Compartment syndrome: pathophysiology, clinical presentations, treatment, and prevention in human and veterinary medicine

Pathophysiology of intraabdominal hypertension and abdominal compartment syndrome and relevance to veterinary critical care

BACKGROUND

Increased intraabdominal pressure, termed intraabdominal hypertension (IAH), is reported as an independent cause of morbidity and mortality in the human ICU but, until recently, has been rarely described in veterinary species outside of experimental models. Failure to identify severe IAH leads to organ dysfunction, termed abdominal compartment syndrome, and rapidly becomes fatal without therapeutic intervention. Although the veterinary community has been slow to address the concept of IAH and associated comorbidities, recent companion and large animal case series and experimental studies suggest IAH may also be common in veterinary species and correlates well with risk factors and grading systems already described in the human literature.

PATHOPHYSIOLOGY

Increasing abdominal pressures exert deleterious local effects through visceral ischemia and reperfusion injury as well as systemic effects on the cardiovascular, pulmonary, renal, and central nervous systems. Even mild grades of IAH increase systemic vascular resistance, impede venous return, increase pulmonary wedge pressure, and decrease pulmonary function. More severe grades cause azotemia, oliguria, decreased coronary blood flow, hypoxia, increased intracranial pressure, and death.

IMPORTANCE

Many of the common diseases in veterinary patients are associated with IAH, including gastric dilatation-volvulus, colon volvulus, closed pyometra, hemoperitoneum, ascites, uroperitoneum, and hydrops. Monitoring of the veterinary patient is difficult, but several experimental studies validate both the presence of IAH and the ability to monitor abdominal pressures in large and small animal species. Moreover, prompt recognition of IAH and subsequent treatment is feasible in the veterinary ICU.

KEY POINTS

Increasing abdominal pressures exert deleterious local effects through visceral ischemia and reperfusion injury as well as systemic effects on the cardiovascular, pulmonary, renal, and central nervous systems. Increases in central venous pressure, systemic vascular resistance, pulmonary wedge pressure, and a decreased cardiac output by way of both decreased preload and increased afterload have been documented as a result of intraabdominal hypertension (IAH). Direct diagnosis of IAH is achieved by blind or ultrasound-guided abdominal needle puncture attached to a water manometer or direct pressure monitoring transducer. Transvesicular measurement of intraabdominal pressure (IAP) is relatively noninvasive, and many patients that would benefit from rapid diagnosis of IAH and abdominal compartment syndrome already have indwelling bladder catheters. Recommendations for interventions are based on the assigned grade of IAH (mild, moderate, severe).

KEY POINTS

If IAH is strongly suspected or diagnosed, abdominal wall compliance may be improved through judicious use of neuromuscular blockers and sedation. Decompression, either minimally invasive or surgical, is absolutely recommended for IAPs consistently above 20 mm Hg, especially in the presence of signs attributed to secondary organ dysfunction.

Effect of intra-abdominal hypertension on the intraocular pressure of the conscious dogs

This study was performed to evaluate the effect of intra-abdominal pressure (IAP) on intraocular pressure (IOP) in conscious dog models using a balloon technique to generate intra-abdominal hypertension. Six healthy dogs without ocular abnormalities were evaluated in this study. A balloon device was placed in the intra-abdominal cavity. The abdomen was insufflated to IAP levels of 15 and 25 mmHg using the balloon device. Intraocular pressure was measured at baseline, at IAP levels of 15 and 25 mmHg, and after decompression. In comparison with the mean baseline IOP (15.1 ± 2.0 mmHg), there was a significant increase in IOP at IAP levels of 15 mmHg (20.0 ± 2.1 mmHg) and 25 mmHg (19.9 ± 2.2 mmHg), corresponding to a 32.4% and 31.7% increase from baseline IOP, respectively. The mean IOP after decompression (14.8 ± 1.7 mmHg) was significantly lower compared to those at IAP levels of 15 and 25 mmHg. The present findings demonstrate that increased IAP has a clinically significant effect on IOP in dogs under conscious conditions. Although more research is needed to determine of increased IAP on IOP, these findings suggest that increased IAP leads to mild and reversible increase in IOP.

