Post-op Prolonged QT in Non-Cardiac Surgery

Dr. C. Chon

Postoperative QT Interval Prolongation in Patients Undergoing Noncardiac Surgery under General Anesthesia

Nagele, Peter, et al. Anesthesiology. August 2012 – Vol 117 – No. 2, pp 321-8

Summary:

12-lead EKG’s were performed on 469 adult patients undergoing major noncardiac surgery in the immediate preoperative period (baseline), within 30 minutes of arriving to the PACU, and on postoperative days 1 and 2. A single experienced anesthesiologist analyzed all of the EKG’s.

At the end of surgery, 51% of the patients demonstrated a prolonged QTc interval -- defined as greater than 440 ms. Moreover, 80% of study participants had significant increases in their QTc interval as compared to their preoperative baseline values. At later time points (ie, postoperative days 1 and 2), QTc intervals were unchanged from baseline. The perioperative QTc interval prolongation, then, can be attributed in large degree to medications administered in the perioperative period. Surgical stress may have also been an important contributing factor, although there was no correlation between increased heart rate and QTc prolongation.

The study found that isoflurane, methadone, ketorolac, calcium and ephedrine, in addition to the antibiotics cefoxitin, unasyn and zosyn, caused the most pronounced QTc prolongation. Surprisingly, neither ondansetron nor droperidol caued postoperative QTc prolongation.

One of the most important points discussed by the authors is the association between QTc prolongation and torsades de pointes. For each 10-ms increase in QTc interval, the risk of developing torsades de pointes increases by 5-7%. Therefore, the anesthesiologists must be ever-vigilant to catch the development of perioperative QTc interval prolongation.

New Predictor of Difficult Intubation???

Dr. C. Chon

Neck circumference to thyromental distance ratio: a new predictor of difficult intubation in obese patients

Kim, W.H., et al. British Journal of Anaesthesia. 2011 Feb 24;doi:10.1093/bja/aer024

Anesthesiologists from an academic medical center in Seoul, South Korea enrolled 260 ASA I or II patients undergoing general anesthesia with tracheal intubation. 123 patients were assigned to the obese group (BMI ³ 27.5, as per the WHO’s Asian obesity criteria) and 125 patients were assigned to the non-obese group (BMI < 27.5). 12 patients were excluded because of incomplete data.

Using the intubation difficulty scale (IDS), difficult intubation -- defined by an IDS ³ 5 -- was more frequent in the obese group than the non-obese group (13.8% vs 4.8%; P=0.016). Multivariate analysis revealed the Mallampati score, the Wilson score, and neck circumference-to-thyromental distance ratio (NC/TM) were independently associated with difficult intubation. Among these, NC/TM showed a higher sensitivity and negative predictive value than the other airway measures.

Numerous studies looking at preoperative airway measures have suggested that single tests have limited value in predicting difficult intubations. However, combining numerous measures and risk factors, as is done to when calculating the El-Ganzouri or Wilson scores, can be cumbersome and time-consuming. This study combines two valuable risk factors (neck circumference and thyromental distance), which the researchers say “may increase the diagnostic value while not increasing the burden of [testing].”

Predictors of LMA Failure

Chang-Ho Chon, DO

Article:
Predictors and Clinical Outcomes from Failed Laryngeal Mask Airway Unique^TM

Ramachandran, Satya K., et al. Anesthesiology. June 2012 – Vol 116 – No. 6, pp 1217-26

Summary:

The reported rate of failure with use of supraglottic airway devices is 0.2-8%. However, little is known about the risk-adjusted prediction of LMA failure requiring rescue tracheal intubation and its impact on patient outcomes.

This prospective study included 15,795 adult (³18 yr) undergoing general anesthesia at a University of Michigan affiliated quaternary care facility with the use of the LMA Unique^TM (uLMA) in both ambulatory and nonambulatory settings. 170 patients (1.1%) experienced the primary outcome of uLMA^TM failure, defined as an airway event requiring uLMA^TM removal and tracheal intubation. More than 60% of patients with uLMA^TM failure experienced significant hypoxia, hypercapnia, or airway obstruction; 42% were unable to be adequately ventilated due to significant leak.

Four risk factors contributing to LMA failure were identified:  surgical table rotation, male sex, poor dentition, thick neck, and increased body mass index. Patients in which the uLMA^TM failed were 3 times more difficult to mask ventilate. Among outpatients with uLMA^TM failure, 13.7% required unplanned admission to the hospital, of whom 5.6% required intensive care for persistent hypoxemia.

The results of this study support the use of the LMA as a safe supraglottic airway device with relatively low failure rate (1.1%). However, there are clear consequences to LMA failure, including unplanned or prolonged hospitalization. Furthermore, the researchers remind us that certain risk factors increase the rate of failure.

Celiac Plexus Block and end of life care, Dr. Chon

 Chang-Ho Chon, DO

Article:
Effect of Neurolytic Celiac Plexus Block on Pain Relief, Quality of Life, and Survival in Patients with Unresectable Pancreatic Cancer

Wong, Gilbert Y., et al. JAMA. Mar 3, 2004 – Vol 291 – No. 2, pp 1092-9

Summary:

Pancreatic cancer is an aggressive malignancy associated with high mortality and often severe upper abdominal pain. Previous studies by Lillemoe, et al. and Kelsen, et al. suggested pancreatic cancer patients to have decreased pain following intraoperative chemical splanchnicectomy and decreased survival when pain was out of control, respectively. This double-blinded, randomized control trial, which was conducted at Mayo Clinic, aimed to test the hypothesis that neurolytic celiac plexus block (NCPB) vs opioids alone can improve pain relief, quality of life (QOL), and survival in patients with unresectable pancreatic cancer.

100 eligible patients were enrolled and randomly assigned to receive either NCPB or systemic analgesic therapy (SAT) with a sham injection. All patients were allowed to receive additional opioids managed by a clinician blinded to the treatment assignment.

At week 1, the mean pain intensity decreased for each group from baseline, but the pain relief was much greater in the NCPB group (53% vs 27%, P=0.005). After week 1, pain intensity decreased gradually and was significantly lower for NCPB than for SAT (P=0.01). Opioid consumption increased over time with no evidence of difference between the groups. Following week 1, QOL gradually declined and did not differ between groups (P=0.46). At 1 year, 16% of NCPB patients and 6% of SAT patients were alive, but survival did not differ significantly (P=0.26).

The study concludes, then, that although NCPB improves pain in this patient population, it does not affect QOL or survival.