Patrick Linton

Isoproternol increases BIS and arousal during catheter ablation of atrial fibrillation
O'Neill D.K.; Rose E.; Linton P.; Hull M.; Aizer A.; Bloom M.
2011 ;112(5 SUPPL 1):?-?, Anesthesia & analgesia
Introduction : With the increase in anesthesia utilization in the electrophysiology laboratory, there is greater potential for arrhythmia suppression during electrophysiology study. Intravenous isoproterenol is frequently used to counteract the significant antiadrenergic impact of anesthesia, as well as induce arrhythmias and identify reconnection of pulmonary vein conduction. The effects of isoproterenol on cerebral and respiratory function during the sedated state have not been well studied. The Bispectral (BIS) Vista TM Monitor is a non-invasive device that measures electrical activity of the brain and computes a BIS value, which corresponds to a level of consciousness. The purpose of this study was to determine changes in BIS values during isoproterenol administration. Methods : Twenty consecutive patients underwent electrophysiology study under total intravenous anesthesia using propofol and remifentanil infusions. Isoproterenol was infused at a rate of 5mcg/kg/min and escalated to up to 20mcg/kg/min over 20 minutes. BIS levels were recorded before and throughout isoproterenol administration. Results : Patients demonstrated significant elevation in BIS value during isoproterenol infusion. The mean difference between pre- and post- BIS values was 21.3 [5.4, 37.2] (p = 0.00013). The isoproterenol doses which triggered a BIS spike ranged from 10.8 mcg to 90.8 mcg. The median effective isoproternol dose was 25.2 mcg. The median onset time for an isoproternol stimulated BIS spike was 6.9 minutes with rates from 2 to 20 mcg/minute. Discussion : Isoproterenol significantly increases BIS values during sedated electrophysiology study. Monitoring BIS values may be helpful in assessing the isoproterenol dosage required to overcome the suppressive effects of anesthesia on arrhythmia induction, as well as the potential need for additional anesthetics to prevent patient arousal. Conversely, decreasing BIS values are known to correlate with hypotensive episodes signaling cerebral hypoperfusion. This may be relevant in cases of hemodynamically unstable tachycardias. BIS appears to be an important tool for the optimization of anesthesia when isoproterenol is administered during electrophysiology study
— id: 146278, year: 2011, vol: 112, page: ?, stat: Journal Article,

Blind orotracheal intubation with the intubating laryngeal mask versus fibreoptic guided orotracheal intubation with the Ovassapian airway. A pilot study of awake patients
Dhar P; Osborn I; Brimacombe J; Meenan M; Linton P
2001 Jun;29(3):252-254, Anaesthesia & intensive care
In a randomized, prospective pilot study, we compared awake blind orotracheal intubation using the intubating laryngeal mask airway (blind-ILM) with awake fibreoptic-guided orotracheal intubation using an Ovassapian airway (FOS-OA). Fifty-four patients (ASA 1 to 3, aged 18 to 85 years) requiring awake intubation for elective surgery were randomly allocated by coin toss into two groups: 31 patients were intubated blindly through the ILM (blind-ILM) and 23 were intubated using fibreoptic guidance through the Ovassapian airway (FOS-OA). Sedation to a target clinical end-point (spontaneous eye-closing, but responsive to verbal command) was obtained with fentanyl/midazolam and a cricothyroid puncture was performed with 3 ml lignocaine 4%. The oropharynx was then topicalized until tolerance of a Guedel airway was achieved. The number of failed attempts (maximum of three allowed), overall success rates, the time from insertion of the airway to capnographic (blind-ILM) or fibreoptic (FOS-OA) confirmation of intubation or until three failed attempts, and cardiovascular responses before and during intubation, were recorded. The first time (blind-ILM, 25/31 [81%]; FOS-OA, 20/23 [87%], P = 0.6) and overall (blind-ILM, 26/31 [84%]; FOS-OA, 22/23 [96%], P = 0.2) intubation success rates were similar. The mean +/- SD time to intubation was shorter for the blind-ILM group (104 +/- 65 vs 158 +/- 115 sec, P = 0.05). There were no clinically significant differences in blood pressure or heart rate between groups. Compared with baseline values, there was no cardiovascular response to intubation in either group. We conclude that the blind-ILM and FOS-OA techniques have similar success rates and cardiovascular responses, but intubation is slightly quicker with the blind-ILM technique
— id: 21146, year: 2001, vol: 29, page: 252, stat: Journal Article,