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.

Guidelines: Lipid Therapy and Local Anesthetic Toxicity

Dr. Lee

Lipid Emulsion Infusion Resuscitation for Local Anesthetic and Other Drug Overdose

Anesthesiology: July 2012 - Volume 117 - Issue 1 - p 180–187

Lipid emulsion therapy is a known antidote for local anesthetic toxicity, but the guidelines for it’s use, it’s mechanism of action, and it’s application beyond local anesthetic toxicity continue to be discussed.  The article listed above provides some practical insight into these issues.

The article lists several websites that differ in their guidelines for lipid emulsion therapy, but generally have an accepted approach.  In the context of local anesthetic toxicity, optimizing oxygenation and ventilation through airway management comes first, then seizure suppression where applicable, then lipid emulsion therapy.  Effective BLS and ACLS are vital as well.  The dosing of lipid emulsion should be 20% lipid emulsion 1.5mg/kg IV Bolus followed by 0.25-0.5ml/kg/min infusion for 10 minutes following recovery of vital signs.

Risperidone and Post-op Delirium

Puja Trivedi, DO

Anesthesiology. 2012 May;116(5):987-97.

Early Treatment with Risperidone for Subsyndromal Delirium after On-pump Cardiac Surgery in the Elderly: A Randomized Trial.

Hakim SM, Othman AI, Naoum DO.

Sources estimate that up to 80% of post cardiac surgery patients experience post operative delirium which has a known association with prolonged ICU stays, ICU readmissions, unnecessary examinations and neurology consults, patient and family frustration and dissatisfaction and as recently noted in the Journal of Thoracic Surgery, increased incidence of strokes. It is for this reason Hakim et al decided to study the effect of early diagnosis and treatment of post operative delirium. The aim of this randomized, parallel-arm trial was to study the effect of treating subsyndromal delirium with risperidone on the incidence of clinical delirium in elderly patients who underwent on-pump cardiac surgery. One hundred one patients aged 65 yr or older who experienced subsyndromal delirium after on-pump cardiac surgery were randomized using a computer-generated list to receive 0.5 mg risperidone or placebo every 12 h by mouth. Patients were assessed at 8 h by a blinded observer using the Intensive Care Delirium Screening Checklist, and those scoring more than 3 were evaluated by a blinded psychiatrist to confirm delirium. Patients in either group who experienced delirium were treated according to the same algorithm. Initially, risperidone was administered and if symptoms were not controlled, haloperidol was administered. Seven (13.7%) patients in the risperidone group experienced delirium versus 17 (34%) in the placebo group (P = 0.031). Due to small patient size, the fact that there is no definitive diagnosis of subsyndromal delirium or accepted diagnostic exam, no consensus on the role of risperidone as a first line agent to treat delirium, cross over obscurity since patients in the placebo portion were given risperidone and/or haldol, as well as the potential side effects; risperidone for the treatment for subsyndromal delirium needs to be further studied before it can be adopted into mainstay practice.

Is Intra-op Hypotension Associated with a CVA? Dr. Halonen

Jeff Halonen, DO

Intraoperative Hypotension and Peripoerative Ischemic Stroke After General Surgery

This case study was performed in order to determine if there is a correlation between intraopertive hypotension and postoperative stroke as this correlation is largely unknown. The findings of this study showed that after correcting for potential confounders and with multiple testing, the duration that the mean blood pressure was decreased more than 30% from baseline remained statistically significantly associated with the occurrence of a postoperative stroke. Some of the limitations of this study that were listed would be in CEA patients, only collecting data on patie ts for 10 days postoperatively and the role of postoperative hypotension.

Will Aspirin prevent acute lung injury in critically ill patients? Dr. Kang

Vimmi Kang, DO

Article Review

The effect of aspirin in transfusion-related acute lung injury in critically ill patients

Source: Anesthesia. 20012 FEB 11

            This article looked to examine if aspirin would protect against transfusion related acute lung injury in critically ill patients. This article stemmed from the recent models that showed aspirin to be beneficial in improving outcomes in transfusion related injury in animals. This study was conducted as a post analysis of a case-control study. It looked at Transfusion-related acute lung injury cases compared with the control. Study consisted of 218 patients of which 66 used aspirin. Results showed that use of aspirin did not change the risk of transfusion related acute lung injury after transfusion of platelets or plasma.

In conclusion, aspirin did not decrease or protect against transfusion-related acute lung injury in critically ill patients.

OSA predicts adverse outcomes, Dr. Halonen

Jeff Halonen, DO

Article

Obstructive Sleep Apnea Predicts Adverse Perioperative Outcome

Bateman, Brian MD and Eikermann, Matthias MD, PhD, Anesthesiology, April 2012- Vol 116- Number 4, p 753-755.

