Intracranial pressure. Effects of pneumoperitoneum in a large-animal model

To assess the safety of laparoscopy in patients with CSF catheters draining distally into the abdomen

PURPOSE

This study evaluates the safety of laparoscopic procedures in patients with cerebrospinal fluid (CSF) catheters draining distally into the abdomen.

METHODS

A systematic search across PubMed, Scopus, and Ovid databases using pertinent keywords yielded 47 relevant papers, encompassing 197 cases, for analysis.

RESULTS

In the pediatric cohort (n = 129), male (49.6%) and female (34.1%) cases were reported, while gender remained unspecified in 16.3%. Shunt indications included unspecified (126 cases) and Meningomyelocele (3 cases). Laparoscopic procedures encompassed gastric (72.1%), urologic (21.7%), and other (6.2%) indications. Peri-operative shunt management included subcostal incision and clamping (1), ICP monitoring and drainage (2), and distal shunt flow confirmation (1). The prevalent complication was mechanical obstruction (10.1%), followed by pseudocyst formation (1.5%) and infection (2.3%). In the adult cohort (n = 61), males (60.6%) and females (39.3%) with a median age of 55 years were observed. Management strategies encompassed sponge packing and mobilization (11), distal shunt flow confirmation (2), shunt clamping (3), Transcranial Doppler monitoring (2), and no manipulation (30). Shunt infection emerged as the primary complication (2). Overall, 24 patients encountered VP shunt-related complications post-laparoscopy.

CONCLUSION

This study underscores the safety of laparoscopic interventions in patients with ventriculoperitoneal or lumboperitoneal shunts when facilitated by interdisciplinary cooperation. A meticulous preoperative assessment for shunt track localization, intraoperative visualization of shunt tip with CSF flow, vigilant perioperative anesthetic monitoring, and shunt dysfunction surveillance are crucial for favorable outcomes in laparoscopic procedures for these patients.

The Influence of Movement on the Cerebrospinal Fluid Pressure of the American Alligator (Alligator mississippiensis)

This study was undertaken to document how the cerebrospinal fluid (CSF) pressure varied during movements and physiological activities. Using surgically implanted pressure catheters; the CSF pressure was recorded from sub-adult American alligators (Alligator mississippiensis) under anesthesia and post-recovery. Pressures were recorded during physiological activities (the cardiac cycle; passive and active ventilation); manual manipulation of the anesthetized animals (foot sweeps; tail oscillations; and body bends); as well as voluntary movements post-recovery (changes in body tone; defensive strikes; and locomotion). The CSF pulsations associated with the cardiac cycle had the lowest mean amplitude (3.7 mm Hg); during active ventilation and defensive strikes; the alligators routinely generated CSF pressure spikes in excess of 100 mm Hg. The recorded CSF pressures appear to be caused by a variety of mechanisms including vascular pressure; fluid inertia; and possible physical displacement of the spinal cord. The results of the study suggest that any model of CSF dynamics or perfusion should incorporate the episodic high-pressure CSF pulsations associated with movement.

The role of Cushing's reflex and the vasopressin-mediated oligoanuric response to intracranial hypertension in patients with abdominal compartment syndrome

BACKGROUND

We examined the link between increased intra-abdominal pressure, intracranial pressure, and vasopressin release as a potential mechanism. Intra-abdominal pressure, produced by abdominal-cavity insufflation with carbon dioxide (CO₂) during laparoscopic abdominal procedures to facilitate visualization, is associated with various complications, including arterial hypertension and oliguria.

METHODS

Mean arterial pressure, optic nerve sheath diameter, measured as a proxy for intracranial pressure, plasma vasopressin, serum and urine osmolarity, and urine output were measured 4 times during laparoscopic sleeve gastrectomy in 42 patients: before insufflation with CO₂ (T₀); after insufflation to 15 cm water (H₂O) pressure, with 5 cm H₂O positive end-expiratory pressure (T₁); after positive end-expiratory pressure was raised to 10 cm H₂O (T₂); and after a return to the baseline state (T₃). Mean values at T₀ to T₃ and the directional consistency of changes (increase/decrease/ unchanged) were compared among the 4 data-collection points.

RESULTS

Statistically significant elevations (all P ≤ .001) were noted from T₀ to T₁ and from T₀ to T₂ in mean arterial pressure, optic nerve sheath diameter, and vasopressin, followed by decreases at T₃. For optic nerve sheath diameter and vasopressin, the increases at T₁ and T₂ occurred in 98% and 100% of patients, ultimately exceeding normal levels in 88 and 97%, respectively. Conversely, urine output fell from T₀ to T₁ and T₂ by 60.9 and 73.4%, decreasing in 88.1% of patients (all P < .001). Patients with class II obesity exhibited statistically greater increases in optic nerve sheath diameter and vasopressin, but statistically less impact on urine output, than patients with class III obesity.

CONCLUSION

Increased mean arterial pressure, intracranial pressure, and vasopressin release appear to be intermediary steps between increased intra-abdominal pressure and oliguria. Further research is necessary to determine any causative links between these physiological changes.

Noninvasive intracranial pressure real-time waveform analysis monitor during prostatectomy robotic surgery and Trendelenburg position: case report

Both robotic surgery and head-down tilt increase intracranial pressure by impairing venous blood outflow. Prostatectomy is commonly performed in elderly patients, who are more likely to develop postoperative cognitive disorders. Therefore, increased intracranial pressure could play an essential role in cognitive decline after surgery. We describe a case of a 69-year-old male who underwent a robotic prostatectomy. Noninvasive Brain4care^TM intraoperative monitoring showed normal intracranial compliance during anesthesia induction, but it rapidly decreased after head-down tilt despite normal vital signs, low lung pressure, and adequate anesthesia depth. We conclude that there is a need for intraoperative intracranial compliance monitoring since there are major changes in cerebral compliance during surgery, which could potentially allow early identification and treatment of impaired cerebral complacency.

Effects of low- and high-pressure carbon dioxide pneumoperitoneum on intracranial pressure during laparoscopic cholecystectomy

BACKGROUND

Laparoscopic surgeries are a risk factor for raised intracranial **pressure and neurological complications. Even though rare, the consequences may be severe.

METHODS

One hundred and one patients of laparoscopic cholecystectomy were enrolled and were randomized into two groups: low-pressure 8 mm Hg (Group A) and high-pressure 14 mm Hg (Group B) carbon dioxide pneumoperitoneum during surgery. Fifty patients were in group A and 51 patients were in group B. Intracranial pressure was measured by measuring the optic nerve sheath diameter (ONSD) using ultrasound examination. Baseline ONSD was recorded followed by ONSD recording at various intervals: at the induction of anesthesia; 30 min, 45 min, at the end of surgery; and 30 min post surgery.

