Why is carbon dioxide used in surgical procedures

Carbon Dioxide in Surgery

Facts and Figures

Current atmospheric CO2 levels are 0.04%

CO2 levels of 0.12% are considered to effect brain metabolism and neural activity 

The density of CO2 is 1.5 times that of air

CO2 is 25 times more soluble in blood and tissue than air is at 37 – 38 °C (Ng and Rosen., 1968)

Why Use CO2 During Surgery?

There are three known benefits to using CO2 during surgical procedures:

1. EMBOLI – CO2 insufflation over a surgical wound displaces the available air. Since CO2 is 25 times more soluble in blood and tissue than air is (at 37°C), arterial CO2 emboli are much better tolerated than air emboli. 

2. INFECTION- CO2 has antimicrobial properties, reducing the incidence rate of surgical site infections.

3. HEALING – CO2 enhances wound healing by enabling the Bohr Effect, resulting in a higher off-load of oxygen from haemoglobin to the surrounding blood and tissues.

EMBOLI: Preventing Air Embolism by Displacing the Available Air 

with Carbon Dioxide.

This process was first reported as a means of preventing cerebral or myocardial damage during open heart surgery procedures in 1967 (Selman et al., 1967). The carbon dioxide is insufflated into the thoracic cavity, it fills the cavity by gravity and replaces the air by displacement. Transoesophageal echocardiography has shown a reduction in the number of intracardiac emboli during procedures where CO2 has been used.

A study in 1968 found that 0.5 ml/kg of air placed into a carotid artery of dogs always sees severe neurological damage, whereas 4 to 8ml /kg of CO2 produced transient signs in only 33% of dogs and in all cases a full recovery was made. (Ng and Rosen., 1968)

Other studies have also reported that CO2 arterial emboli are much better tolerated than air emboli. ( More and Braselton., 1940) (Eguchi and Bosher., 1962)  (Kunkler and King., 1959) (Eguchi et al., 1963) (Goldfarb and Bahnson., 1963) (Spencer et al., 1965)

Several studies conducted a decade ago found that using an open-ended piece of tubing to insufflate the CO2 caused a high velocity jet into the open surgical wound; creating turbulence and thus a poor de-airing efficiency. (Persson et al., 2004) It is more beneficial to use a device that has a diffusing tip as a final exit point for the CO2. This enables the gas flow to be delivered with a low velocity output, reducing the turbulence and enabling efficient de-airing of the thoracic cavity.

INFECTION: CO2 has antimicrobial properties, reducing the rate of surgical site infections.

Carbon dioxide has a dual physiological role in microorganisms since it can either stimulate or inhibit the cell development. (Debs-Louka et al., 1999) Carbon dioxide has been used as a means of preserving liquid and solid foodstuff since the 1930s, owing to its inhibitory effect. (Dixon and Kell., 1989) (Donald et al., 1924) Haas et al., 1989) (Wei et al., 1991).

Before recent times the use of carbon dioxide in the treatment of surgical site infections has been considered impractical. CO2 is now widely used for laparoscopic colorectal surgery (LCS). When these procedures are compared to open colorectal surgery (OCS) they have been shown to develop 40% less surgical site infections (SSI). (Aimag et al., 2011)  (Richards et al., 2003)

Richards et al analysed results from 54,504 inpatient cholecystectomy procedures undertaken between 1992 and 1999. During this period the use of the laparoscopic technique, as opposed to open cholecystectomy, increased from 59% in 1992 to 79% in 1999. The laparoscopic technique is less invasive, requires shorter hospitalisation and is associated with faster recovery rates when compared to open cholecystectomy. The risk of surgical site infections was lower in patients undergoing the laparoscopic technique. Infecting organisms were found to be similar. Carbon dioxide is the most widely used gas during laparoscopic procedures.

Inhibition of bacterial growth has been reported for the pathogen Staphylococcus Aureus.(Persson et al., 2004) In this study SSI data was collected for 342 patients, of which 116 had undergone laparoscopic technique with the remaining  226 undergoing an open procedure. The risk of SSI was significantly lower for laparoscopic cholecystectomy.

