ISSN NUMBER: 1938-7172
Issue 5.12

Michael A. Fiedler, PhD, CRNA

Contributing Editors:
Penelope S Benedik, PhD, CRNA, RRT
Mary A Golinski, PhD, CRNA
Gerard Hogan Jr., DNSc, CRNA
Alfred E Lupien, PhD, CRNA, FAAN
Lisa Osborne, PhD, CRNA
Dennis Spence, PhD, CRNA
Cassy Taylor, DNP, DMP, CRNA
Steven R Wooden, DNP, CRNA

Assistant Editor
Jessica Floyd, BS

A Publication of Lifelong Learning, LLC © Copyright 2011

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

Forced-air warming does not worsen air quality in laminar flow operating rooms

Point-of-care electronic prompts: an effective means of increasing compliance, demonstrating quality, and improving outcome

Smoking and perioperative outcomes

Does the baricity of bupivacaine influence intrathecal spread in the prolonged sitting position before elective cesarean delivery? A prospective randomized controlled study

Interlaminar versus transforaminal epidural steroids for the treatment of subacute lumbar radicular pain: A randomized, blinded prospective outcome study

More Hypotension in Patients Taking Antihypertensives Preoperatively During Shoulder Surgery in the Beach Chair Position

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Forced-air warming does not worsen air quality in laminar flow operating rooms

Anesth Analg 2011;113:1416-1421

Sessler DI, Olmsted RN, Kuelpmann R


Purpose This study was intended to assess whether or not there was a negative effect from current “Forced-Air Warming” techniques on the quality and function of dedicated operating room laminar airflow systems.


Background There is controversy regarding the use of forced-air warming technology in operating rooms equipped with laminar flow air systems. Some surgeons believe that there is a decrease in the effectiveness of laminar flow and an increased likelihood of bacterial dispersal when these warming techniques are used. Both general and neuraxial anesthesia techniques can impair thermoregulation. Hypothermia can impact blood loss, drug metabolism, and patient outcomes. Since studies already exist in the literature showing that forced air warming techniques do not increase risk of infection, this study hypothesized that it also had no negative effect on laminar flow quality.


Methodology Laminar flow was evaluated under three separate test conditions.

  1. forced-air warming machine off
  2. forced-air warming machine on at ambient (cool) setting
  3. forced-air warming machine set on high (43°C +/- 1.5°C)

A smoke plume was used to qualitatively evaluate any change in laminar flow. This was followed up with a quantified measurement of particulate residue left in the operating room. The room was set up, prepped and draped to be identical to an actual surgical case to include volunteers as patient, surgeon, and anesthetist. As a reference, an empty operating room was also tested. The standard for laminar flow includes 20 air exchanges per hour. Both upper and lower body blankets for the forced-air warmer were tested. Particle detectors were used 10 cm above the incision area, and in random positions throughout the room. Particle concentrations were then assessed.  Statistical significance was determined using an Analysis of Variance 1-factor and 2-factor tests at the 95% confidence level.


Result None of the forced-air warming machines tested showed any statistically significant difference in the protective effect of laminar flow regardless of the setting. The concentration of particles suspended in operating room air was unaffected by the use of forced air warming blankets. Direction of the airflow created by the laminar flow system was not affected by any of the tested forced air warming configurations. This left filtered air flowing past the wound, not airflow from the forced air warming device. Of interest was that laminar performance was actually improved in the simulated operating room environment as opposed to the empty (non-draped) operating room.


Conclusion Both the qualitative and quantitative tests were insignificant for disruption of laminar flow when a forced-air warming device was used. There was no compromise in operating room air quality when upper or lower forced-air warming blankets were used. Laminar flow remained well within the rigid functional specifications when warming techniques were employed.



I find this study very interesting. I hadn’t really considered this an issue until discussing it with an Orthopedic Surgeon. This study was well constructed and was thorough in its control of variables that might impact the level of evidence. Since studies now exist proving that forced-air warming technologies do not promote infection or affect laminar flow, they appear to be safe and effective. These findings directly impact CRNA practice since we are all familiar with the negative effects of hypothermia. In a review article by Polderman KH (2009), we have definitive proof that hypothermia can lead to increased risk of infection, immunosuppression, electrolyte disorders, impaired drug clearance, and coagulopathies. Having definitive evidence that forced-air warmers do not contribute to infection or affect laminar flow helps us to use the literature to assure the best care for our patients.

