PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-3 (3)
 

Clipboard (0)
None
Journals
Authors
more »
Year of Publication
Document Types
1.  Ondansetron Does Not Reduce the Shivering Threshold in Healthy Volunteers 
British journal of anaesthesia  2006;96(6):732-737.
Summary
Background
Ondansetron, a serotonin-3 receptor antagonist, reduces postoperative shivering. Drugs that reduce shivering usually impair central thermoregulatory control and may thus be useful for preventing shivering during induction of therapeutic hypothermia. We determined, therefore, whether ondansetron reduces the major autonomic thermoregulatory response thresholds (trigging core temperatures) in humans.
Methods
Ten healthy volunteers were studied on two days: Control and Ondansetron (intravenous infusion to plasma concentrations of 278 (57) ng mL−1, 234 (55) ng mL−1, and 243 (58) ng mL−1at the sweating, vasoconstriction, and shivering thresholds, respectively); this corresponded to ≈50 mg of ondansetron which is roughly ten times the dose used for postoperative nausea and vomiting. Each day, skin and core temperatures were increased to provoke sweating, then reduced to elicit peripheral vasoconstriction and shivering. We determined the core-temperature sweating, vasoconstriction, and shivering thresholds after compensating for changes in mean-skin temperature. Data were analyzed with paired t tests and presented as means (SD)s; P<0.05 was statistically significant.
Results
Ondansetron did not change the sweating (Control: 37.4 (0.4)°C, Ondansetron: 37.6 (0.3)°C, P=0.16), vasoconstriction (37.0 (0.5) vs. 37.1 (0.3)°C; P=0.70), or shivering threshold (36.3 (0.5) vs. 36.3 (0.6)°C; P=0.76). No sedation was observed on either study day.
Conclusions
Ondansetron, therefore, appears to have little potential for facilitating induction of therapeutic hypothermia.
doi:10.1093/bja/ael101
PMCID: PMC1502385  PMID: 16675509
Thermoregulation; ondansetron; therapeutic hypothermia
2.  Tissue Oxygenation Response to Mild Hypercapnia during Cardiopulmonary Bypass with Constant Pump Output 
British journal of anaesthesia  2006;96(6):708-714.
Background
Tissue oxygenation is the primary determinant of wound infection risk. Mild hypercapnia markedly improves cutaneous, subcutaneous, and muscular tissue oxygenation in volunteers and patients. However, relative contributions of increased cardiac output and peripheral vasodilation to this response remains unknown. We thus tested the hypothesis that increased cardiac output is the dominant mechanism.
Methods
We recruited 10 ASA III patients, aged 40–65 years, undergoing cardiopulmonary bypass for this crossover trial. After induction of anaesthesia, a Silastic tonometer was inserted subcutaneously in the upper arm. Subcutaneous tissue oxygen tension was measured with both polarographic electrode and fluorescence-based systems. Oximeter probes were placed bilaterally on the forehead to monitor cerebral oxygenation. After initiation of cardiopulmonary bypass, in random order patients were exposed to two arterial CO2 partial pressures for 30 minutes each: 35 (normocapnia) or 50 mmHg (hypercapnia). Bypass pump flow was kept constant throughout the measurement periods.
Results
Hypercapnia during bypass had essentially no effect on PaO2, mean arterial pressure, or tissue temperature. PaCO2 and pH differed significantly. Subcutaneous tissue oxygenation was virtually identical during the two PaCO2 periods (139 [50,163] vs. 145 [38,158], P=0.335) (median [range]). In contrast, cerebral oxygen saturation (our positive control measurement) was significantly less during normocapnia (57 [28,67]%) than hypercapnia (64 [37,89]%, P=0.025).
Conclusions
Mild hypercapnia, which normally markedly increases tissue oxygenation, did not do so during cardiopulmonary bypass with fixed pump output. This suggests that hypercapnia normally increases tissue oxygenation by increasing cardiac output rather than direct dilation of peripheral vessels.
doi:10.1093/bja/ael093
PMCID: PMC1464052  PMID: 16675511
Carbon Dioxide; Hypercapnia; Hypercarbia; Acidosis; Respiratory; Oxygenation; Oxygen; Tissue; Cutaneous; Subcutaneous; Cerebral; Perfusion; Cerebrovascular; Cardiac Output
3.  The impact of age on bispectral index values and EEG bispectrum during anaesthesia with desflurane and halothane in children 
British Journal of Anaesthesia  2006;96(4):480-485.
Background
The relationship between end-tidal sevoflurane concentration, BIS and the EEG bispectrum in children appears dependent on age. The aim of this study was to quantify the BIS values at 1 MAC for desflurane and halothane, and explore the relationship with age for these anaesthetic agents in children.
Methods
ECG, EEG and BIS were recorded continuously during the anaesthesia of ninety children aged 6–170 months requiring elective surgery. Fifty children were anaesthetised with desflurane, and forty children with halothane. Recordings were performed through to a steady state of 2 MAC, and thereafter at 1 MAC and 0.5 MAC respectively. The bispectrum of the EEG was estimated using MATLAB© software. For analysis, a multiple correspondence analysis (MCA) was used.
Results
At the steady state of 1 MAC, BIS values were significantly higher with halothane 62 (43–80) compared to desflurane 34 (18–64). BIS values were significantly correlated to age in both groups: DES (r2=0.57; p<0.01) and HALO (r2=0.48; p<0.01). Changes in position in the structured model of the MCA (dependent on the pattern of the EEG bispectrum) were different for the two volatile anaesthetic agents.
Conclusions
BIS values are linked to age of children irrespective of the volatile anaesthetic agent used. In children, the difference in BIS values for different agents at the same MAC can be explained by the specific effect on the EEG bispectrum induced by each anaesthetic agent, bringing into question the ability of the EEG bispectrum to accurately determine depth of anaesthesia in children.
doi:10.1093/bja/ael034
PMCID: PMC2034405  PMID: 16500950
Adolescent; Age Factors; Anesthetics, Inhalation; pharmacology; Body Weight; physiology; Child; Child, Preschool; Electrocardiography; drug effects; Electroencephalography; drug effects; Female; Halothane; pharmacology; Humans; Infant; Isoflurane; analogs & derivatives; pharmacology; Male; Monitoring, Intraoperative; methods; Depth of Anesthesia; EEG; Bispectrum; PCA; Factorial Analysis; Classification; Anesthesia; BIS; Monitoring

Results 1-3 (3)