Kentucky Society of Anesthesiologists

Highlights From The Annual Spring Meeting 2009
Masroor Alam, MD, MPH

Problems with Guidelines:

“Evidence based best practices not only target improved outcome but are also geared towards enhancing the process in delivery of medical care," said Dr. John H. Eichhorn, Professor of Anesthesiology at the University of Kentucky (UK).  The title of his talk at the Annual Spring Meeting of Kentucky Society of Anesthesiologists held in Covington, Kentucky at the Marriot River Center was “Problems with Guidelines.”

According to Eichorn (2009) guidelines are a natural offshoot of evidence based medicine (EBM).  The scope of medical knowledge is expanding and the practice is increasingly complex.   Therefore, it may be valid to use guidelines based on EBM to help direct physician's efforts and improve outcome.  Guidelines appear to have a positive impact on quality and safety of care.  Anesthesiology as a specialty has been on the forefront of this effort, starting with the introduction of monitoring standards.

Pronovost has recently received a great deal of recognition for his study demonstrating the impact of guidelines on reduction of CVP line infections.  The cost of vascular catheter infections is estimated at 3 billion dollars annually.  Understanding the recommended guidelines is important for the practitioner because of their implications on clinical practice, in addition to the possible financial consequences.  “Success of guidelines in huge reduction of central line infection guarantees promulgation of guidelines for other no payment complications,” said Dr. Eichhorn.  Hospitals facing a loss of revenue from complications like central line infection will make guidelines mandatory policies to minimize their losses. Hospitals can potentially reduce subsidies to anesthesia groups if CVP infection or other no-pay complications are traced to anesthesia care in OR by the  anesthesia provider Financial pressures on physicians,  including anesthesiologists, to adopt, embrace,  and even write practice guidelines could be substantial (Eichorn, 2009).

The rationale for evidence based best practices is not only to improve outcome but also improve the process in medical care.  The purpose of the guidelines is to deliver goal directed care which by definition is more efficient and economical.

Dr.Eichhorn posed the question, "Are guidelines equivalent to standards of care?"  The answer, he mentioned, is more complicated.  Published guidelines do not necessarily prescribe the standard of care.  However, plaintiff malpractice lawyers want the jury to believe that guidelines are the same as standard of care, and if you stray from following guidelines are prepared to field a barrage of questions from the lawyers.  In the end, Dr. Eichhorn proposed that standard of care is what a jury says it is on any given day.  At the same time, there is no reason to be intimidated by the guidelines, but it is crucial to be aware of what the guidelines are. Coming back to the example of central line sepsis, not following the guidelines and having a complication will be extremely difficult to defend in present day and age.

In anesthesiology, ASA is the main source of guidelines in anesthesia practice.  ASA standards and guidelines can be found on their site or checking the following link:

http://www.asahq.org/publicationsAndServices/sgstoc.htm

ASA practice parameters can be checked at:

http://www.asahq.org/publicationsAndServices/practiceparam.htm#top

ASA practice parameters/advisories are special evidence-based guidelines that carry significant weight.  It is worthwhile to review these guidelines and parameters at the ASA website.

JCAHO guidelines:

JCAHO is another important source of guidelines. One of the JCAHO guidelines affecting anesthesia practice include timings of pre-op antibiotics, pre-incision “time out” and central line infection prevention. Basically the same idea is used for the Surgical Care Improvement Project (SCIP) which is used to determine “pay for performance”.

Checklist as guideline:

Currently, a more structured guideline recommendation is the formal checklist, an actual form having a check-off list.  There is a push to enforce such checklists as they are “forcing functions” in specific circumstances.

WHO has an international “Safe Surgery” initiative, which essentially is a preoperative checklist geared mostly towards less sophisticated operating sites. However there are points that are relevant to operating rooms anywhere.

Hospitals may create and impose ‘standardized order sets’ which are guidelines essentially serving a ‘forcing function’.  There is a potential that hospitals may come up with anesthetic medication guidelines to curtail costs, limiting the number of medications available to anesthesia providers (Eichorn, 2009).

In conclusion Dr. Eichhorn said that guidelines are a fact of life to practice medicine in our present day and age.  With time, they will increase in number, scope and complexity.  It is important to get familiar with the guidelines, get involved and try to abide by them.  If an imposed guideline does not seem to result in any clinical benefit, we can, by our involvement, reshape the guidelines, making changes at the local or the source of origin level.

