Continuous Infusion Technique Research Articles

Invited commentary

After endovascular repair of an aortic aneurysm, the infrarenal aorta continues to demonstrate characteristic changes during follow-up. Even in the successfully excluded aorta, there remains a remodeling process reflected in changes in aortic neck, aneurysm, and iliac artery geometry. With aneurysm sac pressurization these changes are exacerbated and unpredictable, reinforcing the need for long-term surveillance. Until fairly recently, many centers have used static computed tomography (CT) images as their surveillance modality of this dynamic remodeling. Although quite capable of identifying significant endograft migration, contrast-enhanced CT scans are less than perfect in identifying the source of some endoleaks, predicting their physiologic ramifications, and in planning endoleak directed therapies. In the present study, the Baylor group is to be commended for further refining a contrast-enhanced ultrasound protocol for endograft follow-up. They used a continuous infusion technique of an albumin and microsphere suspension-based agent previously used with contrast echocardiography. It proved more accurate than CT imaging in the identification and classification of endoleaks and allowed for longer periods of monitoring compared with ultrasound scans using boluses of contrast. The findings of this 20-patient study certainly suggest further examination of this technique is warranted. This may also prove to be a more cost-effective method of surveillance. Although static (CT) and dynamic (ultrasound) imaging modalities offer extensive detail about endograft integrity, aneurysm geometry, and endoleak identification and classification, they are incapable of predicting the ramifications of these changes. This requires a measure of aneurysm pressurization, of which aneurysm diameter, volume, and endoleak identification are but a surrogate. A noninvasive method of sac pressure measurement has recently been developed that offers the possibility of determining which aneurysms required reintervention based on physiologic parameters.1Ellozy S.H. Carroccio A. Lookstein R.A. Minor M.E. Sheahan C.M. Juta J. et al.First experience in human beings with a permanently implantable intrasac pressure transducer for monitoring endovascular repair of abdominal aortic aneurysms.J Vasc Surg. 2004; 40: 405-412Abstract Full Text Full Text PDF PubMed Scopus (78) Google Scholar As the authors suggest, the perfect surveillance tool after endovascular repair undoubtedly involves an algorithm rather than a single imaging modality. This includes static imaging techniques (plain radiographs, CT, magnetic resonance) to monitor endograft integrity and aneurysm remodeling, dynamic imaging (ultrasound) to accurately identify and classify endoleaks, and physiologic monitoring (intrasac pressure transducer) to determine the need for reintervention. As this surveillance algorithm is elucidated further, it is likely that follow-up regimens will become patient specific, as all aneurysms will not require all surveillance modalities. This continues to be an important and evolving area of endovascular surgery that all vascular surgeons are encouraged to follow closely.

Comparison of obstetric outcome following the introduction of patient-controlled epidural analgesia with background infusion compared with continuous epidural infusion technique

PATIENT-CONTROLLED EPIDURAL ANALGESIA WITH BACKGROUND INFUSION COMPARED WITH CONTINUOUS EPIDURAL INFUSION TECHNIQUE AOIFE O’NEILL, NIAMH HAYES, EVE GAUGHAN, JOHN LOUGHREY, MICHAEL GEARY, Rotunda Hospital, Dublin, Ireland OBJECTIVE: Patient controlled epidural analgesia (PCEA) with low-dose background infusion has been shown in one study to result in fewer epidural rescue interventions, but this has not been a universal finding.PCEA techniques have been associated with reduced analgesic requirements, which may decrease instrumental delivery rates. We compared the effect of PCEA (5 ml bolus every 15 min/as required) with background infusion (6 ml/hour), versus continuous infusion epidural analgesia (CIEA) at 10 mls/hr with the same solution (bupivacaine 0.1% and fentanyl 2 mcg/ml) for nulliparous women. Our outcome measures were instrumental delivery rates, analgesic consumption and the frequency of rescue epidural reinforcement. STUDY DESIGN: A retrospective review of the hospital database prior to and after the introduction of PCEA with background infusion was conducted to assess major obstetric outcomes. A chart review for a sample of parturients in each group was also conducted to examine analgesic consumption and rates of rescue intervention between PCEA with background infusion and CIEA. RESULTS: The groups were demographically similar. There was no statistically significant difference in obstetric outcome between PCEA and CIEA (table). There was a reduction in the frequency of rescue reinforcement by anaesthetic and midwifery staff and a trend towards reduction in the average hourly dose of bupivacaine. CONCLUSION: Decreasing the number of rescue interventions reduces anaesthetic and midwifery workload in maintaining acceptable epidural analgesia on a busy labour ward. However, this technique has not reduced instrumental delivery rates in nulliparous women at our hospital. We conclude that PCEA with background infusion is an acceptable method of epidural analgesia maintenance.

