Predicting Fluid Responsiveness

Dr. Trivedi

Monnet X, Dres M, Ferré A, Le Teuff G, Jozwiak M, Bleibtreu A, Le Deley MC, Chemla D, Richard C, Teboul JL. Prediction of fluid responsiveness by a continuous non-invasive assessment of arterial pressure in critically ill patients: comparison with four other dynamic indices. Br J Anaesth. 2012 Sep;109(3):330-8. Epub 2012 Jun 26.

            A debate within the realm of anesthesia continues over the best hemodynamic monitoring tool. Traditional static measures such as central venous pressure and pulmonary artery occlusion pressures are now being replaced by dynamic indices. Monnet and colleagues sought to compare non invasive arterial pulse pressure variation (PPV) to invasive PPV, respiratory variation of pulse contour-derived stroke volume, and changes in cardiac index induced by passive leg raising (PLR) and end-expiratory occlusion (EEO) tests. The PPV, the respiratory variation of arterial pulse pressures induced by mechanical ventilation, estimates stroke volume with relatively good accuracy. PLR acts as a “self volume challenge” and the effects of PLR on the cardiac output can predict fluid responsiveness. The EEO is a newer tool which involves  occluding the respiratory circuit for a few seconds at end-expiration interrupting the venous return that occurs at each mechanical inspiration resulting increase in cardiac preload.  Patient populations which may have the greatest benefit from new dynamic indices, the critically ill with hemodynamic failure, were chosen as the focus for this study. 47 critically ill patients were chosen. Baseline non-invasive and invasive PPVs, stroke volume variation, and changes in cardiac index induced by PLR and EEO were recorded. The patient was then administered 500 ml of saline and the response recorded. CNAP could not record arterial pressures in 8 patients which the authors attribute to severe vasoconstriction from vasopressors and/or micro thrombi. Fluid increased cardiac index by ≥15% in 17 'responders' out of the remaining 39 patients. A limitation is that in patients with low tidal volumes the changes in intrathoracic pressure might be so low that changes in cardiac preload could be too low to challenge the preload-dependent stroke volume. The PLR may be useful in this case since it would allow testing for fluid responsiveness even in ventilated patients with low tidal volumes and lung compliance. The authors found that combing multiple dynamic indices did not prove to have higher accuracy in terms of fluid responsiveness and that non-invasive assessment of PPV appears to be of great utility in this patient population. 

Estimating fluid status in the post surgical ICU can be challenging as patients indices are increasingly challenged by failing organs and influenced by measures such as dialysis. In addition to the influence of ventilation, the PPV can also be invalidated by developed arrhythmias which are frequent in this population. In addition to the use of PPV and other static and dynamic measures, I found the use of transthoracic ultrasound to be of great utility in a situation of uncertainty. A quick look at the heart by the anesthesiologist at bedside can reveal valuable information about the overall function/contractility of the heart as well as fluid status as the heart may appear overfilled/ volume overloaded or under filled/ “kissing.”

Fluid Resuscitation in Septic Shock

Dr. Perz,

Boyd, J.H., Forbes, J., Nakada, T., Walley, K., Russell, J.A. Fluid Resuscitation in septic shock: A positive fluid balance and elevated central venous pressure are associated with increased mortality. Critical Care Medicine: Volume 39, Issue 2 (Feb 2011).

The objective of this study was to determine when central venous pressure (CVP) and fluid balance after resuscitation for septic shock are associated with mortality by doing a retrospective review of the use of IV fluids during the first 4 days of care.  The study concluded that a more positive fluid balance both early in resuscitation and cumulatively over four days is associated with an increased risk of mortality in septic shock.  CVP may be used to gauge fluid balance <12 hours into septic shock but becomes an unreliable indicated of fluid balance thereafter.  The study referenced a VASST study (Vasopressin in Septic Shock Trial), which noted that optimal survival occurred with a positive fluid balance of approximately 3L at 12 hours.

