Venous gas embolism--a comparison of carbon dioxide and helium in pigs

High intra-abdominal pressure during experimental laparoscopic liver resection reduces bleeding but increases the risk of gas embolism

BACKGROUND

Various recommendations exist regarding intra-abdominal pressure (IAP) during laparoscopic liver resection. A high IAP may reduce bleeding but at the same time increase the risk of gas embolism. This study investigated the effects of two different IAPs during laparoscopic left liver lobe resection in piglets.

METHODS

Sixteen piglets underwent laparoscopic left liver lobe resection using carbon dioxide pneumoperitoneum of either 8 or 16 mmHg (8 per group). A combination of CUSA System 200™ and LigaSure™ instruments was used for parenchymal division. During resection, a standard injury to the left liver vein was also created to increase the risk of bleeding and/or gas embolism during the operation. Heart rate, cardiac output, and arterial, pulmonary arterial, pulmonary capillary wedge and central venous pressures were measured. Arterial blood gases were monitored continuously. Transoesophageal echocardiography was video recorded to detect and quantify gas embolism within the right cardiac ventricle. The duration of operation and bleeding were noted.

RESULTS

High IAP resulted in reduced bleeding (P = 0·016), but gas embolism occurred more frequently (P = 0·001) than with low IAP. Gas embolism disturbed gas exchange, with an increase in arterial pressure of carbon dioxide, and a decrease in arterial partial pressure of oxygen and pH. These effects were sustained for at least 30 min after surgery.

CONCLUSION

High IAP reduces the amount of bleeding but increases the risk of gas embolism. Monitoring for gas embolism is therefore indicated if a high IAP is used during laparoscopic liver resection.

Re-insufflation after deflation of a pneumoperitoneum is a risk factor for CO(2) embolism during laparoscopic prostatectomy -A case report-

Although symptomatic carbon dioxide (CO₂) embolism is rare, it recognized as a potentially fatal complication of laparoscopic surgery. Sudden hemodynamic instability could be a CO₂ embolism especially during insufflation. A 65-year-old man received laparoscopic prostatectomy for 5 hours under CO₂ pneumoperitoneum without any problem. After resection of prostate, it was stopped following deflation. Thirty minutes later, peumoperitoneum was re-induced to continue the operation. Shortly after re-insufflation, the patient revealed hemodynamic instability suggested a CO₂ embolism; severe hypotension, tachyarrythmia, hypoxemia, increased CVP, and changed end-tidal CO₂. Gas insufflation was stopped. He was managed with Durant's position, fluid and cardiotonics for 20 minutes. The residual was completed by open laparotomy. Re-insufflation, inducing gas entry through the injured vessels, might be a risk factor for CO₂ embolism in this case. The risk to the patient may be minimized by the surgical team's awareness of CO₂ embolism and continuous intra-operative monitoring of end-tidal CO₂.

Physiologic changes during helium insufflation in high-risk patients during laparoscopic renal procedures

OBJECTIVES

To assess the efficacy and safety of helium as an insufflant for transabdominal laparoscopic renal surgery.

METHODS

The charts of all patients undergoing laparoscopic renal surgery with helium insufflation by a single physician between May 2003 and April 2006 were reviewed. Ventilatory parameters and postoperative recovery were reviewed.

RESULTS

Ten patients underwent laparoscopic renal surgery with helium. These patients had a mean age of 64 years and suffered from a variety of comorbid conditions, including chronic obstructive pulmonary disease (5), congestive heart failure (1), chronic hypoxia from an intrapulmonary shunt (1), malignant hyperthermia (1), and chronic hypoxia from multiple pulmonary infarcts (1). All patients tolerated helium pneumoperitoneum, with mean O2 saturation of 98.6% +/- 0.6%, end-tidal CO2 31.4 +/- 1.7 mm Hg, respiratory rate 9.3 +/- 0.7 breaths per minute, tidal volumes 598.2 +/- 38.0 mL, and peak airway pressures 26.0 +/- 1.2 cm H2O. One patient developed an end-tidal CO2 of greater than 45 mm Hg. Mean operative time was 146.8 +/- 59 minutes, and estimated blood loss was 280.1 +/- 334 mL. Postoperatively 3 patients required continued maintenance of the endotracheal tube, although none required intubation longer than 22 hours. Five patients had critical care monitoring (1.7 +/- 2.9 days on average).

