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Biomedical subjects

A Yli-Hankala

Publications and source records attributed to A Yli-Hankala.

At least 19 recordsLinked to original sources
PubMed2006

Increase in high frequency EEG activity explains the poor performance of EEG spectral entropy monitor during S-ketamine anesthesia.

OBJECTIVE: To study the effects of S-ketamine on the EEG and to investigate whether spectral entropy of the EEG can be used to assess the depth of hypnosis during S-ketamine anesthesia. METHODS: The effects of sub-anesthetic (159 (21); mean (SD) ng/ml) and anesthetic (1,959 (442) ng/ml) serum concentrations of S-ketamine on state entropy (SE), response entropy (RE) and classical EEG spectral power variables (recorded using the Entropy Module, GE Healthcare, Helsinki, Finland) were studied in 8 healthy males. These EEG data were compared with EEG recordings from 6 matching subjects anesthetized with propofol. RESULTS: The entropy values decreased from the baseline SE 85 (3) and RE 96 (3) to SE 55 (18) and RE 72 (17) during S-ketamine anesthesia but both inter- and intra-individual variation of entropy indices was wide and their specificity to indicate unconsciousness was poor. Propofol induced more pronounced increase in delta power (P<0.02) than S-ketamine, whereas anesthetic S-ketamine induced more high frequency EEG activity in the gamma band (P<0.001). Relative power of 20-70 Hz EEG activity was associated with high SE (P=0.02) and RE (P=0.03) values during S-ketamine anesthesia. CONCLUSIONS: These differences in low and high frequency EEG power bands probably explain why entropy monitor, while adequate for propofol, is not suitable for assessing the depth of S-ketamine anesthesia. SIGNIFICANCE: The entropy monitor is not adequate for monitoring S-ketamine-induced hypnosis.

Adult↗
PubMed2006

Novel multiparameter approach for measurement of nociception at skin incision during general anaesthesia.

BACKGROUND: Direct indicators for the evaluation of the nociceptive-anti-nociceptive balance during general anaesthesia do not exist. The aim of this study was to combine physiological parameters to obtain such an indicator. METHODS: Fifty-five females scheduled for surgery under general anaesthesia combining target-controlled infusions of propofol and remifentanil were studied. Propofol was given to maintain state entropy (SE) at 50 and remifentanil was targeted at 1, 3 or 5 ng ml(-1). The patients' reactions and clinical signs of nociception, remifentanil levels and estimation of noxious intensity of incision were combined into a clinical score [Clinical Signs-Stimulus-Antinociception (CSSA)] to evaluate the nociceptive-anti-nociceptive balance. ECG, photoplethysmography (PPG), response entropy (RE) and SE were recorded from 60 s before to 120 s after skin incision. Differences between post- and pre-incision values of heart rate variability (HRV), PPG and pulse transition time related parameters were analysed off-line to evidence the best predictors of CSSA. Those best predictors of CSSA served to develop a response index of nociception (RN), scaled from 0 to 100. This index was further tested in 10 additional patients. RESULTS: HRV, RE, RE-SE and PPG variability were the best predictors of CSSA. The prediction probability of RN at predicting CSSA was 0.78. RN response was higher after larger incision, in movers and with lower remifentanil concentrations. CONCLUSIONS: The empirically developed algorithm of RN leads to an index that seems to adequately estimate the nociceptive-anti-nociceptive balance at skin incision during general anaesthesia. In the future, CSSA may serve as a reference for studies investigating methods aimed at evaluating this pharmacodynamic component of anaesthesia.

Adult↗
PubMed2006

Bystander mouth-to-mouth ventilation and regurgitation during cardiopulmonary resuscitation.

