ISSN NUMBER: 1938-7172
Issue 3.1 VOLUME 3 | NUMBER 1

Editor:
Michael A. Fiedler, PhD, CRNA

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

Guest Editor:
Lisa Osborne, PhD, 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

OBSTETRIC ANESTHESIA
ELEVATION OF UTERINE BASAL TONE AND FETAL HEART RATE ABNORMALITIES AFTER LABOR ANALGESIA: A RANDOMIZED CONTROLLED TRIAL
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  CONVERSION OF EPIDURAL LABOUR ANALGESIA TO ANAESTHESIA FOR CAESAREAN SECTION: A PROSPECTIVE STUDY OF THE INCIDENCE AND DETERMINANTS OF FAILURE
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  A RANDOMIZED DOUBLE-BLINDED COMPARISON OF PHENYLEPHRINE AND EHPHEDRINE INFUSION COMBINATIONS TO MAINTAIN BLOOD PRESSURE DURING SPINAL ANESTHESIA FOR CESAREAN DELIVERY: THE EFFECTS ON FETAL ACID-BASE STATUS AND HEMODYNAMIC CONTROL
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  FAILURE OF AUGMENTATION OF LABOR EPIDURAL ANALGESIA FOR INTRAPARTUM CESAREAN DELIVRY: A RETROSPECTIVE REVIEW
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GENERAL
  INTERRUPTIONS AND BLOOD TRANSFUSION CHECKS: LESSONS FROM THE SIMULATED OPERATING ROOM
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THE EFFECT OF DIFFERENT CRYSTALLOID SOLUTIONS ON ACID-BASE BALANCE AND EARLY KIDNEY FUNCTION AFTER KIDNEY TRANSPLANTATION
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PAIN
THE ANALGESIA EFFECT OF EPIDURAL CLONIDINE AFTER SPINAL SURGERY: A RANDOMIZE PLACEBO-CONTROLLED TRIAL
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AIRWAY
  ACUTE AIRWAY OBSTRUCTION CAUSED BY THE NEW SINGLE USE LARYNGEAL MASK AIRWAY SUPREME
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Obstetric Anesthesia

Abrao K, Francisco R, Miyadahire S, Cicarelli D, Zugaib, M


 

Elevation of uterine basal tone and fetal heart rate abnormalities after labor analgesia:  a randomized controlled trial

Obstet Gynecol 2009;113:41-47

Abrao K, Francisco R, Miyadahire S, Cicarelli D, Zugaib, M

 

Abstract

Purpose            The purpose of the study was to determine what, if any, fetal heart rate abnormalities were seen in laboring women who received either a combined spinal-epidural or an epidural alone for analgesia.

Background            Regional analgesia for labor is extremely popular. The cause of fetal heart rate (FHR) abnormalities that may occur after the administration of regional analgesia, and how to manage them, remains somewhat controversial. The combined spinal-epidural analgesia technique using opioids has been reported in previous studies to be associated with an increased incidence of non-reassuring FHR tracings. It has been hypothesized that the rapid onset of analgesia offered by a combined spinal-epidural may cause an imbalance in maternal catecholamines. This imbalance may lead to uterine hyperactivity which could be challenging the fetus with a ‘pseudo’ stress test, the result of which is an abnormal fetal heart rate tracing. Research evidence is lacking regarding whether or not the combined spinal-epidural technique leads to fetal heart rate abnormalities when compared with the traditional epidural analgesia technique.

Methodology            This study was a prospective, partially blinded, randomized clinical trial and was approved by the institutional review board. Written informed consent was obtained from each participant. Inclusion criteria included single fetus, cephalic presentation, full-term pregnancies. The women had to request analgesia before they reached 7 cm of cervical dilation. Appropriate exclusion criteria were upheld. Seventy-seven low-risk laboring females were randomly assigned to 1 of 2 groups. Group 1 parturients received a combined spinal-epidural for labor analgesia with an intrathecal solution of 0.05% bupivacaine 2.5 mg and 2.5 mcg of sufentanil, followed by placement of an epidural catheter. Group 2 parturients received a traditional epidural for labor analgesia with an epidural injection of 0.125% bupivacaine 12.5 mg plus 10 mcg of sufenanil. Both groups received bupivacaine epidural boluses upon request, and dosing was determined depending on cervical dilation, as follows:

  • 0.125% until 7 cm dilation was reached
  • 0.25% if the cervical was between 8-9 cm
  • 0.5% when the women were pushing (second stage of labor)

Participants were monitored with an intrauterine pressure transducer for a minimum of 15 minutes pre and post labor analgesia administration. Fetal heart rate was monitored with an external transducer. The types of analgesia used for each patient was unknown by the patient and the obstetric team. Pre-hydration was standardized for all participants.

Primary outcome variables included: occurrence of prolonged decelerations- defined as a fall of 15 beats per minute or greater, lasting > 2 minutes and < 10 minutes, or fetal bradycardia- defined as the fall of baseline to <100 bpm, and an increase in basal uterine tone of 10 mm Hg or more, after analgesia. These analyses were performed in the first 15 minutes after analgesia was begun. The secondary outcome variable assessed was the occurrence of maternal hypotension, defined as a systolic blood pressure <100 mm Hg or a decrease of 20% from baseline. Oxytocin use was allowed. If oxytocin was initiated before analgesia, dosing was maintained during the first 15 minutes of regional analgesia administration. Appropriate demographic variables were recorded; pain scores were measured via a visual analogue scale.