CONCLUSIONS

Helium can be used safely as an insufflant during laparoscopic renal surgery. Patients who may benefit are those with potential difficulty in clearing CO2 gas from their bloodstream or those who rely on sensitive monitoring of end-tidal CO2 to manage comorbid pathology.

Laparoscopic surgery and the parasympathetic nervous system

BACKGROUND

Laparoscopic surgery preserves the immune system and has anti-inflammatory properties. CO2 pneumoperitoneum attenuates lipopolysaccharide (LPS)-induced cytokine production and increases survival. We tested the hypothesis that CO2 pneumoperitoneum mediates its immunomodulatory properties via stimulation of the cholinergic pathway.

METHODS

In the first experiment, rats (n = 68) received atropine 1 mg/kg or saline injection 10 min prior to LPS injection and were randomization into four 30-min treatment subgroups: LPS only control, anesthesia control, CO2 pneumoperitoneum, and helium pneumoperitoneum. In a second experiment, rats (n = 40) received atropine 2 mg/kg or saline 10 min prior to randomization into the same four subgroups described previously. In a third experiment, rats (n = 96) received atropine 2 mg/kg or saline 10 min prior to randomization into eight 30-min treatment subgroups followed by LPS injection: LPS only control; anesthesia control; and CO2 or helium pneumoperitoneum at 4, 8, and 12 mmHg. In a fourth experiment, rats (n = 58) were subjected to bilateral subdiaphragmatic truncal vagotomy or sham operation. Two weeks postoperatively, animals were randomized into four 30-min treatment subgroups followed by LPS injection: LPS only control, anesthesia control, CO2 pneumoperitoneum, and helium pneumoperitoneum. Blood samples were collected from all animals 1.5 h after LPS injection, and cytokine levels were determined by enzyme-linked immunosorbent assay.

RESULTS

Serum tumor necrosis factor-alpha (TNF-alpha) levels were consistently suppressed among the saline-CO2 pneumoperitoneum groups compared to saline-LPS only control groups (p < 0.05 for all four experiments). All chemically vagotomized animals had significantly reduced TNF-alpha levels compared to their saline-treated counterparts (p < 0.05 for all), except among the CO2 pneumoperitoneum-treated animals. Increasing insufflation pressure with helium eliminated differences (p < 0.05) in TNF-alpha production between saline- and atropine-treated groups but had no effect among CO2 pneumoperitoneum-treated animals. Finally, vagotomy (whether chemical or surgical) independently decreased LPS-stimulated TNF-alpha production in all four experiments.

CONCLUSION

CO2 pneumoperitoneum modulates the immune system independent of the vagus nerve and the cholinergic pathway.

The effects of experimental venous carbon dioxide embolization on hemodynamic and respiratory variables

BACKGROUND

Laparoscopic liver resection is a relatively new surgical procedure. Carbon dioxide (CO2) pneumoperitoneum and laparoscopic liver dissection are recognized as risk factors for CO2 embolism to the pulmonary circulation. The embolization can be difficult to detect and can theoretically increase peri-operative morbidity. The aim of this study was to evaluate the cardiopulmonary effects in a pig model during a time period of 4 h after an experimental CO2 embolization.

METHODS

Eleven piglets were anesthesized. Nine were embolized with a single intravenous injection of 0.4 ml/kg CO2 and two served as controls. Respiratory and cardiovascular variables, including pulmonary artery pressure and cardiac output, were monitored for 4 h after embolization, and arterial blood gases were monitored on-line.

RESULTS

The embolized piglets had an increase in ventilatory dead space, pulmonary vascular resistance and pulmonary artery pressure and a decrease in cardiac output that lasted throughout the 4-h observation time. The mean arterial pressure and heart rate were unchanged. An early sign of embolization was a rapid fall in end-tidal CO2 and P(a)O2 and a rise in P(a)CO2.

