Propofol: a review of the pharmacology and applications of an intravenous anesthetic agent

Remimazolam as the Primary Agent for Sedation During Cardiac Catheterization in Three Patients With Comorbid Cardiac Conduction Abnormalities

General anesthesia or procedural sedation may be required to ensure immobility, facilitate completion of the procedure, and ensure patient comfort during diagnostic or therapeutic procedures in the cardiac catheterization suite. Although propofol and dexmedetomidine are two of the more commonly chosen agents, concerns regarding their impact on inotropic, chronotropic or dromotropic function may limit their applicability based on underlying patient comorbid conditions. We present three patients with comorbid conditions involving pacemaker (natural or implanted) function or cardiac conduction which impacted the choice of agent for procedural sedation during procedures in the cardiac catheterization suite. Remimazolam, a novel ester-metabolized benzodiazepine, was used as the primary agent for sedation in an effort to limit detrimental effects on chronotropic and dromotropic function which may be seen with propofol or dexmedetomidine. Remimazolam's potential utility in procedural sedation is discussed, previous reports of its use are reviewed, and dosing algorithms are presented.

MS-222 and Propofol Sedation during and after the Simulated Transport of Nile tilapia (Oreochromis niloticus)

The use of anesthetics has been suggested as a strategy to hamper live fish transport-induced stress. Still, there is insufficient data available on the use of alternative anesthetics to MS-222. This study investigated the use of propofol to mitigate stress in Nile tilapia (Oreochromis niloticus, 143.8 ± 20.9 g and 20.4 ± 0.9 cm) during a 6 h simulated transport. Individuals (n = 7) were divided into three groups: control, 40 mg L-1 MS-222, and 0.8 mg L-1 propofol. A naïve group non-transported was also considered. During the 6 h transport and 24 h after, the response to external stimuli, opercular movements, water quality parameters, behavior, blood hematology and other physiological values, the histopathology of the gills, the quality of the fillet, and oxidative-stress changes in gills, muscle, brain, and liver were evaluated. Propofol increased swimming activity of fish but decreased opercular movements and responses to external stimuli, indicating oscillations of the sedation depth. Water pH and glucose levels increased, while hematocrit (HCT) and lactate decreased in propofol groups at 6 h. At this time-point, MS-222 also induced a decrease in the HCT and lactate levels while increasing cortisol levels. Despite these effects, the stress-related behaviors lessened with anesthetics compared to the control group. After the recovery period, physiological responses normalized in animals from both anesthetic groups, but the control still had high cortisol levels. Overall, propofol is a good alternative for the transportation of this species, showing efficient sedation without compromising health or fillet quality. However, further pharmacodynamics and pharmacokinetics knowledge is required to support its use in aquaculture settings.

Association Between Burst-Suppression Latency and Burst-Suppression Ratio Under Isoflurane or Adjuvant Drugs With Isoflurane Anesthesia in Mice

The same doses of anesthesia may yield varying depths of anesthesia in different patients. Clinical studies have revealed a possible causal relationship between deep anesthesia and negative short- and long-term patient outcomes. However, a reliable index and method of the clinical monitoring of deep anesthesia and detecting latency remain lacking. As burst-suppression is a characteristic phenomenon of deep anesthesia, the present study investigated the relationship between burst-suppression latency (BSL) and the subsequent burst-suppression ratio (BSR) to find an improved detection for the onset of intraoperative deep anesthesia. The mice were divided young, adult and old group treated with 1.0% or 1.5% isoflurane anesthesia alone for 2 h. In addition, the adult mice were pretreated with intraperitoneal injection of ketamine, dexmedetomidine, midazolam or propofol before they were anesthetized by 1.0% isoflurane for 2 h. Continuous frontal, parietal and occipital electroencephalogram (EEG) were acquired during anesthesia. The time from the onset of anesthesia to the first occurrence of burst-suppression was defined as BSL, while BSR was calculated as percentage of burst-suppression time that was spent in suppression periods. Under 1.0% isoflurane anesthesia, we found a negative correlation between BSL and BSR for EEG recordings obtained from the parietal lobes of young mice, from the parietal and occipital lobes of adult mice, and the occipital lobes of old mice. Under 1.5% isoflurane anesthesia, only the BSL calculated from EEG data obtained from the occipital lobe was negatively correlated with BSR in all mice. Furthermore, in adult mice receiving 1.0% isoflurane anesthesia, the co-administration of ketamine and midazolam, but not dexmedetomidine and propofol, significantly decreased BSL and increased BSR. Together, these data suggest that BSL can detect burst-suppression and predict the subsequent BSR under isoflurane anesthesia used alone or in combination with anesthetics or adjuvant drugs. Furthermore, the consistent negative correlation between BSL and BSR calculated from occipital EEG recordings recommends it as the optimal position for monitoring burst-suppression.