OBJECTIVES: To determine whether there is an association between bystander mouth-to-mouth ventilation and regurgitation in prehospital cardiac arrest patients. DESIGN: Prospectively conducted observational study. SETTING: Data were collected from patients treated by the emergency medical service (EMS) systems in three middle-sized or large Finnish urban communities, the Tampere District EMS and the physician-staffed Helicopter EMSs in the Helsinki and Turku areas in southern Finland. SUBJECTS: The study population consisted of 529 consecutive prehospital cardiac arrest patients with attempted resuscitation. Exclusion criteria were cardiac arrest due to trauma or drug overdose. MAIN OUTCOME MEASURES: Regurgitation in prehospital cardiac arrest patients documented by EMS personnel on the scene. RESULTS: Regurgitation occurred in a fourth of patients. Bystander cardiopulmonary resuscitation (CPR) with mouth-to-mouth ventilation was associated with a significantly increased risk of regurgitation compared with no CPR (P < 0.013) and CPR without ventilations (P < 0.01). CONCLUSIONS: The mode and role of bystander CPR in cardiac arrest needs to be further evaluated.

Aged↗
PubMed2006

Effects of cigarette smoking on serum fluoride concentrations and renal function integrity after 1 MAC-h sevoflurane anaesthesia.

BACKGROUND: Tobacco smoke contains various chemicals which may affect drug metabolism. Sevoflurane is metabolized to inorganic fluoride, and elevated serum fluoride concentrations (S-F(-)) may cause deterioration of renal function. Whether smokers develop high S-F(-) and associated disturbances in renal function is not known. METHODS: We investigated sevoflurane metabolism in 25 non-smoking and 25 smoking (> 10 cigarettes/day) generally healthy women, aged 19-68 years, undergoing gynaecological elective surgery under one minimum alveolar concentration-hour (1 MAC-h) standardized sevoflurane anaesthesia. S-F(-) was measured for 24 h. Glomerular and tubular function was assessed by measuring serum and urine tumour-associated trypsin inhibitor (TATI), beta(2)-microglobulin and serum creatinine for 48 h after sevoflurane inhalation. RESULTS: There were no differences between the two study groups with regard to S-F(-). It increased significantly in both groups: in non-smokers, from a baseline between 1.0 and 11 micromol/l (median, 1.6 micromol/l) to a maximum between 8.2 and 40 micromol/l (26 micromol/l) (P < 0.001) and, in smokers, from a baseline between 0.5 and 5.2 micromol/l (1.7 micromol/l) to a maximum between 19 and 71 micromol/l (25 micromol/l) (P < 0.001). In both groups, S-F(-) remained elevated for the entire sampling period (P < 0.001). In all five women (one non-smoker and four smokers) with a maximum S-F(-) of 40 micromol/l or higher and an area under the serum fluoride concentration-time curve (AUC(F0-24)) of 500 micromol/h/l or higher, serum TATI increased above the pathological concentration of 3.0 nmol/l, whereas only six of the 45 patients with S-F(-) below 40 micromol/l had serum TATI above 3.0 nmol/l (P < 0.001). Beta(2)-Microglobulin increased significantly (> 1 mg/l) in two patients with high S-F(-) relative to two of the 45 patients with S-F(-) below 40 micromol/l (P= 0.005). None of the patients developed clinically detectable renal dysfunction. CONCLUSION: Smoking did not affect S-F(-) after sevoflurane anaesthesia. Glomerular dysfunction, seen as increased serum TATI, was noted in five women with S-F(-) above 40 micromol/l. Our results suggest that the renal toxic threshold of S-F(-) seems to be lower than the earlier reported value of 50 micromol/l.

Adult↗
PubMed2006

Maternal haemodynamics in pre-eclampsia compared with normal pregnancy during caesarean delivery.