CONCLUSION

Negative changes in cardiopulmonary physiology persisted for at least 4 h after a single intravenous CO2 injection, in spite of this gas being highly soluble in blood. This is a more prolonged influence of CO2 embolization than previously described. Extensive monitoring for early detection of an embolization may be recommended to limit morbidity in patients undergoing laparoscopic liver surgery.

Adverse cerebrovascular effects of intraarterial CO2 injections: development of an in vitro/in vivo model for assessment of gas-based toxicity

PURPOSE

To assess whether and how CO(2) can cause ischemic injury in the central nervous system after internal carotid artery injection.

MATERIALS AND METHODS

In 14 adult pigs, both internal carotid arteries were catheterized via a transfemoral approach. One carotid artery served as control and the other was injected via a prototype gas injector with defined volumes and pressures of gas. Effects were assessed by clinical observation, repeated magnetic resonance (MR) imaging, histopathology, and vital staining. An in vitro flow circuit was used to model injection parameters.

RESULTS

Single injections of CO(2) did not produce persistent clinical symptomatology. In vitro conditions were created in which bubbles adhered to the tubing of the circuit, creating functional stenoses, or coalesced into larger bubbles that became trapped, thereby reducing flow and augmenting potential embologenic effects of subsequent injections. With in vitro-derived dual injection parameters, seven pigs underwent two sequential injections of CO(2). All did well after the first injections, but all had adverse effects after the second injections, including involuntary tonic-clonic muscular movements, cardiopulmonary arrest, recurrent intractable seizure activity during recovery, hemorrhagic venous infarcts on gross and histopathologic examination, and blood-brain barrier breakdown on vital staining. MR imaging was not sensitive even after symptomatic intraarterial air injection.

CONCLUSIONS

Absence of adverse effects after single bolus injections in pigs does not prove the safety of intracranial CO(2) injections in human patients. Considering the possible deleterious effects of repeat intravascular injections in the highly sensitive system of the brain, it may be prudent for clinical application at other approved sites to let time pass between boluses sufficient to permit absorption of wall-adherent and coalescent bubbles that could cause gas embolic events.

Influence of different gases used for laparoscopy (helium, carbon dioxide, room air, and xenon) on tumor volume, histomorphology, and leukocyte-tumor-endothelium interaction in intravital microscopy

BACKGROUND

Previous studies indicate that helium pneumoperitoneum used for laparoscopic surgery suppresses whereas carbon dioxide pneumoperitoneum increases postoperative tumor growth. The pathomechanisms of decreased tumor growth by helium are unknown. This study was designed to examine the effect of the gases helium, carbon dioxide (CO(2)), and air, and xenon, which can be used to induce pneumoperitoneum in laparoscopy on tumor volume, histomorphology, and leukocyte-endothelium interaction measured by intravital microscopy in rats with implanted liver malignoma (Morris hepatoma 3924A).

METHODS

In 46 rats, Morris hepatoma 3294A cells were implanted intrahepatically. After implantation, rats were randomized into two main groups. In the first main group, 10 animals were prepared for examination of leukocyte-endothelium interaction by intravital video microscopy and were randomized into two groups. Five days after implantation they underwent laparoscopy using either helium (n = 5) or CO(2) (n = 5). Ten days after implantation the rats underwent intravital video microscopy to assess leukocyte-endothelium interaction in the tumor and liver vessels. In the second main group 36 rats were prepared for examination of tumor volume arid histomorphology. They were randomized into five groups. Five days after implantation they underwent laparoscopy using helium (n = 7), carbon dioxide (n = 7), room air (n = 7), or xenon (n = 8). The control group (n = 7) received anesthesia only. Rats were killed 10 days after tumor implantation to assess tumor volume and histomorphology.

