Stabilization and resuscitation in acute abdomen cases (Proceedings)

Case Presentation

                - Signalment: 6 year old female Rottweiler, Miss Pooples, weighing 40 kg

                - Presenting complaint: Vomiting, collapse, acutely painful distended abdomen

                - Last normal: 1 week ago

                - Past Pertinent History: Increased urinations and water consumption for 1 week, vomiting for 3 days, complete anorexia for 24 hours. Acutely unwilling to rise this am.

                - Other medical conditions and pertinent history

                - Past UTI 1 year ago, responded to antibiotics, cranial cruciate rupture 2 years ago, 2 normal litters of puppies, last pregnancy 2.5 years ago, last estrus 1 month ago, vaccines current

                - Medications: glycoflex, glucosamine, Aspirin PRN last given 1 week ago

                - Systems review: no coughing, no sneezing, no diarrhea, no naso-ocular discharge, no seizures, vomiting and PU/PD present

Physical examination findings

                - Temperature: 105.5°F,

                - Pulse: 180 bpm, pulses weak with occasional irregularity

                - Respirations: 50 bpm

                - Airway and Breathing: airway patent, breath sounds increased in all fields

                - Circulation: CRT 2.5 sec, mucous membranes pale and tacky, cardiac auscultation – no murmurs, limbs cold, 7% dehydrated

                - Neurologic: dull and depressed

                - Abdomen: distended, painful, tense, no obvious fluid wave

                - Urogenital: no vulvar discharge, mammary glands normal, unable to palpate bladder

                - Lymph nodes: within normal limits

                - EENT: no additional abnormalities

                - Musculoskeletal: nonambulatory, recumbent

                - Rectal examination: enlarged firm cervix, possible fluctuant uterine body

Initial therapeutic and diagnostic plan

                - Flow-by oxygen, IV catheter

                - ECG: tachycardia with occasional VPC

                - Blood pressure: mean 58 mm Hg 79/43

                - Pulse oximeter: 92%

                - IV fluids

Tissue oxygenation

The first question is whether defects in tissue oxygenation are a result of poor pulmonary function or poor oxygen delivery.

To determine pulmonary function in Miss Pooples calculate the A-a gradient:

                - Alveolar gas equation = Patm – PH2O (713mmHg) x FIO2 (.21) – PaCO2 (39 mmHg)/R (.8)

                - PAO2=150 – 49 = 101

                - PaO2 - PAO2 Gradient = 101 – 68 = gradient 33

      Plan: supplemental O2

                - Alveolar gas equation = Patm – PH2O (713mmHg) x FIO2 (.40) – PaCO2 (41 mmHg)/R (.8)

                - PAO2=236 – 51 = 185

                - a-A gradient = 185-171 = 14

Oxygen delivery

Oxygen delivery is dependent on cardiac output, arterial oxygen content, and blood flow.

Oxygen delivery

                - DO2 = arterial oxygen content (CaO2) x Cardiac output (CO)

Oxygen consumption

                - VO2 = the difference between arterial and mixed venous oxygen content (CaO2-CvO2) x Cardiac output (CO).

Oxygen extraction ratio

                - VO2/DO2 which can be further simplified to evaluate the difference in hemoglobin saturation between arterial and mixed venous blood: SaO2-SvO2/SaO2

Measuring oxygen delivery

Oxygen saturation can be measured in clinical patients, but cardiac output is often not feasible and therefore it can be challenging to determine mechanisms for impaired oxygen delivery. Blood flow to tissues is not easily measured and is often assumed to be adequate based on appropriate mean arterial pressures.

      Cardiac output

Normal CI in the dog is approximately 100 ml/min/kg or 5 L/min/m2 . The relationship between cardiac output and blood pressure is that CO is equal to the difference between mean arterial pressure and central venous pressure divided by the systemic vascular resistance.

      Initial cardiac output in Miss Pooples

                - CO = HR (180 beats/min) x SV (21 ml/beat)

                - = 2.8 L/min

                - CI = 70 ml/min/kg

                - CVP = -5 cm H2O (normal = 1.3-3.2 cm H2O; Haskins in press)

                - MAP = 58

                - ΔP= 63

                - SVRI = 0.9 mm Hg/ml/min/kg (normal = .59-.67 mm)

Most likely explanation for hypotension is decreased CO as a result of decreased preload.

Therefore therapy is to increase preload. In cases in which we can't measure cardiac output, we can use central venous pressure to help determine if preload is the problem.

