Variation of bispectral index under TIVA with propofol in a paediatric population

Comparison of remimazolam and propofol combined with low dose esketamine for pediatric same-day painless bidirectional endoscopy: a randomized, controlled clinical trial

Background: Remimazolam has shown similar or even superior properties to propofol in procedural sedation in adults, but few studies have been conducted in pediatric populations. Thus, we aimed to compare the effect and safety of remimazolam and propofol combined with low dose esketamine for pediatric same-day bidirectional endoscopy (BDE). Methods: Pediatrics <18 years scheduled for elective BDE under sedation were included and randomly assigned to remimazolam group (R group) or propofol group (P group). The primary outcome was the success rate of sedation. Secondary outcomes include sedation-related information and adverse events. Mean arterial pressure (MAP), heart rate (HR), and perfusion index (PI) were recorded during sedation. Results: A total of 106 patients were enrolled and analyzed. The success rate of sedation was 100% in both groups. Compared with the P group, the induction time of the R group was significantly prolonged (p < 0.001), and the incidence of injection pain, intraoperative respiratory depression, hypotension and bradycardia was significantly lower (p < 0.001). The changes in MAP, HR and PI were relatively stable in the R group compared with the P group. Additionally, awake time significantly decreased with age by approximately 1.12 index points for each increase in age in the P group (p = 0.002) but not in the R group (p > 0.05). Furthermore, the decline in PI and PI ratio during BDE was related to body movement in the P group. Conclusion: Remimazolam combined with low dose esketamine has a non-inferior sedative effect than propofol for pediatric BDE, with no injection pain, less respiratory depression, more stable hemodynamics. Moreover, early detection of the decline in PI may avoid harmful stimulation under light anesthesia. Clinical trial registration: https://www.clinicaltrials.gov/study/NCT05686863?id=NCT05686863&rank=1, NCT05686863.

A Retrospective Study of the Patient State Index During General Anesthesia in Infants and Young Children

This study described electroencephalogram (EEG) parameters in children under general anesthesia, which could monitor patient-specific brain responses to anesthetics and assess the effects of anesthesia. The objective was to detect the patient state index (PSI) and associated factors. We analyzed EEG parameters in patients in the age range 1 to 36 months. Patients were stratified into 2 groups as those aged 1 to 12 months and 13 to 36 months. Sixty-two patients were involved. Spectral edge frequency (SEF), PSI, and blood pressure were lower, and burst suppression rate (BSR) and heart rate were higher in the 1 to 12 months group. The SEF was associated with PSI in both groups. Age and blood pressure were positively associated with PSI, and BSR was negatively related to PSI in children under 1 year of age. Blood pressure was not associated with PSI in the 13 to 36 months age group. We found that the PSI levels did not accurately assess the depth of anesthesia in children under 1 year of age.

An approach to using pharmacokinetics and electroencephalography for propofol anesthesia for surgery in infants

Safe and effective techniques for propofol total intravenous anesthesia (TIVA) in infants are not well imbedded into clinical practice, resulting in practitioner unfamiliarity and potential for over- and under-dosing. In this education article, we describe our approach to TIVA dosing in infants and toddlers (birth to 36 months) which combines the use of pharmacokinetic models with EEG multi-parameter analysis. Pharmacokinetic models describe propofol and remifentanil effect site concentrations (Ce) over time in different age groups for a given dosing regimen. These models display substantial biological variability between individuals within age groups, impeding their application to clinical practice. Nevertheless, they reveal that younger infants require a higher propofol loading dose, a lower propofol maintenance dose, and a higher remifentanil dose compared with older infants. Proprietary EEG indices (eg, Bispectral Index) can serve as a biomarker of propofol Ce in adults and children to guide dosing to the individual patient; however, they are not recommended for infants as their validity remains uncertain this population. In our experience, EEG waveforms and processed parameters can reflect propofol Ce in infants, reflected by spectral edge frequency (SEF), density spectral array (DSA), and waveform patterns. In our practice, we use a "lookup table" of age-based dosing regimens or target-controlled infusion (TCI) based on the pharmacokinetic models to deliver a target propofol Ce and co-administer remifentanil and/or regional technique for analgesia. We analyze Electroencephalogram (EEG) waveforms, SEF, and DSA to adjust the propofol dose or TCI target concentration to the individual infant. EEG analysis mitigates against biological variability inherent in the pharmacokinetic models and has improved our experience with TIVA for infants.

