Observational Study of Sublingual Microcirculatory Blood Flow Characteristics in Patients Undergoing Transthoracic Esophagectomy

1. Provide the scientific background, rationale and relevance of this project. The
microcirculation plays a fundamental role in gas and nutrient exchange; it must constantly
adapt by controlling vascular tone and regional blood flow. In disease states, increased
permeability may be necessary to produce the inflammatory response. The assessment and
quantification of the macrovascular hemodynamics and the assumption that it is reflective of
microvascular change is fundamentally flawed. Even when global hemodynamic variables are
corrected, many patients with circulatory failure will develop multi organ failure and
ultimately die. The recent advent of in vivo microcirculation monitoring has begun to
improve our understanding of the relationships between surgery, anesthetic management, and
regulation of the microcirculation.

Microcirculatory alteration also occurs in patients undergoing cardiac surgery. Bauer et al
first reported that microcirculatory perfusion was transiently altered in humans after
cardiopulmonary bypass. Similar findings were reported more recently by other groups. , More
importantly, these alterations can also be observed in patients who undergo surgery without
cardiopulmonary bypass.3 Furthermore the sublingual microcirculation was still slightly
abnormal up to 24 h after surgery in these patients. As in non-cardiac surgery, the severity
of perioperative microvascular alterations correlated with peak lactate levels and severity
of organ dysfunction after surgery.iii High-risk surgery is a new area in which in vivo
microcirculatory alterations have been observed. In patients undergoing high-risk
non-cardiac surgery, Jhanji et al observed that the density and proportion of perfused
capillaries was lower in the 14 patients who subsequently developed postoperative
complications than in the 11 patients with an uneventful postoperative course. Subcutaneous
tissue PO2 and laser Doppler cutaneous blood flow did not differ between the groups, further
highlighting the lack of sensitivity of these methods to detect heterogeneous perfusion.
Interestingly, there was no significant difference in global O2 delivery between the groups.

Non-cardiac thoracic surgeries comprise a subgroup of high risk surgical procedures which
have the potential to significantly affect and impair microcirculatory function. A study of
patients undergoing esophagectomy demonstrated significant impairment of sublingual
microcirculation relative to pancreaticoduodenectomy patients. Esophagectomy surgery
produces a profound systemic inflammatory response which correlates to a number of adverse
outcomes. Interestingly, the time course of microcirculatory impairment and recovery appears
to parallel the SIRS typically seen in surgeries of this type. Transthoracic esophagectomy
is typically facilitated by one lung ventilation (OLV) in an effort to optimize surgical
exposure to the operative hemithorax. The institution of OLV has the potential to
dramatically impair tissue oxygen supply demand relationships via adverse effects on
systemic oxygen desaturation, as a result of an increased venous admixture from right to
left intrapulmonary shunting, as well as decrements in cardiac output. Cerebral oxygen
desaturation accompanying OLV is also well described, though the pathophysiology is not well
understood. It is likely, though unproven, that microcirculatory derangements may underly
these phenomena. Though the study of microcirculatory dysfunction in thoracic surgery is in
its infancy, the body of available evidence at this point supports the following hypotheses;
that microcirculatory derangements and dysfunction 1) occur during major surgeries including
transthoracic esophagectomy 2) may be related to SIRS, OLV or both, 3) may predict adverse
outcomes, and 4) may be amenable to modification via specific therapies.

This is a feasibility study to see if the changes in microcirculatory parameters as observed
by the SDF device can accurately diagnose anastomotic and other complications for the
purpose of leading to a wider study of microcirculatory derangements as an indicator of risk
of surgical complications.

Hypothesis to be Tested:

i. Microcirculatory derangements, as indicated by changes in microcirculation of sublingual
tissue, serosa tunica near the surgical division, or the mucosal lining of the stomach near
the surgical division, occur during transthoracic esophagectomy and in the perioperative
period.

ii. Changes in microcirculation predicts post-operative anastomotic complications iii.
Changes in microcirculation predicts post-operative complications

Specific Aims

1. Determine whether microcirculatory derangements, as indicated by changes in
microcirculation of sublingual tissue, serosa tunica near the surgical division, or the
mucosal lining of the stomach near the surgical division, occur during transthoracic
esophagectomy involving one lung ventilation (OLV), using a side stream dark field
(SDF) imaging system.

1.1. This aim will include measurements of microcirculatory parameters at multiple time
points within the perioperative period.

2. Determine the temporal relationship of microcirculatory dysfunction and recovery, if
any, at the initiation of OLV, reestablishment of two lung ventilation, and cessation
of surgery.

2.1. This aim will include measurements of microcirculatory parameters at multiple time
points within the perioperative period.

3. Determine whether observed changes in microcirculation is predictive of postoperative
organ dysfunction, and perioperative complications.

Inclusion Criteria:

1. Age 18 through 75 years

2. Subjects are undergoing transthoracic esophagectomy utilizing thoracotomy or
thoracoscopy incisions as part of their clinical care. These surgeries include
primarily the Ivor Lewis, and three hole (McKeown) esophagectomy procedures and
variants thereof.

3. A patent arterial line

4. A patent IV line

5. Must be able to read and speak English

6. Subjects may have current diagnosis of cancer that requires esophagectomy as part of
their clinical care.

Exclusion Criteria:

1. Subjects unable/unwilling to give informed consent.

2. Cognitively Impaired

3. Prisoners

4. Pregnant females