Recent advances in intravenous anaesthesia

Why sedative hypnotics often fail in development

PURPOSE OF REVIEW

Drug development to support anaesthesia and sedation has been slow with few candidates emerging from preclinical discovery and limited innovation beyond attempted reformulation of existing compounds.

RECENT FINDINGS

The market is well supported by low-cost generic products and development compounds have not been shown to improve patient outcomes or possess other distinctive characteristics to justify the cost of development.

SUMMARY

To make progress in a large-volume, low margin and highly competitive environment requires meaningful advances in relevant basic science. Opportunities exist, but probably require bolder initiatives than further attempts at reformulation or fiddling with the structure of propofol. Extending development ambitions to include nonanaesthesiologist providers challenges professional boundaries but may facilitate cost-effective changes in patterns of care.

Remifentanil improves left ventricular diastolic parameters in patients with impaired diastolic function: a prospective clinical study

BACKGROUND

Left ventricular diastolic dysfunction has a significant impact on perioperative morbidity and mortality, and its incidence is high in elderly individuals. Anesthetic agents may impair diastolic function, which may increase the incidence of perioperative complications. The aim of this prospective, clinical, phase 4 study was to investigate the effects of remifentanil on left ventricle (LV) diastolic function in patients with diastolic dysfunction. The study was performed on 30 spontaneously breathing subjects (aged 60-80 years) with diastolic dysfunction.

METHODS

Thirty patients (aged 60-80 years) with diastolic dysfunction scheduled for surgery were recruited between November 2019 and March 2023. Left ventricle function was evaluated once the intravenous remifentanil infusion reached a target-controlled concentration of 2 ng/ml with transthoracic echocardiography. Analysis of systolic function focused on left ventricular ejection fraction and mean mitral annular S velocity (Sm), whereas diastolic function focused on changes in transmitral peak flow (E), E/A, mitral septal and lateral e' waves, E/e' ratios and left atrial volume index following remifentanil infusion.

RESULTS

Diastolic function measures of LV (mitral E/e', septal and lateral e' waves) statistically significantly improved (E/e' from 10.6 ± 2.9 cm.sn- 1 to 9.5 ± 2.2 cm.sn- 1; p = 0.006) following remifentanil infusion. Left atrial volume index decreased following remifentanil infusion without statistical significance (from 55 ± 14.4 ml.cm- 2 to 51.6 ± 13.3 ml.cm- 2; p = 0.1). Systolic function (ejection fraction and Sm) did not change following remifentanil infusion.

CONCLUSIONS

Remifentanil improves left ventricular diastolic parameters in patients with preexisting diastolic dysfunction. Our study suggests that remifentanil at a plasma concentration of 2 ng.ml- 1 might be used safely in patients with left ventricular diastolic dysfunction.

Cardiovascular Effects of Adding Epinephrine to Bupivacaine in Children Undergoing Caudal Block: A Double-blind Randomized Clinical Trial

Background: Caudal block is a common, safe, and effective anesthetic technique for lower abdominal, urological, and lower extremity surgeries in pediatrics. Objectives: This study aimed to evaluate the cardiovascular effects of adjuvant epinephrine in the caudal block on heart rate and blood pressure changes in children. Methods: This double-blind, randomized clinical trial was performed on 60 children who underwent elective infra-umbilical surgeries. They were under general anesthesia with midazolam, fentanyl, lidocaine, and propofol. The patients were ventilated through laryngeal mask airway (LMA), and anesthesia was maintained with sevoflurane in O2 and N2O mixture. The intervention group received a caudal block with 0.2% bupivacaine and 1/200000 epinephrine (1 mL/kg), while the control group received a caudal block without epinephrine. Heart rate, blood pressure, and ECG were monitored before the block and in the first, fifth, and 20th minutes after surgery. Results: The two groups showed no statistically significant differences in demographics and systolic and diastolic blood pressures. However, sinus arrhythmia was more prevalent in the study group in the first minute after the block (P < 0.001). No differences were observed in the incidence of arrhythmia in the fifth and 20th minutes after the block. Conclusions: It appears that epinephrine as an adjuvant to the caudal block does not have long-lasting effects after the block, except sinus tachycardia in the first minute. Considering that no changes in blood pressure and other hemodynamic parameters were observed, it seems that epinephrine can be used safely in the caudal block in pediatric patients.

Design, Synthesis, and Activity Study of Water-Soluble, Rapid-Release Propofol Prodrugs

In this work, a series of water-soluble propofol prodrugs were synthesized, and their propofol release rate and pharmacodynamic characteristics were measured. We found that inserting glycolic acid as a linker between propofol and the cyclic amino acid accelerated the release of propofol from prodrugs into the plasma while preserving its safety. In animal experiments, prodrugs (3e, 3g, and 3j) were significantly better than fospropofol (the only water-soluble propofol prodrug that has been used clinically) in terms of safety, onset, and duration time of anesthesia. Their molar dose, onset time, and anesthesia duration time were comparable to those of propofol, helping to maintain the clinical benefits of propofol. The experimental results showed the potential of such compounds as water-soluble prodrugs of propofol.

