Percutaneous and surgical tracheostomy

Percutaneous techniques for elective tracheostomy have provided a quick and relatively simple method that can be performed in the intensive care unit. Evidence-based studies comparing surgical and percutaneous tracheostomies suggest similar complication rates in trained operators of both techniques.     

INTRACORONARY PGE2 AND VERATRINE INHIBITS RENIN RELEASE IN CONSCIOUS DOGS VIA CHEMOSENSITIVE VENTRICULAR AFFERENTS

1. Prostaglandins (PG) and veratrum alkaloids stimulate ventricular sensory receptors with non-myelinated vagal afferents and mediate inhibitory circulatory responses. 2. The present study in conscious instrumented dogs was carried out to determine the effects of intracoronary artery infusions of veratrine (Ver-IC) and PGE2 (PGE2-IC) on plasma renin activity (PRA). 3. A 15-20 mmHg decrease in arterial pressure was produced during Ver-IC (0.2-0.8 micrograms/kg per min) and PGE2-IC (10-50 ng/kg per min), but there was no change in PRA or heart rate. 4. In contrast, significant increases in PRA (+3.51 +/- 0.37 ng angiotensin I/mL per h; P less than 0.01) and heart rate (+38.5 +/- 6.2 beats/min; P less than 0.001) were elicited in response to a 15-20 mmHg decrease in arterial pressure produced by intravenous infusions of nitroprusside. 5. Pharmacological blockade of afferent fibres in the pericoronary region of the left main coronary artery during Ver-IC resulted in significant hypotension-induced increases in PRA (P less than 0.001) and heart rate (P less than 0.001), thus removing the inhibitory influence of chemosensitive ventricular afferents. 6. Therefore, intracoronary veratrum alkaloids and prostaglandins inhibit hypotension-induced increases in PRA and heart rate in the conscious dog. This is mediated by chemosensitive receptors located in the left ventricular myocardium along with afferent nerves in the pericoronary region and cervical vagi.     

A comparison of alfentanil requirements in European and Asian patients during general anaesthesia

Alfentanil requirements were compared in thirty-six Asian and forty-three European patients during general anaesthesia with muscle relaxants. Alfentanil infusion at 5 micrograms/kg/min was started immediately after induction with thiopentone and alcuronium. The infusion rate was reduced to 0.5 microgram/kg/min after ten minutes. An incremental dose of 5 micrograms/kg/min for five minutes was given on each occasion when anaesthesia was clinically judged to be inadequate. Recovery parameters were recorded. Pharmacokinetics were also studied in five Europeans, four Chinese and four Nepalese. The dosage of alfentanil required was comparable in both Asian and European patients, but recovery was slower in the Asian patients. The elimination half-life in the Chinese and the Nepalese were both significantly shorter than that of the Europeans (P less than 0.05), but at the time of recovery of spontaneous ventilation, the mean plasma concentrations were not significantly different.     

Is there a correlation between lung function values and cardiopulmonary exercise outcome?

BackgroundCardiopulmonary exercise testing (CPET) has become an important tool for perioperative assessment because it may identify patients at risk of postoperative cardiopulmonary complications. An anaerobic threshold (AT) less than 11 mL/min/kg has been recommended as a way to stratify postoperative treatment in colorectal surgery patients. The British Thoracic Society guidelines recommend that a peak VO₂ (pVO₂) less than 15mL/min/kg confers high risk in thoracic surgical patients. Because CPET can be challenging to carry out, this study aimed to determine whether lung function values correlated with CPET outcome and therefore could be used as an alternative measure.Methods500 pre-operative colorectal (388) and oesophageal (112) patients were analysed. Gas transfer and spirometry were performed to assess lung function. CPET was performed on a cycle ergometer to calculate pVO₂ and AT. The predictive capacity of forced expiratory volume in 1 s (FEV₁), forced vital capacity (FVC), transfer factor of the lung for carbon monoxide (TLco), and carbon monoxide transfer coefficient (Kco) values compared with pVO₂ and AT was assessed using receiver operating characteristic (ROC) curves.FindingsThe area under the curve (AUC) for pVO₂ and AT for FEV1 was 0·56 and 0·55, respectively; for FVC 0·56 and 0·57; for TLco 0·72 and 0·64, and for Kco 0·63 and 0·56. There was a significant correlation between AT and pVO2 (AUC 0·89); an AT greater than 12 mL/min/kg predicted pVO₂ greater than 15 mL/min/kg (sensitivity 77·3%, 1–specificity 13·7%).InterpretationLung function variables cannot reliably predict pVO₂ or AT outcome. However, of the variables recorded, TLco was the best marker for predicting a pVO₂ greater than 15 mL/min/kg. In preoperative assessment of patients undergoing thoracic surgery, an AT of more than 12 mL/min/kg could be used as an alternative to CPET if the patient is unable to achieve a pVO₂ greater than 15 mL/min/kg.FundingKing's College London.