Case Studies Using the Electroencephalogram to Monitor Anesthesia-Induced Brain States in Children

For this child, at this particular moment, how much anesthesia should I give? Determining the drug requirements of a specific patient is a fundamental problem in medicine. Our current approach uses population-based pharmacological models to establish dosing. However, individual patients, and children in particular, may respond to drugs differently. In anesthesiology, we have the advantage that we can monitor our patients in real time and titrate drugs to the desired effect. Examples include blood pressure management or muscle relaxation. Although the brain is the primary site of action for sedative-hypnotic drugs, the brain is not routinely monitored during general anesthesia or sedation, a fact that would surprise many patients. One reason for this is that, until recently, physiologically principled approaches for anesthetic brain monitoring have not been articulated. In the past few years, our knowledge of anesthetic brain mechanisms has developed rapidly. We now know that anesthetic drug effects are clearly visible in the electroencephalogram (EEG) of adults and reflect underlying anesthetic pharmacology and brain mechanisms. Most recently, similar effects have been characterized in children. In this article, we describe how EEG monitoring could be used to guide anesthetic management in pediatric patients. We review previous evidence and present multiple case studies showing how drug-specific and dose-dependent EEG signatures seen in adults are visible in children and infants, including those with neurological disorders. We propose that the EEG can be used in the anesthetic care of children to enable anesthesiologists to better assess the drug requirements of individual patients in real time and improve patient safety and experience.

A practical guide for anesthetic management during intraoperative motor evoked potential monitoring

Postoperative motor dysfunction can develop after spinal surgery, neurosurgery and aortic surgery, in which there is a risk of injury of motor pathway. In order to prevent such devastating complication, intraoperative monitoring of motor evoked potentials (MEP) has been conducted. However, to prevent postoperative motor dysfunction, proper understanding of MEP monitoring and proper anesthetic managements are required. Especially, a variety of anesthetics and neuromuscular blocking agent are known to attenuate MEP responses. In addition to the selection of anesthetic regime to record the baseline and control MEP, the measures to keep the level of hypnosis and muscular relaxation at constant are crucial to detect the changes of MEP responses after the surgical manipulation. Once the changes of MEP are observed based on the institutional alarm criteria, multidisciplinary team members should share the results of MEP monitoring and respond to check the status of monitoring and recover the possible motor nerve injury. Prevention of MEP-related adverse effects is also important to be considered. The Working Group of Japanese Society of Anesthesiologists (JSA) developed this practical guide aimed to help ensure safe and successful surgery through appropriate anesthetic management during intraoperative MEP monitoring.

Variation of bispectral index in children aged 1-12 years under propofol anesthesia: an observational study

Background

The use of the bispectral index (BIS) is widespread in pediatric anesthesia, but few studies have attempted to perform a detailed evaluation of how BIS varies according to age in children under propofol anesthesia. This prospective study aimed to explore the exact relationship between BIS value and the age of 1- to 12-year-old children under propofol anesthesia.

Methods

This study enrolled 165 children (1 < yr. ≤ 12), scheduled for surgery under anesthesia, and divided them into 11 age groups. Of the 165 participants, 157 completed the study protocol. All patients were anesthetized with propofol for over 30 s. An observation period of 4 min followed. BIS values were recorded at 0 (immediately after propofol injection), 30, 40, 50, 60, 90, 120, 180, and 240 s after the injection. BIS values at each time point corresponding to the 11 age groups were compared using repeated measures ANOVA.

Results

BIS values significantly differed among the nine time points (p < 0.01) as well as among the different age groups (p < 0.01) after propofol administration. Post-hoc Bonferroni tests showed a difference in BIS values between groups 1–4 (1 < yr. ≤ 5) and groups 5–11(5 < yr. ≤ 12). BIS values were lower in the latter than in the former, from 50 to 240 s. The minimum BIS values in group 1 < yr. ≤ 5 and in group 5 < yr. ≤ 12 were recorded at 60 s as 49 ± 17 and 35 ± 14, respectively.

Conclusions

During propofol anesthesia, the BIS values were closely related to age, which can be divided into two groups: 1 < yr. ≤ 5 and 5 < yr. ≤ 12. BIS values of the older age group were lower than those of the younger age group at the same time points.