Result            The analysis of demographic variables (maternal age, gestational age, dilation at analgesia start time, VAS score at analgesia start time, and oxytocin use/dose) did not show any differences between the two groups. Patients in the spinal-epidural group demonstrated an elevated uterine tone, abnormal fetal heart rate, and fetal heart rate abnormalities that were associated with hypertonus, compared with the epidural-alone group. All three variables were statistically significant (p<0.05). Maternal hypotension was present in only a few of the cases that presented with fetal heart rate abnormalities, this was not statistically significant. All women had resolution of uterine hypertonus and non-reassuring fetal heart rate tracing with typical treatments such as hydration, suspension of oxytocin, and oxygen supplementation. The spinal-epidural group demonstrated significantly lower pain scores at the ‘time by treatment’ interaction (mode of analgesia). Additional analysis showed no differences in newborn umbilical artery pH or in Apgar scores upon delivery.

Conclusion            This study demonstrated that combined spinal epidural analgesia is associated with an elevation of baseline uterine tone and fetal heart rate abnormalities when compared with the traditional epidural-alone method of analgesia. A transient increase in uterine tone was present in almost 50% of the patients after the administration of the combined technique. Additionally, among those that presented with an increased uterine tone of more than 10mm Hg, 64.5% had simultaneously occurring fetal heart rate abnormalities within the first 15 minutes of medication injection.

 

Comment

While the combined spinal-epidural technique using bupivacaine and sufentanil demonstrated a significantly more rapid onset of analgesia for the women in labor, it demonstrated that immediate relief of pain can actually be correlated with fetal distress. While the fetal distress was treated, and with a good response, this may not always be the case. The standard epidural technique used for this trial, achieved, as expected, acceptable pain scores in these participants, it was simply a slower onset of analgesia. And, it was correlated with significantly less evidence of fetal distress. In other words, this study showed that the faster the pain relief, the higher the probability of elevation of uterine tone and coincident fetal heart rate changes. While one can certainly appreciate the desire for analgesia during labor, we owe it to our patients to explain that we can take the majority of their discomfort away with the ‘standard’ epidural technique, AND it may be a bit slower onset relative to other techniques, however, the studies are demonstrating that it has the potential for being the safest for their babies.

 

Mary A. Golinski, PhD, CRNA

 

Notes:  Intra-uterine pressure monitoring devices are able to measure uterine contractions and their intensities. The amplitudes of resting uterine tones and peak contraction pressures can be assessed throughout the labor, as well as when key interventions occur. After an intervention, such as labor analgesia, position change, fluid administration, etc, the amplitudes are compared with baseline (those quantified pressures prior to the intervention). These amplitude changes are compared with fetal heart rate traces obtain from the external monitors. This data is critical to help provide timely detection of conditions occurring in real time, which can lead to rapid fetal distress.

© Copyright 2009 Anesthesia Abstracts · Volume 3 Number 1, January 31, 2009





Halpern SH, Soliman JY, Angle P, Ioscovich A


Conversion of epidural labour analgesia to anaesthesia for caesarean section: a prospective study of the incidence and determinants of failure

 

Br J Anaesth 2009;102:240-243

Halpern SH, Soliman JY, Angle P, Ioscovich A

 

Abstract

Purpose            The purpose of this study was to determine the incidence of conversion from epidural anesthesia to general anesthesia for cesarean section in a teaching hospital. A secondary purpose was to identify risk factors for the need to convert from regional to general anesthesia for cesarean section and the failure rate of epidural anesthesia.

Background            Epidural analgesia is commonly used to provide pain relief during labor. Not all epidural catheters placed for labor prove to be reliable when called upon to induce epidural anesthesia for cesarean section. Previous studies have reported that as many as 26% of labor epidurals subsequently used for cesarean section needed anesthesia in addition to that provided via the epidural catheter. Failed transition from labor analgesia to anesthesia resulting in the need for a general anesthetic has been reported to occur in 2.4% of cases.

Methodology            This observational study included all women who had an epidural placed for labor analgesia and subsequently underwent cesarean section throughout a 16 month period. Data was collected in a university teaching hospital with 3,750 deliveries per year. Both epidural and combined spinal-epidural (CSE) techniques were used for labor analgesia. Epidural analgesia was produced with 10 to 20 mL of 0.08% to 0.125% bupivacaine. CSE analgesia was produced with 1.25 mg to 2.5 mg bupivacaine and 5 µg sufentanil. Thereafter, analgesia was continued with patient controlled epidural analgesia: bolus 5 mL to 7 mL, lockout 10 min, background infusion 5 mL to 10 mL of 0.08% bupivacaine with 2 µg/mL fentanyl.

Epidurals were dosed for cesarean section, when necessary, with a solution chosen by the attending anesthesiologist. Data were collected contemporaneously and checked against the chart after the fact.

