Anaesthesia
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A sobering editorial...
- Since 2009 there has been a dramatic increase in reported cases of intrathecal tranexamic acid (TXA), parallel to increasing intraoperative TXA use.
- TXA is powerfully neurotoxic.
- Spinal TXA has a mortality rate > 50%, and high incidence of permanent neurological injury in survivors.
- Almost always results from a drug swap error.
- Because both TXA and bupivacaine are made by many manufacturers, there are many different ampoule designs and drug presentations.
- Risk of harm from TXA error is probably ~ 1 in 10,000 spinals.
- TXA should be physically separated from common spinal drugs and we should consider discarding orphaned ampoules rather than attempting to return to the box.
- Stop and visualise the consequences after your own theoretical spinal drug error: facing the patient, family, colleagues, hospital, regulators...
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What did they find?
This review by Patel, Robertson & McConachie identified 21 published cases of inadvertent spinal TXA administration. Notably 10 patients died, and almost all suffered life-threatening side effects.
What are the common signs?
- Block failure.
- Severe back and buttock pain (universal).
- Seizures.
- HT, tachycardia, arrhythmias, CVS collapse.
How should it be managed?
There are three components to managing intrathecal TXA:
- Treating TXA-induced seizures with anticonvulsants: magnesium; benzodiazepines; barbiturates (thiopentone); phenytoin; possibly propofol. Thiopentone infusion was frequently required to terminate seizures.
- Mitigate TXA neurotoxic effects: maintain head-up; CSF lavage to dilute TXA, infusing crystalloid at an interspace higher than an IT needle draining CSF, 10mL for 10mL, repeated up to 4 times.
- Haemodynamic monitoring & support
How does this happen?
In almost all cases ampoule identification error was the primary cause.
Human factor contributions identified were:
- Failure to check ampoule label.
- Similar ampoule appearance.
- Spinal catheter mistaken for IV (1).
- Lack of drug handling and storage policies.
- Storage of tranexamic acid with LA or lack of physical separation.
- Underestimating potential for error.
summary"All errors could have been prevented..."
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“Inhalational anaesthetic agents are chlorofluorocarbons, ‘greenhouse gases’ that have between 349 (sevoflurane) and 3714 (desflurane) times the global warming potential over a 20 year time horizon of carbon dioxide (isoflurane 1401), equivalent to driving a car 18 (sevoflurane) to ~350 miles (desflurane) per hour of anaesthetic use (isoflurane 30 miles); these figures do not account for the additional carbon cost of heating desflurane vaporisers. Together with nitrous oxide, inhalational anaesthetic agents contribute ~2.5% of the 22.8 million tonnes of carbon dioxide equivalents the NHS produces annually.” - White
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Randomized Controlled Trial
Assessment of gastric emptying of maltodextrin, coffee with milk and orange juice during labour at term using point of care ultrasound: a non-inferiority randomised clinical trial.
Labouring women have been shown to have slower gastric emptying than non-pregnant subjects, and this argument is sometimes used to recommend fasting guidelines such as nil-by-mouth during labour. We performed a parallel group, randomised non-inferiority trial, comparing gastric emptying of 450 ml isocalorically-adjusted maltodextrin, coffee with milk or pulp-free orange juice, with 18 women in each group. The women were initially fasted for 2 h for clear fluids, 6 h for a light meal and 8 h for a high fat or high protein meal. ⋯ The estimated gastric residual volume was lower than baseline from 90 min after drinking maltodextrin. In labouring women, maltodextrin is cleared from the stomach faster than coffee with milk and orange juice. Gastric emptying depends on other factors besides the caloric load and volume of the drink.
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Although bedside screening tests are routinely used to identify people at high risk of having a difficult airway, their clinical utility is unclear. We estimated the diagnostic accuracy of commonly used bedside examination tests for assessing the airway in adult patients without apparent anatomical abnormalities scheduled to undergo general anaesthesia. We searched for studies that reported our pre-specified bedside index screening tests against a reference standard, published in any language, from date of inception to 16 December 2016, in seven bibliographic databases. ⋯ For difficult laryngoscopy, the sensitivity and specificity (95%CI) of the upper lip bite test were 0.67 (0.45-0.83) and 0.92 (0.86-0.95), respectively; upper lip bite test sensitivity (95%CI) was significantly higher than that for the mouth opening test (0.22, 0.13-0.33; p < 0.001). For difficult tracheal intubation, the modified Mallampati test had a significantly higher sensitivity (95%CI) at 0.51 (0.40-0.61) compared with mouth opening (0.27, 0.16-0.41; p < 0.001) and thyromental distance (0.24, 0.12-0.43; p < 0.001). Although the upper lip bite test showed the most favourable diagnostic test accuracy properties, none of the common bedside screening tests is well suited for detecting unanticipated difficult airways, as many of them are missed.