RESULTS

The groups were comparable in terms of demographics and comorbidities. The mean age of group A was 45 years and for group B it was 45.75 years. Most common indication for surgery was symptomatic gall stone disease. Baseline ONSD in group A was 0.427 ± 0.0459 mm, whereas it was 0.412 ± 0.0412 mm in group B. There was a significant rise of ONSD (p < 0.05) 30 min after induction of pneumoperitoneum and up to 30 min post anesthesia. In the low-pressure group 7 (14%) patients had a significant rise of ICP, whereas in the high-pressure group 20 (39%) patients had a significant rise of ICP (p < 0.05).

CONCLUSIONS

High-pressure pneumoperitoneum causes significant rise in intracranial pressure in comparison to low-pressure pneumoperitoneum during laparoscopic cholecystectomy, which can be monitored by ONSD measurement by ultrasound examination and is totally non-invasive.

Abdominal Insufflation Is Associated With Increase of Intracranial Pressure in Patients With Normal Pressure Hydrocephalus

BACKGROUND

Ventriculoperitoneal shunting (VPS) is effective for the treatment of normal-pressure hydrocephalus (NPH) and sometimes requires laparoscopic assistance with abdominal insufflation.

OBJECTIVE

To evaluate the association of abdominal insufflation with opening pressure (OP) in NPH patients undergoing VPS implantation.

METHODS

Between March 2016 and April 2019, 52 consecutive patients who underwent first-time VPS implantation surgery were retrospectively identified by reviewing electronic health records. OP during the large volume lumbar tap test (OPLP) and VPS implantation surgery (OPSURGERY) were measured in 29 patients.

RESULTS

Laparoscopic assistance with abdominal insufflation was used in 20 (69%) cases. There were no differences in patient age (P = .589), gender (P = .822), body mass index (P = .289), weight (P = .789), height (P = .542), and OPLP (P = .476) in patients operated with and without laparoscopic assistance. When compared to patients operated without laparoscopic assistance, laparoscopic assistance was associated with a greater rate of OP increase during surgery relative to OPLP (40% vs 100%, P = .002), a greater increase in OPSURGERY relative to OPLP (-0.40 ± 5.38 vs 10.17 ± 5.53 cm H2O, P < .001), and a greater proportion of patients with OPSURGERY of ≥25 cm H2O during the VPS surgery (0% vs 78%, P < .001).

CONCLUSION

Abdominal insufflation is associated with an increase in intracranial pressure with OPs often exceeding 25 cm H2O. This should be considered when selecting optimal VPS pressure settings.

The Cushing reflex and the vasopressin-mediated hemodynamic response to increased intracranial pressure during acute elevations in intraabdominal pressure

BACKGROUND

Abdominal compartment syndrome has been linked to detrimental hemodynamic side effects that include increased intracranial pressure and diminished renal function, but the mechanisms behind this continue to be elucidated. In this study, we sought to investigate any direct association between acute elevations in intra-abdominal pressure and intracranial hypertension during experimentally induced abdominal compartment syndrome and between acutely elevated intracranial pressure and the hemodynamic response that might be elicited by a vasopressin-induced Cushing reflex affecting urine osmolality and urine output. The aim of this study is to explain the Cushing reflex and the vasopressin-mediated hemodynamic response to intracranial pressure during acute elevations in intra-abdominal pressure.

METHODS

We measured intra-abdominal pressure, intrathoracic pressure, optic nerve sheath diameter as an indirect sign of intracranial pressure, vasopressin levels in blood, urine osmolality, and urine output at 4 time points during surgery in 16 patients undergoing sleeve gastrectomy for morbid obesity. Values for the 4 time points were compared by repeated-measures analysis of variance.

RESULTS

More than 50-fold elevations in serum vasopressin paralleled increases in optic nerve sheath diameter, rising throughout prepneumoperitoneum and tapering off afterward, in conjunction with a marked decrease in urine but not serum osmolality. Mean arterial pressure rose transiently during pneumoperitoneum without elevated positive end-expiratory pressure but was not significantly elevated thereafter.

CONCLUSIONS

These findings support our hypothesis that the oliguric response observed in abdominal compartment syndrome might be the result of the acutely elevated intra-abdominal pressure triggering increased intrathoracic pressure, decreased venous outflow from the central nervous system, increased intracranial pressure, and resultant vasopressin release via a Cushing reflex.

Safety of laparoscopic colorectal surgery in patients with ventriculoperitoneal shunt

INTRODUCTION

This study retrospectively investigated the safety of laparoscopic colorectal surgery in patients with ventriculoperitoneal shunt (VPS) based on the experiences within our department.

METHODS

A total of 866 patients underwent laparoscopic colorectal surgery for colorectal cancer, ulcerative colitis, Crohn's disease, and acute appendicitis at Osaka University during the study period. Laparoscopic colorectal surgery cases were collected from the Osaka University database. Among them, four (0.5%) had VPS when they underwent surgery. In these four cases, we consulted a neurosurgeon and checked the route of the VPS catheter to determine whether it had a unidirectional valve to prevent backflow and whether it was working normally. We retrospectively investigated the clinical characteristics of these four cases.

RESULTS

All cases were safely treated, with the pneumoperitoneum pressure set at 10 mmHg under routine anesthetic monitoring and without any manipulations such as clamping or externalization of the VPS catheter. The four patients were discharged without any VPS-related complications such as increased intracranial pressure, shunt failure, or infection.

CONCLUSIONS

Our study suggests that laparoscopic colorectal surgeries in patients with VPS without any manipulations may be safe. Future studies should aim to better standardize the perioperative management of VPS during laparoscopic colorectal surgery.

Anaesthesia for Robotic-Assisted Radical Prostatectomy: Considerations for Laparoscopy in the Trendelenburg Position

Two cases of anaesthetic complications after robotic-assisted laparoscopic radical prostatectomy using the da Vinci Remote-Controlled Surgical System are presented. Case 1 describes a patient with post-extubation respiratory distress requiring reintubation and subsequent ventilation in an intensive care unit. This was attributed to laryngeal oedema, which was most likely due to the reduction in venous outflow from the head caused by the pneumoperitoneum and prolonged, extreme Trendelenburg position. Case 2 describes a patient with mild brachial plexus neurapraxia, which was most likely due to compression by shoulder braces (to prevent cephalad sliding) during the exaggerated head-down tilt. For this procedure, the authors recommend limiting the duration and extent of head-down tilt as much as possible, avoiding excessive intravenous fluids and careful positioning of the patient with avoidance of shoulder braces whenever possible.

Effects of pneumoperitoneum and Trendelenburg position on intracranial pressure assessed using different non-invasive methods

BACKGROUND

The laparoscopic approach is becoming increasingly frequent for many different surgical procedures. However, the combination of pneumoperitoneum and Trendelenburg positioning associated with this approach may increase the patient's risk for elevated intracranial pressure (ICP). Given that the gold standard for the measurement of ICP is invasive, little is known about the effect of these common procedures on ICP.