Result            Data were gathered from 501 women. Of these, 496 women were dosed with an average of 18.2 mL of 2% lidocaine with epinephrine for cesarean section. Five women were dosed with either bupivacaine or 2-chloroprocaine. An additional 50 µg to 100 µg fentanyl was added to the epidural anesthesia dose of 60% of the women.

Epidural anesthesia was insufficient, by itself, to perform the cesarean section in 30 women (6%). In 9 women (1.8%) the epidural was supplemented but general anesthesia was not induced. In 21 women (4.2%, 95% CI 2.6% - 6.3%) general anesthesia was induced. In 15 cases (3%) general anesthesia was induced because the epidural had failed.  In the other 6 cases general anesthesia was induced due to bleeding (n=1), because there was believed to be inadequate time to dose the epidural (n=3), or because the woman requested it (n=2).

Block failure was predicted by patient height (P=0.023) and the number of epidural boluses administered by an anesthesia provider during labor (P=0.016) (recall that patient controlled epidural analgesia was being used).

Conclusion            Epidural anesthesia was insufficient to perform a cesarean section in 6% of women and general anesthesia was induced in about half of these cases. Block failure was associated with greater maternal height and additional epidural boluses of local anesthetic by an anesthetist during labor analgesia. Block failure was not associated with multiple attempts at placing the epidural, cervical dilation before cesarean section, fetal heart rate abnormalities, or the duration of labor analgesia.

 

Comment

This report makes me crave a national anesthesia statistical database. In my vision of such a database, each anesthesia group would report anesthesia data to a centralized collection agency. That agency would report group specific information only back to the group it came from. Pooled results from all sources would be reported anonymously to all groups. In that way, each group could see how their statistics compared with the national average and averages over time.

How in the world did this article make me think of this? Well, this study was conducted because an anesthesia group wanted to see if they could meet guidelines. The study was performed in Canada. Apparently, the Royal College of Anaesthetists published a guideline saying that the rate of conversion from regional to general anesthesia for cesarean section should not exceed 3%. This, in my view, is one of those guidelines we don’t need to have. What purpose does it serve? What is more important is why the epidural was converted to a general for cesarean section. If the conversion was because the epidural didn’t produce surgical anesthesia that is one thing. If the conversion was because the patient demanded a general that is another thing entirely. Only in knowing the why does a conversion rate have meaning.

How might a guideline be harmful? Let’s say the national average for conversion from epidural to general for cesarean section is 3% and my group’s rate is 9%. With a standard I’m “non-compliant” so we must be doing something wrong. The pressure is on to lower the number. (Note the focus on the number, rather than on the patients.) So, pressure is applied, and before you know it the conversion rate is lower, but at the cost of “making epidurals work” that would previously have been converted to a general. In fact, that may even have gone on during this study. Note that while the epidural was “insufficient by itself” for cesarean section in 6% of cases in only 4.2% of cases was general anesthesia induced. The investigators reported that “14 patients received sedation to supplement epidural anesthesia.” (We don’t know which 14, so it may not have been in patients with “inadequate” epidural anesthesia.) These patients received up to 350 µg fentanyl (n=11), 5 mg morphine (n=1), 40 mg to 60 mg propofol (n=2), 1.5 mg to 2 mg midazolam (n=4), and diazepam 2.5 mg (n=1). Five patients received more than one drug. (The route of administration was not reported. I assume it was intravenous.) To be sure, some epidurals work fine with a little supplementation and don’t need to be converted to general anesthesia but the opportunity here to “fix the number” by trying to get by with sedation when general anesthesia would be a better choice should be obvious.

How would a database be better? If I had the nationwide database I’d see a real, rather than proposed, national average. I’d see this number in the context of time, changing with each passing year. When I saw 9% my response would be, “why are we converting so many women to general anesthesia for their cesarean sections?” (Note the focus on the patient and anesthesia providers, rather than a number.) If our number is three times the national average because our epidurals don’t work that tells me one thing. We look at whose epidurals don’t work and what we can do about it. If our number is 9% because we serve a patient population that includes a lot of women who refuse regional anesthesia for surgery and demand a general anesthetic that is a different thing entirely.

Guidelines for practice can be very helpful when they are proposed by experts who have weighed evidence and experience. Guidelines for outcomes are more likely to be like “one size fits all.” It rarely does.

Michael Fiedler, PhD, CRNA

© Copyright 2009 Anesthesia Abstracts · Volume 3 Number 1, January 31, 2009





Ngan Kee, WD, Lee A., Khaw KS, Ng FF, Karmakar MK, Gin T.


 

 

A randomized double-blinded comparison of phenylephrine and ehphedrine infusion combinations to maintain blood pressure during spinal anesthesia for cesarean delivery:  the effects on fetal acid-base status and hemodynamic control

Anesth Analg 2008;107:1295-1302

Ngan Kee, WD, Lee A., Khaw KS, Ng FF, Karmakar MK, Gin T.

 

 

Abstract

Purpose            The purpose of this study was to compare the effects of an infusion of varying mixtures of phenylephrine and ephedrine after the administration of spinal anesthesia to healthy women with singleton pregnancies undergoing cesarean section.