Efficacy and safety of remifentanil and sulfentanyl in painless gastroscopic examination: a prospective study

We aim to assess efficacy and safety of remifentanil or sulfentanyl combined with propofol during painless gastroscopic examination in patients. In this study, 270 patients were randomly divided into 3 groups: propofol was given only in group P; propofol and remifentanil in group PR; propofol and sulfentanyl in group PS during the gastroscopic examination. Efficiency of group P was significantly higher than that of group PR and PS (P<0.01) [corrected]. Efficiency of group PR was lower than that of group PS (P<0.05). Incidence of chest wall rigidity and oxygen desaturation in group PR were higher than group P and PS (P<0.05), whereas there was no difference between groups P and PS (P>0.05). Propofol combined with remifentanil could provide satisfying anesthesia and more respiratory depression, whereas sulfentanyl at equivalent dose combined with propofol could also provide with satisfying anesthesia and less respiratory depression. Combined sufentanyl with propofol would be an effective anesthesia technique in the daytime procedure.

The effect of ketamine on hypoventilation during deep sedation with midazolam and propofol: a randomised, double-blind, placebo-controlled trial

BACKGROUND

Hypoventilation is a major cause of morbidity and mortality in patients having procedures under sedation. Few clinical strategies have been evaluated to reduce intraoperative hypoventilation during surgical procedures under deep sedation.

OBJECTIVE

The primary objective of this investigation was to examine the effect of ketamine on hypoventilation in patients receiving deep sedation for surgery with midazolam and propofol.

DESIGN

The study was a randomised, placebo-controlled, double-blind clinical trial.

SETTING

Intraoperative.

PATIENTS

Healthy women undergoing breast surgery.

INTERVENTION

Randomised to receive ketamine (0.5 mg kg bolus, followed by an infusion of 1.5 μg kg min) or isotonic saline.

MAIN OUTCOME MEASURE

Duration of hypercapnia measured continuously with a transcutaneous carbon dioxide (TCO2) monitor.

RESULTS

Fifty-four participants were recruited. Patient and surgical characteristics were similar between the study groups. The median percentage of the sedation time with TCO2 more than 6.7 kPa in participants in the ketamine group, 1.2% (95% confidence interval, CI, 0 to 83), was less than that in the isotonic saline group (65%, 95% CI, 0 to 88; P = 0.01). Severe hypoventilation (TCO2 >8.0 kPa) was also less in the ketamine group, median 0% (95% CI, 0 to 11.7) compared with 28% (95% CI, 0 to 79.3; P = 0.0002) for the isotonic saline group. The ketamine group required less airway manoeuvres (chin lift) to keep the SaO2 greater than 95% median (95% CI) [0 (0 to 3) compared with 3 (0 to 16) in the isotonic saline group] (P = 0.004).

CONCLUSION

Ketamine decreased the duration and severity of hypercapnia in patients undergoing deep sedation with propofol. The addition of ketamine may reduce hypoventilation and adverse effects in patients having procedures under sedation.

TRIAL REGISTRATION

clinicaltrials.gov identifier: NCT01535976.

Total intravenous anesthesia will supercede inhalational anesthesia in pediatric anesthetic practice

Inhalational anesthesia has dominated the practice of pediatric anesthesia. However, as the introduction of agents such as propofol, short-acting opioids, midazolam, and dexmedetomidine a monumental change has occurred. With increasing use, the overwhelming advantages of total intravenous anesthesia (TIVA) have emerged and driven change in practice. These advantages, outlined in this review, will justify why TIVA will supercede inhalational anesthesia in future pediatric anesthetic practice.

Anesthetic management of a parturient with glioma brain for cesarean section immediately followed by craniotomy

The anesthetic management of a parturient with an intracranial tumor can be quite challenging for the anesthetist as it requires a fine balance of both maternal and fetal safety. The literature pertaining to anesthetic management of such cases is limited. We describe the anesthetic management and peri-operative concerns of this unusual case of a parturient aged 25 years with 8 months amenorrhea and a high grade glioma in the left temporo-parietal region who underwent cesarean section under general anesthesia immediately followed by craniotomy. Anesthetic management was tailored keeping in mind maternal safety and fetal considerations.