Gerard Hogan Jr., DNSc, CRNA

Polderman KH. Mechanisms of action, physiological effects, and complications of hypothermia. Crit Care Med 2009;37:S187-S202.

© Copyright 2011 Anesthesia Abstracts · Volume 5 Number 12, December 31, 2011

Point-of-care electronic prompts: an effective means of increasing compliance, demonstrating quality, and improving outcome

Anesth Analg 2011;113:869-876

Schwann NM, Bretz KA, Eid S, Burger T, Fry D, Ackler F, Evans P, Lukens H, McLoughlin TM


Purpose The purpose of this study was to evaluate the effectiveness of a point of care electronic prompt (Prompt) to administer antibiotics within 60 minutes of incision to decrease the incidence of surgical site infection.


Background Antibiotic administration within 6o minutes of surgical incision has been shown to decrease the incidence of surgical site infection. The Surgical Care Improvement Project Measure 1 calls for administration of antibiotics within 60 minutes of skin incision. The Center for Medicare and Medicaid Services (CMS) has tied compliance with this metric to reimbursement to hospitals. Unfortunately, compliance with this Surgical Care Improvement Project recommendation is inconsistent ranging from 25 to 95%.


Anesthesia information management systems (AIMS) can be programed to display a Prompt to meet performance standards such as Surgical Care Improvement Project Measure 1. The Prompts can be designed to elicit a specific behavior or response by the anesthesia provider; in this case to administer antibiotics prior to skin incision. Demonstration of increased compliance through the use of Prompts could help anesthesia departments justify the substantial capital investment needed to install an anesthesia information management system.


Methodology At the Lehigh Valley health network a Prompt was incorporated into the anesthesia information management system in all operating rooms. The Prompt appeared real-time within 5 minutes of operating room admission. The prompt was “please dose and document ordered antibiotic within one hour of surgical start time.” Prompts were designed to reappear every 20 minutes until information was entered regarding antibiotic administration. Investigators compared compliance and surgical site infection rates before and after Prompt implementation (Period A and Period B) during 2 consecutive 6 month periods. Compliance was then followed for 2 years after initiation of the project. Statistical analysis was appropriate and a P < 0.05 was significant.


Result A total of 19,744 surgical procedures were performed and analyzed for Surgical Care Improvement Project Measure 1 compliance (Period A n = 9,127 vs. Period B n = 10,617). Preoperative risk factors were similar during Period A and Period B. After implementation of the Prompts, compliance with antibiotic administration within 60 minutes of skin incision increased by 31% from 62% to 92% (P < 0.001). Overall, surgical site infection rates decreased from 1.1% to 0.7% (P = 0.003). Compliance with the Prompts remained > 95% throughout the 2 year follow-up period. Annual surgical site infection rates were significantly lower in the 3 calendar years following Prompt implementation, indicating the Prompts were able to sustain decreased surgical site infection rates (Figure 1).



Figure 1. Annual Surgical Site Infection Rates

Figure 1

Note: *POCEP = Point Of Care Electronic Prompt


Conclusion Implementation of point-of-care electronic prompts on the anesthesia information management system resulted in > 30% increase in Surgical Care Improvement Project Measure 1 compliance, and a 0.4% reduction in surgical site infection rates. This change was sustained during the 3 following years. Prompts may help modify anesthesia provider behavior and provide justification for the capital investment in an anesthesia information management system.



At my facility, we have been using our AIMS system for over a year. Before we can close-out a case we are required to ensure we have documented compliance with administration of antibiotics within 60 minutes of skin incision, if ordered. I think use of the AIMS has improved our compliance; however we do not have point-of-care electronic prompts to remind us to administer the antibiotics prior to skin incision. I like to think I am pretty good at getting the antibiotics administered, however, I know my compliance would be better if I had a visual reminder at the beginning of the case. Likewise, I suspect my anesthesia trainees would also be more compliant with the Surgical Care Improvement Project Measure 1 requirements if they had a visual prompt.


