Michael Irwin - Academia.edu (original) (raw)

Papers by Michael Irwin

British Journal of Anaesthesia, 2018

British Journal of Anaesthesia, 2019

Anaesthesia and Intensive Care, 1996

We analyzed data from 1233 Chinese patients of a wide age range who received patient-controlled a... more We analyzed data from 1233 Chinese patients of a wide age range who received patient-controlled analgesia (PCA) intravenous morphine for postoperative pain relief during the period from January 1992 to May 1995. The analgesic regimen was standardized as follows: PCA bolus 1 to 1.5 mg; lock-out interval 5 minutes; one-hour maximum dose 0.075 to 0.1 mg.kg–1and background infusion 0 or 0.5 mg.h–1. Most patients underwent major surgery that was broadly subclassified according to the anatomical area involved. The median verbal numerical rating scales of pain (0 to 10) at rest and while coughing for the first, second and third 24 hours were 3.0/5.0, 1.5/4.0 and 0/3.0 respectively and the corresponding demand to delivery ratios were 2.8±2.9, 2.6±2.4 and 2.4±2.6. The overall morphine consumptions in 1004 of these Chinese patients were 27.5±16.8, 178±16.1 and 18.1±21.0 μg.kg-1.h–1during the first 16, 17 to 41 and 42 to 66 postoperative hours respectively. These figures were the same as for C...

Anaesthesia, 2018

SummaryInduction of anaesthesia with target‐controlled infusion of propofol may be achieved by st... more SummaryInduction of anaesthesia with target‐controlled infusion of propofol may be achieved by stepwise increases in effect‐site concentration until the patient loses consciousness (titration method), or by setting a high effect‐site concentration target and observing the calculated effect‐site concentration at loss of consciousness (standard method). When the estimated effect‐site concentration at loss of consciousness is accurate, the difference between effect‐site concentration at loss of consciousness and at recovery of consciousness should be small. This prospective, randomised, controlled trial was designed to compare this difference (effect‐site concentration at loss of consciousness – effect‐site concentration at recovery of consciousness) associated with the two techniques. Sixty‐seven healthy patients undergoing elective hemithyroidectomy were recruited. Induction of anaesthesia was achieved using effect‐site target‐controlled infusion with the modified Marsh model and ke0...

Medicine, 2018

Clinical studies have shown that total intravenous anesthesia (TIVA) with propofol is associated ... more Clinical studies have shown that total intravenous anesthesia (TIVA) with propofol is associated with better postoperative pain control compared with inhalational anesthesia, while other studies have not shown any benefit. The analgesic effect of TIVA with propofol in colorectal surgery has not been studied. The aim of this study is to evaluate the postoperative analgesic effects of TIVA with propofol versus inhalational sevoflurane in colorectal surgery.This is a retrospective case-control study. Records of patients undergoing colorectal surgery from 2014 to 2016 (36 months) were retrieved. Ninety-five patients who received TIVA with propofol were matched against 95 patients who received inhalational sevoflurane. Acute postoperative numerical rating scale (NRS) pain scores, postoperative morphine consumption, patient satisfaction, and side effects were compared and analyzed for differences between TIVA with propofol and sevoflurane.There were no significant differences in NRS pain ...

Anesthesia and analgesia, Mar 12, 2016

The Sedation Consortium on Endpoints and Procedures for Treatment, Education, and Research, estab... more The Sedation Consortium on Endpoints and Procedures for Treatment, Education, and Research, established by the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks public-private partnership with the US Food and Drug Administration, convened a meeting of sedation experts from a variety of clinical specialties and research backgrounds with the objective of developing recommendations for procedural sedation research. Four core outcome domains were recommended for consideration in sedation clinical trials: (1) safety, (2) efficacy, (3) patient-centered and/or family-centered outcomes, and (4) efficiency. This meeting identified core outcome measures within the efficacy and patient-centered and/or family-centered domains. Safety will be addressed in a subsequent meeting, and efficiency will not be addressed at this time. These measures encompass depth and levels of sedation, proceduralist and patient satisfaction, patient recall, and...

PloS one, 2016

Patients receiving total intravenous anesthesia (TIVA) with propofol have been shown to experienc... more Patients receiving total intravenous anesthesia (TIVA) with propofol have been shown to experience less postoperative pain. We evaluated the post-operative analgesic effects of propofol compared with sevoflurane maintenance of anesthesia in liver surgery. This study was registered at ClinicalTrials.gov (NCT02179437). In this retrospective study, records of patients who underwent liver surgery between 2010 and 2013 were reviewed. Ninety-five patients anesthetized with propofol TIVA were matched with 95 patients anesthetized with sevoflurane. Numeric pain rating scale (NRS) pain scores, postoperative morphine consumption, side effects and patients' satisfaction with pain relief were evaluated. The TIVA group reported lower NRS pain scores during coughing on postoperative days 1 and 2 but not 3 (p = 0.0127, p = 0.0472, p = 0.4556 respectively). They also consumed significantly less daily (p = 0.001 on day 1, p = 0.0231 on day 2, p = 0.0004 on day 3), accumulative (p = 0.001 on day ...

