Bacterial contamination of an anesthetic agent

Irreversible electroporation for microbial control of drugs in solution

The purpose of this study was to examine the feasibility of using irreversible electroporation (IRE) as a non-chemical method for eliminating microorganisms of liquid drugs. The studied drug was a topical ophthalmic medication, a pharmaceutical field in which the problem of microbial contamination has not yet been adequately solved, especially in the case of eye drops prescribed for chronic use. Commercially available Hylo-Comod preservative-free eye drop solution was subjected to contamination with Escherichia coli bacteria (10(6) colony forming units/mL). Electroporation parameters for bacterial control were investigated by comparing the effects of electrical fields of 5.4, 7.2, and 10 kV/cm, delivered as 100-micros square pulses at 1 Hz in sequences of 10 pulses, 20 pulses, or 20 pulses delivered as four sets of five pulses with 1-min intervals between each set. Microorganism survival after treatment was determined by pour plate counting. Effects of the treatment parameters on temperature and pH were recorded. Bacterial survival was lowest (0.14% +/- 0.03%) after application of 20 pulses delivered as four separate sets. With that application mode, the solution remained at pH 7.5 and the temperature rose to 35.6 degrees +/- 0.2 degrees C. Because IRE can be efficiently delivered under conditions that avoid the potentially deleterious effects of electrical pulses on temperature and pH, it appears to be a feasible method for bacterial control of drugs in solution. The principles established in this study can be applied to any drug in solution and optimized individually according to the solution's composition.

Prevention of intravenous drug incompatibilities in an intensive care unit

PURPOSE

The frequency of drug administration errors and incompatibilities between intravenous drugs before and after an intervention in an intensive care unit (ICU) is discussed.

METHODS

Critically ill adult patients with intoxications, multiorgan failure, and serious infections were included in a retrospective analysis and in a prospective two-period, one-sequence study. In the retrospective analysis, the most frequent brands of i.v. medications used in the ICU of a gastroenterologic department in a teaching hospital were identified. All possible combinations and resulting incompatibilities were defined. Based on the results, a standard operating procedure (SOP) was established to prevent frequent and well-documented incompatibilities among i.v. medications. In the prospective study, trained pharmacy students assessed incompatible coinfusions before and after SOP implementation.

RESULTS

In the retrospective analysis of 100 patients, 3617 brands of drug pairs were potentially given concurrently through one i.v. line and 7.2% of the drug pairs were incompatible. Antibiotics, such as piperacillin-tazobactam and imipenem-cilastatin, were the most frequent incompatible drug pairs. The newly developed SOP mandated that administration of these drugs be separated from all other drugs and suggested the use of an idle i.v. line for infusion whenever possible. In the prospective study of 50 patients, the frequency of incompatible drug pairs was reduced by the time of intervention from 5.8% to 2.4%. Incompatible drug pairs that were governed by the new SOP were reduced from 1.9% to 0.5%.

CONCLUSION

Administration of incompatible i.v. drugs in critically ill patients was frequent but significantly reduced by procedural interventions with SOPs.

Current strategies for prevention of surgical site infections

Surgical site infections (SSIs) are a common complication that follows all types of operative procedures. These infections are usually caused by the exogenous and endogenous microorganisms that enter the operative wound during the course of surgery. The general and procedure-specific risk factors for the development of SSI have been identified and are discussed in this article. Factors that influence the SSI rate and the current strategies for prevention of SSIs are also presented. Emphasis is placed on the efficacious use of antibiotic prophylaxis in surgery. A discussion of the principles of antibiotic prophylaxis, including choice of agents, route of administration, and timing, is offered. It appears that the use of less invasive laparoscopic surgical approaches, as practiced widely today, will be associated with an overall decreased incidence of SSI.

The EmulSiv filter removes microbial contamination from propofol but is not a substitute for aseptic technique

PURPOSE

To evaluate the ability of the EmulSiv filter (EF) to remove extrinsic microbial contaminants from propofol.

METHODS

Aliquots of Staphylococcus aureus (S. aureus), Candida albicans (C. albicans), Klebsiella pneumoniae (K. pneumoniae), Moraxella osloensis (M. osloensis), Enterobacter agglomerans (E. agglomerans), Escherichia coli (E. coli), Serratia marcescens (S. marcescens), Moraxella catarrhalis (M. catarrhalis), Haemophilus influenzae (H. influenzae) and Campylobacter jejuni (C. jejuni) were inoculated into vials containing 20 mL of sterile propofol. The unfiltered inoculated propofol solutions served as controls. Ten millilitres and 20 mL samples of the inoculated propofol were filtered through the EF. All solutions were then subplated onto three culture plates using a precision 1 micro L calibrated platinum loop and incubated. The number of colony forming units (CFU) were counted. Data were analyzed using a one-sample t test, and a P value of less than 0.05 was selected as the level of statistical significance.

