2020 AAHA Anesthesia and Monitoring Guidelines for Dogs and Cats.

Risk for complications and even death is inherent to anesthesia. However, the use of guidelines, checklists, and training can decrease the risk of anesthesia-related adverse events. These tools should be used not only during the time the patient is unconscious but also before and after this phase. The framework for safe anesthesia delivered as a continuum of care from home to hospital and back to home is presented in these guidelines. The critical importance of client communication and staff training have been highlighted. The role of perioperative analgesia, anxiolytics, and proper handling of fractious/fearful/aggressive patients as components of anesthetic safety are stressed. Anesthesia equipment selection and care is detailed. The objective of these guidelines is to make the anesthesia period as safe as possible for dogs and cats while providing a practical framework for delivering anesthesia care. To meet this goal, tables, algorithms, figures, and "tip" boxes with critical information are included in the manuscript and an in-depth online resource center is available at aaha.org/anesthesia.

Veterinary applications of pulsed electromagnetic field therapy.

Pulsed electromagnetic field (PEMF) therapy can non-invasively treat a variety of pathologies by delivering electric and magnetic fields to tissues via inductive coils. The electromagnetic fields generated by these devices have been found to affect a variety of biological processes and basic science understanding of the underlying mechanisms of action of PEMF treatment has accelerated in the last 10 years. Accumulating clinical evidence supports the use of PEMF therapy in both animals and humans for specific clinical indications including bone healing, wound healing, osteoarthritis and inflammation, and treatment of post-operative pain and edema. While there is some confusion about PEMF as a clinical treatment modality, it is increasingly being prescribed by veterinarians. In an effort to unravel the confusion surrounding PEMF devices, this article reviews important PEMF history, device taxonomy, mechanisms of action, basic science and clinical evidence, and relevant trends in veterinary medicine. The data reviewed underscore the usefulness of PEMF treatment as a safe, non-invasive treatment modality that has the potential to become an important stand-alone or adjunctive treatment modality in veterinary care.

Multicenter clinical evaluation of a multi-dose formulation of propofol in the dog.

BACKGROUND: Propofol is a widely used injectable anesthetic agent for induction and short-term maintenance in dogs. A multi-dose formulation of propofol (MDP) has been developed which includes 2% benzyl alcohol as a preservative. In order to document the use of the product under clinical conditions, MDP was tested in a prospective clinical trial conducted at six sites within the United States. One hundred thirty-eight healthy, client-owned dogs were assigned to one of six treatment groups based on premedicants (none, acepromazine/buprenorphine, midazolam/buprenorphine, medetomidine/buprenorphine) and maintenance agents (MDP, inhaled anesthetic). Anesthesia was induced by the intravenous administration of MDP given to effect. Physiological indices including heart rate, respiratory rate and blood pressure were monitored prior to and during anesthesia induction, maintenance and recovery. Adverse events, defined for severity by pre-established limits of these physiological values, as well as side effects, defined as any observation outside the normal range, were noted. RESULTS: The mean intubation dose was 7.6 ± 2.1 mg/kg for MDP alone and 4.7 ± 1.3, 4.0 ± 1.0 mg/kg and 3.2 ± 1.4 mg/kg when buprenorphine was used in combination with midazolam, acepromazine and medetomidine, respectively. Of the 32 adverse events, apnea (12 incidents), bradycardia (9 incidents) and hypotension (7 incidents) were most frequently recorded. Emesis, cyanosis and second degree heart block were each noted once and successfully resolved. The cause of a single death 2 days post-anesthesia was assessed as a surgical complication. CONCLUSIONS: MDP was found to be acceptable for use in healthy dogs for induction and short term maintenance of anesthesia when used alone and in combination with premedicants and inhaled anesthetics.

Control of cancer pain in veterinary patients.

Control of cancer pain is within the capabilities of most veterinarians and is achievable in most animal patients that have cancer with techniques that are currently available. Great satisfaction can be derived from not only treating the pet's cancer but its pain. Incorporating pain management into oncology practice is good for the well-being of the pet, the owner, the staff, the veterinarians, and the practice.

Effect of short-term sequential administration of nonsteroidal anti-inflammatory drugs on the stomach and proximal portion of the duodenum in healthy dogs.

