Technician Update

Urine Trouble: Managing Anesthesia in a Broodmare with a Ruptured Bladder

By Lexie Conrow, LVT

A 13-year-old Thoroughbred broodmare, 7 days post foaling, presented to Rood & Riddle Equine Hospital for being off feed and having general mild colic signs. In other words, “ain’t doing right” (ADR). The referring veterinarian reported she was tachycardic and dehydrated with injected gums and decreased gut sounds in all quadrants. They also reported no significant findings from a rectal exam.

The foal was reported to be normal and would be accompanying the mare into the hospital.

Arrived in Recumbency
On arrival to the facility, the mare was down in the trailer in left sternal recumbency, leaning against the wall of the trailer. Her mentation was dull, but responsive to stimuli. The foal was brought off the trailer within her line of sight, but she made no effort to get up or even call to the foal. Her recumbency made performing a full physical exam difficult, as the priority was to keep our staff safe should she attempt to stand or thrash while inside the trailer. Her heart rate and respiratory rate were both elevated, 80 beats per minute and 24 breaths per minute, respectively. She had decreased borborygmi on the right side (the left side was not auscultated due to recumbency), her mucus membranes were injected/hyperemic, and she was also found to be dribbling urine. Between her history and physical exam, it was unclear why she was recumbent, and there was a debate whether she had a primary abdominal issue or if it was a neurologic episode of some kind. Blood was drawn for analysis.

During the next 10 minutes, after making several attempts to get her to stand, no progress was made other than her moving from sternal to full lateral recumbency. Her blood work showed an elevated packed cell volume (PCV), hyperkalemia, hyponatremia, hyperlactemia and an elevated creatinine (see Table 1 for values). A 14-gauge, 5.25-inch catheter was placed aseptically in her right jugular vein and 2 liters of hypertonic saline were administered, followed by a bolus of Lactated Ringer’s Solution (5 liters). An abdominal ultrasound was also performed, revealing an excessive amount of peritoneal effusion, collapsed small intestine and gas distension to the large colon. An abdominocentesis revealed free urine in the abdomen.

From these findings, the primary diagnosis was assumed to be a ruptured bladder. Permission was granted to take her to surgery for an exploratory celiotomy.

After getting the initial fluids and in the hopes she would be able to walk to an induction stall, the mare was encouraged to get up once more. She attempted but was weak and uncoordinated, falling almost immediately, landing halfway out of the trailer with her front end and head on the trailer ramp, requiring someone to support her head and neck to avoid her falling off the edge. For the safety of both the mare and hospital staff, it was decided to anesthetize her and to transport her to surgery. She was sedated with IV xylazine and then induced with ketamine and midazolam. She was orally intubated and was started on total IV anesthesia (GKX/Triple Drip). A team of people then attached ropes to her legs to move her onto a large animal glide, which was then dragged into the building where an overhead hoist was used to move her to a surgery table. She was prepped for the exploratory celiotomy in routine fashion. The foal was returned to a stall and was eventually moved to a nurse mare.

The first 15 minutes of anesthesia were relatively uneventful. The GKX was discontinued, and she was placed on a ventilator (set at 7 breaths/min) and was maintained on oxygen (10 L/min) and isoflurane inhalant anesthetic. With her abnormal blood work in mind, specifically her high PCV, potassium and electrolyte values, rapid fluid replacement and diuresis was a priority. In addition to her primary IV catheter, two additional temporary 14-gauge by 2-inch catheters were placed in the opposite jugular vein. An arterial catheter was placed in her facial artery to monitor blood pressure. A base fluid of 0.9% sodium chloride was chosen, made to be a 5% dextrose solution and enriched with 23% calcium gluconate. Dobutamine, Hetastarch and normal equine plasma were used to manage hypotension. Her ECG only showed minor changes, with slightly wider than normal QRS complexes and increased amplitude of the T-wave.

Ruptured Bladder Found
Once in surgery, it was confirmed that she did have a ruptured bladder. As the abdomen was being lavaged and bladder repaired, within a span of a few minutes the mare’s heart rate became unstable, oscillating between bradycardia (<20 beats/min) and tachycardia (>60 beats/min). She then lost a palpable pulse before experiencing 2 bouts of cardiac arrest, with her ECG showing ventricular fibrillation. Resuscitative efforts were initiated, beginning with temporarily discontinuing the isoflurane inhalant. Ventilation continued with straight oxygen. She was given 2 doses of epinephrine a few minutes apart. She responded well to the epinephrine, with an initial response of transient ventricular tachycardia, with her arterial blood pressure and heart rate both increasing dramatically, topping out in the 130s and 60s, respectively, both stabilizing over the remainder of the surgery. Her ECG returned to normal sinus rhythm within a few minutes. The inhalant was turned back on after resuscitative efforts were deemed successful.