Propofol protects against oxygen/glucose deprivation‑induced cell injury via gap junction inhibition in astrocytes

Stroke is one of the leading causes of mortality and disability worldwide with limited clinical therapies available. The present study isolated primary astrocytes from the brains of rats and treated them with oxygen-glucose deprivation and re-oxygenation (OGD/R) to mimic hypoxia/reperfusion (H/R) injury in vitro to investigate stroke. It was revealed that propofol (2,6-diisopropylphenol), an intravenous sedative and anesthetic agent, protected against oxygen/glucose-deprivation (OGD) and induced cell injury. Furthermore, propofol exerted a protective effect by inhibiting gap junction function, which was also revealed to promote cell death in astrocytes. The present study further identified that propofol suppressed gap junction function by downregulating the protein expression levels of connexin43 (Cx43), which is one of the most essential components of gap junctions in astrocytes. In addition, when the expression levels of Cx43 were downregulated using small interfering RNA, OGD/R-induced cell death was decreased. Conversely, cell death was enhanced when Cx43 was overexpressed, which was reversed following propofol treatment. In summary, propofol protects against OGD-induced injury in astrocytes by decreasing the protein expression levels of Cx43 and suppressing gap junction function. The present study improved our understanding of how propofol protects astrocytes from OGD/R-induced injury.

A Comparison of Safety and Efficacy of Dexmedetomidine and Propofol in Children with Autism and Autism Spectrum Disorders Undergoing Magnetic Resonance Imaging

Children with autism and autism spectrum disorders have a high incidence of neurologic comorbidities. Consequently, evaluation with magnetic resonance imaging (MRI) is deemed necessary. Sedating these patients poses several challenges. This retrospective study compared the efficacy and safety of dexmedetomidine to propofol in sedating autistic patients undergoing MRI. There were 56 patients in the dexmedetomidine group and 49 in the propofol group. All of the patients successfully completed the procedure. Recovery and discharge times were significantly lower in the propofol group, while the dexmedetomidine group maintained more stable hemodynamics. Both propofol and dexmedetomidine proved to be adequate and safe medications in the sedation of autistic children undergoing MRI.

Intermittent Bolus versus Continuous Infusion of Propofol for Deep Sedation during ABR/Nuclear Medicine Studies

Objective  A comparison of intermittent bolus (IB) versus continuous infusion of propofol for deep sedation. Material and Methods  A retrospective review of patients sedated for Auditory Brainstem Response (ABR)/nuclear medicine studies between September 2008 and February 2015. A ketamine bolus (0.5 mg/kg < 20 kg, 0.25 mg/kg > 20 kg) followed by propofol bolus of 1 mg/kg over 2 minutes. In the IB group, maintenance of deep sedation was with incremental bolus of 10 to 20 mg of propofol. In continuous infusion group (CG), maintenance was with a continuous infusion of 83 mcg/kg/min of propofol. Results  Of the 326 cases completed, 181 were in CG group and 145 were in IB group. There were no statistical differences in patient's age, weight, and American Society of Anesthesiologist (ASA) classification. The cardiovascular and respiratory parameters in the two groups were not different statistically. Mean total propofol dose was higher in CG group versus IB group (CG 7.6 mg ± 3.6 mg, IB 6.5 mg ± 3.6 mg; p  = 0.008). Procedure time in CG group was longer by 8 minutes compared with IB group (CG 49.8 min ± 25.4 min versus 42.3 min ± 19.2 min; p  = .003). CG group has both shorter recovery time (CG 8.1 min ± 4.7 min versus IB 10.0 min ± 8.5 min; p  = 0.01) and discharge time. Conclusion  Satisfactory sedation and completion of the procedure was accomplished with both sedation protocols.

Dexmedetomidine versus Propofol: Is One Better Than the Other for MRI Sedation in Children?