Medicine, 2015

The efficacy of pregabalin in acute postsurgical pain has been demonstrated in numerous studies; ... more The efficacy of pregabalin in acute postsurgical pain has been demonstrated in numerous studies; however, the analgesic efficacy and adverse effects of using pregabalin in various surgical procedures remain uncertain. We aim to assess the postsurgical analgesic efficacy and adverse events after pregabalin administration under different surgical categories using a systematic review and meta-analysis of randomized controlled trials.A search of the literature was performed between August 2014 to April 2015, using PubMed, Ovid via EMBASE, Google Scholar, and ClinicalTrials.gov with no limitation on publication year or language. Studies considered for inclusion were randomized controlled trials, reporting on relevant outcomes (2-, 24-hour pain scores, or 24 hour morphine-equivalent consumption) with treatment with perioperative pregabalin.Seventy-four studies were included. Pregabalin reduced pain scores at 2 hours in all categories: cardiothoracic (Hedge's g and 95%CI, -0.442 [-0.75...

Oxidative Medicine and Cellular Longevity, 2015

Ischemia and inflammation may be pathophysiological mechanisms of complex regional pain syndrome ... more Ischemia and inflammation may be pathophysiological mechanisms of complex regional pain syndrome (CRPS). Ketamine has proposed anti-inflammatory effects and has been used for treating CRPS. This study aimed to evaluate anti-inflammatory and analgesic effects of ketamine after ischaemia-reperfusion injury in a chronic postischaemia pain (CPIP) model of CRPS-I. Using this model, ischemia was induced in the hindlimbs of male Sprague-Dawley rats. Ketamine, methylprednisolone, or saline was administered immediately after reperfusion. Physical effects, (oedema, temperature, and mechanical and cold allodynia) in the bilateral hindpaws, were assessed from 48 hours after reperfusion. Fewer (56%) rats in the ketamine group developed CPIP at the 48th hour after reperfusion (nonsignificant). Ketamine treated rats showed a significantly lower temperature in the ischaemic hindpaw compared to saline (P<0.01) and methylprednisolone (P<0.05) groups. Mechanical and cold allodynia were significa...

Expert Opinion on Pharmacotherapy, 2013

Clinical Science, 2011

Either isoflurane preconditioning or high-dose propofol treatment has been shown to attenuate myo... more Either isoflurane preconditioning or high-dose propofol treatment has been shown to attenuate myocardial IRI (ischaemia/reperfusion injury) in patients undergoing CABG (coronary artery bypass graft) surgery. It is unknown whether isoflurane and propofol may synergistically attenuate myocardial injury in patients. The present study investigated the efficacy of IsoPC (isoflurane preconditioning), propofol treatment (postconditioning) and their synergy in attenuating postischaemic myocardial injury in patients undergoing CABG surgery using CPB (cardiopulmonary bypass). Patients (n=120) selected for CABG surgery were randomly assigned to one of four groups (n=30 each). After induction, anaesthesia was maintained either with fentanyl and midazolam (control; group C); with propofol at 100 μg·kg−1 of body weight·min−1 before and during CPB followed by propofol at 60 μg·kg−1 of body weight·min−1 for 15 min after aortic declamping (group P); with isoflurane 1–1.5% end tidal throughout the su...

British Journal of Anaesthesia, 2002

Background. Use of intraoperative somatosensory evoked potential (SSEP) monitoring is helpful in ... more Background. Use of intraoperative somatosensory evoked potential (SSEP) monitoring is helpful in spinal corrective surgery but may be affected by anaesthetic drugs. An anaesthetic technique that has less effect on SSEP or allows faster recovery is an advantage. We compared the effects on SSEP and the clinical recovery pro®les of sevo¯urane/nitrous oxide and propofol anaesthesia during surgery to correct scoliosis. Methods. Twenty adolescent patients were randomized into two groups of 10. One group received sevo¯urane±nitrous oxide anaesthesia and the other received propofol i.v. anaesthesia. An alfentanil infusion was used for analgesia in both groups. Results. Changes in anaesthetic concentration produced little effect on the latency of SSEP, but the effect on the variability of SSEP amplitude was signi®cant (P<0.05). Sevo¯urane produced a faster decrease in SSEP and a faster recovery than propofol (P<0.05). On emergence, patients who received sevo¯urane tended to have shorter recovery times to eye opening (mean 5.1 vs 20.6 min, P=0.09) and toe movement (mean 7.9 vs 15.7 min, P=0.22). Those who had received sevo¯urane were signi®cantly more lucid and cooperative in recovery. Conclusions. Sevo¯urane produces a faster decrease and recovery of SSEP amplitude as well as a better conscious state on emergence than propofol.

