Outbreak of severe sepsis due to contaminated propofol: lessons to learn

Lethal Gram-negative sepsis in healthy pigs during anaesthesia with contaminated propofol

Two healthy Landrace pigs anaesthetized with propofol suffered rapid onset of fatal sepsis. Clinical signs included severe arterial hypotension, loss of peripheral oxygenation, low end-tidal CO2, clinical onset of pulmonary oedema and cardiac dysfunction. Gross and histopathological examination revealed loss of vascular integrity with severe lung oedema and congestion, haemorrhages in several organs and fluid leakage into body cavities. Large numbers of Gram-negative bacteria, primarily Klebsiella sp., were present in the anaesthetic infusion containing propofol and were also cultured from internal organs of both pigs. The propofol was likely contaminated by bacteria after inappropriate handling and storage in the operating room. This report illustrates the potential for severe nosocomial infection when applying propofol in animals and humans and may serve as a reminder of the importance of strict aseptic practice in general, and specifically in the handling of this anaesthetic agent.

Nanoencapsulation of general anaesthetics

General anaesthetics are routinely used to sedate patients during prolonged surgeries and administered via intravenous injection and/or inhalation. All anaesthetics have short half-lives, hence the need for their continuous administration. This causes several side effects such as pain, vomiting, nausea, bradycardia, and on rare occasions death post-administration. Several clinical trials studied the synergetic effect of a combination of anaesthetic drugs to reduce the drug load. Another solution is to encapsulate anaesthetics in nanoparticles to reduce their dose and side effects as well as achieve their sustained release manner. Different types of nanoparticles were developed as carriers of intravenous and intrathecal anaesthetics generating platforms which facilitate drug transport across the blood-brain barrier (BBB). Nanocarriers encapsulating common anaesthetic drugs such as propofol, etomidate, and ketamine were developed and characterized in terms of size, stability, onset and duration of loss of right reflex, and tolerance to pain in small animal models. The review discusses the types of nanocarriers used to reduce the side effects of the anaesthetic drugs while prolonging the sedation time. More rigorous studies are still required to evaluate the nanocarrier formulations regarding their ability to deliver anaesthetic drugs across the BBB, safety, and finally applicability in clinical settings.

The Additional Cost of Perioperative Medication Errors

ABSTRACT

The purpose of this report was to estimate the additional annual cost to the U.S. healthcare system attributable to preventable medication errors (MEs) in the operating room. The ME types were iteratively grouped by their associated harm (or potential harm) into 13 categories, and we determined the incidence of operations involving each ME category (number of operations involving each category/total number of operations): (1) delayed or missed required perioperative antibiotic (1.4% of operations); (2) prolonged hemodynamic swings (7.6% of operations); (3) untreated postoperative pain >4/10 (18.9% of operations); (4) residual neuromuscular blockade (2.9% of operations); (5) oxygen saturation <90% due to ME (1.8% of operations); (6) delayed emergence (1.1% of operations); (7) untreated new onset intraoperative cardiac arrhythmia (0.72% of operations); (8) medication documentation errors (7.6% of operations); (9) syringe swaps (5.8% of operations); (10) presumed hypotension with inability to obtain a blood pressure reading (2.2% of operations); (11) potential for bacterial contamination due to expired medication syringes (8.3% of operations); (12) untreated bradycardia <40 beats/min (1.1% of operations); and (13) other (13.0% of operations). Through a PubMed search, we determined the likelihood that the ME category would result in downstream patient harm such as surgical site infection or acute kidney injury, and the additional fully allocated cost of care (in 2021 U.S. dollars) for each potential downstream patient harm event. We then estimated the cost of the MEs across the U.S. healthcare system by scaling the number of MEs to the total number of annual operations in the United States (N = 19,800,000). The total estimated additional fully allocated annual cost of care due to perioperative MEs was $5.33 billion U.S. dollars.

[Sepsis outbreak associated with use of contaminated propofol: A new case series and literature review]

INTRODUCTION

Propofol is the most commonly used hypnotic agent for the induction and maintenance of general anesthesia. Due to its lipid-based composition, propofol requires a strict handling protocol to avoid an increased risk of extrinsic contamination.

METHODS

On September 09, 2021, 05 patients with post-anaesthetic Enterobacter cloacae infections were identified in the pediatric exploration department of the Hassan II University Hospital of Fez in Morocco. We describe the investigation into this outbreak. All patient medical records were reviewed to determine patient characteristics and potential risk factors. For the literature review, we identified relevant articles by searching PubMed, Medline, Embase and Science Direct.