Background            The maintenance of systolic blood pressure (SBP) during cesarean delivery following spinal anesthesia can be augmented by the use of phenylephrine and ephedrine; however, the mechanism of action of each drug differs and they are typically given independent of one another. No studies to date have evaluated the effects of varying ratios of phenylephrine and ephedrine during infusion on maternal hemodynamics and fetal well-being. Rather studies utilizing the combination of phenylephrine and ephedrine administration have been based on fixed, single dose ratios.

Methodology            This was a randomized, double-blind study including 125 healthy ASA 1 and 2 term singleton parturients undergoing elective cesarean section under spinal anesthesia conducted by the Department of Anesthesia and Intensive Care at The Chinese University of Hong Kong. The aim of the study was to compare the effects of five different mixtures of phenylephrine and ephedrine upon umbilical cord blood gases and maternal blood pressure and heart rate (HR), at patient baseline and following neuraxial anesthesia. Patients were randomly assigned to receive one of the five vasopressor mixtures containing varying proportions of phenylephrine and ephedrine based upon the assumption that phenylephrine 100 µg shares an equal potency to 8 mg of ephedrine. The makeup of the mixtures was as follows:  100%, 75%, 50%, 25%, or 0% phenylephrine and 0%, 25%, 50%, 75%, or 100% ephedrine respectively.

Standard monitoring was used to establish baseline SPB and HR prior to spinal anesthesia. Each patient received 10 mg of bupivacaine (0.5%) and fentanyl 15 mcg intrathecally in the right lateral position without intravenous prehydration. Following spinal anesthesia, the patient was placed supine with BP recordings conducted at 1 min intervals and hemodynamics recorded. Intravenous fluid infusion was initiated at spinal injection. The randomly assigned vasopressor mixture was administered at 60 mL/hr by syringe pump. The infusion was continued until the uterine incision and patients were treated with 100 µg of phenylephrine IV bolus for SBP ≤ baseline and hypotensive episodes (SBP < 80% baseline). However, if SBP was > baseline, then the infusion was discontinued. The vasopressor infusion mixture was also stopped for bradycardia (HR < 50 ) and refractory bradycardia could be treated with atropine 0.6 mg IV.

The investigators recorded the incidence of nausea and vomiting, sensory level of anesthesia 5 minutes following intrathecal anesthesia, Apgar scores at 1 and 5 minutes, umbilical arterial (UA) and umbilical venous (UV) blood gasses, as well as oxygen content. Supplemental oxygen was provided for pulse oximetry readings of < 95%.

Result            One-hundred-twenty-two patients completed the study protocol. Patient sensory level following spinal anesthesia at 5 minutes was higher in the 100% ephedrine group (E100) when compared to the 100% phenlyephrine group (P100). The total volume of vasopressor mixture administered until incision was less in the 100% ephedrine group than the phenylephrine group, however, the incidence of nausea and vomiting increased as the ratio of ephedrine increased in the vasopressor mixture.

There was no significant difference among the groups to minimal or maximum recorded SBP values, and SBP values tended to follow the patient’s baseline SBP better in the P100 group when compared to the E100 group. Heart rate recordings in the P100 group were lower than in any other group of the study, with a notable increase in HR as the mixture ratio became ephedrine based.

There was no significant difference in Apgar scores among the vasopressor groups, however, UA blood analysis values demonstrated that pH, base excess and oxygen content values all trended downward as the vasopressor mixture progressively became predominantly ephedrine based (pH of 7.29 in P100 group versus 7.21 in E100 group; base excess (mM) of -2.3 in P100 group versus -5.1 in E100 group; oxygen content (mL/dL) of 7.3 in P100 group versus 4.7 in the E100 group). Additionally, Pco2 levels tended to increase from group P100 to group E100. For UV blood, pH and base excess decreased from group P100 to group E100 and the PO2 value trended upward in value from group P100 to group E100.

Conclusion            This study demonstrated that an increasing proportion of phenylephrine in a vasopressor mixture when administered as an infusion results in increasing hemodynamic stability, less hypotension, decreased incidence of nausea and vomiting, as well as increased UA pH, base content, and oxygen content values

 

Comment

This study is important to practice because it confirms that the use of phenylephrine is not only safe, but may lead to improved fetal pH and base excess compared to the use of ephedrine. There is a growing body of evidence that counters the previous research in pregnant ewes that suggested that phenylephrine use would lead to fetal hypoxia1. This study also is important because it showed that there was no advantage to combinations of ephedrine and phenylephrine compared to phenylephrine alone.

The unique part about this study is that the authors administered the vasopressors via infusion. Because most practitioners do not typically administer ephedrine via infusion, the results cannot be directly generalized to the obstetrical practices of bolus dosing. This study needs to be repeated with dosing that is more reflective of clinical practice that is common in the U.S.

Another item of interest in this study is that all of the subjects did not receive a fluid bolus until after the administration of spinal anesthesia and there were no untoward effects. Most providers administer some type of fluid bolus prior to spinal to prevent spinal-induced hypotension. This study demonstrates that the fluid bolus that is typically administered may not be as effective as we think, and is probably due to the fact that it is often timed incorrectly. The crystalloid solution only remains in the intravasculature for 15-20 minutes. If the spinal is difficult to place, or there are other types of delay, the fluid bolus may not be effective. However, if the bolus is infusing as the administration of the spinal is completed, it may be just as effective at alleviating the hypotension. Alas, this will be a topic for another day…

 

Lisa Osborne, PhD, CRNA

 

1. Ralston, DH, Snider SM, deLorimier AA. Effects of equipotent ephedrine, mataraminol, mephentermine, and methoxamine on uterine blood flow in the pregnant ewe. Anesthesiology 1974;40:354-70.