Extended-Release Epidural Morphine (DepoDur™)

D a EPIDURAL MORPHINE HAS been administered by single and intermittent bolus doses, continuous infusion, and patient-controlled analgesia (PCA) for the management of postoperative pain for many years. All of these methods have proven to be safe and effective in controlling pain, but each also has its limitations. A single epidural injection of conventional morphine (Astramorph; AstraZeneca LP, Wilmington, DE) produces pain relief for as long as 24 hours, which may not be long enough for some patients after major surgery. Although continuous epidural infusion and patient-controlled epidural analgesia (PCEA) techniques provide prolonged relief, they require an indwelling catheter, which can impede mobility and carries the risk of intraspinal infection. In addition, guidelines for insertion and removal of indwelling epidural catheters must be carefully followed in patients receiving prophylactic anticoagulant therapy to prevent the occurrence of an epidural hematoma. However, the US Food and Drug Administration (FDA) has recently approved a unique formulation of epidural morphine called extended-release epidural morphine (EREM) (DepoDur; Endo Pharmaceuticals, Chadds Ford, PA) that may provide a better choice for pain control after some surgical procedures. A single epidural bolus of EREM is capable of providing pain relief for as long as 48 hours, which represents an exciting new postoperative pain management option for many patients undergoing major surgery.

Pain management after lumbar spinal fusion surgery using continuous subcutaneous infusion of buprenorphine

The continuous subcutaneous infusion (CSI) technique is a simple, inexpensive method for managing postoperative pain. We examined the analgesic effects of CSI of buprenorphine in patients undergoing lumbar spinal fusion surgery. The patients were randomly assigned to one of three groups for postoperative pain management: control group (n = 17), high-dose buprenorphine group (BH group, n = 17), and low-dose buprenorphine group (BL group, n = 16). Infusion solutions containing buprenorphine at concentrations of 25.0 and 16.7 microg x ml(-1) combined with droperidol at a concentration of 52.0 microg x ml(-1) were used in the BH and BL groups, respectively; and an infusion solution containing droperidol at a concentration 52.0 microg x ml(-1) was used in the control group. CSI of each solution was started at a rate of 1 ml x h(-1) and was continued for 48 h. The BH and BL groups showed significantly lower scores than the control group on the Visual Analogue Scale. There were significantly fewer administrations of flurbiprofen as a supplemental analgesic in the BL and BH groups than in the control group. The incidences of sedation and nausea were comparable in the three groups. The median number of administrations of flurbiprofen was significantly less in the BH group than in the control group on the day of the operation and on the first postoperative day, whereas the number in the BL group was less than that in the C group only on the day of the operation. CSI of buprenorphine effectively reduces pain after lumbar spinal fusion surgery without apparent side effects. This technique is simple and useful for postoperative pain management.

A Comparative Study of Sequential Epidural Bolus Technique and Continuous Epidural Infusion

In this randomized, double-blind study, the authors compared the effectiveness of a sequential epidural bolus (SEB) technique versus a standard continuous epidural infusion (CEI) technique of local anesthetic delivery. Both techniques used the same hourly dose of local anesthetic. Sixteen gynecologic patients undergoing abdominal surgery received postoperative epidural analgesia using 0.75% ropivacaine at a dose of 22.5 mg (3 ml) per hour. Patients were randomly assigned to one of two groups. In the SEB group (n = 8), patients received one third of the hourly dose every 20 min as a bolus. In the CEI group (n = 8), the hourly dose was administered as a continuous infusion. Analgesia was assessed by rest pain scored by a visual analog scale and pinprick to determine the number of separately blocked spinal segments on each side of the body. Doses of rescue medication for pain were also recorded. The median number of blocked spinal segments was 19.5 (range, 18-24) in the SEB group and 11.5 (range, 10-18) in the CEI group (P < 0.001). The median difference in the number of blocked segments between the right and left sides was 0 (range, 0-1) in the SEB group and 2 (range, 0-6) in the CEI group (P < 0.04). No patients in the SEB group but one patient in the CEI group required rescue medication for pain. The visual analog scale pain score was 0 in both groups except for one patient in the CEI group during the study period. The SEB technique with ropivacaine provides superior epidural block compared with an identical hourly dose administered as a continuous infusion.

