Perioperative implications of newer generation drug-eluting coronary stents: A narrative review.

Newer generation drug-eluting stents are the most commonly inserted stent in the setting of percutaneous coronary intervention. This narrative review focuses on the evidence underpinning the perioperative management of patients with newer generation drug-eluting stents undergoing non-cardiac surgery. Six studies reported the incidence of major adverse cardiovascular events according to the time interval from percutaneous coronary intervention to non-cardiac surgery, and the comparative risks of newer and first generation drug-eluting stents. No study demonstrated an increased risk of major adverse cardiovascular events once three months had elapsed between stent implantation and non-cardiac surgery. Only one study included patients with third and fourth generation drug-eluting stents. Seven studies analysed the relationship between antiplatelet therapy, major adverse cardiovascular events and perioperative bleeding. The risks of major adverse cardiovascular events do not appear to be increased if antiplatelet therapy is ceased for less than seven days but are increased if it is discontinued for more than seven days. Most studies reported no differences in the incidence of major bleeding associated with antiplatelet therapy. The risk of perioperative major adverse cardiovascular events in non-cardiac surgery does not appear to be increased after three months following implantation with newer generation drug-eluting stents. However, the possibility of increased risk cannot be excluded as most studies were inadequately powered. The thrombotic risk is substantially reduced in patients with fourth (polymer free) generation drug-eluting stents, and urgent non-cardiac surgery can be considered one month after percutaneous coronary intervention. Larger multicentre studies are needed to define the optimal window for non-cardiac surgery after percutaneous coronary intervention and provide definitive perioperative strategies for patients presenting for non-cardiac surgery after the implantation of newer generation drug-eluting stents.

Anaesthetic considerations for strabismus surgery in children and adults.

Strabismus correction surgery is the most common eye operation in children. Adults have approximately a 4% lifetime risk of developing strabismus. Current treatment options include pharmacological injection of botulinum toxin or bupivacaine, conventional corrective surgery, adjustable suture surgery and minimally invasive surgery. Repeated surgery is common as each operation has a 60%-80% chance of successful correction. The benefits of early surgical correction in large-angle strabismus in children outweigh the risks of anaesthesia. General anaesthesia is suitable for patients of all age groups, for complicated or repeated surgery, and bilateral eye procedures. Regional ophthalmic block reduces the incidence of oculocardiac reflex and emergence agitation, and provides postoperative analgesia, but requires a cooperative patient as many experience discomfort. Topical anaesthesia has been used in pharmacological injection, minimally invasive surgery, uncomplicated conventional strabismus surgery and some adjustable suture strabismus surgery. Its use, however, is only limited to cooperative adult patients. Prophylactic antiemesis with both ondansetron and dexamethasone is recommended, especially for children. A multimodal analgesia approach, including paracetamol, intravenous non-steroidal anti-inflammatory drugs, topical local anaesthetic and minimal opioid usage, is recommended for postoperative analgesia, while a supplementary regional ophthalmic block is at the discretion of the team.

Neuroimmune mechanisms of pain: Basic science and potential therapeutic modulators.

This narrative review aims to describe the role of peripheral and central immune responses to tissue and nerve damage in animal models, and to discuss the use of immunomodulatory agents in clinical practice and their perioperative implications. Animal models of pain have demonstrated that nerve injury activates immune signalling pathways that drive aberrant sensory processes, resulting in neuropathic and chronic pain. This response involves the innate immune system. T lymphocytes are also recruited. Glial cells surrounding the damaged nerves release cytokines and proinflammatory mediators that activate resident immune cells and recruit circulatory immune cells. Toll-like receptors on the glial cells play a crucial role in the pathogenesis of chronic pain. Animal models indicate an immune mechanism of neuropathic pain. Analgesic drugs and anaesthetic agents have varied effects on the neuroimmune interface. Evidence of a neuroimmune interaction is mainly from animal studies. Human studies are required to evaluate the clinical implications of this neuroimmune interaction.

Adding low concentrations of clonidine to ropivacaine for transversus abdominis plane blocks does not reduce plasma ropivacaine levels, suggesting a lack of vasoconstrictor effect.

Clonidine has been used successfully to prolong the duration of action of local anaesthetics in peripheral nerve blocks, but its mechanism of action in this setting remains unclear. Some studies suggest that clonidine exerts a vasoconstrictor effect, limiting the washout of local anaesthetic from its site of deposition. We investigated this potential vasoconstrictor effect, using plasma ropivacaine concentrations as a surrogate measure of vasoconstriction, in patients who received transversus abdominis plane (TAP) blocks with and without clonidine. Eighty women undergoing laparoscopic gynaecological surgery were randomly assigned to receive one of four TAP block solutions: 0.2% ropivacaine (control), ropivacaine with clonidine 2 µg/kg (clonidine), ropivacaine with 1:400,000 adrenaline (adrenaline) or ropivacaine and a subcutaneous injection of clonidine 2 µg/kg (SC clonidine). The primary outcome was total venous plasma ropivacaine concentrations up to 6 h after the block. There were no significant differences in plasma ropivacaine concentrations between the control group and the clonidine group at any timepoint in the study, nor were there differences in either the mean maximum ropivacaine concentration ( Cmax) (1.99 µg/mL versus 2.05 µg/mL, P = 0.712) or the time to maximum concentration ( Tmax) (51.0 min versus 56.0 min, P = 0.537). The SC clonidine group also did not differ significantly from the controls ( Cmax 2.13 µg/mL versus 1.99 µg/mL, P = 0.424; Tmax 43.5 min versus 51.0 min, P = 0.201). Plasma ropivacaine concentrations in the adrenaline group were significantly lower than the controls from 10 to 90 min ( P < 0.003 for each comparison), and the Cmax was less than that of the control group (1.36 µg/mL versus 1.99 µg/mL, P < 0.001) with a longer Tmax (103.5 min versus 51.0 min, P = 0.001). These findings indicate that clonidine at a concentration of 1.35 µg/mL added to ropivacaine for TAP blocks did not produce a reduction in plasma ropivacaine concentrations. This suggests a lack of vasoconstrictor effect during TAP blocks. Further studies should evaluate whether vasoconstriction occurs when clonidine is used at higher concentrations or for other blocks.

Correlation and agreement between the TEG® 5000 and the TEG® 6s during liver transplant surgery.

The TEG® 5000 and novel TEG® 6s measure the viscoelasticity of whole blood during in vitro clot formation. The two devices measure similar coagulation variables but utilize distinctly different technologies. This study aimed to determine the correlation and agreement between the thrombelastographic parameters obtained by the two devices during liver transplant surgery. We obtained blood samples at six predefined intervals during the surgery of 10 consecutive patients. Two operators proficient in the use of the TEG® 6s and TEG® 5000 systems performed thrombelastographic measurements on each sample: non-citrated TEG® 5000, citrated TEG® 5000 and citrated TEG® 6s. Agreement and correlation were assessed using Bland Altman plots and Lin's concordance correlation. There was considerable inter-device variability for the different parameters measured by the TEG® 5000 and TEG® 6s devices. Acceptable agreement was observed when results were within the normal reference ranges. However, with increasing coagulopathy, agreement was poor and results could not be considered interchangeable. Although each of the three tests appeared reliable for qualitative detection of abnormalities of clot formation during liver transplant surgery, we found their quantitative results were not interchangeable.