British Journal of Anaesthesia, 2001

Propofol has been reported to affect blood coagulation. This prospective, randomized study compar... more Propofol has been reported to affect blood coagulation. This prospective, randomized study compared coagulation and blood loss during anaesthetic maintenance with target-controlled intravenous propofol infusion vs. inhaled iso¯urane. Thirty-eight ASA I±III patients undergoing head and neck surgery were allocated randomly to receive either inhaled iso¯urane at end-tidal concentration 1±1.5% (group I, n=20) or target-controlled infusion (TCI) of propofol at target concentration 2±5 mg ml ±1 (group P, n=18). Thrombelastographyâ on recalci®ed whole blood was performed pre-induction, and at 15, 30, 60, 90, 120 min post-induction and 30 min after anaesthesia in both groups. Blood loss was estimated from weighing swabs and the volume in suction bottles. Induced hypotension was not used, and perioperative body temperature was similar between groups. There were no signi®cant differences in thrombelastographic coagulation (R-time, K-time, maximum amplitude and angle) or ®brinolytic variables (lysis index at 30 and 60 min) at all times between groups. Total blood loss was also not signi®cantly different (median group I: 350 ml, range 20±1200 ml; group P: 200 ml, range 50±800 ml). Shortening of R-time and widening of angle developed over time in both groups (P<0.05 groups I and P, repeated measures ANOVA). We conclude that maintenance of anaesthesia with propofol TCI at 2±5 mg ml ±1 does not cause detectable coagulation changes on thrombelastographyâ nor increase surgical blood loss when compared to inhaled iso¯urane.

British Journal of Anaesthesia, 2003

British Journal of Anaesthesia, 1994

British Journal of Anaesthesia, 2007

British Journal of Anaesthesia, 2011

† Dexmedetomidine (DEX) is an alpha 2-adrenoreceptor agonist, which induces sedation and analgesi... more † Dexmedetomidine (DEX) is an alpha 2-adrenoreceptor agonist, which induces sedation and analgesia. † Patients given intranasal DEX experienced significantly less postoperative pain in the early postoperative period compared with placebo. † Intranasal DEX resulted in more sedation perioperatively than placebo but without delay in psychomotor recovery. Background. Dexmedetomidine (DEX) is an alpha 2-adrenoreceptor agonist, which induces sedation and analgesia. This study aimed to determine whether intranasal DEX offered perioperative sedation and better postoperative analgesia. Methods. Patients having unilateral third molar surgery under local anaesthesia were recruited and allocated to receive either intranasal DEX 1 mg kg 21 (Group D) or same volume of saline (Group P) 45 min before surgery. Patient-controlled sedation with propofol was offered as a rescue sedative. Perioperative sedation, postoperative pain relief and analgesic consumption, vital signs, adverse events, postoperative recovery, and satisfaction in sedation and analgesia were assessed. Results. Thirty patients from each group were studied. Areas under curve (AUC) of postoperative numerical rating scale (NRS) pain scores 1-12 h at rest and during mouth opening were significantly lower in Group D (P¼0.003 and 0.009, respectively). AUC BIS values and OAA/S sedation scores were significantly lower before surgery and at the recovery area (all P,0.01) with significantly less intra-operative propofol used in group D (P,0.01). In group D, heart rate was significantly lower at recovery period (P¼0.005) while systolic blood pressure in different periods of the study (all P,0.01), but the decreases did not require treatment. More patients from placebo group experienced dizziness (P¼0.026) but no serious adverse event was found. No difference was found in postoperative psychomotor recovery and satisfaction in pain relief and sedation. Conclusions. Patients receiving intranasal DEX for unilateral third molar surgery with local anaesthesia were more sedated perioperatively with better postoperative pain relief. No delay in psychomotor recovery was seen.

Anesthesiology Clinics, 2010

The middle ear refers to an air-filled space between the tympanic membrane and the oval window. I... more The middle ear refers to an air-filled space between the tympanic membrane and the oval window. It is connected to the nasopharynx by the eustachian tube and is in close proximity to the temporal lobe, cerebellum, jugular bulb, and the labyrinth of the inner ear. The middle ear contains three ossicles-the malleus, incus and stapes-which are responsible for transmission of sound vibration from the eardrum to the cochlea. This air-filled cavity is traversed by the facial nerve before it exits the skull via the stylomastoid foramen. 1,2 The facial nerve provides motor innervation to the muscles of facial expression. COMMON MIDDLE EAR SURGERIES Middle ear disease affects patients of all ages. Common middle ear pathologic conditions requiring surgery in adults include tympanoplasty (reconstructive surgery for the tympanic membrane, or eardrum), stapedectomy or ossiculoplasty for otosclerosis, mastoidectomy for removal of infected air cells within the mastoid bone, and removal of cholesteoma. 2 Common middle ear surgery in children includes tympanoplasty, mastoidectomy, myringotomy, grommet insertion. and cochlear implantation. 2 Some of these procedures can be performed under local anesthesia, although obviously, all surgery can be performed under general anesthesia if necessitated by patient or surgical factors (Box 1). ANESTHETIC CONSIDERATIONS IN MIDDLE EAR SURGERY Given the unique location, size, and delicate content of the middle ear, great care must be taken during the perioperative period. Special considerations include: provision of a bloodless surgical field, attention to patient's head positioning, airway management,