Objective The aim of this article is to determine whether dexmedetomidine or propofol is better for MRI sedation in children. Design This study is a retrospective review of patients sedated with dexmedetomidine or propofol for MRI between July 2007 and July 2015. Dexmedetomidine group (group D) was administered a bolus of 2 µg/kg over 10 minutes followed by a 1 ug/kg/hour infusion. Propofol group (group P) received a bolus of 2 mg/kg over 2 minutes followed by 83 µg/kg/minute infusion. Results Of the 996 cases completed, 452 were in group P and 544 were in group D. Patients in group P were heavier and older than those in group D. All the patients except one in group D completed the procedures. Hypotension occurred in 59% in group P versus 4% in group D (89 ± 11.4 SBP vs. 103.80 ± 19.4; p < 0.05). Bradycardia was observed in 2.9% in group P versus 0.6% in group D. Apnea occurred in two patients in group D. Although procedure time was longer in patients receiving propofol versus dexmedetomidine (58.87 ± 28.17 vs. 45 ± 23.6; p < .05), the discharge time was significantly shorter (37. ± 12.30 vs. 92.61 ± 28.19; p < 0.05). Conclusion Dexmedetomidine appears to provide a useful alternative to propofol for MRI sedation with a longer recovery time, stable hemodynamics, and less reliable respiratory profile, while the propofol had the advantage of quicker onset and rapid recovery.

Quantification of remifentanil and propofol in human plasma: a LC–MS/MS assay validated according to the EMA guideline

Background: Remifentanil and propofol are often used in combination for general anesthesia. We developed a method using LC–MS for their simultaneous measurement in human plasma. Methodology & results: After addition of remifentanil-13C6 and propofol-d18 (IS), 500 µl of plasma were extracted with ethylacetate/hexane. Analysis conditions included gradient elution (water/acetonitrile), electrospray ionization and detection with a triple quadripole mass spectrometer. Remifentanil and propofol were ionized in the positive and negative mode, respectively. The method was validated according to the European Medicines Agency guideline for the validation of bioanalytical methods, then successfully applied to clinical samples from three patients who had undergone liver transplantation. Conclusion: This method is suitable for the simultaneous quantification of remifentanil and propofol in clinical studies.

Complete atrioventricular nodal block after propofol administration in an elderly patient undergoing total knee replacement arthroplasty -A case report-

Complete atrioventricular (AV) block is defined as a dissociation of atrial and ventricular activities. Complete AV block that occurs during the perioperative period is difficult to reverse and usually requires implantation of a pacemaker. Propofol does not affect a normal AV conduction system but may act as a trigger for AV block. It can also potentiate vagal stimulation factors and reduce sympathetic activity. We report a case of complete AV block that may have been related to administration of propofol.

Propofol-ketamine mixture for anesthesia in pediatric patients undergoing cardiac catheterization

OBJECTIVE

To evaluate the safety of a propofol-ketamine mixture to induce and maintain anesthesia in spontaneously breathing pediatric patents during cardiac catheterization.

DESIGN

Prospective clinical study.

SETTING

Departments of Cardiothoracic Surgery, Anesthesiology, and Pediatric Anesthesiology in a university hospital.

PARTICIPANTS

Forty-five children aged 6 months to 16 years with ASA grade II to III undergoing cardiac catheterization.

INTERVENTIONS

Continuous intravenous infusion of a mixture of propofol (4 mg/mL) and ketamine (2 mg/mL) with spontaneous ventilation. The infusion rate was changed and additional boluses of propofol or/and ketamine were given as needed. Hemodynamic, respiratory, and other variables were recorded during the procedure and recovery.

RESULTS

Mean dose of ketamine was 26 +/- 8.3 microg/kg/min and of propofol, 68.3 +/- 21.7 microg/kg/min. Changes in heart rate and mean arterial pressure of more than 20% from baseline were observed in 4 and 5 patients, respectively. A transient reduction in oxygen saturation because of hypoventilation was observed in 3 patients and responded to oxygen administration and manual assisted ventilation. No other complications were observed.

CONCLUSIONS

The propofol-ketamine mixture is a safe, practical alternative for general anesthesia in pediatric patients undergoing cardiac catheterization.

Effects of propofol on GABAA channel conductance in rat-cultured hippocampal neurons

Channels were activated, in ripped-off patches from rat-cultured hippocampal neurons, by propofol alone, propofol plus 0.5 microM GABA (gamma-aminobutyric acid) or GABA alone. The propofol-activated currents were chloride-selective, showed outward-rectification and were enhanced by 1 microM diazepam. The maximum propofol-activated channel conductance increased with propofol concentration from less than 15 pS (10 microM) to about 60 pS (500 microM) but decreased to 40 pS in 1 mM propofol. Fitting the data from 10 to 500 microM propofol with a Hill-type equation gave a maximum conductance of 64 pS, an EC50 value of 32 microM and a Hill coefficient of 1.1. Addition of 0.5 microM GABA shifted the propofol EC50 value to 10 microM and increased the maximum channel conductance to about 100 pS. The Hill coefficient was 0.8. The maximum channel conductance did not increase further when 1 microM diazepam was added together with a saturating propofol concentration and GABA. The results are compared to effects other drugs have on GABAA channels conductance.

