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.”

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.

Risk index for A-Fib after cardiac surgery, Dr. Trivedi

Puja Trivedi, DO

PGY-3 Resident at RCRMC who will do a Cardiac Anesthesia Fellowship at USC upon graduation

Article Review

A multicenter risk index for atrial fibrillation after cardiac surgery. Mathew JP, Fontes ML, Tudor IC, Ramsay J, Duke P, Mazer CD, Barash PG, Hsu PH, Mangano DT; Investigators of the Ischemia Research and Education Foundation; Multicenter Study of Perioperative Ischemia Research Group. JAMA. 2004 Apr 14;291(14):1720-9.

AFIB is the most common sustained rhythm disturbance, affecting 2.3 million people in the United States and is the  most common complication after cardiac surgery is AF (20-60%). Matthew et al set out to develop a comprehensive risk index that can better identify patients at risk for atrial fibrillation undergoing CABG. This was a prospective, observational study which included 5,436 patients from 70 hospitals, spanning 17 countries; the largest study to this date. Patient inclusion criteria included all patients 18 years and over scheduled for a CABG +/- valve repair using cardiopulmonary bypass between 11/1996-6/2000.

The study found that preoperatively advanced age, history of atrial fibrillation and COPD had the highest correlation to post operative development of atrial fibrillation. Intraoperatively, valve surgery with its inherent disruption of cardiac anatomy proved to have the highest post operative arrythrogenic implications. Post operatively, electrolyte disturbances and delays in resuming beta blockers and ace inhibitors showed the highest correlation in the development of atrial fibrillation.

The extent of extra medical intervention and increased hospital days mandates more aggressive therapies aimed at prevention of post operative atrial fibrillation.

Epidural vs General for aortic surgery, Dr. Cartier

Cameron Cartier, DO

Journal of Cardiothoracic Anesthesia, Feb 2004

“Combined epidural and general anesthesia”

            Are epidurals associated with better patient outcome for infrarenal abdominal aortic surgery?  This particular study was a randomized, prospective study to test that hypothesis.  This study was carried out at New York Medical College, and randomly selected patients undergoing infrarenal abdominal aortic surgery into two groups: the first group received a combination of an epidural with “light” general anesthesia, and the second group received general anesthesia alone.  Great care was taken to monitor the hemodynamic status intra-operatively in both groups, as well as monitoring closely how patients did post-operatively.  After the cross-clamping of the aorta, the cardiac index and pulmonary capillary wedge pressures did not change significantly in the group that received the epidural, whereas the patients who received general anesthesia alone had a significant drop in cardiac index as well as an increase in pulmonary capillary wedge pressure.  Post-operatively, the patients who received the epidural demonstrated less incidence of ventilatory dependent respiratory failure, less vasodilatory requirements, and shorter stays in the ICU.  Based on these findings, this article recommends the use of combined epidural/general anesthesia for patients undergoing this particular surgery.  Possible limitations of this study are that this study was only performed in one hospital, which leads to a relatively small patient population