Neuromuscular Blockade:

Dr. Cynthia Lien, Professor of Anesthesiology, Weill Cornell Medical College, New York,  talked about neuromuscular blockade and how to antagonize their effects.  She pointed to the fact, demonstrated by several studies that it may take two times ED 95 to 90% recovery from the effects of the neuromuscular blockers.  She emphasized the importance of nerve stimulator and quantitative monitoring in gauging the extent of the neuromuscular blockade.  For monitoring she felt that double burst suppression may provide better visualization when compared with TO4.  When using orbicularis oculi for neuromuscular block monitoring Dr. Lien emphasized that studies measuring the effect of reversal were done on adductor pollicis and when using orbicularis oculi for monitoring we may be overdosing our patients.

Residual neuromuscular blockade is a risk factor for post operative complications especially in patients having abdominal surgery, patients with advanced age or patients having surgery of long duration.

Perioperative Outcome:

Dr. Ozan Akca, Associate Professor of Anesthesiology & Perioperative Medicine at the University of Louisville talked about the role of anesthesiologists in better perioperative surgical outcome.

Smoking:

Smokers have 2-3 times higher risk of perioperative pulmonary complications.   It is best to stop smoking six weeks prior to surgical procedure to reduce the risk of respiratory complications and wound infection post operatively. Even abstinence for as little as 24 hours can significantly reduce carboxyhemoglobin levels.

Obesity:

A BMI of 30 or more increases the risk of surgical wound infection from 8 to 16%.

Hospital acquired infections:

Prophylaxis with a single dose of antibiotics is usually adequate for most procedures.  Timing of the antibiotics is critical.   Most of the recommended preoperative antibiotics should be administered within thirty minutes of incision.

Lower incidence in hospital infection is seen when there are no trainees, little turnover of surgeons or nurses, no traveling nurses and few breaks during surgery.

Cancer Patients:

There is mounting evidence that the type of anesthetic may have an effect on metastasis of cancer especially as it pertains to breast and prostate cancer surgery.  Natural killer cells constitute a major defense against cancer cells.  In animal studies, opioids are shown to be immunosuppressant.  Regional anesthesia can possibly offer some protection by reducing the stress response.  Para vertebral blocks in breast surgery and epidural blocks in prostate surgery can possibly provide protection against recurrence in these cancer surgeries.  However most of this data so far has come either from animal or retrospective studies and needs to be validated by prospective studies.

Pain management:

Effective pain management improves surgical outcomes. It can possibly improve tissue oxygenation.

Temperature Control:

Hypothermic patients have an increased risk of wound infection.  At temperatures less than 34.7°C the risk of surgical infections is 3 times greater. Meta analysis demonstrates 20% more blood loss per degree centigrade reduction in temperature.

Pulmonary Hypertension:

Dr. Charles Campbell, Assistant Professor of Medicine, Program Director Cardiovascular Diseases at UK, discussed the pathophysiology of pulmonary hypertension and right heart failure and its anesthetic implications.   Intimal thickening in the pulmonary artery results in low flow, high resistance vessel which leads to severe cardiac dysfunction.  It is the right heart failure which is responsible for major morbidity and mortality in these patients.

Mean pulmonary artery pressure of greater than 25mmHg or greater than 30mmHg after exercise is by definition pulmonary hypertension. It is best diagnosed by right heart catheterization.

Medical treatment includes the use of:

1. Digoxin, diuretics, anti-coagulants and calcium channel blockers
2. Prostacyclin analogues
3. Sidenafil

These medications are used individually or in combination.  Optimal combination therapy is not known.

