The Advantages and Problems in Laparoscopic Surgery
An abdominal pressure of up to 12 mmHg has proven to be adequate for most surgical procedures, minimizing adverse effects. With this pressure, in young patients and without comorbidity, the retention of CO 2 is minimal. Significant hemodynamic changes have been observed when intra-abdominal pressure rises above 12 mmHg. Thus, in a prospective observational study the following hemodynamic changes were observed: decreased ejection volume, decreased cardiac output, as well as an increase in systemic vascular resistance. Simulations of laparoscopy is significant choice with Laparoscopic Needle Driver.
A Cochrane review evaluated the benefits and harms of low pneumoperitoneum pressure compared to standard pressure in patients undergoing laparoscopic cholecystectomy. No significant differences were found in terms of mortality, pulmonary complications, postoperative complications or conversion to open cholecystectomy. Due to study biases in some trials in the review and since only patients undergoing cholecystectomy were studied, the safety of using low intra-abdominal pressures is still uncertain.
In laparoscopic surgery, general anesthesia is the method of choice, since it allows the anesthesiologist to precisely control ventilation and modify the ventilatory parameters, based on the alterations that may occur. It has some advantages, such as adequate control of respiration, optimal protection of the airway, excellent muscle relaxation, monitoring of carbon dioxide at the end of expiration with the capnograph among others.
Some complications with the general anesthesia method, as well as some individual characteristics of the patient, make it possible to use regional anesthesia for certain cases. In patients with anesthetic risk, not only will pulse oximetry, capnography, cardioscopy and blood pressure be necessary, but also invasive monitoring is required to have an adequate control of physiological variations or complications.
Hemodynamic changes
The hemodynamic changes observed during laparoscopic surgery will be determined by the changes in position to which the patients are subjected and by the mechanical effect exerted by the compression of CO 2 within the peritoneal cavity. During anesthetic induction, the filling pressures of the left ventricle decrease, in turn causing a decrease in the cardiac index, keeping the mean arterial pressure the same.
These changes are probably due to the depressant action of the inducing drugs, as well as the decrease in venous return due to the position of the patient. At the start of insufflation of the peritoneum with CO2, there will be an increase in arterial pressure, both systemic and pulmonary, which causes a decrease in the heart rate, keeping the mean arterial pressure the same. Enlargement of the peritoneum causes the release of catecholamines that activate a vasoconstrictor response.
There is elevation of blood filling pressures during pneumoperitoneum, because the increase in intra-abdominal pressure will cause a redistribution of the blood content of the abdominal viscera towards the venous system, favoring an increase in filling pressures. A decrease in femoral venous flow has also been observed when intra-abdominal pressure increases due to hyperinflation. As a consequence, there is a decrease in venous return and a fall in cardiac preload. In summary Other studies have shown that during inflation of the pneumoperitoneum there will be an increase in cardiac work and myocardial oxygen consumption.
Respiratory Instabilities
CO2 insufflation into the abdominal cavity and increased intra-abdominal pressure caused by pneumoperitoneum are factors that particularly influence lung function. It has been shown that during laparoscopy there is a decrease in lung compliance, respiratory reserve volume and functional residual capacity, with an increase in inspiratory peak pressure. As a consequence, there is a redistribution of flow to poorly prefused areas during mechanical ventilation, with an increase in intrapulmonary shunt and dead space. Also, an increase in the arterial pressure gradient of CO2 expired pressure of CO2, with a decrease in pH.
This alteration can be corrected by increasing the minute volume between 15 and 20% and using PEEP of 5 cm of H 2 O. There is also an increase in top pressure and table pressure, which will later stabilize. When the Trendelenburg position is used in patients with gynecological surgery under spontaneous ventilation, abdominal pressure as well as the displacement of the viscera in a cephalad direction exert pressure on the diaphragm, making breathing difficult, resulting in tachypnea and hypercarbia.
Regarding the absorption of CO 2 by the peritoneum, it seems that this stabilizes after the first 10 minutes of having increased intra-abdominal pressure. It is said that the pressure exerted by the pneumoperitoneum on the peritoneal capillaries acts as a protective mechanism, preventing the absorption of CO2 through it. At the end of the procedure, when the intra-abdominal pressure decreases due to the exit of CO2, we will find a higher frequency of CO2 absorption that can be recorded by capnography.
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