OBJECTIVE: To evaluate effects of injection with a nonsteroidal anti-inflammatory drug (NSAID) followed by oral administration of an NSAID on the gastrointestinal tract (GIT) of healthy dogs. ANIMALS: 6 healthy Walker Hounds. PROCEDURES: In a randomized, crossover design, dogs were administered 4 treatments consisting of an SC injection of an NSAID or control solution (day 0), followed by oral administration of an NSAID or inert substance for 4 days (days 1 through 4). Treatment regimens included carprofen (4 mg/kg) followed by inert substance; saline (0.9% NaCl) solution followed by deracoxib (4 mg/kg); carprofen (4 mg/kg) followed by carprofen (4 mg/kg); and carprofen (4 mg/kg) followed by deracoxib (4 mg/kg). Hematologic, serum biochemical, and fecal evaluations were conducted weekly, and clinical scores were obtained daily. Endoscopy of the GIT was performed before and on days 1, 2, and 5 for each treatment. Lesions were scored by use of a 6-point scale. RESULTS: No significant differences existed for clinical data, clinicopathologic data, or lesion scores in the esophagus, cardia, or duodenum. For the gastric fundus, antrum, and lesser curvature, an effect of time was observed for all treatments, with lesions worsening from before to day 2 of treatments but improving by day 5. CONCLUSIONS AND CLINICAL RELEVANCE: Sequential administration of NSAIDs in this experiment did not result in clinically important gastroduodenal ulcers. A larger study to investigate the effect of sequential administration of NSAIDs for longer durations and in dogs with signs of acute and chronic pain is essential to substantiate these findings.

Effect of positive end-expiratory pressure on oxygen delivery during 1-lung ventilation for thoracoscopy in normal dogs.

OBJECTIVE: To evaluate the effect of positive end-expiratory pressure (PEEP) on oxygen delivery (DO(2)) with 1-lung ventilation during thoracoscopy in normal anesthetized dogs. STUDY DESIGN: Prospective, controlled experimental study. ANIMALS: Eight, adult, intact Walker Hound dogs weighing 25.6-29.2 kg. METHODS: Anesthetized dogs had 1-lung ventilation during an open-chest condition. A Swan-Ganz catheter was used to measure pulmonary hemodynamic variables and to obtain mixed venous blood samples for blood gas analysis. A dorsal pedal catheter was used for measurement of systemic arterial pressure and to obtain arterial blood samples for blood gas analysis. Oxygen delivery was calculated and used to assess the effect of 0, 2.5, and 5 cm H(2)O PEEP during 1-lung ventilation on cardiopulmonary function. Each dog was its own control at 0 cm H(2)O PEEP. A randomized block ANOVA for repeated measures was used to evaluate the effect of the treatment on hemodynamic and pulmonary variables. RESULTS: Use of 5 cm H(2)O PEEP induced a significant augmentation in the arterial partial pressure of oxygen (PaO(2)). Shunt fraction (Q(s)/Q(t)), physiologic dead space (V(D)/V(T)), and the alveolar-arterial oxygen difference (P(A-a)O(2)) decreased significantly after 5 cm H(2)O PEEP, compared with 1-lung ventilation without PEEP. Use of 2.5 cm H(2)O PEEP had no significant effect on cardiopulmonary variables. Use of PEEP had no significant effect on arterial oxygen saturation (SaO(2)), DO(2), and hemodynamic variables in normal dogs. CONCLUSIONS: PEEP had no effect on DO(2) in normal dogs undergoing open-chest 1-lung ventilation because it had no adverse effect on hemodynamic variables. CLINICAL RELEVANCE: PEEP in normal dogs during open-chest 1-lung ventilation for thoracoscopy is not detrimental to cardiac output and can be recommended in clinical patients.

Cardiopulmonary changes induced during one-lung ventilation in anesthetized dogs with a closed thoracic cavity.

OBJECTIVE: To evaluate the effects of one-lung ventilation (OLV) on oxygen delivery (DO2) in anesthetized dogs with a closed thoracic cavity. ANIMALS: 7 clinically normal adult Walker Hound dogs. PROCEDURE: Dogs were anesthetized. Catheters were inserted in a dorsal pedal artery and the pulmonary artery. Dogs were positioned in right lateral recumbency. Data were collected at baseline (Paco2 of 35 to 45 mm Hg), during two-lung ventilation, and 15 minutes after creating OLV. Hemodynamic and respiratory variables were analyzed and calculations performed to obtain DO2, and values were compared among the various time points by use of an ANOVA for repeated measures. RESULTS: OLV induced a significant augmentation of shunt fraction that resulted in a significant reduction in Pao2, arterial oxygen saturation, and arterial oxygen content. Cardiac index was not significantly changed. The net result was that DO2 was not significantly affected by OLV. CONCLUSIONS AND CLINICAL RELEVANCE: Use of OLV in healthy dogs does not induce significant changes in DO2, which is the ultimate variable to use when evaluating tissue oxygenation. One-lung ventilation can be initiated safely in dogs before entering the thoracic cavity during surgery. Additional studies are necessary to evaluate OLV in clinically affected patients and variations in age, body position, and type of anesthetic protocol.