Management:

When managing these patients, think of aortic stenosis and employ similar treatment strategies:

1. Maintain preload
2. Maintain SVR
3. Maintain contractility
4. Avoid ischemia

The following can be employed to avoid an increase in the pulmonary vascular resistance:

1. Avoid hypoxemia
2. Avoid hypercarbia
3. Use moderate tidal volumes
4. Utilize low levels of PEEP

Pulmonary vasodilators include:

1. Nitric oxide used in concentration of 20 ppm. When discontinuing the medication beware of rebound pulmonary hypertension.
2. Milrinone 0.5 to 0.75ug/kg/min
3. Dipyridamole 0.2 to 0.6ug/kg/min
4. Inhaled or IV Prostacyclin 4 to 10ug/kg/min

Cardiac Diseases in Pregnancy:

Dr. Jobi Balatbat, Assistant Professor of Anesthesiology at the University of Louisville talked about cardiac diseases during pregnancy. The incidence of cardiac disease during pregnancy is 1% to 3% but it is responsible for 10% to 15% maternal mortality.

Peripartum Cardiomyopathy: This disease is responsible for as much as 25% to 50% maternal mortality.  Diagnosis is based on an absence of cardiac disease prior to pregnancy and no determinable cause.  Forty percent increase in cardiac output and stroke volume coupled with increased coagulopathy makes these patients more vulnerable to complications.  Most of these problems are seen during the last month of pregnancy up to five months post partum.  Left ventricular ejection fraction normalizes within six months of delivery.  However these patients will experience about 10% reduction in LVEF during subsequent pregnancies.

Congenital Heart Disease: Because of improved health care, patients with congenital heart disease have a much better life expectancy.  Now that more of these patients are getting pregnant, taking care of them brings in a unique set of challenges.

Right to left shunts: Right to left shunts get worse with reduction in SVR.  Management involves avoiding reduction in afterload, and exercising caution when using regional anesthesia.  Phenylephrine is a good agent to maintain SVR in these patients.

Left to right shunts: Left to right shunts is tolerated much better during pregnancy. Regional anesthesia may actually be beneficial as it will reduce the SVR. An increase in PVR can cause reversal of shunt.

Prosthetic Valves: Mechanical valves create an increased risk of thrombosis during pregnancy.   Anticoagulation use should be continued throughout pregnancy.  Because of risk of teratogenicity, Coumadin is avoided during that period and substituted with heparin.  Even with heparin on board there is an increased risk of valve thrombosis.   Low molecular weight heparin has shown some promise, however data at present time is insufficient.

Perioperative Risk Assessment and Reduction:

Dr. Andrew Friedrich from the Dept. of Anesthesiology at the University of Cincinnati shared his experience of perioperative assessment from his institution.  These assessment strategies have helped reduce the perioperative risk in their surgical patients and led to a significant reduction in cancellations on the day of surgery and an overall increase in the satisfaction among all stake holders.  According to Dr. Friedrich, the following processes are effective:

1. Creating a pre operative system
2. Using standardized diagnostic and therapeutic pathways
3. Developing relationships with surgeons, primary care physicians, specialists and their staff
4. Starting the process as soon as a case is booked so that there is time available to coordinate care
5. Not relying simply on routine labs, tests and “medical clearance” alone but looking at the functional status of the patient. A bigger predictor is the ASA physical status and the invasiveness of the surgical procedure.  As perioperative physicians we need to be familiar with the guidelines recommended by specialty societies, like American College of Cardiology, so we can ask relevant questions from the consultants.  Tests such as resting EKG have low sensitivity in asymptomatic patients.  If there is a clinical suspicion of coronary artery disease stress testing has a higher yield.
6. Communicating with everyone involved so that they know what is happening with the patient and there are no last minute surprises.

Lung Management in ICU:

Dr. Kevin Hatton, Assistant Professor, Dept. of Anesthesiology also from University of Kentucky talked about lung diseases and their ventilator management.

Acute respiratory distress syndrome (ARDS) occurs in two phases but is essentially a continuum of the same disease process:

Acute exudative phase:

1. Associated with diffuse alveolar damage
2. Protein-rich edema formation in alveolus and interstitium
3. Severe hypoxemia and reduced lung compliance

Chronic fibroproliferative phase:

1. Rapid proliferation of fibroblast and type II pneumocytes
2. Collagen deposition and hyaline membrane formation
3. Destruction of pulmonary vasculature

According to Hatton (2009) inciting events for ARDS could be direct or indirect injuries.  Causes of direct injury could include pulmonary infection, aspiration, oxygen toxicity, lung contusion, toxic gas inhalation or near drowning.  Indirect injuries could be triggered by sepsis, severe nonthoracic trauma, transfusion related acute lung injury, cardiopulmonary bypass, pancreatitis , burn injury or shock.  These inciting events induce various local humoral and cellular inflammatory mediators and result in an imbalance

Cytokine imbalance and neutrophil/macrophage activation leads to damage of the alveolar capillary membrane.  Leakage of proteinacaeous fluid across this membrane eventually results in intrapulmonary shunt and severe hypoxemia.   Damage to the alveolar capillary membrane is not homogenous.  Damaged areas are commonly adjacent to normal zones. This is important to remember as there is a potential for secondary damage to unaffected alveoli during ventilation.