RESULTS

Our study included five patients, 80% were boys. The average age was 4.6 years (1-7 years), with no medical history. All five patients underwent exploratory procedures. Immediately after the procedures, all 5 patients presented with chills, tachycardia and fever in the same order of admission. They were all admitted to hospital and blood samples were taken. Blood cultures were positive for E. cloacae. All patients had elevated levels of C-reactive protein (CRP) and an elevated white blood cell count. Bacteriological investigation revealed that the infection was caused by extrinsic contamination of the intravenous anesthetic propofol by E. cloacae.

CONCLUSION

Fatal infections due to contaminated drugs, including propofol, have been reported worldwide. Propofol is a potential source of infections due to its lipophilic nature which promotes microbial growth. This probably remains an underestimated problem that deserves awareness for early recognition.

Propofol and survival: an updated meta-analysis of randomized clinical trials

BACKGROUND

Propofol is one of the most widely used hypnotic agents in the world. Nonetheless, propofol might have detrimental effects on clinically relevant outcomes, possibly due to inhibition of other interventions' organ protective properties. We performed a systematic review and meta-analysis of randomized controlled trials to evaluate if propofol reduced survival compared to any other hypnotic agent in any clinical setting.

METHODS

We searched eligible studies in PubMed, Google Scholar, and the Cochrane Register of Clinical Trials. The following inclusion criteria were used: random treatment allocation and comparison between propofol and any comparator in any clinical setting. The primary outcome was mortality at the longest follow-up available. We conducted a fixed-effects meta-analysis for the risk ratio (RR). Using this RR and 95% confidence interval, we estimated the probability of any harm (RR > 1) through Bayesian statistics. We registered this systematic review and meta-analysis in PROSPERO International Prospective Register of Systematic Reviews (CRD42022323143).

RESULTS

We identified 252 randomized trials comprising 30,757 patients. Mortality was higher in the propofol group than in the comparator group (760/14,754 [5.2%] vs. 682/16,003 [4.3%]; RR = 1.10; 95% confidence interval, 1.01-1.20; p = 0.03; I2 = 0%; number needed to harm = 235), corresponding to a 98.4% probability of any increase in mortality. A statistically significant mortality increase in the propofol group was confirmed in subgroups of cardiac surgery, adult patients, volatile agent as comparator, large studies, and studies with low mortality in the comparator arm.

CONCLUSIONS

Propofol may reduce survival in perioperative and critically ill patients. This needs careful assessment of the risk versus benefit of propofol compared to other agents while planning for large, pragmatic multicentric randomized controlled trials to provide a definitive answer.

Comparative growth dynamics of bacterial and fungal contaminants in bupivacaine liposomal injectable suspension, bupivacaine 0.5%, and propofol

OBJECTIVE

To determine whether bupivacaine liposomal injectable suspension (BLIS) supports microbial growth when artificially inoculated and to evaluate liposomal stability in the face of this extrinsic contamination as evidenced by changes in free bupivacaine concentrations.

STUDY DESIGN

A randomized, prospective in vitro study in which three vials of each BLIS, bupivacaine 0.5%, and propofol were individually inoculated with known concentrations of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans (n = 36) to quantify bacterial and fungal growth was conducted. Over 120 hours, aliquots from contaminated vials were withdrawn, plated, and incubated to determine microbial concentrations. High-pressure liquid chromatography (HPLC) was used to evaluate free bupivacaine concentrations over time in BLIS. Data were analyzed using a mixed effects model with multiple comparisons.

SAMPLE POPULATION

Twelve vials of each BLIS, bupivacaine 0.5%, and propofol.

RESULTS

BLIS did not support significant growth of Staphylococcus aureus or Candida albicans at any time. BLIS supported significant growth of Escherichia coli and Pseudomonas aeruginosa beginning at the 24 hour time point. Bupivacaine 0.5% did not support significant growth of any organisms. Propofol supported significant growth of all organisms. Free bupivacaine concentrations changed minimally over time.

CONCLUSION

Bacterial and fungal contaminant growth in artificially inoculated BLIS is organism dependent. BLIS supports significant growth of Escherichia coli and Pseudomonas aeruginosa. Extra-label handling of BLIS should only be undertaken with caution and with adherence to strict aseptic technique.