The investigators showed that a simple Prompt was able to sustain their compliance at > 95%, which is the benchmark goal. What they also found was, after controlling for all other potential factors, surgical site infection rates actually decreased. I think this finding is clinically relevant and speaks to how Prompts may decrease morbidity.


I think a Prompt to recommend antiemetic therapy based on established PONV guidelines would be another excellent way to use a Prompt. Other Prompts could easily be developed to increase compliance with evidence based guidelines. Certainly one needs to keep in mind alarm fatigue when developing Prompts, however they do have the potential of improving compliance and decreasing morbidity associated with anesthesia and surgery.

Dennis Spence, PhD, CRNA

The views expressed in this article are those of the author and do not reflect official policy or position of the Department of the Navy, the Department of Defense, the Uniformed Services University of the Health Sciences, or the United States Government.

© Copyright 2011 Anesthesia Abstracts · Volume 5 Number 12, December 31, 2011

Smoking and perioperative outcomes

Anesthesiology 2011;114:83746

Turan A, Mascha EJ, Roberman D, Turner PL, You J, Kurz A, Sessler DI, Saager L


Purpose The purpose of this study was to describe the effects of smoking on 30 day postoperative outcomes. Secondarily, the study looked for a dose response relationship between cigarette smoking and postoperative complications.


Background The number of deaths attributed to smoking is staggering, 100 million people in the 20th century alone. It is estimated that 20% of adult Americans smoke cigarettes. Smoking's impact is far-reaching, going beyond disease to include significant economic burden both for smoker and society in general. In addition to causing several types of lung disease, smoking has also been shown to be associated with poor wound healing, wound dehiscence, wound infections, sepsis, cardiovascular disease, and stroke. We have long known that smoking worsens postoperative outcomes, but quantitatively how much smoking increases the risk of poor postoperative outcomes has not been known.


Methodology This retrospective cohort study examined data from the American College of Surgeons National Surgical Quality Improvement Program database (ACS-NSQIP database). The database contained information collected between 2005 and 2008. Although the study itself was retrospective, the ACS-NSQIP database contained patient data collected prospectively according to strict guidelines and data collection was therefore quite complete. From this database records were divided into current smokers and never smokers. Current smokers included those who reported having smoked cigarettes in the year previous to being admitted for surgery. Never smokers included those who reported 0 pack years of cigarette smoking during their lifetime. Those who had not smoked in the year before surgery but had smoked at some point in their life were not included in either group.


Statistical methods were used to ensure that the smoker and never smoker groups had equal distributions of potentially confounding variables that might impact postoperative outcome. These variables included things such as:

  • gender
  • ethnicity
  • age
  • alcohol use
  • diabetes
  • renal failure
  • A S A physical status classification
  • type of anesthesia


The dose-effect relationship between number of pack years smoked and postoperative outcomes was examined using a composite rate of all major postoperative morbidity. Exclusion criteria included patients who had preoperative pneumonia, mechanical ventilation, sepsis, coma, or wound infection.


Result The ACS–NSQIP database included 635,265 surgical cases. After removing records of those who met exclusion criteria or had missing data 391,006 patients remained. Of those, 26.5% were smokers and 73.5% were never smokers. Smokers were more likely to be male, drink alcohol, and have a higher ASA physical status classification.


In an unadjusted analysis, the odds of major postoperative morbidity were significantly higher in smokers versus non-smokers (odds ratio 1.72; P < 0.0001).The increased risk of specific postoperative morbidities in smokers compared to never smokers is summarized in table 1.


Table 1. Increased Risk of Postoperative
Complications in Smokers


Risk Increase



unplanned intubation


ventilation greater than 48 hours


cardiac arrest


myocardial infarction




superficial wound infections


deep wound infections




septic shock


wound dehiscence


When considering the dose response relationship between the number of pack years of cigarettes smoked and postoperative morbidity, smoking less than 10 pack years had a risk of morbidity similar to never smokers. However, patients who had smoked more than 10 pack years had significantly greater risk of postoperative morbidity than did never smokers (P < 0.001). Past 10 pack years, as the number of pack years smoked increased to 20, 30, and 40 pack years the further increase in risk of postoperative complications was slight.