A study of 122 patients (LCS 43, OCS 79), who underwent colorectal resections over a 12 month period in the UK, looked at the difference in infection rate between the laparoscopic and open procedures. The patients’ demographic and operative case-mix were similar for both groups.  Infection rates for LCS were 7% whilst OCS infection rates were 25%. This translates to LCS infection rates being 72% lower than OCS over that period.(Howard et al., 2010) 

Another study of 670 patients in Japan found that rates of surgical site infections for laparoscopic surgery for colon cancer were 4%. (Nakamura et al., 2016)

It is thought that the lower rates of SSIs in LCS compared with OCS procedures may be due to the bacteriostatic effect of carbon dioxide. (Persson et al., 2004)

A study into the effect of CO2 on staphylococcus aureus at body temperature looked at the difference between having S. aureus inoculated on blood agar and then exposed to either; anaerobic gas (5% CO2, 10% H20 and 85% N2), air or 100% CO2, at 37°C and over a 24hr period. The number of S. aureus on blood agar was 100 times lower for the CO2plate than the anaerobic one, and 1000 times lower for CO2 than the plate exposed to air.

In broth there were fewer bacteria with CO2 than with air. After 2h the number of bacteria had increased with the air but not with the CO2. After 8h, the optical density measurement with air had increased from 0 to 1.2; the CO2 saw an increase to 0.01. 

Staphylococcus Aureus accounts for 21% of SSIs detected by the Surgical Site Infection Surveillance Team in the United Kingdom (Public Health England, 2018) 

Public Health England have released a report by the Surgical Site Infection Surveillance team:

The report analyses the rate of surgical site infections (SSIs) for 134,119 procedures including 105,771 from mandatory orthopaedic surveillance and 28,348 from 13 other voluntary surveillance categories. Surveillance was carried out in the UK from April 2017 to March 2018. A total of 201 hospitals reported data on varying procedures and the 1,338 surgical site infections detected during the inpatient stay or on readmission following the initial operation.  It is interesting to note the difference between coronary artery bypass graft (CABG) procedures and those referred to as ‘Cardiac (non-CABG)’ procedures. Rates for SSIs after Coronary Artery Bypass Grafts (CABG) are more than double that of the Cardiac, non-CABG procedures (these are predominantly heart valve surgery procedures). Both of these procedures are performed in the same theatres, by the same surgical teams. Both procedures entail patients undergoing sternotomy, therefore surgical wound sizes are very comparable. Valve surgery is typically a more complicated surgical procedure and therefore one may expect the rate of SSI to be higher than the less complicated CABG procedures. 

In the UK carbon dioxide is routinely used during heart valve surgery, however, it is never used during CABG procedures. The rate of infection (inpatient only) for CABG procedures was reported at 2.12% of the 29,335 operations reported on since April 2013 , compared with 0.87% of the 16,706 other cardiac procedures. For in-patient and re-admission rates we see an increase to 3.5% of CABG procedures and 1.3% for other cardiac procedures. (Public Health England, 2018) This report highlights that in the UK you are more than twice as likely to acquire an SSI from a CABG procedure than you are from other, typically more complicated, cardiac procedures. The main difference being that in the non CABG procedures CO2 is usually used. 

Data taken from: Public Health England, December 2018: Surveillance of surgical site infections in NHS hospitals in England.

2013-2018 (inpatient only) SSI Rate (%)

Cardiac Non CABG (Valve)

Procedures  16,706

SSI rate           0.87

It is interesting that where an effective CO2 delivery device is used, there is a lower SSI rate.

Coronary Artery Bypass Graft (CABG) 

Procedures  29,335

SSI rate            2.12

HEALING: CO2 improves micro circulation and wound healing. 

Wound healing is known to benefit from improved micro-circulation and local oxygen supply. Carbon dioxide administration to a wound has been linked with both an improvement in micro-circulation and an increase in local oxygen supply. (Li et al., 2017) 

Hypoxia is a common cause of chronic wounds. The administration of subcutaneous carbon dioxide has been shown to result in neoangiogenesis and increased arterial sphygmicity on cutaneous ulcers and difficult wounds such as decubitus ulcers. Tissue oxygenation values were found to have significantly increased. Lesions of wounds treated in this way benefitted from increased healing and a reduction in the injured area (Brandi et al., 2010)

Carbon dioxide is one of the molecules that triggers the Bohr Effect. 

The Bohr Effect

The Bohr effect increases the efficiency of oxygen transportation through the blood, allowing oxygen to be delivered to the tissues that require it the most. Naturally a tissue will produce more carbon dioxide as it’s metabolic rate increases. The carbon dioxide causes a drop in the local pH of the blood. It is this drop in PH that promotes the oxygen dissociation from the haemoglobin, allowing the surrounding tissues to obtain enough oxygen to meets its increased demands.

Haemoglobin’s oxygen dissociation is heightened where there are elevated levels of CO2 in the blood. Thus higher levels of oxygen are released into surrounding tissues, accelerating wound healing at the surgical site.

It has been shown that the TEMED Gas Diffuser can create a 100 percent CO2 atmosphere. Data on file with the FDA.

References

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