Trial registration

Registration number: chictr-roc-16008630. Registered on 12 June 2016. Retrospectively registered.

Practicalities of Total Intravenous Anesthesia and Target-controlled Infusion in Children

Propofol administered in conjunction with an opioid such as remifentanil is used to provide total intravenous anesthesia for children. Drugs can be given as infusion controlled manually by the physician or as automated target-controlled infusion that targets plasma or effect site. Smart pumps programmed with pharmacokinetic parameter estimates administer drugs to a preset plasma concentration. A linking rate constant parameter (keo) allows estimation of effect site concentration. There are two parameter sets, named after the first author describing them, that are commonly used in pediatric target-controlled infusion for propofol (Absalom and Kataria) and one for remifentanil (Minto). Propofol validation studies suggest that these parameter estimates are satisfactory for the majority of children. Recommended target concentrations for both propofol and remifentanil depend on the type of surgery, the degree of surgical stimulation, the use of local anesthetic blocks, and the ventilatory status of the patient. The use of processed electroencephalographic monitoring is helpful in pediatric total intravenous anesthesia and target-controlled infusion anesthesia, particularly in the presence of neuromuscular blockade.

Safety and efficacy of propofol anesthesia for pediatric target-controlled infusion in children below 3 years of age: a retrospective observational study

BACKGROUND

Although the requirement of propofol in children is increasing, propofol for induction and maintenance of anesthesia below 3 years old has not been approved in Korea. This study can provide a clinical evidence to increase the range of approval.

RESEARCH DESIGN AND METHODS

We reviewed the medical records of patients below 3 years of age who underwent surgery between September 2013 and December 2016. Safety was evaluated on the basis of vital signs, and laboratory findings and efficacy were evaluated on the basis of the bispectral index (BIS). Adverse events were examined.

RESULTS

A total of 109 patients anesthetized with propofol (propofol group) were compared with 109 patients with volatile anesthetics (volatile group) after propensity score matching. There was a difference in the proportion of patients showing decreased systolic pressure (P < 0.001) and heart rate (P = 0.03), but there was no difference in diastolic pressure (P = 0.238), mean arterial pressure (P = 0.175) during surgery. After surgery, there was no difference in all vital signs and the proportion patients who experienced adverse events of two groups.

CONCLUSIONS

Propofol anesthesia by target-controlled infusion was effective and didn't show serious propofol-related perioperative adverse events.

A Prospective Study of Age-dependent Changes in Propofol-induced Electroencephalogram Oscillations in Children

BACKGROUND

In adults, frontal electroencephalogram patterns observed during propofol-induced unconsciousness consist of slow oscillations (0.1 to 1 Hz) and coherent alpha oscillations (8 to 13 Hz). Given that the nervous system undergoes significant changes during development, anesthesia-induced electroencephalogram oscillations in children may differ from those observed in adults. Therefore, we investigated age-related changes in frontal electroencephalogram power spectra and coherence during propofol-induced unconsciousness.

METHODS

We analyzed electroencephalogram data recorded during propofol-induced unconsciousness in patients between 0 and 21 yr of age (n = 97), using multitaper spectral and coherence methods. We characterized power and coherence as a function of age using multiple linear regression analysis and within four age groups: 4 months to 1 yr old (n = 4), greater than 1 to 7 yr old (n = 16), greater than 7 to 14 yr old (n = 30), and greater than 14 to 21 yr old (n = 47).

RESULTS

Total electroencephalogram power (0.1 to 40 Hz) peaked at approximately 8 yr old and subsequently declined with increasing age. For patients greater than 1 yr old, the propofol-induced electroencephalogram structure was qualitatively similar regardless of age, featuring slow and coherent alpha oscillations. For patients under 1 yr of age, frontal alpha oscillations were not coherent.

CONCLUSIONS

Neurodevelopmental processes that occur throughout childhood, including thalamocortical development, may underlie age-dependent changes in electroencephalogram power and coherence during anesthesia. These age-dependent anesthesia-induced electroencephalogram oscillations suggest a more principled approach to monitoring brain states in pediatric patients.