METHODS

We prospectively studied 40 patients without any history of cerebral disease who were undergoing laparoscopic procedures. Three different methods were used for non-invasive estimation of ICP: ultrasonography of the optic nerve sheath diameter (ONSD); transcranial Doppler-based (TCD) pulsatility index (ICP_PI); and a method based on the diastolic component of the TCD cerebral blood flow velocity (ICP_FVd). The ONSD and TCD were measured immediately after induction of general anaesthesia, after pneumoperitoneum insufflation, after Trendelenburg positioning, and again at the end of the procedure.

RESULTS

The ONSD, ICP_FVd, and ICP_PI increased significantly after the combination of pneumoperitoneum insufflation and Trendelenburg positioning. The ICP_FVd showed an area under the curve of 0.80 [95% confidence interval (CI) 0.70-0.90] to distinguish the stage associated with the application of pneumoperitoneum and Trendelenburg position; ONSD and ICP_PI showed an area under the curve of 0.75 (95% CI 0.65-0.86) and 0.70 (95% CI 0.58-0.81), respectively.

CONCLUSIONS

The concomitance of pneumoperitoneum and the Trendelenburg position can increase ICP as estimated with non-invasive methods. In high-risk patients undergoing laparoscopic procedures, non-invasive ICP monitoring through a combination of ONSD ultrasonography and TCD-derived ICP_FVd could be a valid option to assess the risk of increased ICP.

Tolerance and Efficacy of Enteral Nutrition in Traumatic Brain–Injured Patients Induced Into Barbiturate Coma

BACKGROUND

There is a paucity of data evaluating the efficacy of nutrition support in traumatic brain-injured patients induced into barbiturate coma for refractory intracranial hypertension. Our objective was to evaluate the efficacy of enteral nutrition in a select group of trauma patients.

METHODS

Prospective data were collected on severe traumatic brain-injured patients over a 4-year period. Patients were stratified by whether or not they were induced into a barbiturate coma. Barbiturate coma was defined as per American Association of Neurological Surgeons (AANS) guidelines. All patients were initially fed via the enteral route via a nasogastric feeding tube. Patients who did not tolerate feedings within 48 hours started receiving prokinetic agents. Feeding tolerance was defined as ability to tolerate enteral feedings with <150 mL of gastric residuals every 6 hours for >72 hours.

RESULTS

Fifty-seven patients were induced into a barbiturate coma. All were victims of blunt-force trauma. Forty-two of 57 (74%) patients were men, with a mean age of 37+/-12 years and a mean injury severity score of 24+/-10. Thirty-eight of the 57 (67%) patients had an isolated traumatic brain injury. All 57 patients failed enteral nutrition via the nasogastric route after the first 48 hours of nutrition initiation after barbiturate coma was fully achieved by protocol criteria. Prokinetic agents demonstrated no improvement in feeding tolerance after the subsequent 48-72 hours. Of the 12 patients who had a postpyloric feeding tube placed, only 25% tolerated enteral nutrition for >48 hours.

CONCLUSIONS

Patients with traumatic brain injury induced into barbiturate coma develop a significant ileus that is refractory to prokinetic agents. Only a marginal improvement is seen when the postpyloric route is obtained. Early parenteral nutrition should be considered in this patient population.

Prevalence and impact of incompetence of internal jugular valve on postoperative cognitive dysfunction in elderly patients undergoing robot-assisted laparoscopic radical prostatectomy

Internal jugular vein (IJV) is the main pathway of cerebral venous drainage and its valves prevent regurgitation of blood to the brain. IJV valve incompetence (IJVVI) is known to be associated with cerebral dysfunctions. It occurs more often in male over 50 years old, conditions elevating intra-abdominal or intra-thoracic pressure. In robot-assisted laparoscopic radical prostatectomy (RALRP), elderly male undergoes surgery in Trendelenburg position with pneumoperitoneum applied. Therefore, we assessed the IJVVI during RALRP and its influence on postoperative cognitive function. 57 patients undergoing RALRP were enrolled. Neurocognitive tests including Mini-Mental State Examination (MMSE), Auditory Verbal Learning Test, Digit Symbol Substitution Test, Color Word Stroop Test, digit span test, and grooved pegboard test were performed the day before and 2 days after surgery. During surgery, IJVVI was assessed with ultrasonography in supine position with and without pneumoperitoneum, and Trendelenburg position with pneumoperitoneum. 50 patients underwent sonographic assessment and 41 patients completed neurocognitive examination. A total of 27 patients presented IJVVI, 19 patients in supine position without pneumoperitoneum, 7 patients in supine position with pneumoperitoneum and 1 patient in Trendelenburg position with pneumoperitoneum. In neurocognitive tests, patients with IJVVI showed statistically significant decline of score in MMSE postoperatively (p<0.05). IJVVI occurred in 38% in supine position but the incidence was increased to 54% after Trendelenburg position and pneumoperitoneum. Patients with IJVVI did not show significant differences in cognitive function tests except MMSE. Clinical and neurological significance of physiologic changes associated RALRP should be studied further.

Abdominal insufflation for laparoscopy increases intracranial and intrathoracic pressure in human subjects

BACKGROUND

Laparoscopy has emerged as an alternative to laparotomy in select trauma patients. In animal models, increasing abdominal pressure is associated with an increase in intrathoracic and intracranial pressures. We conducted a prospective trial of human subjects who underwent laparoscopic-assisted ventriculoperitoneal shunt placement (lap VPS) with intraoperative measurement of intrathoracic, intracranial and cerebral perfusion pressures.

METHODS

Ten patients undergoing lap VPS were recruited. Abdominal insufflation was performed using CO2 to 0, 8, 10, 12 and 15 mmHg. ICP was measured through the ventricular catheter simultaneously with insufflation and with desufflation using a manometer. Peak inspiratory pressures (PIP) were measured through the endotracheal tube. Blood pressure was measured using a noninvasive blood pressure cuff. End-tidal CO2 (ETCO2) was measured for each set of abdominal pressure level. Pressure measurements from all points of insufflation were compared using a two-way ANOVA with a post hoc Bonferroni test. Mean changes in pressures were compared using t test.

RESULTS

ICP and PIP increased significantly with increasing abdominal pressure (both p < 0.01), whereas cerebral perfusion pressure (CPP) and mean arterial pressure did not significantly change with increasing abdominal pressure over the range tested. Higher abdominal pressure values were associated with decreased ETCO2 values.

CONCLUSION

Increased ICP and PIP appear to be a direct result of increasing abdominal pressure, since ETCO2 did not increase. Though CPP did not change over the range tested, the ICP in some patients with 15 mmHg abdominal insufflation reached values as high as 32 cmH2O, which is considered above tolerance, regardless of the CPP. Laparoscopy should be used cautiously, in patients who present with baseline elevated ICP or head trauma as abdominal insufflation affects intracranial pressure.

