Self-regulating CAR-T cells modulate cytokine release syndrome in adoptive T-cell therapy

Cytokine release syndrome (CRS) is a frequently observed side effect of chimeric antigen receptor (CAR)-T cell therapy. Here, we report self-regulating T cells that reduce CRS severity by secreting inhibitors of cytokines associated with CRS. With a humanized NSG-SGM3 mouse model, we show reduced CRS-related toxicity in mice treated with CAR-T cells secreting tocilizumab-derived single-chain variable fragment (Toci), yielding a safety profile superior to that of single-dose systemic tocilizumab administration. Unexpectedly, Toci-secreting CD19 CAR-T cells exhibit superior in vivo antitumor efficacy compared with conventional CD19 CAR-T cells. scRNA-seq analysis of immune cells recovered from tumor-bearing humanized mice revealed treatment with Toci-secreting CD19 CAR-T cells enriches for cytotoxic T cells while retaining memory T-cell phenotype, suggesting Toci secretion not only reduces toxicity but also significantly alters the overall T-cell composition. This approach of engineering T cells to self-regulate inflammatory cytokine production is a clinically compatible strategy with the potential to simultaneously enhance safety and efficacy of CAR-T cell therapy for cancer.

Nitro-benzylideneoxymorphone, a bifunctional mu and delta opioid receptor ligand with high mu opioid receptor efficacy

Introduction: There is a major societal need for analgesics with less tolerance, dependence, and abuse liability. Preclinical rodent studies suggest that bifunctional ligands with both mu (MOPr) and delta (DOPr) opioid peptide receptor activity may produce analgesia with reduced tolerance and other side effects. This study explores the structure-activity relationships (SAR) of our previously reported MOPr/DOPr lead, benzylideneoxymorphone (BOM) with C7-methylene-substituted analogs. Methods: Analogs were synthesized and tested in vitro for opioid receptor binding and efficacy. One compound, nitro-BOM (NBOM, 12) was evaluated for antinociceptive effects in the warm water tail withdrawal assay in C57BL/6 mice. Acute and chronic antinociception was determined, as was toxicologic effects on chronic administration. Molecular modeling experiments were performed using the Site Identification by Ligand Competitive Saturation (SILCS) method. Results: NBOM was found to be a potent MOPr agonist/DOPr partial agonist that produces high-efficacy antinociception. Antinociceptive tolerance was observed, as was weight loss; this toxicity was only observed with NBOM and not with BOM. Modeling supports the hypothesis that the increased MOPr efficacy of NBOM is due to the substituted benzylidene ring occupying a nonpolar region within the MOPr agonist state. Discussion: Though antinociceptive tolerance and non-specific toxicity was observed on repeated administration, NBOM provides an important new tool for understanding MOPr/DOPr pharmacology.

Rational Protein Design Yields a CD20 CAR with Superior Antitumor Efficacy Compared with CD19 CAR

Chimeric antigen receptors (CAR) are fusion proteins whose functional domains are often connected in a plug-and-play manner to generate multiple CAR variants. However, CARs with highly similar sequences can exhibit dramatic differences in function. Thus, approaches to rationally optimize CAR proteins are critical to the development of effective CAR T-cell therapies. Here, we report that as few as two amino-acid changes in nonsignaling domains of a CAR were able to significantly enhance in vivo antitumor efficacy. We demonstrate juxtamembrane alanine insertion and single-chain variable fragment sequence hybridization as two strategies that could be combined to maximize CAR functionality, and describe a CD20 CAR that outperformed the CD19 CAR in antitumor efficacy in preclinical in vitro and in vivo assays. Precise changes in the CAR sequence drove dramatically different transcriptomic profiles upon antigen stimulation, with the most efficacious CAR inducing an enrichment in highly functional memory T cells upon antigen stimulation. These findings underscore the importance of sequence-level optimization to CAR T-cell function, and the protein-engineering strategy described here may be applied to the development of additional CARs against diverse antigens. See related Spotlight by Scheller and Hudecek, p. 142.

Capping the dose of paclitaxel in endometrial cancer patients: Does this affect clinical outcome?