Pharmacokinetics of propofol in elderly coronary artery bypass graft patients under total intravenous anesthesia

The present paper investigates the pharmacokinetics of propofol in the plasma of two elderly patients operated on under total intravenous anesthesia using propofol. A 78-year-old (patient A) and a 76-year-old (patient B), both Japanese men with unstable angina pectoris, were operated on for coronary artery bypass grafts. For the induction of anesthesia, 1.5 mg/kg propofol was administered as a single bolus infusion, and anesthesia was maintained using the step-down infusion regimens of propofol. Propofol concentration in the plasma was measured by HPLC with a fluorescence detector. The simulation curves, following the two-compartment model, fitted well to the profiles of the individual data of propofol concentrations in the plasma. When 4 mg/kg/h of propofol was administered to both patients while maintaining anesthesia, propofol concentrations in the plasma were maintained at over 1.0 microg/ml. In patient A, the propofol concentration in the plasma was 140 ng/ml at 6 h after the end of the infusion. In patient B, the propofol concentrations in the plasma were 73 ng/ml at 6 h and 35 ng/ml at 12 h after the end of the infusion. The apparent distribution volumes of patients A and B were 1.43 and 1.62 l/kg, respectively. The half-lives of propofol in the plasma of patients A and B were estimated to be 13.3 and 17.4 min as the a phase, and 10.1 and 10.5 h as the beta phase, respectively. In elderly patients with cardiac surgery, the maintenance concentrations of propofol in the plasma were enough to maintain a concentration of 1.0 microg/ml, and the half-life may be longer than previously reported values in adult patients.

Effect of dexmedetomidine on propofol requirements in healthy subjects

Dexmedetomidine-propofol pharmacodynamic interaction was evaluated in nine healthy subjects in a crossover design. Dexmedetomidine/placebo was infused using a computer-controlled infusion pump (CCIP) to maintain a pseudo-steady-state plasma concentration of 0.66 +/- 0.080 or 0 ng/mL, respectively. Forty-five minutes after the dexmedetomidine/placebo infusion was started, propofol was infused using a second CCIP to achieve a stepwise logarithmically ascending propofol concentration (1.00 to 13.8 microg/mL) profile. Each propofol step lasted 10 min. Blood was sampled for plasma concentration determination, and pharmacodynamic endpoint assessments were made during the study. Propofol and dexmedetomidine/placebo infusions were terminated when three endpoints (subjects were too sedated to hold a syringe, followed by loss of eyelash reflex, followed by loss of motor response to electrical stimulation) were achieved sequentially. The concentration of propofol associated with 50% probability of achieving a pharmacodynamic endpoint in the absence of dexmedetomidine (EC50; placebo treatment) was 6.63 microg/mL for motor response to electrical stimulation and ranged from 1.14 to 1.98 microg/mL for the ability to hold a syringe, eyelash reflex, and sedation scores. The apparent EC50 values of propofol (EC50APP; concentration of propofol at which the probability of achieving a pharmacodynamic endpoint is 50% in the presence of dexmedetomidine concentrations observed in the current study; dexmedetomidine treatment) were 0.273, 0.544-0.643, and 3.89 microg/mL for the ability to hold a syringe, sedation scores, and motor response, respectively. Dexmedetomidine reduced propofol concentrations required for sedation and suppression of motor response. Therefore, the propofol dose required for sedation and induction of anesthesia may have to be reduced in the presence of dexmedetomidine.

Propofol inhibits renal cytochrome P450 activity and enflurane defluorination in vitro in hamsters

PURPOSE

To determine the effect of propofol on renal cytochrome P450 activity and defluorination of enflurane.

METHODS

Renal microsomes were prepared by homogenization and differential centrifugation from pooled hamster kidneys. Defluorination of enflurane was assessed by measuring free fluoride metabolites after reacting enflurane with renal microsomes incubated with various concentrations, 0.05 - 1.0 mmol x L(-1) propofol in the NADPH-generating system. Drug metabolizing activities of renal cytochrome P450 mono-oxygenase enzymes were evaluated within microsomes preincubated with propofol and reacted with the specific marker substrates, aniline, benzo(a)pyrene, erythromycin and pentoxyresorufin, for cytochrome P450 2E1, 1A1, 3A4 and 2B1, respectively.