Equine Antebrachial Compartment Syndrome Secondary to Flexor Muscle Myopathy With Subsequent Muscle Atrophy And Tendonitis: A Case Report

This case report describes a 16-year-old jumping stallion that had a marked swelling over the left antebrachial area along with substantial lameness after a fall. The horse was weight bearing but lame (4/5; AAEP scale) at the walk with marked enlargement in the caudal aspect of the antebrachial region. After a static musculoskeletal examination, radiography and ultrasonography the horse was diagnosed with flexor muscle myopathy and presumptive extremity compartment syndrome. Following medical treatment, the horse improved clinically over several days. Six-months post injury the horse showed flexor muscle atrophy but was sound at the walk and trot. The horse was presented again 3 months later with an enlargement of the palmar left metacarpus that was diagnosed as a superficial digital flexor tendonitis. This report describes the episodes from the onset of extremity compartment syndrome until the superficial digital flexor tendonitis, discusses anatomical features of the region, physiopathology of compartment syndrome and the possible biomechanics behind the flexor muscle atrophy and the tendonitis.

Prevalence of intra-abdominal hypertension in horses with colic

OBJECTIVE

To determine an abdominal pressure cutoff value for intra-abdominal hypertension (IAH) in the horse and characterize IAH in horses with acute colic.

DESIGN

Prospective clinical cohort.

SETTING

University teaching hospital.

ANIMALS

Nine healthy adult horses and 56 horses with acute colic.

INTERVENTIONS

Ventral intra-abdominal pressure (IAP) was measured in triplicate at end expiration and averaged. Each colic case was classified as medical or surgical and large intestine (LI) or small intestine (SI). Management and final outcome (alive, euthanized, or died) were recorded. IAH was defined as ≥32 mm Hg (mean + 2 SDs of ventral IAP in control horses). Proportions of horses with and without IAH for different lesions were expressed as fractions and percentages. Differences in IAP between groups were determined using ANOVA with post-testing or t-tests. Odds ratio for management strategy (ie, need for medical or surgical) in horses with IAH was performed using Fisher's exact test. P < 0.05 was considered significant.

MEASUREMENTS AND MAIN RESULTS

IAP was higher in horses with colic compared to controls (P = 0.025). Over 18 months, 30.4% of horses with colic had IAH (n = 10 LI lesions, n = 7 SI lesions). Horses with LI medical lesions had the highest IAP of all lesions (mean 36.5 mm Hg). IAH horses with medical lesions were 15 times more likely to survive than IAH horses requiring surgery (P = 0.03).

CONCLUSIONS

Acute colic in horses is associated with an increased ventral IAP compared with healthy controls. IAH does exist in horses with colic, notably LI medical lesions, and is associated with nonsurvival in horses that require surgery.

Intra-abdominal Pressure Screening of Horses With Colic

The objective of this study was to evaluate changes in intra-abdominal pressure (IAP) in horses with colic by associating the underlying etiologies with directly acquired IAP values and survival rate. This is a 2-year cohort study (2014-2016). Horses with clinical signs of colic were admitted to the veterinary teaching hospital during the period 2014-2016. Twenty-eight horses, of different breeds, males (stallions and geldings) and females, aged between 2 and 20 years, and weighing from 300 to 450 kg presenting with clinical signs of colic, were included in the study. IAP was directly acquired at the right flank (standing under sedation) and at the linea alba (supine position under general anesthesia). Twenty IAP measurements were recorded at end expiration for each recording site. IAP values >0.0 mmHg, obtained at the upper right flank in the standing position, were associated with surgical treatment (P < .05). In these cases, signs of colic were associated with strangulated obstructions of the large colon, and a greater likelihood of death as a result of colic (P < .001). Intra-abdominal pressure varied considerably in horses with colic, even for the same underlying etiologies. Horses with colic related to strangulating obstructions of the large intestine had IAP >.0 mmHg, at the upper right flank. These horses were also considerably more likely to require surgical intervention (P < .05) and death/euthanasia was more likely in this group of horses (P < .001).

Effect of intra-abdominal hypertension on plasma exogenous creatinine clearance in conscious and anesthetized dogs

OBJECTIVE

To evaluate the effect of intra-abdominal pressure (IAP) on plasma exogenous creatinine clearance in both conscious and anesthetized dog models using a balloon technique to generate intra-abdominal hypertension.

DESIGN

Prospective, cross-over, experimental study.

SETTING

University-based small animal research facility.

ANIMALS

Six healthy male Beagle dogs.