Modifying methoxycarbonyl etomidate inter-ester spacer optimizes in vitro metabolic stability and in vivo hypnotic potency and duration of action

BACKGROUND

Methoxycarbonyl etomidate is the prototypical very rapidly metabolized etomidate analog. Initial studies suggest that it may be too short acting for many clinical uses. We hypothesized that its duration of action could be lengthened and clinical utility broadened by incorporating specific aliphatic groups into the molecule to sterically protect its ester moiety from esterase-catalyzed hydrolysis. To test this hypothesis, we developed a series of methoxycarbonyl etomidate analogs (spacer-linked etomidate esters) containing various aliphatic-protecting groups and spacer lengths.

METHODS

Spacer-linked etomidate esters were synthesized and their hypnotic potencies and durations of action following bolus administration were measured in rats using a loss-of-righting reflexes assay. Octanol:water partition coefficients and metabolic half-lives in pooled rat blood were determined chromatographically.

RESULTS

All spacer-linked etomidate esters produced hypnosis rapidly and in a dose-dependent manner. ED50s for loss of righting reflexes ranged from 0.69 ± 0.04 mg/kg for cyclopropyl-methoxycarbonyl metomidate to 11.1 ± 0.8 mg/kg for methoxycarbonyl metomidate. The slope of a plot of the duration of loss of righting reflexes versus the logarithm of the dose ranged 12-fold among spacer-linked etomidate esters, implying widely varying brain clearance rates. The in vitro metabolic half-lives of these compounds in rat blood varied by more than two orders of magnitude and were diastereometrically selective.

CONCLUSIONS

We created 13 new analogs of methoxycarbonyl etomidate and identified two that have significantly higher potency and potentially address the too-brief duration of action for methoxycarbonyl etomidate. This work may provide a blueprint for optimizing the pharmacological properties of other soft drugs.

Efficacy comparison of the novel water-soluble propofol prodrug HX0969w and fospropofol in mice and rats

BACKGROUND

HX0969w is a novel water-soluble prodrug designed to release propofol and gamma-hydroxybutyrate (GHB) and has a sedative-hypnotic effect. This study was performed to compare the efficacy of HX0969w with fospropofol in mice and rats.

METHODS

We performed hydrolysis studies in the plasma from mice and rats. The half-maximal effective doses (ED50) and half-maximal lethal doses (LD50) of fospropofol and HX0969w were determined. A pharmacodynamics comparison of these two compounds was also performed. Time to loss of righting reflex, time to return of righting reflex, recovery time, and adverse effects were recorded.

RESULTS

The hydrolysis studies demonstrated that HX0969w released propofol as expected. HX0969w ED50 values in mice and rats were 133.03 and 53.79 mg kg(-1), respectively, and LD50 values were 607.11 and 283.79 mg kg(-1), respectively. The calculated therapeutic index (TI), safety index (SI), and certain safety factor (CSF) of HX0969w were 4.56, 3.33, and 2.92 for mice, and 5.28, 3.94, and 3.49 for rats, respectively. The pharmacodynamic comparison studies suggest that HX0969w has a longer onset time and shorter duration than fospropofol.

CONCLUSIONS

Similar to fospropofol, HX0969w is an effective, water-soluble prodrug that is capable of inducing a sedative-hypnotic effect in mice and rats. Unlike fospropofol, HX0969w releases GHB instead of formaldehyde. Further studies regarding the efficacy and safety of HX0969w are necessary.

Intravenous anaesthesia in goats: A review

Intravenous anaesthesia is gradually becoming popular in veterinary practice. Traditionally, general anaesthesia is induced with intravenous drugs and then maintained with inhalation agents. Inhalation anaesthetic agents cause more significant dose-dependent cardiorespiratory depression than intravenous anaesthetic drugs, creating a need to use less of the inhalation anaesthetic agents for maintenance of general anaesthesia by supplementing with intravenous anaesthesia drugs. Better still, if anaesthesia is maintained completely with intravenous anaesthetic drugs, autonomic functions remain more stable intra-operatively. Patient recovery from anaesthesia is smoother and there is less pollution of the working environment than happens with inhalation anaesthetic agents. Recently, a number of drugs with profiles (pharmacokinetic and pharmacodynamic) suitable for prolonged intravenous anaesthesia have been studied, mostly in humans and, to a certain extent, in dogs and horses. There is currently very little scientific information on total intravenous anaesthesia in goats, although, in the past few years, some scholarly scientific articles on drugs suitable for partial intravenous anaesthesia in goats have been published. This review article explored the information available on drugs that have been assessed for partial intravenous anaesthesia in goats, with the aim of promoting incorporation of these drugs into total intravenous anaesthesia protocols in clinical practice. That way, balanced anaesthesia, a technique in which drugs are included in anaesthetic protocols for specific desired effects (hypnosis, analgesia, muscle relaxation, autonomic stabilisation) may be utilised in improving the welfare of goats undergoing general anaesthesia.

