ISSN NUMBER: 1938-7172
Issue 3.5 VOLUME 3 | NUMBER 5

Editor:
Michael A. Fiedler, PhD, CRNA

Contributing Editors:
Mary A. Golinski, PhD, CRNA
Alfred E. Lupien, PhD, CRNA
Dennis Spence, PhD, CRNA
Steven R. Wooden, MS, CRNA

Guest Editor:
Gerard T. Hogan, Jr., DNSc., CRNA

Assistant Editor
Jessica Floyd, BS

A Publication of Lifelong Learning, LLC © Copyright 2009

New health information becomes available constantly. While we strive to provide accurate information, factual and typographical errors may occur. The authors, editors, publisher, and Lifelong Learning, LLC is/are not responsible for any errors or omissions in the information presented. We endeavor to provide accurate information helpful in your clinical practice. Remember, though, that there is a lot of information out there and we are only presenting some of it here. Also, the comments of contributors represent their personal views, colored by their knowledge, understanding, experience, and judgment which may differ from yours. Their comments are written without knowing details of the clinical situation in which you may apply the information. In the end, your clinical decisions should be based upon your best judgment for each specific patient situation. We do not accept responsibility for clinical decisions or outcomes.

Table of Contents

AIRWAY
ASSOCIATION OF SLEEP-DISORDERED BREATHING WITH POSTOPERATIVE COMPLICATIONS
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PREDICTION AND OUTCOMES OF IMPOSSIBLE MASK VENTILATION: REVIEW OF 50,000 ANESTHETICS
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  CHOOSING A LUNG ISOLATION DEVICE FOR THORACIC SURGERY: A RANDOMIZED TRIAL OF THREE BRONCHIAL BLOCKERS VERSUS DOUBLE-LUMEN TUBES
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GENERAL
NONINFECTIOUS SERIOUS HAZARDS OF TRANSFUSION
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PHARMACOLOGY
  PERIOPERATIVE DRUG THERAPY IN ELDERLY PATIENTS
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QUALITY IMPROVEMENT
REDUCTION IN INTRAOPERATIVE BACTERIAL CONTAMINATION OF PERIPHERAL INTRAVENOUS TUBING THROUGH THE USE OF A NOVEL DEVICE
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BACTERIAL CONTAMINATION OF STETHOSCOPES ON THE INTENSIVE CARE UNIT
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PEDIATRIC ANESTHESIA
THE EFFECTIVE TIME AND CONCENTRATION OF NITROUS OXIDE TO REDUCE VENIPUNCTURE PAIN IN CHILDREN
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Airway

Hwang D, Shakir N, Limann B, Sison C, Kalra S, Shulman L, Souza ADC, Greenberg H


 

Association of sleep-disordered breathing with postoperative complications

Chest 2008;133:1128-1134

Hwang D, Shakir N, Limann B, Sison C, Kalra S, Shulman L, Souza ADC, Greenberg H

 

Abstract

Purpose            The purpose of this study was to determine if simple preoperative screening for obstructive sleep apnea (OSA) and follow up home nocturnal oximetry in surgical patients could identify patients at increased risk for perioperative complications.

Background            OSA is a form of sleep-disordered breathing (SDB) associated with increased perioperative risk and possible postoperative complications. However, attempts to reduce postoperative risk are difficult to implement because formal diagnosis of SDB or OSA is not always available at the time of surgery. Additionally, screening guidelines and management protocols are based largely on expert opinion and not clinical studies.

Methodology            Adults scheduled for elective surgical procedures at a large tertiary hospital were screened for SDB based on an established clinical protocol. Patients without a diagnosis of OSA but who had at least two symptoms suggestive of OSA (e.g., snoring, excessive daytime somnolence, witnessed apnea, or crowded oropharynx) were selected for nocturnal oximetry testing prior to surgery. Results of the studies were made available to the anesthesia and surgical teams.

Nocturnal oximetry data included the number of episodes per hour of oxygen desaturation of ≥4% (termed the Oxygen Desaturation Index 4% or ODI 4%) and percent of time with an absolute oxygen saturation of <90% (T 90%). Postoperative data were collected by blinded chart reviewers on demographic data (age, sex, race, type of surgery, height and weight), outcomes (type and presence or absence of postoperative complications) and length of stay. Complications were defined as adverse events affecting major organ systems that required further monitoring, testing or direct therapeutic interventions. Patients with abnormal nocturnal oximetry test suggestive of SDB underwent prolonged postanesthesia care (PACU) per hospital protocol. Subjects with ODI 4% of ≥ 5 were compared to those with ODI 4% ≤ 5. ODI 4% severity was classified as mild (5-20), moderate (20-40) and severe (≥ 40). Logistic regression was used to determine predictors associated with the presence of postoperative complications.