Conclusion This analysis of a large validated database indicated that smoking was associated with increased postoperative risk of cardiovascular, pulmonary, wound infection, and septic complications. However, the number of pack years smoked did not correlate directly with increased morbidity. Smoking less than 10 pack years was associated with risk of postoperative complications similar to never smokers. Smoking more than 10 pack years incurred significantly greater risk of postoperative complications compared to never smokers but additional pack years increased risk only modestly.



The percentage of surgical patients who are smokers is higher than the percentage of smokers in the general population. Smokers still make up a significant portion of our patients. In the past we've known that smoking was associated with a host of cardiovascular and pulmonary complications but we haven't known how much smoking was associated with how large an increase in that risk. This study provides us with specific information about how much smoking is associated with how large an increase in the risk of specific postoperative complications. Having such information is incredibly important when planning an anesthetic. With it, we know that we probably don’t need to take any additional precautions for the two cigarette a day smoker. And we know that the 20 pack year smoker is at significantly greater risk of a number of postoperative complications. We can tailor our anesthetic plan to help prevent some of those complications and to prevent harm from some others.


One example of how we can use this information when planning an anesthetic is found in all the information about wound and systemic infections. In 2008 postoperative wound infections were the second most common complication in healthcare, affecting 252,695 patients a year in the USA at an average cost of $3,364 per patient.(1) We know that regional anesthesia and keeping patients warm both increase wound blood flow and oxygenation resulting in a decreased likelihood of wound infections. In a 10 plus pack year smoker (30% - 42% increased risk for wound infection) considering a regional anesthesia and taking every precaution to keep the patient normothermic perioperatively should be strongly considered. All the more so if they have additional risk factors for wound infections like diabetes. Doing so is not only good for the patient, it helps prevent wound infections from sucking money out of the healthcare system. A lower cost of care due to preventing wound infections ultimately means health care is more affordable. This is but one example of how we can identify patients at higher risk and make plans that will reduce incidence or severity of their postoperative complications.


I was surprised by one finding of this study. I have always assumed that more pack years of smoking resulted in more pathology and sicker patients. Apparently past about 10 pack years that is only a little bit true. This is the beauty of good research; we have a chance to unlearn what we’ve gotten wrong.

Michael A. Fiedler, PhD, CRNA

1. Van Den Bos J, Rustagi K, Gray T, Halford M, Ziemkiewicz E, Shreve J. The $17.1 billion problem: the annual cost of measurable medical errors. Health Aff 2011;30:596-603.

© Copyright 2011 Anesthesia Abstracts · Volume 5 Number 12, December 31, 2011

Obstetric Anesthesia
Does the baricity of bupivacaine influence intrathecal spread in the prolonged sitting position before elective cesarean delivery? A prospective randomized controlled study

Anesth Analg 2011;113:811-817

Loubert C, Hailworth S, Fernado R, Columb M, Patel N, Sarang K, Sodhi V


Purpose This study sought to determine what effect gravity had on the spread of local anesthetic solutions of different baricity in patients undergoing elective cesarean delivery with combined spinal epidural anesthesia (CSE). The investigators hypothesized that a HYPERbaric solution would result in a significantly lower block level when compared to an ISObaric or HYPObaric local anesthetic.


Background CSE anesthesia is a popular technique for cesarean delivery because it provides rapid onset of spinal anesthesia with the ability to increase the anesthetic level if needed. One of the criticisms of CSE is that there are more steps involved and the procedure takes longer to complete. If it takes a long time to place the epidural catheter during a CSE in a sitting position, then there is a chance that HYPERbaric local anesthetics will not spread upward, increasing the likelihood of inadequate surgical anesthesia.


Methodology The investigators conducted a randomized, double-blind, clinical investigation of 90 parturients scheduled for elective cesarean delivery. Patients were excluded if they were < 16 years old, < 150 cm or > 180 cm, weighed < 50 kg or > 100 kg, had a history of bleeding disorders, pregnancy-related HYPERtension, cardiac disease, gestational age < 36 weeks, in active labor, or infection at the injection site. Patients were randomized to receive either a HYPObaric, ISObaric or HYPERbaric local anesthetic solution during placement of the CSE in the sitting position. 


