Effects of abdominal Co2 insufflation on renal and hepatic blood flows during acute hemorrhage in anesthetized pigs

Prospective, randomized, clinical trial on the effects of laparoscopic insufflation pressures on portal pressures in dogs

OBJECTIVE

The adverse effects of intra-abdominal pressure from capnoperitoneum on cardiovascular and pulmonary systems have been well documented, but the effects on portal pressures in dogs with various insufflation pressures is poorly defined. The aim of the present study was to measure the effect of a range of insufflation pressures on the portal pressure, using direct pressure measurements in patients undergoing laparoscopy.

STUDY DESIGN

Clinical randomized prospective study.

ANIMALS

Nine client-owned dogs undergoing routine laparoscopy.

METHODS

Two rounds of direct portal pressure assessments were performed, at insufflation pressures of 0, 6, 10, and 14 mmHg in a predetermined randomized sequence. The data were analyzed for effects of insufflation pressure, hemodynamic alterations, and round. A best-fit exponential model of the relationship between portal pressure and insufflation pressure was created.

RESULTS

Portal pressure increased by 38% at 6 mmHg, 95% at 10 mmHg, and 175% at 14 mmHg compared to baseline. Portal pressure increased at an average rate of 7.45% per mmHg of insufflation pressure. Effects of weight, weight/insufflation pressure interaction, and round of insufflation were not statistically significant. No systemic hemodynamic adverse events were observed.

CONCLUSION

Portal pressure increased as insufflation pressure increased. There was no clinically significant difference in baseline portal pressure between rounds of insufflation.

CLINICAL SIGNIFICANCE

This exponential model of portal pressure supports the use of the minimum insufflation pressure to allow visualization during laparoscopy. The return of portal pressure to baseline following desufflation supports the comparison of portal pressure measurements before and after laparoscopic shunt attenuation.

Incidence, Risk Factors, and Outcomes of Intra-Abdominal Hypertension in Critically Ill Patients-A Prospective Multicenter Study (IROI Study)

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Objectives:

To identify the prevalence, risk factors, and outcomes of intra-abdominal hypertension in a mixed multicenter ICU population.

Design:

Prospective observational study.

Setting:

Fifteen ICUs worldwide.

Patients:

Consecutive adult ICU patients with a bladder catheter.

Interventions:

None.

Measurements and Main Results:

Four hundred ninety-one patients were included. Intra-abdominal pressure was measured a minimum of every 8 hours. Subjects with a mean intra-abdominal pressure equal to or greater than 12 mm Hg were defined as having intra-abdominal hypertension. Intra-abdominal hypertension was present in 34.0% of the patients on the day of ICU admission (159/467) and in 48.9% of the patients (240/491) during the observation period. The severity of intra-abdominal hypertension was as follows: grade I, 47.5%; grade II, 36.6%; grade III, 11.7%; and grade IV, 4.2%. The severity of intra-abdominal hypertension during the first 2 weeks of the ICU stay was identified as an independent predictor of 28- and 90-day mortality, whereas the presence of intra-abdominal hypertension on the day of ICU admission did not predict mortality. Body mass index, Acute Physiology and Chronic Health Evaluation II score greater than or equal to 18, presence of abdominal distension, absence of bowel sounds, and positive end-expiratory pressure greater than or equal to 7 cm H₂O were independently associated with the development of intra-abdominal hypertension at any time during the observation period. In subjects without intra-abdominal hypertension on day 1, body mass index combined with daily positive fluid balance and positive end-expiratory pressure greater than or equal to 7 cm H₂O (as documented on the day before intra-abdominal hypertension occurred) were associated with the development of intra-abdominal hypertension during the first week in the ICU.

Conclusions:

In our mixed ICU patient cohort, intra-abdominal hypertension occurred in almost half of all subjects and was twice as prevalent in mechanically ventilated patients as in spontaneously breathing patients. Presence and severity of intra-abdominal hypertension during the observation period significantly and independently increased 28- and 90-day mortality. Five admission day variables were independently associated with the presence or development of intra-abdominal hypertension. Positive fluid balance was associated with the development of intra-abdominal hypertension after day 1.