OBJECTIVE: To determine how pre-eclampsia modifies maternal haemodynamics during caesarean delivery. DESIGN: Prospective study. SETTING: Tampere University Hospital, Finland. POPULATION: Ten pre-eclamptic parturients and ten healthy parturients with uncomplicated pregnancies scheduled for elective caesarean section under spinal anaesthesia. METHODS: Haemodynamic parameters were assessed by whole-body impedance cardiography noninvasively. MAIN OUTCOME MEASURES: Stroke index (SI), heart rate (HR), cardiac index (CI), systemic vascular resistance index (SVRI) and mean arterial pressure (MAP) were recorded before operation, continuously during caesarean section, during the period of dissipation of anaesthesia and on the second to fifth postpartum day. RESULTS: Baseline haemodynamics in women with pre-eclampsia differed significantly from healthy women in higher SVRI and MAP and lower SI and CI. In women with pre-eclampsia, preload infusion increased both SI and HR, causing a significant rise in CI, while in healthy parturients, only HR rose. In both the groups, spinal blockade reduced SVRI but CI remained stable. At the moment of delivery, CI increased in both groups. In uncomplicated pregnancies, both SI and HR increased, but in women with pre-eclampsia, SI was not altered and the rise in CI was due to an increase in HR only. After the reversal of anaesthesia, haemodynamics in the control group returned to baseline values, whereas in women with pre-eclampsia, SI and CI fell to levels that were significantly lower than the levels observed before surgery. CONCLUSIONS: In women with pre-eclampsia, inability to increase SI at the moment of delivery may suggest dysfunction of the left ventricle to adapt to volume load caused by delivery and prompts concern for the increased risk of pulmonary oedema.

Adult↗
PubMed2005

Is peri-operative cortisol secretion related to post-operative cognitive dysfunction?

BACKGROUND: The pattern of cortisol secretion is influenced by surgery. As cortisol can adversely affect neuronal function, this may be an important factor in the development of post-operative cognitive dysfunction (POCD). We hypothesized that the incidence of POCD would be related to changes in cortisol level. METHODS: We studied 187 patients aged over 60 years undergoing major non-cardiac surgery with general or regional anaesthesia. Saliva cortisol levels were measured pre-operatively and at 1 day, 7 days and 3 months post-operatively in the morning (08.00 h) and in the afternoon (16.00 h) using salivettes. Cognitive function was assessed pre-operatively, on day 7 and at 3 months using four neuropsychological tests. POCD was defined as a combined Z score of greater than 1.96. RESULTS: After surgery, salivary cortisol concentrations increased significantly. POCD was detected in 18.8% of subjects at 1 week and in 15.2% after 3 months. The pre-operative ratios between the morning and afternoon cortisol concentrations (am/pm ratios) were 2.8 and 2.7 in patients with POCD at 1 week vs. those without POCD at 1 week, respectively. The am/pm ratios decreased significantly post-operatively to 1.9 and 1.6 at 1 week, respectively (P = 0.02 for both). In an analysis considering all am/pm ratios, it was found that the persistent flattening in am/pm ratio was significantly related to POCD at 1 week. CONCLUSION: The pattern of diurnal variation in cortisol level was significantly related to POCD. Thus, circadian rhythm disturbance or metabolic endocrine stress could be an important mechanism in the development of cognitive dysfunction after major surgery.

Aged↗
PubMed2004

No effect of cardiopulmonary bypass on hypnosis in patients anaesthetized with propofol and alfentanil.

BACKGROUND: The effect of cardiopulmonary bypass (CPB) on the level of anaesthetic depth has not been studied previously in a randomized way. METHODS: We assessed the effect of CPB on the propofol needed to maintain a fixed bispectral index score, and on the recovery from anaesthesia in 22 patients undergoing coronary artery bypass graft surgery with CPB (on-pump) compared with 18 patients operated on without CPB (off-pump). Anaesthesia was induced and maintained with propofol and alfentanil. Throughout the procedure, the infusion rate of propofol was adjusted to keep the BIS value at 40 +/- 5. RESULTS: With the off-pump technique, the duration of surgery and anaesthetic administration were significantly greater. The need for propofol in proportion to time was exactly the same in both groups. During anaesthesia and the first 3 h thereafter, the BIS recordings were similar in both groups. No differences were detected in the time to awakening or tracheal extubation. CONCLUSIONS: CPB does not affect propofol requirements or immediate postoperative recovery compared with the off-pump technique.

Aged↗
PubMed2004

Time-frequency balanced spectral entropy as a measure of anesthetic drug effect in central nervous system during sevoflurane, propofol, and thiopental anesthesia.

