ISSN NUMBER: 1938-7172
Issue 13.1

Editor:
Michael A. Fiedler, PhD, CRNA

Contributing Editors:
Mary A Golinski, PhD, CRNA
Dennis Spence, PhD, CRNA

Assistant Editor
Heather Whitten, MEd.


A Publication of Lifelong Learning, LLC © Copyright 2019

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


Pharmacology
Effect of sevoflurane versus isoflurane on emergence time and postanesthesia care unit length of stay: an alternating intervention trial

Anesth Analg. 2019 Mar 7 ahead of print

DOI: 10.1213/ANE.0000000000004093

Maheshwari K, Ahuja S, Mascha EJ, Cummings III KC, Chahar P, Elsharkawy H, Kurz A, Turan A, Sessler DI


Abstract

 

Purpose   The purpose of this study was to test the hypothesis that emergence and PACU length of stay was longer with isoflurane than sevoflurane anesthesia.

 

Background   Anesthetic technique and duration of surgery are primary factors influencing the time needed for emergence and PACU length of stay. In general, potent inhalation agents that are more soluble in human tissue require longer emergence times and are associated with longer PACU times. Sevoflurane has a lower blood : gas solubility than isoflurane but it is significantly more expensive. In general, in the absence of other depressant medications, patients awaken from general anesthesia with a potent inhalation agent at about 0.3 MAC (MAC-awake). Emergence time is thus largely dependent upon how quickly the end tidal concentration of inhalation agent falls to 0.3 MAC and below.

 

In a previous study of ambulatory surgery patients, emergence times were 2.5 minutes longer with isoflurane than sevoflurane. In a study comparing isoflurane-nitrous vs. sevoflurane-nitrous emergence was 2.7 minutes longer in the isoflurane group. A systematic review found that emergence times were the same between isoflurane and sevoflurane when the duration of surgery was one hour or less.

 

Methodology   This was a secondary analysis of data from a previous prospective study. The previous study examined the length of hospital stay following isoflurane or sevoflurane anesthesia. Neither the anesthesia provider nor the surgeon was blinded to the agent being used. This secondary analysis compared emergence time and PACU time following these anesthetics.

Exclusion criteria:

  • more than one potent inhalation agent administered
  • emergency surgery
  • hospitalized for medical condition
  • ICU direct admit
  • less than 0.3 MAC administered

The original study controlled only the inhalation agent administered. Both isoflurane and sevoflurane were used exclusively for alternating two week periods for six months.

 

Result   Data was analyzed from 1,498 anesthetics. Isoflurane (iso) was used for 674 and sevoflurane (sevo) for 824. The median duration of anesthesia was 2.5 hours. The iso and sevo groups were demographically different in a number of categories. The analysis was performed once ignoring the demographic differences and again adjusted for the differences. The results of both analyses were the same with one exception. Interestingly, iso patients who did not have abdominal surgery spent an average 11 min less time in the PACU than sevo patients irrespective of the length of the procedure (P<0.006).

 

Median emergence time was 16 min for iso and 14 min for sevo (P<0.001). Median PACU stay was 2.6 hours for iso and 2.6 hours for sevo (P=0.56).

 

Conclusion   Emergence was about 2 minutes slower in the isoflurane group. This difference should be even smaller for shorter procedures. PACU time was no different between anesthetics. Isoflurane costs much less to use than sevoflurane and does not significantly delay emergence or prolong PACU time.

 

Comment

 

While they didn’t come right out and say it, the investigators clearly wanted to compare emergence and PACU discharge times with iso and sevo because they wanted to save money on inhalation agents. Iso, of course, is way less expensive than sevoflurane. But comparing the cost of these agents isn’t nearly as simple as looking up the cost of a bottle of the liquid. So let’s talk a minute about what we need to know to compute the actual cost of an anesthetic with an inhalation agent.

 

Step One — the cost per mL of anesthetic liquid. Different pharmacies pay different prices, and, of course, the bottles are different sizes, but a major university system I know pays 4.43 times as much (per mL liquid) for sevo vs. iso.

 

Step Two— the mL of anesthetic vapor produced by a mL of anesthetic liquid. Iso makes 195 mL vapor per liquid mL. Sevo makes only 184 mL vapor per liquid mL.