Noninvasive Assessment of Intra-Abdominal Pressure Using Ultrasound-Guided Tonometry: A Proof-of-Concept Study

BACKGROUND

Intra-abdominal hypertension jeopardizes abdominal organ perfusion and venous return. Contemporary recognition of elevated intra-abdominal pressure (IAP) plays a crucial role in reducing mortality and morbidity. We evaluated ultrasound-guided tonometry in this context hypothesizing that the vertical chamber diameter of this device inversely correlates with IAP.

METHODS

IAP was increased in six 5 mmHg steps to 40 mmHg by instillation of normal saline into the peritoneal cavity of eight anesthetized pigs. Liver and renal blood flows (ultrasound transit time), intravesical, intraperitoneal, and end-inspiratory plateau pressures were recorded. For ultrasound-based assessment of IAP (ultrasound-guided tonometry), a pressure-transducing, compressible chamber was fixed at the tip of a linear ultrasound probe, and the system was applied on the abdominal wall using different predetermined levels of external pressure. At each IAP level (reference: intravesical pressure), two investigators measured the vertical diameter of this chamber.

RESULTS

All abdominal flows decreased (by 39%-58%), and end-inspiratory plateau pressure increased from 15 mbar (14-17 mbar) to 38 mbar (33-42 mbar) (median, range) with increasing IAP (all P < 0.01). Vertical chamber diameter decreased from 14.9 (14.6-15.2) mm to12.8 (12.4-13.4) mm with increasing IAP. Coefficients of variations between and within observers regarding change of the vertical tonometry chamber diameter were small (all <4%), and the results were independent of the externally applied pressure level on the ultrasound probe. Correlation of IAP and vertical pressure chamber distance was highly significant (r = -1, P = 0.0004). Ultrasound-guided tonometry could discriminate between normal (baseline) pressure and 15 mmHg, between 15 and 25 mmHg) and between 25 and 40 mmHg IAP (all P ≤ 0.18). Similar results were obtained for end-inspiratory plateau pressures.

CONCLUSIONS

In our model, values obtained by ultrasound-guided tonometry correlated significantly with IAPs. The method was able to discriminate between normal, moderately, and markedly increased IAP values.

Arterioportal shunting, splanchnic capillary perfusion, and the effects of colloids during capnoperitoneum in neonatal and adolescent pigs

BACKGROUND

Clinical and experimental data indicate that neonates are sensitive to the CO₂ pneumoperitoneum. An impaired splanchnic perfusion during laparoscopy in adults has been reported. We recently confirmed that intravenous colloids improve macrocirculatory function in neonates. We aimed to determine the impact of CO₂ pneumoperitoneum on the perfusion of splanchnic organs in the young including effects of colloid application.

METHODS

Male piglets (n = 25) were divided into four groups: (1) neonatal controls, (2) neonates with crystalloid restitution, (3) neonates with colloidal restitution, and (4) adolescents with crystalloid restitution. Animals were ventilated and subjected to a 3-h, 10 mmHg CO₂ pneumoperitoneum followed by 2 h resuscitation. Hepatic, splanchnic, and arteriovenous shunt perfusion was assessed via central and portal venous catheters. Capillary organ flow was detected by fluorescent microspheres. The rate of bile flow was measured.

RESULTS

The neonatal crystalloid group showed a significant decrease in the intestinal capillary perfusion at the end of the recovery period. This was not detectable in the adolescent and colloid group. There was a significant increase in microcirculatory arterioportal shunt flow during the CO₂ pneumoperitoneum in both neonatal groups but not in the sham and adolescent groups (p < 0.05). Hepatic arterial perfusion increased after insufflation in all groups and dropped during capnoperitoneum to levels of about 70% baseline. There was no significant impairment of splanchnic perfusion or bile flow as a result of the pneumoperitoneum in all groups.