© Copyright 2009 Anesthesia Abstracts · Volume 3 Number 1, January 31, 2009





Lee S, Lew E, Lim Y, Sia AT


 

 

Failure of augmentation of labor epidural analgesia for intrapartum cesarean delivry: a retrospective review

Anesth Analg 2009;108:252-254

Lee S, Lew E, Lim Y, Sia AT

 

 

Abstract

Purpose            The purpose of this study was to identify factors associated with the failure of epidurals for cesarean section anesthesia when they had been previously used for labor analgesia. The failure rate was also determined.

Background            Labor epidural analgesia is commonly converted to anesthesia with a more concentrated local anesthetic when cesarean section becomes necessary. When the epidural fails to produce anesthesia sufficient for a cesarean section general anesthesia is often used. Converting to general anesthesia is associated with increased maternal and fetal risk. The failure rate for converting an epidural from labor analgesia to cesarean anesthesia has been reported to be 0% to 38%.

Methodology            This study retrospectively examined a database with information about all women who received labor epidural analgesia over an 18 month period. Both epidurals and combined spinal-epidurals were used for labor analgesia. With both techniques ropivacaine or bupivacaine with or without fentanyl was used to establish and maintain analgesia. Breakthrough labor pain, defined as a visual analogue pain score greater than 3, was treated with an epidural bolus of 1.5% lidocaine, ropivacaine, or bupivacaine with or without no more than 100 µg fentanyl.

Result            During the study 4,825 women received combined spinal-epidural analgesia and 658 received epidural analgesia. Most women (87%) received a continuous epidural infusion. Only 131 (13%) women received epidural PCA. Epidurals were dosed for cesarean section in 1025 women. Failed block occurred in 17 women (1.7%) and they received general anesthesia. Failed epidural anesthesia was due to block height below T-5, inadequate anesthesia, or a “spotty” block. Failure to transition an epidural from labor analgesia to cesarean anesthesia was associated with the length of time the epidural had been in place, epidural analgesia alone rather than combined spinal-epidural analgesia, and a greater number of complaints of inadequate labor pain relief.

Conclusion            At this institution, the failure rate for converting a labor epidural to anesthesia for cesarean section was 1.7%. Failure was associated with epidurals that had been in place longer, inadequate block height, and “spotty” blocks.

 

Comment

Earlier in this section we reviewed another article reporting on the incidence of epidural failure when dosed for cesarean section. (“Conversion of epidural labour analgesia to anaesthesia for caesarean section: a prospective study of the incidence and determinants of failure”) It is interesting to compare the two reports, since they have a number of differences. Both studies described the rate of epidural failure and looked for factors associated with that failure. The failure rates were different, 6% (or 4.2% depending upon your point of view) in the previous study and 1.7% in this one. Factors associated with epidural failure differed except for the number of times a woman complained of inadequate epidural analgesia during labor. This common factor should be no surprise to anyone who provides labor analgesia. When an epidural is positioned suboptimally local anesthetic doesn’t get where you want it and women have pain. No surprise than, that dosing an epidural for a cesarean section that had never worked well was quite likely to produce a poor surgical block.

In this study, while the length of time an epidural had been in place was statistically significantly associated with the failure rate at cesarean section the difference (Odds ratio 1.06, P=0.02) was of questionable clinical significance.

In the end, neither of these studies provides a great benchmark for the failure rate of epidurals at cesarean section. In my view, the failure rate is probably most related to the technique of the anesthesia provider who placed and managed the epidural. Yes, there are occasional anatomic variations that affect the quality of a block, but, in the end, strong work almost always produces superior results.

 

Michael Fiedler, PhD, CRNA

 

 

© Copyright 2009 Anesthesia Abstracts · Volume 3 Number 1, January 31, 2009




General

Liu D, Grundgeiger T, Sanderson PM, Jenkins SA, Leane TA


 

Interruptions and blood transfusion checks: lessons from the simulated operating room

Anesth Analg 2009;108:219-222

Liu D, Grundgeiger T, Sanderson PM, Jenkins SA, Leane TA

 

Abstract

Purpose            The purpose of this study was to determine whether or not a purposeful interruption would result in the failure of an anesthesia provider to check blood before administration in a simulated operating room / anesthesia setting.

Background            The operating room environment often involves multiple interruptions. An average of 17.4 interruptions an hour have been previously reported. Interruptions can be a good thing or a bad thing in regards to patient care. They can increase the incidence of errors and threaten patient safety or they can make the anesthesia provider aware of new information important to patient care. Interruptions are more likely to result in distraction from more important tasks when the status of the interrupter is perceived to be high, when workload is high, and when the individual is fatigued. Interruptions have been cited as a contributing factor in blood administration errors. One study reported that 26.5% of errors in blood transfusion were due to a failure to check blood immediately prior to administration.