BACKGROUND: Time-frequency balanced spectral entropy of electroencephalogram (EEG) and frontal electromyogram (FEMG) is a novel measure of hypnosis during anesthesia. Two Entropy parameters are described: Response entropy (RE) is calculated from EEG and FEMG; and State Entropy (SE) is calculated mainly from EEG. This study was performed to validate their performance during transition from consciousness to unconsciousness under different anesthetic agents. METHODS: Response entropy, SE [S/5 Entropy Module, M-ENTROPY (later in text: Entropy), Datex-Ohmeda Division, Instrumentarium Corp., Helsinki, Finland] and BIS (BIS XP, A-2000, Aspect Medical Systems, Newton, MA) data were collected from 70 patients; 30 anesthetized with propofol 2 mg kg-1, 20 with sevoflurane inhalation, and 20 with thiopental 5 mg kg-1. Loss and regaining of consciousness (LOC, ROC) was tested every 10 s, and sensitivity, specificity, and prediction probability (Pk) were calculated. Behavior of the indices was studied. RESULTS: Sensitivity, specificity, and Pk values for consciousness were high and similar for all indices. During regaining of consciousness after propofol bolus, RE, SE, and BIS values recovered by 81 +/- 22%, 75 +/- 26%, and 59 +/- 18% (mean +/- SD), respectively, from the minimum relative to their baseline. After thiopental bolus, RE, SE, and BIS values recovered by 86+/-21%, 88 +/- 13%, and 63 +/- 14%, respectively. The relative rise was higher in RE and SE compared with BIS (P < 0.01). During deep levels of hypnosis, RE and SE decreased monotonously as a function of burst suppression ratio, while BIS showed biphasic behavior. On average, RE indicated emergence from anesthesia 11 s earlier than SE, and 12.4 s earlier than BIS. CONCLUSIONS: All indices, RE, SE, and BIS, distinguished excellently between conscious and unconscious states during propofol, sevoflurane, and thiopental anesthesia. During burst suppression, Entropy parameters RE and SE, but not BIS, behave monotonously. During regaining of consciousness after a thiopental or propofol bolus, RE and SE values recovered significantly closer to their baseline values than did BIS. Response entropy indicates emergence from anesthesia earlier than SE or BIS.

Adolescent↗
PubMed2003

Fluoride metabolism in smokers and non-smokers following enflurane anaesthesia.

BACKGROUND: Inorganic fluoride is released by the metabolism of enflurane and the increased serum fluoride concentrations may impair renal function. Tobacco smoke consists of numerous reactive compounds that can either induce or inhibit drug metabolism. Studies on the interaction of smoking with anaesthetic drug metabolism and possible toxicity are warranted. METHODS: Sixteen non-smoking and 17 smoking (>10 cigarettes day(-1)) generally healthy women undergoing elective gynaecological surgery were given 1 MAC (minimum alveolar concentration)-hour standardized anaesthesia with enflurane in oxygen-air mixture. The serum inorganic fluoride and renal function markers beta(2)-microglobulin, tumour-associated trypsin inhibitor (TATI) and serum creatinine were measured for 48 h. RESULTS: The greatest inorganic fluoride concentration was between 8.4 and 21.0 (mean 13.8 (SD 3.4)) micromol litre(-1) in the non-smokers and between 8.6 and 38.0 (18.7 (7.0)) micromol litre(-1) in the smokers; the mean difference was 4.9 micromol litre(-1) (95% confidence interval (CI) 1.0-8.8, P<0.05). Serum beta(2)-microglobulin, TATI and creatinine were not increased. Serum inorganic fluoride concentrations were significantly greater in the smokers compared with the non- smokers 1, 2, 3 and 6 h after 1 MAC-hour inhalation with enflurane (P<0.05). Inorganic fluoride concentrations were still increased 24 h after anaesthesia in both groups. Urine beta(2)-microglobulin and TATI creatinine ratio remained at low values during the whole 48-h period in both groups. CONCLUSIONS: Regular smoking is associated with an increase in serum inorganic fluoride concentration after anaesthesia with enflurane, but there are no signs of renal damage.