Result            A total of 172 subjects were investigated (ODI 4% of ≥ 5: n=98 (57%); ODI 4% ≤ 5: n=74 (43%). Of these, 58 subjects had mild ODI 4% severity (33.7%), 30 were in the moderate range (17.4%) and 10 were in the severe range (5.8%). The T 90% was 17.7% ± 25% in the ODI 4% of ≥ 5 and 2.1±4.8% in the ODI 4% ≤ 5 group (P<0.0001). No significant difference was found between groups in terms of age, BMI, number of medical comorbidities, respiratory disease, or smoking history. However, there were significantly more overweight subjects with ODI 4% ≥ 5 than non-overweight subjects (61% vs. 37.5%, P=0.02). Men had a significantly higher prevalence of ODI 4% ≥ 5 than women (64.7% vs. 49.5%, P=0.05). While not statistically significant, a larger proportion of patients in the ODI 4% ≥ 5 group had hypertension (62% vs. 45.9%) and diabetes (20.4% vs. 12.2%) than those in the ODI 4% ≤ 5. Seventeen perioperative complications occurred, with 15 (88%) in the ODI 4% ≥ 5 group compared to only two (12%) in the ODI 4% ≤ 5. Perioperative complications were significantly higher in patients with ODI 4% ≥ 5 than those with ODI 4% ≤ 5 (15.3% vs. 2.7%, P <0.01). After adjusting for sex and BMI, the odds ratio for perioperative complications was 7.2 (95% confidence interval, 1.5 to 33.3, P=0.01). The majority of complications were respiratory (nine patients) and cardiovascular (five patients).

Conclusion            In patients with clinical features of OSA, an ODI 4% ≥ 5 measured by nocturnal oximetry is independently associated with an increased rate of postoperative complications.

 

Comment

Obstructive sleep apnea syndrome has significant implications for anesthesia providers because it is associated with increased perioperative morbidity and mortality (e.g., potential for difficult intubation and life-threatening apnea postoperatively because of sleep architecture alterations and sensitivity to respiratory depression induced by opioids). This study is important because it demonstrates, at least in this sample, that a majority of patients (57%) who did not have a formal diagnosis, but who had symptoms consistent with OSA, had a significant number of nocturnal desaturations (ODI 4% ≥ 5). More importantly, these patients were found to have a higher rate of respiratory and cardiovascular postoperative complications.  This has significant implications for anesthesia providers because patients with undiagnosed OSA are presenting every day to our operating room. This study reinforces my opinion that anesthesia departments should develop departmental OSA perioperative management guidelines (i.e., ASA OSA practice guidelines) to manage patients with a diagnosis of OSA and those with clinical features of OSA.1 I think this is especially important to anesthetists that work in small, rural hospitals because these facilities may have limited resources to manage postoperative complications. Having a plan in place may help prevent problems later.

 

Dennis Spence PhD, CRNA

 

1. Gross JB, Bachenberg KL, Benumof JL, et al. Practice guidelines for the perioperative management of patients with obstructive sleep apnea: A report by the American Society of Anesthesiologists task force on perioperative management of patients with obstructive sleep apnea. Anesthesiology. 2006;104:1081-93.

2. McNicholas WT. Diagnosis of obstructive sleep apnea in adults. Proc Am Thorac Soc 2008;5:154-160.

 

Obstructive sleep apnea syndrome (OSA) diagnosis requires the presence of excessive daytime sleepiness not explained by other factors or two or more of the following: choking or gasping during sleep, recurrent awakenings from sleep, unrefreshing sleep, daytime fatigue or impaired concentration. Additionally, overnight monitoring demonstrating five or more obstructive apneas / hypopneas or respiratory effort-related arousals (RERA) is needed to make the diagnosis.2 Apnea is defined as a cessation of airflow for greater than 10 seconds. The event is obstructive if during apnea there is effort to breathe. Hypopnea is an abnormal respiratory event with at least ≥30% reduction in thoracoabdominal movement or airflow, as compared to baseline lasting at least 10 seconds, and with ≥ 4% oxygen desaturation. RERAs are a series of breaths characterized by increasing respiratory effort leading to an arousal from sleep, but do not meet diagnostic criteria of apnea or hypopnea. These events must last at least 10 seconds and show a pattern of more progressively negative esophageal pressure, terminated by a sudden change to a less negative pressure with an arousal. The formal diagnosis of OSA is made by polysomnography with severity based upon the apnea-hypopnea index (number of apneic + hyponeic events per hour of sleep). An AHI of 5-15 is mild; 15-30 is moderate and greater than 30 severe.1 Some sleep studies may present the respiratory disturbance index (RDI), which is a sum of the number of apneas, hypopneas and RERAs per hour.

 

The oxygen desaturation index (ODI), as measured by home nocturnal oximetry, was the primary index used to asses sleep disordered breathing and OSA in this study. The ODI is reported to have a wide range of sensitivity and specificity for OSA.2 Reports suggest the ODI correlates with the apnea-hypopnea index (AHI; number of apnea and hypopnea events per hour). The use of home noctural oximetry is one of the simplest and most inexpensive methods for evaluating OSA, however, it may be less helpful in milder cases of OSA because desaturation can be absent with hypopnea. 

 

This topic was suggested by Johnny J. Sacco, CRNA. 

© Copyright 2009 Anesthesia Abstracts · Volume 3 Number 5, May 31, 2009





Kheterpal S, Martin L, Shanks AM, Tremper KK


 

Prediction and outcomes of impossible mask ventilation: review of 50,000 anesthetics

Anesthesiology 2009;110:891-897

Kheterpal S, Martin L, Shanks AM, Tremper KK

Abstract

Purpose            To determine the incidence, predictors, and outcomes associated with impossible mask ventilation.

