Small Animal Laparoscopy and Thoracoscopy. Группа авторов

surgical complication rates for laparoscopy and laparotomy vary. Initial reports suggested that surgical complications occurred with a lower frequency for laparoscopy, but as the complexity of procedures performed using this approach has increased, the complication rate is now more comparable [32, 33]. Complication rates and surgical time, which can additionally contribute to morbidity, tend to decrease with surgeon experience [12].

      Surgical complications may be related specifically to the procedure, positioning for the procedure (discussed later), or be of a more general nature. Again, prior preparation will facilitate rapid treatment should this occur.

Hemorrhage from inadvertent puncture of organs or vessels during placement of the Veress needle or introduction of the trocars is a reported complication in human and animal patients (Figure 7.1) even during entry into the abdomen for routine procedures and requires a quick response from the anesthetist [32–38]. Hemorrhage from either cause might also necessitate conversion from the laparoscopic to open approach during which time the patient will need to continue to be supported aggressively until the surgeon can visualize and control the source of hemorrhage. A recent report in veterinary patients indicates excessive hemorrhage as one of the significant causes for conversion to celiotomy during diagnostic procedures [39]. Although the occurrence of hemorrhage within the pneumoperitoneum is typically readily identified, the increased intra‐abdominal pressure may cause venous tamponade and delay recognition of active bleeding into the postoperative period [7]. Hemorrhage has also been reported at the surgical site during routine procedures such as ovariectomy in dogs [35, 40] suggesting vigilance on the part of the anesthetist for this complication is important. A recent study in 161 dogs undergoing laparoscopic ovariectomy performed by supervised novice surgeons, reported only minor blood loss, caused by splenic puncture during insertion of the Veress needle (12.4%), and bleeding from the ovarian pedicle (2.5%), but conversion to laparotomy was not required in any dogs [37].

Figure 7.1 Inadvertent splenic puncture.

      Source: Courtesy of Eric Monnet.

Figure 7.2 Radiographic image showing inadvertent placement of insufflation gas into the bladder.

      Source: Courtesy of David Twedt.

In addition to vascular entry and organ puncture with subsequent hemorrhage as previously mentioned, surgical complications include bladder (Figure 7.2), bowel or stomach puncture and gas distention, trauma to the bile duct, peritoneal detachment, etc. A 7.5% emergent conversion rate from laparoscopy to laparotomy due to surgical complications such as hemorrhage and biliary tract rupture was reported in dogs and cats [39].

      Other causes of surgical complications are related to the unique equipment used for intervention. Just as it is important for the surgeon to have basal knowledge of anesthesia, it is important for the anesthetist to have at least a similar level of understanding of the surgical equipment used to facilitate laparoscopy. Complications associated with puncture of organs/vessels with the Veress needle have already been discussed. Additional complications may arise from use (intentional or accidental) of high insufflation pressures, intra‐abdominal use of cautery (especially if a potentially flammable gas is used), heat from the light source and cable, etc.

Pathophysiology of Pneumoperitoneum

      Hemodynamic Effects

Hemodynamic changes and complications result from many factors including surgical intervention as previously mentioned, patient position, anesthesia, and variations in carbon dioxide (CO₂) tension. There is a body of literature that indicates peritoneal insufflation, regardless of the gas used, alters hemodynamics in both human beings and animals. While variability is reported, the most consistent changes are those to cardiac output and vascular resistance. A decrease in cardiac output and concomitant increase in systemic vascular resistance are the most typical changes associated with increased abdominal pressure [41–45]. This occurs despite the frequently observed slight increase in heart rate with insufflation. The decrease in cardiac output has been measured using many different tools (e.g., pulmonary artery catheterization, esophageal Doppler echocardiography) and interestingly is seen in human and veterinary patients regardless of whether they are in a head‐up or head‐down position [33, 46, 47]. The decrease in cardiac output tends to parallel decreases in venous return, which is believed to occur as a result of caval compression (with increasing insufflation pressure), pooling of blood in the caudal extremities and changes in venous resistance [41, 42, 48]. These effects seem to be enhanced in the reverse Trendelenburg position while less pronounced in the Trendelenburg position, likely due to gravity further influencing venous return [49]. It is interesting that despite a decrease in cardiac output, blood pressure changes are not consistent. In fact, blood pressure is often elevated in healthy patients with the increase in systemic vascular resistance offsetting the decrease in cardiac output [32, 42, 43, 45, 48]. This increase in resistance is thought at least in part to be the result of abdominal aortic compression and neuroendocrine effects during peritoneal stretch resulting from insufflation [31, 42,49–51]. Plasma levels of norepinephrine, epinephrine, cortisol, vasopressin, atrial naturetic peptide, renin, and aldosterone have been shown to be elevated during pneumoperitoneum [52]. The anesthetist is cautioned not to become complacent when recording normal blood pressure values, as there is evidence that tissue perfusion to abdominal organs is progressively decreased with increases in abdominal insufflation pressures.

      As insufflation pressures increase into the range of 10–15 mmHg, hepatic, renal, and mesenteric blood flows are decreased. In studies with pigs, intra‐abdominal pressures greater than 10 mmHg were associated with significant reductions in hepatic artery and splanchnic blood flow [53, 54]. In dogs intra‐abdominal pressures in the range of 16–20 mmHg decreased portal venous and mesenteric arterial flow [55, 56]. Impairment of blood flow in other vessels (e.g., celiac artery) and to the intestinal mucosa is also reported for both dogs and pigs in this similar pressure range [42, 54, 57]. Oliguria is reported with pressures in the 15–20 mmHg range and anuria may be seen when pressures exceed this ranges [42, 57, 58]. The decrease in renal blood flow leads to an increase in renin and aldosterone levels [59]. In dogs, renal blood flow and glomerular filtration were decreased by over 75% with intra‐abdominal pressures of 20 mmHg, and anuria was observed when abdominal pressures reached 40 mmHg [42, 58]. Similar findings were reported in pigs, where oliguria was observed with pressures over 15 mmHg [57]. Albeit uncommon, patients with chronic kidney disease may be at higher risk for acute kidney injury during laparoscopic surgery [60–62].

      Interestingly, in a single study in healthy cats, pneumoperitoneum up to an intra‐abdominal pressure of 16 mmHg with carbon dioxide as the insufflation gas did not significantly influence cardiovascular parameters, albeit ventilation seemed to be negatively impacted; regional blood flow was not evaluated [63]. While healthy cats did not show changes in measured parameters during peritoneal insufflation, it is important to remember that cardiovascular function may be further influenced by the patient's health status, positioning during anesthesia and surgery, duration of the procedure, and the type of insufflation gas.

Figure 7.3 Dog prepared for laparoscopic intervention in Fowler position (reverse Trendelenburg).

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