September 2013 Journal Articles

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In this issue of Anesthesiology, Walsh et al.9 confirm and extend these growing data when they report that mean arterial pressure (MAP) less than 55 mmHg during noncardiac surgery is associated with risk for postoperative acute kidney injury (AKI) or myocardial infarction (MI).

 

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Relationship between Intraoperative Mean Arterial Pressure and Clinical Outcomes after Noncardiac Surgery: Toward an Empirical Definition of Hypotension.

Walsh M, Devereaux PJ, Garg AX, Kurz A, Turan A, Rodseth RN, Cywinski J, Thabane L, Sessler DI.


Source

* Assistant Professor, Departments of Medicine, and Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada. † Associate Professor, Departments of Medicine, and Clinical Epidemiology and Biostatistics, and the Population Health Research Institute, McMaster University, Hamilton Health Sciences, Hamilton, Ontario, Canada. ‡ Professor, Departments of Medicine, and Epidemiology and Biostatistics, Western University, London, Ontario, Canada. § Professor, ‖ Associate Professor, ‡‡ Professor and Department Chair, Department of Outcomes Research, ** Assistant Professor, Departments of General Anesthesiology and Outcomes Research, Cleveland Clinic, Cleveland, Ohio. # Research Fellow, Department of Anesthesia, University of KwaZulu-Natal, Durban, South Africa, and Department of Clinical Epidemiology and Biostatistics, McMaster University. ††Professor, Department of Clinical Epidemiology and Biostatistics, McMaster University.


Abstract


BACKGROUND::

Intraoperative hypotension may contribute to postoperative acute kidney injury (AKI) and myocardial injury, but what blood pressures are unsafe is unclear. The authors evaluated the association between the intraoperative mean arterial pressure (MAP) and the risk of AKI and myocardial injury.

METHODS::

The authors obtained perioperative data for 33,330 noncardiac surgeries at the Cleveland Clinic, Ohio. The authors evaluated the association between intraoperative MAP from less than 55 to 75 mmHg and postoperative AKI and myocardial injury to determine the threshold of MAP where risk is increased. The authors then evaluated the association between the duration below this threshold and their outcomes adjusting for potential confounding variables.

RESULTS::

AKI and myocardial injury developed in 2,478 (7.4%) and 770 (2.3%) surgeries, respectively. The MAP threshold where the risk for both outcomes increased was less than 55 mmHg. Compared with never developing a MAP less than 55 mmHg, those with a MAP less than 55 mmHg for 1-5, 6-10, 11-20, and more than 20 min had graded increases in their risk of the two outcomes (AKI: 1.18 [95% CI, 1.06-1.31], 1.19 [1.03-1.39], 1.32 [1.11-1.56], and 1.51 [1.24-1.84], respectively; myocardial injury 1.30 [1.06-1.5], 1.47 [1.13-1.93], 1.79 [1.33-2.39], and 1.82 [1.31-2.55], respectively].

CONCLUSIONS::

Even short durations of an intraoperative MAP less than 55 mmHg are associated with AKI and myocardial injury. Randomized trials are required to determine whether outcomes improve with interventions that maintain an intraoperative MAP of at least 55 mmHg.

 

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Anesth Analg. 2013 Sep;117(3):677-85. doi: 10.1213/ANE.0b013e31829cfd21. Epub 2013 Aug 6.

The efficacy of 2 doses of epidural morphine for postcesarean delivery analgesia: a randomized noninferiority trial.

Singh SI, Rehou S, Marmai KL, Jones AP.


Source

FRCPC, Department of Anesthesia & Perioperative Medicine, St. Joseph's Hospital, Schulich School of Medicine & Dentistry, The University of Western Ontario, Room A1-609, 268 Grosvenor St., London, ON N6A 2V2, Canada. [email protected].c.


Abstract


BACKGROUND:

A single dose of epidural morphine is effective in reducing pain after cesarean delivery but is associated with adverse effects. In this study, we sought to establish whether half the traditional dose of epidural morphine, when administered as part of a multimodal analgesia regimen after cesarean delivery, was associated with noninferior analgesia and fewer adverse effects.