RESULTS

The EF was able to completely remove CFU of S. aureus, C. albicans, K. pneumoniae, M. osloensis, E. agglomerans, E. coli, S. marcescens, and M. catarrhalis (P < 0.05). A small number of H. influenzae CFU were able to evade filtration in both the 10 mL and 20 mL samples. C. jejuni CFU were able to evade filtration in only the 10 mL sample.

CONCLUSIONS

The EF removes the majority of microbial contaminates from propofol with the exception of H. influenzae and C. jejuni. Although the EF is capable of removing most of the microbial contamination produced by H. influenzae and C. jejuni, a few CFU are capable of evading filtration. Consequently, even the use of a filter capable of removing microbial contaminants is not a substitute for meticulous aseptic technique and prompt administration when propofol is used.

Re-use of equipment between patients receiving total intravenous anaesthesia: a postal survey of current practice

In order to establish current practice with regard to the reuse of infusion equipment between patients receiving total intravenous anaesthesia (TIVA), a postal survey of 393 consultants was carried out. Additionally, consultants' awareness of relevant guidelines was assessed. Overall, 46% of consultants change all equipment between cases, 37% change one-way valves and 17% change distal lengths of the infusion tubing. Only 13% of consultants reported knowledge of any guidelines. In the absence of any data relevant to the current techniques of administering TIVA, the level of risk associated with the reuse of infusion components is impossible to quantify. Disposal of all equipment between cases incurs a 26% greater cost when compared to changing one-way valves alone. Variation in practice between consultants creates the potential for system errors. Practice should be standardised and, to comply with the published guidelines, should involve disposal of all equipment between cases.

Microbial viability in preparations packaged for single use

We evaluated microbial viability in preparations packaged for single use only which mandate that residual solution be discarded such as albumin and globulin preparations as blood products, preparations containing albumin (such as urokinase and interferon), fat emulsions, and a preparation containing fat emulsions (propofol). In most preparations, Serratia marcescens and Burkholderia cepacia proliferated rapidly at 30 degrees C. However, in globulin preparations containing 1-2.25% glycine to prevent protein degradation (Gamma-Venin P, Venilon-I, Globulin Injection, and Ahlbulin), no growth of S. marcescens and B. cepacia was detected over 24 h at 30 degrees C. For globulin preparations containing 1-2.25% glycine, the injunction to "Discard residual solution after the package has been used" in the package inserts can be revised to "It is possible to use residual solution within 24 h after the package has been used with storage in a cool place."

Warming of infusion syringes caused by electronic syringe pumps

PURPOSE

To evaluate inadvertent warming of the infusion syringe in four different types of electronic syringe pumps.

METHODS

Ambient temperature and syringe surface temperature were simultaneously measured by two electronic temperature probes in four different models of commercially available syringe pumps. Experiments were performed at an infusion rate of 1 ml h(-1) using both battery-operated and main power-operated pumps. Measurements were repeated four times with two pumps from each of the four syringe pump types at a room temperature of approximately 23 degrees C. Differences among the four syringe pump brands regarding ambient to syringe temperature gradient were compared using ANOVA. A P-value of less than 0.05 was considered statistically significant.

RESULTS

Syringe warming differed significantly between the four syringe brands for both the battery-operated and main power-operated mode (ANOVA, P< 0.001 for both modes). Individual differences between syringe surface and ambient temperature ranged from 0.3 to 1.9 degrees C for battery operation and from 0.5 to 11.2 degrees C during main-power operation.

CONCLUSION

Infusion solutions can be significantly warmed by syringe pumps. This has potential impact on bacterial growth and the stability of drug solutions and blood products infused, as well as on the susceptibility to hydrostatic pressure changes within the infusion syringe.

Routine handling of propofol prevents contamination as effectively as does strict adherence to the manufacturer's recommendations

PURPOSE

Propofol is a potential vector of infection, because it contains no preservative. Thus, the manufacturer's specific recommendations for preparing injections or infusions go beyond the guidelines commonly used in our operating rooms for preparing other iv drugs. The purpose of the present study was to determine whether in the daily routine of an operating theatre a modified propofol handling technique can prevent contamination as effectively as do the manufacturer's handling recommendations.