Patient Selection and Trial Methods for Intraspinal Drug Delivery for Chronic Pain: A National Survey

Objectives Intraspinal drug delivery via indwelling pump is an effective means of treating refractory pain. Before a patient is selected for pump implantation, an intraspinal drug delivery trial must be performed to establish side-effects and efficacy profiles. No consensus protocol currently exists for such trials. As a preliminary step in this process, we surveyed a group of interventional pain physicians to explore attitudes on patient selection criteria, drug choice, trial techniques, and efficacy assessment. Methods The questionnaire was sent for self-administration to 1500 interventional pain physicians, each of whom had implanted one or more Medtronic(®) implantable infusion pumps. Results We received 205 completed surveys. Among the respondents, most were anesthesiologists (76%) and in private practice (82%). Nearly half (45%) of the respondents use the continuous intrathecal infusion technique to select patients for permanent implants. Conclusions Trial practices vary widely in terms of patient selection, medication choice, technique, and efficacy evaluation. We hope that our findings will encourage a concerted effort to evaluate existing trial protocols in order to establish a reliable standard of care.

Non-Anesthesiologist Propofol Sedation with Continuous Infusion Technique for ERCP and EUS Is Safe: A Single Center Experience of 600 Procedures

Non-Anesthesiologist Propofol Sedation with Continuous Infusion Technique for ERCP and EUS Is Safe: A Single Center Experience of 600 Procedures

Relationship of carpal canal contents volume to carpal canal pressure in carpal tunnel syndrome patients

Forty patients long-term haemodialysis with a second recurrence of carpal tunnel syndrome and concomitant loss of flexor tendon function due to flexor adhesions were treated by excision of the flexor digitorum superficialis tendons. During the procedure the carpal canal pressure was measured using a continuous infusion technique. The preoperative mean carpal canal pressure was 81 (SD, 53) mmHg. After removal of all the flexor digitorum superficialis tendons, the carpal canal pressure decreased to 10 (SD, 8) mmHg. The clinical symptoms of carpal tunnel syndrome were relieved and hand strength and finger motion were improved in all patients.

The rate of de novo galactose synthesis in patients with galactose-1-phosphate uridyltransferase deficiency

Using both a continuous infusion of isotopically labeled [1- 13C]galactose with a steady-state analysis and a single injection kinetic approach, we have calculated the apparent galactose appearance rate (GAR) in patients with galactose-1-phosphate uridyltransferase deficiency and control subjects. With the steady-state protocol, the GAR in 18 patients less than 18 years of age was 1.34 ± 0.53 mg/kg/h (mean ± SD) and was significantly greater than the mean of 0.56 ± 0.01 mg/kg/h ( p=0.004) in five patients above 18 years of age. Patients who were given a priming dose of [1- 13C]galactose had a reduced GAR compared to those without a priming dose, 0.73 ± 0.05 ( n=9) vs 1.46 ± 0.62 ( n=14) mg/kg/h ( p=0.005). The GAR in controls was lower than in patients ranging from 0.58 to 0.68 mg/kg/h in children and 0.07–0.09 mg/kg/h in adults. In the single bolus studies the plasma [ 13C]galactose enrichment decreased in a biexponential pattern suggesting at least a two-compartment system. The calculated GAR in three adult patients was similar to that found in them by the continuous infusion technique. The GAR in patients suggests the source of galactose for the continued elevation of galactose metabolites as well as the basis for the long-term complications in galactosemia despite restricted dietary galactose intake.

Epidural analgesia for labor: safety and success

Safe and successful provision of epidural analgesia for labor requires an understanding of the risks of the technique and attention to detail when performing the technique. The frequency of the commonest complication of epidural analgesia, accidental dural puncture, can probably best be minimized by regular practice of the technique. Some catheters, intended for the epidural space, will find themselves intrathecal, intravascular, or subdural. Although such misplacements probably cannot be prevented, their consequences can be minimized by careful, incremental injection of small doses of local anesthetic. The traditional epidural “test dose” of 45 mg of lidocaine and 15 μg of epinephrine can have undesired effects when injected intrathecally, intravenously, or epidurally. Successful epidural analgesia requires first placing a catheter in the epidural space. The combined spinal epidural technique is a very reliable way to accomplish this task. Subsequently, an appropriate dose of drug must be injected or infused by using an effective delivery system. Continuous infusion of ultra-dilute solutions of local anesthetics and opioids will relieve labor pain in some women, but the frequent need for supplemental medications severely limits their efficacy. Patient-controlled epidural analgesia, using slightly more concentrated local anesthetic solutions produces excellent analgesia with less local anesthetic and less need for rescue medication than continuous infusion techniques.