Background            The ability to provide effective mask ventilation is essential in the management of difficult intubation. A large body of literature exists on predictors and outcomes of difficult intubation, however there is little data on difficult or impossible mask ventilation. Previous reviews by this research group found 313/22,000 (1.4%) cases of difficult mask ventilation, and 37/22,000 (0.16%) cases of impossible mask ventilation. History of snoring and limited thyromental distance were identified as predictors of impossible mask ventilation. Unfortunately, the previous data did not include a detailed, manual review of the anesthetic record to identify the ultimate clinical management of the event. The primary goal of the study was to identify airway outcomes and management of a large set of impossible mask ventilation cases. A secondary goal was to derive a set of clinical predictors of impossible mask ventilation.

Methodology            An observational study of all adult patients undergoing general anesthesia over a 4-year period (2004 to 2008) was conducted at a large tertiary hospital. Data was collected on anthropomorphic details, airway physical exam and history elements (i.e., cervical spine, neck anatomy, thyromental distance, mouth opening, mandibular protrusion test, Mallampati classification, full beard, dentition, neck radiation, snoring and obstructive sleep apnea). From the intraoperative record, ease or difficulty with mask ventilation and intubation, direct laryngoscopy view, airway adjuvants, alternative and advanced airway management data, and experience of anesthetist were recorded. Logistic regression was used to determine predictors of impossible mask ventilation.

Result            In this study 77 of 53,041 (0.15%) patients were impossible to mask ventilate, resulting in an incidence of 1 in 690. One quarter (25%; 19 of 77) of these patients were difficult intubations (overall incidence 1 in 2,800), with 15 of 19 patients being successfully intubated. Four of 77 were not intubated and in six cases a laryngeal mask airway was used as a temporizing measure. In 12 patients an alternative intubation technique was used, including two surgical airways and two patients awakened for a successful awake fiberoptic intubation. Overall 73 of 77 cases of impossible mask ventilation received neuromuscular blockers, with 65 of 77 patients receiving succinycholine in the process of induction or management of the airway.

Logistic regression identified five independent predictors of impossible mask ventilation (P <0.05; ranked largest to smallest hazard ratio): neck radiation changes, male sex, sleep apnea, Mallampati III or IV, and presence of a beard. Patients with three of more or these risk factors were 8.9 (odds ratio 95% confidence interval: 5.2-15.4) times more likely to be impossible to mask ventilate when compared to patients with no risk factors.

Conclusion            Impossible mask ventilation is a rare event that is associated with difficult intubation, and this data set demonstrates most patients can be managed without a surgical airway. The most significant clinical predictor of impossible mask ventilation is neck radiation changes.

 

Comment

This is an important study because it provides anesthetists with a list of predictors of impossible mask ventilation. More significant is that 25% of these cases were the worst-case scenario of cannot ventilate-cannot intubate. Fortunately, most of these cases could be managed without a surgical airway. However, the investigators were clear in pointing out the results of this study might undermine some provider’s practice of awakening or avoiding neuromuscular blockers when impossible mask ventilation occurs. They also pointed out that they cannot offer concrete guidelines on the management of impossible mask ventilation.

I believe the way I will apply these results is to have a low threshold for preparing for an impossible mask ventilation or potential difficult intubation when I have a patient who presents with several of these risk factors. To me this means ensuring proper positioning (i.e., ramping, good sniff position), having appropriate adjuncts (i.e, multiple blades, intubating LMA, intubating stylet, glidescope, ect, fiberoptic bronchoscope), and most importantly having an experienced set of hands to assist me if I decide to proceed with a general anesthetic in a patient with these risk factors. Also I believe it is important to consider performing an awake fiberoptic intubation in a patient who presents with three or more of these risk factors or other predictors of difficult intubation.

 

Dennis Spence PhD, CRNA

 

 

© Copyright 2009 Anesthesia Abstracts · Volume 3 Number 5, May 31, 2009





Narayanaswamy M, McRae K, Slinger P, Dugas G, Kanellakos G, Roscoe A, Lacroix M


 

Choosing a lung isolation device for thoracic surgery: A randomized trial of three bronchial blockers versus double-lumen tubes

Anesth Analg 2009;108:1097-1101

Narayanaswamy M, McRae K, Slinger P, Dugas G, Kanellakos G, Roscoe A, Lacroix M

 

Abstract

Purpose            The purpose of this study was to compare the clinical performance of three different bronchial blockers with left sided double-lumen endobronchial tubes. The study also gauged the difficulty and time to insertion for all devices studied.

Background            There is currently no consensus as to which technique for lung isolation in thoracic surgery is best. Within the past ten years, a number of new bronchial blockers (BBs) have found their way to the market. As an alternative to double lumen endobronchial tubes (DLTs), the comparative efficacy of these bronchial blockers has not been studied.

