Rita Katznelson

Preoperative use of statins is associated with reduced early delirium rates after cardiac surgery.

Background:Delirium is an acute deterioration of brain function characterized by fluctuating consciousness and an inability to maintain attention. Use of statins has been shown to decrease morbidity and mortality after major surgical procedures. The objective of this study was to determine an association between preoperative administration of statins and postoperative delirium in a large prospective cohort of patients undergoing cardiac surgery with cardiopulmonary bypass. Methods:After Institutional Review Board approval, data were prospectively collected on consecutive patients undergoing cardiac surgery with cardiopulmonary bypass from April 2005 to June 2006 in an academic hospital. All patients were screened for delirium during their hospitalization using the Confusion Assessment Method in the intensive care unit. Multivariable logistic regression analysis was used to identify independent perioperative predictors of delirium after cardiac surgery. Statins were tested for a potential protective effect. Results:Of the 1,059 patients analyzed, 122 patients (11.5%) had delirium at any time during their cardiovascular intensive care unit stay. Administration of statins had a protective effect, reducing the odds of delirium by 46%. Independent predictors of postoperative delirium included older age, preoperative depression, preoperative renal dysfunction, complex cardiac surgery, perioperative intraaortic balloon pump support, and massive blood transfusion. The model was reliable (Hosmer-Lemeshow test, P = 0.3) and discriminative (area under receiver operating characteristic curve = 0.77). Conclusions:Preoperative administration of statins is associated with the reduced risk of postoperative delirium after cardiac surgery with cardiopulmonary bypass.

Non-invasive prospective targeting of arterial P(CO2) in subjects at rest.

Accurate measurements of arterial P  CO 2 (P  a,CO 2 ) currently require blood sampling because the end‐tidal P  CO 2 (P  ET,CO 2 ) of the expired gas often does not accurately reflect the mean alveolar P  CO 2 and P  a,CO 2. Differences between P  ET,CO 2 and P  a,CO 2 result from regional inhomogeneities in perfusion and gas exchange. We hypothesized that breathing via a sequential gas delivery circuit would reduce these inhomogeneities sufficiently to allow accurate prediction of P  a,CO 2 from P  ET,CO 2. We tested this hypothesis in five healthy middle‐aged men by comparing their P  ET,CO 2 values with P  a,CO 2 values at various combinations of P  ET,CO 2 (between 35 and 50 mmHg), P  O 2 (between 70 and 300 mmHg), and breathing frequencies (f; between 6 and 24 breaths min−1). Once each individual was in a steady state, P  a,CO 2 was collected in duplicate by consecutive blood samples to assess its repeatability. The difference between P  ET,CO 2 and average P  a,CO 2 was 0.5 ± 1.7 mmHg (P= 0.53; 95% CI −2.8, 3.8 mmHg) whereas the mean difference between the two measurements of P  a,CO 2 was −0.1 ± 1.6 mmHg (95% CI −3.7, 2.6 mmHg). Repeated measures ANOVAs revealed no significant differences between P  ET,CO 2 and P  a,CO 2 over the ranges of P  O 2, f and target P  ET,CO 2. We conclude that when breathing via a sequential gas delivery circuit, P  ET,CO 2 provides as accurate a measurement of P  a,CO 2 as the actual analysis of arterial blood.

Dexmedetomidine versus Propofol Sedation Reduces Delirium after Cardiac Surgery: A Randomized Controlled Trial.

Background:Postoperative delirium (POD) is a serious complication after cardiac surgery. Use of dexmedetomidine to prevent delirium is controversial. The authors hypothesized that dexmedetomidine sedation after cardiac surgery would reduce the incidence of POD. Methods:After institutional ethics review board approval, and informed consent, a single-blinded, prospective, randomized controlled trial was conducted in patients 60 yr or older undergoing cardiac surgery. Patients with a history of serious mental illness, delirium, and severe dementia were excluded. Upon admission to intensive care unit (ICU), patients received either dexmedetomidine (0.4 &mgr;g/kg bolus followed by 0.2 to 0.7 &mgr;g kg−1 h−1 infusion) or propofol (25 to 50 &mgr;g kg−1 min−1 infusion) according to a computer-generated randomization code in blocks of four. Assessment of delirium was performed with confusion assessment method for ICU or confusion assessment method after discharge from ICU at 12-h intervals during the 5 postoperative days. Primary outcome was the incidence of POD. Results:POD was present in 16 of 91 (17.5%) and 29 of 92 (31.5%) patients in dexmedetomidine and propofol groups, respectively (odds ratio, 0.46; 95% CI, 0.23 to 0.92; P = 0.028). Median onset of POD was on postoperative day 2 (1 to 4 days) versus 1 (1 to 4 days), P = 0.027, and duration of POD 2 days (1 to 4 days) versus 3 days (1 to 5 days), P = 0.04, in dexmedetomidine and propofol groups, respectively. Conclusions:When compared with propofol, dexmedetomidine sedation reduced incidence, delayed onset, and shortened duration of POD in elderly patients after cardiac surgery. The absolute risk reduction for POD was 14%, with a number needed to treat of 7.1.