Methodology            This retrospective simulation study included 7 novice and 5 experienced anesthesia providers undergoing a 35 to 40 minute anesthesia simulation. The “checking blood” scenario was one of 24 events presented to the participants during the simulation period. Twenty minutes into the case major bleeding began. The anesthesia provider had to order blood and manage hemodynamics with IV fluids until it arrived. An assistant nurse was involved in the scenario who would proceed with blood administration without checking it unless stopped from doing so by the anesthesia provider. At the same time as the blood arrived in the simulated OR, the surgeon distracted the anesthesia provider with a discussion of making arrangements to admit the patient to an ICU bed postoperatively. The anesthesia provider was to make the arrangements. During this time the nurse would attempt to carry the blood past the anesthesia provider and hang it without performing a check.

Result            Anesthesia providers responded to the simultaneous arrival of the blood and the surgeon’s demand for attention in one of four ways. Some were completely distracted by the surgeon. Some talked with the surgeon while checking the blood with the nurse. Some checked the blood or delegated the check to someone else and then returned to the discussion with the surgeon. Some simply told the surgeon, “no,” and stayed on task checking the blood.

In all, 3 of the 8 anesthesia providers (37.5%) allowed the blood to be started without being checked, focusing in stead on the surgeon. The other 5 anesthesia providers quickly intervened to insure that the blood was checked prior to being infused.

Conclusion            An interruption perceived to be important by the anesthesia provider resulted in blood being hung without first being checked in 37.5% of cases.

 

Comment

From a methodological perspective this study really wasn’t one I’d want to present to anyone as “evidence” upon which to base practice. Nevertheless, I think it raises some issues that we can learn from; some obvious and some not so obvious.

I resist protocols and strict procedures because I often see them interfering with intelligent decision making. Specific procedures can really get in the way when the context they were designed to fit into changes but the procedure hasn’t changed and the system rigidly adheres to the procedure. But, I must admit that there are situations where procedures serve a very useful purpose. I’m guessing that most of us work in an OR environment where there is a pretty strict procedure that no one hangs blood during an anesthetic without the anesthetist either participating in checking the blood or delegating the task to someone else. If that is not the case, this simulation is a strong argument that it should be. Anesthesia really must “rule the roost” in regards to patient care in the OR.

We all know that the OR can get to be a busy place. During some more challenging cases we are constantly dealing with more than one thought process at a time; assessing blood loss visually while administering a drug with one hand and adjusting a flowmeter with the other, all the while listening to an update from the surgeon and prioritizing the 11 other tasks on our immediate “to do” list. We understand the importance of being able to process more than one task (cognitive or manual) at a time. In this study, those who allowed blood to be hung without being checked made, as I see it, two distinct mistakes. First, they mistakenly prioritized talking with the surgeon about something that could wait ahead of checking blood. Second, and this may speak to ability rather than choice, they focused on a single task to the exclusion of others. It is hard for me to imagine a successful anesthetist who couldn’t handle both tasks at once. But in any case, each of us should be willing to and have a strategy for politely telling anyone that we’ll be with them in a minute, right after we complete this task that involves the immediate safety of the patient.

Oh, and by the way, two of those who were distracted from checking blood were novice anesthesia providers but one was an experienced provider. All of us need to think about and guard against distraction.

Michael Fiedler, PhD, CRNA

 

 

© Copyright 2009 Anesthesia Abstracts · Volume 3 Number 1, January 31, 2009





Hadimioglu N, Saadawy I, Saglam T, ertug Z, Dinckan A


 

 

the effect of different crystalloid solutions on acid-base balance and early kidney function after kidney transplantation

Anesth Analg 2008;107:264-269

Hadimioglu N, Saadawy I, Saglam T, ertug Z, Dinckan A

 

 

Abstract

Purpose            The purpose of this study was to compare the metabolic profile and renal function (evidenced by electrolyte profile) in those undergoing kidney transplantation who received three different crystalloid intravenous solutions during the transplant:  normal saline, ringer’s lactate, or Plasmalyte electrolyte solution.

Background            End stage renal disease has a negative impact on virtually every body system. It creates monumental challenges for the anesthetist during renal transplantation. Acid-base and electrolyte disturbances are markedly noted in those with renal failure and these disturbances further aggravate the hemodynamic status of the recipient at a time that could not be more inappropriate. Crystalloid use, attempting to create and/or maintain a normo-volume status, is crucial to ensure optimal graft perfusion and function. Normal saline use has been noted to worsen an existing metabolic acidosis due to the chloride ion content. Ringer’s lactate has been reported to aggravate existing hyperkalemia due to the potassium ion content. Plasmalyte, in terms of its ability to maintain a stable acid-base balance and/or potassium values, has not been studied nor reported in the literature.

