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Biomedical subjects

G A Baer

Publications and source records attributed to G A Baer.

At least 19 recordsLinked to original sources
PubMed2005

Requirements of propofol at different end-points without adjuvant and during two different steady infusions of remifentanil.

BACKGROUND: Some reports show no interaction between propofol and opioids, whereas others state such interactions. We evaluated the influence of remifentanil on propofol requirements at certain anesthesia end-points. METHODS: Elective surgical patients were randomly assigned to three groups of 15 patients each. Premedication was with oral diazepam 0.1 mg kg(-1). Patients were blindly given equal volumes of saline or remifentanil (7.5 or 30 microg kg(-1). h(-1)) 1 min before induction of anesthesia with infusion of propofol, 30 mg kg(-1). h(-1). We recorded times to, propofol requirements, and bispectral index at loss of counting (LC), loss of verbal command (LVC), loss of reaction to tetanic stimulation (LRT), and onset of burst suppression pattern (BSP) of electroencephalography. RESULTS: In the remifentanil groups end-points were attained significantly faster and with lower doses of propofol than in the saline group. BIS-values were significantly different at LRT and BSP end-points. CONCLUSIONS: We conclude that remifentanil infusion started before induction of propofol anesthesia significantly reduces propofol requirements at all end-points. The results suggest that remifentanil accelerates the hypnotic onset of propofol.

Adolescent↗
PubMed2001

Laparoscopically assisted vaginal and abdominal hysterectomy: comparison of postoperative pain, fatigue and systemic response. A case-control study.

BACKGROUND AND OBJECTIVE: Laparoscopic and open surgery have been compared with conflicting results regarding their systemic responses. The sensitivity of biochemical markers that are used to discriminate between the stress responses to different types of surgery varies from study to study. We wanted to evaluate the stress response and the sensitivity of clinical and biochemical stress markers in patients undergoing laparoscopically assisted vaginal or abdominal hysterectomy. METHODS: We performed a case-control study with patients undergoing laparoscopically assisted vaginal hysterectomy (n=20) or abdominal hysterectomy (n=20). Pain scores were assessed at rest and during coughing, and active leg elevation and fatigue scores using a visual analogue scale. In 10 patients of each group, haematocrit, white cell count, C-reactive protein, glucose, cortisol, adrenocorticotrophic hormone, beta-endorphin immunoreactivity, interleukin-6 and urine excretion of epinephrine and norepinephrine were measured preoperatively and during the first 44 postoperative hours. RESULTS: The most sensitive symptoms and markers of the systemic response were pain scores during mobilization, fatigue scores, C-reactive protein and interleukin-6 (P < 0.01 in all comparisons). Pain scores at rest, and all other laboratory markers of the systemic response, did not discriminate between the two types of surgery. CONCLUSION: Follow-up of postoperative pain scores during mobilization and fatigue levels might be an easy tool for the evaluation of postoperative recovery. Using an identical anaesthetic technique, the neuroendocrine response was of the same magnitude after both types of surgery.

Adult↗
PubMed2000

Does monitoring of post-tetanic count prevent alarms of airway pressure or visible muscle activity during intratracheal jet ventilation? A prospective study with five different neuromuscular blocking agents.

OBJECTIVE: Profound neuromuscular block (NMB) quantified by post-tetanic count (PTC) may prevent all muscle activity during anesthesia. We studied whether monitoring of PTC prevents airway pressure alarms or visible movements of the vocal cords and the abdomen during endolaryngeal procedures (ELPs). METHODS: In this prospective, double blind, study 50 healthy (ASA 1-3) patients scheduled for ELPs were randomized into five groups: atracurium, mivacurium, rocuronium, vecuronium and succinylcholine. During alfentanil-propofol anaesthesia, profound NMB was controlled by monitoring the PTC (target level PTC 0-2, 50 Hz tetanic stimulation) of the adductor pollicis muscle. The muscle relaxants were administered using bolus dosing in all groups but in the succinylcholine group. The early signs of recovery of NMB to be observed were: 1) airway pressure alarms, 2) movements of vocal cords on the laryngeal video monitor and 3) movements of the abdomen. The inference was based on 90% confidence interval tests. RESULTS: During 50 ELP:s following signs of early recovery of NMB were recognized: 2 alarms of airway pressure, 16 laryngeal movements and 11 movements of the abdomen. The proportion of airway pressure alarms was significantly lower than proportion of all detectable movements (95% confidence interval analysis). Twelve of the movements were recorded at PTC zero level. The signs of early recovery of NMB were detected in all groups. CONCLUSIONS: PTC-monitoring following 50 Hz stimulation does not ensure total inactivity of muscles during alfentanil-propofol anesthesia, regardless which relaxant has been chosen. During ELPs, simultaneous observation of the vocal cords and the abdomen is more sensitive in detecting early recovery of NMB compared to our method of airway pressure monitoring.