Measurement of forces applied during Macintosh direct laryngoscopy compared with GlideScope® videolaryngoscopy*

Laryngoscopy can induce stress responses that may be harmful in susceptible patients. We directly measured the force applied to the base of the tongue as a surrogate for the stress response. Force measurements were obtained using three FlexiForce Sensors® (Tekscan Inc, Boston, MA, USA) attached along the concave surface of each laryngoscope blade. Twenty‐four 24 adult patients of ASA physical status 1–2 were studied. After induction of anaesthesia and neuromuscular blockade, laryngoscopy and tracheal intubation was performed using either a Macintosh or a GlideScope®(Verathon, Bothell, WA, USA) laryngoscope. Complete data were available for 23 patients. Compared with the Macintosh, we observed lower median (IQR [range]) peak force (9 (5–13 [3–25]) N vs 20 (14–28 [4–41]) N; p = 0.0001), average force (5 (3–7 [2–19]) N vs 11 (6–16 [1–24]) N; p = 0.0003) and impulse force (98 (42–151 [26–444]) Ns vs 150 (93–207 [17–509]) Ns; p = 0.017) with the GlideScope. Our study shows that the peak lifting force on the base of the tongue during laryngoscopy is less with the GlideScope videolaryngoscope compared with the Macintosh laryngoscope.

Experience is not enough: repeated breaches in epidural anesthesia aseptic technique by novice operators despite improved skill.

Background:Invasive procedures such as epidural anesthesia carry risks for complications such as erroneous placement arising from inadequate manual skills and infection secondary to breaches in aseptic technique. Although it is assumed that improvement in aseptic technique parallels improved dexterity, this assertion remains unproven. The aim of this study was to determine whether increased proficiency in the manual skills for epidural anesthesia is associated with improved aseptic technique. Methods:Second-year anesthesia residents were repeatedly videotaped performing epidural anesthesia over 6-month periods. Three independent examiners blinded to the level of training of the residents evaluated the procedures for manual skills and aseptic technique. Each procedure was graded using a manual skills checklist, a global rating scale, and an aseptic technique checklist. The main outcome measures were the scores for these three tools. Results:Thirty-five sessions were videotaped over 1 yr. Interrater reliability was nearly perfect. A strong positive association was found between increased experience and manual skills, as reflected by the scores achieved on both the manual skills checklist and the global rating scale. In contrast, a nonsignificant or very weak correlation was found between the aseptic technique checklist total scores and the number of epidurals performed. Conclusion:Manual skills for invasive procedures improved with increasing experience, but aseptic technique did not, despite formal teaching. These findings reflect major gaps in the understanding and teaching of the principles of aseptic technique, most likely due to lack of structured training. Educational initiatives are needed to correct these teaching gaps.

The association between tranexamic acid and convulsive seizures after cardiac surgery: a multivariate analysis in 11 529 patients

Because of a lack of contemporary data regarding seizures after cardiac surgery, we undertook a retrospective analysis of prospectively collected data from 11 529 patients in whom cardiopulmonary bypass was used from January 2004 to December 2010. A convulsive seizure was defined as a transient episode of disturbed brain function characterised by abnormal involuntary motor movements. Multivariate regression analysis was performed to identify independent predictors of postoperative seizures. A total of 100 (0.9%) patients developed postoperative convulsive seizures. Generalised and focal seizures were identified in 68 and 32 patients, respectively. The median (IQR [range]) time after surgery when the seizure occurred was 7 (6–12 [1–216]) h and 8 (6–11 [4–18]) h, respectively. Epileptiform findings on electroencephalography were seen in 19 patients. Independent predictors of postoperative seizures included age, female sex, redo cardiac surgery, calcification of ascending aorta, congestive heart failure, deep hypothermic circulatory arrest, duration of aortic cross‐clamp and tranexamic acid. When tested in a multivariate regression analysis, tranexamic acid was a strong independent predictor of seizures (OR 14.3, 95% CI 5.5–36.7; p < 0.001). Patients with convulsive seizures had 2.5 times higher in‐hospital mortality rates and twice the length of hospital stay compared with patients without convulsive seizures. Mean (IQR [range]) length of stay in the intensive care unit was 115 (49–228 [32–481]) h in patients with convulsive seizures compared with 26 (22–69 [14–1080]) h in patients without seizures (p < 0.001). Convulsive seizures are a serious postoperative complication after cardiac surgery. As tranexamic acid is the only modifiable factor, its administration, particularly in doses exceeding 80 mg.kg−1, should be weighed against the risk of postoperative seizures.

The interaction of carbon dioxide and hypoxia in the control of cerebral blood flow.