Adult↗
PubMed2001

Gastric air tonometry during laparoscopic cholecystectomy: a comparison of two PaCO2 levels.

PURPOSE: Pneumoperitoneum can cause disturbances in acid-base balance and splanchnic perfusion. We studied the effect of ventilation on acid-base balance and gastric mucosal tonometric values in patients undergoing laparoscopic cholecystectomy. METHODS: Twenty-four patients (ASA I-II) were randomly allocated into two groups. In the fixed ventilation group, ventilation was constant allowing free increase in PCO2, while in the constant CO2 group end-tidal PCO2 was fixed with ventilatory adjustment. Intraabdominal pressure was limited to 12 mmHg. Arterial acid-base balance, automated air tonometric variables and gastric mucosal to arterial PCO2 gap were determined frequently from anesthesia induction until three hours postoperatively. RESULTS: During pneumoperitoneum, in the fixed ventilation group arterial PCO2 changed from 5.0 +/- 0.2 to 6.6 +/- 0.4 kPa and pH from 7.43 +/- 0.03 to 7.33 +/- 0.04, tonometric PCO2 from 5.1 +/- 0.5 to 6.9 +/- 0.4 and pH from 7.44 +/- 0.04 to 7.33 +/- 0.04. In the constant CO2 group these variables remained at control levels (P < 0.01 between groups). The PCO2 gap remained unchanged without any differences between the groups. In the recovery room all measured variables were within normal range in both groups. CONCLUSION: Despite inter-group differences in arterial and tonometric PCO2 and pH values during CO2 pneumoperitoneum, the patients did not develop splanchnic hypoperfusion detectable by air tonometric method, as indicated by normal PCO2 gap in both groups throughout the study.

Acid-Base Equilibrium↗
PubMed2001

Propofol anesthesia induces phase synchronization changes in EEG.

OBJECTIVE: Phase coupling between EEG channel pairs in various frequency bands was evaluated during propofol anesthetic induction and recovery periods. METHODS: Twenty-three patients participated in the study. Phase synchronization indices based on the Hilbert transform were investigated on frequency bands 0.05-1 Hz, 1-4 Hz, 4-8 Hz, 8-12 Hz and 12-16 Hz for all pairs of the 9 EEG channels covering midline and frontal areas. A straight line was used to approximate the index values as a function of time and the Sign Test statistics were applied to the slope parameters. RESULTS: Systematic phase synchronization changes were detected. Generally, phase synchronization in the sub-delta band decreased during the induction and increased during the recovery, while the directions were reversed in the alpha band. The changes were dependent on the channel pair. In the delta, theta and beta bands, the changes were aligned more irregularly than in the sub-delta or in the alpha bands. Highly asymmetric behavior between the induction and the recovery periods was also observed in these bands. CONCLUSIONS: Induction and recovery from propofol anesthesia changes the phase synchronization between the EEG channels. The passband and location-specific behavior of these changes reveals the effects of the anesthetic to the different neural mechanisms.

Adult↗
PubMed2001

Sevoflurane mask induction of anaesthesia is associated with epileptiform EEG in children.

BACKGROUND: Sevoflurane inhalation induction of anaesthesia is widely used in paediatric anaesthesia. We have found that this method is frequently associated with epileptiform electroencephalogram (EEG) in adults, especially if controlled hyperventilation is used. METHODS: We assessed EEG during sevoflurane inhalation induction in 31 children, aged 2-12 yr. Anaesthesia was induced with 8% sevoflurane in O2 in N2O 1:2. The patients were randomized to undergo controlled ventilation (CV group), or to breathe spontaneously (SB group) for 5 min. EEG was recorded as were noninvasive blood pressure and heart rate (HR). EEG recordings were classified by a clinical neurophysiologist. RESULTS: Three different types of interictal epileptiform discharge were detected. Suppression with spikes (SSP) was found in 25% and 0% in the CV and SB groups, rhythmic polyspikes (PSR) in 44% and 20%, and periodic epileptiform discharges (PED) in 44% and 0% (P<0.01), respectively. The incidence of all different types of interictal epileptiform discharge (SSP+PSR+PED) was 88% and 20% (P<0.001), respectively. Epileptiform EEG was associated with increased heart rate and blood pressure during anaesthetic induction. CONCLUSION: Both ventilation modes produced epileptiform EEG. With controlled ventilation, epileptiform discharges were seen in 88% of children. This warrants further studies of the suitability of this induction type in general, and especially in children with epilepsy.