This study was a retrospective review of 778 patients from the VASST, all of whom were in septic shock and receiving at least 5mcg of norepinephrine per minute; they analyzed whether a positive fluid balance in the first 12 hours of resuscitation and during the next 4 days was associated with an increase in 28-day mortality. Using the Surviving Sepsis guidelines from 2008, the study grouped patients into those who fell into the recommended range (CVP = 8-12), those with CVP < 8 and those with a CVP >12 and analyzed whether a CVP of 8-12 had a survival advantage.  In this VASST, the patients at 12 hours with a CVP <8 had a lower mortality over those with CVPs of 8-12 and those with CVPs >12.  However, the study also concluded that there is a point when too little fluid is also detrimental.  It also concluded that CVP may be useful along with other measures to gauge adequacy of fluid resuscitation <12 hours into septic shock but becomes an unreliable marker of fluid balance thereafter.  Optimal survival in the VASST study occurred with a positive fluid balance of appx. 3L at 12 hours.  

Ketamine and Pain Relief

Dr. Shannon Granger                   

August 21, 2012

Estimation of the Contribution of Norketamine to Ketamine-induced Acute Pain Relief and Neurocognitive Impairment in Healthy Volunteers

Summary:          

                Ketamine is an NMDA receptor antagonist that is metabolized in the liver to an active metabolite, norketamine. The goal of this study was to assess norketamine’s role in analgesia and cognitive effects as no study to date has been performed elucidating these points. 

                12 healthy male volunteers aged 18-37 were selected and given rifampicin or placebo pretreatment to assess the effects of ketamine versus norketamine. Previous to the study, researchers showed that pretreatment with the antibiotic rifampicin caused a 10% reduction in ketamine and a 50% reduction of norketamine, thus the effect of norketamine could be deduced. It was hypothesized that norketamine contributed 20% to the ketamine induced effects such as analgesia. Subjects underwent three days of testing at three week intervals, one day 6 subjects took rifampicin and 6 took the placebo pill and received on normal saline infusion, on day 2 all 12 took the rifampicin and received an infusion of ketamine, on the third occasion all patients took the placebo pill and all received treatment with ketamine. Patients underwent a heat tolerance test in which heat pain was induced and pain was scored by the visual analogue scoring system, drug high was scored form 0-10 meaning maximal effect, and cognition was measured using a neurocognitive battery test.

                A descriptive analysis showed that ketamine produced greater analgesia, psychotropic effects and impaired cognition than did placebo. Additionally, norketamine had a negative contribution to pain intensity and appreciation when testing patients for heat sensitivity (meaning that norketamine had an opposing effect on ketamine). When norketamine levels were low, such as after rifampicin administration the VAS response was reduced and no hyperalgesia was observed. Norketamine also showed fewer effects on cognitive abilities in this study. Further studies are needed to confirm this study’s findings; however this study suggests that norketamine produces opposing effects to ketamine.

Will reducing anesthesia turn over time add a case?

Dr. Cartier

Decreases in Anesthesia-Controlled Time Cannot Permit One Additional Surgical Operation to Be Reliably Scheduled During the Workday.

Franklin Dexter, M.D., Ph.D.; Stacy Coffin, M.D.; and John H. Tinker, M.D.;Anesthesia & Analgesia, Vol. 81, pp. 1263-1268, 1995

            This study was designed in order to analyze how anesthesia controlled time (ACT) can be more effectively managed in order more efficiently treat patients, and thus optimizing the number of cases performed in a given work day.  ACT was defined as the time the patient arrived in the OR until the patient left the OR, minus the surgical case time.  709 consecutive cases were statistically analyzed, and the results showed that ACT would have to be decreased by over 100% in order to permit increasing the total number of cases by one case in a given workday.  This is a very interesting study.  It seems to indicate that at this particular facility the ACT was already fairly efficient if such a drastic improvement would be necessary in order to increase the case load by one, suggesting that perhaps other factors, such as surgical time, or check-in/nursing factors may need to be analyzed to more effectively operate more cases in one day.