Validation of the bispectral index as an indicator of anesthetic depth in Thoroughbred horses anesthetized with sevoflurane

To evaluate the bispectral index (BIS) as an indicator of anesthetic depth in Thoroughbred horses, BIS values were measured at multiple stages of sevoflurane anesthesia in five horses anesthetized with guaifenesin and thiopental following premedication with xylazine. There was no significant difference between the BIS values recorded at end-tidal sevoflurane concentrations of 2.8% (median 60 ranging from 47 to 68) and 3.5% (median 71 ranging from 49 to 82) in anesthetized horses. These BIS values during anesthesia were significantly lower (P<0.01) than those in awake horses (median 98 ranging from 98 to 98) or sedated horses (median 92 ranging from 80 to 93). During the recovery phase, the BIS values gradually increased over time but did not significantly increase until the horses showed movement. In conclusion, the BIS value could be useful as an indicator of awakening during the recovery period in horses, as previous reported.

Clinical Electroencephalography for Anesthesiologists: Part I: Background and Basic Signatures

The widely used electroencephalogram-based indices for depth-of-anesthesia monitoring assume that the same index value defines the same level of unconsciousness for all anesthetics. In contrast, we show that different anesthetics act at different molecular targets and neural circuits to produce distinct brain states that are readily visible in the electroencephalogram. We present a two-part review to educate anesthesiologists on use of the unprocessed electroencephalogram and its spectrogram to track the brain states of patients receiving anesthesia care. Here in part I, we review the biophysics of the electroencephalogram and the neurophysiology of the electroencephalogram signatures of three intravenous anesthetics: propofol, dexmedetomidine, and ketamine, and four inhaled anesthetics: sevoflurane, isoflurane, desflurane, and nitrous oxide. Later in part II, we discuss patient management using these electroencephalogram signatures. Use of these electroencephalogram signatures suggests a neurophysiologically based paradigm for brain state monitoring of patients receiving anesthesia care.

Feasibility of Closed-loop Titration of Propofol and Remifentanil Guided by the Bispectral Monitor in Pediatric and Adolescent Patients

Background:

This study was designed to assess the feasibility of dual closed-loop titration of propofol and remifentanil guided solely by the Bispectral Index (BIS) monitor in pediatric and adolescent patients during anesthesia.

Methods:

Children undergoing elective surgery in this single-blind randomized study were allocated into the closed-loop (auto) or manual (manual) group. Primary outcome was the percentage of time with the BIS in the range 40 to 60 (BIS40–60). Secondary outcomes were the percentage of deep (BIS&lt;40) anesthesia and drug consumption. Data are presented as median (interquartile range) or number (%).

Results:

Twenty-three patients (12 [10 to 14] yr) were assigned to the auto group and 19 (14 [7 to 14] yr) to the manual group. The closed-loop controller was able to provide induction and maintenance for all patients. The percentage of time with BIS40–60 was greater in the auto group (87% [75 to 96] vs. 72% [48 to 79]; P = 0.002), with a decrease in the percentage of BIS&lt;40 (7% [2 to 17] vs. 21% [11 to 38]; P = 0.002). Propofol (2.4 [1.9 to 3.3] vs. 1.7 [1.2 to 2.8] mg/kg) and remifentanil (2.3 [2.0 to 3.0] vs. 2.5 [1.2 to 4.3] μg/kg) consumptions were similar in auto versus manual groups during induction, respectively. During maintenance, propofol consumption (8.2 [6.0 to 10.2] vs. 7.9 [7.2 to 9.1] mg kg−1 h−1; P = 0.89) was similar between the two groups, but remifentanil consumption was greater in the auto group (0.39 [0.22 to 0.60] vs. 0.22 [0.17 to 0.32] μg kg−1 min−1; P = 0.003). Perioperative adverse events and length of stay in the postanesthesia care unit were similar.

Conclusion:

Intraoperative automated control of hypnosis and analgesia guided by the BIS is clinically feasible in pediatric and adolescent patients and outperformed skilled manual control.