Abdomen↗
PubMed2000

Efficacy and safety of premedication with oral ketamine for day-case adenoidectomy compared with rectal diazepam/diclofenac and EMLA.

BACKGROUND: Because of its pain-attenuating and sedative properties oral ketamine has been used as premedication in children and adults. We wanted to compare in children scheduled for adenoidectomy safety and efficacy of oral ketamine with a premedication that causes similar preoperative sedation and relief of pain at the venepuncture site. We also evaluated the effect of i.v. glycopyrrolate added to these combinations. METHODS: One hundred children between 10 and 15 kg of body weight scheduled for day-case adenoidectomy were randomly assigned to one of four groups: groups DG and DS received diclofenac 12.5 mg and diazepam 0.5 mg/kg rectally, EMLA cream at the venepuncture site, and placebo orally; groups KG and KS received ketamine 6.0 mg/kg orally, placebo cream at the puncture site, and placebo rectally; additionally, groups DG and KG received glycopyrrolate 5 microg/kg, and groups DS and KS received placebo intravenously. We recorded perioperatively scores (open scale 1-9) for stridor, sedation, bleeding, nausea, pain, heart rate, the need for analgesics and registered psychotomimesis and well-being at home. RESULTS: The children of the K-groups became more tearful during separation from their parents (P=0.0072). No other differences were found between the ketamine and diazepam/diclofenac groups before and after premedication until induction of anaesthesia. Oral ketamine produced unpleasant psychotomimesis in four out of 59 children. During the first 10 min postoperatively, the score for stridor was significantly higher in group KS than in the D-groups; stridor scores > or = 6 were seen in one child of the D-groups (DS) and in six children of the K-groups (n.s.), of whom three developed laryngospasm (one reintubation). Glycopyrrolate diminished salivation in all groups, but had no effect on stridor scores. Additionally, glycopyrrolate delayed the onset of eating at home. CONCLUSION: Premedication with racemic oral ketamine 6 mg/kg does not seem to be suitable for upper airway procedures. Addition of i.v. glycopyrrolate before the induction of anaesthesia significantly reduced the scores for salivation.

Adenoidectomy↗
PubMed2000

Potency of propofol, thiopentone and ketamine at various endpoints in New Zealand White rabbits.

Effective plasma concentrations of propofol, thiopentone and ketamine were determined at different endpoints in a study with randomized, crossover design in nine New Zealand White rabbits. A continuous infusion was used (30 ml/h) with concentrations of 10 mg/ml for propofol, 25 mg/ml for thiopentone and 20 mg/ml for ketamine. The endpoints were loss of the righting reflex, loss of purposeful reactions to tail clamping (as an example of a peripheral pain stimulus) or to intranostril insufflation of ammonia vapour (as an example of a central reflex stimulus), and the recovery of these reflexes and reactions. According to the ED50 values the potency ratios of propofol, thiopentone and ketamine were at the loss of righting reflex 1:1.8:1.2, at the loss of reaction to ammonia vapour 1:1.5:1.6, and at the loss of reaction to tail clamping 1:1.5:3.9, respectively. Recovery was significantly faster after propofol than after thiopentone and ketamine. Measuring the effective plasma concentrations of intravenous anaesthetics provides a method of relating dose to effect, but there still remains a variable gap between plasma concentration and effect.

Anesthetics, Intravenous↗
PubMed1999

Neuromuscular blocking characteristics of vecuronium after tubocurarine-induced "fade". An experimental double-blind clinical study.