Summary

OSA is an important risk factor for cardiovascular disease, myocardial infarction, stroke and perhaps has an association with postoperative delirium (POD). The definition for this review of delirium is an acute, fluctuating impairment in attention and cognition. OSA, independent of obesity, has been shown by most studies to be an independent risk of Perioperative complications. These complications may be from drug side effects, inflammation and hypercoaguability.

While this study can not link OSA and PoD directly, they do make some interesting speculations. Frequent episodes of airway collapse in OSA lead to hypoxia, disrupted sleep, sleep inertia, daytime sleepiness and increased arousal threshold from sleep, all of which may be consider as potential precipitating and/or augmenting factors of delirium. These are all associated with inflammation and OSA is also, in part, an inflammatory disease.  From this, the associated observed between OSA and POd should be considered "hypothesis-generating" rather than "proven."

Propofol/Desflurane/Isoflurane in Morbid Obese Patients, Dr. Cartier

Cameron Cartier, DO

Article Review

Postoperative Recovery After Desflurane, Propofol, or Isoflurane Anesthesia Among Morbidly Obese Patients: A Prospective, Randomized Study

A & A September 2000 vol. 91 no. 3 714-719

Background:  Morbidly obese patients can present with several complications after surgery, one of which is delayed emergence times.

Results/Discussion: Patients were randomly selected to receive Desflurane, Propofol, or Isoflurane for maintenance of anesthesia during laparoscopic gastroplasties.  Patients who received Desflurane recovered more quickly and consistently, demonstrated higher oxygen saturation levels and were more mobile quicker than those patients who received Propofol or Isoflurane.  The article concludes with the recommendation that morbidly obese patients should receive Desflurane for anesthetic maintenance in order to improve postoperative status of the patient.

Paradoxical Anesthetic Reactions, Dr. Inoue

Akiko Inoue, DO

“Increase of Paradoxical Excitement Response During Propofol-induced Sedation in Hazardous and Harmful Alcohol Drinkers” by S. Jeong; H.G> Lee; W. M. Kim; C.W. Jeong; S. H. Lee; M. Yoon; J. I. Choi

Br J Anesth. 2011; 107(6):930-933.

This is a prospective observational study of two consecutive sessions (study 1 n=70, study 2 n=120) on a total of 190 patients who underwent elective knee joint surgery in the supine position under spinal anesthesia.  They were asked 10 questions related to frequency of alcohol consumption, alcohol-related problems, and dependence symptoms.  The sum of scores to these questions ranged from 0-40 and based on the scores the subjects were categorized either hazardous and harmful drinkers (HD) or non hazardous drinkers (NHD).  Paradoxical excitement responses were scored by response such as increased talkativeness, brief spontaneous movement without repostioning (mild), restlessness, loss of cooperation, spontaneous movements requiring repositioning, (moderate), and agitation and spontaneous movements with a need to restrain the patient (severe).  The response was observed for 30 min and scored every 5 min.  In the first study the propofol infusion was started at the target effect-site concentration of 2.0 mcg/ml until BIS score reached 80, then it was controlled to maintain the BIS score in the range 70-80. In the second study the effect-site concentration was fixed in the whole study time at 0.8 mcg/ml (study 2/Low; Group HD=30, Group NHD=30) or 1.4 mcg/ml (study 2/High; Group HD=30, Group NHD=30.   The results were analyzed using SPSS and X² or Fisher’s exact test. In study 1 the incidence of paradoxical excitement response was higher in Group HD than in Group NHD (71.4% vs 43.8%; P=0.022), an odds ratio of 3.2 [95% confidence interval (CI): 1.2–8.8].  In study 2 the incidence was higher in Group HD (70.0% vs 34.5%; P=0.006), an odds ratio of 4.4 (95% CI: 1.5–13.2) only at high target effect-site concentration but not at the low concentration.  The incidence of moderate-to-severe response was significantly higher in Group HD of both study 1 (28.6% vs 3.1%; P=0.0005) and study 2 at the higher infusion rate (23.3% vs 3.4%; P=0.029).   Thus, authors concluded that “paradoxical excitement occurred more frequently and severely in hazardous and harmful alcohol drinkers than in social drinkers during propofol-induced moderate-to-deep sedation but not during light sedation”.  Some of the limitations of the study are 1) not a randomized double blind study 2) lack of diagnostic criteria for paradoxical response thus it may be overestimating the incidence.  However, this study is significant in suggesting that hazardous and harmful alcohol use may be one of the risk factors for developing paradoxical excitement responses during propofol-induced sedation.