Cardiopulmonary effects of positive end-expiratory pressure during one-lung ventilation in anesthetized dogs with a closed thoracic cavity.

OBJECTIVE: To evaluate the effects on oxygen delivery (DO2) of 2.5 and 5 cm H2O of positive end-expiratory pressure (PEEP) applied to the dependent lung during one-lung ventilation (OLV) in anesthetized dogs with a closed thoracic cavity. ANIMALS: 7 clinically normal adult Walker Hound dogs. PROCEDURE: Dogs were anesthetized, and catheters were inserted in a dorsal pedal artery and the pulmonary artery. Dogs were positioned in right lateral recumbency, and data were collected during OLV (baseline), after application of 2.5 cm H2O of PEEP for 15 minutes during OLV, and after application of 5 cm H2O of PEEP for 15 minutes during OLV. Hemodynamic and respiratory variables were analyzed and calculations performed to obtain DO2, and values were compared among the various time points by use of an ANOVA for repeated measures. RESULTS: PEEP induced a significant decrease in shunt fraction that resulted in a significant increase in arterial oxygen saturation. However, it failed to significantly affect arterial oxygen content (CaO2) or cardiac output. Thus, DO2 was not affected in healthy normoxemic dogs as a net result of the application of PEEP. CONCLUSIONS AND CLINICAL RELEVANCE: The use of PEEP during OLV in anesthetized dogs with a closed thoracic cavity did not affect DO2. Use of PEEP during OLV in dogs with a closed thoracic cavity is recommended because it does not affect cardiac output and any gain in CaO2 will be beneficial for DO2 in critically ill patients.

Effect of sevoflurane on hemodynamic and cardiac energetic parameters in ferrets.

OBJECTIVE: To determine the effect of sevoflurane on cardiac energetic and hemodynamic parameters in ferrets. ANIMALS: 7 healthy domesticated ferrets. PROCEDURE: Sevoflurane was used as the sole anesthetic agent for general anesthesia in ferrets. Standard midline laparotomy and median sternotomy were performed to permit instrumentation. Myocardial blood flow was determined by use of colored microsphere technology. Measurements and blood samples were obtained at 1.25%, 2.5%, and 3.75% expired concentration of sevoflurane. RESULTS: A dose-dependent decrease in arterial blood pressure, left ventricular pressure, systemic vascular resistance, aortic flow, and dp/dt (an index of contractility) was detected as expired concentration of sevoflurane increased. Heart rate, central venous pressure, coronary vascular resistance, myocardial oxygen extraction ratio, and tau (the time constant of relaxation) were unchanged. Cardiac external work decreased, as did myocardial oxygen consumption, causing increased cardiac efficiency at higher concentrations of sevoflurane. CONCLUSIONS AND CLINICAL RELEVANCE: Sevoflurane caused minimal and predictable cardiovascular effects in ferrets without increasing myocardial metabolic demands. Data obtained from this study have not been previously reported for a species that is being commonly used in cardiovascular research. These findings also support use of sevoflurane as a safe inhalant anesthetic in ferrets for clinical and research settings.

Cardiopulmonary effects of thoracoscopy in anesthetized normal dogs.

