analgesia remained available to patients. Venous blood samples for determination of morphine levels were obtained every 30 min during iontophoresis, then every 60 min for 2 hr following iontophoresis. Of the 38 patients, 17 received iontophoresed morphine, and 21 received iontophoresed lactated ringers. The morphine group utilized the PCA device more than the control group during the baseline period. However, following the institution of iontophoresis and continuing up to 12 hr following completion of iontophoresis, the morphine group used significantly less PCA meperidine to maintain analgesia than the control group (p = 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Fentanyl and sufentanil increase intracranial pressure in head trauma patients.

Although opioids frequently are administered to patients with severe head trauma, the effects of such drugs on intracranial pressure are controversial. Nine patients with severe head trauma were studied for the effects of fentanyl and sufentanil on intracranial pressure (ICP). In all patients, ICP monitoring was instituted before the study. Full neuromuscular blockade was achieved with vecuronium bromide before the administration of either fentanyl (3 micrograms.kg-1) or sufentanil (0.6 microgram.kg-1) as an intravenous bolus over a 1-min period in a masked and random fashion. Patients received the other opioid in the same fashion 24 h later. Arterial blood pressure, heart rate, and ICP were recorded continuously for the 1 h after drug administration. Fentanyl was associated with an average ICP increase of 8 +/- 2 mmHg, and sufentanil with an increase of 6 +/- 1 mmHg. These increases were statistically significant. Both drugs produced clinically mild decreases in mean arterial blood pressure (fentanyl, 11 +/- 6 mmHg; sufentanil, 10 +/- 5 mmHg) that nevertheless were statistically significant. No significant changes in heart rate occurred. These results indicate that modest doses of potent opioids can significantly increase ICP in patients with severe head trauma.

Adult↗
PubMed1992

Anesthetic techniques during surgical repair of femoral neck fractures. A meta-analysis.

Fracture of the hip typically occurs in older women. These patients usually have serious accompanying chronic illnesses. There is a difference of opinion as to the choice of regional versus general anesthesia for surgery in these patients. This meta-analysis compared survival of patients with traumatic femoral neck fractures undergoing operative repair during regional or general anesthesia. The data sources were articles comparing regional and general anesthesia from peer reviewed journals. Thirteen randomized controlled trials were found. Besides 1-month mortality, variables used were estimated operative blood loss and the incidence of deep venous thrombosis. For dichotomous outcomes, two effect measures were calculated: the difference in probabilities and the odds ratio. For blood loss, a continuous variable, the effect measure was the mean difference in blood loss. A random-effects Bayesian meta-analysis was used to combine study data, estimate parameters and create 95% confidence intervals. Only the incidence of deep venous thrombosis was clearly greater for patients receiving general anesthesia, being 31 percentage points higher than for patients receiving regional anesthesia. By the odds ratio, deep venous thrombosis was almost four times more likely following general anesthesia. There was no difference in estimated operative blood loss. By probability difference, mortality was a non-significant 2.7 percentage points less following regional anesthesia. By odds ratio effect measure, death was 1.5 times more likely following general anesthesia, but the lower bound of the 95% confidence interval was close to 1. Meta-analysis does not allow a conclusion that important differences in mortality exist between regional and general anesthesia for traumatic hip fracture surgery.

Aged↗
PubMed1991

Respiratory effects of clonidine alone and combined with morphine, in humans.