OBJECTIVE: The fade in train-of-four (TOF) monitoring is considered to be due to blocking of the prejunctional nicotinic acetylcholine receptors (AchRs). During onset of the neuromuscular block (NMB) tubocurarine (TC) causes more fade in the TOF responses than vecuronium (VEC). Therefore we wanted to investigate whether onset or duration of action of VEC or TC would be improved with a priming dose of an agent with different prejunctional activity. METHODS: The rates of NMB were measured following priming doses of 0.15 mg x kg(-1) of TC and 0.015 mg x kg(-1) of VEC with 6 min priming time. The individual time course of action of 0.6 mg x kg(-1) of TC (1.13 x ED 95) and 0.1-0.2 mg x kg(-1) of VEC (1.75-3.5 x ED95) were examined with a priming dose of the same agent or the other agent, by measurement of changes in the evoked compound EMG from the hypothenar muscle. RESULTS: Priming doses of TC decreased mean TOF ratio to 67% [95% confidence interval (CI) = 56-78] during priming time, which was significantly lower than after priming with VEC 87% (76-97; P < 0.001). Despite the higher TOF ratio, the priming dose of VEC accelerated the onset time of intubation dose of TC more than the priming dose of TC (P = 0.0018). Priming with TC prolonged the duration of VEC-induced NMB by 35-70 min compared with priming with VEC, which means that a small priming dose of TC changes VEC from a muscle relaxant with intermediate action to a long-acting agent. CONCLUSION: Priming with TC caused a lower TOF ratio; however, priming with TC did not accelerate the onset time of either agent as much as priming with VEC. It appears that potentiation of NMB after combination of VEC and TC is not dependent on "fade" receptors.

Adult↗
PubMed1999

The costs of intense neuromuscular block for anesthesia during endolaryngeal procedures due to waiting time.

UNLABELLED: The goal of this double-blinded, prospective study was to compare the costs incurred by waiting time of intense neuromuscular block while posttetanic count (PTC) was maintained at 0-2 during jet ventilation. Fifty patients were randomized into five groups to receive atracurium (ATR), mivacurium (MIV), rocuronium (ROC), vecuronium (VEC), and succinylcholine (SUCC). PTC < or =2 was maintained until completion of laryngomicroscopy by administering additional doses of relaxants or by adjusting the speed of the infusion of SUCC. We compared waiting time, i.e., onset time and recovery time, and costs of intense neuromuscular block. The expenses due to waiting time were calculated based on the average costs in the otorhinolaryngological operating room in Tampere University Hospital: FIM 40 (approximately $8) per minute in 1997. MIV and SUCC differ favorably from ATR, ROC, and VEC when waiting time and costs are concerned. The recovery times with MIV and SUCC were considerably shorter than those with ATR, ROC, and VEC (P < 0.001 in all pairwise comparisons). Using the muscle relaxant with the longest waiting time instead of that with the shortest waiting time (difference 21.8 min) cost more than FIM 800 (approximately $160) extra per patient. IMPLICATIONS: In this randomized, double-blinded, prospective study, we evaluated the costs of intense neuromuscular block due to waiting time. Succinylcholine and mivacurium are the most economical muscle relaxants to use when intense neuromuscular block is mandatory. Using intermediate-acting muscle relaxants results in unduly prolonged recovery time and extra costs.

Adult↗
PubMed1998

Does abstinence from smoking or a transdermal nicotine system influence atracurium-induced neuromuscular block?

UNLABELLED: The purpose of the present study was to investigate the interaction of chronic smoking and the actions of atracurium (ATR). Twenty nonsmokers (NON-SMOK) were compared with 80 smokers, who were randomized into three groups: 30 patients received 21 mg/d transdermal nicotine system > or = 10 h before fentanyl/thiopental/N2O/O2/isoflurane anesthesia (TD-NICO), whereas the abstinent group received a placebo transdermal system (ABST, n = 30). The TD-NICO and ABST groups refrained from smoking for at least 10 h before the induction of anesthesia. A third group was allowed to smoke until 1-3 h before anesthesia (SMOK, n = 20). Neuromuscular block was monitored using a Relaxograph (Datex, Helsinki, Finland). The electromyographic response was recorded from the first dorsal interosseus muscle of the hand. The inspiratory isoflurane concentration was kept constant at 0.7 vol% in all patients. After an initial bolus dose of 0.5 mg/kg ATR, no significant difference was observed among the groups regarding onset time and maximal neuromuscular block. In Group ABST, the duration of block until 25% recovery of T1 was 48.2 +/- 10.1 min, which was significantly longer (analysis of variance post hoc tests) than in Groups TD-NICO, SMOK, and NON-SMOK (42.7 +/- 7.1, 41.4 +/- 10.4, and 42.8 +/- 7.3 min, respectively). The maintenance dose of ATR in Group ABST (0.23 +/- 0.03 mg x kg(-1) x h(-1)) was smaller than in Groups TD-NICO, SMOK, and NON-SMOK (0.30 +/- 0.07, 0.32 +/- 0.06, and 0.32 +/- 0.05 mg x kg(-1) x h(-1), respectively). We conclude that abstinence from smoking increases the duration of ATR-induced neuromuscular block and reduces the maintenance dose of ATR in smokers. Perioperative use of a transdermal nicotine system prevents these abstinence-induced changes in duration and maintenance-dose. IMPLICATIONS: The purpose of the present study was to investigate the interaction of chronic smoking and atracurium. Smokers who refrain from smoking for > 10 h require a smaller maintenance dose of atracurium than nonsmokers. However, using a transdermal nicotine system prevents the decrease in maintenance dose during abstinence.