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Background: Various protocols recommend capping chemotherapy dosing of paclitaxel at 2m2 while other protocols dose paclitaxel according to actual body weight (ABW). In endometrial cancer where a significant portion of patients are obese this dosing difference may affect clinical outcome. We performed a retrospective review of patients with endometrial cancer who received paclitaxel and carboplatin after surgical staging. We compared patients who received paclitaxel dosed according to ABW with patients whose dose was capped at 2m2 to determine if differences in dosing affected progression free survival (PFS). Methods: Patients with endometrial cancer undergoing adjuvant treatment with paclitaxel and carboplatin from January 2000 to January 2008 were identified. Patient age, endometrial histology, stage, BSA, and paclitaxel treatment dose were collected and progression free survival was determined. Differences in outcome were compared and evaluated using student's t test. Results: 109 women were identified of whom 70 were treated according to their ABW (<2m2) and 39 obese patients received paclitaxel dose capped at 2m2. 95% of all the patients received the complete course of chemotherapy. PFS for both groups were 21.4±2.2 and 23.2±2.2 months with no significant difference in PFS (p = 0.62). When evaluating patients with endometrioid histology alone, no difference between patients receiving dosages according to ABW compared to those whose dosages were capped at 2m2 (25 patients vs. 19 patients, PFS 19.3±3.7 and 27.0±3.7 respectively, p = 0.16). However for patients with serous histology, PFS was significantly greater in those patients treated per their ABW when compared to patients capped at 2m2 (45 patients vs. 20 patients, PFS 30.2±3.2 and 19.6±3.5 months respectively, p = 0.05). Conclusions: There was no difference in PFS for patients with endometrioid cancer who were treated with ABW vs. capped doses of paclitaxel. However patients with serous histology experienced longer PFS when receiving paclitaxel dosed per ABW as compared to patients whose dose was capped at 2m2. This difference may reflect increased sensitivity of serous cancers to chemotherapy or other unknown biologic variables. Capping paclitaxel dosing in patients with serous endometrial cancers may affect their PFS.

No significant financial relationships to disclose.

Hematologic toxicities before and during bevacizumab chemotherapy in women with gynecologic malignancy

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Background: Many women undergoing chemotherapy for gynecologic malignancy experience hematologic toxicity that delays therapy or requires supportive intervention. In animal models anti-VEGF antibodies increase erythropoietin levels. We examined the hematologic toxicities experienced by patients prior to (PR) and during bevacizumab (BR) treatment. Methods: Retrospective, single-institution study of women with gynecologic malignancy treated at the University of North Carolina with bevacizumab as part of their therapy from January 2005 to June 2007. Data collected included prior therapies, blood product and growth factor use, and interruptions in therapy. Comparisons were made between individual patients’ hematologic parameters during the PR and BR. Median differences between hematologic nadirs were compared using Wilcoxon Signed Rank Tests. Differences in proportions were compared by Chi-Square or Fisher's Exact tests. Results: 43 patients ware identified, 40 with complete data. Most women were Caucasian (88%) and had ovarian or primary peritoneal carcinoma (77%); median (range) age was 53 (23–73). 32 (74%) received three or more different chemotherapy drugs before starting bevacizumab. The median difference in HCT nadir (31.2 vs. 33, p = 0.01) and ANC nadir (1.2 vs. 1.4, p = 0.04) during the PR and BR were significant in favor of the bevacizumab regimens. The median nadir differences for WBC (2.7 vs. 3.1, p = 0.1) and PLT (129 vs. 150, p = 0.07) were non-significant favoring BR. For HCT toxicity grades, 22 (55%) had the same grade during their PR and BR, 15 (38%) had a lower grade during BR, and 3 (7%) had a higher grade during BR (p = 0.001). Similar trends were seen for WBC (p = 0.27), ANC (p = 0.1), and PLT (p = 0.15). During BR there was a trend toward fewer patients receiving darbepoetin (66% vs. 44%, p = 0.07) and filgastrim (29% vs. 14%, p = 0.1). Conclusions: Patients receiving bevacizumab had no worse hematologic toxicity compared to their prior regimens and may have had less severe anemia. While not statistically significant, there were trends toward less growth factor use with bevacizumab. Patients who have had prior hematologic toxicity should be considered for bevacizumab. The effect of bevacizumab on hematologic toxicity should be evaluated with prospective data.

No significant financial relationships to disclose.