Intraoperative non invasive intracranial pressure monitoring during pneumoperitoneum: a case report and a review of the published cases and case report series

Non-invasive measurement of ICP (nICP) can be warranted in patients at risk for developing increased ICP during pneumoperitoneum (PP). Our aim was to assess available data on the application of nICP monitoring during these procedures and to present a patient assessed with an innovative combination of noninvasive tools. Literature review of nICP assessment during PP did not find any studies comparing different methods intraprocedurally and only few studies of any nICP monitoring were available: transcranial Doppler (TCD) studies used the pulsatility index (PI) as an estimator of ICP and failed to detect a significant ICP increase during PP, whereas two out of three optic nerve sheath diameter (ONSD) studies detected a statistically significant ICP increase. In the case study, we describe a 52 year old man with a high grade thalamic glioma who underwent urgent laparoscopic cholecystectomy. Considering the high intraoperative risk of developing intracranial hypertension, he was monitored through parallel ONSD ultrasound measurement and TCD derived formulae (flow velocity diastolic formula, FVdnICP, and PI). ONSD and FVdnICP methods indicated a significant ICP increase during PP, whereas PI was not significantly increased. Our experience, combined with the literature review, seems to suggest that PI might not detect ICP changes in this context, however we indicate a possible interest of nICP monitoring during PP by means of ONSD and of TCD derived FVdNICP, especially for patients at risk for increased ICP.

What is the evidence for the use of low-pressure pneumoperitoneum? A systematic review

Background

Laparoscopic surgery has several advantages when compared to open surgery, including faster postoperative recovery and lower pain scores. However, for laparoscopy, a pneumoperitoneum is required to create workspace between the abdominal wall and intraabdominal organs. Increased intraabdominal pressure may also have negative implications on cardiovascular, pulmonary, and intraabdominal organ functionings. To overcome these negative consequences, several trials have been performed comparing low- versus standard-pressure pneumoperitoneum.

Methods

A systematic review of all randomized controlled clinical trials and observational studies comparing low- versus standard-pressure pneumoperitoneum.

Results and conclusions

Quality assessment showed that the overall quality of evidence was moderate to low. Postoperative pain scores were reduced by the use of low-pressure pneumoperitoneum. With appropriate perioperative measures, the use of low-pressure pneumoperitoneum does not seem to have clinical advantages as compared to standard pressure on cardiac and pulmonary function. Although there are indications that low-pressure pneumoperitoneum is associated with less liver and kidney injury when compared to standard-pressure pneumoperitoneum, this does not seem to have clinical implications for healthy individuals. The influence of low-pressure pneumoperitoneum on adhesion formation, anastomosis healing, tumor metastasis, intraocular and intracerebral pressure, and thromboembolic complications remains uncertain, as no human clinical trials have been performed. The influence of pressure on surgical conditions and safety has not been established to date. In conclusion, the most important benefit of low-pressure pneumoperitoneum is lower postoperative pain scores, supported by a moderate quality of evidence. However, the quality of surgical conditions and safety of the use of low-pressure pneumoperitoneum need to be established, as are the values and preferences of physicians and patients regarding the potential benefits and risks. Therefore, the recommendation to use low-pressure pneumoperitoneum during laparoscopy is weak, and more studies are required.

Optic nerve sheath diameter remains constant during robot assisted laparoscopic radical prostatectomy

Background

During robot assisted laparoscopic radical prostatectomy (RALRP), a CO₂ pneumoperitoneum (CO₂PP) is applied and the patient is placed in a head-down position. Intracranial pressure (ICP) is expected to acutely increase under these conditions. A non-invasive method, the optic nerve sheath diameter (ONSD) measurement, may warn us that the mechanism of protective cerebrospinal fluid (CSF) shifts becomes exhausted.

Methods

After obtaining IRB approval and written informed consent, ONSD was measured by ocular ultrasound in 20 ASA I–II patients at various stages of the RALRP procedure: baseline awake, after induction, after applying the CO₂PP, during head-down position, after resuming the supine position, in the postoperative anaesthesia care unit, and on day one postoperatively. Cerebral perfusion pressure (CPP) was calculated as the mean arterial (MAP) minus central venous pressure (CVP).

Results

The ONSD did not change during head-down position, although the CVP increased from 4.2(2.5) mm Hg to 27.6(3.8) mm Hg. The CPP was decreased 70 min after assuming the head-down position until 15 min after resuming the supine position, but remained above 60 mm Hg at all times.

Conclusion

Even though ICP has been documented to increase during CO₂PP and head-down positioning, we did not find any changes in ONSD during head-down position. These results indicate that intracranial blood volume does not increase up to a point that CSF migration as a compensation mechanism becomes exhausted, suggesting any increases in ICP are likely to be small.

The influence of intra-abdominal hypertension on the central nervous system: current insights and clinical recommendations, is it all in the head?

INTRODUCTION

Intra-abdominal hypertension (IAH) and abdominal compartment syndrome are a common occurrence in ICU patients. The deleterious effects of IAH on organ function are well known and increasingly appreciated in recent years, especially where renal and respiratory function are concerned.

METHODS

This review will focus on the available literature from the last years. A Medline and PubMed search was performed in order to find an answer to the question "What is the impact of increased IAP on neurologic function in the critically ill?"

RESULTS

The amount of data on the influence of IAH on the central nervous system is more scarce, but several animal and human studies have demonstrated a clear correlation between intra-abdominal pressure (IAP) and intracranial pressure (ICP). This correlation is probably due to transmission of the increased IAP to the thorax leading to increased intrathoracic, pleural pressure and central venous pressure, decreased venous return from the brain and increased ICP. This hypothesis is supported by the observation that the increase in ICP is abolished when a sternotomy and pleuropericardotomy are performed, and by the fact that abdominal decompression has produced good results in treating refractory intracranial hypertension (ICH) in patients with both IAH and ICH.

CONCLUSIONS

A close relationship between IAP and ICP has been observed in several animal and human studies. The clinical impact of this association is dependent on the baseline ICP and the compensatory reserve of the patient. Some studies have reported good results in treating refractory ICH by abdominal decompression in patients with concomitant IAH. Monitoring of IAP and ICP in risk patients is essential.

Gasless laparoscopic assisted surgery for abdominal trauma

BACKGROUND

Numerous studies have described the effectiveness of laparoscopy for trauma patients. In gas-filling laparoscopic surgery, most of the disadvantages are related to a positive pressure pneumoperitoneum that compromises the cardiopulmonary function. The main advantage of gasless laparoscopic assisted surgery (GLA) is that it does not affect the haemodynamic status, which is particularly critical for trauma patients. The purpose of this study was to investigate the feasibility and safety of GLA for abdominal trauma.

MATERIALS AND METHODS

This was a retrospective, 1:2 matched case-control study of all trauma gasless assisted laparoscopies performed from January 2010 until January 2013 in a Level I trauma centre. In total, 965 patients with abdominal trauma were admitted. According to the abdominal trauma protocol, a total of 93 hemodynamically stable patients required the operation; we selected fifteen patients to undergo GLA and matched 30 other patients to undergo laparotomy. Demographic information, perioperative findings, injury severity score, and postoperative recovery were recorded and analyzed.