CONCLUSIONS

Capillary perfusion of the abdominal organs was stable during capnoperitoneum and recovery in adolescents and neonates with colloid restitution, but not with crystalloid restitution. Significant arterioportal shunting during capnoperitoneum could affect hepatic microcirculation in neonates. Our data confirm that moderate pressure capnoperitoneum has no major effect on the perfusion of abdominal organs in neonates with adequate substitution.

The effects of intra-abdominal hypertension on the secretory function of canine adrenal glands

Intra-abdominal hypertension (IAH) can damage multiple organ systems, but the explicit impact on the adrenal gland is unclear. To evaluate the effects of intra-abdominal pressure (IAP) on the secretory function of the adrenal glands, we established canine models of IAH. By comparing morphology; hemodynamics; plasma cortisol, aldosterone, epinephrine, and norepinephrine concentrations; and the expression of IL-1, IL-6, and TNF-α in adrenal gland tissue from these dogs, we found that hemodynamic instability occurred after IAH and that IAH increased the plasma cortisol, aldosterone, epinephrine, and norepinephrine concentrations. Higher IAPs resulted in more significant changes, and the above indicators gradually returned to normal 2 h after decompression. Compared with the sham-operated group, IAH significantly increased IL-1, IL-6, and TNF-α levels in adrenal tissue, with larger increases in the presence of higher IAPs. However, the concentrations of these markers remained higher than those in the sham-operated group despite their decrease after 2 h of decompression. Histopathological examination revealed congestion, red blood cell exudation, and neutrophil infiltration in the adrenal glands when IAP was elevated; these conditions became more significant with more severe IAH. These results suggest that the secretion of adrenal hormones and adrenal gland inflammation are positively correlated with IAP and that abdominal decompression effectively corrects adrenal gland function.

Perioperative renal protection

Acute kidney injury (AKI) is a significant cause of perioperative patient morbidity and mortality. The definition of AKI has recently changed and further research is underway to identify clinically relevant biomarkers to aid in the diagnosis of the syndrome. AKI is often multi-factorial in origin and patients with certain preoperative risk factors are at elevated risk of perioperative AKI. An anesthesiologist's main objective for perioperative renal protection is prevention by maintenance of euvolemia, preservation of adequate renal perfusion, and avoidance of nephrotoxins. This review will address the definition and diagnosis of AKI, identify patients at risk of AKI, and critically appraise management options for perioperative renal protection.

Abdominal Insufflation Decreases Blood Loss and Mortality after Porcine Liver Injury

BACKGROUND

Uncontrolled intra-abdominal bleeding is a common cause of death in trauma patients in the prehospital and perioperative settings. The detrimental effects of abdominal hypertension are well studied, but the potential therapeutic use of abdominal insufflation for hemostasis has not been fully explored. We measured the effect of abdominal insufflation on blood loss and physiologic outcomes in a swine model of blunt liver injury.

METHODS

Twenty-one anticoagulated swine (32 +/- 3 kg) were anesthesized; laparotomy was performed to localize liver anatomy and to place loose tourniquettes isolating the porta hepatis and supra/infrahepatic vena cava. A captive bolt gun was used to create a grade V hepatic laceration, producing massive parenchymal injury as well as complex tears of the middle and right hepatic veins. Animals were randomized into either control (n = 10) or abdominal insufflation at 20 cm H(2)O pressure (n = 11) groups. Crystalloid was used to maintain a mean arterial pressure of 30 mm Hg. Arterial pressure and other physiologic variables were recorded for 20 minutes. Animals were then sacrificed and blood loss measured.

RESULTS

Blood loss was 69% lower in insufflated animals compared with controls (384 +/- 51 versus 1252 +/- 88 cc, p < 0.001). After 20 minutes, insufflated animals had significantly higher mean arterial blood pressure (32.2 +/- 4.2 versus 21.2 +/- 4.0 mm Hg) and lower total resuscitation volume (195 +/- 83 versus 1356 +/- 95 cc). Three pigs died in the control group (30%), whereas no insufflated animals died (p < 0.05).