Propofol effect on cerebral oxygenation in children with congenital heart disease

Propofol is a short-acting, intravenously administered hypnotic agent which is used in procedural sedation in children. Propofol is known to decrease systemic vascular resistance, arterial blood pressure and can lead to desaturations and decreased systemic perfusion in children with cardiac shunting. This may result in a reduction in cerebral blood flow and oxygenation. Near-infrared spectroscopy (NIRS) can monitor cerebral tissue oxygenation in the frontal neocortex. The objective of our study was to measure the changes in cerebral oxygen and blood supply after Propofol infusion in children with congenital heart disease. Propofol infusion may reduce cerebral oxygenation in children with congenital heart disease. The study group consisted of 32 children (f:m = 18:14), with median age of 49 (5-112) months and median weight of 15 (5-34) kg. We performed NIRS derived continuous measurement of cerebral oxygenation and cardiac output using Electrical velocimetry for 5 min before and after sedation with Propofol (1-2 mg/kg i.v.) for cardiac catheterization. Simultaneously, non-invasive arterial blood pressure and transcutaneous oxygen saturation were measured. Propofol sedation led to a significant decrease in mean arterial pressure (79 ± 16 vs. 67 ± 12 mmHg) (p = 0.01) and cardiac index (3.2 ± 0.8 vs. 2.9 ± 0.6 ml/min/m(2)) (p = 0.03). In contrast, cerebral tissue oxygenation index, increased significantly from 57 ± 11 to 59 ± 10 % (p < 0.05). Sedation with Propofol increased cerebral tissue oxygenation despite a decrease in cardiac index and arterial blood pressure. This may be caused by a decreased oxygen consumption of the sedated brain with intact cerebral auto-regulation.

Impact of bispectral index for monitoring propofol remifentanil anaesthesia. A randomised clinical trial

BACKGROUND

Previous research has shown that the use of the bispectral index (BIS) monitor to measure the depth of anaesthesia reduces the amount of anaesthetics administered and the recovery time from general anaesthesia. The effect of BIS on recovery from anaesthesia and consumption of anaesthetics in a paediatric population receiving total intravenous anaesthesia (TIVA) with propofol and remifentanil has not been studied.

METHODS

A single-blind, single-centre clinical trial. One hundred fifty-seven patients were enrolled. They were scheduled for ear, nose, and throat surgery and stratified according to age groups (1-3 years, 4-11 years, 12-17 years, 18-65 years) and type of operation, yielding a total of nine subgroups. Patients were randomly allocated to receive either a TIVA with propofol and remifentanil according to conventional clinical practice (control) or guided by BIS. Normalised propofol (μg/kg/min) and remifentanil (μg/kg/min) consumption and time to extubation (s) were the outcome measures.

RESULTS

Children aged 1-3 years in the BIS group had a longer time to extubation compared with controls (P: 0.04). Patients aged 12-17 years in the BIS group received higher maintenance infusion rates of propofol compared with controls (P = 0.02). No significant difference for the outcome variables was evidenced in the other age groups.

CONCLUSION

BIS monitoring for guidance of propofol-remifentanil anaesthesia does not result in reduced consumption of anaesthetics and does not reduce time to extubation in adult and children compared with conventional practice.

Propofol and children--what we know and what we do not know

The pharmacokinetics of propofol are relatively well described in the pediatric population. Recent work has confirmed the validity of allometric scaling for predicting propofol disposition across different species and for describing pediatric ontogenesis. In the first year of life, allometric models require adjustment to reflect ontogeny of maturation. Pharmacodynamic data for propofol in children are scarcer, because of practical difficulties in data collection and the limitations of currently available depth of anesthesia monitors for pediatric use. Hence, questions relating to the comparative sensitivity of children to propofol, and differences in time to peak effect relative to adults, remain unanswered. K(eo) half-lives have been determined for pediatric kinetic models using time to peak effect techniques but are not currently incorporated into commercially available target-controlled infusion pumps.

A randomized trial of propofol consumption and recovery profile with BIS-guided anesthesia compared to standard practice in children

AIM

To evaluate the impact of bispectral index (BIS) monitoring on the consumption of propofol and recovery from anesthesia compared to the standard clinical practice in children.

BACKGROUND

Titrating propofol administration using BIS reduces its requirement and shortens the recovery from anesthesia in adults. However, there is still mixed evidence for utility of anesthesia depth monitors in reducing anesthesia requirement in children.

METHODS/MATERIALS

A prospective randomized study was conducted in 50 ASA I children of 2-12 years, randomly assigned into standard practice (SP) or BIS group. After induction with propofol, anesthesia was maintained with 150 microg x kg(-1) x min(-1) propofol infusion. The propofol infusion rate was altered by 20 microg x kg(-1) x min(-1) to maintain the systolic blood pressure within 20% of the baseline (SP group) or BIS value between 45 and 60 (BIS group). The rate of propofol infusion was reduced by 50% about 15 min before the end of surgery. The amount of propofol used and the times from stopping the propofol infusion to eye opening, extubation, response to commands and attaining Steward score of 6 were recorded.