Spinal anesthetic solutions consisted of 10 mg bupivacaine with fentanyl 15 mcg in a total of 2.5 mL of volume. Glucose or normal saline were used to make either the HYPERbaric or HYPObaric solution. A density meter was used to verify baricity of the solutions. The anesthesia provider administering the CSE and managing the case was blinded to the patient’s group assignment. A second anesthesia provider, also blinded to group assignment, collected intraoperative data.


All patients received oral ranitidine 150 mg and metaclopramide 10 mg preoperatively. After monitors were placed all patients were administered 1 L of 0.9% normal saline. All CSEs were placed at the L3-4 interspace using a 16-guage Tuohy needle and a 27-g, 119-mm Whitacre spinal needle. Spinal anesthetics were injected over 15-20 seconds and CSF was aspirated at the end of injection to confirm correct placement. The patient was kept in the sitting position for 5 minutes after the end of spinal anesthetic injection and then moved to the supine position with a 15 degree left lateral tilt. After 25 minutes if the patient had less than a T4 sensory level to cold (using ethyl chloride spray) they were administered incremental 5-mL boluses of bupivacaine 0.5% through the epidural catheter until an adequate sensory level was achieved. If this was inadequate, then fentanyl could be titrated or general anesthesia could be administered. Sensory and motor block were evaluated every 5 minutes for 25 minutes.


The primary outcome was the sensory block level to cold during the 25 minutes after spinal injection. Secondary outcomes included the percent of patients with a complete motor block, incidence of a cervical sensory level at 25 minutes, need for intraoperative supplementation, incidence of hypotension (systolic < 90 mm Hg or 25% decrease below baseline), incidence of nausea or vomiting, and total ephedrine administered. Power and statistical analysis was appropriate.


Result A total of 89 subjects completed the study. No significant differences in demographics were found between the three groups.


There were significant differences in sensory dermatome levels between the three groups. After spinal injection the median sensory dermatome level was significantly higher in the HYPObaric group when compared to the ISObaric or HYPERbaric solution (P < 0.001)

  • HYPObaric T-6 [T8-T4]
  • ISObaric T-9 [T10-T7]
  • HYPERbaric T-10 [T11-T8]

Hypobaric bupivacaine resulted in a sensory dermatome level that was 2.5 and 3.6 dermatome levels higher than the ISObaric and HYPERbaric solutions, respectively (P = 0.049). Sensory dermatome levels were significantly higher at 10 minutes in the ISObaric group when compared to the HYPERbaric group; however at all other time points they were similar. Considering only the spread of block while patients were positioned supine, between 10 and 25 minutes after the spinal was injected, the sensory dermatome level spread over 11 dermatomes in the HYPERbaric group, over 10 dermatomes in the ISObaric group, and over only 4 dermatomes in the HYPObaric group (P = NS).


All patients in the HYPObaric group achieved at least a T-4 level at 25 minutes, as compared to only 80% in the ISObaric and HYPERbaric groups (P = 0.04). Not surprisingly, there was a higher incidence of a cervical sensory dermatome level in the HYPObaric group (P = 0.01). However, no patient complained of difficulty breathing or upper extremity weakness. The incidence of complete motor block was significantly greater in the HYPObaric group; 90% HYPObric vs. 43% HYPERbaric (P < 0.001; Figure 1).


Five patients in the HYPERbaric and ISObaric groups required 1 or 2 5-mL boluses of 0.5% bupivacaine via the epidural catheter to achieve a T-4 level compared to only 2 patients in the HYPObaric group. No patient required general anesthesia.


No significant differences were found in the incidence of hypotension, nausea or vomiting between the three groups. However, significantly more patients in the ISObaric and HYPObaric groups required ephedrine to treat hypotension (HYPObaric: 18 mg [9-30 mg], ISObaric: 11 mg [6-20 mg], and HYPERbaric: 6 mg [6-12 mg], P = 0.002). Apgar and neonatal blood gas results were similar between the groups (P = NS).