Process Analytical Technology for the Production of Parenteral Lipid Emulsions According to Good Manufacturing Practices

The good manufacturing practices (GMP) and process analytical technology (PAT) initiatives of the US Food and Drug Administration, in conjunction with International Council for Harmonisation (ICH) quality guidelines Q8, Q9, and Q10, ensure that manufacturing processes for parenteral formulations meet the requirements of increasingly strict regulations. This involves the selection of suitable process analytics for process integration and aseptic processing. In this article, we discuss the PAT requirements for the GMP-compliant manufacturing of parenteral lipid emulsions, which can be used for clinical nutrition or for the delivery of lipophilic active ingredients. There are risks associated with the manufacturing processes, including the potential for unstable emulsions and the formation of large droplets that can induce embolisms in the patient. Parenteral emulsions are currently monitored offline using a statistical approach. Inline analytics, supplemented by measurements of zeta potential, could minimize the above risks. Laser scanning technology, ultrasound attenuation spectroscopy, and photo-optical sensors combined with image analysis may prove to be useful PAT methods. In the future, these technologies could lead to better process understanding and control, thus improving production efficiency.

Outbreak of Sepsis Following Surgery: Utilizing 16S RNA Sequencing To Detect the Source of Infection

Background

Nosocomial infections are a significant health concern. Following surgery, infections are most commonly associated with the surgical site, yet there are other potential sources for infections after surgical interventions. Identification of the source of infections can be very challenging.

Methodology

An outbreak of postoperative infections following surgery led to intensive care unit (ICU) admission of patients immediately after the surgical procedure. The blood cultures of two patients were positive for Citrobacter freundii. The only connection between all cases was the anesthesiologist. An epidemiological inquiry could not definitively identify the source of the outbreak. Therefore, we utilized an RNA sequencing technique to evaluate the microbiome of the anesthesiologist and compared the results to bacteria cultured from the bloodstream of the two patients.

Results

The anesthesiologist’s microbiome contained amplicons that were identical to those of the bacteria in the patient’s bloodstream. Because Citrobacter freundii is an uncommon source of bloodstream infections, and in the normal human microbiome, the results establish the source of a cluster of infections to the anesthesiologist.

Conclusions

In cases of nosocomial infections, when conventional microbiological techniques do not clearly establish the source of the infection, using 16S RNA sequencing should be considered.

[An analysis of medication errors in patients admitted to surgery rooms and post-anesthetic recovery at a high-complexity hospital in Bogota, Colombia]

Medication errors represent one of the main causes of incidents and adverse events during the perioperative period. Therefore, this study analyzes errors before, during, and after the administration of general anesthesia for abdominal surgery at a high-complexity hospital in Bogota, Colombia. A descriptive cross-sectional study was conducted with 390 patients between January and September 2019. Of the 3,677 medication administrations, some type of error was made in 60% of cases, mostly in emergency surgeries. The pharmacological group with the most errors was general anesthetics, with 32%. All identified errors constituted situations with harm potential, indicating the need to promote the standardization of activities involving the use of medications and a culture of healthcare safety in order to avoid adverse events.

Investigation of Variables Associated with Surgical Site Infection following the Management of Canine Cranial Cruciate Ligament Rupture with a Lateral Fabellotibial Suture

OBJECTIVE

 This study investigated variables associated with surgical site infection (SSI) in dogs with cranial cruciate ligament rupture managed with stifle joint examination and lateral fabellotibial suture stabilization.

STUDY DESIGN

 A retrospective study of dogs that had stifle arthroscopy, stifle arthrotomy, or a combination of both, followed by lateral fabellotibial suture stabilization for cranial cruciate ligament rupture. All cases had a minimum follow-up of 90 days. Lameness grades were recorded preoperatively, and at 6-week and final follow-up.

RESULTS

 One hundred fifty procedures in 130 dogs met the inclusion criteria. Overall, SSI rate was 17.3% and removal of the lateral fabellotibial suture was performed in 53% of SSI. Multivariable analysis showed significant association between SSI and bodyweight (p = 0.013), and induction using propofol (p = 0.029). Multilevel ordinal logistic regression analysis showed a greater proportion of dogs had a higher lameness grade at 6-week (p = 0.021) and final follow-up (p = 0.002) assessments in the infected compared with non-infected dogs.