Methodology            This prospective, randomized study included 104 adults undergoing left sided thoracic procedures requiring one lung ventilation for a period of 30 minutes or more. The induction protocol was standardized. Patients were assigned to one of four lung isolation groups. The device groups were as follows: the Arndt ® wire guided BB (Cook ® Critical Care, Bloomington, IN), the Cohen Flexi-tip ® BB (Cook ® Critical Care, Bloomington, IN), the Fuji Uni-blocker ® (Fuji Systems, Tokyo), and the left-sided DLT (Mallinckrodt Medical, Cornamadde, Athlone, Westmeath, Ireland). Each group was then randomly divided into two sub-groups (n=13 per subgroup): group 1 had 20cm H2O suction immediately applied after placement, group 2 had the same suction applied 20 minutes after placement. Thoracic surgeons were blinded as to the device being used. They utilized a verbal analog scale to describe which techniques achieved optimal lung deflation.

A power calculation was completed and data analysis performed using ANOVA with a Tukey test for multiple comparisons. DLT repositionings were compared using Fisher’s exact test. Continuous data were evaluated using a t test. P values <0.05 indicated statistical significance.

Result            There were no differences in lung collapse scores between BBs and DLTs. The differences were noted in the time to lung isolation after induction. The BBs took significantly longer to place, and had a greater need for repositioning than the DLTs did. Among the BBs, there was no significant difference in time to placement. There were also significant differences in the mean peak airway pressures between the BBs and the DLTs. The BB groups had a greater sustained peak airway pressure at a controlled tidal volume of 5-6 mL/kg of ideal body weight than the DLT group did.

Conclusion            Although left sided tubes are the standard for one lung ventilation, bronchial blockers are an available alternative. There are limitations to the use of DLTs, especially in difficult airway scenarios. DLTs require change to a single lumen tube if prolonged mechanical ventilation is required. DLTs are significantly more traumatic, with complaints of severe postoperative hoarseness and pain quite common. BBs offer an alternative to DLTs in certain situations, but are limited due to exaggerated placement times, expertise in placement, more frequent repositioning, and average airway pressures.

 

Comment

I found this article to be very interesting. One limitation is that the devices were placed by thoracic anesthesia fellows (in Australia) who were not seasoned experts in placing bronchial blockers. The authors were looking to determine which device was best, but in the end realized that placement, repositioning and airway pressures were as important a consideration as to the device being used. All BBs provided equivalent exposure to the left-sided DLT, but seemed prone to displacement and intraoperative repositioning. This article seems to add more to the controversy regarding BBs vs. DLTs.

 

Gerard T. Hogan, Jr., DNSc., CRNA

 

 

© Copyright 2009 Anesthesia Abstracts · Volume 3 Number 5, May 31, 2009




General

Hendrickson JE, Hillyer CD


 

Noninfectious serious hazards of transfusion

Anesth Analg 2009;108:759-769

Hendrickson JE, Hillyer CD

 

Abstract

Purpose            The purpose of this article was to highlight the changing concerns regarding the hazards related to transfusion of blood and/or blood products.

Background            Noninfectious serious hazards of transfusions (NISHOTs) have emerged as the most common complications involved in blood and blood therapy.  Liberal vs. restrictive transfusion practices, as well as morbidity and mortality were discussed.

Methodology            This was a comprehensive review of the current literature regarding NISHOTs.

Result            As the list of NISHOTs continues to grow, we must increase our awareness that infectious disease is not the only concern in transfusion therapy.  As donor questionnaires and testing methods have improved, the risk of HIV and/or hepatitis have decreased substantially in the past 10 years.

Conclusion            NISHOTs as a concern related to transfusion therapy should be as important (if not more important) than the concern for transmission of infectious disease when determining the appropriateness of blood and/or blood products in the hospitalized patient.  Understanding NISHOTs allows for earlier recognition and management of transfusion related complications when they occur, and allows the development of strategies to minimize their impact and occurrence.

Comment

This exhaustive review of current literature was enlightening.  The authors stated that the “risk of transfusion transmitted infectious diseases has decreased approximately 10,000 fold” with the advent of nucleic acid testing and other sophisticated methods of screening.  Accompanying this reduction in disease threat, Non-infectious serious hazards of transfusion (NISHOTs) has emerged as the primary consideration in the appropriateness of blood and/or blood products.  Patients are up to 1,000 fold more likely to experience a NISHOT than an infectious complication of transfusion.

NISHOTs include a wide variety of complications caused by transfusion therapy.  These are divided into immune and non-immune mediated reactions.  Immune mediated hazards included hemolytic transfusion reactions, febrile nonhemolytic transfusion reactions, allergic/urticarial/anaphylactic reactions, transfusion related acute lung injury (TRALI), posttransfusion purpura, transfusion associated graft vs host disease, microchimerism, transfusion-related immunomodulation, and alloimmunization.  Non-immune mediated hazards included septic transfusion reactions, nonimmune hemolysis, mistransfusion, transfusion-related circulatory overload, metabolic derangements, coagulopathic complications of massive transfusion, complications of stored red cell lesions, over/undertransfusion, and iron overload.

The FDA in 2000 stated that death rates due to hemolytic transfusion reactions alone were more than twice that due to all infectious hazards combined. Fever, chills, rigors, back pain, nausea, vomiting, and impending doom are all symptoms of a hemolytic reaction.  The most frequent offending antibodies are immunoglobulin M (IgM) and naturally occurring anti-A and anti-B antibodies. The incidence of hemolytic reactions is estimated as 1:10,000 transfusions.