Figure 1. Primary and Secondary Outcomes

Figure 1

Note: Spinal blockade assessment at 25 minutes.


Conclusion Patients undergoing CSE with HYPObaric bupivacaine for cesarean delivery who remained sitting for 5 minutes after injection of the spinal anesthetic had a higher sensory dermatome level at 25 minutes after injection when compared to those who received an ISObaric or HYPERbaric solution. However, this was at the cost of a higher incidence of hypotension and ephedrine administration.



Combined spinal-epidural anesthesia is a popular technique for cesarean delivery. This technique is especially useful when you think the cesarean delivery is going to take longer than your spinal anesthetic will last. It is also very useful for morbidly obese parturients and twin deliveries, or in those cases when you are just not sure how much local to administer (e.g., patients who are really short or really tall).


I found this well designed study interesting because the investigators tried to simulate what effect delay in laying the patient supine can have on spread of the spinal anesthetic. One of the frustrating things that can occasionally happen with a CSE is you get a great flow of CSF and are able to inject the spinal anesthetic, however you are unable to thread the catheter. Then you feel rushed to place the epidural catheter because you are worried that you will not get a level high enough to start the surgery in a timely manner. Fortunately, the advantage of the CSE is that you can bolus through the epidural catheter, and more times than not achieve an adequate level.


The finding of a higher sensory level with a HYPObaric solution is not surprising. However, this study is a nice demonstration of the effect of baricity on the speed and spread of spinal anesthesia. Other factors that can influence the sensory level include dosage, speed of injection, and positioning. I tend to use a slightly higher dosage for cesarean delivery in most average height patients, such as 12 mg of 0.75% bupivacaine with fentanyl 10 mcg and duramorph 0.20 mg. This dosage reliably achieves a T-4 level in most patients. However, if I decide to place a CSE, I occasionally use a smaller dose. If the level is not rising fast enough then I will use a little trendelenburg position to hasten cephalad spread of the local anesthetic. If that does not work, then bolusing the epidural catheter usually achieves an adequate surgical block.


I would have liked to have seen the investigators include preservative free morphine in their spinal injections since this is commonly used to provide postoperative analgesia after cesarean delivery. I don’t think the results will make me consider using a HYPObaric or ISObaric solution for cesarean delivery. However, it does provide a nice review on spinal anesthetic baricity and positioning. If you teach students this might be a good study to go over the next time you are providing anesthesia for a cesarean delivery.

Dennis Spence, PhD, CRNA

The views expressed in this article are those of the author and do not reflect official policy or position of the Department of the Navy, the Department of Defense, the Uniformed Services University of the Health Sciences, or the United States Government.

© Copyright 2011 Anesthesia Abstracts · Volume 5 Number 12, December 31, 2011

Interlaminar versus transforaminal epidural steroids for the treatment of subacute lumbar radicular pain: A randomized, blinded prospective outcome study

Pain Physician 2011;14:499-511

Charibo C, Variotta G, Rhame E, Liu E, Bendo J, Perioff M


Purpose This study was conducted to determine the short term benefit of interlaminar epidural steroid injections as compared to steroid injections administered using a transforaminal approach.


Background It is a common practice to treat back pain associated with nerve root inflammation by using steroids injected into the epidural space. Although the long term benefits of epidural steroid injections are questionable, short term benefits of pain relief for weeks to months is accepted. Studies have shown modest pain relief for 3 to 6 weeks using epidural steroids when compared to epidural injections with normal saline. The two most common approaches for epidural needle placement are the common midline interlaminar approach, and the transforaminal approach. Some studies have suggested that the transforaminal approach is superior when used for back pain that radiates down to the lower extremities.


Methodology This was a prospective, randomized, blinded, cohort study. Patients selected to participate in the study complained of lower back pain radiating to one lower extremity, and lasting longer than one month but less than one year. The evaluating physician was separate from the treating physician.

