Laparoscopy
Historical Background
The term laparoscopy belongs to an area of surgery that crosses all traditional disciplines , from general surgery to neurosurgery. It is a minimally invasive surgery ( MIS ) . Minimally invasive surgery is a means of performing major operations through small incisions, often using miniaturized high – tech imaging systems , to minimize the trauma of surgical exposure .
The newest and most popular variety of MIS , laparoscopy , is infact the oldest . Primitive laparoscopy , placing a cystoscope within an inflated abdomen , was first performed by Kelling in 1901 . It was dangerous because of hot elements at the tip of the scope . In the late 1950s , Hopkins described the rod lens , a method of transmitting light through a solid quartz rod with no heat and little light loss . At the same time , thin quartz fibers were discovered to be capable of trapping light internally and conducting it around corners . This important discovery , opend the field of fiberoptics and allowed the rapid development of flexible endoscopes . By the mid 1970s , rigid and flexible endoscopes made a rapid transition from diagnostic instruments to therapeutic ones .
The Team of Laparoscopy
The team may consist of a laparoscopic surgeon and an operating room nurse with an interest in laparoscopic surgery . Adding laparoscopic assistants and circulating staff with an intimate knowledge of the equipment will add to and enhance the team nucleus . Having a good designated laparoscopic team reduces the conversion rate and overall operative time , and leads to a cost saving for patient and hospital .
Physiologic changes
There is occurance of physiologic changes even with the least invasive procedures .Many minimally invasive procedures require minimal or no sedation , so there are few alterations in cardiovascular , endocrine and immune systems function .
Those that require general anesthesia , have a greater physiologic impact , because of the anesthetic agent , the incision and the pneumoperitoneum .
Laparoscopy
Nitrous oxide and carbon dioxide are used for inflating the abdomen . N2O is physiologically inert and absorbs rapidly . It provides better analgesia for laparoscopic performance under local anesthesia , when compares with co2 or air . N2O would not suppress combustion , but controlled clinical trials have established its safety within the peritoneal cavity .
There are two types of the physiologic effects of co2 pneumoperitoneum : 1 – gas effects and 2 – pressure effects
CO2 is rapidly absorbed across the peritoneal membrane into the circulation and creats a respiratory acidosis ( generation of carbonic acid ) .
Te largest reserve of body buffers lies in bone . They absorb co2 ( up to 120 ) , and minimize the development of hypercarbia or respiratory acidosis during brief endoscopic procedures . With saturation of body buffers , respiratory acidosis developes rapidly . The respiratory system assumes the burden of keeping up with the absorption of co2 and its release from these buffers . In patients with normal respiratory function , this is not difficult . The anesthesiologist increases the ventilatory rate or vital capacity on the ventilator . In cases with respiratory rate more than 20 per minute , there may be less efficient gas exchange and increasing hypercarbia . * Hypercarbia causes tachycardia and increases systemic vascular resistance . Therefore elevates blood pressure and increases myocardial oxygen demands .
***Pressure effects of the Pneumoperitoneum : In the hypovolemic individual , excessive pressure on the inferior vena cava ( IVC ) and a reverse Trendelenburg position with loss of lower extremity muscle tone may cause decreased venous return and cardiac output .
*The most common arrhythmia created by laparoscopy is bradycardia . A rapid stretch of the peritoneal membrane often causes a vasovagal response with bradycardia and occasionally hypotension . Increased intra-abdominal pressure compresses the inferior vena cava ( IVC ) and therefore diminishes venous return from the lower extremities , more prominently in the patient placed in the reverse Trendelenburg position for upper abdominal operations . Venous engorgement and decreased venous return promote venous thrombosis . It is an avoidable complication with the use of sequential compression stockings , subcutaneous heparin or LMWH .
Increased intra-abdominal pressure decreases renal blood flow , glomerular filtration rate and urine output . These effects may be mediated by direct pressure on the kidney and the renal vein . Decreased renal blood flow causes increase of plasma renin release , thereby increasing sodium retention . Rise of ADH level during the pneumoperitoneum causes more free water reabsorption in the distal tubules .
*Intraoperative oliguria is common during laparoscopy . Serum cortisol levels after laparoscopic operations are often higher than after the equivalent operation performed through an open incision . The greatest difference between open and laparoscopic surgery is the more rapid equilibration of most stress – mediated hormone levels after laparoscopic surgery .
Immune suppression is less after laparoscopy than after open surgery .
To be continued ... تاريخ بروز رساني : شنبه 12/05/87 ساعت 14:19
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