Delayed hemolytic reactions are much more likely and far less dramatic, occurring in 1:1,500 transfusions.  These hyperhemolytic reactions may take 3-10 days after transfusion to appear.  They can exacerbate anemia at a critical time in postoperative recovery.  Septic complications are another concern.  From 2001-2003, the FDA reported that 15% of transfusion related deaths were due to bacterial contamination.  Contaminated blood transfusions are theorized to occur at a rate of 1:3,000 transfusions, but rarely lead to clinical sepsis.  This is of particular concern in pooled platelet infusions.

Mistransfusion is either administering the wrong product or to the wrong individual.  With all of the safety procedures, cross checks, time outs, and paperwork associated with transfusion therapy, the occurrence is still between 1 in 14,000 to 1 in 38,000 RBC infusions.  This was disappointing because it has not improved in the past 20 years.  Transfusion related acute lung injury (TRALI) is an important cause of post transfusion morbidity and mortality.  In 2006 TRALI was the leading cause of transfusion related death reported to the FDA.  TRALI is not improved with diuretic therapy, and is difficult to treat.

In vitro hemolysis can occur when blood is not stored properly.  A study done looking at post cardiothoracic surgery patients noted that mortality rates were higher in the group receiving “old” blood (greater than 14 days old) than in the group receiving “new” blood (less than 14 days old).

While I could continue to go on about their findings, the bottom line is this:  Our traditional concern for transmission of infectious disease as a deterrent to blood component therapy is antiquated.  NISHOTs are the new consideration for the relevancy and appropriateness of transfusion therapy.

 

Gerard T. Hogan, Jr., DNSc., CRNA

 

 

© Copyright 2009 Anesthesia Abstracts · Volume 3 Number 5, May 31, 2009




Pharmacology

Rivera R, Antognini J


 

 

Perioperative drug therapy in elderly patients

Anesthesiology 2009;110:1176-81

Rivera R, Antognini J

 

 

Abstract

Purpose            The purpose of this article was to review the effect that aging has on anesthetic drug therapy.

Background            As our population lives longer, anesthesia providers are treating a more elderly group of patients. Compared to patients under the age of 65, elderly patients often respond differently to the drugs that are used in anesthesia.

Methodology            During the aging process, organ function declines for a variety of reasons. Even when elderly patients appear healthy, their reserves may be diminished so that the stress of anesthesia and surgery could significantly impact the patient’s ability to react to a drug in a normally expected way. Fluid given during surgery is also a concern in the elderly because of changes in the cardiovascular system such as myocardial hypertrophy, stiffening of the left ventricle secondary to increased collagen content, and blunted baroreflexes. Other changes in body mass such as increased fat and decreased muscle mass also contribute to the way drugs react to the elderly when compared to younger patients. Laboratory studies do not always reveal potential problems. As an example, glomerular filtration rate in the kidneys decrease with age but because the elderly have a diminished muscle mass their serum creatinine may be normal.

Result

Pharmacokinetics: The body’s ability to retain and clear a drug changes with age. Total body water decreases, body protein decreases as much as 20%, and body fat increases, Drugs such as morphine, which is hydrophilic, will have a decreased volume of distribution and may have an increased effect on the elderly by as much as 50%. Propofol is highly protein bound and equivalent doses may result in more free drug available in the elderly. Diazepam, which is very lipophilic, will have an increased elimination half-life.

Hepatic: Between the age of 25 and 65 hepatic blood flow diminishes 40%. Drugs such as ketamine, flumazenil, morphine, fentanyl, sufentanil, and lidocaine are “high extraction” drugs. High extraction drugs depend on adequate hepatic blood flow to clear the system.

Renal: Glomerular filtration decreases as much as 50% between the age of 20 and 90. All drugs are affected to some extent by glomerular filtration. Some neuromuscular blocking agents are heavily dependent on renal elimination. Other drugs, such as morphine, that are broken down by non-renal body systems still have active metabolites that are dependent on renal clearance.

Pharmacodynamics: Drug receptor sites generally change and diminish with age. Receptor site changes may increase the sensitivity of a drug such as benzodiazepines. However, many drugs depend on receptor site numbers and become less effective with age. Examples of those types of drugs include Beta adrenergic agonists and antagonists such as isoproterenol and propranolol.

Anesthetic Drugs: The minimum alveolar concentration (MAC) of inhalation anesthetic agents decreases with age. MAC decreases an average of 0.6% each year starting at age 40. Altered pharmacokinetics and pharmacodynamics make the elderly more sensitive to drugs such as thiopental, propofol, and midazolam. Decreased volume of distribution makes the elderly more sensitive to etomidate. All of these drugs should be given more slowly in the elderly in order to avoid unexpected side effects.

Cardiovascular: Half life is prolonged and clearance is decreased for drugs such as propranolol and atenolol. Some drugs such as lidocaine and digoxin require reduced intravenous doses because of diminished renal clearance. Diltiazem, nifedipine, and verapamil undergo hepatic elimination and therefore may have a prolonged effect in the elderly.

Opioids: There is a 50% decrease in dosing requirement for fentanyl, sufentanil and alfentanil between the age of 20 and 89. The decreased volume of distribution in the elderly can exaggerate the hypotensive and bradycardic side effects of opioids. A dose of 50% less remifentanil is necessary to produce electroencephalographic depression in the elderly as compared to younger patients.

