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Background: Age-based formulas (ABFs) are commonly used in paediatric anaesthesia to determine the correct size of an endotracheal tube (ETT). However, these formulas often predict an incorrect size. The aim of this study was to determine if the tracheal internal diameter as determined on axial ultrasound images better predicts paediatric ETT size than Cole's ABF. Methods: This study is a prospective observational study that involved 106 paediatric patients aged 1-10 years classified as ASA I and ASA II according to the American Society of Anesthesiologists Classification of Physical Status. These paediatric patients were scheduled for elective surgery and required general anaesthesia. They were randomly allocated to one of two groups by blind balloting. There were 53 participants in each group: the ultrasound-predicted endotracheal tube size (UPE) group and the (agebased) formula-predicted endotracheal tube size (FPE) group. For both groups, the actual ETT size used for intubation was noted and compared to the predicted size. Results: The two groups (UPE and FPE) were comparable with respect to demographic and clinical variables. Airway ultrasound scans predicted the appropriate ETT size in 52 out of the 53 participants in the UPE group. This is a better prediction than the Cole's ABF, which accurately predicted appropriate ETT size in 35 out of the 53 participants in the FPE group (p < 0.001). Conclusion: Data from this study shows that an airway ultrasound scan predicted the ETT size more accurately than Cole's ABF in paediatric patients. [ABSTRACT FROM AUTHOR]

Background: Anaesthesia in the perioperative period is characterized by acute changes in plasma potassium (K+) which may be caused by anxiety. Anxiety leads to an intracellular shift of potassium which may lead to hypokalaemia. These fluctuations in plasma potassium may sometimes induce arrhythmias. This study was designed to determine the acute changes in plasma potassium levels in the immediate pre-induction period in a sample of Nigerian patients and to determine the incidence of arrhythmias correlating with these changes., Methods: Sixty ASA I and II adults aged 14 to 70 years, both genders, undergoing elective surgery under general anaesthesia at the Lagos University Teaching Hospital were prospectively and consecutively recruited. Preoperative plasma potassium level was determined 1-3 days before surgery. Premedication was with oral diazepam 10-20 mg given nocte and on the morning of surgery. Pre-induction plasma potassium level was determined within 5 minutes before induction of anaesthesia., Results: Mean preoperative K+ was 3.98 +/- 0.38 mEq.L(-1) (range of 3.5 - 4.9 mEqL(-1)). The mean pre-induction plasma K+ level was 3.01 +/- 0.35 mEq.L(-1) (range of 2.1 - 3.6). This represented a fall of 24% (0.97 +/- 0.39 mEq.L(-1)) which was significantly different (p < 0.001). More than 80% of the patients exhibited some fall in plasma K+. No arrhythmias were recorded during the study period., Conclusion: Pre-induction hypokalaemia occurred frequently despite the administration of anxiolysis with diazepam. There is a need to consider this phenomenon and measure K+ levels immediately pre-induction especially in patients with existing borderline normal K+ levels.