Anesthesia Management
During INDEX-STAR and sabsequent abdominal Entries
Recommendations
The anesthetic care of patients with an open abdomen consists of three phases:
- Pre-op evaluation and transport from ICU to the operating room
- Intra-operative care
- 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 considered:
- Physical and recent lab results
- information about recent intra-abdominal pressure measurements,
- ventilator management and
- recent urine output.
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 well-functioning. If not, consider replacement 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
Good muscle relaxation as well as use of a peep valve on the ambu bag will improve hand ventilation/oxygenation
Negative Pressure Control
The abdominal dressing drain should be maintained on suction to avoid contamination and fluid leaks.
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
IC sedatives or inhalation anesthetics work fine. Maintaining complete paralysis 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 does not need to be replaced.
Once the surgeon opens the abdomen the venous reservoir will increase and 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 ?because 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 vasopressin 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 IAP and thus the airway pressures will decrease over the next day. If the patient has not begun to improve, keep airway pressures low because they may increase when IAP increases and cause 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.
Tranport 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 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.