METHODS:

Ninety term parturients undergoing cesarean delivery under epidural anesthesia were enrolled in this randomized, double-blinded, noninferiority study. Patients were randomly allocated to receive either 3 mg epidural morphine or, half this dose, 1.5 mg epidural morphine. In addition, subjects received regular systemic ketorolac and acetaminophen. Rescue analgesia (oral oxycodone) was administered for breakthrough pain. The primary outcome was the difference between groups in total opioid consumption (measured in median IV morphine equivalents) within the first 24 hours. A prespecified noninferiority margin of 3.33 mg was used. Secondary outcomes included total opioid consumption from 24 to 48 hours, numerical rating scale pain scores, time to first request for analgesics, overall pain relief, maternal satisfaction, quality of recovery, and adverse effects.

RESULTS:

Data were analyzed for 87 participants. Noninferiority was demonstrated as the difference in median 24-hour opioid consumption between the 1.5 mg epidural morphine (EM) and 3 mg EM groups was 0 mg (1-sided 95% confidence interval [CI], 2.5 mg), which was less than the prespecified noninferiority margin of 3.33 mg. No significant differences were found between groups in the median 24- to 48-hour opioid consumption or the median total opioid consumption within 48 hours. Pain scores, overall pain relief, and satisfaction at 24 and 48 hours were not significantly different between groups. The 1.5 mg EM group had a lower incidence of moderate and severe pruritus at 6 and 12 hours (relative risk [RR] 0.44, 95% CI, 0.2-0.9 and RR 0.41, 95% CI, 0.2-0.8, respectively) and had less nausea and vomiting at 6 hours (RR 0.22, 95% CI, 0.05-0.9). There was no difference in average pain scores at 12 weeks between the 2 groups.

CONCLUSION:

When used as part of a multimodal analgesia regimen, 1.5 mg epidural morphine provided noninferior postcesarean analgesia and caused fewer adverse effects compared with 3 mg epidural morphine.

 

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Anesth Analg. 2013 Sep;117(3):731-9. doi: 10.1213/ANE.0b013e3182a00767. Epub 2013 Aug 6.

Peripheral nerve injury after local anesthetic injection.

Farber SJ, Saheb-Al-Zamani M, Zieske L, Laurido-Soto O, Bery A, Hunter D, Johnson P, Mackinnon SE.


Source

Division of Plastic and Reconstructive Surgery, Washington University in St. Louis, 660 S Euclid Ave., 1150 NW Tower Campus Box 8238, St. Louis, MO 63110. [email protected].


Abstract


BACKGROUND:

A well-known complication of peripheral nerve block is peripheral nerve injury, whether from the needle or toxicity of the medication used. In this study, we sought to determine the extent of damage that results from intrafascicular injection of various commonly used local anesthetics (LAs).

METHODS:

Sixteen Lewis rats received an intrafascicular injection of saline (control) or 1 of 3 LAs (bupivacaine, lidocaine, or ropivacaine) into the sciatic nerve (n = 4). At a 2-week end point, the sciatic nerves were harvested for histomorphometric and electron microscopic analysis.

RESULTS:

Animals that received intrafascicular LA injections showed increased severity of injury as compared with control. In particular, there was a significant loss of large-diameter fibers as indicated by decreased counts (P < 0.01 for all LAs) and area (P < 0.01 for all LAs) of remaining fibers in severely injured versus noninjured areas of the nerve. There was a layering of severity of injury with most severely injured areas closest to and noninjured areas furthest from the injection site. Bupivacaine caused more damage to large fibers than the other 2 LAs. In all groups, fascicular transection injury from the needle was observed. Electron microscopy confirmed nerve injury.

CONCLUSIONS:

Frequently used LAs at traditional concentrations are toxic to and can injure the peripheral nerve. Any combination of motor and/or sensory sequelae may result due to the varying fascicular topography of a nerve

 

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From the study posted above:


In general, most drugs
caused nerve injury when injected intrafascicularly, and, in
contrast, extrafascicular injections produced little to no damage.
A few exceptions, dexamethasone, botulinum toxin,
and bovine collagen, demonstrated little to no axonal damage
after intrafascicular injection.7,9,38 LAs have been shown
to have a direct toxic effect on the nerve


In summary, peripheral nerve injury from LA injection
into the nerve occurs and remains a real clinical danger.
The sequelae from such an injury may be long lasting and
require surgical intervention. Intentional intraneural injection,
as recommended by some clinicians to hasten the onset
of the block, is not recommended