Patients were randomly assigned to receive either an interlaminar or transforaminal injection. Needle placement was verified using fluoroscopic guidance and contrast media. Both approaches used 40 mg of triamcinolone and 0.25% bupivacaine in a total volume of 4 ml as an injectate. The primary outcome measure was a numeric rating scale for pain and the Oswestry Disability Index (ODI). Subjects were reevaluated 10 to 16 days after the first injection. Those who did not have at least 75% relief of pain were eligible for a second injection of the same type. Those with more than 75% improvement were contacted again a month later for follow-up evaluation. Those who had a second injection were reevaluated after another 10 to 16 days.


Following the previous criteria, those who did not have at least 75% pain relief after the second injection were offered a third injection after 2 to 4 weeks. For this third injection, the patient was provided the opposite injection type they had received for the first 2 injections. All patients received a final evaluation one month after their last injection.


A 2-tailed t test was used to compare the differences between groups and a P value less than 0.05 was considered statistically significant. A power analysis determined that 20 patients in each group were needed for valid results.


Result A total of 38 patients completed the study, 18 in the interlaminar group and 20 in the transforaminal group. The most common diagnosis was disc herniation. Three patients in the interlaminar group required a second injection, and 2 of those required a third injection. One patient in the transforaminal group required a second injection and none required a third injection. In the final analysis, both groups had significant improvement in pain (lower numeric rating scale for pain) and function (assessed with the ODI). Regardless of approach, there was a 75% overall improvement in pain scores after epidural steroid injection in 90% of the study patients.


Conclusion Short term reduction in pain provides for improvement in function. The transforaminal approach was not superior to the interlaminar approach for steroid injection in this study. When considering that the interlaminar approach has a lower risk of complications than the transforaminal approach, and that the interlaminar approach creates less discomfort on injection for the patient, the interlaminar approach should be considered for the initial injection of epidural steroids for low back pain with radiculopathy.



This study had some significant methodological problems. The most obvious problem was that their power analysis determined a need for at least 20 patients in each group and they failed to obtain that number of patients in one of their groups. The number of patients evaluated was so small that I would have to question the validity of this study as well as the clinical value. An additional problem I saw with this study was that they restricted the selection of their patients to those who had back pain with radiculopathy down one extremity. Although these symptoms are common, I find when a patient has unilateral radiculopathy it is easier to identify a specific nerve root pain generator that can be treated effectively with a transforaminal injection. Patients who present with bilateral radiculopathy respond better to interlaminar injections. I believe this study was too narrow and limited.


I would have liked to have seen the results of a crossover effort as described in this study where patients who did not respond to one type of injection were given the other injection later. Unfortunately, they did not study enough patients to provide valid results in this area either. With that being said, it does generate an interesting discussion concerning the value of interlaminar epidural steroid injections. While many studies has suggested that there is greater value in using transforaminal epidural steroid injection in most situations, there still is a place for interlaminar injections. In order to effectively use a transforaminal injection it is important to identify the specific pain generator. In reality, not all patients have symptoms or imaging that can help identify that specific pain generator. In addition, the authors of this study were correct that the transforaminal approach has complication risks that the interlaminar approach does not have. For both of those reasons, I cannot disagree with the authors when they suggest that using the interlaminar approach for the initial injection may have some value.


Many things need to be considered when determining the best approach for epidural steroid injections. Do the patients demonstrate symptoms that would favor the use of one approach over the other? Does the provider have adequate skill and training for a particular approach? Is fluoroscopic guidance available? These are just a few questions that need to be considered, as we continue to debate the value of one approach over the other.

Steven R Wooden, DNP, CRNA

© Copyright 2011 Anesthesia Abstracts · Volume 5 Number 12, December 31, 2011

More Hypotension in Patients Taking Antihypertensives Preoperatively During Shoulder Surgery in the Beach Chair Position

Can J Anesth 2011;58:993-1000

Trentman TL, Fassett SL, Thomas JK Noble BN, Renfree KJ, Hattrup SJ


Purpose The purpose of this retrospective chart review was to quantify the number of hypotensive episodes in patients taking antihypertensive medication preoperatively who were placed in the beach-chair position for shoulder surgery. They were then compared to a group of normotensive patients not taking antihypertensives who underwent the same types of procedures.