Because only limited and controversial data exist concerning the respiratory effects of clonidine in humans, the authors evaluated the respiratory effects of clonidine alone and in combination with morphine, in 12 healthy adult males. Subjects received clonidine (0.3-0.4 mg orally), morphine (0.21 mg/kg intramuscularly), or the same doses of the two drugs combined, at three separate sessions in a randomized fashion. The study was balanced for all possible sequences of drug administration. Blood pressure, heart rate, hemoglobin oxygen saturation via finger pulse oximetry, and ventilatory and occlusion pressure responses to CO2 were obtained before and 20, 40, 60, 90, 120, 180, 240, 300, and 360 min after administration of drug or drug combination. Systolic blood pressure decreased significantly only in the clonidine and clonidine plus morphine groups (P less than 0.05). Hemoglobin oxygen saturation decreased by a statistically significant (P less than 0.05), though clinically minor, degree only in the morphine or morphine plus clonidine groups. Clonidine alone did not depress the slope of either the ventilatory or the occlusion pressure response to CO2. In addition, clonidine did not significantly worsen morphine-induced depression of the slope of the ventilatory and occlusion pressure responses in the drug combination group. Both the ventilatory and occlusion pressure responses to CO2 were shifted to the right in all three drug groups (P less than 0.05) but were shifted to a significantly lesser degree by clonidine alone than by morphine and morphine plus clonidine. In healthy young adult males, clonidine alone produces little respiratory depression and does not significantly potentiate morphine-induced respiratory depression.

Adolescent↗
PubMed1991

Simultaneous comparison of intraarterial, oscillometric, and finapres monitoring during anesthesia.

In 30 patients (15 with normal peripheral vascular status and 15 with peripheral vascular disease, hypertension, or a heavy smoking history), systolic, mean, and diastolic arterial pressures were recorded simultaneously every 5 min using a radial arterial catheter, an oscillometric arm cuff, and a Finapres finger cuff during 1-6 h of anesthesia and operation. The average accuracy of oscillometric and Finapres pressure measurements was good. Comparisons of arterial, oscillometric, and Finapres pressures showed only a small bias in the oscillometric and Finapres pressure estimations. Finapres pressures underestimated arterial pressures by 1 mm Hg more than oscillometric pressures did. Peripheral vascular status had no effect on comparisons made between pressures measured with these two techniques. Although bias was small, precision was often lacking as shown by the large variability of the difference between individual values from the three monitors. However, the precision of Finapres pressure measurements was about the same order of magnitude as that of oscillometric measurements.

Blood Pressure↗
PubMed1990

Oral transmucosal fentanyl citrate for premedication in paediatric outpatients.

Two doses (10-15 micrograms.kg-1, Group I, and 15-20 micrograms.kg-1, Group II) of oral transmucosal fentanyl citrate (OTFC) plus a placebo (Group III) were evaluated for premedication in 105 healthy children, aged 2 to 13 yr, undergoing short (less than 1 hr) operations in the hospital short-stay unit. The study was randomized and double-blinded and 91 of the 105 children also received droperidol, 25 micrograms.kg-1 IV, after induction of anaesthesia with halothane and N2O in oxygen. Both doses of OTFC produced significantly greater sedation (first present at 20 min) and anxiolysis (first present in Group I at 40 min) than the placebo. Recovery times were similar in the three groups and analgesic requirements in the recovery room were significantly lower in Group I than Group III. Both OTFC groups took longer to tolerate oral fluids in the postoperative discharge unit than the placebo group and this caused patients in Group I to have a delayed discharge from the hospital compared to Group III. Preoperative pruritus occurred significantly more frequently in Groups I and II (58 and 76 per cent, respectively) than Group III (23 per cent). Although the incidences of nausea and vomiting tended to be slightly higher in the OTFC groups in the preoperative holding and postoperative discharge units, the differences among the groups were not statistically significant. Likewise droperidol did not reduce the incidence of postoperative nausea or vomiting. The data indicate that OTFC may be a safe and effective premedicant in paediatric patients having short operations but delays discharge from the hospital (by 30-50 min) by delaying the time patients tolerate fluids early after operation.

Administration, Oral↗
PubMed1990

Cardiovascular effects of large doses of pentamorphone in the dog.