METHODS

A total of 160 consecutive neurosurgical patients were allocated to either Group I (manufacturer's handling recommendations: i.e., 1) disinfecting propofol vials and ampoules before filling syringes; 2) replacing empty syringes; 3) discarding all material at the end of surgery); or Group II (modified propofol handling protocol: i.e., 1) refilling empty syringes; 2) renewing only the infusion line to the patient).

RESULTS

Total contamination rates were comparable in both groups (Group I: 14/160 (8.75%), Group II: 13/160 (8.13%) (chi2= 0.074; P=0.96). Frequency of contamination was not different between groups; either in sample 1 taken at the beginning of the procedure, (Group I: 5/80 (6.25%) vs Group II: 6/80 (7.5%); chi2=0.098; P=0.76) or in sample 2, taken at the end, (Group I: 9/80 (11.25%) vs Group II: 7/80 (8.75%); chi2=0.278; P=0.598).

CONCLUSION

We conclude that in the daily routine of the operating theatre following a modified propofol handling protocol prevents contamination of propofol syringes as effectively as does adhering to the manufacturer's specific handling recommendations. However, neither of the tested guidelines completely prevented contamination.

Use of propofol and other nonbenzodiazepine sedatives in the intensive care unit

Sedatives continue to be used on a routine basis in critically ill patients. Although many agents are available and some approach an ideal, none are perfect. Patients require continuous reassessment of their pain and need for sedation. Pathophysiologic abnormalities that cause agitation, confusion, or delirium must be identified and treated before unilateral administration of potent sedative agents that may mask potentially lethal insufficiencies. The routine use of standardized and validated sedation scales and monitors is needed. It is hoped that reliable objective monitors of patients' level of consciousness and comfort will be forthcoming. Each sedative agent discussed in this article seems to have a place in the ICU pharmacologic armamentarium to ensure the safe and comfortable delivery of care. Etomidate is an attractive agent for short-term use to provide the rapid onset and offset of sedation in critically ill patients who are at risk for hemodynamic instability but seem to need sedation or anesthesia to perform a procedure or manipulate the airway. Ketamine administered through intramuscular injection or intravenous infusion provides quick, intense analgesia and anesthesia and allows patients to tolerate limited but painful procedures. The risk/benefit ratio associated with the use of this neuroleptic agent must be weighed carefully. Ketamine is contraindicated in patients who lack normal intracranial compliance or who have significant myocardial ischemia. Barbiturates are reserved mainly to induce coma in patients at risk for severe CNS ischemia, which frequently is associated with refractory intracranial hypertension, or in patients with status epilepticus. When administered in high doses, these drugs have prolonged sedative and depressant effects. Judicious hemodynamic monitoring is required when barbiturate coma is induced. Haloperidol is indicated in the treatment of delirium. Patients should be monitored for extrapyramidal side effects and, when they require higher doses, for potential electrocardiographic prolongation of the QT interval. Dexmedetomidine may evolve into an agent with qualities comparable with midazolam and propofol, and it may even become a drug of choice in select patients. Further study is required, however. Propofol has many of the qualities of an ideal sedative agent. Benzodiazepines and narcotics often are used in concert with propofol to provide reliable amnesia and to relieve pain, respectively. Propofol frequently causes hypotension when administered as a bolus or infusion, particularly in patients with limited cardiac reserve or hypovolemia. More data must be obtained to identify potential deleterious effects of hypertriglyceridemia, and further evaluation of the potential benefits in certain patient populations, such as neurosurgical patients, is needed.

Pharmaceutics for the anaesthetist

Pharmaceutics is that branch of science concerned with the manufacture and formulation of pharmaceutical products, and is a subject almost exclusively in the domain of pharmacists and those concerned with pharmaceutical manufacture. However, there are some aspects of pharmaceutics that are of particular importance to the anaesthetist, such as the pharmacology of the various preservatives, antimicrobials and other additives found in anaesthetic products, and an understanding of basic processes such as emulsification and lyophylisation. This review aims to survey those areas.