Indication for surgery and the risk of postoperative nausea and vomiting after craniotomy: a case-control study

BACKGROUND

The primary hypothesis of the study is that acoustic neuroma (AN) surgery and microvascular decompression (MVD) of cranial nerves increase the risk of postoperative nausea and vomiting (PONV).

METHODS

We designed a retrospective case-control study matched on age, sex, and year of surgery (≤2005 and >2005). Year of surgery was noted as a potential confounder, because routine antiemetic prophylaxis was strongly encouraged at the study site in 2005. Cases of PONV in the recovery room were matched to controls in a 1:2 manner using a perioperative database. Charts were then reviewed for the following data: American Society of Anesthesiologists grade, smoking status, craniotomy location, craniotomy indication, and type of anesthetic administered.

RESULTS

The final analysis included 117 cases that were matched with 185 controls. Patients had a mean age of 50 years (SD=13), and 65% were female. Overall, the majority of craniotomies were supratentorial (70%) and performed for tumor resection (41%). On multivariable analysis, MVD [odds ratio (OR)=6.7; 95% confidence interval (CI), 2.0-22.7; P=0.002], AN (OR=3.3; 95% CI, 1.0-11.0; P=0.05), and epilepsy surgery (OR=2.8; 95% CI, 1.1-7.5; P=0.04) were associated with an increased likelihood of PONV when compared with tumor surgery. There was effect modification of total intravenous anesthesia by location of surgery (P-interaction=0.02). The benefit of total intravenous anesthesia on PONV was observed in supratentorial (OR=0.41; 95% CI, 0.17-0.96; P=0.04) but not infratentorial location (OR=2.6; 95% CI, 0.78-8.7; P=0.11).

CONCLUSIONS

MVD and AN resection were associated with an increased likelihood of PONV compared with craniotomies performed for other tumor resection.

Electroencephalographic recovery, hypnotic emergence, and the effects of metabolite after continuous infusions of a rapidly metabolized etomidate analog in rats

BACKGROUND

Methoxycarbonyl etomidate is an ultrarapidly metabolized etomidate analog. It is metabolized to methoxycarbonyl etomidate carboxylic acid (MOC-ECA), which has a hypnotic potency that is 350-fold less than that of methoxycarbonyl etomidate. The authors explored the relationships between methoxycarbonyl etomidate infusion duration, recovery time, metabolite concentrations in blood and cerebrospinal fluid (CSF), and methoxycarbonyl etomidate metabolism in brain tissue and CSF to test the hypothesis that rapid metabolism of methoxycarbonyl etomidate may lead to sufficient accumulation of MOC-ECA in the brain to produce a pharmacologic effect.

METHODS

A closed-loop system with burst suppression ratio feedback was used to administer methoxycarbonyl etomidate infusions of varying durations to rats. After infusion, recovery of the electroencephalogram and righting reflexes were assessed. MOC-ECA concentrations were measured in blood and CSF during and after methoxycarbonyl etomidate infusion, and the in vitro half-life of methoxycarbonyl etomidate was determined in rat brain tissue and CSF.

RESULTS

Upon termination of continuous methoxycarbonyl etomidate infusions, the burst suppression ratio recovered in a biexponential manner with fast and slow components having time constants that differed by more than 100-fold and amplitudes that varied inversely with infusion duration. MOC-ECA concentrations reached hypnotic concentrations in the CSF with prolonged methoxycarbonyl etomidate infusion and then decreased during a period of several hours after infusion termination. The metabolic half-life of methoxycarbonyl etomidate in brain tissue and CSF was 11 and 20 min, respectively.

CONCLUSION

In rats, methoxycarbonyl etomidate metabolism is sufficiently fast to produce pharmacologically active MOC-ECA concentrations in the brain with prolonged methoxycarbonyl etomidate infusion.

Electroencephalogram-based pharmacodynamic measures: a review

Pharmacokinetics and pharmacodynamics can provide a useful modeling framework for predicting drug activity and can serve as a basis for dose optimization. Determining a suitable biomarker or surrogate measure of drug effect for pharmacodynamic models can be challenging. The electroencephalograph is a widely-available and non-invasive tool for recording brainwave activity simultaneously from multiple brain regions. Certain drug classes (such as drugs that act on the central nervous system) also generate a reproducible electroencephalogram (EEG) effect. Characterization of such a drug-induced EEG effect can produce pharmacokinetic/pharmacodynamic models useful for titrating drug levels and expediting development of chemically-similar drug analogs. This paper reviews the relevant concepts involved in pharmacokinetic/pharmacodynamic modeling using EEG-based pharmacodynamic measures. In addition, examples of such models for various drugs are organized by drug activity as well as chemical structure and presented.