CONCLUSION

 Our study demonstrated a higher SSI incidence than previously reported in dogs undergoing a lateral fabellotibial suture for cranial cruciate ligament rupture. Bodyweight and induction with propofol were identified as significant risk factors for postoperative SSI. Owners could be advised of an increased SSI risk in larger dogs and consideration should be given to selection of induction agent. Dogs that develop an SSI have a worse lameness grade at 6-week and final follow-up.

Survival of Staphylococcus epidermidis in Propofol and Intralipid in the Dead Space of Intravenous Injection Ports

We tested whether propofol or Intralipid inoculated with Staphylococcus epidermidis would promote bacterial growth within an intravenous (IV) injection hub, a site prone to bacterial contamination. In tubes incubated under optimal conditions, S epidermidis exhibited growth in Intralipid, but not in propofol. In contrast, within the IV hub incubated with either propofol or intralipid at room temperature, S epidermidis bacterial numbers declined with time, and virtually no contamination remained after 12 hours. These data suggest that certain IV lines are inhospitable for S epidermidis.

Serratia marcescens sepsis outbreak caused by contaminated propofol

We presented a sepsis outbreak caused by Serratia marcescens from contaminated propofol to raise awareness. Three patients had sepsis syndrome after chest surgery. Isolation of S marcescens from patients' respiratory and blood samples alerted us to a possible outbreak. Four syringes filled with propofol and 1 saline solution yielded S marcescens. Nine of 10 isolates from samples of patients and environment genotyped by pulsed-field gel electrophoresis were the same. Disobeying aseptic injection rules of propofol is still causing outbreaks.

A systematic review and meta-analysis of microbial contamination of parenteral medication prepared in a clinical versus pharmacy environment

PURPOSE

Preparation of parenteral medication in hospitals is a complex process with a risk of microbial contamination of the product, especially when inappropriately prepared. Contaminated parenteral medications can cause severe complications to patients and increase morbidity in hospitals. The aim of this literature review is to systematically evaluate the contamination rate of parenteral medications in hospitals prepared in a pharmacy environment and a clinical environment.

METHODS

A literature search of PubMed and EMBASE from 2000 to 2018 was performed. Two different environments where preparation may be carried out were defined. Point estimates and 95% confidence intervals for contamination rates were calculated for each environment of medication preparation. The meta-analysis was performed using a random effects model.

RESULTS

The contamination rates in the clinical environment (n = 13 studies) varied between 1.09 and 20.70%. In the pharmacy environment (n = 5), all contamination rates were 0.00% except for one study (0.66%). The point estimates (random effect model) for the overall contamination rate of doses prepared in the clinical environment was 7.47% (5.16-9.79%), and 0.08% for doses prepared in the pharmacy environment. The point estimates (random effect model) for the overall contamination rate of doses prepared by nursing/ medical staff was 7.85% (5.18-10.53%), and 0.08% for doses prepared by pharmacy staff.

CONCLUSIONS

Significantly higher contamination rates were found for the preparation of parenteral medication in the clinical environment compared to pharmacy environment. In accordance with recent guidance, the almost 100-fold higher changes of contamination when reconstitution is performed in the clinical environment should urge hospitals to review their reconstitution process and apply risk-reducing measures to improve patient safety of parenteral therapy.

Outbreak of bacterial endocarditis associated with an oral surgery practice: New Jersey public health surveillance, 2013 to 2014

BACKGROUND

In October and November 2014, the New Jersey Department of Health received reports of 3 patients who developed Enterococcus faecalis endocarditis after undergoing surgical procedures at the same oral surgery practice in New Jersey. Bacterial endocarditis is an uncommon but life-threatening condition; 3 patients with enterococcal endocarditis associated with a single oral surgery practice is unusual. An investigation was initiated because of the potential ongoing public health risk.

METHODS

Public health officials conducted retrospective surveillance to identify additional patients with endocarditis associated with the practice. They interviewed patients using a standardized questionnaire. An investigative public health team inspected the office environment, interviewed staff, and reviewed medical records.

RESULTS

Public health officials identified 15 confirmed patients with enterococcal endocarditis of those patients who underwent procedures from December 2012 through August 2014. Among these patients, 12 (80%) underwent cardiac surgery. One (7%) patient died from complications of endocarditis and subsequent cardiac surgery. Breaches of recommended infection prevention practices were identified that might have resulted in transmission of enterococci during the administration of intravenous sedation, including failure to perform hand hygiene and failure to maintain aseptic technique when performing procedures and handling medications.