Epidural Clonidine as the sole anesthetic for abdominal surgery

Dr. Waxer

A.A. Abd-Elsayed, S. Zaky

Epidural Clonidine as a sole analgesic agent during and after abdominal surgery

University of Cincinnati, Cincinnati, Anesthesiology, Cleveland Clinic, Cleveland, OH, USA

Clonidine is a well known agent that can provide analgesia with epidural anesthesia.  If this is so widely known, then why do people not use clonidine more regularly with epidural anesthesia?

In a study conducted by Dr. Abd-Elsayed and colleagues from the University of Cincinnati Academic Health Center, 40 ASA I-II patients aged 18-50 whom had elective lower abdominal surgery were studied.  Patients were randomized into receiving either epidural clonidine or epidural bupivacaine for supplemental anesthesia.  As it turns out, pain scores were found to be significantly lower in the patients who received clonidine.  With reduced postoperative nausea, vomiting and urinary retention in the clonidine group when compared with bupivacaine.  From Dr. Abd-Elsayed, “Clonidine was very effective at controlling pain and hemodynamic parameters in our patients.”

With such promising results, it certainly does beg a question; why do the majority of anesthesia providers no longer use clonidine on a regular basis for epidural anesthesia?

Perhaps this will be the beginning of a new resurgence in the use of clonidine for epidural analgesia.   

Two Glycemic Control Algorithms Compared

Dr. T. Chon

The comparison of two glycemic control algorithms for postoperative surgical patients

  

A Novel Computerized Fading Memory Algorithm for Glycemic Control in Postoperative Surgical Patients

Mayumi Horibe, MD,*† Bala G. Nair, PhD,* Gary Yurina, CRNA,† Moni B. Neradilek, MS,‡ and Irene Rozet, MD*†

Anesthesia & Analgesia June 2012

Hyperglycemia is an important predictor of morbidity and mortality, especially in critically ill patients. This study compared the use of a “Fading Memory” algorithm (FM) and an established algorithm (VA) used at their institution. The innovative FM algorithm was designed to mimic the pancreatic cell response of an initial, transient/rapid increase in insulin, then a slower increase of insulin that remains elevated for the duration of hyperglycemia. The study used Regular Insulin infusion and used target goals as 140 +/- 20mg/dl. Four comparisons were made between the two algorithms; the 1) time to reach the target glucose level and, 2) glucose level within target range during maintenance were not statistically significant; whereas the 3) the ability to maintain glucose levels with minimal variability and, 4) mean insulin dosage used in the maintenance phase was found to be statistically significant. The use of the FM algorithm is a helpful addition to the various debates/studies with glucose control. One of the strengths of this study is selecting a target glucose range that was not too low, avoiding hypoglycemia. In the future, the FM algorithm should be studied during the intraoperative setting and applied to patients with other co-morbidities such as end-stage renal disease and/or patients with greater insulin resistance, such that is seen in our county population.

TAP Blocks and Same Day Lap Choli Surgery

Jeff Halonen, DO

The Beneficial Effects of Transverse Abdominid Plane Block After Laparoscopic Cholecystectomy in Day-Case Durgery: A Randomized Clinical Trial. Premillennialism Lykke Petersen, MD et al. Anesthesiology. September 2012- Vol 115- Number 3, p 527-533.

Summary

Patients generally have moderate pain in the early postoperative period following. There have been RCT's that suggest the use of transversal abdominis block following abdominal surgeries for analgesia. The purpose of this trial was to see of this TAP block could decrease the pain with rest and coughing, decrease opioid use and side effects after laparoscopic cholecystectomies in day-case surgery.

This trial put patients into one of two categories. One received bilateral TAP block with Ropivicaine while the other received a placebo block. Their goal was then to see if there was a difference in the above measures.

What was found was that there was a difference in the pain scores when coughing and total opioid consumption. These differences were thought to only be a small difference however.