INTERVENTIONS

A balloon device comprising a Foley urinary catheter and latex balloon was placed in the intra-abdominal cavity. Plasma exogenous creatinine clearance was compared after intravenous administration of exogenous creatinine solution at 80 mg/kg under 4 different treatment conditions as follows: control and IAP levels of 25 mm Hg in conscious dogs and control and IAP levels of 25 mm Hg in anesthetized dogs (CC, C25, AC, and A25, respectively). Samples were obtained before (T0) and 10, 20, 30, 60, 90, 120, 240, 360, 480, and 600 min after administration of creatinine in all treatment groups.

MEASUREMENTS AND MAIN RESULTS

There were no significant differences in plasma creatinine concentration for CC, AC, and C25 during the treatment period. However, in the A25 treatment condition, the plasma creatinine concentration increased significantly at 10, 20, 30, 60, 90, and 120 min after administration of creatinine (P < 0.05). Plasma creatinine clearances were 5.0 ± 0.5, 4.7 ± 1.2, 5.5 ± 0.9, and 2.5 ± 0.5 mL/kg/min for 600 min (CC, AC, C25, and A25, respectively). In the A25 treatment condition, the plasma exogenous creatinine clearance decreased significantly to 50%, 47%, and 55% of that under control conditions (CC, AC, and C25, respectively). After decompression of the abdomen, plasma creatinine concentrations declined rapidly and returned to basal concentrations.

CONCLUSIONS

Intra-abdominal hypertension under general anesthesia could cause renal hypoperfusion. Timely decompression may improve the outcome of acutely increased IAP when surgery and/or general anesthesia is required in canine patients.

Compartment syndrome of the muscles of mastication in a working dog following a traumatic training incident

OBJECTIVE

To describe acute compartment syndrome (CS) of the muscles of mastication in a working dog associated with a traumatic training event.

CASE SUMMARY

A 2.5-year-old male Belgian Malinois was evaluated for acute blindness, severe diffuse swelling of the head, and inability to close the jaw following a traumatic incident during a bite training drill. During the exercise, the maxillary canine teeth were locked on a bite sleeve. Magnetic resonance imaging of the head and ocular system identified diffuse muscle swelling and hyperintensity, most severe in the muscles of mastication. Ocular abnormalities were not identified. Rhabdomyolysis, CS, and indirect optic nerve injury were supported by measurement of increased intramuscular pressure. Bilateral decompressive fasciotomies over the masseter and temporalis muscles resulted in immediate and marked resolution of the swelling and jaw movement. Blindness, however, did not resolve.

NEW OR UNIQUE INFORMATION PROVIDED

CS involving the muscles of mastication may occur as a complication of bite training and may result in irreversible and even life-threatening complications. Emergent decompressive fasciotomy is indicated to reverse swelling; however, visual deficits may not resolve.

Computed tomographic features of intra-abdominal hypertension in three dogs

OBJECTIVE

To describe computed tomographic (CT) features of intra-abdominal hypertension (IAH) in 3 dogs with abdominal distension.

CASE SUMMARY

Three dogs with anorexia, distended abdomen, or labored breathing were presented for CT imaging. All 3 dogs were premedicated with IV butorphanol (0.2 mg/kg). A Foley urinary catheter was aseptically placed and the transvesical technique was used to obtain intra-abdominal pressure (IAP). The IAP measurements were obtained with the dogs in a standing position after a stabilization period of 5 minutes. The mean IAP values for each of the 3 dogs were 26.0, 12.0, and 13.0 mm Hg. Anesthesia was induced with IV propofol (2.0-4.0 mg/kg, to effect) in all 3 dogs and maintained with sevoflurane in 2 dogs. Compression of the caudal vena cava and elevation of the diaphragm were observed in all 3 dogs, whereas renal compression and the extension of peritoneal fluid to the vaginal canal and cavity were seen in the dog with the highest IAP.

NEW OR UNIQUE INFORMATION PROVIDED

Compression of the caudal vena cava, direct renal compression, and the extension of peritoneal fluid into the vaginal canal and vaginal cavity are consistent with a diagnosis of IAH. Measurement of IAP and detection of these CT features should alert clinicians to the possible presence of IAH in veterinary patients.