CONCLUSIONS

This investigation highlights the importance of adhering to infection prevention recommendations in dental care settings. No additional patients with endocarditis were identified after infection prevention and control recommendations were implemented.

PRACTICAL IMPLICATIONS

Infection prevention training should be emphasized at all levels of professional dental training. All dental health care personnel establishing intravenous treatment and administering intravenous medications should be trained in safe injection practices.

Infectious Disease Risk Associated with Contaminated Propofol Anesthesia, 1989-2014(1)

Transmission of illness to 144 patients, resulting in 10 deaths, has been linked to extrinsic contamination.

Administration of propofol, the most frequently used intravenous anesthetic worldwide, has been associated with several iatrogenic infections despite its relative safety. Little is known regarding the global epidemiology of propofol-related outbreaks and the effectiveness of existing preventive strategies. In this overview of the evidence of propofol as a source of infection and appraisal of preventive strategies, we identified 58 studies through a literature search in PubMed, Embase, and Lilacs for propofol-related infections during 1989–2014. Twenty propofol-related outbreaks have been reported, affecting 144 patients and resulting in 10 deaths. Related factors included reuse of syringes for multiple patients and prolonged exposure to the environment when vials were left open. The addition of antimicrobial drugs to the emulsion has been instituted in some countries, but outbreaks have still occurred. There remains a lack of comprehensive information on the effectiveness of measures to prevent future outbreaks.

Ralstonia mannitolilytica infections in an oncologic day ward: description of a cluster among high-risk patients

BACKGROUND

Ralstonia spp, an environmental microorganism, has been occasionally associated with healthcare infections. The aim of this study was to investigate an outbreak caused by Ralstonia mannitolilytica in oncology patients.

METHODS

Case definition: Oncology outpatients attending a day ward, with positive blood and/or central venous catheter (CVC) culture for Ralstonia spp from September 2013 - June 2014. We analysed medical records, procedures and environmental samples. R. mannitolilytica was identified by 16S rRNA sequencing, and typed by Pulsed Field Gel Electrophoresis (PFGE); resistance to carbapenemes was investigated by phenotypic and molecular methods.

RESULTS

The patients (N = 22) had different malignancies and received different therapy; all had a CVC and 16 patients presented chills and/or fever. R. mannitolilytica was isolated from both blood and CVC (n = 12) or only blood (n = 6) or CVC tips (n = 4). The isolates had indistinguishable PFGE profile, and showed resistance to carbapenems. All the isolates were negative for carbapenemase genes while phenotypic tests suggests the presence of an AmpC β-lactamase activity,responsible for carbapenem resistance. All patients had had CVC flushed with saline to keep the venous access pervious or before receiving chemotherapy at various times before the onset of symptoms. After the first four cases occurred, the multi-dose saline bottles used for CVC flushing were replaced with single-dose vials; environmental samples were negative for R. mannitolilytica.

CONCLUSIONS

Although the source of R. mannitolilytica remains unidentified, CVC flushing with contaminated saline solution seems to be the most likely origin of R. mannitolilytica CVC colonization and subsequent infections. In order to prevent similar outbreaks we recommend removal of any CVC that is no longer necessary and the use of single-dose solutions for any parenteral treatment of oncology patients.

Bacterial contamination of propofol vials used in operating rooms of a third-level hospital

We found a 6.1% bacterial contamination rate among 198 propofol vials collected after clinical use in 12 operating rooms of a high-complexity hospital in Cali, Colombia. Some propofol vials were used for extended periods (up to 72 hours), and only 26.1% of vials were punctured once. Median time of use, although not statistically significant, was higher in positive samples (7.2 vs 3.5 hours, P = .08). Education on the topic should stress that vials are single-patient use and must be immediately discarded after use.

Leaving more than your fingerprint on the intravenous line: a prospective study on propofol anesthesia and implications of stopcock contamination

BACKGROUND

Acute care handling of IV stopcocks during anesthesia and surgery may result in contaminated IV tubing sets. In the context of widespread propofol use, a nutrient-rich hypnotic drug, we hypothesized that propofol anesthesia increases bacterial contamination of IV stopcocks and may compromise safety of IV tubing sets when continued to be used after propofol anesthesia.