Renal length and inulin clearance in the radiologically normal single kidney.

Compensatory hypertrophy of a single functioning kidney is well described and has been shown to occur in utero. The long-term effects of hypertrophy and hyperfiltration in this situation are unknown. This study defined the growth parameters for single kidneys during childhood and correlated them with inulin clearance. Patients were those who had a radiologically "normal" single kidney, where the contralateral kidney was known to be non-functioning from infancy. Data were obtained from 74 children (40 boys and 34 girls) drawn from a registry of cases with a single kidney, and in whom simultaneous measurements of inulin clearance and renal length had been made at around 5, 10, and 16 years of age. Renal length was taken as the maximal bipolar measurement using real-time ultrasound scan. Inulin clearance was by continuous infusion technique. Nomograms for single kidney growth were determined against age, height, weight, and body surface area. Renal growth was correlated with inulin clearance. Renal length was found to correlate best with body surface area ( r=0.85, P<0.001), but this was not significantly superior to correlations with age, height, or weight separately. Inulin clearance per body surface area correlated positively with standardized renal length, i.e., Z score for renal length normalized for body surface area ( r=0.53, P<0.001). The larger kidneys have a higher glomerular filtration rate. Provided that the nephron number in the single kidney is similar to that in a paired kidney, single kidneys are hypertrophied and the single nephron glomerular filtration rate is likely to be abnormally high in these children.

Continuous lateral sciatic blocks for acute postoperative pain management after major ankle and foot surgery.

We developed a continuous lateral sciatic nerve infusion technique for postoperative analgesia. A 10-cm insulated Tuohy needle connected to a nerve stimulator was introduced posteriorly between the biceps femoris and vastus lateralis groove 10 cm cephalad from the tip of the patella. After proper positioning of the insulated needle, a 20-gauge catheter was placed in proximity to the sciatic nerve. Continuous lateral sciatic infusion of 0.2% ropivacaine was associated with a significant reduction of morphine consumption by 29% and 62% during postoperative days one and two, respectively, in patients who underwent open reduction and internal fixation of the ankle. Continuous lateral sciatic infusion of 0.2% ropivacaine represents an alternative for acute postoperative pain control after major ankle and foot surgery.

Improved Anti-tumor Activity and Safety of Interleukin-13 Receptor Targeted Cytotoxin by Systemic Continuous Administration in Head and Neck Cancer Xenograft Model

IL-13 receptor (IL-13R) targeted cytotoxin, IL13-PE38QQR, has been shown to have very potent anti-tumor activity to IL-13R-expressing head and neck tumor cells in vitro and in vivo. However, its effect is limited in aggressive tumors. To further improve the anti-tumor activity and safety of IL-13 cytotoxin, we employed continuous infusion technique in animal model of head and neck cancer. We surgically implanted continuous infusion (CI) pump intraperitoneally that released drug for 7 days, and its anti-tumor effect was evaluated. A comparison was made for antitumor activity and safety with intravenously (IV) administered IL-13 cytotoxin in a head and neck (KCCT873 and HN12) subcutaneous (SC) xenograft tumor models in nude mice. Vital organ toxicities were assessed by histologic examinations and blood serum chemistry analyses. The 50 or 75 micro g/kg/day for 7 days of IL-13 cytotoxin either by IV or CI administration did not show any difference in safety or anti-tumor activity. IV administration of 150 or 200 micro g/kg/day of IL-13 cytotoxin for 7 days was lethal to nude mice, whereas 200 micro g/kg/day X 7 days of CI administration was highly effective in the regression of established tumors without any toxicities. Additionally, CI administration of IL-13 cytotoxin (200 micro g/kg/day) showed growth inhibition of larger HN12 tumors in nude mice. With a CI schedule, IL-13 cytotoxin can be systemically administrated at approximately twice the dose otherwise given by daily IV bolus administration.