The cardiovascular effects of large doses of pentamorphone were evaluated in nine mongrel dogs basally anesthetized with sodium thiopental, 25 to 30 mg/kg, intravenously. All dogs were mechanically ventilated with 100% oxygen, and the PaCO2 was maintained between 35 and 40 mm Hg. Mean arterial pressure (MAP), central venous pressure, heart rate (HR), cardiac output (CO), pulmonary artery pressure, and pulmonary artery occluded pressure were measured, and stroke volume and systemic and pulmonary vascular resistances were calculated. Baseline measurements were obtained, then pentamorphone, 10 micrograms/mL, was given as an intravenous infusion at 2.5 micrograms/kg/min. Additional data were obtained after infusion of 25, 50, 75, 100, 125, 150, 200, 250, 300, and 350 micrograms/kg of pentamorphone. The inspired gases were then changed to 50% nitrous oxide in oxygen, and after a 20-minute equilibration period, an additional set of data was collected. Pentamorphone, 25 micrograms/kg, decreased HR 50%, MAP 65%, and CO 54%. No further changes in any measured or calculated variables were observed with additional doses of pentamorphone. The addition of 50% nitrous oxide to the inspired gas mixture had no effect on any measured or calculated hemodynamic variable. The minimal hemodynamic effects of pentamorphone in the dog suggest that further investigation into its use as an anesthetic is warranted.

Analysis of Variance↗
PubMed1990

Transdermal scopolamine reduces nausea and vomiting after outpatient laparoscopy.

The authors evaluated the effect of transdermal scopolamine on the incidence of postoperative nausea, retching, and vomiting after outpatient laparoscopy in a double-blind, placebo-controlled study. A Band-Aid-like patch containing either scopolamine or placebo was placed behind the ear the night before surgery. Anesthesia was induced with fentanyl (0.5-2 micrograms/kg iv), thiopental (3-5 mg/kg iv), and succinylcholine (1-1.5 mg/kg iv) and maintained with isoflurane (0.2-2%) and nitrous oxide (60%) in oxygen. Scopolamine-treated patients had less nausea, retching, and vomiting compared with placebo-treated patients (P = 0.0029). Severe nausea and/or vomiting was present in 62% of the placebo group but only 37% of those getting the scopolamine patch. Repeated episodes of retching and vomiting were also less frequent in the scopolamine group compared with the placebo group (23% vs. 41%; P = 0.0213) as was the need for additional antiemetic therapy (13% vs. 32%; P = 0.0013). Patients in the scopolamine group were also discharged from the hospital sooner (4 +/- 1.3 vs. 4.5 +/- 1.5 h; P = 0.0487). Side effects were more frequent among those patients treated with the scopolamine patch (91% vs. 45%; P less than 0.05) but were not troublesome. The authors conclude that transdermal scopolamine is a safe and effective antiemetic for outpatients undergoing laparoscopy.

Administration, Cutaneous↗
PubMed1990

Frequent hypoxemia and apnea after sedation with midazolam and fentanyl.

More than 80 deaths have occurred after the use of midazolam (Versed), often in combination with opioids, to sedate patients undergoing various medical and surgical procedures. We investigated the respiratory effects of midazolam (0.05 mg.kg-1) and fentanyl (2.0 micrograms.kg-1) in volunteers. The incidence of hypoxemia (oxyhemoglobin saturation less than 90%) and apnea (no spontaneous respiratory effort for 15 s) and the ventilatory response to carbon dioxide were evaluated. Midazolam alone produced no significant respiratory effects. Fentanyl alone produced hypoxemia in half of the subjects and significant depression of the ventilatory response to CO2, but did not produce apnea. Midazolam and fentanyl in combination significantly increased the incidence of hypoxemia (11 of 12 subjects) and apnea (6 of 12 subjects), but did not depress the ventilatory response to CO2 more than did fentanyl alone. Adverse reactions linked to midazolam and reported to the Department of Health and Human Services highlight apnea- and hypoxia-related problems as among the most frequent adverse reactions. Seventy-eight per cent of the deaths associated with midazolam were respiratory in nature, and in 57% an opioid had also been administered. All but three of the deaths associated with the use of midazolam occurred in patients unattended by anesthesia personnel. We conclude that combining midazolam with fentanyl or other opioids produces a potent drug interaction that places patients at a high risk for hypoxemia and apnea. Adequate precautions, including monitoring of patient oxygenation with pulse oximetry, the administration of supplemental oxygen, and the availability of persons skilled in airway management are recommended when benzodiazepines are administered in combination with opioids.