Effect of Lap-Band-induced weight loss on type 2 diabetes mellitus and hypertension

BACKGROUND

Severe obesity is associated with type 2 diabetes and hypertension. Improvement in these comorbidities after surgically-induced weight loss has been documented, and laparoscopic adjustable gastric banding (LAGB) is an effective weight loss operation.

METHODS

Of 840 patients who underwent Lap-Band, data are available in 402 out of 413 patients whose surgery took place at >/= 1 year ago. Preoperative and follow-up data were studied retrospectively to examine the effect of Lap-Band-induced weight loss on diabetes and hypertension.

RESULTS

Of 413 patients with at least 1 year postoperative follow-up, 53 (12.8%) were taking medications for type 2 diabetes preoperatively and 189 (45.7%) were on antihypertensive medications. 66% (n=35) of diabetic patients were also hypertensive. Resolution of diabetes was observed in 66% at 1-year and 80% at 2-year follow-up. HbA1c dropped from 7.25% (5.6-11.0, n=53) preoperatively to 5.58% (5.0-6.2, n=15) at 2 years after surgery. Hypertension resolved in 59.8% and 74% at 1 and 2 years, respectively. Percent excess weight loss (%EWL) was lower for diabetic patients than for our cohort population (39.2% vs 41.2% at 1 year, 46.7% vs 54.2% at 18 months, and 52.6% vs 63.3% at 2 years, respectively). Patients in whom diabetes was improved but not resolved had lower %EWL than did those whose diabetes went into remission (27.0% at 1 year and 26.5% at 2 years). Patients with the shortest duration of diabetes (<5 years) and better weight loss after surgery achieved higher resolution rates.

CONCLUSIONS

Dramatic improvement in - and frequent resolution of - diabetes and hypertension have been observed as a result of weight loss after Lap-Band surgery.

Researching medicine in context: the Arts and Humanities Medical Scholars Program

In 2000, the Arts and Humanities Medical Scholars Program at Stanford University School of Medicine issued its first grants to medical students interested in researching an area of the medical arts or humanities in depth. To date, 34 projects have been funded, including renewals. The projects encompass a range of genres and topics, from a website on Asian American health and culture to an ethnographic study of women physicians in training in Spain. Two projects are highlighted here: an online history of medicine course and a poetry project. Students are mentored by faculty from a wide array of university departments and centres and submit completion documents to the committee overseeing the programme. Students are encouraged to present their work at conferences, such as the programme's annual symposium, as well as in publication or other appropriate formats. Future directions include integration with the scholarly concentrations initiative at the medical school.

Patient threats present an ethical dilemma for the anesthesiologist

IMPLICATIONS

Patients who receive sedation occasionally divulge thoughts that they would not usually express. This report describes a sedated patient who threatened to murder two family members. Immediate consultation with an attorney and psychiatrist is recommended when the anesthesiologist may be required to breach patient confidentiality to warn potential victims.

Tetracycline-regulatable expression vectors tightly regulate in vitro gene expression of secreted proteins

The regulation of gene expression by the tetracycline system has attracted a high level of interest in the recent past. However, expression of secreted proteins has not been evaluated precisely. In this study, we constructed two versions of a one-plasmid system containing the elements necessary for the regulation of gene expression. The regulatable elements and the selectable marker (Neor) were set up in two different configurations, pTRIN31 and pTRIN76. With these two regulatable versions, the levels of protein expression after transfection into the NIH/3T3 cell line were measured by insertion of three different genes encoding the secreted proteins (hGH, ApoE3, hGM-CSF). The maximum levels of gene expression obtained with the pTRIN76-derived plasmids were 100ng/24h/106 cells for hGH, 427ng/24h/106 cells for ApoE3 and 108ng/24h/106 cells for hGM-CSF. For the pTRIN31-derived plasmids the maximum levels were 2.7ng/24h/106 cells for hGH and 47ng/24h/106 for ApoE3. Both plasmids give rise to an expression of the transfected gene that can be tightly regulated by three different molecules: tetracycline, minocycline and doxycycline. The levels of the secreted proteins are below the detectable level when the reporter genes are repressed. This repression is reversible within 48h after the regulator has been removed from the medium.

Complications of sedation with midazolam in the intensive care unit and a comparison with other sedative regimens

OBJECTIVE

To describe the various complications that have been reported with use of midazolam for sedation in the intensive care unit (ICU).

