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Biomedical subjects

D Chartrand

Publications and source records attributed to D Chartrand.

10 recordsLinked to original sources
PubMed2003

Antagonism of sevoflurane anaesthesia by physostigmine: effects on the auditory steady-state response and bispectral index.

BACKGROUND: Physostigmine, a centrally acting anticholinesterase, antagonizes the hypnotic effect of propofol, as shown by the return of consciousness (response to commands) or wakefulness (spontaneous eye-opening without response to commands) and by recovery of auditory evoked potentials (40 Hz auditory steady-state response (ASSR)) and the bispectral index (BIS). We measured the effects of physostigmine on the hypnotic effect of inhaled volatile anaesthetics, using sevoflurane as the representative agent. METHODS: Eight healthy volunteers received sevoflurane adjusted to produce loss of consciousness. Physostigmine (plus glycopyrrolate) was given while the end-tidal concentration of sevoflurane was kept constant. RESULTS: Loss of consciousness was accompanied by a significant (P<0.02) decrease in ASSR amplitude (to 21% of awake value) and BIS (to 70% of awake value). Five subjects had return of consciousness or wakefulness after physostigmine. The others showed no behavioural change. Physostigmine caused a significant increase of the mean ASSR amplitude from 0.11 (SD 0.04) to 0.17 (0.06) microV (P<0.05). The BIS also increased, from 66 (12) to 74 (12), but the difference was not significant. CONCLUSIONS: Physostigmine can antagonize, at least partially, the hypnotic effect of sevoflurane and changes in arousal after physostigmine are shown by ASSR measurements. However, the antagonism is not as clear or reliable as with propofol.

Adolescent↗
PubMed1998

Efficacy and costs of patient-controlled analgesia versus regularly administered intramuscular opioid therapy.

BACKGROUND: Many studies have shown the efficacy of patient-controlled analgesia (PCA). However, it is not clear whether PCA has clinical or economic benefits in addition to efficient analgesia. The current study was designed to evaluate these issues by comparing PCA with regularly administered intramuscular injections of opioids after hysterectomy. METHODS: This prospective study included 126 patients who underwent abdominal hysterectomy and were randomly assigned to receive PCA or regularly timed intramuscular injections of morphine during a period of 48 h. Doses were adjusted to provide satisfactory analgesia in both treatment groups. Pain at rest and with movement, functional recovery, drug side effects, and patient satisfaction were measured using rating scales and questionnaires. The costs of PCA and intramuscular therapy were calculated based on personnel time and drug and material requirements. RESULTS: Comparable analgesia was observed with the two treatment methods, with no significant differences in the incidence of side effects or patient satisfaction. The medication dosage had to be adjusted significantly more frequently in the intramuscular group than in the PCA patients. The PCA did not favor a faster recuperation time compared with intramuscular therapy in terms of times to ambulation, resumption of liquid and solid diet, passage of bowel gas, or hospital discharge. The results of the economic evaluation, which used a cost-minimization model and sensitivity analyses, showed that PCA was more costly than regular intramuscular injections despite the fact that no costs for the pump were included in the analyses. Cost differences in nursing time favoring PCA were offset by drug and material costs associated with this type of treatment. CONCLUSIONS: Compared with regularly scheduled intramuscular dosing, PCA is more costly and does not have clinical advantages for pain management after hysterectomy. Because of the comparable outcomes, the general use of PCA in similar patients should be questioned.

Analgesia↗
PubMed1997

Clinical reassessment of malignant hyperthermia in Abitibi-Témiscamingue.

PURPOSE: In 1992, 1812 individuals (1.2% of the population) were labelled at risk for malignant hyperthermia (MH) in seven families from Abitibi-Témiscamingue. To evaluate the effective risk in this population, a multidisciplinary study was undertaken which included clinical, genealogical and molecular aspects. This paper presents the clinical aspects of the study. METHOD: For each of the 1546 individuals reached, all anesthetic exposures were screened for elements relevant to MH. Malignant hyperthermia events were analyzed with "the clinical grading scale." All 44 reports of caffeine halothane contracture tests were reappraised. Finally, genealogical study was done to complete each family tree up to the initial French settlers in order to identify links between these seven families through common ancestors. RESULTS: Following this reassessment, the families were compared and classified into four groups. Two families (1097 individuals) are not considered to be at a higher risk for MH than the population in general. Two families are still considered possibly at risk. Finally, one family (402 individuals) is highly at risk and two other families are probably at risk. Family trees did not show any link up to the colonization of Abitibi-Témiscamingue in the beginning of this Century but common ancestors were found around the 9th generation. CONCLUSION: This clinical reassessment will help to focus education and prevention on a much smaller group of individuals still considered potentially at risk for MH. By adequate evaluation of phenotypes, combined with the use of a genealogical approach, it will be possible to target families for molecular research.

Adolescent↗
PubMed1994

Diaphragmatic and abdominal muscle activity after endoscopic cholecystectomy.

We studied diaphragmatic and abdominal muscle activity immediately and 16 h after laparoscopic cholecystectomy (LAPC). Tidal volumes (VT), partitioning of VT between the rib cage and the abdomen, and esophageal, gastric, and transdiaphragmatic pressures were recorded for 5 min every 15 min up to 90 min after the end of anesthesia in 10 young patients submitted to an elective LAPC. All had chest radiographs in full inspiration and expiration as well as lung function tests (LFTs) before and 16 h after surgery. In 5 of the 10 patients, thoracoabdominal patterns of breathing were also measured before both LFTs. After LAPC, VT did not change. There was no significant shift from abdominal to thoracic respiration. No paradoxical respiration developed. Functional residual capacity (FRC) and residual volume (RV) remained normal. However, all measures of LFTs requiring maximum inspiratory effort decreased up to 20%. Tonic and phasic activity of the abdominal muscle appeared early in the recovery period and disappeared after 75 min. The diaphragm adjusted to this additional load so that VT remained constant. These results indicate that diaphragm function is intact during quiet breathing after LAPC, but slightly reduced when maximum effort is needed. However, this represents a net gain over the changes previously described after classic "open" cholecystectomy (OC).