RESULTS

Renal defluorination of enflurane was inhibited by clinical concentrations, 0.05 mmol x L(-1) of propofol (P < 0.05). Dose-dependent inhibition of defluorination, aniline and benzo(a)pyrene hydroxylase within kidney microsomes was related to propofol concentration. Propofol demonstrated a profound inhibition of renal pentoxyresorufin dealkylase activity even at low concentrations, 0.05 mmol x L(-1) (P < 0.01). Propofol did not exhibit inhibition of erythromycin N-demethylation of kidney microsomes except at high concentration, 1.0 mmol x L(-1). Spectral analyses of key coenzymes of renal cytochrome P450 monooxygenase, cytochrome b5 and cytochrome c reductase, demonstrated an inhibition when incubated with high concentrations of propofol (P < 0.05).

CONCLUSION

In an in vitro study in an NADPH-generating system of hamster kidney microsomes, propofol, in clinical concentrations, exhibited a broad-spectrum of inhibition to renal monooxygenase activities and enflurane defluorination.

Prevention of topical and ocular oxidative stress by positively charged submicron emulsion

A positively charged submicron emulsion with zeta potential values ranging from 35 to 45 mV and mean droplet size around 150-250 nm has recently been developed and characterized. This formulation is based on three surface-active agents, an egg yolk phospholipid mixture, poloxamer 188, and stearylamine, a cationic lipid with a pKa of 10.6. The emulsion toxicity was evaluated in three animal studies. The results of the ocular tolerance study in the rabbit eye indicated that hourly administration of one droplet of the positively charged emulsion vehicle was well tolerated without any toxic or inflammatory response to the ocular surface during the five days of the study. No marked acute toxicity was observed when 0.6 mL of positively charged emulsion was injected intravenously to BALB/c mice. Furthermore, no difference was noted between this group of animals and the group injected with the marketed and clinically well accepted negatively charged Intralipid emulsion. These observations were further confirmed in a four week toxicity study following intravenous administration to rats of 1 mL/kg of the positively charged emulsion as compared to Intralipid. No toxic effect was noted in any of the various organs examined, whereas the results of the hematological and blood chemistry tests remained in the normal range for both emulsions, confirming the preliminary safety study findings. In addition, it was demonstrated by means of a non-invasive technique that alpha-tocopherol positively charged emulsions prevented oxidative damage in rat skin subjected to UVA irradiation. The intrinsic ability of positively charged emulsified oil droplets to protect against reactive oxygen species cannot be excluded, and could act synergistically with the antioxidant alpha-tocopherol itself. The effect of blank and piroxicam positively charged emulsions on rabbit eye following alkali burn was also evaluated. The blank emulsion showed a very rapid healing rate during the first three days with a breakdown in day 14. Complete re-epithelialization was observed in day 28. The same behavior (albeit less pronounced), was noted in piroxicam emulsion, although piroxicam is known to inhibit the epithelial healing process. It can therefore be deduced that the positively charged emulsion vehicle prevented piroxicam from interfering with the epithelial healing process due to the intrinsic free radical scavenger ability of the positively charged submicron emulsion previously demonstrated. Finally, the efficacy of this promising emulsion vehicle containing effective cosmetic ingredients in preventing skin damage and aging following oxidative stress is evaluated.

Propofol anesthesia for invasive procedures in ambulatory and hospitalized children: experience in the pediatric intensive care unit

OBJECTIVES

To describe our experience with propofol anesthesia to facilitate invasive procedures for ambulatory and hospitalized children in the pediatric intensive care unit (PICU) setting.

METHODS

We retrospectively reviewed the hospital records of 115 children who underwent 251 invasive procedures with propofol anesthesia in our multidisciplinary, university-affiliated PICU during a 20-month period. All patients underwent a medical evaluation and were required to fast before anesthesia. Continuous monitoring of the patient's cardiorespiratory and neurologic status was performed by a pediatric intensivist, who also administered propofol in intermittent boluses to obtain the desired level of anesthesia, and by a PICU nurse, who provided written documentation. Data on patient demographics, procedures performed, doses of propofol used, the occurrence of side effects, induction time, recovery time, and length of stay in the PICU were obtained.