OBJECTIVE: To evaluate the effect of an open-chest condition on oxygen delivery in anesthetized dogs. STUDY DESIGN: Prospective, controlled experimental study. ANIMALS: Eight clinically normal adult Walker Hound dogs weighing 25.6-29.2 kg. METHODS: Eight anesthetized dogs underwent an open-chest operation after the insertion of thoracoscopy cannulae in the lateral chest walls. A Swan Ganz catheter was used to both measure hemodynamic parameters and obtain mixed venous blood samples for blood gas analysis. A dorsal pedal catheter was placed to both measure arterial blood pressure and obtain blood samples for blood gas analysis. Oxygen delivery index and oxygen extraction ratio were calculated. A randomized block anova for repeated measures was used to evaluate the effect of the treatment on hemodynamic and pulmonary parameters. RESULTS: Creation of an open chest did not significantly affect oxygen delivery index (DO(2)I; p = 0.545). It induced a significant decrease in arterial oxygen partial pressure (PaO(2); p = 0.018) and arterial oxygen content (CaO(2); p = 0.025). It induced a significant increase in shunt fraction (p = 0.023), physiologic dead space (p = 0.015), and alveolar-arterial oxygen difference (p = 0.019). Arterial partial pressure of carbon dioxide (PaCO(2); p = 0.766) and arterial hemoglobin oxygen saturation (SaO(2); p = 0.178) were not significantly affected. Diastolic (DPAP; p = 0.050) and mean (MPAP; p = 0.033) pulmonary arterial pressures were significantly increased by opening the chest. Other hemodynamic parameters were not significantly affected. CONCLUSIONS: Opening the thoracic cavity is not detrimental to hemodynamic function and oxygen delivery in normal dogs, although impaired gas exchange does occur. CLINICAL RELEVANCE: Close monitoring of patients is recommended during open-chest thoracoscopy as adverse effects on gas exchange can contribute to hypoxemia.

Comparison of isoflurane and sevoflurane for anesthesia in beaver.

We compared the hemodynamic and respiratory effects, recovery time, and cost of two gas inhalants (isoflurane and sevoflurane) for anesthetic induction and maintenance of beaver (Castor canadensis) during surgery to implant radio transmitters in the peritoneal cavity. Heart rate, respiratory rate, relative hemoglobin saturation with oxygen (SpO2), and body temperature were measured every 5 min for the first 45 min, and arterial blood gas was measured once, 25 min into the anesthetic procedure. Induction for either agent was smooth and rapid. Heart rate and respiratory rate both decreased during the procedure though neither was lower than baseline values reported in the literature for beaver. Relative hemoglobin saturation with oxygen, body temperature, and blood gas variables did not differ between each anesthetic regime. Both inhalants caused slight respiratory acidosis. Recovery time from anesthesia was highly variable (1-178 min) but did not differ statistically between drugs. Sevoflurane costs ($22.30/60 min) were much higher than isoflurane costs ($3.50/60 min). We recommend isoflurane or sevoflurane for anesthetic induction and maintenance of beaver because of the lack of physiologic differences.

The sedative and behavioral effects of nalbuphine in dogs.

We compared the degree of sedation and frequency and intensity of adverse behaviors in dogs associated with nalbuphine when combined with acepromazine or xylazine compared with those of acepromazine or xylazine alone. Twenty-four dogs (13 female, 11 male) undergoing routine ovariohysterectomy or castration were randomly assigned to one of four groups. Group NX received 0.5 mg/kg nalbuphine and 0.5 mg/kg xylazine subcutaneously (s.c.). Group X received 0.5 mg/kg xylazine s.c. Group NA received 0.5 mg/kg nalbuphine and 0.05 mg/kg acepromazine s.c. Group A received 0.05 mg/kg acepromazine s.c. All dogs received 0.01 mg/kg glycopyrrolate s.c. All doses were administered preoperatively. Preoperative resting measurements of heart rate, respiratory rate, rectal temperature, and body weight were obtained. Sedation was scored both inside and outside a kennel prior to drug administration and at 10, 20, and 30 min after drug administration. Dogs were assessed for behavioral responses (leg withdrawal, shivering, rigidity, orienting, panting, struggling, vocalization, wide-eyed facial expression, breath holding, salivating, hiding, biting, or requiring a muzzle) during three time periods: placing the dog on the table, clipping and prepping of forelimb, and intravenous catheterization. Postoperative recovery behaviors were scored. Expired halothane concentrations were recorded at 15, 30, and 45 min postinduction. Significant differences occurred in the level of sedation at 30 min between dogs receiving nalbuphine and xylazine or xylazine only compared with dogs receiving acepromazine. There was a significant difference in behavioral scores with respect to leg withdrawal and orienting during clipping/prepping between dogs receiving nalbuphine and xylazine compared with dogs receiving xylazine. The combination of nalbuphine and xylazine is a useful premedicant which provided greater sedation than acepromazine and reduced some anxiety behaviors more than did xylazine alone. Nalbuphine is an inexpensive opioid and currently is not a controlled substance in the U.S.