RESULTS

Compared to the control group or groups that received CO(2), room air, or xenon for pneumoperitoneum, the establishment of helium pneumoperitoneum caused a significantly smaller tumor volume (Kruskal-Wallis test, p = 0.001; median tumor-volume: control group, 44 mm(3); helium 19 mm(3)). There was no significant difference in histomorphology between the groups. There was only a statistically significant difference in the development of central tumor necrosis in accordance to tumor volume (Mann-Whitney test, p = 0.03). In the tumor samples, roller counts were statistically significantly higher in the helium group compared to the CO(2) group (p = 0.04). For sticker counts, no statistically significant effects due to liver/tumor (p = 0.13) or treatment (p = 0.48) were observed.

CONCLUSIONS

There was a significant decrease in tumor volume using helium pneumoperitoneum for laparoscopy compared to the other gases. Here, we demonstrate that suppression of tumor growth is not due to variation of histomorphology. It seems that helium pneumoperitoneum effects a higher leukocyte-endothelium interaction and thereby a higher immune activation. This could be one explanation for the statistically significantly smaller tumor volume after laparoscopy with helium compared to laparoscopy with CO(2).

Peritoneal pH during laparoscopy is dependent on ambient gas environment: helium and nitrous oxide do not cause peritoneal acidosis

BACKGROUND

Little is know about the effects of different insufflation gases on peritoneal pH during laparoscopy. However, these changes may influence the intracellular signalling system, resulting in altered cell growth or adhesiveness. The aim of this study was to determine the effects of carbon dioxide (CO(2)), nitrous oxide (N(2)O), and helium (He) on parietal and visceral peritoneal pH. The effect of different intraabdominal pressures on parietal and visceral peritoneal pH was also examined.

METHODS

We conducted both an ambient gas study and a pressure study. For the ambient gas study, 20 pigs were divided into the following four groups: (a) CO(2), (b) He, (c) N(2)O, and (d) abdominal wall lift (Lift) laparoscopy. Parietal and visceral peritoneal pH were measured at 15 min intervals for 180 min. For the pressure study, 15 pigs were divided into the following three groups: (a) CO(2), (b) He, (c) N(2)O laparoscopy. Baseline values were established for parietal and visceral peritoneal pH. Intraabdominal pressure was then increased stepwise at 1-mmHg intervals to 15 mmHg. After pressure was maintained for 15 min at each setting, parietal and visceral peritoneal pH were measured.

RESULTS

Ambient gas environment was the major determinant of parietal peritoneal pH. Carbon dioxide caused parietal peritoneal acidosis. Helium, N(2)O, and Lift caused alkalotic parietal peritoneal pH. Intraabdominal pressure had a minor effect on parietal peritoneal pH. At higher intraabdominal pressure (12-15 vs 5-8 mmHg), CO(2) caused a slight decrease in parietal peritoneal pH, whereas N(2)O and He caused a slight increase in parietal peritoneal pH. Visceral peritoneal pH remained relatively unaffected during all studies.

CONCLUSIONS

Parietal peritoneal pH during laparoscopy was highly dependent on the ambient gas environment. The effect of intraabdominal pressure on parietal peritoneal pH was of minor significance. Carbon dioxide caused a slight worsening of parietal peritoneal acidosis at higher intraabdominal pressure, whereas, N(2)O, He, and Lift did not cause parietal peritoneal acidosis.

When the blood-back detection system fails: an IABP case report

A 74-year-old male patient's circulation was supported by an intra-aortic balloon for a period of six days following multiple cardiac infarcts. On the sixth day, several 'leak in IAB circuit' alarms appeared. The nursing staff checked the tubing and refilled the balloon, as described in the manual, without notifying the medical staff or perfusionist. A few hours later, the balloon showed a leak, as blood was seen in the catheter tubing. This leak resulted in considerable damage to the device caused by a large amount of blood migrating back to the tubing and flooding the internal drive system, due to a failing 'blood detection' sensor. The balloon catheter was removed percutaneously and intra-aortic counterpulsation was discontinued. The patient died 20 days later of heart failure. This raises doubts over the adequacy of the protective sensors of such devices and, importantly, how to interpret the present user manuals and the instructions for troubleshooting.