RESULTS

Propofol anesthesia was performed successfully in all children (mean age, 6.4 years; range, 10 days to 20.8 years) who had a variety of underlying medical conditions, including oncologic, infectious, neurologic, cardiac, and gastrointestinal disorders. Procedures performed included lumbar puncture with intrathecal chemotherapy administration, bone marrow aspiration and biopsy, central venous catheter placement, endoscopy, and transesophageal echocardiogram. The mean dose of propofol used for induction of anesthesia was 1.8 mg/kg, and the total mean dose of propofol used was 8.8 mg/kg. In 13% of cases, midazolam also was administered but did not affect the doses of propofol used. The mean anesthesia induction time was 3.9 minutes, and the mean recovery time from anesthesia was 28.8 minutes for all patients. The mean PICU stay for ambulatory and ward patients was 140 minutes. Hypotension occurred in 50% of cases, with a mean decrease in systolic blood pressure of 25%. The development of hypotension was not associated with propofol doses, the concomitant use of midazolam, or the duration of anesthesia, but was associated with older patient age. Hypotension was transient and not associated with altered perfusion. Intravenous fluid was administered in 61% of the cases in which hypotension was present. Respiratory depression requiring transient bag-valve-mask ventilation occurred in 6% of cases and was not associated with patient age, propofol doses, concomitant use of midazolam, or the duration of anesthesia. Transient myoclonus was observed in 3.6% of cases. Ninety-eight percent of procedures were completed successfully, and no procedure failures were considered secondary to the anesthesia. Patients, parents, and health care providers were satisfied with the results of propofol anesthesia.

CONCLUSIONS

Propofol anesthesia can safely facilitate a variety of invasive procedures in ambulatory and hospitalized children when performed in the PICU and is associated with short induction and recovery times and PICU length of stay. Hypotension, although usually transient, is common, and respiratory depression necessitating assisted ventilation may occur. Therefore, appropriate monitoring and cardiorespiratory support capabilities are essential. Propofol anesthesia in the PICU setting is a reasonable therapeutic option available to pediatric intensivists to help facilitate invasive procedures in ambulatory and hospitalized children.

Cardiac arrest as a possible sequela of critical airway management and intubation

Immediate cardiac arrest may occur as a result of the physiological consequences of critical airway management, which may include one or all of the following: (1) sedation and/or paralysis, (2) tracheal intubation, and (3) positive pressure ventilation. Two patients are reported, both with myocarditis, who developed cardiac arrest within minutes of simple intubations. Their arrests were not related to technical difficulties of critical airway management. Any disease process that creates a preload-dependent cardiovascular system also creates a situation wherein critical airway management may cause cardiac decompensation. All medications administered to sedate patients and facilitate intubation, as well as mechanical ventilation itself, can cause a decrease in preload. This may be a significant mechanism through which immediate decompensation occurs. Potential conditions that cause preload-dependent cardiovascular systems, as well as alternate therapeutic considerations, are outlined. In these patients intubations should not be delayed, but should be done with extreme caution in anticipation of possible cardiac arrest.

Left ventricular systolic and diastolic function is unaltered during propofol infusion in newborn swine

Propofol is a cardiac depressant with minimal diastolic effects in the adult myocardium. Cardiac effects of propofol in the newborn are unknown. We examined hemodynamic variables and systolic and diastolic left ventricular function in 12 newborn pigs exposed to propofol at three different infusion rates (7.5, 15, and 30 mg x kg(-1) x h(-1)) in random order with a background of fentanyl (100 microg x kg(-1) x h(-1)). Left ventricular (LV) pressure (Plv) and LV anterior-posterior dimension, determined by sonomicrometry, were continuously monitored. Mean arterial pressure (MAP), heart rate (HR), and LV end-diastolic pressure (LVEDP) were determined at every infusion. Systolic function was assessed by the maximal pressure-time derivative (dP/dt(max)), the slope of the end-systolic pressure-dimension relationship (ESP-D), and by the preload recruitable stroke work index (PRSWI). Diastolic function was assessed by relaxation indices, the minimal pressure-time derivative (dP/dt(min)) and the relaxation time constant (tau), and by a stiffness index, the slope of the EDP-D relationship. MAP decreased approximately 25%, from 75.9 +/- 15.6 to 56.3 +/- 14.8 mm Hg (P < 0.05) with propofol, with no dose effect. HR and LVEDP were unchanged from control. Both dP/dt(max) and dP/dt(min) decreased with propofol infusion, but load-independent indices of systolic function (ESP-D slope and PRSWI) and tau were unchanged. Diastolic stiffness was not affected with either 7.5- or 30-mg x kg(-1) x h(-1) infusions but decreased significantly from 0.27 +/- 0.18 mm Hg/mm at control to 0.18 +/- 0.18 mm Hg/mm (P < 0.05) with propofol 15 mg x kg(-1) x h(-1). With this profile, propofol may be useful for the newborn requiring anesthesia.

