Pharmacology

Accidental Intra-arterial Injection

Severe digit or limb injury including amputation has occurred from accidental intra-arterial injection of medications as well as illicit drugs. Common sites include the brachial artery at the elbow or dorsum of the hand in the radial artery, as well as inadvertent injection into arterial lines in-situ.

The most severe limb injury has occurred after Pentothal, Diazepam, Penicillin, and Clindamycin. The most commonly injected illicit medications were crushed benzodiazepines (most commonly flunitrazepam). The potential for damage depends on the drug injected, and also its formulation – benzyl alcohol appears more harmful; commonly used agents like Propofol, Succinylcholine, Rocuronium, Fentanyl, amd Ketamine have not resulted in severe injury generally, although Propofol may cause severe pain.

Incidence is difficult to determine and has been estimated between 1:3,440 and 1:56,000 with old data. Mechanisms of injury can variously or in combination include direct endothelial injury, vasospasm, drug crystallization, and thrombosis.

Many empirical treatments have been reported with a less than strong evidence base, including steroids, vasodilators and nerve blocks. The most common regimes now recommended usually include anticoagulation with Heparin, Prostacyclin, and intra-arterial thrombolytics like TPA.

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Intravenous Dexmedetomidine and Dexamethasone for Postop Analgesia

Many agents have been added to peripheral nerve blocks to prolong analgesia. In some cases intravenous administration has been as successful without potential nerve toxicity concerns.

This small randomized study evaluated the difference in time to first rescue analgesic request between patients receiving co-administered intravenous dexamethasone and dexmedetomidine and patients receiving intravenous dexamethasone alone after single-shot interscslene brachial plexus block for arthroscopic shoulder surgery. Saline controls were used.

Co-administration of intravenous dexamethasone (0.11 mg kg−1) with dexmedetomidine (1.0 μg kg−1) significantly prolonged the time to first rescue analgesic request more than Dexamethasone alone, and both more so than saline controls. Also both groups had reduced postoperative opioid consumption, less sleep disruption and improved patient satisfaction compared with the control group.

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Intravenous Acetaminophen & Hip and Kneee Arthroplasty

Intravenous Acetaminophen was hailed as a useful addition to anesthesia care, but almost every study has shown little to be gained compared to oral Acetaminophen.

This latest, albeit a database study in total hip and knee arthroplasty, once again shows no (or less) benefit compared to oral Acetaminophen, which should always where possible be the first choice.

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Tramadol and Mortality Among Patients With Osteoarthritis

Tramadol has many drawbacks but is frequently prescribed as a perceived safer agent with less misuse potential.

This cohort study of nearly 89,000 patients aged 50 years and older with osteoarthritis found that initial prescription of tramadol was associated with a significantly higher rate of mortality over 1 year compared with commonly prescribed nonsteroidal anti-inflammatory drugs, but not compared with codeine.

The authors point out the risk of confounding by indication, and further research is needed to determine if this association is causal.

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Lidocaine and Neurologic Outcomes after Cardiac Surgery

50% of cardiac surgery patients leave hospital with cognitive dysfunction which tends to improve but may persist at 5 years in some. Based on previous suggestion that Lidocaine may ameliorate such issues due to postulated anti-inflammatory, blood flow, and cerebral metabolism mechanisms, this randomized study failed to find benefit with use of Lidocaine infusion during and for 48 hours after cardiac surgeries.

Conclusion: Intravenous lidocaine administered during and after cardiac surgery did not reduce postoperative cognitive decline at 6 weeks.

The authors note the complex issues involved in cognitive dysfunction that could not be expected to benefit from a single agents – preoperative cognitive impairment, genetic predisposition, cerebral microembolism or hypoperfusion during CPB, inflammatory responses, hemodilution, hyperglycemia, hyperthermia, unmasking of Alzheimer disease, and acceleration of amyloid deposition associated with inhalational anesthetics.

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Methylprednisolone for AKI in Cardiac Surgery

A sub study of a randomized trial finds: “Intraoperative corticosteroid use did not reduce the risk of acute kidney injury in patients with a moderate-to-high risk of perioperative death who had cardiac surgery with cardiopulmonary bypass. Our results do not support the prophylactic use of steroids during cardiopulmonary bypass surgery”.

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A previous review casts doubt on the use of steroids for various purposes in cardiac surgery, finding that they had “an unclear impact on mortality, increased the risk of myocardial injury, and the impact on atrial fibrillation should be viewed with caution given that large trials showed no effect”. link

Dexamethasone in Surgical Patients

Dexamethasone use as an anti-emetic has become near universal in anesthesia practice. This systematic review sought to ascertain whether it causes adverse side-effects.

The primary outcomes were postoperative systemic or wound infection, delayed wound healing and glycemic response within 24 h.

No link to wound infections was found, while it was unclear whether it affected wound healing. Mild increases in glucose within 12 hours occurred (mean difference 0.7mmol/L).

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Dexmedetomidine vs. Midazolam for Intraoperative Sedation

The reputation of benzodiazepines continues to take a hit.

This study compared older patients undergoing regional anesthesia and receiving intraoperative sedation. Dexmedetomidine wins, with Midazolam associated with higher psychomotor agitation, arterial hypotension, and respiratory depression.

During postanesthesia care, the incidence rates of shivering, residual sedation, and use of supplemental oxygen were significantly lower in the Dexmedetomidine group.

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Opioid Free Anesthesia

A review article (gated) looked at the impact of a growing technique using opioid free anesthesia. They found no significant difference in pain at 2 hours post-op or length of stay in the Recovery area, but a significant reduction in nausea and vomiting in the opioid free group.

The overall conclusion would favour opioid free anesthesia. In its current iteration, it frequently involves agents such as Ketamine, Lidocaine, Dexmedetomidine along with multimodal analgesia strategies using non-opioid agents like NSAIDs and peripheral nerve blocks.

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Intravenous Acetaminophen Before Pelvic Organ Prolapse Repair

This randomized study from the “green journal” compared preoperative intravenous acetaminophen 1g with placebo in women undergoing either laparoscopic or vaginal prolapse repair.

The findings were that “preoperative IV acetaminophen did not reduce pain scores or opioid use and had no effect on patient satisfaction or QOL. Routine use of preemptive IV acetaminophen alone is not supported by this study”.

This joins other studies showing little gain from intravenous acetaminophen.

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