Abdominal Muscles↗
PubMed1994

Can anesthesia ventilators provide high-frequency ventilation?

We measured the tidal volumes (VT) delivered by two anesthesia ventilators (the Narkomed 2B and the Ohmeda 7800) to a model lung at frequencies of 60 breaths/min and 99-100 breaths/min under two conditions of compliance and resistance designed to mimic mild and severe adult respiratory distress syndrome (ARDS) (mild ARDS = S1 and severe ARDS = S2). The VT produced were measured with a pneumotachometer at the ventilator outflow and distal to the anesthesia circuit. With the Narkomed 2B, the VT measured at the entrance to the model lung decreased from 216 mL to 129 mL in S1, and from 152 mL to 88 mL in S2 as the ventilatory frequency increased from 60 to 99 breaths/min. With the Ohmeda 7800, the VT decreased from 213 mL to 118 mL in S1, and from 134 mL to 73 mL in S2 when the frequency was changed from 60 to 100 breaths/min. Since the delivered VT are similar to those previously reported to maintain adequate ventilation at these rates using standard high-frequency ventilation (HFV), it may be possible to use these newer anesthesia ventilators for this purpose.

Anesthesia↗
PubMed1993

Measurement of respiratory mechanics using the Puritan-Bennett 7200a ventilator.

This study was designed in order to validate the respiratory mechanical variables measured by the Puritan-Bennett 7200a ventilator equipped with the 30/40 module. Two ventilators were connected to a lung model and submitted to several breathing patterns by modifying the respiratory rate, the tidal volume, the inspiratory flow-rate and the model resistance. The inspiratory flow-rate (V), tidal volume (VT), peak inspiratory pressure (Pmax), plateau pressure (Pplat) and PEEP measured by the ventilators were compared with the same variables measured at the connection between the breathing circuit and the lung model. The compliance (C30/40) and the resistance (R30/40) calculated by the 30/40 module were compared with those calculated by using the variables measured by the reference equipment. Both ventilators made a constant underestimation of V by 2.8 and 3.7 L.min-1, respectively. The VT was measured with a mean error of less than 10 ml but did not reflect the preselected values in the presence of an intrinsic PEEP. The Pplat was overestimated by 7 and 10%, respectively. The same calibration error was observed with Pmax which was also affected by a pressure gradient due to the resistance of the breathing circuit. Even in the absence of intrinsic PEEP, C30/40 presented an error due to the combination of the measurement errors on VT, Pplat and PEEP. Finally, R30/40 presented a high percentage of error due to the combination of the measurement errors on V, Pmax, and Pplat, and to a sporadic aberrant selection of V. Due to these numerous sources of error, the two ventilators studied did not give reliable estimates of resistance and compliance.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗
PubMed1993

Comparison between patient-controlled analgesia and intramuscular meperidine after thoracotomy.

A prospective randomized controlled study was performed to assess the efficacy and safety of patient-controlled analgesia (PCA) in patients undergoing thoracotomy. This method was compared with a conventional pain management technique consisting of regularly scheduled im injections of analgesics. Forty adult patients were randomly assigned to receive intravenous PCA or im meperidine treatment over a 48-hr period after surgery. Care was taken to optimize analgesia in patients of both groups. The McGill Pain Questionnaire, visual analogue and verbal-numeric scales were administered at regular intervals to measure various components of the patients' pain experience, degree of pain relief, adverse side effects and overall treatment efficacy. Functional recovery after surgery was also examined. The results showed good and comparable analgesia with both pain-control methods. However, a greater number of patients receiving im injections required dosage adjustments than in the PCA group. Patients' and nurses' evaluations of overall treatment efficacy also favoured PCA treatment. There were no major group differences in the side effect profile. Recovery pattern was also comparable in the two groups except for the length of hospitalisation. There were fewer long-stay patients in the PCA than in the im group. Meperidine intake was similar in both groups but considerable interpatient variation was seen. In conclusion, PCA is a safe, effective and individualized treatment method for controlling pain after thoracotomy. There appears to be some clinical advantages of PCA over im dosing regimens for analgesia after thoracotomy.

Adult↗
PubMed1985

Volume-time profile during relaxed expiration in the normal dog.

Airway opening pressure, esophageal pressure, and flow were obtained during relaxed expirations in two normal anesthetized paralyzed dogs. The signal-to-noise ratio in the flow signals was greatly increased by averaging 10 different signals obtained with the same lung inflation volume. Numerical integration of an averaged flow signal then yielded the time course of the volume of the respiratory system above functional residual capacity (the elastic equilibrium volume). Comparison of volume signals obtained with different inflation volumes suggests that the resistance of the respiratory system increases with flow. The flow-volume and semilog volume curves show that expiration is induced by two apparently separate mechanisms: one causes emptying of most of the expired volume over a time interval of much less than 1 s, whereas the other contributes a relatively small amount to the expired volume over a significantly longer time (greater than or equal to 1 s). We postulate the first mechanism to be due to that of the respiratory system behaving like a single unit, with an elastance that is slightly volume dependent, emptying through a single airway which has a resistance that increases with flow. From the nature of airway opening pressure and esophageal pressure measured after occlusion in midexpiration, we conclude that the second mechanism is due to the viscoelastic properties (i.e., creep) of the respiratory system. The properties are manifest mainly in the chest wall.

Animals↗