 

Step Three— the MAC of each agent. To produce the same MAC level of anesthesia you need 1.91 times more sevoflurane vapor than isoflurane vapor. So not only does sevoflurane produce less vapor, you need more of it to produce a MAC concentration in the fresh gas flow.

 

Step Four— For any given total fresh gas flow the cost per MAC hour =
(Fresh gas flow in mL x (agent MAC / 100)) x cost per mL vapor x 60.

 

For any given fresh gas flow rate sevo is about 4.6 times more expensive than iso. Now let’s think about doing cases in a moderately sized OR suite all year with iso vs. sevo. Say you are running a 2 L FGF and delivering an average of 1.3 MAC in 10 ORs doing 6 one hour anesthetics 5 days a week, 50 weeks a year. Iso $17,843 to sevo $82,294; that’s why they are asking whether or not sevo is really faster.

 

For the record, I’m not saying we shouldn’t use sevo. It is a great anesthetic and I have no criticism of it’s use. But, while it is really gentle on the airways compared to other agents, it is not as fast out as it’s blood : gas solubility of 0.65 would make you think. Part of the reason sevo is not faster out, especially in longer cases, is that it’s fat : blood partition coefficient is 52 compared to a slightly lower 50 for iso. Sevo is faster into the brain, but about the same speed as iso coming out of the rest of the body. So use your judgment and don’t dismiss isoflurane as an “old, slow” agent. There are cases where sevo has important advantages for our patients. Other times there is no disadvantage to iso but potentially big cost savings. Furthermore, our techniques have progressed to the point that slow awakening doesn’t keep patients in the PACU nearly as often as pain control or paperwork in the first place. Some things to consider.

Michael A. Fiedler, PhD, CRNA


© Copyright 2019 Anesthesia Abstracts · Volume 13 Number 1, March 28, 2019





Comparison of intravenous ibuprofen and acetaminophen for postoperative multimodal pain management in bariatric surgery: A randomized controlled trial

J Clin Anesth 2018;50:5-11

DOI: 10.1016/j.jclinane.2018.06.030

ErdoganKayhan G, Sanli M, Ozgul U, Kirteke R, Yologlu S


Abstract

 

Purpose   The purpose of this study was to compare the effect of intravenous ibuprofen vs. acetaminophen on postoperative opioid consumption and pain scores in patients undergoing bariatric surgery.

 

Background   Over 40% of laparoscopic bariatric surgery patients report experiencing severe postoperative pain in the first 48 hours. Poorly treated pain can delay healing and increase the risk of complications. Opioid sparing multimodal analgesic strategies are being used to decrease pain after bariatric surgery. The most common non-opioid used postoperatively is acetaminophen. It works centrally to decrease pain signals. In contrast, ibuprofen has central and peripheral analgesic activity and thus may provide better postoperative pain management for laparoscopic bariatric surgery. However, no studies have compared the analgesic efficacy of ibuprofen and acetaminophen in patients undergoing laparoscopic bariatric surgery.

 

Methodology   This was a prospective, randomized, double-blind trial comparing opioid consumption and pain scores during the first 24 hours after bariatric surgery. Patients received either 800 mg IV ibuprofen or 1g IV acetaminophen every 6 hours. Patients were ASA II-III undergoing either laparoscopic sleeve gastrectomy or laparoscopic Roux-en-Y gastric bypass surgery. A standard anesthetic and postoperative pain management plan was used. Patients received either 800 mg ibuprofen (Group I) or 1g IV acetaminophen (Group A) 30 minutes before skin closure. This dose was repeated every six hours for the first 24 hours after surgery. Patients, surgical team, anesthesia providers, and data collectors were blinded to group assignment.

 

Postoperative pain was evaluated with a visual analogue scale (VAS 0-100) at rest and with movement. Morphine consumption and pain scores were measured at 1, 2, 4, 6, 12, 18, and 24 hours postoperatively. The primary outcome was total morphine consumption during the 24 h postoperative period. Secondary outcomes included pain scores using area under the curve (AUC pain) during the first 24 h, between 6 and 24 h, and 12 and 24 h postoperatively.

 

Statistical analysis and sample size calculations were appropriate. Investigators conducted a pilot study and determined the average difference in morphine consumption was 30% with ibuprofen; investigators determined they would need 35 subjects per group.