DATA SOURCES

Publications in scientific literature.

DATA EXTRACTION

Computer search of the literature.

SYNTHESIS

Sedation is required in the ICU in order for patients to tolerate noxious stimuli, particularly mechanical ventilation. Under- and oversedation can lead to complications. To sedate patients in the ICU, midazolam is commonly administered via titrated, continuous infusions. Cardiorespiratory effects tend to be minimal; however, hypotension can occur in hypovolemic patients. Prolonged sedation after cessation of the midazolam infusion may be caused by altered kinetics of the drug in critically ill patients or by accumulation of active metabolites. In addition, paradoxical and psychotic reactions have been rarely reported. Tolerance and tachyphylaxis may occur, particularly with longer-term infusions (> or = 3 days). Benzodiazepine withdrawal syndrome has also been associated with high dose/long-term midazolam infusions. Compared with propofol infusions, midazolam infusions have been associated with a decreased occurrence of hypotension but a more variable time course for recovery of function after the cessation of the infusion. Lorazepam is a more cost-effective choice for long-term (> 24 hrs) sedation.

CONCLUSION

Continuous infusion midazolam provides effective sedation in the ICU with few complications overall, especially when the dose is titrated.

Vancomycin control measures at a tertiary-care hospital: impact of interventions on volume and patterns of use

OBJECTIVE

Evaluate vancomycin prescribing patterns in a tertiary-care hospital before and after interventions to decrease vancomycin utilization.

DESIGN

Before/after analysis of interventions to limit vancomycin use.

SETTING

420-bed academic tertiary-care center.

INTERVENTIONS

Educational efforts began August 10, 1994, and involved lectures to medical house staff followed by mailings to all physicians and posting of guidelines for vancomycin use on hospital information systems. Active interventions began November 15, 1994, and included automatic stop orders for vancomycin at 72 hours, alerts attached to the medical record, and, for 2 weeks only, computer alerts to physicians following each vancomycin order. Parenteral vancomycin use was estimated from the hospital pharmacy database of all medication orders. Records of a random sample of 344 patients receiving vancomycin between May 1, 1994, and April 30, 1995, were reviewed for an indication meeting published guidelines.

RESULTS

Vancomycin prescribing decreased by 22% following interventions, from 8.5 to 6.8 courses per 100 discharges (P<.05). The estimated proportion of vancomycin ordered for an indication meeting published guidelines was 36.6% overall, with no significant change following interventions. However, during the 2 weeks that computer alerts were in place, 60% of vancomycin use was for an approved indication.

CONCLUSIONS

Parenteral vancomycin prescribing decreased significantly following interventions, but the majority of orders still were not for an indication meeting published guidelines. Further improvement in the appropriateness of vancomycin prescribing potentially could be accomplished by more aggressive interventions, such as computer alerts, or by targeting specific aspects of prescribing patterns.

Cue reactivity in cocaine-dependent subjects: effects of cue type and cue modality

Thirty cocaine-dependent subjects were enrolled into a cue-laboratory study to determine the specificity and sensitivity of this paradigm as a craving measure. Subjects experienced three cue types (i.e., cocaine, arousing, and neutral stimuli) in three cue modalities (i.e., audio, visual, and manual). Cue types were administered in different experimental sessions with a period of 2 to 3 days between sessions. Our results showed that subjective and physiological craving for cocaine was relatively specific for the cocaine cue as compared with either the arousing or the neutral cue. The relative sensitivities of the cue modalities in decreasing order was manual, audio, and visual. We suggest that a modified conditioned-cue paradigm could be a useful tool in the repeated assessment of craving during a clinical study.

The expression of leptin and its receptors in pre-ovulatory human follicles

The expression of leptin and its receptors was examined by reverse transcriptase-polymerase chain reaction and immunofluorescence in granulosa and cumulus cells of pre-ovulatory follicles and in meiotically mature oocytes obtained from women undergoing in-vitro fertilization. Leptin concentrations were measured in newly aspirated follicular fluids and in maternal serum before and after the administration of an ovulatory dose of human chorionic gonadotrophin. The findings demonstrate leptin expression at the mRNA and protein levels by granulosa and cumulus cells, and the presence of leptin in mature human oocytes. While an association between follicular leptin concentration and embryo development was not observed, a post-ovulatory increase in serum leptin concentration was associated with implantation potential. The results are discussed with respect to possible roles of leptin in early human development.