Effect of one-lung ventilation on oxygen delivery in anesthetized dogs with an open thoracic cavity.

OBJECTIVE: To evaluate effects of one-lung ventilation on oxygen delivery in anesthetized dogs with an open thoracic cavity. ANIMALS: 8 clinically normal adult Walker Hound dogs. PROCEDURE: Each dog was anesthetized and subjected to one-lung ventilation during a period when it had an open thoracic cavity. A Swan-Ganz catheter was used to measure hemodynamic variables and obtain mixed-venous blood samples. A catheter was inserted in the dorsal pedal artery to measure arterial pressure and obtain arterial blood samples. Oxygen delivery index was calculated and used to assess effects of one-lung ventilation on cardiopulmonary function. Effects on hemodynamic and pulmonary variables were analyzed. RESULTS: One-lung ventilation caused significant decreases in PaO2, arterial oxygen saturation (SaO2), mixed-venous oxygen saturation, and arterial oxygen content (CaO2). One-lung ventilation caused significant increases in PaCO2, physiologic dead space, and alveolar-arterial oxygen difference. Changes in SaO2, CaO2, and PaCO2, although significantly different, were not considered to be of clinical importance. One-lung ventilation induced a significant increase in pulmonary arterial wedge pressure, mean pulmonary artery pressure, and shunt fraction. One-lung ventilation did not have a significant effect on cardiac index, systemic vascular resistance index, pulmonary vascular resistance index, and oxygen delivery index. CONCLUSIONS AND CLINICAL RELEVANCE: One-lung ventilation affected gas exchange and hemodynamic function, although oxygen delivery in clinically normal dogs was not affected during a period with an open thoracic cavity. One-lung ventilation can be used safely in healthy dogs with an open thoracic cavity during surgery.

Use of low doses of ketamine administered by constant rate infusion as an adjunct for postoperative analgesia in dogs.

OBJECTIVE: To compare indicators of postoperative pain and behavior in dogs with and without a low-dose ketamine infusion added to usual perioperative management. DESIGN: Prospective, randomized, blinded clinical study. ANIMALS: 27 dogs undergoing forelimb amputation. PROCEDURE: Dogs were anesthetized with glycopyrrolate, morphine, propofol, and isoflurane. Thirteen dogs were treated with ketamine IV, as follows: 0.5 mg/kg (0.23 mg/lb) as a bolus before surgery, 10 microg/kg/min (4.5 microg/lb/min) during surgery, and 2 microg/kg/min (0.9 microg/lb/min) for 18 hours after surgery. Fourteen dogs received the same volume of saline (0.9% NaCl) solution. All dogs received an infusion of fentanyl (1 to 5 microg/kg/h [0.45 to 2.27 pg/lb/h]) for the first 18 hours after surgery. Dogs were evaluated for signs of pain before surgery, at the time of extubation, and 1, 2, 3, 4, 12, and 18 hours after extubation. Owners evaluated their dogs' appetite, activity, and wound soreness on postoperative days 2, 3, and 4. RESULTS: Dogs that received ketamine infusions had significantly lower pain scores 12 and 18 hours after surgery and were significantly more active on postoperative day 3 than dogs that received saline solution infusions. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that perioperative administration of low doses of ketamine to dogs may augment analgesia and comfort in the postoperative surgical period.

Surgical correction of double-chambered right ventricle in dogs.

Double-chambered right ventricle (DCRV) is possibly an emerging congenital cardiac anomaly in dogs. The defect causes clinical and pathophysiologic signs similar to those of congenital pulmonic stenosis in dogs but has distinct diagnostic features, breed predilections, and implications for treatment. The defect is often associated with clinical signs early in life. Surgical correction of DCRV can be undertaken with the aid of cardiopulmonary bypass and offers the prospect of an improved clinical outcome.

Effect of perioperative oral carprofen on postoperative pain in dogs undergoing surgery for stabilization of ruptured cranial cruciate ligaments.

A randomized, placebo-controlled, parallel study was conducted to investigate the effectiveness of oral carprofen for the control of postoperative pain in dogs undergoing knee surgery for stabilization of ruptured cranial cruciate ligaments. Dogs were randomly assigned to treatment with carprofen (n = 10) or placebo (n = 9). Pain was assessed at 1, 2, 4, 6, 24, and 48 hours and 10 and 21 days postoperatively. Eight of 10 dogs treated with carprofen and five of nine dogs treated with placebo were given at least one dose of morphine as rescue therapy. The mean relative dose of morphine given at 1 hour (P =.01) and 24 hours (P =.02) after surgery was greater for dogs treated with carprofen than for dogs given a placebo. There were no significant postoperative differences in cortisol levels or any measured variable. It appears that the scoring system used was not sensitive enough to detect differences in pain between a known analgesic and a placebo.