RESULTS

A total of fifteen patients (ten men, five women) with a mean age of 44.4, standard deviation (SD) 13.2 years underwent GLA for abdominal trauma. Eight patients had penetrating injuries, while seven had blunt injuries. Overall, 73% patients had multiple injuries. The mean time to the identified lesion was 23.1, SD 10.9min, and the mean operative time was 109.7, SD 33.5min. Most of the lesions were repaired concurrently by GLA. One conversion to laparotomy was done. The mean length of hospital stay (HLOS) was 9.1, SD 4.5 days. No mortality occurred in this series. The mean follow-up was 22.0, SD 7.9 months, and there were no significant events during this period. The mean operative times were comparable in the GLA and open surgery group (109.7, SD 33.5 vs. 131.2, SD 43.6min; p=0.076). Compared with the open surgery group, the HLOS was significantly shorter in the GLA group (9.1, SD 4.5 vs.16.3, SD 6.4 days; p=0.030).

CONCLUSION

GLA offers both therapeutic and diagnostic advantages for patients with abdominal trauma. GLA shares the advantages of laparoscopy and prevents the cardiopulmonary function from being compromised due to pneumoperitoneum, which is especially critical for trauma patients.

Late Onset of CSF Rhinorrhea in a Postoperative Transsphenoidal Surgery Patient Following Robotic-Assisted Abdominal Hysterectomy

Cerebrospinal fluid (CSF) leak is the most commonly encountered perioperative complication in transsphenoidal surgery for pituitary lesions. Direct closure with a combination of autologous fat, local bone, and/or synthetic grafts remains the standard of care for leaks encountered at the time of surgery as well as postoperatively. The development of the vascularized nasoseptal flap as a closure technique has increased the surgeon's capacity to correct even larger openings in the dura of the sella as well as widely exposed anterior skull base defects. Yet these advances in the technical nuances for management of post-transsphenoidal CSF leak are useless without the ability to recognize a CSF leak by physical examination, clinical history, biochemical testing, or radiographic assessment. Here, we report a case of a patient who developed a CSF leak 28 years after transsphenoidal surgery, precipitated by a robotic-assisted hysterectomy during which increased intra-abdominal pressure and steep Trendelenberg positioning were both factors. Given the remote nature of the patient's transsphenoidal surgery and relative paucity of data regarding such a complication, the condition went unrecognized for several months. We review the available literature regarding risk and pathophysiology of CSF leak following abdominal surgery and propose the need for increased vigilance in identification of such occurrences with the increasing acceptance and popularity of minimally invasive abdominal and pelvic surgeries as standards in the field.

Laparoscopic cholecystectomy in the presence of lumboperitoneal shunt

Laparoscopic cholecystectomy remains the mainstay of treatment in patients with gallstone disease. Nowadays more than ever before, patients present with more comorbidities and entities that make the laparoscopic approach composite. One of these is the presence of lumboperitoneal (LP) shunts. Herein, we describe a case of successful laparoscopic cholecystectomy in a patient with an LP shunt and an occipital nerve stimulator in the anterior abdominal wall. We describe alterations in technique, aiming at surgeons that perform laparoscopic cholecystectomies with useful tips in order to successfully deliver the operation. A brief review of the literature in the current subject is also given.

Evaluation of a new large animal model for controlled intracranial pressure changes induced by capnoperitoneum

BACKGROUND

A standardized large animal model for controlled ICP manipulation within a relevant range and repetitive ICP measurements is missing. We sought to develop such a model on the base of controlled IPP changes induced by capnoperitoneum.

METHODS

We utilized six female pigs (mean body weight 59.5 ± 18.4 kg) for experiments. A ventricular catheter connected with a burr hole reservoir was implanted. ICP was measured directly as cm H2O within a riser tube after percutaneous cannulation of the reservoir. A noninvasive intraperitoneal pressure (IPP) measurement was established (intravesical). Animals were placed in lateral position and a capnoperitoneum was induced. Measurements of ICP, IPP, MAP and respiratory parameters were performed at baseline IPP and after CO2 insufflation to IPP levels of 20 and 30 mmHg.

RESULTS

Baseline IPP in lateral position referenced to median line was 9.8 (±2) mm Hg, while corresponding ICP was 10 (±2.2) mm Hg. After IPP elevation to 20 mmHg, ICP increased to 18.8 (±1.9) mm Hg. At 30 mmHg IPP, ICP increased to 22.8 (±2.8) mm Hg. Except peak airway pressure, all other parameters were kept constantly. Mean ICP variation in the individual subject was 13.4 (±2.5) mm Hg, while a ICP range from minimum 9 to maximum 31 mmHg was documented.

CONCLUSIONS

We report a large animal model that allows (1) repeated measurement of the ICP and (2) manipulation of the ICP within a large pressure range by controlled IPP changes due to capnoperitoneum.

Transcranial Doppler monitoring of middle cerebral flow velocity in a patient with a ventriculoperitoneal shunt undergoing laparoscopy

Laparoscopic surgery is possibly associated with a risk of intracranial pressure (ICP) increase due to pneumoperitoneum in patients with ventriculoperitoneal shunts (VPS). Invasive techniques for shunt pressure monitoring are not routinely used because of the possible complications. Transcranial Doppler (TCD) is a non-invasive, safe method which gives accurate information about blood-flow velocities in basal cerebral arteries and indirectly about the ICP. Moreover it is inexpensive and simple in use. We report the use of TCD for middle cerebral flow velocity monitoring in a patient with a VPS who underwent laparoscopic surgery. In the case we present, during 60 min of pneumoperitoneum, TCD showed a sustained, but not clinically significant increase of the Pulsatility Index, with a recorded maximum change of 31 %. We consider that the use of TCD may increase the safety of laparoscopic procedures in patients with preexisting VPS.

Safety of Laparoscopy in Ventriculoperitoneal Shunt Patients

There has been an increasing trend in Laparoscopic surgeries. There is also a higher incidence of patients with ventriculoperitoneal (VP) shunts due to the advances in the techniques of cerebral shunts. Surgeons may come across patients of VP shunts presenting with an indication for laparoscopic surgery. Although there is no absolute contraindication for laparoscopy in VP shunts, there is always a risk of raised intracranial pressure. We describe a case of VP shunt presenting with an ectopic pregnancy and undergoing laparoscopic salpingectomy. Patient withstood the procedure well and had an uneventful recovery. Reviewing the literature, we found that laparoscopy is safe in VP shunts. However, there should always be accompanied by good monitoring facilities.

Ischemia as a possible effect of increased intra-abdominal pressure on central nervous system cytokines, lactate and perfusion pressures

INTRODUCTION

The aims of our study were to evaluate the impact of increased intra-abdominal pressure (IAP) on central nervous system (CNS) cytokines (Interleukin 6 and tumor necrosis factor), lactate and perfusion pressures, testing the hypothesis that intra-abdominal hypertension (IAH) may possibly lead to CNS ischemia.