Later, she did get a bit light under anesthesia, showing slow nystagmus and muscle tension in her neck. A small bolus of ketamine was given to return her to a proper plane of anesthesia. Her intra-op arterial blood gasses were mostly unremarkable, primarily displaying a metabolic acidosis (low pH, high bicarbonate), which was compensated by increasing her set respiratory rate over the course of the surgery. She was also given a dose of insulin subcutaneously. By the end of surgery, her PCV had decreased to 53.5%, and her serum potassium decreased to 5.9 mmol/L.

The surgery itself was uneventful, her bladder was repaired and 30 L of urine and fluid was lavaged from her abdomen. An abdominal drain, urinary catheter and incisional stent were placed intraoperatively. She recovered from anesthesia in a bedded recovery stall. After resuming spontaneous respiration in recovery, she was sedated with IV xylazine, IM detomidine and IM acepromazine. She also received furosemide IV. The total surgery time was 1 hour, 40 minutes; total anesthesia time was 2 hours, 8 minutes; and the total time in recovery from sedation to standing and returning to her stall was 90 minutes.

Postsurgical Care
She was kept on dextrose/calcium enriched NaCl fluids for the first 24 hours, then was switched to plain Lactated Ringer’s Solution. Fluid therapy was discontinued on the third day post-op. Her abdomen was lavaged daily for 2 days and the incisional stent was removed on day 6 post-op. Her blood work stabilized within the first 48 hours and all values were within normal limits on day 7 post-op, when she was discharged. All follow-up care was provided by another veterinarian and as of writing the mare has not returned to our practice. MeV

Teaching Points
The difficulty in this case was primarily the major electrolyte imbalances, particularly the hyperkalemia. Hyperkalemia causes deterioration of cardiac muscle, which is exacerbated by concurrent hypocalcemia and hypovolemia. It is a serious condition that can be fatal if left untreated. 

The treatment for hyperkalemia is often boiled down to the adage, “the solution to pollution is dilution.” More specifically, the objective for treatment is to move potassium from extracellular/vascular spaces (ECF) to the intracellular spaces (ICF). Ruptured bladders are commonly seen in foals (often neonates), and their smaller size makes it easier to accomplish appropriate diuresis than in an adult horse. In an ideal world, diuresis should be done preoperatively.

That was not an option in this case primarily due to her being recumbent inside the confines of a trailer, posing safety concerns for herself and hospital staff. As pre-op diagnostics seemed to point to a surgical issue, the risks of taking her directly to surgery instead of first to a stall for fluid therapy/further treatment were deemed acceptable.

Something to consider when diuresing a hyperkalemic patient is the type of fluid to use.

Due to the buffers they contain, the risk of inducing hyperkalemia in a normal patient is low when using a balanced crystalloid like Lactated Ringer’s Solution (or other isotonic crystalloids on the market). However, a patient that is hyperkalemic is inherently at higher risk. Therefore, choosing a low (or no) potassium fluid, such as isotonic saline, is ideal. Fluid additives and medications are also helpful in decreasing potassium levels. One such example is calcium-gluconate, which with its positive charge helps stabilize the cell membrane, creating an environment where the shift from ECF to ICF can occur more easily. Dextrose and insulin also help lower serum potassium levels by activating the Na+/K+ pumps, allowing glucose and potassium to enter the cell together. Lastly, as a beta-receptor agonist, epinephrine acts by essentially hyperpolarizing the cell membrane, forcing a potassium shift.

This case was a textbook example of the effects of hyperkalemia, especially regarding the negative cardiovascular effects. Luckily, this case was also a textbook example of an ideal response to treatment. The value of having well-trained staff cannot be understated as well.

A downed horse in a trailer can be a stressful situation for veterinary staff, let alone a mare with a foal by her side, compounded by an unclear diagnosis. It’s vital to have a good number of people to help move a recumbent animal, while also being aware to not put people in needlessly risky situations in confined spaces. Having an experienced technician running anesthesia was also extremely helpful in this case, as changes to the patient’s status were caught early and could be treated quickly.

Thankfully, all these things combined led to a favorable outcome in this case.

For more information:
Grimm K, Lamont L, Tranquilli W, et al. (Eds). (2015). Veterinary Anesthesia & Analgesia (5th Ed). John Wiley & Sons, Inc. Miur W, Hubbell J, (Eds). (2009). Equine Anesthesia: Monitoring & Emergency Therapy (2nd Ed). Saunders