METHODS

We conducted an in vitro trial by collecting IV tubing sets at the time of patient discharge from same-day ambulatory procedures performed with and without propofol anesthesia. These extension sets were then held at room temperature for 6, 24, or 48 hours. We cultured 50 samples at each interval for both cohorts. Quantitative cultures were done by aspirating the IV stopcock dead space and plating the aspirate on blood agar for colony count and speciation.

RESULTS

Positive bacterial counts were recovered from 17.3% of propofol anesthesia stopcocks (26/150) and 18.6% of nonpropofol stopcocks (28/150). At 6 hours, the average bacterial counts from stopcocks with visible residual propofol was 44 colony forming units (CFU)/mL, compared with 41 CFU/mL with no visible residual propofol and 37 CFU/mL in nonpropofol anesthesia stopcocks. There was a 100-fold increase in bacterial number in contaminated stopcock dead spaces at 48 hours after propofol anesthesia. This difference remained significant when comparing positive counts from stopcocks with no visible residual propofol and nonpropofol anesthesia (P = 0.034).

CONCLUSIONS

There is a covert incidence and degree of IV stopcock bacterial contamination during anesthesia which is aggravated by propofol anesthetic. Propofol anesthesia may increase risk for postoperative infection because of bacterial growth in IV stopcock dead spaces.

Investigating the impact of clinical anaesthetic practice on bacterial contamination of intravenous fluids and drugs

Syringes (N = 426), ventilator machine swabs (N = 202) and intravenous (IV) fluid administration sets (N = 47) from 101 surgical cases were evaluated for bacterial contamination. Cultures from the external surface of syringe tips and syringe contents were positive in 46% and 15% of cases, respectively. The same bacterial species was cultured from both ventilator and syringe in 13% of cases, and was also detected in the IV fluid administration set in two cases. A significant association was found between emergency cases and contaminated syringes (odds ratio 4.5, 95% confidence interval 1.37-14.8; P = 0.01). Other risk factors included not using gloves and failure to cap syringes.

[A guide to successful public relations for hospitals and emergency medical services]

Tragic accidents, e.g. involving celebrity patients or severe incidents in hospital occur suddenly without any advance warning, often produce substantial interest by the media and quickly overburden management personnel involved in both hospitals and emergency medical services. While doctors, hospitals and emergency medical services desire objective media reports, the media promote emotionalized and dramatized reports to ensure maximum attention and circulation. When briefing the media, the scales may quickly tilt from professional, well-deliberated information to unfortunate, often unintended disinformation. Such phenomena may result in continuing exaggerated reports in the tabloid press, which in the presence of aggressive lawyers and a competitive hospital environment can turn into image and legal problems. In this article, several aspects are discussed in order to achieve successful public relations.Interviews should be given only after consultation with the responsible press officer and the director of the respective department or hospital director. Requests for information by the media should always be answered as otherwise one-sided, unintentional publications can result that are extremely difficult to correct later. One should be available to be contacted easily by journalists, regular press conferences should be held and critics should be taken seriously and not be brushed off. Questions by journalists should be answered in a timely manner as journalists are continuously under time pressure and do not understand unnecessary delays. Information for the media should always be provided at the same time, no publication should be given preference and an absolutely current list of E-mail contacts is required. When facing big events a press conference is preferred as many questions can be answered at once. Always be well prepared for an interview or even for just a statement. Each interview should be regarded as an opportunity to put a story forward which you wanted to do for a long time and your message should not contain more than three main points.Each hospital or emergency medical service should have a professional department for public relations, an exact knowledge of the regional and national media and strategies how to handle an incident that is of interest for the media. The media should be provided with information not only when a negative incident has happened but should be provided with regular positive messages as well. An interview must be carefully prepared to achieve a good image.

Pharmacokinetics and pharmacodynamics of propofol with or without 2% benzyl alcohol following a single induction dose administered intravenously in cats

OBJECTIVE

To compare the pharmacokinetics and pharmacodynamics of propofol with or without 2% benzyl alcohol administered intravenously (IV) as a single induction dose in cats.

STUDY DESIGN

Prospective experimental study.

ANIMALS

Six healthy adult cats, three female intact, three male castrated, weighing 4.8 ± 1.8 kg.

METHODS

Cats received 8 mg kg(-1) IV of propofol (P) or propofol with 2% benzyl alcohol (P28) using a randomized crossover design. Venous blood samples were collected at predetermined time points to 24 hours after drug administration to determine drug plasma concentrations. Physiologic and behavioral variables were also recorded. Propofol and benzyl alcohol concentrations were determined using high pressure liquid chromatography with fluorescence detection. Pharmacokinetic parameters were described using a 2-compartment model. Pharmacokinetic and pharmacodynamic parameters were analyzed using repeated measures anova (p < 0.05).