Adolescent↗
PubMed1990

Automated sulfur hexafluoride washout functional residual capacity measurement system for any mode of mechanical ventilation as well as spontaneous respiration.

A new sulfur hexafluoride (SF6) washout functional residual capacity (FRC) measurement system has been developed which will work with any mode of mechanical ventilation, as well as with spontaneous respiration. This system was evaluated in three different human studies. In the first two studies, the accuracy of the system was compared with He dilution and body plethysmography in 12 spontaneously breathing normal volunteers and in 12 spontaneously breathing chronic obstructive pulmonary disease (COPD) patients. In the third study, the reproducibility and efficacy of using the system in the ICU was tested in 12 adult respiratory distress syndrome (ARDS) patients who were mechanically ventilated with PEEP. In the normal volunteers, there was no significant difference between the three measurement techniques. In the COPD group, there was an overall significant difference between measurement techniques (F[2,28] = 17.18, p less than .0001) and the rank of the magnitude of the FRC measurements from lowest to highest was SF6 washout, He dilution, and body plethysmography. There was a significant difference in accuracy between the COPD and normal volunteer groups (F[2,28] = 12.24, p less than .0002). There were a total of 1,227 FRC measurements made on the 12 ARDS patients. The number of FRC measurements per patient was 102 +/- 13 (SEM). The "stable" periods were 14 +/- 2 h long and ranged from 60 min to 63.5 h. The reproducibility for all 12 patients was 188 +/- 17 ml or 11.7 +/- 0.7%. This automated SF6 washout system should make routine FRC measurements in patients who are being mechanically ventilated simple and easy to do.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Is there central respiratory depression after intravenous administration of propranolol?

Beta-adrenergic blockers have been reported to depress central ventilatory drive. The authors investigated this possibility in a double-blind, randomized fashion in 12 healthy volunteers who received 0.1 mg.kg-1 of propranolol and normal saline intravenously at two separate study sessions. A modified Read rebreathing technique was used. Both ventilatory and occlusion pressure responses to CO2 were measured to help separate peripheral (airway) from central mechanisms. Significant beta blockade was demonstrated by statistically lower heart rate responses to CO2 rebreathing after propranolol, but not normal saline. Nevertheless, propranolol exerted no significant effect on resting end-tidal CO2 or the ventilatory and occlusion pressure responses to CO2. Although health subjects appear to have minimal alterations in their ventilatory response to CO2 after beta-adrenergic blockade, patients with airway disease may still experience significant changes in ventilation. In addition, drug interaction studies may give further insight into the presence or absence of any respiratory effects of propranolol.

Adult↗
PubMed1990

Differences in magnitude and duration of opioid-induced respiratory depression and analgesia with fentanyl and sufentanil.

The magnitude and duration of analgesia and respiratory depression induced by fentanyl (1.0, 2.0, and 4.0 micrograms/kg) and sufentanil (0.1, 0.2, and 0.4 microgram/kg) after intravenous administration over 30 s were measured in 30 healthy young adult male volunteers divided into three groups and studied in a double-blind, randomized fashion. Each volunteer received one dose of fentanyl or sufentanil and no sooner than 48 h later, the corresponding equipotent dose of the other opioid. End-tidal CO2 and ventilatory and occlusion pressure responses to CO2 rebreathing were used to measure drug-induced respiratory effects. Analgesic effects were assessed by changes in the pain threshold to electric shock applied to the forearm. Plasma levels of fentanyl and sufentanil were measured by radioimmunoassay. Testing and sampling intervals were 5, 30, 60, 90, 120, 240, 300, and 360 min after drug administration. The magnitude and duration of depression of the ventilatory and occlusion pressure response were significantly less with sufentanil compared with fentanyl, irrespective of dose. Ventilatory and occlusion pressure responses returned to control values by 30 and 30 min, respectively, after sufentanil and by 240 and 120 min, respectively, after fentanyl. Statistically significant elevations of the pain threshold were, however, greater and longer lasting after sufentanil compared with fentanyl. Pain threshold returned to control values 180 min after sufentanil but only 90 min after fentanyl. These results suggest that sufentanil may provide better patient comfort with less respiratory depression than does fentanyl.