 

Result   There were n = 35 in Group A and n = 39 in Group I included in the final analysis. No differences were found in baseline demographics. Group I required 6.3 mg less morphine during the first 24 hours after surgery compared to Group A; mean 24 mg vs. 30 mg. Pain at rest during the first 24 hours was slightly lower in the ibuprofen group. Pain scores with movement were moderately lower in the ibuprofen group compared Group A (P < 0.001; Figure 1). No significant differences were found in PONV (69% vs. 72%). Patients in Group I experienced significantly higher rates of dizziness compared to Group A (43% vs. 15%, P = 0.011). No differences were found in length of stay.

 

Conclusion   IV ibuprofen decreased pain but did not significantly decrease opioid consumption during the first 24 hours after surgery compared to IV acetaminophen in patients undergoing bariatric surgery.

 

Figure 1. Pain Scores at Rest and Movement

 

Comment

 

Nonsteroidal anti-inflammatory drugs inhibit prostaglandin biosynthesis, which results in reduced peripheral sensitization, and reduced central sensitization through suppression on prostanoid formation in the spinal cord and brain. In this study investigators found that compared to IV acetaminophen, IV ibuprofen significantly decreased pain at rest and with movement (except at rest at 6-24 hours) and decreased morphine consumption by 21%. However, this latter finding was not statistically significant. The differences in pain outcomes may be due to the peripheral and central effects of ibuprofen. Unfortunately, patients in the IV ibuprofen group experienced significantly higher rates of dizziness. Therefore, anesthesia providers should let patients know that they may experience dizziness with IV ibuprofen administration.

 

I think these results are good to know; however, at my facility we do not have IV ibuprofen. I usually administer an NSAID and IV acetaminophen to bariatric patients. My preference is to administer ketorolac 30 mg (as long as there are no contraindications) and 1g IV acetaminophen every six hours until the patient can transition to oral medications. Opioids are ordered for breakthrough pain. It is also important for the surgeon to infiltrate long acting local anesthetic into the incision sites. The synergistic effect of both drugs is very effective.

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 2019 Anesthesia Abstracts · Volume 13 Number 1, March 28, 2019





Efficacy of dexmedetomidine for prevention of emergence agitation in patients posted for nasal surgery under desflurane anaesthesia: A prospective double‑blinded randomised controlled trial

Indian J Anaesth 2018;62:524-30

DOI: 10.4103/ija.IJA_788_17

Garg A, Kamal M, Mohammed S, Singariya G, Chouhan DS, Biyani G


Abstract

 

Purpose   The purpose of this study was to determine if a dexmedetomidine 1.0 μg/Kg bolus followed by 0.4 μg/Kg/h infusion after induction of anesthesia would reduce the incidence of emergence agitation in adults undergoing nasal surgery.

 

Background   Patients who receive desflurane have faster emergence times compared to other volatile anesthetics. Unfortunately, this may lead to emergence agitation, which increases the risk of patient and perioperative staff injury and negative postoperative behaviors. While it is short-lived, it may require treatment with agents such as propofol, clonidine, opioid, and ketamine. Unfortunately, some of these agents increase the risk of postoperative nausea and vomiting (PONV), and sedation, and may delay the time to extubation and post anesthesia care unit (PACU) discharge.

 

Dexmedetomidine is an alpha-2 adrenergic agonist that produces sedation, hypnosis, and anxiolysis without respiratory depression. It has been shown to reduce the incidence of emergence agitation in pediatric patients. There are limited studies examining the efficacy of dexmedetomidine to decrease emergence agitation in adults undergoing nasal surgery. The investigators of this study hypothesized that dexmedetomidine 1.0 μg/Kg bolus followed by 0.4 μg/Kg/h after induction of anesthesia would reduce the incidence of emergence agitation in adults undergoing nasal surgery.

 

Methodology   This was a prospective, randomized, double-blind, placebo controlled clinical trial conducted on 72 ASA I and II adults, aged between 18 and 65 years scheduled for elective nasal surgery of 1 h or more under desflurane anesthesia. Patients were randomized to receive either dexmedetomidine (Dex) or saline (Control) after induction of anesthesia. Anesthesia providers, nurses, and surgeons were all blinded to group assignment.