Methodology            This research was conducted as a prospective, randomized, double-blinded clinical trial. After obtaining Ethics Committee approval and written informed consent from participants, 90 patients were randomized to one of three groups. Group 1 (n = 30) received 0.9% normal saline; group 2 (n = 30) received Ringer’s lactate; and group 3 received Plasmalyte (n = 30). The anesthetic was standardized for all including monitoring modalities used. Fluids were administered at a rate of 20-30 mL/kg/hour to maintain a central venous pressure value of 12-15 mm Hg. The total volume of intravenous fluids was recorded and patients were kept normothermic intra-anesthetically. At the end of surgery the study fluid was discontinued and patients were then given intravenous fluids in the form of D5/0.45% normal saline. Arterial blood gas samples (via an arterial line), electrolyte profile and lactate levels were drawn at the following times:  before the induction of anesthesia, every 30 minutes during the transplant, and at the end of operation. Additionally, total urine volume and further electrolyte profiles were drawn every 24 hours until the third post operative day and then once on the 7th post operative day. Patient demographic data was also collected. Statistical analysis was performed and for all tests used, values were considered to be significant at P < 0.05.

Result            The demographic data for all groups was comparable, including the characteristics of the donors, as well as the volume of fluid administered during the transplant. The pH in the group who received 0.9% normal saline was significantly lower than the pH measured in the other two groups; however no patient developed a true acidosis. Changes in base excess (lower) corresponded with the change in pH, and only for the saline group. Understandably, the saline group also demonstrated a significant decrease in bicarbonate levels not seen in the other two groups. Also seen in the saline group was a significant elevation in serum chloride levels which remained elevated for three days post operatively. As expected, those who received Ringer’s lactate showed a significant increase in serum lactate levels, but without a change in pH. None of the patients in any group demonstrated significant changes in serum potassium. Of interest also, no patients required insulin during the procedures and blood glucoses ranged within tight control (<140 mg/dL). While the cumulative urine output was significantly larger in the normal saline group for the first three postoperative days, there were no significant differences between groups in post operative renal function tests or the need for hemodialysis.

Conclusion            This study demonstrated that for renal transplant surgery, 0.9% normal saline, Ringer’s lactate, or Plasmalyte can be safely used for intravenous fluid administration in uncomplicated relatively short duration surgeries. Because the pH, base-excess levels, and lactate values were outside of normal ranges in all groups except the Plasmalyte group (albeit not affecting graft patency or hemodynamic stability), the best metabolic profile (no values outside of normal range) was seen in the Plasmalyte group.

Comment

This much needed study provided us with a small yet significant amount of evidence that we need to help us make scientific decisions regarding types of crystalloid to administer for the patient with end stage renal disease undergoing renal transplantation. And the evidence, albeit from a study with a small to moderate sample size, speaks volumes. I took the liberty to access the literature and provide the chemical constituents of the three crystalloid solutions, below (in mmol/L and adapted in part from Critical Care and Resuscitation 1999;1:151-156). This article in Critical Care Medicine is nearly a decade old however, its detail and content is very clear in describing the theories of acid-base physiology and the controversies that exist regarding acid-base balance and intravenous fluid administration. I encourage everyone to review the concepts in order to understand why we are administering certain crystalloid solutions and what the evidence is suggesting regarding what is appropriate for the renal transplant patient.

 

 

 

0.9% saline

Plasmalyte

Ringers

Sodium

150

140

144

Chloride

15

98

152

Potassium

0

5

4

Calcium

0

0

2

Magnesium

0

1.5

0

Bicarbonate

0

27(acetate)

0

 

 

23(gluconate)

 

 

Mary Golinski PhD, CRNA

 

 

© Copyright 2009 Anesthesia Abstracts · Volume 3 Number 1, January 31, 2009




Pain

Farmery AD, Wilson-MacDonald J


 

 

The analgesia effect of epidural clonidine after spinal surgery: a randomize placebo-controlled trial

Anesth Analg 2009;108:631-634

Farmery AD, Wilson-MacDonald J

 

 

Abstract

Purpose            The purpose of this pilot study was to assess the analgesic potency of low-dose epidural clonidine following uncomplicated spinal surgery.

Background            Clonidine is an α2 receptor agonist with analgesic, sedative, and MAC reducing effects. The analgesic effects of clonidine are primarily mediated at the spinal level. Epidural administration of clonidine results in lower plasma levels than administration of the same dose by other routes. Following spinal surgery, local anesthetics can mask signs of neurologic injury and are not generally used for postoperative pain following spinal surgery.

Methodology            This prospective study included 66 patients scheduled for elective lumbar nerve root decompression surgery. Patients who had been taking strong opioids preoperatively or had a history of chronic pain were excluded. After randomization, patients were divided into an epidural clonidine infusion group and a control group. All patients received a specified general anesthetic with acetaminophen, ibuprofen, ranitidine, propofol, fentanyl, atracurium, nitrous oxide and isoflurane. Before wound closure an epidural catheter was positioned in all patients. Next, clonidine patients received an epidural bolus of 1.5 µg/kg clonidine and an infusion of 25 µg/h clonidine for 36 hours. Control patients received an equal volume saline bolus and infusion over the same time period. All patients received standard morphine IVPCA.

Result            The clonidine group used 43% less IVPCA morphine over the first 36 hours postop than the control group, 35 mg vs. 61 mg (P=0.011). While there was notable interindividual variability in pain scores, the clonidine group consistently reported lower pain scores (P=0.002). The clonidine group had mean heart rates over time that were 11% to 17% lower than the control group. The clonidine group also had mean systolic blood pressures over time that were 8% to 12% lower than the control group. Sedation scores were no different between groups. Postoperative nausea and vomiting was more common in the control group than the clonidine group (38% vs. 6.5%, P=0.0023). Slightly fewer patients in the clonidine group required catheterization for urinary retention but the difference was not statistically significant.