Adolescent↗
PubMed1990

Prevention of succinylcholine myalgias: a meta-analysis.

Meta-analysis is a term used to describe statistical methods for evaluating a series of research reports; this analysis transcends the limitations that may be inherent in each of the individual studies summarized. Forty-five research reports of clinical trials for the prevention of myalgias after succinylcholine were assembled. Four classes of preventive drugs (nondepolarizing muscle relaxants, benzodiazepines, succinylcholine in "self-taming" doses, and local anesthetics) were reported in detail sufficient to allow for inclusion in a meta-analysis of clinical efficacy. Each study was summarized by determining the difference in the incidence of myalgias on the first postoperative day between treatment and control groups. A random-effects variance components approach was used. Seven meta-analyses were performed (atracurium, d-tubocurarine, gallamine, pancuronium, diazepam, succinylcholine in self-taming doses, and lidocaine). For each meta-analysis there was statistically significant heterogeneity among studies. Atracurium, d-tubocurarine, gallamine, pancuronium, diazepam, and lidocaine all significantly decreased the frequency of myalgias by about 30%. Succinylcholine in self-taming doses alone was not efficacious.

Humans↗
PubMed1989

Implementation of a computerized patient advice system using the HELP clinical information system.

A COMputerized Patient Advice System (COMPAS) was designed to test the feasibility of using the HELP clinical information system to direct the respiratory therapy of intensive care (ICU) patients acutely ill with adult respiratory distress syndrome. A modified black-board control architecture allowed the application of knowledge in either a forward or a backward chaining mode. Expert clinicians recommended decision logic and actions for five different modes of ventilatory support. The clinical staff used COMPAS to manage the ICU ventilatory support of five patients for a total of 624 hr. During that time there were 407 decision-making opportunities. COMPAS automatically generated therapy suggestions 379 (93.1%) times and the clinical staff accepted COMPAS's recommendation in 320 (84.4%) of these cases. These results suggest that the ventilatory support of severely ill ICU patients can be managed by a clinical information system using a blackboard control architecture.

Algorithms↗
PubMed1989

Comparison of oral transmucosal fentanyl citrate and an oral solution of meperidine, diazepam, and atropine for premedication in children.

The safety and efficacy of premedication with oral transmucosal fentanyl citrate (OTFC) was compared with that of an orally administered solution of meperidine, diazepam, and atropine and no premedication in 59 children about to undergo elective operations. The patients were randomly assigned to receive no premedication (n = 19); 0.25 ml/kg of the oral solution (containing meperidine, 1.5 mg/kg, diazepam, 0.2 mg/kg, and atropine, 0.02 mg/kg, n = 20); or OTFC (15-20 micrograms/kg, n = 20). Children had activity (sedation) and anxiety scores, vital signs (including systolic and diastolic arterial blood pressures and heart and respiratory rates) and pulse oximetry determined oxygen saturation measured before and at 10-min intervals after premedication until they were taken to the operating room. Quality of induction and recovery was evaluated using scoring schedules; recovery times were measured and side effects noted. OTFC was readily accepted and provided significant reductions in preoperative activity (sedation) and anxiety starting after 30 min. After OTFC, sedation and anxiolysis were significantly greater than in children having no premedication but similar to children having the oral solution for premedication. Vital signs and oxygen saturations remained unchanged preoperatively in all groups. Induction and recovery evaluations and recovery times were similar in the three groups, although children having OTFC had the lowest requirements for narcotics in the recovery room. OTFC caused an 80% incidence of mild preoperative facial pruritus and a higher overall incidence of postoperative vomiting (37%) than premedication with the oral solution (5%) or no premedication (18%).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