Anesthetics, Inhalation↗
PubMed2000

Epileptiform EEG during sevoflurane mask induction: effect of delaying the onset of hyperventilation.

BACKGROUND: Hyperventilation during sevoflurane-N2O-O2 mask induction in adults is associated with a hyperdynamic circulatory response and epileptiform electroencephalogram (EEG). We tested the hypothesis that delaying onset of hyperventilation will prevent severe (periodic) epileptiform EEG and hyperdynamic response. METHODS: Thirty patients were randomized to receive either delayed (group D, n=15) or immediate (group I, n=15) onset of hyperventilation during sevoflurane (8% in N2O 50%) mask inhalation induction with single-breath method for unconsciousness. Fifteen patients were allowed to breathe spontaneously for 2 min after loss of consciousness and controlled hyperventilation (ETCO2 <4%) was started thereafter. In 15 patients controlled hyperventilation was started immediately after loss of consciousness. EEG was recorded, and mean arterial pressure (MAP) and heart rate (HR) registered. RESULTS: Epileptiform EEG patterns were seen in 13 patients in group I and in 9 patients in group D (n.s.). Periodic epileptiform discharges (PED) tended to occur more often in group I (P=0.07). Heart rate and MAP were higher in group I than in group D from 2 min to 3 min (P < 0.05), and both HR and MAP rose significantly from the baseline in group I. In group D, HR but not MAP rose significantly from baseline. CONCLUSION: Regardless of its timing, hyperventilation at a high sevoflurane concentration produced severe epileptiform EEG with a hyperdynamic response. PED tended to occur more often with immediate onset of hyperventilation.

Adult↗
PubMed2000

Are electrocardiogram electrodes acceptable for electroencephalogram bispectral index monitoring?

BACKGROUND: The monitoring of electroencephalogram bispectral index (EEG-BIS) during anaesthesia reduces anaesthetic use and improves recovery. However, it also increases the direct costs of anaesthesia due to the need for special EEG electrodes. In the present study we tested the feasibility of less expensive electrocardiogram (ECG) electrodes for EEG-BIS monitoring. METHODS: In the first part of the study we compared skin-electrode impedances when EEG electrodes were used after alcohol swab pretreatment of skin to impedances when ECG electrodes were used after alcohol swab pretreatment with or without skin abrasion paste. In the second part of the study we evaluated the difference in parallel BIS values collected with two BIS monitors, using either ECG electrodes or EEG electrodes. In the third part of the study we compared parallel BIS values collected with two sets of EEG electrodes. RESULTS: Skin pretreatment with abrasion paste led to lower impedances with ECG electrodes than did alcohol swab pretreatment of skin with EEG electrodes. When the skin was pretreated with alcohol swab, higher impedances were measured with ECG electrodes than with EEG electrodes. In most patients, BIS values collected with ECG electrodes were also higher than those collected with adhesive EEG electrodes. The difference between parallel BIS values collected with two sets of adhesive EEG electrodes was smaller than the difference between BIS values collected with ECG and EEG electrode sets. CONCLUSION: Low skin-electrode impedances indicating reliable skin-electrode contact can be ensured with inexpensive pregelled ECG electrodes only if the skin is carefully prepared with both abrasion paste and alcohol. When only alcohol pretreatment of skin is used, the BIS values collected with EEG electrodes and ECG electrodes are not equal. EEG-BIS monitoring with pregelled ECG electrodes is recommended only if skin is prepared with abrasion paste before attaching the electrodes.

Adult↗