      Immediately Following 3 liters of crystalloid

                - CO = HR (140 bpm) x SV (34 ml/beat)

                - = 4.7 L/min

                - CI = 118 ml/min/kg

                - CVP = 1 cm H2O

                - MAP = 72 mm Hg

                - ΔP= 71

                - SVRI = 0.6 mm Hg/ml/min/kg

                - Positive response to fluid therapy

      30 minutes later

                - CO = HR (180 bpm) x SV (33 ml/beat)

                - = 5.9 L/min

                - CI = 147 ml/min/kg

                - CVP = -1 cm H2O

                - MAP = 60 mm Hg

                - ΔP= 59

                - SVRI = 0.4 mm Hg/ml/min/kg

                - The hypotension despite an increase in heart rate and increase in CO is most likely a result of vasodilation (low SVR).

                - Therefore therapy is to increase SVR.

      Oxygen content

Oxygen content is calculated by the following formula: CaO2 in ml O2/dL= (1.34 ml O2/g x Hemoglobin concentration in g/dL x % hemoglobin saturation [SaO2]) + the dissolved oxygen (0.003 ml O2/dL/mm Hg x PaO2 in mm Hg). Normal oxygen content is approximately 20 mL/dL.

      Initial oxygen content in Miss Pooples:

                - SaO2=92%

                - PaO2 68 mm Hg

                - Hb 14.3 g/dl

                - CaO2 = 1.34 x 14.3 x .92 + (0.003 ml x 68) =17.6 + 0.2 = 17.8 ml/dl

                - The best way to increase CaO2 in this situation is to increase SaO2

      After resuscitation with 3 L of crystalloid and 40% O2

                - SaO2= 100%

                - PaO2 171 mmHg

                - Hb 12.6 g/dl

                - CaO2 = 1.34 x 12.6 x 1.0 + (0.003 ml x 171) =16.8 + 0.5 = 17.3 ml/dl

                - The best way to increase CaO2 in this situation is to increase Hb

      30 minutes later

                - SaO2 95%

                - PaO2 88 mmHg

                - Hb 12 g/dl

                - CaO2 = 1.34 x 12 x .95 + (0.003 ml x 88) =15.3 + 0.3 = 15.6 ml/dl

                - The best way to increase CaO2 in this situation is to increase Hb and SaO2

      Oxygen delivery: DO2 = arterial oxygen content (CaO2) x cardiac output (CO)

      Initial

                - DO2 = CaO2 (17.8 ml/0.1L) x CO (2.8 L/min) = 498 ml/min (expected = 1100 ml/min)

      After resuscitation with 3 L of crystalloid and 40% O2

                - DO2 = CaO2 (17.3 ml/0.1L) x CO (4.7 L/min) = 813 ml/min

      30 minutes later

                - DO2 = CaO2 (15.6 ml/0.1L) x CO (5.9 L/min) = 920 ml/min

Measuring oxygen uptake

     Oxygen consumption in Miss Pooples

                - VO2 = the difference between arterial and mixed venous oxygen content (CaO2-CvO2) x cardiac output (CO).

                - Initial:

                - SMVO2 = 54%

                - PmvO2=32 mmHg

                - CvO2 = 1.34 x 14.3 x .54 + (0.003 ml x 32)= 10.3 + .1 =10.4 mg/dl

                - CaO2 = 17.8 ml/dl

                - VO2 = 7.4 mg/.1L x CO 2.8 L/min = 207 mg/min

                - VO2/DO2 = 207/498 = .42

                - Lactate 7.4 - Extraction is high but still anaerobic metabolism, need to increase oxygen delivery.

      After resuscitation with 3 L of crystalloid and 40% O2

                - SMVO2 = 72%

                - PmvO2= 42 mmHg

                - CvO2 = 1.34 x 12.6 x .72 + (0.003 ml x 42) = 12.2 + .1 =12.3 mg/dl

                - CaO2 = 17.3 ml/dl

                - VO2 = 5 mg/.1L x CO 4.7 L/min = 235 mg/min

                - VO2/DO2 = 235/813 =.29

                - Lactate 4.4

                - Extraction has decreased, lactate is decreasing, therapy headed in the right direction

      30 minutes later

                - SMVO2 = 76%

                - PmvO2= 46 mmHg

                - CvO2 =1.34 x 12 x .76 + (0.003 ml x 46) = 12.2 + .1 = 12.3 mg/dl

                - CaO2 = 1.34 x 12 x .95 + (0.003 ml x 88) =15.3 + 0.3 = 15.6 ml/dl

                - VO2 = 3.3 mg/.1L x CO 5.9 L/min = 195 ml/min

                - VO2/DO2 = 195/920 = .21

                - Lactate 6

                - Extraction is low, lactate is increasing, suggesting that oxygen uptake is impaired. Need to improve oxygen delivery, but also treat underlying sepsis and regional abnormalities of perfusion or mitochondrial dysfunction.

Definitive care

Once the patient is oxygen delivery and uptake is optimized, the underlying cause of the acute abdomen must be addressed. Given the history and physical examination findings, there is a high level of suspicion for pyometra. This is confirmed by abdominal ultrasound and now surgery can be pursued knowing that you have done all you can to prepare your patient.

References available on request