Continuous subgluteus sciatic nerve block after orthopedic foot and ankle surgery: Comparison of two infusion techniques

Background and Objective: To compare continuous infusion or a patient-controlled technique for postoperative analgesia after foot surgery, using a new subgluteus approach for continuous sciatic nerve block. Methods: Fifty healthy patients, undergoing orthopedic foot surgery, received a continuous sciatic nerve block using a new subgluteus approach. All blocks were placed with the aid of a nerve stimulator using a 10-cm, 18-gauge insulated Tuohy needle. After either plantar flexion or dorsiflexion of the operated foot was elicited at [le ] 0.5 mA, 20 mL of 0.75% ropivacaine was injected incrementally using repeated aspiration tests, then followed by the introduction of a 20-gauge epidural catheter. Postoperatively, 0.2% ropivacaine was infused with either a 10 mL/h continuous infusion (group Continuous, n = 25) or with a 5 mL/h basal rate with 5 mL bolus every 60 minutes (group patient-controlled analgesia [PCA], n = 25). Intraoperative analgesic supplementation, as well as postoperative pain relief, morphine consumption, incidence of complication, and patient satisfaction were recorded by an observer unaware of group assignment. Results: The sciatic catheter was successfully placed in all patients. Intravenous fentanyl supplementation (dose range, 50 to 150 [mu ]g) was required in 4 patients in each group, but no patient required general anesthesia. Catheter dislocation was reported in 2 patients (4%). The quality of pain relief was good in both groups, and none experienced complications. Nine patients of the Continuous group (37%) and 7 patients of the PCA group (29%) required rescue morphine analgesia because of pain in the femoral dermatomes (P = .76). Ropivacaine consumption was 240 mL in the Continuous group (range, 200 to 240 mL) and 140 mL in the PCA group (range, 120 to 290 mL) (P = .0005). Patient acceptance was good in both groups. Conclusions: The continuous subgluteus sciatic nerve block represents an easy and reliable option for postoperative analgesia after foot surgery; using a patient controlled rather than a continuous infusion technique reduces the consumption of local anesthetic solution without affecting the quality of pain relief. Reg Anesth Pain Med 2002;27:168-172.

Obstetric analgesia and anesthesia in Switzerland in 1999

This survey investigated the common practice of obstetric analgesia and anaesthesia in Swiss hospitals and evaluated the influence of the Swiss interest group for obstetric anaesthesia. In March 1999 we submitted 145 questionnaires to all Swiss hospitals providing an obstetric service. The rate of epidural analgesia (EA) was higher in large hospitals (> 1,000 births/year) than in small services. EA was maintained by continuous infusion techniques in 53% of the responding hospitals. For elective caesarean section, spinal anaesthesia (SA) and EA were performed in 77% and 16% of the patients, respectively. General anaesthesia (5%) was only used in small hospitals (< 500 births/year). Emergency caesarean section was performed under SA in 75% of all hospitals and only in 25% was a general anaesthesia used. An already existing EA for labour analgesia was continued for anaesthesia for caesarean section in 63% of Swiss hospitals. Regional anaesthesia was most commonly used for obstetric anaesthesia in Swiss hospitals. Epidemiological studies, recommendations of the Swiss interest group for obstetric anaesthesia, as well as the expectations of pregnant women, increased the numbers of regional anaesthesia compared with the first survey in 1992.

Bispectral analysis during cardiopulmonary bypass: the effect of hypothermia on the hypnotic state

Study Objective: To evaluate the hypothesis that the bispectral index (BIS) is not affected by the hypothermia that is associated with cardiopulmonary bypass (CPB). Design: Prospective, observational study. Setting: Cardiac surgical operating suite of a university medical center. Patients: 100 patients undergoing cardiac surgery requiring CPB. Interventions: A constant effect site concentration of 2.2 ng/mL for fentanyl and 60 ng/mL for midazolam was maintained throughout surgery using a computer-assisted continuous infusion technique. Measurements: The BIS value, percent isoflurane administered, predicted brain concentrations of midazolam and fentanyl, and nasopharyngeal temperature were recorded before CPB, at 15 minutes after the onset of CPB, at placement of the aortic cross-clamp, at start of rewarming, on separation from CPB, and 15 minutes after the end of CPB. Data were analyzed using a repeated-measures mixed-effects method, taking into account temperature, age, and predicted level of each anesthetic. Main Results: A significant overall association between temperature and BIS was observed independent of patient age, predicted brain midazolam or fentanyl concentration, percent isoflurane administered, and surgical time point (p < 0.001). The BIS is estimated to decrease by 1.12 units for each degree Celsius decrease in body temperature. Conclusions: Hypothermia decreases the BIS by 1.12 units per degree Celsius decline in temperature.