Acute masticatory muscle compartmental syndrome in a dog

CASE DESCRIPTION A5.5-year-old sexually intact male Bull Terrier was referred for evaluation because of sudden facial swelling and an inability to close its mouth. CLINICAL FINDINGS Physical examination revealed bilaterally elevated nictitating membranes, an inability to adduct the mandible without assistance, and severe, diffuse, firm masticatory muscle swelling. Computed tomographic examination of the head revealed symmetric bilateral enlargement of the temporalis, masseter, and pterygoid muscles with heterogeneous contrast enhancement. Intracompartmental pressures in the left and right temporalis muscles as measured with an invasive arterial blood pressure transducer were 72 and 96 mm Hg, respectively. TREATMENT AND OUTCOME Emergent fasciotomy of the temporalis and masseter muscles was performed, followed by medical management with corticosteroids and analgesics. The diffuse facial swelling resolved within 1 week after surgery. Results of serologic testing for antibody against masticatory 2M muscle fibers were negative. Results of histologic examination of temporalis muscle specimens were consistent with mild to moderate multifocal neutrophilic and histiocytic myositis with myofiber degeneration and necrosis. CLINICAL RELEVANCE Acute compartmental syndrome should be considered as a differential diagnosis for dogs with a sudden onset of severe skeletal muscle swelling, signs of pain, and dysfunction. Findings for this dog with acute compartmental syndrome isolated to the masticatory muscles suggested that emergent fasciotomy followed by medical management may be an effective technique for treatment of this rare disease in dogs.

A novel balloon technique to induce intra-abdominal hypertension and its effects on cardiovascular parameters in a conscious dog model

OBJECTIVE

To evaluate a new balloon technique to induce intra-abdominal hypertension (IAH) and abdominal compartment syndrome in a conscious dog model, and to evaluate the effect of intra-abdominal pressure (IAP) on cardiovascular, respiratory, and arterial blood gas values in conscious dogs with IAH.

DESIGN

Prospective, experimental study.

SETTING

University-based small animal research facility.

ANIMALS

Six healthy Beagle dogs, 4 males, and 2 females.

INTERVENTIONS

A new balloon device designed for this study using a Foley urethral catheter and latex balloon was placed in the abdominal cavity. Consecutive measurements of IAP were made by measuring the intravesicular pressure. The abdomen was inflated with air to IAPs of 10, 15, 20, and 25 mm Hg. Heart rate, respiratory rate, systolic arterial blood pressure, and arterial blood gases were evaluated at baseline and at 15, 30, 45, 60, 120, 240, and 300 minutes after IAP increase.

MEASUREMENTS AND MAIN RESULTS

The air insufflated into the intra-abdominal balloon device significantly increased the IAP and led to sustained IAH. The respiratory rate increased significantly (P < 0.05) when IAP was increased to 15, 20, and 25 mm Hg. Although heart rate, systolic arterial blood pressure, PaO₂ , and PaCO₂ did not show statistically significant differences between baseline and posttreatment values over time, the dogs with increased IAP showed a distended abdomen and apparent discomfort, and 4/6 (67%) vomited. After measurement of IAP, air was removed. There were no adverse effects noted after removal of the balloon device.

CONCLUSION

The balloon device was successfully insufflated and led to sustained IAH in conscious dogs. This balloon technique does not require general anesthesia for instillation or removal of gas after installment. An acute IAP increase in normal conscious dogs induced discomfort, vomiting, and increased respiratory effort.

Prospective evaluation of the incidence of wound infection in rattlesnake envenomation in dogs

OBJECTIVE

To evaluate the incidence of wound infection following crotalidae envenomation in dogs and determine if the use of prophylactic antibiotics is warranted.

DESIGN

Prospective observational study.

SETTING

A 24-hour private practice specialty and emergency center in Murrieta, California.

ANIMALS

One hundred and two dogs with acute rattlesnake envenomation.

INTERVENTIONS

One hundred and forty-three consecutive cases of suspected acute rattlesnake envenomation were evaluated between March of 2012 and May of 2013. One hundred and two cases received no antimicrobials as part of management. Eight cases were placed on prophylactic antimicrobials by the primary care veterinarian prior to referral and were excluded. Two cases were excluded because they were initiated on antimicrobials during hospitalization for reasons unrelated to snakebite. Three cases involved cats and were excluded. Three patients died acutely near the time of presentation and were excluded. Twenty-one cases of suspected envenomation were excluded for lack of strong evidence of snakebite. Four cases were lost to follow-up and were excluded. Follow-up was conducted within 2 weeks either by phone or by direct inspection of the wound.

RESULTS

Of the 102 patients included in the study only 1 infection developed. This patient developed an abscess subsequent to suspected compartment syndrome.

CONCLUSION

The incidence of wound infection in rattlesnake envenomation is low, and the use of prophylactic antimicrobials is not recommended. The use of antimicrobials should be reserved for wounds with necrosis or abscess and the choice of antimicrobial should be based on a culture and sensitivity of the wound.