Pediatric models for adult target-controlled infusion pumps

Target-controlled infusion (TCI) pumps currently do not satisfactorily cater for the pediatric population, particularly for those under 5 years. Growth and development are two major aspects of children not readily apparent in adults, and these two aspects influence clearance (CL) and volume of distribution (V). In simple terms, V determines initial dose, and CL determines infusion rate at steady state. Three major covariates (size, age, and organ function) contribute to parameter variability in children. Size can be standardized for clearance in a 70-kg person using the allometric (3/4) power model. Remifentanil, a drug cleared by hydrolysis, can be modeled in all age groups by simple application of this model using a standardized clearance of 2790 ml x min(-1) for a 70-kg person. Allometry alone is insufficient to predict clearance in neonates and infants from adult parameters for most drugs used in anesthesia. The addition of a model describing maturation is required. The sigmoid Emax or Hill model has been found useful for describing this maturation process. Propofol maturation has been described with a mature clearance of 1.83 l x min(-1) x 70 kg(-1), a maturation half-time (TM(50)) of 44 weeks and a Hill coefficient of 4.9. Organ function also affects clearance, and propofol clearance is reduced in neonates and infants after cardiac surgery. Although pharmacokinetics (PK) in children is receiving increasing attention and is eminently programmable into a TCI device, pharmacodynamic (PD) measures in children remain poorly defined, partly because the depth of anesthesia monitoring are inadequate. Both PK and PD are necessary for safe use of TCI pumps.

TIVA, TCI, and pediatrics: where are we and where are we going?

The current role of TIVA in children is limited because of hardware limitations, and pharmacokinetic and monitoring issues. Nonetheless, the role of TIVA in children has been increasing in the past decade, in part because of surgical and medical indications. If TIVA is to become more widely used, it must be easy and simple to set up, without serious drawbacks and without added risks. Currently, many drugs destined for use with TIVA in children are off-label, and their pharmacology is poorly understood. Such off-label designations must be resolved if TIVA is to become more widely used. At the same time, many institutions have a limited number of infusion pumps, which creates a serious bottleneck and restriction on the use of TIVA.. If a true TIVA technique is used, i.v. access must be established before induction of anesthesia, which will require a means to establish i.v. access painlessly, e.g., using a topical local anesthetic. This is not a common practice in a number of jurisdictions but must be introduced if TIVA is to expand in its scope in children. Currently, I believe that we deliver a 'partial' TIVA technique in which TIVA occasionally follows an inhalational induction but in the future when the current obstacles have been resolved, I believe that we will be able practice a true TIVA technique ubiquitously in children.

[Intravenous remifentanyl for labor analgesia]

BACKGROUND

Intravenous remifentanil may be the preferred analgesic when regional techniques are contraindicated.

OBJECTIVE

To perform a systematic review on the use of remifentanil for analgesia in labor.

METHODS

We searched MEDLINE (January 1995-August 2007) for studies on obstetric analgesia with remifentanil.

RESULTS

We found 32 references representing the use of remifentanil in 257 women in labor. In most cases, patients reported relief of pain and a high level of satisfaction, with no severe side effects in mothers or neonates. When compared with meperidine and nitrous oxide in clinical trials, remifentanil provided better analgesia with fewer adverse effects.

CONCLUSION

Analgesia with intravenous remifentanil is more effective and safer than other alternatives to regional analgesic techniques in obstetrics. Nevertheless, the optimum system for infusing the drug must b e established and further studies of maternal and fetal safety should be carried out.

Future directions in endoscopic sedation

The role of sedation in endoscopic procedures has increased and so has the demand for advances in its administration. The pursuit of new agents or administration techniques and their study specific to endoscopic nonsurgical procedures is necessary to improve patient comfort and safety.The science of moderate and deep sedation specific to endoscopy is fledgling but approaching new horizons.

The effects of age and sex on electroconvulsive therapy using remifentanil as the sole anesthetic agent

OBJECTIVE

This study examines electroencephalographic (EEG) and motor seizure duration and dynamic energy according to age and sex using remifentanil anesthesia in standard electroconvulsive therapy (ECT).

BACKGROUND

In an earlier study, we showed that remifentanil provides superior anesthesia for ECT in terms of providing adequate seizure duration with lower stimulus doses in patients refractory to maximal ECT settings with methohexital.

METHODS

Patients, refractory to maximal ECT settings with methohexital, received remifentanil as the sole anesthetic agent. Stimulus dose was determined by the dose-titration method. Electroencephalographic seizure duration, motor seizure duration, and dynamic energy in joules (j) were compared between male and female subjects and among patients aged 40 years or younger, older than 40 years but aged 65 years or younger, and older than 65 years.

RESULTS

Seventy-two patients were included in the study. There was no significant difference in remifentanil doses between female and male subjects. There was no significant statistical difference between female and male subjects regarding motor seizure duration, EEG seizure duration, or dynamic energy (P > 0.05). There were significant statistical differences among different groups in terms of motor seizure duration, EEG seizure duration, and dynamic energy (P< 0.05). The younger age group had longer motor and EEG seizure durations and required lower dynamic energy.