Leptin stimulates fetal and adult erythroid and myeloid development

The ob gene product, leptin, has been shown in several studies to be involved in weight control and recombinant leptin recently has entered clinical trials to treat obesity. The leptin receptor (OB-R/B219) is expressed in a variety of protein isoforms not only in the central nervous system, but also in reproductive, and hematopoietic tissues. We reported recently that the OB-R/B219 was associated with a variety of hematopoietic lineages as well as the small fraction of cells containing the long-term reconstituting hematopoietic stem cells. Herein we report that leptin significantly stimulates the proliferation and differentiation of yolk sac cells and fetal liver cells and stimulates directly hematopoietic precursors. Leptin alone can increase the number of macrophage and granulocyte colonies, and leptin plus erythropoietin act synergistically to increase erythroid development. These data show that leptin has a significant, direct effect on early hematopoietic development and can stimulate the differentiation of lineage-restricted precursors of the erythrocytic and myelopoietic lineages. These observations along with a recent report strongly support our previous hypothesis that leptin has an unanticipated important role in hematopoietic and immune system development.

Preoperative anxiety and fear: a comparison of assessments by patients and anesthesia and surgery residents

We sought to compare self-assessment of preoperative anxiety levels and selection of worst fears by surgical patients with the assessments made by the anesthesia and surgery residents providing intraoperative care for those patients. One hundred inpatients at a Veterans Affairs hospital (Group 1) and 45 patients at a University hospital (Group 2) were asked to complete a brief questionnaire; the residents were asked to complete the same questionnaire. Group 1 results showed that median patient visual analog scale (VAS) scores were lower for anxiety about anesthesia compared to surgery (16 vs 22, P < or = 0.05). Anesthesia resident VAS scores were higher than patient or surgery resident scores. Neither type of resident was able to predict their individual patient's VAS score (Kendall's tau). The fear chosen with the greatest incidence by Group 1 patients and residents was "whether surgery would work". A significant number of residents (34%, anesthesia or surgery, P < or = 0.05) matched their patient's fear choice. Residents commonly chose fears related to their specialty (e.g., anesthesia residents chose anesthesia-related fears more often than surgery residents, 50% vs 28%, P < or = 0.001). In Group 2, residents demonstrated an improved ability to predict patient scores. For instance, both surgery and anesthesia residents were able to predict individual University patient VAS scores (P < or = 0.01). The fear chosen with the greatest frequency by Group 2 patients was "pain after the operation". Sixty percent of anesthesia residents matched their patients' fear choice (P < or = 0.001). This study indicates a variable ability of anesthesia and surgery residents to predict patient anxiety and fear which may be due, in part, to difficulty in understanding a Veterans Affairs hospital patient population.

A call for narrative: the patient's story and anesthesia training

Narrative plays a key role in medical education and knowledge, via the case history, the case presentation, or even the patient's chart. Hospitalization for elective surgery provides the structure for a discrete story in a person's life. The details make the story unique for each patient. By analyzing themes and content of narratives obtained from patients and medical trainees, the reader gains insight into the realms of patients' and residents' lives. We believe that even anesthesiologists, who work at the procedure-oriented end of the spectrum of patient care, can benefit from a narrative approach to understanding the patient's perspective. An unanticipated reward of the study is the therapeutic benefit that some of the patients express in their narratives. Patients write that they hope future patients will benefit ("Use this information to the betterment of anyone in need & etc" [patient 15]) or physicians and nurses will improve their interactive skills (patient 09). Perhaps physicians may share the rewards of narrative creation that patient 10 expresses when he triumphantly exclaims, "EUREKA!!! ... I hope you learn something from it (as I have from remembering it)." Patients can provide medical personnel not only with signs and symptoms, but also with insight into the human aspects of the medical process. Reading or writing narratives about such processes may enhance physicians' understanding of their patients' experiences.