Efeitos do pneumoperitônio com ar e CO2 na gasometria de suínos

OBJETIVO: O pneumoperitônio produz várias alterações na fisiologia humana. Algumas destas alterações, como hipercapnia e acidose, dependem ou são agravadas com o uso de CO2, tendo maior repercussão em pacientes com problema cardio-respiratório. A necessidade de uma melhor alternativa para insuflação da cavidade; a observação de que as cirurgias abertas, assim como as laparoscópicas com suspensão mecânica, são realizadas na presença de Ar ambiente; e a escassez de trabalhos testando o Ar em substituição ao CO2 para insuflação da cavidade, foram motivos para a realização deste trabalho. MÉTODOS: Vinte (0) suínos anestesiados foram submetidos a pneumoperitônio com 1 hora de duração. Os animais foram distribuídos em 4 grupos de 5 animais: Grupo A1 - Pneumoperitônio de Ar a 10 mmHg; Grupo A - Pneumoperitônio de Ar a 16 mmHg; Grupo B1 - Pneumoperitônio de CO2 a 10 mmHg; Grupo B - Pneumoperitônio de CO2 a 16 mmHg. O pneumoperitônio foi realizado pela técnica aberta com trocater de Hasson. Através de um cateter venoso central colhe-se amostra de sangue para exame de gasometria em 3 momentos. RESULTADOS: A análise da gasometria venosa não revelou alterações significativas entre os grupos em relação a PaO2 e a saturação do O2. Nos Grupos A1, A e B1 não foram observadas alterações no equilíbrio ácido-básico. No Grupo B após uma hora de pneumoperitônio houve nítida tendência a hipercapnia e acidose. CONCLUSÃO: O ar, com a técnica aberta de pneumoperitônio foi uma opção segura para insuflação de cavidade em procedimentos laparoscópicos diagnósticos de suínos.

Influence of different gases used for laparoscopy (helium, carbon dioxide, room air, xenon) on tumor volume, proliferation, and apoptosis

BACKGROUND

Previous reports suggest that helium pneumoperitoneum used for laparoscopic surgery suppresses postoperative tumor growth. The present study was designed to determine the effects of gases used in laparoscopy on tumor volume, proliferation, and apoptosis in rats with implanted malignoma.

METHODS

In 36 rats Morris hepatoma 3294A cells were implanted intrahepatically. Then, after 5 days, they underwent laparoscopy using helium ( n = 7), CO(2) ( n = 7), room air ( n = 7), or xenon ( n = 8). One group received anesthesia only ( n = 7). Rats were killed 10 days after implantation to assess tumor volume, proliferation, and apoptosis.

RESULTS

Helium pneumoperitoneum caused a significant smaller tumor volume compared to other groups (Kruskal-Wallis test: p = 0.001; median tumor volume: control: 44 mm3; helium: 19 mm3). There was no significant difference in tumor cell proliferation (PCNA) and apoptosis (TUNEL reaction) between the groups.

CONCLUSIONS

There was a significant decrease of tumor volume using helium pneumoperitoneum compared to the other gases, but no decreased tumor cell proliferation or increased tumor cell apoptosis.

Anaesthesia for minimally invasive surgery in children

There continues to be an increase in the applications of minimally invasive surgical techniques in infants and children. This increase includes their use for new surgical procedures as well as their application in younger patients including neonates. As with any new surgical procedure, specific modifications of the anaesthetic technique may be necessary. This chapter reviews (1) the pre-operative evaluation of infants and children scheduled for minimally invasive surgery; (2) techniques for pre-medication and anaesthetic induction; (3) intra-operative anaesthetic implications of laparoscopy, including the cardiorespiratory consequences of CO2 pneumoperitoneum; (4) intra-operative anaesthetic implications of thoracoscopy, including techniques for one-lung ventilation (OLV); and (5) post-operative issues, including pain management and monitoring of cardiorespiratory function as they apply to the patient of paediatric age.

Extending the limits: minimally invasive surgery

Minimally invasive technology is being applied to an increasing number of surgical procedures. It remains to be seen which techniques will eventually become a 'gold standard' as has the laparoscopic cholecystectomy, and which will fall by the wayside. In the meantime, anesthesiologists must be aware of the unique requirements and complications of laparoscopic surgery.