METHODS

Fifteen pigs were studied. Helium pneumoperitoneum was established and IAP was increased initially at 20 mmHg and subsequently at 45 mmHg, which was finally followed by abdominal desufflation. Interleukin 6 (IL-6), tumor necrosis factor alpha (TNFa) and lactate were measured in the cerebrospinal fluid (CSF) and intracranial (ICP), intraspinal (ISP), cerebral perfusion (CPP) and spinal perfusion (SPP) pressures recorded.

RESULTS

Increased IAP (20 mmHg) was followed by a statistically significant increase in IL-6 (p = 0.028), lactate (p = 0.017), ICP (p < 0.001) and ISP (p = 0.001) and a significant decrease in CPP (p = 0.013) and SPP (p = 0.002). However, further increase of IAP (45 mmHg) was accompanied by an increase in mean arterial pressure due to compensatory tachycardia, followed by an increase in CPP and SPP and a decrease of cytokines and lactate.

CONCLUSIONS

IAH resulted in a decrease of CPP and SPP lower than 60 mmHg and an increase of all ischemic mediators, indicating CNS ischemia; on the other hand, restoration of perfusion pressures above this threshold decreased all ischemic indicators, irrespective of the level of IAH.

Laparoscopic cholecystectomy in a morbidly obese patient with Chiari I malformation and craniocervical anomalies

Chiari I malformation is the downward herniation of cerebellar tonsils through the foramen magnum, and is frequently associated with craniocervical anomalies. Laparoscopic surgery can cause an increase in intracranial pressure due to the obstruction of the foramen magnum. The successful administration of general anesthesia in a 50-year-old, morbidly obese woman with a difficult airway, scheduled for laparoscopic cholecystectomy, who was incidentally diagnosed with Chiari I malformation associated with craniocervical anomalies, is presented.

Intermittent pneumatic sequential compression of the lower extremities restores the cerebral oxygen saturation during laparoscopic cholecystectomy

BACKGROUND

Pneumoperitoneum causes intracranial pressure elevation and blood stasis at lower extremities. This study investigates cerebral oxygen saturation changes during laparoscopy and the effects of intermittent sequential compression (ISC) of the lower extremities in patients during elective laparoscopic cholecystectomy.

PATIENTS AND METHOD

Sixty patients were randomly divided into two groups according to the application of ISC to the lower extremities. Group I served as control group whereas ISC was applied to group II. Cerebral oxygen saturation, peripheral blood oxygen saturation, heart rate, mean blood pressure, and associated changes have been recorded during the operation.

RESULTS

Peripheral blood oxygen saturation and mean blood pressure values did not change significantly after pneumoperitoneum. Cerebral oxygen saturation levels of the group II patients were higher in than the group I patients and the difference between the groups was statistically significant (p = 0.0001). The difference became more prominent following the 35(th) minute of the operation. Mean heart rate of the patients in group II was lower than the patients in group I and the difference was also statistically significant (p = 0.0001).

CONCLUSION

In this study, it was found that the decrease in cerebral oxygen saturation was recovered with ISC application. This simple and reliable technique helps to restore cerebral oxygen saturation levels while increasing blood return from the lower extremities.

Effects of Pneumoperitoneum and LPS-induced Endotoxemia on Cerebral Perfusion Pressure in Pigs

Multitrauma patients commonly develop abdominal compartment syndrome, which is defined as the end result of sustained, uncorrected, intra-abdominal hypertension. We aimed to assess the effects of increased intra-abdominal pressure (IAP) upon intracranial pressure (ICP) and cerebral perfusion pressure (CPP) in the presence or absence of lipopolysacharide (LPS)-induced endotoxemia using an experimental porcine model of pneumoperitoneum. Experimental procedures were approved by the Animal Care Review Committee of the National Veterinary Institute. Sixteen female pigs weighing 20 to 25 kg, aged 3 to 4 months were used. The animal model of increased IAP employed in our studies was produced with intraperitoneal administration of helium at 25 mm Hg under general anesthesia. After induction of pneumoperitoneum, 16 animals were randomly divided into 2 groups of 8 pigs each. One group received LPS intravenously (endotoxin group) and the second group received saline (control group). ICP, CPP, and hemodynamic variables were continuously monitored and recorded. A significant reduction of the cardiac output and concurrent increases in systemic vascular resistance and central venous pressure were observed in both groups after induction of pneumoperitoneum. ICP increased whereas CPP decreased significantly compared with baseline values in both groups after elevation of IAP. After LPS administration (endotoxin group), the cardiac output and mean arterial pressure decreased significantly. The CPP decreased further in the endotoxin group after LPS administration, whereas ICP remained unchanged. IAP increases produce significant increases in the ICP and decreases in the CPP in this animal model. LPS-induced endotoxemia further decreased CPP.

Correlation between intra-abdominal and intracranial pressure in nontraumatic brain injury

OBJECTIVE

To examine on the basis of a large number of measurements whether increased IAP is associated with increased ICP and decreased CPP in ventilated patients with nontraumatic brain injury.

DESIGN AND SETTING

Observational clinical study in the medical and surgical intensive care unit of a tertiary teaching hospital.

PATIENTS

We included 11 patients with nontraumatic brain injury who had an ICP and an IAP-monitoring device because of ischemic (n=4), hemorrhagic (n=5), and metabolic (n=2) encephalopathy.

METHODS

IAP was continuously measured in the stomach, and ICP was continuously measured through an intraventricular catheter; 214 consecutive measurements were compared. Because of repeated measurements in the patients we used analysis of covariance to control for the variation in ICP and CPP between patients.

MEASUREMENTS AND RESULTS

Patients' mean IAP was 3.8-11.8 mmHg, ICP 6.7-15 mmHg, and CPP 70.8-123 mmHg. For ICP the regression coefficient associated with IAP was 0.64+/-0.05 (95% CI 0.56-0.73, partial correlation 0.70) and for CPP -1.36+/-0.3 (95% CI -1.94 to -0.78; partial correlation -0.30).

CONCLUSIONS

Increases in IAP are associated with increases in ICP and decreases in CPP in ventilated patients with nontraumatic brain injury, even at low levels of IAP.

Intra-abdominal hypertension in the critically ill: it is time to pay attention

PURPOSE OF THE REVIEW

There has been an exponentially increasing interest in intra-abdominal hypertension (IAH). Comparison of the published data however is difficult due to the lack of consensus definitions. This review will focus on the available literature from the last 2 years. A Medline and PubMed search was performed using 'intra-abdominal pressure' (IAP), 'intra-abdominal hypertension' (IAH), and 'abdominal compartment syndrome' (ACS) as search items. The aim was to find an answer to the question 'Isn't it time to pay attention to intra-abdominal pressure in the critically ill?'