Outpatient premedication: use of midazolam and opioid analgesics

The perioperative effects of administering sedative and analgesic drugs prior to outpatient surgery were evaluated. One hundred fifty adult outpatients were randomly assigned to one of six study groups according to a double-blind protocol design. Patients were given placebo (saline) or midazolam (5 mg im) 30-60 min prior to surgery, and then either placebo, oxymorphone (1 mg iv), or fentanyl (100 micrograms iv) 3-5 min prior to a standardized anesthetic technique. Preoperatively, midazolam premedication was associated with a significantly lower anxiety level (37 +/- 29 mm vs. 50 +/- 32 mm, P less than 0.05), higher sedation level (254 +/- 136 mm vs. 145 +/- 109 mm, P less than 0.01), worsening of psychomotor skill (5 +/- 5 vs. 2 +/- 2 dots missed, P less than 0.01; midazolam vs. placebo), and impaired recall abilities. In addition, use of midazolam did not prolong the discharge time. Compared to control patients, those who received fentanyl had a decreased incidence of intraoperative airway difficulties such as coughing (28% vs. 0%, P less than 0.01). Although use of opioids increased the incidence of postoperative nausea (42% vs. 18%, P less than 0.01) and vomiting (23% vs. 2%, P less than 0.01; opioid vs. no opioid), average recovery times were not affected by opioid administration. Oxymorphone use was associated with a lower incidence of pain at home compared with that following fentanyl (46% vs. 74%, P less than 0.05). Finally, preoperative administration of both midazolam and fentanyl or oxymorphone prior to a standardized methohexital-nitrous oxide anesthetic technique did not adversely affect recovery after outpatient surgery.

Benzodiazepine antagonism does not provoke a stress response

Acute anxiety reactions have been reported following antagonism of benzodiazepine-induced sedation. In this study, the level of sedation and anxiety was assessed in 30 patients randomly assigned to receive either saline or flumazenil (a benzodiazepine antagonist) after midazolam sedation according to a double-blind protocol. Carefully titrated doses of flumazenil, 0.8 +/- 0.2 mg (mean +/- SD), effectively reversed residual midazolam-induced sedation without producing significant changes in the patients' level of anxiety. In addition, plasma epinephrine, norepinephrine, vasopressin, and beta-endorphin concentrations were measured in a subset of patients (n = 5) from each group. The levels of these stress hormones did not acutely change following flumazenil (or saline). These results indicate that flumazenil, 0.6-1.0 mg iv, can antagonize midazolam sedation without producing acute anxiety or evidence of a stress response.

Pharmacokinetics and pharmacodynamics of propofol infusions during general anesthesia

The pharmacokinetic and pharmacodynamic properties of propofol were studied in 50 surgical patients. Propofol was administered as a bolus dose, 2 mg/kg iv, followed by a variable-rate infusion, 0-20 mg/min, and intermittent supplemental boluses, 10-20 mg iv, as part of a general anesthetic technique that included nitrous oxide, meperidine, and muscle relaxants. For a majority of the patients (n = 30), the pharmacokinetics of propofol were best described by a two-compartment model. The propofol mean total body clearance rate was 2.09 +/- 0.65 1/min (mean +/- SD), the volume of distribution at steady state was 159 +/- 57 l, and the elimination half-life was 116 +/- 34 min. Elderly patients (patients older than 60 yr vs. those younger than 60 yr) had significantly decreased clearance rates (1.58 +/- 0.42 vs. 2.19 +/- 0.64 l/min), whereas women (vs. men) had greater clearance rates (33 +/- 8 vs. 26 +/- 7 l.kg-1.min-1) and volumes of distribution (2.50 +/- 0.81 vs. 2.05 +/- 0.65 l/kg). Patients undergoing major (intraabdominal) surgery had longer elimination half-life values (136 +/- 40 vs. 108 +/- 29 min). Patients required an average blood propofol concentration of 4.05 +/- 1.01 micrograms/ml for major surgery and 2.97 +/- 1.07 micrograms/ml for nonmajor surgery. Blood propofol concentrations at which 50% of patients (EC50) were awake and oriented after surgery were 1.07 and 0.95 microgram/ml, respectively. Psychomotor performance returned to baseline at blood propofol concentrations of 0.38-0.43 microgram/ml (EC50). This clinical study demonstrates the feasibility of performing pharmacokinetic and pharmacodynamic analyses when complex infusion and bolus regimens are used for administering iv anesthetics.