RESULTS

There was no evidence of a difference in the mean propofol consumption in the two groups (BIS 232.6 +/- 136.7 mg, SP 250.8 +/- 118.2 mg). The intraoperative hemodynamics and BIS values were similar in the two groups. There was no evidence for a difference between groups in the mean times from termination of anesthetic to eye opening, extubation, response to commands and to achieve a Steward Recovery score of 6.

CONCLUSIONS

Our study showed no benefit of BIS-guided propofol administration on anesthetic consumption or recovery compared to standard anesthetic practice.

Evaluation of bispectral index (BIS) as an indicator of central nervous system depression in horses anesthetized with propofol

The bispectral index (BIS) was evaluated as an indicator of central nervous system (CNS) depression in horses anesthetized with propofol. Five non-premedicated horses were anesthetized with 7 mg/kg, IV propofol and the minimum infusion rate (MIR) of propofol required to maintain anesthesia was determined during intermittent positive pressure ventilation in each horse. The BIS was determined 20 min later and after stabilization at 2.0 MIR, 1.5 MIR, and 1.0 MIR. The BIS was also recorded after the cessation of propofol infusion when the horses regained spontaneous breathing and swallowing reflex. The MIR and plasma concentration (Cp) of propofol were 0.20 +/- 0.03 mg/kg/min and 17.5 +/- 4.0 microg/ml, respectively. The BIS value and Cp were 59 +/- 13 and 26.7 +/- 8.6 microg/ml at 2.0 MIR, 63 +/- 9 and 22.9 +/- 9.7 microg/ml at 1.5 MIR, 64 +/- 13 and 20.1 +/- 5.9 microg/ml at 1.0 MIR, 64 +/- 24 and 13.0 +/- 2.8 microg/ml at return of spontaneous breathing, and 91 +/- 4 and 11.0 +/- 3.4 microg/ml when the swallowing reflex returned, respectively. The BIS value was significantly less in anesthetized horses compared to horses once swallowing returned (p=0.025). The BIS value was significantly correlated with the propofol Cp (r=-0.625, p=0.001). There was not a significant difference in the BIS values during the MIR multiples of propofol. The BIS was a useful indicator of awakening but did not indicate the degree of CNS depression during propofol-anesthesia in horses.

Current world literature

This bibliography is compiled by clinicians from the journals listed at the end of this publication. It is based on literature entered into our database between 1 February 2008 and 31 January 2009 (articles are generally added to the database about two and a half months after publication). In addition, the bibliography contains every paper annotated by reviewers; these references were obtained from a variety of bibliographic databases and published between the beginning of the review period and the time of going to press. The bibliography has been grouped into topics that relate to the reviews in this issue.

The optimum bolus dose of remifentanil to facilitate laryngeal mask airway insertion with a single standard dose of propofol at induction in children

The purpose of this study was to determine the optimal bolus dose of remifentanil required for the successful insertion of the laryngeal mask airway during propofol induction in children without a neuromuscular blocking agent. Twenty-six paediatric patients, aged 3-10 years, requiring anaesthesia for short ambulatory surgery were recruited. A predetermined bolus dose of remifentanil was injected over 30 s, followed by propofol 2.5 mg.kg(-1) over 10 s. The bolus dose of remifentanil was determined by a modified Dixon's up-and-down method, starting from 0.5 microg.kg(-1) (0.1 microg.kg(-1) as a step size). Laryngeal mask insertion was attempted 90 s after the end of remifentanil injection and the response of patients was classified as either 'movement' or 'no movement'. The bolus dose of remifentanil at which there was a 50% probability of successful laryngeal mask insertion (ED(50)) during induction with 2.5 mg.kg(-1) propofol was 0.56 (0.07) microg.kg(-1) in children without a neuromuscular blocking agent. From probit analysis, the ED(50) and ED(95) of remifentanil were 0.52 microg.kg(-1) (95% confidence limits, 0.42-0.62 microg.kg(-1)) and 0.71 microg.kg(-1) (95% confidence limits, 0.61-1.40 microg.kg(-1)), respectively.