CONCLUSIONS

There is no significant effect of sex on ECT with remifentanil anesthesia regarding EEG or motor seizure durations or dynamic energy; however, statistically significant differences were observed based upon age. Younger patients had both increased motor and EEG seizure duration compared with older patients who may require higher stimulus doses than younger patients for comparable motor and EEG seizure durations.

The effects of desflurane and propofol-remifentanil on postoperative hepatic and renal functions after right hepatectomy in liver donors

Various volatile anesthetics have been used in hepatectomy in living donors, and their effects on major organs have been extensively evaluated. However, the impact of total intravenous anesthesia (TIVA) on postoperative liver and renal functions after large liver resections has been less extensively investigated than that of volatile agents. The aim of this study was to compare the postoperative hepatic and renal functions between volatile anesthesia with desflurane and TIVA with propofol-remifentanil in living donors undergoing right hepatectomy. Seventy adult patients were randomly allocated into 2 groups: the desflurane group (n = 35) and TIVA group (n = 35). Aspartate aminotransferase, alanine aminotransferase, prothrombin time (PT), albumin, total bilirubin (TB), blood urea nitrogen (BUN), creatinine (Cr), BUN/Cr ratio, estimated glomerular filtration rate (GFR), platelet count, and hemoglobin levels were analyzed in the preoperative period, immediately after the operation, and on the first, second, third, fifth, seventh, and thirtieth postoperative days (PODs). Most of the liver function test results were not significantly different between the 2 groups. However, PT (international normalized ratio) and TB were significantly greater on POD 5 in the TIVA group. Among the renal function tests, Cr was significantly higher and estimated GFR was significantly lower on POD 1 in the TIVA group. The platelet counts and hemoglobin levels were similar between the 2 groups. In conclusion, the results of our study suggest that living related donors for liver transplant may have a better outcome following anesthesia with desflurane. However, further testing will be necessary to prove this hypothesis.

[Agents for sedation and analgesia in the intensive care unit]

Sedation-analgesia for critically ill patients is usually performed with the combination of a sedative agent and an opioid. Midazolam and propofol are the agents most commonly used for sedation in ICU. The quality of the sedation is quite comparable with both agents, but pharmacokinetic properties of propofol allow a more rapid weaning process from mechanical ventilation. However, implementation of algorithms to adjust drug dosages reduces ventilator days and limits the kinetic differences between propofol and midazolam. Among the adverse events associated with propofol, propofol infusion syndrome is a rare but lethal aspect of propofol therapy. Opioids are the mainstay of analgesic therapy. They interact synergistically with hypnotics. Sufentanil, fentanyl and morphine are the most frequently used opioids. Remifentanil is an ultrashort acting opiate that does not appear to accumulate with prolonged use. The advent of remifentanil has allowed the use of analgesia-based sedation.

Closed-loop strategies for patient care systems

Military operations, mass casualty events, and remote work sites present unique challenges to providers of immediate medical care, who may lack the necessary skills for optimal clinical management. Moreover, the number of patients in these scenarios may overwhelm available health care resources. Recent applications of closed-loop control (CLC) techniques to critical care medicine may offer possible solutions for such environments. Here, feedback of a monitored variable or group of variables is used to control the state or output of a dynamic system. Some potential advantages of CLC in patient management include limiting task saturation when there is simultaneous demand for cognitive and active clinical intervention, improving quality of care through optimization of the titration of medications, conserving limited consumable supplies, preventing secondary insults in traumatic brain injury, shortening the duration of mechanical ventilation, and achieving appropriate goal-directed resuscitation. The uses of CLC systems in critical care medicine have been increasingly explored across a wide range of therapeutic modalities. This review will provide an overview of control system theory as applied to critical care medicine that must be considered in the design of autonomous CLC systems, and introduce a number of clinical applications under development in the context of deployment of such applications to austere environments.

Understanding modes of moderate sedation during gastrointestinal procedures: a current review of the literature

Recommendations for routine screening for colorectal cancer with colonoscopy are likely to substantially increase the demand for provision of sedation for these procedures. Because of this burgeoning caseload and associated economic constraints, it is unlikely that anesthesiologists will be available for all such procedures, particularly those involving average-risk patients. Thus, sedative agents that can be safely administered by nonanesthesiologists, appropriately trained in monitoring and managing the patient's airway, are desperately needed. New concepts in sedation for colonoscopy include enhanced mechanisms for drug delivery such as patient-controlled sedation/analgesia and target-controlled infusion, along with the development of new drugs such as a modified cyclodextrin-based formulation of propofol and fospropofol disodium (Aquavan Injection), a water-soluble prodrug of propofol.