The clinical and biochemical effects of propofol infusion with and without EDTA for maintenance anesthesia in healthy children undergoing ambulatory surgery

We conducted this randomized, double-blinded, comparative, parallel-group study to determine whether adding EDTA to propofol would affect the clinical profile, calcium and magnesium homeostasis, or renal function in healthy children. After the induction of anesthesia with halothane, 69 ambulatory surgical patients (1 mo to <17 yr old), received propofol without EDTA (n = 33) or propofol with EDTA (n = 36). Blood samples were obtained for the measurement of ionized calcium, ionized magnesium, and laboratory indicators of renal function. Hemodynamic measurements, recovery, and adverse events were recorded. Propofol with EDTA produced no significant effects on clinical efficacy or renal function. Propofol and propofol EDTA produced a statistically significant decrease from baseline in serum concentrations of ionized calcium and magnesium during infusion (P<0.05), but with no apparent clinical effect. Hemodynamic measurements generally remained stable and were similar for both groups. Statistically significant changes in systolic blood pressure, mean arterial pressure, and heart rate were not considered clinically significant. Adverse events were mild or moderate. The addition of EDTA does not alter the clinical profile of propofol in pediatric ambulatory surgical patients. With or without EDTA, propofol is associated with a decrease in ionized calcium with no apparent clinical effect.

IMPLICATIONS

The addition of EDTA does not alter the clinical profile of propofol in pediatric ambulatory surgical patients. With or without EDTA, propofol is associated with a decrease in ionized calcium with no apparent clinical effect.

Evaluation of the safety and efficacy of repeated sedations for the radiotherapy of young children with cancer: a prospective study of 1033 consecutive sedations

PURPOSE

A prospective observational study to examine our current practice of either conscious sedation (C.S.) or general anesthetic (G.A.) for children undergoing radiation therapy (we use the term sedation to include both C.S. and G.A.). Specifically, the study examines the reasons for selection of patients, choice of drugs, safety and effectiveness of the procedure, side effects of repeated daily sedation, and compliance of the family with the regimen.

METHODS AND MATERIALS

Recorded data included patient demographics, sedation technique, time for various stages of the procedure, breathing support required, sedation outcome, and complications.

RESULTS

One hundred ninety-eight consecutive children underwent 4232 procedures involving either simulation or radiation treatment, an average of 21 procedures each. Seventy-four (37%) required sedation for a total of 1033 procedures, an average of 14 sedations each. For those patients who received sedation, the age ranged from 9 months to 14 years (median, 3.8) and 96% had a mold, (85% of the head and neck). The doctor's assessment of the need for sedation was correct 89% of the time. Thirty-seven percent required sedation at the start of treatment, but, even after 30 fractions, 15% still required sedation. Presedation status correlated with successful sedation and treatment (p = 0.0001). Ninety-six percent had some form of i.v. access, usually a portacath (76%); 883 sedations were performed with G.A. and 148 with C.S.; 93% of sedations were completed satisfactorily, 5% with some difficulty, and the patient was unable to be treated in 2%. With G.A., satisfactory sedation was achieved 97% of the time, whereas, with C.S., satisfactory sedation was achieved only 68% of the time. There were no complications for 97% of observations. Not one serious complication occurred. An endotracheal tube was used only twice during G.A. For C.S., the results for chloral hydrate, meperidine, and midazolam were, respectively, at least one complication, 23%, 0%, 5%; satisfactory sedation for treatment, 60%, 60%, 82%; and unable to treat 20%, 13%, 5%. For G.A., only 1 patient was unable to be treated. The median time from start of medication to the end of radiation treatment was a median of 10 min (75% complete within 15 min) for G.A., vs. 30 min (75% complete in 50 min) for C.S. On multivariate analysis, the only significant factor predicting a successful outcome was a G.A. using propofol (odds ratio, 20.6), vs. C.S. using either chloral hydrate, meperidine, or midazolam. (p = 0.0001).

CONCLUSION

In this study, there were no serious complications of sedation in 1033 procedures. As a result of the study, we developed improved methods for better preparation of the patient and family to try to reduce the need for sedation, and reduce the indications for C.S., while confirming the safety and efficacy of a G.A. with propofol for children needing sedation for daily radiation therapy.

Preventing surgical site infections: a surgeon's perspective

Wound site infections are a major source of postoperative illness, accounting for approximately a quarter of all nosocomial infections. National studies have defined the patients at highest risk for infection in general and in many specific operative procedures. Advances in risk assessment comparison may involve use of the standardized infection ratio, procedure-specific risk factor collection, and logistic regression models. Adherence to recommendations in the 1999 Centers for Disease Control and Prevention guidelines should reduce the incidence of infection in surgical patients.