RECENT FINDINGS

Although the number of studies published on this topic is steadily increasing and confirms the pathophysiologic implications of IAH on end-organ function within and outside the abdominal cavity it remains difficult to compare the literature data because the measurement methods and definitions used are not uniform. Provocative data have been published regarding the interactions between the abdominal and thoracic compartments especially in patients with capillary leak and fluid overload; most of this data raises even more questions than it gives answers and may therefore strengthen the nonbelievers who consider IAP, IAH and ACS as epiphenomena in critically ill patients. Unless the international scientific community does not come forward with clear-cut definitions we will keep comparing 'apples with oranges.'

SUMMARY

It is time to pay attention to intra-abdominal pressure in the critically ill. It is also time for standardized IAP measurement methods, good consensus definitions and randomized interventional studies.

Papel da laparoscopia no trauma abdominal penetrante

OBJETIVO: O papel da laparoscopia na redução da taxa de laparotomias não-terapêuticas e da morbidade em pacientes vítimas de trauma abdominal penetrante tem sido amplamente discutido durante os últimos anos. O objetivo do presente estudo é relatar a experiência inicial de um hospital universitário no manejo laparoscópico de pacientes com trauma abdominal penetrante. MÉTODO: Durante um período de três anos, a laparoscopia foi realizada em 37 pacientes vítimas de trauma abdominal penetrante, hemodinamicamente estáveis. Os prontuários médicos foram revisados e os parâmetros analisados foram as indicações do procedimento, lesões associadas, necessidade de conversão, tempo de permanência hospitalar e complicações. RESULTADOS: Houve 18 (48,6%) casos de laparoscopias diagnósticas (LD) positivas e 19 (51,4%) negativas. Dos pacientes com LD positiva, oito (44,4%) foram submetidos à laparotomia exploradora com finalidade terapêutica ou para melhor delineamento da lesão. Houve 10 (55,6%) LD positivas nas quais não foi realizada conversão para cirurgia aberta. Quatro pacientes apresentaram lesões reparáveis laparoscopicamente, sendo realizado hepatorrafia (n=2) e frenorrafia (n=2). Os outros seis pacientes apresentavam lesões isoladas sem sangramento ativo, e a laparotomia não-terapêutica foi evitada. Os pacientes receberam dieta no primeiro dia de pós-operatório e o tempo médio de hospitalização foi de 3,8 dias. CONCLUSÕES: Nossa experiência inicial confirma que a laparoscopia é um bom método de avaliação e tratamento no trauma penetrante. A morbidade relacionada à laparotomias desnecessárias pode ser minimizada quando o procedimento é bem indicado, e o tratamento pode ser realizado com sucesso em casos selecionados.

Anaesthesia for laparoscopic urological surgery

Laparoscopy for urological surgery is a relatively recent surgical innovation. Some centres have substantial experience of single operations, but very few have experience with a comprehensive range. Our programme began with nephrectomy and pyeloplasty, and has expanded to provide for a living related kidney donor programme and for other procedures usually conducted open. Recently, it has included prostate and bladder cancer surgery. The learning curve and implications for anaesthesia are described on the basis of the experience of one anaesthetist with 124 patients. Perioperative care issues, in common with other abdominal laparoscopic procedures, relate to operating positions, the consequences of carbon dioxide under pressure in the abdomen and postoperative analgesia. There is only a small requirement for regional anaesthesia supplementation and invasive analgesia. The corporate laparoscopic cholecystectomy experience was used as the foundation for anaesthesia and to delineate specific organ system issues and any interventions. Significant differences were found in the spectrum of the urological patient population and comorbidity, notably renal function or dysfunction, and complications.

Laparoscopic surgery in a patient with ventriculoperitoneal shunt: monitoring of shunt function with transcranial Doppler

We describe the use of transcranial Doppler (TCD) monitoring during laparoscopic resection of an ovarian cyst in a young woman who previously underwent ventriculoperitoneal shunting for hydrocephalus. Shunt function was not altered by pneumoperitoneum, except during transient episodes of high intra-abdominal pressure. The role of TCD monitoring during laparoscopic procedures in patients with cerebrospinal fluid shunt is discussed.

Transcranial Doppler Monitoring During Laparoscopic Anterior Lumbar Interbody Fusion

We studied the consequences on cerebral hemodynamics of lengthy laparoscopic procedures requiring pneumoperitoneum and head-down positioning. From October 1995 to April 1999, 17 ASA status I or II patients (16 women and 1 man; mean age, 38 yr) were treated with laparoscopic anterior lumbar fusion. Besides standard perioperative monitoring for laparoscopic surgery, the mean blood-flow velocity of both middle cerebral arteries and the pulsatility index were determined by transcranial Doppler ultrasound. Adequate acoustic windows were encountered in 11 of the 17 patients, and the remaining 6 were excluded from the analysis. PaCO(2) and end-tidal CO(2) were maintained within normal limits (<40 mm Hg); ventilation was optimized in all cases. There was a significant increase (P < 0.05) in heart rate and central venous pressure with the change from supine to head-down position in all patients. Transcranial Doppler results for mean middle cerebral artery blood-flow velocity and pulsatility index showed no significant variations at any of the four time points studied during the procedure. There were no technique-related complications, except for moderate postoperative headache in eight patients that resolved with rest and oxygen therapy. We conclude that lengthy laparoscopic procedures in the head-down position performed in otherwise healthy patients do not significantly affect intracranial circulation.

IMPLICATIONS

This study assessed the consequences of lengthy laparoscopic surgery with head-down (Trendelenburg) positioning on cerebral blood circulation by transcranial Doppler ultrasound, a noninvasive technique. It is important to investigate whether there are cerebral hemodynamic changes because these may be detrimental to some patients for whom this surgery is considered.

The Value of Laparoscopy in Management of Abdominal Trauma

The role of laparoscopy (LS) in abdominal trauma is controversial. Concerns remain regarding missed injuries and safety. Our objective for this study was to determine the safety and better define the role of LS in abdominal trauma victims. We performed a retrospective review of all patients who sustained abdominal trauma and underwent LS in a level I trauma center. The main outcome measures were age, gender, mechanism of injury (MOD, indication for laparoscopy, presence of intra-abdominal injury (IA), therapeutic laparoscopy (TxLS), need for laparotomy, length of hospital stay (LOS), missed injuries, complications, and deaths. Forty-eight patients underwent LS (62 per cent male; average age, 28 years; MOI, 35 (85%) penetrating, 7 (15%) blunt; mean ISS, 8). At laparoscopy, 58 per cent of patients had no intra-abdominal injury. IA injury was treated with laparotomy in 14 (29%) and TxLS in 6 (13%). One patient had a negative laparotomy (2%). No injuries were missed. No patients required reoperation. There was one complication: a pneumothorax. There were no deaths. LS was most valuable in penetrating trauma, avoiding laparotomy in more than two-thirds of patients with suspected intra-abdominal injury. LS can serve as a useful adjunct for the evaluation of blunt trauma. In a level I trauma center with LS readily available, the procedure is associated with a low rate of complications and missed injury.