Deep sedation with intravenous infusion of combined propofol and ketamine during dressing changes and whirlpool bath in patients with severe epidermolysis bullosa

Continuous i.v. infusion of propofol, or propofol plus ketamine for deep sedation and analgesia was carried out in two patients with severe epidermolysis bullosa (EB) during extensive dressing changes and deep whirlpool baths. Intermittent small doses of narcotics were given as supplement for pain relief as needed. Both patients had typical features of severe EB, including extremity contractures, severe digit deformity, difficult airways, extensive blisters and broken skin with denuded areas and severe wound infections. SpO(2) was roughly estimated by holding the probe around the earlobe periodically and no other monitors could be applied because of the skin conditions and the settings of the procedures. Retrospective anesthesia record review showed that the combined propofol and ketamine infusions provided satisfactory sedation with significantly reduced narcotic requirements compared with propofol alone. There were no noticeable side effects when ketamine was added. Ketamine appears to be a good addition to propofol and narcotics to provide sedation and analgesia when there are great concerns for respiration depression, apnea, difficult pain management and potential unstable hemodynamics during dressing changes and whirlpool baths in severe EB patients.

Teletherapeutic drug administration by long distance closed-loop control of propofol †

BACKGROUND

The objective of this pilot study was to investigate the feasibility of an EEG-controlled closed-loop administration of propofol over a long distance of about 200 km.

METHODS

We performed a teletherapeutic propofol infusion during total intravenous anaesthesia with propofol in 11 patients undergoing general surgery. The teletherapeutic system consisted of a computer at the patient site in Munich and a computer at the control site in Erlangen, which were connected via the internet through a virtual private network. The patient's EEG signal was sent to the control site computer, where the median frequency (MEF) of the EEG power spectrum was calculated. The propofol infusion, determined by a model-based adaptive feedback algorithm to maintain a MEF of 1.5 to 2 Hz, was sent to the patient site computer connected to the infusion pump. The quality of the control was assessed by the performance error defined as the percentage deviation of the measured MEF from the set point and the necessity of interventions by the anaesthetist at the patient site.

RESULTS

During closed-loop administration of propofol [83 (52) min] the median performance error of the system was - 4.6 (4.4)% and the median absolute performance error was 18.8 (5.7)%. From a total number of 10 905 transmitted EEG epochs, there were five epochs with transmission errors, without further consequences for drug control. In one patient, teletherapy was stopped because the internet connection was interrupted.

CONCLUSIONS

Teletherapeutic drug administration could be realized over a longer distance. Further studies have to investigate the practicability and safety of teletherapeutic drug control in anaesthesia.

Drug development in anaesthesia: industrial perspective

PURPOSE OF REVIEW

In this review, we summarize the new drugs in development in the anaesthesia field.

RECENT FINDINGS

There are some interesting approaches, including pro-drugs of propofol such as Aquavan (MGI Pharma, Bloomington, Minnesota, USA) and novel 'soft-drug' sedatives and hypnotics (e.g. CNS-7259X and TD-4756) as well as a novel approach to terminate the action of steroidal neuromuscular blockers (sugammadex). There is also significant activity in the field of novel analgesics. Particularly addressing the fields of sedatives, hypnotics and neuromuscular blockers, however, there is relatively little drug discovery activity currently. Part of the reason for this may be that the mechanisms of action of anaesthetics are not fully understood. This cannot be the whole story, however, since attractive new targets have recently been identified. For example, an agent with selective actions at the beta3-containing subunit of the gamma-amino butyric acid-A receptor is likely to have the hypnotic effects of propofol without the cardiac depressant side-effects.

SUMMARY

We consider the main reason for low activity is the perception in industry that there is little need for new drugs in anaesthesia because the needs are well addressed by existing agents. If this is not the case then anaesthesiologists need to be more effective in communicating their requirements.

Propofol formulated with long-/medium-chain triglycerides reduces the pain of injection by target controlled infusion

BACKGROUND

Propofol is a widely used intravenous anesthetic although its injection pain is a common and unpleasant problem. Long-/medium-chain triglyceride (LCT/MCT) propofol has been introduced, as its low free propofol content is expected to reduce injection pain compared with LCT propofol. Target controlled infusion (TCI) differs from conventional induction in the initial infusion pattern. During induction using TCI, we investigated injection pain caused by two propofol solutions with different triglyceride compositions.

METHODS

Fifty patients, ASA I-II, with adequate communicative ability, were randomly assigned to two groups. TCI was conducted with Diprifusor for LCT and with BeComSim (custom-made software) for LCT/MCT. The target blood concentration was set at 4 microg/ml for both groups. At 30, 60, and 120 s after the infusion, patients were asked questions regarding the severity of pain on a 0-10 pain score. The total dose of propofol and the time required to induce anesthesia were also investigated.