CONCLUSION

In a swine model of catastrophic blunt hepatic injury, abdominal insufflation significantly decreased blood loss and mortality.

Is Pneumoperitoneum Harmful During Intra-Abdominal Hemorrhage in Rats?

BACKGROUND

Laparoscopic surgical interventions are being used in trauma patients for diagnostic and therapeutic purposes, but there are limited studies on this subject. The effect of pneumoperitoneum during intra-abdominal hemorrhage has not been elucidated. The aim of this study was to investigate the hemodynamic, respiratory, and renal effects of pneumoperitoneum in the splenic injury/ hemorrhagic shock model in rats.

MATERIAL AND METHODS

In this study, 80 anesthetized Wistar male rats (294.5 +/- 31.2 g) were randomized into 2 main groups: nontraumatized (group A) and traumatized (group B). After initial preparation and monitoring, each group was divided according to the degree of pneumoperitoneum. The nontraumatized subgroups were A1, sham-operated; A2, 4-8 mm Hg; A3, 9-13 mm Hg; and A4, 14-18 mm Hg. The traumatized subgroups were B1, splenic injury without pneumoperitoneum; B2, B3, and B4, splenic injury with pneumoperitoneum at 4-8 mm Hg, 9-13 mm Hg, and 14-18 mm Hg, respectively. Mean arterial pressure, heart rate, and respiratory rate were monitored continuously. Blood samples were obtained for hemoglobin, hematocrit, arterial blood gases, and biochemical analyses. Twenty-four hour urine output was collected.

RESULTS

In group B4, pH, pCO2, and HCO3 levels were lower than in all other groups, while pCO2 and base deficit levels were significantly higher (P < 0.05). Both blood and urine analysis results showed that 24-hour urine output and the glomerular filtration rate of groups A4 and B4 were significantly lower (P < 0.05), while urinary osmolarity and fractional sodium excretion levels were significantly higher (P < 0.05).

CONCLUSION

High-pressure pneumoperitoneum in splenically traumatized rats amplifies acidosis, decreases urine output, decreases glomerular filtration rate, and increases urinary osmolarity and fractional sodium excretion significantly.

Abdominal insufflation for prevention of exsanguination

BACKGROUND

Currently, traumatic intra-abdominal hemorrhage continues unchecked during transport and triage, and a simple technique of prehospital hemostasis might improve outcomes. The hemostatic effect of abdominal hypertension has not been studied.

PURPOSE

To examine the effect of iatrogenic abdominal insufflation on blood loss and hemodynamic performance after major abdominal vascular injury.

METHODS

Following laparotomy, a 2.7 mm hole was created in the inferior vena cava of 10 anticoagulated pigs and controlled with a partially occlusive, laparoscopic vascular clamp. After abdominal closure the clamp was released and the pig was randomized to either control (n = 5) or immediate abdominal CO2 insufflation at 20 cm H2O pressure (n = 5). Lactated Ringer's solution was used as needed to maintain a mean arterial pressure of 60 mm Hg. After 15 minutes of hemorrhage and hemodynamic monitoring, the animals were killed and blood loss measured. Mean blood loss was compared between groups using the Student test, as were final values for physiologic variables. Temporal changes in physiologic parameters were compared using analysis of variance.

RESULTS

Mean blood loss was reduced by 61% in insufflated pigs versus controls (695 +/- 244 versus 1764 +/- 328 cc, p < 0.001). Compared with controls, insufflated pigs had significantly higher mean arterial pressure (64 versus 25 mm Hg, p < 0.001), end-tidal CO2 (40.8 versus 17.8 mm Hg, p < 0.001), and pulmonary capillary wedge pressure (10.2 versus 5.8 mm Hg, p = 0.026) immediately before the pigs were killed.

CONCLUSION

Iatrogenic abdominal insufflation significantly decreased blood loss and improved hemodynamics in a porcine model of traumatic venous hemorrhage. Iatrogenic abdominal insufflation may be useful in the prehospital management of abdominal injury.