RESULTS

Plasma concentrations of benzyl alcohol were below the lower limits of quantification (LLOQ) at all time points for two of the six cats (33%), and by 30 minutes for the remaining four cats. Propofol pharmacokinetics, with or without 2% benzyl alcohol, were characterized by rapid distribution, a long elimination phase, and a large volume of distribution. No differences were noted between treatments with the exception of clearance from the second compartment (CLD2), which was 23.6 and 38.8 mL kg(-1)  minute(-1) in the P and P28 treatments, respectively. Physiologic and behavioral variables were not different between treatments with the exception of heart rate at 4 hours post administration.

CONCLUSIONS AND CLINICAL RELEVANCE

The addition of 2% benzyl alcohol as a preservative minimally altered the pharmacokinetics and pharmacodynamics of propofol 1% emulsion when administered as a single IV bolus in this group of cats. These data support the cautious use of propofol with 2% benzyl alcohol for induction of anesthesia in healthy cats.

The antimicrobial effects of ketamine combined with propofol: An in vitro study

BACKGROUND AND OBJECTIVES

Ketamine and propofol are the general anesthetics that also have antimicrobial and microbial growth-promoting effects, respectively. Although these agents are frequently applied together during clinical use, there is no data about their total effect on microbial growth when combined. In this study, we investigated some organisms' growth in a ketamine and propofol mixture.

METHOD

We used standard strains including Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans in this study. Time-growth analysis was performed to assess microbial growth rates in 1% propofol. Antimicrobial activity of ketamine, alone and in propofol was studied with microdilution method.

RESULTS

In propofol, studied strains grew from 10(3)-10(4) cfu/mL to ≥10(5) cfu/mL concentrations within 8-16 hours depending on the type of organism. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) (for candida, minimal fungicidal concentration) of ketamine were determined as follows (MIC, MBC): E.coli 312.5, 312.5 μg/mL; S.aureus 19.5, 156 μg/mL; P.aeruginosa 312.5, 625 μg/mL; and C.albicans 156, 156 μg/ml. In ketamine+propofol mixture, ketamine exhibited antimicrobial activity to E.coli, P.aeruginosa and C.albicans as MBCs at 1250, 625 and 625 μg/mL, respectively. Growth of S. aureus was not inhibited in this mixture (ketamine concentration=1250 μg/mL).

CONCLUSION

Ketamine has sustained its antimicrobial activity in a dose-dependent manner against some organisms in propofol, which is a strong microbial growth-promoting solution. Combined use of ketamine and propofol in routine clinical application may reduce the risk of infection caused by accidental contamination. However, one must keep in mind that ketamine cannot reduce all pathogenic threats in propofol mixture.

Serratia infections: from military experiments to current practice

Serratia species, in particular Serratia marcescens, are significant human pathogens. S. marcescens has a long and interesting taxonomic, medical experimentation, military experimentation, and human clinical infection history. The organisms in this genus, particularly S. marcescens, were long thought to be nonpathogenic. Because S. marcescens was thought to be a nonpathogen and is usually red pigmented, the U.S. military conducted experiments that attempted to ascertain the spread of this organism released over large areas. In the process, members of both the public and the military were exposed to S. marcescens, and this was uncovered by the press in the 1970s, leading to U.S. congressional hearings. S. marcescens was found to be a certain human pathogen by the mid-1960s. S. marcescens and S. liquefaciens have been isolated as causative agents of numerous outbreaks and opportunistic infections, and the association of these organisms with point sources such as medical devices and various solutions given to hospitalized patients is striking. Serratia species appear to be common environmental organisms, and this helps to explain the large number of nosocomial infections due to these bacteria. Since many nosocomial infections are caused by multiply antibiotic-resistant strains of S. marcescens, this increases the danger to hospitalized patients, and hospital personnel should be vigilant in preventing nosocomial outbreaks due to this organism. S. marcescens, and probably other species in the genus, carries several antibiotic resistance determinants and is also capable of acquiring resistance genes. S. marcescens and S. liquefaciens are usually identified well in the clinical laboratory, but the other species are rare enough that laboratory technologists may not recognize them. 16S rRNA gene sequencing may enable better identification of some of the less common Serratia species.