Administration, Cutaneous↗
PubMed1997

Pharyngeal patency caused by stimulation of the hypoglossal nerve in anaesthesia-relaxed patients.

Impaired function of the genioglossal muscle is the most frequent reason for upper airway obstruction during sleep. Functional electrical stimulation (FES) of the hypoglossal nerve may be used to push the tongue forward to release the obstruction. Anaesthesia-induced upper airway obstruction resembles the situation during obstructive sleep apnea (OSA) syndrome. In order to develop an implantable FES system for treatment of OSA, we stimulated the exposed hypoglossal nerve in 6 patients undergoing radical cancer surgery of the head and neck region. Tongue movements during stimulation were video filmed and the amount of unobstructed airway achieved with stimulation was estimated using the adjacent intubation tube as reference. In every case, stimulation created an unobstructed airway, larger than the intubation tube.

Anesthesia, General↗
PubMed1996

Diaphragm pacing with a quadripolar phrenic nerve electrode: an international study.

We sought to determine the international experience with the quadripolar diaphragm pacer system and to test two hypotheses: the incidence of pacer complications would be (1) increased among pediatric as compared to adult patients; and (2) highest among active pediatric patients with idiopathic congenital central hypoventilation syndrome (CCHS). Data were collected via a questionnaire coupled with the Atrotech Registry data for a total of 64 patients (35 children and 29 adults) from 14 countries. Thoracic implantation of electrodes and bilateral pacer use each occurred in 94% of all subjects. Tetraplegic (vs pediatric CCHS) patients were more typically paced 24 hours/day (P = 0.001). Pacing duration averaged 2.0 +/- 1.0 years among children and 2.2 +/- 1.1 years among adults. Infections occurred among 2.9% of surgical procedures, all in pediatric CCHS patients (vs pediatric tetraplegic patients, P = 0.01). The incidence of mechanical trauma was 3.8%, without significant differences among patient groups. The incidence of presumed electrode and receiver failure were 3.1% and 5.9%, respectively, with internal component failure greater among pediatric CCHS than pediatric tetraplegic patients (P < 0.01). Intermittent or absent function of 0-4 electrode combinations occurred among 19% of all patients, with increased frequency among pediatric CCHS than pediatric tetraplegic patients (P < 0.03). Complication-free successful pacing occurred in 60% of pediatric and 52% of adult patients. In all, 94% of the pediatric and 86% of the adult patients paced successfully after the necessary intervention. Although pacer complications were not increased among pediatric as compared to adult patients, the incidence of complications was highest among the active pediatric patients with CCHS. Longitudinal study of these patients will provide invaluable information for modification and improvement of the quadripolar system.

Adult↗
PubMed1995

End-tidal oxygen concentration and pulse oximetry for monitoring oxygenation during intratracheal jet ventilation.

OBJECTIVE: In this study, we evaluated the usefulness of end-tidal oxygen monitoring during intratracheal jet ventilation (ITJV) for endolaryngeal laser surgery. METHODS: A total of 20 consecutive patients of both genders scheduled for endolaryngeal procedures under general anesthesia were studied. Inspiratory oxygen concentration and respiratory rate were varied, with patients serving as their own controls. Readings of pulse oximetry, airway oxygen, and carbon dioxide concentrations were recorded, and arterial blood samples for blood gas analysis were taken. RESULTS: At jet cycle rates of 20 cycles/min, end-tidal oxygen (ETO2) concentration indicated alveolar hypoxia 30 to 60 sec before hypoxemia was detected by pulse oximetry. Jet mixing of inspiratory and expiratory gas caused a larger difference between end-tidal and arterial gas concentrations than normally seen with conventional ventilation. Correlations between ETO2 concentrations, oxygen saturations, and arterial oxygen levels depended on respiratory rate and inspiratory oxygen concentration; correlations were stronger at low than at high inspiratory oxygen concentrations and stronger at low than at high respiratory rates. CONCLUSIONS: ETO2 concentration should be maintained well over 21% during ITJV to prevent alveolar and arterial hypoxia. Monitoring of respiratory oxygen concentrations at jet cycle rates of 20 cycles/min and less verifies safe oxygen levels during laser surgery, and confirms adequate alveolar oxygenation.

Adult↗