Muscle Relaxants: Generally, muscle relaxants have a prolonged onset of action and an increased dose response because of decreased muscle blood flow, diminished cardiac output, decreased body water, and lower hepatic blood flow. Vecuronium and rocuronium are both prolonged by as much as 200% because of reduced hepatic blood flow in the elderly. Studies have found that atracurium and mivacurium both have prolonged durations of action in the elderly. Succinylcholine has a normal duration of action in the elderly but the onset of action may be prolonged because of lower cardiac output.

Conclusion            The elderly populations typically respond differently to anesthetic drugs than younger patients do. These changes can most often be attributed to changes in body fat, total body water, and muscle mass. Hepatic blood flow and renal clearance also contribute to these differences. Prolonged onset of drug actions, increased sensitivity, and extended action should be expected when administering anesthetic agents to the elderly.

 

Comment

I found this particular review a bit weak, but its conclusion was accurate. We must continue to remind ourselves and re-educate ourselves about the age related changes that effect our patients. When I began my practice almost 30 years ago, I seldom had patients over the age of 80. I now find myself anesthetizing patients over 90 years old and occasionally over the age of 100. Many of these patients appear to be reasonably healthy. I guess anyone that makes it to 90 must have some pretty good protoplasm, but that does not mean we should treat them like we treat a 20 year old. This review did point out the physiologic changes we should expect in the elderly. Understanding the pharmacologic actions of the drugs we use, and identifying how these physiologic changes will affect the drugs action is critically important.

 

Steven Wooden, MS CRNA

 

 

© Copyright 2009 Anesthesia Abstracts · Volume 3 Number 5, May 31, 2009




Quality Improvement

Koff M, Loftus R, Buchman C, Schwartzman J, Read M, Henry E, Beach M


 

 

Reduction in intraoperative bacterial contamination of peripheral intravenous tubing through the use of a novel device

Anesthesiology 2009;110:978-85

Koff M, Loftus R, Buchman C, Schwartzman J, Read M, Henry E, Beach M

 

 

Abstract

Purpose            This study evaluated the use of a hand sanitation device in reducing the risk of intraoperative contamination.

Background            Lack of hand disinfection remains a problem in health care. An observational study of health care providers revealed that anesthesiologists were worst among all physicians in hand washing adherence. Hospital acquired infection contributes to the death of approximately 90,000 patients a year in the United States and an increased health care cost of $4.5 billion. Aseptic technique, hand washing, and barrier practices are the key to reducing hospital acquired infections.

Methodology            The hypothesis was that improved hand hygiene would reduce bacterial transmission in the operating room and reduce post-operative infections. The study compared standard hand washing techniques to the use of an alcohol based device worn by anesthesia providers. The dependent variables were contamination of anesthesia surfaces and 30 day post-operative infection rates. The control group, anesthesia providers using typical hand washing techniques, included 58 cases. The treatment group, anesthesia providers using alcohol based disinfection devices, included 53 cases. The study included only the first cases of the day to exclude operating room cross contamination. Each stopcock, Anesthesia pop-off valve, and agent dial were sanitized and cultured before each case and then again at the end of each case. Any increase in bacterial count was recorded along with the number of anesthesia providers present, level of training, surgical procedure, duration, type of anesthesia, physical status, age, and sex of patient. Medical records for each patient were reviewed for post-operative infections.

Result            Infections occurred in 17% of the control group and 4% of the treatment group. Two patients who acquired infections in the control group died while no patients died from infection in the treatment group. When stopcocks were cultured post-operatively, 32% of the control group had positive cultures where 7.5% of the treatment group had positive cultures. Five of the patients acquired infections from the same bacteria as was found on the stopcock and 2 of these patients died from hospital acquired infections.

Conclusion            Acceptance of proper aseptic practices among anesthesia providers remains elusive. This study showed that aseptic interventions including hand hygiene can significantly reduce the risk of hospital acquired infections. Although there are several limitations to this study, it concluded that the use of an alcohol based hand cleaner on a regular basis can play a major role in reducing the contamination and spread of bacteria.

 

Comment

I found the results of this study to be impressive but the report of the study was confusing and the study methodology was flawed in many ways. Observational studies tend to create behavioral changes. I suspect that the providers used the alcohol based devices more frequently because they were being watched and they were expected to use the devices. I question if providers would be as focused on hand hygiene if they were not being observed. Of course the control group was being observed as well, but their routine was not changed by being provided a special device and instructions as the treatment group was. I suspect if the hand washing were more controlled that it might be more effective than this study shows.

Regardless of the limitations and flaws of this study, it does point out the important fact that hospital acquired infections continue to be a major health care problem. Anesthesia providers have frequent opportunities to spread infection because we are such a mobile group and frequently travel between highly infectious environments like the emergency room or patient rooms, and then back to the operating room.

The alcohol based device recommended in the study is an excellent idea. Similarly, we can keep alcohol based cleaners at our workstation, but we have to use them frequently for them to be effective. We also must keep in mind that alcohol based cleaners have limitations. They must be at least 60% alcohol to be effective. They are good at killing most bacteria and fungi, but not effective in killing bacterial spores. For that reason, hand washing is still an essential tool in preventing the spread of infection.

