Cardiovascular responses to prolonged carbon dioxide pneumoperitoneum in neonatal versus adolescent pigs

Partial amniotic carbon dioxide insufflation for fetal surgery

Partial amniotic carbon dioxide insufflation (PACI) involves insufflating the amniotic sac with carbon dioxide (CO₂ ) and, in some cases, draining some of the amniotic fluid. The creation of a gaseous intra-amniotic compartment improves visualization, even in the presence of limited bleeding, and creates the work space required for complex fetoscopic procedures. Clinically, PACI is mostly used to perform fetoscopic myelomeningocele (MMC) repair, enabling a minimally invasive alternative to open fetal surgery. However, evidence of the fetal safety of PACI is limited. Previous animal experiments in sheep demonstrate that PACI induces fetal hypercapnia and acidosis with largely unknown short and longer term implications. In this review, we examine the literature for the physiological effects of intrauterine insufflation pressure, duration, humidity, and the role of maternal hyperventilation on fetal physiology and well-being.

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 effect of intermittent intraabdominal pressure elevations and low cardiac output on the femoral to carotid arterial blood pressure difference in piglets

BACKGROUND

Our previous work in a laparoscopic setting in piglets revealed that the systolic femoral artery pressure was approximately 5 % higher than its carotid counterpart, whereas the mean and diastolic values showed no significant difference. This remained idem when the intraabdominal pressure (IAP) was gradually increased. In this study, we aimed to investigate the effect of (1) intermittent IAP elevations and (2) a low cardiac output (CO) on the blood pressure (BP) difference cranially (carotid artery) and caudally (femoral artery) of a capnoperitoneum (ΔP = P _{a fem}-P _{a carot}).

METHODS

A total of twenty-two piglets (mean body weight 11.0 kg; range 8.9-13.3 kg) were studied. Of these, 14 underwent intermittent IAP elevations at 8 and 16 mmHg, and ΔP was measured. In another 8 piglets, a model of reduced CO was created by introducing an air embolism (2 ml/kg over 30 s) in the inferior caval vein (VCI) at 12 mmHg IAP to further assess the influence of this variable on ΔP.

RESULTS

Systolic ΔP remained at a mean of 5.6 mmHg and was not significantly affected by insufflation or exsufflation up to an IAP of 16 mmHg. Diastolic and mean values showed no differences between P _{a carot} and P _{a fem}. P _{a fem, systol} remained higher than its carotid counterpart as long as the cardiac index (CI) was above 1.5 l/min/m², but fell significantly below P _{a carot, systol} at a low CI. There was no CO-dependent effect on diastolic and mean ΔP. Repeated IAP elevations do not significantly influence ΔP.

CONCLUSIONS

Intermittent IAP elevations do not significantly influence ΔP. Despite of a CO-dependent inversion of systolic ΔP, mean BP measurements at the leg during laparoscopy remain representative even at low CO values.

Awake caudals and epidurals should be used more frequently in neonates and infants

The current literature provides fundamental insights regarding the neurotoxic potency of various general anesthetic drugs in neonates and small infants. Therefore, considerations to minimize the use of general anesthetic drugs in this age group are required. The use of caudal and epidural anesthesia under sedation is one possibility to minimize the use of general anesthetic drugs. A large number of surgical procedures can be managed with this anesthetic concept. Training, practical hand skills, good infrastructure, a well-defined indication, and a team approach including the entire operation room staff are the major prerequisites to implement these techniques in the daily clinical practice. This review article discusses all present aspects and possible future evolutions of caudal and epidural anesthesia under sedation.

Minimal invasive surgery in the newborn: current status and evidence

The evolution of minimally invasive surgery (MIS) in the newborn has been delayed due to the limited working space and the unique physiology. With the development of smaller instruments and advanced surgical skills, many of the initial obstacles have been overcome. MIS is currently used in specialized centers around the world with excellent feasibility. Obvious advantages include better cosmesis, less trauma, and better postoperative musculoskeletal function, in particular after thoracic procedures. However, the aim of academic studies has shifted from proving feasibility to a critical evaluation of outcome. Prospective randomized trials and high-level evidence for the benefit of endoscopic surgery are still scarce. Questions to be answered in the upcoming years will therefore include both advantages and potential disadvantages of MIS, especially in neonates. This review summarizes recent developments of MIS in neonates and the evidence for its use.

Enthusiasm, evidence and ethics: the triple E of minimally invasive pediatric surgery

Minimally invasive techniques are applicable in more than 60% of abdominal and thoracic operations in children. Enthusiasts promoted these techniques for many years. However, level 1 evidence on advantages of minimally invasive surgery in children remains limited. Randomized controlled trials have been conducted for some types of procedures such as laparoscopic appendectomy, fundoplication, pyloromyotomy, and inguinal hernia repair. The results of these studies confirm some advantages of minimally invasive surgery, but for most types of laparoscopic and all types of thoracoscopic procedures, such data remain to be established. This article also focuses on reports on complications and disadvantages which are relevant for final conclusions and recommendations. The ethical implications of the application of new techniques in children are also discussed. On the basis of evidence based data and ethical principles, minimally invasive techniques may be appropriately used in the future.

Comparison of femoral and carotid blood pressure during laparoscopy in piglets

PURPOSE

The impact of a capnoperitoneum on the known blood pressure (BP) difference of the upper and lower limb was studied in piglets.

METHODS

Eleven German Landrace piglets (body weight, 4.3-7.4 kg; mean body weight, 6.2 kg) were studied. Arterial lines were placed in the right carotid and right femoral artery for pressure monitoring. Intraabdominal pressure levels were increased in steps of 6 mm Hg up to 24 mm Hg.

RESULTS

We found that elevated intraabdominal pressures up to 24 mm Hg did not change the preexisting systolic BP difference between the carotid and femoral arteries. Systolic femoral artery pressure constantly remained 5% higher than its carotid counterpart. In addition, mean and diastolic values were not affected.

CONCLUSIONS

Arterial BP measurements recorded at the legs of piglets when abdominal pressure is increased by up to 24 mm Hg can be used for intraoperative assessment of systemic arterial BP.

Minimally invasive surgery in the neonate

The advent of minimally invasive surgical techniques in the neonate has been delayed due to the limited working space and the unique physiology of the newborn. In the last decade, with the introduction of new instruments and techniques, many of the initial problems have been solved making minimally invasive surgery feasible for a variety of indications in the neonate and a favored approach in specialized centers around the world. Although an increasing number of reports document the feasibility of this exciting technique, data demonstrating its benefit compared to conventional surgery is limited. This review focuses on recent developments in minimally invasive surgery in neonates and the evidence for its use.