Conclusion            Low dose epidural clonidine produced postoperative analgesia resulting in significantly reduced IVPCA morphine consumption.

 

Comment

Most of us would probably be surprised by how little research has been done on drugs other than local anesthetics that we sometimes inject into the epidural and subarachnoid spaces. In general I think most would agree that extreme caution is warranted when one considers moving a drug from an IV to a neuraxial route of administration. That said, however, there is a lot of research looking at spinal and epidural clonidine. Most often it is used in conjunction with opioids. We know clonidine produces useful spinal analgesia. But, hypotension and bradycardia can be troublesome side effects. While administering epidural clonidine as an infusion and limiting the dose reduces the incidence of hemodynamic instability, neuraxial clonidine is certainly not for everyone. That said, in selected patients with proper monitoring an epidural clonidine infusion for postoperative pain can be a useful technique. This study shows us that it may be useful as a solo infusion rather than in combination with opioids or local anesthetics. And, by the way, this is not the only study to show a lower incidence of PONV in patients receiving a clonidine infusion, perhaps another advantage.

Even as we understand more and more about preventing and alleviating pain, it is my opinion that we in anesthesia do not put enough thought into treating postoperative pain. We should do more to make our patients comfortable. There is a lot more we can do than simply loading patients up with fentanyl before they hit the PACU. For some patients an epidural clonidine infusion, properly dosed and monitored, is one of those things.

 

Michael Fiedler, PhD, CRNA

 

 

© Copyright 2009 Anesthesia Abstracts · Volume 3 Number 1, January 31, 2009




Airway

Kleine-Brueggeney M, Theiler LG, Luyet C, Greif R


 

 

Acute airway obstruction caused by the new single use laryngeal mask airway supreme

Anesthesiology 2009;110:189-190

Kleine-Brueggeney M, Theiler LG, Luyet C, Greif R

 

 

Abstract

Purpose            This report describes a case of complete airway obstruction with a properly inserted LMA Supreme.

Background            The LMA Supreme was developed as a disposable, single-use alternative to the LMA ProSeal. Like the ProSeal, the Supreme includes a gastric drain tube. LMAs are used for airway management in a number of situations including routine and emergency airway management. LMAs can produce complications; most commonly hoarseness or dysphagia

Methodology            A 62 year old male with a body mass index of 30 was scheduled for an elective resection of a melanoma and lymph nodes. General anesthesia was induced with propofol and 150 µg of fentanyl and maintained with propofol and remifentanil. Ventilation with a standard face mask was achieved. Next, a #5 LMA Supreme was placed without difficulty and the cuff inflated. Subsequent to LMA placement, positive pressure ventilation was impossible. With a fiberscope the epiglottis was seen to be pushed down completely obstructing the glottis. The epiglottis was pulled away from the glottis with the aid of the fiberscope and the glottic opening was visible. Ventilation was attempted again but was inadequate to proceed with surgery. The LMA was removed and the patient ventilated by face mask, which was, again, easy to do. When the LMA Supreme was placed a second time ventilation was possible, but difficult. Inspiratory and expiratory stridor was audible and ventilation became increasingly difficult. Another look through the fiberoptic scope revealed severe narrowing of the laryngeal inlet that appeared to be due to supraglottic laryngeal edema. At this point the LMA Supreme was removed and an endotracheal tube was placed. No laryngeal edema was visible during direct laryngoscopy for ETT placement. The surgical procedure was then performed uneventfully. There were no respiratory events during recovery.

Result            Difficulty ventilating the patient with the LMA Supreme in place was initially attributed to edema caused by the device putting pressure on soft tissue airway structures. This was not the case, however, as direct laryngoscopy during ETT placement and after the ETT was removed at the end of the case did not reveal any airway edema. In light of this, the airway obstruction was judged to be due to mechanical obstruction of the airway by the LMA Supreme. With the cuff inflated the LMA Supreme was believed to push the cuneiform and corniculate cartilages toward midline pinching the laryngeal inlet closed. This was observed through the fiberoptic laryngoscope.

Conclusion            In this case, the disposable LMA Supreme caused a mechanical narrowing of the laryngeal inlet obstructing positive pressure ventilation.

 

Comment

The LMA Proseal is a popular airway device and I’m glad to see that a disposable version has been introduced. The problem with LMAs is that even when manufacturer’s instructions for scrubbing and autoclaving them are meticulously followed research has shown that reusable LMAs are still contaminated with biologic material from the last patient after cleaning. Any airway device may not perform as expected occasionally. We’ll have to watch and see if airway obstruction is a problem with the LMA Supreme. If not, a disposable LMA gets my vote every time.

 

Michael Fiedler, PhD, CRNA

 

Clery G, Brimacombe J, Stone T, Keller C, Curtis S. Routine cleaning and autoclaving does not remove protein deposits from reusable laryngeal mask devices. Anesth Analg 2003;97:1189-91.

 

© Copyright 2009 Anesthesia Abstracts · Volume 3 Number 1, January 31, 2009