Both hypoxia and carbon dioxide increase cerebral blood flow (CBF), and their effective interaction is currently thought to be additive. Our objective was to test this hypothesis. Eight healthy subjects breathed a series of progressively hypoxic gases at three levels of carbon dioxide. Middle cerebral artery velocity, as an index of CBF; partial pressures of carbon dioxide and oxygen and concentration of oxygen in arterial blood; and mean arterial blood pressure were monitored. The product of middle cerebral artery velocity and arterial concentration of oxygen was used as an index of cerebral oxygen delivery. Two-way repeated measures analyses of variance (rmANOVA) found a significant interaction of carbon dioxide and hypoxia factors for both CBF and cerebral oxygen delivery. Regression models using sigmoidal dependence on carbon dioxide and a rectangular hyperbolic dependence on hypoxia were fitted to the data to illustrate this interaction. We concluded that carbon dioxide and hypoxia act synergistically in their control of CBF so that the delivery of oxygen to the brain is enhanced during hypoxic hypercapnia and, although reduced during normoxic hypocapnia, can be restored to normal levels with progressive hypoxia.

Preventive analgesia and novel strategies for the prevention of chronic post-surgical pain

Chronic post-surgical pain (CPSP) is a serious complication of major surgery that can impair a patient’s quality of life. The development of CPSP is a complex process which involves biologic, psychosocial, and environmental mechanisms that have yet to be fully understood. Currently perioperative pharmacologic interventions aim to suppress and prevent sensitization with the aim of reducing pain and analgesic requirement in acute as well as long-term pain . Despite the detrimental effects of CPSP on patients, the body of literature focused on treatment strategies to reduce CPSP remains limited and continues to be understudied. This article reviews the main pharmacologic candidates for the treatment of CPSP, discusses the future of preventive analgesia, and considers novel strategies to help treat acute post-operative pain and lessen the risk that it becomes chronic. In addition, this article highlights important areas of focus for clinical practice including: multimodal management of CPSP patients, psychological modifiers of the pain experience, and the development of a Transitional Pain Service specifically designed to manage patients at high risk of developing chronic post-surgical pain.

Heart rate/blood pressure response and airway morbidity following tracheal intubation with direct laryngoscopy, GlideScope and Trachlight: a randomized control trial

Background and objective Haemodynamic response to tracheal intubation might be detrimental in high-risk patients. Minimizing oropharyngo-laryngeal stimulation or avoiding laryngoscopy may attenuate this response. We hypothesized that intubations performed with GlideScope or Trachlight would generate a lesser haemodynamic response than the conventional method of direct laryngoscopy. The objective of this study was to compare the haemodynamic response following tracheal intubation, using three different techniques of intubation. We also examined postoperative airway morbidities as our secondary outcome. Methods This was a prospective randomized control trial, conducted at Mount Sinai Hospital of Toronto. After Ethics Board approval, 60 adult ASA status I and II patients, scheduled for elective surgery requiring general anaesthesia with orotracheal intubation, were randomly allocated into three groups. Intubation was performed by a single experienced anaesthesiologist, using direct laryngoscopy, GlideScope or Trachlight. The haemodynamic variables were measured noninvasively at specific time intervals. We also recorded the number of attempts and total time for intubation. Postoperative airway symptoms following surgery were assessed using a questionnaire. Results There was no significant difference in blood pressure and heart rate between the groups. Direct laryngoscopy intubation times were significantly lower than those of the other techniques (both P < 0.0001). The occurrence of sore-throat symptoms in recovery was significantly higher in the Trachlight group (P = 0.0033). Conclusion There was no benefit of using any of the three intubation techniques for attenuation of haemodynamic changes. There was a higher incidence of airway symptoms associated with Trachlight intubation.

Accelerated recovery from sevoflurane anesthesia with isocapnic hyperpnoea.

BACKGROUND:Isocapnic hyperpnoea (IH) reduces recovery time from isoflurane anesthesia in animals and humans. We studied the effect of IH on the emergence profile of sevoflurane-anesthetized patients by comparing postoperative recovery variables in patients administered IH (IH group) to those recovered in the customary fashion (control group). METHODS:We enrolled 30 ASA I–III patients undergoing elective gynecological surgery. Induction and maintenance of anesthesia were standardized with a protocol consisting of fentanyl, propofol, rocuronium, and sevoflurane in air/O2. Patients were randomly assigned to control (C) or IH groups at the end of the surgery. We recorded time intervals from discontinuing sevoflurane to recovery milestones. RESULTS:Time to tracheal extubation was much shorter in the IH group compared with group C (6.2 ± 2.1 vs 12.3 ± 3.8 min, respectively, P < 0.01). The IH group also had shorter times to initiation of spontaneous ventilation (4.2 ± 1.7 vs 6.5 ± 3.8 min, P = 0.047), eye opening (5.5 ± 1.4 vs 13.3 ± 4.4 min, P < 0.01), bispectral index value >75 (3.9 ± 1.1 vs 8.8 ± 3.7 min, P < 0.01), leaving operating room (7.7 ± 2.0 vs 15.3 ± 3.4 min, P < 0.01), and eligibility for postanesthetic care unit discharge (67.2 ± 19.3 vs 90.6 ± 20.0 min, P < 0.01). CONCLUSION:IH accelerates recovery from sevoflurane anesthesia and shortens operating room and postanesthetic care unit stay.