Propofol-nitrous oxide versus thiopental-isoflurane-nitrous oxide for general anesthesia

One hundred and twenty patients undergoing elective operations were randomly assigned to receive anesthesia with either thiopental, 4 mg/kg-isoflurane, 0.2-3%-nitrous oxide, 60-70% (control) or propofol, 2 mg/kg-propofol infusion, 1-20 mg/min-nitrous oxide, 60-70% (propofol). Although anesthetic conditions were similar during the operation, differences were noted in the recovery characteristics. For non-major (superficial) surgical procedures, the times to awakening, responsiveness, orientation, and ambulation were significantly shorter in the propofol group (4 +/- 3, 5 +/- 4, 6 +/- 4, and 104 +/- 36 min) than in the control group (8 +/- 7, 9 +/- 7, 11 +/- 9, and 142 +/- 61 min, respectively). In addition, less nausea and vomiting (20 vs. 45%) and significantly less psychomotor impairment was noted in the non-major propofol (vs. control) group. Following major abdominal operations, recovery characteristics did not differ between propofol and control groups. Delayed emergence (greater than 20 min), significant psychometric impairment, and a high overall incidence of postoperative side effects (55-60%) were noted in both drug treatment groups. The authors conclude that propofol-nitrous oxide compares favorably to thiopental-isoflurane-nitrous oxide for maintenance of anesthesia during short outpatient procedures. However, for major abdominal operations, propofol anesthesia does not appear to offer any clinically significant advantages over a standard inhalational anesthetic technique.

Pharmacokinetics and pharmacodynamics of alfentanil infusions during general anesthesia

The pharmacokinetic and pharmacodynamic properties of alfentanil were studied in 64 surgical patients. Alfentanil was administered as a loading infusion (25-130 micrograms/kg) followed by a maintenance infusion (0.25-1.3 micrograms X kg-1 X min-1) as part of a nitrous oxide-narcotic-muscle relaxant technique. Although alfentanil doses of at least 50 micrograms/kg (in combination with thiopental, 2 mg/kg) were required to prevent hemodynamic changes during intubation, apnea or chest wall rigidity frequently occurred with alfentanil loading infusions exceeding 75 micrograms/kg. The alfentanil clearance rate was significantly lower in patients with liver dysfunction (2.3 +/- 1.3 vs 4.2 +/- 2.0 ml X kg-1 X min-1, mean +/- SD). In addition, the patients who required opioid antagonists to reverse postoperative respiratory depression had lower clearance rates (1.5 +/- 0.7 vs 4.1 +/- 1.9 ml X kg-1 X min-1) and longer elimination half-life values (406 +/- 304 vs 87 +/- 53 min). For maintenance of hemodynamic stability during superficial and intraabdominal operations, alfentanil serum concentration-response curves revealed ED95 values exceeding 300 ng/ml and 400 ng/ml, respectively. Our study also demonstrated a wide range of clinical responses to fixed doses of alfentanil. At equivalent doses, some patients required supplemental anesthetics, whereas others required an opioid antagonist. Careful titration of the alfentanil maintenance infusion is recommended to minimize the possibility of postoperative respiratory depression.

Comparative pharmacology of the ketamine isomers. Studies in volunteers

The clinical and electroencephalographic (EEG) effects of the individual ketamine isomers were compared with the racemic mixture in five volunteers who received each drug on a separate occasion. Racemic ketamine 275 +/- 25 mg, s(+) ketamine 140 +/- 21 mg or R(-) ketamine 429 +/- 37 mg produced an anaesthetic state lasting 6 +/- 2 min (mean +/- SD). However, the EEG evaluation of the R(-) isomer revealed less overall slowing, and an absence of the large slow wave complexes produced by the S(+) isomer and the racemic mixture. The pharmacokinetic profiles for the individual isomers of ketamine did not differ significantly from the racemic mixture. Even though the apparent anaesthetic state produced in these healthy volunteers did not differ qualitatively between the three drug groups, recovery times (assessed using a standardized battery of psychometric tests) were consistently shorter following the individual isomers compared with the racemic mixture. The serum ketamine concentrations associated with regaining consciousness and orientation were consistent with an S(+):R(-) isomer potency ratio of 4:1. In terms of their ability to impair psychomotor function, the S(+):R(-) potency ratio varied from 3:1 to 5:1. After comparable degrees of CNS depression, we conclude that the more potent S(+) isomer of ketamine was associated with a more rapid recovery of psychomotor skills than the currently used racemic mixture.