 

Steven Wooden, MS, CRNA

 

 

© Copyright 2009 Anesthesia Abstracts · Volume 3 Number 5, May 31, 2009





Whittington AM, Whitlow G, Hewson D, Thomas C, Brett SJ


 

 

Bacterial contamination of stethoscopes on the intensive care unit

Anaesthesia 2009;64:620-624

Whittington AM, Whitlow G, Hewson D, Thomas C, Brett SJ

 

 

Abstract

Purpose            The purpose of this study was to 1) identify actual stethoscope cleaning practices in a specific ICU, 2) identify the baseline level of stethoscope bacterial contamination, and 3) identify the level of stethoscope bacterial contamination after usual cleaning methods.

Background            Stethoscopes are frequently contaminated with pathologic organisms including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci. Cleaning stethoscopes can reduce bacterial colonization by more than 94% but even regular cleaning has little impact on the colonization of the ear pieces. The frequency with which stethoscopes must be cleaned to significantly limit cross contamination has not been established. It has been demonstrated, however, that more frequent cleaning correlates with a lower degree of stethoscope contamination.

In the study environment, a bedside stethoscope was available at each ICU bed. Infection control guidelines mandated that bedside stethoscopes be cleaned at the start of every shift.

Methodology            This prospective, descriptive study was performed in the same ICU on two separate days, three months apart. It was conducted 18 months after the launch of a “clean your hands” infection control campaign. Nursing staff working at the bedside in the ICU and all healthcare professionals who entered a patient room carrying their own stethoscope were asked to complete an anonymous questionnaire about how often and how they cleaned their stethoscope. Bedside ICU nurses were questioned about the bedside stethoscope. The diaphragm, bell, and ear pieces of each stethoscope were then cultured. Next, the individual was asked to clean the stethoscope and the cleaning method recorded. Once dry, each stethoscope was cultured again. An experienced microbiologist blinded to the source of the samples identified, quantified, and, when appropriate, conducted sensitivity testing, of all organisms grown on the auger plates.

Result            All personnel asked to participate in the study did so. The study included 24 bedside ICU nurses (12 unique nurses on each of two data collection days) and 22 healthcare professionals carrying their own stethoscopes; 10 physicians, 9 physiotherapists, 2 medical students, and 1 nurse.

Of the bedside ICU nurses, 91% reported cleaning their stethoscope every time it was used while 9% cleaned their stethoscope only at the start of the shift. Physicians and medical students reported cleaning their stethoscope less frequently; 25% reported cleaning daily or after every use, 25% reported cleaning every 1 to 6 months, and 17% reported they had never cleaned their stethoscope. Non-physician healthcare providers entering the ICU reported cleaning their stethoscopes at least daily.

Stethoscopes were cleaned with isopropyl alcohol prep swabs by 63% of participants. Another 12.5% used alcohol hand washing gel. Seven ICU nurses (15%) cleaned bedside stethoscopes with detergent wipes provided for cleaning equipment. One individual (2%) cleaned their stethoscope with soap and water.

Stethoscope diaphragm cultures before cleaning showed that 8% of personal stethoscopes and 14% of ICU bedside stethoscopes were colonized with pathogenic bacteria. Overall, 11% of stethoscope diaphragms were colonized with pathogenic bacteria. Cleaning reduced the contamination rate to 2%. Pathogenic bacteria found on personal stethoscopes were commonly multi-drug resistant. One was colonized with both MRSA and multi-drug resistant Enterobacter cloacae. Cleaning did not completely eliminate pathogenic organisms from two stethoscopes.

Stethoscope ear pieces cultured before cleaning showed that 23% of personal stethoscopes and 21% of ICU bedside stethoscopes were colonized with pathogenic bacteria. Overall, 22% of stethoscope ear pieces were colonized with pathogenic bacteria. Cleaning reduced the contamination rate to 7%. As with diaphragm cultures, cleaning did not completely eliminate pathogenic organisms from colonized ear pieces.

Conclusion            In the study institution, stethoscope cleaning was performed inconsistently, especially by medical staff. Regular stethoscope cleaning with isopropyl alcohol was insufficient to prevent colonization with pathogenic bacteria. Bacterial colonies could be further reduced if stethoscopes were cleaned after every use. Care should be taken not to contaminate the stethoscope diaphragm with the ear pieces, which were more frequently colonized with pathogenic organisms.

 

Comment

This study was yet another example of how a simple piece of research without any complicated statistics can be incredibly illuminating. It also points out how blind we can be to our own behavior. I am fastidious about washing my hands during and between cases. I carry and use hand sanitizer during cases, I always wash my hands with soap and water between cases. I always clean the ear pieces of my stethoscope after lending it to someone else. Yet, I am not in the habit of cleaning my entire stethoscope every day, let alone after every use. (Come on, I know I’m not the only one who is this stupid?) This is another habit I’m going to have to change based upon some pretty good evidence.