Background There remains a great deal of controversy over the timing and/or discontinuation of antihypertensive medications prior to general anesthesia. There are numerous reports of catastrophic cerebral and spinal ischemic events in patients placed in the beach-chair position. Many of these episodes have been attributed to prolonged and unanticipated hypotension resulting in lower than acceptable Cerebral Perfusion Pressure (CPP). The authors hypothesized that the number and severity of these hypotensive episodes were greater in patients taking Angiotensin Converting Enzyme Inhibitors and/or Angiotensin Receptor Antagonists.


Methodology The medical records of all patients undergoing shoulder surgery in the beach-chair position with both a plexus block and general endotracheal anesthesia were reviewed. Of the 492 available records, 384 were analyzed. Patients in which the surgeon requested a hypotensive technique and those treated for intraoperative hypertension were excluded. Of the 384 records, 199 were taking an antihypertensive medication and 185 patients were not on an antihypertensive agent. The researchers considered a single blood pressure reading of ≤ 85 mmHg systolic as a hypotensive episode. The groups were compared using the Student’s t test. Adjusted comparisons were used for differences in BMI and age between the groups.


Result In the group taking preoperative maintenance antihypertensives, 31% were taking a drug that addressed the angiotensin system. There was a statistically significant increase in hypotensive episodes in those on maintenance antihypertensive medications. The incidence of hypotension in those who took at least one antihypertensive medication was 62% compared to 44% in those who did not take antihypertensives (P < 0.001). Likewise, the average number of hypotensive episodes per case was 1.7 in the group who took at least one antihypertensive compared to 1.2 in those who did not take antihypertensives (P = 0.01).


Patients taking at least one antihypertensive agent were significantly older and were more likely to be classified as an ASA II or higher. After adjusting for age and BMI, the incidence and severity of hypotension were still significantly higher in the group taking maintenance antihypertensives preoperatively. Thirteen patients required treatment with a phenylephrine infusion. Of that 13, 11 were on an Angiotensin Converting Enzyme Inhibitor or Angiotensin Receptor Antagonist daily. The timing of Angiotensin Converting Enzyme Inhibitor or Angiotensin Receptor Antagonist administration on intraoperative hypotension was not significant. No adverse outcomes related to hypotension occurred in any patient.


Conclusion Patients taking antihypertensive medications had more frequent and severe episodes of hypotension during general endotracheal anesthesia in the beach-chair position. The authors believed that many primary care physicians who medically cleared patients for surgery did not understand the significance of the beach-chair position for those on antihypertensive medications. Although the long-term impact of holding Angiotensin Converting Enzyme Inhibitors and Angiotensin Receptor Antagonists is unknown, there may be merit in holding these medications the day of surgery.



This is a fascinating study. I recall in Comfere, that the timing of Angiotensin Converting Enzyme Inhibitors and Angiotensin Receptor Antagonists mattered. In patients who took their medication less than 10 hours before surgery there was a statistically higher probability of perioperative hypotension. These researchers did not find that difference. Limitations included the retrospective nature of the research as well as the quality of documentation.


The incidence and magnitude of cerebral hypotension may have been even greater than suggested in this study. In a 5’11” male 90° head up in beach chair position with the blood pressure cuff properly applied on the upper arm, there may be as much as 30 cm between the cuff and the Circle of Willis. This hydrostatic gradient results in a 23 mm Hg decrease in mean arterial pressure (MAP) between the arm, where the BP is being measured, and the head, where Cerebral Perfusion Pressure is calculated (1 cm whole blood = 0.7796 mm Hg). Thus, an MAP of 70 mm Hg in the arm may be as low as 47 mm Hg in the head, below the auto-regulatory threshold. Fortunately, increased awareness and vigilance in the maintenance of Cerebral Perfusion Pressure in hypertensive patients may have played a role in the decision to treat hypotension, and the lack of morbidity, in this study.

Gerard Hogan Jr., DNSc, CRNA

Comfere T, Sprung J, Kumar MM, et al. Angiotensin system inhibitors in a general surgical population. Anesth Analg 2005;100:636-44.

© Copyright 2011 Anesthesia Abstracts · Volume 5 Number 12, December 31, 2011