Continuous regional analgesia: can we afford not to use it?

Continuous regional analgesia: can we afford not to use it?

The hepatosplanchnic area is not a common source of lactate in patients with severe sepsis.

To investigate the role of the splanchnic region in the hyperlactatemia of septic patients. Prospective, observational study. Thirty-one-bed mixed medicosurgical intensive care unit. Ninety invasively monitored and mechanically ventilated patients with severe sepsis. Splanchnic lactate balance was measured in all patients. Splanchnic blood flow was determined by using the primed continuous indocyanine green infusion technique in 69 patients. In 71 patients, gastric mucosal Pco2 and the Pco2 gap (the difference between gastric and arterial Pco2) also were determined by using gas tonometry with an automated gas analyzer. In each patient, arterial, mixed-venous, and hepatic venous blood samples were obtained to determine hemoglobin oxygen saturations and lactate concentrations. Arterial and hepatic venous lactate concentrations were determined in triplicate and were averaged, and the arterial hepatic venous difference in lactate and lactate consumption were calculated. The splanchnic region produced lactate in only six of the 90 patients. Mean arterial pressure, cardiac index, arterial lactate, hepatic venous oxygen saturation, and catecholamine use were similar in the six patients with splanchnic lactate production and in the 84 others. The arterial hepatic venous differences in lactate and splanchnic lactate consumption were related directly to arterial lactate concentrations (y = 0.073x + 0.209, r(2) =.06, p <.05, and y = 0.06x + 0.183, r(2) =.08, p <.05, respectively) but were not related to Pco2 gap, to the gradient between mixed-venous and hepatic venous oxygen saturations, or to bilirubin concentrations. Splanchnic lactate release is uncommon in septic patients, even when hyperlactatemia is severe.

A comparison between low-dose ropivacaine and bupivacaine at equianalgesic concentrations for epidural analgesia during the first stage of labor

The aim of this study was to evaluate the efficacy, onset and duration of analgesia of two equianalgesic epidural doses of ropivacaine and bupivacaine during the first stage of labor. The study included 190 healthy nulliparous parturients who presented spontaneous onset of labor and required epidural analgesia. They were divided randomly to receive epidural analgesia with an initial dose 0.10% ropivacaine or 0.0625% bupivacaine 20 mL both with the addition of 10 μg of sufentanil. There were no significant differences in onset time, quality of analgesia, maternal hypotension and ability to ambulate. Ropivacaine produced more prolonged analgesia then bupivacaine (89 vs 119 min;P<0.0003). The clinical value of this prolonged analgesia after the first dose needs further evaluation when a continuous infusion technique is used.

Does gastric tonometry monitor splanchnic perfusion?

To define whether the gastric mucosal-arterial PCO2 gradient (PCO2 gap) reliably reflects hepatosplanchnic oxygenation in septic patients. Prospective observational clinical study. An adult, 31-bed medical/surgical department of intensive care of a university hospital. A total of 36 hemodynamically stable, invasively monitored, mechanically ventilated, sedated, paralyzed patients with severe sepsis. In each patient, hepatosplanchnic blood flow was determined by the continuous indocyanine green infusion technique and gastric mucosal PCO2 by the saline tonometry technique. Suprahepatic venous blood oxygen saturation and PCO2 also were measured. The mesenteric veno-arterial PCO2 gradient was determined as the difference between the suprahepatic venous blood PCO2 and the arterial blood PCO2. There were significant correlations between the hepatosplanchnic blood flow and the suprahepatic venous blood oxygen saturation (r2 = .56; p<.01), between the hepatosplanchnic blood flow and the mesenteric veno-arterial PCO2 gradient (r2 = .55; p<.01), and also between the suprahepatic venous blood oxygen saturation and the mesenteric veno-arterial PCO2 gradient (r2 = .64; p<.01). There was no statistically significant correlation between the PCO2 gap and the hepatosplanchnic blood flow, the suprahepatic venous blood oxygen saturation or the mesenteric veno-arterial PCO2 gradient. In stable septic patients, the PCO2 gap is not correlated with global indexes of gut oxygenation. The interpretation of PCO2 gap is more complex than previously thought.