Clinical consequences of ARDS/ ALI include massive heterogeneous pulmonary edema resulting in enormous intrapulmonary shunt, severe hypoxemia, reduced lung compliance and increased work of breathing.  Ventilation flows to compliant alveoli.  The consequences could be over distention of the compliant alveoli and under filling of the low compliance alveoli.   This tends to happen during both positive and negative pressure ventilation (Hatton, 2009).

Treatment:

The treatment for ARDS/ALI is entirely supportive.  None of the therapies to date have been shown to improve the inflammatory response even though high dose steroids and cytokine specific antagonists have been used.  Surfactant therapy has not been shown to improve survival.

Mechanical ventilation is the mainstay of respiratory support in severe ARDS/ALI with two main strategies of lung protective tidal volume and open lung ventilation.

When it comes to ventilator associated lung injury, the following four mechanisms may be involved:

• Volutrauma:  Lung injury caused by alveolar over distention most commonly due to high tidal volumes.
• Barotrauma:  Lung injury caused by rupture of air filled spaces.
• Atelectrauma:  Lung injury caused by cyclical collapse of alveoli followed by re-expansion of previously closed alveoli
• Biotrauma:  Injury resulting from intrapulmonary release of cytokines in response to mechanical ventilation (Hatton, 2009).

ARDSnet was founded in 1994 by the NHLBI and NIH with the goal to “efficiently test promising agents, devices or management strategies to improve the care of patients with ARDS."  To that effect it has sponsored several ARDS based trials.  ARMA was one of such trials comparing ‘lung protection strategy’ against ‘control’ ventilation strategy. Previous animal studies showed that lungs ventilated with ‘normal’ tidal volume ventilation showed more volutrauma on histological examination.  In clinical trials patients were randomized to one of the two groups of ventilator management, a low tidal volume and a control group within 36 hours of development of ARDS.  In the low tidal volume group initial tidal volumes used were 6ml/kg with a target plateau pressure of 25-30 cm of water. In the control group the initial tidal volume used was 12/kg with a target plateau pressure of 45-50 cm of water. The trial was stopped because of statistical difference between the two groups.  Patients assigned to the low tidal volume “lung protective” group did much better (Hatton, 2009).

Hatton (2009) further emphasized that control of secondary lung injury improves outcomes.  Can outcome be further improved by reducing atelectrauma? The answer may lie in open lung ventilation. This type of ventilation strategy has two main goals:

1. Open (recruit) collapsed alveoli
2. Prevent closure of alveoli

Recruitment of alveoli improves compliance, oxygenation and work of breathing.  The idea is to titrate the amount of PEEP (PEEPflex) these ARDS patients are getting based on lung compliance.  Open lung ventilation appears to improve outcome in ARDS patients, however, in studies, many of these patients received low tidal volume ventilation as well.   Therefore,  it is hard to discern that the benefit was not just because of lower tidal volumes (Hatton, 2009).

In conclusion Dr. Hatton emphasized that while managing these patients the goal is to think about the long term consequences of our management strategies because any damage averted early in the disease process has in an impact on the entire course of the disease process.

Use of Ultrasound in Anesthesia Practice

Drs. Anupama Wadhwa, Kevin Hatton and Kit Montgomery from Dept. of Anesthesiology at UK and University of Louisville conducted a workshop on the use of ultrasound in anesthesia practice.  A link to Dr. Wadhwa’s presentation is available here. Please allow several minutes for download.

References:
Eichhorn, J. H.  (2009).  Problems with guidelines.  Handout at the Kentucky Society of Anesthesiologists spring meeting 2009.
Hatton, K.  (2009).  Mechanical ventilation.  Handout at the Kentucky Society of Anesthesiologists spring meeting 2009.