Anesthesia Management

The anesthetic care of patients with an open abdomen consists of three phases:

  1. Pre-op evaluation and transport from ICU to the operating room
  2. Intra-operative care
  3. Transport back to the intensive care unit

Pre-anesthetic evaluation for and transport to operating room

Pre-op Evaluation

These patients are usually ASA class 4 based on their acute or resolving intra-abdominal processes along with underlying chronic or acute respiratory, cardiac and other systemic problems.  In addition to the usual history the following information should be requested:

Peek airway pressures and gas exchange information is important as it will guide the eventual “tightening” of the abdomen at the end of the procedure.

Access

 An arterial line should be present and well-functioning. If not, a replacement may be considered prior to moving to the operating room.

Large bore central access for CVP measurement as well as volume replacement and inotropic support should be in place unless the patient has been hemodynamically stable for several days.

Transport

Intra-operative care

Ventilator

Often the present IAP may only allow low VTs (4-5cc/kg) to avoid high peek airway pressures.  If the patient’s lungs are already significantly injured, frequent ABGs may be appropriate to help optimize ventilator settings.

Anesthesia maintenance

ICU sedatives or inhalation anesthetics work fine.  Complete paralysis should be maintained as this will help surgical exposure and facilitate the best possible fascial reapproximation.

Fluid management can be limited to maintenance requirements plus insensible losses (6-10cc/kg/hr).  Removed ascites do not need to be replaced.

Once the surgeon opens the abdomen the venous reservoir will increase afterload will decrease.  Significant hypotension may ensue.  This should be treated with a combination of liberal fluid administration and judicious vasopressor therapy as dictated by arterial systolic pressure variation (or CVP) and the patient’s cardiac, pulmonary and renal status.

Drugs

While muscle relaxant choice should be determined by renal and hepatic function, the choice is less critical because the patients will remain intubated and relaxed for some time.  Alpha agonists as well as intropic drugs should be available.

Vasopressin may be necessary to maintain pressures as these patient’s vasopressin stores may have been depleted over days of sympathetic stimulation.  In the face of suboptimal vascular response of alpha/beta agonists, 2-6 units vasopressing IV push or a low dose drip may be indicated.

Closure of the Abdomen

At the conclusion of the procedure the surgeon will close the abdomen with the intent of keeping the intra-abdominal pressure somewhat elevated. Bladder pressure measurements can aid in determining the ideal fascial approximation levels.  The anesthesiologist can supplement bladder pressure information by monitoring the peek airway pressures. Some amount of increased intra-abdominal pressure is desirable, but high peek airway pressures should be avoided.

When considering appropriate airway pressures one must take into account whether the patient is over all improving or expected to remain critically ill for the next 24 hours.  In patients expected to improve, higher airway pressures can be accepted as the IAPwand thus the airway pressures will decrease over the next day.  If the patient has not begun to improve, lower airway pressures are indicated because they may increase with worsening IAP and lung injury.

One other indicator for a “too tight” closure is the new or increased need of vasoactive drugs.  Decreasing IAP by loosening the fascia closure should be discussed with the surgeon.  Here, again, management depends on the expect course over the next 24 hours.  A little increased vasopressor support may be acceptable if the expectation is that the patient will improve and the IAP is expected to decrease.

Transport to ICU

During transport to the ICU a “peep” adapter for the ambu bag may be needed again. Care should be taken to either continue suction on the abdominal dressing drain or to clamp the drain so the vacuum is not lost and the wound contaminated.

Once in the ICU the abdominal drain needs to be attached to wall suction as soon as possible to prevent the loosening of the adhesive dressing from fluid seepage.