Bacterial contamination of propofol in the operating theatre

There have been several reports of propofol becoming extrinsically contaminated with bacteria. These reports have usually related to infusions or delays in administration after the ampoule has been opened. This observational study was performed to examine bacterial contamination of propofol during usual practice in the operating theatres of a single large hospital group. One hundred samples of propofol were collected and cultured. Samples were taken immediately after administration in cases where the delay between opening the ampoule and administration was at least 15 minutes. The samples were classified according to whether the propofol was kept in the ampoule or a syringe after opening the ampoule and whether the intended use was for a single patient or multiple patients. The time between opening the ampoule and administration was recorded. There were three positive bacterial cultures. These samples all came from ampoules used for more than one patient, without the later dose (does) being drawn into a syringe at the time the ampoule was opened. This common clinical practice, especially in paediatric anaesthesia, does not comply with the manufacturer's recommendations. The clinical significance of the bacterial contamination detected is not clear. It is recommended that propofol should be handled in an aseptic fashion and measures taken to minimize the risk of bacterial contamination.

The association of propofol usage with postoperative wound infection rate in clean wounds: a retrospective study

OBJECTIVE

To determine if the use of propofol influences the postoperative infection rate of clean surgical wounds in dogs and cats.

STUDY DESIGN

Retrospective study.

SAMPLE POPULATION

863 dogs and cats undergoing clean surgical procedures.

METHODS

Medical and anesthetic records of surgical cases used as part of a previously described epidemiologic study on postoperative wound infection rates were reviewed. The records of all animals with clean surgical wounds were reviewed to determine if propofol had been used for anesthetic induction or maintenance during the procedure. To determine the effect of propofol use on wound infection rate, data were analyzed using Fisher's exact test, followed by multiple logistic regression to adjust for various factors, including surgery time, time from clipping to surgery, antibiotic usage, coexisting distant infection, endocrine disease, and the use of immunosuppressive drugs in the perioperative period.

RESULTS AND CONCLUSIONS

Of 863 dogs and cats with clean surgical wounds, 46 received propofol as part of the anesthetic protocol. A total of 6 of 46 animals (13%) receiving propofol developed postoperative wound infections, compared with 33 of 817 animals (4%) not receiving propofol (P = .014; % difference = 9%; 95% CI = 0.5% to 24%). Adjusting for all other factors evaluated, animals receiving propofol were 3.8 times more likely to develop postoperative wound infections compared to animals not given propofol (95% CI = 1.5-9.9).

CLINICAL IMPLICATIONS

Propofol is a lipid-based emulsion capable of supporting microbial growth. Administration of a potentially contaminated solution may contribute to surgical wound infection or other patient morbidity or mortality. Strict aseptic technique in the preparation of the solution and prompt disposal of unused drug are imperative to curtail the potential for extrinsic contamination.

Management of bacterial complications in critically ill patients: surgical wound and catheter-related infections

The occurrence of surgical wound infections and/or bacteremia associated with central venous catheter use are of growing concern to all physicians who treat critically ill patients. The physician must be aware that some patients have an even greater risk for infection, such as those with multiple risk factors, those who are on central lines, or those patients who undergo multiple invasive diagnostic or therapeutic procedures. The emergence of resistant pathogens, particularly Gram-positive pathogens, is an important factor in the morbidity and mortality of hospitalized patients. In the face of this growing resistance among target organisms, the selection of the correct antimicrobial and nonpharmacologic interventions, based on correct identification and susceptibility test data, has become increasingly challenging. Methicillin-resistant Staphylococcus aureus and, more recently, glycopeptide-resistant enterococci and staphylococci represent a significant danger to the patient. As a consequence, earlier and more precise identification of the pathogens most frequently associated with infection is essential. The role of exacting surgical technique, infection control measures, and the appropriate use of prophylactic and therapeutic antibiotics cannot be overestimated in helping to reduce potential morbidity and mortality associated with severe surgical infection. The development of new antibiotics may help treat the difficult cases attributable to resistant Gram-positive bacteria.

Infectious risks associated with the use of propofol

BACKGROUND

Investigations of the Centers for Disease Control into postoperative infections have implicated extrinsically contaminated propofol.

METHODS

To evaluate the infectious risk associated with intravenous anaesthetic agents, we surveyed the literature from 1971 to 1995 using the Medline database. Papers covering infections related to intravenous anaesthetic agents were included.

RESULTS

The review of the literature on infections associated with propofol and other intravenous anaesthetics shows that this infectious risk is minimal and often caused by breakdowns in aseptic techniques.

CONCLUSIONS

We conclude that, if standard hygienic precautions are taken, the risk of in-use contamination of intravenous anaesthetics is low. If strict hygienic guidelines are followed in handling propofol, this agent can be safely administered to patients.