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.

Does covering a child on induction impact body temp? Dr. Trivedi

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

Does the covering of children during induction of anesthesia have an effect on body temperature at the end of surgery?

Due to anesthesia induced impairment of thermoregulation as well as the cold environment of the operating room, surgical patients are prone to disturbances of his/her body temperature. Hypothermia under anesthesia follows a characteristic pattern of a large drop in core temperature due to core to peripheral heat redistribution. This is followed by a slow linear regression as more body heat is lost than generated. A plateau ensues as a thermal steady state is reached. A benefit of hypothermia has been exploited in the care of patients who have suffered a catastrophic myocardial and traumatic brain injury. Complications of hypothermia are more devastating and include coagulopathy secondary to cold induced platelet dysfunction, delayed wound healing, myocardial infarction, hypermetabolism secondary to shivering, a catecholamine surge resulting in tachycardia and hypertension due to discomfort and longer recovery time. 

Neonatal and pediatric patients are especially vulnerable in developing hypothermia due to an immature thermoregulatory system and greater heat loss due to an increased surface area to body weight ratio.  Shukry et al from the Children’s Hospital of Oklahoma City investigated the effect of covering children during induction of anesthesia and end of surgery core body temperatures, measured at the temporal artery and rectally. 50 healthy (ASA 1 or 2) children ranging from the age of 6 months to 3.5 years undergoing simple urologic procedures were selected. The majority of urological patients received caudal blocks which the author estimates can take anywhere from 10-20 minutes. They were either covered with a blanket during induction or remained uncovered, but both groups were re warmed using a forced air blanket at 43 degrees after the blue drapes were placed. Shukry et al found no change in core temperature at the end of the surgical procedure between patients covered with a blanket during anesthesia induction and those that were not. Limitations include small sample size and a higher than normal ambient operating room temperature which has a greater influence on the patient’s body temperature.

                 

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.

Is NPO after Midnight Archaic? Dr. Trivedi

Puja Trivedi, DO

Time to Abolish “NPO After Midnight” by Mark Singleton MD

Dr. Singleton highlights an archaic term, "NPO after midnight," which
was coined with patient safety at heart but in the modern day context
can actually harm our patients. In the past, patients were asked not
to eat or drink anything after midnight to ensure an empty stomach.
However. this led to both binge eating at 11:45pm (which may lead to a
bloated, uncomfortable, sleep deprived patient the morning of surgery)
or conversely, starvation due to case delays or cancellations. As
surgical care transitions from a solely in patient practice where all
surgical patients had been admitted in the past to more of an emphasis
on outpatient, ambulatory surgical centers, patients are scheduled and
asked to arrive at specifc times. For example, a patient scheduled for
an elective procedure at 3pm should be allowed to eat a light
breakfast. Unfortunately this is only one part of the battle. The
notion of NPO after midnight is often echoed by surgical team members,
pre op nursing and hospital staff. It is for this reason that Dr.
Singleton advocates the concept of having an anesthesiologist contact
the patient the night before to answer and address the issue of "NPO."