 

All subjects received midazolam 0.05 mg/Kg IV and fentanyl 2μg/Kg IV. Anesthesia was induced with propofol 2.0 - 2.5 mg/Kg IV. Atracurium 0.5 mg/Kg IV was used to facilitate tracheal intubation. After induction, subjects in the dexmedetomidine group (Dex) received a 1.0 μg/Kg bolus followed by 0.4 μg/Kg/h. Those in the control group (Control) received a saline bolus and infusion. Anesthesia was maintained with air : oxygen at a 50:50 mixture and desflurane. Intermittent boluses of fentanyl 1 μg/Kg IV and atracurium 0.1mg/Kg IV were administered as needed during surgery. End tidal carbon dioxide was maintained at 35-40 mm Hg. Acetaminophen 1 gram and 4 mg ondansetron were administered a half hour before surgery completion. Upon completion of surgery patients were reversed with neostigmine 0.05 mg/Kg and glycopyrrolate 0.01 mg/Kg IV. Desflurane and the study drug were stopped when the surgical dressing was applied.

 

Outcomes included the incidence of emergence agitation, end tidal desflurane concentration, time to extubation, and time to verbal response, Ramsey sedation scores, and length of time to PACU discharge. An emergence agitation event was defined as a Ricker Sedation-Agitation scale of 5 or greater:

  • 5 = agitated; anxious or physically agitated and calms to verbal instructions
  • 6 = very agitated; requiring restraint and frequent verbal reminding of limits
  • 7 = dangerous agitation; trying to remove catheters, climbing over bedrail, thrashing side to side, or striking at staff

The measurement of emergence agitation was taken every 2 minutes until a peak score was achieved. Patients with Ricker Sedation-Agitation score of 5 or 6 received verbal redirection and those with a score of 7 were treated with propofol 1 mg/Kg.

 

Statistical analysis and sample size calculations were appropriate. A P < 0.05 was considered significant.

 

Result   There were n = 32 subjects enrolled in each group. No significant differences were seen in demographics, surgery type, or surgery and anesthesia time. Intraoperative blood pressures were similar between the groups. Heart rate and average desflurane concentration were significantly lower in the Dex group than the Control group (both P < 0.0001). Desflurane concentration was on average 29% lower in Group Dex. The time to extubation (5.5 vs. 8.5, P<0.0001) and time to verbal response (5.6 vs. 9.2, P < 0.0001), were significantly shorter in the Control group compared to group Dex. Peak pain scores were similar (P = NS).

 

The incidence of emergence agitation was 53% in the Control group vs. 5.6% in the Dex group (P < 0.00001). Two patients (5.6%) in the Control group had dangerous agitation vs. none in the Dex group. Median Ramsey sedation scale scores were 1 in the Control group vs. 2 in the Dex group (P = 0.009). Time to PACU discharge was 16 min. in the Dex group vs. 12 min. in the Control group (P <0.0001).

 

Conclusion   Dexmedetomidine decreased the incidence of emergence agitation; however, it was associated with somewhat delayed time to extubation, increased sedation, and time to PACU discharge.

 

Comment

 

Surgeons like a smooth emergence after nasal surgery to minimize bleeding. The results of this study suggest that a dexmedetomidine bolus and infusion when anesthesia is maintained with desflurane significantly decreases the incidence of emergence agitation and may help minimize the risk of bleeding after nasal surgery. However, this was at the cost of an increased time to extubation and PACU length of stay. Although, I am not sure an average seven minute difference in combined time to extubation and PACU length of stay is clinically relevant, especially given the advantages achieved.

 

One limitation of this study was that the investigators did not state who measured emergence agitation; was it a single investigator or several different ones? If the latter, what was the inter-rater reliability?

 

An important finding of this study was that dexmedetomidine decreased desflurane requirements by a third in healthy ASA I and II patients undergoing nasal surgery.

 

At my institution many anesthesia providers are administering small boluses of dexmedetomidine (5-20 μg), rather than running a dexmedetomidine infusion, prior to emergence to minimize the risk of emergence agitation. Anecdotally, they are finding good results; however, I would like to see a dose ranging study published to determine the optimal bolus dose.

Dennis Spence, PhD, CRNA


Notes: this article is available free full text at the following url: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6053886/

 

For more information about emergence agitation consider reading Anesthesia Abstracts issues 7.2, 7.6, 9.10, 12.14, and 12.15.

 

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 2019 Anesthesia Abstracts · Volume 13 Number 1, March 28, 2019