Use of a pulsed electromagnetic field for treatment of post-operative pain in dogs: a pilot study.

OBJECTIVE: To determine if pulsed electromagnetic field (PEMF) therapy reduces post-operative pain in dogs following ovariohysterectomy, and to evaluate PEMF interaction with post-operative morphine analgesia. STUDY DESIGN: Randomized controlled clinical trail. ANIMALS: Sixteen healthy dogs weighing 18 (10-32) kg [median (range)] and aged 13 (3-36) months. MATERIALS AND METHODS: Anesthesia consisted of atropine (0.04 mg kg-1, SC), acepromazine (0.02 mg kg-1, SC), fentanyl (0.01 mg kg-1, SC), thiopental (10-15 mg kg-1, IV) and halothane in oxygen. Ovariohysterectomies were performed by senior veterinary students. Pain score (numeric rating scale, 0-28), pulse rate, respiratory rate, indirect mean arterial pressure (MAP), and body temperature were evaluated prior to anesthetic premedication, at extubation, 30 minutes after extubation, and then hourly for 6 hours. Following extubation, dogs were randomly divided into four groups: a control group that received 0.9% NaCl, IV, and no PEMF; a magnet group that received 0.9% NaCl, IV, and PEMF; a morphine group that received morphine 0.25 mg kg-1, IV, and no PEMF; and, a magnet/morphine group that received morphine 0.25 mg kg-1, IV, and PEMF. A single observer, blinded to treatment, obtained all behavioral observations and physiologic data. Data were analyzed using the Kruskal-Wallis statistical test with a significance of p < 0.05. RESULTS: Significant differences in MAP (mm Hg) [median (range)] occurred at 300 minutes [morphine 108 (83-114) and magnet/morphine 90 (83-97) < magnet 135 (113-117)], and at 360 minutes [magnet/morphine 93 (81-100) < control 127 (111-129) and magnet 126 (111-129)]. At 30 minutes the total pain score for the magnet/morphine group [1.5 (0-5)] was significantly less than control [8 (6-13)], but not different from magnet [5.5 (4-7)] or morphine [4.5 (2-9)]. CONCLUSIONS AND CLINICAL RELEVANCE: Although no clear benefit was seen in this study, the results suggest that PEMF may augment morphine analgesia following ovariohysterectomy in dogs, and that further study of the analgesic effects of PEMF is warranted.

Evaluation of splanchnic oxygen extraction ratio as an index of portal vein pressure in dogs.

OBJECTIVE: To determine changes in splanchnic oxygen extraction ratio during experimentally induced portal hypertension in dogs. ANIMALS: 6 clinically normal dogs. PROCEDURE: Standard midline laparotomy and median sternotomy were performed in anesthetized dogs. Baseline measurements of arterial blood pressure, aortic blood flow, portal vein blood flow, and portal vein pressure were acquired, and arterial, venous, and portal vein blood samples were obtained to determine systemic and splanchnic oxygen extraction ratios. The portal vein was gradually occluded until a pressure of 18 cm of H2O was reached; this pressure was maintained for 30 minutes, and measurements and collection of blood samples were repeated. RESULTS: Portal vein blood flow decreased significantly from 457 +/- 136 ml/min before to 266 +/- 83 ml/min after induction of portal hypertension. Oxygen content in the portal vein significantly decreased from 12.3 +/- 1.85 to 8.2 +/- 2.31%, and splanchnic oxygen extraction ratio significantly increased from 15.8 +/- 6.2 to 37.4 +/- 10.9% during portal hypertension. There was a significant inverse correlation between portal vein blood flow and splanchnic oxygen extraction ratio at baseline and during portal hypertension. CONCLUSIONS AND CLINICAL RELEVANCE: An increase in splanchnic oxygen extraction ratio is evident with partial attenuation of the portal vein and the concurrent decrease in portal vein blood flow. Correlation of oxygen extraction ratio with portal vein blood flow may be a more important indicator for determination of an endpoint to prevent congestion and ischemia of the gastrointestinal tract and pancreas during ligation of portosystemic shunts.