Be Vigilant During Placement of the Camera in Laparoscopic Procedures and Always Watch Carefully for the Physiologic Effects of Carbon Dioxide (CO2) Insufflation
Jennifer A. DeCou MD
Randal O. Dull MD, PhD
Laparoscopic surgery presents challenging issues for the anesthesiologist. It is one of the few procedures in which the surgical “incision” has resulted in life-threatening events. It is also in the category of surgical procedures (much like the methylmethacrylate cases in orthopedic surgery) in which the surgeons administer a substance with wide-ranging physiologic sequelae.
The first task for the anesthesiologist is to ascertain by query or observation the planned technique for initial entry into the abdomen. Surgical practice has tended to evolve away from the Veress needle technique, which involves picking up the skin on either side of the umbilicus and using a “blind” technique to first pass a needle followed by a trochar. This technique has resulted in the uncommon but devastating complications of aorta and bowel injury. Much more common today is the Hassan cannula technique, which involves a microlaparotomy and placement of the initial intra-abdominal instrument (which is blunt-tipped) under direct observation. Subsequent trochars are then placed under camera visualization after insufflation.
Try to observe the placement of the trochars personally. It is not necessarily true that several attempts to place trochars and/or failure to initially insufflate to a proper pressure means trouble, especially with the Hassan technique. The trochars have a “cocking” mechanism that allows the sharp point to protrude out of the sheath, and this may need to be reset if activated when the surgeon attempts to place the trochar through the layers of the abdominal wall. Also, there may be leakage around the Hassan cannula, and the surgeon may ask for Xeroform to wrap around the cannula to get a seal. In general, however, placement of the trochars should go fairly smoothly without an excessive number of attempts.
Of course, it is the insufflation of the abdomen or pelvis with gas (usually CO2) to improve visualization of the surgical field that results in the physiologic changes that are of interest to us. The high solubility of CO2 allows rapid diffusion into the blood compartment and causes predictable changes in blood gas chemistries and hypercapnia. It must be remembered at all times
that the physiologic effects of insufflation and the resulting hypercapnia are multisystemic and quite complex.
that the physiologic effects of insufflation and the resulting hypercapnia are multisystemic and quite complex.
CARDIOVASCULAR EFFECTS
The potential cardiovascular effects are the ones most pronounced at the time of and just after insufflation. They require that a range of resuscitative drugs be available. Hypercarbia and the associated acidosis cause direct cardiac depression and peripheral vasodilatation, which can lead to hypotension. However, hypercarbia also promotes a strong sympathetic reflex and increases in plasma catecholamine levels may offset this depressant activity. The result is a hyperkinetic circulation with hypercarbia causing a tachycardia, increased cardiac output, increased contractility, and increased systemic blood pressure. These changes may increase myocardial O2 demand, and patients with known or suspected coronary artery disease will require appropriate interventions. In addition, arrhythmias are a commonly encountered problem during laparoscopic procedures. Hypercarbia, acidosis, and the associated increase in catecholamines may sensitize the myocardium and induce a variety of arrhythmias. Vagally mediated reflexes caused by insufflation can induce a variety of bradyarrhythmias, including asystole. Lastly, increases in intra-abdominal pressure can inhibit venous return, resulting in decreased cardiac output and hypotension; adjustments to intravascular volume may be required to normalize venous return and maintain cardiac output.
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