The dangers of diagnostic laparoscopy in the head injured patient

Pneumoperitoneum during laparoscopy has been known to result in a rise in intracranial pressure (ICP) in experimental studies. There are no reports of the effect of pneumoperitoneum during diagnostic laparoscopy in patients suffering closed head injuries. We present the case of a 39 year old male with a closed head injury. Diagnostic laparoscopy was performed while intracranial pressure was monitored. ICP increased from 9 mmHg to over 60 mmHg within 10 min of pneumoperitoneum. Laparoscopy was terminated and the ICP returned to normal levels within 35 min. The authors recommend that pneumoperitoneum laparoscopy should not be used in the trauma setting where head injury is suspected.

Laparoscopic surgery of the liver and biliary tract

Laparoscopic treatment of liver and biliary tract disease is growing in popularity but requires extensive experience. Among the lesions now managed with minimally invasive methods are simple cysts, polycystic liver disease, hydatid cysts, biliary stones, and benign solid tumors. Patient selection, surgical techniques, and outcomes are described.

Anaesthetic considerations for laparoscopic cholecystectomy

Minimally invasive surgical procedures aim to minimize the trauma of the interventional process but still achieve a satisfactory therapeutic result. Tissue trauma is significantly less than that with conventional open procedures, offering the advantages of reduced post-operative pain, shorter hospital stay, more rapid return to normal activities and significant cost savings. Laparoscopic cholecystectomy is now a routinely performed procedure and has replaced conventional open cholecystectomy as the procedure of choice for symptomatic cholelithiasis. Public expectation and developments in instrumentation have fuelled this change. The physiological effects of intraperitoneal carbon dioxide insufflation combined with variations in patient positioning can have a major impact on cardiorespiratory function, particularly in elderly patients with co-morbidities. Intra-operative complications may include traumatic injuries associated with blind trocar insertion, gas embolism, pneumothorax and surgical emphysema associated with extraperitoneal insufflation. Appropriate monitoring and a high index of suspicion can result in early diagnosis of, and treatment of, complications. Laparoscopic cholecystectomy has proven to be a major advance in the treatment of patients with symptomatic gallbladder disease.

Low-pressure laparoscopy may ameliorate intracranial hypertension and renal hypoperfusion

BACKGROUND

Increased abdominal pressure is associated with elevations in the intracranial pressure (ICP) and impaired renal function. These adverse effects are potentially important in clinical situations such as severe abdominal trauma and laparoscopic donor nephrectomy. It was hypothesized that the secondary elevation of ICP leads to release of vasoconstrictors, which may affect renal function by decreasing the renal blood flow (RBF). We investigated the effect of laparoscopy on ICP and renal blood flow in a porcine model.

MATERIALS AND METHODS

The abdominal pressure of swine (N = 5; 20-25 kg) was gradually increased from baseline to 5, 15, and 25 mm Hg by insufflation of nitrogen into the abdominal cavity. The ICP was measured using a Camino monitor, and RBF was simultaneously measured using a Transonic Doppler probe placed on the renal artery. Results were analyzed using repeated measures ANOVA and the paired t-test.

RESULTS

No significant change from baseline was observed in ICP and RBF when the abdominal pressure was 5 mm Hg. However, both ICP and RBF were affected by increasing the abdominal pressure to 15 and 25 mm Hg (P = 0.035 and 0.04 for ICP and P = 0.074 and 0.034 for RBF, respectively).

CONCLUSIONS

Low-pressure laparoscopy may reduce the adverse effects of pneumoperitoneum on ICP and RBF. It may be advisable to use low pressures in laparoscopic surgery, especially when changes in ICP or renal perfusion may have significant clinical implications.

Effects of carbon dioxide pneumoperitoneum on cerebral hemodynamics in pigs

Previous studies have shown that laparoscopic interventions are associated with increases in intracranial pressure. However, the consequences on cerebral blood flow (CBF) are unknown. This study investigates the effects of carbon dioxide (CO2) pneumoperitoneum on CBF in pigs. Ten pigs (weight, 20-26 kg) were anesthetized with 1.4% isoflurane and fentanyl (1 microg/kg per minute). Mechanical ventilation (fraction of inspired oxygen = 0.4) was set to maintain normocapnia (end-tidal CO2 tension = 35 mm Hg). Arterial and central venous catheters were placed for measurement of mean arterial blood pressure and central venous pressure. Bilateral internal carotid artery blood flow was measured using two transient time flow probes placed around both carotid arteries (with ligated external carotid arteries). Cortical and subcortical cerebral blood flow was measured using laser Doppler flowmetry. Sagittal sinus pressure was measured via a superior sagittal sinus catheter. After baseline measurements, the peritoneal cavity of the animals was insufflated with CO2 to achieve an intraabdominal pressure of 12-mm Hg. After 10 minutes of stable CO2, pneumoperitoneum measurements were repeated. Increases in central venous pressure (6.3 +/- 2.1 to 11.1 +/- 3.0 mm Hg) and sagittal sinus pressure (8.0 +/- 2.8 to 11.9 +/- 3.0 mm Hg) were noted during CO2 pneumoperitoneum (P < .05). Bilateral internal carotid artery blood flow (46.0 +/- 7.4 vs 47.7 +/- 7.1 mL/100g per minute), cortical CBF (263 +/- 115 vs 259 +/- 158 tissue perfusion units), and subcortical CBF (131 +/- 145 vs 133 +/- 149 tissue perfusion units) did not change during CO2 pneumoperitoneum. The current data show that CO2 pneumoperitoneum increases sagittal sinus pressure without changing CBF. Increases in sagittal sinus pressure are likely related to decreases in cerebral venous drainage caused by increases in intraabdominal pressure.

Physiologic changes during laparoscopy

The short-term benefits of minimal access techniques include less pain, early mobilization, and shorter hospital stay. Nonetheless, significant data have accumulated regarding the complications associated with laparoscopic techniques, including those that are unique to laparoscopic surgery such as bile duct injury and disruption of major blood vessels. Other problems such as myocardial ischemia and respiratory acidosis are associated with the cardiopulmonary effects of pneumoperitoneum and systemic CO2 absorption. These physiologic changes, although tolerated by healthy patients, could have particular adverse consequences for infirm and critically ill patients. It would appear that minimizing IAP during insufflation decreases the risk of potentially marked cardiovascular changes and regional blood flow alterations. In turn, this could arguably decrease the risk of perioperative myocardial events, or organ dysfunction or failure. Laparoscopy in the critically ill patient is questionable because the role is not established. An ICU patient has little to gain from the benefits of early mobilization. Conversely, in the presence of raised ICP or borderline organ function, the physiologic changes associated with pneumoperitoneum and laparoscopy could have profound detrimental effects.