IMPLICATIONS

Most anesthetics depress heart function in the newborn. We examined both heart contraction and relaxation during anesthesia with propofol in newborn pigs. Propofol had minimal influence on heart function in this model at the doses studied. This may therefore be a useful anesthetic to test in the newborn human.

Propofol Anesthesia for Elective Cardioversion of, Pediatric Intensive Care Unit Patients with Congenital Heart Disease

Propofol is an intravenous sedative-hypnotic anesthetic agent that has been increasingly employed to facilitate elective direct current cardioversion in adult patients. Little information is available about use of propofol in pediatric intensive care unit patients with congenital heart disease undergoing elective cardioversion. We report our experience with 33 cardioversions performed in our pediatric intensive care unit using propofol anesthesia. Propofol provided good subjective conditions for cardioversion in all patients, and 97% of cardioversions successfully converted atrial flutter into a sinus rhythm. Mean induction time was 5.97 ± 3.54 minutes, and recovery time was 28.08 ± 22.88 minutes. Length of stay in the pediatric intensive care unit was 3.84 ± 1.20 hours. Transient hypotension occurred during 24% of cardioversions, whereas brief periods of respiratory depression were present during 30% of cardioversions. Propofol anesthesia can be successfully administered during elective cardioversion in pediatric intensive care unit patients with congenital heart disease provided that appropriate cardiorespiratory monitoring and supportive therapies are in place.

Concentration-EEG effect relationship of propofol in rats

Propofol is a unique highly lipid-soluble anesthetic that is formulated in a fat emulsion (Diprivan) for intravenous (i.v.) use. It has the desirable properties of rapid onset and offset of effect following rapid i.v. administration and minimal accumulation on long-term administration. Based on physicochemical properties and preliminary brain solubility data, propofol should have an extended effect-site turnover and a resulting prolonged effect. However, a preliminary study in humans has reported a rapid blood-brain equilibration half-time (T1/2 kE0) of only 2.9 min. We used a chronically instrumented rat model to examine the unique disposition and electroencephalographic (EEG) pharmacodynamics of propofol. Although the pharmacokinetics were variable, there was low interindividual variability in the concentration-EEG effect relationship. The duration of EEG sleep was 26 (+/- 44% CV) min following 11-15 mg/kg doses of propofol. The T1/2 kE0 was 1.7 (+/- 32%) min. Apparent effect-site concentrations of 0.5-1 microg/mL were required to maintain sleep in rats. Like other general anesthetics, the concentration-EEG effect relationship of propofol is biphasic. At a propofol concentration of 0.6 (+/- 35%) microg/mL, the number of EEG waves/s was maximal at 175% of baseline awake state. Further increases in the concentration of propofol depressed EEG activity until complete suppression occurred at 7 (+/- 22%) microg/mL.

A pharmacokinetically based propofol dosing strategy for sedation of the critically ill, mechanically ventilated pediatric patient

OBJECTIVE

To assess the pharmacokinetics and pharmacodynamics of propofol sedation of critically ill, mechanically ventilated infants and children.

DESIGN

A prospective clinical study.

SETTING

A pediatric intensive care unit (ICU) in a university hospital.

PATIENTS

Clinically stable, mechanically ventilated pediatric patients were enrolled into our study after residual sedative effects from previous sedative therapy dissipated and the need for continued sedation therapy was defined. Patients were generally enrolled just before extubation.

INTERVENTIONS

A stepwise propofol dose escalation scheme was used to determine the steady-state propofol dose necessary to achieve optimal sedation, as defined by the COMFORT scale, a validated scoring system which reliably and reproducibly quantifies a pediatric patient's level of distress. When in need of continued sedation, study patients received an initial propofol loading dose of 2.5 mg/kg and were immediately started on a continuous propofol infusion of 2.5 mg/kg/hr. The propofol infusion rate was adjusted and repeat loading doses were administered, if needed, using a coordinated dosing scheme to maintain optimal sedation for a 4-hr steady-state period. After 4 hrs of optimal sedation, the propofol infusion was discontinued and simultaneous blood sampling and COMFORT scores were obtained until the patient recovered. Additional blood samples were obtained up to 24 hrs after stopping the infusion and analyzed for propofol concentration by high-performance liquid chromatography.