RESULTS

The LCT/MCT propofol group had a larger number of pain-free patients and showed lower severity of pain than the LCT group [the number of pain-free patients being 11 and 3, respectively (P < 0.05), and median maximum pain being 0 and 4.5, respectively (P < 0.01)]. The dose and time required for induction were not significantly different between the groups (dose of 84 +/- 27 and 80 +/- 24 mg, respectively, and time of 119 +/- 60 and 107 +/- 55 s, respectively).

CONCLUSION

Our study showed that the frequency and severity of pain during TCI induction with propofol could be significantly reduced using LCT/MCT propofol rather than LCT propofol.

Development of a recursive finite difference pharmacokinetic model from an exponential model: Application to a propofol bolus**Glen M. Atlas is an Associate Professor, Adjunct Member of the Graduate Faculty, and Adjunct Associate Professor; Sunil Dhar is an Associate Professor

Propofol is commonly administered, as a single bolus dose, for the induction of general anesthesia. The purpose of this study was to mathematically assess the ability to model propofol induction-dose serum levels with a recursive finite difference equation (RFDE). Using data obtained from a prior published study, propofol induction pharmacokinetics were accurately modeled, on a subject-specific basis, with a third-order homogeneous finite difference equation with constant coefficients: P((k + 3)) = AP((k + 2)) + BP((k + 1)) + CP((k)). Furthermore, each RFDE model is derived directly from the coefficients of a traditional three-compartment pharmacokinectic exponential equation. Based on this study, third-order RFDE models can have identical accuracy as three-compartment exponential models. In this particular application, it should be noted that each RFDE model required only three coefficients whereas each exponential model required six. Also, there was overall less patient-to-patient variability of the coefficients of the RFDE models. In general, it appears that RFDE models uniquely allow for predicting subsequent drug levels from preexisting ones. However, RFDE models require initial conditions whereas exponential models do not. Additional studies and applications of exponentially-derived RFDE pharmacokinetic models may be warranted.

Remifentanil supplementation of propofol during electroconvulsive therapy: effect on seizure duration and cardiovascular stability

OBJECTIVES

Electroconvulsive therapy (ECT) is standard treatment of severe depression. The induction of a seizure is a core event in successful ECT. Although propofol is a frequently used anesthetic agent, one of its limitations is a reduction of seizure duration. No such effects have been reported regarding remifentanil, an ultrarapid-acting opioid that is used to induce and maintain anesthesia. The simultaneous administration of propofol and remifentanil may have similar safety and efficacy in terms of induction of anesthesia during ECT as propofol alone and significantly increase seizure duration.

METHODS

Twenty-one ECT patients (10 men, 11 women, aged 24 to 81 years) were recruited. Muscle paralysis was achieved with succinylcholine (0.5-0.75 mg/kg intravenously [IV]). Unconsciousness was induced by either propofol (1 mg/kg IV) or propofol (0.5 mg/kg IV) + remifentanil (1 microg/kg) in a crossover format. ECT was administered according to established clinical protocols at the Sheba Medical Center, Israel. No changes in ECT current were permitted in the 2 protocols of each patient. Statistical analysis was based on paired t tests.

RESULTS

In all but 2 cases, seizure duration was significantly longer in the remifentanil group than in the control group (motor seizure 53.7 +/- 28.3 seconds vs. 29.5 +/- 10.9 seconds, t = 4.017, P = 0.0007; Electroencephalographic (EEG) seizures 60.8 +/- 25.1 seconds vs. 40.1 +/- 17.0 seconds, t = 3.971, P = 0.001). No significant differences were found in mean recovery time, post-treatment elevation in blood pressure, heart-beat, or oxygen saturation.

CONCLUSION

During anesthesia, the addition of remifentanil to propofol appears to be as effective as propofol alone with regard to anesthesia efficacy and cardiovascular function while significantly increasing seizure duration. Whether this discovery is of relevance to the clinical efficacy of ECT remains to be tested.

Anaesthesia In Austere Environments

The scope of this review is by necessity somewhat limited and, as said in the introduction, methods used will depend on the skills and experience of the practitioner involved. The triservice apparatus remains the system of choice for delivering volatile anaesthetic agents to patients in areas without the infrastructure to supply an endless quantity of medical gases, the planned isolated or battle conditions of Boultons scenarios. The TSA's portability, robust design and versatility have stood the test of time. By reviewing intravenous agents the author has attempted to find an evidence base for the most appropriate agent for a non anaesthetic trained doctor finding his or herself called on to provide emergency anaesthesia in the field. The most useful drug is ketamine which has the advantage of cardiovascular stability, preservation of airway reflexes, ease of administration via different routes and versatility for providing analgesia, sedation or general anaesthesia.