interventions are well established in veterinary medicine and offer several benefits when compared to standard laparotomy [1–6]. Reduced tissue trauma, with minimized incision size, and decreased manipulation of the gastro‐intestinal tract leading to improved comfort and faster recovery times are some of its major advantages [3, 5,7–12]. A decrease in inflammatory mediators (e.g., C‐reactive protein, interleukin‐6) and cells (e.g., WBC's) and a decrease in metabolic responses suggestive of stress (e.g., hyperglycemia) in patients undergoing laparoscopic versus open surgical intervention are taken as support of this [9,13–15]. In addition, direct and indirect evidence from animal studies [3, 13, 16] supports that as for human patients there is less pain associated with a laparoscopic versus traditional surgical approaches for the same procedure. The consequent reduced need for analgesic drugs and shortened hospital stays are well established in human patients and seem to be also true in animals [12]. Additional advantages include reduced adhesion formation [17], lower infection rates [5, 18, 19], a shorter healing time, improved cosmetic results, and quicker return to function [3,20–22]. Because of these benefits, laparoscopy is being used both as a diagnostic [23, 24] and surgical tool [25–27] with increasing frequency, as well as complexity, in veterinary medicine.
Despite the many advantages associated with laparoscopic versus traditional approaches, laparoscopic procedures have their own specific risks and potential complications. In additions to effects related to the disease state of the animal, the positioning for surgery, and the surgical procedure itself, the anesthetist must consider the physiological changes associated with insufflating gas into the abdomen and the consequences to various organ systems, specially the cardiovascular and respiratory systems. These considerations will be the focus of this chapter and are discussed in more detail in the subsequent text.
Anesthesia Considerations Related to Disease
In addition to routine procedures in healthy dogs and cats, animals with significant disease are increasingly presented for laparoscopy. The anesthetist must therefore be aware of the considerations related to the primary and any secondary disease processes in these patients. This information is available in broad based anesthesia textbooks. As an example, consider the patient presenting for a liver biopsy. On the surface, this would seem a fairly straightforward procedure. However, if circulation is compromised due to hypoproteinemia, acid–base and electrolyte changes, insufflation of the abdomen can result in serious hypotension. If coagulation status is also compromised, significant blood loss from the biopsy site may exacerbate this and the animal may require a transfusion. If lung metastases are present, respiratory complications are possible. The potential for side effects tends to increase with more complex procedures as in an animal with an adrenal pheochromocytoma where manipulation can increase catecholamine release and result in hypertension and cardiac rhythm abnormalities. Timely intervention is facilitated if these potential complications are anticipated.
Patients with significant cardiovascular and pulmonary disease (congenital heart defects, valvular heart disease, congestive heart failure, and pulmonary hypertension) are at a higher risk for complications related to the hemodynamic and ventilatory changes associated with the increase in intra‐abdominal pressure [28]. These patients may be unable to compensate, leading to further worsening of their condition [29]. Understanding the influence of the unique physiological effects of the laparoscopic approach on the pathophysiology of the disease process allows for adequate patient preparation and tailored perioperative monitoring and management to mitigate adverse outcomes [30, 31].
Anesthesia Considerations Related to Surgery
Reported 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,