Infection control has always been something we all believed we knew enough about and practiced on a daily basis. But there is now developing a body of knowledge in the anesthesia setting that common, subtle practices can contribute to significant, even fatal, patient infections.1 It is hard to be aware of how often we contaminate ourselves and the equipment we use and even harder to insure that everything that may have been contaminated is adequately cleaned between patients. This past week I removed an LMA at the end of a case and thoroughly slimed my gloved hand. I threw the LMA away, placed the anesthesia mask on the patient and adjusted the pop off valve. At that instant, I realized I was turning the pop off valve with a hand still covered in slime. I wonder if it is possible to become aware of all the sources of cross contamination. Even then, I wonder if we can develop practices that prevent this contamination of our equipment and ourselves and / or allow for adequate cleaning between cases in a way that is feasible not only when things are going well, but also in demanding cases when the first and only priority is preserving the airway and vital signs. It would be nice if someone could develop anesthesia equipment that “kills germs on contact.” Until then, it may be time for a long, hard, renewed look at infection control in the anesthesia setting. Even better than an antibiotic that works is when your patient doesn’t need it.

 

Michael Fiedler, PhD, CRNA

 

1) Loftus R, Koff M, Corey B, Schwartzman J, Thorum V, Read M, Wood T, Bearch M. Transmission of pathogenic bacterial organisms in the anesthesia work area. Anesthesiology 2008;109:399-407. (See the December 2008 issue of Anesthesia Abstracts for coverage of this article.)

 

© Copyright 2009 Anesthesia Abstracts · Volume 3 Number 5, May 31, 2009




Pediatric Anesthesia

Furuya A, Ito M, Suwa M, Nishi M, Horimoto Y, Sato H, Okuyama K, Ishiyama T, Matsukawa T


 

 

The effective time and concentration of nitrous oxide to reduce venipuncture pain in children

J Clin Anesth 2009;21:190-193

Furuya A, Ito M, Suwa M, Nishi M, Horimoto Y, Sato H, Okuyama K, Ishiyama T, Matsukawa T

 

 

Abstract

Purpose            The purpose of this study was to compare the percent concentration of and exposure time to Nitrous Oxide (N2O) on the pain and anxiety experienced by children aged 6 years to 15 years during IV catheter insertion.

Background            It is sometimes preferable to induce general anesthesia intravenously in school aged children, but starting an IV in an awake child may be a fearful experience. Sedation may be beneficial given sufficient time but can sometimes work unpredictably or wear off before it is time to start the IV. EMLA cream does not prevent the child from becoming anxious when they see a needle and may cause vasoconstriction making IV insertion more challenging. N2O may reduce pain and anxiety during venipuncture in children. Some reports show that 70% N2O is a more effective analgesic than 50% N2O when starting IVs in children.

Methodology            This prospective, blinded study included healthy children between 6 years and 15 years old scheduled to receive general anesthesia. Patients with mental retardation, problems with oxygenation, or otitis media were excluded from the study. Parents remained with children in the OR until after the IV was started. Patients were randomly assigned to receive one of the following treatments prior to IV insertion: 50% N2O for 3 minutes, 50% N2O for 5 minutes, 70% N2O for 3 minutes, and 70% N2O for 5 minutes. None of the study patients received a premedication.

After the prescribed concentration and exposure time to N2O, a 24 gauge IV was started in the back of the hand. Following IV insertion all children breathed 100% oxygen for 3 minutes and were then asked to report their pain by picking one of six faces depicting increasing levels of discomfort. (Bieri face scale.) The face for “0” was smiling and the face for “10” appeared to be screaming in pain. Pain “scores” were analyzed with appropriate non-parametric, ordinal statistics. If more than one attempt was needed to start the IV the patient was excluded from analysis.

Result            Demographic factors were similar between the four groups. One patient was excluded from analysis resulting in the analysis of 72 patients; 18 per group. Pain scores from both 70% N2O groups were lower than both 50% N2O groups. The median pain score during 50% N2O was 2 or 3. The median pain score during 70% N2O was 0. N2O 70% was more likely to cause excitement, restlessness, movement, nausea, or vomiting.

Conclusion            Inhalation of either 50% or 70% nitrous oxide for 3 minutes was associated with little to no pain during insertion of a 24 gauge IV in children aged 6 years to 15 years old. Inhalation of 70% N2O prevented pain more reliably than did 50% N2O.

 

Comment

While simple, this study was adequately designed, though I would liked to have seen nitrous compared to their standard method with sedation only. I guess I’m left wondering what the investigators thought was going to happen. Were they surprised that 50% to 70% nitrous produced pretty good analgesia in children and allowed starting a 24 gauge IV without much fuss? And, for that matter, if they had them breathing 70% nitrous for three to five minutes why not simply turn on the sevoflurane and be done with induction. They cited airway obstruction and laryngospasm as reasons for wanting to perform an IV induction. Is the risk of induction with an inhalation agent high enough that breathing 70% nitrous to get an IV started is a better option? If so, that’s news to me. Lastly, while the difference between 50% nitrous and 70% nitrous was statistically significant, I question whether it was clinically significant or not.

The investigators tried to make the case that 70% nitrous provided much better analgesia and no greater side effects, such as vomiting (which most would see as more likely with 70% nitrous in kids). But their study wasn’t really big enough to convince me that their 70% nitrous kids didn’t throw up more often. All in all, I see this study as an overly optimistic solution looking for not much of a problem.

 

Michael Fiedler, PhD, CRNA

 

 

© Copyright 2009 Anesthesia Abstracts · Volume 3 Number 5, May 31, 2009