MEASUREMENTS AND MAIN RESULTS

Twenty-nine patients were enrolled into this study. One patient was withdrawn from this study because of an acute decrease in blood pressure occurring with the first propofol loading dose; 28 patients completed the study. All patients were sedated immediately after the first 2.5-mg/kg propofol loading dose. Eight patients were adequately sedated with the starting propofol dose regimen, whereas five patients required downward dose adjustment and 11 patients required dosage increases to achieve optimal sedation. Four patients failed to achieve adequate sedation after five dose escalations and the drug was stopped. Recovery from sedation (COMFORT score of > or = 27) after stopping the propofol infusion was rapid, averaging 15.5 mins in 23 of 24 evaluable patients. In 13 patients who were extubated after stopping the propofol infusion, the time to extubation was also rapid, averaging 44.5 mins. Determination of the blood propofol concentration at the time of recovery from propofol sedation was possible in 15 patients. The blood propofol concentration was variable, ranging between 0.262 to 2.638 mg/L but < or = 1 mg/L in 13 of 15 patients. Similarly, tremendous variation was observed in propofol pharmacokinetics. Propofol disposition was best characterized by a three-compartment model with initial rapid distribution into a small central compartment, V1, and two larger compartments, V2 and V3, which are two-and 20-fold greater in volume, respectively, than V1. Redistribution from V2 and V3 into V1 was much slower than ingress, underscoring the importance of the propofol concentration in V1 as reflective of the drug's sedative effect. Propofol was well tolerated. Two patients experienced an acute decrease in blood pressure which resolved without treatment.

CONCLUSIONS

We conclude that a descending propofol dosing strategy, which maintains the propofol concentration constant in the central compartment (V1) while drug accumulates in V2 and V3 to intercompartmental steady-state, is necessary for effective propofol sedation in the pediatric ICU. Our proposed dosing scheme to achieve and maintain the blood propofol concentration of 1 mg/L would appear effective for sedation of most clinically stable, mechanically ventilated pediatric patients.

Changes in intraocular pressure during low dose intravenous sedation with propofol before cataract surgery

AIMS

This study examined the effects on intraocular pressure, pulse rate, and blood pressure of low dose intravenous sedation with propofol.

METHODS

Twenty adult patients who were scheduled to undergo cataract surgery were given a single intravenous bolus (0.98 (SEM 0.4) mg/kg) of propofol for sedation before administering the local anaesthetic for cataract surgery. A small intravenous dose of lignocaine was the only other anaesthetic or sedative agent given. The intraocular pressure in the non-surgery eye, the pulse rate, and the blood pressure were measured before and after propofol induction.

RESULTS

Compared with the preinduction baseline, there was a 17% to 27% (from 16.2 (0.7) mm Hg to 11.8 (0.7) mm Hg) decrease in intraocular pressure after propofol induction. A significant decrease in intraocular pressure occurred within the first minute and was still evident at 7 minutes when the measurements were stopped. There was also a 7%-12% increase in pulse rate during the first 4 minutes, a 12% decrease in mean systolic blood pressure, and a 7% decrease in mean diastolic blood pressure from baseline after propofol induction.

CONCLUSION

A single low dose bolus of propofol used for sedation before cataract surgery caused a moderate reduction in intraocular pressure with minimal, easily managed side effects.

[Use of Diprivan for digestive system endoscopy]

After evaluation of the patient's clinical condition and appropriate premedication is seems reasonable to suggest for: 1. Endoscopic procedures involving the gastro-intestinal tract: slow, titrated induction, using 0.5 to 1 mg.kg-1 of propofol, until the required level of sedation has been achieved; this may or not be preceded by the injection of a low dose of midazolam (0.02 to 0.03 mg.kg-1) or of alfentanil (5 micrograms.kg-1); maintenance is achieved by bolus injections of 20 mg (up to 0.5 mg.kg-1); maintenance of spontaneous ventilation, with oxygen administration is the rule; SpO2 is monitored routinely; anaesthesia has to be performed according to the recommendations of the French Society of Anaesthesia and Intensive Care (SFAR) and the anaesthetist must be prepared to manage any incident during the endoscopy and the recovery period. 2. Procedures involving the biliary tract and the oesophagus, which require deeper anaesthesia: induction should again be titrated using a very slow infusion, with doses ranging from 0.9 to 2.2 mg.kg-1); the maintenance requires a continuous infusion, doses ranging from 4 to 6 mg.kg-1.h-1 when propofol is administered alone and from 4 to 12 mg.kg-1.h-1 when combined with an opioid; continuous oxygenation is necessary using a nasal airway; the need for intubation depends on the type of procedure and the status of the patient; the same monitoring devices and similar safety measures are required during and after procedure as for any anaesthetic or sedation, especially when it is performed in day-case patients or outside the operating theatre.